Eawag Water Supply & Sanitation P.O. Box 611 8600 D¼bendorf

EawagÜberlandstrasse 133P.O. Box 6118600 DübendorfSwitzerlandPhone +41 (0)44 823 52 86Fax +41 (0)44 823 53 [email protected]

Abundant information exists about sanitation solutionsbut it is scattered throughout hundreds of books andjournals; this Compendium aims to pull it all together inone volume.By ordering and structuring a huge rangeof information on tried and tested technologies into oneconcise document, the reader is provided with a usefulplanning tool for making more informed decisions.

Part 1 describes different system configurations fora variety of contexts.Part 2 consists of 52 differentTechnology InformationSheets, which describe the main advantages, disadvanta-ges, applications and the appropriateness ofthe technologies required to build a comprehensivesanitation system. EachTechnology Information Sheetis complemented by a descriptive illustration.

ISBN: 978-3-906484-44-0

Compendiumof Sanitation Systems

and Technologies

Water Supply & SanitationCollaborative Council

International Environment HouseChemin des Anémones 91219 Châtelaine-GenevaSwitzerlandPhone +41 22 917 [email protected]

Cover: Sanitation Options Workshop in Dodoma, Tanzaniain 2008 moderated by Mr. Rukeha from the local NGO Mamado

Compendium

ofSanitationSystemsandTechnologies

Compendium of Sanitation Systems and Technologies

Elizabeth Tilley, Christoph Lüthi, Antoine Morel,Chris Zurbrügg and Roland Schertenleib.

Our special thanks go to:the NETSSAF Consortium, the GTZ ecosan programme

and the Sustainable Sanitation Alliance (SuSanA).

We would like to thank the following individualsfor their contributions and comments:

Chris Buckley, Pierre-Henri Dodane, Barbara Evans, Doulaye Koné,Elisabeth Kvarnström, Duncan Mara, Peter Morgan, Arne Panesar,

Eddy Perez, Elias Rosales, Arno Rosemarin, Sören Rud, Darren Saywell,Margaret Scott, Steven Sugden, Kevin Tayler, Kai Udert,

Carolien van der Voorden,Yvonne Voegeli, AnitaWittmer.

We would like to acknowledge support from:the Swiss National Centre of Competence in Research (NCCR)

North-South: Research Partnerships for Mitigating Syndromes ofGlobal Change, co-funded by the Swiss National Science Foundation (SNSF)

and the Swiss Agency for Development and Cooperation (SDC).

Investing in sanitation and hygiene is not only about sav-ing human lives and dignity; it is the foundation for inves-ting in human development, especially in poor urban andperi-urban areas. However, one of the main bottlenecksencountered the world over, is the limited knowledgeand awareness about more appropriate and sustainablesystems and technologies that keep project costsaffordable and acceptable.Abundant information exists about sanitation technolo-gies but it is scattered throughout dozens of books, re-ports, proceedings and journals; this Compendium aimsto pull the main information together in one volume.Another aim of the Compendium is to promote a systemsapproach; sanitation devices and technologies shouldalways be considered as parts of an entire system.In 2005, Sandec and the WSSCC published ProvisionalGuidelines for Household-centred Environmental Sani-tation (HCES), a new planning approach for implement-ing the Bellagio Principles on Sustainable Sanitation inUrban Environmental Sanitation. The HCES approachemphasizes the participation of all stakeholders – be-ginning at the household/neighbourhood – in planningand implementing sanitation systems. By ordering andstructuring a huge range of information on fully andpartly tested technologies into one concise document,this Compendium is an important tool for stakehold-ers to make well informed decisions during the plan-ning process.Although this source book is primarily addressed toengineers and planners dealing with infrastructure deliv-ery, the technology sheets also allow non-experts tounderstand the main advantages and limitations of dif-ferent technologies and the appropriateness of differentsystem configurations. It is our hope that this Compen-dium will allow all stakeholders to be involved in selectingimproved sanitation technologies and to help promotepeople-centred solutions to real sanitation problems.This is the first edition of the Compendium and we arelooking forward to receiving your feedback – experiencesand suggestions for a next edition are very welcome!

Eawag-Sandec–SanitationSystems

Foreword

Foreword

3

Roland SchertenleibEawag/Sandec

Jon LaneWSSCC


TableofContents

Table of Contents

5

Introduction: The Aim and Use of this CompendiumBackground 7Target User of the Compendium 7Objective of the Compendium 7Structure of the Compendium 7

Part 1: Systems Templates

General Informations about Sanitation Systems 9Products 11Functional Groups 13Technologies 13Using the System Templates 14

Description of the System TemplatesSystem 1: Single Pit System 16System 2: Waterless System with Alternating Pits 18System 3: Pour Flush System with Twin Pits 20System 4: Waterless System with Urine Diversion 22System 5: Blackwater Treatment System with Infiltration 24System 6: Blackwater Treatment System with Sewerage 26System 7: (Semi-) Centralized Treatment System 28System 8: Sewerage System with Urine Diversion 30

Part 2: Functional Groups with Technology Information Sheets

Reading the Technology Information Sheets 33

Functional Group U: User Interface 35U1: Dry Toilet 37U2: Urine Diverting Dry Toilet (UDDT) 39U3: Urinal 41U4: Pour Flush Toilet 43U5: Cistern Flush Toilet 45U6: Urine Diverting Flush Toilet (UDFT) 47

Functional Group S: Collection and Storage/Treatment 49S1: Urine Storage Tank/Container 51S2: Single Pit 53S3: Single Ventilated Improved Pit (VIP) 55S4: Double Ventilation Improved Pit (VIP) 57S5: Fossa Alterna 59S6: Twin Pits for Pour Flush 61S7: Dehydration Vaults 63S8: Composting Chamber 65S9: Septic Tank 67

S10: Anaerobic Baffled Reactor (ABR) 69S11: Anaerobic Filter 71S12: Anaerobic Biogas Reactor 73

Functional Group C: Conveyance 75C1: Jerrycan/tank 77C2: Human-Powered Emptying and Transport 79C3: Motorized Emptying and Transport 81C4: Simplified Sewers 83C5: Solids-Free Sewer 85C6: Conventional Gravity Sewer 87C7: Transfer Station (Underground Holding Tank) 89C8: Sewer Discharge Station (SDS) 91

Functional Group T: (Semi-) Centralized Treatment 93T1: Anaerobic Baffled Reactor (ABR) 95T2: Anaerobic Filter 97T3: Waste Stabilization Ponds (WSP) 99T4: Aerated Pond 101T5: Free-Water Surface Constructed Wetland 103T6: Horizontal Subsurface Flow Constructed Wetland 105T7: Vertical Flow Constructed Wetland 107T8: Trickling Filter 109T9: Upflow Anaerobic Sludge Blanket Reactor (UASB) 111T10: Activated Sludge 113T11: Sedimentation/Thickening Ponds 115T12: Unplanted Drying Beds 117T13: Planted Drying Beds 119T14: Co-Composting 121T15: Anaerobic Biogas Reactor 123

Use and/or Disposal 125D1: Fill and Cover/Arborloo 127D2: Application of Urine 129D3: Application of Dehydrated Faeces 131D4: Application of Compost/Eco-Humus 133D5: Irrigation 135D6: Soak Pit 137D7: Leach Field 139D8: Aquaculture Ponds 141D9: Floating Plant (Macrophyte) Pond 143D10: Water Disposal/Groundwater (GW) Recharge 145D11: Land Application of Sludge 147D12: Surface Disposal 149

Glossary 151


TableofContents

6


Introduction

7

BackgroundThis document was developed in the context of theHousehold Centered Environmental Sanitation (HCES)planning approach shown in Figure 1. The HCES ap-proach is a 10-step multi-sector and multi-actor partici-patory planning process. The guidelines for implement-ing HCES are available from www.sandec.ch.

Target User of the CompendiumThis Compendium is intended to be used by engineers,planners and other professionals who are familiar withsanitation technologies and processes. It is not a train-ing manual or stand-alone resource for people with noexperience in sanitation planning.The user of this document must have an interest inlearning more about alternative or novel technologieswhich may not be part of the common suite employedor taught in the local context. The approach and infor-mation presented herein is meant to broaden the spec-trum of innovative and appropriate technologies consid-ered for sanitation planning.

Objective of the CompendiumThe objective the Compendium is threefold:1. Expose the Compendium user to a broad range of

sanitation systems and innovative technologies;2. Help the Compendium user understand and work

with the system concept, i.e. the process of buildinga complete system, by iteratively choosing and link-ing appropriate technologies;

3. Describe and fairly present the technology-specificadvantages and disadvantages.

Structure of the CompendiumThe Compendium is divided into 2 Parts; (1) the SystemTemplates and a description about how to use them;and (2) the Technology Information Sheets.It is recommended that the Compendium user reviewsPart 1: Sanitation Systems to become familiar with theterminology and structure of the System Templates andtheir components. The user can then familiarize them-selves with the technologies of interest in Part 2:Technology Information Sheets. The user can movebetween the System Templates and the TechnologyInformation Sheets (they are cross-referenced) untilhe/she has identified some systems and/or technolo-gies that could be appropriate for further investigation.Eventually, the user should be able to develop one, orseveral system configurations that can be presented tothe community. The Compendium can then be used, fol-lowing the community’s suggestions, to re-evaluate andredesign the system accordingly.

The first four steps of the HCES planning approach definethe project-specific social, cultural, economic, health andenvironmental priorities which will influence technologyselection and the system design. The goal of steps five(5) and six (6) is to identify specific technological optionsand to evaluate feasible service combinations. The fol-lowing steps, seven (7) through ten (10), lead to the for-mulation or design of a comprehensive Urban Environ-mental Sanitation Services (UESS) plan.This Compendium is designed to serve as a resourcetool during steps 5 and 6 of the HCES planning approach.It is presupposed that the user of this Compendium hasa well-developed awareness of the context and priori-ties of the community and other stakeholders as thesocial-cultural elements of sanitation planning are notexplicitly addressed in this document.

Figure 1. The 10-step process in the HCES planning approach(EAWAG, 2005)

1 Request for assistance2 Launch of the planning and consultative process3 Assessment of current status4 Assessment of user priorities5 Identification of options6 Evaluation of feasible service combinations7 Consolidated UESS plans for study area8 Finalizing of consolidated UESS plans9 Monitoring (internal) evaluation and feedback10Implementation

The 10-Step process

Introduction

Enabling Environment

Government Support Legal FrameworkCredit and other Finacial Arrangements

Institutional Arrangements Required Skills


SystemTemplates

8

This Compendium defines sanitation as a multi-stepprocess in which wastes are managed from the point ofgeneration to the point of use or ultimate disposal. Asanitation system is comprised of Products (wastes)which travel through Functional Groups which containTechnologies which can be selected according to thecontext. A sanitation system also includes the manage-ment, operation and maintenance (O&M) required toensure that the system functions safely and sustain-ably. By selecting a Technology for each Productfrom each applicable Functional Group, one candesign a logical sanitation system.The purpose of this Part is to clearly explain the SystemTemplates by describing what they consist of, whatqualities they have and how they are to be used.

This Compendium describes eight (8) different SystemTemplates.System 1: Single Pit SystemSystem 2: Waterless System with Alternating PitsSystem 3: Pour Flush System with Twin PitsSystem 4: Waterless System with Urine DiversionSystem 5: Blackwater Treatment System with

InfiltrationSystem 6: Blackwater Treatment System with

SewerageSystem 7: (Semi-) Centralized Treatment SystemSystem 8: Sewerage System with Urine Diversion

A System Template defines a suite of compatibleTechnology combinations from which a system can bedesigned. Each System Template is distinct in terms ofthe characteristics and the number of Products gener-ated and processed. The System Templates present log-ical combinations of Technologies, but the planner mustnot lose a rational, engineering perspective. It must alsobe noted that although this Compendium is thorough, itis not an exhaustive list of Technologies and/or associ-ated systems.

Although the System Templates are predefined, theCompendium user must select the appropriateTechnology from the options presented. The choice iscontext specific and should be made based on the localenvironment (temperature, rainfall, etc.), culture (sit-ters, squatters, washers, wipers, etc.) and resources(human and material).System templates 1 to 8 range from simple (with fewTechnology choices and Products) to complex (withmultiple Technology choices and Products).The first section of this chapter defines the parts of theSystem Templates. Products, Functional Groups, andTechnologies are explained.The second part of this chapter explains how theSystem Templates can be read, understood, and usedto build a functional Sanitation System.The final section of this Chapter presents a descriptionof how the system works, what are the main considera-tions, and what type of applications that system isappropriate for.


SystemTemplates

Part 1: System Templates

9


SystemTemplates

10

ProductsProducts are materials that are also called ‘wastes’or ‘resources’. Some Products are generated directlyby humans (e.g. urine and faeces), others arerequired in the functioning of Technologies (e.g. flushwater to move excreta through sewers) and some aregenerated as a function or storage or treatment (e.g.faecal sludge).For the design of a robust sanitation system, it is nec-essary to define all of the Products that are flowing into(Inputs) and out (Outputs) of each of the sanitationTechnologies in the system. The Products referencedwithin this text are described below.

Urine is the liquid waste produced by the body torid itself of urea and other waste Products. In this con-text, the urine Product refers to pure urine that is notmixed with faeces or water. Depending on diet, humanurine collected during one year (ca. 500 L) contains2–4 kg nitrogen. With the exception of some rare cases,urine is sterile when it leaves the body.

Faeces refers to (semi-solid) excrement withouturine or water. Each person produces approximately50 L per year of faecal matter. Of the total nutrientsexcreted, faeces contain about 10% N, 30% P, 12% Kand have 107–109 faecal coliforms /100 mL.

Anal cleansing water is water collected after ithas been used to cleanse oneself after defecatingand/or urinating. It is only the water generated by theuser for anal cleansing and does not include dry mate-rials. The volume of water collected during anal cleans-ing ranges from 0.5 L to 3 L per cleaning.

Stormwater is the general term for the rainfallrunoff collected from roofs, roads and other surfacesbefore flowing towards low-lying land. It is the portionof rainfall that does not infiltrate into the soil.

Greywater is the total volume of water generatedfrom washing food, clothes and dishware as well asfrom bathing. It may contain traces of excreta andtherefore will also contain pathogens and excreta.Greywater accounts for approximately 60% of the

wastewater produced in households with flush toilets. Itcontains few pathogens and its flow of nitrogen is only10–20% of that in blackwater.

Flushwater is the water that is used to transportexcreta from the User Interface to the next technology.Freshwater, rainwater, recycled greywater, or any combi-nation of the three can be used as a Flushwater source.

Organics refers here to biodegradable organic mate-rial that could also be called biomass or green organicwaste. Although the other Products in this Compendiumcontain organics, this term refers to undigested plantmaterial. Organics must be added to some technologies inorder for them to function properly (e.g. compostingchambers). Organic degradable material can include butis not limited to leaves, grass and market waste.

Dry Cleansing Materials may be paper, corncobs,rags, stones and/or other dry materials that are used foranal cleansing (instead of water). Depending on the sys-tem, the dry cleansing materials may be collected anddisposed of separately. Although extremely important,we have not included a separate Product name for men-stral hygiene products like sanitary napkins and tam-pons. In general (though not always), they should betreated along with the Dry Cleansing Materials that aredescribed here.

Blackwater is the mixture of urine, faeces and flush-water along with anal cleansing water (if anal cleansing ispracticed) and/or dry cleansing material (e.g. toiletpaper). Blackwater has all of the pathogens of faeces andall of the nutrients of urine, but diluted in flushwater.

Faecal Sludge is the general term for the raw (orpartially digested) slurry or solid that results from thestorage of blackwater or excreta. The composition offaecal sludge varies significantly depending on the loca-tion, the water content, and the storage. For example,ammonium (NH4-N) can range from 300–3000 mg/Lwhile Helminth eggs can reach up to 60,000 eggs/L.The composition will determine the type of treatmentthat is possible and the end-use possibilities.


SystemTemplates

11

Treated Sludge is the general term for partiallydigested or fully stabilized faecal sludge. The USEnvironmental Protection Agency has strict criteria todifferentiate between degrees of treatment and conse-quently, how those different types of sludges can beused. ‘Treated Sludge’ is used in the System Templatesand in the Technology Information Sheets as a generalterm to indicate that the sludge has undergone somelevel of treatment, although it should not be assumedthat ‘treated sludge’ is fully treated or that it is automat-ically safe. It is meant to indicate that the sludge hasundergone some degree of treatment and is no longerraw. It is the responsibility of the user to inquire aboutthe composition, quality and therefore safety of thelocal sludge.

Excreta consists of urine and faeces that is notmixed with any flushing water. Excreta is small in volume,but concentrated in nutrients and pathogens. Dependingon the quality of the faeces it is solid, soft or runny.

Brownwater consists of faeces and flushwater(although in actual practice there is always some urine,as only 70–85% of the urine is diverted). Brownwater isgenerated by urine-diverting flush toilets and therefore,the volume depends on the volume of the flushwaterused. The pathogen and nutrient load of faeces is notreduced, only diluted by the flushwater.

Dried faeces are faeces that have been dehydrat-ed at high temperatures (and high pH) until theybecome a dry, sanitized powder. Very little degradationoccurs during dehydration and this means that thedried faeces are still rich in organic material. Faeces willreduce in volume by around 75%. There is a small riskthat some organisms can be reactivated in the rightenvironments.

Stored urine is urine that has been hydrolyzednaturally over time, i.e. the urea has been converted byenzymes into carbon dioxide and ammonia. Storedurine has a pH of approximately 9. After 6 months ofstorage, the risk of pathogen transmission is reducedconsiderably.

Effluent is the general term for liquid that hasundergone some level of treatment and/or separationfrom solids. It originates at either a Collection andStorage/Treatment or a (Semi-) Centralized TreatmentTechnology. Depending on the type of treatment, theeffluent may be completely sanitized or may require fur-ther treatment before it can be used or disposed of.

Compost/EcoHumus is the earth-like, brown/blackmaterial that is the result of decomposed organic mat-ter. Generally Compost/EcoHumus has been hygien-ized sufficiently that it can be used safely in agriculture.Because of leaching, some of the nutrients are lost, butthe material is still rich in nutrients and organic matter.

Biogas is the common name for the mixture ofgases released from anaerobic digestion. Typically bio-gas is comprised of methane (50–75%), carbon dioxide(25–50%) and varying quantities of nitrogen, hydrogensulphide, water and other components.

Forage refers to aquatic or other plants that grow inplanted drying beds or constructed wetlands and may beharvested for feeding livestock.

This Compendium is primarily concerned with systemsand Technologies directly related to excreta and doesnot address the specifics of greywater or stormwatermanagement but shows when they can be co-treatedwith excreta. So although greywater and stormwaterare shown as Products in the System Templates, therelated Technologies are not described in detail. For amore comprehensive summary of dedicated greywaterTechnologies refer to the following resource:

_ Morel A. and Diener S. (2006). Greywater Management inLow and Middle-Income Countries, Review of different treat-ment systems for households or neighbourhoods. SwissFederal Institute of Aquatic Science and Technology(Eawag). Duebendorf, Switzerland.Available free for download: www.eawag.ch


SystemTemplates

12

Functional GroupsA Functional Group is a grouping of technologies whichperform a similar function. There are five (5) differentFunctional Groups from which the technologies used tobuild a system are chosen. It is not necessary for a Pro-duct to pass through a technology from each FunctionalGroup; however, the ordering of the Functional Groupsshould usually be maintained regardless of how many ofthem are included within the sanitation system. Also,each Functional Group has a distinctive colour; techno-logies within a given Functional Group share the samecolour code so that they are easily identifiable.The five (5) Functional Groups are:

User Interface (Technologies U1–U6): Red

Collection and Storage/Treatment(Technologies (S1–S12): Orange

Conveyance (Technologies C1–C8): Yellow

(Semi-) Centralized Treatment(Technologies T1–T15): Green

Use and/or Disposal (Technologies D1–D12): Blue

Each technology within a given Functional Group is as-signed a reference code with a single letter and number;the letter corresponds to the Functional Group (e.g. U forUser Interface) and the number, going from lowest tohighest, indicates approximately how resource intensive(i.e. economic, material and human) the technology is.

User Interface (U) describes the type of toilet, pe-destal, pan, or urinal that the user comes in contactwith; it is the way that the user accesses the sanitationsystem. In many cases, the choice of User Interface willdepend on the availability of water. Note that greywaterand stormwater do not originate at the User Interface,but may be treated along with the Products that origi-nate at the User Interface.

Collection and Storage/Treatment (S) describesthe ways of collecting, storing, and sometimes treatingthe Products that are generated at the User Interface.

S

U

D

T

C

S

U

Treatment that is provided by these Technologies isoften a function of storage and usually passive (e.g. noenergy inputs). Thus, Products that are ‘treated’ bythese Technologies often require subsequent treatmentbefore use or disposal.

Conveyance (C) describes the transport ofProducts from one Functional Group to another.Although Products may need to be transferred in vari-ous ways between Functional Groups, the longest, andmost important gap is between Collection and Storage/Treatment and (Semi-) Centralized Treatment; thus, forsimplicity, conveyance is limited to transporting Pro-ducts at this point.

(Semi-) Centralized Treatment (T) refers to treat-ment Technologies that are generally appropriate forlarge user groups (i.e. multiple households). The opera-tion, maintenance, and energy requirements for Techno-logies within this Functional Group are more intensive.The Technologies are divided into 2 groups: Techno-logies T1–T10 are primarily for the treatment of black-water, whereas Technologies T11–T15 are primarily forthe treatment of sludge.

Use and/or Disposal (D) refers to the methods inwhich Products are ultimately returned to the environ-ment, as either useful resources or reduced-risk mate-rials. Furthermore, Products can also be cycled backinto a system (e.g. the use of treated greywater forflushing).

TechnologiesTechnologies are defined as the specific infrastructure,methods, or services that are designed to contain,transform, or transport Products to another FunctionalGroup. There are between 6 and 15 different techno-logies within each Functional Group. The TechnologyInformation Sheets located in Part 2 provide a detaileddescription of each technology identified within eachSystem Template.

D

T

C


SystemTemplates

13

Using the SystemTemplatesEach system is a matrix of Functional Groups (columns)and Products (rows) that are linked together where log-ical connections exist. Where these logical connectionsexist, a Technology choice is presented (i.e. for a certainProduct (row) intersecting a specific Functional Group(column)).Each Functional Group is colour-coded and the samecolour code is used within a System Template. To facil-itate efficient reference between System Templates andTechnology Information Sheets the Technologies withineach Functional Group adopt the same colour-code.The colour-code for each Functional Group within theSystem Template is presented below in Figure 2.Figure 3 is an example from a System Template. A boldcolour-coded box indicates a Technology choice withina given Functional Group. This System Template showshow three Products (Faeces, Urine and Flushwater)enter into a User Interface (Pour Flush Toilet and some-

times a Urinal) and emerge as Blackwater. Blackwaterthen enters the Collection and Storage/TreatmentFunctional Group and is transformed in the Twin Pits forPour Flush into Compost/EcoHumus and Effluent. TheCompost/EcoHumus is transported (Human Powered)to a final point of use and the Effluent is absorbed bythe soil (Disposal/Recharge).

Bold lines with arrows are used to link the most appro-priate Functional Groups for a given Product. Thin linesindicate other flow paths which are possible, but notalways common or recommended (see Figure 4).


SystemTemplates

14

U User Interface S Collection and Storage/Treatment

C Conveyance T (Semi-)CentralizedTreatment

D Use and/orDisposal

Inputs/OutputsInputs Inputs/Outputs Inputs/Outputs

Figure 2. System Template header with colour-code for the Functional Groups

for

11Three Inputs (Faeces, Urine and Flushwater) enter into 22Functional Group U “User Interface” (Pour Flush Toilet). The Blackwater generated 33 then enters into 44Functio nal Group S “Collection and Storage/Treatment” (Twin Pits For PourFlush Latrine) and is transformed into 55Compost/EcoHumus and Effluent. The Com post/EcoHumus enters into 66Functio nal Group C “Conveyance” (Human Powered Emptying & Transport) and passes 77Functional Group T “(Semi-)Centralized Treatment“ without treatment with no further 88 Inputs/Outputs. Compost/EcoHumus is transported directly tothe final 99Functional Group D “Use and/or Disposal” (Compost/Eco-Humus, Surface Disposal).The 55Effluent does not enter into 66Functional Group C nor 77Functional Group T (therefore there are 88no Inputs/ Outputs)but the Effluent is directly discharged 99 in Functional Group D (Disposal/Recharge).

Figure 3. System Template: how Inputs enter into Functional Groups and are transformed

1 2 3 4 5 6 7 8 9

Although the most logical combinations are presentedherein, the Technologies and associated links are notexhaustive. The designer should attempt to minimizeredundancy, optimize existing infrastructure and makeuse of local resources.

This methodology should be followed for each area(region or planning zone) under consideration. However,any number of systems can be chosen and it is not nec-essary that each home, compound, or community with-in the area choose the same Technologies. Some Tech -nologies may already exist; in that case it is the goal ofthe planners and engineers to optimize existing infra-structure and reduce redundancy but maintain flexibili-ty with user satisfaction as the primary goal.

Eawag-Sandec – Sanitation Systems

System Templates

15

Dry CleansingMaterial

Flushwater

Anal CleansingWater

Greywater

Stormwater

U.4 Pour Flush Toilet Blackwater

EffluentGreywater Treatment

D.12 Surface

Disposal

D.5 Irrigation

D.6 Soak Pit

D.10 Disposal/

Recharge

D.10 Disposal/

Recharge

Sanitation System 3: Pour Flush System with Twin Pits

EffluentD.10 Disposal/

Recharge

Stormwater Drains

S.6 Twin Pits for

Pour Flush

U Dry Toilet S Collection and Storage/Treatment

C Conveyance T (Semi-)CentralizedTreatment

D Use and/orDisposal

Inputs/OutputsInputs stuptuO/stupnIstuptuO/stupnI

Figure 4. Bold lines with arrows are used to link the most appropriate Functional Groups for a given Input or Output.Thin lines indicate other flowstreams which are possible.

> The eight System Templates are presented and des -cribed on the following pages. Each System Temp late isexplained in detail.

Steps for selecting a System Template:

a) Identify the Products that are generated and/or are available locally (e.g. Anal CleansingWater or Flushwater).

b) Identify the System Templates that process the defined Products

c) For each template, select a Technology fromeach Functional Group where there is a Tech no -logy choice presented (bold coloured box); theseries of Technologies makes up a System

d) Compare the systems and iteratively change individual Technologies or use a different System Template based on user priorities, economic constraints, and technical feasibility.


System Template 1 – Single Pit System

16

CConveyance Input/OutputProducts

Input/Output

Faecal Sludge

C.7

S.2Single Pit

S.3Single Pit VIP

C.8Sewer

C.2Human Powered

Em pty ing &

Transport

C.3Motorized Em pty -

Excreta

UUser Interface

SCollection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Input/Output

Products

Input

Products

Input/Output

Products

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Sanitation System 1:

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T.5

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oile

t


System Template 1 – Single Pit System

17

U1: DRY TOILET

slab

option 1

option 2

S3: SINGLE PIT VIP

> 30

cm

air currents

>11cm vent pipe

fly screen

D1: FILL AND COVER 117

1 2

System 1: Single Pit System

This system is based on the use of a single pit to col-lect and store the excreta. The system can be usedwith or without Flushwater depending on the UserInterface. The inputs to the system can include Urine, Faeces, AnalCleansing Water, Flushwater and Dry Cleansing Materials.The use of Flushwater and/or Anal Cleansing Water willdepend on water availability and local habit. There are two different User Interfaces for this system,which include a Dry Toilet (U1) or a Pour Flush Toilet (U4).The User Interface is directly connected to a Collectionand Storage/Treatment Technology: a Single Pit (S2) or aSingle Ventilated Improved Pit (VIP) (S3). When the pit is full there are several options. If there isspace, the pit can be filled with soil and planted with atree, as per the Fill and Cover (D1), and a new pit built.This is generally only possible when the superstructureis mobile. Alternatively, the Faecal Sludge that is gen-erated from the Collection and Storage/TreatmentTechnology has to be removed and transported for fur-ther treatment. The Conveyance Technologies that canbe used include Human Powered Emptying andTransport (E&T) for solid sludge (C2) or Motorized E&Tfor liquid sludge (C3). When the Faecal Sludge is thin-ner, it must be emptied with a vacuum truck. As theFaecal Sludge is highly pathogenic prior to treatment,human contact and agricultural applications should beavoided. When it is not feasible to empty the full pit,(Semi-) Centralized Treatment can be omitted and thepit can be filled and covered with a suitable material fordecommissioning (Fill and Cover: D1). The decommis-sioned pit can be planted with a fruit or flowering treesince it will thrive in the nutrient rich environment. Faecal Sludge that is removed can be transported to adedicated Faecal Sludge treatment facility (Technolo giesT11 to T15). In the event that the treatment facility is noteasily accessible, the Faecal Sludge can be discharged toeither a Sewer Discharge Station (C8) or a Transfer Station(C7). From the Sewer Discharge Station, the FaecalSludge is transported by the sewer and is co-treated withthe Blackwater flowing in the sewer network (Techno -logies T1 to T10). The Faecal Sludge from the Sewer Di s -charge station is released either directly into the sewer orat timed intervals. If sludge is introduced directly into a

sewer, there must be enough water to adequately diluteand transport the sludge to the treatment facility. From theTransfer Station the Faecal Sludge must be transportedto a dedicated Faecal Sludge treatment facility (Tech -nologies T11 to T15) by a motorized vehicle (C3).All (Semi-) Centralized Treatment Technologies, T1 toT15, produce both Effluent and Faecal Sludge, whichrequire further treatment prior to Use and/or Dis po sal.Technologies for the Use and/or Disposal of the treat-ed Effluent include Irrigation (D5), Aquaculture (D8),Macrophyte Pond (D9) or Discharge to a water body orRecharge to groundwater (D10).

Considerations This system is best suited to ruraland peri-urban areas where there is appropriate soil fordigging and absorbing the Effluent from the pit. Thissystem should be chosen only where there is eitherspace to continuously dig new pits or when there is anappropriate manner of emptying and disposing of theFaecal Sludge. In dense urban settlements, there maynot be sufficient transportation or access to empty ormove to another pit. This system is also best suited toareas that are not prone to heavy rains or flooding,which may cause the pits to overflow. Some Greywaterin the pit may help degradation, but excessive additionsof Greywater may shorten the life of the pit. Although different types of pits are common in mostparts of the world, a well designed pit-based systemwith appropriate transport, treatment and use or dis-posal, is still very rare. This system is one of the least expensive to construct(capital cost) however the maintenance costs may beconsiderable, depending on the depth of the pit andhow often it must be emptied. If the ground is appropri-ate, i.e. good absorptive capacity, the pit may be dugvery deep (e.g. >5m) and can be used for several years(up to 30 years) without emptying. All types of solid cleansing materials can be discardedinto the pit, although they may shorten the life of the pitand make pit emptying more difficult. Whenever possi-ble, solid cleansing materials should be disposed ofseparately.


System Template 2 – Waterless System with Alternating Pits

18

Org

anic

s

Anal

Cle

ansi

ngW

ater

Dry

Cle

ansi

ngM

ater

ial

Gre

ywat

er

Stor

mw

ater

U.1

Dry

Toi

let

Excr

eta

Efflu

ent

C.2

Hum

an P

ower

ed

Em pt

y ing

&

Tran

spor

t

Gre

ywat

er T

reat

men

t

D.4

Appl

icat

ion

D.12

Surf

ace

Dis

posa

l

D.5

Irrig

atio

n

D.6

Soak

Pit

D.10

Dis

posa

l/

Rech

arge

D.10

Dis

posa

l/

Rech

arge


Waterless System with Alternating Pits

Com

post

/Ec

oHum

us

Faec

es

Stor

mw

ater

Dra

ins

S.4

Dou

ble

VIP

S.5

Foss

a Al

tern

a

S.8

Com

post

ing

Cha

mbe

r

Urin

e

UUser Interface

SCollection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Input/Output

Products

Input

Products

Input/Output

Products

Input/Output

Products

This system is designed to produce a dense, compost-like material by using alternating pits without the addi-tion of Flushwater. The inputs to the system can include Urine, Faeces,Organics, Anal Cleansing Water, and Dry CleansingMaterials. A Dry Toilet (U1) is the only recommended User Inter -face for this system. A Dry Toilet does not require waterto function and in fact, water should not be input intothis system; Anal Cleansing Water should be kept to aminimum or even excluded from this system if possible.Depending on the Collection and Storage/Treat mentTechnology, the Dry Cleansing Materials can be addedto the pit, otherwise they should be collected separate-ly and directly transferred for disposal (D12). Excreta is produced at the User Interface. The UserInterface is connected directly to a Collection andStorage/Treat ment Technology: a Double VIP (S4),Fossa Alterna (S5) or a Composting Chamber (S8).Alternating the pits gives the material an opportunityto drain, degrade, and transform into a nutrient-rich,hygienically-improved, humic material that can be usedor disposed of safely. While one pit is filling withExcreta (and potentially organic material), the other pitremains out of service. When the first pit is full, it iscovered and temporarily taken out of service. Thedrained and degraded Excreta within the second pit isemptied and the pit is put back into service. The sec-ond pit collects Excreta until it is filled, covered andtaken out of service and the cycle is repeated indefi-nitely. Although a ‘Composting Chamber’ is not strictlyan alternating pit technology, it can have multiplechambers and produces a safe, useable compost-Product. For these reasons it is included in this SystemTemplate. The Compost/EcoHumus that is generated from theCollection and Storage/Treatment Technology can beremoved and transported for Use and/or Disposalmanually using a Human Powered E&T (C2) Convey -ance Technology. Since it has undergone significantdegradation, the humic material is quite safe to handleand use in agriculture. If there are concerns about thequality, it can be composted further in a dedicatedcom posting facility but there is no need to transport

the Com post/ EcoHumus to a (Semi-) Centralized Treat -ment facility as decomposition of the Excreta takesplace onsite. For the Use and/or Disposal of Compost/EcoHumus,the Application of Compost/EcoHumus (D4) Techno -logy is utilized. This system is different than System 1 because of theConveyance and Use and/or Disposal options: in theprevious system, the sludge requires further treatmentbefore it can be used, whereas the Compost/EcoHu -mus produced in this system is ready for Use and/orDisposal following Collection and Storage/Treatment.

Considerations Because the system is permanentand can be used indefinitely (as opposed to some sin-gle pits, which may be filled and covered), it can beused where space is limited. Additionally, because theProduct must be removed manually, this system isappropriate for dense areas that do not have access tomechanical emptying/trucks. The success of this system depends on an extended stor-age period. If a suitable and continuous source of soil,ash or organic matter (leaves, grass clippings, coconut orrice husks, woodchips, etc.) is available, the decomposi-tion process is enhanced and the storage period can bereduced. The storage period can be minimized if thematerial in the pit remains well aerated and not toomoist. Therefore, the Greywater must be collected andtreated separately. Too much moisture in the pit will fillthe air-voids and deprive the microbes of oxygen, whichmay impair the degradation process.This system is especially appropriate for water-scarceareas and where there is an opportunity to use thehumic material. Dry cleansing materials can be discard-ed into the pit/chamber, especially if they are carbona-ceous (e.g. toilet paper, newsprint, corncobs, etc.) asthis may help with degradation and airflow.


System Template 2 – Waterless System with Alternating Pits

System 2: Waterless System with Alternating Pits

19

U1: DRY TOILET

slab

option 1

option 2

D4: APPLICATION OF COMPOST/ECO-HUMUS S5: FOSSA ALTERNA

1 2 3


System Template 3 – Pour Flush System with Twin Pits

20

Dry

Cle

ansi

ngM

ater

ial

Urin

e

Flus

hwat

er

Anal

Cle

ansi

ngW

ater

Gre

ywat

er

Stor

mw

ater

U.4

Pour

Flu

sh T

oile

tBl

ackw

ater

Efflu

ent

C.2

Hum

an P

ower

ed

Em pt

y ing

&

Tran

spor

t

Gre

ywat

er T

reat

men

t

D.12

Surf

ace

Dis

posa

l

D.11

Appl

icat

ion

D.12

Surf

ace

Dis

posa

l

D.5

Irrig

atio

n

D.6

Soak

Pit

D.10

Dis

posa

l/

Rech

arge

D.10

Dis

posa

l/

Rech

arge


Pour Flush System with Twin Pits

Efflu

ent

Trea

ted

Slud

ge

Faec

es

D.10

Dis

posa

l/

Rech

arge

Stor

mw

ater

Dra

ins

S.6

Twin

Pits

for

Pour

Flu

sh

S.12

Biog

as R

eact

or

UUser Interface

SCollection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Input/Output

Products

Input

Products

Input/Output

Products

Input/Output

Products

This is a water-based system utilizing the Pour FlushToilet (pedestal or squat pan) to produce a partiallydigested, humus-like Product, which can be used as asoil amendment. If water is not available, please refer toSystems 1, 2 and 4. Greywater can be used in systemand does not require separate treatment. The inputs to the system can include Faeces, Urine,Flushwater, Anal Cleansing Water, Dry CleansingMaterials and Greywater. The User Interface Technology for this system is a PourFlush toilet (U4). A Urinal (U3) should only be used inaddition to, and not instead of, the Pour Flush Toilet. Twin Pits for Pour Flush (S6) is one of the technologiesused for the Collection and Storage/Treatment of theBlack water output from the User Interface. The TwinPits are lined with a porous material that allows theEffluent to infiltrate into the ground while solids accu-mulate and degrade at the bottom of the pit. While onepit is filling with Blackwater, the other pit remains out ofservice. When the first pit is full, it is covered and tem-porarily taken out of service. It should take a minimumof two (2) years to fill a pit. When the second pit is full,the first pit is re-opened and the contents are removed.The Treated Sludge that is generated in the pit after two(2) years is removed and transported for Use and/ orDisposal manually using a Human Powered E&T (C2)Conveyance Technology. Since it has undergone signi -ficant degradation, it is not as pathogenic as raw, undi-gested sludge. There is no need to transport the treat-ed sludge to a (Semi-) Centralized Treatment facility astreatment of the Blackwater takes place onsite.Dry Cleansing Mate rials may clog the pit and preventwater from infiltrating into the soil and so it should becollected separately and transferred for SurfaceDisposal (D12). Alternatively, the blackwater can be directed towardsan Anaerobic Biogas Reactor (S12). The reactor willfunction better if animal manure and organic waste arealso added; liquid imputs like Greywater should be keptto a minimum. The Biogas that is generated (not shown)can be used for cooking, and the Treated Sludge can beused as a soil amendment.

For the Use and/or Disposal component of the SystemTemplate, the Application of Sludge (D11) Technologyis utilized. Effluent from the Twin Pits for Pour Flush(S6) is directly Infiltrated into the soil (D10) onsite fromeach pit. Therefore, this system should only be installedwhere there is a low groundwater table that is not atrisk of contamination from these pits.

Considerations Depending on the Collection andStorage/Treatment technology chosen, the system willdepend on different criteria. In the case of the doublepits, the system will depend on soil which can continu-ally and adequately absorb moisture; clayey or denselypacked soils are not appropriate. The material that isremoved should be in a safe, useable form, although thetask of removing, transporting and using it may not befavourable in some circumstances. The use of a house-hold biogas digester is best suited to peri-urban or ruralareas where there is a source of organic and/or animalwaste material and a need for the digested sludge. Thepiping system for the gas must be well maintained toprevent leaks and potential explosions.This system is well-suited for anal cleansing withwater. Dry cleansing materials should be disposed ofseparately because they could easily clog the pit orthe reactor (D12).


System Template 3 – Pour Flush System with Twin Pits

System 3: Pour Flush System with Twin Pits

21

U5: CISTERN FLUSH TOILET U5: CISTERN FLUSH TOILET S6: TWIN PIT POUR-FLUSH LATRINE (TPPFL)

leach pit

leach pit

D4: APPLICATION OF COMPOST/ECO-HUMUS


System Template 4 – Waterless System with Urine Diversion

22

Dry

Cle

ansi

ngM

ater

ial

Faec

es

Urin

e

C.2

Hum

an P

ower

ed

Em pt

y ing

&

Tran

s por

t

Stor

mw

ater

Dra

ins

C.1

Jerr

ycan

C.2

Hum

an P

ower

ed

Em pt

y ing

&

Tran

s por

t

D.12

Surf

ace

Dis

posa

l

D.3

Appl

icat

ion

D.12

Surf

ace

Dis

posa

l

D.2

Appl

icat

ion

D.5

Irrig

atio

n

D.6

Soak

Pit

D.10

Disp

osal

/Rec

hare


Waterless System with Urine Diversion

S.7

Dou

ble

Deh

y -

drat

ion

Vaul

ts

Anal

Cle

ansi

ngW

ater

Drie

d Fa

eces

Stor

ed U

rine

Efflu

ent

D.2

Appl

icat

ion

Gre

ywat

er T

reat

emen

t

Anal

Cle

ansi

ngW

ater

Urin

e

UUser Interface

SCollection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Input/Output

Products

Input

Products

Input/Output

Products

Input/Output

Products

Gre

ywat

er

Stor

mw

ater

U.2

Urin

e D

iver

ting

Dry

Toi

let

U.3

Urin

al

Faec

es

S.1

Stor

age

Tank

D.6

Soak

Pit

This system is designed to separate Urine and Faecesto allow Faeces to dehydrate and/or recover the Urinefor beneficial use. This system can be used anywhere,but it is especially appropriate for rocky areas wheredigging is difficult, where there is a high groundwatertable, or in water-scarce regions. The inputs to the system can include Faeces, Urine, AnalCleansing Water and Dry Cleansing Materials. There are two User Interface Technologies for this sys-tem; a Urine Diverting Dry Toilet (UDDT) (U2) or a Urinal(U3). UDDTs with a third diversion for Anal Clean singWater are not common, but can be manufactured local-ly or ordered depending on local washing customs. Drycleansing materials will not harm the system, but theyshould be collected separately from the UDDT (U2) anddirectly transferred for Surface Disposal (D12). Double Dehydration Vaults (S7) are used for the Col -lection and Storage/Treatment Technology for Faeces.Anal Cleansing Water should never be put into Dehy -dration Vaults, but it can be diverted and put into a SoakPit (D6). When storing the Faeces in chambers, theyshould be kept as dry as possible to encourage dehydra-tion and hygienization. Therefore, the chambers shouldbe watertight and care should be taken to ensure that nowater is introduced during cleaning. Also important is a constant supply of ash, lime, or dryearth to cover the Faeces to minimize odours and pro-vide a barrier between the Faeces and potential vectors(flies). The pH increase will also help to kill organisms.A separate Greywater system is required since it shouldnot be introduced into the Dehydration Vaults andpreferably not into the pits. Urine can be disposed of easily and without risk to theenvironment because it is generated in relatively smallvolumes and is nearly sterile. The Urine can be diverteddirectly to the ground for Use and/or Disposal as LandApplication (D2), Irrigation (D5) or soil infiltrationthrough a Soak Pit (D6). Storage Tanks (S1) can be usedfor the Collection Storage/Treatment of Urine. The Dried Faeces that are generated from the Col -lection and Storage/Treatment Technology can beremoved and transported for Use and/or Disposal. TheConveyance Technology that can be used is HumanPowered E&T (C2). The Dried Faeces pose little human

health risk. Stored Urine can be transported for Useand/ or Disposal using either the Jerrycan (C1) or Moto -rized E&T (C3) Technologies. Guidelines for the safe use of Excreta, Faecal Sludgeand Urine have been published by the World HealthOrganization (WHO) and are referenced on the relevantTechnology Information Sheets.

Considerations The success of this system de -pends on the efficient separation of urine and faecesas well as the use of a suitable drying agent; a dry, hotclimate can also contribute considerably to the rapiddehydration of the faeces. The system can be usedregardless of the users’ acceptance to Urine use; itcan be adapted to suit the agricultural and culturalneeds of the users.All types of solid cleansing materials can be used,although they should be discarded separately. AnalCleansing Water must be separated from the Faecesalthough it can be mixed with the Urine before it istransferred to the Soak Pit (not shown in the SystemTemplate). If Urine is used in agriculture, Anal CleansingWater should be kept separate and treated along withGreywater.


System Template 4 – Waterless System with Urine Diversion

23

System 4: Waterless System with Urine DiversionD6: SOAK PIT 131

inletS1: URINE STORAGE TANK/CONTAINER

U2: URINE DIVERTING DRY TOILET (UDDT)

option 2

option 2

option 1

option 1 urine urine


System Template 5 – Blackwater Treatm

ent System with Infiltration

24

Stor

mw

ater

Gre

ywat

er

Faec

es

Urin

e

Flus

hwat

er

Anal

Cle

ansi

ngW

ater

Dry

Cle

ansi

ngM

ater

ial

U.4

Pour

Flu

sh

Toile

t

U.5

Cis

tern

Flu

sh

Blac

kwat

er

Faec

al S

ludg

e

Stor

mw

ater

Dra

ins

C.7

Tran

sfer

Sta

tion

T.3

WSP

T.4

Aera

ted

Pond

T.5

FWS

CW

T.6

HSF

CW

T.7

VF C

W

T.8

Tric

klin

g Fi

lter

T.9

UAS

B

T.10

Activ

ated

Slu

dge

T.11

Sedi

men

tatio

n/

Thic

keni

ng

T.12

Unp

lant

ed d

ryin

g

beds

T.13

Plan

ted

dryin

g be

ds

T.14

Co-

Com

post

ing

T.15

Biog

as R

eact

or

Efflu

ent

Trea

ted

Slud

ge

D.10

Dis

posa

l/

Rech

arge

D.5

Irrig

atio

n

D.8

Aqua

cultu

re

D.9

Mac

roph

yte

D.10

Dis

posa

l/

Rech

arge

D.11

Land

App

licat

ion

D.12

Surf

ace

Dis

posa

l

D.12

Surf

ace

Dis

posa

l


Blackwater Treatm


S.9

Sept

ic T

ank

S.10

ABR

S.11

Anae

robi

c Fi

lter

Efflu

ent

D.6

Soak

Pit

D.7

Leac

h Fi

eld

C.8

Sew

er D

isch

arge

Stat

ion

UUser Interface

SCollection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Input/Output

Products

Input

Products

Input/Output

Products

Input/Output

Products

C.2

Hum

an P

ower

ed

Em pt

y ing

&

Tran

s por

t

C.3

Mot

orize

d Em

pty -

ing

& T

rans

port

This is a water-based system that requires a flush toiletand a Collection & Storage/Treatment Technology thatis appropriate for storing large quantities of water. The inputs to the system can include Faeces, Urine,Flushwater, Anal Cleansing Water, Dry Cleansing Mate -rials and Greywater. There are two User Interface Technologies that couldbe used for this system: a Pour Flush Toilet (U4) or aCistern Flush Toilet (U5). In the event that DryCleansing Materials are collected separately from theflush toilets, they can be directly transferred forSurface Disposal (D12). The User Interface is directly connected to aCollection and Storage/Treatment Technology for theBlackwater generated: either a Septic Tank (S9), aAnaerobic Baff led Reactor (ABR) (S10), or anAnaerobic Filter (S11) may be used. The anaerobicprocesses reduce the organic and pathogen load, butthe Effluent is still not suitable for direct use.Greywater should be treated along with Blackwater inthe same Collection & Storage/Treat ment Technology,but if there is a need for water-recovery, it can betreated separately (not shown on the SystemTemplate).Effluent generated from the Collection and Storage/Treatment can be diverted directly to the ground forUse and/or Disposal through a Soak Pit (D6) or a LeachField (D7). For these Technologies to work there mustbe sufficient space available and the soil must have asuitable capacity to absorb the Effluent. If this is not thecase, refer to System 6: Blackwater Treatment Systemwith Sewerage. Although it is not recommended, theEffluent can also be discharged into the StormwaterDrainage network for Use and/or Disposal as Ground -water Recharge (D10). This should only be considered ifthe quality of the Effluent is high and there is not capac-ity for onsite infiltration or transportation offsite. The Faecal Sludge that is generated from the Collectionand Storage/Treatment Technology must be removedand transported for further treatment. The ConveyanceTechnologies that can be used include Human PoweredE&T (C2) or Motorized E&T (C3). As the Faecal Sludge ishighly pathogenic prior to treatment, human contactand direct agricultural applications should be avoided.

Faecal Sludge that is removed can be transported to adedicated Faecal Sludge treatment facility (Techno -logies T11 to T15). In the event that the treatment facili-ty is not easily accessible, the Faecal Sludge can be dis-charged to either a Sewer Discharge Station (C8) or aTransfer Station (C7). From the Sewer Discharge Station,the Faecal Sludge is transported by the sewer and is co-treated with the Blackwater flowing in the sewer net-work (Technologies T1 to T10). The Faecal Sludge fromthe Sewer Discharge station is released either directlyinto the sewer or at timed intervals (to optimize the per-formance of the (Semi-) Centralized Treatment facility).If sludge is introduced directly into a sewer, there mustbe enough water to adequately dilute and transport thesludge to the treatment facility. From the TransferStation, the Faecal Sludge must be transported to a ded-icated Faecal Sludge treatment facility by a motorizedvehicle (Technologies T11 to T15). All (Semi-) Centralized Treatment Technologies, T1 toT15, produce both Effluent and Faecal Sludge, whichrequire further treatment prior to Use and/or Dis -posal. Technologies for the Use and/or Disposal of thetreated Effluent include Irrigation (D5), Aquaculture(D8), Macrophyte Pond (D9) or Dis charge to a waterbody or Recharge to groundwater (D10). Technolo giesfor the Use and/or Disposal of the treated FaecalSludge include Land Application (D11) or Surface Dis -posal (D12).

Considerations This system is only appropriate inareas where desludging services are available andaffordable and where there is an appropriate way to dis-pose of the sludge. This system can be adapted for usein colder climates, even where there is ground frost.The system requires a constant source of water. The capital investment for this system is considerable(excavation and installation of an onsite storageTechnology), but the costs can be shared by a numberof households if the system is designed for a largernumber of users.This water-based system is suitable for Anal CleansingWater, and since the solids are settled and digestedonsite, easily degradable Dry Cleansing Materials canalso be used.




25

System 5: Blackwater Treatment System with Infiltration

U4: POUR FLUSH TOILET

slab

water seal

S9: SEPTIC TANK

sludge

settlement zone

scum

outlet

inlet inlettee liquid level

access covers

D7: Leach Field

settling tanks

settled effluent



ent System with Sewerage

26

Stor

mw

ater

Gre

ywat

er

Faec

es

Urin

e

Flus

hwat

er

Anal

Cle

ansi

ngW

ater

Dry

Cle

ansi

ngM

ater

ial

U.4

Pour

Flu

sh T

oile

t

U.5

Cis

tern

Flu

shBl

ackw

ater

C.4

Sim

plifi

ed

Sew

er

C.5

Solid

s-fr

ee

Sew

er

Stor

mw

ater

Dra

ins

TT.3

WSP

T.4

Aera

ted

Pond

T.5

FWS

CW

T.6

HSF

CW

T.7

VF C

W

T.8

Tric

klin

g Fi

lter

T.9

UAS

B

T.10

Activ

ated

Slu

dge

T.11

Sedi

men

tatio

n/

Thic

keni

ng

T.12

Unp

lant

ed d

ry-

ing

beds

T.13

Plan

ted

dryin

g be

ds

T.14

Co-

Com

post

ing

T.15

Biog

as R

eact

or

Efflu

ent

Trea

ted

Slud

ge

D.10

Dis

posa

l/

Rech

arge

D.5

Irrig

atio

n

D.8

Aqua

cultu

re

D.9

Mac

roph

yte

D.10

Dis

posa

l/

Rech

arge

D.11

Land

App

licat

ion

D.12

Surf

ace

Dis

posa

l

D.12

Surf

ace

Dis

posa

l


Blackwater Treatm


Efflu

ent

Faec

al S

ludg

e

C.8

Sew

er D

isch

arge

Stat

ion

C.2

Hum

an P

ower

ed

Empt

ying

&

Tran

s por

t

C.3

Mot

orize

d Em

pty -

ing

& T

rans

port

C.7

Tran

sfer

Sta

tion

UUser Interface

SCollection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Input/Output

Products

Input

Products

Input/Output

Products

Input/Output

Products

S.9

Sept

ic T

ank

S.11

ABR

S.10

Anae

robi

c Fi

lter

T.15

Biog

as R

eact

or

This system is characterized by the use of a household-level Technology to remove and digest settleable solidsfrom the Blackwater, and a simplified or settled sewersystem to transport the Effluent to a (Semi-) CentralizedTreatment facility. The inputs to the system can include Faeces, Urine,Flushwater, Anal Cleansing Water, Dry CleansingMaterials and Greywater. This system is comparable toSystem 5: Blackwater Treatment System with Infil -tration except the management and processing of theEffluent generated during Collection and Storage/Treat ment of the Blackwater is different. As such,please refer to System Template for System 5: Black -water Treatment System with Infiltration, for a detaileddescription of the components. There are two transport pathways for the Effluent gen-erated from the Collection and Sto rage/ Treatment ofthe Blackwater. Similar to System 5, Effluent can be dis-charged into the Stormwater Drainage network for Useand/or Disposal as Groundwater Recharge (D10),although this is not the recommended approach. TheEffluent should be transported from a Collection andStorage/Treatment facility to a (Semi-) CentralizedTreat ment facility via a Simplified Sewer network (C4)or a Solids-Free Sewer network (C5). An interceptortank is required before the Effluent enters the sewer, oralter natively, this system can be used as a way of up -grading under-performing onsite Technologies (e.g. sep-tic tanks) by providing improved, (Semi-) CentralizedTreatment. Effluent trans ported to a (Semi-) CentralizedTreatment facility is treated using one of the Tech -nologies T1 to T10. All (Semi-) Centralized Treatment Technologies, T1 toT15, produce both Effluent and Faecal Sludge, whichrequire further treatment prior to Use and/orDisposal. Technologies for the Use and/or Disposal ofthe treated Effluent include Irrigation (D5), Aqua -culture (D8), Macrophyte Pond (D9) or Discharge to awater body or Recharge to Groundwater (D10). Tech -nologies for the Use and/or Disposal of the treatedFaecal Sludge include Land Application (D11) or Sur -face Disposal (D12).

Considerations With the offsite transport of theEffluent to a (Semi-) Centralized Treatment facility, thecapital investment for this system is moderate to con-siderable. Excavation and installation of the onsite stor-age technology as well as the infrastructure required forthe simplified sewer network may be costly (althoughcosts would be considerably less than the design andinstallation of a conventional sewer network). As well, ifthere is no pre-existing treatment facility, one must bebuilt to ensure that discharge from the sewer is notdirectly input to a water body.The success of this system depends on high user com-mitment to operation and maintenance of the sewernetwork; alternatively, a person or organization can bemade responsible on behalf of the users. There must bean accessible, affordable and systematic method fordesludging the interceptor (or septic) tanks since oneuser’s improperly kept tank could adversely impact theentire community. Also important is a well-functioningand properly managed Centralized Treatment facility; insome cases this will be managed at the municipal /re -gio nal level, but in the case of a more local solution (e.g.wetland), there must also be a well-defined structure foroperation and maintenance. This system is especially appropriate for dense, urbansettlements where there is little or no space for onsitestorage technologies or emptying. Since the sewer net-work is shallow and (ideally) watertight, it is also appli-cable for areas with high groundwater tables.This water-based system is suitable for Anal CleansingWater inputs, and, since the solids are settled anddigested in one of the Collection and Storage/Treat -ment Technologies, easily degradable Dry CleansingMaterials can also be used. However, durable materials(e.g. leaves, rags) could clog the system and causeproblems with emptying and therefore, should not beused.




27

System 6: Blackwater Treatment System with SewerageU5: CISTERN FLUSH TOILET U5: CISTERN FLUSH TOILET

C4: SIMPLIFIED SEWERS

inspection chamber

D8: Aquaculture Ponds

sludge

inlet

outlet


System Template 7 – (Semi-) Centralized Treatm

ent System

28

Stor

mw

ater

Gre

ywat

er

Faec

es

Urin

e

Flus

hwat

er

Anal

Cle

ansi

ngW

ater

U.4

Pour

Flu

sh T

oile

t

U.5

Cis

tern

Flu

shBl

ackw

ater

C.4

Sim

plifi

ed

Sew

er

C.6

Gra

vity

Sew

er

Stor

mw

ater

Dra

ins

T.1

ABR

T.2

Anae

r. Fi

lter

T.3

WSP

T.4

Aera

ted

Pond

T.5

FWS

CW

T.6

HSF

CW

T.7

VF C

W

T.8

Tric

klin

g Fi

lter

T.9

UAS

B

T.10

Act.

Slud

ge

T.11

Sedi

men

tatio

n/

Thic

keni

ng

T.12

Unp

lant

ed d

ry-

ing

beds

T.13

Plan

ted

dryin

g be

ds

T.14

Co-

Com

post

ing

T.15

Biog

as R

eact

or

Efflu

ent

Trea

ted

Slud

ge

D.10

Dis

posa

l/

Rech

arge

D.5

Irrig

atio

n

D.8

Aqua

cultu

re

D.9

Mac

roph

yte

D.10

Dis

posa

l/

Rech

arge

D.11

Land

App

licat

ion

D.12

Surf

ace

Dis

posa

l

D.12

Surf

ace

Dis

posa

l


(Semi-) Centralized Treatm

ent System

UUser Interface

SCollection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Input/Output

Products

Input

Products

Input/Output

Products

Input/Output

Products

US

Collection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Dry

Cle

ansi

ngM

ater

ial

This is a water-based sewer system in which Blackwateris transported to a centralized treatment facility. Theimportant characteristic of this system is that there isno Collection and Storage/Treatment. The inputs to the system include Faeces, Urine, Flush -water, Anal Cleansing Water, Dry Cleansing Materials,Stormwater, and Greywater. There are two User Interface Technologies that can beused for this system, a Pour Flush Toilet (U4) or aCistern Flush Toilet (U5). Dry Cleansing Materials canbe handled by the system or they can be collectedseparately and directly transferred for SurfaceDisposal (D12). The Blackwater generated at the User Interface is di -rectly connected to a (Semi-) Centralized Treatmentfacility by a Simplified Sewer network (C4) or a GravitySewer network (C6). Greywater is co-treated with theBlack water. Stormwater collected within the Storm -water drains can be input to the Gravity Sewer network,al though Stormwater overflows are required.As there is no Collection and Storage/Treatment, all ofthe Blackwater is transported to a (Semi-) Cen tralizedTreatment facility. The inclusion of Greywater in theConveyance Technology helps to prevent solids fromaccumulating in the sewers. One of the Techno logiesT1 to T10 is required for the treatment of the trans -ported Blackwater. The Faecal Sludge generated fromthe treatment of the Technologies T1 to T10 must befurther treated in a dedicated Faecal Sludge treatmentfacility (Technologies T11 to T15) prior to Use and/ orDisposal. All (Semi-) Centralized Treatment Technologies, T1 toT15, produce both Effluent and Faecal Sludge. Techno -logies for the Use and/or Disposal of the treated Effluentinclude Irrigation (D5), Aquaculture (D8), MacrophytePond (D9) or Discharge to a water body or Recharge togroundwater (D10). Technologies for the Use and/or Dis -posal of the treated Faecal Sludge include Land Appli -cation (D11) or Surface Disposal (D12).

Considerations The capital investment for this sys-tem can be high; gravity sewers require extensive exca-vation and installation can be expensive, whereasSimplified Sewers are generally less expensive if thesite conditions permit a condominial design. This sys-tem is only appropriate when there is a high willingnessto pay for the capital investment and maintenancecosts and where there is a pre-existing treatment facil-ity that has the capacity to accept additional flow.Depending on the type of sewers used, this system canbe adapted for both dense urban and peri-urban areas.It is not well-suited to rural areas. There must be a con-stant supply of water to ensure that the sewers do notbecome blocked. Users may be required to pay user-fees to pay for the centralized treatment and mainte-nance. Depending on the sewer type and management struc-ture (simplified vs gravity, city-run vs community oper-ated) there are varying degrees of operation or main -tenance responsibilities for the homeowner.


System Template 7 – (Semi-) Centralized Treatm

ent System

29

System 7: (Semi-) Centralized Treatment SystemU5: CISTERN FLUSH TOILET U5: CISTERN FLUSH TOILET

C6: CONVENTIONAL GRAVITY SEWER

sewer main

street drainage

T8: TRICKLING FILTER 99

feed pipeeffluent channelair

filter

sprinkler

collection

filter support


System Template 8 – Sewerage System with Urine Diversion

30

Stor

mw

ater

Gre

ywat

er

Anal

Cle

ansi

ngW

ater

Dry

Cle

ansi

ngM

ater

ial

Faec

es

Flus

hwat

er

Urin

e

Brow

nwat

er

Urin

eSt

ored

Urin

e

C.4

Sim

plifi

ed

Sew

er

C.6

Gra

vity

Sew

er

Stor

mw

ater

Dra

ins

C.1

Jerr

ycan

C.3

Mot

orize

d Em

pty -

ing

& T

rans

port

T.1

ABR

T.2

Anae

r. Fi

lter

T.3

WSP

T.4

Aera

ted

Pond

T.5

FWS

CW

T.6

HSF

CW

T.7

VF C

W

T.8

Tric

klin

g Fi

lter

T.9

UAS

B

T.10

Activ

ated

Slu

dge

T.11

Sedi

men

tatio

n/

Thic

keni

ng

T.12

Unp

lant

ed d

ryin

g

beds

T.13

Plan

ted

dryin

g be

ds

T.14

Co-

Com

post

ing

T.15

Biog

as R

eact

or

Efflu

ent

Trea

ted

Slud

ge

D.10

Dis

posa

l/

Rech

arge

D.5

Irrig

atio

n

D.8

Aqua

cultu

re

D.9

Mac

roph

yte

D.10

Dis

posa

l/

Rech

arge

D.11

Land

App

licat

ion

D.12

Surf

ace

Dis

posa

l

D.2

Appl

icat

ion


Sewerage System with Urine Diversion

S.1

Stor

age

Tank

UUser Interface

SCollection

and Storage/

Treatment

CConveyance

T(Semi-)

Centralized

Treatment

DUse and/or

Disposal

Input/Output

Products

Input

Products

Input/Output

Products

Input/Output

Products

U.6

Urin

e D

iver

ting

Flus

h To

ilet

U.3

Urin

al

This is a water-based sewer system that requires aUrine Diverting Flush Toilet (UDFT). The UDFT is a spe-cial User Interface that allows for the separation andcollection of Urine without water, but that also useswater to flush Faeces. The inputs to the system can include, Faeces, Urine,Flushwater, Anal Cleansing Water, Dry CleansingMaterial, Stormwater, and Greywater. There are two User Interface Technologies that can beused for this system, a UDFT (U6) and a Urinal (U3). TheUrinal however, should be used in conjunction with theUDFT, as an alternative for men who do not wish to siton the pedestal.Both Brownwater and Urine are separated at the UserInterface. Brownwater bypasses a Collection and Sto -rage/Treatment facility and is conveyed directly to a(Semi-) Centralized Treatment facility using a SimplifiedSewer network (C4) or a Gravity Sewer network (C6).Greywater is also transported in the sewer and is nottreated separately. In some circumstances, Stormwatercan be connected to a Gravity Sewer network, althoughStormwater overflows are required. Urine separated at the User Interface is directly linked to aStorage Tank (S1). The Stored Urine is transferred for Useand/or Disposal using a Jerrycan (C1) or Moto rized E&T(C3) for Urine Application to agricultural lands (D2).Brownwater is treated at a (Semi-) Centralized Treat -ment facility using one of the Technologies T1 to T10.The Faecal Sludge generated from the treatment of theTechnologies T1 to T10 must be further treated in a de -dicated Faecal Sludge treatment facility (Techno logiesT11 to T15) prior to using the Land Application (D11) orSurface Disposal (D12) Use and/or Disposal technolo-gies. Technologies for the Use and/or Disposal of thetreated Effluent collected from one of the Techno logiesT1 to T10 include Irrigation (D5), Aqua cul ture (D8),Macrophyte Pond (D9) or Discharge to a water body orRecharge to Groundwater (D10).

Considerations UDFTs are not common and thecapital cost for this system can be high. This is partlydue to the fact that there is limited competition in themarket and also because high quality plumbing isrequired for the dual plumbing system. The GravitySewers require extensive excavation and installation canbe expensive, whereas Simplified Sewers are generallyless expensive if the site conditions permit a condo-minial design. This system is only appropriate whenthere is a need for the separated Urine and/or whenthere is a desire to limit water consumption by collectingUrine without flushing water. The system still re quires aconstant source of water and uses significantly morethan a waterless system. Depending on the type of sewers used, this system canbe adapted for both dense urban and peri-urban areas.It is not well-suited to rural areas. There must be a con-stant supply of water to ensure that the sewers do notbecome blocked. This system is appropriate where thereis a need and a desire to collect, transport and use theUrine. There may also be benefits to the treatment plantif it is normally overloaded; the reduced nutrient load (byremoving the Urine) could optimize treatment. However,if the plant is currently, underloaded (i.e. the plant hasbeen overdesigned) then this system could furtheraggravate the problem. Depending on the sewer type and management struc-ture (simplified vs gravity, city-run vs community oper-ated) there will be varying degrees of operation or main-tenance responsibilities for the homeowner.


System Template 8 – Sewerage System with Urine Diversion

31

System 8: Sewerage System with Urine Diversion U6: FLUSH TOILET WITH URINE SEPARATION

S1: URINE STORAGE TANK/CONTAINER

D11: LAND APPLICATION 137

sludge


Functional Groups

32

Reading the Technology Information Sheets

For each Technology described in the System Tem -plates, there is a Technology Information Sheet whichincludes a summary of the Technology, appropriateapplications and limitations. The page is not intended tobe a design manual or technical reference; rather it is astarting point for further detailed design. Moreover, theTech nology descriptions are meant to serve as a sourceof inspiration and discussion amongst engineers andplanners who may not have previously considered oneor several of the feasible options.

Each Technology Information Sheet is colour codedaccording to the associated Functional Group. The let-ter code (e.g. U for User Interface) also indicates theFunctional Group to which the Technology belongs.Figure 5 on the following page presents and explains anexample of a Technology Information Sheet heading.


Functional Groups

Part 2: Functional Groups with Technology Information Sheets

33

S.9 Septic TankApplicable to:System 5, 6

Application LevelHouseholdNeighbourhoodCity

Management LevelHouseholdSharedPublic

Inputs: Blackwater Greywater

Outputs: Faecal Sludge Effluent

��

��

��

��

��

2

3 4

5

6

1


Functional Groups

34

Figure 5. Heading and subheading of a Technology Information Sheet

1) The title with colour, letter and number code. Thecolour-code (orange) and the letter (S) indicate that theTechnology belongs to the Functional Group ‘Collection andStorage/Treatment (S). The number (9) indicates that it is theninth (9th) technology within that Functional Group. Each Technology description page has a similar colour, letterand number code for easy access and cross-referencing.

2) Applicable to System 5, 6. This indicates in whichSystem Template the Technology can be found. In this case,the Septic Tank can be found (and only found) in System 5and 6. Other Technologies may be found in only one or inseveral systems.

3) Application Level. Three spatial levels are defined underthis heading:•Household implies that the technology is appropriate forone or several households

•Neighbourhood implies that the technology is appropriatefor several up to several hundred households

•City implies that the technology is appropriate at the city-wide level (either one unit for the whole city, or manyunits for each part of the city or household)

Stars are used to indicate how appropriate each level is forthe given technology:• two stars means suitable,•one star means less suitable; and•no star means not suitable.It is up to the Compendium user to decide on the appropraitelevel for the specific situation that he/she is working on. The ‘Application Level’ graphic is only meant as a rough guideto be used in the preliminary planning stage.The technologies within the Functional Group ‘User Interface’do not include an Application Level since they can only ser-vice a limited number of people.

4) Management Level describes the organizational stylethat is best used for the operation and maintenance (O&M) of the given Technology:•Household implies that the household, e.g. the family, isresponsible for all O&M

•Shared implies that a group of users (e.g. school, marketvendors, community-based organization) assumes the O&Mthemselves either by ensuring that a person or committeeis responsible on behalf of all the users. Shared facilites aredefined by the fact that the community of users decideswho is allowed to the use the facility and what their respon-sibilities are; it is a self-defined group of users.

•Public implies institutional or government run facilities. AllO&M is assumed by the agency that operates the facility.Usually, only users who can pay for the service are per -mitted to use public facilities.

The Septic Tank in this example can be managed in all threestyles.The technologies within the Functional Group ‘User Interface’do not include a Management Level since maintenance isdependent on the subsequent technologies, and not simplythe User Interface.

5) Inputs: refers to the Products that flow into the givenTechnology. The icons shown are those Products that can pos -sibly go into the Technology, but not all of them MUST enter the technology. In this example, Blackwater and Grey -water can be processed by the Septic Tank

6) Outputs: refers to the products that flow out of the givenTechnology. The icons show those Products that can beexpected to flow out of the technology. In this example, theSeptic Tank produces Faecal Sludge and Effluent.


FunctionalGroupU:UserInterface

UUser Interface

35

This section describes the technologies with which the user interacts.The User Interface is the way in which the sanitation system is accessed.

©GTZ



36

U

A Dry Toilet is a toilet that operates without water.The Dry Toilet may be a raised pedestal that the usercan sit on, or a squat pan that the user squats over.In both cases, excreta (both urine and faeces) fallthrough a drop hole.

In this Compendium, a Dry Toilet refers specificallyto the device that the user sits or squats over. Inother literature, a Dry Toilet may refer to a variety oftechnologies, or combinations of technologies (espe-cially pits).The Dry Toilet is usually placed over a pit; if two pits areused, the pedestal or slab should be designed in such away that it can be lifted and moved from one pit toanother.The slab or pedestal base should be well sized to the pitso that it is both safe for the user and preventsstormwater from infiltrating the pit (which may cause itto overflow).

Adequacy Dry Toilets are easy for almost everyoneto use. Because there is no need to separate urineand faeces, they are often the most physically com-fortable and natural option.

Pedestals and squatting slabs can be made locally withconcrete (providing that sand and cement are avail-able). Wooden or metal molds can be used to produceseveral units quickly and efficiently. When dry toiletsare made locally, they can be specially designed tomeet the needs of the target users (e.g. smaller onesfor children). Fibreglass, porcelain and stainless steelversions may also be available. They are appropriate foralmost every climate.

Health Aspects/Acceptance Squatting is a natu-ral position for many people and so a well-kept squat-ting slab may be the most acceptable option.Since Dry Toilets do not have a water seal, odours maybe a problem depending on the Collection and Storage/Treatment technology to which it is connected.

Maintenance The sitting or standing surface shouldbe kept clean and dry to prevent pathogen/diseasetransmission and to limit odours.There are no mechanical parts and so the Dry Toiletshould not need repairs except in the event that itcracks.

slab

option 1

option 2



U.1U.1 Dry ToiletApplicable to:System 1, 2

37

Inputs: Faeces UrineAnal Cleansing Water

Outputs: Excreta

Pros & Cons:+ Does not require a constant source of water+ Can be built and repaired with locally availablematerials

+ Low capital and operating costs+ Suitable for all types of users (sitters, squatters,washers, wipers)

- Odours are normally noticeable (even if the vaultor pit used to collect excreta is equipped with a ventpipe).

- The excreta pile is visible, except where a deeppit is used

References

_ Brandberg, B. (1997). Latrine Building. A Handbook forImplementation of the Sanplat System. Intermediate Tech-nology Publications, London. pp 55–77(Describes how to build a squatting slab and the mouldsfor the frame, footrests, spacers, etc.)

_ Morgan, P. (2007). Toilets That Make Compost: Low-cost,sanitary toilets that produce valuable compost for crops in anAfrican context. Stockholm Environment Institute, Sweden.(Excellent description of how to make support rings andsquatting slabs (pages 7–35) and pedestals (39–43) usingonly sand, cement, plastic sheeting and wire.)Available: www.ecosanres.org

_ Netherlands Water Partnership (NWP) (2006). SmartSanitation Solutions. Examples of innovative, low-costtechnologies for toilets, collection, transportation, treatmentand use of sanitation products. NWP, Netherlands.(Provides country specific data and links for furtherinformation.)



38

U.1

A Urine Diverting Dry Toilet (UDDT) is a toilet thatoperates without water and has a divider so that theuser, with little effort can divert the urine away fromthe faeces.

The UDDT toilet is built such that urine is collected anddrained from the front area of the toilet, while faeces fallthrough a large chute (hole) in the back. Depending onthe Collection and Storage/Treatment technology thatfollows, drying material such as lime, ash or earth shouldbe added into the same hole after defecating.It is important that the two sections of the toilet arewell separated to ensure that a) faeces do not fallinto, and clog the urine collection area in the front,and that b) urine does not splash down into the dryarea of the toilet.There are also 3-hole separating toilets that allow analcleansing water to be separated from the urine and thefaeces into a third, dedicated hole. It is important thatthe faeces remain separate and dry. When the toilet iscleaned with water, care should be taken to ensure thatthe faeces are not mixed with water.Both a pedestal and a squat slab can be used to sepa-rate urine from faeces depending on user preference.

Adequacy The UDDT is simple to design and buildusing such materials as concrete and wire mesh or plas-tic. The UDDT design can be altered to suit the needs ofspecific populations (i.e. smaller for children, peoplewho prefer to squat, etc.) They are appropriate foralmost every climate.

Health Aspects/Acceptance The UDDT is not in-tuitive or immediately obvious to some users. At first,users may be hesitant about using it and mistakes (e.g.faeces in the urine bowl) may deter others from accept-ing this type of toilet as well. Education and demonstra-tion projects are essential in achieving good accept-ance with users.

Maintenance A UDDT is slightly more difficult to keepclean compared to other toilets because of both the lackof water and the need to separate the solid faeces and liq-uid urine. For cleaning, a damp cloth may be used to wipedown the seat and the inner bowls. Some toilets are eas-ily removable and can be cleaned more thoroughly. Nodesign will work for everyone and therefore, some usersmay have difficulty separating both streams perfectlywhich may result in extra cleaning and maintenance.

option 2

option 2

option 1

option 1 urine urine



U.2U.2 Urine Diverting Dry Toilet (UDDT)Applicable to:System 4

39

Inputs: Faeces UrineAnal Cleansing Water

Outputs: Faeces UrineAnal Cleansing Water

Faeces can be accidentally deposited in the urine sec-tion, causing blockages and cleaning problems. As well,urine pipes/fittings can become blocked over time andmay require occasional maintenance.This is a waterless technology and water should not bepoured down the toilet. As well, urine tends to rust mostmetals; therefore, metals should be avoided for the con-struction and piping of the UDDT.

Pros & Cons:+ Does not require a constant source of water+ No real problems with odours and vectors (flies) ifused and maintained correctly (i.e. kept dry)

+ Can be built and repaired with locally availablematerials

+ Low capital and operation costs+ Suitable for all types of users (sitters, squatters,washers, wipers)

- Requires education and acceptance to be usedcorrectly

- Is prone to clogging with faeces and misuse

References

_ Morgan, P. (2007). Toilets That Make Compost: Low-cost,sanitary toilets that produce valuable compost for crops in anAfrican context. Stockholm Environment Institute, Sweden.Available: www.ecosanres.org(Provides step-by step instruction on how to build aUDDT using a plastic bucket and how to construct a urinediverting squat plate.)

_ Netherlands Water Partnership (NWP) (2006). SmartSanitation Solutions. Examples of innovative, low-cost tech-nologies for toilets, collection, transportation, treatmentand use of sanitation products. NWP, Netherlands.(Provides country specific data and links for furtherinformation.)

_ Winblad, U. and Simpson-Herbert, M. (2004). EcologicalSanitation. Stockholm Environment Institute, Sweden.Available: www.ecosanres.org(Provides a good, general overview of different types ofUDDTs – see especially page 59.)



40

U.2

A Urinal is only used for collecting urine. Urinals aregenerally for men, although Urinals for women havealso been developed.

Urinals for women consist of raised foot-steps and asloped channel or catchment area for conducting theurine to a collection technology. For men, Urinals caneither be wall-mounted units that are vertical, or squatslabs that the user squats over.Most Urinals use water for flushing, but waterlessUrinals are becoming increasingly popular.

Adequacy The Urinal can be used with or withoutwater and the plumbing can be developed accordingly.If water is used, it is mainly used for cleaning and limit-ing odours (with a water-seal). Water-based Urinals use8 to 12 litres of flushwater, whereas low-flush modelsuse less than 4 litres of flushwater. Because the Urinalis exclusively for urine it is important to also provideanother toilet to be used for faeces.Waterless Urinals are available in a range of styles andcomplexities. Some Urinals come equipped with anodour seal that may have a mechanical closure, a mem-brane, or a sealing liquid. To minimize odours in simple

Urinal designs, each Urinal should be equipped with adedicated pipe that is submerged in the collected urine(or tank) to provide a basic water-seal.Portable waterless Urinals have been developed for useat large festivals, concerts and other gatherings, toimprove the on-site sanitation facilities and reduce thepoint load of wastewater discharged at the site. In thisway, a large volume of urine can be collected (and eitherused or discharged at a more appropriate location ortime) and the remaining urine/faeces toilets can bereduced or used more efficiently. Urinals can be used inhomes as well as within public facilities.By putting a small target, or painted fly near the drain,the amount of spraying or splashing can be reduced;this type of user-guidance can help improve the cleanli-ness of the facility.Urinals are appropriate for every climate.

Health Aspects/Acceptance The Urinal is a com-fortable and easily accepted User Interface. In somecases, the provision of a Urinal is useful to prevent themisuse of dry systems (e.g. UDDT). Urinals, althoughsimple in construction and design, can have a largeimpact on the well-being of a community. When men

option 1 option 2



U.3U.3 UrinalApplicable to:System 4, 8

41

Inputs: Urine Flushwater

Outputs: Urine Flushwater

have access to a Urinal, they may be encouraged torefrain from urinating in public, which reducesunwanted odours and allows women to feel more com-fortable.Men have generally accepted waterless Urinals, as theydo not call for any change of behaviour.

Maintenance Maintenance is simple, but should bedone frequently. Minerals and salts may build up inpipes and on surfaces where urine is constantly pres-ent. To prevent scaling, slightly acidic water and/or hotwater can be used to dissolve any minerals that form.All of the surfaces should be cleaned regularly (bowl,slab and steps) to prevent odours and to minimizesolids formation.

Pros & Cons:+ Does not require a constant source of water+ Can be built and repaired with locally availablematerials

+ Low capital and operating costs- No real problems with odours if used and main-tained correctly

References

_ Austin, A. and Duncker, L. (2002). Urine-diversion. Ecolo-gical Sanitation Systems in South Africa. CSIR, Pretoria,South Africa.(Directions for making a simple Urinal using a 5L plasticcontainer.)

_ CREPA (2008). Promotion de latrines ECOSAN à la 20èédition du FESPACO: Ecosan Info No. 8. Centre Régionalpour l'Eau Potable et l'Assainissement à faible coût(CREPA), Burkina Faso.Available: www.reseaucrepa.org

_ GTZ (1999). Technical data sheets for ecosan components:Waterless Urinals. GTZ, Germany.Available: www.gtz.de(Information about specialized urinals, which include stenchtraps and other specialized features.)

_ Netherlands Water Partnership (NWP) (2006). SmartSanitation Solutions. Examples of innovative, low-cost tech-nologies for toilets, collection, transportation, treatmentand use of sanitation products. NWP, Netherlands.(Provides country specific data and links for furtherinformation.)



42

U.3

A Pour Flush Toilet is like a regular Flush Toilet exceptthat instead of the water coming from the cisternabove, it is poured in by the user. When the watersupply is not continuous, any cistern Flush Toilet canbecome a Pour Flush Toilet.

Just like a traditional Flush Toilet, there is a water sealthat prevents odours and flies from coming back upthe pipe.Water is poured into the bowl to flush the toilet of excre-ta; approximately 2 to 3L is usually sufficient. The quan-tity of water and the force of the water (pouring from aheight often helps) must be sufficient to move the exc-reta up and over the curved water seal.Both pedestals and squatting pans can be used in thepour flush mode. Due to demand, local manufacturershave become increasingly efficient at mass-producingaffordable, Pour Flush Toilets and pans.The S-shape of the water seal determines how muchwater is needed for flushing. To reduce water require-ments, it is advisable to collect toilet paper or other drycleansing materials separately.The waterseal at the bottom of the Pour Flush Toilet orpan should have a slope of 25 to 30°. Water seals should

be made out of plastic or ceramic to prevent clogs and tomake cleaning easier (concrete may clog more easily if itis rough or textured). The optimal depth of the water sealis approximately 2cm to minimize the water required toflush the excreta. The trap should be approximately 7cmin diameter.

Adequacy The water seal is effective at preventingodours and it is appropriate for those who sit or squat(pedestal or slab) as well as those who cleanse withwater. It is only appropriate when there is a constantsupply of water available. The Pour Flush Toilet requires(much) less water than a traditional cistern Flush Toilet.However, because a smaller amount of water is used,the Pour Flush Toilet may clog more easily and thus,require more maintenance.If water is available, this type of toilet is appropriate forboth public and private applications.Pour Flush Toilets are adequate for almost all climates.

Health Aspects/Acceptance The Pour Flush Toilet(or squatting pan) prevents users from seeing or smel-ling the excreta of previous users. Thus, it is generallywell accepted. Provided that the water seal is working

slab

water seal



U.4U.4 Pour Flush ToiletApplicable to:System 1, 3, 5, 6, 7

43

Inputs: Urine FaecesFlushwater Anal Cleansing Water

Outputs: Blackwater

well, there should be no odours and the toilet should beclean and comfortable to use.

Maintenance Because there are nomechanical parts,Pour Flush Toilets are quite robust and rarely requirerepair.Despite the fact that water is used continuously in thetoilet, it should be cleaned regularly to prevent the buildup of organics and or/stains.To prevent clogging of the Pour Flush Toilet, it is recom-mended that dry cleansing materials be collected sepa-rately and not flushed down the toilet.

Pros & Cons:+ The water seal effectively prevents odours+ The excreta of one user are flushed away beforethe next user arrives

+ Suitable for all types of users (sitters, squatters,wipers and washers)

+ Low capital costs; operating costs depend on theprice of water

- Requires a constant source of water (can berecycled water and/or collected rain water)

- Cannot be built and/or repaired locallywith available materials

- Requires some education to be used correctly

References

_ Mara, DD. (1996). Low-Cost Urban Sanitation.Wiley, Chichester, UK.(Provides detailed drawings of Indian glass-fibre squat panand trap with dimensions and critical design criteria.A description of how to modify a Pour Flush Toilet to acistern Flush Toilet is included.)

_ Roy, AK., et al. (1984). Manual on the Design, Constructionand Maintenance of Low-Cost Pour Flush Waterseal Latrinesin India (UNDP Interreg. Project INT/81/047). The WorldBank + UNDP, Washington.(Provides specifications for Pour Flush Toilets andconnections.)



44

U.4

The Cistern Flush Toilet is usually porcelain and is amass-produced, factory made User Interface. TheFlush Toilet consists of a water tank that supplies thewater for flushing the excreta and a bowl into whichthe excreta are deposited.

The attractive feature of the Flush Toilet is that it incor-porates a sophisticated water seal to prevent odoursfrom coming back up through the plumbing. Dependingon the age and design of the toilet, approximately 3 to20L of water may be used per flush.Water that is stored in the cistern above the toilet bowlis released by pushing or pulling a lever. This allows thewater to run into the bowl, mix with the excreta and car-rying them away.

There are different low-volume Flush Toilets currentlyavailable that use as little as 3L of water per flush. Insome cases, the volume of water used per flush is notsufficient to empty the bowl and consequently the useris forced to use two or more flushes to adequately cleanthe bowl, which negates the intended water saving.

A good plumber is required to install a Flush Toilet. Theplumber will ensure that all valves are connected andsealed properly, therefore minimizing leakage.

Adequacy A Cistern Flush Toilet should not be con-sidered unless all of the connections and hardwareaccessories are available locally.The Cistern Flush Toilet must be connected to both aconstant source of water for flushing and a Collectionand Storage/Treatment or Conveyance technology toreceive the blackwater.The Cistern Flush Toilet is suitable for both public and pri-vate applications and can be used in every climate.

Health Aspects/Acceptance It is a safe and com-fortable toilet to use provided it is kept clean.

Maintenance Although flushwater continuously rin-ses the bowl, the toilet should be scrubbed cleanregularly. Maintenance is required for the replacementor repair of some mechanical parts or fittings.



U.5U.5 Cistern Flush ToiletApplicable to:System 5, 6, 7

45

Inputs: Urine FaecesFlushwater Anal Cleansing Water

Outputs: Blackwater

Pros & Cons:+ The excreta of one user are flushed away beforethe next user arrives

+ No real problems with odours if used correctly+ Suitable for all types of users (sitters, squatters,wipers and washers)

- High capital costs; operating costs depend on theprice of water

- Requires a constant source of water- Cannot be built and/or repaired locally withavailable materials

References

_ Maki, B. (2005). Assembling and Installing a New Toilet.Available: www.hammerzone.com(Describes how to install a toilet with full colour photos andstep-by-step instructions.)

_ Vandervort, D. (2007). Toilets: Installation and Repair.HomeTips.com.Available: http://hometips.com/content/toilets_intro.html(Describes each part of the toilet in detail as well asproviding links to other tools such as how to install a toilet,how to fix a leaking toilet and other toilet essentials.)



46

U.5

The Urine Diverting Flush Toilet (UDFT) is similarin appearance to a Cistern Flush Toilet except forthe diversion in the bowl. The toilet bowl has twosections so that the urine can be separated fromthe faeces.

When the user sits on the toilet, urine is collected in adrain in the front (where there is no water) and faecesare collected in the back (where there is water). Theurine is collected without water, but a small amount ofwater is used to rinse the urine-collection bowl afterthe user stands up. The urine flows into a storage tankfor further use or processing, while the faeces areflushed with water to be treated. The system requiresdual plumbing (i.e. plumbing for the urine and for thebrownwater).

Adequacy The toilet should be installed carefully withan understanding of how and where clogs may occur sothat they can be easily removed.A UDFT is adequate when there is a limited supply ofwater for flushing, a treatment technology for the brown-water (i.e. faeces, dry cleansing material and flushingwater) and a use for the collected urine.

To improve diversion efficiency, Urinals for men are rec-ommended.UDFTs are suitable for public and private applicationsalthough significant education and awareness is re-quired in public settings to ensure proper use and tominimize clogging.This technology requires dual plumbing (separate forurine and brownwater), which is more complicated thanplumbing for Cistern Flush Toilets.

Health Aspects/Acceptance Information cardsand/or diagrams are essential for ensuring proper useand for promoting acceptance; if users understand whythe urine is being separated they will be more willing touse the UDFT properly. Proper plumbing will ensure thatthere are no odours.

Maintenance As with any toilet, proper cleaning isimportant to keep the bowl(s) clean and prevent organ-ic residues and stains from forming.Because urine is collected separately, calcium- andmagnesium-based minerals can precipitate out andbuild up in the fittings and pipes. Washing the bowl witha mild acid and/or hot water can prevent the build-up



U.6U.6 Urine Diverting Flush Toilet (UDFT)Applicable to:System 8

47

Inputs: Urine Faeces FlushwaterDry Cleansing Material Anal Cleansing Water

Outputs: Urine Brownwater

of mineral deposits; stronger (>24% acetic) acid or acaustic soda solution (2 parts water to 1 part soda) canbe used for removing blockages however, some manualremoval may be required periodically.To limit scaling, all connections (pipes) to storage tanksshould be kept as short as possible; whenever theyexist, pipes should be installed with at least a 1% slopeand sharp (90°) angles should be avoided. Larger diam-eter pipes (75mm for low maintenance and 50mm forhigher maintenance) should be used.

Pros & Cons:+ Requires less water than a traditional Flush Toilet+ No real problems with odours if used correctly+ Looks like, and can be used almost like, a CisternFlush Toilet

- Limited availability; can not be built or repairedlocally

- High capital and low to moderate operating costs(depending on parts and maintenance)

- Labour-intensive maintenance- The toilet is not intuitive; requires education andacceptance to be used correctly

- Is prone to clogging and misuse- Requires a constant source of water- Men usually require a separate Urinal for optimumcollection of urine.

References

_ GTZ (1999). Technical data sheets for ecosan components:Urine diversion Toilets. GTZ, Germany.Available: www.gtz.de(Provides a thorough comparison of the Flush Toilets withUrine diversion currently on the market. Information inclu-des contact information and pricing as well as a descriptionof the installation and maintenance requirements.)

_ Kvarnström, E., et al. (2006). Urine Diversion – One steptowards sustainable sanitation. Report 2006–1.Ecosan Res: Ecosan Publication Series, Stockholm.Available: www.ecosanres.org



48

U.6


FunctionalGroupS:CollectionandStorage/Treatment

S

49

Collection and Storage/Treatment

This section describes the technologies that collect and store the intermediate products thatare generated at the User Interface. Some of the technologies presented herein are designedspecifically for treatment, while others are designed specifically for collection and storage,although they provide some degree of treatment depending on the storage time.



50

S

When urine cannot be used immediately or transport-ed using a Conveyance Technology (i.e. Jerrycans) itcan be stored onsite in containers or tanks. TheStorage Tank must then be moved or emptied intoanother container for transport.

The Storage Tank should be appropriately sized toaccommodate the number of users and the time re-quired to sanitise the urine. The storage guidelines forurine correspond to the temperature of storage andthe intended crop, but all urine should be stored for atleast 1 month (see WHO guidelines for specific stor-age and application guidelines). Smaller volume Sto-rage Tanks can be used and transported to another,centralized Storage Tank at, or close to, the point ofuse (i.e. the farm).Mobile Storage Tanks should be plastic or fibreglass,but permanent Storage Tanks can be made of concreteor plastic. Metal should be avoided as it can be easilycorroded by the high pH of stored urine.With storage time, a layer of organic sludge and pre-cipitated minerals (primarily calcium and magne-sium phosphates) will form on the bottom of thetank. Any tank used for urine storage should have an

opening large enough so that it can be cleaned and/or pumped out.Neither the Storage Tank, nor the collection pipesshould be ventilated, but they both need to be pressureequalized. If the Storage Tank is emptied using a vacu-um truck, the inflow of air must be maintained at a suf-ficient rate to ensure that the tank does not implodedue to the vacuum.If the Storage Tank is connected to the toilet or urinaldirectly with a pipe, care should be taken to minimizethe length of the pipe since precipitates will accumu-late. If pipes must be used, they should have a steepslope (greater than 1% slope), no sharp angles, largediameters (up to 110mm for underground pipes) and beeasily removable in case of blockages.To minimize odours, the tank should be filled from thebottom, i.e. the urine should flow down through a pipeand be released near the bottom of the tank; this willprevent the urine from spraying as well as preventback-flow.

Adequacy Long-term storage is the best way to san-itize urine without the addition of chemicals or mechan-ical processes.



S.1S.1 Urine Storage Tank/ContainerApplicable to:System 4, 8

51



Inputs: Urine

Outputs: Stored Urine

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Urine Storage Tanks can be used in virtually every envi-ronment; tanks should be well-sealed to prevent leaks,infiltration and evaporation. Urine Storage Tanks canbe installed indoors, outdoors, above ground and be-low ground depending on the climate, space available,and soil.

Health Aspects/Acceptance The risk of diseasetransmission from stored urine is low. Extended storagewith storage times greater than 6 months provides nearcomplete sanitation.

Maintenance A viscous sludge will accumulate onthe bottom of the Storage Tank. When the Storage Tankis emptied, the sludge will usually be emptied alongwith the urine, but if a tap is used and the tank is neverfully emptied, it may require desludging. The desludgingperiod will depend on the composition of the urine andthe storage conditions.Mineral and salt build-up in the tank or on connectingpipes can be manually removed (sometimes with diffi-culty) or can be dissolved with a strong acid (24%acetic).

Pros & Cons:+ Can be built and repaired with locally availablematerials

+ No electrical energy required+ Can be used immediately+ Small land area required+ Low capital and operating costs- Mild to strong odour when opening and emptyingtank (depending on storage conditions)

References

_ GTZ (2007). Technical data sheet, urine diversion: Piping andstorage. GTZ, Germany.Available: www.gtz.de

_ Kvarnström, E., et al. (2006). Urine Diversion - One steptowards sustainable sanitation. Report 2006-1.Ecosan Res: Ecosan Publication Series, Stockholm.Available: www.ecosanres.org

_ WHO (2006). Guidelines for the safe use of wastewater,excreta and greywater- Volume 4: Excreta and greywater usein agriculture. WHO, Geneva.Available: www.who.int



52

S.1

The Single Pit is one of the most widely used sanita-tion technologies. Excreta, along with anal cleansingmaterials (water or solids) are deposited into a pit.Lining the pit prevents it from collapsing and pro-vides support to the superstructure.

As the Single Pit fills, two processes limit the rate ofaccumulation: leaching and degradation. Urine and analcleansing water percolate into the soil through the bot-tom of the pit and wall while microbial action degradespart of the organic fraction.On average, solids accumulate at a rate of 40 to 60Lper person/year and up to 90L per person/year if drycleansing materials such as leaves, newspapers, andtoilet paper are used. The volume of the pit should bedesigned to contain at least 1,000L. Ideally the pitshould be designed to be at least 3m deep and 1 m indiameter. If the pit diameter exceeds 1.5m there is anincreased risk of collapse. Depending on how deep theyare dug, some pits may last up to 20 years without emp-tying. If the pit is to be reused it should be lined. Pit lin-ing materials can include brick, rot-resistant timber,concrete, stones, or mortar plastered onto the soil. Ifthe soil is stable (i.e. no presence of sand or gravel de-

posits or loose organic materials), the whole pit need notbe lined. The bottom of the pit should remain unlined toallow the infiltration of liquids out of the pit.As the effluent leaches from the Single Pit and migratesthrough the unsaturated soil matrix, faecal organismsare removed. The degree of faecal organism removalvaries with soil type, distance travelled, moisture andother environmental factors and thus, it is difficult toestimate the necessary distance between a pit and awater source. A distance of 30m between the pit and awater source is recommended to limit exposure tochemical and biological contamination.When it is impossible or difficult to dig a deep pit, thedepth of the pit can be extending by building the pitupwards with the use of concrete rings or blocks. Thisadaptation is sometimes referred to as a cesspit. It isa raised shaft on top of a shallow pit with an open bot-tom that allows for the collection of faecal sludge andthe leaching of effluent. This design however, is proneto improper emptying since it may be easier to breakor remove the concrete rings and allow the faecalsludge to flow out rather than have it emptied and dis-posed of properly.

20-4

0cm

>3m

support ring



S.2S.2 Single PitApplicable to:System 1

53



Inputs: Excreta FaecesAnal Cleansing Water

Outputs: Excreta Faecal Sludge

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Another variation is the unlined shallow pit that may beappropriate for areas where digging is difficult. Whenthe shallow pit is full, it can be covered with leaves andsoil and a small tree can be planted. This concept iscalled the Arborloo and is a successful way of avoidingcostly emptying, while containing excreta, and refor-esting an area. The Arborloo is discussed in more detailon the D1: Fill and Cover/Arborloo Technology Infor-mation Sheet.

Adequacy Treatment processes in the Single Pit (aer-obic, anaerobic, dehydration, composting or otherwise)are limited and therefore, pathogen reduction andorganic degradation is not significant. However, sincethe excreta are contained, pathogen transmission tothe user is limited.Single Pits are appropriate for rural and peri-urban areas;Single Pits in urban or dense areas are often difficult toempty and/or have sufficient space for infiltration.Single Pits are especially appropriate when water isscarce and where there is a low groundwater table.They are not suited for rocky or compacted soils (thatare difficult to dig) or for areas that flood frequently.

Health Aspects/Acceptance A simple Single Pitis an improvement to open defecation; however, it stillposes health risks:• Leachate can contaminate groundwater;• Stagnant water in pits may promote insect breeding;• Pits are susceptible to failure/overflowing during floods.Single Pits should be constructed at an appropriate dis-tance from homes to minimize fly and odour nuisancesand to ensure convenience and safe travel.

Upgrading A Ventilated Improved Pit (VIP) is slightlymore expensive but greatly reduces the nuisance offlies and odours, while increasing comfort and usability.For more information on the VIP please refer to S3:Single Pit VIP Technology Information Sheet.When two pits are dug side-by-side, one can be usedwhile the contents of the other pit are allowed tomature for safer emptying. For more information ondual pit technologies refer to S4: Double Pit VIP and S6:Twin Pits for Pour Flush Technology Information Sheets.

Maintenance There is no daily maintenance associ-ated with a simple Single Pit. However, when the pit isfull it can be a) pumped out and reused or b) the super-structure and squatting plate can be moved to a new pitand the previous pit covered and decommissioned.


+ Does not require a constant source of water+ Can be used immediately after construction+ Low (but variable) capital costs dependingon materials

- Flies and odours are normally noticeable- Sludge requires secondary treatment and/orappropriate discharge

- Costs to empty may be significant comparedto capital costs

- Low reduction in BOD and pathogens

References

_ Brandberg, B. (1997). Latrine Building. A Handbookfor Implementation of the Sanplat System. IntermediateTechnology Publications, London.(A good summary of common construction problemsand how to avoid mistakes.)

_ Franceys, R., Pickford, J. and Reed, R. (1992). A guide to thedevelopment of on-site sanitation. WHO, Geneva.(For information on accumulation rates, infiltration rates,general construction and example design calculations.)

_ Lewis, JW., et al. (1982). The Risk of GroundwaterPollution by on-site Sanitation in Developing Countries.International Reference Centre for Waste Disposal,Dübendorf, Switzerland.(Detailed study regarding the transport and die-off ofmicroorganisms and implications for locating technologies.)

_ Morgan, P. (2007). Toilets That Make Compost: Low-cost,sanitary toilets that produce valuable compost for crops in anAfrican context. Stockholm Environment Institute, Sweden.(Describes how to build a support ring/foundation.)

_ Pickford, J. (1995). Low Cost Sanitation. A Survey ofPractical Experience. Intermediate Technology Publications,London.(Information on how to calculate pit size and technology life.)



54

S.2

The Single VIP is a Ventilated, Improved Pit. It is animprovement over the Single Pit because continuousairflow through the ventilation pipe vents odoursand acts as a trap for flies as they escape towardsthe light.Despite their simplicity, well-designed Single VIPs can becompletely smell free, and be more pleasant to use thansome other water-based technologies.Flies that hatch in the pit are attracted to the light at thetop of the ventilation pipe. When they fly towards thelight and try to escape they are trapped by the fly-screenand die. The ventilation also allows odours to escapeand minimizes the attraction for flies.The vent pipe should have an internal diameter of at least110mm to a maximum of 150mm and reach more than300mm above the highest point of the toilet superstruc-ture. The vent works better in windy areas but wherethere is little wind, its effectiveness can be improved bypainting the pipe black; the heat difference between thepit (cool) and the vent (warm) creates an updraft thatpulls the air and odours up and out of the pit. To test theefficacy of the ventilation, a small, smoky fire can be lit inthe pit; the smoke should be pulled up and out of the ventpipe and not remain in the pit or the superstructure.

The mesh size of the fly screen must be large enough toprevent clogging with dust and allow air to circulatefreely. Aluminium screens, with a hole-size of 1.2 to1.5mm have proven to be the most effective.The top diameter of the Single VIP should be between 1 to1.5mand be dug at least 3mdeep, although the deeper thebetter. Deep pits can last up to 15, 20, 30 or more years.As the effluent leaches from the Single VIP and migratesthrough unsaturated soils, faecal organisms are removed.The degree of faecal organism removal varies with soiltype, distance travelled, moisture and other environmen-tal factors and thus, it is difficult to estimate the neces-sary distance between a pit and a water source. A mini-mum distance of 30m between the pit and a water sourceis recommended to limit exposure to chemical and biolog-ical contamination.

Adequacy Treatment processes in the Single VIP (aer-obic, anaerobic, dehydration, composting or otherwise)are limited, and therefore, pathogen reduction and organ-ic degradation is not significant. However, since the exc-reta are contained, pathogen transmission to the user islimited. This technology is a significant improvement overSingle Pits or open defecation.

>30

cm

air currents

>11cm vent pipe

fly screen



S.3S.3 Single Ventilated Improved Pit (VIP)Applicable to:System 1

55




Outputs: Faecal Sludge

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Single VIPs are appropriate for rural and peri-urbanareas; single pits in urban or dense areas are often dif-ficult to empty and/or have insufficient space for infil-tration. Depending on the pit depth, depth to the watertable, number of users and soil conditions, some pitscan be used for 20 years without emptying.VIPs are especially appropriate when water is scarceand where there is a low groundwater table. Theyshould be located in an area with a good breeze. Theyare not suited for rocky or compacted soils (that are dif-ficult to dig) or for areas that flood frequently.

Health Aspects/Acceptance A Single VIP can bea very clean, comfortable, and well accepted sanitationoption. However some health concerns exist:• Latrine leachate can contami¬nate groundwater;• Pits are susceptible to failure/overflowing during floods;• Health risks from flies are not completely removedby ventilation.

Upgrading A Single VIP toilet can be upgraded to aDouble VIP, a Urine Diverting Dry Toilet (UDDT) if thereis a use for urine, or a water-based Pour Flush Toilet ifwater is available. A Double VIP has the addition of anextra pit so that while one pit is in use, the contents ofthe full pit are draining, maturing and undergoing degra-dation. Pathogens are destroyed much more thorough-ly in a Double VIP and therefore, the contents are lesshazardous to remove from the pit, although because thecontents are so solid, the contents cannot be pumped,but rather, must be manually emptied.

Maintenance To keep the Single VIP free of flies andodours, regular cleaning and maintenance is required.Dead flies, spider webs, dust and other debris should beremoved from the ventilation screen to ensure a goodflow of air.

Pros & Cons:+ Flies and odours are significantly reduced(compared to non-ventilated pits)

+ Does not require a constant source of water+ Suitable for all types of user (sitters, squatters,washers and wipers)


+ Can be used immediately after construction+ Low (but variable) capital costs depending onmaterials and pit depth

+ Small land area required- Sludge requires secondary treatment and/orappropriate discharge

- Costs to empty may be significant comparedto capital costs

- Low reduction in BOD and pathogens

References

_ Mara, DD. (1996). Low-Cost Urban Sanitation.Wiley, Chichester, UK.(Provides detailed design information.)

_ Mara DD. (1984). The Design of Ventilated Improved PitLatrines (UNDP Interreg. Project INT/81/047). The WorldBank + UNDP, Washington.

_ Morgan, PR. (1977). The Pit Latrine – Revived.Central African Journal of Medicine, 23(1).

_ Morgan, PR. (1979). A Ventilated Pit Privy. AppropriateTechnology, 6 (3).

_ Morgan PR. and Mara, DD. (1982). Ventilated Improved PitLatrines: Recent Developments in Zimbabwe. World BankTechnical Paper no.3.Available: www.worldbank.org

_ Morgan PR. (1990). Rural Water Supplies and Sanitation.Blair Research Laboratory & Ministry of Health + MacMillan,Harare, Zimbabwe.

General Information:_ Franceys, R., Pickford, J. and Reed, R. (1992). A guide tothe development of on-site sanitation. WHO, Geneva.

_ Lewis, JW., et al. (1982). The Risk of Groundwater Pollutionby on-site Sanitation in Developing Countries.International Reference Centre for Waste Disposal,Dübendorf, Switzerland.(A detailed study regarding the transport and die-off ofmicroorganisms and implications for locating technologies.)

_ The World Bank (1986). Information and Training for Low-CostWater Supply and Sanitation (UNDP Project INT/82/002).The World Bank, Washington.



56

S.3

The Double VIP has almost the same design as theSingle VIP (S3) with the added advantage of a secondpit that allows the technology to be used continuous-ly and allows for safer and easier emptying.

By using two pits, one pit can be used while the contentsof the second pit rests, drains, reduces in volume, anddegrades. When the second pit is almost full (the excretais 50cm from the top of the pit), it is covered, and the con-tents of the first pit are removed. Due to the extendedresting time (at least 1 year of filling/resting) the materialwithin the pit should be sanitized and humus-like. TheDouble VIP is similar to the Fossa Alterna (S5) technologywith the exception that the Fossa Alterna is specificallydesigned to produce humus and as such, it requires regu-lar additions of soil, ash and/or leaves.The superstructure may either extend over both holesor it may be designed to move from one pit to the other.In either case, the pit that is not being filled should befully covered and sealed to prevent water, garbage andanimals (and/or people) from falling into the pit. Theventilation of the two pits can be accomplished usingone ventilation pipe moved back and forth between thepits or each pit can be equipped with its own dedicated

pipe. The two pits in the Double VIP are continuallyused and should be well lined and supported to ensurelongevity.

Adequacy The Double VIP is more appropriate thanthe Single VIP for denser, peri-urban areas. The materialis manually emptied (it is dug out, not pumped out), sovacuum truck access to the pits is not necessary.The users can remove the pit material after a sufficientresting time of one or more years even though the treat-ment processes in the pit are not complete and thematerial is not entirely hygienic. The Double VIP tech-nology will only work properly if the two pits are usedsequentially and not concurrently. Therefore, an ade-quate cover for the out of service pit is required.Double VIPs are especially appropriate when water isscarce and where there is a low groundwater table.They should be located in an area with a good breeze.They are not suited for rocky or compacted soils (thatare difficult to dig) or for areas that flood frequently.

Health Aspects/Acceptance The Double VIP canbe a very clean, comfortable and well accepted sanita-tion option, in some cases even more so than a water-

fly screen

1

>11cm vent pipe

sludge

air currents

fly screen

2

>11cm vent pipe

sludge

sludge

air currents



S.4S.4 Double Ventilated Improved Pit (VIP)Applicable to:System 2

57




Outputs: Compost/EcoHumus

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based technology. However some health concerns exist:• Latrine leachate can contaminate groundwater;• Pits are susceptible to failure/overflowing duringfloods; and

• Health risks from flies are not completely removedby ventilation.

Maintenance To keep the Double VIP free of fliesand odours, regular cleaning and maintenance isrequired. Dead flies, spider webs, dust and other debrisshould be removed from the ventilation screen toensure a good flow of air. The out of service pit shouldbe well sealed to reduce water infiltration and a properalternating schedule must be maintained.

Pros & Cons:+ Longer life than Single VIP (indefinite if maintained)+ Potential for use of stored faecal material as soilconditioner

+ Flies and odours are significantly reduced(compared to non-ventilated pits)



+ Can be used immediately after construction+ Small land area required- Low/moderate reduction in pathogens- Higher capital cost than Single VIP; reducedoperating costs if self-emptied

References

_ Mara DD. (1984). The Design of Ventilated ImprovedPit Latrines (UNDP Interreg. Project INT/81/047).The World Bank+ UNDP, Washington.(A good reference for detailed Double Pit VIP designinformation.)

_ Mara, DD. (1996). Low-Cost Urban Sanitation.Wiley, Chichester, UK.(General description of VIPs with a focus on theventilation system.)

General Information:_ Franceys, R., Pickford, J. and Reed, R. (1992). A guide tothe development of on-site sanitation. WHO, Geneva.

_ Lewis, JW., et al. (1982). The Risk of Groundwater Pollutionby on-site Sanitation in Developing Countries.International Reference Centre for Waste Disposal,Dübendorf, Switzerland.(Detailed study regarding the transport and die-off ofmicroorganisms and implications for locating technologies.)

_ The World Bank (1986). Information and Training forLow-Cost Water Supply and Sanitation (UNDP ProjectINT/82/002). The World Bank, Washington.



58

S.4

The Fossa Alterna is an alternating, waterless (dry)double pit technology. Compared to the Double VIPwhich is just designed to collect, store and partiallytreat excreta, the Fossa Alterna is designed to makeEcoHumus. The Fossa Alterna is dug to a maximumdepth of 1.5 m and requires a constant input of soil.

One of the Fossa Alterna pits should fill over a period of12–24 months depending on the size of the pit and thenumber of users. The full pit degrades during the periodof time that the second pit is filling, which, ideally,should take one year. The material in the full pit willdegrade into a dry, earth-like mixture that can be easilyremoved manually.Soil, ash, and/or leaves should be added to the pit afterdefecation (not urination). The soil and leaves introducea variety of organisms like worms, fungi and bacteriawhich help in the degradation process. Also, the porespace is increased, which allows for anaerobic condi-tions. Additionally, the ash helps to control flies, reduceodours and make the mix slightly more alkaline.The Fossa Alterna should be used for urine, but watershould not be added (small amounts of anal cleansingwater can be tolerated). Water encourages the develop-

ment of vectors and pathogens but it also fills the pore-spaces and deprives the aerobic bacteria of the oxygenthat is required for degradation. The choice of UserInterface will determine the material that enters the pit.Since bulking material is used to continuously cover theexcreta, smells are reduced but the addition of a venti-lation pipe can reduce the smells even further.The Fossa Alterna pits are relatively shallow with adepth of 1.5m. Even though the pits are shallow, thisshould be more than enough space to accommodate afamily of 6 for one year. To optimize the space, thematerial that mounds in the centre of the pit (under-neath the toilet) should be pushed to the sides period-ically. Unlike a simple or ventilated pit which will be cov-ered or emptied, the material in the Fossa Alterna ismeant to be reused. Therefore, it is extremely importantthat no garbage is put into the pit as it will reduce thequality of the material recovered, and may even make itunusable.Emptying the Fossa Alterna is easier than emptyingother pits: the pits are shallower and the addition of soilmeans that the material is less compact. The materialthat is removed is not offensive and presents a reducedthreat of contamination.

1 2 3



S.5S.5 Fossa AlternaApplicable to:System 2

59



Inputs: Excreta OrganicsAnal Cleansing Water


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Adequacy The Fossa Alterna is appropriate for ruraland peri-urban areas. It is especially adapted to water-scarce environments. It is a useful solution for areasthat have poor soil and could benefit from the compost-ed humic material as a soil amendment. A constantsource of soil, ash and/or leaves is required.The Fossa Alterna is not appropriate for greywater asthe pit is shallow and the conditions must remain aero-bic for degradation. Another greywater treatment sys-tem must be used in parallel. A UDDT can be used withthe Fossa Alterna, but only in circumstances when thesoil cannot sufficiently absorb the urine or when urineis highly valued for application.The material is manually emptied from the FossaAlterna (it is dug out, not pumped out), so vacuum truckaccess to the pits is not necessary.The Fossa Alterna technology will only work properly ifthe two pits are used sequentially and not concurrently.Therefore, an adequate cover for the out of service pitis required.The Fossa Alterna is especially appropriate when water isscarce. It is not suited for rocky or compacted soils (thatare difficult to dig) or for areas that flood frequently.

Health Aspects/Acceptance By covering faeceswith soil/ash, flies and odours are kept to a minimum.Users may not understand the difference between theFossa Alterna and a Double VIP, although if given theopportunity to use one, people should have a goodappreciation of the advantages. Demonstration unitscan be used to show how easily one can empty a FossaAlterna in comparison to emptying a Double Pit.Keeping the contents sealed in the pit for the durationof at least one year makes the material safer and easyto handle. The same precautions that are taken whenhandling compost should be taken with the humusderived from the Fossa Alterna.

Maintenance When the first pit is put into use, alayer of leaves should be put into the bottom of the pit.

Periodically, more leaves should be added to increasethe porosity and oxygen availability. Following the addi-tion of faeces to the pit, a small amount of soil or ashshould be added. To lengthen the filling time of the pitsoil is not added to the pit following urination. Occasionally,the mounded material beneath the toilet hole should bepushed to the sides of the pit for an even distribution ofmaterials.Depending on the dimensions of the pits, materialsshould be emptied every year.


+ Because double pits are used alternately, their lifeis virtually unlimited

+ Excavation of humus is easier than faecal sludge+ Potential for use of stored faecal material as soilconditioner

+ Flies and odours are significantly reduced(compared to non-ventilated pits)


+ Low (but variable) capital costs depending onmaterials; no or low operating costs if self-emptied

+ Small land area required+ Significant reduction in pathogens- Requires constant source of cover material(soil, ash, leaves, etc.)

- Garbage may ruin reuse opportunities ofCompost/EcoHumus

References

_ Morgan, P. (2007) Toilets That Make Compost: Low-cost,sanitary toilets that produce valuable compost for crops in anAfrican context. Stockholm Environment Institute, Sweden.Available: www.ecosanres.org(Step-by-step guide for building a Fossa Alterna.)



60

S.5

This technology consists of two alternating pits con-nected to a Pour Flush Toilet. The blackwater (andgreywater) is collected in the pits and allowed toslowly infiltrate into the surrounding soil. With time,the solids are sufficiently dewatered and can beman-ually removed with a shovel.

The superstructure, toilet and pits, for the Twin Pits withPour Flush technology can be designed in various ways:the toilet can be located directly over the pits or at adistance from the pits. The superstructure can be per-manently constructed over both pits or it can movefrom side to side depending on which pit is in use. Nomatter how the system is designed, only one pit is usedat a time. In this way, a continuous cycle of alternatingpits means that they can be used indefinitely.While one pit is filling with excreta, cleansing water andflushing water, the other full pit is resting. The pitsshould be an adequate size to accommodate a volumeof waste generated over one or two years. This allowsthe contents of the full pit enough time to transforminto a safe, inoffensive, soil-like material that can beexcavated manually. The difference between this tech-nology and the Double VIP or Fossa Alterna is that it

allows for the addition of water and does not includethe addition of soil or organic material. As this is awater-based (wet) technology, the full pits require alonger retention time to degrade the material before iscan be excavated safely. A retention time of 2 years isrecommended. The degraded material is too solid to beremoved with a vacuum truck.As the effluent leaches from the pit and migratesthrough an unsaturated soil matrix, faecal organismsare removed. The degree of faecal organism removalvaries with soil type, distance travelled, moisture andother environmental factors. There is a risk of ground-water pollution whenever there is a high or variablewater table, fissures and/or cracks in the bedrock.Viruses and bacteria can travel hundreds of metres insaturated conditions. As soil and groundwater proper-ties are often unknown, it is difficult to estimate thenecessary distance between a pit and a water source. Aminimum distance of 30m should be maintainedbetween the pit and a water source to limit exposure tochemical and biological contamination.It is recommended that the Twin Pits be constructed1m apart from each other to minimize cross-contami-nation between the maturing pit and the one in use. It

leach pit

leach pit



S.6S.6 Twin Pits for Pour FlushApplicable to:System 3

61



Inputs: Blackwater GreywaterAnal Cleansing Water


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is also recommended that the pits be constructed over1m from any structural foundation as leachate can neg-atively impact structural supports.Water within the pit can impact the structural stabilityof the pit. Therefore, all walls should be lined up to thefull depth of the pit to prevent collapse and the top30cm should be fully mortared to prevent direct infiltra-tion and ensure that the superstructure is supported.

Adequacy The Twin Pits with Pour Flush is a perma-nent technology that is appropriate for areas where it isnot appropriate to continuously move a pit latrine. It is awater-based technology and is only appropriate wherethere is a constant supply of water for flushing (e.g. recy-cled greywater or rainwater). Greywater can be co-man-aged along with the blackwater in the twin pits.This technology is not appropriate for areas with a highgroundwater table or areas that are frequently flooded.In order for the pits to drain properly, the soil must havea good absorptive capacity; clay, tightly packed or rockysoils are not appropriate.As long as water is available, the Twin Pits with PourFlush technology is appropriate for almost every type ofhousing density. However, too many wet pits in a smallarea is not recommended as there may not be sufficientcapacity to absorb the liquid into the soil matrix from allof the pits and the ground may become water-logged(oversaturated).The material is manually emptied from the Twin Pits (itis dug out, not pumped out), so vacuum truck access tothe pits is not necessary.The Twin Pits with Pour Flush technology will only workproperly if the two pits are used sequentially and notconcurrently. Therefore, an adequate cover for the outof service pit is required.

Health Aspects/Acceptance The waterseal pro-vides a high level of comfort and cleanliness, with fewodours. It is a commonly accepted sanitation option,however some health concerns exist:• Latrine leachate can contaminate groundwater;• Stagnant water in pits may promote insect breeding;• Pits are susceptible to failure/overflowing duringfloods.

Maintenance The pits must be emptied regularlyand care must be taken to ensure that they do not floodduring rainy seasons. After a recommended two yearresting time, the pits should be emptied manually usinglong handled shovels and proper personal protection.If the pits are self-emptied there are no operationalcosts except for any replacements to the structure orslab in the event of damage.

Pros & Cons+ Can be built and repaired with locally availablematerials

+ Because double pits are used alternately, their lifeis virtually unlimited

+ Excavation of humus is easier than faecal sludge+ Potential for use of stored faecal material as soilconditioner

+ Flies and odours are significantly reduced(compared to pits without a waterseal)

+ Low (but variable) capital costs depending onmaterials; no or low operating costs if self-emptied

+ Moderate reduction in pathogens- Excreta require manual removal- Clogging is frequent when bulky cleansing materialsare used

References

Detailed Design information:

_ Roy, AK., et al. (1984). Manual on the Design, Constructionand Maintenance of Low-Cost Pour Flush Waterseal Latrinesin India. (UNDP Interreg. Project INT/81/047). The WorldBank + UNDP, Washington.

General Information:

_ Franceys, R., Pickford, J. and Reed, R. (1992). A guide tothe development of on-site sanitation. WHO, Geneva.

_ Mara, DD. (1996). Low-Cost Urban Sanitation. Wiley,Chichester, UK.

_ The World Bank (1986). Information and Training forLow-Cost Water Supply and Sanitation. (UNDP ProjectINT/82/002). The World Bank, Washington.



62

S.6

Dehydration vaults are used to collect, store and dry(dehydrate) faeces. Faeces will only dehydrate whenthe vaults are watertight to prevent external mois-ture from entering andwhen urine and anal cleansingwater are diverted away from the vaults.

When urine is separated from faeces, the faeces dryquickly. In the absence of moisture, organisms cannotgrow and as such, smells are minimized and pathogensare destroyed. Vaults used for drying faeces in theabsence of urine have various local names. One of themost common names for this technology is theVietnamese Double Vaults.A family of 6 will produce 500L of faeces in approximate-ly six months. For design purposes it is recommended toassume that one person will require almost 100L of fae-ces storage space every six months. The vaults should beslightly oversized to account for airflow, visitors and thenon-even distribution of faeces in the chamber. Eachvault is sized to accommodate six months of faeces accu-mulation which in turn, results in a six month drying timein the out-of-service vault.Two alternating vaults allow the faeces to dehydrate inone vault while the other vault fills. When one vault is full

it is sealed with a lid and the UDDT (U2) is moved to thesecond vault. While the second vault fills up, the faecesin the first vault slowly dry and decrease in volume.When the second vault is full, it is sealed, the dry mate-rial from the first vault is removed and the first vault isthen put back into service.The vaults must be watertight to keep the faeces as dryas possible. Chambers should be constructed of sealedblock or formed concrete to ensure that rainwater, sur-face run-off, greywater and urine are prevented fromentering the vaults. Urine can be collected in a bucketand discharge to the ground (garden) or stored in a tankfor future transport and use.A vent is required to help keep the vaults dry and con-trol flies and odours.

Adequacy Dehydration Vaults can be installed inalmost every setting from rural to dense urban becauseof the small land area required, the minimal odours andthe ease of use. They are especially appropriate forwater scarce and rocky areas. In areas that are fre-quently flooded, Dehydration Vaults are appropriatebecause they are constructed to be watertight. Further-more, where there is no plot of land available, the vaults

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S.7S.7 Dehydration VaultsApplicable to:System 4

63



Inputs: Faeces

Outputs: Dried Faeces

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can be installed indoors, which also makes this technol-ogy applicable for colder climates (where leaving thehouse is less desirable).

Health Aspects/Acceptance Dehydration Vaultscan be a clean, comfortable, and easy-to-use technolo-gy. When users are well educated and understand howthe technology works they may be more willing toaccept it as a viable sanitation solution.When the vaults are kept dry, there should be no prob-lems with flies or odours. Faeces from the double vaultsshould be very dry and relatively safe to handle provid-ed they were continuously covered with material andnot allowed to get wet.There is a low health risk for those whom have to emptyor change the urine container. Faeces that have beendried for over one year also pose a low health risk.

Upgrading There is a risk however when using singlevaults, that the top portion of the faeces will not be fullydried and/or hygienized. Single vaults are not recom-mended (because of the need to handle fresh faeces) andshould, whenever possible be upgraded to a double vault.

Maintenance To prevent flies, minimize odours andencourage drying, a small amount of ash, soil, or limeshould be used to cover faeces after each use. Care shouldbe taken to ensure that no water or urine gets into theDehydration Vault. If this happens, extra soil, ash, lime,or sawdust can be added to help absorb the liquid.Because the faeces are not actually degraded (just dried),dry cleansing materials must not be added to the Dehy-dration Vaults as they will not decompose. Occasionally,the mounded faeces beneath the toilet hole should bepushed to the sides of the pit for an even drying.Where water is used for cleansing, an appropriate UserInterface should be installed to divert and collect itseparately. To empty the vaults, a shovel, gloves andpossibly a face mask (cloth) should be used to limit con-tact with the dried faeces.


+ Because double pits are used alternately, their life isvirtually unlimited

+ Good in rocky and/or flooded areas+ Excavation of dried faeces is easier than faecal sludge+ No real problems with flies or odours if usedcorrectly


+ Low (but variable) capital costs depending onmaterials; no or low operating costs

+ Small land area required- Requires education and acceptance to be usedcorrectly

- Requires constant source of ash, sand or lime- Requires a use/discharge point for urine and faeces- Urine and faeces require manual removal

References

_ (-) Manual del Sanitario Ecologico Seco.Available: www.zoomzap.com(A very comprehensive manual on dry chamber constructionincluding detailed instruction and material lists. In Spanish.)

_ GTZ (2005). Urine diverting dry toilets programmedissemination (data sheet). GTZ, Germany.Available: www.gtz.de(General overview of Dehydration Chambers with somedimensioning and materials lists.)

_ Winblad, U., and Simpson-Herbert, M. (eds.) (2004).Ecological Sanitation - revised and enlarged edition.SEI, Stockholm, Sweden.(A general description of various designs and adaptations,especially Chapter 3.)

_ Women in Europe for a Common Future (2006). Urinediverting Toilets: Principles, Operation and Construction.Available: www.wecf.de(Photos and explanation of how to build a double vaultand superstructure.)



64

S.7

Composting refers to the process bywhich biodegrad-able components are biologically decomposed underaerobic conditions by microorganisms (mainly bac-teria and fungi). A Composting Chamber converts exc-reta and organics into Compost. Compost is a stable,inoffensive product that can be handled safely andused as a soil conditioner.

This technology usually requires four main parts:1) a reactor (storage chamber);2) a ventilation unit to provide oxygen and allow gases(CO2, water vapour) to escape;

3) a leachate collection system ; and4) an access door to remove the mature product.

A Composting Chamber can be designed in various con-figurations and constructed above or below ground.UDDT can be used as a User Interface for specificallydesigned Composting Chambers. Anal Cleansing Watershould not be added to the composting chamber as itcould cause anaerobic conditions, foul smells and re-duced collection capacity.There are four factors that will ensure the good func-tioning of the system:

a) sufficient air (oxygen), provided by active aeration(pumped air) or passive aeration;

b) proper moisture (ideally moisture content should bebetween 45–70%);

c) internal (heap) temperature of 40–50°C (can be con-trolled with proper chamber dimensioning); and

d) a 25:1 carbon to nitrogen ratio (theoretically) whichcan be adjusted by adding an external source of car-bon such as toilet paper, wood chips, and/or veg-etable scraps.

It is appropriate to assume a design value of 300L/per-son/year to calculate the required chamber volume.

Adequacy Although simple in theory, CompostingChambers are not always easy to operate. The moisturemust be controlled to prevent anaerobic conditions, theratio of carbon and nitrogen must be well balanced andthe volume of the unit must be such that the tempera-ture of the compost pile remains between 40 to 50°C.However, once the composting process is well estab-lished, the system is quite robust.Depending on the design, Composting Chambers canbe used indoors with the comfort and convenience of aflush toilet.

leachate

ventilation

fan

leachate barrier



S.8S.8 Composting ChamberApplicable to:System 2

65



Inputs: Organics Excreta


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This technology is appropriate to almost all areas, butsince it is compact and waterless, it is especially suitedto warm climates and to areas where land and water arelimited. In colder climates, a Composting Chamber canalso be used indoors to ensure that low temperaturesdo not impede the composting process. A CompostingChamber cannot be used for the Collection and Sto-rage/Treatment of anal cleansing water or greywater; ifthe reactor becomes too wet, anaerobic conditions willform and there will be problems with odour and improp-er degradation.

Health Aspects/Acceptance If the CompostingChamber is well designed and constructed, thereshould be no reason for the users to handle the materi-al for at least the first year, and thus, little opportunityto come in contact with pathogens.A well functioning Composting Chamber should not pro-duce odours, and should be easy to maintain. If there isample cover/bulking material there should not be prob-lems with flies or insects.

Upgrading A simple Composting Chamber can beupgraded to include a small ventilation fan, a mechani-cal mixer, or multiple compartments to allow forincreased storage and degradation time.

Maintenance Depending on the design, the Com-posting Chamber should be emptied every 2 to 10 years.Only the completely mature compost should be removed.With time, salt or other solids may build up in the tankor in the leachate-collecting system, which can be dis-solved with hot water and/or scraped out.A squeeze test can be used to check the moisture levelwithin the Composting Chamber. A squeeze test re-quires the user to squeeze a handful of compost. Thecompost should not crumble and feel dry, nor should itfeel like a wet sponge. Rather, the compost should onlyleave a few drops of water in the user’s hand.

Pros & Cons:+ The compost that is removed is safe to handle andcan be used as a soil conditioner

+ Can help reduce the volume of solid wastegenerated by diverting organic material into thecomposting unit


+ Long service life+ No real problems with flies or odours if used correctly+ Low-moderate capital costs depending on emptying;low operating costs

+ High reduction of pathogens+ Does not require constant source of water- Leachate requires secondary treatment and/orappropriate discharge

- Requires expert design and construction supervision- May require some specialized parts- May require long start up time

References

_ Del Porto, D. and Steinfeld, C. (1999). The CompostingToilet System Book. A Practical Guide to Choosing, Planningand Maintaining Composting Toilet Systems, a Water-Saving,Pollution-Preventing Alternative. The Center for EcologicalPollution Prevention (CEPP), Concord, Massachusetts.(Comprehensive installation and maintenance for pre-fabri-cated units.)

_ Drescher, S., Zurbrügg, C., Enayetullah, I. and Singha, MAD.(2006). Decentralised Composting for Cities of Low- andMiddle-Income Countries – A User’s Manual. Eawag/Sandecand Waste Concern, Dhaka.Available: www.sandec.ch

_ Jenkins, J. (1999). The Humanure Handbook-2nd Edition.Jenkins Publishing, Grove City, PA, USA.Available: www.jenkinspublishing.com(Theory, history, and do-it-yourself guide to compostingtoilets.)

_ USEPA (1999). Water Efficiency Technology Fact Sheet:Composting Toilets- EPA 832-F-99-066. US EnvironmentalProtection Agency, Washington.Available: www.epa.gov/owm/mtb/comp.pdf(Information related to microbial die off rates and risks.)



66

S.8

A Septic Tank is a watertight chamber made of con-crete, fibreglass, PVC or plastic, for the storage andtreatment of blackwater and greywater. Settling andanaerobic processes reduce solids and organics, butthe treatment is only moderate.

A Septic Tank should typically have at least two cham-bers. The first chamber should be at least 50% of thetotal length and when there are only two chambers, itshould be 2/3 of the total length. Most of the solids set-tle out in the first chamber. The baffle, or the separationbetween the chambers, is to prevent scum and solidsfrom escaping with the effluent. A T-shaped outlet pipewill further reduce the scum and solids that are dis-charged.Liquid flows into the tank and heavy particles sink tothe bottom, while scum (oil and fat) floats to the top.With time, the solids that settle to the bottom aredegraded anaerobically. However, the rate of accumula-tion is faster than the rate of decomposition, and theaccumulated sludge must be removed at some point.Generally, Septic Tanks should be emptied every 2 to 5years, although they should be checked yearly to ensureproper functioning.

The design of a Septic Tank depends on the number ofusers, the amount of water used per capita, the averageannual temperature, the pumping frequency and thecharacteristics of the wastewater. The retention timeshould be designed for 48 hours to achieve moderatetreatment.A variation of the Septic Tank is called an aquaprivy,which is a simple storage and settling tank locateddirectly below the toilet, so that the excreta fall into thetank. To prevent odours from surfacing, a watersealmust be maintained but it may not completely preventsmells and the tank must be frequently desludged.The effluent must be dispersed by using a Soak Pit (D6)or Leach Field (D7) or by transporting the effluent toanother treatment technology via a Simplified Sewer(C4) or Solids-Free (C5).

Adequacy A Septic Tank is appropriate where thereis a way of dispersing or transporting the effluent.Because the Septic Tank must be desludged regularly, avacuum truck should be able to access the location.Often Septic Tanks are installed in the home, under thekitchen or bathroom which makes emptying difficult.If Septic Tanks are used in densely populated areas,

sludge

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S.9S.9 Septic TankApplicable to:System 5, 6

67





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onsite infiltration should not be used otherwise theground will become oversaturated and excreta may riseup to the surface posing a serious health risk. Instead,the Septic Tank should be connected to a sewer and theeffluent should be transported to a subsequent treat-ment or disposal site. Larger, multi-chamber SepticTanks can be designed for groups of houses and/orpublic buildings (i.e. schools).Generally, the removal of 50% of solids, 30 to 40 % ofbiochemical oxygen demand (BOD) and a 1-log remo-val of E.coli can be expected in a well designedSeptic Tank although efficiencies vary greatly de-pending on operation and maintenance and climacticconditions.Septic Tanks can be installed in every type of climatealthough the efficiency will be affected in colder cli-mates. Even though the Septic Tank is watertight, itshould not be constructed in areas with high groundwa-ter tables or where there is frequent flooding.Aquaprivies can be built indoors and above ground andare appropriate for rocky or flood-prone areas wherepits or other technologies would not be appropriate.However, because they require frequent emptying andconstant maintenance, they are only recommended forvery specific applications.

Health Aspects/Acceptance Although the remo-val of pathogens is not high, the entire tank is below thesurface so users do not come in contact with any of thewastewater.Users should be careful when opening the tank becausenoxious and flammable gases may be released. SepticTanks should have a vent.A vacuum truck should be used to empty the sludgefrom the Septic Tank. Users should not attempt toempty the pit themselves except with a manual technol-ogy like the Gulper (C2).

Upgrading A Septic Tank that is connected to aLeach Field (D7) or a Soak Pit (D6) can later be connect-ed to a Solids-Free Sewer (C5) if/when one is installed.

Maintenance Septic Tanks should be checked toensure that they are watertight and the levels of the

scum and sludge should be monitored to ensure thatthe tank is functioning well. Because of the delicateecology, care should be taken not to discharge harshchemicals into the Septic Tank.The sludge should be removed annually using a vacuumtruck to ensure proper functioning of the Septic Tank.


+ Long service life+ No real problems with flies or odours if usedcorrectly

+ Low capital costs, moderate operating costsdepending on water and emptying

+ Small land area required+ No electrical energy required- Low reduction in pathogens, solids and organics- Effluent and sludge require secondary treatmentand/or appropriate discharge

- Requires constant source of water

References

Detailed Design Information:_ Mara, DD. (1996). Low-Cost Urban Sanitation.Wiley, Chichester, UK.(Sizing, volume and emptying calculations and exampledesign solutions, Chapter 6.)

_ Polprasert, C. and Rajput, VS. (1982). EnvironmentalSanitation Reviews: Septic Tank and Septic Systems.Environmental Sanitation Information Center, Bangkok,AIT, Thailand. pp 68–74. (Comprehensive design manual)

_ Sasse, L. (1998). DEWATS. Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.(Excel® Spreadsheet codes for sizing septic tanks.)

General Information:_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems.WCB and McGraw-Hill, New York, USA.



68

S.9

An Anaerobic Baffled Reactor (ABR) is an improvedseptic tank because of the series of baffles underwhich thewastewater is forced to flow. The increasedcontact time with the active biomass (sludge) resultsin improved treatment.

The majority of settleable solids are removed in the sed-imentation chamber at the beginning of the ABR, whichtypically represents 50% of the total volume. The up-flow chambers provide additional removal and digestionof organic matter: BOD may be reduced by up to 90%,which is far superior to that of a conventional septictank. As sludge is accumulating, desludging is requiredevery 2 to 3 years. Critical design parameters include ahydraulic retention time (HRT) between 48 to 72 hours,up-flow velocity of the wastewater less than 0.6 m/hand the number of up-flow chambers (2 to 3).

Adequacy This technology is easily adaptable andcan be applied at the household level or for a smallneighbourhood (refer to Technology Information SheetT1: Anaerobic Baffled Reactor for information aboutapplying an Anaerobic Baffled Reactor at the communi-ty level).

An ABR can be designed for a single house or a group ofhouses that are using a considerable amount of water forclothes washing, showering, and toilet flushing. It is most-ly appropriate if water use and supply of wastewater arerelatively constant.This technology is also appropriate for areas where landmay be limited since the tank is installed undergroundand requires a small area. It should not be installedwhere there is a high groundwater table as infiltrationwill affect the treatment efficiency and contaminate thegroundwater.Typical inflows range from 2,000 to 200,000L/day. TheABR will not operate at full capacity for several monthsafter installation because of the long start up time re-quired for the anaerobic digestion of the sludge. There-fore, the ABR technology should not be used when theneed for a treatment system is immediate. To help theABR to start working more quickly, it can be ‘seeded’, i.e.active sludge can be introduced so that active bacteriacan begin working and multiplying immediately.Because the ABR must be emptied regularly, a vacuumtruck should be able to access the location.ABRs can be installed in every type of climate althoughthe efficiency will be affected in colder climates.

sludge

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scum

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inletliquid level

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S.10S.10 Anaerobic Baffled Reactor (ABR)Applicable to:System 5, 6

69





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Health Aspects/Acceptance Although the remo-val of pathogens is not high, the ABR is contained sousers do not come in contact with any of the waste-water or disease causing pathogens. Effluent andsludge must be handled with care as they contain highlevels of pathogenic organisms.To prevent the release of potentially harmful gases, thetank should be vented.

Maintenance ABR tanks should be checked to en-sure that they are watertight and the levels of the scumand sludge should be monitored to ensure that the tankis functioning well. Because of the delicate ecology,care should be taken not to discharge harsh chemicalsinto the ABR.The sludge should be removed annually using a vacuumtruck to ensure proper functioning of the ABR.

Pros & Cons:+ Resistant to organic and hydraulic shock loads+ No electrical energy required+ Greywater can be managed concurrently+ Can be built and repaired with locally availablematerials

+ Long service life+ No real problems with flies or odours if used cor-rectly

+ High reduction of organics+ Moderate capital costs, moderate operating costsdepending on emptying; can be low cost dependingon number of users

- Requires constant source of water- Effluent requires secondary treatment and/orappropriate discharge

- Low reduction pathogens- Requires expert design and construction- Pre-treatment is required to prevent clogging

References

_ Bachmann, A., Beard, VL. and McCarty, PL. (1985).Performance Characteristics of the Anaerobic BaffledReactor. Water Research 19 (1): 99–106.

_ Foxon, KM., Pillay, S., Lalbahadur, T., Rodda, N., Holder,F. and Buckley, CA. (2004). The anaerobic baffled reactor(ABR): An appropriate technology for on-site sanitation.Water SA 30 (5) (Special edition). Available: www.wrc.org.za

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.(Design summary including and Excel-based design program.)



70

S.10

An Anaerobic Filter is a fixed-bed biological reactor.As wastewater flows through the filter, particles aretrapped and organic matter is degraded by the bio-mass that is attached to the filter material.

This technology consists of a sedimentation tank (orseptic tank) followed by one or more filter chambers.Filter material commonly used includes gravel, crushedrocks, cinder, or specially formed plastic pieces. Typicalfilter material sizes range from 12 to 55mm in diameter.Ideally, the material will provide between 90 to 300m2

of surface area per 1m3 of reactor volume. By providinga large surface area for the bacterial mass, there isincreased contact between the organic matter and theactive biomass that effectively degrades it.The Anaerobic Filter can be operated in either upflow ordownflow mode. The upflow mode is recommendedbecause there is less risk that the fixed biomass will bewashed out. The water level should cover the filtermedia by at least 0.3m to guarantee an even flowregime.Studies have shown that the HRT is the most importantdesign parameter influencing filter performance. AnHRT of 0.5 to 1.5 days is a typical and recommended.

A maximum surface-loading (i.e. flow per area) rate of2.8m/d has proven to be suitable. Suspended solidsand BOD removal can be as high as 85% to 90% but istypically between 50% and 80%. Nitrogen removal islimited and normally does not exceed 15% in terms oftotal nitrogen (TN).

Adequacy This technology is easily adaptable andcan be applied at the household level or a small neigh-bourhood (refer to Technology Information Sheet T2:Anaerobic Filter for information about applying anAnaerobic Filter at the community level).An Anaerobic Filter can be designed for a single houseor a group of houses that are using a lot of water forclothes washing, showering, and toilet flushing. It isonly appropriate if water use is high, ensuring that thesupply of wastewater is constant.The Anaerobic Filter will not operate at full capacity forsix to nine months after installation because of the longstart up time required for the anaerobic biomass to sta-bilize. Therefore, the Anaerobic Filter technology shouldnot be used when the need for a treatment technologyis immediate. Once working at full capacity it is a stabletechnology that requires little attention.

sludge

settlement zone

scum

outlet

filter support

inlet inlettee

baffle

liquid level

access covers

filter



S.11S.11 Anaerobic FilterApplicable to:System 5, 6

71





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The Anaerobic Filter should be watertight but it shouldstill not be constructed in areas with high groundwatertables or where there is frequent flooding.Depending on land availability and the hydraulic gradi-ent of the sewer (if applicable), the Anaerobic Filter canbe built above or below ground. It can be installed inevery type of climate, although the efficiency will beaffected in colder climates.

Health Aspects/Acceptance Because the Anaero-bic Filter unit is underground, users do not come in con-tact with the influent or effluent. Infectious organismsare not sufficiently removed, so the effluent should befurther treated or discharged properly. The effluent,despite treatment, will still have a strong odour and careshould be taken to design and locate the facility suchthat odours do not bother community members.To prevent the release of potentially harmful gases, theAnaerobic Filters should be vented.The desludging of the filter is hazardous and appropri-ate safety precautions should be taken.

Maintenance Active bacteria must be added to startup the Anaerobic Filter. The active bacteria can comefrom sludge from a septic tank that has been sprayedonto the filter material. The flow should be graduallyincreased over time, and the filter should be working atmaximum capacity within six to nine months.With time, the solids will clog the pores of the filter. Aswell, the growing bacterial mass will become too thickand will break off and clog pores. A sedimentation tankbefore the filter is required to prevent the majority of set-tleable solids from entering the unit. Some cloggingincreases the ability of the filter to retain solids. Whenthe efficiency of the filter decreases, it must be cleaned.Running the system in reverse mode to dislodge accu-mulated biomass and particles cleans the filters. Alter-natively, the filter material can be removed and cleaned.

Pros & Cons:+ Resistant to organic and hydraulic shock loads+ No electrical energy required+ Can be built and repaired with locally availablematerials

+ Long service life+ Moderate capital costs, moderate operating costsdepending on emptying; can be lowered dependingon the number of users

+ High reduction of BOD and solids- Requires constant source of water- Effluent requires secondary treatment and/orappropriate discharge

- Low reduction of pathogens and nutrients- Requires expert design and construction- Long start up time

References

_ Morel, A. and Diener, S. (2006). Greywater Managementin Low and Middle-Income Countries, Review of differenttreatment systems for households or neighbourhoods.Swiss Federal Institute of Aquatic Science and Technology(Eawag), Dübendorf, Switzerland.(Short summary including case studies, page 28.)

_ Polprasert, C. and Rajput, VS. (1982). EnvironmentalSanitation Reviews: Septic Tank and Septic Systems.Environmental Sanitation Information Center, AIT,Bangkok, Thailand. pp 68–74.(Short design summary.)

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.(Design summary including Excel-based design program.)

_ von Sperlin, M. and de Lemos Chernicharo, CA. (2005).Biological Wastewater Treatment in Warm Climate Regions.Volume One. IWA, London. pp 728–804.(Detailed design instructions.)

_ Vigneswaran, S., et al. (1986). Environmental SanitationReviews: Anaerobic Wastewater Treatment-Attached growthand Sludge blanket process. Environmental SanitationInformation Center, AIT Bangkok, Thailand.(Design criteria and diagrams in Chapter 2.)



72

S.11

An Anaerobic Biogas Reactor is an anaerobic treat-ment technology that produces (a) a digested slurryto be used as a soil amendment and (b) biogas whichcan be used for energy. Biogas is a mix of methane,carbon dioxide and other trace gasses that can beeasily converted to electricity, light and heat.

An Anaerobic Biogas Reactor is a chamber or vault thatfacilitates the anaerobic degradation of blackwater,sludge, and/or biodegradable waste. It also facilitatesthe separation and collection of the biogas that is pro-duced. The tanks can be built above or below ground.Prefabricated tanks or brick-constructed chambers canbe built depending on space, resources and the volumeof waste generated.The hydraulic retention time (HRT) in the reactor should aminimum of 15 days in hot climates and 25 days in tem-perate climates. For highly pathogenic inputs, a HRT of 60days should be considered. Normally, Anaerobic BiogasReactors are not heated, but to ensure pathogen destruc-tion (i.e. a sustained temperature over 50°C) the reactorshould be heated (although in practice, this is only foundin the most industrialized countries).Once waste products enter the digestion chamber, gases

are formed through fermentation. The gas forms in thesludge but collects at the top of the reactor, mixing theslurry as it rises. Biogas reactors can be built as fixeddome or floating dome reactors. In the fixed dome reac-tor the volume of the reactor is constant. As gas is gener-ated it exerts a pressure and displaces the slurry upwardinto an expansion chamber. When the gas is removed, theslurry will flow back down into the digestion chamber. Thepressure generated can be used to transport the biogasthrough pipes. In a floating dome reactor, the dome willrise and fall with the production and withdrawal of gas.Alternatively, the dome can expand (like a balloon).Most often biogas reactors are directly connected toindoor (private or public) toilets with an additionalaccess point for organic materials. At the householdlevel, reactors can be made out of plastic containers orbricks and can be built behind the house or buriedunderground. Sizes can vary from 1,000L for a singlefamily up to 100,000L for institutional or public toiletapplications.The slurry that is produced is rich in organics and nutri-ents, but almost odourless and partly disinfected (com-plete pathogen destruction would require thermophilicconditions). Often, a biogas reactor is used as an alter-

sludge

inlet biogas outlet

biogas

expansion chamberoutlet

outletseal



S.12S.12 Anaerobic Biogas ReactorApplicable to:System 3, 6

73



Inputs: Faecal Sludge OrganicsBlackwater

Outputs: Treated Sludge EffluentBiogas

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native to a conventional septic tank, since it offers asimilar level of treatment, but with the added benefitof biogas. Depending on the design and the inputs,the reactor should be emptied once every 6 monthsto 10 years.

Adequacy This technology is easily adaptable and canbe applied at the household level or a small neighbour-hood (refer to Technology Information Sheet T15:Anaerobic Biogas Reactor for information about applyingit at the community level).Biogas reactors are best used for concentrated products(i.e. rich in organic material). If they are installed for asingle household that is using a significant amount ofwater, the efficiency of the reactor can be improved sig-nificantly by also adding animal manure and biodegrad-able organic waste.Depending on the soil, location, and size required, thereactor can be built above or below ground (even belowroads). For more urban applications, small biogas reac-tors can be installed on the rooftops or in a courtyard.To minimize distribution losses, the reactors should beinstalled close to where the gas can be used.Biogas reactors are less appropriate for colder climates asgas production is not economically feasible below 15°C.

Health Aspects/Acceptance The digested slurryis not completely sanitized and still carries a risk ofinfection. There are also dangers associated with theflammable gases that, if mismanaged, could be harmfulto human health.The Anaerobic Biogas Reactor must be well built andgas tight for safety. If the reactor is properly designed,repairs should be minimal. To start the reactor, activesludge (e.g. from a septic tank) should be used as aseed. The tank is essentially self-mixing, but it shouldbe manually stirred once a week to prevent unevenreactions.Gas equipment should be cleaned carefully and regular-ly so that corrosion and leaks are prevented.Grit and sand that has settled to the bottom should be

removed once every year. Capital costs for gas trans-mission infrastructure can increase the project cost.Depending on the quality of the output, the gas trans-mission capital costs can be offset by long-term energysavings.

Pros & Cons:+ Generation of a renewable, valuable energy source+ Low capital costs; low operating costs+ Underground construction minimizes land use+ Long life span+ Can be built and repaired with locally availablematerials

+ No electrical energy required+ Small land area required (most of the structure canbe built underground)

- Requires expert design and skilled construction- Gas production below 15°C is not economicallyfeasible

- Digested sludge and effluent still requires treatment

References

_ Food and Agriculture Organization (FAO) (1996). BiogasTechnology: A Training Manual for Extension. ConsolidatedManagement Services, Kathmandu. Available: www.fao.org

_ ISAT (1998). Biogas Digest Vols. I–IV. ISAT and GTZ,Germany. Available: www.gtz.de

_ Koottatep, S., Ompont, M. and Joo Hwa, T. (2004). Biogas:A GP Option For Community Development. AsianProductivity Organization, Japan.Available: www.apo-tokyo.org

_ Rose, GD. (1999). Community-Based Technologies forDomestic Wastewater Treatment and Reuse: optionsfor urban agriculture. IDRC, Ottawa. pp 29–32.Available: http://idrinfo.idrc.ca

_ Sasse, L. (1998). DEWATS: Decentralised Wastewater Treat-ment in Developing Countries. BORDA, Bremen OverseasResearch and Development Association, Bremen, Germany.



74

S.12


FunctionalGroupC:Conveyance

CConveyance

75

The technologies in this section are responsible for moving or transporting Products

from an onsite Collection and Storage/Treatment technology to a subsequent offsite

treatment, use or disposal technology.



76

C

Jerrycans are light, plastic containers that can be eas-ily carried by one person and are readily available.When sealed, they can be used to store or transporturine easily and without spills. In case separatedurine cannot be used near the point of production, itcan be transported in a Jerrycan or tank to a centralcollection/storage facility or to agricultural land forapplication.

On average, a person generates 1.5L of urine a dayalthough this quantity may very significantly dependingon the climate and fluid consumption. A family of 5 canbe expected to fill a 20L Jerrycan with urine in approxi-mately two days. The urine can then be either stored onsite or transported immediately.For compounds or communities that all have urinediverting systems, it may be more appropriate to have alarger, semi-centralized storage tank that can be trans-ported by other means. Where urine-diversion systemsare common, a micro-enterprise may specialize in thecollection and transport of Jerrycans using a bicycle,wagon or donkey and cart.

Adequacy A well-sealed Jerrycan is an effective wayof transporting urine short distances. It is inexpensive,easy to clean and re-useable. This type of transport isonly appropriate for areas where the points of genera-tion and use (i.e. home and field) are close together,otherwise a more formalized collection and distributionsystem is necessary.Jerrycans can be used in cold environments (whereurine freezes) as long as they are not completely filled.Stored frozen urine can be then used in warmer monthswhen it is needed for agriculture.Because of safety concerns and difficulty with trans-port, no other liquids (blackwater or greywater) shouldbe transported in Jerrycans

Health Aspects/Acceptance There should not beany health risks to those carrying a Jerrycan as urineis generally sterile and the Jerrycans seal well. Whilecarrying a Jerrycan may not be the most pleasantactivity, it is likely more convenient and less costlyemptying a pit.In some locations, urine has an economic value and itmay be collected from the household for free. Familieswho invest the time to transport and use their own urine



C.1C.1 Jerrycan/tankApplicable to:System 4, 8

77



Inputs/Outputs:Urine Stored Urine��

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may be rewarded with increased agricultural productionimproving the families health and/or increasing theirincome.

Upgrading If urine is viewed as a commodity, locallyrun businesses may collect and transport it for free orfor a small fee.

Maintenance To minimize bacterial growth, sludgeaccumulation and unpleasant odours, Jerrycans shouldbe washed frequently.

Pros & Cons+ Very low capital and operating costs+ Potential for local job creation and incomegeneration

+ Easy to clean and reusable+ Low risk of pathogen transmission- Heavy to carry- Spills may happen

References

_ Austin, A. and Duncker L. (2002). Urine-diversion.Ecological Sanitation Systems in South Africa.CSIR, Pretoria, South Africa.

_ GTZ (2005). Technical data sheets for ecosan components-01 Urine Diversion-Piping and Storage. GTZ, Germany.Available: www.gtz.de

_ Morgan, P. (2007). Toilets that make compost. StockholmEnvironment Institute, Stockholm, Sweden.Available: www.ecosanres.org

_ Morgan, P. (2004). An Ecological Approach to Sanitationin Africa: A Compilation of Experiences. Aquamor, Harare,Zimbabwe. Chapter 10: The usefulness of Urine.Available: www.ecosanres.org

_ NWP (2006). Smart Sanitation Solutions. Examples ofinnovative, low-cost technologies for toilets, collection,transportation, treatment and use of sanitation products.Netherlands Water Partnership, Netherlands.

_ Schonning, C. and Stenstrom, TA. (2004). Guidelines for theSafe Use of Urine and Faeces in Ecological SanitationSystems-Report 2004-1. EcosanRes, Stockholm Environ-ment Institute, Stockholm, Sweden.Available: www.ecosanres.org

_ Winblad, U. and Simpson-Herbert, M. (eds.) (2004).Ecological Sanitation – revised and enlarged edition.Stockholm Environment Institute, Stockholm, Sweden.Available: www.ecosanres.org

_ WHO (2006). Guidelines for the safe use of wastewater,Excreta and Greywater- Volume 4: Excreta and Greywater usein agriculture. WHO, Geneva.Available: www.who.int



78

C.1

Human-powered Emptying and Transport refers thedifferent ways in which people can manually emptyand/or transport sludge and septage.

Human-powered Emptying and Transport of pits andtanks can mean one of three things:1)using buckets and shovels;2)using a hand-pump specially designed for sludge(e.g. the Pooh Pump or the Gulper); and

3)using a portable, manually operated pump(e.g. MAPET: MAnual Pit Emptying Technology).

Some sanitation technologies can only be emptied man-ually, for example, the Fossa Alterna (S5) or DehydrationVaults (S7). These technologies must be emptied with ashovel because the material is solid and cannot beremoved with a vacuum or a pump. When sludge is vis-cous or watery it should be emptied with a hand-pump,a MAPET or a vacuum truck, and not with bucketsbecause of the high risk of collapsing pits, toxic fumes,and exposure to the unsanitized sludge. The type ofemptying that can, and should be employed, is very spe-cific to the technology that needs emptying.Manual sludge pumps like the Pooh Pump or the Gulperare relatively new inventions and have shown promise

as being low-cost, effective solutions for sludge empty-ing where, because of access, safety or economics,other sludge emptying techniques are not possible. Thepump works on the same concept as a water pump: thehandle is pumped, the liquid (sludge) rises up throughthe bottom of the pump and is forced out of a tap(sludge spout). Hand-pumps can be made locally withsteels rods and valves in a PVC casing. The bottom ofthe pipe is lowered down into the pit/tank while theoperator remains at the surface to operate the pump,thus removing the need for someone to enter the pit. Asthe operator pushes and pulls the handle, the sludge ispumped up through the main shaft and is then dis-charged through the V-shaped discharge spout. Thesludge that is discharged can be collected in barrels,bags or carts, and removed from the site with littlemess or danger to the operator.A MAPET consists of a hand pump connected to a vac-uum tank mounted on a pushcart. A hose is connectedto the tank and is used to suck sludge from a pit. Whenthe hand pump is turned, air is sucked out of the vacu-um tank and sludge is sucked up into the tank.Depending on the consistency of the sludge, the MAPETcan pump up to a height of 3m.

58cm

60cm

35cm

70cm

10cm



C.2C.2 Human-Powered Emptying and TransportApplicable to:System 1, 2,3, 4,5

79



Inputs/Outputs:Faecal Sludge Dried FaecesCompost/EcoHumus Blackwater

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Adequacy Hand-pumps are appropriate for areas thatare either not served by vacuum trucks, where vacuum-truck emptying is too costly, or where narrow streets andpoor roads may limit the ability of a vacuum truck toaccess the site. The hand-pump is a significant improve-ment over the bucket method and could prove to be a sus-tainable business opportunity in some regions. TheMAPETis also well suited to dense, urban and informal settle-ments, although in both cases, the distance to a suitablesludge discharge point is a limiting factor. These technolo-gies are more feasible when there is a Transfer Station(C7) or Sewage Discharge Station (C8) nearby.One government-run emptying programme implement-ed a manual emptying scheme with great success byproviding employment to community members with ade-quate protection and an appropriate wage.

Health Aspects/Acceptance Depending on cul-tural factors and political support, manual emptiersmay be viewed as providing an important service to thecommunity.Government-run programmes should strive to legitimizethe work of the labourer and help improve the social cli-mate by providing permits, licences and helping to legal-ize of the practice of manually emptying latrines.The most important aspect of manual emptying is ensur-ing that workers are adequately protected with gloves,boots, overalls and facemasks. Regular medical examsand vaccinations should be required for everyone work-ing with sludge.

Upgrading To save time, vacuum trucks can be usedrather than manual labour if it is appropriate and/oravailable.

Maintenance The MAPET and Sludge Pumps requiredaily maintenance (cleaning, repairing and desinfec-tion). Workers that manually empty latrines shouldclean and maintain their protective clothing and tools toprevent contact with the sludge.If manual access to the contents of a pit require break-ing open the slab, it may be more cost effective to usea Gulper to empty the latrine. The Gulper cannot emptythe entire pit and therefore, emptying may be required

more frequently (once a year), however, this may be acheaper alternative than replacing a broken slab.

Pros & Cons:+ Potential for local job and income generation+ Gulper can be built and repaired with locallyavailable materials

+ Low to moderate capital; variable operating costsdepending on discharge point (sludge transportover 0.5km is impractical)

+ Provides service to unsewered areas/communities+ Easy to clean and reusable- Spills may happen- Time consuming: can take several hours/daysdepending on the size of the pit

- MAPET requires some specialized repair (welding)

References

_ Eales, K. (2005). Bringing pit emptying out of the darkness:A comparison of approaches in Durban, South Africa, andKibera, Kenya. Building partnerships for Development inWater and Sanitation, UK.Available: www.bpd-waterandsanitation.org(A comparison of two manual emptying projects.)

_ Ideas at Work (2007). The ‘Gulper’ – a manual latrine/drainpit pump. Ideas at Work, Cambodia.Available: www.ideas-at-work.org

_ Muller, M. and Rijnsburger, J. (1994). MAPET. ManualPit-latrine Emptying Technology Project. Development andpilot implementation of a neighbourhood based pitemptying service with locally manufactured handpumpequipment in Dar es Salaam, Tanzania. 1988–1992.WASTE Consultants, Netherlands.

_ Oxfam (n.d.). Manual Desludging Hand Pump (MDHP)Resources. Oxfam, UK.Available: http://desludging.org

_ Pickford, J. and Shaw, R. (1997). Emptying latrine pits,Waterlines, 16(2): 15–18. (Technical Brief, No. 54).Available: www.lboro.ac.uk

_ Sugden, S. (n.d.). Excreta Management in Unplanned Areas.London School of Hygiene and Tropical Medicine,London, UK.Available: http://siteresources.worldbank.org



80

C.2

Motorized Emptying and Transport refers to a vacu-um truck or another vehicle equipped with a motor-ized pump and a storage tank for emptying and trans-porting faecal sludge, septage and urine. Humans arerequired to operate the pump and manoeuvre thehose, but they do not lift or transport the sludge.

The pump is connected to a hose that is lowered downinto a constructed tank (e.g. septic tank or aquaprivy)or pit, and the sludge is pumped up into the holdingtank on the truck. Generally the storage capacity ofa vacuum tanker is between 3,000 and 10,000L.Multiple truckloads may be required for large septictanks.Both the agencies responsible for sewerage and pri-vate entrepreneurs may operate vacuum trucks,although the price and level of service may vary signif-icantly. Some public operators may not service infor-mal settlements, whereas some private operators mayoffer a reduced price, but can only afford to do so ifthey do not empty the sludge at a certified facility. Thecost of hiring a vacuum truck can sometimes be themost expensive part of operating a sanitation systemfor some homeowners.

The UN-HABITAT Vacutug Project was conceived in1995 with the goal of developing ‘fully sustainablesystem for emptying pit latrines in unplanned, peri-urban areas and refugee camps in the developingcountries’. The Vacutug consists of a 0.5 m³ steelvacuum tank connected to vacuum pump which isconnected to a gasoline engine. On level ground, thevehicle is capable of around 5km/h. The wastesludge can be discharged under gravity or by slightpressurization from the pump. Recent results indicatethat under certain circumstances (constant numberof pits, transfer station, short transfer distance, etc.)the Vacutug can be sustainable and cover its operat-ing and maintenance costs.

Adequacy Although smaller more mobile vehicleshave been developed, large vacuum trucks remain thenorm for municipalities and sanitation authorities.Unfortunately, large trucks cannot access allpits/septic tanks especially in areas with narrow ornon-driveable roads. Also, vacuum trucks can rarelymake trips to peri-urban or rural areas since the incomegenerated from emptying, may not offset the cost offuel and time.

sludge



C.3C.3 Motorized Emptying and TransportApplicable to:System 1, 5, 6, 8

81



Inputs/Outputs:Urine Faecal SludgeBlackwater

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Depending on the collection or treatment technology,the material that needs to be pumped can be so densethat it cannot be pumped easily. In these situations it isnecessary to thin the solids with water so that they flowmore easily, but this may be inefficient and costly. Ifwater is not available, it may be necessary for the wasteto be manually removed. In general, the closer the vac-uum can be to the pit, the easier it is to empty. The crit-ical velocity of the sludge required for pumping isdependent on the distance from, and strength of, thevacuum pump; sludge is extremely site specific.Garbage and sand also makes emptying the pit muchmore difficult.

Health Aspects/Acceptance The use of a vacuumtanker for emptying a pit latrine or septic tank presentstwo health improvements: (1) emptying maintains theCollection and Storage/Treatment technology andreduces the risk of overflows and (2) the use of a tankerreduces the need for manual emptying, which is quiteunsafe and unhygienic. Still, those who operate vacuumtrucks may be demonized by the community and mayface difficulties with finding appropriate locations todump and treat the collected sludge.

Maintenance Maintenance is a crucial part of vacu-um truck operation. Trucks are not usually brand newand they often require constant attention to preventbreakdowns. The lack of preventive maintenance isoften the cause for major repairs.Most pump trucks are manufactured in North Americaor Europe. As such, it is difficult to locate spare truckparts and a local mechanic to repair broken pumps andtrucks. New trucks are difficult to obtain, very expen-sive and thus rarely purchased. Local trucks are com-monly adapted to serve as vacuum trucks by equippingthem with holding tanks and vacuums.Maintenance accounts for at least one quarter of thecosts incurred by the operator of a vacuum truck. Fueland oil account for another quarter of the total operat-ing costs. Owners/operators must be conscientious tosave money for the purchase of expensive replacementparts, tires and equipment, whose replacement couldbe essential to the working of the vacuum truck.

Pros & Cons:+ Fast, and generally efficient+ Potential for local job creation and incomegeneration

+ Provides essential service to unsewered areas- Cannot pump thick dried sludge (must be manuallyremoved or thinned with water)

- Garbage in pits may block hose- Very high capital costs; variable operating costsdepending on use and maintenance

- Pumps can usually only suck down to a depth of2 to 3m and the pump must be located within30m of the pit

- Not all parts and materials may be available locally- May have difficulties with access

References

_ Brikké, F. and Bredero, M. (2003). Linking technology choicewith operation and maintenance in the context of communitywater supply and sanitation: A reference document for plan-ners and project staff. WHO and IRC Water and SanitationCentre, Geneva.Available: www.who.int(Chapter 8 provides an assessment of vacuum emptying.)

_ Boesch, A. and Schertenleib, R. (1985). Pit Emptying On-Site Excreta Disposal Systems. Field Tests with MechanizedEquipment in Gaborone (Botswana). IRCWD, Switzerland.Available: www.sandec.ch(Comprehensive summary of technical components, perfor-mance with different sludge types, and maintenance.)

_ Issaias, I. (2007). UN-HABITAT Vacutug Development Project:Technical report of field trials 2003–2006. Water, Sanitationand Infrastructure Branch, UN-HABITAT, Nairobi, Kenya.



82

C.3

Simplified Sewers describe a sewerage network thatis constructed using smaller diameter pipes laid at ashallower depth and at a flatter gradient than conven-tional sewers. The Simplified Sewer allows for amoreflexible design associated with lower costs and ahigher number of connected households.

Expensive manholes are replaced with simple inspec-tion chambers. Each discharge point is connected to aninterceptor tank to prevent settleable solids and trashfrom entering the sewer. As well, each householdshould have a grease trap before the sewer connection.Another key design feature is that the sewers are laidwithin the property boundaries, rather than beneath thecentral road. Because the sewers are more communal,they are often referred to as condominial sewers.Oftentimes, the community will purchase, and connectto, a single legal connection to the main sewer; thecombined effluent of the condominal sewer networkflows into the main sewer line.Because simplified sewers are laid on or around theproperty of the users, higher connection rates can beachieved, fewer and shorter pipes can be used and lessexcavation is required as the pipes will not be subject-

ed to heavy traffic loads. However, this type of Convey-ance technology requires careful negotiation betweenstakeholders since design and maintenance must bejointly coordinated.All greywater should be connected to the SimplifiedSewer to ensure adequate hydraulic loading. Inspectionchambers also function to attenuate peak dischargesinto the system. For example, a 100mm diameter sewerlaid at a gradient of 1m in 200m (0.5%) will servearound 200 households of 5 people (10,000 users) witha wastewater flow of 80L/person/day.Although watertight sewers are the ideal, they may bedifficult to achieve, and therefore the sewers should bedesigned to take into account the extra flow that mayresult from stormwater infiltration.Blocks of community-based Simplified Sewers are con-nected to an existing Conventional Gravity Sewer orrouted to a Simplified Sewer main constructed withpipes of a larger diameter. A Simplified Sewer main canstill be placed at a shallow depth providing it is placedaway from traffic.

inspection chamber



C.4C.4 Simplified SewersApplicable to:System 6, 7, 8

83



Inputs/Outputs:Blackwater Greywater

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Adequacy Where the ground is rocky or the ground-water table is high, the excavation of trenches for pipesmay be difficult. Under these circumstances, the cost ofinstalling sewers is significantly higher than in favour-able conditions. Regardless, Simplified Sewerage is lessexpensive than Conventional Gravity Sewerage becauseof its shallow installation depth.Simplified Sewers can be installed in almost all types ofsettlements and are especially appropriate for dense,urban settlements. To prevent clogging and maintainthe sewers, good pre-treatment is required. It is recom-mended that the scum from greywater, heavy solids andgarbage be removed from the wastewater prior to enter-ing the sewer.

HealthAspects/Acceptance If constructed andmain-tained well, sewers are a safe and hygienic means oftransporting wastewater. Users must be well educatedabout the health risks associated with maintaining/cleaning blockages and inspection chambers.

Upgrading Household inspection chambers can beupgraded to septic tanks so that fewer solids enter theSimplified Sewer network, but this will increase mainte-nance costs associated with emptying the septic tank.

Maintenance Pre-treatment with interceptor tanksand a grease trap is essential. The homeowner mustmaintain the interceptor tanks and the grease trap.Ideally, households will also be responsible for themaintenance of the sewers, however in practice thismay not be feasible. Alternatively, a private contractoror users committee can be hired to assume responsibil-ity for the maintenance as inexperienced users may notdetect problems before they become severe, and there-fore, more costly to repair. A related problem is thathouseholds may drain stormwater into the sewer. Thispractice should be discouraged whenever possible.Blockages can usually be removed by opening thesewer and forcing a length of rigid wire through thesewer. Inspection chambers must be emptied periodi-cally to prevent grit overflowing into the system.


+ Construction can provide short-term employmentto local labourers

+ Capital costs are between 50 and 80% less thanConventional Gravity Sewers; operating costsare low

+ Can be extended as a community changes and grows- Requires expert design and construction supervision- Requires repairs and removals of blockages morefrequently than a Conventional Gravity Sewer

- Effluent and sludge (from interceptors) requiressecondary treatment and/or appropriate discharge

References

_ Azevedo Netto, MM. and Reid, R. (1992). Innovative andLow Cost Technologies Utilized in Sewerage. TechnicalSeries No. 29, Environmental Health Program. PanAmerican Health Organization, Washington DC.(Refer to Chapters 3 and 4 for component diagrams anddesign formulae.)

_ Bakalian, A., Wright, A., Otis, R. and Azevedo Netto, J. (1994).Simplified sewerage: design guidelines. Water and SanitationReport No. 7. The World Bank + UNDP, Washington.(Design guidelines for manual calculations.)

_ HABITAT (1986). The design of Shallow Sewer Systems.United Nations Centre for Human Settlements (HABITAT),Nairobi, Kenya.(Detailed design tools and practical examples.)

_ Mara, DD. (1996). Low-Cost Urban Sanitation. Wiley,Chichester, UK. pp 109–139.(Comprehensive summary including design examples.)

_ Mara, DD. (1996). Low-Cost Sewerage. Wiley, Chichester, UK.(Assessment of different low-cost systems and case studies.)

_ Mara, DD., et al. (2001). PC-based Simplified Sewer Design.University of Leeds, England.(Comprehensive coverage of theory and design including aprogram to be used as a design aid.)

_ Watson, G. (1995). Good Sewers Cheap? Agency-CustomerInteractions in Low-Cost Urban Sanitation in Brazil. TheWorld Bank, Water and Sanitation Division, Washington, DC.(A summary of large scale projects in Brazil.)



84

C.4

A Solids-Free Sewer is a network of small diameterpipes that transports solids-free or pre-treatedwastewater (such as septic tank or settling tankeffluent) to a treatment facility for further treatmentor to a discharge point. Solids-Free Sewers are alsoreferred to as settled, small-bore, small-diameter,variable-grade gravity, or septic tank effluent gravitysewers.

A precondition for Solids-Free Sewer networks is effi-cient pre-treatment at the household level. The inter-ceptor, septic or settling tank removes settleable parti-cles that could clog small pipes. A grease trap shouldalso be added. Because there is little risk of clogging,the sewers do not have to be self-cleaning (i.e. no min-imum flow velocity) and can therefore be laid at shallowdepths, can have fewer inspection points (manholes),can follow the topography more closely and have inflec-tive gradients (i.e. negative slope). When the sewerroughly follows the ground contours, the flow in thesewer is allowed to vary between open channel flowand pressure (full-bore) flow. However, care should betaken with negative slopes as they may lead to surgingabove the ground level during peak flows. Inspection

points should be provided at major connection points orwhen the size of the pipe changes.Despite the presence of inflective gradients, thedownstream end of the sewer must be lower than theupstream end. When choosing a pipe diameter (atleast 75mm), the depth of water in the pipe duringpeak flow within each section must be less than thediameter of the pipe. In sections where there is pres-sure flow, the invert of any interceptor tank outletmust higher than the hydraulic head within the sewerjust prior to the point of connection otherwise the liq-uid will backflow into the tank. If this condition is notmet, then either select the next larger pipe diameterfor the sewer or increase the depth at which the seweris laid.

Adequacy Solids-Free Sewers are appropriate forboth full and partially filled flows. Although a constantsupply of water is required, less water is needed com-pared to the Simple Sewer because self-cleansingvelocities are not required.Septic Tanks and Solids-Free Sewers can be built fornew areas, or a Solids-Free Sewer can be connectedto an existing primary treatment technology where

settling tanks



C.5C.5 Solids-Free SewerApplicable to:System 6

85



Inputs/Outputs:Effluent

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local infiltration is inappropriate. A Solids-Free Sewercan be built for 20% to 50% less than ConventionalGravity Sewerage.This technology must be connected to an appropriate(Semi-) Centralized Treatment technology that canreceive the wastewater. It is appropriate for densely pop-ulated areas where there is no space for a Soak Pit (D6)or Leach Field (D7). This type of sewer is best suited tourban and less appropriate in low-density or rural areas.

Health Aspects/Acceptance This technology re-quires regular maintenance on the part of the users andis therefore, not as passive as Conventional GravitySewers. Users must assume some level of responsibili-ty for the technology and accept that some potentiallyunpleasant maintenance may be required. Also, usersshould be aware that, because the system is communi-ty based, they may have to work with and/or coordinatemaintenance activities with other users. The system willprovide a high level of service and may offer a signifi-cant improvement to non-functioning Leach Fields (D7).

Upgrading Solids-Free Sewers are good upgradingoptions for Leach Fields (D7) that have become cloggedand/or saturated with time as well as for rapidly grow-ing areas that would not accommodate more SepticTanks with Leach Fields.

Maintenance The septic/interceptor tank must beregularly maintained and desludged to insure optimalperformance of the Solids-Free Sewer network. If thepre-treatment is efficient, the risk of clogging in thepipes is low, but some maintenance will be requiredperiodically. The sewers should be flushed once a yearas part of the regular maintenance regardless of theirperformance.

Pros & Cons:+ Greywater can be managed at the same time+ Can be built and repaired with locally availablematerials


+ Capital costs are less than Conventional GravitySewers; low operating costs

+ Can be extended as a community changes and grows- Requires expert design and construction supervision- Requires repairs and removals of blockages morefrequently than a Conventional Gravity Sewer

- Requires education and acceptance to be usedcorrectly

- Effluent and sludge (from interceptors) requiressecondary treatment and/or appropriate discharge

References

_ Azevedo Netto, MM. and Reid, R. (1992). Innovative andLow Cost Technologies Utilized in Sewerage. EnvironmentalHealth Program, Technical Series No. 29. Pan AmericanHealth Organization, Washington DC.(A Short summary and component diagrams-Chapter 5.)

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems. WCB andMcGraw-Hill, New York, USA. pp 355–364.(A short summary of design and construction considerations.)

_ Mara, DD. (1996). Low-Cost Sewerage. Wiley, Chicheser, UK.(Assessment of different low-cost systems and case studies.)

_ Mara, DD. (1996). Low-Cost Urban Sanitation. Wiley,Chichester, UK. pp 93–108.(Comprehensive summary including design examples.)

_ Otis, RJ. and Mara, DD. (1985). The Design of Small BoreSewer Systems (UNDP Interreg. Project INT/81/047).TAG Technical Note No.14. United Nations DevelopmentProgramme + World Bank, Washington.Available: www.wds.worldbank.org(Comprehensive summary of design, installation andmaintenance.)



86

C.5

Conventional Gravity Sewers are large networks ofunderground pipes that convey blackwater, greywa-ter and stormwater from individual households to acentralized treatment facility using gravity (andpumps where necessary).

The Conventional Gravity Sewer system is designedwith many branches. Typically, the network is subdivid-ed into primary (main sewer lines along main roads),secondary, and tertiary networks (network at the neigh-bourhood and household level).Conventional Gravity Sewers do not require onsite pre-treatment or storage of the wastewater. Because thewaste is not treated before it is discharged, the sewermust be designed to maintain self-cleansing velocity(i.e. a flow that will not allow particles to accumulate).A self-cleansing velocity is generally 0.6–0.75m/s. Aconstant downhill gradient must be guaranteed alongthe length of the sewer to maintain self-cleaning flows.When a downhill grade cannot be maintained, a pumpstation must be installed. Primary sewers are laidbeneath roads, and must be laid at depths of 1.5 to 3mto avoid damages caused by traffic loads.Access manholes are placed at set intervals along the

sewer, at pipe intersections and at changes in pipelinedirection (vertically and horizontally). The primary net-work requires rigorous engineering design to ensurethat a self-cleansing velocity is maintained, that man-holes are placed as required and that the sewer line cansupport the traffic weight. As well, extensive construc-tion is required to remove and replace the road above.

Adequacy Because they carry so much volume,Conventional Gravity sewers are only appropriate whenthere is a centralized treatment facility that is able toreceive the wastewater (i.e. smaller, decentralized facil-ities could easily be overwhelmed).Planning, construction, operation and maintenancerequire expert knowledge. Conventional Gravity Sewersare expensive to build and, because the installation of asewer line is disruptive and requires extensive coordina-tion between the authorities, construction companiesand the property owners, a professional managementsystem must be in place.When stormwater is also carried by the sewer (called aCombined Sewer), sewer overflows are required. Seweroverflows are needed to avoid hydraulic surcharge oftreatment plants during rain events. Infiltration into the

sewer main

street drainage



C.6C.6 Conventional Gravity SewerApplicable to:System 7, 8

87



Inputs/Outputs:Blackwater GreywaterBrownwater Stormwater�

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sewer in areas where there is a high water table maycompromise the performance of the ConventionalGravity Sewer.Conventional Gravity Sewers can be constructed in coldclimates as they are dug deep into the ground and thelarge and constant water flow resists freezing.

Health Aspects/Acceptance This technology pro-vides a high level of hygiene and comfort for the user atthe point of use. However, because the waste is con-veyed to an offsite location for treatment, the ultimatehealth and environmental impacts are determined bythe treatment provided by the downstream facility.

Maintenance Manholes are installed wherever thereis a change of grade or alignment and are used forinspection and cleaning. Sewers can be dangerous andshould only be maintained by professionals although, inwell-organised communities, the maintenance of terti-ary networks might be handed over to a well-trainedgroup of community members.

Pros & Cons:+ Stormwater and greywater can be managed at thesame time

+ Construction can provide short-term employment tolocal labourers

- A long time required to connect all homes- Not all parts and materials may be available locally- Difficult and costly to extend as a communitychanges and grows

- Requires expert design and construction supervision- Effluent and sludge (from interceptors) requires sec-ondary treatment and/or appropriate discharge

- High capital and moderate operation cost

References

_ ASCE (1992). Gravity Sanitary Sewer Design andConstruction, ASCE Manuals and Reports on EngineeringPractice No. 60, WPCF MOP No. FD-5. American Societyof Civil Engineers, New York.(A standard design text used in North America althoughlocal codes and standards should be assessed beforechoosing a design manual.)

_ Tchobanoglous, G. (1981). Wastewater Engineering: Col-lection and Pumping of Wastewater. McGraw-Hill, New York.

_ Tchobanoglous, G., Burton, FL. and Stensel, HD. (2003).Wastewater Engineering: Treatment and Reuse, 4th Edition.Metcalf & Eddy, New York.



88

C.6

Sometimes termed Underground Holding Tanks,Transfer Stations act as intermediate dumpingpoints for faecal sludge when it cannot be easilytransported to a (Semi-) Centralized Treatment facili-ty. A vacuum truck must empty Transfer Stationswhen they are full.

Manual, or small scale sludge emptiers who use theMAPET or the Gulper, for example, dump the sludge ina local transfer station rather than either a) dumping itillegally or b) trying to travel to a distant collectionpoint.When the Transfer Station is full, a vacuum truck emp-ties the contents and takes the sludge to a suitabletreatment facility. If the municipality or sewerageauthority is operating the Transfer Station they maycharge for permits to dump in the Transfer Station tooffset the cost of maintaining the facility.The Transfer Station consists of a parking place for thevacuum truck or sludge cart, a connection point for thedischarge hose, and a storage tank. The dumping pointat the Transfer Station should be built low enough tominimize spills when labourers are manually emptyingtheir sludge carts. Additionally, the Transfer Station should

include a vent, a trash screen to remove large debris(garbage) and a washing facility for vehicles.A variation is the Sewer Discharge Station (SDS), which islike a Transfer station, but is directly connected to aConventional Gravity Sewer main (for more information,refer to Technology Information Sheet C8: Sewer Dis-charge Stations). Sludge emptied into the SDS is releasedeither directly or at timed intervals into the sewer main tooptimize the performance of the sewer and the waste-water treatment plant, and/or reduce peak loads.

Adequacy Transfer Stations are especially appropriatefor dense, urban areas where there is no alternative dis-charge point (e.g. faecal sludge thickening pond). MultipleTransfer Stations in a city may help to reduce the inci-dence of illegal sewage dumping. The quality and quantityof the faecal sludge will significantly affect the treatmenttechnology that is subsequently required.Transfer stations are adequate when there are many loca-tions where small-scale sludge emptying is practiced. Theconstruction of a Transfer Station may also stimulate theindependent-emptying market. The site for the TransferStation should be easily accessible, conveniently located,and easy to use. The underground holding tank must be

inlet

outlet

sludge



C.7C.7 Transfer Station (Underground Holding Tank)Applicable to:System 1, 5, 6

89



Inputs/Outputs:Faecal Sludge

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well constructed to prevent leaching and/or surfacewater infiltration. Depending on the maintenance of thefacility, odours can be unappealing to local residents.However, the benefits gained compared to open-airdumping would likely offset the odour nuisance.The system for issuing permits or charging access feesmust be carefully designed so that those who mostneed the service are not excluded because of highcosts, while still generating enough income to be sus-tainable and well-maintained.

Health Aspects/Acceptance Transfer Stations havethe potential to significantly increase the health of acommunity by providing an inexpensive, local solutionto faecal sludge and septage disposal. By providing aTransfer Station, independent or small-scale emptiersare no longer forced to dump sludge illegally; homeown-ers are more motivated to have their pits emptied.Transfer Stations can be a low-cost, effective Convey-ance technology for faecal sludge. When pits are emp-tied regularly and illegal dumping is minimized, the over-all health of a community can be improved significantly.The location must be carefully chosen to maximize effi-ciency, while minimizing odours and disturbances tonearby residents.

Upgrading Transfer stations are relatively commonin North America. There, they are equipped with digitaldata recording devices to track quantities, input typesand origin, as well as collect data from the individualswho dump there. In this way, the facilitators can collectdetailed information and more accurately plan andadapt to the changing loads.

Maintenance Racks (screens) must be cleaned fre-quently to ensure a constant flow and prevent back-ups. Sand and grit must also be periodically removedfrom the holding tank. There should be a well-organizedsystem for emptying the transfer-station; if the holdingtank fills up and overflows it is no better than an over-flowing pit. The pad and loading area should be cleanedregularly to minimize odours, flies and other vectorsfrom becoming a nuisance.

Pros & Cons:+ Reduces transport distance and may encouragemore community-level emptying solutions

+ May reduce illegal dumping of faecal sludge+ Moderate capital and operating costs; can be offsetwith access permits

+ Potential for local job creation and incomegeneration

- Requires expert design and construction supervision- Sludge requires secondary treatment and/orappropriate discharge

References

_ African Development Fund (2005). Accra sewerageimprovement project- appraisal report. InfrastructureDepartment Central and West Regions.Available: www.afdb.org

_ Boot, NLD. and Scott, RD. (2008). Faecal Sludge in Accra,Ghana: problems of urban provision. Proceedings: SanitationChallenge: New Sanitation Concepts and Models ofGovernance. Wageningen, The Netherlands.

_ USEPA (1994). Guide to Septage Treatment and Disposal:EPA/625/R-94/002. United States EnvironmentalProtection Agency, Office of Research and Development,Cincinnati, Ohio, USA.Available: www.epa.gov



90

C.7

A Sewer Discharge Station (SDS) is a point along thesewermain that can be legally accessed and used fordischarging septage and sludge directly into thesewer so that it can be transported to a (Semi-) Cen-tralized Treatment facility. SDSs are intermediatetransfer points for sludge that cannot easily be trans-ported to a dedicated treatment facility. Sludge canbe dumped in a local SDS rather than either a) dump-ing it illegally or b) trying to travel to a distant col-lection point.

Sludge is dumped into the SDS and then eitherreleased directly to the sewer or held in a temporarystorage tank before being released to the sewer at aset time. Timed release can help prevent solids frombuilding up in the sewer line and also help optimize thetreatment efficiency of the treatment technology byreducing peak loading.A SDS consists of a parking place or discharge dock forthe vacuum truck or sludge cart and a connection pointfor the discharge hose. The SDS may also have a stor-age tank and pumping system. The dumping pointshould be built low enough to minimize spills whenlabourers are manually emptying their sludge carts.

Additionally, SDS should include a vent, a trash screento remove large debris (garbage) and a washing facilityfor vehicles. The station should be well protected andmaintained to prevent random dumping into the sewerand to ensure the safety of the users.A variation is a stand-alone Transfer Station that is notconnected to a sewer main (for more information, referto C7: Transfer Station (Underground Holding Tank)Technology Information Sheet). When the TransferStation is full, a vacuum truck must empty the storedcontents and take the sludge to a suitable treatmentfacility. If the municipality or sewerage authority is oper-ating the Transfer Station they may charge for permitsto dump in the Transfer Station to offset the cost ofmaintaining the facility.

Adequacy SDSs are especially appropriate fordense, urban areas where there is no alternative dis-charge point (e.g. faecal sludge thickening pond) andwhere there is a sewer main. Multiple SDSs in a citymay help to reduce the incidence of illegal sewagedumping. The quality and quantity of the faecal sludgewill significantly affect the treatment technology that isreceiving the sludge.

pump sewer

inlet

sludge



C.8C.8 Sewer Discharge Station (SDS)Applicable to:System 1, 5, 6

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Inputs/Outputs:Faecal Sludge

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SDSs are adequate when there are many locationswhere sludge is manually removed from pit latrines. Theconstruction of an SDS may also stimulate the inde-pendent-emptying market. The site for the SDS shouldbe easily accessible, conveniently located, and easy touse. If there is an underground holding tank for timedreleases of sludge, it must be well constructed to pre-vent leaching and/or surface water infiltration. Depen-ding on the maintenance of the facility, odours can beunappealing to local residents. However, the benefitsgained compared to open-air dumping would likely off-set the odour nuisance.The system for issuing permits or charging access feesmust be carefully designed so that those who mostneed the service are not excluded because of highcosts, while still generating enough income to be sus-tainable and well-maintained.

Health Aspects/Acceptance SDSs have thepotential to significantly increase the health of a com-munity by providing an inexpensive, local solution tofaecal sludge and septage disposal. Many informal set-tlements are located near to, if not directly on top of, asewer line. By building a legitimate access point, therisk of sewer damage and illegal access points may bereduced. When pits are emptied regularly and illegaldumping is minimized, the overall health of a communi-ty can be improved significantly.The location must be carefully chosen to maximize effi-ciency, while minimizing odours and disturbances tonearby residents.

Upgrading SDSs are relatively common in NorthAmerica, especially in rural communities where septictanks are common. There, they are equipped with digi-tal data recording devices to track quantities, inputtypes and origin, as well as collect data from the indi-viduals who dump there. In this way, the facilitators cancollect detailed information and more accurately planand adapt to the changing loads.

Maintenance Racks (screens) must be cleaned fre-quently to ensure a constant flow and prevent back-ups. Sand and grit must also be periodically removedfrom the holding tank. The pad and loading area shouldbe cleaned regularly to prevent smells, flies and othervectors from becoming a nuisance.

Pros & Cons:+ Reduces transport distance and may encouragemore community-level emptying solutions

+ May reduce illegal dumping of faecal sludge+ Moderate capital and operating costs; can beoffset with access permits


- Requires expert design and construction supervision- May cause blockages and disrupt sewer flow- Sludge requires secondary treatment and/orappropriate discharge

References

_ African Development Fund (2005). Accra sewerage improve-ment project- appraisal report. Infrastructure DepartmentCentral and West Regions.Available: www.afdb.org

_ Boot, NLD. and Scott, RD. (2008). Faecal Sludge in Accra,Ghana: problems of urban provision. Proceedings: SanitationChallenge: New Sanitation Concepts and Models ofGovernance. Wageningen, The Netherlands.

_ USEPA (1994). Guide to Septage Treatment and Disposal:EPA/625/R-94/002. United States EnvironmentalProtection Agency, Office of Research and Development,Cincinnati, Ohio, USA.Available: www.epa.gov



92

C.8


FunctionalGroupT:(Semi-)CentralizedTreatment

T(Semi-) Centralized Treatment

93

This section describes the technologies that can be used for the treatment of faecalsludge and blackwater.These treatment technologies are designed to accommodateincreased volumes of flow and provide, in most cases, improved removal of nutri-ents, organics and pathogens than household-centered storage technologies.



94

T

An Anaerobic Baffled Reactor (ABR) is an improvedseptic tank because of the series of baffles overwhich the incoming wastewater is forced to flow. Theincreased contact time with the active biomass(sludge) results in improved treatment.

The majority of settleable solids are removed in thesedimentation chamber at the beginning of the ABR,which typically represents 50% of the total volume.The up-flow chambers provide additional removal anddigestion of organic matter: BOD may be reduced byup to 90%, which is far superior to that of a conven-tional septic tank. As sludge is accumulating, desludg-ing is required every 2 to 3 years. Critical design para-meters include a hydraulic retention time (HRT)between 48 to 72 hours, up-flow velocity of the waste-water less than 0.6m/h and the number of up-flowchambers (2 to 3).

Adequacy This technology is easily adaptable andcan be applied at the household level or for a smallneighbourhood (refer to Technology Information SheetS10: Anaerobic Baffled Reactor for information aboutapplying an ABR at the household level).

A (semi-) centralized ABR is appropriate when there isan already existing Conveyance technology, such as aSolids-Free Sewer (C5). This technology is also appro-priate for areas where land may be limited since thetank is installed underground and requires a small area.It should not be installed where there is a high ground-water table as infiltration will affect the treatment effi-ciency and contaminate the groundwater.This technology can be efficiently designed for a dailyinflow of up to 200,000L/day. The ABR will not operateat full capacity for several months after installationbecause of the long start up time required for theanaerobic digestion of the sludge. Therefore, the ABRtechnology should not be used when the need for atreatment system is immediate.Because the ABR must be emptied regularly, a vacuumtruck should be able to access the location.ABRs can be installed in every type of climate althoughthe efficiency will be affected in colder climates.

Health Aspects/Acceptance Although the remo-val of pathogens is not high, the ABR is contained sousers do not come in contact with any of the waste-water or disease causing pathogens. Effluent and sludge

sludge

settlement zone

scum

outlet

inletliquid level

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T.1T.1 Anaerobic Baffled Reactor (ABR)Applicable to:System 7

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must be handled with care as they contain high levels ofpathogenic organisms.To prevent the release of potentially harmful gases, thetank should be vented.

Maintenance ABR tanks should be checked toensure that they are watertight and the levels of thescum and sludge should be monitored to ensure thatthe tank is functioning well. Because of the delicateecology, care should be taken not to discharge harshchemicals into the ABR.The sludge should be removed annually using a vacuumtruck to ensure proper functioning of the ABR.

Pros & Cons:+ Resistant to organic and hydraulic shock loads+ No electrical energy required+ Greywater can be managed concurrently+ Can be built and repaired with locally availablematerials

+ Long service life+ No real problems with flies or odours if used cor-rectly

+ High reduction of organics+ Moderate capital costs, moderate operating costsdepending on emptying; can be low cost dependingon number of users

- Requires constant source of water- Effluent requires secondary treatment and/orappropriate discharge

- Low reduction pathogens- Requires expert design and construction- Pre-treatment is required to prevent clogging

References

_ Bachmann, A., Beard, VL. and McCarty, PL. (1985).Performance Characteristics of the Anaerobic BaffledReactor. Water Research 19 (1): 99–106.

_ Foxon, KM., et al. (2004). The anaerobic baffled reactor(ABR): An appropriate technology for on-site sanitation.Water SA 30 (5) (Special edition).Available: www.wrc.org.za

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.(Design summary including and Excel®-based designprogram.)



96

T.1

An Anaerobic Filter is a fixed-bed biological reactor.As wastewater flows through the filter, particles aretrapped and organic matter is degraded by the bio-mass that is attached to the filter material.

This technology consists of a sedimentation tank orseptic tank (refer to Technology Information Sheet S9:Septic Tank) followed by one to three filter chambers.Filter material commonly used includes gravel,crushed rocks, cinder, or specially formed plasticpieces. Typical filter material sizes range from 12 to55mm in diameter. Ideally, the material will providebetween 90 to 300m2 of surface area per 1m3 of reac-tor volume. By providing a large surface area for thebacterial mass, there is increased contact betweenthe organic matter and the active biomass that effec-tively degrades it.The Anaerobic Filter can be operated in either upflowor downflow mode. The upflow mode is recommendedbecause there is less risk that the fixed biomass willbe washed out. The water level should cover the filtermedia by at least 0.3m to guarantee an even flowregime. Pre-treatment is essential to remove settleablesolids and garbage which may clog the filter.

Studies have shown that the HRT is the most importantdesign parameter influencing filter performance. AnHRT of 0.5 to 1.5 days is a typical and recommended. Amaximum surface-loading (i.e. flow per area) rate of2.8m/d has proven to be suitable. Suspended solidsand BOD removal can be as high as 85% to 90% but istypically between 50% and 80%. Nitrogen removal islimited and normally does not exceed 15% in terms oftotal nitrogen (TN).

Adequacy This technology is easily adaptable andcan be applied at the household level or a small neigh-bourhood (refer to Technology Information Sheet S11:Anaerobic Filter for information about applying anAnaerobic Filter at the household level).An Anaerobic Filter can be designed for a single houseor a group of houses that are using a lot of water forclothes washing, showering, and toilet flushing. It isonly appropriate if water use is high ensuring that thesupply of wastewater is constant.The Anaerobic Filter will not operate at full capacity forsix to nine months after installation because of the longstart up time required for the anaerobic biomass to sta-bilize. Therefore, the Anaerobic Filter technology should

sludge

settlement zone

scum

outlet

filter support

inlet inlettee

baffle

liquid level

access covers

filter



T.2T.2 Anaerobic FilterApplicable to:System 7

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not be used when the need for a treatment system isimmediate. Once working at full capacity it is a stabletechnology that requires little attention.The Anaerobic Filter should be watertight but it shouldstill not be constructed in areas with high groundwatertables or where there is frequent flooding.Depending on land availability and the hydraulic gradi-ent of the sewer, the Anaerobic Filter can be builtabove or below ground. It can be installed in every typeof climate, although the efficiency will be affected incolder climates.

Health Aspects/Acceptance Because the Ana-erobic Filter is underground, users should not come incontact with the influent or effluent. Infectious organ-isms are not sufficiently removed, so the effluentshould be further treated or discharged properly. Theeffluent, despite treatment, will still have a strongodour and care should be taken to design and locatethe facility such that odours do not bother communitymembers.To prevent the release of potentially harmful gases, theAnaerobic Filters should be vented.The desludging of the filter is hazardous and appropri-ate safety precautions should be taken.

Maintenance Active bacteria must be added tostart up the Anaerobic Filter. The active bacteria cancome from sludge from a septic tank that has beensprayed onto the filter material. The flow should begradually increased over time, and the filter should beworking at maximum capacity within six to ninemonths.With time, the solids will clog the pores of the filter.As well, the growing bacterial mass will become toothick and will break off and clog pores. A sedimenta-tion tank before the filter is required to prevent themajority of settleable solids from entering the unit.Some clogging increases the ability of the filter toretain solids. When the efficiency of the filter de-creases, it must be cleaned. Running the system inreverse mode to dislodge accumulated biomass andparticles cleans the filters. Alternatively, the filtermaterial can be removed and cleaned.

Pros & Cons:+ Resistant to organic and hydraulic shock loads+ No electrical energy required+ Can be built and repaired with locally availablematerials

+ Long service life+ No real problems with flies or odours if usedcorrectly

+ Moderate capital costs, moderate operating costsdepending on emptying; can be lowered dependingon the number of users

+ High reduction of BOD and solids- Requires constant source of water- Effluent requires secondary treatment and/orappropriate discharge

- Low reduction pathogens and nutrients- Requires expert design and construction- Long start up time

References

_ Morel, A. and Diener, S. (2006). Greywater Managementin Low and Middle-Income Countries, Review of differenttreatment systems for households or neighbourhoods.Swiss Federal Institute of Aquatic Science and Technology(Eawag), Dübendorf, Switzerland.(Short summary including case studies, page 28.)

_ Polprasert, C. and Rajput, VS. (1982). EnvironmentalSanitation Reviews: Septic Tank and Septic Systems.Environmental Sanitation Information Center, AIT,Bangkok, Thailand. pp 68–74. (Short design summary.)

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.(Design summary including Excel-based design program.)

_ von Sperlin, M. and de Lemos Chernicharo, CA. (2005).Biological Wastewater Treatment in Warm Climate Regions.Volume One. IWA, London. pp 728–804.(Detailed design instructions.)

_ Vigneswaran, S., et al. (1986). Environmental SanitationReviews: Anaerobic Wastewater Treatment-Attached growthand sludge blanket process. Environmental SanitationInformation Center, AIT, Bangkok, Thailand.(Design criteria and diagrams in Chapter 2.)



98

T.2

Waste Stabilization Ponds (WSPs) are large, man-made water bodies. The ponds are filled with waste-water that is then treated by naturally occurringprocesses. The ponds can be used individually, orlinked in a series for improved treatment. There arethree types of ponds, (1) anaerobic, (2) facultativeand (3) aerobic (maturation), each with differenttreatment and design characteristics.

For the most effective treatment, WSPs should belinked in a series of three of more with effluent beingtransferred from the anaerobic pond to the facultativepond and finally the aerobic pond. The anaerobic pondreduces solids and BOD as a pre-treatment stage. Thepond is a fairly deep man-made lake where the entiredepth of the pond is anaerobic. Anaerobic ponds arebuilt to a depth of 2 to 5m and have a relatively shortdetention time of 1 to 7 days. The actual design will de-pend on the wastewater characteristics and the loading;a comprehensive design manual should be consultedfor all types of WSPs. Anaerobic bacteria convert organ-ic carbon into methane and in the process, remove upto 60% of the BOD. Anaerobic ponds are capable oftreating strong wastewaters.

In a series of WSPs the effluent from the anaerobic pondis transferred to the facultative pond, where further BODis removed. A facultative pond is shallower than an anaer-obic pond and both aerobic and anaerobic processesoccur within the pond. The top layer of the pond receivesoxygen from natural diffusion, wind mixing and algae-driven photosynthesis. The lower layer is deprived of oxy-gen and becomes anoxic or anaerobic. Settleable solidsaccumulate and are digested on the bottom of the pond.The aerobic and anaerobic organisms work together toachieve BOD reductions of up to 75%. The pond shouldbe constructed to a depth of 1 to 2.5m and have a deten-tion time between 5 to 30 days.Following the anaerobic and the facultative ponds can beany number of aerobic (maturation) ponds to achieve ahighly polished effluent. An aerobic pond is commonlyreferred to as a maturation, polishing, or finishing pondbecause it is usually the last step in a series of ponds andprovides the final level of treatment. It is the shallowestof the ponds, usually constructed to a depth between 0.5to 1.5m deep to ensure that the sunlight penetrates thefull depth for photosynthesis. Because photosynthesis isdriven by sunlight, the dissolved oxygen levels are high-est during the day and drop off at night. Whereas anaer-

sludge

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T.3T.3 Waste Stabilization Ponds (WSP)Applicable to:System 1, 5, 6, 7, 8

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obic and facultative ponds are designed for BODremoval, maturation ponds are designed for pathogenremoval. Dissolved oxygen in the lake is provided bynatural wind mixing and by photosynthetic algae thatrelease oxygen into the water. If used in combinationwith algae and/or fish harvesting, this type of pond iseffective at removing the majority of nitrogen and phos-phorus from the effluent.To prevent leaching, the ponds should have a liner. Theliner can be clay, asphalt, compacted earth, or anotherimpervious material. To protect the pond from runoffand erosion, a protective berm should be constructedaround the pond using the excavated material.

Adequacy WSPs are among the most common andefficient methods of wastewater treatment around theworld. They are especially appropriate for rural commu-nities that have large, open unused lands, away fromhomes and public spaces. They are not appropriate forvery dense or urban areas.WSPs work in most climates, but are most efficient inwarm, sunny climates. In the case of cold climates, theretention times and loading rates can be adjusted sothat efficient treatment can be achieved.

Health Aspects/Acceptance Although effluentfrom aerobic ponds is generally low in pathogens, theponds should in no way be used for recreation or as adirect source of water for consumption or domestic use.

Upgrading Ideally, several aerobic ponds can bebuilt in series to provide a high level of pathogen remo-val. A final aquaculture pond can be used to generateincome and supply a locally grown food source.

Maintenance To prevent scum formation, excesssolids and garbage from entering the ponds, pre-treat-ment (with grease traps) is essential to maintain theponds. The pond must be desludged once every 10 to 20years. A fence should be installed to ensure that peopleand animals stay out of the area and excess garbagedoes not enter the ponds. Rodents may invade the bermand cause damage to the liner. Raising the water levelshould prompt rodents to evacuate the berm.

Care should be taken to ensure that plant material doesnot fall into the ponds. Vegetation or macrophytes thatare present in the pond should be removed as it mayprovide a breeding habitat for mosquitoes and preventlight from penetrating the water column.

Pros & Cons:+ High reduction in pathogens+ Can be built and repaired with locally availablematerials


+ Low operating cost+ No electrical energy required+ No real problems with flies or odours if designedcorrectly

- Requires expert design and supervision- Variable capital cost depending on the price of land- Requires large land area- Effluent/sludge requires secondary treatmentand/or appropriate discharge

References

_ Arthur, JP. (1983). Notes on the Design and Operation ofWaste Stabilization Ponds in Warm Climates of DevelopingCountries. The World Bank+ UNDP, Washington.

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems.WCB and McGraw-Hill, New York, USA.

_ Mara, DD. and Pearson, H. (1998). Design Manual for WasteStabilization Ponds in Mediterranean Countries.Lagoon Technology International Ltd., Leeds, England.

_ Mara, DD. (1997). Design Manual for Waste StabilizationPonds in India. Lagoon Technology International Ltd.,Leeds, England.

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.(Detailed description and Excel ® Spreadsheet codesfor design.)

_ von Sperlin, M. and de Lemos Chernicharo, CA. (2005).Biological Wastewater Treatment in Warm Climate Regions.Volume One. IWA, London. pp 495–656.



100

T.3

An Aerated Pond is a large, outdoor, mixed aerobicreactor. Mechanical aerators provide oxygen and keepthe aerobic organisms suspended andmixed with thewater to achieve a high rate of organic degradationand nutrient removal.

Increased mixing and aeration from the mechanicalunits means that the ponds can be deeper and can tol-erate much higher organic loads than a maturationpond. The increased aeration allows for increaseddegradation and increased pathogen removal. As well,because oxygen is introduced by the mechanical unitsand not by light-driven photosynthesis, the ponds canfunction in more northern climates. Influent should bescreened and pre-treated to remove garbage andcoarse particles that could interfere with the aerators.Because the aeration units mix the pond, a subsequentsettling tank is required to separate the effluent fromthe solids.The smaller area requirement (compared to a matura-tion pond) means that it is appropriate for both rural,and peri-urban environments.The pond should be built to a depth of 2 to 5m andshould have a detention time of 3 to 20 days.

To prevent leaching, the pond should have a liner. Theliner can be clay, asphalt, compacted earth, or anotherimpervious material. Using the fill that is excavated, aprotective berm should be built around the pond to pro-tect it from runoff and erosion.

Adequacy A mechanically aerated pond can efficient-ly handle high concentration influent and can reducepathogen levels significantly. It is especially importantthat electricity service is uninterrupted and that replace-ment parts are available to prevent extended downtimesthat may cause the pond to turn anaerobic.Aerated lagoons can function in a larger range of cli-mates than WSPs. They are most appropriate for regionswith large areas of inexpensive lands that are away fromhomes and businesses.

Health Aspects/Acceptance The pond is a largeexpanse of pathogenic wastewater; care must be takento ensure that no one comes in contact with, or goesinto the water.The aeration units can be dangerous to humans andanimals. Fences, signage, or other measures should betaken to prevent entry to the area.

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T.4T.4 Aerated PondApplicable to:System 1, 5, 6, 7, 8

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Maintenance A permanent skilled staff is requiredto repair and maintain aeration machinery. The pondmust be desludged once every 2 to 5 years.Care should be taken to ensure that the pond is notused as a garbage dump, especially considering thedamage that could be done to the aeration equipment.

Pros & Cons:+ Good resistance against shock loading+ High reduction in pathogens+ Construction can provide short-term employmentto local labourers

+ Requires large land area+ No real problems with insects or odours if designedcorrectly

- Effluent/sludge requires secondary treatmentand/or appropriate discharge

- Requires expert design and construction supervision- Requires full time operation and maintenance byskilled personnel

- Not all parts and materials may be available locally- Constant source of electricity is required- Moderate-high capital and variable operating costsdepending on the price of land, electricity

References

_ Arthur, JP. (1983). Notes on the Design and Operation ofWaste Stabilization Ponds in Warm Climates of DevelopingCountries. The World Bank + UNDP, Washington.(Notes on applicability and effectiveness.)

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems.WCB and McGraw-Hill, New York, USA. pp 527–558.(Comprehensive summary chapter.)

_ Tchobanoglous, G., Burton, FL. and Stensel, HD. (2003).Wastewater Engineering: Treatment and Reuse, 4th Edition.Metcalf & Eddy, New York. pp 840–85.(Detailed design and example problems.)



102

T.4

A Free-Water Surface ConstructedWetland is a seriesof flooded channels that aims to replicate the natural-ly occurring processes of a natural wetland, marsh orswamp. As water slowly flows through the wetland,particles settle, pathogens are destroyed, and organ-isms and plants utilize the nutrients.

Unlike The Horizontal Subsurface Flow ConstructedWetland (T6), the Free-Water Surface ConstructedWetland allows water to flow above ground, exposed tothe atmosphere and direct sunlight. The channel orbasin is lined with an impermeable barrier (clay or geo-textile) covered with rocks, gravel and soil and plantedwith native vegetation (e.g. cattails, reeds and/or rushes).The wetland is flooded with wastewater to a depth of 10to 45cm above ground level. As the water slowly flowsthrough the wetland, simultaneous physical, chemicaland biological processes filter solids, degrade organicsand remove nutrients from the wastewater.Raw blackwater should be pretreated to prevent theexcess accumulation of solids and garbage. Once in thepond, the heavier sediment particles settle out, alsoremoving nutrients that are attached to particles.Plants, and the communities of microorganisms that

they support (on the stems and roots), take up nutrientslike nitrogen and phosphorus. Chemical reactions maycause other elements to precipitate out of the waste-water. Pathogens are removed from the water by natu-ral decay, predation from higher organisms, sedimenta-tion and UV irradiation.Although the soil layer below the water is anaerobic,the plant roots exude (release) oxygen into the areaimmediately surrounding the root hairs, thus creatingan environment for complex biological and chemicalactivity.The efficiency of the Free-Water Surface ConstructedWetland also depends on how well the water is distrib-uted at the inlet. Wastewater can be input to the wet-land using weirs or by drilling holes in a distribution pipeto allow it to enter in even spaced intervals.

Adequacy Free-Water Surface Constructed Wetlandscan achieve high removals of suspended solids andmoderate removal of pathogens, nutrients and otherpollutants such as heavy metals. Shade from plants andprotection from wind mixing limit the dissolved oxygenin the water, therefore, this technology is only appropri-ate for low strength wastewater. Usually this requires

aquatic plants (macrophytes)

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T.5T.5 Free-Water Surface ConstructedWetlandApplicable to:System 1, 5, 6, 7, 8

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that Free-Water Surface Constructed Wetlands are onlyappropriate when they follow some type of primarytreatment to lower the BOD.Depending on the volume of water, and therefore thesize, wetlands can be appropriate for small sections ofurban areas or more appropriate for peri-urban andrural communities. This is a good treatment technologyfor communities that have a primary treatment facility(e.g. Septic Tanks (S9)). Where land is cheap and avail-able, it is a good option as long as the community isorganized enough to thoroughly plan and maintain thewetland for the duration of its life.This technology is best suited to warm climates but canbe designed to tolerate some freezing and periods oflow biological activity.

Health Aspects/Acceptance The open surfacecan act as a potential breeding ground for mosquitoes.However, good design and maintenance can preventthis.The Free-Water Surface Constructed Wetlands are gen-erally aesthetically pleasing, especially when they areintegrated into pre-existing natural areas.Care should be taken to prevent people from coming incontact with the effluent because of the potential fordisease transmission and the risk of drowning in deep-er waters.

Maintenance Regular maintenance should ensurethat water is not short-circuiting, or backing up becauseof fallen branches, garbage, or beaver dams blockingthe wetland outlet. Vegetation may have to be cut backor thinned out periodically.

Pros & Cons:+ Aesthetically pleasing and provides animal habitat+ High reduction in BOD and solids; moderatepathogen removal



+ No electrical energy required+ No real problems with flies or odours if used correctly- May facilitate mosquito breeding- Long start up time to work at full capacity- Requires large land area- Requires expert design and supervision- Moderate capital cost depending on land, liner, etc.;low operating costs

References

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems. WCB andMcGraw-Hill, New York, USA. pp 582–599.(Comprehensive summary chapter including solved pro-blems.)

_ Mara, DD. (2003). Domestic wastewater treatment in deve-loping countries. Earthscan, London, UK. pp 85–187.

_ Poh-Eng, L. and Polprasert, C. (1998). Constructed Wet-lands for Wastewater Treatment and Resource Recovery.Environmental Sanitation Information Center, AIT,Bangkok, Thailand.

_ Polprasert, C., et al. (2001). Wastewater Treatment II,Natural Systems for Wastewater Management. IHE Delft,The Netherlands. Chapter 6.

_ QLD DNR (2000). Guidelines for using free water surfaceconstructed wetlands to treat municipal sewage.Queensland Government, Department of Natural Resour-ces, Brisbane, Australia.Available: www.epa.qld.gov.au



104

T.5

AHorizontal Subsurface FlowConstructedWetland isa large gravel and sand-filled channel that is plantedwith aquatic vegetation. As wastewater flows hori-zontally through the channel, the filtermaterial filtersout particles and microorganisms degrade organics.

The water level in a Horizontal Subsurface Flow Con-structed Wetland is maintained at 5 to 15cm below thesurface to ensure subsurface flow. The bed should bewide and shallow so that the flow path of the water ismaximized. A wide inlet zone should be used to evenlydistribute the flow. Pre-treatment is essential to preventclogging and ensure efficient treatment.The bed should be lined with an impermeable liner (clayor geotextile) to prevent leaching. Small, round, evenlysized gravel (3–32mm in diameter) is most commonlyused to fill the bed to a depth of 0.5 to 1m. To limit clog-ging, the gravel should be clean and free of fines. Sandis also acceptable, but is more prone to clogging. Inrecent years, alternative filter materials such as PEThave been successfully used.The removal efficiency of the wetland is a function ofthe surface area (length multiplied by width), while thecross-sectional area (width multiplied by depth) deter-

mines the maximum possible flow. A well-designed inletthat allows for even distribution is important to preventshort-circuiting. The outlet should be variable so thatthe water surface can be adjusted to optimize treat-ment performance.The filter media acts as both a filter for removing solids,a fixed surface upon which bacteria can attach, and abase for the vegetation. Although facultative and anaer-obic bacteria degrade most organics, the vegetationtransfers a small amount of oxygen to the root zone sothat aerobic bacteria can colonize the area and degradeorganics as well. The plant roots play an important rolein maintaining the permeability of the filter.Any plant with deep, wide roots that can grow in the wet,nutrient-rich environment is appropriate. Phragmites aus-tralis (reed) is a common choice because it forms hori-zontal rhizomes that penetrate the entire filter depth.Pathogen removal is accomplished by natural decay, pre-dation by higher organisms, and sedimentation.

Adequacy Clogging is a common problem and there-fore the influent should be well settled with primarytreatment before flowing into the wetland. This technol-ogy is not appropriate for untreated domestic waste-

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T.6T.6 Horizontal Subsurface Flow ConstructedWetlandApplicable to:System 1, 5, 6, 7

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water (i.e. blackwater). This is a good treatment for com-munities that have primary treatment (e.g. Septic Tanks(S9) or WSPs (T3)) but are looking to achieve a higherquality effluent. This is a good option where land ischeap and available, although the wetland will requiremaintenance for the duration of its life.Depending on the volume of water, and therefore the size,this type of wetland can be appropriate for small sectionsof urban areas, peri-urban and rural communities. Theycan also be designed for single households.Horizontal Subsurface Flow Constructed Wetlands arebest suited for warm climates but they can be designedto tolerate some freezing and periods of low biologicalactivity.

Health Aspects/Acceptance The risk of mosqui-to breeding is reduced since there is no standing watercompared to the risk associated with Free-WaterSurface Constructed Wetlands (T5). The wetland is aes-thetically pleasing and can be integrated into wild areasor parklands.

Maintenance With time, the gravel will clog withaccumulated solids and bacterial film. The filter materi-al will require replacement every 8 to 15 or more years.Maintenance activities should focus on ensuring thatprimary treatment is effective at reducing the concen-tration of solids in the wastewater before it enters thewetland. Maintenance should also ensure that trees donot grow in the area as the roots can harm the liner.

Pros & Cons:+ Requires less space than a Free-Water SurfaceConstructed Wetland

+ High reduction in BOD, suspended solids andpathogens

+ Does not have the mosquito problems of the Free-Water Surface Constructed Wetland (T5)



+ No electrical energy required- Requires expert design and supervision- Moderate capital cost depending on land, liner, fill,etc.; low operating costs

- Pre-treatment is required to prevent clogging

References

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems. WCB andMcGraw-Hill, New York, USA. pp 599–609.(Comprehensive summary chapter including solved problems.)

_ Mara, DD. (2003). Domestic wastewater treatment indeveloping countries. Earthscan, London. pp 85–187.

_ Poh-Eng, L. and Polprasert, C. (1998). ConstructedWetlands for Wastewater Treatment and Resource Recovery.Environmental Sanitation Information Center, AIT,Bangkok, Thailand.

_ Polprasert, C., et al. (2001). Wastewater Treatment II,Natural Systems for Wastewater Management. Lectur Notes,IHE Delft, The Netherlands. Chapter 6.

_ Reed, SC. (1993). Subsurface Flow Constructed WetlandsFor Wastewater Treatment, A Technology Assessment.United States Environmental Protection Agency, USA.Available: www.epa.gov(Comprehensive design manual.)



106

T.6

A Vertical Flow Constructed Wetland is a filter bedthat is planted with aquatic plants. Wastewater ispoured or dosed onto the wetland surface fromabove using a mechanical dosing system. The waterflows vertically down through the filter matrix. Theimportant difference between a vertical and horizon-tal wetland is not simply the direction of the flowpath, but rather the aerobic conditions.

By dosing the wetland intermittently (four to ten timesa day), the filter goes through stages of being saturatedand unsaturated, and accordingly, different phases ofaerobic and anaerobic conditions. The frequency ofdosing should be timed such that the previous dose ofwastewater has time to percolate through the filter bedso that oxygen has time to diffuse through the mediaand fill the void spaces.The Vertical Flow Constructed Wetland can be designedas a shallow excavation or as an above ground con-struction. Each filter should have an impermeable linerand an effluent collection system. Vertical Flow Con-structed Wetlands are most commonly designed totreat wastewater that has undergone primary treat-ment. Structurally, there is a layer of gravel for drainage

(a minimum of 20cm), followed by layers of either sandand gravel (for settled effluent) or sand and fine gravel(for raw wastewater).The filter media acts as both a filter for removing solids,a fixed surface upon which bacteria can attach and abase for the vegetation. The top layer is planted and thevegetation is allowed to develop deep, wide roots whichpermeate the filter media.Depending on the climate, Phragmites australis, Typhacattails or Echinochloa Pyramidalis are common options.The vegetation transfers a small amount of oxygen to theroot zone so that aerobic bacteria can colonize the areaand degrade organics. However, the primary role of veg-etation is to maintain permeability in the filter and pro-vide habitat for microorganisms.During a flush phase, the wastewater percolates downthrough the unsaturated bed and is filtered by thesand/gravel matrix. Nutrients and organic material areabsorbed and degraded by the dense microbial popula-tions attached to the surface of the filter media and theroots. By forcing the organisms into a starvation phasebetween dosing phases, excessive biomass growth canbe decreased and porosity increased. A drainage net-work at the base collects the effluent. The design and

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T.7T.7 Vertical Flow ConstructedWetlandApplicable to:System 1, 5, 6, 7, 8

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size of the wetland is dependent on hydraulic and orga-nic loads.Pathogen removal is accomplished by natural decay,predation by higher organisms, and sedimentation.

Adequacy Clogging is a common problem. Therefore,the influent should be well settled with primary treat-ment before flowing into the wetland. This technology isnot appropriate for untreated domestic wastewater (i.e.blackwater).This is a good treatment for communities that have pri-mary treatment (e.g. Septic Tanks (S9) or WSPs (T3))but are looking to achieve a higher quality effluent. Thisis a good option where land is cheap and available,although the wetland will require maintenance for theduration of its life.There are many complex processes at work, and accord-ingly, there is a significant reduction in BOD, solids andpathogens. In many cases, the effluent will be adequatefor discharge without further treatment. Because of themechanical dosing system, this technology is mostappropriate for communities with trained maintenancestaff, constant power supply, and spare parts.Vertical Flow Constructed Wetlands are best suited towarm climates but can be designed to tolerate somefreezing and periods of low biological activity.

Health Aspects/Acceptance The risk of mosqui-to breeding is low since there is no standing water. Thesystem is generally aesthetic and can be integrated intowild areas or parklands. Care should be taken to ensurethat people do not come in contact with the influentbecause of the risk of infection.

Maintenance With time, the gravel will become cloggedwith accumulated solids and bacterial film. The materialmay have to be replaced every 8 to 15 or more years.Maintenance activities should focus on ensuring thatprimary treatment effectively lowers organics andsolids concentrations before entering the wetland.Testing may be required to determine the suitability oflocally available plants with the specific wastewater.The vertical system requires more maintenance andtechnical expertise than other wetland technologies.

Pros & Cons:+ Does not have the mosquito problems of the Free-Water Surface Constructed Wetland

+ Less clogging than in a Horizontal Flow ConstructedWetland

+ Requires less space than a Free-Water SurfaceConstructed Wetland

+ High reduction in BOD, suspended solids andpathogens


+ Constant source of electrical energy required- Not all parts and materials may be available locally- Requires expert design and supervision- Moderate capital cost depending on land, liner, fill,etc.; low operating costs

- Pre-treatment is required to prevent clogging- Dosing system requires more complex engineering

References

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems.WCB and McGraw-Hill, New York, USA. pp 599–609.(Comprehensive summary chapter including solvedproblems.)

_ Mara, DD. (2003). Domestic wastewater treatment indeveloping countries. London, Earthscan, pp 85–187.

_ Poh-Eng, L. and Polprasert, C. (1998). ConstructedWetlands for Wastewater Treatment and Resource Recovery.Environmental Sanitation Information Center, AIT,Bangkok, Thailand.

_ Polprasert, C., et al. (2001). Wastewater Treatment II,Natural Systems for Wastewater Management. LectureNotes. IHE Delft, The Netherlands. Chapter 6.

_ Reed, SC. (1993). Subsurface Flow Constructed WetlandsFor Wastewater Treatment, A Technology Assessment.United States Environmental Protection Agency, USA.Available: www.epa.gov(Comprehensive design manual.)



108

T.7

A Trickling Filter is a fixed bed, biological filter thatoperates under (mostly) aerobic conditions. Pre-set-tled wastewater is ‘trickled’ or sprayed over the filter.As the water migrates through the pores of the filter,organics are degraded by the biomass covering thefilter material.

The Trickling Filter is filled with a high specific surface-areamaterial such as rocks, gravel, shredded PVC bottles,or special pre-formed filter material. A material with a spe-cific surface area between 30 and 900m2/m3 is desirable.Pre-treatment is essential to prevent clogging and toensure efficient treatment. The pre-treated wastewater is‘trickled’ over the surface of the filter. Organisms thatgrow in a thin biofilm over the surface of themedia oxidizethe organic load in the wastewater to carbon dioxide andwater while generating new biomass.The incoming wastewater is sprayed over the filter withthe use of a rotating sprinkler. In this way, the filtermedia goes through cycles of being dosed and exposedto air. However, oxygen is depleted within the biomassand the inner layers may be anoxic or anaerobic.The filter is usually 1 to 3m deep but filters packed withlighter plastic filling can be up to 12m deep. The ideal

filter material has a high surface to volume ratio, is light,durable and allows air to circulate. Whenever it is avail-able, crushed rock or gravel is the cheapest option. Theparticles should be uniform such that 95% of the parti-cles have a diameter between 7 and 10cm.Both ends of the filter are ventilated to allow oxygen totravel the length of the filter. A perforated slab thatallows the effluent and excess sludge to be collectedsupports the bottom of the filter.With time, the biomass will grow thick and the attachedlayer will be deprived of oxygen; it will enter an endoge-nous state, will lose its ability to stay attached and willslough off. High-rate loading conditions will also causesloughing. The collected effluent should be clarified in asettling tank to remove any biomass that may have dis-lodged from the filter. The hydraulic and nutrient load-ing rate (i.e. how much wastewater can be applied tothe filter) is determined based on the characteristics ofthe wastewater, the type of filter media, the ambienttemperature, and the discharge requirements.

Adequacy This technology can only be used follow-ing primary clarification since high solids loading willcause the filter to clog. A skilled operator is required to

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T.8T.8 Trickling FilterApplicable to:System 1, 5, 6, 7, 8

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monitor and repair the filter and the pump in case ofproblems. A low-energy (gravity) trickling system canbe designed, but in general, a continuous supply ofpower and wastewater is required.Compared to other technologies (e.g. WSPs), tricklingfilters are compact, although they are still are best suit-ed for peri-urban or large, rural settlements.Trickling Filters can be built in almost all environments,although special adaptations for cold climates arerequired.

Health Aspects/Acceptance The odour and flyproblems require that the filter be built away fromhomes and businesses. There must be appropriatemeasures taken for pre-treatment, effluent dischargeand solids treatment, all of which can still pose healthrisks.

Maintenance The sludge that accumulates on thefilter must be periodically washed away to prevent clog-ging. High hydraulic loading rates can be used to flushthe filter.The packing must be kept moist. This may be problem-atic at night when the water flow is reduced or whenthere are power failures.

Pros & Cons:+ Can be operated at a range of organic and hydraulicloading rates

+ Small land area required compared to ConstructedWetlands

- High capital costs and moderate operating costs- Requires expert design and construction- Requires constant source of electricity and constantwastewater flow

- Flies and odours are often problematic- Not all parts and materials may be available locally- Pre-treatment is required to prevent clogging- Dosing system requires more complex engineering

References

_ U.S. EPA (2000). Wastewater Technology Fact Sheet-Trickling Filters, 832-F-00-014. US Environmental ProtectionAgency, Washington.Available: www.epa.gov(Design summary including tips for trouble shooting.)

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.(Provides a short description of the technology.)

_ Tchobanoglous, G., Burton, FL. and Stensel, HD. (2003).Wastewater Engineering: Treatment and Reuse, 4th Edition.Metcalf & Eddy, New York. pp 890–930 .(Detailed description and example calculations.)



110

T.8

The Upflow Anaerobic Sludge Blanket Reactor (UASB)is a single tank process. Wastewater enters the reac-tor from the bottom, and flows upward. A suspendedsludge blanket filters and treats the wastewater asthe wastewater flows through it.

The sludge blanket is comprised of microbial gran-ules, i.e. small agglomerations (0.5 to 2mm in diam-eter) of microorganisms that, because of their weight,resist being washed out in the upflow. The microor-ganisms in the sludge layer degrade organic com-pounds. As a result, gases (methane and carbon diox-ide) are released. The rising bubbles mix the sludgewithout the assistance of any mechanical parts.Sloped walls deflect material that reaches the top ofthe tank downwards. The clarified effluent is extract-ed from the top of the tank in an area above thesloped walls.After several weeks of use, larger granules of sludgeform which in turn act as filters for smaller particlesas the effluent rises through the cushion of sludge.Because of the upflow regime, granule-forming organ-isms are preferentially accumulated as the others arewashed out.

The gas that rises to the top is collected in a gas collec-tion dome and can be used as energy (biogas).An upflow velocity of 0.6 to 0.9m/h must be maintainedto keep the sludge blanket in suspension.

Adequacy A UASB is not appropriate for small orrural communities without a constant water supply orelectricity. A skilled operator is required to monitorand repair the reactor and the pump in case of prob-lems. Although the technology is simple to design andbuild, it is not well proven for domestic wastewater,although new research is promising.The UASB reactor has the potential to produce higherquality effluent than septic tanks (S9), and can do soin a smaller reactor volume. Although it is a well-established process for large-scale industrial waste-water treatment processes, its application to domes-tic sewage is still relatively new. Typically it is used forbrewery, distillery, food processing and pulp andpaper waste since the process can typically remove85% to 90% of Chemical Oxygen Demand (COD).Where the influent is low strength, the reactor maynot work properly. Temperature will also affect per-formance.

outlet

inlet

biogas

gasbubbles sludge granule



T.9T.9 Upflow Anaerobic Sludge Blanket Reactor (UASB)Applicable to:System 1, 5, 6, 7, 8

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Health Aspects/Acceptance UASB is a central-ized treatment technology that must be operated andmaintained by professionals. As with all wastewaterprocesses, operators should take proper health andsafety measures while working in the plant.

Maintenance Desludging is infrequent and only ex-cess sludge is removed once every 2 to 3 years.A permanent operator is required to control and moni-tor the dosing pump.

Pros & Cons:+ High reduction in organics+ Can withstand high organic loading rates (up to10kg BOD/m3/d) and high hydraulic loading rates

+ Low production sludge (and thus, infrequentdesludging required)

+ Biogas can be used for energy (but usually requiresscrubbing first)

- Difficult to maintain proper hydraulic conditions(upflow and settling rate must be balanced)

- Long start up time- Treatment may be unstable with variable hydraulicand organic loads

- Constant source of electricity is required- Not all parts and materials may be available locally- Requires expert design and construction supervision

References

_ Crites, R. and Tchobanoglous, G. (1998). Small and de-centralized wastewater management systems.WCB and McGraw-Hill, New York, USA.(Short overview.)

_ Lettinga, G., Roersma, R. and Grin, P. (1983). AnaerobicTreatment of Raw Domestic Sewage at AmbientTemperatures Using a Granular Bed UASB Reactor Bio-technology and Bioengineering 25 (7): 1701–1723.(The first paper describing the process.)

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.(Short overview.)

_ von Sperlin, M. and de Lemos Chernicharo, CA. (2005).Biological Wastewater Treatment in Warm Climate Regions.Volume One. IWA, London, pp 741–804.(Detailed design information)

_ Tare, V. and Nema, A. (n.d). UASB Technology-expectationsand reality. United Nations Asian and Pacific Centre forAgricultural Engineering and Machinery.Available: http://unapcaem.org(Assessment of UASB installations in India.)

_ Vigneswaran, S., et al. (1986). Environmental SanitationReviews: Anaerobic Wastewater Treatment- Attached growthand sludge blanket process. Environmental SanitationInformation Center, AIT, Bangkok, Thailand.(Chapter 5 provides a good technical overview.)



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T.9

Activated Sludge is a multi-chamber reactor unit thatmakes use of (mostly) aerobic microorganisms todegrade organics in wastewater and to produce ahigh-quality effluent. To maintain aerobic conditionsand to the keep the active biomass suspended, a con-stant and well-timed supply of oxygen is required.

Different configurations of the Activated Sludgeprocess can be employed to ensure that the wastewateris mixed and aerated (with either air or pure oxygen) inan aeration tank. The microorganisms oxidize theorganic carbon in the wastewater to produce new cells,carbon dioxide and water. Although aerobic bacteria arethe most common organisms, aerobic, anaerobic,and/or nitrifying bacteria along with higher organismscan be present. The exact composition depends on thereactor design, environment, and wastewater charac-teristics. During aeration and mixing, the bacteria formsmall clusters, or flocs. When the aeration stops, themixture is transferred to a secondary clarifier where theflocs are allowed to settle out and the effluent moveson for further treatment or discharge. The sludge isthen recycled back to the aeration tank, where theprocess is repeated.

To achieve specific effluent goals for BOD, nitrogen andphosphorus, different adaptations and modificationshave been made to the basic Activated Sludge design.Aerobic conditions, nutrient-specific organisms (espe-cially for phosphorus), recycle design and carbon dos-ing, among others, have successfully allowed ActivatedSludge processes to achieve high treatment efficiencies.

Adequacy Activated Sludge is only appropriate for acentralized treatment facility with a well-trained staff,constant electricity and a highly developed centralizedmanagement system to ensure that the facility is oper-ated and maintained correctly.Activated Sludge processes are one part of a complextreatment system. They are used following primarytreatment (that removes settleable solids) and before afinal polishing step. The biological processes that occurare effective at removing soluble, colloidal and particu-late organic materials for biological nitrification anddenitrification and for biological phosphorus removal.This technology is effective for the treatment of largevolumes of flows: 10,000 to 1,000,000 people.Highly trained staff is required for maintenance andtrouble-shooting. The design must be based on an accu-

compressed air

recirculation extracted sludge

clarifier

sludge

inlet outlet



T.10T.10 Activated SludgeApplicable to:System 1, 5, 6, 7

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Outputs: Treated Sludge Effluent

rate estimation of the wastewater composition and vol-ume. Treatment efficiency can be severely compro-mised if the plant is under- or overdesigned.An Activated Sludge process is appropriate for almostevery climate.

Health Aspects/Acceptance Because of spacerequirements, Centralized treatment facilities are gen-erally located away from the densely populated areasthat they serve. Although the effluent produced is ofhigh quality, it still poses a health risk and should not behandled directly.

Maintenance The mechanical equipment (mixers,aerators and pumps) must be maintained constantly. Aswell, the influent and effluent must be monitored con-stantly to ensure that there are no abnormalities thatcould kill the active biomass and to ensure that detri-mental organisms have not developed that could impairthe process (e.g. filamentous bacteria).

Pros & Cons:+ Good resistance against shock loading+ Can be operated at a range of organic and hydraulicloading rates

+ High reduction of BOD and pathogens (up to 99%)+ Can be modified to meet specific discharge limits- Prone to complicated chemical and microbiologicalproblems

- Effluent might require further treatment/ disinfec-tion before discharge

- Not all parts and materials may be available locally- Requires expert design and supervision- High Capital cost; high operation cost- Constant source of electricity is required- Effluent and sludge require secondary treatmentand/or appropriate discharge

References

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems.WCB and McGraw-Hill, New York, USA. pp 451–504.(Comprehensive summary including solved problems.)

_ Ludwig, HF. and Mohit, K. (2000). Appropriate technologyfor municipal sewerage/Excreta management in develo-ping countries, Thailand case study. The Environmentalist20(3): 215–219.(Assessment of the appropriateness of Activated Sludgefor Thailand.)

_ von Sperling, M. and de Lemos Chernicharo, CA. (2005).Biological Wastewater Treatment in Warm Climate Regions,Volume Two. IWA, London.




114

T.10

Sedimentation or Thickening Ponds are simple set-tling ponds that allow the sludge to thicken anddewater. The effluent is removed and treated, whilethe thickened sludge can be treated in a subsequenttechnology.

Faecal sludge is not a uniform product and therefore,its treatment must be specific to the characteristicsof the specific sludge. In general, there are two typesof faecal sludges: high strength (originating fromlatrines and unsewered public toilets) and lowstrength (originating from Septic Tanks (S9)). Highstrength sludge is still rich in organics and has notundergone significant degradation, which makes itdifficult to dewater. Low strength sludge has under-gone significant anaerobic degradation and is moreeasily dewatered.In order to be properly dried, high strength sludgesmust first be stabilized. Allowing the high strengthsludge to degrade anaerobically in Settling/ThickeningPonds can do this. The same type of pond can be usedto thicken low strength sludge, although it undergoesless degradation and requires more time to settle. Thedegradation process may actually hinder the settling of

low strength sludge because the gases produced bub-ble up and re-suspend the solids. To achieve maximumefficiency, the loading and resting period should notexceed 4 to 5 weeks, although much longer cycles arecommon. When a 4-week loading, and 4-week restingcycle is used, total solids (TS) can be increased to 14%(depending on the initial concentration).As the sludge settles and digests, the supernatant mustbe decanted and treated separately. The thickenedsludge can then go on to be dried or composted further.

Adequacy Settling/Thickening Ponds are appropri-ate where there is inexpensive, available space that isfar from homes and businesses; it should be on theedge of the community.The sludge is not hygienized and requires further treat-ment before disposal. Ideally this technology should becoupled with an onsite Drying (T13) or Co-Composting(T14) facility to generate a hygienic product.Trained staff for operation and maintenance is requiredto ensure proper functioning.This is a low-cost option that can be installed in mosthot and temperate climates. Excessive rain may preventthe sludge from properly settling and thickening.

thickened sludge

scum

supernatantramp for desludging liquid outlet

grid



T.11T.11 Sedimentation/Thickening PondsApplicable to:System 1, 5, 6, 7, 8

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Inputs: Faecal Sludge


Health Aspects/Acceptance The incoming sludgeis pathogenic, so workers should be equipped withproper protection (boots, gloves, and clothing). Thethickened sludge is also infectious, although it is easierto handle and less prone to splashing and spraying.The pond may cause a nuisance for nearby residentsdue to bad odours and the presence of flies. Therefore,the pond should be located sufficiently away fromurban centres.

Maintenance Maintenance is an important aspectof a well-functioning pond, although it is not intensive.The discharging area must be maintained and keptclean to reduce the potential for disease transmissionand nuisance (flies and odours). Grit, sand, and solidwaste that are discharged along with the sludge mustbe removed.The thickened sludge must be removed mechanically(front end loader or specialized equipment) when thesludge has thickened sufficiently.


+ Low capital cost; low operating cost+ Potential for local job creation and incomegeneration

+ No electrical energy required- Requires large land area- Odours and flies are normally noticeable- Long storage times- Requires front-end loader for monthly desludging- Requires expert design and operation

References

_ Heinss, U., Larmie, SA. and Strauss, M. (1999).Characteristics of Faecal Sludges and their Solids-LiquidSeparation. Eawag/Sandec Report, Dübendorf, Switzerland.Available: www.sandec.ch

_ Heinss, U., Larmie, SA. and Strauss, M. (1998). SolidsSeparation and Pond Systems for the Treatment of FaecalSludges in the Tropics-Lessons Learnt and Reccomendationsfor Preliminary Design. Second Edition. Eawag/SandecReport 05/98, Dübendorf, Switzerland.Available: www.sandec.ch

_ Montangero, A. and Strauss, M. (2002). Faecal SludgeTreatment. Lecture Notes, IHE Delft.Available: www.sandec.ch



116

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drainage water, to treatment

outlet

drainage layer

80cm



T.12T.12 Unplanted Drying BedsApplicable to:System 1, 5, 6, 7, 8

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An Unplanted Drying Bed is a simple, permeable bedthat, when loaded with sludge, collects percolatedleachate and allows the sludge to dry by evaporation.Approximately 50% to 80% of the sludge volumedrains off as liquid. The sludge however, is not stabi-lized or treated.

The bottom of the drying bed is lined with perforatedpipes that drain away the leachate. On top of the pipesare layers of sand and gravel that support the sludgeand allow the liquid to infiltrate and collect in the pipe.The sludge should be loaded to approximately 200kgTS/m2 and it should not be applied in layers that are toothick (maximum 20cm), or the sludge will not dry effec-tively. The final moisture content after 10 to 15 days ofdrying should be approximately 60%. A splash plateshould be used to prevent erosion of the sand layer andto allow the even distribution of the sludge.When the sludge is dried, it must be separated fromthe sand layer and disposed of. The effluent that is col-lected in the drainage pipes must also be treated prop-erly. The top sand layer should be 25 to 30cm thick assome sand will be lost each time the sludge is manual-ly removed.

Adequacy Sludge drying is an effective way ofdecreasing the volume of sludge, which is especiallyimportant when it requires transportation elsewhere fordirect use, Co-Composting (T14), or disposal. The tech-nology is not effective at stabilizing the organic fractionor decreasing the pathogenic content.Sludge drying beds are appropriate for small to mediumcommunities with populations up to 100,000 peopleand there is inexpensive, available space that is far fromhomes and businesses. It is best suited to rural and peri-urban areas. If it is designed to service urban areas, itshould be on the edge of the community.The sludge is not hygienized and requires further treat-ment before disposal. Ideally this technology should becoupled with a Co-Composting (T14) facility to generatea hygienic product.Trained staff for operation and maintenance is requiredto ensure proper functioning.This is a low-cost option that can be installed in mosthot and temperate climates. Excessive rain may preventthe sludge from properly settling and thickening.

Health Aspects/Acceptance The incoming sludgeis pathogenic, so workers should be equipped withproper protection (boots, gloves, and clothing). Thethickened sludge is also infectious, although it is easierto handle and less prone to splashing and spraying.The pond may cause a nuisance for nearby residentsdue to bad odours and the presence of flies. Therefore,the pond should be located sufficiently away fromurban centres.

Maintenance The Unplanted Drying Bed should bedesigned with maintenance in mind; access for humansand trucks to pump in the sludge and remove the driedsludge should be taken into consideration.Dried sludge must be removed every 10 to 15 days. Thedischarge area must be kept clean and the effluentdrains should be flushed regularly. Sand must bereplaced when the layer gets thin.


+ Moderate Capital Cost; low operating Cost+ Potential for local job creation and incomegeneration

+ No electrical energy required- Requires large land area- Odours and flies are normally noticeable- Long storage times- Requires expert design and operation- Labour intensive removal- Leachate requires secondary treatment

References


_ Heinss, U. and Koottatep, T. (1998). Use of Reed Beds forFaecal Sludge Dewatering – A Synopsis of ReviewedLiterature and Interim Results of Pilot Investigations withSeptage Treatment in Bangkok, Thailand. UEEM ProgramReport, AIT/EAWAG, Dübendorf, Switzerland.(Comparison to planted drying beds.)


_ Tchobanoglous, G., Burton, F.L. and Stensel, H.D. (2003).Wastewater Engineering: Treatment and Reuse, 4th Edition.Metcalf & Eddy, New York.



118

T.12

A Planted Drying Bed is similar to an UnplantedDrying Bed (T12) with the benefit of increased tran-spiration. The key feature is that the filters do notneed to be desludged after each feeding/dryingcycle. Fresh sludge can be applied directly onto theprevious layer; it is the plants and their root systemsthat maintain the porosity of the filter.

This technology has the benefit of dewatering as well asstabilizing the sludge. Also, the roots of the plants cre-ate pathways through the thickening sludge to allowwater to escape more easily.The appearance of the bed is similar to a Vertical FlowConstructed Wetland (T7). The beds are filled with sandand gravel to support the vegetation. Instead of efflu-ent, sludge is applied to the surface and the filtrateflows down through the subsurface to collect in drains.A general design for layering the bed is: (1) 250mm ofcoarse gravel (grain diameter of 20mm); (2) 250mm offine gravel (grain diameter of 5 mm); and (3)100–150mm of sand. Free space (1m) should be leftabove the top of the sand layer to account for about 3to 5 years of accumulation.

When the bed is constructed, the plants should beplanted evenly and allowed to establish themselvesbefore the sludge is applied. Echinochloa pyramidalis,Cattails or Phragmites are suitable plants depending onthe climate.Sludge should be applied in layers between 75 to100mm and should be reapplied every 3 to 7 days de-pending on the sludge characteristics, the environmentand operating constraints. Sludge application rates ofup to 250kg/m2/year have been reported.The sludge can be removed after 2 to 3 years (althoughthe degree of hygienization will vary with climate) andused for agriculture.

Adequacy This is an effective technology at decreas-ing sludge volume (down to 50%) through decomposi-tion and drying, which is especially important when thesludge needs to be transported elsewhere for directuse, Co-Composting (T14), or disposal.Planted drying beds are appropriate for small to medi-um communities with populations up to 100,000 peo-ple. It should be located on the edge of the community.The sludge is not hygienized and requires further treat-

ventilation pipe

wall

drainage pipeconcrete blocksor coarse gravel

mesh gravel

aquatic plants(macrophytes)

screeningchamber

outletdrainage layer

sludgesand



T.13T.13 Planted Drying BedsApplicable to:System 1, 5, 6, 7, 8

119



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Outputs: Treated Sludge EffluentForage

ment before disposal. Ideally this technology should becoupled with a Co-Composting (T14) facility to generatea hygienic product.Trained staff for operation and maintenance is requiredto ensure proper functioning.

Health Aspects/Acceptance Because of the plea-sing aesthetics, there should be few problems withacceptance, especially if located away dense housing.Faecal sludge is hazardous and anyone working with itshould wear protective clothing, boots and gloves.

Maintenance The drains must be maintained andthe effluent must be properly collected and disposed of.The plants should be periodically thinned and/or har-vested.

Pros & Cons:+ Can handle high loading+ Fruit or forage growing can generate income+ Can be built and repaired with locally availablematerials


+ No electrical energy required– Requires large land area– Odours and flies are normally noticeable– Long storage times– Requires expert design and operation– Labour intensive removal– Leachate requires secondary treatment

References


_ Heinss, U. and Koottatep, T. (1998). Use of Reed Beds forFaecal Sludge Dewatering - A Synopsis of ReviewedLiterature and Interim Results of Pilot Investigations withSeptage Treatment in Bangkok, Thailand. UEEM ProgramReport , AIT/EAWAG, Dübendorf, Switzerland.Available: www.sandec.ch

_ Koottatep, T., et al. (2004). Treatment of septage in con-structed wetlands in tropical climate – Lessons learnt afterseven years of operation. Water Science & Technology,51(9): 119–126.Available: www.sandec.ch


_ Tchobanoglous, G., Burton, FL. and Stensel, HD. (2003).Wastewater Engineering: Treatment and Reuse, 4th Edition.Metcalf & Eddy, New York, pp 1578.

_ Kengne Noumsi, IM. (2008). Potentials of Sludge dryingbeds vegetated with Cyperus papyrus L. and Echinochloapyramidalis (Lam.) Hitchc. & Chase for faecal Sludge treat-ment in tropical regions. [PhD dissertation]. Yaounde(Cameroon): University of Yaounde.Available: www.nccr-north-south.unibe.ch



120

T.13

Co-Composting is the controlled aerobic degradationof organics using more than one feedstock (Faecalsludge and Organic solid waste). Faecal sludge has ahigh moisture and nitrogen content while biodegrad-able solid waste is high in organic carbon and hasgood bulking properties (i.e. it allows air to flow andcirculate). By combining the two, the benefits of eachcan be used to optimize the process and the product.

For dewatered sludges, a ratio of 1:2 to 1:3 of dewa-tered sludge to solid waste should be used. Liquidsludges should be used at a ratio of 1:5 to 1:10 of liq-uid sludge to solid waste.There are two types of Co-Composting designs: open andin-vessel. In open composting, the mixed material (sludgeand solid waste) is piled into long heaps called windrowsand left to decompose. Windrow piles are turned period-ically to provide oxygen and ensure that all parts of thepile are subjected to the same heat treatment. Windrowpiles should be at least 1m high, and should be insulatedwith compost or soil to promote an even distribution ofheat inside the pile. Depending on the climate and avail-able space, the facility may be covered to prevent excessevaporation and protection from rain.

In-vessel composting requires controlled moisture andair supply, as well as mechanical mixing. Therefore, it isnot generally appropriate for decentralized facilities.Although the composting process seems like a simple,passive technology, a well-working facility requirescareful planning and design to avoid failure.

Adequacy A Co-Composting facility is only appropri-ate when there is an available source of well-sortedbiodegradable solid waste. Mixed solid waste withplastics and garbage must first be sorted. Whendone carefully, Co-Composting can produce a clean,pleasant, beneficial product that is safe to touch andwork with. It is a good way to reduce the pathogenload in sludge.Depending on the climate (rainfall, temperature andwind) the Co-Composting facility can be built toaccommodate the conditions. Since moisture plays animportant role in the composting process, coveredfacilities are especially recommended where there isheavy rainfall. The facility should be located close tothe sources of organic waste and faecal sludge (to min-imize transport) but to minimize nuisances, it shouldnot be too close to homes and businesses.

sludge sludge + organicsorganics



T.14T.14 Co-CompostingApplicable to:System 1, 5, 6, 7, 8

121



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Inputs: Faecal Sludge Organics


A well-trained staff is necessary for the operation andmaintenance of the facility.

Health Aspects/Acceptance Although the finishedcompost can be safely handled, care should be takenwhen handling the faecal sludge. Workers should wearprotective clothing and appropriate respiratory equip-ment if the material is found to be dusty.

Upgrading Robust grinders for shredding largepieces of solid waste (i.e. small branches and coconutshells) and pile turners help to optimize the process,reduce manual labour, and ensure a more homogenousend product.

Maintenance The mixture must be carefully de-signed so that it has the proper C:N ratio, moisture andoxygen content. If facilities exist, it would be useful tomonitor helminth egg inactivation as a proxy measureof sterilization. Maintenance staff must carefully moni-tor the quality of the input materials, keep track of theinflows, outflows, turning schedules, and maturingtimes to ensure a high quality product. Manual turningmust be done periodically with either a front-end loaderor by hand. Forced aeration systems must be carefullycontrolled and monitored.

Pros & Cons:+ Easy to set up and maintain with appropriatetraining

+ Provides a valuable resource that can improvelocal agriculture and food production

+ High removal of helminth eggs possible(< 1 egg viable egg/g TS)



+ No electrical energy required- Long storage times- Requires expert design and operation- Labour intensive- Requires large land area (that is well located)

References

_ Cofie, O., et al. (2006). Solid–liquid separation of faecalSludge using drying beds in Ghana: Implications fornutrient recycling in urban agriculture. Water Research40(1): 75–82.

_ Koné, D., et al. (2007). Helminth eggs inactivation efficien-cy by faecal Sludge dewatering and co-composting in tropi-cal climates. Water Research 41(19): 4397–4402.

_ Obeng, LA. and Wright, FW. (1987). Integrated ResourceRecover. The Co-Composting of Domestic Sold and HumanWastes. The World Bank + UNDP, Washington.

_ Shuval, H I., et al. (1981). Appropriate Technology for WaterSupply and Sanitation; Night-soil Composting. UNDP/WBContribution to the IDWSSD. The World Bank, Washington.

The following reports can all be found in the Faecal SludgeCo-Composting section of the Sandec Website:www.sandec.ch

_ Montangero, A., et al. (2002). Co-composting of FaecalSludge and Soil Waste. Sandec/IWMI, Dübendorf,Switzerland.

_ Strauss, M., et al. (2003). Co-composting of Faecal Sludgeand Municipal Organic Waste- A Literature and State-of-Knowledge Review. Sandec/IMWI, Dübendorf, Switzerland.

_ Drescher. S., Zurbrügg, C., Enayetullah, I. and Singha, MAD.(2006). Decentralised Composting for Cities of Low- andMiddle-Income Countries - A User’s Manual.Eawag/Sandec and Waste Concern, Dhaka.



122

T.14

An Anaerobic Biogas Reactor is an anaerobic treat-ment technology that produces (a) a digested slurryto be used as a soil amendment and (b) biogas whichcan be used for energy. Biogas is a mix of methane,carbon dioxide and other trace gases that can be eas-ily converted to electricity, light and heat.

An Anaerobic Biogas Reactor is a chamber or vault thatfacilitates the anaerobic degradation of blackwater,sludge, and/or biodegradable waste. It also facilitatesthe separation and collection of the biogas that is pro-duced. The tanks can be built above or below ground.Prefabricated tanks or brick-constructed chambers canbe built depending on space, resources and the volumeof waste generated.The hydraulic retention time (HRT) in the reactorshould a minimum of 15 days in hot climates and 25days in temperate climates. For highly pathogenic in-puts, a HRT of 60 days should be considered. Normally,Anaerobic Biogas Reactors are not heated, but toensure pathogen destruction (i.e. a sustained temper-ature over 50°C) the reactor should be heated(although in practice, this is only found in the mostindustrialized countries).

Once waste products enter the digestion chamber,gases are formed through fermentation. The gas formsin the sludge but collects at the top of the reactor, mix-ing the slurry as it rises. Biogas Reactors can be built asfixed dome or floating dome reactors. In the fixed domereactor the volume of the reactor is constant. As gas isgenerated it exerts a pressure and displaces the slurryinto an expansion chamber. When the gas is removed,the slurry will flow back down into the digestion cham-ber. The pressure generated can be used to transportthe biogas through pipes. In a floating dome reactor, thedome will rise and fall with the production and with-drawal of gas. Alternatively, the dome can expand (likea balloon).Most often Biogas Reactors are directly connected toindoor (private or public) toilets with an additionalaccess point for organic materials. At the householdlevel, reactors can be made out of plastic containers orbricks and can be built behind the house or buriedunderground. Sizes can vary from 1,000L for a singlefamily up to 100,000L for institutional or public toiletapplications.The slurry that is produced is rich in organics and nutri-ents, but almost odourless and partly disinfected (com-

sludge

inlet biogas outlet

biogas

expansion chamberoutlet

outletseal



T.15T.15 Anaerobic Biogas ReactorApplicable to:System 1, 5, 6, 7, 8

123



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Inputs: Faecal Sludge BlackwaterOrganics


plete pathogen destruction would require thermophilicconditions). Often, a Biogas Reactor is used as an alter-native to a conventional septic tank, since it offers asimilar level of treatment, but with the added benefit ofenergy capture. Depending on the design and theinputs, the reactor should be emptied once every 6months to 10 years.

Adequacy This technology is easily adaptable andcan be applied at the household level or a small neigh-bourhood (refer to Technology Information Sheet S12:Anaerobic Biogas Reactor for information about apply-ing an Anaerobic Biogas Reactor at the householdlevel).Biogas reactors are best used for concentrated prod-ucts (i.e. rich in organic material). If they are installedat a public toilet, for example, and the sludge is toodilute, additional organic waste (e.g. from the market)can be added to improve the efficiency. Because theyare compact and can be built underground, biodi-gestors are appropriate for dense housing areas orpublic institutions that generate a lot of sludge, butwhere space is limited.To minimize distribution losses, the reactors should beinstalled close to where the gas can be used.Biogas reactors are less appropriate for colder climates asgas production is not economically feasible below 15°C.

Health Aspects/Acceptance The digested slurryis not completely sanitized and still carries a risk ofinfection. There are also dangers associated with theflammable gases that, if mismanaged could be harmfulto human health.

Maintenance The Anaerobic Biogas Reactor mustbe well built and gas tight for safety. If the reactor isproperly designed, repairs should be minimal. To startthe reactor, active sludge (e.g. from a septic tank)should be used as a seed. The tank is essentially self-mixing, but it should be manually stirred once a week toprevent uneven reactions.Gas equipment should be cleaned carefully and regular-ly so that corrosion and leaks are prevented.

Grit and sand that has settled to the bottom should beremoved once every year. Capital costs for gas trans-mission infrastructure can increase the project cost.Depending on the quality of the output, the gastransmission capital costs can be offset by long-termenergy savings.

Pros & Cons:+ Generation of a renewable, valuable energy source+ Low capital costs; low operating costs+ Underground construction minimizes land use+ Long life span+ Can be built and repaired with locally availablematerials

+ Low capital cost; low operating cost+ No electrical energy required- Requires expert design and skilled construction- Gas production below 15°C, is not longer econo-mically feasible

- Digested sludge and effluent still requires furthertreatment

References

_ Food and Agriculture Organization (FAO) (1996). BiogasTechnology: A Training Manual for Extension. ConsolidatedManagement Services, Kathmandu.Available: www.fao.org

_ ISAT (1998). Biogas Digest Vols. I-IV. ISAT and GTZ,Germany.Available:www.gtz.de

_ Koottatep, S., Ompont, M. and Joo Hwa, T. (2004).Biogas: A GP Option For Community Development. AsianProductivity Organization, Japan.Available: www.apo-tokyo.org

_ Rose, GD. (1999). Community-Based Technologies forDomestic Wastewater Treatment and Reuse: options forurban agriculture. IDRC, Ottawa. pp 29–32.Available: http://idrinfo.idrc.ca

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association,Bremen, Germany.



124

T.15


FunctionalGroupD:Useand/orDisposal

DUse and/or Disposal

125

This section presents different technologies and methods that use or dispose of theoutput products in ways that are the least harmful to the user and the environment.



126

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To decommission a pit, it can simply be filled withsoil and covered. Although there is no benefit recov-ered, the full pit poses no immediate health risk, andwith time, the contents will degrade naturally. Alter-natively, the ‘Arborloo’ is a shallow pit that is filledwith excreta and soil/ash and then covered withsoil; a tree planted on top will grow vigorously in thenutrient-rich pit.

When a single pit or a single VIP is full, and can not beemptied, Fill and Cover, i.e. filling the remainder of thepit and covering it is an option, albeit one with limitedbenefits to the environment or the user.In the Arborloo, a tree is planted on top of the full pitwhile the superstructure, ring beam and slab are con-tinuously moved from pit to pit in an endless cycle(usually moved once every 6 to12 months). A shallowpit is needed, about 1m deep. The pit should not belined as the lining would prevent the tree or plant fromgrowing properly. Before the pit is used, a layer ofleaves is put into the bottom. After each defecation, acup of soil, ash or a mixture should be dumped into thepit to cover the excreta. If they are available, leaves canalso be added occasionally to improve the porosity and

air content of the pile. When the pit is full, the top15cm of the pit is filled with soil and a tree is plantedin the soil. Banana, papaya and guava trees (amongmany) have all proven to be successful. A tree shouldnot be planted directly in the raw excreta. The treestarts to grow in the soil and its roots penetrate thecomposting pits as it grows. It may be best to wait forthe rainy season before planting if water is scarce.Other plants such as tomatoes and pumpkins can alsobe planted on top of the pit if trees are not available.

Adequacy Filling and covering pits is an adequatesolution when emptying is not possible and when thereis space to continuously re-dig and fill pits.The Arborloo can be applied in rural, peri-urban, anddenser areas if space is available.Planting a tree in the abandoned pit is a good way toreforest an area, provide a sustainable source of freshfruit and prevent people from falling into old pit sites.

Health Aspects/Acceptance There is a minimalrisk of infection if the pit is properly covered and clear-ly marked. It may be preferable to cover the pit andplant a tree rather than have the pit emptied, especial-

1 2



D.1D.1 Fill and Cover /ArborlooApplicable to:System 1

127



Inputs:Excreta FaecesCompost/EcoHumus

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ly if there is no appropriate technology available fortreating the faecal sludge.Users do not come in contact with the faecal materialand thus there is a very low risk of pathogen transmis-sion. Demonstration projects that allow communitymembers to participate are useful ways of showing boththe ease of the system, it’s inoffensive nature, and thenutrient value of composted excreta.

Maintenance A cup of soil and/or ash should beadded to the pit after each defecation and leavesshould be added periodically. Also, the contents of thepit should be periodically levelled to prevent a cone-shape from forming in the middle of the pit.There is little maintenance associated with a closed pitother than taking care of the tree or plant. If a tree isplanted in the abandoned pit, it should be watered reg-ularly. A small-fence should be constructed with sticksand sacks around the sapling to protect it from animals.

Pros & Cons:+ Simple technique for all users+ Low cost+ Low risk of pathogen transmission+ May encourage income generation(tree planting and fruit production)

- Labour intensive

References

_ Morgan, P. (2007). Toilets that make compost. StockholmEnvironment Institute, Stockholm, Sweden. pp 81–90.Available: www.ecosanres.org

_ Morgan, P. (2004). An Ecological Approach to Sanitationin Africa: A Compilation of Experiences. Aquamor, Harare,Zimbabwe. Chapter 10 – The usefulness of urine.Available: www.ecosanres.org

_ NWP (2006). Smart Sanitation Solutions. Examples ofinnovative, low-cost technologies for toilets, collection,transportation, treatment and use of sanitation products.Netherlands Water Partnership, The Netherlands. pp 51.



128

D.1

Separately collected, stored urine is a concentratedsource of nutrients that can be applied as a liquid fer-tilizer in agriculture to replace all or some commer-cial chemical fertilizer.

The guidelines for urine use are based on storage timeand temperature (please see WHO guidelines for specif-ic requirements). However, it is generally accepted thatif urine is stored for at least 1 month, it will be safe foragricultural application at the household level. If urine isused for crops that are eaten by those other than theurine producer, it should be stored for 6 months. Urineshould not be applied to crops within one month beforethey are harvested.From normal, healthy people, urine is virtually free ofpathogens. Urine also contains the majority of nutrientsthat are excreted by the body. Urine varies dependingon diet, gender, climate and water intake among otherfacts, but roughly 80% of nitrogen, 60% of potassiumand 55% of phosphorus that is excreted from the bodyis excreted through urine.Because of its high pH and concentration, stored urineshould not be applied directly to plants. Rather it can beused:

1)mixed undiluted into soil before planting;2)poured into furrows sufficiently away from plantroots and covered immediately (once or twice duringthe growing season); and

3)diluted several times and used frequently (twiceweekly) poured around plants.

To calculate the application rate, one can assume that1m2 of cropland can receive the urine from 1 personper day (1 to 1.5L), per crop harvested (e.g. 400 m2 ofcropland per year can be fertilized). A 3:1 mix of waterand urine is an effective dilution for vegetables, appliedtwice weekly, although the amount depends on the soiland the type of vegetables. During the rainy season,urine can also be applied directly into small holes nearplants, where it will be diluted naturally.

Adequacy Urine is especially beneficial where cropsare lacking nitrogen. Examples of some crops that growwell with urine include: maize, rice, millet, sorghum,wheat, chard, turnip, carrots, kale, cabbage, lettuce,bananas, paw-paw, and oranges.Urine application is ideal for rural and peri-urban areaswhere agricultural lands are close to the point of urinecollection. Households can use their own urine on their

urine



D.2D.2 Application of UrineApplicable to:System 4, 8

129



Inputs:Stored Urine��

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own plot of land. Alternatively, if facilities and infrastruc-ture exist, urine can be collected at a semi-centralizedlocation for distribution and transport to agricultural land.Regardless, the most important aspect is that there is aneed for nutrients otherwise, the urine can become asource of pollution and nuisance if dealt with improperly.

Health Aspects/Acceptance There is a minimalrisk of infection, especially with extended storage. Still,urine should be handled carefully and should not beapplied to crops less than one month before they areharvested.Social acceptance may be difficult. Stored urine has astrong smell and some may find it offensive to workwith or be near. If urine is diluted, and/or immediatelytilled into the earth, the smells can be reduced. The useof urine may be less accepted in urban or peri-urbanareas where household gardens are close to housesthan in rural areas, where houses and crop lands areseparated.

Maintenance With time, some minerals in urine willprecipitate (especially calcium and magnesium phos-phates). Any equipment that is used to collect, transportor apply urine (i.e. watering cans with small holes) maybecome clogged over time. Most deposits can easily beremoved with hot water and a bit of acid (vinegar), or inmore extreme cases, chipped off manually.

Pros & Cons:+ Simple technique for all users+ Low cost+ Low risk of pathogen transmission+ Reduces dependence on costly chemical fertilizers+ May encourage income generation (tree plantingand fruit production)

- Urine is heavy and difficult to transport- Smell may be offensive- Labour intensive

References

_ Austin, A. and Duncker, L. (2002). Urine-diversion.Ecological Sanitation Systems in South Africa.CSIR, Pretoria, South Africa.

_ GTZ (2005). Technical data sheets for ecosan compo-nents-01 Urine Diversion. GTZ, Germany.Available: www.gtz.de

_ Morgan, P. (2007). Toilets that make compost.Stockholm Environment Institute, Stockholm, Sweden.Available: www.ecosanres.org

_ Morgan, P. (2004). An Ecological Approach to Sanitationin Africa: A Compilation of Experiences. Aquamor, Harare,Zimbabwe. Chapter 10 – The usefulness of urine.Available: www.ecosanres.org


_ Schonning, C. and Stenstrom, TA. (2004). Guidelines forthe Safe Use of Urine and Faeces in Ecological SanitationSystems-Report 2004-1. EcosanRes, StockholmEnvironment Institute, Stockholm, Sweden.Available: www.ecosanres.org

_ Winblad, U. and Simpson-Herbert, M. (eds.) (2004).Ecological Sanitation- revised and enlarged edition.Stockholm Environment Institute, Stockholm, Sweden.Available: www.ecosanres.org

_ WHO (2006). Guidelines for the safe use of wastewater,excreta and greywater – Volume 4: Excreta and greywateruse in agriculture. WHO, Geneva.Available: www.who.int



130

D.2

When faeces are stored in the absence of moisture(i.e. urine) they dehydrate into a crumbly, white-beigecoarse, flaky material or powder. Dehydration meansthat the moisture naturally present in the faecesevaporates and/or is absorbed by the addition of adrying material (e.g. ash, sawdust, lime).

Dehydration is different from composting becausethe organic material present is not degraded or trans-formed; only the moisture is removed. After dehydration,faeces will reduce in volume by about 75%. The shellsand carcasses of worms and insects that also dehydratewill remain in the dried faeces.The degree of pathogen inactivation will depend on thetemperature, the pH (e.g. lime raises the pH) and stor-age time. It is generally accepted that faeces should bestored between 12 to 18 months, although pathogensmay still exist after this time.When the faeces are completely dry they will emergeas a crumbly, powdery substance. The material is richin carbon and nutrients, but may still contain patho-gens or oocysts (spores which can survive extremeenvironmental conditions and re-animate under fa-vourable conditions). The material can be mixed into

soil, either for agriculture or at another site (dependingon acceptance).Faeces that are dried and stored between 2 and 20°Cshould be stored for between 1.5 to 2 years before theyare used at the household or regional level. At highertemperatures (i.e. greater than 20°C) storage over oneyear is recommended to inactivate Ascaris eggs (a typeof parasitic worm). A shorter storage time of six monthsis required if the faeces have a pH above 9 (i.e. lime willincrease the pH of the faeces). The WHO has publishedguidelines and these should be consulted before usingdried faeces.

Adequacy Dried faeces are not as well treated or asuseful as a soil amendment as composted faeces. How-ever, they are useful at replenishing poor soils and forboosting the carbon and water-storing properties of asoil with low-risk of pathogen transmission.

Health Aspects/Acceptance The handing and useof dried faeces may not be acceptable to some.However, because the dried faeces should be dry, crum-bly, and odour free, the use of dried faeces may bemore acceptable than that of manure or sludge. Dry

urine tank dried faeces



D.3D.3 Application of Dehydrated FaecesApplicable to:System 4

131



Inputs:Dried Faeces��

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faeces are a hostile environment for organisms andconsequently, they do not survive (for long). If water orurine mixes with the drying faeces, odours and organ-isms may become problematic; wet faeces allow bacte-ria to survive and multiply. A warm, moist environmentwill permit anaerobic processes to generate offensiveodours.When removing the dehydrated faeces from the dehy-dration vaults, care must be taken to prevent the powerfrom blowing and being inhaled.

Maintenance Faeces should be kept as dry as pos-sible. If by accident, water or urine enters mixes withthe drying faeces, more ash, lime or dry soil can beadded to help absorb the moisture. Prevention is thebest way of keeping the faeces dry.

Pros & Cons:+ Can improve the structure and water-holdingcapacity of soil

+ Simple technique for all users+ Low cost+ Low risk of pathogen transmission+ May encourage income generation (tree plantingand fruit production)

- Labour intensive- Pathogens may exist in a dormant stage (oocysts)which may become infectious if moisture is added

- Does not replace fertilizer (N, P, K)

References

_ Austin, A. and Duncker, L. (2002). Urine-diversion. Eco-logical Sanitation Systems in South Africa. CSIR, Pretoria.

_ Schonning, C. and Stenstrom, TA. (2004). Guidelines for theSafe Use of Urine and Faeces in Ecological SanitationSystems-Report 2004-1. EcosanRes, StockholmEnvironment Institute, Stockholm, Sweden.Available: www.ecosanres.org

_ WHO (2006). Guidelines for the safe use of wastewater,excreta and greywater – Volume 4: Excreta and greywateruse in agriculture. WHO, Geneva.Available: www.who.int

_ Winblad, U. and Simpson-Herbert, M. (eds.) (2004).Ecological Sanitation- revised and enlarged edition.Stockholm Environment Institute, Stockholm, Sweden.Available: www.ecosanres.org



132

D.3

Composting is the term used to describe the con-trolled aerobic degradation of organics into a soil-likesubstance called compost. ‘EcoHumus’ is a termtaken from Peter Morgan (see references) and is amore appropriate word to use for the material re-moved from a Fossa Alterna because it is producedpassively underground and has a slightly differentcomposition.

The process of thermophilic composting generates heat(50 to 80°C) which kills the majority of pathogens pres-ent. For the composting process to occur there must beadequate carbon, nitrogen, moisture, and air.The Fossa Alterna (S5) and Arborloo (D1) are ambient-temperature variations of high-temperature compostingIn these technologies, there is almost no temperaturerise because vegetable matter is lacking. For that rea-son, the material is not actually ‘compost’ and is there-fore referred to as ‘EcoHumus’.The WHO guidelines stipulate that the compost shouldachieve and maintain a temperature of 50°C for atleast one week before it is considered safe (although toachieve this value, a significantly longer period of com-posting is required). The WHO guidelines should be

consulted for detailed information. For systems thatgenerate EcoHumus in-situ (i.e. Fossa Alterna), a mini-mum of 1 year of storage is recommended to eliminatebacterial pathogens and reduce viruses and parasiticprotozoa.Compost/EcoHumus can be used beneficially to im-prove the quality of soils by adding nutrients and organ-ics and improving the soil’s ability to store air and water.The texture and quality of the EcoHumus depends onthe materials which have been added to the excreta(especially the type of soil).

Adequacy Compost/EcoHumus can be mixed intothe soil before crops are planted, used to startseedlings or indoor plants or simply mixed into an exist-ing compost pile for further treatment.For poor soils, equal parts of compost and top soil haveshown to improve productivity. The output from oneFossa Alterna should be sufficient for two 1.5m by3.5m beds. Vegetable gardens filled with the Eco-Humus from the Fossa Alterna have shown dramaticimprovements over gardens planted without compost,and has even made agriculture possible in areas whichwould have not otherwise supported crops.



D.4D.4 Application of Compost/EcoHumusApplicable to:System 2

133



Inputs:Compost/EcoHumus��

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Health Aspects/Acceptance A small risk of patho-gen transmission exists, but if in doubt, any materialremoved from the pit can be composted further in aregular compost heap, or mixed with additional soil andput into a ‘tree pit’, i.e. a nutrient-filled pit used forplanting a tree.As opposed to sludge, which originates from a varietydomestic, chemical and industrial sources, composthas very few chemical inputs. The only chemicalsources that could contaminate compost might origi-nate from contaminated organic material (e.g. pesti-cides) or from chemicals that are excreted by humans(e.g. medication). Compared to the cleaning, pharma-ceutical and processing chemicals that may find theirway into sludge, compost can be considered as a lesscontaminated product.Acceptability may be low at first, but demonstrationunits and hands-on experience are effective ways ofdemonstrating the non-offensive nature of the material.

Maintenance The material must be allowed to matureadequately before it is removed from the system andthen it can be used without further treatment.

Pros & Cons:+ Potential income generation (improved yield andproductivity of plants)

+ Low risk of pathogen transmission+ Can improve the structure and water-holdingcapacity of soil

+ Simple technique for all users+ Low cost- Requires a year or more of maturation- Does not replace fertilizer (N, P, K)

References

_ Del Porto, D. and Steinfeld, C. (1999). The CompostingToilet System Book. A Practical Guide to Choosing, Planningand Maintaining Composting Toilet Systems, an Alternative toSewer and Septic Systems. The Center for EcologicalPollution Prevention (CEPP), Massachusetts, USA.

_ Jenkins, J. (1999). The Humanure Handbook: a Guide toComposting Human Manure. (2nd ed.). Jenkins Publishing,Grove City, Pa, USA.Available: www.jenkinspublishing.com

_ Morgan, P. (2004). An Ecological Approach to Sanitation inAfrica: A Compilation of Experiences. Aquamor, Harare,Zimbabwe.Available: www.ecosanres.org

_ Morgan, P. (2007). Toilets that make compost. StockholmEnvironment Institute, Stockholm, Sweden. pp 81–90.Available: www.ecosanres.org




134

D.4

To reduce dependence on freshwater and maintain aconstant source of irrigation water throughout theyear, waste waters of varying qualities can be usedin agriculture. Generally, only waters that have hadsecondary treatment (i.e. physical and biologicaltreatment) should be used to limit the risk of cropcontamination and the health risk to workers.

There are two kinds of irrigation technologies that areappropriate for using treated wastewaters:1)Drip irrigation where the water is dripped slowly onor near the root area; and

2)Surface water irrigation where water is routed over-land in a series of dug channels or furrows.

To minimize evaporation and contact with pathogens,spray irrigation should be avoided.Properly treated wastewater can significantly reducedependence on freshwater, and/or improve crop yieldsby supplying increased water and nutrients to plants.Raw sewage or untreated blackwater should not beused, and even well-treated water should be used withcaution. Long-term use of poorly or improperly treatedwater may cause long-term damage to the soil structureand its ability to hold water.

Adequacy Generally, drip irrigation is the mostappropriate irrigation method; it is especially good forarid and drought prone areas. Surface irrigation isprone to large losses from evaporation but requires lit-tle/no infrastructure and may be appropriate in somesituations.Crops such as corn, alfalfa (and other feed), fibres (cot-ton), trees, tobacco, fruit trees (mangos) and foodsrequiring processing (sugar beet) can be grown safelywith treated effluent. More care should be taken whengrowing fruits and vegetables that may be eaten raw(e.g. tomatoes) that could come in contact with thewater. Energy crops like eucalyptus, poplar, willow, orash trees can be grown in short-rotation and harvestedfor biofuel production. Since the trees are not for con-sumption, this is a safe, efficient way of using lower-quality effluent.There are potential health risks if water is not properlypre-treated (i.e. inadequate pathogen reduction). Soilquality can be degraded over time (e.g. accumulation ofsalts) if poorly treated wastewater is applied. The appli-cation rate must be appropriate for the soil, crop andclimate, or it could be damaging.

treatedwastewater



D.5D.5 IrrigationApplicable to:Systems 1–8

135



Inputs:Effluent Stormwater��

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Health Aspects/Acceptance Appropriate pre-treat-ment should precede any irrigation scheme to limithealth risks to those who come in contact with thewater. As well, depending on the degree of treatmentthat the effluent has undergone, it may be contaminat-ed with the different chemicals that are discharged intothe system. When effluent is used for irrigation, house-holds and industries connected to the system should bemade aware of the products that are and are not appro-priate for discharging into the system.Drip irrigation is the only type of irrigation that shouldbe used with edible crops, and even then, care shouldbe taken to prevent workers and harvested crops fromcoming in contact with the treated effluent.Despite safety concerns, irrigation with effluent is aneffective way to recycle nutrients and water.

Maintenance Drip irrigation systemsmust be cleanedperiodically to remove any built-up solids. The pipesshould be checked for leaks as they are prone to dam-age from rodents and humans.Drip irrigation is more costly than conventional irriga-tion, but has improved yields and decreased water/operating costs.

Pros & Cons:+ Reduces depletion of ground water and improvesavailability of drinking water

+ Reduced need for fertilizer+ Low to moderate capital cost; low to moderateoperating cost


+ Low risk of pathogen transmission if water isproperly pre-treated

+ Potential to improved health, self-reliance incommunity

- Must be well settled - very sensitive to clogging- May require expert design and installation- Not all parts and materials may be available locally

References

_ Ayers, RS. and Westcot, DW. (1994). FAO Irrigation andDrainage Paper 29 Rev. 1. Water Quality for Agriculture.FAO, Rome.Available: www.fao.org

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems.WCB and McGraw-Hill, New York, USA. pp 878–886.

_ Mara, DD. (1996). Low-Cost Urban Sanitation.Wiley, Chichester, UK. pp 150–152.

_ Mara, DD. (2004). Domestic Wastewater Treatment inDeveloping Countries. Earthscan, London. pp 231–245.

_ Okun, DA. and Ponghis, G. (1975). Community WastewaterCollection and Disposal. WHO, Geneva. pp 211–220.

_ Sasse, L. (1998). DEWATS: Decentralised WastewaterTreatment in Developing Countries. BORDA, BremenOverseas Research and Development Association, Bremen,Germany.

_ WHO (2006). Guidelines for the safe use of wastewater,excreta and greywater- Volume 2: Wastewater and excretause in agriculture. WHO, Geneva.



136

D.5

A Soak Pit, also known as a soakaway or leach pit, isa covered, porous-walled chamber that allows waterto slowly soak into the ground. Pre-settled effluentfrom a Collection and Storage/Treatment or (Semi-)Centralized Treatment technology is discharged tothe underground chamber from where it infiltratesinto the surrounding soil.

The Soak Pit can be left empty and lined with a porousmaterial (to provide support and prevent collapse), orleft unlined and filled with coarse rocks and gravel. Therocks and gravel will prevent the walls from collapsing,but will still provide adequate space for the waste-water. In both cases, a layer of sand and fine gravelshould be spread across the bottom to help dispersethe flow. The soak pit should be between 1.5 and 4mdeep, but never less than 1.5m above the ground watertable.As wastewater (pre-treated greywater or blackwater)percolates through the soil from the Soak Pit, small par-ticles are filtered out by the soil matrix and organics aredigested by micro-organisms. Thus, Soak Pits are bestsuited to soils with good absorptive properties; clay,hard packed or rocky soils are not appropriate.

Adequacy A Soak Pit does not provide adequatetreatment for raw wastewater and the pit will clogquickly. A Soak Pit should be used for discharging pre-settled blackwater or greywater.Soak pits are appropriate for rural and peri-urban settle-ments. They depend on soil with a sufficient absorptivecapacity. They are not appropriate for areas that areprone to flooding or have high groundwater tables.

Health Aspects/Acceptance As long as the SoakPit is not used for raw sewage, and as long as the previ-ous Collection and Storage/Treatment technology isfunctioning well, health concerns are minimal. The tech-nology is located underground and thus, humans and ani-mals should have no contact with the effluent. It is impor-tant however, that the Soak Pit is located a safe distancefrom a drinking water source (ideally 30m).Since the Soak Pit is odourless and not visible, it shouldbe accepted by even the most sensitive communities.

Maintenance A well-sized Soak Pit should last bet-ween 3 and 5 years without maintenance. To extend thelife of a Soak Pit, care should be taken to ensure thatthe effluent has been clarified and/or filtered well to

inlet



D.6D.6 Soak PitApplicable to:Systems 1–5

137



Inputs:Effluent GreywaterUrine Anal Cleansing Water

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prevent excessive build up of solids. The Soak Pitshould be kept away from high-traffic areas so that thesoil above and around it is not compacted. When theperformance of the Soak Pit deteriorates, the materialinside the soak pit can be excavated and refilled. Toallow for future access, a removable (preferably con-crete) lid should be used to seal the pit until it needs tobe maintained.Particles and biomass will eventually clog the pit and itwill need to be cleaned or moved.


+ Small land area required+ Low capital cost; low operating cost+ Can be built and maintained with locally availablematerials

+ Simple technique for all users- Pretreatment is required to prevent clogging,although eventual clogging is inevitable

- May negatively affect soil and groundwaterproperties

References

_ Ahrens, B. (2005). A Comparison of Wash Area and SoakPit Construction: The Changing Nature of Urban, Rural, andPeri-Urban Linkages in Sikasso, Mali. Peace Corp, USA.Available: www.cee.mtu.edu/peacecorps/reports/Brooke_Ahrens_Final_Report.pdf(Detailed construction instructions)

_ Mara, DD. (1996). Low-Cost Urban Sanitation.Wiley, Chichester, UK. pp 63–65.(Dimensioning calculations)

_ Polprasert, C. and Rajput, VS. (1982). EnvironmentalSanitation Reviews: Septic Tank and Septic Systems.Environmental Sanitation Information Center, AIT, Bangkok,Thailand. pp 31–58.



138

D.6

A Leach Field, or drainage field, is a network perforat-ed pipes that are laid in underground gravel-filledtrenches to dissipate the effluent from awater-basedCollection and Storage/Treatment or (Semi-) Centra-lized Treatment technology.

Effluent is fed into a distribution box which directs theflow into several parallel channels. A small dosing sys-tem releases the pressurized effluent into the LeachField on a timer (usually 3 to 4 times a day). Thisensures that the whole length of the Leach Field is uti-lized and that aerobic conditions are allowed to recoverbetween dosings. Each trench is 0.3 to 1.5m deep and0.3 to 1m wide. The bottom of each trench is filled withabout 15cm of clean rock and a perforated distributionpipe is laid overtop. More rock covers the pipe so thatit is completely surrounded. The layer of rock is coveredwith a layer of geotextile fabric to prevent small parti-cles from plugging the pipe. A final layer of sand and/ortopsoil covers the fabric and fills the trench to theground level. The pipe should be placed 15cm from thesurface to prevent effluent from surfacing. The trench-es should be dug no longer than 20m in length at least1 to 2m apart.

Adequacy Leach Fields require a large area and soilwith good absorptive capacity to effectively dissipatethe effluent.To prevent contamination, a Leach Field should belocated 30m away from a drinking water supply. Leachfields are not appropriate for dense urban areas. Theycan be used in almost every temperature, althoughthere may be problems with pooling effluent in areaswhere the ground freezes.Homeowners who have a Leach Field must be aware ofhow it works and what their maintenance responsibili-ties are. Trees and deep-rooted plants should be keptaway from the Leach Field as they can crack and disturbthe tile bed.

Health Aspects/Acceptance Since the technolo-gy is underground and it requires little attention, userswill rarely come in contact with the effluent and so itshould pose no health risk. The Leach Field must bekept as far away as possible from (>30m) any potentialpotable water sources to avoid contamination.

Upgrading A Leach Field should be laid out such thatit would not interfere with a future sewer connection.

settling tanks

settled effluent



D.7D.7 Leach FieldApplicable to:System 5

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Inputs:Effluent��

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The collection technology which precedes the LeachField (e.g. Septic Tank: S9) should be equipped with asewer connection so that if, or when, the Leach Fieldneeds to be replaced, the changeover can be done withminimal disruption.

Maintenance A Leach Field will become cloggedover time, although with a well-functioning pre-treat-ment technology, this should take many years.Effectively, a Leach Field should require minimal main-tenance, however if the system stops working efficient-ly, the pipes should be cleaned and/or removed andreplaced. To maintain the Leach Field, there should beno plants or trees above it and no heavy traffic, whichmay crush the pipes or compact the soil.

Pros & Cons:+ Can be used for the combined treatment ofblackwater and greywater

+ Has a lifespan of 20 or more years (dependingon conditions)

+ Low to moderate capital cost, low operating cost- Requires expert design and construction- Requires a large area (on a per person basis)- Not all parts and materials may be available locally- Pretreatment is required to prevent clogging- May negatively affect soil and groundwaterproperties

References

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems.WCB and McGraw-Hill, New York, USA. pp 905–927.

_ Polprasert, C. and Rajput, VS. (1982). EnvironmentalSanitation Reviews: Septic Tank and Septic Systems.Environmental Sanitation Information Center, AIT,Bangkok, Thailand.

_ USEPA (1980). Design manual- on-site wastewater treat-ment and disposal systems. EPA-625/1-80-012. Office ofResearch and Development, Municipal EnvironmentalResearch Laboratory, Cincinnati, Ohio.Available: www.epa.gov



140

D.7

Aquaculture refers to the controlled cultivation ofaquatic plants and animals; this technology sheetrefers exclusively to the raising of fish while the fol-lowing page on Floating Macrophytes (D9) addressesthe cultivation of plants. Fish can be grown in pondswhere they feed on algae and other organisms thatgrow in the nutrient-rich water. Through feeding, thenutrients from the wastewater are removed and thefish are eventually harvested for consumption.

Three kinds of aquaculture designs for raising fish exist:1) fertilization of fish ponds with excreta/sludge;2) fertilization of fish ponds with effluent; and3) fish grown directly in aerobic ponds.When introducing nutrients in the form of effluent orsludge it is important to limit the additions such thataerobic conditions are maintained. BOD should notexceed 1g/m2d and oxygen should be at least 4mg/L.Fish introduced to aerobic ponds can effectively reducealgae and help control mosquito populations.The fish themselves do not dramatically improve thewater quality, but because of their economic value theycan offset the costs of operating a treatment facility.Under ideal operating conditions, up to 10,000kg/ha of

fish can be harvested. If the fish are not acceptable forhuman consumption, they can be a valuable source ofprotein for other high-value carnivores (like shrimp) orconverted into fishmeal for pigs and chickens.

Adequacy A fish pond is only appropriate when there isa sufficient amount of land (or preexisting pond), a sourceof fresh water and a suitable climate. The water that isused to dilute the waste should not be too warm, and theammonia levels should be kept low or negligible.Only fish that are tolerant of low dissolved oxygen levelsshould be chosen. They should not be carnivores andthey should be tolerant to diseases and adverse environ-mental conditions. Different varieties of carp, milkfishand tilapia have been successful, but the specific choicewill depend on local preference and suitability.This technology is only appropriate for warm or tropicalclimates with no freezing temperatures, and preferablywith high rainfall and minimal evaporation.

Health Aspects/Acceptance Where there is noother source of readily available protein, this technolo-gy may be embraced. The quality and condition of thefish will also influence local acceptance. There may be

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D.8D.8 Aquaculture PondsApplicable to:System 1, 5, 6, 7, 8

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concern with contamination of the fish, especially dur-ing the harvesting, cleaning and preparation of the fish.If it is cooked well it should be safe, but it is advisableto move the fish to a clear-water pond for several weeksbefore they are harvested for consumption.

Maintenance The fish need to be harvested whenthey reach an appropriate age/size. Sometimes afterharvesting, the pond should be drained so that (a) it canbe desludged and (b) it can be left to dry in the sun for1 to 2 weeks to destroy any pathogens living on the bot-tom or sides of the pond.

Pros & Cons:

+ Can provide a cheap, locally available protein source+ Low to moderate capital cost; operating costsshould be offset by production revenue


+ Can be built and maintained with locally availablematerials

- Fish may pose a health risk if improperly preparedor cooked

- Requires abundance of fresh water- Requires large land (pond) area- May require expert design and installation

References

_ Cointreau, S., et al. (1987). Aquaculture with treated waste-water: a status report on studies conducted in Lima, Perú.Technical Note 3. UNDP/World Bank, Washington D.C.USA. 1987.

_ Cross, P. and Strauss, M. (1985). Health Aspects ofNightsoil and Sludge Use in Agriculture and Aquaculture.International Reference Centre for Waste Disposal,Dübendorf, Switzerland.

_ Edwards, P. and Pullin, RSV. (eds) (1990). Wastewater-FedAquaculture. Proceedings: International Seminar onWastewater Reclamation and Reuse for Aquaculture,Calcutta, India.(Compilation of topical papers)

_ Iqbal, S. (1999). Duckweed Aquaculture-Potentials,Possibilities and Limitations for Combined WastewaterTreatment and Animal Feed Production in DevelopingCountries. Sandec, Dübendorf, Switzerland.

_ Joint FAO/NACA/WHO Study Group (1999). Food safetyissues associated with products from aquaculture. WorldHealth Organization Technical Report Series No. 883.Available: www.who.int

_ Mara, DD. (2004). Domestic Wastewater Treatment inDeveloping Countries. Earthscan, London. pp 253–261.

_ Polprasert, C., et al. (2001). Wastewater Treatment II,Natural Systems for Wastewater Management. LectureNotes. IHE, Delft.Available: www.who.int(Chapter 8 - Aquaculture and Reuse Aspects).

_ Rose, GD. (1999). Community-Based Technologies forDomestic Wastewater Treatment and Reuse: options forurban agriculture. IDRC Ottawa.Available: http://idrinfo.idrc.ca

_ Skillicorn, W., Journey, K. and Spira, P. (1993). Duckweedaquaculture: A new aquatic farming system for developingcountries. World Bank, Washington, DC.Available: http://www.p2pays.org/ref/09/08875.htm(Comprehensive manual)



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A floating plant pond is a modified maturation pondwith floating (macrophyte) plants. Plants such aswater hyacinths or duckweed float on the surfacewhile the roots hang down into the water to uptakenutrients and filter the water that flows by.

Water hyacinths are perennial, freshwater, aquaticmacrophytes that grow especially fast in wastewater.The plants can grow large: between 0.5 to 1.2m fromtop to bottom. The long roots provide a fixed mediumfor bacteria which in turn degrade the organics in thewater passing by.Duckweed is a fast growing, high protein plant that canbe used fresh or dried as a food for fish or poultry. It isalso tolerant of a variety of conditions and can removesignificant quantities of nutrients from wastewater.To provide extra oxygen to a floating plant technology,the water can be mechanically aerated but at the costof increased power and machinery. Aerated ponds canwithstand higher loads and can be built with smallerfootprints. Non-aerated ponds should not be too deepotherwise there will be insufficient contact between thebacteria-harbouring roots and the wastewater.

Adequacy The technology can achieve high removalrates of both BOD and suspended solids, althoughpathogen removal is not substantial.Harvested hyacinths can be used as a source of fibrefor rope, textiles, baskets, etc. Depending on the in-come generated, the technology can be cost neutral.Duckweed can be used as the sole food source to someherbivorous fish.This technology is only appropriate for warm or tropicalclimates with no freezing temperatures, and preferablywith high rainfall and minimal evaporation. Different,locally appropriate plants can be selected depending onavailability and the wastewater type.Trained staff is required for the constant operation andmaintenance of the pond.

Health Aspects/Acceptance Water hyacinth hasattractive, lavender flowers. A well designed and main-tained system can add value and interest to otherwisebarren land.Adequate signage and fencing should be used to pre-vent people and animals from coming in contact withthe water.

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D.9D.9 Floating Plant (Macrophyte) PondApplicable to:System 1, 5, 6, 7, 8

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Inputs:Effluent

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Maintenance Floating plants require constant har-vesting. The harvested biomass can be used for smallartisanal businesses, or it can be composted. Mosquitoproblems can develop when the plants are not harvest-ed regularly. Depending on the amount of solids enter-ing, the pond must be desludged periodically.

Pros & Cons:+ Water hyacinth grows rapidly and is attractive+ High reduction of BOD and solids; low reductionof pathogens

+ Low to moderate capital cost; operating cost canbe offset by revenue


+ Can be built and maintained with locally availablematerials

- Can become an invasive species if released intonatural environments

- Requires large land (pond) area

References

_ Abbasi, SA. (1987). Aquatic plant based water treatmentsystems in Asia. pp 175–198, In: Aquatic Plants for WaterTreatment and Resource Recovery, K .R. Reddy andW.H. Smith (eds.), Magnolia Publishing Inc., Orlando,Florida.

_ Bagnall, LO., Schertz, CE. and Dubbe, DR. (1987).Harvesting and handling of biomass. pp. 599–619,In: Aquatic Plants for Water Treatment and ResourceRecovery, K.R. Reddy and W.H. Smith (eds.),Magnolia Publishing Inc., Orlando, Florida.

_ Crites, R. and Tchobanoglous, G. (1998). Small andDecentralized Wastewater Management Systems.WCB and McGraw-Hill, New York, USA, pp 609–627.(Comprehensive summary chapter including solved problems)

_ Gerba, CP., et al. (1995). Water-Quality Study ofGraywater Treatment Systems. Water Resources Bulletin31(1): 109–116.

_ Iqbal, S. (1999). Duckweed Aquaculture-Potentials,Possibilities and Limitations for Combined WastewaterTreatment and Animal Feed Production in DevelopingCountries. Sandec, Dübendorf, Switzerland.

_ McDonald, RD. and Wolverton, BC. (1980). Comparativestudy of wastewater lagoon with and without water hya-cinth. Economic Botany: 34 (2): 101–110.

_ Polprasert, C., et al. (2001). Wastewater Treatment II,Matural Systems for Wastewater Management. IHE, Delft.(Comprehensive Design Manual: see Chapter 4 – WaterHyacinth Ponds.)

_ Rose, GD. (1999). Community-Based Technologies forDomestic Wastewater Treatment and Reuse: optionsfor urban agriculture. IDRC, Ottawa.Available: http://idrinfo.idrc.ca

_ Skillicorn, W., Journey, K. and Spira, P. (1993). Duckweedaquaculture: A new aquatic farming system for developingcountries. World Bank, Washington, DC.Available: www.p2pays.org/ref/09/08875.htm(Comprehensive manual)

_ US Environmental Protection Agency (1988). DesignManual: Constructed Wetlands and Aquatic Plant Systems forMunicipal Wastewater Treatment. USEPA, Cincinnati, Ohio.Available: www.epa.gov/owow/wetlands/pdf/design.pdf



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Treated effluent and/or stormwater can be dis-charged directly into receiving water bodies (such asrivers, lakes, etc.) or into the ground to rechargeaquifers.

It is necessary to ensure that the assimilation capacityof the receiving water body is not exceeded, i.e. that thereceiving body can accept the quantity of nutrientswithout being overloaded. Parameters such as turbidity,temperature, suspended solids, BOD, nitrogen andphosphorus (among others) should be carefully con-trolled and monitored before releasing any water into anatural body. The use of the water body, whether it isused for industry, recreation, spawning habitat, etc.,will influence the quality and quantity of treated waste-water that can be introduced without deleteriouseffects.Local authorities should be consulted to determine thedischarge limits for the relevant parameters as they canvary widely. For especially sensitive areas, chlorinationmay be required to meet microbiological limits.Alternatively, water can be discharged into aquifers.Groundwater recharge is increasing in popularity asgroundwater resources deplete and as saltwater intru-

sion becomes a greater threat to coastal communities.Although the soil is known to act as a filter for a varietyof contaminants, groundwater recharge should not beviewed as a treatment method. Once an aquifer is con-taminated, it is next to impossible to reclaim it. Thequality of water extracted from a recharge aquifer is afunction of the quality of the wastewater introduced,the method of recharge, the characteristics of theaquifer, the residence time, the amount of blending withother waters and the history of the system. Carefulanalysis of these factors should precede any rechargeproject.

Adequacy The adequacy of discharge into a waterbody or aquifer will depend entirely on the local envi-ronmental conditions and legal regulations. Generally,discharge to a water body is only appropriate whenthere is a safe distance between the discharge pointand the next closest point of use. Similarly, groundwa-ter recharge is most appropriate for areas that are atrisk from salt water intrusion or aquifers that have along retention time.Depending on the volume, the point of discharge and/orthe quality of the water, a permit may be required.

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D.10D.10 Water Disposal/Groundwater (GW) RechargeApplicable to:Systems 1–7

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Inputs:Effluent Stormwater��

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Health Aspects/Acceptance Generally, cations(Mg2+, K+, NH4

+) and organic matter will be retained with-in a solid matrix, while other contaminants (such asnitrates) will remain in the water. There are numerousmodels for the remediation potential of contaminantsand microorganisms, but predicting downstream, orextracted water quality for a large suite of parameters israrely feasible. Therefore, potable and non-potablewater sources should be clearly identified, the mostimportant parameters modelled and a risk assessmentcompleted.

Maintenance Regular monitoring and sampling isimportant to ensure compliance with regulations and toensure public health requirements. Depending on therecharge method, some mechanical maintenance maybe required.

Pros & Cons:+ May provide a ‘drought-proof’ water supply(from groundwater)

+ May increase productivity of water-bodies bymaintaining constant levels

- Discharge of nutrients and micropollutants mayaffect natural water bodies and/or drinking water

- Introduction of pollutants may have long-term impacts- May negatively affect soil and groundwaterproperties

References

_ ARGOSS (2001). Guidelines for assessing the risk to ground-water from on-site sanitation. British Geological SurveyCommissioned Report, CR/01/142.Available: www.worldbank.org

_ Seiler, KP. and Gat, JR. (2007). Groundwater Recharge fromRun-off, Infiltration and Percolation. Springer, TheNetherlands.


_ WHO (2006). Guidelines for the safe use of wastewater,excreta and greywater- Volume 3: Wastewater and excretause in aquaculture. WHO, Geneva.



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Digested or stabilized Faecal Sludge is refered to as‘Biosolids’. Depending on the quality of the biosolids,they can be applied to public or private lands, forlandscaping or for agriculture.

The USEPA defines different levels of biosolids depend-ing on the treatment and quality, and therefore the healthrisk. Class A biosolids (i.e. biosolids that can be sold forpublic use) can be used with nearly no restrictions.Please consult the guidelines for specific use criteria.Biosolids can be used in agriculture, home gardening,forestry, sod and turf growing, landscaping, parks, golfcourses, mine reclamation, dump cover, or erosion con-trol. Although biosolids have lower nutrient levels thancommercial fertilizers (for nitrogen, phosphorus andpotassium respectively), they can be used to replacepart or all of commercial fertilizers that are used.Additionally, biosolids have been found to have proper-ties that are superior to those of fertilizers, such asbulking properties, water retention properties and theslow, steady release of nutrients.Biosolids are spread on the ground surface using conven-tional manure spreaders, tank trucks or speciallydesigned vehicles. More liquid biosolids (e.g. from anaer-

obic reactors) can be sprayed onto, or injected into, theground. Dewatered biosolids may be ‘flung’, which ismost common in forests.

Adequacy Although biosolids are sometimes criti-cized for containing potentially high levels of metals orcontaminants, commercial fertilizers are also contami-nated to varying degrees, most likely with cadmium orother heavy metals. Faecal sludge from pit latrines hasno, if any, chemical inputs and is therefore not a highrisk source of contamination. Faecal sludge that origi-nates at large-scale wastewater treatment plants ismore likely to be contaminated since it receives indus-trial and domestic chemicals, as well as surface waterrun-off which may contain hydrocarbons and metals.Depending on the sludge source, biosolids can serve asa valuable and often much-needed source of nutrients.Land application of biosolids may be less expensivethan disposal.Application rates and usages for biosolids shouldtake into account not only the presence of pathogensand contaminants, but also the quantity of nutrientssuch that they are spread at a sustainable and ‘agro-nomic’ rate.

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D.11D.11 Land Application of SludgeApplicable to:System 1, 3, 5, 6, 7, 8

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Inputs:Treated Sludge

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Appropriate safety and application regulations shouldbe followed.

Health Aspects/Acceptance The greatest barrierto biosolid use is generally acceptance. However, evenwhen biosolids are not accepted in agriculture or bylocal industries, they can still be useful for municipalprojects and can actually provide significant savings topublic projects (e.g. mine reclamation).Depending on the source of the faecal sludge and onthe treatment method, biosolids can be treated to alevel where they are generally safe and without signifi-cant odour or vector problems.

Maintenance Spreading equipment must be main-tained to ensure continued use. The amount and rate ofbiosolid application should be monitored to preventoverloading and thus, the potential for nutrient pollution.

Pros & Cons:+ Can accelerate reforestation+ Can reduce use of chemical fertilizers and improvewater retention of soils

+ Can reduce erosion+ Low cost- May pose public health risk, depending on thequality and application

- Odours are normally noticeable (depending on priortreatment)

- May require special spreading equipment- Micropollutants may accumulate in the soil andcontaminate groundwater

References

_ U.S. EPA (1999). Biosolids Generation, Use, and Disposalin the United States, EPA-530/R-99-009. U.S. EnvironmentalProtection Agency: Washington, D.C.Available: www.epa.gov

_ U.S. EPA (1994). A Plain English Guide to the EPA Part 503Biosolids Rule, EPA832-R-93-003. U.S. EnvironmentalProtection Agency: Washington, D.C.Available: www.epa.gov



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Surface Disposal refers to the stockpiling of sludge,faeces, biosolids, or other materials that cannot beused elsewhere. Once the material has been taken toa Surface Disposal site, it is not used later. This tech-nology is primarily used for biosolids, although it isapplicable for any type of dry, unusable material.

One application of Surface Disposal that is shown onthe System Templates is the disposal of dry cleansingmaterials, such as toilet paper, corn cobs, stones, news-paper and/or leaves. These materials can not always beincluded along with other water-based products insome technologies and must be separated. A rubbishbin should be provided beside the User Interface to col-lect the cleansing materials. Dry materials can beburned (e.g. corn cobs) or disposed of along with thehousehold waste. For simplicity, the remainder of thisTechnology Information Sheet will be dedicated to fae-cal sludge, since standard solid-waste practices arebeyond the scope of this Compendium.

When there is no demand or acceptance for the benefi-cial use of biosolids, they can be placed in monofills(biosolids-only landfills) or heaped into permanent

piles. The main difference between Surface Disposaland Land Application is the application rate. There is nolimit to the quantity of biosolids that can be applied tothe surface since there are no concerns about nutrientloads or agronomic rates. There is however, concernrelated to groundwater contamination and leaching.More advanced surface disposal systems may incorpo-rate a liner and leachate collection system in order toprevent nutrients and contaminants from infiltrating thegroundwater.Landfilling biosolids along with Municipal Solid Waste(MSW) is not advisable since it reduces the life of alandfill which has been designed for the containment ofmore noxious materials. As opposed to more central-ized MSW landfills, Surface Disposal sites can be situat-ed close to where the faecal sludge is treated, limitingthe need for long transport distances.

Adequacy Since there are no benefits gained fromthis type of disposal technology, it should not be consid-ered as a primary option. However, where acceptancetowards biosolid use does not exist, the contained andcontrolled stockpiling of biosolids is far preferable touncontrolled dumping.



D.12D.12 Surface DisposalApplicable to:Systems 1–8

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Inputs:Faecal Sludge FaecesTreated Sludge Dry Cleansing Material

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Biosolids can be applied in almost every climate andenvironment, although they should not be stored wherethere is frequent flooding or where the groundwatertable is high.

Health Aspects/Acceptance Since the SurfaceDisposal site is located far from and protected from thepublic, there should be no risk of contact or nuisance.Care should be taken to protect the disposal site fromvermin and from pooling water, both of which couldexacerbate smell and vector problems.

Maintenance Maintenance staff should ensure thatonly appropriate materials are disposed of at the site,and must maintain control over the traffic and hours ofoperation.

Pros & Cons:+ Can make use of vacant or abandoned land+ Low cost+ May prevent unmitigated disposal- Non-beneficial use of a resource- Odours are normally noticeable (depending onprior treatment)

- May require special spreading equipment- Micropollutants may accumulate in the soil andcontaminate groundwater

References

_ U.S. EPA (1999). Biosolids Generation, Use, and Disposalin the United States, EPA-530/R-99-009. U.S. EnvironmentalProtection Agency: Washington, D.C. Available:www.epa.gov

_ U.S. EPA (1994). A Plain English Guide to the EPA Part 503Biosolids Rule. EPA832-R-93-003. U.S. EnvironmentalProtection Agency: Washington, D.C.Available: www.epa.gov



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Glossary

Glossary

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Aerobic: means ‘requiring oxygen’. Aerobic processes canonly function in the presence of molecular oxygen (O2), andaerobic organisms are those that use oxygen to drivecellular respiration and store energy.

Anaerobic: means ‘in the absence of oxygen’. Anaerobicprocesses are either hindered, or halted by the presence ofoxygen. Anaerobic processes are often more foul-smellingthan aerobic processes.

Anal cleansing water: is water that is collected after havingbeen used to clean oneself after defecating (and/orurinating). It is generated by those who use water, ratherthan dry material for anal cleansing.

Anoxic: means ‘deficient in oxygen’. Organisms that can livein an anoxic environment can use oxygen that is boundin other molecules (e.g. nitrate, sulphate). Anoxic conditi-ons are often found at the interface between aerobicand anaerobic environments (e.g. in trickling filters or infacultative ponds).

Bacteria: bacteria are simple, single cell organisms. Bacteriaobtain nutrients from their environments by excretingenzymes which dissolve complex molecules into moresimple ones that can then pass through the cell membrane.Bacteria live everywhere on earth and are essential formaintaining life and performing essential ‘services’ such ascomposting, aerobic degradation of waste, and digestingfood in our stomachs; some types however can bepathogenic and cause severe illness.

BOD/Biochemical Oxygen Demand: a measure of theamount of oxygen used by bacteria to degrade organic mat-ter in wastewater (expressed in mg/L). It is a proxy measurefor the amount of organic material that is present in water:the more the organic content, the more oxygen required todegrade it (high BOD); the lower the organic content, theless oxygen required to degrade it (low BOD).

Biological treatment: the use of living organisms (e.g. bac-teria) to treat waste; this is in contrast to chemical treat-ment which relies on chemicals to transform or removecontaminants from waste.

Biodegradable: a substance that can be broken down intobasic molecules (e.g. carbon dioxide, water) by organicprocesses carried out by bacteria, fungi, and other micro-oganisms.

Biomass: refers to the quantity of living organisms. It isoften used to describe the ‘active’ part of the sludge that isresponsible for degrading the organic matter.

Biogas: the common name for the mixture of gases releasedfrom anaerobic digestion. Typically biogas is comprisedof methane (50–75%), carbon dioxide (25–50%) and vary-ing quantities of nitrogen, hydrogen sulphide, water andother components.

Biosolids: faecal sludge that has been digested/stabilized.Biosolids can be used and applied with reduced riskcompared to raw faecal sludge.

Blackwater: the mixture of urine, faeces and flushing wateralong with anal cleansing water (if anal cleansing is prac-ticed) or dry cleansing material (e.g. toilet paper). It is highin organics and pathogens.

Brownwater: the mixture of faeces and flushing water, butwith NO urine.

CBO: Community Based Organization (CBO) is a smallorganization that does not have the registered status of anNGO (Non-Governmental Organization) but is a structuredgroup of volunteers who work together to achieve a com-mon goal. Anyone can start their own CBO.

Cesspit: a covered hole or pit to receive drainage or sewage.

Chemical treatment: the treatment of wastewater usingchemicals to remove pollutants from the wastewater.A common example is the use of alum for coagulation orchlorine for oxidation.

C:N ratio: carbon to nitrogen ratio. This ratio describes therelative amounts of dry available carbon to dry availablenitrogen. The ideal value for microbes is around 30:1 (usu-ally expressed as just 30).

Coagulation: the process of forming small clumps soparticles so that they may be more easily settled out ofwastewater.

COD/Chemical Oxygen Demand: Quantitative measure ofthe amount of oxygen required for chemical oxidationof carbonaceous (organic) material in a sample by a strongchemical oxidant, expressed in mg/L. COD is always equalto or higher than BOD since it is the sum of the oxygenrequired for both biological and chemical oxidation.


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Combined Sewers: sewers that are designed to carry bothblackwater and greywater from homes and stormwater(rainfall). Combined sewers must be larger than SeparateSewers to account for the high volume.

Compost/EcoHumus: the earth-like, brown/black materialthat is the result of decomposed organic matter;generally is has been hygienized sufficiently that it can beused safely in agriculture.

Composting: the process by which biodegradable compo-nents are biologically decomposed under controlledconditions by microorganisms (mainly bacteria and fungi).

Concrete: A mixture of cement, sand, gravel and water thatwill harden into a solid, stone-like material.

Decentralization: the shift of decision making and respon-sibility from central authorities to the same level at whichthe policies are directed.

Decomposition: the transformation of dead organic material(plants, animals, etc.) into more basic compounds andelements.

Desludging: the process of removing sludge from a tank,pit, or other storage unit.

Digestion: similar to decomposition, but usually applied tothe decomposition of organic materials (including bacteria)by bacteria, in sludge.

Dry Cleansing Materials: may be paper, corncobs, stonesor other dry materials that are used for anal cleansing(instead of water). Depending on the system, the dry clean-sing materials may be collected and disposed of separately.

E. Coli: the common abbreviation of Escherichia Coli. It is atype of bacteria that inhabits the intestinal tract of humans,and other mammals. It is not necessarily harmful, but it isused to indicate the presence of other, more dangerousbacteria.

Ecological Sanitation: is a term applied to waste treatmenttechnologies when they not only limit the spread of disease,but protect the environment and return nutrients to the soilin a beneficial way.

Effluent: the general name for a liquid that leaves the placeor process from where it originated.

Environmental Sanitation: as opposed to simply ‘sani-tation’, seeks to include all aspects of the physical environ-ment which may affect human health and well-being; typicalexamples of an environmental sanitation program mayinclude potable water, solid waste management, drainage,stormwater management, and sanitation.

Eutrophication: describes excess nutrient concentrationsin an aquatic ecosystem which leads to: (i) increased pro-ductivity of autotrophic green plants and to the blockingout of sunlight, (ii) elevated temperatures within the aquaticsystem, (iii) depletion of oxygen, (iv) increased algae growth,and (v) reduction in fauna and flora variety.

Evaporation: the process of water changing from a liquidstate to a gaseous state.

Evapotranspiration: evaporation that is facilitated byvegetation. Plants emit water through their stoma (pores)thus providing a greater surface from which water canevaporate.

Excreta: the mixture of urine and faeces that is notmixed with any flushing water.

Faecal Sludge: the general term for the undigested orpartially digested slurry or solid that results from the storageor treatment of blackwater or excreta.

Faeces: refers to (semi-solid) excrement without anyurine or water.

Filtrate: the liquid that has passed through a filter.

Floatation: The processes whereby lighter fractions of awastewater, including fats, oils, soaps, etc., rise above thewater and the solids, and can thus be separated.

Flushwater: the water that is used to transport excreta,urine and/or faeces from the User Interface to the nextFunctional Group technology.

Forage: aquatic or other plants that grow in planted dryingbeds or constructed wetlands and may be harvested forfeeding livestock.

Greywater: the total volume of water generated fromthe washing of food, clothes, dishware and people. It doesnot contain excreta, but it does contains pathogens andorganics.


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Groundwater: water that is naturally present beneath thesurface of the ground. In some instances groundwater maybe found several centimetres below the surface, or it maybe up to a hundred metres below the surface. Groundwateris generally quite clean and can be used for drinking water;for this reason care must be taken not to contaminategroundwater with sewage.

HCES: Household-Centred Environmental Sanitation is a10-step participatory planning process. The goal of theHCES approach is to involve stakeholders to developan Urban Environmental Sanitation Services Plan which willallow people to lead healthy and productive lives, protectthe natural environment while conserving and reusingresources. The guidelines for implementing HCES are avai-lable from www.sandec.ch.

Health: “is a state of complete physical, mental and socialwell-being and not merely the absence of disease orinfirmity.” (WHO, 1948).

Helminth: A parasitic worm, i.e. one that lives in or on itshost, causing it damage. Examples include especiallyparasitic worms of the human digestive system, such asroundworm (e.g. Ascaris) or hookworm.

Humus: an earth-like dark brown or black material com-prised primarily of decomposed organic material.

Hydraulic Retention Time (HRT): defines the (average)amount of time that a liquid stays in a reactor.It has the unit of time (t) and is calculated by diving thevolume of the reactor (m3) by the flow (m3/h).

Hydraulic Gradient: the surface slope of a liquid in a pipe,i.e. the liquid will flow along the hydraulic gradient ofthe system and if there is a inflow that is lower than thegradient, water will flow upwards to meet the gradient line.

Influent: the general name for the liquid that enters into aplace or process; the effluent of one process is the influentof the next.

Invert: the bottom of the inside of a pipe. The depth of theinvert is especially important when designing sewers.

Leachate: the liquid fraction of a mixed waste that, throughgravity or filtration, is separated from the solid component.

Lime: the common name for calcium hydroxide. It is a white,caustic powder that is produced by heating limestone.

Macrophytes: large aquatic plants visible to the naked eye.Their roots and differentiated tissues may be emergent(cattails, bulrushes, reeds, wild rice), submergent (watermilfoil, bladderwort) or floating (duckweed, lily pads).

Microbe: general name given to a microorganism; a micro-scopic bacterium.

Microorganisms: neither plant nor animal, but small, simpleunicellular or multicellular organisms such as protozoa,algae, fungi, viruses, and bacteria.

Micropollutants: pollutants which are present in extremely lowconcentrations, but whose effect is known to be significant.Pharmaceuticals and hormones are two groups of micropollu-tants which are causing increasing concern for their effectson the endocrine system and sexual development.

Monitoring: the continuous collection and assessmentof data (qualitative and quantitative) with the intended goalof optimizing performance and minimizing flaws.

Nightsoil: the name generally given to excrement that maybe collected manually. Generally this practice is carried outwhere there is neither infrastructure for collection andstorage or where there is agricultural land that can receivethe waste. Unprotected handling and use in agricultureshould be treated with caution.

Nutrient: any substance (including protein, fat, carbohydrate,vitamins, or minerals) that is used for growth. In wastewatertreatment systems, ‘nutrient’ usually refers to nitrogenand/or phosphorus since they are primarily responsible foreutrophication.

Oocyst: a thick-walled spore into which different organisms(like Cryptosporidium) can transform as a way of resisting,and surviving through periods of environmentally harshconditions.

Operation and Maintenance: all work relating to the day-to-day activities that keep a process or system functioningsmoothly to prevent delays, repairs and/or downtime.

Organics: general name given to organic materials. Anorganic is any molecule that contains carbon. Examples oforganic compounds are proteins, lipids, amino acids,vitamins, and other building blocks of life. Organics refersto the organic material that must be added to some techno-logies in order to make them function properly (e.g. com-posting chambers).


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155

Pathogen: infectious biological agent (bacteria, protozoa,fungi, parasites, viruses) that inflicts disease or illness onits host.

Parasite: any organism that lives on or in another organismand damages its host.

Percolation: the movement of liquid through soil with theforce of gravity.

PET: PET is the common name for Polyethylene terephthalate.It is a clear plastic that can be recycled.

pH: the measure of the acidity or alkalinity of a substance.A pH value below 7 indicates that it is acidic, a pH valueabove 7 indicates that it is basic (alkaline).

Retention time: the theoretic time that one unit of water(or sludge) stays in one tank or pond. When referring tounits of water, the term Hydraulic Retention Time is oftenused (HRT) and is calculated by: HRT= V/Q, where Vis the volume of the tank and Q is the rate at which thewater leaves (e.g. m3/h).

Runoff: also referred to as Surface Runoff. It is the quantityof water that falls as precipitation but does not infiltrate tothe groundwater table.

Sanitation: general term used to describe a battery ofactions that all aim to reduce the spread of pathogens andmaintain a healthy living environment. Specific actionsrelated to sanitation include, wastewater treatment, solidwaste management and stormwater management.

Scum: general name given to the top, floating layer ofmaterial that sits above the water. It is most noticeable inseptic tanks where distinct layers of scum, water, andsludge form over time.

Sedimentation: gravity settling of particles in a liquid suchthat they accumulate. Also called settling.

Septage: ‘liquid and solid material pumped from a septictank, cesspool or other primary treatment source’.(Bellagio, 2005).

Sewage: general name given to the mixture of water andexcreta (urine and faeces), although in the Compendium itreferred to as blackwater.

Sewer: an open channel or closed pipe used to convey sewage.

Sewerage: all the components of a system used for col-lecting, transporting and treating sewage (including pipes,pumps, tanks, etc.).

Sitter: the general name given to someone who prefers to siton the User Interface, rather than squat over it.

Sludge: the thick, viscous layer of materials that settles tothe bottom of septic tanks, ponds, and other sewagesystems. Sludge is comprised mostly of organics, but alsosand, grit, metals, and various chemical compounds.

Specific Surface Area (SSA): describes the property of asolid material. SSA is defined as the ratio of the surfacearea to the volume in units of m2/m3.

Squatter: the general name given to someone who prefers tosquat over the User Interface, rather than sit directly on it.

Stabilized: the term used to describe the state of organicmaterial that has been completely oxidized and sterilized.When most of the organic matter has been degraded,bacteria begin to starve and consume their own cytoplasm.The organic matter left by the dead bacteria is then de-graded by other organisms, which results in a fullystabilized product.

Stakeholder: any group, person, or agency that has aninterest in or is affected by a policy, plan, or project.

Stormwater: the general term for the rainfall that runs off ofroofs, roads and other surfaces before flowing towards low-lying land. It is the portion of rainfall that does notinfiltrate into the soil.

Sullage: synonym for greywater. It includes wastewaterfrom cooking, washing, and bathing, but does not includeany excreta.

Superstructure: name given to the structure that providesprivacy to a person using a toilet/bathing facility. A super-structure may be permanent (made of concrete or bricks)or mobile (made of bamboo or cloth).

Surface water: term to describe rainwater that runs over-land (i.e. does not infiltrate the ground). Surface water,unlike ground water is generally not safe for consumptionas it accumulates pathogens, metals, nutrients andchemicals as it flows across contaminated surfaces.


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Sustainability: “meets the needs of the present generationwithout compromising the ability of future generations tomeet their own needs” (Brundtland Commission, 1987).

Sustainable Sanitation: “The main objective of a sanitationsystem is to protect and promote human health by pro-viding a clean environment and breaking the cycle ofdisease. In order to be sustainable a sanitation system hasto be not only economically viable, socially acceptable,and technically and institutionally appropriate, it shouldalso protect the environment and the natural resources”(SuSanA, 2007).

TS: Total Solids (TS) is the sum of Total Dissolved Solids(TDS) and Total Suspended Solids (TSS). When a water orsludge sample is filtered and dried at 105°C, the residuethat remains is referred to as the Total Solids. It is measu-red in mg/L (mass per volume).

Urea: the organic molecule (NH2)2CO that is excreted in urineas a way of ridding the body of excess nitrogen. With time,the urea in urine breaks down into carbon dioxideand ammonia, which is readily used by organisms in soil.

Urine: is the liquid waste produced by the body to rid itself ofurea and other waste products.

Vector: the organism that transmits a disease to the host(the vector itself may be a host, but is not the ‘true host’).Flies are vectors as they can transmit pathogens fromfaeces to humans.

Ventilation: the movement of air; air is both supplied to,and removed from a space.

WC: derived from the words ‘Water Closet’. It is an ambi-guous term that can either refer to the actual room wherea toilet is located, or the actual toilet itself.

Washer: the general name for those who use water tocleanse after defecating.

Wastewater: traditionally described as any water that hasbeen used and is unfit for further use. The term isapplied broadly to all waters originating in toilets, showers,sinks, washing areas, factories, etc. More recentlyterms such as ‘blackwater’, ‘greywater’ and ‘yellow water’have been adopted both as a way to describe the com-position more accurately, and to emphasize the fact thatused waters have nutrients, are valuable, and shouldnot be ‘wasted’.

Water table: the top level of the groundwater; also referredto as the groundwater table. A water table is not staticand can vary with season, year, and usage.

Wiper: the general name for those who use solid materials,like paper, to cleanse after defecating.

Yellowwater: is the name for urine combined with flushingwater. It is not included in any of the systems in thisCompendium.


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Imprint

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Bibliographic reference:Tilley, Elizabeth et al, 2008. Compendium of Sanitation Systemsand Technologies. Swiss Federal Institute of Aquatic Scienceand Technology (Eawag). Dübendorf, Switzerland.

ISBN: 978-3-906484-44-0

© Eawag/Sandec; Swiss Federal Institute of Aquatic Scienceand Technology / Water and Sanitation in Developing Countries,Dübendorf, Switzerland, www.sandec.ch© WSSCC; Water Supply and Sanitation Collaborative Council,Geneva, Switzerland, www.wsscc.org

Permission is granted for reproduction of this material, inwhole or part, for education, scientific or development relatedpurposes except those involving commercial sale, providedthat full citation of the source is given.

Graphic Design: Pia Thür, ZürichTechnical Drawings: Paolo Monaco, ZürichPhotos: Eawag-SandecFirst edition: 2000 copiesPrinted by: Mattenbach AG, Winterthur, Switzerland

EawagÜberlandstrasse 133P.O. Box 6118600 DübendorfSwitzerlandPhone +41 (0)44 823 52 86Fax +41 (0)44 823 53 [email protected]

Abundant information exists about sanitation solutionsbut it is scattered throughout hundreds of books andjournals; this Compendium aims to pull it all together inone volume.By ordering and structuring a huge rangeof information on tried and tested technologies into oneconcise document, the reader is provided with a usefulplanning tool for making more informed decisions.

Part 1 describes different system configurations fora variety of contexts.Part 2 consists of 52 differentTechnology InformationSheets, which describe the main advantages, disadvanta-ges, applications and the appropriateness ofthe technologies required to build a comprehensivesanitation system. EachTechnology Information Sheetis complemented by a descriptive illustration.

ISBN: 978-3-906484-44-0

Compendiumof Sanitation Systems

and Technologies

Water Supply & SanitationCollaborative Council

International Environment HouseChemin des Anémones 91219 Châtelaine-GenevaSwitzerlandPhone +41 22 917 [email protected]

Cover: Sanitation Options Workshop in Dodoma, Tanzaniain 2008 moderated by Mr. Rukeha from the local NGO Mamado

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