INFORMATION FOR ACTION FROM THE WATER AND … · - for landscape irrigation, toilet flushing, and industrial purposes, the water must be adequately disinfected and a chlorine residual

INFORMATION FOR ACTION FROM THE WATER AND SANITATION FOR HEALTH PROJECT

Water Reuse in Developing CountriesIncluding Guidelines for Wastewater Reuse

REFERENCEWATER SUPPLY AN'O

As communities around the world reach the limits of their water supplies, wastewater is increasingly being reusedto conserve and increase available water resources and to reduce pollution. However, standards and regulations tomanage and plan water reuse programs have been lacking.

In 1992, the U.S. Environmental Protection Agency's 1980 Guidelines for Water Reuse was revised and up-dated by Camp Dresser & McKee Inc., with funding from E.P.A. and the U.S. Agency for International Developmentthrough AJ.D.'s Water and Sanitation for Health (WASH) Project. The primary purpose of the Guidelines is to pro-vide information about how to develop effective wastewater reuse programs. They are intended for U.S. utilities andregulatory agencies that are seeking to establish standards or regulations on the reclamation and reuse of wastewater.They also provide useful information for developing countries.

The Guidelines address water reclamation for nonpotable urban, industrial, and agricultural use. Also, attentionis given to augmentation of potable water supplies by indirect reuse. Although sources of reclaimed water may rangefrom industrial wastewaters to the return flows from agricultural irrigation systems, the Guidelines cover only theuse of water reclaimed from the effluents generated by domestic wastewater treatment facilities.

The revised edition of the Guidelines incorporates recent institutional and technical advances in water reuse. In addition,it includes a chapter on water reuse applications in countries outside the United States—mainly in developing countries,particularly the arid and semi-arid countries of North Africa, although the manual is applicable to all countries.

— This Fact Sheet provides a summary of the Guidelines, outlining the basic issues for water reuse in de-veloping countries.

The Golden Rule of Wastewater Reuse

-; Whether wastewater is being reused in industrialized or developing countries, it must be treated. The ex-tent of the treatment depends upon how it will be used. Higher-level uses, such as irrigation of vegetablesto be consumed without processing, require a higher level of treatment than lower-level uses, such as pas-ture irrigation. In urban reuse, where there is a high potential for human exposure to reclaimed water used

- for landscape irrigation, toilet flushing, and industrial purposes, the water must be adequately disinfectedand a chlorine residual must be maintained in the distribution system.

The Basic Rationale for Wastewater Reuse

Many urban residential, commercial, and industrial uses can be satisfied with water of less than potablequality: irrigation of lawns, parks, and roadway borders; air conditioning and industrial cooling towers; in-dustrial processing; toilet and urinal flushing; construction; cleaning and maintenance, including vehiclewashing; scenic waters and fountains, and environmental and recreational purposes. Customarily, publicwater supplies provide water of potable quality to serve all these purposes. When reclaimed water is substi-tuted for potable water formerly used for nonpotable purposes it is as if a "new" source has been discov-ered, and it becomes possible to maintain the highest quality for public consumption and to extend potablewater to an increased population.

While the need for additional water supply has been the impetus for numerous water reuse programs inthe United States, many programs have been initiated in response to rigorous and costly requirements foreffluent discharge to surface waters. In developing countries the rationale for reuse is generally to increasewater supplies, although pollution abatement is a growing concern.

Water I

The Current Situation in Developing Countries

A number of conditions that prevail in developing countries have an impact on the potential for reusingwastewater.

• Lack of wastewater collection ana treatment. Indeveloping countries only about 7% of the population isserved by wastewater collection and treatment facilities.Many cities are unsewered, and the sewers that do existoften discharge untreated wastewater into the nearestdrainage channel or water course. Collecting thewastewaters for treatment is a formidable andexpensive task, but reuse cannot begin until sewers,interceptors, trunk sewers, and treatment plants arebuilt.

• Inadequate treatment of wastewater. The majorcities of developing countries, including Eastern Europeand the former Soviet Union, generally do have sewersand often wastewater treatment plants, but treatment isseldom sufficient for safe reuse. As these countriesrehabilitate their urban infrastructure, there will besignificant opportunities to upgrade wastewatertreatment plants to reclaim wastewater for urbannonpotable reuse.

• Protection of public health. High-quality water isgenerally not available for irrigating high-valuemarket crops near developing country cities. Thecommon practice today is to use raw wastewater forirrigation or to withdraw water from streams that arepolluted with raw wastewater. The consequentcontamination of food stuffs to be eaten rawmaintains a high level of enteric disease. Althoughwastewater reuse is common in developing countries,the protection of public health has not yet providedan incentive for initiating safe agricultural reusepractices in these countries.

• Potential for wastewater reuse. Almost all waterreuse in developing countries currently is foragricultural purposes; however, meeting a range ofurban nonpotable water demands through reuse is apromising option in the growing urban areas of Asia,Africa, Latin America, Europe, the former Soviet Union,and Australia. By 2020, more than half the populationof Asia, Africa, and Latin America will be living incities. With urban growth, water reclamation fornonpotable reuse may be less costly and more feasiblethan developing new sources of fresh water. Urbanreuse has two main advantages over agricultural reuse.

• It is partially nonconsumptive. Urban uses,such as toilet flushing, vehicle washing,stack gas cleaning, and industrial ;processing are nonconsumptive. The watercan be reclaimed again for subsequent

reuse, including consumptive use inagriculture or evaporative cooling.

• It is more feasible. Urban markets forreuse are generally closer to the point oforigin of the reclaimed water thanagricultural markets. Also, the value ofwater for urban reuse is generally fargreater than for agricultural reuse. It can bemetered and costs can be recovered. Thecosts of providing water for domestic urbanreuse may be higher than water for someirrigation uses because more treatment isnecessary. For market crops, the qualityrequirements are much the same as forunrestrictive urban use.

• The best prospects for wastewater reuse. Thedeveloping areas of larger, richer, rapidly growing citieswith short water supplies, some sewerage, and pressuresto control pollution are ideal candidates for wastewaterreuse. Sao Paulo, Brazil, is a good example. There thehigh quality effluent produced by the first module of anactivated sludge treatment plant inspired studies ofreuse for industry.

Institutional & Financial Aspects ofWastewater ManagementRelated WASH Reports

Point Source Pollution in the Danube Basin:Vol. 1—Summary: Vol. II—InstitutionalStudies: Vol. Ill: Country Technical Reports;Users Manual for the Danube EmissionsManagement Decision Support System.(FR 374)

Guidelines for Improving Wastewater and SolidWaste Management, (forthcoming)

Andean Regional Workshop on Alternative Ap-proaches to Wasteii'v^r Management.(FR394)

To obtain a copy of these reports or acomplete list of WASH reports^ contactWASH headquarters.

2 Water Reuse Fact Sheet

Typesof Reuse

Urban Reuse

All types of landscapeirrigation, also vehiclewashing, toilet flushing, usein fire protection systemsand commercial airconditioners, and otheruses with similar access orexposure to the water

Restricted AccessArea Irrigation

Sod farms, silviculture sites,and other areas wherepublic access is prohibited,restricted, or infrequent

Agricultural Reuse—Food Crops NotCommercially Processed3

Surface or spray irrigationof any food crop, includingcrops eaten raw

Agricultural Reuse—Food Crops CommercialProcessed

Agricultural Reuse—Non-Food Crops

Pasture for milking animals;fodder, fiber and seed crops

Treatment1

• Secondary• Filtration• Disinfection

• Secondary• Disinfection




Table 2:1

Reclaimed WaterQuality2

• p H = 6 - 9• <10 mg/l BOD• <2NTU• No detectable

fecal coif 100 ml3

• 1 mg/l CI2residual (min.)

• p H = 6 - 9• <30 mg/1 BOD• <30mg/ISS• £200 fecal

cosnoomi4


• p H = 6 - 9• <10 mg/l BOD• S2NTU• No detectable

fecalcoli/IOOml3


• pH = 6 - 9• ¿30 mg/l BOD• £30mg/ISS• £200 fecal

coli/100 ml*• 1 mg/t Cfe

residual (min.)

• pH = 6 - 9• <30 mg/l BOD• <30mg/ISS• £200 fecal

coliH 00ml4

• 1 mg/l Ckresidual (min.)

PA. Comprehensive Guidelines for Wastewater Reuse

ReclaimedWater

Monitoring

pH—weeklyBOD-weeklyTurbidity-continuousCol ¡form—dailyCI2 residual-continuous

• pH—weekly• BOD—weekly• SS—daily

Coliform—daily« CI2 residual—

continuous

• pH—weekly• BOD—-weekly• Turbidity—

continuous• Coliform—daily• CI2 residual-

continuous

• pH—weekly• BOD—weekly• SS—daily• Coliform—daily• CI2 residual—

continuous

• pH—weekly• BOD—weekly• SS—daily• Coliform—daily• CÍ2 residual—

continuous

SetbackDistances6

• 15 m topotablewater supplywells

• 90 m to potablewater supplywells

• 30 m to areasaccessible tp thepublic (if sprayirrigation)



• 30 m to areasaccessible tothe public

• 90 m to potablewater supplyweils

• 30 m to areasaccessible tothe public ¡ifspray irrigation)

Comments

• At controHed-access irrigation sites where design and operational measuressignificantly reduce the potential of public contact with reclaimed water, alower level of treatment, e.g., secondary treatment and disinfection toachieve <14 fecal coli/100 ml, may be appropriate.

• Chemical (coagulant and/or polymer) addition prior to filtration may benecessary to meet water quality recommendations.

• The reclaimed water should not contain measurable levels of pathogens.7

• Reclaimed water should be clear, odorless, and contain no substances thatare toxic upon ingestion.

• A higher chlorine residual and/or a longer contact time may be necessary toassure that viruses and parasites are inactivated or destroyed.

• A chlorine residual of 0.5 mg/l or greater in the distribution system isrecommended to reduce odors, slime, and bacterial regrowth.

• If spray irrigation, SS less than 30 mg/l may be necessary to avoid cloggingof sprinkler heads.

• Chemical (coagulant and/or polymer) addition prior to filtration may benecessary to meet water quality recommendations.



* High nutrient levels may adversely affect some crops during certain growthstages.

• If spray irrigation, SS less than30mg/l may be necessary to avoid cloggingof sprinkler heads.

• High nutrient levels may adversely affect some crops during certain growthstages.

• If spray irrigation, SS less than 30 mg/l may be necessary to avoid cloggingsprinkler heads.

• High nutrient levels may adversely affect some crops during certain growthperiods.

• Milking animals should be prohibited from grazing for 15 days after irrigationceases. A higher level of disinfection, e.g., to achieve <14 fecal coli/100 ml,should be provided if this waiting period is not adhered to.

Continued...

Typesof Reuse

RecreationalImpoundments

Incidental contact (e.g.,fishing and boating) and fullbody contact with reclaimedwater allowed

Landscape Impoundments

Aesthetic impoundmentwhere public contact withreclaimed water is notallowed

Construction Uses

Soil compaction, dustcontrol, washing aggregate,making concrete

Industrial Reuse

Once-through cooling

Recircufating cooling towers

Other Industrial Uses

Treatment1




• Secondary


(chemicalcoagulation andfiltration may beneeded)


• p H = 6 - 9• <10 mg/l BOD• <2 NTU• No détectable

fecalcoli/IOOmí3


* <30 mg/l BOD* 530 mg/l SS• S200 fecal

fecal ooli/100 mi4

• 1 mg/l Cferesidual (min.)

• <30 mg/l BOD• ¿30 mg/l SS• <200 fecal

fecaJcoliiiOOml4


• p H = 6 - 9• <30 mg/l BOD• <30mg/ISS• S200 fecal

coli/IOOml4


• Variable,depends onrecirculationratio

ReclaimedWater

Monitoring

• pH—weekly• BOD—weekly• Turbidity—

continuous• Col ¡form—daily• CI2 residual-

continuous

• pH—weekly• SS-daily• Coiiform—daily• Cfe residual—

continuous

• BOD—weekly• SS-daily• Coiiform—daily• CÎ2 residual-

continuous

• pH—daily• BOD-^weekly• SS—weekly• Coiiform—daily• CI2 residual—

continuous

SetbackDistances6

• 150 m to potablewater supplywells (minimum)if bottom notsealed

• 150 m topotablewater supplywells (minimum)if bottom notsealed

• 90 m to areasaccessible tothe public

• 90 m to areasaccessible tothe public.May be reducedif high level ofdisinfection isprovided.

Comments

• Dechtorination may be necessary to protect aquatic species of flora and fauna.• Reclaimed water should be non-irritating to skin and eyes.• Reclaimed water should be clear, odorless, and contain no substances that

are toxic upon ingestion.* Nutrient removal may be necessary to avoid aigae growth in impoundments.• Chemical (coagulant and/or polymer) addition prior to filtration may be

necessary to meet water quality recommendations.• The reclaimed water should not contain measurable levels of pathogens.7


• Fish caughl in impoundments can be consumed.

• Nutrient removal processes may be necessary to avoid algae growth inimpoundments.

• Dechlorination may be necessary to protect aquatic species of flora andfauna.

• Workercontactwithreclaimedwatershould be minimized.• A higher level of disinfection, e.g., to achieve <14 fecal coli/100 ml, should

be provided where frequent worker contact with reclaimed water is likely.

• Windblown spray should not reach areas accessible to users or the public.

• Windblown spray should not reach areas accessible to the public.• Additional treatment by user is usually provided to prevent scaling, corrosion,

biological growths, fouling and foaming.

Continued...

Typesof Reuse

Environmental Reuse

Wetlands, marshes, wildlifehabitat, streamaugmentation

Groundwater Recharge ,

By spreading or injectioninto non potable aquifers

Indirect Potable Reuse

Groundwater recharge byspreading into potableaquifers

Groundwater recharge byinjection into potableaquifers

Treatment1

• Variable• Secondary and

disinfection(min.)

• Site specific anduse dependent

• Primary (min.)for spreading

• Secondary (min.)for injection

• Site specific• Secondary and

disinfection (min.)May abo needfiltration and/oradvanced waste-water treatment

• Secondary• Filtration• Disinfection• Advanced

wastewatertreatment


Variable, but notto exceed:• <30 mg/l BOD• <30 mg/l SS* <200 fecal

coli/100 ml*

• Site specificand usedependent

• Site specific• Meet drinking

water standardsafter percolationthrough vadosezone

Includes, but notlimited to, thefollowing:• pH = 6.5-8.5• <2NTU• No detectable

fecal coli/100 ml3


• Meet drinkingwater standards

ReclaimedWater

Monitoring

• BOD—weekly• SS-daily* Coliform—daily• CI2 residual—

continuous

• Depends ontreatment anduse

Includes, but notlimited to, thefollowing:• pH—daily• Coliform—daily• CI2 residual-

continuous* Drinking water

standards—quarterly

• Other5—depends onconstituent

Includes, but notlimited to, thefollowing:* pH—daily• Turbidity—

continuous• Coliform—daily• CI2 residual—

continuous• Drinking water

standards-quarterly


SetbackDistances6

• Site specific

• 600 m toextraction wells.May varydepending ontreatmentprovided andsite-specificconditions.

• 600 m toextraction wells.May varydepending onsite-specificconditions.

Comments

• Dechlorination may be necessary to protect aquatic species of flora andfauna.

• Possible effects on groundwater should be evaluated.• Receiving water quality requirements may necessitate additional treatment• The temperature of the redaiimed water should not adversely affect

ecosystem.

• Facility should be designed to ensure that no reclaimed water reachespotable water supply aquifers.

• For injection projects, filtration and disinfection may be needed to preventclogging.

• The depth to groundwater (i.e., thickness of the vadose zone) should be atleast 2m at the maximum groundwater mounding point.

• The reclaimed water should be retained underground for at least 1 year priorto withdrawal.

• Recommended treatment is site-specific and depends on factors such astype of soil, percolation rate, thickness of vadose zone, native groundwaterquality, and dilution.

• Monitoring wells are necessary to detect the influence of the rechargeoperation on the groundwater.

• The reclaimed water should not contain measurable levels of pathogensafter percolation through the vadose zone.7

• The reclaimed water should be retained underground for at least 1 year priorto withdrawal.

• Monitoring wells are necessary to detect the influence of the rechargeoperation on the groundwater.

• Recommended quality limits should be met at the point of injection.• The reclaimed water should not contain measurable levels of pathogens at

the point of injection.7

• A higher chlorine residual and/or a longer contact time may be necessary toassure virus inactivation.

Continued...

3í/5<D

3-O

1

XI

w<D

?2-CO3"S>

s.

Typesof Reuse

Indirect Potable Reuse

Augmentation of surfacesupplies ...-'

Treatment1

• Secondaiy

• Filtration

• Disinfection• Advanced

wastewatertreatment


Includes, but notlimited to, the

following:• pH =6.5-8.5• <2NTU• No detectable

fecalcoli/IOOml3

• 1 mg/l Cfcresidual (min.)

• Meet drinkingwater standards

ReclaimedWater

Monitoring

Includes, but notlimited to, the

following:• pH—daily• Turbidity—

continuous• Coliform—daily

• Cl2 residual-continuous

• Drinking waterstandards-quarterly


SetbackDistances6

• Site specific

Comments

• Recommended levei of treatment is site-specific and depends on factorssuch as receiving water quality, time and distance to point of withdrawal,dilution and subsequent treatment prior to distribution for potable uses.


• A higher chlorine residual and/or a longer contact time may be necessary toassure virus ¡nactivation.

• . • • •

Note: Portions of this table are discussed in detailin theGt/(tfef;nes.Ariy country interested in using the table to develop standards is advised to obtain a copy of theGLf/dei/nesforreference. Copies may be obtained or»request from WASH headquarters or from Camp Dresser & McKee Inc. in Cambridge, Massachusetts.

For virtually ail types of reuse, other recommended levels for trace heavy metals and other parameters may apply. Also.ahigh standard of treatment reliability is required, because of the potential for harm in theuse of improperly treated water. A number of fallible elements combine to make up a water reclamation system. These include the power supply, individual treatment units, mechanical equipment, the maintenanceprogram, and the operating personnel. Design features and backup systems are important in maintaining reclaimed system reliability, similar to drinking water reliability because customers depend upon continuity ofsupply as well as quality.

Footnotes

1. Types of treatment are as follows: Primary—a. physical treatment process to remove settteable organic and inorganic solids by sedimentation and floating materials by skimming; Secondary— includes activated sludgeprocesses, trickling f¡Itera, rotating biological contactors, and stabilization pond systems (secondary treatment should produce effluent in which both the BOD [biochemical oxygen demand] and SS [suspended solids] donot exceed 30 mg/l); Filtration—the passing of wastewater through undisturbed filter media such as sand and/or anthracite; Disinfection—the destruction, ¡nactivation, or removal of pathogenic micro-organisms bychemical, physical, or biological means (disinfection may be accomplished by chlorination, ozonation, other chemical disinfectants, UV radiation, and membrane and other prooesses); Advanced WastewaterTreatment—in cludeschemicaldarification, carbon aci sorption, reverse os mos is, and othe r mem brane processes , ai r stripp i ng, u I trafiltration, and ¡on exchange.

2. Unless otherwise noted, recommended quality limits appty to the reclaimed water at the point of discharge from the treatment facility. Concerning taking measurements of BOD, NTU, fecal coliforms and chlorine residual,please note the following. BOD levels are as determined from the 5-day BOD test. NTU (nephelometric turbidity units) limits should be met prior to disinfection; the average turbidity should be based on a 24-hour timeperiod; the turbidity should not exceed 5 NTU at any time; if SS is used in lieu of turbidity, the average SS should not exceed 5 mg/l. Unless otherwise noted, recommended coliform limits are median values determinedfrom the bacteriological results of the last 7 days for which analyses have been completed. Either the membrane filter or fermentation tube technique may be used. Total chlorine residual should be measured after aminimum contact time of 30 minutes.

3. The number of fecal coliform organisms should not exceed 14/100 ml in any sample.

4. The number of fecal coliform organisms should not exceed 800/1 (SO ml in any sample. Some stabilization pond systems may be able to meet this coliform limit without disinfection.

5. Monitoring should include inorganic and organic compounds, or dasses of compounds, that are known or suspected tobe toxic, carcinogenic, teratogenic, or mutagenic and are not included in #ie drkiking waterstandards.

7. It is advisable to fully characterize the microbiological quality of the reclaimed water prior to implementation of a reuse program.

8. Commercially processed food crops are those that, prior to sale to the public or others, have undergone chemical or physical processing sufficient to destroy pathogens.

Developing-Country Wastewater Reuse Issues

Planning Issues

ould

• ^intensive designs are to be preferred indeveloping countries. While the principles ofwastewater reclamation facility design andoperation are the same in developing andindustrialized countries, i m p l i c a t i o n ofprojects dlffers. Industrialized countries tendto be capital-intensive while developingcountries are labor-intensive. In develop™countries a facility that can be built andoperated with local labor will be more cost

any

teCEvAi

P.O. oi . .

Tel. (070)

-(.Ci

— —

effective than one which uses more modemcapital -intensive technology. In instanceT

17-f l ^ k t o b e Perf°rmed cannot bemadüy performed by even lowest labor,however, mechanization and automationare appropriate in the developing world.

* The difference in availability of qualifieden&neers, sdntists, and technicians calls for adifferent approach to planning. I n developingcountnes, where qualified staff and supportinstitutions are not readily availableinvestments in equipment that is reliableand simple, even though the initial costsmay be higher, may be advisable.

The advantages of new constructionover

t e 7 a t h e r * » * Points of disposalreclamation facilities is far more costly than

Technical Issues

• The need for infrastructure. The first technical

municipal wastewater treatment pllms fn

L £ f T % technol°gies- While the planning anddesign of sewerage systems is beyond the scopíof theGuidelines, it l s an important consideration. The c o s of

* Reducing the minimum slopes to reduceconstruction and pumping costs.

* Increasing the distance betweenmanholes.

• Using indigenous materials.

* Using computer-aided design to obtainleast-cost sewerage system layouts.

Most of these modifications increase maintenance

' Tthe l0W C0StS °f lab0r in d e ^ P « Sn d e ^ P « S; g e a t e r m a i n t e n a ^ «ste are offset by

ngs in construction. Also required are stroneinstuutions that can provide the nelssaTy per o n S forpreventive maintenance and other labor-intensiveprograms of construction and operation

Water Reuse Fact Sheet 3

• Water quality standards. A critical objective for anyreuse program is assurance that health protection is notcompromised by the use of reclaimed water. Althoughother objectives—such as preventing environmentaldegradation and meeting user requirements—are alsoimportant, the major consideration, especially indeveloping countries, is the safe delivery and use ofappropriate quality reclaimed water. Therefore waterquality standards must be established.

Public health is protected by reducing concentrationsof pathogenic bacteria, protozoa, and enteric viruses inthe reclaimed water; controlling chemical constituentsin reclaimed water; and limiting human exposure(contact, inhalation, ingestion) to the reclaimed water.Although potable reuse may not be intended,inadvertent ingestion may occur. Reclaimed water forunrestricted nonpotable reuse to which the public atlarge is exposed must be free of pathogenicmicroorganisms.

The box on pages 5-6 and the four-page table on theinsert provide guidance on setting standards forwastewater reuse. The box summarizes the WHOguidelines for wastewater reuse in agriculture andaquaculture that were prepared partly to meet the needfor reuse standards in developing countries.

The table summarizes guidelines for all types ofwastewater reuse, not just for agriculture. Suggestedtreatment processes, reclaimed water quality,monitoring frequency, and setback distances are givenfor the following reuse categories: unrestricted urbanreuse, restricted access area irrigation, irrigation of foodcrops, irrigation of non-food crops, recreationalimpoundments, landscape impoundments, constructionuses, industrial reuse, environmental reuse,groundwater recharge, and indirect potable reuse.

The table is intended for use mainly by utilities andregulatory agencies in the United States that have notdesigned their own standards. It is based principally onwater reclamation and reuse practice in the UnitedStates, but is included here because no othercomprehensive guidelines are available. It shouldprovide reasonable guidance but should not be viewedas definitive. Also, it should be noted that A.I.D. doesnot use the direct application of the guidelines in thetable as a strict criterion for funding.

• Monitoring water quality, A protocol for monitoringthe quality of wastewater is required. Deviations in theestablished standards may be permissible for wastewaterdischarges to a river; for reclaimed water, particularly inurban reuse, deviations are no more acceptable than theyare for drinking water. On-line, real-time monitoring ispreferable to sampling and laboratory analysis where theresults arrive too late to take corrective action. Althoughsome tests, like fecal coliform counts, take time, a simpleand useful measure of reclaimed water quality isturbidity. A sudden increase in turbidity provides awarning that corrective action is required.

• Monitoring water quantity. Because reclaimed wateris a product, the provision of promised quantity, as wellas quality, must be assured. For agricultural applications,brief intervals of nondelivery may be tolerable; for mosturban applications, a continuous supply is mandatory,

• Choice of treatment. In developing countries, thechoice of treatment—conventional with primarysedimentation, secondary treatment (activated sludge,trickling filtration, rotation biological contactors orsomething similar), sand filtration, and disinfection, orthe use of stabilization ponds—is usually determinedby local circumstances.

• If nearby lands are available at a low cost,stabilization ponds may be the mostappropriate choice. The effluent producedwill be suitable for agricultural irrigation,and the WHO guidelines indicate theeffluent may be acceptable for marketcrops, recognizing that fruit and vegetableproducts may need disinfecting beforeuse. Filtration and chemical disinfectionof pond effluents may not beoperationally feasible; the cost may alsobe prohibitive.

• In larger cities that have sewerage systems,conventional treatment will likely be thetreatment of choice. In such areas, wherereclamation and reuse may be promising,sufficient land for ponds may be unavailable,too expensive, or unacceptable to the publicas the city expands.

In countries where wastewater is used for irrigation, treatmentlike these trickling filters at a wastewater treatment facility inMelipilla, Chile, improve the quality of water for reuse.


WHO Guidelines for Wastewater Reuse In Agriculture and Aquaculture

Guidance in establishing regulations is provided by the World Health Organiza-tion. In 1973, WHO recommended health criteria and treatment processes for reuseapplications ranging from irrigation of crops not intended for human consumption allthe way to potable reuse. These recommendations were reviewed in 1985, and a re-vised approach to the nature of health risks associated with agriculture and aquacul-ture was developed (other nonpotable uses were not reviewed). The 1989 WHOpublication, Health Guidelines for the Use of Wastewater in Agriculture and Aquaculture(Technical Series No. 778), is consistent with the revised approach.

Agricultural Reuse

The 1989 guidelines are based on the conclusion that the main health risks asso-ciated with agricultural reuse in developing countries are associated with helminthicdiseases and, therefore, a high degree of helminth removal is necessary for the safe useof wastewater for agriculture and aquaculture. The WHO Guidelines for wastewateruse in agriculture are summarized in the table below.

WHO Recommended Microbiological Guidelines for Wastewater Use In Agriculture

ReuseCategory Conditions

A Irrigation of cropslikely to be eatenuncooked, sportsfields, public parks

B irrigation of cereacrops, industrial crops,fodder crops, pastureand trees

ExposedGroup

Workers,consumers,public

Workers

intestinalnematodes(arithmetic

mean no. ofeggs per

liter)2

S1

S1

Fecalconforms

(geometricmean no. per

100 ml)2

£1,000

No standardsrecommended

Wastewatertreatment expected

to achieve therequired

microbiologicalquality

A series of stabilization pondsdesigned to achieve themicrobiological quality indicated, orequivalent treatment

Retention in stabilization ponds for8-10 days or equivalent helminthand fecal coliform removal

Localized irrigation of None Not Notcrops in Category B if applicable applicableexposure of workers andthe public does not occur

Pretreatment as required by theirrigation technology, but not lessthan primary sedimentation

Note: In specific cases, local epidemiológica!, socioculturel, and environmental factors should be taken into account, and the guidelines modifiedaccordingly.

Footnotes1. Ascaris and Trichuris species and hookworms.2. During the irrigation period.3. In the case of fruit trees, irrigation should cease 2 weeks before fruit Is picked, and no fruit should be picked off the ground. Sprinkler Irrigation

should not be used.

Source: WHO, 1989.


WHO Guidelines Continued

Additional water quality considerations include:

• Agricultural irrigation near cities. Where dual urban watersystems exist (fresh water for potable purposes in one systemand reclaimed water for nonpotable purposes in another) andwhere water is used for agricultural irrigation near the city,the irrigation water should meet the quality requirements forunrestricted urban reuse.

• No land available for stabilization ponds. If the use of stabilizationponds is not feasible and conventional wastewater treatment isused, chlorine disinfection is required for irrigation of marketcrops.

• Standards for exports. If fruits and vegetables are exported, thestandards must be those of the target country.

Aquaculture

Concerning aquaculture, a number of infections caused by excreted pathogensare of concern, including invasion of fish muscle by bacteria and high pathogenconcentrations in the digestive tract and the intraperitoneal fluid of the fish. Due tothe limited available data, the following guidelines are tentative.

• A geometric mean of 1,000 fecal coliforms per 100 rril to insurethat bacterial invasion of fish muscle is prevented. The same stan-dard should be maintained for pond water in which aquatic vege-tables are grown.

• High standards of hygiene during fish handling andgutting.

• Total absence of viable trematode eggs is recommended as theappropriate helminths quality guideline. This can be readilyachieved by stabilization pond treatment.

The WHO guidelines have been and continue to be controversial. Some viewthem as too stringent; others as not stringent enough. However, in many locationswhere raw sewage or rivers heavily polluted with raw sewage are used for irriga-tion, any treatment would be an improvement. If stabilization ponds are feasibleand the WHO guidelines Can be attained, that would be a major public health ad-vance. If ponds are not feasible, the standards may be approached in stages by pro-viding conventional treatment facilities.


Institutional Issues• Institutional development. In some instances, theneed for reuse may prompt institutional development.When large investments are to be made in urbansewerage, the government will often assign responsibilityfor sewerage and wastewater treatment to the wateragency instead of creating or strengthening a sewerageagency. An advantage of this approach is that an operatingorganization with experienced officials is involved in theenterprise. It also offers economies and efficiencies of scaleand provides a mechanism for cost recovery.

Examining the relevant institutions and a plan fortheir modification to permit them to undertake thecapital program should be the first order of business.

• Lack of funds and agencies for wastewater.Developing countries have relatively strong institutionsfor managing water-supply systems, but agencies formanaging wastewater collection, treatment, and disposalare poorly organized and lacking in funds. Water-supplyagencies, which can recover some of their costs throughuser fees for water service, resist being joined withagencies responsible for sewerage since these agenciesdepend almost entirely on the limited financial resourcesof local government.

Legal Issues

• Vested water rights. Traditional practice orcustomary law in most developing countries, andformal law in many, recognize that a water useracquires vested rights to use a certain amount of waterunder defined circumstances. If the amount of wateravailable to a current user changes, vested rights mayentitle the user to compensation such as monetarypayment or a supplemental water supply. Rights inreclaimed water are uncertain; they may be vested inthe producer or in riparian downstream ownersdeprived of the water, who may require compensation.

• Regulations. Water reuse projects should includedevelopment and implementation of regulations toprevent or moderate public health or environmentalproblems. These regulations include: permit systems forauthorizing wastewater discharges; technical controlson wastewater treatment; water quality standards for

reclaimed water appropriate for various uses; controls,such as use restrictions, that will reduce humanexposure; access controls on reclaimed water systemsand controls preventing cross-connections betweendrinking water and reclaimed water distributionnetworks; regulations on sludge disposal and facilitysiting; and mechanisms to enforce these regulationsincluding monitoring requirements, inspectionauthority, and authority to assess violation penalties.

• Legal and procedural issues touched on above.

• An agreed-upon definition of "reclaimedwater".

• Specified rights of ownership to reclaimedwater.

• A licensing system for use of reclaimed water.

Economic and Financial Issues

• Cost recovery. In the United States it is now generallyaccepted that the user is responsible for meeting thecosts of water and sanitation services; however, indeveloping countries water has often been providedfree or at a nominal charge. The economic justificationfor water reuse is that the costs of developing additionalwater sources can be offset, but, where such costs aresubsidized by governments or external supportagencies, they appear low. Unless the real costs ofproviding water and sewerage are passed through tousers, a reclaimed water system will be no moresustainable than a system that does not recover its costsfrom users.

• Integrated approach. Because water supply andsewerage costs in water reclamation and reuse shouldbe considered together, all the agencies involved,including external support agencies, should approachwater reclamation projects in an integrated way.

• Economic rationale. The economic rationale forwater reuse in developing countries must take intoconsideration costs savings from new sources thatwould not be required or that could be postponed. Also,the costs of collection and treatment can be construed asbenefits in terms of providing sewerage services thatwould be necessary in any case.

Continued on page 8.


Continued from page 7.

• Cost/benefit calculations. Benefits other than costsavings need to be considered more carefully than indeveloped countries. For example, a wastewater reuseproject may free potable water service andaccompanying benefits to be extended to people whootherwise would have had to haul water for theirhouseholds, purchase high priced water, or usecontaminated water.

• Setting tariffs. A reuse program can be the means ofintroducing a rational pricing structure, based on arational market price for water. All reclaimed watercustomers should be metered. The price for fresh orreclaimed wastewater to all customers should reflect thefull production cost. The full resource costs of reclaimedwater, if conventional sewerage and wastewatertreatment are considered separately, should be less thanthat of fresh water, and this difference should bereflected in tariff structures.

Conclusion

Water reclamation and reuse is a viable option for expanding usable water resources in developingcountries. However, it is not sufficient to imitate methods used in industrialized countries; what is donemust be adjusted for the specific problems encountered in developing countries. Reuse of untreatedwastewater, without regulation by public authorities, is already common practice in urban areas of devel-oping countries where water is scarce. This has resulted in serious health problems.

Implementation of wastewater reuse in most cities in the developing world must begin with provision ofbasic sanitation services.

Resources

Guidelines for Water Reuse by James Crook, David K. Ammerman, Daniel A. Okun, and Robert L. Matthews. Cambridge,MA: Camp Dresser & McKee Inc., 1992. (Also issued by WASH as Technical Report No. 81.)

Health Guidelines for the Use of Wastewater in Agriculture and Aquaculture, report of a World Health OrganizationScientific Report, Technical Report Series 778. Geneva, Switzerland: WHO, 1989.

Irrigation with Reclaimed Municipal Wastewater—A Guidance Manual, edited by G. Stuart Pettygrove and Takashi Asano.Chelsea, MI: Lewis Publishers, Inc., 1985.

Proceedings of Four Symposia on Water Reuse sponsored by the American Water Works Association, Denver, CO.

Use of Human Wastes in Agriculture and Aquaculture. Utilization Practices and Health Perspectives by Martin Strauss andUrsula J. Blumenthal. IRCWD Report No. 08/90. International Reference Center for Waste Disposal, Duebendorf,Switzerland.

Wastewater Irrigation in Developing Countries. Health Effects and Technical Solutions. Summary of World Bank Technical PaperNumber 51 by Hillel I. Shuval. World Bank, 1990.

"Wastewater Reclamation and Reuse," edited by R. Mijeriego and T. Asano. Report of a symposium sponsored by theInternational Association on Water Pollution Research and Control. Water Science and Technology, 24(9) (1991): 36.

I l

This fact sheet, prepared byDiane Bendahmane, is basedprimarily on Chapter 8 of theGuidelines by Daniel Okun.

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