Sanitation - Amazon Web Servicespmg-assets.s3-website-eu-west-1.amazonaws.com/131008...2 GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN Chapter 10 Sanitation Household Sanitation,

Sanitation

Chapter 10

10

TABLE OF CONTENTS

SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Sanitation improvement must be demand-responsive, and supported by an intensive health andhygiene programme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Community participation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Integrated planning and development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Sanitation is about environment and health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Basic sanitation is a human right . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

The provision of access to sanitation services is a local government responsibility . . . . . . . . . . . . . . . . 2

“Health for all” rather than “all for some” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Equitable regional allocation of development resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Water has an economic value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

The “polluter pays” principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Sanitation services must be financially sustainable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Environmental integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

PLANNING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

HYGIENE IN SANITATION PROJECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

TECHNICAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Categories of sanitation systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Description of sanitation systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

FACTORS AFFECTING THE CHOICE OF A SANITATION SYSTEM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

The cost of the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Sanitation at public facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

DISPOSAL OF SLUDGE FROM ON-SITE SANITATION SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Composition of pit or vault contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Methods of emptying pits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Sludge flow properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Vacuum tankers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Disposal of sludge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN

Sanitation Chapter 10Revised August 2003

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Chapter 10 Sanitation

EVALUATION OF SITES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Topographical evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Soil profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Percolation capacity of the site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

POLLUTION CAUSED BY SANITATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Surface pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Groundwater pollution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

SULLAGE (GREYWATER) DISPOSAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Health aspects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Disposal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Disposal systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Sullage treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

TOILET PEDESTALS AND SQUATTING PLATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

DESIGN OF VIP TOILETS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

TOILET FACILITIES FOR PHYSICALLY DISABLED PERSONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

TRAINING OF MAINTENANCE WORKERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

UPGRADING OF SANITATION FACILITIES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

OFF-SITE WASTEWATER TREATMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Pond systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Package purification units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

APPENDIX A: INFORMATION REQUIRED FOR THE PLANNING AND DESIGN OF SANITATION PROJECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

COMMUNITY MANAGEMENT APPROACH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Phase 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Phase 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Phase 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Phase 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Phase 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Phase 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Phase 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

HUMAN-RELATED DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Socio-cultural data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Community preferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Economic and social conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Health and hygiene conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Institutional framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Environmental and technical aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

INFORMATION REQUIRED FOR POST-PROJECT EVALUATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

APPENDIX B: UPGRADING OF EXISTING SANITATION SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

BASIC UPGRADING ALTERNATIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Alternative 1 - Aesthetic upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Alternative 2 - Introduction of a water seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Alternative 3 - Removal of liquids from the site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

UPGRADING ROUTES FOR THE VARIOUS SANITATION SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Group 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Group 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Group 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Group 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

APPENDIX C: DESIGN GUIDELINES FOR WATERBORNE SANITATION SYSTEMS. . . . . . . . . . . . . . . . . . 28

SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

DESIGN CRITERIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Design flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Hydraulic design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Physical design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Pipes and joints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Manholes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Pumping installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Pipework. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

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Structural steelwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Electrical installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Other materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

GLOSSARY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

BIBLIOGRAPHY AND RECOMMENDED READING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

LIST OF TABLES

Table 10.1 Categories of sanitation systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Table 10.2 Sullage generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Table C.1 Average daily flows per single-family dwelling unit (du) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Table C.2 Minimum sewer gradients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Table C.3 Minimum internal dimensions of manhole chambers and shafts . . . . . . . . . . . . . . . . . . . . . . .32

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LIST OF FIGURES

Figure 10.1 Chemical toilet unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Figure 10.2 VIP toilet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Figure 10.3 VIDP toilet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Figure 10.4 Ventilated vault toilet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Figure 10.5 Urine-diversion toilet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Figure 10.6 Waterborne sewerage system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Figure 10.7 Shallow sewer system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Figure 10.8 Flushing toilet with conservancy tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Figure 10.9 Settled sewage system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Figure 10.10 Flushing toilet with septic tank and soakaway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Figure 10.11 Aqua-privy toilet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Figure 10.12 Minimum dimensions of a toilet room for physically disabled persons . . . . . . . . . . . . . . . . . .19

Figure C.1 Attenuation of peak flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Figure C.2 Protection of pipes at reduced depths of cover (e.g. Class B bedding) . . . . . . . . . . . . . . . . . . .31

Figure C.3 Steep drops in sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

SCOPE

The guidelines for sanitation provision cover aspectsthat need to be considered when planning andimplementing sanitation projects for existingresidential areas and developing communities. Theguidelines will also be of assistance where the WaterServices Authority compiles a Water ServicesDevelopment Plan (the latter forms part of themunicipality’s Integrated Development Plan).

The guidelines will also assist in determining andsetting objectives, developing a strategy andidentifying the required planning activities forimplementing sanitation projects. Technical guidelinesare given for use in feasibility studies and the detaileddesign of sanitation provision.

The guidelines form part of a planned series ofmanagement guidelines intended for use by decisionmakers. The series of guidelines is shown in Table 9.1of Chapter 9: Water Supply.

INTRODUCTION

Water services (i.e. water supply and sanitation) inSouth Africa are controlled by the Water Services Act(Act 108 of 1997) and the National Water Act (Act 36of 1998). The Water Services Act deals with waterservices provision to consumers, while the NationalWater Act deals with water in its natural state.

As in the case of water supply, the provision ofsanitation to a community should take place in termsof the relevant Water Services Development Plan,which is required in terms of the Water Services Act.The Water Services Development Plan (which should,of course, be compiled taking cognisance of theNational Sanitation Policy) defines the minimum levelof sanitation as well as the desired level of sanitationfor communities that must be adhered to by a WaterServices Provider in its area of jurisdiction. It describesthe arrangements for water services provision in anarea, both present and future. Water services are alsoto be provided in accordance with regulationspublished in terms of the Water Services Act.

The provision of appropriate sanitation to acommunity should take place in accordance withnational policy. Among the major aims set out in theNational Sanitation Policy are the following:

• to improve the health and quality of life of thewhole population;

• to integrate the development of a community inthe provision of sanitation;

• to protect the environment; and

• to place the responsibility for household sanitationprovision with the family or household.

The minimum acceptable basic level of sanitation is(Department of Water Affairs & Forestry, 2001):

• appropriate health and hygiene awareness andbehaviour;

• a system for disposing of human excreta,householdwastewater and refuse, which is acceptable andaffordable to the users, safe, hygienic and easilyaccessible, and which does not have anunacceptable impact on the environment; and

• a toilet facility for each household.

The safe disposal of human excreta alone does notnecessarily mean the creation of a healthyenvironment. Sanitation goes hand in hand with aneffective health-care programme. The importance ofeducation programmes should not be overlooked, andthe Department of Health is able to assist in this (referto the following section “Hygiene in sanitationprojects”).

Sanitation education is part of the National SanitationPolicy and should embrace proper health practices,such as personal hygiene, the need for all familymembers (including the children) to use the toilet andthe necessity of keeping the toilet building clean.Education should also include the proper operation ofthe system, such as what may and may not be disposedof in the toilet, the amount of water to add ifnecessary, and what chemicals should or should not beadded to the system. The user must also be madeaware of what needs to be done if the system fails orwhat options are available when the pit or vault fillsup with sludge.

Current policy is that the basic minimum facility shouldbe a ventilated improved pit (VIP) toilet, or itsequivalent. In this chapter, therefore, levels of servicelower than this will not be discussed.

The use of ponds is frequently considered for dealingwith wastewater in rural areas, and hence theirinclusion in this document.

The five main criteria to be considered when providinga sanitation system for a community are:

• reliability;• acceptability;• appropriateness;• affordability; and• sustainability.

With these criteria in mind, designers should note thefollowing principles from the White Paper on Basic

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Household Sanitation, September 2001:

Sanitation improvement must bedemand-responsive, and supported by anintensive health and hygiene programme

Household sanitation is first and foremost a householdresponsibility and must be demand-responsive.Households must recognise the need for adequatetoilet facilities for them to make informed decisionsabout their sanitation options. For users to benefitmaximally, they must also understand the linkbetween their own health, good hygiene and toiletfacilities.

Community participation

Communities must be fully involved in projects thatrelate to their health and well-being, and also indecisions relating to community facilities, such asschools and clinics. Communities must participate indecision-making about what should be done and how,contribute to the implementation of the decisions, andshare in the benefits of the project or programme. Inparticular, they need to understand the costimplications of each particular sanitation option.

Integrated planning and development

The health, social, and environmental benefits ofimproved sanitation are maximised when sanitation isplanned for and provided in an integrated way withwater supply and other municipal services.

The focal mechanism of achieving integrated planningand development is the municipality-driven IntegratedDevelopment Planning (IDP) process (of which theWater Services Development Plan is a component).

Sanitation is about environment andhealth

Sanitation improvement is more than just theprovision of toilets; it is a process of sustainedenvironment and health improvement. Sanitationimprovement must be accompanied by environmental,health and hygiene promotional activities.

Basic sanitation is a human right

Government has an obligation to create an enablingenvironment through which all South Africans cangain access to basic sanitation services.

The provision of access to sanitationservices is a local governmentresponsibility

Local government has the constitutional responsibilityto provide sanitation services.

Provincial and national government bodies have aconstitutional responsibility to support localgovernment in a spirit of co-operative governance.

“Health for all” rather than “all forsome”

The use of scarce public funds must be prioritised, inorder to assist those who are faced with the greatestrisk to health due to inadequate sanitation services.

Equitable regional allocation ofdevelopment resources

The limited national resources available to support theincremental improvement of sanitation services shouldbe equitably distributed throughout the country,according to population, level of development, andthe risk to health of not supporting sanitationimprovement.

Water has an economic value

The way in which sanitation services are provided musttake into account the growing scarcity of good qualitywater in South Africa.

The “polluter pays” principle

Polluters must pay the cost of cleaning up the impactof their pollution on the environment.

Sanitation services must be financiallysustainable

Sanitation services must be sustainable, in terms ofboth capital and recurrent costs.

Environmental integrity

The environment must be protected from thepotentially negative impacts of sanitation systems.

PLANNING

The various planning stages and other informationrelated to the planning of projects are fully describedin Chapter 9 (Water supply). The planning steps andapproach with respect to sanitation do not differ fromthose described in that chapter, and are not repeatedhere. The reader is thus referred to Chapter 9 forplanning information.

HYGIENE IN SANITATION PROJECTS

An introductory discussion on hygiene in water andsanitation projects can be found in Chapter 9.

For people to change their cultural practices andbehaviours – some of which are developed arounddeeply seated values – a lot of motivation is required,accompanied by marketing of the new or modifiedpractices. For instance, when people are accustomedto defecating in the open (free of charge) it will takea lot of effort to motivate them to install toilets (at acost), and to use those toilets, which come in as a newpractice. Furthermore, the motivation for installingtoilets or practising a higher level of hygiene mustclearly emphasise the benefits to the individual and tothe community.

The main components of a hygiene-promotion and -education strategy in a project should include thefollowing:

• motivation and community mobilisation;• communication and community participation;• user education (operation and maintenance);• skills training and knowledge transfer;• development of messages;• presentation of messages; and• maintenance of good practice.

Many of these components overlap, or cut across thewhole programme of implementation. For instance,motivation and community mobilisation would needto be maintained throughout the programme andafter. The same goes for communication, which isrequired at all stages of a hygiene-promotion and -education programme. In practice there is noparticular cut-off point between one component andanother.

The following should be implemented during theprojects’ stages (see Appendix A) to ensure that watersupply and sanitation projects have a positive impacton the quality of life and level of hygiene incommunities:

• Development and structuring of a strategic plan forthe implementation of hygiene promotion andeducation in water and sanitation projects: Thisstrategic plan should fit in and dovetail withnational and provincial strategies for health andhygiene in South Africa, and should includeadvocacy, training and capacity-building,implementation, monitoring and evaluation.

• Liaison with other programmes/projects active inthe health and hygiene field: Other initiativesregarding hygiene (PHAST, etc) should beidentified and coordinated to prevent duplication,and to optimally address the needs of governmentand the communities. A number of other activitiesand programmes in schools, clinics, hospitals andthe media (TV, radio, newspapers, magazines),should be identified and coordinated for a broaderimpact of hygiene promotion and education.

• Informing and training local governmentstructures, environmental health officers (EHOs),non-governmental organisations (NGOs),community-based organisations and consultants: Aprogramme should be developed to inform andtrain all local, regional and national institutionsand structures involved in water supply andsanitation, health and hygiene promotion andeducation.

• Monitoring and evaluating the implementation ofhygiene in water and sanitation projects: A bodyor organisation should be established and taskedto monitor the quality and standard of hygienepromotion and education. The results of hygienepromotion and education should be evaluatedagainst key health indicators set up at the start ofa project.

• Disseminating information regarding hygiene inwater and sanitation projects: The process andresults of hygiene promotion and education in aproject should be disseminated in articles,conference papers, reports, seminars andworkshops with other researchers in the field ofhealth and hygiene.

TECHNICAL INFORMATION

Before a sanitation system is selected, the availableoptions should be examined. This section describes thevarious systems and factors that could influence theselection. Detailed design information is not includedin this chapter. Instead, reference is made to variouspublications in which all the required information maybe found. Some general background information onthe different sanitation technologies is, however,included.

Only sanitation systems commonly used or accepted inSouth Africa are described.

Categories of sanitation systems

There are two ways to handle human waste. It caneither be treated on site before disposal, or removedfrom the site and treated elsewhere. In either case, thewaste may be mixed with water or it may not. On thisbasis the following four groups may be distinguished:

Group 1: No water added – requiring conveyance.

Group 2: No water added – no conveyance.

Group 3: Water added – requiring conveyance.

Group 4: Water added – no conveyance.

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Table 10.1 illustrates the sanitation systems associatedwith each of the above groups. Note that some of thesystems fall somewhere between the four categoriesas, for example, where solids are retained on eachproperty and liquids are conveyed from site, or wherewater may be added, but only in small quantities.Since increasing the number of categories wouldcomplicate the table unnecessarily, these systems havebeen included in the categories that best describe thetreatment of the waste. The operating costs of systemsin which waste is conveyed and treated elsewhere canbe so high that these systems may in the long term bethe most expensive of all. The capital and installationcosts of any conveyance network using largequantities of clean water to convey small quantities ofwaste are very high, and a possibly inappropriatelyhigh level of training and expertise is also required toconstruct and maintain such systems.

Developers should consider all the sanitationalternatives available before deciding on the mostappropriate solution for the community in question. Asolution that may be appropriate in one communitymay be a total failure in another because of cost,customs and religious beliefs, or other factors. Asolution must also not be seen as correct purelybecause developers and authorities have traditionallyimplemented it.

Description of sanitation systems

The main types of sanitation systems are describedbelow. The list is not complete and many commercialmanufacturers provide systems that may be a variantof one or more.

The advantages and disadvantages of each system willdepend on its particular application. What may be adisadvantage in one situation may in fact be anadvantage in another. Thus the advantages and

disadvantages listed after each description should beseen not as absolutes, but merely as aids to selectingthe right sanitation system for a particular application.

Group 1: No water added – requiringconveyance(for treatment at a central treatment works)

Chemical toilets (not a preferred option)A chemical toilet stores excreta in a holding tankthat contains a chemical mixture to prevent odourscaused by bacterial action. The contents of theholding tank must be emptied periodically andconveyed to a sewage works for treatment anddisposal. Some units have a flushing mechanismusing some of the liquid in the holding tank torinse the bowl after use. The chemical mixtureusually contains a powerful perfume as well as ablue dye. Chemical toilets can range in size fromthe very small portable units used by campers tothe larger units supplied with a hut. The system canprovide an instant solution and is particularlyuseful for sports events, construction sites or othertemporary applications where the users areaccustomed to the level of service provided by awaterborne sanitation system. The system can alsobe used where emergency sanitation for refugees isrequired, in which case it can give the planners thenecessary breathing space to decide on the bestpermanent solution. It should not be considered asa permanent sanitation option.

Factors to consider before choosing this option arethe following:

• Chemical toilets have relatively high capital andmaintenance costs.

• It is necessary to add the correct quantity ofchemicals to the holding tank.

Table 10.1: Categories of sanitation systems

REQUIRING CONVEYANCE NO CONVEYANCE REQUIRED(off-site treatment) (treatment, or partial treatment, on site;

accumulated sludge also requires periodic removal)

NO WATER GROUP 1 GROUP 2ADDED Chemical toilet (temporary use only). Ventilated improved pit toilet.

Ventilated improved double-pit toilet.Ventilated vault toilet.Urine-diversion toilet.

WATER GROUP 3 GROUP 4ADDED Full waterborne sanitation. Flushing toilet with septic tank and subsurface soil

absorption field.

Flushing toilet with conservancy tank. Low-flow on-site sanitation systems (LOFLOs):Shallow sewers. Aqua-privy toilet.

• Periodic emptying of the holding tank isessential; this requires vacuum tankers, so accessshould be possible at all times.

• The system only disposes of human excreta andcannot be used to dispose of other liquid waste.

• The units can be installed very quickly andeasily.

• They can be moved from site to site.

• They require no water connection and requirevery little water for operation.

• They are hygienic and free from flies and odour,provided that they are operated andmaintained correctly.

• The chemicals could have a negative effect onthe performance of wastewater treatmentworks.

Group 2: No water added – no conveyance(treatment or partial treatment on site beforedisposal)

Ventilated improved pit (VIP) toiletThe VIP toilet is a pit toilet with an externalventilation pipe. It is both hygienic and relativelyinexpensive, provided that it is properly designed,constructed, used and maintained. Detailedinformation on VIP design is available in thepublication Building VIPs by Bester and Austin(1997), which is obtainable from the Department ofWater Affairs & Forestry, Pretoria. Information ondifferent soil conditions, as they affect the buildingof VIP toilets, is also included. A SABS Code ofPractice for the construction of VIPs is currentlyunder preparation by the SABS. There are alsovariations of VIP toilets available – the Archloo,

Phungalutho, Sanplat, etc. Those mentioned havebeen used with success and are firmly establishedin the industry.

It is possible to construct the entire toilet from localmaterials, although it is more usual to usecommercial products for the vent pipe and thepedestal. Several toilet superstructures are alsocommercially available. When the pit is full, thesuperstructure, pedestal, vent pipe and slab arenormally moved to a freshly dug pit and the old pitis covered with soil. The VIP toilet can be mademore permanent by lining the pit with open-jointed brickwork or other porous lining. The pitcan then be emptied when required, using asuitable vacuum tanker, without the danger of thesides of the pit collapsing. Water (sullage) pouredinto the pit may increase the fill-up rate(depending on soil conditions) and should beavoided; this sanitation technology is therefore notrecommended where a water supply is available onthe site itself.

Factors to consider before choosing this option:

• If the stand is small there may be insufficientspace to allow continual relocation of the toilet;therefore arrangements should exist foremptying the toilet.

• Unlined pit walls may collapse.

• The excreta are visible to the user.

• The system may be unable to drain all the liquidwaste if large quantities of wastewater arepoured into the pit.

• The cost of the toilet is relatively low; itprovides one of the cheapest forms ofsanitation while maintaining acceptable healthstandards.

• The toilet can be constructed by the recipients,even if they are unskilled, as very little trainingis required.

• Locally available materials can be used.

• If required, the components can bemanufactured commercially and erected on alarge number of plots within a short space oftime.

• The system is hygienic, provided that it is usedand maintained correctly.

• The system can be used in high-density areasonly if a pit-emptying service exists.

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Figure 10.1: Chemical toilet unit

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• The system can be upgraded at a later stage toincrease user convenience (e.g. to a urine-diversion toilet).

• The system cannot ordinarily be installed insidea house.

• The quantity of water supplied to the siteshould be limited.

• If a pit-emptying service exists, proper access tothe pit should be provided.

Ventilated improved double-pit (VIDP) toiletThe VIDP toilet, also known as the twin-pitcomposting toilet, was developed mainly for use inurban areas where, because of limited space on thesmaller plots, it may be impossible to relocate thetoilet every time the pit becomes full. The VIDP is arelatively low-cost and simple but permanentsanitation solution for high-density areas. Twolined shallow pits, designed to be emptied, areexcavated side by side and are straddled by a singlepermanent superstructure. The pits are usedalternately: when the first pit is full it is closed andthe prefabricated pedestal is placed over thesecond pit. After a period of at least one year theclosed pit can be emptied, either manually (if this isculturally acceptable) or mechanically, and then itbecomes available for re-use when the other pit isfull. Each pit should be sized to last a family two tothree years before filling up. It is important thatthe dividing wall between the pits be sealed, toprevent liquids seeping from the pit currently inuse into the closed pit, thus contaminating it. TheVIDP toilet can be built partially above the groundin areas where there is a high water table, but thedistance between the pit floor and the highestwater table should be at least 1 m.

Detailed information on VIDP design is alsoavailable in the publication Building VIPs by Besterand Austin (1997), obtainable from theDepartment of Water Affairs & Forestry, Pretoria.

Factors to consider before choosing this option aresimilar to those for the VIP, but include thefollowing:

• Some training is required to ensure that the pitlining is properly constructed.

• The contents of the used pit may be safely usedas compost after a period of about two years inthe closed pit.

• The user may not be prepared to empty the pit,even though the contents have composted.

• The superstructure can be a permanentinstallation.

• The system can be regarded as a permanentsanitation solution.

• The system can be used in high-density areas.

• The system can be used in areas with hardground, where digging a deep pit is impractical.

Ventilated vault (VV) toiletsThe VV toilet is basically a VIP toilet with awatertight pit that prevents seepage. It can beregarded as a low-cost, permanent sanitationsolution, especially in areas with a highgroundwater table or a poor capacity for soilinfiltration, or where the consequences of possiblegroundwater pollution are unacceptable.

Figure 10.3: VIDP toilet

Figure 10.2: VIP toilet

The amount of wastewater disposed of into thevault should be limited to avoid the need forfrequent emptying, so it is advisable not to use thistype of sanitation technology where a water supplyis available on site. Should an individual waterconnection be provided to each stand at a laterdate, as part of an upgrading scheme for theresidential area, then the vault can be utilised as asolids-retention tank (digester) and liquids can bedrained from the site using a settled-sewagesystem, also called a solids-free sewer system (seethe section on “settled-sewage systems” underGroup 3). Ventilation, odour and insect controloperate on the same basis as the VIP toilet.

Factors to consider before choosing this option aresimilar to those of the VIP, but include thefollowing:

• It is necessary to make use of a vacuum-tankerservice for periodic emptying of the vaults.

• Builder training and special materials arerequired if a completely waterproof vault isrequired.

• The system can be used in areas with a highwater table if the vault is properly constructed.

• The system can be used in areas where pollutionof the groundwater is likely if a VIP toiletsystem is used.


• This system provides very good opportunitiesfor upgrading since the vault can be used as asolids-retention tank when upgrading to solids-free sewers.

• The cost of emptying equipment and theoperation of a vacuum-tanker service could beexcessive (see also the section on vacuumtankers).

Urine-diversion (UD) toiletThe urine-diversion toilet, also known as the “dry-box”, is a superior type of dry toilet thatcircumvents the problems sometimes encounteredwith the implementation of VIP toilets, namelyunfavourable geotechnical or hydrologicalconditions, high-density settlements with smallerven, etc. The main advantage is that a pit is notrequired, so the toilet may be installed inside thehouse, if desired by the owner. Urine is diverted atsource by a specially designed pedestal and, owingto the relatively small volumes involved, may simplybe led into a shallow soakpit. Alternatively, urinecan be easily collected in a container and re-usedfor agricultural fertiliser, as it is rich in plantnutrients such as nitrogen, phosphorus andpotassium. Faeces are deposited in a shallow vaultand covered with a sprinkling of ash or dry soil,which absorbs most of the moisture. They arefurther subjected to a dehydration process insidethe vault, which hastens pathogen die-off.Depending on the temperature and degree ofdesiccation attained in the vault, the faeces may besafe to handle after a period of six to eighteenmonths, and can then be easily removed from thevault and either disposed of or re-used as soilconditioner, depending on individual preferences.

Other favourable aspects of this type of toilet arean absence of odours or flies (if it is properly used),a relatively low capital cost that may, depending onthe specific circumstances, be even less than a VIPtoilet, and a negligible operating cost. There arealso environmental advantages, due to the factthat no pit is required.

Detailed guidelines on the implementation of thistechnology are contained in the publication Urine-diversion ecological sanitation systems in SouthAfrica by Austin and Duncker (CSIR, 2002).

Factors to consider before choosing this option:

• The technology is well suited to dense urbansettlements and places where environmentalconditions do not favour other types ofsanitation.

• Use of the toilet requires an adherence tocertain operational requirements, and a propercommitment from owners is required. Gooduser education is therefore especiallyimportant.

• Building materials similar to those for a VIPtoilet may be used, and the toilets can be

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Figure 10.4: Ventilated vault toilet

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constructed by relatively unskilled persons.Components can also be manufacturedcommercially.

• The system is hygienic, provided that it is usedand maintained correctly. Safe re-use of theurine and faeces is also facilitated.

• The system can be installed inside a house, ifdesired.

• There may be reluctance on the part of the userto empty the vault, even though the contentsare innocuous.

• The system can be regarded as a permanentsanitation solution that will never needupgrading.

Group 3: Water added – requiring conveyance(treatment at a central works)

Full waterborne sanitationThis is an expensive option and requires ongoingmaintenance of the toilet installation, the sewerreticulation and the treatment works, and therecipient community should be informedaccordingly. The system requires a water supplyconnection to each property. The water is used toflush the excreta from the toilet pan and into thesewer, as well as to maintain a water seal in thepan. The excreta are conveyed by the water, inunderground pipes, to a treatment works that maybe a considerable distance from the source. Thetreatment works must be able to handle the highvolume of liquid required to convey the excreta.The quantity of water required (usually 6-10 litresper flush) can be reduced by using low-flush pansdesigned to flush efficiently with as little as three

litres. Research has indicated that the operation ofthe sewer system is not adversely affected by low-volume flush toilets. Flush volumes of 8-9 litres arenormally used, however. In an area where water iscostly or scarce, it may be counter-productive topurify water only to pollute it by conveying excretato a treatment and disposal facility.


• The system is expensive to install, operate andmaintain.

• The system can be designed and installed onlyby trained professionals.

• The treatment works must be operated andmaintained properly if pollution of waterwaysis to be avoided.

• The system requires large amounts of water tooperate effectively and reliably.

• The system is hygienic and free of flies andodours, provided that it is properly operatedand maintained.

• A high level of user convenience is obtained.

• The system should be regarded as a permanentsanitation system.

• The toilet can be placed indoors.

• This system can be used in high-density areas.

• An adequate, uninterrupted supply of watermust be available.Figure 10.5: Urine-diversion toilet

Figure 10.6: Waterborne sewerage system

Shallow sewersThe shallow sewer system is basically aconventional system where a more simpleapproach with respect to design and construction isfollowed. Basically it entails a system wheregradients are flatter, pipes are smaller and laidshallower, manholes are smaller and constructed ofbrickwork, and house connections are simpler.Where such systems are installed, communityinvolvement in management and maintenanceissues is preferred.

Design of sewer networks:

The professional responsibility in design remainswith the engineer, and guidelines should never beregarded as prescriptive. Most local authoritieshave their own requirements and preferences ontechnical detail, such as pipe slopes, manholedetails, materials, and so on. These are based ontheir own particular experiences and new designsshould therefore be discussed with the relevantcontrolling authority.

Designers should not assume that sewer systemswill always be properly maintained, and allowanceshould be made for this.

The hydraulic design of the sewers should be doneaccording to acceptable minimum and maximumvelocities in the pipeline. A number of pipemanufacturers have design charts available in theirproduct manuals and these can be used in theabsence of other guidelines.

The construction of a system should be inaccordance with the relevant sections of SABS1200:1996. The depth of the sewer is normallydetermined by its position on site. Sewers in mid-block positions and on sidewalks can normally belaid at shallower depths. Should laying of sewerand water pipes in the same trench be considered,workmanship should be of a high standard.Appendix C gives design guidelines that should beuseful.

Flushing toilet with conservancy tankThis system consists of a standard flushing toiletthat drains into a storage or conservancy tank onthe property; alternatively, several properties’toilets can drain into one large tank. A vacuumtanker regularly conveys the excrement to a centralsewage treatment works for purification beforethe treated effluent is discharged into awatercourse. The appropriate volume of theconservancy tank should be calculated on the basisof the planned emptying cycle and the estimatedquantity of wastes generated. Tank volumes aresometimes prescribed by the service provider.


• The system is expensive to install, operate andmaintain, although the capital cost is lowerthan the fully reticulated system.

• The system can be designed and installed onlyby trained professionals.

• A treatment works must be operated andmaintained properly to avoid the pollution ofwaterways.

• A fleet of vacuum tankers must be maintainedby the local authority.

• Regular collection is essential.

• The system is hygienic and free of odours,provided that it is properly operated andmaintained.




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Figure 10.7: Shallow sewer system Figure 10.8: Flushing toilet with conservancy tank

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• This system has good potential for upgradingsince the conservancy tank can be used as adigester when upgrading to a settled-sewagesystem.

• An adequate, uninterrupted supply of watermust be available.

Settled sewage system In settled sewage systems, also known as solids-freesystems or Septic Tank Effluent Drainage (STED),the solid portion of excreta (grit, grease andorganic solids) is retained on site in an interceptortank (septic tank), while the liquid portion of thewaste is drained from the site in a small-diametersewer. Such sewers do not carry solids, and havevery few manholes. Tolerances for excavation andpipe laying may be greater than for conventionalsewers, allowing lesser skilled labour to be used.Although the liquid portion of the waste must betreated in a sewage works, the biological designcapacity of the works can be greatly reducedbecause partial treatment of the sewage will takeplace in the retention tank on the site. The tankwill also result in a much lower peak factor in thedesign of both the reticulation and the treatmentworks. The retention tank should be inspectedregularly and emptied periodically, to preventsludge overflowing from the tank and entering thesewer. This system is an easy upgrading route fromseptic tanks with soakaways, conservancy tanks,and other on-site systems, as they can be connectedto a settled-sewage system with very littlemodification. Tipping-tray pedestals and water-saving devices can also be used in settled-sewageschemes without fear of causing blockage resultingfrom the reduced quantity of water flowing in thesewers.


• The system requires a fairly large capital outlayif new interceptor tanks have to be constructed(i.e. if there are no existing septic tanks whichcan be used).

• Care must be taken to ensure that only liquidwaste enters the sewers; this may mean regularinspection of the on-site retention tanks.

• Vacuum tankers must be maintained by thelocal authority.

• The system is hygienic and free of flies andodours, provided that it is properly operatedand maintained.


• The system can be regarded as a permanentsanitation system.


• All household liquid waste can be disposed ofvia this sanitation system.

• The sewers can be installed at flatter gradientsand can even be designed to flow underpressure.

• The system provides an easy and reasonablypriced option when areas with on-sitesanitation need to be upgraded, because ofincreased water consumption and higher livingstandards.


• An adequate uninterrupted supply of watermust be available.

• Regular inspection of the septic tank/digester isrequired to prevent an overflow of sludge.

Technical information on the design of thesesystems may be found in the CSIR, Division ofBuilding and Construction Technology publicationSeptic tank effluent drainage systems (1997).

Group 4: Water added – no conveyance(treatment or partial treatment on site beforedisposal)

These systems generally dispose of all or part of theeffluent on site. Some systems retain only the solidportion of the waste on site and the liquids areconveyed to a suitable treatment and disposal facility.

Figure 10.9: Settled sewage system

Systems that dispose of the liquid fraction on siterequire a soil percolation system, and the amount ofliquid that can be disposed of will depend on thesystem’s design and the permeability of the soil.

Flushing toilet with septic tank and soakawayWater is used to flush the waste from aconventional toilet pan into an underground septictank, which can be placed a considerable distancefrom the toilet. The septic tank receives the sewage(toilet water and sullage (greywater)) and thesolids digest and settle to the bottom of the tank inthe same manner as in the settled-sewage system.The septic tank therefore provides for storage ofsludge. The effluent from the tank can containpathogenic organisms and must therefore bedrained on the site in a subsoil drainage system.The scum and the sludge must be prevented fromleaving the septic tank as they could causepermanent damage to the percolation system. It istherefore advisable to inspect the tank at intervalsto ascertain the scum and sludge levels. Most tankscan be emptied by a conventional vacuum tanker.Liquid waste from the kitchen and bathroom canalso be drained to the septic tank. Septic tanksshould be regarded as providing a high level ofservice.


• It is relatively expensive and requires a waterconnection on each stand.

• It requires regular inspection, and sludgeremoval every few years, depending on thedesign capacity of the septic tank.

• Percolation systems may not be suitable in areasof low soil permeability or high residentialdensity.

• It provides a level of service virtually equivalentto waterborne sanitation.

• The system is hygienic and free of flies.

• The toilet can be inside the dwelling.

• This system has excellent potential forupgrading, since the septic tank outlet caneasily be connected to a settled-sewage systemat a future date.


Designers are referred to the publication Septictank systems (BOU/R9603), available from the CSIR,Division of Building and Construction Technology,for information on the design of septic tanks.

Reference to the percolation capacity of soils ismade later in this chapter under the section“Evaluation of sites”.

Low-flow on-site sanitation systems ( LOFLOs)The term LOFLOs refers to the group of on-sitesanitation systems that use low volumes of waterfor flushing (less than 2,5 litres per flush). Thesesystems include a pedestal, digestion capacity andsoakaway component. They are:

• aqua-privies;• pour-flush toilets* and low-flush systems*; and• low-flow septic tanks*.

*These types are not generally found in SouthAfrica.

Aqua-privies:

An aqua-privy is a small, single-compartment septictank directly under or slightly offset from thepedestal. The excreta drops directly into the tankthrough a chute, which extends 100 mm to 150 mmbelow the surface of the water in the tank. Thisprovides a water seal, which must be maintained atall times to prevent odour and keep insects away.The tank must be completely watertight; it maytherefore be practical to use a prefabricated tank.The tank must be topped up from time to time withwater to compensate for evaporation losses ifflushing water is not available. This can be done bymounting a wash trough on the outside wall of thesuperstructure and draining the used water into thetank. The overflow from the tank may containpathogenic organisms and should therefore run intoa soil percolation system (it can also be connected toa settled-sewage system at a later stage).

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Figure 10.10: Flushing toilet with septic tank andsoakaway

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• The excreta are visible to the user.

• The tanks must be completely watertight.

• The user must top up the water level in theaqua-privy to compensate for evaporationlosses.

• The system is hygienic, provided that it is usedand maintained correctly.

• It is relatively inexpensive.

• The system can be regarded as a permanentsanitation solution.

• This system has excellent potential forupgrading, since the tanks work in the sameway as a septic tank and can thus be connecteddirectly to a settled-sewage system.

• The tanks need regular inspection, and sludgeremoval is required from time to time.


FACTORS AFFECTING THE CHOICE OFA SANITATION SYSTEM

General considerations

The primary reason for installing a sanitation system ina community is to assist in the maintenance of healthand should be seen as only one aspect of a total healthprogramme. The choice of a sanitation system by acommunity will be influenced by several factors, suchas the following:

• The system should not be beyond the technologicalability of the community insofar as operation andmaintenance are concerned.

• The system should not be beyond the community’sability to meet the capital as well as themaintenance costs.

• The system should take into account the level ofwater supply provided, and possible problems withsullage (greywater) management.

• The likelihood of future upgrading should beconsidered, particularly the level of service of thewater-supply system.

• The system should operate well despite misuse byinexperienced users.

• In a developing area the system should require aslittle maintenance as possible.

• The system chosen should take into account thetraining that can be given to the community, froman operating and maintenance point of view.

• The system should be appropriate for the soilconditions.

• The community should be involved to the fullestextent possible in the choice of an appropriatesystem.

• To foster a spirit of real involvement andownership, the community should be trained to doas much as possible of the development workthemselves.

• Local customs should be carefully considered.

• The local authority should have the institutionalstructure necessary for the operation andmaintenance of the system.

• The existing housing layout, if there is one, shouldnot make the chosen system difficult to construct,maintain or operate.

Figure10.11: Aqua-privy toilet

• Environmental factors should be considered:surface pollution, possible groundwatercontamination, etc.

The cost of the system

Many people in developing areas are not only unableto afford sophisticated sanitation systems, but thesesystems may also be technically inappropriate forthem. At the same time, the sanitation alternativewith the lowest overall cost may also be inappropriatebecause of the community’s cultural background orbecause of its unwillingness or inability to operate thesystem correctly.

When the costs of different systems are compared, allrelevant factors should be taken into account.Examples of costs often ignored are the following:

• A pit toilet may require relocation on the site oremptying every 4-10 years, depending on itscapacity.

• Sludge from septic tanks and other on-sitesanitation systems may require treatment beforedisposal.

• Training may be required for operators andmaintenance staff.

• The community may have to be trained in the useof the system for it to operate effectively.

• Regional installations such as treatment works maybe required.

• Special vehicles and equipment may be requiredfor operation or maintenance.

To keep costs to a minimum, several issues arerelevant:

• Who pays what? For example, if a governmentinstitution or development agency is paying all ofthe capital costs, then the community will generallydemand the most expensive, highest level ofsanitation. If, on the other hand, the capital costsare to be recovered from the community, then itschoice of sanitation system may be quite different.The lack of income to pay for maintenance couldhave serious financial implications as well as healthrisks.

• Would the community prefer lower capital costsand higher maintenance costs, or vice versa?

• Will the cost comparison between options changeif all the potential benefits and costs are included?

• Are any of the costs incorrectly or dishonestlyrepresented? For example, have capital grants or

soft loans been ignored? Do certain services havehidden subsidies that produce misleadingcomparisons (for example, where treatment costsare paid by regional authorities)?

Where finance is limited, developers should consultthe community, determine its priorities, and seek waysto achieve the improvements desired. This may takeextra time but a motivated community will contributemore to successful project implementation and,perhaps more importantly, to the long-term operationand maintenance of the system selected.

Sanitation at public facilities

Sanitation facilities are required at public buildingssuch as schools and clinics. The large number of peopleusing a concentrated facility can cause problems ifthere is inadequate on-site drainage and a lack ofgeneral maintenance, such as cleaning of the toiletand replacement of toilet paper. Most types of on-sitesanitation systems can be used, provided thatdevelopers take note of the special requirements forpublic facilities.

Generally speaking, the system should use as littlewater and require as little routine maintenance aspossible. Before choosing a system that requires dailymaintenance for effective operation, one must ensurethat maintenance tasks will in fact be performed. Arural school may not be able to afford the services of ajanitor to look after routine maintenance.

The number of sanitation units required at schools iscovered in the National Building Regulations (SABS0400:1990). Because of the number of users, careshould be taken to prevent pollution of thegroundwater, particularly if there is a boreholesupplying the school with water.

Urinals that do not require water for flushing areavailable from commercial sources. These can be usedeffectively in sanitation facilities. However, theyrequire the weekly addition of a special oil to the trapand the application of a special deodorised cleanser tothe bowl or slab. They perform satisfactorily as long asthe weekly maintenance is carried out and shouldtherefore be used only where the necessary trainingcan be given to the cleaners and where the supply ofoil and cleanser can be assured.

DISPOSAL OF SLUDGE FROM ON-SITESANITATION SYSTEMS

All forms of on-site sanitation will result in anaccumulation of sludge that, at intervals, must beremoved from the pit or tank and conveyed to sometreatment or disposal facility. If the pit or tank containsfresh sewage, the sludge must be treated or disposedof in a way that will not be harmful to the

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environment or a threat to health; if the waste matterhas been allowed to decompose to the extent wherethere are no longer any pathogens present, the sludgecan be spread on the land as compost.

Sludge can be disposed of only in accordance with theprescribed methods. See Water Research Commission(1997) Permissable utilisation and disposal of sewagesludge.

An effective refuse-collection system should be inoperation in high-density residential areas and peopleshould be encouraged to use it. If this is not done, theresidents will probably use the toilet to dispose of tins,bottles, plastic and other forms of refuse which willresult in the pits filling very rapidly. This will presentproblems when emptying pits with a vacuum tanker.Where regular emptying will be required, it isadvisable to construct permanent pits with lined wallsto prevent damage during emptying, which could leadto the collapse of the pit walls. Note, however, that pitlinings should make allowance for percolation ofeffluent into the surrounding soil (e.g. by leaving thevertical joints of a brick lining unfilled). A regularprogramme for pit emptying in an area is better thanresponding to individual ad hoc calls for pit emptying.

Composition of pit or vault contents

In a sealed tank or vault, human excreta will usuallyseparate into three distinct layers, namely a layer offloating scum, a liquid layer and a layer of sediment.Well-drained pits may have no distinct liquid layer, andtherefore no floating scum layer. The scum layer seemsto be caused by the presence of paper, oil and greasein the tank and it is also more prominent in tanks witha large number of users. It is usually possible to breakup the scum layer without much effort. The watercontent of pits can vary between 50% and 97%,depending on the type of sanitation system, thepersonal habits of the users, the permeability of thesoil, and the height of the groundwater table.Cognisance should be taken of the fact that differentmaterials used for anal cleansing will have differentbreakdown periods. Newspaper will require more timeto break down than ordinary toilet paper, and in somecases will not break down at all. This will obviouslycause the pit to fill up more quickly.

Methods of emptying pits

It is possible to empty pits manually, using scoops andbuckets, and to dig out the thicker sludge with spades,but this poses obvious health risks to the workersinvolved. The use of ventilated improved double-pittoilets overcomes this unpleasantness by allowing theexcreta to decompose into a pathogen-free, humus-rich soil, after storage in the sealed pit for about twoyears. However, many people do not like to emptytheir pits manually.

The most suitable method of emptying a pitmechanically involves the use of a vacuum tanker,where a partial vacuum is created inside a tank andatmospheric pressure is used to force the pit contentsalong a hose and into the tank. The use of a vacuum ispreferred to other pumping methods, because thecontents do not come into contact with the movingparts of the pump, where they can cause damage orblockages. Various techniques can be used to conveythis sludge along the pipe to the tank. Thin sludgewith a low viscosity can be conveyed by immersing thenozzle below the surface of the sludge, drawing aconstant flow into the tank.

Thicker, more viscous sludge requires a pneumaticconveying technique, where the particles of wastematter are entrained in an air stream. This can beachieved by holding the end of the nozzle a fewcentimetres above the surface of the waste and relyingon the high velocity of the air to entrain particles andconvey them along the pipe to the holding tank. Thistechnique requires very high-capacity air pumps tooperate effectively. Devices such as an air-bleed nozzlecan be used to obtain the same effect with lessoperator skill and smaller air pumps. Pneumaticconveyance can also be achieved with a low-capacityair pump by using the plug-drag (or suck-and-gulp)technique. This method relies on submerging the hoseinlet, allowing a vacuum pump to create a vacuuminside the tank, then drawing the hose out to allow ahigh-velocity air stream to convey a plug of waste intothe tank. The plug-drag technique works best with avehicle with a fairly high-capacity pump (say 10 m3/min) and a relatively small holding tank(1,5-2 m3).

Sludge flow properties

Sludge generally exhibits a yield stress, shear thinningbehaviour and thixotropy. In effect, this means thatthe hardest part of the operation is to get the sludgemoving. The addition of small quantities of water tothe sludge can assist greatly in getting it to move bycausing shearing to take place. Being thixotropic, thesludge “remembers” this and exhibits a lower shearingstress next time.

Vacuum tankers

Most vacuum tankers available today are designed foruse in developed countries, where roads are good andmaintenance is properly done. However, somemanufacturers are realising the special conditions thatexist in developing countries and are now adaptingtheir designs or, even better, are developingcompletely new vehicles designed to cope with theactual conditions under which these vehicles will haveto work.

The size of conventional vacuum tanker vehiclesprevents their gaining easy access to toilets. They are

high off the ground, which may limit the depth of pitthat can be emptied, and they are so heavy whenloaded that travelling over bad or non-existent roadsis extremely difficult. The equipment on the vehicle isoften complex and requires regular maintenance,which is seldom carried out by the unskilled peoplewho, in most cases, will operate the vehicles. Waterysludge from conservancy tanks and septic tanks maynot be a problem, but the tankers often cannot copewith the more viscous sludge found in pit toilets.

A purpose-designed pit-toilet-emptying vehicle shouldhave the following attributes:

• a low mass;

• a low overall height;

• high manoeuvrability;

• ability to travel on extremely poor roads;

• a small-capacity holding tank with a relatively high-capacity pump, to facilitate the use of plug-dragtechniques;

• the ability to transfer its load to another vehicle ortrailer if there are long haul distances to thedisposal site;

• both vehicle and equipment must be robust;

• little skill should be required to operate the vehicleand the equipment;

• capital and operating costs must be as low aspossible, to facilitate operation by emergingcontractors or entrepreneurs;

• a small pressure pump and water for washingdown must be provided; and

• storage compartments must be provided for thecrew’s personal effects.

Disposal of sludge

Pit-toilet sludge can be disposed of by burial intrenches.

Dehydrated faecal matter from urine-diversion toiletsmay be safely re-used as soil conditioner, or,alternatively, disposed of by burial, if preferred. It mayalso be co-composted with other organic waste.

Sludge from septic tanks, aqua-privies, etc, can bedisposed of only in accordance with the prescribedmethods. See Water Research Commission (1997)Permissable utilisation and disposal of sewage sludge.

Unless the sludge has been allowed to decomposeuntil no more pathogens are present, it may pose athreat to the environment, particularly where theemptying of pits is practised on a large scale. Thedesign of facilities for the disposal of sludge needscareful consideration, as the area is subject tocontinuous wet conditions and heavy vehicle loads.The type of equipment employed in the disposal effortshould be known to the designer, as discharge speedand sludge volume need to be taken into account.Cognisance should be taken of the immediateenvironment, as accidental discharge errors may causeserious pollution and health hazards.

Emptying facilities at treatment works need not beelaborate, and could consist of an apron on which todischarge the contents of the vehicle and a wash-downfacility. The nature of the sludge can vary widely andthis should be taken into account when designing thesewage works. Depending on the habits of the pitowners and the effectiveness of refuse removal in thearea, there may also be a high proportion of rags,bottles and other garbage in the sludge. Generally ahigher grit load will also come from developingcommunities. Pond systems can be very effective intreating sludge from on-site sanitation systems. If theponds treat only sludge from pit latrines it may benecessary to add water to prevent the ponds fromdrying out before digestion has taken place. Sludgefrom on-site sanitation systems can also be treated bycomposting at a central works, using forced aeration.

Although it is usually still necessary to treat sludgefrom on-site sanitation systems, the cost of treatmentis lower than for fully waterborne sanitation. This isbecause partial treatment has already taken place onthe site through the biological decomposition of thewaste in the pit or tank. In addition, the treatmentworks do not have to be designed to handle the largequantities of water which must be added to the wastefor the sole purpose of conveying solids along anetwork of sewer pipes to the treatment and disposalworks.

EVALUATION OF SITES

It is not possible to lay down rigid criteria for thesuitability of a site for on-site sanitation, because soiland site conditions vary widely. Two basic criteriashould, however, be considered – namely, whether thesoil can effectively drain the liquids brought to the siteand whether there is any danger of pollution of thegroundwater or surface water.

Topographical evaluation

All features that can affect the functioning of thesanitation system should be noted and marked on thesite plans during a visual survey of the site. Theposition of depressions, gullies, rock outcrops and

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other features should be noted and an assessmentmade of how they are likely to affect the functioningof the system. The type and gradient of slopes shouldalso be noted as steep slopes can result in the surfacingof improperly treated effluent, especially duringperiods of high rainfall. Surface and subsurfacedrainage patterns, as well as obvious flood hazards,should be reported. The vegetation on the site willoften reflect soil-drainage characteristics.

Soil profiles

Sampling holes should be excavated to a depth of atleast one metre below the bottom of proposed pittoilets or soakaways. Soil properties (such as texture,structure and type) should be determined. Thepresence of bedrock, gravel, groundwater or a layerwith poor permeability should be noted. Soil mottlingindicates the presence of a high seasonal groundwatertable, which can affect soil percolation.

Percolation capacity of the site

If the soil is unable to drain liquid waste effectively,swampy, unsanitary conditions can result. This canoccur in areas with very shallow water tables or withpoor permeability, or where a shallow, restrictive layersuch as bedrock occurs. On-site sanitation can be usedin low-permeability soils, but the system must becarefully selected in relation to the quantity of watersupplied to the site. If the efficient functioning of asoil-percolation system is in doubt, it is advisable tocreate an inspection point where the level of thewater in the subsoil drain can be monitored, so thatadequate warning of failure is obtained to allow thelocal authority to plan for an alternative solution toliquid drainage problems before a crisis develops. Thiswill be effective only if the recipient community fullyunderstands the need for regular inspection of thedrain, as well as the consequences of failure. On-sitesanitation can be used in areas with poor percolation,but it may be necessary to retain all the liquids on thesite in a sealed vault and provide a regular emptyingservice, or to drain the site with settled sewagesystems.

The percolation test is designed to quantify themovement of liquids in the soil at a specific time of theyear. Percolation rates usually change as the soil’smoisture content changes, and it is best to conduct thetest in the rainy season. The percolation test should beregarded only as an indication of the suitability of thesoil for a specific sanitation system. The followingprocedures should be complied with:

Calculation of number of test holes

The number of test holes needed is determined by thesize of the settlement and the variability of the soilconditions. Usually test holes should be spaceduniformly throughout the area, at the rate of five to

ten holes per hectare, if soil conditions are fairlyhomogeneous.

Percolation test

The test procedure to be followed is described in SABS0400.

POLLUTION CAUSED BY SANITATION

When there is a high density of people living in anarea, both the surface water and groundwater can beexpected to become polluted to some degree,irrespective of the type of sanitation system used inthe area. Some basic precautions will minimise the riskof serious pollution.

Surface pollution

The surfacing of partially treated effluent can create adirect health risk, and can cause pollution of surfacewaters. This type of pollution should and can usuallybe avoided. It is most likely to occur in areas where thegroundwater table is very high or in areas with steepslopes where a shallow, permeable layer of topsoilcovers an impermeable subsoil. In areas where cut-and-fill techniques are used to provide platforms forhouse construction, sanitation units and soakawaysshould be carefully sited to minimise the possibility ofsurface pollution. Sanitation units and soakawaysshould also be sited in such a way that rainwateringress cannot occur, as this could cause flooding, withresultant surface pollution.

Poor maintenance of reticulation systems, pumpingstations and sewage-purification works can causeserious pollution with associated health risks,especially in remote areas close to streams and rivers.

Groundwater pollution

Groundwater can be contaminated by a sanitationsystem; therefore the risk should be assessed or thegroundwater periodically monitored, particularlywhere this water is intended for human consumption.The guidelines made available in the publication Aprotocol to manage the potential of groundwatercontamination from on-site sanitation by theDirectorate of Geohydrology of the Department ofWater Affairs & Forestry (1997), should be observed.The soil around the pit toilet or subsurface drainprovides a natural purification zone, and tests carriedout both in South Africa and other parts of Africaindicate that on-site sanitation does not pose a seriousthreat, provided the water is not intended for humanconsumption. Generally, the susceptibility of a watersource to pollution decreases quite sharply withincreasing distance and depth from the source ofpollution, except in areas with fissured rock, limestone,very coarse soil or other highly permeable soils.

Soakaways attached to on-site sanitation systemsshould, wherever possible, be located downstream ofdrinking water supplies. The following could be usedas a guide for the location of a soakaway:

• 7,5 m from the drinking-water source if the highestseasonal water table is more than 5 m below thebottom surface of the pit or soakaway;

• 15 m from the water source if the highest seasonalwater table is 1-5 m below the bottom surface ofthe pit or soakaway;

• 30 m from the water source if the highest seasonalwater table is less than 1 m below the bottom ofthe pit or soakaway; and

• there is no safe distance from a source of drinkingwater in areas that have fissured rock, limestone orvery coarse soil.

These distances are given as a guide only. Permeabilityof the soil is not the only factor. Geology, topography,the presence of trees, groundwater flow direction, etc,also influence the position of the borehole (Xu andBraune 1995).

SULLAGE (GREYWATER) DISPOSAL

General

On-site excreta-disposal technologies require thatseparate provision be made for the disposal of sullage.Sullage, also referred to as greywater, is defined as alldomestic wastewater other than toilet water. Thisrefers to wastewater from baths, sinks, laundry andkitchen waste. Although this “greywater” is supposednot to contain harmful excreted pathogens, it oftendoes: washing babies’ nappies, for example,automatically contaminates the water. Sullage,however, contains considerably fewer pathogenicmicro-organisms and has a lower nitrate content thanraw sewage. It also has a more soluble andbiodegradable organic content.

Sullage is produced not only on private residentialstands but also at communal washing places and taxistands, and provision should therefore be made for itsdisposal.

Volumes

The per capita volume of sullage generated dependson the water consumption. The water consumption isto a large extent dependent on the level of watersupply and the type of on-site sanitation thecontributor enjoys. It is not difficult to find localfigures of generation and one should try to obtainthese, even if it requires actual measurement in thefield. Typical figures are given in Table 10.2.

Health aspects

Mosquito breeding can take place where ponds arecreated by casual tipping of sullage, and conditionsfavourable for the development of parasitic wormscould also be created in this way. Infection can alsooccur in constant muddy conditions. In order to reducepotential health hazards, it is of the utmostimportance to choose the right option for sullagedisposal. See also Figure 6.31, Chapter 6.

Disposal

The type of disposal system chosen by the designer willdepend on various factors such as the availability ofland, the volume of sullage generated per day, the riskof groundwater pollution, the availability of opendrains, the possibilities of ponding and thepermeability of the soil. Where water is available onthe site, a disposal facility should definitely beconsidered.

Disposal systems

Sullage can be used to effect flushing of certainsystems.

Casual tipping

Casual tipping in the yard can be tolerated, providedthe soil has good permeability and is not continuallymoist. Where casual tipping takes place under otherconditions it may result in ponding and/or muddyconditions, with adverse health effects as mentionedabove. Good soil drainage and a low populationdensity can accommodate this practice.

Garden watering

This practice can also be tolerated, provided plants andvegetables that are watered in this manner are noteaten raw, for disease transmission may occur.

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Standpipes, water vendors. Pit toilets. 20 - 30

On-site single-tap supply (yard connection). Pit toilets. 30 - 60

Table 10.2: Sullage generation

AVAILABLE WATER SUPPLY AND SANITATION SULLAGE GENERATION – LITRES PER CAPITA PER DAY

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Soakaways

A soakaway is probably the safest and mostconvenient way of disposing of sullage, as long as soilconditions permit this. The design of the soakaway canbe done according to the guidelines given in SABS0400. Designers should be aware that groundwaterpollution is still a possibility, though to a much lesserextent. Where simple maintenance tasks are able to becarried out, the use of grease traps should beconsidered.

Piped systems

The disposal of sullage in piped systems is hardly everan economical solution, although it may be a viableoption when dealing with communal washing pointsgenerating large amounts of sullage. Solids-free sewersystems are ideal for this purpose.

Sullage treatment

The fairly high BOD5 value of sullage (typically 100mg/l) makes it unsuitable for discharging into riversand streams. If treatment is required, single facultativeponds could be used.

TOILET PEDESTALS AND SQUATTINGPLATES

Various types of toilet pedestals and squatting platescan be used with on-site sanitation systems. Membersof some cultures are used to squatting for defecation,and cases of constipation have been recorded whenthey change to a sitting position. Some cultures alsorequire water for anal cleansing.

The simplest form of appliance is a plain seat orpedestal, or a squatting plate. The hole should beapproximately 250 mm in diameter for adults, andhave a cover to restrict the access of flies and otherinsects to the pit. It is good practice to provide asecond seat with a hole size of approximately 150 mmfor young children, so that they need not fear fallinginto the pit. The plain seat found in a VIP toiletnormally has similar dimensions.

Pedestals with water seals can be used in conjunctionwith most sanitation systems. Various methods can beemployed to effect a water seal in a toilet system. Theysignificantly increase user convenience by eliminatingodour and screening the contents of the pit. Somewater seal appliances require a piped water supply.These are not recommended for on-site sanitationsystems, unless the extra water can be disposed of onthe site (see the section on sullage disposal). Mostwater seal appliances can operate efficiently on a tankfilled by a bucket of household wastewater.

A conventional toilet bowl is an example of a water

seal pedestal, but it can require between 6 and 12litres per flush. Special pans or bowls, so-called low-volume flush pans, have been developed that requireonly three litres per flush. These low-volume flushtoilets do not have any negative effects on the self-cleaning capacity of waterborne sewerage systems.Various tipping-tray designs are also available, withflush requirements varying from 0,75 to 2 litres,depending on the design. These appliances have ashallow pan or tray that holds the water necessary forthe seal. After use the tray is cleared by tipping it,allowing the waste matter to fall into the pit below.Thus the water is used solely for maintaining the seal,not for clearing the pan.

Pour-flush bowls can also be used to maintain a waterseal. These pans are flushed by hand, using a bucket,and generally require about two litres per flush. Thebiggest disadvantage of this appliance is that theeffectiveness of the flush depends on the humanelement – which varies greatly – and there is nocontrol over the amount of water used per flush.

The pedestal of an aqua-privy does not have its ownwater seal. The water seal is effected by directing thepipe straight into the digester. No water is needed forflushing, but the level of liquid in the tank must bemaintained.

DESIGN OF VIP TOILETS

Detailed design information can be obtained from thepublication Building VIPs by Bester and Austin. A VIPCode of Practice is currently also under preparation bythe SABS.

TOILET FACILITIES FOR PHYSICALLYDISABLED PERSONS

Some introductory remarks on water and sanitationfacilities for disabled persons can be found under thesection “Public or communal water-supply terminals”in Chapter 9.

Toilet aids help to preserve the dignity andindependence of disabled persons. Outdoor toiletsshould be situated on smooth, even pathways, andramps should be provided in lieu of steps. Rampsshould be not less than 1100 mm wide, with a slopenot exceeding 1:12. The appropriate layout anddimensions of a toilet room suitable for wheelchairusers are shown in Figure 10.12. If there is enoughspace for a person using a wheelchair, then thereshould be enough space for ambulant people usingcrutches or technical aids. Taps or washbasins, if fitted,should also be in an accessible position and at anappropriate height for use from a wheelchair.Reference should be made to Part S of SABS 0400-1990for further design information.

TRAINING OF MAINTENANCEWORKERS

The training of local people as maintenance workersshould be seen as an integral part of capacity-buildingwithin the community. Training should not take placemerely because it is a fundamental principle or policyof the day.

Members of the community should be trained toinstall and operate a system, or to act as advisers toothers who would like to install their own system. Thiscan be achieved by establishing a “sanitation centre”where the community can purchase a variety ofappliances and other necessary materials. Themanager of this centre can be trained to become thelocal sanitation expert and can advise the populationon maintenance requirements when necessary.

When assessing training needs, one must expect thatsome of the people trained will move to other areaswhere greater employment opportunities areavailable.

The degree of training and the amount of institutionalsupport required will increase with the level ofcomplexity of the sanitation system. On-site sanitationhas the advantage that the greater part of the systembelongs to the users. Sewer systems, on the otherhand, have long lengths of underground piping andmanholes, as well as pumping installations, which arethe property of the local authority and must beregularly maintained by properly trained people inorder for the system to work properly.

UPGRADING OF SANITATIONFACILITIES

Possible upgrading routes should be considered whenthe initial choice of a system is made, particularly if anappreciable increase in the water supply is expected atsome time in the future. However, it is unlikely that allthe residents of a township will be able to affordupgraded services at the same time, which will benecessary if one is upgrading to full waterbornesanitation.

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Figure 10.12: Minimum dimensions of a toilet room for physically disabled persons

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Most forms of pit toilet can be greatly improved byproviding a water seal between the user and theexcreta. This effectively stops odours and flies fromexiting the pit via the toilet pedestal, and removeschildren’s fears of falling into the pit. A water seal canbe provided by a tipping-tray, a pour-flush or a low-flush toilet bowl. Designers should ensure that thequantity of water used with every cleaning operationdoes not increase the water content of the pit to apoint where it can no longer be drained by the soil.

When the water supply is increased to the point atwhich the soil can no longer absorb it naturally(usually when an individual water connection isprovided to each stand), it will be necessary to makespecial arrangements to remove the wastewater fromeach site in order to maintain healthy livingconditions.

This is a major step in the upgrading process and willrequire additional financial input from the residents.The most economical solution may be a settled-sewagesystem, as this would be far easier to install in anexisting settlement than a conventional sewer system.

If the developer is reasonably confident that the area’swater supply will be upgraded within a few years, itmay be advantageous to install septic tanks at the timeof the original development. If this is done, then thesettled-sewage system can be connected directly to theoutlet from these systems and the soakaway can bebypassed and left inactive on the site.

Some possible upgrading routes are described inAppendix B.

OFF-SITE WASTEWATER TREATMENT

Off-site wastewater treatment is considered aspecialised subject and, except for some generalcomments on pond systems and package purificationunits, falls outside the scope of this document. Wherethe introduction of a treatment works is considered,specialist consultants should be involved. The qualityof effluent emanating from a wastewater treatmentworks is prescribed by legislation and has to meetlicensing requirements. Water Services Providersshould be licensed in terms of the National Water Act.

Pond systems

Although pond systems are regarded as treatmentplants, the effluent does not normally meet acceptableeffluent standards. Pond effluents have therefore tobe irrigated. A pond system is regarded as awastewater treatment works and its owner should alsoobtain a licence from the Department of Water Affairs& Forestry.

Pond systems are usually used in remote or developingareas, normally where land is available and relativelycheap. Skilled operators are not required and,depending on the circumstances, electricity need notbe a requirement. Stabilisation (or oxidation) ponds are cheaper to build than conventional sewagepurification works.

Although pond systems are regarded as beingcomparatively less sophisticated than otherpurification systems, they nevertheless require properplanning, application, design, construction andmaintenance. Ponds do not need daily attendance,but should never be allowed to fall into disrepair.

The Water Institute of South Africa (WISA) has madeavailable a design manual based on South Africanexperience. This manual can be used as a guide to thedesign of pond systems.

Stabilisation or oxidation ponds are classifiedaccording to the nature of the biological activitytaking place, as follows:

• facultative-aerobic ponds (where aerobic andfacultative conditions exist) – facultative organismsuse dissolved oxygen when it is available, butconvert to anaerobic processes in its absence; and

• anaerobic-aerobic ponds (where the primary pondsare completely anaerobic and the secondary pondsare mainly aerobic).

The following important aspects should be consideredregarding siting and land requirements:

• the cost of the land;

• the minimum distance between pond systems andthe nearest habitation;

• the direction of the prevailing winds – pondsshould, as far as possible, be downwind of townlimits;

• possible groundwater pollution;

• geotechnical conditions that will influence costs;

• the land required for irrigation purposes, which isan integral part of the pond system; and

• the topography of the site, which can influencecosts.

Irrigation of crops may take place only as prescribed inthe publication Permissable utilisation and disposal ofsewage sludge by the Water Research Commission1997.

Package purification units

The use of package purification units is dependent onfactors similar to those mentioned above, but the

operational costs involved when opting for package purification plants should be carefully considered. It is not a preferred option.

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This appendix gives information regarding data thatshould be collected for the proper planning, designand implementation of a sanitation project. Note thatthe definition of sanitation in the White Paper onBasic Household Sanitation of 2001 is the following:

“Sanitation refers to the principles and practicesrelating to the collection, removal or disposal ofhuman excreta, household wastewater and refuseas they impact upon people and the environment.Good sanitation includes appropriate health andhygiene awareness and behaviour, and acceptable,affordable and sustainable sanitation services.

The minimum acceptable basic level of sanitationis:

(a) appropriate health and hygiene awareness andbehaviour;

(b) a system for disposing of human excreta,household wastewater and refuse, which isacceptable and affordable to the users, safe,hygienic and easily accessible and which doesnot have an unacceptable impact on theenvironment; and

(c) a toilet facility for each household.”

COMMUNITY MANAGEMENT APPROACH

Research done and projects launched in culturallydifferent communities require an openness andadaptability to the issues that are important to thecommunity. A growing awareness of the failures ofconventional development approaches in meeting theneeds of people with few resources has led to theexploration of alternative methodologies forinvestigating resource-management issues, andplanning, implementing and evaluating developmentinitiatives. There is a wide range of approaches withstrong conceptual and methodological similarities.These include:

• Participatory rural appraisal (PRA); • Participatory learning methods (PALM); • Rapid rural appraisal (RRA);• Rapid assessment procedures (RAP);• Participatory action research (PAR);• Rapid rural systems analysis (RRSA);• The demand responsive approach (DRA);• The SARAR approach;

and many others. The themes common to all of theseapproaches are:

• the full participation of people in the processes;

• the concept of learning about their needs andopportunities; and

• the action required to address them.

The experience gained in the past decade in particularhas pointed to the need for three key elements to besuccessful both in water-supply and in sanitationprojects, namely:

• involvement of the community in all aspects of theprojects;

• the use of appropriate technology; and

• the need for institution-building and -trainingactivities in conjunction with the project.

Community development, however, does not takeplace in a vacuum; it is always situated in a concretesocial, economic and political context. Therefore, it isof the utmost importance that a multi-disciplinaryteam be involved in community development. Becausedevelopment is development for the people, thepeople should remain central to the process. To ensurethis, it is inevitable that social engineering shouldprecede any development project, and run parallelwith it until completion of the project.

Over the past few years, holistic development hasbecome a vital aspect of sustainable development. It isrecognised worldwide that projects that take humanfactors into consideration are more likely to besuccessful than those that do not. It is therefore of theutmost importance for development agencies tocollaborate closely with communities at inception andthrough all stages of infrastructural development.

As distinct from community participation, communitymanagement means that beneficiaries ofinfrastructural services have the responsibility for, andauthority and control over the development of suchservices.

Although the spin-offs of this approach are obvious,they are not easy to achieve within a short space oftime. It should also be noted that the mereparticipation of communities in the project is not asolution, but a necessary forerunner of successful

APPENDIX A

INFORMATION REQUIRED FOR THE PLANNING AND DESIGN OF SANITATIONPROJECTS

community projects. It is imperative that participationshould be coupled with capacity-building effortsthrough training.

The application of scientific research methods (such asfact-finding and community surveys) is recommendedin the initial stages of community development. Thesemethods can be adapted in research forums thatpromote community participation, and which willcreate opportunities for interaction between thedeveloper and the identification of needs bycommunity members themselves. Examples includecommunity surveys, social reconnaissance and actionresearch. This emphasises a systems approach andinter-disciplinary teamwork, continued involvement ofthe community members in all decisions and activities,development as a learning process (including the needfor training), and continued monitoring andevaluation activities.

Seven phases have been identified in the participatorystrategy for integrated rural development.

Phase 1

This phase consists of an initial reconnaissance of thecommunity among which the project is going to beimplemented by the social scientist or communityworker. Existing documentary sources about thecommunity are studied and field visits, mini-surveysand interviews with key people, etc, are undertaken.The main aim is to identify initial goals and to committhe development committee, which must includerepresentatives (male and female) from thecommunity, to these goals.

Phase 2

The second phase is the identification of priorities bymeans of field studies and research. Theplanner/developer performs specific investigations inorder to identify areas of priority or problems.Community members and other agents are trained inproblem identification and analysis. Insight is alsogained in the functioning of the system and itsproblems.

Phase 3

The third phase consists of the formulation of possiblesolutions for the identified problems. The social scientistor community worker gives direction, but communitymembers are involved fully in exercises of discoveringsolutions. Continued involvement and participation ofthe community members should be ensured.

Phase 4

In the fourth phase feasibility studies are performed. Itis important that objectives be compatible with eachother.

Phase 5

This phase is the implementation of the project. Theimplementation implies various political and planningactivities, such as official approval of the project,planning and design, formal project descriptions,communication with the authorities, liaison andlinkage with other institutional agencies, financialsupport, physical input and specific services.

Phase 6

This phase consists of planning the completion,termination, or continuation of the project.Community members should be trained in theoperation and maintenance of the system, andsupported in their efforts for a period of time toensure sustainability.

Phase 7

The seventh phase refers to project evaluation. Formalproject evaluation, preferably by an external agent, issupported by internal evaluation procedures as anongoing activity in the development process.Monitoring and auditing form part of the evaluationactivities. The main function of evaluation is toidentify weaknesses in a project, in order to avoidsimilar problems and facilitate sound planning infuture projects.

HUMAN-RELATED DATA

The following data are necessary to ensuresustainability.

Socio-cultural data

Religious and tribal customs, as well as cultural factorsaffecting the choice of technology (for example,traditional materials and practices for cleansing andablution), include:

• the general level of literacy and education,especially hygiene education;

• important watersource-related activities (such aslaundry, bathing and animal watering); and

• community attitudes to the recycling and handlingof decomposed human waste.

Community preferences

After considering costs, note preferences of thecommunity regarding the following:

• the type of sanitation service;

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• the position of the toilet (for example, should it beinside or outside the house? If outside, should thetoilet door face the house? How far should thetoilet be from the house?);

• the appearance of the toilet building and pedestal(colour, form, etc);

• the size of the toilet;

• the seats or squatting plates; and

• the permanency of the superstructure.

Economic and social conditions

These include:

• present living conditions, types of housing(including condition, layout and building materialsused) and occupancy rates;

• population numbers according to income levels(present and projected), and the age and sexdistribution of the community ethnic groups, andsettlement patterns in the project area;

• land-use and land-tenure patterns;

• locally available skills (managerial and technical);and

• major occupations, approximate distribution,unemployment and under-employment.

Health and hygiene conditions

These include:

• location of toilet/defecation sites;• toilet maintenance (structure and cleanliness);• disposal of children’s faeces;• hand-washing and use of cleansing materials;• sweeping of floors and yard;• household refuse disposal;• drainage of surrounding area;• incidence and prevalence of water- and faeces-

related diseases;• treatment of diseases; and• access to doctors/clinics/hospitals.

Institutional framework

These include:

• The identification and description (responsibility,effectiveness and weaknesses) of all institutionsand organisations, both governmental and non-governmental, that are providing the followingservices in the project area:

- water and sanitation;- education and training;- health and hygiene;- housing;- building material supplies; and - transport.

• Identification of all other major local organisations(social and political), the type and number ofmembers they have and the influence they couldhave on the project.

Environmental and technical aspects

Important factors to consider are:

• the position of the site in relation to existingsettlements;

• existing supplementary services (type, availability,reliability, accessibility, cost, etc) such as watersupply, roads, energy sources and sanitationschemes;

• environmental problems such as sullage removal,stormwater drainage, refuse removal, transportroutes;

• site conditions such as topography, geology (soilstability, rockiness, permeability, etc);

• groundwater data, such as availability, quality anduse;

• prevailing climatic conditions such as rainfall,temperature and wind;

• type and quantity of local building materials thatmay be suitable;

• existing building centres supplying buildingmaterials and equipment (type of materials andequipment, availability, quality and cost); and

• the need for, and existence of, appropriatebuilding regulations and by-laws.

INFORMATION REQUIRED FOR POST-PROJECT EVALUATION

To evaluate the success and sustainability of asanitation project, it is necessary to correlateenvironmental conditions in the project area with thehealth profile of the community concerned after thescheme has been in operation for some time(especially projects where the upgrading of existingservices is planned). To be able to do this, additionalinformation should be collected – for example thefollowing:

• A concise description of the community’s livingconditions in general, and their existing sanitationand water supply facilities in particular.

• How long have the people been living in the areaand for what period have the existing sanitationfacilities been in use?

• With regard to the community’s perception of thepresent situation and sanitary practices, and theirinterest in or susceptibility to change:

- Do they regard the present water supply assatisfactory, in quantity and quality?

- What arrangements are there for refuseremoval – do they regard them as satisfactory?

- What facilities exist for personal hygiene –where do they bathe or wash themselves?

- Are they aware of any advisory service onhealth and hygiene, and do they make use of it?

- What amount of money do they spend on

doctors, clinics, medicines and other health-related aspects?

- Do they regard the present sanitation facilitiesas adequate?

• Identify all major health problems in thecommunity:

- List all diseases recorded in the area that can berelated to water supply and sanitation.

- Obtain figures on present morbidity andmortality rates.

- Identify possible disease-contributing factors,such as possible contamination of drinkingwater.

- What was the actual total cost of the project?

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BASIC UPGRADING ALTERNATIVES

Alternative 1 – Aesthetic upgrading

The options in this category can be implemented byindividual stand-owners, as the necessary financialresources become available. These are limited to thesuperstructure and the pedestal. An example would bewhere a functional superstructure is replaced with amore permanent or more aesthetic structure, such asone built from bricks and mortar. The property ownercan decide on factors such as the size of thesuperstructure and whether the door should openinward or outward. The door and roof materials of theoriginal superstructure could be re-used.

Alternative 2 – Introduction of a waterseal

This will effectively remove odours emanating fromthe pit and will ensure that the user cannot see theexcreta. This will also reduce the fear, particularlyamong children, of falling into the pit. A water sealcan be introduced by installing a tipping tray, a pour-flush pan or a low-flush pan. The difference betweenthe three types of water seal lies mainly in the quantityof water required, and thus their suitability would alsodepend on the ability of the soil to drain theadditional quantity of water supplied to the site. Thistype of upgrading can be undertaken by the individualowner whenever funds are available. Depending onwhat type of water-seal appliance is used, it may ormay not be necessary to provide an individual waterconnection to each stand.

Alternative 3 – Removal of liquids fromthe site

When individual water connections are provided toeach stand, the situation will often arise where the soilcan no longer adequately drain the additional water.This makes the removal of water necessary to maintainhealth standards. Liquids can be removed from the siteby means of sewers (either a full waterborne sanitationsystem or a settled sewage system), or they may beretained on site in a conservancy tank and thenremoved periodically by a vacuum-tanker service. Theinstallation of a sewer system will be a costly step in theupgrading process, and will require each resident tocontribute to the construction costs, or some form ofoutside subsidy will need to be found. The ability of thelocal authority to manage and maintain these sanitationsystems must be assessed when considering theintroduction of the system. Generally, the sewers would

need to be laid in the entire township at the same time.Upgrading should be undertaken only when thecommunity can afford to pay for the higher level ofservice. Practically, this means that upgrading in Group1 and 2 can be implemented at any time by individualproperty owners, independently of neighbours. Onthe other hand, upgrading in Group 3 will requireboth the greatest financial outlay from the propertyowners and implementation of the entiredevelopment at the same time. Note that, in the caseof a settled sewage system, the sewers will need to belaid to neighbourhoods at the same time, butindividual owners need not all connect to the systemsimultaneously, since it is not necessary to maintaincleansing velocities in sewers that convey only theliquid portion of the wastes. Thus, property ownerscould connect to the system when they have thefinancial means to construct the necessary solids-retention tank. Note that some on-site sanitationsystems, for example septic tanks, can be used assolids-retention tanks and therefore can be connectedto the settled-sewage system with only minoralterations.

UPGRADING ROUTES FOR THE VARIOUSSANITATION SYSTEMS

There are many possible upgrading routes that couldbe taken and the following should be seen as anindication of the various possibilities for the systems asdefined in Table 10.1, which categorises sanitationsystems.

Group 1

Upgrading chemical toilets

The use of chemical toilets would probably be atemporary solution in a developing community.Upgrading to a more permanent system wouldtherefore take the form of total replacement with anyone of the other sanitation systems. The chemicaltoilet would be removed from the site as a unit; thusthere would not be any re-use of materials.

Group 2

Upgrading unventilated pit toilets

The first and most important step in upgrading wouldbe to install a vent pipe to convert the toilet into aventilated improved pit (VIP) toilet. This upgradingshould be undertaken at the earliest possible

APPENDIX B

UPGRADING OF EXISTING SANITATION SYSTEMS

opportunity. After the addition of a vent pipe, furtherupgrading would follow the same route as a VIP toilet.

Upgrading ventilated improved pit (VIP) toilets

The VIP toilet provides several opportunities forupgrading. A major improvement can be obtained byintroducing a water seal between the user and theexcreta, thus providing a level of convenience that ismore acceptable to users.

It may thus be necessary to consider Alternative 3upgrading (removal of liquids from the site) only ifproblems arise with the drainage of excessivequantities of water, which situation can be expectedwhen individual water connections are provided toeach site. Since the pit of a VIP toilet is not watertight,it will probably be necessary to construct a new tankon the site for solids retention if upgrading to asettled-sewage system is required. The pit of the VIPtoilet will then become redundant. Thus, if at theoutset the final stage of the upgrading route is knownto be a conservancy-tank or settled-sewage system, itis preferable to begin with a sealed-tank system (suchas a vault toilet, aqua-privy or on-site digester), toavoid constructing a new tank when the upgradingtakes place.

The installation of a urine-diversion pedestal will makea significant difference to a VIP toilet. The contents ofthe existing pit should be covered with a layer ofearth, and the structure may thereafter be operated asa normal urine-diversion toilet, where urine is divertedto a soakpit or collection container and faeces arecovered with ash or dry soil.

Upgrading ventilated vault (VV) toilets

This system is a variation of the VIP toilet, with theimportant distinction that it has a waterproof pit orvault. The comments on upgrading in Alternatives 1and 2, for VIP toilets, also apply to this system.Upgrading to Alternative 3 will be different from thatof the VIP toilet because the VV toilet has a lined,waterproof vault that can be used. The option ofupgrading to a conservancy tank is not mentionedbecause the ventilated vault toilet is a type ofconservancy tank. Because the VV toilet already has awaterproof tank, this system is ideal for upgrading toa settled sewage system and it is therefore highlyunlikely that this system would be upgraded to a fullywaterborne sewer system.

Upgrading ventilated improved double pit(VIDP) toilets

This system is basically a variation of the VIP toilet, sothe comments for the VIP also apply to the VIDP toilet.

Group 3

Upgrading full waterborne sanitation

No upgrading of this system is necessary, but the standowner can implement aesthetic improvements to thepedestal and superstructure.

Upgrading conservancy tank systems

A conservancy tank provides an ideal opportunity forupgrading to a settled sewage system, since the tankcan be used to retain solids on the site.

Upgrading the settled sewage system

No upgrading of this system is necessary, but the standowner can implement aesthetic improvements to thesuperstructure.

Group 4

Upgrading septic tank systems

A septic tank also provides an ideal opportunity forupgrading to a reticulated system, since the outletfrom the septic tank can be connected to a settledsewage system without any further alterations beingnecessary. Solids would be retained on the site anddigested in the septic tank.

Upgrading aqua-privies

The aqua-privy has a rough water seal, but this can begreatly improved by removing the pedestal and chuteand replacing them with a device such as a tipping-tray, pour-flush or low-flush pan. An aqua- privy alsoprovides an ideal opportunity for upgrading to asettled sewage system, since the outlet from the aqua-privy can be connected into the reticulation systemwithout any further alterations. Solids would then beretained on the site and digested in the aqua-privytank.

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SCOPE

These guidelines are applicable to the design andconstruction of sewerage reticulation for undevelopedresidential areas, where the future houses are to beprovided with full waterborne sanitation. They do notapply to on-site drainage, and do not cover any formof on-site disposal such as septic tanks and soil-percolation systems. They also do not apply to settledsewage systems.

Certain basic guidelines applicable to non-gravitysystems (i.e. pump stations and rising mains) areincluded, but detailed design criteria for these systemsare not included, as they are regarded as bulk services.

Except in cases where illustrations are provided, thereader is referred to various figures in the relevantsections of SABS 1200.

DESIGN CRITERIA

Design flows

Flow-rate units

The unit of flow rate used in these guidelines is litresper second (l/s).

Depth of flow and infiltration

Sewers should be designed to flow full at the peakdesign flow. An allowance of 15 per cent forstormwater infiltration and other contingenciesshould be incorporated in the design figures used forsingle-family dwelling units.

Average daily flow (A)

The average daily flow per single-family dwelling unitis given in Table C.1.

General residentialFor erven zoned as “general residential”, includingblocks of flats and hotels, an average daily flow of600 litres per day for every 100 m2 of erf size shouldbe used.

Notes:(i) The above figure is based on a dwelling unit

with a floor area of 100 m2 and a floor spaceratio (FSR) of 0,6. If a FSR other than 0,6 isprescribed, the flow figure above should beadjusted accordingly.

(ii) Maximum density allowable under the schemeis the overriding factor.

Church sitesA church site should be treated as a “specialresidential” erf.

Schools and business sitesThe discharge from day schools and business sitesneed not be taken into account, since these arerelatively minor flows that do not peak at the sametime as the main residential flow.

Peak design flows

In these guidelines the following factors apply tosingle-family dwelling units:

Peak Factor (PF) = 2,5Percentage allowed for extraneous flow = 15 %

To calculate the unit design flow rate:

Average daily flow (l/du/d) = A

Average daily flow rate (l/s) = A24 x 60 x 60

= A86 400

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APPENDIX C

DESIGN GUIDELINES FOR WATERBORNE SANITATION SYSTEMS

Litres per dwelling unit per day 500 750 1 000Based on average total personsper dwelling unit 7 6 5

Table C.1: Average daily flows per single-family dwelling unit (du)

INCOME GROUP LOWER MIDDLE HIGHER

Peak flow rate = Average daily flow rate x peak factor

A x 2,5 = B86 400

Design flow rate = Peak flow rate + % of peak flowrate for extraneous flows

B x 1,15 = A x 2,5 x 1,15

86 400= 0,000 033 A= C

Thus, for a population up to 1 500,

C = A (l/s/du)

30 000

Thus, from Table C.1:

C = 0,0167 l/s/du for lower income group= 0,0250 l/s/du for middle income group= 0,0333 l/s/du for higher income group

If unit design flows are, instead, obtained from actualflow-gauging of adjacent settlements of similarnature, these unit design flows should not exceedthose given above.

Attenuation

To take advantage of the attenuation of peak flows ingravity sewer systems as the contributor area andpopulation increases, design peak factors may bereduced in accordance with the graph in Figure C.1 for

sizing any sewer receiving the flow from a populationgreater than 1 500. If actual local attenuation factorsare available, however, these should be used instead.

Hydraulic design

Flow formulae

The following flow formulae are acceptable for thecalculation of velocity and discharge in sewers:

Manning (n = 0,012)Crimp and Bruges (n = 0,012)Colebrook-White (Ks = 0,600)Kutter (n = 0,012)

Any formula can be used as long as it produces valuesapproximately the same as the equivalent Colebrook-White formula using Ks = 0,6.

Minimum size of sewers

The minimum diameter of pipe in sewer reticulationshould be 100 mm.

Limiting gradients

Sewers may follow the general slope of the ground,provided that a minimum full-bore velocity of 0,7 m/sis maintained.

Table C.2 shows the minimum grades required toachieve this minimum full-bore velocity for variouspipe sizes up to 300 mm in diameter.

If flatter grades and lower velocities than those in

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Figure C.1: Attenuation of peak flows

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Table C.2 are contemplated, it is essential that adetailed cost-benefit study be carried out. This shouldtake into account the cost of the regular systematicmaintenance and silt/sand removal that will berequired when flatter grades and lower velocities areused, instead of the additional first cost required tomaintain the above minimum grades and full-borevelocity of 0,7 m/s.

Non-gravity systems

Rising mainsVelocities:The minimum velocity of flow in a rising mainshould be 0,7 m/s.

The maximum velocity of flow in a rising mainshould be 2,5 m/s.

Minimum diameter:The minimum diameter of a rising main should be100 mm, except where a macerator system is used,in which case the diameter can be reduced to 75mm.

Gradient:Wherever practicable, rising mains should begraded so as to avoid the use of air and scourvalves.

Stilling chambers:Stilling chambers should be provided at the headsof all rising mains, and should be so designed thatthe liquid level always remains above the soffitlevel of the rising main where it enters thechamber. Stilling chambers should preferably beventilated.

Sumps for pump stationsEmergency storage:A minimum emergency storage capacityrepresenting a capacity equivalent to four hoursflow at the average flow rate should be provided,over and above the capacity available in the sumpat normal top-water level (i.e. the level at whichthe duty pump cuts in). This provision applies onlyto pump stations serving not more than 250dwelling units. For pump stations serving largernumbers of dwelling units, the sump capacity

should be subject to special consideration inconsultation with the local authority concerned.Emergency storage may be provided inside oroutside the pump station.

Sizing:In all pump stations, sumps should be sized andpump operating controls placed so as to restrictpump starts to a maximum of six per hour.

Flooding:Care should be taken in the design of pumpstations in order to avoid flooding of the dry welland/or electrical installations by stormwater orinfiltration.

Screens:Adequate protection, where necessary, in the formof screens or metal baskets, should be provided atthe inlets to pump stations for the protection ofthe pumping equipment.

PumpsStandby:All pump stations should be provided with at leastone standby pump of a capacity at least equal tothe capacity of the largest duty pump. The standbypump should come into operation automatically ifa duty pump or its driving motor fails due tomechanical failure.

Safety precautionsSafety precautions in accordance with the relevantlegislation should be incorporated into the designof all pump stations and, in particular:

• all sumps and dry wells should be adequately ventilated;

• handrails should be provided to all landings and staircases and to the sides of open sumps and dry wells;

• skid-proof surfaces should be provided to all floors and steps; and

• the layout of the pumps, pipework and equipment should allow easy access to individual items of equipment without obstruction by pipework.

Physical design

Minimum depth and cover

Except under circumstances discussed in the followingparagraph, the following are the recommendedminimum values of cover to the outside of the pipebarrel for sewers other than connecting sewers:

100 1 : 120150 1 : 200200 1 : 300225 1 : 350250 1 : 400300 1 : 500

Table C.2: Minimum sewer gradients

SEWER DIAMETER (MM) MINIMUM GRADIENTS

• in servitudes 600 mm• in sidewalks 1,4 m below final kerb level• in road carriageways 1,4 m below final

constructed road level

Lesser depths of cover may be permitted, subject tointegrated design of all services including trunkservices allowed for in development plans, providedthat, where the depth of cover in roads or sidewalks isless than 600 mm, or in servitudes less than 300 mm,the pipe should be protected from damage by:

• The placement of cast-in-situ or precast concreteslab(s) over the pipe, isolated from the pipe crownby a soil cushion of 100 mm minimum thickness.The protecting slab(s) should be wide enough anddesigned so as to prevent excessive superimposedloads being transferred directly to the pipes (seeFigure C.2); or

• The use of structurally stronger pipes able towithstand superimposed loads at the depthconcerned; or

• The placement of additional earth filling over theexisting ground level in isolated cases where this ispossible.

Except in very special circumstances, the encasementof pipes in concrete is not recommended. Whereencasement is unavoidable, it should be madediscontinuous at pipe joints, so as to maintain jointflexibility (see Figure LD-6 of SABS 1200 LD).

Trenching, bedding and backfilling

The trenching, bedding and backfilling for all sewersshould be in accordance with the requirements ofSABS 1200 LB and the supporting Specifications.

Under normal ground conditions, structural designconsiderations for pipe strength and increasedbedding factors do not come into play for sewers up to

225 mm diameter. Standard rigid pipes are laid oneither Class D or Class C beds, as depicted in DrawingLB-1 of SABS 1200 LB, while flexible pipes (plastic orpitch fibre) are laid according to Drawing LB-2 of SABS1200 LB.

Structural design of the pipe/bedding should bechecked where trenches are:

• located under roads;

• deeper than 3 metres; and

• other than those classified as “narrow” (i.e. whereoverall trench width is greater than nominal pipediameter d + 450 mm for pipes up to 300 mmdiameter).

Where grades steeper than 1 in 10 are required, 15MPa concrete anchor blocks should be provided thatare at least 300 mm wide and embedded into the sidesand bottom of the trench for at least 150 mm, asshown on Drawing LD-1 of SABS 1200 LD.

Curved alignment

A straight alignment between manholes shouldnormally be used, but curvilinear, horizontal or verticalalignment may be used where the economiccircumstances warrant it, subject to the followinglimitations:

• the minimum radius of curvature is 30 m;

• curvilinear alignment may be used only whenapproved flexible joints or pipes are used;

• in the construction of a steep drop, bend fittingsmay be used at the top and bottom of the steepshort length of pipe, thus providing a curvedalignment between the flat and steep gradients.

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Figure C.2: Protection of pipes at reduced depths of cover (e.g. Class B bedding)

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Siting

Sewers should be sited so that they provide the mosteconomical design, taking the topography intoaccount (i.e. in road reserves, servitudes, parks, openspaces, etc). When the sewer is to be located in atrench by itself, the minimum clear width to beallocated to it in the road reserve should be 1,5 m.

Manholes

Location and spacingManholes should be placed at all junctions and,except in the case of curved alignment and at thetop of shallow drops, at all changes of grade and/ordirection.

The maximum distance between manholes oneither straight or curved alignment should be:

• 150 m where the local authority concerned haspower rodding machines and other equipmentcapable of cleaning the longer lengths betweenmanholes;

• 100 m where the local authority concerned hasonly hand-operated rodding equipment.

Note:The economics of acquiring power cleaningequipment in order to permit a greater manholespacing should be demonstrated to localauthorities.

Where manholes have to be constructed within anyarea that would be inundated by a flood of 50-years recurrence interval, they should, whereverpracticable, be raised so that the covers are abovethis flood level.

SizesThe minimum internal dimensions of manholechambers and shafts should be as shown in TableC.3. The minimum height from the soffit of themain through pipe to the soffit of the manholechamber roof slab, before any reduction in size ispermitted, should be 2 m.

BenchingAn area of benching should be provided in eachmanhole so that a man can stand easily,comfortably, and without danger to himself, onsuch benching while working in the manhole.

Manhole benching should have a grade not steeperthan 1 in 5 nor flatter than 1 in 25, and should bebattered back equally from each side of themanhole channels such that the opening at thelevel of the pipe soffits has a width of 1,2 d, whered is the nominal pipe diameter.

DesignAll manholes, including the connection betweenmanhole and sewer, should be designed inaccordance with the requirements of SABS 1200 LDand, where manholes are of cast-in-situ concrete,chambers, slabs and shafts should be structurallydesigned to have a strength equivalent to a brickor precast concrete manhole.

For manholes located in road reserves, spacer ringsor a few courses of brickwork should be allowedfor between the manhole roof slab and the coverframe, in order to facilitate minor adjustments inthe level of the manhole cover. Adjustablemanhole frames may also be used.

Steep dropsSteep drops should be avoided wherever possible,but where this is unavoidable (e.g. to connect twosewers at different levels), use should be made of asteep, short length of pipe connected to the highersewer by one or more 1/16 bends and to a manholeon the lower sewer also by one or more 1/16 bends,as shown in Figure C.3.

Sewer connections

Size and sitingEach erf, excepting those listed below, should beprovided with a 100 mm (minimum) diameterconnecting sewer, terminating with a suitablewatertight stopper on the boundary of the erf orthe boundary of the sewer servitude, whichever isapplicable. The connecting sewer should be locateddeep enough to drain the full area of the erfportion on which building construction ispermitted.

Figure C3: Steep drops in sewers

SHAPE CHAMBER SHAFT

Table C.3: Minimum internal dimensions of manholechambers and shafts

Circular 1 000 mm 750 mmRectangular 910 mm 610 mm

Exceptions• In special residential areas, where an erf

extends for a distance of more than 50 m fromthe boundary to which the connecting sewer islaid, provision need only be made to drain thearea of the erf within 50 m of this boundary.

• School sites should be given specialconsideration with regard to the position,diameter and depth of the connection(s)provided.

• Where detailed development proposals aresubmitted for subdivided erven as groupschemes, one connecting sewer may beprovided to serve such group of erven.

Note:Where erven have to be connected to a sewer onthe opposite side of a street, consideration shouldbe given to the economics of providing 100 mmdiameter sewer branches across the road to servethe connecting sewers from two or more erven.

The sewer connection should be provided at thelowest suitable point on the erf. On streetboundaries the connection should be locatedeither at a distance of 1,15 m or at a distance of 5 m or more from a common boundary with anadjacent erf, unless a local authority has already anaccepted standard location.

Depth and coverExcept under the circumstances described in thefollowing paragraph, recommended minimumvalues of cover to the outside of the pipe barrel forconnecting sewers are:

• in servitudes 600 mm• in road reserves 1 000 mm

Where lesser depths of cover are permitted, thisshould be subject to the same conditions discussedpreviously in this appendix, and the sameprotection should be provided.

When designing the invert depth of the mainsewer in order to ensure that all the erven candrain to it, the fall required from ground level atthe head of the house drain to the invert of themain sewer at the point where the connectingsewer joins the main sewer should be taken as thesum of the following components:

• 450 mm to allow for a minimum cover, at thehead of the house drain, of 300 mm, plus 150 mm for the diameter and thickness of thehouse drain;

• the fall required to accommodate the length of the house drain and the connecting sewer,

assuming a minimum grade of 1 in 60 and taking into account the configuration of the erf and the probable route and location of the house drains; and

• the diameter of the main sewer (see Figure LD-7 of SABS 1200LD).

Note:In the case of very flat terrain, and where the housedrains may be laid as an integral part of theengineering services, flatter minimum grades than1 in 60 for the house drains may be considered. Thisrelaxation could also be applied to isolated ervendifficult to connect, or the ground in such ervencould be filled to provide minimum cover to thedrains.

Junction with main sewerA plain 45º junction should be used at the pointwhere the connecting sewer joins the main sewer.Saddles should not be permitted during initialconstruction.

Type detailsDetails of the connecting sewer should be inaccordance with one of the types shown in FiguresLD-7 and LD-8 of SABS 1200LD.

Invert levels

The invert levels indicated at a manhole locationshould be the levels projected at the theoretical centreof the manhole by the invert grade lines of the pipesentering and leaving such manhole. In cases wherebranch lines with smaller diameters enter a manhole,the soffit levels of these branch lines should matchthose of the main branch line. However, in areaswhere pipes are laid to minimum grades, this practicemay need to be relaxed.

The slope of the manhole channel should be asrequired to join the invert levels of the pipes enteringand leaving the manhole, without allowing anyadditional fall through the manhole chamber.

MATERIALS

Pipes and joints

Pipes suitable for the conveyance of sewage, under theparticular working and installation conditions towhich they will be subjected, should be in accordancewith Sections 3.1 and 3.2 of SABS 1200 LD.

All joints for rigid pipes should be of a flexible type,and rigid joints should only be used where the pipesthemselves are flexible.

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Manholes

All materials used for manholes should be inaccordance with Section 3.5 of SABS 1200 LD.

Pumping installations

In general, all materials should be durable and suitablefor use under the conditions of varying degrees ofcorrosion to which they will be exposed.

Pipework

The relevant requirements for materials given in SABS1200 L and 1200 LK should apply if a rising main formspart of the sewerage system.

Concrete

Structural reinforced concrete and plain concretebelow ground level and/or in contact with sewage

should be designed and constructed in accordancewith SABS 1200 G or 1200 GA, whichever is applicable.

Structural steelwork

All exposed steelwork should be adequately protectedagainst corrosion with a suitable approved paintsystem, and should otherwise be designed andconstructed in accordance with SABS 1200 H or 1200HA, whichever is applicable.

Electrical installations

All electrical installations should comply with theFactories Act and with the relevant local authorityelectricity supply by-laws/regulations.

Other materials

Other materials used should comply with therequirements of SABS 1200 LD where relevant.

GLOSSARY

BOD5: The oxygen used for bacterial oxidation oforganic pollutants or ammonia, determined understandard conditions of incubation at 20º C over 5 days.

Sullage: Wastewater emanating from baths, kitchensinks, laundries and showers (toilet water is excluded).

Thermophilic bacteria: A kind of bacteria functioningbest at a certain temperature range.

Thixotropic: Refers to the property of becomingtemporarily liquid when disturbed and returning to itsoriginal state when stationary.

BIBLIOGRAPHY AND RECOMMENDEDREADING

Austin, L M and Van Vuuren, S J (2001) Sanitation,public health and the environment: Looking beyondcurrent technologies. Journal of the South AfricanInstitution of Civil Engineering, 43 (1).

Austin, A and Duncker, L (2002). Urine-diversionecological sanitation systems in South Africa. BoutekReport no BOU/E0201, CSIR.

Bakalian, A, Wright, A, Otis, R and Deazevedo, N J(1994). Simplified sewerage: Design guideline. UNDPWorld Bank Water & Sanitation Programme.

Bester, J W and Austin, L M (1997). Building VIPs:Guidelines for the design and construction of domesticVentilated Improved Pit Toilets. Division of BuildingTechnology, CSIR. Issued by the Department of WaterAffairs & Forestry.

CSIR, Division of Building Technology (1987). Septictank systems. Report no BOU/R9603.

CSIR, Division of Building Technology (1997). Septictank effluent drainage systems. Report no BOU/R9706.

DWAF (1997). A protocol to manage the potential ofgroundwater contamination from on-site sanitation.Edition 1. Directorate Geohydrology, Department ofWater Affairs & Forestry.

DWAF (2001). White Paper on Basic HouseholdSanitation. Department of Water Affairs & Forestry,September.

DWAF (2002). Sanitation for a healthy nation:Summary of the White Paper on Basic HouseholdSanitation 2001. Department of Water Affairs &Forestry, September.

Kolsky, P (1997). Engineers and urban malaria: Part ofthe solution, or part of the problem? Waterlines. Vol16, October.

Lines, J (2002). How not to grow mosquitoes in Africantowns. Waterlines. Vol 20, October.

Mvula Trust and CSIR Building and ConstructionTechnology (2001). Study report on management offaecal waste from on-site sanitation systems in SouthAfrica. Report No BOU/C356, November. Departmentof Water Affairs & Forestry.

Palmer Development Group (1999). The applicabilityof shallow sewer systems to dense settlements in SouthAfrica. WRC Report TT113/99.

Parkinson, J (2002). Urban drainage in developingcountries: Challenges and opportunities. Waterlines.Vol 20, April.

SABS 0365-1, nd. Code of Practice: On-site sanitationsystems. Part 1: Ventilated improved pit toilets. SouthAfrican Bureau of Standards Unpublished Edition.

Wright, A (1999). Groundwater contamination as aresult of developing urban settlements. WRC Report514/1/99.

WRC (1997). Permissable utilisation and disposal ofsewage sludge. Water Research Commission, Pretoria.

Xu, Y and Braune, E (1995). A guideline forgroundwater protection for the community watersupply and sanitation programme. Department ofWater Affairs & Forestry, Pretoria.

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Sanitation - Amazon Web Servicespmg-assets.s3-website-eu-west-1.amazonaws.com/131008...2 GUIDELINES FOR HUMAN SETTLEMENT PLANNING AND DESIGN Chapter 10 Sanitation Household Sanitation,