Table Of Content

A project of Volunteers in Asia Small Communitv Wat_;a_r Sur)@tu Technical Paper No. .!3 Edited by: E.H. Hofkes Published by; WHO International Reference Centre for Community Water Supply P.O. Box 5500 2280 HM Rijswijk The Hague The Netherlands Paper copies are free to serious groups. Available from: WHO International Reference Centre for Community Water Supply P.O. Box 5500 2280 HM Rijswijk The Hague The Netherlands Reproduced by permission of the WHO International Reference Centre for Community Water Supply. Reproduction of this microfiche document in any form is subject to the same restrictions as those of the original document. Small Community Water Suppiies 18. Technical Paper Series International Reference Centre for Cummunity Water Supply and Sanitation Small Community Water Supplies Technology of Small Water Supply Systems in Develaping Countries Prep4 with contributions from and under the joint supervision of L. Huisman Profmsor of Sanitary Engineering Delft University of Technology Netherlands J.M. De Azevedo Netto Pro~essqr of Sanitary Engineering IJrmnty of Sao Paul0 B.B. Sundaresan Director, National Environmental Engineering 5k;;awch Institute J.N. Lanoix Formerly: Division of E+ronmental Health W$;~3JIealth Orgamzatlon Compiled and edited by: E.H. Hofkes International Reference Centre for Community Water Supply and Sanitation The Hague Technical paper 18 august 1981 1 abstract Small Community Water Supplies, August '1981 A handbook/source document on technology of small community water supply systems. Subjects: planning and management of small water systems, drinking water quantity and quality, water sources, rainwater harvesting, springwater tapping, groundwater withdrawal, surface water intake, artificial recharge, pumping, water treatment (g;;~;~~~ioaeration of water, coagulation and flocculation, , slow sand filtration, rapid filtration, disinfection of water, water transmission, and water distribution. Selected references added to each chapter. Annexes provide information on: sanitary survey, well drilling methods, experimental studies for water treatment plant design, chemicals used in water treatment, and conversion of measurement units. 378 pages; 244 figures; 24 tables (c) Copyright 1981 International Reference Centre for Community Water Supply and Sanitation P.O. Box 5500, 2280 RM Rijswijk (The Hague) The Netherlands Permission to reproduce material from this handbook may be granted on request. This handbook is issued on the responsibility of the International Reference Centre for Community Water Supply and Sanitation. It does not necessarily reflect the views or policies of the World Health Organization. contents PREFACE 1. 2. 3. 4. 5. 6. 7. a. INTRODUCTION t-2'- 1:3: Water and Human Health Water Supply and Development Small Community Water Supplies in Developing Countries PLANNING AND MANAGEMENT 2.1. Planning 2.2. Management and Supervision 2.3. Manpower and Training 2.4. community Involvement 2.5. Maintenance 2.6. Emergency Operation WATER QUANTITY AND QUALITY 3.1. Water Use and Consump::ion 3.2. Water Quality WATER SOURCES 4.1. Water Occurrence and Hydrology 4.2. Quality of Water SOUrCeS 4.3. Water Source Selection RAINWATER HARVESTING 5.1. Rainwater as a Source of Water Supply 5 -2. Roof Catchments 5.3. Ground Catchments 5.4. Storage 5.5. Water Quality Preservation SPRINGWATER TAPPING z: Introduction Basic Considerations 6.3. Tapping Gravity Springs 6.4. Tapping Artesian Springs GROUNDWATER WITHDRAWAL 7.1. Introduction 7.2. Groundwater Occurrence and Prospecting E Methods of Gromdwater Withdrawal Infiltration Galleries 7.5. Dug Wells 7.6. Tube Wells SURFACE WATER INTAKE iz: River Water Intake Lake Water Intake 8.3. Typical Intake Constructions 8.4. Small Dams and Village Ponds 0.5. Screens 3 Paqe 9 13 14 19 24 26 28 32 35 36 42 51 53 55 59 60 63 65 70 75 79 a0 a4 91 92 100 106 109 121 137 140 142 144 145 9. ARTIFICIAL RECHARGE 9.1. Introduction 9.2 Bank Infiltration 9.3 Water Spreading 9.4 SandDams 10. PUMPING 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9 10.10 Introduction Power Sources for Pumping Types of Pumps Reciprocatl:rlg Pumps Rotary (positive displacement) Pumps Axial-Flow Pumps Centrifugal Pumps Pump Drive Arrangements Air-Lift Pumps Hydraulic Ram 11. WATER TREATMENT 11.1 Introduction 11.2 Groundwater Quality and Treatment 11.3 Surface Water Quality and Treatment 12. AEFATION 12.1 Introduction 12.2 Waterfall Aerators 12.3 Bubble Aerators 13. COAGULATICN AND FLOCCULATION 13.1 Introduction 13.2 Coagulants 13.3 Rapid Mixing 13.4 Flocculation 13.5 Hydraulic Flocculators 14. SEDIMENTATION 14.1 Introduction 14.2 Settling Tank Design 14.3 Construction 14.4 Plate and Tube Settlers 15. SLOW SAND FILTRATION 15.1 Introduction 15.2 Theory of Slow Sand Filtration 15.3 Principles of Operation 15.4 Design Considerations 15.5 Construction 15.6 Cleaning 149 150 155 159 163 163 167 170 175 177 178 175 la3 la5 191 194 195 201 202 208 213 214 217 220 222 229 230 233 237 245 247 250 253 255 261 16. 17. 18. 19 1. 2. 3. 4. 5. RAPID FILTRATION 16.1 Introduction 269 16.2 Theoretical Aspects 274 16.3 Rapid Filter Operation and Control 275 16.4 Design Considerations 281 16.5 construction 290 16.6 Villaue-Scale Rapid Filtration 293 16.7 Roughing I'iltration 295 DISINFECTION 17.1 Introduction 299 17.2 Physical Disinfection 299 17.3 Chemical Disinfectants 300 17.4 chlorination 301 17.5 Chlorination Technology for Rural Water su?Bply 304 17.6 Disinfection using Chlorine Gas 309 17.7 Disinfection of New Tanks, Pipes and Wells 311 17.8 Disinfection of Water Supply in Emergency situations 312 WATER TRANSMISSION 18.1 Introduction 18.2 Types of Water Conduits 18.3 Design Considerations 10.4 Hydraulic Design la.5 Water Transmission by Pumping 18.6 Pipe Materials 317 317 320 322 324 332 WATER DISTRIBUTION 19.1 '-Introduction 339 19.2 Types of Distribution Systems 339 19.3 Design Considerations 347 19.4 Distribution System Design 356 19.5 Pipe Materials 359 ANNEXES Sanitary Survey Well Drilling Experimental Studies for Water Treatment Plant Design Chemicals Used In Water Treatment Measurement Units Conversion 5 preface The United Nations has designated the period 1981 - 1990 the Inter- national Drinking Water Supply and Sanitation Decade. Many hope and trust that there will be vastly increased efforts to provide adequate water supply and sanitation services to all those needing them. The needs are enormous. Hundreds of millions of people living in developing countries lack reasonable access to an adequate supply of safe drinking water. The problems are particularly acute for count- less small communities in the rural areas, as well as for urban fringe areas. Their water supply situation often is grossly inade- quate. In providing water supply systems to small communities, factors such as organization, administration, community'involvement aud finance are frequently the major constraints, rather than technical considerations. However, the selection of suitable technology remains important since other problems are compounded when techniques, methods and equipment are used that are not compatible with the conditions and situations of small communities. It is a misconception to regard small community water supply systems as 'scaled down' versions of urban installations requiring less engineering skill or ingenuity. The exact opposite may be the case. Simplicity and smallness should not be regarded as backward or second-rate, but rather as appropriate for the purpose. Technologies must be selected that can be integrated with the approach of community involvement which is so essential in small-scale schemes. ?lisapplication of technologies is likely when the designer does not clearly understand the basic assumptions implicit in them. This usually will result in costly overdesigns and unrealistic manpower, operation and maintenance requirements. This handbook has been designed to provide a broad introduction into the technology of small Community water supplies. It provides information and guidance that should be most readily used by those having some technical background in civil engineering, public health or irrigation, but with no formal training or experience in water supply. It should serve engineers and public health inspectors whq are called upon to assume responsibility for the design and/or maintenance of small water supply systems. This group also includes provincial and town engineers who have responsibility for water supply and sanitation, amongst many other tasks. The book, therefore, has not been written as a textbook for engineering students nor as a design manual addressed to technicians. Some theoretical explanations have been included but such material has been kept. to a minimum. For in-depth information reference is made to monographs and textbooks. 7 acknowledgement This handbook has been compiled and furt!ler developed from the contributions of many. The main contributions have been made by a group of authors who each supplied selected chapters, and who collectively supervised the preparation of the handbook. These authors are Prof. i. Huisman (Netherlands), Prof. J.M. de Azevedo Netto (Brazil), Dr. B.E. Sunda- resan (India) and Dr. J.N. Lanoix (WHO, Geneva). Further, we are indebted to Messrs. L.G. Hutton and W. Morfat (&,%DC Gro:ap, Loughborough University of Technology, England) for the material they supplied on groundwater occurrence and prospectin:,?, and to Mr. P.K. Cruse (George Stow & Co. Ltd., Water Well Engineers, Henley-on-Thames, England) who prepared the section on well drilling methods. Mr. R. Trietsch (DHV Consulting Engineers, Amersfoort, Netherlands) assisted by preparing from earlier assembled materials a preliminary draft for the chapters on water transmission and distribution. Dr. B.C.J. Zoeteman (National Institute for Water Supply * Netherlands) advised on the presentation of water quality and health aspects, and the guidelines for drinking water quality. Grateful mention is made of those who helped by reviewing the draft manuscript; their comments were invaluable as a basis for corrections and improvements. We feel the following persons should be specially mentioned: Dr. G. Bachmann (WHO, Geneva), Mr. Edwin Lee (WHO-WPRO, Manila), Mr. D.V. Subrahmanyam (WHO-SEARO, New Delhi), Mr. David Donaldson (PAHO, Washington), Mr. F.E. McJunkin (US AID, Washington), and Mr. T.K. Tjiook (IRC, The Hague). In compiling and editing the various contributions, and in processing the numerous comments made to the subsequent drafts, Mr. E .H. Hofkes (IRC, The Hague) found himself charged with the task of integrating, re-organising, revising and, in several instances, completely rewriting sections and even complete chapters. In the editing of the material, Mr. G. Bedard provided important assistance. Ms. Hannie Wolsink did an outstanding job of extensive text processing and administrative coordination without which the preparation of the handbook would not have been possible. The present document is likely to require revision at a future stage. It is intended to undertake that work when appropriate. Comments and suggestions from readers for changes, corrections or additions will be most welcome. These will be gratefully used in the future revision of the handbook, and will be duly acknowledged therein. Communica,tions should be directed to: IRC, P.O. Box 5500, 2280 HM Rijswijk (The Hague), Netherlands. 8 introduction introduction 1.1. Water supply and human health Water is essential to man, animals and plants and without water life on earth would not exist. From the very beginning of human civilization, people have settled close to water sources, along rivers, besides lakes or near natural springs. Indeed where people live, some water is normally available for drinking, domestic use, and possibly for watering animals. This does not imply, however, that the available source of water is convenient and of sufficient capacity, nor that the water is safe and wholesome. On the con- trary , in many countries people live in areas where water is scarce. Often it has to be carried over long distances, particularly during dry periods. Scarcity of water may also lead people to use sources that are contaminated by human or animal faeces, and are thus dangerous to human health. A few litres of wa?er each day are sufficient for a person's basic drinking and food preparation requirements, depending on climate and lifestyle. Much larger quantities dre necessary when water is used for other purposes such as personal hygiene, cleans- ing of cooking utensils, laundry and house cleaning. Safe, adequate and accessible supplies of water, combined with proper sanitation, are surely basic needs a;ld easential components of primary health care. They can help reduce many of the diseases gffecting underprivileged populations, especially those who live in rural and urban fringe areas. Safe drinking water is important in the control of many diseases. This is particularly well-established for diseases such as diarrhoea, cholera, typhoid and paratyphoid fever, infectious hepatitis, amoebic and bacillary dysentery. It has been estimated that as many as 80 percent of all diseases in the world are associated with unsafe water. This association can take a number of different forms, and diseases may be grouped accordingly (Table 1.1). 9 introduction Table 1.1. Diseases related to deficiencies in water supply and/or sanitation GROUP DISEASES * Diseases transmitted by water Cholera (water-borne diseases) Typhoid Water acts only as a passive vehicle Bacillary dysentery for the infecting agent. Infectious hepatitis All of these diseases depend also on Leptospirosis poor sanitation. Giardiasis Cazr_co enteritis . Diseases due to lack of water Scabies (water-washed diseases) Skin sepsis and ulcers Lack of adequate quantity of water and Yaw.6 poor personal hygiene crcate conditions Leprosy favourable for their spread. The intestinal Lice and typhus infections in this group also depend on Trachwa lack of proper human waste disposal. Conjunctivitis Bacillary dysentery Amoebic dysentery Salmonellosis Enterovirus diarrhoeas Paratyphoid fever Ascariasis Trihcuriasis Whipworm (Enterobius) Hookworm (Ankylostoma) . Diseases caused by infecting agents Schistosomiasis (urinary L rectal) spreaded by contact with or ingestion - Dracunculosis (guinea worm) >f water. Bilharziosis (Uaterbased diseases) Philariosis An essential part of the life cycle of Oncholersosis the infecting agent takes place in an Treadworm aquatic animal. Some are also affected by waste disposal. . Diseases transmitted by insects which live Yellow fever mosquito close to vater Dengue + dengue (water-related vectors) hemorrhagic fever mosquito Infections are spread by mosquitoes, flies, West-Nile and insects that breed in water or bite near it. Rift Valley’fever mosquito These are especially active and agBrcssive Arbovirus near stagnant open water. Unaffected by disposal. Encephalitides mosquito Eancroftian Filariaeie mosquito !4alaria (diarrboea)* Onchocerciasis* mosquito Simulium fly Sleeping sickness* Tsetse fly . Diseases caused by infecting agents. Mostly Clonorchiasis Fish contracted by eating uncooked fish and Diphyllobcthriasis Fish other food. Fasciolopsiasis Edible plant (Faecal-disposal diseases) Paragonimiasis Crayfish * Unusual for domestic water to affect these much Source: Saunders, J.; Warford, J. Village Uacer Supply: Economics and policy in the Developing World. Published for the Uorld Bank by the Johns Hopkins University Ress, Baltimore, 1976 10 Water-borne diseases are those carried by water that is contaminated with infecting agents from human or animal origin. When the water is drunk the infecting agents will be ingested and may cause disease. Control of such diseases calls for improving the quality of the water. Diseases due to lack of water tend to be a serious health hazard. When people use very little water, either because there is little availabLe or because it is too far away to be carried home in quantity, it may be impossible to maintain a reasonable personal hygiene. There may be simply too little water for wz:hing oneself properly, or for cleaning food utensils and clothes. Skin or eye infections are thus allowed to develop, and intestinal infections can much more easily spread from one person to another. Clearly, the prevention of these water-washed diseases depends on the availability of, and access to adequate supplies of water rather than its quality. introduction* Figure 1.1. WHO Photo by A.S. Kochar Water carried home ouer a long distance will be used very sparingly I 11 introduction Water-based diseases do not spread directly from person to person. They are caused by infecting agents that for an essential part of their life cycle develop in specific ;,later animals, chiefly snails and crustaceans. Over a period of days or wreks# the parasite larvae or eggs mature in these intermediate hosts, and then are shed into the water. The matured larvae or worms are infective to people drinking the water or having contact with it. In tropical countries biting insects are common. Most of these, notably the mosquitoes, breed in pools or other open water, and sometimes even in household water containers. Tsetse flies are also active near the water. Such water-related vectors carrying patho- gens can transmit disease. Health hazards also emanate from infection sources other than water. Diseases may spread through direct contact (e.g. soiled hands) or through food, particularly fish, vegetables and fruit eaten raw. Besides safe water supply, the necessary measures to control disease therefore should include personal hygiene and inspection of food storage and market places. Very important is the provision of adequate sanitation, including sanitary facilities for human waste disposal. All the water-borne and many of the water- based diseases depend for their dispersion on infecting agents from human faeces getting into drinking water or into food. The diseases' chain of transmission may be broken as effectively by sanitary disposal of faeces as by the provision of safe and adequate water supplies. There are certain agents, such as hookworm, where sanitation is much more important than water supply in the prevention of disease because transmission is from the faeces to the soil, and then by direct contact and penetration through the human skin. Improvements in the quality of community water supplies will basically only affect the water-borne diseases such as bacillary typhoid, dysentery, cholera, and possibly schistosomiasis. Many of the diarrhoeal disease probably are more due to a lack of adequate quantities of water. Certainly, skin and eye infections are in this group of water-related diseases. The provision of a wash tap, shower or some similar washing facility frequently has proven to improve the user's health situation. There is, however, no con- 12 introduction vincing evidence yet that once each family has a tap or shower, further improvement of the water supply will appreciably affect health. When water supplies are developed without complementary improvements in personal hygiene, food handling and preparation, and in general health care, they are unlikely to produce the expected health benefits. 1.2. Water supply and socio-economic development In the industrialized countries, community water supply systems were first provided for the larger cities. Smaller cities and towns followed. The water supply systems were built by the state, district or town authorities, or by private companies. In rural areas, community water supplies were installed much later since public health considerations were less pressing than in urban areas. In the first half of the 20th century many national governments started giving financial and technical assistance to small communities and the extension of water supplies to the rural population was then greatly accelerated. For significant socio-economic development of a community, an adequate supply of safe water is a prerequisite. Factors such as time and energy saving in the collection of drinking water, and a sub- stantial reduction in the incidence of disease can contribute to development, provided the time and energy gained are utilized economically. The new water supply could help activities such as fruit and vegetable processing or fish conservation. Whether potential productivity benefits are realized or not depends on the specific circumstances. One important factor is how the time and energy saved in carrying water might otherwise be used. In some villages the ill health of the labour force seriously affects agricultural development, whereas in others there is underemployment and benefits may not be realized unless the water supply project forms part of an integrated rural development providing increased employment. A new water supply may open opportunities for handicraft manufacture, livestock keeping or vegetable growing. Thus, when productive work is stimulated and personal hygiene, health care and food preparation are improved, side by side, a community water supply can be expected to have a positive socio-economic development impact. 13