Manual For Rural Water Supply
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A project of Voluntesrs in Asia by: Swies Ca?ter for Appropriate Published by: Swiss Center for Appropriate Varnbuelstraese 14 CH-9000 St. Gall Switzerland Rapes clot A 9, whl , I include Technology 10 diagrams, Available from: Swiss Center for Appropriate Varnbuelstrasse 14 CHL?3000St. Gall Switzerland Reproduced by permission Appropriate Technology. Technology are $20. Technology of the Swiss Center for Reproduction of thipr microfiche document in any form is aabject to the Bame restrictions as those of the original document. WITHMANYDETAILED CONSTRUCTIONAL SCALE -DRAWINGS Publication No. 8 St.Gall 1980 Varnbgelstr 14 CH-9000 St .Gallen Tel. 071 I 23 34 81 MAT wsiwisohe Konllllttslelle tPr AngepamteT@hnik ull J~rtltut fgr Lsteinamsrikafaraahung wd Entwldrlunguuwnmen~wJM&zr HrMWwle WWlen SKAT SWISSCenter for Appropriate Technology at the lnrtltute Iw Lstln-American Research and for Development Cooperstlon, St.Gall University SKAT Centre Suisse pour la Technologle ApproprMe a I’lnstltut Latino-Ambricain et de Coop4ration au DBveloppement, Unlversitb de St-Gall SKAT Centro Suizo para TAcnologla Apropiada en el lnstituto Latinoamericano y de Cooperacih Tknica, Universidad de Sankt-Gallen MANUAL FOR WATER SUPP WITHMANYDETAILED CONSTRUCTIONAL SCALE .-DRAWINGS Publication No. 8 St.Gail 1980 Edited and compiled by: Helvetas, Swiss Association for Technical Assistance, Zurich, Switzerland and Yaounde, Cameroon Cover photo: HELVETAS Published SKAT, Swiss Center for Appropriate Technology at the Institute for Latin-American Research and for Development Cooperation, St. Gall University by: Comments, enquiries: All questions and commeri'ts concerning this publication and its contents are welcome at SKAT. Please use the postcard-questionnaire enclosed. Copyright: Material of this publication may be freely quoted, translated or otherwise used. Acknowledgement is requested. Price: SFr. 34.-- Preface by the Editor Helvetas (SATA! and the Community Development Department of the United Republic of Cameroon (CD) have been closely working together since 1964. The purpose of this cooperation is to support the effort of the rural population to build up a local infrastructure by giving technical assistance. All these community development activities are self-help projects, initiated by the local people. Priority is given to the most deprived areas. Water evidently plays a very important role in the development of rural areas. A supply of clean drinking water not only reduces the numerous diseases caused step towards and transmitted by polluted water, but is very often the first other development scopes like health, nutrition, sanitary programmes, etc. and socio-economical When a water supply is being planned, all technical As one of the consequences simple aspects have to be considered carefully. techniques, simple designs, and a simple system are used. In this context greatest attention has to be paid to the fundamental problem of maintenance, of a project. that is even before starting with the construction Assisting the rural areas and their population in im+:oving the quality and accessibility of drinking water is one of the major concerns of the Community Development Department in Cameroon. During all these years of collaboration the technical staff of CD/Helvetas has gained valuable experience in the planning and execution of rural water supply and water point projects. Intending engineers and field staff who arc to provide Community Development officials, planning and implementing water schemes in rural areas with useful information, a Manual for Rural Water Supply was first issued in 1975 (SATA-Helvetas Buea, Cameroon). Since then, improved and more adapted techniques and material have been developed which lead to this revised second edition of the Manual for Rural Water Supply. The technical data and drawings needed for the Manual have been compiled by the CD/Helvetas field engineers in Cameroon and partly completed by referring to various international publications. We hope that this Manual will serve its purpose by contributing improvement of the water conditions in developing countries. Our sincere thanks go to all of this Manual. persons who have been involved to a general in the preparation May 1980 HELVETAS Swiss Associa'tion for Technical Assistance St. Moritzstrasse 15 HELVETAS Swiss Association for Technical Assistance P.O. Box 279 8042 Yaounde / U.R. Cameroon Zurich / Switzerland (SATA) I Foreword by the It is very fitting an organization construction in and compile and a comprehensive Publisher at the beginning of the UN decade dedicated to water that that has got a vast experience in rural water supply developing countries should decide to make a special effort edit material of field engineers to make tv,e publication of practical manual on this subject possible. The result of this effort is the manual presented here. It is based on actual field activities during the last fifteen years in the United Republic of Despite its being based on experience in one specific Cameroon (West Africa). country the material is certainly very useful in the context of other countries also and provides a guide line on how to identify, plan, organize and execute drinking water projects. safety standards for drinking water, Manyfold aspects such as hydrology, and maintenance, spring catchments, design of water schemes, construction systems and water lifting are barrage and river intake systems, distribution treated. The material is suitable specially for ::ngineers and construction supervisors but serves also to give a comprehensive overview of all aspects of rural water supply to non-technical people. The technology that has evolved and that is documented in this manual is first class craftmanship using traditional western techniques and materials. Emphasis is on solid, longlasting structures of simple design and on the use of labour intensive methods and local materials wherever possible. The goal is stable quality of drinking water to achieve systems of trouble free operation, and minimal,simple maintenance and management requirements. The field of well digging is covered very briefly only, and the exploitation of alternative energies for water lifting is referred to only in connection with alternative technologies such as alternative the use of hydraulic rams. Specific cements, the use of bamboo and other local material for reinforcement and traditional, local construction skills are net included since the manual is based on action oriented projects rather than research. Although the publication is based on actual field experience and presents practical examples, it is not presumed to be either exhaustive or final. It is certain that local adaption and modifications will always be necessary. With this publication, SKAT intends to create an opportunity for field testing and feedback of information. The reader therefore i., requested to give his comments and suggestions for changes, corrections and additions which he considers necessary or useful. Such contributions will be gratefully accepted by SKAT and will be used in the future revision of the manual. It would not have been possible for SKAT to publish the manual without the help of Helvetas who not only compiled and edited all the material but also sponsored the publication. It is therefore only appropriate that we express our thanks to Helvetas and to all the people who contributed to this work. St. Gall, May 1980 SKAT, Swiss Center for Appropriate Technology , TABLE OF CONTENTS ..-m__ - SUMMARY 1. HYDROLOGY l-l l-2 1-3 l-4 2. 3. 4. CHARACTERISTICSOF WATER 15 2-l 2-2 2-3 2-4 17 19 22 2G 6. Water sources Standards for drinking water Aggressivity of water towards Prevention of corrosion building material INVESTIGATIONS AND BASIC DATA FOR RURAL WATERSUPPLIES 31 3-l 3-2 3-3 3-4 3-5 33 34 35 35 40 General fieldwork Specific consumption Location cf water source Measuring of water quantities Analysis of water DESIGN AND CONSTRUCTIONOF RURAL WATERSUPPLIES 45 General lay-out Wells Spring catchment Water point Barrage and river intake Water treatment Storage Distribution system Water lifting 49 55 65 78 80 83 99 103 139 ADMINISTRATION OF PROJECTS 151 5-l 5-2 5-3 153 156 156 4-l 4-2 4-3 4-4 4-5 4-6 4-7 4-S 4-9 5. 5 6 13 14 Definition and hydrologic cycle Climatic pattern and rainfall Run-off and infiltration Drainage in Cameroon Technical report Execution of project Completed project MAINTENANCEOF RURAL WATERSUPPLIES 159 6-l 6-2 161 161 Maintenance Maintenance general instructions 7. SELECTEDBIBLIOGRAPHY 167 8. INDEX OF KEY WORDS 169 Appendix: PLANS AND SCHEMEPLANS (Constructional Scale Drawings) NORM 1 Chapter 1: HYDROLOGY Table of contents page l-l DEFINITION AND HYDROLOGICCYCLE 5 1-2 CLIMATIC PATTERNAND RAINFALL 6 1 - 2.1 Quantity 6 1 - 2.2 Variation 1 - 2.3 Tables of monthly 1 - 2.4 Intensity 1-3 RUN-OFF AND INFILTRATION 1-4 DRAINAGE IN CAMEROON of rainfall of rainfall 6 rainfall 11 of rainfall 12 3 , 13 14 DEFINITION AND HYDPOLOGICCYCLE l-l Hydrology is the science of distribution and behaviour of water in nature. Cycle The cycle of water or Hydrologic Hydrology is a part of climatology. is without beginning or end and consists of the following: - Precipitation: of the earth All water from the atmosphere deposited as either rain, snow, hail or dew. on the surface The water which is derived directly from precipitation - Surface run off: and passes over-ground into water-courses is known as surface run off. The surface run off then consists of the precipitation less the losses '. from infiltration and evaporation. Combined loss of water - Evaporation, transpiration: surfaces by evaporation and plant transpiratjon. from land and water- - Percolation; The term percolation describes the passage of water into, through and out of the ground. The term infiltra;.ioll is frequently used to describe the entrance of water into the grclane ant: its vertical movement down to the ground-water table, while percola?ion LP ground-water flow is applied to the movement of water after i+- kss reached the watertable. Fig. 1 Hydrologic Cycle CLIMATICPATTERWAND RAINFALL l-2 / The main features of the climate in Cameroon are the 4 - 5 months-long dry season from November to March and the corresponding rainy season of 7 - 8 months. ; / I Notes on the climatic characteristics of the various areas are based on inadequate records in terms of duration and number of stations. Nevertheless, an idea of the main climatic zones can be found when considering some basic factors: I - Throughout most of West Africa, the rainfall and the humidity decrease with increasing distance from the coast, but in South-West and NorthWest Province of Cameroon this pattern is sharply modified by the topography. ' - The main rain-bearing winds come from the south-west. Wherever these are interrupted by high land, heavy precipitations result over all south-wes facing slopes with complementary rain shadows in the N.E. For example, Dibundcha on the south-west side of Mount Cameroon averages 10.4 m of rain per annum, whereas Mpundu at the northern side receives only 1.5 m per annum. Similarly Fontem, at the south-west of the high plateau1 averages 4.3 m compared to Ndop with 1.6 m per annum. I 1-2.1 QUANTITY OF RAINFALL Rainfail quantities same annual rainfal1 of the distribution l-2.2 can be mapped with isohyets, are linked and the resulting of the rainfall in a region. i.e. all points with the lines give us an idea (see Fig. 2 and 3! VAFKIATIONOF RAINFALL The rainfall varies greatly throughout the year and from one year to the other as well as from one station to another (see annual rainfall map). The monthly variations have been analysed by Brown and Clarkson for the are shown in Fig. 6. Bamenda Station records 1923 - 1953 and the results In the diagram, the upper and the lower ends of the monthly pillar show the greatest and least rainfall recorded during this period. In four out of five years the monthly rainfall may be expected within the dotted lines. The black line across indicates the arithmetic means of 30 years of records. 6 ,m Fig. 2 _Isohyetes West-Coast (1967) Fig. 3 Distribution 1 2 3 4 I OVER 375 cm 200 - 375 cm SO - 200 cm 100 -1SOcm 700--tOOem 6 BELOW 70 of annual rainfall 6 !s IT FouRtAU 70 am cm . . . . . , . . ..*... . . ..a.. . . . . l . . l A . l l . ‘* ‘**: . . ---I * . ’ . . . * . . . FiG.('$ Bnd 5 .,. rainfall . . ..i -3 ,., ,ring (continuous flow). Fig. cracks the flow volume of the spring. will influence the flow volume of SPRINGS SPRING -1 ,- ARTESIAN SPRINGS NWL a ~I&CRW#W~~R PCRC~ATCINTO LWL 2-1.3 = GAOlJM WaTLR fLows INTO TM RIVER (INVISIU SPRINGS) STREAMS The run-off or stream-flow is the water which is gathered into rivulets, brooks and rivers. The volume and variation of run-off are influenced chiefly by the rainfall and its distribution by the size, shape, cover and general topography of the catchment area and by the nature and condition of the qround, 2-2 STANDARDSFOR DRINKING-WATER - 2-2.1 INTERNATIONAL STANDARDS 2-2.1.1 GENERAL RRMARKS Water intended for human consumption must always be free from any substances which provide a hazard to health. Supplies of drinking-water should not only be safe and free from dangers to health, but should also be as aesthetically attractive as possible. The location, construction, operation and supervision of a water supply - its sources, reservoirs, treatment and distribution - must exclude all potential sources of pollution and contamination. The problems of defining standards of quality for safe and acceptable water supplies have been studied by experts concerned with matters of water sanitation. The World Health Organization (WHO) has studied these problems to offer technical guidance for health and sanitation administrations to tighten or revise their regulations on water-quality control. 2-2.1.2 HACTERIOLOGICALSTANDARDS Water circulating in the distribution system , whether treated or not, should not contain any organisms which may be of faecal origin. The presence of the coliform group should be considered as indication of recent or remote faecal pollution. A standard demanding the absence of coliform organisms from each 100 ml sample taken from water entering the distribution system - whether the water be disinfected or naturally pure - and from at least 90% of the samples taken from the distribution system , can be applied in many parts of the world, Although there is no doubt that this is a standard that should be aimed at everywhere, there are many areas in which the attainment of such a high standard is not economically or technically practicable. In such circumstances there would appear to be economical and technical reasons for establishing different bacteriological standards for public water supplies with treated or disinfected water and for those with untreated water. The following bacteriological standards are recommended for treated and untreated drinking-water for present use throughout the world. Coliform density 100 ml of water, is estimated in terms of the "most probable called "MPN" Index. To get the coliform bacterial count (MPN Index) Laboratory can be used (see chapter 3-5.1). of the water, number" in the Millipore sted Water (by chemicals1 ia shall not be shall be less than 1. detected or the MPN index of coliform micro-organisms None Of the samples shall have an MPN index of &lifarm bacteria in excess of 19. 19 c An HPN index of 8 - 10 should not occur in consecutive samples. When the microfilter c hnique is used, the arithmetic mean of numbers of coliform group organids shall he less than 1 per 100 ml, and shall not samples or in mDre than exceed 4 per 100 ml either in any two consecutive 10 % of the samples examined. Cheamical treatment of water (e.g. chlorination) CD/SATA-Nelvetas projects in Cameroon , mainly a continuous rupply of the products. b) Untreated Very often dieinfected etand water (incl. slow sand filter has not been applied because of uncertainty without in of chlorination) communal drinking-water is not chlorinated or otherwise before being distributed. In such water schemes the following - in 90% of the samplera examined in any year, the MPN index of coliform microcorganisms should be less than 10. None of the samples should show an MPN index graater than 20. - if the MPN index is consistently 20 or greater , application to the water supply should be considered. _ when the micro-filter technique is arithmetic mean of the numbers of shall be less than 10 per 100 ml, two consecutive samples or in nmre This standard 2-2.1.3 is applicable for all of treatment used in examination of water, the coliform group bacteria determined and shall not exceed 20 per 100 ml in than lo& of the samples examined. the CD-SATA-Helvetas water supplies. CHEMICAL STANDARDS Chemical analysis plays an important role in the investigation of water supplies and water quality. Attention is largely directed to the detection and estimation of certain toxic chemical substances which may affect health. a) Toxic substances There are certain substances which, if present in supplies of drinkingwater and at concentrations above certain levels, may give rise to actual danger to health. A list of such substances and of the levels of concentration which should not be exceeded in communal drinking-water supplies is given below: Substance Maximum allowable concentrations in mg/l Lead Arsenic 0.05 0.05 Bel.enam 0 ,Ol Chromium Cyanide Cadmium 6axium 0.05 0.2 0.01 1.0 20 These substances cannot be analysed by simple field tests. Samples of the chosen water source should be sent to a laboratory for specific analyeis, @specially if the local population calls the water harmful. (see chapter 34.2) b) Chemical substances affecting the potability of water The following criteria are important in assessing the ootability of water. In view of the wide variations in the chemical analyses of water from cannot different parts of the world , rigid standards of chemical quality be established. The limits thereafter designated "acceptable" apply to a water quality which would be generally acceptable to consumers8 values greater than listed as "allowable" would markedly impair the potability of the water. These limiting concentrations in specific instances. are indicative IIHX. 500 mg/l solids Iron (Fe) Magnesium (Mg) Wanganeee (Wn) Copper (C-u) Zinc (Zn) Calcium (Cal Sulphate (So) Chloride (Cl) Wagn. and Sodium Sulphate Phenolic substances Carbon Chloroform extract Alkyl Benzyl Sulphonates 1500 mg/l 1.0 150 0.5 1.5 15 200 400 600 1000 0.002 0.5 1.0 0.3 mg/l " 50 0.1 W 1.0 W 5.0 lo II 75 II 200 II 200 ,s 500 0.001 lU 0.2 )) 0.5 @a 7.0 - 8.5 pH Range * *This item can be analysed by field tests, the out only in a laboratory (see chapter 3-5.2) 2-2.2 -S all0wabl.e concentration max. acceptable concentration Substance Total only and can be disregarded w mg/l I, In W " II w I, I, w w (( less than 6.5 or greater than 9.2 others can be found FOR DRIWKIWG-WATERIN CAMEROON 1 The standards of Cameroon correspond with the standards of France which are laid down in article 1 of the Decree of 10th August, 1961 of the "Conseil HupBrieur d'hygiine publique" and the decrees of 28th February, 1962 and 7th September, 1967. There correspond mite or less with 21 international standards. ? i ; ~ 2-3 AGGRBSSIVITY OF WATERON BUILDING MATERIAL 2-3.1 GENERAL The aggressivity of water plays a very large role in a water supply. Corrosion caused by the aggressivity of water means not only loss of building-material but in addition reduction of the water quality technically and hygienically. Especially endangered are those parts of a water scheme which are invisible like underground pipes, the exterior of covered constructions etc. The aggressivity of water is mainly determined by its pH-value. In addition the free carbon dioxide plays an important role. Whether or not depends much on the *these two values prove aggressive carbonate hardness ot the water. That is why these three magnitudes are described more in detail below, PH - VALUE 2-3.2 The pH-value is very important in water technology. It indicates how acid or alkaline (basic) a water sample is. It is the measure of H+-ions (hydrogen ions) dissociated in one liter of water (the pH-value is the negative logarithm of H+-ions concentration). One litre of pure and neutral (neither acid nor basic) water contains an equal amount of Ii+-itins and OH--ions (hydroxyl ions) , at a temperature of 22O a concentration of 10s7 H-ions and 10-7 OH-ions = pH-value of 7. In acid water the H-ions are overwhelming the OH-ions and accordingly the pH-value is below 7. In alkaline water it is the opposite and the pH-value is above 7. In practice this neutral point of pH-value = 7 varies with the content of calcium salt (hardness, see chapter 2-3.4). For instance water of pH-values exceeding 7 can also be aggressive if its calium salt content is very low (see Fig. 11). , Fig. 11 PH-value for neutral on the calcium salt watk- depending content 8,8 w 8,4 8,2 8,O %7,8 T76 ’ 7:4 E7,2 7,O d-’ ! ’ ! ’ ! ! ! ’ ! ’ DG’ I !H ! ’ 1 20 &I 60 Bo loo 120 140 160 fixed carbon dioxide mg/l 0 2 4 6 8 10 12 14 16 18 20 C.r.‘.‘.‘.‘-‘.‘-‘.‘.1 carbonate hardness 0 2-3.3 CARBONDI@JXDfI Summary : Only part of the carbon dioxide in water (the excess CO21 is aggressive The theory on this page shows the contowards cement and iron products. text, The figures 13 and 14 show the practical application (compare with examples of chap,ter 2-4.5). CO-J: Carbon dioxide in water A \ Fixed carbon dioxide Freee carbon dioxide / ------. Fully fixed CO2 Half Associated CO2 CaC03 in carbonates) not aggressive (harmless to concrete! total excess (prevents formation of anti rust layer) fixed CO2 Ca (HC03) 2 in hydrogen carbonates 1 not aggressive (e.g. Partial excess (lime aggressive, attacks concrete) Free and fixed carbon dioxide (CO21 is found in every natural water. Surface water generally contains much less free carbon dioxide than ground water. The fully Therefore hardness: fixed carbon dioxide is combined with calcium or magnesium. its amount can be calculated according to the carbonate ODG 7,f35 = mg/l of fixed carbon dioxide. l The half fixed carbon dioxide is combined with bicarbonates or hydrogen carbonates. Its amount is equal to the one of fully fixed CO2. Part of the free carbon dioxide, the associated CO2, is necessary to maintain the calcium hydrogen carbonates in solution. Therefore the associated CO2 is depending on the carbonate hardness (see Fig. 12). Fig. The associated 12 0 d 0 2il carbon dioxide EiO 100 W 140 160 fixed CO2 mgll 2I - 4I . 6I . 8I _ 10 I . I2‘ 11 a - I6y120 1 . I . J carbonate hardness DG* The part of free carbon dioxide exceeding the associated CO2 is the excess CO2.The excess carbon dioxide is able to attack and dissolve the metallic materia as well as the calcium carbonate in mortar or concrete. Small amounts of calcium hydrogen carbonate, corresponding to a hardness of less than 2O DG, do not require any associated CO2, The total free carbon dioxide of soft water is thus aggressive (compare Fig. 13 and 14). Fig. f3 ~ggressivfty towards cement products (concrete, mortar, AC-pipes) depmding on the DG and the free CO2 0 Fig. 14 2 4 6 8 10 12 14 16 18 '20 22 carbonate hardness ” DG Aggressivity towards iron products on the DG and the free CO2 0 0 2 (steel 4 6 8 Dl2l416182022 Carbonate hardness @DG 24 pipes) depending The hardness of water is dictated by its content of calcium and magnesium salts, Water containing much calcium ano magnesium is termed hard, that soft, This is expressed numerically by the degree of containing little, hardness. Unfortunately there is no international unit established so far. Degree of hardness - conversion 1 grain CaCOJ/gallon 10 mg CaO / liter 10 mg CaC03/0,7 liter 10 mg CaC03/ liter 10 DG lo DG Degree of hardness modulus: = = = = = = 17,l mg CaC03/1 = 0,96ODG 1 German degree of hardness (ODG) 1 English degree of hardness 1 French degree of hardness 1,25 English degree of hardness 1,78 French degree of hardness This water is termed as OlG o48 12 18 over 4 8 12 18 30 30 Three different very soft soft medium hard considerably hard very hard kinds of hardness hard are distinguished: - Total hardness In natural w'ater, calcium and magnesium are largely combined with carbon dioxide, namely as hydrogen carbonate. Usually a small amount is combined also as sulphate, chloride, nitrate, silicate and phosphate. The sum of all these calcium and magnesium compounds yields the total hardness. - Carbonate hardness This includes only the part of calcium and magnesium which is combined with carbon dioxide. When water is boiled for a longer period, the calcium and magnesium combined with carbon dioxide are almost entirely precipitated as insoluble carbonates. One refers thus to a temporary or transient hardness, now generally spoken of as carbonate hardness. - Non carbonate hardness The fraction of the calcium and magnesium remaining in solution as 5 sulphate, chloride and nitrate after boiling constitutes the residual hardness, formerly also referred to as permanent or mineral acid hardness. Wow this is more accurately termed non carbonate hardness. 2-3.5 OTHER IWFLYEWCES Concentrations above certain limits of sulphate (*3Omg/l) or sulphite, chloride@100 mg/l), humic acid etc. can also be very aggressive towards building materiels. m describe all these influences in detail is beyond the framework of this book, Moreover such detailed analyses require a very well *equiped laboratory. 25 24.2 Cement, mortar, vhich dissolves concrete, aslmstas cemant pipe in contact with sggre conbin calcim carbn&te 2-4.2.1 - Acid v&tar @I v&u@ kmlow ths neutral am h88rmfui to concrete, It hamu* blow thf3 neutral than 1 to 2 point , Pig, 11.) must kr regrrdd rmful if the pH value is more 1 line. - AS it can be seen from Fig. 13, soft water (with IOU carbnate hardness) This becumes always very aggressive if it contains free carbon dioxide. concrete and mortar and aclgresoive CO2 dissolves the calcium salts of the ng water with such ic dastroys gradually theBe cement product very rapidly. cr Alkmlim watw 11, the mg/l in flowing wif %xtrPnt also the corresponding Qnt ~11 - Ham%ul if line) can ill~ilo CBUP~ d above 300 mq/l in satanding magnesium 5ulphates and, tc3 zi , dsetroy concrete, chloride to concrete is als~s wetlsr containing alfum salt5 (@.g. wa - cuncrQt;8 is ( (Fig. &x’oducto idly ttackQd by vat r containing in ceartal arsPrs1. 26 hydrogen sulphide and larger ~~Iium hydrogen carbonate nt than porous concrete. t pus”Lbla water- t E*ternd such as spetrion), plastic occuxfng 27 wkth &SW It the o%yfpn content bilky W&ld&ty im OXUW~IVI, of wtex), iron not in genuinely diouolved form attacked. irr likmhe - Iron im elbmymattmkad and bimsohd ky water uhich preventa ena Pig. 14) containing ~ree8tv.e of a protective layer against thm forution l - I& &B-value @hould altray be equal unprotected iron piparr -Cl,5 point* to or juot below the equilibrium for for gelvanieed steel pipes (see Fig. - Unp+akcted by hydrogen iron pipem ere attacked - Wnt8r with a high rtmmgly. The Limit chloride eontmt for unprotected mulphlde (e.g. in B-soilr brackish vater) attacks iron pipes icr L5Omg/Liter in aoft (e.g. iron pipe6 water, - sp+cibl - Steel bar to bm given to the e&mnal attack. pipes ue mre twuceptib~e to chemlcrrl attacks &ton pipee ue more reeirrtant than steel pipes oxygen eontent and aggremive properties. bet high 24.3.2 rttention of corro8ion * of the recrreroive crcbn Ptevuntbn - llrdwtion - &on piper c?ailatd m&l@, have to be coated *@ynapLmt~~in lou end clay GIW dioridsr ~4th little 28 re chapter cast iron pipes. soft water of 2-4.2.2. of coal4.ar pitch (eoamm3eelvity (e.g. in acid peaty calc$un and in salty ground water etc.1 . by relted of than against ewtawnal bit-n 11) 2-4.4 PMSTIC PIPES Plastic pipes are either (see chapter 4-8.2.31. of PVC (polyvinyl Since 1959 the fabrication of plastic to the claims of water engineering. chloride) or of PE (polyethylene) pipes has been adapted more and more Plastic pipes have the advantage of not beeing attacked by any aggressive water They suffer no destruction from carbon dioxide, humic acids, sulphates and chlorides of any concentration in tapped water or soil. They have smooth walls and no incrustations. That is why plastic pipes are applied more and more in in particular with aggressive water and soil. Nevertheless water supplies, much attention has to be paid to an adequate fabrication. Some plastic notably poor polyethylene pipes, serve as nutrient of bacteria. materials, 2-4.5 EXAMPLESOF PRACTICAL,APPLICATION To show the practical application samples will be analysed: Sample A: of chapter 2-4 three different water PH = 6,6 Hardness = 2 grains CaC03/gallon (=2O DGI Content of carbon dioxide (CO2) = 20mg/l This "very soft" water (chapter 2-3.4) is acid (Fig. 11) and "very much aggressive*’ (Fig. 13 and 14! towards cement and steel products. Conclusions: In this water supply project plastic pipes have to be applied and the concrete tanks have to be provided with protective coatings. Asbestos pipes should not be used. Sample B: This "soft" aggressive" PH = ,7,4 Hardness = 7 grains CaC03/gallon (=7,7ODG) Content of carbon dioxide (CO21 = 42 mg/l water (Fig. (chapter 2-3.4) is little acid (Fig. 11) and "very 13 and 14) towards cement and steel products. Conclusions: Plastic pipes or coated asbestos pipes (see chapter 2-4.2.3) can be applied. Steel pipes should only be used for parts of the pipeline where other piping material cannot be applied (e.g. crossing of rocky areas). Concrete and plastering should be protected by additions or coatings. Otherwise the cement plastering has to be replaced after a few years. Sample C: PH 1 7,l (=10,5O DG) Hardness = 11 grains CaCO3/gallon Content of carbon dioxide (CO2) = 18 mg/l This “medium hard” "little aggressive" water (chapter 2-3.4) is little acid (Fig. (Fig. 13 and 14) towards cement and steel Conclusions: In this water project all common building.znd applied. 29 piping materials 111 and products. can be Chapter 3: INVESTIGATIONS AND BASIC DATA FOR RURAL WATER SUPPLIES page Table of contents 3-1 GENERAL FIELD WORK 33 3-2 SPECIFIC CONSUMPTION 34 3-3 LOCATION OF WATER SOURCE 35 3 - 3.1 Source situated 35 3 - 3.2 Spring 3 - 3.3 Source situated 3-4 MEASURING OF WATERQUANTITIES 35 3 - 4.1. General 35 3 - 4.2 Estimating 3 - 4.3 Measuring 3 - 4.4 Flow measurements with a weir 3-4.4.1 Thompson weir 3-4.4.2 Rectangular weir 37 37 38 3-5 ANALYSIS OF WATER 40 3 - 5.1 Bacteriological. 3 - 5.2 Chemical analysis above consumer 35 water 35 below consumer water quantities water quantities 36 of a stream with a bucket and a watch 36 test 40 of water 41 field 31 GENERALFIELD WORK 3-l The following list intends to give a summary of the field planning and construction of a rural water supply: work during - Application for assistance is sent by the community concerned Community Development Department (CD) or to the local council. to the - Meeting will be organized by Community Development Officer (CD01 for introduction of Department to local officials and community, eventually forming a project committee. - Search out water sources - Preliminary the results (springs, river, etc.) followed survey with pocket altimeter, with the community. - If the project is feasible collection a) Situation: Geographical function of the village by discussion of more information of and data on: and administrative situation, in the region, etc. place and b) Population: Number of inhabitants, ethnological composition, development of the population during the past years, denominations, etc. Present infrastructure and development plans of roads, c) Infrastructure: schools, markets, health centres, cooperatives, missions, other development projects, etc. d) Economic aspects: Produce and income, potential, farms, markets, industries, development projects, etc. - Contacts to other - Measuring of the water quantity - Biological - Detailed Government Services, and chemical cooperatives, coordination agricultural with other Local Administration of source water tests (see chapter 3-5) survey - Occurence and quality stones and wood. - Technical report, - Organization of a project of local estimate building (see chapter materials: Sand, gravel, 5-l) of community by Community Development Department committee if not already done) (organization - Financing of project: application for government grants and foreign aid, commitment to an amount for village contribution - Organization of community work by project committee Development Department according to the instructions - Implementation - Organization of project of maintenance (see chapter , 33 ,:,,. ' , ', : 6) and Community of the technical staff 3-2 SPECIFIC CONSUMPTION average daily at present Stage O* Village in remote areas per head Village with school, maternity and max.lO% private connections per head Urban areas with max 20% private connections per head Residential areas (private connections) per head Primary school per pupil College per student Maternity per bed Hospital without Surgery per bed Hospital with Surgery per bed water consumption in litres in future Stage I* Stage II* 25 5r)' 70 50 70 100 50 1c:o 120 100 10 100 100 100 200 200 10 120 100 150 300 250 10 120 130 150 300 The above figures merely give the design engineer a guide to the average consumptionsi he has to use his own judgement to choose specific consumptions based on experience in the country and the details of the particular project. The consumption during one day in rural water supplies can have big variation! Market The smaller the community, the greater, in general, is the variation. days and local celebrations can have a big influence on daily water consumptic The following values have been experienced: Ratio Maximum day: Maximum hour: average day average hour Normal rate (from 1.2 to 2.0) (from 2.0 to 3.0) : : 1 1 Average 1.5 : 1 2.5 : 1 Measurements in the Ngondzen water supply have shown the same results. * see chapter Fig. 15 Q% Daily 4-1.2.2 consumption in a rural water supply 3-3 LOCATION OF WATERSOURCE 3-3.1 SOURCESX_?~Ui'i'l'ED ABOVE CONSUMER all possible water sources have to be investlqatf~~i wtrtttlrbr With tl, they can supply wst?r by gravia to the consumer. It is *.ast prf~fcrdt~lf~ get water by gravity in order to avoid the installation of an enqinr: (Imp, water to the consumer). In this way the maintcnancr: will ram, etc. to lift tJf> simplified and the running cost kept low; moreover a continuous supply i:; tJy far safer. 3-3.2 SPRING WATER With second priority preference has to be given to spring water whictl car1 tjf? caught from inside .the ground avoiding any contamination. In this car:13 no treatment will be required, which again simplifies the maintcnancc r,f tllfs w,ltczr supply . 3-3.3 SOURCESITUATED BELOWCONSUMER With third priority sources have to be investigated which are situated below the consumer in case of failing to find a source above the village. But also in this case preference has to be given to spring water which can be caught from inside the ground. It has also to be investigated whether the water can be lifted to the consumer by natural resources (e.g. water power: hydraulic ram, possibly turbine, or wind, etc.). 3-4 MEASURINGOF WATERQUANTITIES 3-4.1 GENERAL The most important water available. Before we start be considered. figure detailing for any kind of water-works a project is the quantity we need to know how much water of has to - for barrage, catchment, overflows - for intake, sedimentation, filter Gauging should be done regularly once a week for more than one year if possible. If only one year measuring is possible, it is a necessity to measure the water quantity of the source as well as the rainfall. Compare the mtaasured rainfall with available rainfall statistics over a long period, which helps to determine whether it is a dry or wet year. This enable@ to decids if the water quantity will be sufficient. In case of a river, msa@ursment should be taken in the morning as well as in the afternoon (morning : afternoon w 1 : 0.8). 35 ,. $j& ,6 ,: : ” ~ 34.2 ESTImTI?$ The quantity Q A v s = = = = WATERQUANTITIES Of? A STREAM of water flowing steadily In a stream is quantity of water (m3/sec!) cross-sectional area of flow (m2) velocity of water (m/set) surface: for plastered surfaces for rough rocky surfaces average To estimate the flow of a stream carry = 0,9 = 0,s = 0,6 - 0,8 out the following procedure: - determinesthe cross-sectional area of the water flowing (average depth of water x width of stream = A) velocity of water: take the distance that a piece of wood or a leaf second (Xm/sec), out of three measurements. in a stream - measure - calculate 3-4.3 the quantity of water as a result travels during of 1 and 2 Q=Axv one MEASURINGWATERQUANTITIES WITH A BUCKETAND A WATCH This is an easy and exact method for quantities up to 300 (600) l/min. Procedure: - One or more pipes, depending on the quantity, earthdam so that all the water passes through are fitted the pipes. into a temporary - The flow from one pipe should not exceed a quantity which fills a bucket in less thar) 3 seconds. . - Calculate the volume of the bucket if it is not a graduated one. - Gauge the flow of each pipe three records. - Calculate the quantity in l/min. 36 times and enter or l/set. the results into the 3-4.4 FLQWMEASUREMENTS WITH A WEIR 3-4.4.1 Thompson weir This method is suitable The following Fig. for quantities arrangements up to about 50 l/see. have to be made: 16 UM. ‘ URR WATfR LEVEL LW i LOWLR WATER LCVCL TNf In,& LWL snouw NEVER BE tllGNfR I’MAN POINT 2, - minimum H = 2h - maximum velocity of water at the - normally a 900 weir is used x Y - important: The gauging rod must the weir. The zero point of the crest of the weir. be in a distance of at least rod must be on the same level Fig. 0 04 0.4 0.6 00 1.0 1.2 1.4 I.6 10 2.0 U IN 0 37 IN 1 m/set gauging rod = = 2 17 2.2 U5LI; L/SEC 2.4 Discharge over 2.6 3.2 2.0 3.0 3 h from as the Thomson weir 34 3.6 3.0 4.0 44 4.6 18 Fig. Discharge tl- = oyer Thompson weir 11 - 20 cm xb r I h ON 1 2 3 : t6 ! 14 $ u I2 .E I II I I IY i 10 11 I I I I I 12 #a 2 &-=90’ 13 14 15 h=19om :; 18 1Y 20 22 ’ 3-4.4.2 2 0 4’6 Rectangular 12 14 16 0 in L/SEC. 10 Fig. 20 22 for quantities arrangements 19 - maximum velocity 26 20 80 0.008 047 Alo 266 465 733 l.UlO 1.5% 0.014 081 224 461 805 1.270 1.867 2.606 3.50 4.55 5.78 7.18 8.W lo.% 12.54 14.75 17.16 19.79 2.020 2.63 3.34 4.15 5.07 6.10 7.25 0.51 9.91 11.43 13.cq 14.87 18.88 23.47 20.66 34.5 41.0 22.67 25.76 32.7 40.6 49.6 59.7 71.0 above 10 l/set. have to be made: SalION PROFILE - minimum H = 24 2 900 weir 'This method is applicable The following 10 Pb 28 30 1.155 600 4 h of water at the gauging rod = lm/sec - important: The gauging rod must be in a distance of at least 3 h from the weir, the zero point of the rod must be on the same level as the cxest of the weir. - normally - the crest the minimum width for a weir should be 50 cm, better of the weir must have a sharp edge. 38 1.00 m Fig. 20 Discharge t 15 14 L over 1 rectangular I I weir I I I I h=lZcm b= BOcm EXAMPLE FROM TABLE Q = 748 llsec x 08m = 6OOllsec FROM GFfAPH 0 = 750 llsec x OBm = 600 llsec la-;- I I I I 1 lo 20 I / sec. h in a '3 i~ll/s &r3-L& bin AAL 26 $ $ ::; 6.7 5.1 3 4 5 6 7 i 9.4 14.4 20.1 26.5 33.3 48.6 40.7 10 ll 12 56.9 65.7 74.8 13 14 2:: 104.6 15 16 ii u5.2 137.5 126.2 19 20 22 24 149.2 25 225 161.0 l86 2l2 V in l/o for B -l.oq 239 267 : :: ;: 357 :2 38 40 42 44 45 46 48 z :; 60 65 70 75 80 85 tit 70 50.60 40 30 422 455 490 525 543 561 599 z 1054 2169 la8 1411 % 39 m I 80 90 loo ‘;-.“: ,I i 3-5 ANALYSIS OF WATER 3-5.1 BACTERIQLOGJCALFIELD TEST (MILLIPO~E,) Millipore is a membrane microfilter technique for detecting coliform bacteria and other bacterial organisms in water - the principal criterion of sanitary quality for public drinking-water. In many cases, the membrane filter method has made it possible to substitute field testing for laboratory analysis. A real and reliable information about the quality of water can only be got if the tests are done over all seasons. This means tests have to be done in dry season and in rainy season in particular after heavy rains. Test, procedure with portable with CD-SATA-Helvetas: kit and monitors from a bacteriological Remove the plastic aside. 2. Carefully insert the syringe valve connection side) of the monitor. Avoid excesz,ive force. 3. Remove a sterile sampling tube from its into the inlet hole of the monitor. 4. Draw the syringe plunger back slowly on the initial stroke (to avoid the risk of an "air lock" before the monitor fills with water) and hold the plunger forward to expel the filtered water from the syringe. 5. Filter an entire measured amount of sample water through the monitor. Samples of 100 ml are normal for potable water, but samples of 50 ml are normal when testing stream-water. 6. Invert the assembly and draw the last few ml from the filter. quick strokes to pull the monitor as dry as possible. 7. Remove and discard 8. Crack off the ti.p do not remove the the plastic tube, bottom tip of the 9. Remove the monitor from the syringe and insert the bottom tip into the BOTTOMof the monitor, placing it against the pad beneath the filter. Release the forefinger and by controlling the pressure of the ampoule against the pad, allow the medium to flow into the monitor. the sampling tube, monitor which is availab 1. 10. plugs water analysis into and set them the bottom sleeve and insert ("spoked" the nylon tip Use short, but do not remove the monitor. of an ampoule (covered by a short plastic tube), but tip or the tube. Place the forefinger over the end of as when using a pipette, and break off and discard the ampoule. Replace the plastic plugs, invert the monitor, and incubate at 35OC for 18 to 24 hours. Pry off the monitor top, remove and dry the filter, and count the coliform colonies which are blue-grey coloured with a metallic lustre. In some cases it may be difficult fecal origin (from intestines of from other environmental sources. at 44OC for 24 hours. The colonies Conditions are certainly coliform to differentiate between coliform of warm-blooded animals) and coliforms In this case a sample may be incubated which are growing under these of fecal origin, 11. The count should be determined and recorded as the number of coliform organisms (colonies) per lOOm1 of sample tested. (compare with 2-2.1.2) 12. For more detailed instructions see "Millipore-Manual". I 3-5.2 CHEMICAL ANALYSIS OF WATER general laboratory A chemical analysis of water has to be carried (e.g. of a hospital or a high school). out by a well equipped general analysis a sample of at least 2 litres is required. It should collected in a chemically clean bottle made of good quality (neutral) glass, practically colourless and fitted with a ground-glass stopper. For be In the collection completely filled of samples from mineralized sources, and the stopper securely fastened. the bottle should be Samples should be transported to the laboratory with as little delay as possible and should be kept cool during transport. Chemical analysis should be started as soon as practicable after the collection of the samples and in any case should not be delayed for more than 72 hours. Fig. 21 shows the result of such a chemical CD/SATA-Helvetas water supplies. partial If a general chemical analysis is not possible, analyse the water by a field test. Additionally out from the local population whether the water Chemical field test - Content of carbon dioxide - Content of dissolved - PH-value The test procedure of different the design engineer has to the engineer has to find is potable or not. (Hach) With the portable water analysis available with CD-SATA-Helvetas, measured: - Hardness in grain analysis kit (model CA-24WP) of Hach, which is the following chemical values can be (CO2) in mg/l (see 2-3.3) oxygen in mg/l CaCO3/gallon (see 2-3.4) (see 2-3.2) is described in Fig. 41 22. ChemLc8.l water Dreignation of tha estsr aelmas: OIAW~ 35 223 c-’ Helvetas sehweiter Aufbauwerk EntwickluIlgsl~er - wlalslmob--m wngNnn*tYOvrnJUOr*w -ucaewemmNr- (in %G]: hnrdness Urbanate fiir vom 1, Derember 1975; Ref. W/ii m: wmw-. Result Sanplss: five the ootties rith very Taxxings Chmical malysis The analyzed extraordinary samples litt+e samples (but (lime-aggressive eeeciafiy &cause of catian the tested waters Dn the orher 1 litre pure rater, each and an admixture are salts and little and "Kai" aCditiOt%?+lly 3i calcium Settles ccrznnate. with 0 0 0 0 0 cl.17 0.17 1.45 0.1 I.7 1 1 1 1 I 0.5 0.5 0.5 0.5 005 0.15 0.2 0.B 0.1 G.75 herdnesr of as/l): (in Sulfate8 60, Chlorides Cl acia to also very ana *‘:ieh”j neutral iittle heve and extremely soft. They contain orgnic pollution. All the 3 high anility to dissclve iiira dioxide). small hardness are aggressive hand. tnare is soft rater) ails cement as well qejection to the use (very ?cwards no tha acid as towards cf plastic character, steel. material. Co, dioxide Natrium NanCOg Uagnesium examinatmn the 7.0 Total Calculated five 6.0 1.7 7.7 (Hey-f tCUdl4 consixrmtifm in mail (translation! 6.b 0.1 csrtmn Vemuchsefgebnir - Msultat - Rlsultato 5.9 1.0s Alkalinity ml/l: Yethyromnge nach Angaben 6.6 0.17 Lime-eggressive Chemische Analyse sehn 0.17 colltent Ksmmm Gsh - carbo~te hsrdllsss Non FXtnf Doppelproben ksser betr. &A.T.A. Wasserversorguag. Brief 3etrifff: PH -U&la Htwdness Zurich G==%l amlysis Dueoendorf. in 1.6 37.4 0.6 a.6 0.9 8.e 1.6 11 0.9 mgjl: olWnete 7 ISg D the gth of December l2 0 195 24 2.4 5 0 13 3.5 1. Fill the ptsta crteas~rr~ tube H Iull Wllh the wmw to be IR5ld wd translw to the mlrirth) boltk bv p~acmg ttw minhy) bottle over the tube and turnim the bottle rr$htWietc-up. 2. Add one drop of f%dphl)uCin lndi. catot solullon. = 1 mQ!t 001 1. FIII the plawstopene4 00 boltle with the wmtr to be tesoted by allowing the water to overflow the battlg far 2 or 3 minutes. Be certrtn there are 1~) air bubbler present m the bottle. 2. Add the cont@nto al one ~~ttow each of OisrolveJ OrvQen 1 ReaQe!rrt POWdsr and 01palued E)xvQen : Aeapwrt Powder. Stopper lirmly and carefully ~0 that no au is trappud rn the bottle. Sea Nore A. Grip the bottle and sbaka vigorousiiy to ~IIJR. See Note B. A flocculmt prmipitate will form. If u~y~~ IS pmwnt the preclpltate will be brownish.oranps in color. 3. Allow the sample to stand un111 thr flue has wttld halfway and leaves thr half of the bottle clw. Then shake the bolt16 and ,aQam let it stand unbl the upper half of the bottlr )S CIQW. see Nate a 4. Rumwa the smpper and add the con. tents of onu pillow of D~swlved Omxgen 3 Resgcnt Powder. Carefully m-stopper and shake to mix. The floe will dissolve and a yellow color will develop if orryQen is present. This is the prepuraf sample. 6. Fill the platic messurrnQ tuba lwsl full with prt!porrad wmpk and pour it Olto the mirinQbottlr. W. Whila swirling the samplr IO mir. add PAO Titrant dropwise, countmg arch drop, until the sample chanyrs from ysllow IO colorless, The dropper must be held in a vertical manner, Each drop is eoual to 1 mrr/l dissolved orvQml al01. SW Not47 L tf the result from Step 6 4s very us 3 mq/l or less. It (s Jdv~wble IWQW wmple to nbtam a more rmult. Thcs may be dclne by duectlv m the DO ra~lpls f0llwn: low. such to test a %anrltwo tltratmp bottle as 1. tJunQ the preparhlj sample left over from Stet8 4 abwe. pour off the cantents ot the 00 bottle untrl the Ia& just rcaclm tho 3&ml m&k on ths bottle. 2. Wbllra sw~hy the DO hettle Ia mm the sample. &d PA0 Tltrant dtopw~re. countmp mch drop, untd the bwnple chwges from yellow lo rolorlasr Edch drop at PA0 Titrant added 8squaI to 0 2 rndl dissolved oxygen m thr sam pte. &e Note E. MODEL CA 24WR Hdness Test 1. Add 3 drops of Mutter Solution. ~WSS1 and swirl to mlrr 4. Add llttcmt Ihqwt, tt.rrthm .I a drop al a time. with %vwl~lmy ul Ihe mhlrlr) hnttlo WbllS the drrlps JPP cuunt@d. Urllll the YIIutIcJrl 11, IhC tnlrmfj bulllr ch;mqw Irr~rrc pwk 10 hlus Thr Iltrant Ac,lyvnt. tldrdnl-.. 1 druppur sl~uuld t,r IISIII II, ,i Vt A I I CAL rnanncr and thl? drops shmrlrl br dlspamed at a rate not tartw than one drop per smnnd The dropper rhouki ba held shghtlv above the rap ot thy mtrmg bottle 50 that It WIII WYW come mto corrtxt wt.1 the wle of ttw nvxmy boftle THIS IS IMPORTANT NOTES Dwx~lvedOryga, A. It 8s a bt trtcky IO stopper the DO bottle vrlthout tropp:ng an air bubble. To avotd this problem. tnchne the 00 bottle Jv#tly and msertthe stu~oet with a quick thrust. This WIII forts air bubbles auf. Ilowever. it bubbtes do become trapped m Steps 2 or 4. the sample should be dwza,ded and the lest stuted aver. 9. A small amount of powdered reaQen1 may remam stuck to the bottom of iha DO bottls et this pomt, but this will not alfect lhe test. C. Do not oltow the PA0 Titrant to stand m direct sunhqht. ~5 it is decompod Itv ultrar~olsl radtatian. 0. In samples that contain high conce” tnbons of chloride, such JS seawater, this floe wrll not settle. However, no interference is observed as long as the sample 1s allowed to stand m contact with the floe for 4 or 5 minutes. L. A more sensitive twt can be performed bv using Starch indicator Solution (Cat. No. 34$.13, not includnf in kltj while litratrng the ~lmple wtth PAD fitrant. 70 uw aflectlvrlv. titrute tha sample until ths color /us1 bagmr to thenr from yellow-brown to IiQht yellow, Add two drops of Starch lndteator Solubon. ContmuP tltretlon, counting the drops of PA0 Tltrant unrd the sample colar changes from blue to colorlms. The total number of drops of PA0 Tltrant uwd md~cates IhS exact concentration of dissolved orvyen in the sampI*. 43 It& 5. The hJrdnr%. m gr.r~rls iwr ~JJIIO~I a. calcium carbonate lCKO3J. 0z equ,?~ to thr number ot drops of i~!rdnt ft0aQent. Hardness 3 requ~rnl IO brmq atrrut the color ChJnyr pH Test 1. Fill ths Iwo glass sample tulres to the 6ml mark with the water sample /r ,s imperJtrve thaf Ihe t&x! be cornplele~ y rrnrrd free of dory mlot~onr thdt rwy hvr been uredprcvrotrdy 2. Add 6 drops of Intl~cJtor Solutmn end zwwl to m,x. Wide HJnge 1 pH to me of the tubes 3. Insert the prepared sample an th? rqht openmg of the color comparator 4. insert the tube of untreated water sample m the left openmy of the color comparator. 6. Hold the color comparator UP to a I&t such as the sky, a wmda;v. or J lamp and VIR.‘~ through the two W&R--, bide m the front. ftolcrts the color (11% until a color match 1s obta~nril Rrdd the pH throuyh the scale wmdoiv NOTE The pH praEencs a! chlorww mple ~111 cd”w J slqht an Ihe vrJtrt rnlerferenre 1,~ the test. Wemove up IO 50 mQ!I chlr)f~~x? by addmg one drop of OechlorlnJt~i-q Solution (Cat. Plo. 1069 13. not ~ncltrrlrd in kit) to the water sample betorr J&I lion of rho pH lndrcator 4-l 4 - 1,l Syetxm of 4-1.1.1 4-1.1.3 4-1.1.4 4-1.1.5 4-1.1.6 lMnp0ral 4-1.2.2 4 - 1.4 4-2 water 49 supply lay-out in stagea Servicxz life tbsign in otago&3 4-1,Z.l 4 - 1.3 th? Spring water by gravity Stream water by gravity Spring water bl?low the consumers Supply of ground water Stream below the consumers Rain water storage 4-1.1.2 4 - 1.2 49 LAY-OUT GENERAL 50 WWIpl@~ 52 Materials and construction methods 54 WELLS 55 - 2.1 General 55 4 - 2.2 Types of wells 56 4 - 2.3 sire 57 4 - 2.4 Construction methods 4-2.4.1 Native system 4 of well 4-2.4.2 4-2e4.3 4-2.4.4 58 Dug welis Sunk welle Sinking a tube well SPRING CATCHNHNT 4-3 4 - 3.1 Quality 4 - 3.2 Location 4 - 3.3 a = 3.4 and quantity 65 of spring water of springs 66 Catchment area Spring 4-3.4.2 4-3.4.3 4-3.4.4 4-3.4.5 4-3.4.6 catchment 65 67 (conetructlon) 67 The 'real' catchment Supply pipe to the inspection chamber inspection chamber Outlet building Common mistakes on spring catchment WATERPOTNT 70 cawrwl 78 Construction of a water point 45 78 80 BARRAGE AND RIVER INTAKE Determining magnitudes for the position of the barrage 80 4 - 5.2 Design of barrages 81 4 - 5.3 Design of intakes 02 4-6 WATER 4 - 6.1 General 83 4 - 6.2 Sedimentation 4-6.2.1 Definition general 4-6.2.2 Design of sedimentation 4-6.2.3 Construction details 03 03 TREATMENT tanks 4 - 6.3 Slow sand filter 4-6.3.1 Mode of action 4-6.3.2 Hydraulic system 4-6.3.3 Size and number of filters 4-6.3.4 Construction details 90 4 - 6.4 Other filter types 4-6.4.1 Rapid gravity filter 4-6.4.2 Pressure filter 96 4 - 6.5 Treatment 97 4-7 STORAGE 99 4 - 7.1 General 99 4 - 7.2 Capacity 4 - 7.3 Design of storage 4-8 DISTRIBUI'ION SYSTEM 103 4 - 8.1 Lay-out 4-8.1.1 4-8.1.2 4-8.1.3 103 4 - 8.2 Piping material 4-8.2.1 General 4-8.2.2 Asbestos cement pipes 4-8.2.3 Plastic pipes 4-8.2.4 Steelpipes 4-8.2.5 Valves 4 - 8.3 Design 4-8.3.3 4-8.3.2 g-8.3.3 4-8.3.4 station: Lay-out of a storage tank 99 101 tanks of the distribution system Type of distribution systems Pressure zones Disposition of taps of the distribution system Hydraulic calculation of piping Prevention of air pockets Prevention of vacuum Air release valves and anti vacuum valves 46 105 110 4 - 8.4 Implementation 4-8.4.1 Trenching 4-0.4.2 Laying of pipes 4-8.4.3 Thrust blocks and anchoring 4-8.4.4 Pressure test of the pipeline 4-8.4.5 Valve chambers 4-8.4.6 Pipe connections to buildings 1.20 4 - 8.5 Distribution buildings 4-8.5.1 Public standpipe 4-8.5.2 Public washplaces 4-8.5.3 Public shower house 135 4-9 WATERLIFTING 139 4 - 9.1 Types of pumps 139 4 - 9.2 Hand pumps 4-9.2.1 Deep well pump 4-9.2.2 Wing pump 140 4 - 9.3 Centrifugal 4-9.3.1 4-9.3.2 4-9.3.3 4-9.3.4 143 4 - 9.4 Other pumping system 4-9.4.1 Hydraulic ram 4-9.4.2 Hydro pump pumps Planning of centrifugal pump installations Pump drives Pumping stations Data needed by an enquirer 148 GENERALLAY-OUT 4-l The results of the investigations in the field (chapter 3-l) have to be compiled and different solutions have to be compared with respect to economy, technique, maintenance, running cost etc. It depends on the skill of the engineer to find an optimal lay-out. In the following a brief guideline and a few examples will be given. 4-1.1 SYSTEMOF THE WATERSUPPLY The available water has to be compared with the actual water consumption as well as with the expected water consumption in future. The balances of water have to be determined in the water budget. In accordance to the balance oE water the water source to supply the village is chosen. The system of the water scheme is decided accordingly with regard to the simpiest, clearest and most appropriate lay-out. Special attention has to be given to a simple maintenance as described below. 4-1.1.1 Spring water by gravity In this case the 'spring water' will be caught inside the ground (see chapter 4-3.4). Preference is always given to this system because it is requires little the simplest : It supplies water of best quality, maintenance, keeps running cost low and gives greatest safety. That's why it is applied no matter whether the spring is situated in a far distance or not and accordingly the cost of construction may even be higher than the cost of a water supply from a nearby stream (incl. treatment station). In case the available spring water is sufficient only to supply part of the required quantity of water for stage 1 of the project, water will still be supplied from this spring in a first phase. During the dry to drinking and cooking season the water consumption may be restricted purposes only and washing may still have to be done in a nearby stream. 4-1.1.2 Stream water by gravity Preference will be given to an open stream which can supply water by gravity in case there is no spring available higher than the village. Its advantages are almost the same as 4-1.1.1 . But a treatment station cansisting of sedimentation basins and slow sand filters is usually required. 4-1.1.3 Spring below the consumers 5 In case there is no way to supply water by gravity is situated on the top of a hill) preference will which can supply water of good quality. a) Water situated is collected I (e.g. if the village be given to a spring from the source by the consumer In or'der to ensure good quality of water and some storage a water point (see chapter 4-4) is constructed. facility (see chapter b) are different possibilities to natural driving energy (e.g. turbine or wind etc.). There 4-1.1.4 mly of ground 4-9) to do this. Preference will be given water power: hydraulic ram, water water Underground water is usually of good quality if the covering stratum is waterproof. The catchment consists of a well construction (see chapter 4-2). Except of an artesian well the ground water has to be lifted before it can be consumed. In remote areas the ground water is usually lifted either by a bucket on a chain or by a handpump, but only to the surface from where it is carried to the houses. 4-1.1.5 Stream situated In case of above, this maintenance should only technically 4-l .I. 6 Pain below the consumers failing to get water supplied from a source as described But this system requires skilled system may be applied. and the running cost will be high. That's why this system be applied in areas where the maintenance is assured and financially. water storage In areas where no springs , streams and no ground water are existing rain water may be stored to supply drinking-water. The storage capacity has to be calculated according to a maximum length of the dry season. Tile minimal water consumption for drinking and cooking use only (no washing, per person and bathing etc.) should be calculated with 10 - 15 liters day. In tropical climate the rain water whould be stored in covered cisterns (without any light) and it should be kept as cool as possible. The rain water stored for a long period needs to be treated before consumption Such a system consists usually (preferably by small slow sand filters). ot the waterproof catchment area, the seasonal storage tank, the small treatment station and a little storage tank for the daily consumption. 4-1.2 TEMPORALLAY-OUT IN STAGES After the system of the water supply has been decided upon, the engineer has to consider which stage the various elements of the system have to be designed for. He has to consider the actual project cost, the running cost, the expected increase of the population, their financial situation, the facility of extension and the durability ('service life') of the various elements. 50 4-1.2.1 Service-_life Etvery element of a water supply can be used in good working order during a certain duration of time only. This period is called the 'service life' of this element. The following list shows the service life of different elements water supply. These declarations are experience-data of solidly elements under skilled maintenance: expected Element spring- and stream catchment storage tank, treatment station buildings (in concrete or masonry) installations under ground pipes pumps, engines 4-1.2.2 of a rural constructed 1 ife service 30 - 50 years over 10 over 10 - 50 20 50 20 years years years years Design in stages first At the different stages are defined: Stage 0: Actual stage -, present population as base of the calculations for the future development. Stage I: This is the moment when the village has the double population (2 x the actual population). This is equal to a yearly increase in population of 3%, within 24 years. Also the future development of industries, markets, cattle-ranges, roads, colleges, hospitals, etc. A co-n village in has to be taken into consideration. the rural area of the U.R.C. will reach stage I within 20 - 25 years. In a very fast growing village, a regional centre with functions of a rural centre, stage I may be reached within 15 years. Stage II: A water supply designed for stage II is able to provide water to a population four times the actual population. This moment will be reached within 30 - 50 years. Compare with 'specific consumption', chapter 3-2. The different elements of a water supply for a village are usually designed for the following stages: in the rural area Element Stage I Stage 0 Stage II Catchment intake inetallatione X X x X X PLping eystein main pLpee d&rtribution X x pipee Starage tank, treatment buildings inetallatlons pmpsr engines x station x x X El X with extension facility 4-1.3 EXAMPLES Before the single elements can be designed, a clear lay-out of the whole should water supply has to be worked out. This base for the calculations be included in the technical report. Example ,& Short description of the water supply: A rich spring situated above the village. Actual population 2'000 persons. Expected water consumption: Stage 0: Stage I: Stage II: 2'000 persons at 30 l/day 4'000 persons at 60 l/day 8'000 persons at 80 l/day = 60 m3/day = 240 m3/day = 640 m3/day to,7 l/s) (2,8 l/s) (7,4 l/s) Water balance: The yield of the spring is over 800 m3/day at the end of the dry season. This is enough to cover the whole consumption of the stage II. Lay-out of the water supply 1 Spring catchment with inspection designed for stage II. 2 Pipe line calculated (q=7,4 l/s). for chamber stage II 3 Interruption chamber. After stage I a storage tank has to be constructed at this site. 4 Main pipe. Calculated for stage I without storage tanks and for stage II with two storage tanks (q=lO l/s). 5 For stage II an additional is required. 6 Distribution pipe, storage calculated for tank stage I. 7 Any likely extension would have to be included into the calculations. I Example 2 Short description of the water supply: A spring situated above the village. Actual population 800 persons. Expected water consumption: Stage 0: Stage I: Stage II: 800 persons at 25 l/day 1'600 persons at 50 l/day 3'200 persons at 70 l/day 52 = = = 20 m3/day 80 m3/day 224 m3/day (O,2 l/s) (0,9 l/s) (2,6 l/s) Water balance: The and dry the Lay-out yield of the spring is 50 m3/day at the end of the dry season about 140 m3/day at the peak of the rainy season. During the season in stage I the consumption has to be limited. For stage II yield of this spring is not sufficient. of the water supply: 1 Spring catchment with designed for stage I. inspection 2 Transport pipe designed (q=O,9 l/s). chamber for stage I 3 Storage tank calculated for (capacity about 40 m3). stage I for the peak4 Supply pipe, calculated consumption of stage I (q = 3 l/s). Example 3 Short description of the water supply: No spring available, the stream is below the village. Actual population 1'400 persons. Expected water consumption: Stage 0: Stage I: Stage II: (* = reduced 1'400 2'800 5'600 due persons at 25 l/day persons at 40 l/day* persons at 50 l/day* to high running cost) = 35 m3/day = 112 m3/day = 280 m3/day l/s) (1,3 l/s) to,4 (3,2 l/s) Water balance: The stream yields during the dry season at least the consumption of stage II can be covered. Lay-out 15 l/s. Therefore of the water supply .. 1 Stream catchment with a short-timesedimentation. dam and intake for stage II for stage I sedimentation TER After stage I this is the proposed for a pumping station. site 2 Driving pipe and hydro ram calculated for stage I. The driving water is not sufficient for stage II. Therefore after stage I the hydro ram has to be replaced by a pumping station at site 1. 3 Pressure pipe, (q = 1,3 l/s). 53 calculated for stage I 4 Treatment station: Sedimentation and slow sand filters for stage I (q = 1,3 l/s) with extension facilities. Storage tank for stage I (capacity about 60 m3). 5 After stage I an additional 6 Main supply pipe, 7 Distribution 4-1.4 pipe, calculated calculated storage for designed tank is required. stage II. for stage I. MATERIALS AND CONSTRUCTIONMETHODS The materials and construction methods have to be chosen according to local availability and to the skill of local workmen (e.g. stony area but no gravel-c stone masonry, unamployment *labour intensive method etc) . The skill of local workmen has to be developped in such a way that all constructions are done in best quality in order to increase their lifetime. Much attention has to be paid to the possible aggressivity of water in choosing the piping material as well as in designing the watertight coat in tanks etc. (see chapter 2-3 and 2-4) 54 4-2 WELLS 4-2.1 GENERAL Wells make it possible to use the underground applications (e.g. water supplies, irrigation). water The quality depends on: of the water obtained from a well for economical - The thickness of the stratum which covers the water-bearing soil. This is important because of indirect contaminations for example by latrines, fertilizers etc. - The porosity process. Fig. of the subsoil which influences the natural filtration 23 The quantity vatmahod Point a I suriaa Point b I subtrrrumaa ntwahad of water obtainable from a well depends on: - The intake area: It is important to realize that the topographical does not necessarily correspond with the geological or hydrological drainage area. (see Fig. 23) - The annual rainfall percolation: this (forest, area, e.g. kind of vegetation - The perviousness of the ground: this stratification and its homogeneity. - The storage capability of the ground: as perviousness and intake area. - Type of well: its diameter and depth. 55 depends on the nature farm, bush) basin of the intake depends on the kind of material this depends on the same factors 4-2.2 Fig. TYPES OF WELLS 24 m Pelw4bla lzzil a) otrrt4 4b4llowwell deepwall 01 artaaiianwrll a- b - fipprrumablr rtmta Shallow well The shallow well draws its water from the permeable strata between surface and soil. The storage possibility in this upper permeable strata is very limited and consequently the capacity of such a well is unreliable and probably intermittent. The well is supplied by surface water which is liable to pollution (no natural filtration). A shallow well should be lined with impervious material to within a few meters of the bottom. b) Deep well The supply is-derived from strata unaffected by surface impurities. There is at least one impervious stratum between the water-bearing stratum and the surface water (natural filtration). It is however possible for surface water from the upper strata to gain access to the well through cracks and joints in the impervious stratum. Compared to a shallow well the yield of a deep well will be much more dependable. The yield will be greatest when the well has just been opened. If the water has to pass through a porous stratum before it reaches the well the pores tend to become choked in time and the flow is considerably reduced. This does not occur with limestone or volcanic stone as the water finds its way through cracks and fissures and gradually dissolves the rocks so that the voids are increas,d. cl Artesian well These have similar characteristics to deep wel.ls, the essential difference being that the underground water is tapped under pressure and may rise to the surface of the ground under its own head. well is rarely found in Cameroon. 56 I’,p; i l’ 4-2.3 1 SITE OF' WELL It is not always easy to determine the site of a well. Only test but in general in large plane boreholes could give certain information, areas or near the sea shore, the river or lake,we can be sure to reach a water table within a certain limit. / Choosing d good well site is one of the most important The site should be also placed in a well construction. avoiding the vicinity of overhanging trees. Fig. 25 Siting to prevent poilution a = bad site for b = suitable site C = latrine d = flow direction The site of a well of pollution. phases in well drained ground, shallow for well shallow well should be upstream of any possible source CONSTRUCTIONWETHODS 4-2.4.1 Traditional This well consist of a hole with a diameter of 00 to 120 cm. The life of such wells is short because there is no protection of the walls and the surface around the wells. 4-2.4.2 Dug wells These wells are protected during construction by consolidating the surface. After a certain depth is reached the walls will be secured either by cpnccete or masonry before digging deeper. A dug well is usually constructed with a diameter can be dug to depths of about 60 to 80 m. The site should be carefully chosen. any possible source of contamination. should be avoided if possible. from 90 to 300cm. It It should be at a good distance from Areas known to contain rock layers It has been found that the cost of a lined well varies in proportion to its diameter. The minimum diameter is limited by the room available for one or several men to work in. A diameter of about 90 to 100 cm is necessary for one man and 120 to 130 cm for tw men. It has also been found that the efficiency of two diggers working togethor is more than twice that of a single man, we can then say that a diameter of 120 to 13Ocm is a convenient standard size. With the exception permanent material it is a protection after completion. construction thus of collapse which concrete is usually af wells sunk into consolidated rock, a lining of is always necessary. This lining serves several purposesr it retains the walls against caving in and collapses, It is better to build a permanent lining already during avoiding the expense of temporary supports and the danger may occur when the temporary lining is removed. Reinforced employed for the lining. In normal ground the shaft is sunk from ground level to the top of the water level by the method known as "alternate sinking and lining". The hole is excavated and trimmed to a diameter of 120 to 130cm and depth depending upon soil conditions. The excavation can be done as deep as it is possible without endangering the workers in the well. In any case the first meter dug should be secured properly before the digging continuesi This met$od is applied until the water level is reached. From this depth onward! -.he -caisson ring method is adopted, The caissons have to be precast on the sl*rEcrce. Thr? are caissons should have a height of no more than 50cm. These caisson-rings lowered singly into the lined well and each one is fastened to the ring below The depth to which the caisson-rings can be lowered depends on the depth of water which can be removed by bailing. (see Fig. 26) 58 Fig. 26 hrkinq method for a dug- w&J 1. Digging as deep as possible, according the soil conditions 3 2 2. Concrete lining 3. Digging as deep as possible or until the water-level is reached water-pi --L-L- 4. Concrete lining 5. Lowering of caisson digging continuously 6 5 to ring, 6. Lowering of caisson rings digging as deep as possible into the water. This job has to be carriet out during the driest period of the year when the water table is at its lowest point. b) Precautions The following accidents. during points Most of the accidents collapse of walls lined properly the construction are very important. in a well which are not Nobody should work alone in a well. In case of an accident the workman on top should organize aid. If possible the workman who works inaide the well rhauld be secured with a They should help to prevent are caused by: Falling into the well. Sudden collapse of water1 danger of drowning --I Before entering the well, make sure that there is no accumulation of sulfuric or carbonic gas. Introduce a lit lamp (kerosene) into the well. If the flame dies it means that there is gas and danger. This gas can be removed either by sending air down into the well with a compressor or by using a bunch of grass or paper tied to a rope as a fan by twisting it energetically. Never place a combustion engine inside or near a well as the carbonic exhaust gas being heavier than air will fill the well and endanger the workers. It is always advisable to construct a protection at ground level all around the well in order to prevent accidents. 60 - Porous STRATUM The superstructure or sealing of a well must bc done wry carefully. It is ilt@Xtant to look for a good drainage for excess water; furtht?rrn(Jr':, the well should always be completely sealed except for a man hole. If possible a hand pump should be installed to avoid conta~~~inatiorl ~.jt tttv water with buckets (see chapter 4-9). Fig. 27 HAND PUMP WASTE In case water should be lifted with bucket an pulley, a margelle must be built at 70 - 90 cm above ground level. A cement apron around it will keep the place free of stagnant water. WATER MARGELLE 4 61 AQUIFERE ZONE AT LEAST 2m DEEP link 4-2,4,3 wells These wells consist of prefabricated rings which sink through their own weight ,a8 soon as digging is done. This system cannot be applied in all types of ground. But it is very good for homogeneous ground (e.g. sand). WORKING ORDER , 1 CONCREtE RING (WATERTIGHT) WATER TABLE CONCRETE RING (POROUS) :r V SINK WELL IRON CUTTlhG EDGE 4-2.4.4 Sinking a tube well In areas where the subsoil is sandy and the water table situated between 5 to 20 m deep, there is a good possibility to sink a well without using a drilling machine nor any other machine. All that is needed are a few bamboo or other wooden poles, several lengths of rope, sufficient water to fill the pipe, an iron beak (with a small hole on the side), a plastic filter of 1,20 to 2,00 m and the necessary tools and fittings for joining the pipes together. of three men is sufficient for sinking 5 cm diameter and 15 m depth. Bigger diameter more people. A team 62 a tube well and greater of a size up to depth require ' Procedure of sinking: the site of the well is chosen, dig the soil about 30 cm deep in a diameter of 2,00 meters; moisten the hole with water, install a small scafolding and tie a pipeetjuippedwith an iron beak at the bottom up and (see Fig. 28a). Move the lever in order to have a perpendicular down movement. The pipe will sink with these movements provided it is filled with water. Once the next pipe element is screwed to the first The sinking continues; and so on, until it reaches the water table (see Fig. 28b and 28~). one If pressure water is available and can be fixed directly to the top of The structure of the the pipe, the sinking can be done much faster. subsoil is the main factor for sinking a well. If rock or other hard soil is found a new site for the well has to be chosen. As soon as the pipe has reached the water table it is necessary to remove it entirely by lifting it carefully (see Fig. 28d). (note that the hole created is about 15 to 25 cm diameter) . This operation is needed to allow the filter to be placed at the head of the pipe instead of the iron &dk. The tube well is sunk. Fine gravel or coarse sand should be placed into the space between the tube and the soil. A hang pump or motor pump can now be installed. A shallow pump (with the plunger situated above the ground) will be able to lift water from a depth of 6,50 meter maximum. For depth greater than 6,50 m a deep well pump has to be chosen and the diameter of the suction pipe must be big enough to allow the plunger cylinder to enter it. Fig. 28a Fig. 63 28b Fig. 28 c 28 Fig. d 28 e 1 --- --- - x c- __--- - -- - - -- -- -- - . -- low& w&r table - - -m-w--- 64 . 4-3 SPRING CATCHMENT General description 4-3.1 of springs: See chapter 2-1.2 'Springs'. QUALITY AND QUANTITY OF SPRING WATER The quality continuously of spring-water depends on factors flowing spring: similar to those in a - The thickness of the stratum which covers the water-bearing soil: is important to prevent indirect contamination (e.g. from latrines, fertilizer). - The perviousness - The storage capability influences the water velocity. If the water velocity in the saturated stratum gets too high, the pores through which the water passes tend to become choked so that the flow becomes considerably reduced, This does not occur in limestone or in volcanic rock. influences the natural As continuous flow and quality take the relation between of a spring spring capacity in the rainy spring capacity in the dry season as a criterion for filtration this process. depend on the same factors, we season the quality = and quantity 3- 5 for good springs which is available. There is a time interval between maximum/minimum rainfall and maximum/minimum yield of a spring. This means that the lowest yield should not be expected at the end of the dry season but 2 to 4 months later. The springs intended to feed a water supply should be gauged before starts for at least one year but better over a longer period. constructio The water temperature may also give some information about the quality of the spring: E.g. in the grass land zone of Cameroon an underground source of good quality shows a temperature of 18oC (if it is not in a volcanic area). Especially the way the water-temperature changes during a day informs about the quality of the spring. Spring water of good quality will show constant temperature. A special problem in the grassland: Raffia bushes cause the growing of ferric bacteria in supplying carbon hydrates. In connection with air the ferric bacteria develop rapidly and cause a coloration (red) and an unpleasant taste although the water is still harmless to human beings. In order to avoid this occurance, springs should always be caught above raffia bushes. 65 4-3.2 LOCATION OF SPRINGS We distinguish three Grass-land - zones: Forest springs In grass-lands, inside raffia bushes. - Volcanic are mainly areas found in valleys and along streams In forest areas, springs usually appear at the bottom of valleys, but it is difficult to locate them because rich vegetation covers everything. In volcanic areas, springs can suddenly appear and disappear almost anywhere, especially during and after eruption or earthquakes. Geological springs normally - Where the impermeable - Where two different - Where topsoil Tracing appear stratum reaches kinds of subsoil the surface meet meets rock of springs: Villagers and hunters, who know the area, may be most able to give information about the possible water sources. In addition it is often necessary to follow all streams and springs to of construction of a discover the rising points, where the possibility spring catchment has to be investigated. Sometimes it may be essential to measure the change of the water quantity along the stream in order to discover possible underground side drains. Most important is to investigate on the area above the rising point of the spring, because it may happen that an open stream sinks into the ground above the rising point and passes underground before reappearing on the surface as a spring. That is why it is also necessary to gauge should the yield of the spring over the whole year. Special attention be given to the yield of the spring and the colour ot the water after heavy rains. If abrupt increase of flow or change of colour or temperature it is, proved that short connection to the of the water is discovered, surface does exist and that accordingly the spring is certainly not of reliable quality. 66 4-3.3 CATCHMENTAREA The catchment area includes catchment and may drain into protective zone. The radius depends on the depth of the covering stratum. The radius spring catchment is and the at least 50 m. the area which is situated above the as it. This area has to be established of the protective zone from the catchment spring catchment and the nature of the should be the bigger the shallower the more permeable the covering stratum is, but no fish Within this area strictly no farming, no domestic animal grazing, no rubbish pits (oil), no stables or houses, etc. are allowed. ponds, Existing streams and drains situated in the catchment area have to be made water-tight. In case of danger that surface water may enter the spring catchment or may cause erosion, it has to be drained off. To have a good control over the protective area it is advisable to plant grass within a radius of 10 m and keep it cut short. Outside of this radius the protective area should be afforested. Attention has to be given to the fact that some trees like Eucalyptus suck much water and are, therefore, not useful in this zone. Suitable trees are for instance Cypress or Pine trees. It is also advisable to fence the area with barbed wire. In areas with long dry seasons attention has to be given to protect the afforested area from bushfires. In an extended protective area (water intake area above the spring: Radius 100 to 200m) there should be no petrol-stations or workshops where waste mineral oil or petrol are thrown away. Also no fertilizer should be used within this area. It is advisable to afforest the extended protective area too. 4-3.4 4-3.4.1 SPRING CATCHMHNT General A spring catchment has to be constructed depends on the topographical situation, the type of source. in a simple and practical way. It the structure of the ground and No attempt should be made to change the spring's natural flow rate. If there is any obstruction the spring can get dirty or the water will try to find another route. The installation water pollution has to be carefully built to avoid the possibility by accident or negligence or even on purpose. of The depth and the construction of the catchment depend on geological and hygienic consideration as well as on material covering the water-bearing soil. The spring catchment should be covered at least by 3 m. If it is not it is necessary to make special protective possible to cover it properly, arrangements. If possible the catchment should be built right up to the impermeable strata. Blasting near springs should be avoided. The free flow of the water must be guaranteed during the construction. 67 There are three main parts catchment in a spring catchment: pipes or a channel - The actual (perforated - The supply pipe to the inspection - The inspection chamber (not to be confused The inspection chamber has two parts: with Spring catchnent ORAIM - Lau-out FOR SUlFhCE WATER MAllUS FOR CATCNMENT OIRECTION MAIN - 8OUNDARY MARUS FOR FOR .uJRFRCE WATER PROTECTIVE ZONE rr1 r ORAIM PIPE(IF NECESSAIIY) SUPPLY kk - PlPE .-I 68 the storage tank) installation The purpose of the inspection chamber is to control quality (sometimes by sedimentation). 29 with dry walls) chamber an entrance basin for the water and an operation chamber for the appropriate Fig. built -- water quantity and 4-3.4.2 The actual catchment It is important to construct the catchment most carefully because it is the heart of the water supply. In case of failure to do so, it may cause a total breakdown of the entire water supply. Moreover the catchment will not be accessible after backfilling. Much experience is required and to design and construct to interpret the flow of the source underground the catchment accordingly. a) Excavation Normally the digging on the source is started comes out of the ground. While following the ground a drain has always to be kept open to is required to avoid any increase of pressure ground and hereby forcing it to find another controlled anymore. Moreover, this provision have a clear picture of the direction of the The few following on the point where the water flow of the source into the ensure a free flow off. This of the source inside the way out which may not be will enable the technician to flow of the source. examples are given as a guideline: Example 1: The amount of water coming out at the mouth of the trench decreases digging. Therefore, water is entering on one or both sides along the In this case the trench has to be split up in a V or T shape to the sides as soon as the cover on the mouth of the trench is big enough. way the bypassing water may be caught behind the dam with sufficient with trench. two In this cover. Example 2: Spring water is coming up from the ground. The drain has to be dug down till the horizontal layer is discovered out of which the water is originating. In case the cover is insufficient the excavation has to follow the source level till the cover becomes sufficient (at least 3m). 3m Example 3: In case the drain cannot be dug as deep as the horizontal layer the construction has to be done like for an artesian well. Example 4: Much care has to be taken during excavation not to cut through the impermeable layer on which the source is running. Otherwise the source water may penetrate into the permeable stratum below. Therefore the foundation of the dam has to be cast into the excavation directly against the ground, before the dam is built in masonry or concrete. ’ . ‘, I . . . . ; Example 5: The distance between the catchment to be sure that no roots can enter and any tl ? should be the catchment. large enough b) Building Once the excavation is completed the building work can be started. There are two parts: A permeable construction into which the water enters and a barrage which has to avoid the bypassing of water. - The permeable construction consists usually of a drain in dry stone masonry or perforated pipes. The cross section of this catchment drain should be sufficiently large to ensure the maximum out-flow without any obstruction to the natural spring flow. The drain has to be sloped 1 to 2%. In case of firm ground no flooring is done. But in case of sandy ground a dry pavement has to be foreseen. The speed of water should be limited by providing additional catchment drains, because the speed increases the drag force of the water. Around the drains a filter will be built with gravel. The minimum diameter of the gravel has to be in relation to the holes of the perforated pipes or the spaces in the dry wall. To avoid any contamination never walk on this gravel. A water tight cover of 5 to 1Ocm concrete has to be placed on the top of the drains and the gravel. This cover needs to be extended on all sides 20cm into the walls. Syrface water reaching this cover needs to be drained off. - A“, I' The barrage is constructed on the opposite side of the point where the water is entering into the catchment. It guides the water to enter the supply pipe "leading to the inspection chamber. The barrage has to be built into the impermeable stratum as well as into both side walls to prevent the water fro1 byjas'sing. The foundation of the barrage (dam) is cast into the excavation directly against the ground in order to get a tight connection to the ground The barrage is constructed on top of the foundation, either in concrete or stone masonry. The height water-tight Compare with Fig. 30 Spring cover which figures of the darn should only be to the height is on top of the drainage. 30 and 31 catchment in line 4 IMPERMEABLE STRATA WATER- BEARING SOIL COVER OF WATER BEARING BED PLATE l-2 x DRY WALL SLABS PERFORATED PIPE of the 5 6 SOIL 6 9 10 11 12 13 14 GRAVEL WATER-TIGHT COVER DAM PERMEABLE MATERIAL IMPERMEABLE BACKFILLING SUPPLY PIPE 2 x DRAIN FOR SURFACE WATER PLAN CROSS- SECTION CROSS - SECTION TYPE 2 TYPE 1 11 9 6 , ,’ Fig. 31 Spriklg SECTIONAL ELEVATION ------v- ca tchtnent __ in shape of a T -I_-- --- -I_-- -- 5 1 2 3 4 5 6 7 IMPERMEABLE STRATA WATER- BEARING SOIL COVER OF WATER-BEARING BED PLATE (l-2 X J DRY WALL SLABS PERFORATED PIPES 8 9 10 11 12 13 14 SOIL - - -’ 6 9 11 12 GRAVEL WATERTIGHT COVER DAM PERMEABLE MATERIAL IMPERMEABLE BACKFILLING SUPPLY PlPEs(2 L) DRAIN FOR SURFACE WATER 5 CROSS-SECTION 8 10 CROSS-SECTION COLLECTION CHAMBER 14 72 - - -.- 4-3.4.3 Supply pipe to the inspection chamber The piping material has to be resistant to aggressive water. The pipe should slope at least 2%. The diameter of the pipe has to be according to the maximum yield of the source, but at least 8Onun. It is advisable to install one additional pipe in reserve. This extra pipe should be installed a bit higher than the first one, so that the carctaker knows when the first pipe is not working that a failure has occured which he has to follow up. The installation of an extra pipe is necessary because once the catchment is blocked,' the source will build up pressure behind the catchmcnt and force another outlet. This may cause an unrepairable failure because the source may disappear completely. 4-3.4.4 Inspection chamber Every catchment should be equipped with an inspection chamber to allow easy access to the spring. The chamber should not be too small to ensurs sufficient room for all the installation works. It may be necessary to calculate the inspection chamber as a small sedimentation chamber with a retention time of 10 minutes. The building has to be water-tight inside and outside. Corners and edges have to be rounded. Each chamber should be ventilated, if Possible in or an entrance. Ventilators and manholes combination with a drain-pipe should not be directly above the water , they should rather be placed in the operation room. Entrances or manholes should be 50 cm above groundlevel with door-steps at 25 cm. Manhole covers should be locked to prevent unauthorized Persons from opening them. It is advisable to cover entrance) and all openings (incl. overflow and doors) the chamber (incl. so as to prevent any Possibility of Pollution and the entering of small animals into the chamber. Each spring cat&sent needs its own entrance basin, from where the water flows into a collection basin. If necessary it should be Possible to cut off a single spring from the supply. The inlet must be 20 cm above the highest Possible water level.It is imPortaM that each basin can be drained.Thereshould be no obstruction to the water flow caused by placing the inspection chamber too high in relation to the spring. The dimensions of overflows the maximum spring capacity and drains have to be capable of draining without restricting spring flow. off Note: For hygienic reasons, it is important that timber is not used as a building material and that no timber is left in the catchment or inspection chamber (the timber gets rotten and will become a breeding place for insects). Stone masonry and concrete seem to be the most suitable and long-lasting in stone masonry may building materials for spring catchments. Buildings require an outside plastering ,:u,?t in a swampy area. The chemical behaviour of the water and the ground influences the building material (see chapters 2-3 and 2-4). See figures 32 and 33 73 Inspection ch+mber 6 =+==- ‘f _' I'I',, WATERPRODF PLASKRING INTERNAL AND EXTERNAL 1 Pipe from the spring catchment 2 Baffle plate 3 Overflow pipe 4 Overflow edge 5 Cleaning pipe 6 Supply pipe to consumer 7 Drain pipe 8 Ventilation (with wire net) 9 Aeration pipe 10 Climbing iron 11 Strainer 12 Main valve 13 Entrance (Min 60 x 70 cm) 74 Fig. 33 Inspection and collection chamber (Incl. connection of an upper catchment which has dlready ~II inspection chamber. An additional overflow may be foreseen in the entrance in case of much overflow expected from lower source in order to get sufficient retention time in the entrance basin.) ,/--- /.,’ /I . I,I‘. ENTRANCE ( min.Wx70cm) - FROM LOWER VENTILATION (WITH WIRE NET ) /’ .’ /’ ,’ ,I’ /’ SUPPLY PIPE TO U3NSUMER ,/’ t 2 2 1 CREST- WEIR I I II ,’ /7lt L =-====L DRAIN PIPE 8 9- J FROM UPfJER SPRING CATCHMENT I .’ .’ / ,,” ‘, /,/ ‘,‘,, 1 ,-VENTIATION DRAIN PIPE 1 2 3 4 5 6 cleaning pipe entrance basin cleaning pipe collection basin main valve ball-valve for upper source overflow entrance basin averflow collection basin 7 8 9 10 baffle plate strainer climbing iron aeration pipe x = operating ball-valve height of the + 30 cm 4-3.4.5 Outlet The outlet inspection Fig. 34 buildings building has to prevent chamber. animals the Simple outlet -II?&, FAVMNT Fig. to enter 35 Siphon outlet 76 a-- WI- WlT+l Bb- -- -- ’ II Commonmistakes 4-3.4.6 Fig. on spring catchments 36 b a) permeable cover b) leakage from pipe joints cl covering d) no surface e) chamber cover should be above ground level f) position of overflow g) position of oulet h) no wire-mesh over the spring surface is inadequate water can pollute the spring water water drainage too high too high covering 1 J the overflow 77 t obstruction animals pollute to spring flow or dirt can the spring water 4.4 WATERPOINT 4-4.1 GENERAL Water points can be built anywhere if there is a small spring with a supply of minimum one l/min. during the dry season and the possibility to get at least 1 m difference in height from the catchment to the drainage of the storage chamber. The construction of a water point - improvement of the quality - hcxage of water during gives two main advantages: of the water the night for use in the day-time If the spring supplies more than 15 l/min. in the dry season there is no need for a storage chamber. A wash-basin into which the water enters directly from the catchment can be built instead. If the spring delivers less than 3 l/min. during part of the year only a storage tank should be built, since a basin would never be filled, not even during the night. 4-4.2 CONSTRUCTIONOF A WATERPOIWT normally consists of a storage chamber and a washThe water point itself basin. Attention has to be given to provide a good foundation, especially in swampy areas and on hill sides. A proper drainage for 311 overflowing and used wash water has to be installed. The design ,hould be such that all water runs to a certain pint, from where a drainage trench with a good'slope will lead it quickly to a nearby natural gutter. A storage tank should be built if the spring gives less than 15 l/min. in the dry season. Usually a wash-basin is connected to the storage tank if the spring flow is above 3 l/min. minimum, below 3 l/min. minimum. The water should be limited for drinking purposes only. See figures 37 and 38. Fig. 37 Small water point = EFFECTIVE STORPGE VOLUME (INTO WASH BASIN 1 PIPE Fig. 38 Large water point = EFFECTIVE STORAGE VOLUME SPRING I, CATCHMENT SUPPLYPIPE . .STORAGE TANK1 DISTRIBUTIONPIPE 79 . , WASH BASIN #. BARRAGEAND RIVER INTAKE 4-5 In the construction of a barrage its size, height and foundations determined by the stream, its bed and its embankments. are For our purposes the barrage does not retain water for storage and later but is only built to assure consumption (dry season, weekly variations), the supply. It should be perpendicular to the streambed. Special attention is needed for the foundation to guard against: - 4-5.1 seepage washouts, leakages extensions of the wing-walls erosion of the river bed DETERMININGMAGNITUDESFOR THE POSITION OF THE BARRAGE above consumer above populated areas (if necessary resettlement before the construction work starts) above farming areas, if not possible farming m,ust be stopped along the stream no cutting of trees in the catchment area, afforestation at least 100 m to each side of the stream and on a length of 500 m to 1000 m no watering place for cattle above the barrage no laundry and no washing of cars above the barrage good soil-bearing capacity perpendicular to the stream bed narrow stream bed which allows high speed to avoid standing water behind the barrage and settlement in stream bends the intake should always be at the outside of the bend a) b) cl d) 4 f) 9) i-4 i) k) = low speed V2 = high deposits of sand, dirt, leaves etc. no or little settlements Vl speed 4-5.2 DESIGN OF BARRAGES The cross section of the barrage must be constructed in a way that the overflowing water never separates from the barrage-surface because tklis would cause heavy erosion on the foot of the barrage. (see Fig. 33 and 40) The overflow area (Ab,) has to be equal by high water or it will be calculated Any standing water behind water before the barrage, be as high as possible. Fig. 39 Cross section to the river cross section from the flow measurements. the barrage must be avoided. The speed of the in the spillway and along the sidegate should of a construction in concrete IMPERMEABLE Fig. 40 Cross section (Ar) of a construction STRATUM in stone masonry RMCABLE STRATUM 81 4-5.3 DESIGN OF INTAKES The most suitable type of intake under these conditions are sidegates, the entrance velocity Ventrance should bee 0.1 m/set, using a spillway as a cleaner and regulator. The current along the gate helps to wash away leaves, sticks and sand. The bottom of the spillway should be low enough to allow dry season water to flow past the bottom of the intake. It is useful to keep the deviation pipes which are used during construction so as to permit maintenance and repairs by lowering the water. The gate with the strainer which must be removable should be at least 5 cm, better more, below the low water-level (LWL) . The gate should have a minimum height of 8 cm. (see Fig. 41) Fig. 41 Intake Construction lntdke chamber -.AB - SpillWdY w 3 GROUNOPLAN ---em-- SECTION A -A HWL . High LifL - Low water Udter sedimentation level level cleaning pipe SECTION B - B intake chamber retaining or 82 stone wall 4-6 WATERTREATMENT 4-6.1 GENERAL It is obvious that rural water supplies should be designed to safeguard the quality of the natural water selected. It should always be the policy of a responsible engineer to restrict the use of water treatment under rural conditions to only those cases where such treatment is absolutely essential and where correct plant operation and maintenance can be secured and supervised. The design engineer should also vigorously oppose the use to of treatment processes which the community concerned can ill-afford procure, operate and maintain with meagre financial resources. This explains in part why a careful study, based on engineering and economic analysis may have to be made to compare, in doubtful situations, the relative merits of water treatment against those of long pipelines bringing untreated water from distant springs, wells, etc. Experience shows that whenever possible it is wise to make a large investment in order to eliminate operational and maintenance problems. for Rural Areas and Small Communities" WHO) (partly from "Water Supplies all the water supplies constructed in the Technical Section Furthermore, of CD/SATA-Helvetas apply to the WHOStandards of untreated water (see this water quality as sufficient for any rural chapter 2-2). We consider water supply. In a future step chlorination can be introduced easily. Treatment calculated 4-6.2 4-6.2.1 stations (sedimentation and slow sand filters) for con:inuous fl% over 24 hours in stage I are normally (see 4-l.:'). SEDIMENTATION General Definition: than water definition Sedimentation by gravitation is the removal settling. of suspended particles heavier In the rainy season the erosion of the land by run-off Natural existence: from rain-storms carries vast amounts of soil into streams and other watercourses. Some of the eroded particles are heavy enough to settle when flood often to be picked up again and be redeposited further waters subside, downstream during successive floods until eventually reaching the ocean. Influence on water supplies: such suspended particles prevent water supplies from working continuously because they block pipes and filters, reduce the capacity of storage tanks and the water quality. Therefore, these particles have to be removed immediately after the catchment. Methods of sedimentation: The undesired in a special - Plain fluid suspended particles are removed from raw water tank. There are three kinds of sedimentation: sedimentation: by gravitation by ser.iimentation The impurities are separated from the suspending and natural aggregation of the particles. 83 - Coagulation: aggregation substances - Chemical impurities ------------I Chemical substances are added to induce and settling of finely suspended matter, and large molecules. or hasten colloidal precipitation: Chemicals are added to precipitate out of solution by changing them into insoluble dissolved substances. Plain sedimentation would be used where water contains much suspended matter and particularly in warm climates, where higher temperatures lower the viscosity of the water permitting thus more effective sedimentation. The plain sedimentation requires less and simpler maintenance than the other methods of sedimentation. Therefore, only this method is employed by CD/SATA-Helvetas for rural water supplies in Cameroon. All the following 4-6.2.2 Design remarks refer of sedimentation to plain tanks Sedimentation tanks are designed so as to permit suspended solids The raw water (of rivers) sedimentation. to reduce to settle contains the velocity of the water flow out of the water by gravity. impurities of three - Particles large enough to be strained settle gravitationally in still water - Particles of microscopic or colloided form which still water and are too small to be strained out required to remove these substances) - Substances held completely can be removed by chemical a) Factors affecting settling velocity -----I! - drag force - concentration wall effect) ---F-I---1 of suspended or which will not (filtration dissolved kinds: will settle is in in the water efficiency: 7 - out of the water (sedimentation) in solution, i.e. treatment only. sedimentation physical solids 84 mass density of suspended particle shape density of suspended particle mass density of the fluid viscosity of the fluid shape of suspended particle velocity of the fluid viscosity of the fluid mass density of the fluid in the fluid (settling hindered by The only factor velocity. The is the velocity depends on the sedimentation need less flow top-soils. The efficiency which is altered by plain sedimentation is the fluid smaller the size of the particles removed, the smaller of the fluid. The reduction in flow velocity needed nature of th*: sediment and the required efficiency of (e.g. gritty, granitic or volcanic sediments being heavier, velocity reduction to deposit them than fine lateritic depends also on design: - inlet and outlet prevented; have to be constructed so that short-circni - agitation of settled solids from the sludge zone has to be prevented. Hence certain relations between length and depth are needed, ting is The required efficiency of a sedimentation-basin will depend on the need to prevent blockage of the sand-filters (following). Further details have to be determined by observation and resea:rch on similar existing installations. bl Calculation of the required dimensions The dimensions of a sedimentation load and the period of detention. "Surface SL = In the s, = load" Entity surface reverse quantity surface is the tank settling of water of tank velocity p er h we can calculate of water_eer load can be calculated of the particles m3 m2 x h the necessary h = (quantity of m3 -xh h water per h) surface m3/h m/h x (period in the water: m h =- as follows: m2 zz The capacity or volume of the basin can be calculated of water per hour and the period of detention: v from the --surface with the quantity of detention) =m3 The surface load and the period of detention varies widely because of the kind of material to be retained, the stage of extension considered, and the treatment added after passing the sedimentation (e.g. granitic and volcanic soils bring heavier material than lateritic top-soils so the surface load can be bigger and the period of detention shorter or viceversa). 85 The figures SL = below,should only be taken as an approximate surface Load max. (0.6 m/h is the settling of 0.01 mm) = 0.6 m/h velocity of' a silt = 4 - 6 h of detention value: grain with a diameter t = periode d = depth of tanks 1.50 m - 2.50 m (2.50 should be the maximum) relation between length and depl-h 5:l up to 1O:l The effect of sedimentation varies only the depth of the tank. The smaller the surface load the better with the surface load and not with the sedimentation. Example: quantity of water surface load period of detention relation between length therefore: necessary surface capacity and depth Sn v depth length .c width = 20 m3/h = 0.6 m/h = 4h 5 :l = 20.0 0.6 m3/h m/h = 33.3 m2 ====z==== = 20.0 m3/h x 4 h = 80 m3 --------___------ = 80.0 33.3 m3 m2 = 5x2.40m = 33.3 12.0 m2 m width = 2.70 ____-_--_------___------------- length = 12.00 m ====================== = 2.40 m = 12.0 m = m 2.70 = 2.40 m depth ______---------_------------_-- = 2.40m I LENGTH = .12.00 m I 86 m 4-6.2.3 Construction details Rectangular sedimentation tank s are most commonly used in Cameroon because their construction is easier than that of circular tanks. Therefore, all the following construction details are with reference to rectangular tanks. a) Slope of the tank bottom The cleaning of the sedimentation tank a slope of min. 3%. I., 1 Inlet zone is much easier Outlet if its bottom has zone i i min max = 3% = 8% b) and outlets -Inlets It is importantto achieve uniform flow of the water over the cross-section. A straight inlet creates an equal straight flow to the outlet and a reduction of the activ&capacity so that the efficiency is reduced. Influence of 'water temperature on the operation of the sedimentation tank: -__I The operation of a sedimentation tank can be disturbed greatly by the different temperatures of the inflow and the tank-water. Spring-water has a constant temperature but stream-water temperature varies with sunshine as well as with the change of day and night. Simplified the following pattern appears in the sedimentation tank: night (inflow cold) day inactive therefore: period reduced These disturbances temperature about Well designed temperature. inlets warm) 8 zone of detention shorter efficiency appear already l/l0 (inflow with very little to 2/10 OC between inflow and outlets differences and tank-water. reduce the influences 87 in of the water Fig. 42 Inlet: Variant 1 PREFABRICATEDSLABS Vl (: 1.0 m/s Fig. 43 Inlet: VO s 1.0 m/s A good working V2 -c 0.3 m/s OUTLET UXS Variant 2 Vl e 1.0 m/s inlet V2 c 0.3 m/s shows a horizontal 88 calm watersurface in the gutter Fig. 44 Outlet BAFFLEPLATE The crestweir is necessary to have an equal overflow along the weir /+ ,.’ . The outlet gutter should always be reasonably deep to avoid submerging the crestweir because there is a considerable slope of the water surface in the gutter ././ 89 4-6.3 SLOWSAM) FILTER Slow sand filters have been installed in ----many CD/SATA-Helvetas water supplies with a stream or river as a source. This is due to the fact that these filters can be easily maintained by the communities concerned if they are properly instructed. Also, slow sand-filters show good results in respect of water treatment, and their mode of action is quite simple Definition: Slow sand filters are filters with a surface 7,25 m3/m2 day (filter velocity 0,3 m/h) or less. 4-6.3.1 charge of Mode of action The raw water is led gently on the filter bed and percolates downwards. Suspended matter in the raw water is deposited on the surface of the filter bed. This layer of organic and inorganic material increases the friction loss through the bed. The water level therefore rises gradually until it reaches a predetermined value, not more than 100 cm. The bed must then be taken out of service and cleaned. The slow sand-filter does not act by a simple straining process. It works by a combination of straining and bacteriological action of which the latter is the more important. The mode of operation is complex. There is no doubt that the purification of the water takes place not only at the surface of the bed but for some distance below. Dr. A. Van de Vloed distinguishes three zones of purification in the bed. lst, the surface coating, 2nd the autotrophic zone existing a few millimeters below and 3rd the heterotrophic zone which extends some 30 cm into the bed. 1st stage = acts as an extremely fine-meshed 2nd stage = decomposes plankton chemical reaction and the filtrate 3rd stage = bacteriological In order be paid to guarantee to achieving: strainer becomes oxidised by filtration a good bacteriological for bacteriological filtration., reproduction attention should - favourable conditions and digestion - slow filter velocity - raw water quality (pre-treated additives like chlorine etc.) - Minimal charge (steady flow) ca. 5 - 10% of the max. charge, in order to keep the temperature on the filter steady and to avoid the growing of seaweed. . 90 by sedimentation only, no chemical 4-6.3.2 Hydraulic system From the hydraulic point of view a slow sand-filter and sedimentation basin form an inseparable unit. Our main aim is to increase the service First, we treat the raw water by time of a filter as much as possible. the filter charge in such a way sedimentation and secondly, we regulate Flow into the sedimentation basin that no unnecessary water is filtered. should be determined as exactly as possible by water requirements. This can be done by choosing different sizes of inlet pipes, or better, by constructing a distribution chamber with a weir (measuring weir). An adjustment of the inlet by throttle valves is not advisable; it may cause blockages due to leaves etc. in the raw water. There are two ways to control the filter: a) In controlling the filter outlet: this can easily be done by installation of a ball valve in the storage tank. A redu tion tee fitted immediately before the ball valve guarantees a minimum filter charge (steady flow = 5 - 10% of.the nominal charge). A continuous circulation through the storage tank is ensured if the storage tank overflow is installed at the opposite end of the tank to the inlet. b) In controlling the sedimentation tank outlet: this can be done with a similar installation as the one above. This solution has the advantage of no extra water being retained in the filters. Therefore, the growth of the algae is reduced and the service time of the filter increases. In Case a) and b) the excess water overflows System a) : in the sedimentation - steadv flow L-,---l control tstorage I of filter A overflow I tankioutlet System b) steady flow stor'age control / 91 of filter inlet tank. tank 4-6.3.3 Size and number of filters The size equation: S of the filter1 =A bed can easily S = Q = v v = The ratio of length surface quantity velocity to width be calculated witn the follqwing m2 of water per h or per day, m3/h or m3/day below 7.25 m3/m2/day or 0.3 m/h should be between 1 and 4. The number of filter beds depends upon the quantity of water desired as well as on the size of each bed. Nevertheless, it must be kept in mind that the filters will have to be cleaned from time to time and therefore, at least one additional stand-by bed must be available to avoid interruption of the supply. If the two filters work together the velocity will only be 0,15 m/h. Example: Quantity of water Filter velocity Surface required = = 20m3/h 0,3m/h = 20m3/h 0,3m/h = a) Chosen: 2 filter beds in action plus Hence the dimensions are as follows: A per filter chosen width Total filter = = - surface one stand-by 67m2 : 2 = 33,5m2 3m 33Am2 = 11,2m 3m (incl. stand-by) b) Chosen: 3 filter beds in action plus Hence the dimensions are as follows: Total 67m2 = 3 x 3.0 x 11,2 one stand-by A per filter chosen width = = 67m2 : 3 2,5m = 22,5m2 length = 22,5m2 2,5m = 9,Om filter surface (incl. stand-by) = 100,8m2 = 4 x 2,s x 9,0 = 9Om2 Preference may be given to solution b) because less surface will be required, But cleaning a surface smaller than in a) will be more often required. It is up to the engineer to decide which solution is most adequate for the actual site circumstances. 92 4-6.3.4 Construction Fig. Filter 45 details bed construction mu. WATERWm. 1 WATER f ;_- *. . . ',. .. . : . mu SAND LtvtL . SAND B0.~-1.oomm SScm. Or SIN0 CAN BC . RfMOVfO FOR CLfANlNG min. SAM0 LtvLL GRAVEL 5cm B S-lfmm 15cm P15-40mm 10 cm HOSLABS Fig. 46 Filter - t* lOmm Scm long section CONCRETE SLAB OR ClVERFUW LEVEL SED.TANK y / r’ /J SLABS WITH SPACE2 cm-l 93 Fig. 47 Filter - grou~$plan~ OUTLETTo THE WEFwm ROOM Fig. 48 Filter bottom . . . . . .. . ‘. . * v _, r. ..- _- . . *. 3’ ‘00 *-ie )e : 06) I ,:,’ ,’,’ Lmr -L, ,.’ :!::,‘;’ :,:i I,,. , ‘( cross - . . . . -. . . .,. ‘. - . ..-- l * . section . . . : ., . . . , . -_. : * . : : . . -*,. -. .* ,. :A.-;. o’er0 -..: . . . . . * b \--..* . @l :e\.’ I ’ L CEMENT BLOCK L SLABS 60&40/5cm SPACE 2cm ,, 94 Fig. 49 Inlet gutter details GROUND PLAN ALU PROFILE -1.00 = MAX. SAND LEVEL I 1 i I SECTION A -A CLEANING PiPE Li ‘Lb- MIN. WATER LEVEL w ml - MAX. SAND LEVEL WOODEN BOARDS, TO BE REMOVED ACCORDING TO THE SAND LEVEL 1” CLEANING PIPE SECTION B-B 95 4-6.4 OTHER FILTER TYPES 4-6.4.1 Rapid gravity filter Rapid gsavity-filters owe their name to the fact that the rate of flow through them is about twenty times faster than through the slow sandfilter (144 m3/m2/day for tropical areas only). Rapid filters work on other principles than those of a slow sand-filter. There is no "Schmutzdecke" film acting as a strainer on their surface; the sand bed is cleaned regularly by forcing air and water upwards through the bed and discharging the dirty wash water to waste; also the incoming water must be chemically treated. The rapid gravity filter acts more as a "strainer in depth" than the slow sand-filter but the process of water purification is not entirely one of straining. As with the slow sand-filter, certain complex biological and chemical changes are induced in the water as it passes through the bed and these - as far as is known - are believed to be the chief mode of action of the filter. Rapid gravity-filters vision to be adopted generally require in rural areas. too much maintenance and super- Nevertheless a rapid gravity filter has been introduced in a treatment station as an experiment. The reasons are the following: It has been experienced in slow sand filters that they are blocked after one to two weeks in rainy season because streams carry a lot of suspended matter which cannot be settled out by the common plain sedimentation. Due to this blockage filters need to be cleaned continuously and the biological purification is disturbed. After cleaning, it takes several days to build up the biological process again. In order to avoid this continuous disturbance on the operation of slow sand filters a rapid gravity filter has been preinstalled. It is expected that this rapid gravity filter (v=60m3/day) will work as a strainer to the suspended matters which have passed the sedimentation tank. While this rapid gravity filter will require continuous cleaning the slow sand filters are expected to work for months without blockage. 4-6.4.2 Pressure filter Pressure filters are identical in bed construction and mode of action open rapid gravity-filters, except that they are contained in a steel pressure vessel. to The advantage of pressure filters is that the pressure of water in the mains (not above 75 m pressure) is not lost when the filter process takes loss place, as is the case with an open rapid gravity plant (friction 1 m to 3 m). 96 4-6.5 TREATMENT STATION: Lay out storage Fig. 50 LAY-OUT for one sedimentation tank, tank (collection basin). two sand filters Hydraulic system - ground plan According to system bl in chapter 3TG?AGE TANK 4-6.3.2 FILTER 1 FILTER 2 SEDIMENTATION TANK (the cleaning 1 2 3 4 5 6 7 pipes are not shown) inlet outlet ball inlet outlet inlet outlet to sedimentation tank of sedimentation tank valve (depending on storage tank water level) to slow sand filters of slow sand filters to storage tank (collection basin) of storage tank (supply to consumer) p& valve 0 overflow I idle pipe s steady flow See section in Fig. 51 97 and one SLOW SAND FILTER SEDiM~NTATlON TANK OPERATION ROOM STORAGE TANK MtN. WATERLEVEL. I C 7’ , ,’ _-. rCllLICICL--.*->-1C&31. ,.. . . . . . :. .. .. _ . .. *. _ . ..* .’ * 1 2 3 4 5 6 7 inlet outlet ball inlet outlet inlet outlet sedimentation tank sedimentation tank valve slow sand filter slow sand filter storage tank storage tank 0 I S C overflow idle pipe steady flow cleaning pipe W valve (Ground plan see Fig. 50) 4-7 STORAGE 4-7.1 GENERAL The necessity points: of providing a storage tank is depending on the following a) continuous supply A storage tank has to be provided in case the source's over a day is just sufficient to cover the daily demand of the consumer. Because the hourly rate of consumption varies widely during the 24 hours of a day water has to be stored during the time of lower consumption. The maximum hourly consumption amounts up to 3 times the average consumption. (compare chapter 3-2) b) In case the continuous supply of the source is sufficient to cover no storage tank is required. peak demand of the consumer, generally the supply pipe from the source to the consumer has to be designed peak consumption. cl Between the critical 4-7.2 cases a) and b) are many other / possible the But for cases c). CAPACITY OF A STORAGETANK When designing a storage tank the first thing to consider is the capacity which has to be provided. This depends mainly on the amount of supplied water compared to the amount of consumed water. In some circumstances a certain amount of water has to be stored additionally to cover normal breakdowns or maintenance interruptions (e.g. for hospitals). In the following cases a) to c) a) the determination of the storage (as described above) are shown: tank capacity for the Water has to be stored during time of lower consumption to be available at the time of high consumption. Hence it follows that the required storage capacity depends on the consumption by a village over a day. The conditions vary in different parts of the world. Also local customs cause local variations. A typical pattern of consumption in area of the United Republic of Cameroon: a village in a rural 30 % of 10 % of 35 % of 20,% of 5 % of the the the the the day's day's day's day's day's supply supply supply supply supply between 6am and 8 am between 8am and 2 pm between 2pm and 5.30 pm during the other hours of day light between sunset and sunrise A diagram of consumption has been drawn (Fig. 52) according to above figures. In case ai;) of a continuous supply of the daily demand a storage volume of 40 % is required as it can be seen from the diagram Fig. 52. b) I .., As described above in case b) generally no storage tank is required. In practice the supply pipe from the source to the proposed storage tank for stage II is calculated for a continuous supply of stage II (compare example I, chapter 4-1.3). This capacity of the pipeline may be slightly below the peak demand of stage I. Normally a small storage tank, in form of an interruption tank , will only be constructed at the proposed site for the storage tank stage II in case of hydraulic requirements (pressure at taps). 99 Fig. 1 1 As an example the case c) is shown in the diagram of colrJumption (Fig. 521 where the source is able to supply the daie 3emand in 16 hours As it can be seen from the diagram the required capacity of the storage tank is about 23 % Icl + c2) of the daily consumption. cl 52 Water consumption cases of supply. Lvvw in a rural viilage with different coNsuMpTK)N CASE a) 60 .I. /df* ti n’ i i iA ----............ Pig. 53 diagram case a) case b) case c) of hourly consumption the daily supply is equal to the daily consumption the supply is equal to the peak consumption storage capacity required = cl + c2 Daily water consumption in Nqonzen water (an other example of case a) x II 100 no _ 00 ., 70 . I I I I I I I I I I I 100 (grassland) I VW = \6+ v4 = 22st lBZ= 412 INFLOW EOUhL TO DAILY CONSUMPTION IF IN’FLOWWORE THAN OAILY CONSUMPTY)N I- THE STORAGE VOtlJMC WILL BE REDUCED my/I t/ 0i-- supply f - 4-7.3 DESIGN OF STORAGETANKS The site for a storage tank should be chosen as close as possible area of highest consumption. to the The minimum water level in the reservoir should be between 20 - 80 m above If the level difference is exceeding the area which will be supplied. 80 - 100 m the system has to be divided in several pressure zones and the necessary storage tanks or pressure reducing stations (interruption chambers) have to be provided for. The water has to oL the water has peration must be There screens). be protected against external influences. A good circulation countries. to be ensured, due to the warm climate in tropical provided. Doors and windows have to be insectproof (mosquito should be no entrance above the water level. The operation chamber as well as the storage room have to be provided with good access for installation, checking, maintenance and repairs. During cleaning work the supply must continue. Therefore two independent chambers must each have an overflow capable of draining all the incoming water. Each chamber has to be provided with a cleaning pipe to allow complete emptying of the chamber. Independent chambers have to be provided with volumes above 30 m3. Storage tanks are usually constructed rectangular in shape, but it might be more economical to. construct masonry tanks in circular shape. Rectangular tanks allow easy extension. The water depth in the tanks should be as follows: Volume 100 m3 100 - 200 m3 200 - 300 m3 Water depth in m usual 2.00 - 2.50 2.50 - 3.50 3 .oo - 4.00 101 optimal 2.50 3.00 4.00 I,” i’, r3.g. 34 xorage ianlc construction IR VENTILATION ,- - INLE T (El/, WITH 4AU _ VALVE 1 * iii/ 1/1/i min ZOcm t L/1 -.--‘.--” DlSTRiWTlON DISTRIBUTION SYSTEM 4-8 The aim of the distribution system is to transport the water safely from the main pipe to different places of consumption, such as standshowerhouses, etc. pipes, wash-places, 4-8.1 LAY-OUT OF THE DISTRIBUTION SYSTEM When designing a distribution points have to be considered: system of a water - the advantages systems and and disadvantages - the subdivision of the system 4--8.1.1 Types of distribution a) Branch system or dead-end supply of the different into different the types pressure following two of distribution zones; if necessary. systems system In this system the distribution is done from a distribution main to the different points of consumpti.on. The service pipes for individual supplies are like branches of a tree. This system has the disadvantage of possibly causing stagnant water in the dead-ends. b) Gridiron system This system is similar to the Branch system but here connected together with the result that the circulation and the possibility of stagnant water is reduced. the dead-ends are is much better Of 103 dead-ends cl Ring system . In this system the distribution advantages are considerable: - 4-8.1.2 main is connected as a ring. The good circulation of the water safe in case of breakdowns supply not interrupted in case of repairs Pressure zones The distribution system must be divided in different pressure zones if the difference in height between the lowest and the highest tap is mot-c-. than 80 maters. The maximum water pressure at the tap is 60 to 80 IIJ.. from the source d 4-8.1.3 Disposition of taps Public standpipes requirements: a) b) population technical and wash-places concentration: considerations: are installed ,“;!: ,, ,‘. ,, ., 2 ; 1, /,.A !” y to the following not more than 80 - 100 persons per tap; no one should have to carry water mere 100 to 150 m cleaning 104 8’ according and aeration than 4-8.2 PIPING MATERIAL 4-8.2.1 General There are three it it it a) b) cl for must convey the quantity must resist all external must be durable In order pipelines - requirements to &al with this into the following a pipeline: of water required and internal forces subject adequately categories which it is necessary to classify may be defined as follows: "Trunk mains" are for bulk conveyance of water over long or short distances from the source to selected focal points in the distribution system. The following trunk main categories have to be distinguished their main functions: a) "supply (spring, mainsW for the conveyance of water river, lake) to the storage tank; from the water b) "distribution or service mains" are, as their name implies, mains" frorr. which individual house supplies are tapped; cl "gravity d) "pumping - mains" These last rains" the physical two classifications working source the "street are made to specify principle of the supply. "ring main" is a special case of connecting two distribution mains together. Ring mains are always of great value to a distribution system because: they tend to reduce the size of service main required they maintain good pressure and flow within a distribution they give alternative means of feeding an area when shut repairs are necessary they avoid stagnation of water at dead-end of main . by - "Service a village pipe" is the supply line, laid under ground section quarter, a house, or a farm. - "Plumbing pipes" are pipework within of water to the various appliances. The following types of pipes are in use for Applicable cast iron pipes ---_-__.* .-.- -.- _ asbestos-cement pipes .~ galvanized steel pipes -----.- - ._.___. .._..___. bitumen coated steel pipes --prestressed concrete pipes ,._.-.-.,. _ plastic pipes (PVC + PE) .-. _I copper pipes x = applicable 0 = 1 = a building applied in CD/SATA projects in special cases only Trunk for frcm a main to the distribution the construction main Service system downs for pipe of mains: Plumbing X X 0 0 01 0 0 0 x X X 0 X in Cameroon pipe ‘,‘” 4-8.2.2 Asbestos cement pipes Asbestos pressure pipes are made exclusevely out of standard cement grades, mainly Portland cement. The other raw material, asbestos, is a mineral of magmatic origin, crystallized into very slender fibres (l/lO'OOO mm). Crude asbestos fibre bundles are broken up into fine fibres between edge runner rollers and are then fed into a pulp mill. Here, about 10 - 15 parts of asbestos are mixed with 85 - 90 parts of cement, with the addition of water. , Classification: Asbestos pressure pipes are supplied in nominal sizes in pressure classes 5, 12, 20, 25 and 30 kg/cm2. The classes denote the test pressure manufacturer's wcxks. The tightness pressure of the pipes. of 50 to 1'500 in kg/cm2 of the tightness test in the test pressure is twice the working Pipes are marked in the customary way, e.g. a pipe of 250 mm inside designed for a working pressure of 10 kg/cm bears the code: Durabest Couplings 4 are similarly 6 All pipes class 250, coded, 250, are tested class at twice mm and diameter 20 i.e.: 20 the working pressure before leaving the factory. Note: Asbestos cement pipes in Cameroon are only used bitumen coated inside and outside (compare chapter 2-4). They were the main type used for CD-SATAHelvetas projects until 1976. Now plastic pipes are applied more often due to appearance of corrosion in AC pipes by aggressive water 4-8.2.3 Plastic pipes Plastic pressure pipes advantages compared to resistance towards all their light weight and The raw material for is Polyvinylchlorid The plastic pressure (PE) mixed in powder and plastic pressure hoses offer considerable pipes made of &her material, due to their great known aggres,ive matter (see chapter 2-4.41, to their easy handling. plastic pressure pipes (e.g. Symadur pressure pipes) (PVC) in powder form. hoses (e.g. Symalit PE-hoses) are made of Polyethylene form. Much attention has to be paid tc an adequate fabrication, Plastic pipes for be fabricated according to the purpose of transporting drinking water must A well equipped established regulations (e.g. in Germany: DIN 19'532). laboratory is required to examine the plastic material accordingly. Only plastic: pipes marked with a test mark which guarantees adequate quality, mu8t br! used for water supplies. Of course, as we know from other material, we have to consider simple rules to gain the required result. Care has to be taken when offloading, storing or laying the pipes. 106 I 1 ); 1, The following explanations are based on many years factory internal experience. international and Transport: it is essential that the bottom row of When transporting plastic pipes, pipes is supported along the entire length of the truck. The following layers of pipes have to be piled up in such a way that sliding and damaging of the pipes is avoided. Stacking: Symadur pressure pipes are resistant to influence of weather and corrosion. The pipes can be stored outside for an unlimited time but/ it is advisable The pipes must be stacked on to cover them during long stacking periods. The manufacturer advises to use wooden'batons at the base an even surface. and between.each layer. The sealing rings are to be stored in a cool and dry place. They have to be protected against direct sun rays. Trenching: Large stones and rocks are pointsupports which may cause the pipe to break. In case of rocky soil, the pipe has to be covered at least with a 15 cm thick layer of stonefree material (e.g. sand?. In normal dry soil without stones, it is not necessary to take special-precautions. 4-8.2.4 Steel pipes Steel pipes are widely used because they are among the cheapest form of They are supplied in straight service pipes and can sustain high pressure. length of 6 m. Note : Only untreated bent to curves will start. pipes (black) the protection can be bent to curves. may get cracks where If treated pipes are in due course corrosion Steel pipes may be supplied black (untreated) or galvanized, or bitumen coated inside and out, or additionally sheathed on the exterior with glass compound. They have screwed fibre cloth and a further coating of bituminous A great variety of special ones ends and are connected by steel couplings. are made, including flanges which are screwed on to the pipe ends. Most steel service pipes laid by water undertakings are galvanized. Applicability on CD/SATA-Helvetas projects in URC: Galvanized steel pipes-are applied mainly as plumbing pipes. But they are also used on trunk mains and service pipes where the pipes have to be exposed or where the earth cover is insufficient (e.g. crossing of streams, rocks, roads, etc.). 107 4-0.2.5 Valves There are three - main reasons for including valves in a pipeline system: to alLow easy closing of a pipeline to control the flow to control the pressure Types of valves in general: - applicable sluice for valve tight (gate plug valve --.. . ---._--.-.--__ butterfly valve valve .. .._ screw down plug valve (stopcock) -.--. _. non return valve control pressure 4, b), 1) only * closure flow -- X control -." x 1) X - 2) x 1) X - 2) X X - 2) valve special control valve (gate b) - 2) cl - 2) d) X - c) and d) are applied with control a) X X reducing pressure X valve 2) pressure a) Sl;ice .- in CD/SATA-Helvetas projects in Cameroon equipment functions only if water is flowing valve) They are used to force a gate across a pipeline. The gate is wedge shaped and is lowered into a groove cast in the body of the valve. Sluice valves which are left shut for a long time tend to stick and it requires great force to lift the gate off the sealing. Similarly valves which have been left open for a long time may not close properly because of the collection of dirt in the gate groove which prevents proper insertion of the gate. The difficulty with sticking valves and dirt on the gate groove can be greatly reduced by operating valves regularly. If valves are not operated for years they probably will not close. Serious difficulties could arise if it became essential to close such a valve effectively. The sluice valve is not the through a pipe because only closure has any substantial pressure of the water in the proper device for controlling the rate of flow the last 10 % travel of the gate towards effect on the flow rate (depending on the pipeline). 108 b) Screw down plug valve (stopcock) These are normally made only in smaller sizes. The body of the valve is cast so that the water must pass through an orifice which is normally arranged in the horizontal plan. A plug, a diaphragm or a jumper can then be forced down on to this orifice by a screwed handle, thus shutting off the water flow. The principle is used in all sorts of valves for shutting off or controlling flow. The same principle applies to ball valves, to pressure or flow control valves, to hydrant valves etc. When the size of pipe (and therefore of orifice) is small then high pressure can be controlled. 'as is the case with the ordinary domestic tap. The defects of these particular types of stopcocks are that their sealing need renewal from time to time if they are frequently in use and that, even when wide open, they cause a considerable loss of pressure head. c) Non return 1( 'I ', ::'1 :!' ';,',,,I, i,B:',,, P', i'!: , ,I',,,',' fp; v;,,:: 5' q,;< ,~_) g;y,' I_, $,‘ I Li' i':.,,,a,, : : Fig. $8 of friction Diagram Pipes according k = 0,l loss in galvanized steel pipes to DIN - Norm 2440 mm the inside diameter d The nominal diameter ND 3/Ofb or 10 mm 12,5 ma l/2" or 15 mm 16,0 mm 3/q" or 20 mm 21,6 mm 1" or 25 mm 27,2 mm 11/4" or 32 mm 35,9 mm 1 l/2" or 40 mm 41,8 mm 2" 21/2" 3" 4" or 50 65 80 100 or or or B mm mm ml nun 53,0 68,8 80,8 105,3 mm nun mm mn IOMnin 80 IlOI/min 200 300 500 100 XXII/mm 100*/w 10 80 w 60 !a 50 10 40 30 30 20 20 I ‘. 1 6 678 0 19 xl QUANTI’TVOF WATER ( llmin 1 , 200 “” , 3m 1 1%a ,‘,I’ 500 lea It is quite economical. Trunk main-lines, stage I Main-lines stage I stage supply velocity in the pipes is most give a general guideline:- pump discharge stage v = 1.0 m/set of air II pipes v = 1.S m/set connections stage II v = 1.5 m/set stage II v = 1.8 m/set pockets The presence of air in a water main can cause serious wren when the main is of a large diameter. blockages to the flow Air pockets a) b) where the static head on the pipe is lower than 5 m by high points in the pipeline and where the pressure in the pipeline decreases (compared to the hydraulic gradient) by operating a pipeline with insufficient means of aeration when the flow capacity of the pipeline is bigger than the inflow c) d) can be caused: The minimum pressure Fig. - 2.0 m/set main v = 1.0 m/set Prevention water should house or stand-pipe or service I main, v = 0.8 m/set without Distribution 4-8.3.2 clear that a certain The following table in a pipeline should be at least 5 m. 59 hydraulic gradient at least 5m --correct hydraulic diameter gradient Fig. 60 Longitudinal section showing desirable valves on a length of pipeline -. v -. -, -. Point Point gxadient -.-.-, Arrows show the possible of the air accumulation a: Air likely to accumulate and steeper downgrade in b: Lessening of upgrade in of air c: Summit; large air valve because direction direction for of lessening of flow of flow will filling hd * special aeration because Fig. 61 for air -.- -.-.- desirable positions for air valves A low point with cleaning pipe Point static -.-. -.-.-. positions case: in point hd * he Hydraulic purposes direction (-) of hydraulic cause accumulation will be required he e profile correct wrong profile 116 gradient profiles - It is obvious that air can collect tit high points in a main, but what is not so obvious is that the high points are determined relative to the A hydraulic gradient existing on the main. (Fig. 60 shows an example). water main should not bc laid parallel to the hydraulic gradient (Fig. 61) it should be laid with a rise or a fall (if possible). At the top of each An air valve must also be inserted rise there must be an air release valve. and then changes gradient so as to rise less where a pipeline rises steepl?!, steeply. The valve should be ut the point of change of grade, even when there is no definite high point on the main. When filling a main, large valves for releasing air need to be fixed only at those high points where it is obvious that air will have to emerge to permit filling of the pipeline. Elsewnere, a smaller diameter air valve will suffice Where long stretches of main exist with no distinct high point, one air valve should be inserted at least every 1 to 1.5 km. This is especially important when the pressure along the main is decreasing and thus allows air to come out of solution from the water. On flat pipelines subjected to very pipes taken above the static gradient can be low heads, open-ended vertical used instead of air release valves, provided precautions are taken to prevent pollution of water.(Compare with Fig. 62) It should the water erratically be kept in mind that air does not necessarily move forward with but may move backward against the flow of water, slowly or (waterhammer). - Before a pipeline can be filled with water releasing air from it. Once 'the pipe is full for release of air must be closed so that no high points should be open as long as air is , means must be provided for of water, however, any aperture water is lost. Ventilation on escaping. - When the outflow is bigger than the inflow it is obvious that the outlet basin is empty all the time and therefore, the top of the outlet pipe will not be covered with the required 20 cm of water. If this happens the outflowing water sucks air into the pipe and air bubbles will reduce the capacity of the pipeline (more friction) more and more until the inflow is bigger than the outflow. The water level in the basin will then increase so that no air enters into the pipe. The capacity of the pipe will then increase to be greater than the inflow and the process will repeat itself again. Note: Intermittent flow cannot occur with automatic air but blockages to flow can happen with hand-operated air because air pockets can build up in a very short time. Special case of air hammer: pocket which reduces the flow rate correct 117 --. release release valves, valves and can cause water- . Prevention 4-8.3.3 of vacuum Vacuum can be caused: - if the hydraulic gradient drops below the pipe axis - if there is a closed valve in a main and the water from the continuous main which is lower than the valve is drawn out for emptying purposes. There is no doubt that in a well-planned supply system a vacuum caused of the hydraulic gradient below the pipe axis can be avoided. But if a pipeline bursts at a low point a vacuum will occur at each of the it is important to install automatic anti-vacuum high points. Therefore, valves on all extreme high points, if there is a possibility of more than 5 m vacuum (and in steel pipes of large diameter, even less). Where the high points have a very low head, open-ended vertical pipes taken above the static gradient can be used instead of anti-vacuum valves, provided that precautions are taken to prevent pollution of water (see Fig. 62). a) by dropping b) Means to ventilate the pipeline should be provided after each main valve to prevent building up of vacuum when the main valve is closed. 4-8.3.4 Fig. Air 62 release Automatic valves and anti-vacuum valves valves STATIC GRADIENT -- -. Ventilation pipe min. b 1" with return bend and sieve to prevent pollution of water caused by animals or dirt Open ended pipes taken above the static air release or anti vacuum valves. gradient -cleaning pipe can be used instead of (with little steady flow} ENTILATION AIR - REGULATOF sv DRAIN LARGE AIR VALVE ’ w FOR fll.LlNC OF PIPE -LINE AT HIGHPOINTS 0I-iY - -- 118 L VALVE FOR MAINTE NANCE Fig. 63 Intermittent ventilatiofi ‘a) stand The ventilation valve pipe-line (prevention (a) Also Fig. 64 Anti regularly has to be opened from time of air pockets) used standpipes can prevent air to time pockets to ventilate at high pipe the points. vacuum valve After closing the main valve (prevention of vacuum). the ventilation valve must be opened VENT11.ATION VALVE CONNECTION . Note: The greatest care should be taken to keep all air valves well above the highest possible ground-water level that can occur in any pit in which ground-water could enter they are sited. If this is not done, then polluted The pit in which the air valve is sited should the main if it is emptied. have a permanent drain leading to an open outfall which cannot be drowned. This factor is an important one which will decide on the exact location of the air valve. 119 4-8.4 IMPLEMENTATION 4-8.4.1 Trench:z1g The pipeline shoulci crossings should b<) laid along the straightest route possible. Road ne at a right-angle to the road whenever possible. rise of about 2% Every length of main should k,: laid with a continuous so that air can be released through air valves, or to 5% to high points, where a cleaning valve should be with a continuous fall to a low point, of pipelines, fixed for emptying &at portion of the main. Flat lengths or those laid parallel with the hydraulic gradient, should be avoided since they may give air-lock problems. Changes of direction - flexible )ling CC - r:iid TiZ”;. F‘ r should be made, whenever such as Viking joints, for A/C pipes allowing joints using Johnson gradual prefabricated, flanged .ed steel pipes should not be bent into It would ctive coating may get cracks. 3 with screwed joints. possible, coupling deflection For other Note: allow joints recommended for - according for or screwed steel asbestos pipe pipes, the internal to remove be done along the out after the pipe is $ = 50. (5O = 9 cm to the manufacturer the trench has to be wider at a bend than along a straight, space needed to complete the above pipe-laying instruction. 120 or RK bends. curves because be very difficult drtion of pipe into a coupling should preferably the shift being carried itxis of pipes already laid, has been inserted. The maximum deflection offset/m length) by using: to - DOTTohi COIIRCCT DOTTOM PLANNED TRCMH depends I:', . IOTTOW TOO HIGH - soil type and conditions - cost considerations The recommended economical at least a = 60 cm. on: _ width of trench 121 at pipe level is In order to protect the pipe against damage from traffic and from weather conditions, it is buried in the ground at a suitable depth. In the tropics an earth cover of -,_.-at leas‘- "3 - cm (min. 60 cm) should be provided in order to protect the pipes agai, t great variations of temperature, root growth into flexible joints (between sealing rings and pipe) and against falling the water temperature increases and If the pipe is not buried, trees. provides excellent breeding conditions for microbes, and any tree falling onto the pipeline may cause damage. When pipes are laid with more than investigation is called for to ensure that 1.5 m to 1.8 m cover, a special -ough to stand the earth pressure. If they are not the they are strong I remedy is to bed or fully surround the pipeline with concrete. Trench depth like trench width also costs. All factors should, therefore, excavating the trench. Recommended depths Fig. - through - along - underneath 66 pressure \ roads lines in different bearing on laying very carefully before situations 100 cm (min 60 cm) 100 cm roads Crossinq normal Note bush for has an important be considered back-filling 150 cm of main roads The pipe should into a sand bed covered with at 20 cm sand. The ning back-filling done normally. be laid and be least remaiis The pipe should be laid into a sand bed and be covered with approx. 20 to 30 cm sand. An additional concrete slab will help to reduce the load caused by traffic. The remaining back-filling is done normally. : Back-filling unsuitable should always be completed in layers. as it results in excessive settling. 122 Bulk back-fil .ling is 4-8.4.2 Laying of pipes The pipe should be laid on firm ground or foundation in order to prevent uneven settlement, which may damage pipe joints. In rocky soils,rocks and stones should be cleared away from the bottom of the trenches for 15 cm beyond the pipes and should be replaced by plain earth, sand, pea-size gravel or concrete. A very large proportion of burst mains are caused by pipes settling on large stones or rock points. All tren roots between the surface and a depth of 1 prevent damage to pipes from root growth (moving or or by uprooted trees. This is very important if the rigid couplings because an uprooted tree can damage a rigidly joined pipeline. m should squeezing pipes are a lengthy be cut to of the pipe) joined with section of Just before lowering pipes into the trench the pipes should be reinspected (the first inspection having been done when the pipes were delivered and stacked). This inspection should be concerned with finding cracks, blemishes, punctures or other discontinuities of the external protection of all pipes. At the same time - just before lowering them into the trench, the inside of the pipes should be inspected for foreign bodies (like snakes, mice, gravel or sand). The pipes, as well as their joining ends should be wiped and cleaned. A small depression should be dug out under the to allow an adequate support for the pipe over couplings its entire the couplings (rubber sealing 123 rings) so as correct The pipe over its wrong The pipe is supported on two or more points only (i.e. on the couplings). Statically it acts like a beam. When back-filled the whole weight of the cover rests on the pipe which may cause it to fracture in due course. wrong Moreover leak. or sockets length. may be loaded is supported entire lenght. unevenly and Instructions for back-filling: Back-filling onto a pipe requires as much care as preparing the trench. The material must be soft and must not contain lumps of rock or large material stones. Once the pipe has been covered with 20 cm of suitable bulk filling of the remaining trench can be permitted. If there are a lot of big stones that have been excavated it is not advisable to use them for the bulk back-filling of the trench. If these stones are replaced by soft material it will make it easier to excavate if the need arises !i.e. repair-)-Initial back-filling (at least 20 cm above the top of the pipe) should be done as soon as possibl c after the pipe has been laid to protect the pipe from falling rocks, trees, flooding and cave-ins. Frovide a continuous bed by carefully selecting the material for use under the pipe and couplings and between the pipeline and the trench walls. A proper back-filling between the pipeline and the trench walls is also important to prevent a horizontal movement of the pipe wilich will occur if the pipe is not laid in a straight Sine. Water tamping tamping. may be used where drainage is good. Do not lift the pipe while Couplings or sockets are normally left exposed until the line has been tested. After testing, the initial back-filling around the couplings should proceed until each coupling has been covered by at least 30 cm of well-selected material. Fig. 67 Back-filling 1. Place 2. Tamp soil under pipes and between pipeline and trench wall at both side. Water tamping may be used where drainage is good. 3. Place 124 soil soil up to l/2 external diameter. up to the top of the pipe. 4. Tamp soil between at both sides. 5. Back-filling by hand until 20 cm over pipe. Tamp each 10 cm layer. 6. Bulk-filling pipeline and trench of the remaining wall the trench. If the pipe trace has not been marked during construction it will later be difficult and sometimes very costly to find the pipe trace. It is important that immediately after back-filling the pipe trace should be marked by permanent signs to be able to follow the pipe if need arises (e.g. building of new houses or roads). A concrete peg which contains the following to mark the pipe trace permanently: Fig. a) Pipe material b) The directions cl Continuous 68 Examples and diameter laid of the pipe into information may be the best the ground trace numeration in sequence of markinq peqs of all concrete pegs. marks for direction pipe trace Asbestos cement pipe gi 200 m Peg No. 12 (continuous i ,’ a m llem min 125 numeration) way , _, Example for pipe sizes buried into the ground up to 4 100 mm ipaicate A piece of pipe embedded into a concrete peg which is identical to the pipe laid in the ground, e.g. a 1 l/4" galv. pipe piece concreted into the peg means that a 1 l/4" galv. pipeline is buried in the ground. The concrete because: pegs should generally be buried to one side of the pipe a) In case of a burst pipeline some of the pegs may be removed while looking for the leak and aeterwards they may not be correctly replaced. b) The material above the pipe initially will and the pegs may sink with any subsidence ACCORDING TO PIPETRACE BUT NOT MORE THAN 300 m -- 0 -. 126 4 not be fully and eventually axis, consolidated get covered. 4-8.4.3 Thrust-blocks and anchoring A pipe laid on sloping ground should be anchored frequently by having a concrete anchor-block cast around it. Further thrust-blocks are necessary at bends, tees, valves and tapers, and also at branch take-off unless flanged joints are used. These blocks often have to be very large and they must, of course, be well keyed into firm ground. Note: The size of the thrust-block has to be decided on according to the external forces occurring during testing of the pipeline, as the operating pressure is lower than the testing pressure. In soft soils, make sure that the concrete thrust-block attached to the line, or it may endanger line safety down unevenly. Fig. 69 Thrust-blocks required ig, 73 (d - for thrust-block Thrust forces area R soil-bearing = is not firmly the line beds of directions P in metric of pipe mm changes if tons internal power (T =LxW=A at end closures: pressure p = kg/cm2 10 15 0.57 0.75 1.13 0.57 0.85 1.13 1.70 0.52 0.87 1.31 1.74 2.61 0.25 0.75 1.24 1.87 2.49 3.73 200 0.44 1.31 2.19 3.28 4.37 6.56 300 0.94 2.82 4.70 7.05 9.40 1 3 5 7.5 80 0.08 0.23 0.38 100 0.11 0.34 125 0.17 150 127 14 .lO -- Factors for calculating Bends: Factors: thrust 90° 1.41 Branches factor = thrus tforce R = 1,41 x P 0.70 force 60° 1.00 R at bends and branches: 450 0.76 (em&.rically 300 0.52 71 longitudinal This thrust 1 R= 0,70 x P = branches factor ' Thrust-blocks 111/4o 0.20 drawn from experience The thrust-block at changes of directions the forces so that the foundation pressure soil-bearing power. Fig. 221/2o 0.39 for changes relies on its R=P in the ground plan distributes does not exceed the permissible of slopes section block weight to withstand OCCIEing forces. The following calculations to those for a thrust-block changes of directions. are similar for Examples of calculation: #I125 Example 1: Thrust-block for Water pressure a branch d 100 mm / = 10 kg/cm2 Permissible soil-bearing Out of Fig. 70: The required Chosen: - II power P = 1,13 tons, thrust-block L = 40 cm W = 30 cm r= 0,75 kg/cm2 the factor area A = with R r = for b I100 branches - 0,70 0,70 x 1130 kg 0,75 kg/cm2 = 1060 cm2 ======== 30 x 40 cm = 12nO cm2 Example 2: Thrust-block for a change of slope Pipe B 150 mm Water pressure Specific = 7,5 kg/cm2 weight Out of Fig. The required of concrete = 2,4 t/m3 70: P = 1,87 tons, thrust-block Chosen concrete thrust-block the factor volume = & I for = 0,76 x I,87 2,4 t/m3 of 0,85 m x 0,85 129 45O = 0,76 t = o 5g m3 I =======: m x 0,85 m (with 0,61 m3) $125 ., d4.4 Pressure test of the pipeline It is very important to test the pipeline before the trench is backfilled to discover in time leaks and damages on the pipes (e.g. cracks). After laying the pipes, the initial back-filling should be done as soon as possible. Fig. 72 Initial back-filling for the pressure test This initial back-Eilling prevents a movement of the pipe duril:g the testing and protects the pipe from falling stones, trees, etc. Before the test can be started all the changes of directions and slopes have to be secured according to chapter 4-8.4.3 by thrust-blocks and anchors. Where lines cannot be tested under pressure in a single +zration, they In that case, the joints linking individual shall be tested in sections. test sections shall be tested for leaks by a final overall test. The test pressure should be 20% to 50% higher than the service pressure But at the lowest point of the section it of the very pipe section. should never be higher than 1,2 times the nominal pressure of the pipes. Fig. 73 Testing - bq pump end cap pressure gauge test apparatus (hand pump) Calibrated pressure gauges shall be used for testing, graduated to permit correct reading to 0,l kg/cm2 pressure changes. It should be placed at the lower end of the section. For plastic tight. pipes, the pressure should be constant if the pipe-line is The limit for A/C pipes: The correct test pressure shall be restored every half-how, Restoring is done by pumping water from the test apparatus into the pipeline. The volume of water required to compensate the loss by abeorbtion shall not exceed 0,05 l/m2 inner surface per hour. Fig. 74 Testing For plastic water hose. by natural pipes, there slope should For A/C pipes, the refilled inner surface per hour. be no loss amount of water of water should in the transparent not exceed 0,05 l/m2 Notes: - The testing pressure shall last for 15 minutes/100 - The air pipeline - The test procedure for asbestos cement pipes must take into account the limited degree of water absorbed by the pipe raw material. Therefore, the A/C-pipeline has to be filled with water under service pressure for at least 24 hours before the main test can start. at high-points has to be released with water for the testing. 131 during m length the filling of pipeline. of the Valve 4-8.4.5 chambers It is necessary to have valves at intervals along a pipeline which be used to control the flow of water. These valves are preferably situated in a chamber built of concrete or cement blocks. Fig. 75 c= Chambers with min 20 cm for min 25 cm for a depth pipes pipes can up to 1,O m 4 50 and 80 rd 100 and 150 1 depending on the length of 1 the spanner to open the screw of the joint a ;: min 6Oun or 2 x 6 + WTSIDE & OF VALVE t b = min 60 or LENGTH OF VALVE Note: + 2 x 10 cm Length of valve always ventilation valve. TEE PLUS includes min10 length of main valve and of . OF VALVE klel min 30 I + min 30 4 132 ,I. ,_ Fig. 76 Chambers with Iir a depth more than 1,O m LENGTH 0F \(ALvE + 2 x iocm Bi OF VALVE 0 @ 1 a= .E L CLIMBING 60 + c + OUTSIDE 0 OF VALVE IRONS CLIMBING Note: Length of valves always ventilation valve. includes 133 lengths of main valve IRONS and of If a pipe passes through a wall, it and could damage the pipe. It stresses by using constructional I i certain stresses from outside is, therefore, very important details as shown. may affect to prevent 6 A Rigid connection applicable cleaning pipes or pipeline a building only for inside To make sure that there will be no leak where the pipes enter into the tank a single flange fitting with one flange in the middle of the wall is very useful Flexible connection applicable for pipelines between different buildings or for pipelines which are laid into the ground and must be connected into a tank (rigid) At the end of PVC pipes a layer sand can be glued (with plastic This solution allows to connect pipe end directly to concrete of glue). this pipe-line water tank pipe bridge working space during constr uction expansion/contraction slip joints 134 To prevent the pipeline from breaking by the settling down of the soil, a pipe bridge has to be constructed 4-8.5 DISTRIBUTION BUILDINGS The most important - the the food and public public crops public distribution buildings are standpipes from where the consumers carry water washplaces where the population washes clothes, or coffee shower houses. Public standpipes requirements: and washplaces are installed according to the following a) Population concentration: Not more than 100 persons per tap b) Distances: No one should have to carry water more than 100 to 150 m. c) Technical consideration: Possible combination with high-points (aeration) or low-points (cleaning pipe). Public shower houses should be constructed in projects where enough water is available and where no natural bathing facilities are at hand. A standard rate is loo-150 persons per shower head. No one should have to walk more than 500 m to the nearest shower house. Constructional hint: Every connection of a distribution building to the main pipe must have a valve or a stop-cock so that repairs on the pipe branch can be made without interruption of the main water supply. 4-8.5.1 Fig. 77 Public standpipe Public standpipe The standard designs in the appendix show the construction details and the list of materials for the public standpipe (Fig. 77) and the public fountain (Fig. 78). 135 Usually centres 4-8.5.2 the public of towns. fountain Public washplaces is constructed Fig. 79 Public washplace in concrete Fig. 80 Public washplace in stone on market places or in construction masonry construction The standard designs of Fig. 79 and Fig. 80 are shown in the appendix 136 Fig. 81 Standpipe Ground with washtable plan .L.* -’ TIE! A -.d wash table Section A- A pipes :hors 80 Fig. 82 Coffee 71 1.20 1 wash-place I I L rlevel \1 1 I I I-i--i- Section A-A Section B-B 4-8.5.3 Fig. public 83 shower housq Standard shower house lbI roof I I Ground plan Fig. 84 (scale Section 1 :lOO) Public shower house with and 2 washplaces 8 heads combined t I I I I I I I I pipe 4 I I i I I stacking f I a fitting ----------l l-----------I with A-A I I I I L I 9 fi I Ia I 4 I i! I n, I I I I I I --- L -------A--- Ground plan (scale 1: 100 1 138 --- --- 1 -roof store WATERLIFTING 4-9 In rural areas, some to obtain their water and should always be start. It can be said by gravity, which works pumping. The gravity cost low. The running high for a commllnity cases it is inevitable 4-9.1 villages may be situated in a way that enables them supplies entirely by gravity. This is a big advantage considered first when investigations for a water supply that it is always safer to ccnstruct a water supply if this is possible, than one which requires system needs less maintenance and keeps the running cost and maintenance for pumps can be considerably which is financially weak. Nevertheless, in certain to install pumps to obtain the necessary water. TYPES OF PUMPS There are two main types - plunger pump (or piston centrifugal pump , The following diagram discharge and delivery of pumps which are suitable for water supplies pump) shows the application head. Ii of each one in relation P = Plunger to pumps C = Centrifugal pumps m The economical the application or centiifugal the ratio: (l/see) H (m) Q Plunger 1 pump: The most common pump of this type which water is moved by the direct reciprocates in a closed horizontal Centrifugal = limit between of plunger pumps pumps lies at is the reciprocating plunger push of a plunger or piston or vertical cylinder. pump in which pump: The pump-wheel turns with very high speed and centrifuges outwards producing the water pressure. 139 the water Summary: Pumping systems type of pumpr application driving remarks plunger deep well pump (the pumping mechanism is located inside the well) for pumping-heights over 5m (see chapter 4-9.2.1) ... Wing pump for suction-heights to 5 meters - hand pump up for of water pump centrifugal other pump systems 4-9.2 HAND PUkPS 4-9.2.1 Deep well high discharges energy, 1 hand pump driven by wind mill animal drive electrical or diesel erlgi ne requires fast running drives: - electrical engine - diesel engine - petrol engine - water turbine hydraulic ram (see chapter 4-9.4.1) self drive by water (waterhammer) hydro pump (see Fig. 90) - foot bucket and rope with rope pulley for wells - manpower - animal drive - diesel engine pump pum& The hand-operated pump can be usedin welis of any depth. In those which is usually placed have a suction lift of less than 5 m, the pump-cylinder above ground (shallow well pump, cominon pitcher pump). When the static water lift is more than 5 m, the cylinder is attached to a drop-pipe and placed in the well (deep well lift pump). The deep well lift pump is one in which the driving mechanism (or power head) is separated from the pumping mechanism (or cylinder). The deep well operating p&p must be located directly'over the top of the water source, with the cylinder either submerged or'w'ith'in the suction lift (ca. 5 m) of the water. Since the water table level changes at different seasons of it is best to have the cylinder in or very close to the water. the year, The experience has shown that this type of pump needs proper maintenance and frequent checking. Specially the stuffing box, made of brass, is not resistant to wear. The bolts for the pump head-connection have to be tightened properly. Heavy use of the hand pump can produce wear on loose bolts. Properly used, these pumps rarely require any expensive replacements, and any work done on them can be carried out by relatively unskilled persons. A well lift ;I, designed water deep well from a deep well. lift pump is a simple and economical - solut.ion to _---- Fiig, 85 Deep well pump. construction and maintenance needs _ 1 J Fig. 86 Deep well pump with fly-wheel This hand pump is also suitable for other drives: Wind mill, animal drive, engines, etc. DEUVEW (Un AND FORCE) MAX TAPPIN r B.&P. Fig. 87 Nomograph for hand pump discharge Literature 4-9.2.2 Fig. reference: 7 (see selected Bibliography) Wing pump 88 L handle, The wing pump is constructed differently to the plunger pumps but the working system is the same. Applicable for suction heights up to 5 meters only (with foot valve). Without a foot valve, wing pumps are only satisfactory for very short suction lifts. 142 4-9.3 CENTRIFUGAL PUMPS These pumps are often used because they are light, simple and need only are normally not required. limited space for installation. Air vessels Regulation is done by the use of throttle valves. The connection to fast running engines is required. Caution-if the water The dif,ferent - types contains sand ! of construction: with vertical axle for installation in wells with horizontal axle for normal installation one or more stage units to meet high delivery heads Mode of action: In the centrifugal pump, energy is applied by a rapidly rotating impeller in which kinetic energy is transformed into waterpressure. As a result water is propelled out of the discharge opening. 4-9.3.1 Planning of centrifugal pump installations It must be very clear that the planning of centrifugal pumping plants should be done by an experienced engineer. The following explanations are not aimed to give all the required information in this respect. For more detailed "Planning of Centrifugal Pumping Plants" by Sulzer Brothers information see Ltd, 8400 Winterthur/Switzerland, or other relevant literature. II_ will always be necessary when designing a pumping manufacturer of the pump and the pump drive as early planning. 1 system to involve the as possible in the L Pump characteristics: Each centrifugal pump has a characteristic ratio This characteristic delivery head and revolutions. called characteristic line. The characteristic line of a pump is checked with a test installation. There are pumps with characteristic lines: - steep characteristic change of Q results - flat characteristic very much even if a little. steep calculated between discharge, is shown in a curve by the manufacturer and H and flat line: small big change of H line: Q changes H is changed only The head H as shown in the characteristic curves of centrifugal pumps is the total or manometric head, i.e. the increase in pressure that takes place between the suction and discharge branches of the pump, expressed in meters liquid column. The head losses in piping installations include all losses due to friction, losses due to changes of direction of flow and sectional area, and any inlet and outlet losses into and out of containers. Velocity in suction pipe: g! e 100 sun max. 1.0 m/see 6 100 mm max. 1.5 m/set a 0.6 m/set normally Velocity in discharge high but with this it Required pipe 1.5 m/set to 2.5 m/set. This veloci%y is quite is possible to keep lower the costs for fittings. number of pumps: Each pumping station needs at least two independent pumping sets capable of providing the required delivery in order to ensure an adequate stand-by facility. Also, the system should be capable of pumping the maximum daily requirement ideally in 16 hours , and always in less than 20 hours. Parallel running of centrifugal pumps is never economical. conditions have to be checked seriously if a second plant run parallel to an existing one. 4-9.3.2 The discharge is installed to Pump drives governed There are various ways of driving a pump. The choice is generally by a community's financial resources. Always contact the manufacturer during the planning stage. Look for a drive which is sold on the local market (maintenance, repairs), if possible. Water turbines: A water turbine has the lowest running the initial investment is quite high, than other drives. cost as a pump drive. Even though this system is in the long run cheaper The rotation of the turbine wheel or runner is caused by water flowing over curved vanes fixed to the rim. The action of these blades is to change the velocity of the water in magnitude and direction. The impulse given to the wheel is entirely due to this change of velocity. A force causing rotation results as the water passes over the vanes. Turbines can be used in all cases where water is available in sufficient quantity with a head of at least 1.0 m. It is essential to contact the manufacturer in order to determine the correct type of turbine for a specific project as early as possible. Diesel engines: as such an engine is quite The most common pump-drive is a diesel engine, independent. It only requires gasoil and lubricants and these can be transported to nearly any place. In the diesel engine, air is compressed to a high pressure, hereby raising its temperature to over 1OOOoC. Gasoil is in:jected by the injection pump through the injection nozzles and ignites spontaneously. Diesel engines are four stroke engines (some are two-stroke). Diesel engines can be used to drive plunger as well as centrifugal pumps, provided suitable transmissions are fitted. A diesel engine should have about 25 % to 30 % more power than is required to drive the pump under normal conditions. For exact determination of the engine it is necessary to get in touch with both the engine and the pump manufacturer. It is important to state in your enquiry the altitude above sea-level, because the output of an engine decreases with increasing height. Electric drive: Electric drive is to be preferred if electricity is available at reasonable cost. Electric motors are relatively low in original cost and are economical to operate. Mains electricity supplies can rarely be used for our purposes. this drive is not explained more detailed. t Therefore, 4-9.3.3 Pumping stations Pumps are installed in a covered pumping station to protect them from rain and bad weather. If the pump is driven by a diesel engine it is necessary Fuel should,whenever possible, to provide adequate space for fuel storage. be stored in a separate room planned for this purpose. The pumps as well as the engines (electric or diesel) should be placed to allow easy access. The height of the pump-basis should be about 70 cm above the floor. The minimum distance between two pumps should be at least 80 cm. Some more important - - points are: suction lift never more than 5.0 m install always a strainer with a non return foot valve in the suction pipe the suction pipe and the reducers should be laid without any slope to avoid air-pockets install always a valve before and after the pump (possibly throttle valves) the stuffing boxes of the pumps should be leaking always pumps with big manometric heads should be operated in the following way: 1. starting the pump 2. open the valve 3. running 4. close the valve 5. stop the pump the exhaust system of diesel drives should be properly installed. Ensure good aeration and ventilation of the operation room Never run the pump without water! If possible a security switch should be installed to avoid working of the pump without water. L 145 4-9.3.4 Data needed by an enquirer 1) Arrangement or as per enclosed level ................ m 2) Purpose sketch No. .,...I.... altitude above sea of pump . . . . . . . . . . . . . . . . . ..I................................... 3) Duty of pump . ........ a) Discharge in l/set . . . . . . . . . . . . . . . . . . . . . . . . . . . or cu.m/sec m liquid column b) Manometric suction head .,........*..*........ m liquid dolumn c) Manometric head .,"........................... (including manometric suction head under 3b) 4) Data for installation (only above cannot be answered) a) Static Hd '90 or geodetic head: = Height between answer questions 4a and 4b if 3b and 3c pump centre line and upper water level ..... m line and lower water level ..... m HS gee = Height between pump centre H geo = Height between upper and lower = Height between lower water water levels ............... m H max or H' max b) Piping rd level outlet .......... m data: = Inside diameter of suction pipe diameter of strainer and foot . ..I...... .......... m = Total length of suction'pipe L.5 Number of bends in suction pipe Inside and free .. .... .. .. valve . . . . . . . . . . mm c) Supplementary information: .......................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..*......... ..,..........~....................................................... . . . . . . . . OC 5) Water temperature Specific gravity Is pure water being handled? ..,.....*.................................. Has the water corrosive properties? . . . . . . . . . . . . . . . . . ..I................ Solid constituents, nature and quantity of mud, sand, quartz, etc. If large foreign bodies are present in the liquid, state maximum diameter .......... of these 6) Drive a) Electric motor drive: Type of current: Direct, single or three-phase alternating current. Frequency . . . . . . . . . . . . . . Hz (cycles/set) Voltage .*............ volts Is the installation subject to dry, damp, wet or dusty conditions or is there a fire explosion hazard? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- . . . . . . I I i 146 ~&:~~.‘,‘,,; . 1 “~ b::. .,{‘, 1 .- ‘: %“’ I II,.,. . i,~’ ,:,‘.I b) Other drives: Petrol engine, Diesel engine, steam turbine .. .... ...... ... ...... If existent: Power N = . . . . . . . . . . Speed n = . . . . . . . . . . . . . . . . . . . r.p.m. : ;'I :'.. ‘/ :- , c) Belt drive: Driving pulley .I Diameter Width Speed . . . . . . . . . . . . . . . . . . mm . . . . . . . . . . . . . . . . . . mm . . . . . . . . . . . . . . . . . . r.p.m. 7) Service and economy Is the pump to work in parallel with an existing unit and discharge into the same system ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . If so, was the existing pump supplied by us ? . . . . . . . . . . . . . . . . . . . . . . Order No. ...................... enclose characteristic curve of pump. IS the If of other manufacture, pump to operate occasionally under conditions other than stated under 3a and 3b? If so, what are these conditions? ....................... Approximate number of working hours per year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...*.. In case of electric drive, cost per kWh of electricity 8) Information required for approximate calculation of pressure in the piping The following additional data is necessary for this purpose a) For the working conditions at maximum discharge - If the new pump is to discharge into a common pipe with pump or pumps, how great is the total maximum discharge ......... Hmano would then be ......... fluctuations an existing quantity? . . . . . . l/set ...... m b) Discharge pipe: - Total length of the pipeline ............... m . . . . . . . . ..I.... IMU - Mean inside diameter - Static head at the pump ............... m - Longitudinal cross-section of the pipeline, also showing vertical elevations as per Sketch No. . . . . . . . . . . . or Drawing No. . . . . . . . . . (If necessary indicate the various inside diameters) . . . . . . . . . . ..I..... - Is the pipe directly connected to a reservoir? - Is the pipe indirectly connected to a reservoir through a . ....... .......... reticulation network? - Is water continuously being tapped along the pipe, and if so, . . . . . . . . . . . . . ..I.. how much? c) Existing equipment to counteract pressure fluctuations. These may be: controlled non-return and discharge valves, flywheels, air vessels, surge tanks, etc. If any such device is available air injectors, please give brief particulars of its design, size, arrangement and the experience acquired with it . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~.................................. d) Remarks: 147 . 4-9.4 OTHER PUMPING SYSTEMS 4-9.4.1 Hydraulic ram A hydram is the best water lifting device, provided sufficient water flow (drinking water) and head are available. Drinking water must be available in sufficient quantity because it is also used as driving water. Mode of action: In the hydraulic ram (hydram), power is derived from water-hammer effect, produced intentionally, The force of the water is captured in a chamber where air is compressed by the sudden stopping of the main flow of water, and released when the compressed air expands, pushing a small amount of the water to a higher elevation than that from which it originally came. The water not lifted to the higher level is wasted. Each compression and decompression of the air in the chamber propels a definite quantity of water up to a storage tank (reservoir). There are two types of hydrams. Both types are in operation in North-West and South-West Provinces of the United Republic of Cameroon. The two types are supplied by: - John Blake Limited, P.O. Box 43, Accrington Lancashire, England - Schlumpf AG, Maschinenfabrik, 6312 Steinhausen, Switzerland Installation: - Blake; this hydram must be firmly bolted to a concrete base Schlumpf; this hydram must be firmly bolted to its drive pipe (no concrete base). Only steel pipes should be used as drive pipes. Ensure that the hydram is installed level. When a stop-valve is fitted on the drive pipe close to the ram, the valve should be fixed in a horizontal or oblique position to ensure that no air-pockets will form in the valve. Note: If a sluice valve is installed near a hydraulic ram it is necessary to fix the valve with its horizontal spindle (level) or if a special valve with an air tap is fixed the spindle should be at a 45O angle so that the air tap in the crown of the valve would be in a vertical position, so as to release any air which might accumulate there occasionally. If this point is not taken into consideration air may accumulate in the crown of the valve and this will influence the smooth operation of the ram or in some cases the ram will either stop or fail to pump water. 148 Fig. 89 Hydraulic A C R St Qi 0 S Ql Ll Hl H2 = = = = = = = = = = = w = = = = Q2 L2 D ram airation of driving pipe collection tank or sedimentation tank hydraulic ram storage tank supply from source over flow strainer at drive pipe driving water length of drive pipe difference in elevation between ram and supply - power head difference in elevation between ram and storage tank to which water is to be elevated - pumping head waste-water daily consumption supply from ram to tank - possible length of supply pipe distribution pipe similar to that shown in which Given suitable circumstances - a situation the supply of water is considerably in excess of the needs, and is situated in a way that permits the ram to be located well below the supply - the hydram can be an excellent solution to a pumping problem. It requires practically no maintenance and will work 24 hours per day requiring neither attention nor operating costs: When the driving water is delivered by a stream, the water has to pass a sedimentation tank in order to permit sand to settle out of the water. Period of detention approx. 1 hour. When writing Ql, Ll, HI, to the manufacturer about Q2, L2, H2 is necessary. Hl Keep in mind ~2 = 1:4 to 1:8. (1:4 to 1:5, ram sizes, the information in items The drive pipe should have a static pressure of max 15 m, if more, we need more stages. for rams of the make "Blake") . 149 Hl 4-9.4.2 The hydro Fig. pump Hydro pump can be used in wells 90 The principle of the hydro of depths up to 60 m. pump i . Discharge ---., valve closed L The sleeve retracts Suction open valve A ----- - - Suction: The pedal goes up, the sleeve retracts: water is sucked into the stainless steel pump body. Discharge valve open -- The sleeve extends +----- Suction closed valve Discharge: The pedal goes down. Hydraulic pressure is exerted in closed circuit on the elastic sleeve which expands and chases water to the surface. The advantages of this pumping system - the easy installation of the pump - the simple maintenance (all wearing and are directly accessible). are: parts are located Hydro pumps can be adapted for other types of drive: hrnd tyos wlnd whwl lypa in the pump head I Chapter Table 5: ADMINISTRATION OF PROJECTS of contents page 153 5-1 TECHNICAL REPOKT 5 - 1.1 The aim of the technical 5 - 1.2 Contents 5-2 EXECUTION OF PROJECT 156 5 - 2.1 Before starting 156 5 - 2.2' During the 5-3 COMPLETEDPROJECT 156 5 - 3.1 Financial 156 5 - 3.2 Final 5 - 3.3 Drawing 5 - 3.4 Document file of the technical 153 report report a project construction 156 statement report and handing-over file 157 157 of plans of a completed 153 project 157 5-l TECHNICAL REPORT 5-1.1 THE AIM OF THE TECHNICAL REPORT in the various The technical report is an important document, necessary steps of planning and implementing water schemes or other constructions. In the hands of the Ministry concerned, the technical report is the basic tool for preparing the budget of the new financial year as well as for the planning of the yearly activities. The technical report is required by the engineer or the technician in order to plan and to start a project. Foreign aid organizations all necessary information interested and details in co-financing a project in the technical report. will find The technical report must be well presented and should be attractive to the reader. Each page should be numbered and clear reference to the various chapters should be given. 5-1.2 CONTENTS OF THE TECHNICAL REPORT Listed below, as a guide line for technicians and engineers, are the Emphasis should be put on main points that make up a technical report. the preliminary surveys of the sources, before drafting the technical report (see chapter 3-4.1). 1. Introduction Reasons for proposing the project (e.g. present water conditions) Situation and actual infrastructure Population and demographic development and clear information is Socio-economical aspects (here, detailed especially necessary) Self help activities Map of the country showing the situation of the village 2. Water budget Available water and analysis Water consumption, actual and future Water balance 3. Project description Hydraulic system (general lay-out, chapter 4-l) Catchment Sedimentation, other purification plants (e.g. slow Pumping station, interruption chamber Storage tank, other tanks Distribution Construction methods, choice of material sand filter) 4, Estimated cost The estimated cost should be as accurate as possible. It is necessary to indicate the size and quantity of material (cement, reinforcing iron, include the inflation cost during the estimated pipes, etc.). If possible, construction time. Cost in cash: a) Buildings Catchmant Sedimentation tank (Or interruption Storage tank Stand pipes, wash basins Shower house & store b) Hydraulic tank) installations Pipes (plastic, galvanized, asbestos, Pump with driving engine (motor-pump) etc.) c) Sundries & hydraulics) (10 to 15 % of buildings Transport Tools, lubricant, Contingencies spare Parts Cost in kind: a) Community opening Bush clearing, and pits (foundations) supply of stones, Organization access gravel, of community b) CD Department roads sand, - excavating wood and other & backfilling material work / SATA-Helvetas Survey, projecting & planning Administration and supervision Total cost cost of the project per capita 5. Proposed / actual (= cash + kind) & stage I financing 10 % 10 % Village contribution in Cash Village contribution in kind Government contribution in cash (various grants) CD / SATA-Helvetas in kind Foreign aid in cash 20 % 20 % 40 % 100 % 154 available of trenches locally 6. Organization The Project organizes organizes collects prepares of the project Committee: meetings & community work the supply of local material the village cash contribution applications for grants (government Consultants to the Committee: - the community development to the Conslittee 7. Maintenance officer and the engineer remark These remarks project. are meant to recommend in a summary the construction to the technical Map of the country Plans of the village to be constructed. Hydraulic points to consider before planning Chapter 6 where all important and recommendation The completed report will be signed by the CD-Officer of the area. Annexes are consultants of the project Maintenance is one of the most important a water scheme. Please read with attention information is given. 8. Final & other) profile by the engineer of the (or technician) report indicating (lay-out) of a water the situation including supply. 155 of the village. all buildings and installations and 5-2 EXECUTION OF PROJECT 5-2.1 BEFORE STARTING A PROJECT A project should not start before it is approved Department and by the local authorities. by the Community Development It is necessary to have a clear picture of the financial sources as: dates of instalment from external aid, confirmation of government grants, etc. At least 50% of the village contribution should be paid to the project account before starting the construction work. It is necessary - to to to to 5-2.2 have have have have also: recruited all masons & labourers needed all tools, material & machines ready completed the technica,4L report with execution prepared the list of m,'iterial to be ordered DURING THE CONSTRUCTION Close supervision of a construction is necessary project. At the project site, daily book must be kept regularly plans ! to build properly the different elements reports must be made and a iog book with by the foreman. material Periodic reports have to be prepared by the engineer. These reports show the progress of the work, the problems, the contact with the local population, the financial situation and include a proposition of how the project will continue. When financial grants are given according to the progress d report and a financial statement are required in order amounts (Progress Report). 5-3 COMPLETEDPROJECT 5-3.1 FINANCIAL STATEMENT of the construction, to receive further As soon as the project has been completed a financial statement handed over to the department concerned (Community Development departments). will be or other The statement will show clearly the cost in cash on one side and the cost in kind on the other side for each partner involved in the project. 156 !+3.2 FZNAL REPORTAND HANDING-OVER FILE A final report of the completed time as the financial statement Committee. project will be handed over at the same to the CD department and to the Project The final the report should Technical - A brief - Comments on the technical aspects (possibility of extension, lifetime special care) and on the expected expectation of installations, output, influence of the new construction an the villagers and their surroundings. - Handing over note concerning the buildings & installations -Committee and a duty sheet to the caretaker. - history technical following: - 5-3.3 report, isnclude details & plans of all constructions. of the project. to the Project DRAWINGOF PLANS A complete set of execution plans for all constructed buildings and installations of the project should be drawn. These plans must include all modifications made during the construction. A site plan (lay-out) of the project should be drawn to scale 1 : 1000, 2000 or 5000 and show all new buildings and hydraulic installations (air etc.) and houses of the village with foot path. valves, cleaning valves, 5-3.4 DOCUMENTFILE OF A COMPLETEDPROJECT Technical report, other engines). Correspondence estimates, and receipts Minutes of meetings Repairs, possibilities Final All report situation with calculations, of material. and opening addresses. of extension. financial and execution statement. plans. instructions (pumps, turbines & Chapter Table 6: MAINTENANCE OF RURAL WATER SUPPLIES of contents page 6-l MAINTENANCE GENERAL 161 6-2 MAINTENANCE-INSTRUCTIONS 161 161 6- 2.1 Maintenance of wells 6- 2.2 Maintenance of catchments 6-2.2.1 Maintenance of spring catchments 6-2.2.2 Maintenance of barrages and river 162 intakes 6- 2.3 Maintenance of treatment stations 6-2.3.1 Maintenance of sedimentation tanks 6-2.3.2 Maintenance of slow sand filters 163 6- 2.4 Maintenance of storage 164 6 - 2.5 Maintenance of water 6- 2.6 Maintenance of distribution 6 - 2.7 Maintenance of pumping tanks 165 points system stations 159 165 165 MAINTENANCE GENERAL 6-1 Once a water scheme is completed it is necessary to pay great attention its maintenance so as to ensure a continuous supply of drinking water good quality and sufficient quantity. to of The completed construction of a water scheme has to fulfill all expected hygienic and technical requirements. Therefore, an improperly maintained water scheme can be a great danger to the entire population of a village because everybody assumes that the water flowing from the tap is good drinking water. Water is one of the most important elements of your life. WITHOUT WATERNO LIFE : Organization of the maintenance: Before the completed project is handed over to the villagers of the water supply should be organized taking the following consideration: the maintenance points into - A water supply maintenance committee should be formed in the village which takes the responsability of the completed project. - A caretaker should be employed. He will carry out the entire of the project as it is described in the following chapters. - The engineer handing over - All financial maintenance concerned is responsible the project. to instruct the caretaker matters and distribution of responsibilities should be regulated in advance. 6-2 MAINTENANCE-INSTRUCTIONS 6-2.1 MAINTEN.ANCEOF WELLS maintenance for before an efficient Every week: Control the cleanliness of the well, hand pump and surroundings. If necessary by the population. The drainage arrange for cleaning work, to be carriedout of waste water (overflow) is very important, to prevent any contamination of the ground water. Every month: Grease or lubricate pump, follow strictly maintenance. Every four every hand pump (compare Fig. 85). With an engine-driven the manufacterer's instructions regarding service and months: Check the construction should be done without and buildings and repair all damages. delay as soon as they are disccvered. Minor repairs All necessary maintenance work should contact cannot be solved by yourself, Office, which will give the necessary community and local council concerned. 6-2.2 MAINTENANCE OF CATCHMENTS 6-2.2.1 Maintenance Protective of spring be done regularly. If any problem the nearest Community Development assistance in cooperation with the catchments zone of the catchment area: Do not permit clearing and cutting of trees from the catchment area but maintain the fire boundaries (gaps) around the area (in the grassfield). Weekly inspections are necessary, especially during the farming season. people concerned to Prevent any farming inside the catchment area, report Special attention must be the local authority or to the administration. given to hair roots entering the catchment; if they are not removed they can cause a blockage in a short time. Spring catchment and inspection chamber: Once a month the overflow and surface drainages have to be inspected and Water measurements should be taken whenever the grass must be kept short. possible. Additional checking is necessary after heavy rainfalls. Two times a year (March and September) inspect and clear the collection and inspection chambers if necessary. Clean and grease locks. Check up whether there are any damage or cracks in slabs, chambers, pipes etc. Miner repairs: Carnage such as leaking pipes, cracked slabs etc. have to be repaired without any delay as soon as they are discovered. If the supply has to be stopped for necessary repairs the population has to be informed in advance. Major repairs: Repairs which require the attention soon as they are discovered. of the engineer have to be reported as Comments: All necessary maintenance work should be done regularly. If any problem contact the nearest Community Development cannot be solved by yourself, Office, which will give you the necessary assistance in cooperation with the community and local council concerned. 2 Maintenance of barrages and river intakes Inspections: Weekly: inspect dam, especially the spillway and intake. Check water If unusual contamination is observed find its cause (farming, latrines etc.) fertilizer, washing, fishponds, 162 quality. I Monthly: Minor inspect the overflow, damage. check if there are any cracks or other repairs: Minor repairs, delay. Major once a fault is discovered, have to be done without any repairs: Repairs which require the attention of the engineer have to be reported as to prevent waste of water, contamination and soon as they are discovered, further damage. 6-2.3 MAINTENANCE OF TREATMENT STATIONS 6-2.3.1 Maintenance of sedimentation tanks Inspections: clean and drain the tank. Keep installations, holes and drains clean. Cut the grass arount Grease doors, locks, valves etc. Monthly: Twice a year: general check up of the buildings leakages. for overflow, vent the entrances. damages such as cracks or Minor repairs: Minor repairs, once a fault is discovered, to prevent waste of water and contamination. Major have to be done without any delay repairs: Repairs which require the attention of the engineer have to be reported as to prevent waste of water, contamination and soon as they are discovered, further damage. 6-2.3.2 Maintenance Cleaning of slow sand filters_ of the filter: the water has to be drained first. Then 1 cm If a filter requires cleaning, to 2 cm of the sand surface must be carefully scraped off. When the sand-bed requires cleaning again a further layer of 1 cm to 2 cm of sand is removed This process is repeated until the minimum thickness for from the surface. efficient filtering of about 45 cm is reached. This level is marked in every filter. After each cleaning the filter is returned to service. Though the flow of water is reduced at first and the effluent is not connected to the supply until it shows that it is properly purified after an interval of about one to two weeks. The intervals for cleaning will depend on the amount of water which passes through the filter as well as on the contamination. It might be necessary in some areas to clean the filters every 3 to 4 weeks and in others every 8 to 12 weeks. 163 If the sand-bed has reached the minimum thickness it is necessary to wash out all the sand removed previously as well as the remaining sand in the filter. After this it will take at least 2 weeks until water from this filter can be used again for drinking. Washing of contaminated sand: Is is absolutely essential to stir the sand in such a way that all contamiand rub nation is washed out. To check if the sand is clean , take a hand-full it between your hands, if there is any sign of dirt on your hands the sand is not yet clean enough. The above should be understood as a general guideline. All mhould be followed strictly. by the engineer for each project instructions given Engineers in Cameroon are presently testing special sand wash places. results are available, a standard design could be worked out. General Once the inspection: Twice a month: Inspect the filter plant, keep installations, overflows drains clean. Cut the grass around the entrance. Twice a year: General check up of buildings once a fault is discovered, Minor repairs, to prevent waste of water or contamination, for damages (cracks have to be done without and or leakages). any delay Major repairs, requiring the attention of the engineer, have to be reported as soon as a fault is discovered, to prevent waste of water, contamination and further damage. 6-2.4 MAINTENANCE OF STORAGETANKS Inspections: Monthly: Clear the surroundings. Keep vents, drains, water quality and for possible contamination. (valves), look for leaks. Twice a year: look Clean the storage-tank, cracks, leakages, plastering, Minor for damages on the buildings, installation. repairs: Once a fault is discovered, repairs waste of water or contamination. Major etc. clean. Check the Check installation have to be done without delay to prevent repairs: Repairs which require the attention of the engineer have to be reported soon as a fault is discovered, to prevent waste of water, contamination further damage. 164 as and 6-2.5 MAINTENANCE OF WATER POINTS . _--- Maintenance of the spring catchment: clean Monthly: clear the surroundings, cut grass. Keep air vents, drain, etc. clean, check quality of water and for possible contamination. twice Important: a year: Greatest if 6-3.1 Weekly; At least wash-basin, see chapter any clean the storage-chamber, as cracks. attention must be given Minor repairs, once a fault is discovered, to prevent waste of water or contamination. 6-2.6 look damages such to the drainage. have to be done without any delay MAINTENANCE OF DISTRIBUTION SYSTEM Stand pipes, wash places Daily: Cleaning pipe. Weekly: General Monthly: and shower houses: by the consumer. check Special up and special Valve care should be given to the drain to avoid loss cleaning. Cut the grass if necessary. Leaking taps have to be repaired Soakaways don't need much maintenance. have to be cleaned immediately. immediately In case they are blocked of water. by dirt they chambers: Twice a year: Inspect and clean them. Any broken slab Repairs have to be done without delay once a fault is should be closed and opened during these inspections. 6-2.7 for should be replaced. discovered. All valves MAINTENANCE OF PUMPING STATIONS Pump and drive: The manufacturer's A special instruction can be made available maintenance instructions have to be strictly manual for each pumping station (from the appropriate engineer). regarding followed. maintenance Buildings: Monthly: Check installation for correct functioning Look for leakages. Paint the installation, that overflows and drains are clear. (valves or stopcocks). grease locks, etc. Check Chapter 7: SELECTED BIBLIOGRAPHY 1. - Hand Dug Wells and Their 1977, ISBN 0.903031.27.2 Construction (f 3.95) 2. - Hand Pump Maintenance in the Context Pacey, A., 1977, ISBN 0.903031.44.2 3. - Water for the Thousand Millions, ISBN 0.08.021805.9 (f 2.50) 4. - Water Treatment (f 2.00) 5. - Water, Wastes and Health 1977, ISBN 0.471.99.4103 by Watt, of Community (E 1.25) by Pacey, and Sanitation S. and Wood, W-E., A., by Mann, H.T., in Hot Climates (f 10.75) Note: All titles above from: Intermediate 9 King Street, London WC2E EHN, U.K. Well Projects. 1977, 1976, ISBN 0.903031.23X by Feachem, Technology R., et al., Publications Ltd., 6. - Slow Sand Filtration Countries by Dijk, 7. - Hand Pumps by McJunkin, E.F., Technical 8. - Water Supply for Rural Areas 1959, Monograph No. 42 and Small 9. - Typical Designs for Engineering Components in Rural Water Supply, published by WHORegional Publication South East Asia Series, World Health House, Indrapratha Estate, Ring Road, New Dehli 110 002, India for Community Water Supply in Developing J.C. van, Technical Paper No. 11, 1978 (US$ 10) Paper No. 10, 1977 (US$ 10) Communities by Wagner & Lanoix, Note: All titles from: WHO International Reference Centre for Community Water Supply, P.G. Box 140, 2260 AC Leidschendam, The Netherlands 10. - Shallow Wells, Report (approx. US$ 18) 11. - Small Water Supplies Note: Both titles Mauritskade bla, 12. - Handpumps for (US$ 1.95) 13. - Using Digging in Tanzania, 1978, US$ 4.50) from: TOOL Foundation, Communications 1092 AD, Amsterdam, The Netherlands Collective, Village from: Ave., by Ross Institute, Project 1978 (approx. Water Ressources, Note: Both titles 3706 Rhode Island of a Well Wells by Spangler, VITA 1977, C.D., VITA 1975, No. 28, No. 38 (US$ 5.50) VITA, Volunteers in Technical Mt. Rainier, Maryland 20822, 167 Assistance, U.S.A. 14. - Water and Waste Water Disposal, 1968, Wiley, New York 15. - Rural Water Supply New York 16. - Taschenbuch der Wasserversorgung Stuttgart, Germany and Sanitation All titles may also be ordered CH-9000 St. Gall, Switzerland through: 168 Volume II, by Wright, by Fair F.B., & Geyer, 1977, Krieger, by Mutschmann-Stimmelmayr, SCAT, Varnbiielstrasse 14, 1973, Chapter A 8: INDEX OF KEY WORDS Administration ,Aggressivity Air prevention 115 of... 40 of water Anchoring of pipe Asbestos cement aggressivity friction loss pressure test prevention of B 22 of water pockets, Analysis 151 of projects Back-filling 127 line 106 24 112 130 27 pipes towards AC-pipes in AC-pipes of AC-pipes corrosion of trenches Bacteriological field Bacteriological standards 124 40 test for drinking 167 Bibliography Calculation of piping Carbon dioxide 110 23 (CO2) Cement products aggressivity towards cement products prevention of corrosion I 19 80, 162 Barrage C water Centrifugal analysis Chemical standards of water for.drinking 41 water of water Climatic pattern Coffee washplace Coliform 15 of water Chemical Chlorination 143 pumps Characteristics 24 26 bacterial 20 20 6 137 count 19, 40 Completed project 156 Connection 134 details Consumption of water peak eonmumption. specific consumption Corrosion, prevention 111 34 26 of... 169 0 Daily water Deep well consumption 34 pump 141 Degree of hardness Distribution 25 buildings 135 Distribution system type of distribution systems design of the distribution system maintenance of the... 103 103 110 165 Drainage in Cameroon 14 Drinking water 19 standards E Execution of project F Field test 40 Field work 33 156 Filtration Final 90, report 157 Flow measurement Fountain, 35 public... 136 110 112 - 114 Friction loss in pipes . ..diagrams 0 Galvanized steel pipes friction loss in galvanized prevention of corrosion Gravity, steel Hand pumps calculation cycle Intakes 110 3 5 13 Infiltration Inspection of piping 150 Hydr0 pump 'I 112 148 ram Hydrology hydrologic 17 50 25 Head loss in pipes Hydraulic 107 114 28 140 Hardness of water Hydraulical pipes 49 supply by... Ground water supply of ground water H 96 chamber 73 82 12 - 114 K L Laying of pipes 123 Lay-out of water supplies lay-out in stages lay-out of distribution 49 50 103, 51 Location M of water Maintenance system 35 sources of rural water supplies 159 125 Marking of pipeline Measuring of water quantities 35 MPN Index (coliform) 19 test 40 . ..field N 0 Organization . ..of maintenance . ..of project Outlet P 161 155 76, 89 building 111 Peak consumption 22 PH - value Pipes pipe connections piping material laying of pipes to buildings Plastic pipes friction loss in plastic prevention of corrosion Plunger pump Pressure test Pressure zones Project pipes 134 105 123 106 113 29 139 130 of the pipeline 104 151 administration Pumps, types of pumps maintenance of pumping stations pump drives of water measurements ,..of spring water 139 165 144 Quantities 35 65 171 R s Rainfall intensity of rainfall quantity of rainfall tables of monthly rainfall 6 12 6 11 Rain water storage 50 Rectangular 38 weir River intake 80 Run-off 13 Sedimentation 83, 163 Service 51 life Shower house, public... 138 Slow sand filter 90, 163 Specific 34 consumption Spring location of spring spring catchment 17, 65 35, 49, 66 67, 162 Stages, 51 design in stages Standards for drinking Standbipe . ..with wash table water 19 135 137 Steelpipes Storage, 107 storagetank 99, 164 Stream . . . catchment t Technical Testing 18, 49 80, 162 report 153 the pipe line 130 Thompson weir 37 Thrust-blocks 127 Treatment of water lay-out of treatment station: maintenance of treatment station 83 97 163 Trenching 120 U V Vacuum, prevention of... 118 Vt31&3 valve chambers 108, 118 132 172 W 136 137 Washplace, public... Coffee washplace Water aggressivity of water analysis of water characteristics of water ground water standards for drinking water 22 40 15 17 19 Water lifting 139 Water point 78, Water sources location of water source Water treatment Wells handpumps for wells maintenance of wells 17 35 83 55 140 161 165 Appendix: NORMPLANS AND SCHEMEPLANS Norm plan No. Title of plan Public stand pipe Public wash place (in concrete Public wash place (in masonry construction) Public:fountain Interruption Water point construction) (in masonry construction) chamber with ball valve (in masonry construction) Scheme plan No. 7 Plumbing scheme of single storage tank 8 Plumbing scheme of double storage tank Project plans as examples Mankaha Bafut Water Supply (Situation plan) Mankaha Bafut Water Supply (Hydraulic Profile) [ 150m,n SECTION B-B SECTION A- A LIST OF MATERIALS STAND EISNT SOAKAWAY CEYE”T 1 N&o STD”ES IOIn’ PIPE 5 8165 WCLDCD WESN 26 I 46c.m RODS 0 6mm SOm Pm @ lmrn YND oN~y-Q----JDN 2rm. 0 6mm ?m. ’ 6- t2p-J. 16 4M 0 cmm IO am 0 10 6mm Ollm’ = 1.45m 1.2om AC 50 4Om 1 PIECE G.I. 4’ 0.25m 1 PIECE. TAP 4’ 1 6.1. SOUKET Y 1. 0.I. ELEW u STOKf5 5m’ SANII lm’ eMoN BLOCKS 6~ 16 a 20s4Dom : lm77m 10 3 I 1.5Dm 130 = OJOrn 4’or v 1 *’ nr I’ -------T 51 SLOPE 1s e+ r L-J L- - 1 50 . z .-. &!! 1 IS I ---5 - ---~---~~-~---~ SECTION B-B SECTION A- A LIST OF MATERIALS WASH PLACE CfMfNT - 15 BAGS SAND 2m’ GRAVEL - 2.5d STONES 2.5,x* G.I. 4’ THREADEO WTN ENDS I PIF.GE(OR V,‘) 6.1. a’ dOCrn 4 PlEOES 50cm WITH S0cKfT 1 PIECE G.I. 2’ 3Ocm TNREAOED ONE EN0 1 PIfCL TAP w 1 *I?? e SCCKETC I # , ” ELKlwtl , 1, WELDED MESH 1”s 210 I 0.70m’ Zno 195 I 0.75 In’ 1 no 0.35 .s 0.25 m* AC 100 4m RODS lo-. I em ,,& . O.,sn -3.1. 2’ “ II I Tn.. ,6nn SOAKAWAV CWNT - 15 l&S SAN0 - id Y” 166 10 , . IWIn R005; #‘mm 141 j2D’ 20000 360 /2D!lDj 40 !2G! ,;,‘, -- SECTION A-A 30 - 45 30 I SECT& B- Ei I W",W.JAY SECTIOiJ C-C LIST OF MATERIALS I - :: N 200 mxoE0 A.c.100 5mrvlr 5GND WLIll mN 5LM5 4m 1011' 414 SOAUAWAV CEnaY a05 4ilhc5 ~~54Nl l A9 WELaD 5rom YIQ YW roll 12d 1Rl' &?w LlITMNOE SUI 451 lW*m ORAIM PIPE - t Ii ’ !4 ’ ” 1 - hl ’ I t/!-l 1 1 I -0m uA5ONRY . LEAN CONCRE:TE 90 130 90 30 1 7 ‘I Y SECTION A A LIST OF MATERIALS FOUNTAIN 370 CEMENT 15 BAGS G.I. PIPES Y 3Ocm 9 PIECES G.I. SOCKETS +t’ 4 y Y’ 4 I iAPs w a’$2 ” G.I. TEES ** Y&1 y G. I. TEE G.I. NIPPLES @I’ 2 c G.I. PIPES fi’ 25cm 4 , G.I. PIPE r 115om 1 Y 0.1. ELBOW REO 18’-++’ G.I. PIPE N’min 250cm A.C. PIPE II 6Omm 4m , 30 I SOAKAWAY CEMENT ROOS ‘9 ‘g 140 14no 0 6mm 10 c WELDED MESH EOR ENTRANCE STONES SAN0 r.PAVFI 1 ^I PAVED 160cm. 10 -) = 170 SLAB = 45x 190cm 105 cm I.[10 , -91 7 - t 12 ml 1 m’ n*?“l . I FLOOR 110 4 BAGS 0 6mm 54m 17no $6mm L 30 310 L 1 t.llNlsTRY OF A4mcuLIuRE CC6iNNNlTy DEVELOPMENT DEPARMENT . LWREO REPUBLIC OF CAMERa HElMETAS SWtS6 ASS4YJATION FOR TEcHNlw ASSISTANCE ( 5ATA 1 MANUAL FOR RURAL MITER SLWLY PUBLIC FOUNTAIN IN MASONRY CONSTRUCTION PLAN KEY: EEZZZl CEMENT BLOCKSOR STONE MASONRY EZZil CAST CONCRETEOR STONE MASONRY lSZZZ?Y REINFORCEDCONCRETE (a) D ACCORDING TO THE MEASJJREMENTS OF THE BALL VALVE OVERFLOW AND CLEANING PIPE - SECTION B - B SECTION A -A Cl = CLIMBING IRONS BALL VALVE - ISOMETRIC VIEW OF MANHOLE VIEW C-C J COMMUNITY DEVELOPMENT DEPARTMENT UNITED REPUBLIC OF CAMEROON MINISTRY OF AGRICULTURE I/ I DRAIN PIPE I I HELVETAS SWISS ASSOCIATIONFOR TECHNICAL ASSISTANCE ( SATA) “. _” ,_ _I_ ‘, ,’ ,, -./ ), r GROUND PLAN > MANUAL FOR RURAL WATER SUPPLY INTERRUPTIONCHAMBER .( ‘,:..’ WITH BALL VALVE .‘b~..‘;‘,,.. ,,’ :,’ ._I) (.f,.‘ <‘,. I~ i2;I._,;, ;, -, ’i‘ .-?,...’ ‘, ,,‘(,‘. .,: DRAWN: BH DATE : MAY 1980 NORM PLAN No. 5 STORAGE VOLUME : ACCORRINGTO THE YIELD OF THE SPRING DURING DRY SEASON AND TO THE DAILY CONSUMPTION RETAINING WALLS TO THE TERRAIN ACtOR KEY : - STONE MASONRY CAST CONCRETE SECTION B -B REINFORCED CONCRETE ISOMETRIC VIEW SECTION StLIIUN C-C A -A SECTION D- D SToRAGE :IEANING L. I ., : YYI.1,. -4uNlTY DEVELOPMENT DEPARTMENT :n Dcc4im tm -- -. . .-m--m. UNITL, I &:;Q.:, ,;. I ‘)_ J,.i :,,. c.,,,._, ‘‘,’ ,r *,>..” C’.~s,. l-h1 QJPLIL ur LAMkKUUN MINISTRY OF AGRICULTURE 1 ,?% HELVETAS _,.,I _^ -mm--. -->WI>S ASSLKIATION FOR TECHNICAL ASSISTANCE ( SATA) MANUAL FOR RURAL WATER SUPPLY & . .;,)WATERPOINT -.I:‘.’ :,I_i ,. I.’ / IN MASONRY CONSTRUCTION ORAWN : DATE : MAY 1:: NORM PLAN PIPE DRAIN PIPE OR DRAIN CHANNEL GROUND PLAN f+ T’T- AERATION WITH PROTECTIVE COVER BALL VALVE .-__ -. - b AERATION DISTRIBUTION --w -- I TAP 7 > GATE VALVE OVERFLOW ~ i+r I SUPPLY FROM CATCHMENT (FILTER ) DISTRIBUTION STRAINER [ KUGLER 619111 - COMMUNITY DEVELOPMENT DEPARTMENT UNITED REPUBLIC OF CAMEROON :.~ OVERFLOW PIECE [ KUGLER 61642 1 AND CLEANINGPIPE MINISTRY OF AGRICULTURE HELVETAS SW&S ASSOCIATION FOR TECHNICALASSISTANCE (SATA 1 DRAWN BY BTC DATE : MAY 1900 PLUMBING SCHEME SINGLE STORAGE TANK AERATION WITH PROTECTIVE COVER I AERATION WITH PROTECTIVE COVER -. 7 BALL VALVE BALL VALVE r AERATION DISTRIBUTION TAP OVERFLOW GATE VALVE c GATE VALVE OVERFLOW I t. . i I I STRAINER [KUGLER 61911I STRAINER [KUGLER 61911 I-- @ DISTRIBUTION TO VILLAGE -; I- L - : CC%ll’dJNlTY COMl’dJNlTY DEVELOPMENT DEPARTMENT UNITED REf’UBUC OF CAMEROON ,; !, HELVETAS SWISS ASSOCIATIONFOR TECtiNlCAL ASSISTANCE (SATA 1 ;;,:: ,; I .,_ I\: :: 2.. I.$ ’ l:; I.i ;,._, i..,: b’j. : &IL: ,p:> 2:, -,;,; ;f,;; ; OVERFLOW PIECE IKUGLER 616421 GATE VALVES MINISTRY OF AGRICULTURE MANUAL FOR RURAL WATER SUPPLY PLUMBING SCHEME OF DOUBLE STORAGETANK DRAWN BY BTC DATE : MAY 1960 SCHEME PLAN No. 0 SUPPLY FROM CATCHMENT(FILTER1 PLUMBING SCHEME DOUBLE STORAGE TANK COMMUNITY TECHNICAL MANKAHA WATER DEVELOPMENT SERVICE - DEPARTMENT BAMENDA BAFUT DRAWN: DATE l : 10:03:?5 HODiFYD:O.NC HYDRAULIC I MUM NEKURU SEAT PUBLICATIONS Publ. No. 1. Jean-Max Baumer: Schweizerische Kontaktstelle fur Angepasste gratis Technologie (SEAT), St. Gallen 1977, 39 Seiten, 2. Jean-Max Baumer: Angepasste Technologien fiir Entwicklungslgnder, Literaturstudie, St. Gallen 1977, 132 Seiten (out of print) 3. Jean-Max Baumer: Angepasste Technologien fiir Entwicklungsldnder, Bibliographie, St. Gallen 1977, 307 Seiten (out of print) 4. Jiirg 5. Sabine Huber: Probleme des Technologie-Transfers 13ndern in EntwicklungslBnder, St. Gallen 43 Seiten (out of print) 6. Gerhard Schwarz: des Konzepts Cindern, St. 7. Otto 8. Helvetas: Manual for Rural Water Supply, St. Gall 1980, 175 pages, with many detailed constructional scale-drawings, SFr. 34.-(US$ 20.--j Nipkow: Angepasste Technologien fur EntwicklungslZnder, Sonnenenergie-Gerate fur Haushalte, St. Gallen 1977, 62 Seiten, Fr. 8.50 Langenegger: in Aethiopien, von Industrie1978, Hemmnisse und Hindernisse bei der Verwirklichung der Angepassten Technologie in EntwicklungsGallen 1978, 53 Seiten, Fr. 14.-Einsatz von Bohrmaschinen fiir die Wasserbeschaffung St. Gallen 1979, 43 Seiten, Fr. 14.--
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