National Water Supply And Drainage Board - Irc

The standards tor water quality in Sri Lanka are based ontheSLS614, 1983 - Part 1 Physical and ChemicalRequirements, and Part 2, Bacteriological Requireidenis ,which are similar to the WHO Standards (See Table 2.1,2.2).These standards should always be applied with. commonsense, particularly for small community and rural watersupplies where. the choice of source, and the opportunitiesfor treatment are limited.The criteria should not in themselves be the basis forrejection of a groundwater source having somewhat highervalues for iron, manganese, sulphates or* nitrates than inthe Table. Care must be exercised in respect of toxicsubstances such as heavy metals, which should be allowedonly after expert opinion of the health authorities hasbeen obtained.For small supplies which frequently axe to be providedfrom individual wells, boreholes or springs, the waterquality criteria may have to be relaxed. Obviously, inall instances, everything possible should- be done to limitthe hazards of contamination of water.j Using relativelysimple measures such as the lining and covering of a well,it should be possible to reduce the bacterial content ofwater (measured as coliform count) to less than 10 per 100nL, even for water from a shallow well, persistent failureto achieve this (particularly if E. doli is repeatedlyfound) should as a general rule lead to condemnation ofthe supply.\-6-

Table 2.1SLS 614 (1963)PART 1 - PHYSICAL AND CHEMICAL REQUIREMENTSCharacterist ie{!i ''PHColourOdourTasteTurbidityElect.Conduct iv ityChloride (Cl)Chlorine—Free resid(Cl'Alkalinity (as CaCOAmmon i a—FreeAmmon i a—A1bum ino idNitrate (as N)Nitrite (as N Fluoride (as F)Phosphates-Total (PO )Total SolidsHardness Total(as Ca Co )Iron-Total (as Fe SulphateCalciumMagnesiumCopperManganesei ZincMaximum DesirableLevel7.0 8.5 units5 un itsUnobjectionable2-JTU750 uS/cm200 mg/L2000.6""—500I Mercury8-ïJTU35pO uS/em1200mg/L4000.06"250 "0.3 "200 "100 "30 to 150 *0.050.05 "5.0 ;tiO.Pl«!1.5ti200060D40024b;- 15D:1,50.515 00.20.050 .i)050.Ò5O.p5o.poiCh '"tí 1! (COD)i 10Î2.-0'MÊÊÈÉÊ&ÍChromiumAnionic Detergents(as HBAS-LAS)Phenolic Compounds: (as Phenolic OH)Oil & Grease Pesticide Residue\ Chem. OKvsen DemandH0.Í15———— Cadmium! Cyanide\ Lead&.5 - 9.0 units30; unitsUnobjectionablerr, AluminiumI ArsenicMaximum PermissibleLevel0.05HitHfiHHiiHi!!!0.2 mg/L1.00.001 "0.002H1.0II -(Refer to WHO &!FAO requirements) 10 m 8 /Li¡Depending on sulphate content, i.e. for 250 me/h sulphate,max Mg. is 30 mg/L; for less sulphate, wore Mg is allowed-7-

Table 2.2SLS 614 (1963)PART 2 - BACTERIOLOGICAL REQUIREMENTSPipe—borne water supplies:2,oThroughoutany year, 95 per cent of the samples shallnot contain any col i for» organists in 100 mL.oNone of the samples examined shall contain «tore than10 coliforw organisms per 100 iL.oColiform organisms shall not be detectable in 100 mLof any two consecutive samples.oNone of the samples examined shall contain E.coli100 mL. (Faecal coliform).inIndividual or small community supplies:NOTE:oNone of the20coliformexam i nat i on.oNo samplecoliform)samples examined shall contain more thanorganismsper100 mL on repeatedshallIndividual or sinal1bores and springs *containE.communitycoli in 100 mL, (Faecal suppliesincludeWei Is „::1 Populat ionServedMinimum Number ofSamples;to be TakenFrom Whole Distrib.System Each Monthtnt erv a 1piSuccessiveSamplesiLess than20,00020,000 to 50,00050,000 to 100,000More than 100,00012A1MonthWeeksDaysDay-8- :1 Sample-per 5000 popn.1-do - do 1 Sample per 10000 popn.

2.4WATER RELATED DISEASESWriterr e l a t e d d i s e a s e s are tho.se t r a c e a b l e to w a t e r supplyande x c r e t a d i s p o s a l . T h e most important of t h e s e d i s e a s e slav be c l a s s i f i e d as iollows;CategoryT r a n s m i s s i onWater—s iteinsect c a r r i e dSpecificDiseases African t r i p a n o s o m i a s i sD i sease—carry i rtginsects breed in o r I (sleeping s i c k n e s s )near water.SOnchocerciasis (river!blindness):¡Halaría!Arboviruses(yellow f e v e rland d e n g u e )JFilariasis (includinge 1 e p h a n t i as i s )J a p a n e s e eiíicephalit isWatercontactWater qualitymicrobiological] Disease transmitted Schistosowiiasis by direct contact'(hi lhar ziasis )I with water.! -,Disease transmittedby c o n s u m p t i o n ofm i c r o b i o logicallycont am i nat edwater.CholeraîTyphoid feverDiarrheaDy s ent ery (amoeb i c,bacillar ; y)Guinea worm( d r acorit i a s i s )Sanitation—! related/water! hygieneD i s e a s e t r a n s m i t t e d Shigellosiisby inadequate u s e( b a c i 1 lary d y s e n t e r y ) ., of w a t e r .Trachoma andconjuct iiy it isEscarias i s (roundworm)Scabies-The various categories are:oWater—site%in s iot- carried — where thei source or supplysite provides a breeding ground for insects such asmosquitos, which transmit diseases by biting people —it is not necessaryfor people to ,cose into contactwith the water. Transmission is complex, involving ahost(man or animal), a parasite that causes v.hedisease(protozoa or worm) and a carrier (insect, flyor mosquito). Malaria, filariasis, dengue and Japaneseencephalitiscarriedby mosquitos.Pipedwatersupplies, and elimination of mosquito breeding places,would help to control these diseases.;-9-

oWater contact. - where contact with water such asswimming ¡w sufficient to produce infection in people,usually through a disease-eausine orgímisn penetratingthe feet, legs, hands or other part of;the body.oWater quality — microbiological — where consumption ot«¿ ater causes disease by ingestion of a geriu, or toxicsubstance.These diseases are endemic in areas whereexcreta disposal is haphazard and can achieve? epidemicproportions in serious cases of contamination.oSanitation-related water hygiene — infection is mostcommon due to faecal contamination of water, food, andfingers and might have been eliminated through properwashing or cleaning.-10-

3.SAMPLING AND TESTINGA sanitary survey is essential for the adequate interpretation of chemical and bacteriological analyses ofdrinking water supplies.It consists of an extensivefield inspection and evaluation of local environmental aridhealthconditions by assessing current and potentialhazards to the water supply or existing water system.Sanitary surveys are important as backup information wheninterpret ing the results of water analyses. If analysesindicate contamination of the water supply, a sanitarysurvey should be conducted to identify the source of thecontamination.Sanitary surveys should be conducted for:odevelopment of new water sources;""orehabii itat ion/inspect ion of existing schemes.Simple observation is the major parti of all sanitarysurveys.Inspections of existing waiter supply systemsinvolve checking facilities and operational practices forsigns of contamination. For example, * «ater from a wellshould be considered as possibly contaminated if the wellis uncovered or unprotected, or when the, collection vesselis not kept clean.Leaking pipes «ay- draw in sewage orothercontaminationfromthesoil? particularly inintermittent systems.-,If a sanitary survey reveals possible bacteriologicalcontamination, further investigation shoXild should be doneto determine the source and the level of contamination anddeterminethetreatmentneeded, or. steps taken toeliminate the source of contamination - \Sanitary surveys of existing systems can reveal physicaland chemical impurities. Water that isfturbid may not besafe or aesthetically acceptable. If pipelines, pumps orother system components are corroded, thje water supply maybe chemica5Í pâ ia»inated, Hard, scaly! deposits on pipesor pumps ítffifiííSt water with high mirteral content whichmay be unsuitable for many domestic purposes. Hiñeraiscan encrust pipes and pots.If red stains appear onplumbing the water may be high in iron;. If the commun i tybeliev«sawatersourceisharmfuleven thoughcontamination is not évident, the water should be testedfor harmful toxic chemicals.-11-

It. .i sanitary survey reveals possible physical or- chemicalcontamination, a complete laboratory art.ilysis should bedone to verity conditions. It analysis reveals that thewater system is seriously contaminated either physical]yor chemically, the problem should be solved iiuuted » ate-1 y oranother water source should be developed.3-2I PES OF ANALYSI.SThe following types of analysis are listed in Reference 4as being carried out by NWSDB Central Laboratory.oPartial Analysis (Short)Theparametersassessedfor a partial analysisinclude: temperature ( C), residual chlorine (RCl)thardness(EDTA), alkalinity(ALK), : chloride C1),hydrogenionconcentration pH.- ,electricalconductivity(EC) t turbidity (NTU)t: and sometimes,colour and ion. Other parameters may be included whendemanded — such as copper, sulphides, sulphates, andnitrogen as ammonia and albuminoid,;oComplete Analysis (Major Constituents) ?The traditional "Complete" analysis,- in addition totheparametersmeasuredfor partialanalysis,includes:silica (S1O2), calcium, j(Ca) , magnesium(Mg), sodium (Na) , potassium (K), sulphate (SO ),chloride C1), nitrate (NO3), fluoride (F) , boron(B), and total filterable residue (TFjR) . Values to es (CO3), bicarbonates (HCO3), free carbondioxide (CG2), percent sodium (%Na , ¡ total dissolvedsolids TDS), and the sulphate to [chloride ratio(SG Cl),Ammonia nitrogen and albuminoid nitrogenmay require analysis as demanded by the nature of thesource water.o- -Hinor and Trace Inorganic Analysis(Metals and Nonmetals)T' :The analyses J.».this group are scheduled on a rotatingbasis .- á l t f'inor and trace inorganic constituentsinclude: S WMTn'ítim (Al), arsenic (Ajs), barium (Ba) ,beryIlium (Be), cadmium (Cd , chromium (Cr), cobalt(Co), copper (Cu), iron (Fe , lithium Li), lead (Pb),manganese (Mn), mercury (Hg , molybdenum Mo), nickel(Ni), selenium (Se), silver (Ag), strontium (Sr), andzi ne (Zn)TNonmetalminorand trace inorganic constituentsincl ide sulphate (H2S), phosphates (PO4), nitrates(NO2-ÍÍ),ammonianitrogen(NH —N) ,and organicnitrogen (Org.N). -12-

oOrganic AnalysisChemical. oxygen demand (COD), biological oxygen dewiand(BOD), extractable oil arid grease, and total organiccarbon (TOC) are included in this group,oMicrobiological AnalysisThis analysis of water includes tests for col i form andfaecalcol i for» organisms.In addition, specialstraining techniques such as the gram stain are usedwhen applicable.oBiological Analysis;Thisanalysis of water from surface sources andreservoirs includes the identification and enumerationof observable organises, Included in the grouping arethe green and blue—green algae, and ther floral formssuch as submerged aquatics, and animate forms such asthe aquatic invertebrates.oReservoir and source waterThesewatersaremonitored for fluctuations indissolved oxygen, pH, conductivity, and turbidity (oran equivalent) as a function of location, depth andtime with the objective of obtaining improved waterquality through better reservoir management."i ¿Another analysis which is ofrehabilitation of schemes is:ointerest'iindesignandFilter Media Cleanliness Déterminât ioij.Designedto provide a quantitative evaluation offilter media condition (cleanliness) and/or backwashefficiency.Thisprocedurecanbe used forcleanliness determination on any type of filter media.Media samples can be taken in depth increments for thedetermination of accumulated solids at any particularlayer, or a standard 300 mm core sample can be takenfor the determination of the total accumulated solidsremain ing j r tOfcAwme of filter media. ;The results in g»/L are compared to those of a newmedia placement or specially washed used media. Afilter bed should be investigated at least twice peryear to determine the condition of the media in orderto advise on maintenance or to evaluate filtrationeffectiveness. The need for this type of determinationcan be observed in the monitoring of filter effluentturbidit les,I-13-

In addition, it should he noted that the Laboratoryconductsanalysesto measure the characteristics oítreatment chemicals and the characteristics of sludge.3,3SAMPL¿NG PROCEDfJRESAccurate analysis of a water sample depends on propercollection of the sample. Samples must be taken fromseveral locations at different times so that they arerepresentative of the entire water supply. Samples forspecific analysis are those collected when a new watersource is being developed, when an outbreak of waterrelated disea.se occurs, when a scheme is being rehabilitated, or when water pollution is suspected. Samplescollected regularly to monitor an existing water systemare for routine analysis.Methodsofsample collection depend on whether theanalysis to be made is bacteriological or physical andchemical, and on whether the sampling and analysis areroutine or specific. The main considerations in samplingare to collect representative samples; of the water andtransportthem quickly to the laboratory. Where theequipment is available, field testing m&y also be carriedout.I\Samples must be collected irt the correct volume, with theright device and in the right container. They must bemarked properly showing the date, time md exact locationof the sampling point, and be accompanied by &n analysisrequest form showing the required tests. In addition,samples should be adequately preserved if required, andtransported to the laboratory with a;minimum of delay.Analyses only represent the water quality at the time ofsampling, and it will often be necessary to take a seriesof samples at different times or seasons in order toobtain a more complete picture of the water qualityvariations.This is particularly true for bacteriologicalsamples — analysis of a single sample is not reliable.For routine bacteriological sampling, i the frequency ofsampling is established in SLS 614. (See Table 2.2)Samples fo feaet:eiráological analysis must be collected insterile. - ia - Jliíles with sterile stoppers. A paper orfoil hood over the stopper and bottle neck is necessary.Stoppers can be made of ground glass or rubber. Normally,fre-steri 1 i seds amp* lebottles are obtained from theCentral Laboratory.In an emergency, well—washed bottlesfan be sterilizedin the field by boiling them for fiveminutes. If sample bottles are not sterile, any bacteriapresent on them will wake the analysis useless. Thesample bottle must be kept sealed, and the stoppers andbattle neck should be covered with parchment paper or thinaluminium foil.The covering should be kept in placeafter sampling.Each sample should be at leastf 100 mL inorder to perform all tests required for bacteriologicalcontamination,,.

Samplerforphysicalandchemicalaria lys is mustbecollectedinchie if¡ Í ca 1 lycleanp l a s t i c or f;lass b o t t l e s .Atleast2litresofwaterneed to be collected for ac o m p l e t e physical and c h e m i c a l a n a l y s i s dasanewsourceshouldnot be collected tooclosetothebank n o r too d e e p u n d e r the s u r f a c e .Areasofstagnationshouldbeavoided.Samples should not bedrawnfromthesame spot every time, but should be takenf rom d i f fereiit po i nt s .Inpiped w a t e r s y s t e m s , s a m p l e s should be collected at allpointswherewaterentersthed i s t r i b u t i o n system.Inaddition,samplesshouldbedrawnfromtaps c o n n e c t e ddirectly to the w a t e r main andnot from s t o r a g e t a n k s .Specialsamples need to be d r a w n from known problem a r e a s ,suchasareas w i t h low p r e s s u r e , areas w i t h high leakage,andareasfarfrom t h e treatment plant, 1 When c o l l e c t i n gbacteriologicals a m p l e s , great c a r e must ïj e taken to avoidcontaminationofthe sample by t o u c h i n g the inside of thestopperor b o t t l e n e c k or c o n t a m i n a t i o n from o t h e r sourcesapartfromthewaterbeingtested.Bottles should belabelled immediately a f t e r s a m p l i n g .Thefollowingproceduresdifferent sources:should be used for sampling fromoStreamor r i v e r — collect fro» m i d s t r e a m , if p o s s i b l e ,holdingbaseof b o t t l e and s c o o p w a t e r in an u p s t r e a mdirection beneath the locations,plungingbottleneckd o w n , into the w a t e .oShallowwell—useaweightedrequired d e p t h , u n t i l full.oHandpumpwell—b e f o r e sampling.oTap— ÈÏ SÊ'" 1 -'runbefore sampling.Sampleoooooopumpto w a s t e for attow a s t e for atlabels should g i v e the f o l l o w i n gS a m p l e number;R e a s o n for sampling;Exact p l a c e of .sampling and type ofT e m p e r a t u r e of sample s o u r c e ;D a t e and time of sampling;Sample d e p t h (if r e q u i r e d ) ;-15-b o t t l e andlower toleast1 minuteleast1 minuteinformation:source;-,

Additional ¡informai ion, as shown itt Table 3,1 should be.kepi for each sample, to aid in the in.terprM.at ion ofresults.It is also useful to sketch on the reverse sideof the. form the example location.Storage of s W ElesChanges occur in the bacteriologicalcontent of water when it is stored. To get an accurateanalysis, bacteriological testing of the water sample isbest begun within one hour of collection. Samples forbacteriological analysis must, be tested within 24 hours ofcollection.When a field kit is used to analyse samples,testing within one hour of collection is possible. Ifsamples must be transported to another site, they must ntative of the water supply at th

5. 7 Horizontal Flow Sedimentation Tank 51 5. 8 Radial and Vertical Flow Sedimentation Tanks 52 5. 9 Sedimentation Tank — Typical Design 54 5.10 Sedimentation Tank - Simple Inlet & Outlet Arrangements 57 5.11 Tilted Plate Clarifier 59 5.12 Rapid Sand Filter - Main Features 62 5.13 Rapid Filter - Typical Design 63 5.14 Declining Rate Operation 68