L2 - Sources of water.ppt

Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, including being safely returned to the environment. Water treatment removes contaminants and undesirable components, or reduces their concentration so that the water becomes fit for its desired end-use. This treatment is crucial to human health and allows humans to benefit from both drinking and irrigation use.

1. WATER SUPPLY ENGINEERING
ENVIRONMENT ENGINEERING I
SOURCES OF WATER

2. Public Water Supply Projects
In any public water supply project, following steps are essential -
1.Estimationofwaterdemandduringdesignperiod(quantityrequirementinservicelife)
2.Identificationofwatersourceandmeansofwaterwithdrawalfromthesource
3.Arrangementforconveyingrawwaterfromwithdrawalpointtothetreatmentfacility
4.Watertreatmentforproducingusablequalitywaterattreatmentplant
5.Transmissionofwaterfromtreatmentplanttostoragestructures
6.Waterdistributiontoendconsumers
2ASST.PROF. PRACHI DESSAI

3. Criteria for Water Source Selection
Characteristicsofthesource(s)ofwater,and
wateritself:
1.AvailabilityofWater
2.GenerallongevityoftheSources(short-
termandlong-term)
3.Waterquality
4.Potentialforfuturepollution
5.Accesstothesource
3ASST.PROF. PRACHI DESSAI

4. Criteria for Water Source Selection
Regionalgeographicproperties:
1.Distanceofsourcefromthecenterofwater
consumption
2.Availabilityofnaturalorman-madewater
storagecapacities
3.Availabilityofanynearbyelevatedterrain
4.Natureofsoilstobeusedforinstalling
waterconveyance
Feasibilityforstage-wisedevelopment
1.Economicsandcost
4ASST.PROF. PRACHI DESSAI

5. Natural Sources of Water
Wateristhemostabundantcompoundinnature.Itcovers75%oftheearthsurface.About97.3%of
wateriscontainedinthegreatoceansthataresalineand2.14%isheldinicecapsglaciersinthe
poles,whicharealsonotuseful.
Surface water
◦Streams & Rivers
◦Ponds & Lakes
◦Impounding
◦reservoir
Subsurface water
◦Infiltration galleries
◦Infiltration wells
◦Springs
5ASST.PROF. PRACHI DESSAI

6. Rivers & Streams
Riversandstreamsarethemainsourceof
surfacesourceofwater.
Insummerthequalityofriverwaterisbetter
thanmonsoonbecauseinrainyseasontherun-
offwateralsocarrieswithclay,sand,siltetc
whichmakethewaterturbid.
Someriversaresnowfedandperennialand
havewaterthroughouttheyear.
Mostlyallthecitiesaresituatedneartherivers
dischargetheirusedwaterofsewageinthe
rivers,thereforemuchcareshouldbetaken
whiledrawingwaterfromtheriver.
6ASST.PROF. PRACHI DESSAI

7. Natural Ponds & Lakes
Alakeisaninlandbodyofwaterthatisnot
partoftheocean.
Formedwithimperviousbedbyspringsand
streams.
Lakeslargeranddeeperthanapond.
Qualityoflakedependsupon:
◦BasinsCapacity
◦Catchmentarea
◦Annualrainfall
◦Groundporosity
7ASST.PROF. PRACHI DESSAI

8. Impounding Reservoirs
Someriversflowbecomesverysmalland
cannotmeetrequirementsofhotweather
WaterisstoredbyconstructionBundorweir
wheremaxquantityofwatercanbestored.
Suspendedparticlessettleatthebottom,
growthofalgaewhichproducebadtasteand
odor.
Purificationisnecessarybeforeconsumption.
8ASST.PROF. PRACHI DESSAI

9. Infiltration Galleries
Usedtocollectwaterfromtheaquifer
underlyingariver.
HorizontalTunnel
Constructedthroughwaterbearingstratum
Masonryorconcrete
Weepholes=5*10cm
9ASST.PROF. PRACHI DESSAI

10. Infiltration Wells
Infiltrationwellsaresunkinseriesinthebanks
ofriver.
Closedontop&openatthebottom
Brickmasonrywithopenjoints.
Waterinfiltratesthroughthebottomgets
purified.
Connectedbyporouspipestocollectingsump
calledjackwellthenwateristakentotheplant
10ASST.PROF. PRACHI DESSAI

11. Springs
GravitySprings:Whensurfaceoftheearthdropssharply
thewaterbearingstratumisexposedtotheatmosphere
andgravityspringsareformed
SurfaceSprings:Itisformedwhenan
imperviousstratumwhichissupportingthe
groundwaterreservoirbecomesanoutcrop.
11ASST.PROF. PRACHI DESSAI

12. Springs
ArtesianSprings
◦Whengroundwaterrisesthroughafissurein
theupperimperviousstratum.
◦Anartesianaquiferisconfinedbetween
impermeablerocksorclaywhichcauses
positivepressure.Thiscausesthewaterlevel
inawelltorise.
12ASST.PROF. PRACHI DESSAI

13. Groundwater Systems
Confined(orpressureorartesian)Aquifer:
Boundedbothaboveandbelowbyimpervious
stratawheregroundwaterisconfinedunder
pressure.
Unconfined(orphreatic)Aquifer:Boundedby
afreesurfaceattheupperboundary,whichis
knownaswatertable,wherewaterisat
atmosphericpressure.
13ASST.PROF. PRACHI DESSAI

14. Groundwater Systems
PerchedAquifer:Occurswhenevera
groundwaterbodyisseparatedfromthemain
groundwaterbyarelativelyimpermeable
stratumofsmallarealextentandbythezoneof
aerationabovethemainbodyofgroundwater.
LeakyAquifer:Overlainorunderlainbyasemi
perviousaquitard,orsemiconfininglayer,
theseaquifers(confinedorunconfined)loses
orgainswaterthroughadjacentlayers
14ASST.PROF. PRACHI DESSAI

15. Groundwater Systems
Aquitard:Asaturatedbutpoorlypermeable
stratumthatimpedesgroundwatermovement
anddoesnotyieldwaterfreelytowellsbutthat
maytransmitappreciablewatertoorfrom
adjacentaquifers.Example-sandyclay
15ASST.PROF. PRACHI DESSAI

16. Groundwater Systems
WELLS:
Awellisdefinedasanartificialholeorpitmadein
thegroundforthepurposeoftappingwater.
InIndia75to85%ofIndianpopulationhasto
dependonwellsforits
watersupply.
Thethreefactorswhichformthebasisoftheoryof
wellsare
1.Geologicalconditionsoftheearth’ssurface
2.Porosityofvariouslayers
3.Quantityofwater,whichisabsorbedandstored
indifferentlayers.
16ASST.PROF. PRACHI DESSAI

17. Groundwater Systems
Thefollowingaredifferenttypesofwells
1.Shallowwells
2.Deepwells
3.Tubewells
4.Artesianwells
17ASST.PROF. PRACHI DESSAI

18. Groundwater Systems
ShallowWells:
1.Constructedintheuppermostlayerofthe
earth’ssurface.
2.Diameter-2to6m,Depth-7m.
3.Linedorunlinedfrominside.
4.Quantityofwateravailablefromshallow
wellsislimitedastheirsourceofsupplyis
uppermostlayerofearthonlyandsometimes
mayevendryupinsummer.
18ASST.PROF. PRACHI DESSAI

19. Groundwater Systems
Deepwells:
1.Obtaintheirquotaofwaterfromanaquifer
belowtheimperviouslayer
2.Treatmentwouldbenecessarytoremovethe
hardnessofwater.
3.Thewateravailableatapressuregreater
atmosphericpressure,thereforedeepwells
arealsoreferredtoasapressurewells.
19ASST.PROF. PRACHI DESSAI

20. Groundwater Systems
Artesianwell:
1.Wellfromwhichwaterflowsundernatural
pressurewithoutpumping.
2.Pressurefromthewater’sweight(hydrostatic
pressure)forceswatertothesurfaceofawell
drilleddownintotheaquifer;thepressurefor
thesteadyupflowismaintainedbythe
continuingpenetrationofwaterintothe
aquiferattheintakearea.
20ASST.PROF. PRACHI DESSAI

21. Groundwater Systems
Tubewell:
1.Long,100–200millimeters(3.9–7.9in)-wide
2.Stainlesssteeltubeorpipeisboredintoan
undergroundaquifer.
3.Thelowerendisfittedwithastrainer,anda
pumpliftswaterforirrigation.
4.Therequireddepthofthewelldependson
thedepthofthewatertable.
21ASST.PROF. PRACHI DESSAI

22. Types of tube wells
StrainerTypeTubeWell
Thistubewellconsistsofblindpipesand
strainerpipesorscreenpipes.
Thistubewellisgenerallyunsuitableforvery
finesandystrata,becauseinthatcasescreen
openingsarelikelytogetchokedeasily.
Theboringoftheholeisgenerallycarriedoutby
usingcasingpipeofabout5to10cmlargerthan
thediameterofthewellpipe.
Thusa15cmdiameterwell,willrequireabore
holeof20to25cmdiameter.
22ASST.PROF. PRACHI DESSAI

23. Types of tube wells
23
Afterboringthehole,thewellpipeassembly
consistingofblindandstrainerpipesislowered
intotheborehole.
Thelengthsofblindandstrainerpipesareso
adjustedthattheblindpipesaboutagainst
imperviouslayersandstrainerpipesagainstthe
waterbearingaquifers
Ashortblindpipeshouldbeprovidedatthe
bottomsoastopermitsettlementofanysand
particlesthathavepassedthroughthestrainer.
Thewellisgenerallypluggedatbottomby
cementconcrete.
ASST.PROF. PRACHI DESSAI

24. Types of tube wells
24
CavityTypeTubeWell.
Thisissuchatubewellwhichdoesnotrequire
anystrainer.
Itdrawsitssuppliesfromacavitydevelopedin
thewaterbearinglayeratthebottomendofthe
well.
Instrainertypetubewellsflowofwaterthrough
strainersishorizontalandradial.
Butinthiswellwaterenterswellfrombottomof
thewellwithoutpassingthroughanyscreenand
flowofwaterisnormaltothesphericalcavity
formedatthebottom.
ASST.PROF. PRACHI DESSAI

25. Types of tube wells
25
CavityTypeTubeWell.
Theimperviouslayerispuncturedandacavityis
developedbypumping,byasandpump.
Intheinitialstageofpumping,finesandcomes
outwithwaterandconsequentlyacavityis
formed.
Asthesphericalsurfaceareaofthecavity
increasesoutwards,theradialcriticalvelocity
decreasesandsandparticlesstopentering.
ASST.PROF. PRACHI DESSAI

26. Types of tube wells
SlottedTypeTubeWell..
Thiswellismadeatsuchplaceswheresufficient
depthofwaterbearingstratumisnotavailable
evenatadepthof80mto100mandalsowhen
suitablestrongroofinglayerisnotavailablefor
theconstructionofacavitywell.
Thiswellconsistsofaslottedwroughtirontube
penetrateahighlyperviousconfineaquifer.
Thesizeoftheslotsmaybe25mm×3mmand
space10to12cmcentretocentre.
26ASST.PROF. PRACHI DESSAI

27. Development of Tube Wells
1.Itclearsthewaterbearingformationcloggedbythemudinthedrillingoperation.
2.Itcausesthegravelpackandsurroundingformationtosettleandtogetcompactedagainstthe
screen,thusitmakesthetubewellstructurestable.
3.Itservestobreakdownthebridgingofsandgrainsacrossthescreenopeningsandinthe
surroundinggravelpackandaquiferformationandmakesthewellefficient.
4.Ithelpsinreducingheadlossesnearthescreen.
5.Itbringsthewelltoitsmaximumcapacitythatismaximumyieldisavailableat
minimumdrawdown.
6.Itgivesameasureofavailablewatersupplyandhelpsindeterminingtherequired
characteristicsofapumpandpowerunittobeinstalled.
7.Ithelpsinobtainingsandfreewaterbystabilizingthesandformationaroundthescreen.
27ASST.PROF. PRACHI DESSAI

28. Method # 1. Development by Pumping:
1.Inthismethodwaterisultimatelypumpedfromthewellatadischargeequaltoorhigherthanthe
designdischarge.
2.Avariablespeedpumpoflargecapacityisused.
3.Wateriswithdrawnatveryslowrateinthebeginning.
4.Thentherateofwithdrawalisincreasedinsteps.
5.Inbetweenthestepstherateofwithdrawaliskeptconstantuntilnofurthersandparticlesare
removed.
6.Pumpingshouldbecontinueduntilthemaximumdischargeisreachedandnofurthersand
particlesarewithdrawn.
7.Thewaterwithdrawalisthenstoppedandthewaterlevelisallowedtorisetoitsnormalposition.
8.Theprocedureisagainrepeateduntilnofurthersandparticlesareremoved.
28ASST.PROF. PRACHI DESSAI

29. Method # 2. Development by Surging:
1.Asurgeisformedbythereciprocatingmovementofaplungerinthewell.
2.Thewatermovesalternatelyintothesoilandcomesoutinthewellduringdownwardand
backwardstrokerespectively.
3.Thespeedoftheplungerisslowlyincreased.
4.Theplungerisoperatedinthecasingpipeprovidedabovethescreenedportionofthewell.
5.Therepeatedapplicationofsurgingforcedrawsthefineparticlesintothewell,leavingcoarser
particlesintactintheaquifer.
6.Alternatesurgingandbailingiscontinuedtodrawsandfromaquiferandtoremovethatwater
fromthewellrespectivelytillnosandisdrawnintothewell.
29ASST.PROF. PRACHI DESSAI

30. Method # 3. Development by Back-
Washing:
1.itisaprocessinwhichthewaterismadetoflowintotheaquiferformationfromthewellthrough
thescreen.
2.Theback-washingcausesagitationoftheformationandbreaksdownthebridgingofsand
particles.Back-washingthushelpsineffectiveremovaloffineparticles.
3.Variousmethodscanbeusedforcreatingback-washorcausingreverseflow.
4.Themainmethodsare:
(a)Intermittentpumpingmethod;
(b)Back-washingwithbailers;and
(c)Back-washingwithairpressure.
30ASST.PROF. PRACHI DESSAI

31. Method # 4. Development by Using
Chemicals:
i.Dispersingagentsaremanytimesaddedtothewaterusedforback-washingorjetting.
ii.Thedispersingagentscounteractthepropertyofclaytosticktosandparticles.
iii.Thecommondispersingagentswhicharequiteeffectivearevariouspolyphosphateslike
Tetrasodiumpyrophosphate,Sodiumtripolyphosphate,sodiumhexametaphosphate(Calgon)
andsodiumdeptaphosphate.
iv.Oncethedispersingagentneutralizescolloidalpropertyofclayitcanbeeasilyremovedby
surgingandback-washing.
31ASST.PROF. PRACHI DESSAI

32. Yield of Wells and Specific Yield of
Wells
PumpingTest:
1.Inthismethodwateriswithdrawnfromthewellfreelytillacriticaldepressionheadorasafe
maximumheadiscreated.
2.Oncethisstageisreachedtherateofpumpingissoadjustedastomaintaintheconstantwater
levelinthewell.Thusthedepressionheadremainsconstant.
3.Naturallyatthisstagetherateatwhichwaterispumpedoutofthewellwillbeequaltotherateat
whichwaterpercolatesintothewell.
4.Thisrateisexpressedinm3/hrandwillbeobviouslytheyieldofthewell.
32ASST.PROF. PRACHI DESSAI

33. Yield of Wells and Specific Yield of
Wells
RecuperationTest:
1.Waterlevelinthewellisdepressedbypumpingtoanylevelbelowthenormallevel.
2.Thenthepumpingisstoppedandtimetakenbythepercolatingwatertofillthewelltoany
particularlevelisnoted.
3.Totalquantityofwaterpercolatedintothewelliscalculatedbyknowingcross-sectionalareaand
riseinthewaterlevelafterstoppageofpumping.
4.Therateofpercolationortheyieldofwellcanbearrivedatbydividingthequantityofwaterby
thetime.
5.Thistestiscarriedoutgenerallyinadriestperiodtotakeworstconditionintoaccount.
33ASST.PROF. PRACHI DESSAI

34. Specific Yield of Wells:
Specificyielddependson:
◦positionofthewater-table
◦permeabilityandporosityofthesoilformation
◦therateofwaterwithdrawalfromthewell
◦quantityofwaterstorageinthewell.Specificyieldofthewellisalsocalledspecificcapacityof
thewell.
Itcanbecalculatedfromthefollowingformula:
K = 2.303 [A/T log H1/H2]
WhereKisspecificyieldofawellinm3/hrunderdepressionheadofonemeter.
Aisareaofwellinplaninm2.
TistotaltimeofrecuperationtobringwaterlevelfromdepthH1toH2
H1isdifferenceofwaterlevelinthewelljustafterstoppageofpumpingandthenormalwaterlevel
ofthewell
H2isdifferenceofwaterlevelinthewellaftertimeTandnormalwaterlevelofthewell.
34ASST.PROF. PRACHI DESSAI

35. 35ASST.PROF. PRACHI DESSAI

36. Recommended Readings
i.Mark J. Hammer; Water and Waste Water Technology; Prentice Hall of India.
ii.S. K. Garg; Water Supply Engineering; Khanna Publ.
iii.B. C. Punmia, A. K. Jain; Water Supply Engineering; Laxmi Publication.
iv.G. S. Birdie; Water Supply Engineering and Sanitary Engineering; Dhanpat Rai.
v.R. C. Rangwala; Water Supply Engineering, Charotar Publ. House.
ASST. PROF. PRACHI DESSAI 36