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1PartOneIntroductionUnit1IntroductionofWaterSupplyThehumansearchforpurewatersuppliesmusthavebeguninprehistorictimes.Muchofthatearliestactivityissubjecttospeculation.Someindividualsmayhaveledwaterwheretheywanteditthroughtrenchesdugintheearth.Laterahollowlogwasperhapsusedasthefirstwaterpipe.Thousandsofyearsprobablypassedbeforeourmorerecentancestorslearnedtobuildcitiesandenjoytheconvenienceofwaterpipedtothehomeanddrainsforwater-carriedwastes.ArchaeologicalevidenceshowstheexistenceoflatrinesanddrainsinNeolithicdwellingsandtheMinoancivilizationinCrete2000yearsB.C.hadclaywaterandsewagepipeswithflushingtoiletsinthehouses.TheRomanshadhighlydevelopedwatersupplyanddrainagesystemsandtheircitiesusedlargeamountsofwaterwithcontinuouslyoperatingfountainsbeingamajorsourceofsupplyforthemajorityofthepopulationalthoughwealthyfamilieshadtheirownpipedsupplies.Largeaqueducts,someofwhichstillremain,wereconstructedoverdistancesupto80kmtobringadequatesuppliesofgood-qualitywaterintothecities.Stonesewersinthestreetsremovedsurfacewaterandcollectedthedischargesfromlatrinesforconveyancebeyondthecitylimits.WiththedemiseoftheRomanEmpiremostoftheirpublicworksinstallationsfellintodisuseandforcenturieswatersupplyandsanitationprovisionswerevirtuallynon-existent.IntheMiddleAges,townsstartedtodevelopatimportantcrossingpointsonriversandtheseriversusually2providedaconvenientsourceofwaterandanapparentlyconvenientmeansofwastedisposal.AlthoughsewerswerebuiltinthelargetownstheywereintendedsolelyfortheremovalofsurfacewaterandintheUKthedischargeoffoulsewagetothesewerswasforbiddenbylawuntil1815.Sanitaryprovisionswereusuallyminimal:in1579onestreetinLondonwithsixtyhouseshadthreecommunallatrines.Dischargesofliquidandsolidwastesfromwindowsintothestreetwerecommonanditisnotsurprisingthatlifeexpectancywaslessthanhalfthecurrentfigureinthedevelopedworld.Inanattempttoimprovemattersalawwaspassedin1847whichmadeitobligatoryinLondonforcesspitandlatrinewastestobedischargedtothesewers.London’ssewersdrainedtotheThames,fromwhichmuchofthecity’swaterwasobtained,andinadditionthepoorstateofrepairofmanyofthesewersallowedthecontentstoleakintotheaquiferwhichwastheothermainsourceofwater.Theinevitableconsequencesofthisstateofaffairswerethatwatersourcesbecameincreasinglycontaminatedbysewage,theThamesbecameobjectionabletobothsightandsmell,andmostseriously,waterbornediseasesbecamerampantinthecity.In1854,Dr.JohnSnow,apublic-healthworkerinLondon,notedahighcorrelationbetweencholeracasesandconsumptionofwaterfromawellonBroadStreet.Notonlywascholerarunningrampantintheneighborhoodaroundthewell,butoutbreakofthediseaseinotherpartsofthecitycouldbetracedtoindividualswhohadoccasiontodrinkfromtheBroadStreetwell,whichcaused10,000deathsandprovidedtheevidenceforhimtodemonstratetheconnectionbetweensewagepollutionofwaterandentericdiseaseslikecholeraandtyphoid.Publicoutcryresulted3inthecommissioningofthefirstmajorpublichealthengineeringworksofmoderntimes.Thusby1870waterborneoutbreakshadbeenlargelybroughtundercontrolintheUKandsimilardevelopmentsweretakingplaceinWesternEuropeandthecitiesoftheUSA.TheIndustrialRevolutiongreatlyincreasedtheurbanwaterdemandandthelatenineteenthcenturysawtheconstructionofmajorwater-supplyschemes.Onlybycontinualandcostlyattentiontowaterqualitycontrolhasitbeenpossibletovirtuallyeradicatewaterbornediseasesfromdevelopedcountries.Suchachievementsmustnot,however,beallowedtomasktheappallingsituationregardingwatersupplyandsanitationinmuchofthedevelopingworld.Thegrowthofpopulationindevelopingcountries,duetothehighbirthrate,issuchthatunlessstrenuouseffortstoincreasewatersupplyandsanitationfacilitiesaremade,thepercentageoftheworld’spopulationwithsatisfactoryfacilitieswouldactuallydecreaseinthefuture.Indevelopedcountries,demandsforwaterarenowfairlystaticandbasicwastequality-controlmeasuresarewellestablished.However,manyoftheexistingwater-supplyandsewageschemesarenowrelativelyoldsothattheirreconstructionwillposeproblemsinthefuture.Asknowledgeoftheeffectsofallformsofenvironmentalpollutionincreasessonewpotentialhazardsappear,forexamplethereiscurrentconcernaboutthepossiblecarcinogenichazardsarisingfromthepresenceofminuteconcentrationsofsomeorganiccompoundsinwater.Anthropogenic,orhuman-induced,pollutantshaveoverloadedourenvironment.Todaytheenormousdemandsbeingplacedonwatersupplyandwastewaterdisposalfacilitieshavenecessitatedthedevelopmentandimplementationoffar4broaderconceptsinenvironmentalengineeringthanthoseenvisionedonlyafewyearsago.Thestandardsforwaterqualityhavesignificantlyincreasedconcurrentwithamarkeddecreaseinraw-waterquality.Thelessonisthatpopulationsincrease,butwaterandlandresourcesdonot.Consequently,theuseandcontroloftheseresourcesmustbenearlyperfecttomaintainourwayoflife.Exercisingthiscontrolwillrequiretheskillfulblendingofstate-of-thearttechnologywithahostofpolitical,social,legal,economic,andorganizationalelements.Itisthetechnologyofwatersupplyandpollutioncontrolthatisthemainconcernofthisbook.5NewWordsandExpressionsdrainv.排水n.排水（管）latrinen.公共厕所Neolithica.新石器时代的clayn.粘[泥，白]土sewag