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1.TheEnvironmentandEnvironmentalEngineeringSimplysaid,theenvironmentcanbedefinedasone'ssurroundings.Intermsoftheenvironmentalengineer'sinvolvement,however,amorespecificdefinitionisneeded.Totheenvironmentalengineer,thewordenvironmentmaytakeonglobaldimensions,mayrefertoaverylocalizedareainwhichaspecificproblemmustbeaddressed,ormay,inthecaseofcontainedenvironments,refertoasmallvolumeofliquid,gaseous,orsolidmaterialswithinatreatmentplantreactor.Theglobalenvironmentconsistsoftheatmosphere,thehydrosphereandthelithosphereinwhichthelife-sustainingresourcesoftheeartharecontained.Theatmosphere,amixtureofgasesextendingoutwardfromthesurfaceoftheearth,evolvedfromelementsoftheearththatweregasifiedduringitsformationandmetamorphosis.Thehydrosphereconsistsoftheoceans,thelakesandstreamsandtheshallowgroundwaterbodiesthatinterflowwiththesurfacewater.Thelithosphereisthesoilmantlethatwrapsthecoreoftheearth.Thebiosphere,athinshellthatencapsulatestheearth,ismadeupoftheatmosphereandlithosphereadjacenttothesurfaceoftheearth,togetherwiththehydrosphere.Itiswithinthebiospherethatthelifeformsofearth,includinghumans,live.Life-sustainingmaterialsingaseous,liquid,andsolidformsarecycledthroughthebiosphere,providingsustenancetoalllivingorganisms.Life-sustainingresources¡ª¡ªair,food,andwater¡ª¡ªarewithdrawnfromthebiosphere.Itisalsointothebiospherethatwasteproductsingaseous,liquid,andsolidformsaredischarges.Fromthebeginningoftime,thebiospherehasreceivedandassimilatedthewastesgeneratedbyplantandanimallife.Naturalsystemshavebeeneveractive,dispersingsmokefromforestfires,dilutinganimalwasteswashedintostreamsandrivers,andconvertingdebris,ofpastgenerationsofplantandanimallifeintosoilrichenoughtosupportfuturepopulations.¡ª¡ª¡ª¡ªForeverynaturalactofpollution,foreveryundesirablealterationinthephysical,chemicalorbiologicalcharacteristicsoftheenvironment,foreveryincidentthaterodedthequalityoftheimmediate,orlocalenvironment,therewerenaturalactionsthatrestoredthatquality.Onlyinrecentyearshasitbecomesapparentthatthesustainingandassimilativecapacityofthebiosphere,thoughtremendous,isnot,afterall,infinite.Thoughthesystemhasoperatedformillionsofyears,ithasbeguntoshowsignsofstress,primarilybecauseoftheimpactofhumansupontheenvironment.Environmentalengineeringhasbeendefinedasthebranchofengineeringthatisconcernedwithprotectingtheenvironmentfromthepotential,deleteriouseffectsofhumanactivity,protectinghumanpopulationfromtheeffectsofadverseenvironmentalfactors,andimprovingenvironmentalqualityforhumanhealthandwell-being.Astheabovedefinitionimplies,humansinteractwiththeirenvironment¡ª¡ªsometimesadverselyimpactingtheenvironmentandsometimesbeingadverselyimpactedbypollutantsintheenvironment.Anunderstandingofthenatureoftheenvironmentandofhumaninteractionwithitisanecessaryprerequisitetounderstandingtheworkoftheenvironmentalengineer.¡ª¡ª2.EcologyTherecognitionthatalllifeformsareinextricablydependentononeanotherandonthephysicalenvironmentisafairlyrecentphenomenon.Theword¡°ecology¡±wasnoteveninventeduntilthemid-1800s,andthestudyofecologyasabranchofnaturalscienceswasnotwidespreaduntilafewdecadesago.¡°¡±19Thescienceofecologydefines¡°ecosystems¡±asgroupsoforganismswhichinteractwitheachotherandthephysicalenvironment,andwhichaffectthepopulationofthevariousspeciesintheenvironment.Forexample,thesimplesttypeofecosystemconsistsoftwoanimalssuchasthehareandthelynx.Iftheharepopulationinaspecificlocalityishigh,thelynxhaveanabundantfoodsupply,procreate,andincreaseinpopulationuntiltheyoutstriptheavailabilityofhares.Asthelynxpopulationdecreasesduetotheunavailabilityoffood,theharesincreasesincethenumberofpredatorsisfewer,andthecyclerepeats.Suchasystemisdynamicinthatthenumbersofeachpopulationarecontinuouslychanging,butoveralongtimespanisatasteadystateForeverynaturalactofpollution,foreveryundesirablealterationinthephysical,chemicalorbiologicalcharacteristicsoftheenvironment,foreveryincidentthaterodedthequalityoftheimmediate,orlocalenvironment,therewerenaturalactionsthatrestoredthatquality.Onlyinrecentyearshasitbecomesapparentthatthesustainingandassimilativecapacityofthebiosphere,thoughtremendous,isnot,afterall,infinite.Thoughthesystemhasoperatedformillionsofyears,ithasbeguntoshowsignsofstress,primarilybecauseoftheimpactofhumansupontheenvironment.Environmentalengineeringhasbeendefinedasthebranchofengineeringthatisconcernedwithprotectingtheenvironmentfromthepotential,deleteriouseffectsofhumanactivity,protectinghumanpopulationfromtheeffectsofadverseenvironmentalfactors,andimprovingenvironmentalqualityforhumanhealthandwell-being.Astheabovedefinitionimplies,humansinteractwiththeirenvironment¡ª¡ªsometimesadverselyimpactingtheenvironmentandsometimesbeingadverselyimpactedbypollutantsintheenvironment.Anunderstandingofthenatureoftheenvironmentandofhumaninteractionwithitisanecessaryprerequisitetounderstandingtheworkoftheenvironmentalengineer.¡ª¡ª2.EcologyTherecognitionthatalllifeformsareinextricablydependentononeanotherandonthephysicalenvironmentisafairlyrecentphenomenon.Theword¡°ecology¡±wasnoteveninvented