一、阅读理解单项选择题Waterproblemsinthefuturewillbecomemoreintenseandmorecomplex.Ourincreasingpopulationwilltremendouslyincreaseurbanwastes,primarilysewage.Ontheotherhand,increasingdemandsforwaterwilldecreasesubstantiallytheamountofwateravailablefordilutingwastes.Rapidlyexpandingindustrieswhichinvolvemoreandmorecomplexchemicalprocesseswillproducelargevolumesofliquidwastes,andmanyofthesewillcontainchemicalswhicharepoisonous.Tofeedourrapidlyexpandingpopulation,agriculturewillhavetobeintensified.Thiswillinvolveever-increasingquantitiesofagriculturechemicals.Fromthis,itisapparentthatdrasticstepsmustbetakenimmediatelytodevelopcorrectivemeasuresforthepollutionproblem.Therearetwowaysbywhichthispollutionproblemcanbelessened.Thefirstrelatestothetreatmentofwastestodecreasetheirpollutionhazard.Thisinvolvestheprocessingofsolidwastes"priorto"disposalandthetreatmentofliquidwastes,oreffluents(废料),topermitthereuseofthewaterorbestreducepollutionuponfinaldisposal.　　Asecondapproachistodevelopaneconomicuseforallorapartofthewastes.Farmmanureisspreadinfieldsasanutrient(养料)ororganicsupplement.Effluentsfromsewagedisposalplantsareusedinsomeareasbothforirrigationandforthenutrientscontained.Effluentsfromotherprocessingplantsmayalsobeusedasasupplementalsourceofwater.Manyindustries,suchasmeatandpoultryprocessingplants,arecurrentlyconvertingformerwasteproductionintomarketablebyproducts.Otherindustrieshavepotentialeconomicusesfortheirwasteproducts.1.Thepurposeofthispassageis_______.