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本科生毕业设计外文翻译BacterialInfluenceonTextileWastewaterDecolorizationAamrAlalewi,CuilingJiang1DepartmentofHydrologyandWaterResources,HohaiUniversity,Nanjing,China;2StateKeyLaboratoryofHydrology-WaterResourcesandHydraulicEngineering,HohaiUniversity,Nanjing,China.Email:aamralewi@hotmail.comReceivedMay12th,2012;revisedJune15th,2012;acceptedJuly17th,2012ABSTRACTThestudyaimstoisolateandoptimizebacterialstrainshavingtheabilitytodegradeanddecolorizeazodyesproducedinthefinaleffluentoftextiledyingindustries.Inthisregard,tenbacterialstrainswereisolatedfromwastewatertreat-mentplants,andmostofthemweresubjectedtothecoloredeffluentsresultingfromdilapidatedhouses.Theabilityofthesebacterialisolationstouseawiderangeofazodyestodeterminethesolecarbonsourcewasdetermined.Keywords:Decolorization;Biodegradation;AzoDys;TextileWastewater1.IntroductionEnvironmentalpollutionhasbeenidentifiedasamajorprobleminthemodernworld.Theincreasingdemandfordrinkablewater,anditsdwindlingsupply,hasmadethetreatmentandreuseofindustrialeffluentsanattractiveoption.Oneofthemostimportantenvironmentalpollu-tionproblemsisthecolorinwatercourses;althoughsomeofthesecolorsarenormallypresentandof“natu-ral”origins(e.g.thecolororiginatesfromtheactivityofmicroorganismsinponds),aconsiderableproportion,especiallyinthelowerreachesofriversthatdrainlargeindustrialconurbations,originatesfromindustrialefflu-ents.Somecoloredeffluentsareassociatedwiththepro-ductionanduseofdyes.Azodyes,thelargestchemicalclassofdyeswiththegreatesvarietyofcolors,havebeenusedextensivelyfortextile,dyeing,andpaperpainting[1].Thesedyescannotbeeasilydegraded,andsomearetoxictohigheranimals.Azodyesconsistofadiazotizedaminecoupledwithanamineorphenol,andcontainoneormoreazolinkages.Atleast300differentvarietiesofazodyesareexten-sivelyusedinthetextile,paper,food,cosmeticsandpharmaceuticalindustries.TheeffectsofpH,temperature,typeandconcentrationofrespirationsubstrates,andoxygentensionontherateofbiologicalreductionofavarietyofazodyeshavepreviouslybeeninvestigated[4,5].Severalcombinationsoftreatmentmethodshavebeendevelopedsofarinordertoeffectivelyprocesscotton-textilewastewater,withdecolorizationamongthemaingoalsfortheseprocesses.2.Methodology2.1.IsolationandCultivationoftheMostEfficientDecolorizingBacteriaSixactivesludgesampleswereobtainedfromthreewastewatertreatmentplants.Allsamplesweretransportedtothelaboratoryandscreenedtoobtainthedyedecolo-rizingorganisms.Allbacterialisolationswerecultivatedonmineralsaltsbasicmediumwiththefollowingcom-position(g/l):Na2HPO4,2.13;KH2PO4,1.3;NH4Cl,0.5;MgSO4,0.2;1Ltapwaterand1mltraceelementsolutionperliter.Thetraceelementsolutionhadthefollowingcomposition(g/l):MgSO4·7H2O,7.12;ZnSO4·7H2O,0.044;MnSO4·4H2O,0.081;CuSO4·5H2O,0.0782;Na2MoO4·2H2O,0.025;FeSO4·7H2O,0.498;Boricacid0.1+0.27mlofH2SO4.ThefinalPHwasadjustedat7.0.Themineralsaltsmediumwassupplementedwith1(g/l)yeastextract.Theactivatedsludgesamples(2.5ml)weretransferredinto250mlflaskscontaining50mlmineralsaltsmediumanddye(preparedusingamixtureof9typesofdyes).Alldyeswaremixedtogethertogetstocksolu-tionofmixtureofdyes0.9(g/l)(0.1g/lofeachdye).Thestocksolutionwassupplementedwithabasicsaltmediumtogetafinalconcentrationof0.1(g/l).Eachflaskcon-tained50mlofasterilemineralsaltsliquidmediummixedwithazodyesmixturedispensedwithonegramofyeastextract.Eachflaskwasinoculatedwith2.5mlofactivatedsludge.Allwereincubatedinarotaryincubatorat150rpmfor24hoursat30°C.Similarflaskswerepreparedandinoculatedwith1mlofthecontentoftheflasksofthefirstgroup.Thesewereincubatedfor24hours.Thisstepwasrepeatedthreetimesinaperiodof72hours.Thelast(third)groupofflaskswasincubatedforfivedays.Theseflaskswereusedtoisolatethetargetmicroorganismsbystreakingamineralsaltsagarmediumcontainingthesameingredientsofthepreviousbrothmedium,plusagarand100ppmofanazodyesmixture.Separatecoloniesofthepredominanttypesofmicroor-ganismswerepurifiedbyre-streakingonthesameme-dium.Thepurifiedisolateswereexaminedmicroscopi-callytocheckforpurity.Obtainedpureculturesweremaintainedonnutrientagarat4°C(inrefrigerator)[11-13].Tenmorphologicallydifferentisolateswereobtainedfromthepreviousstepandstudiedforcolonymorpho-logy2.2.ScreeningProgram(Testes)toSelecttheMostPotentOrganismsFirstscreeningwasdonetotesttheabilityofthepurifiedisolatestoutilizedifferentgroupsofdyesasthesolecarbonsource.Screeningtotesttheabilityofisolatedorganismstoutilizedirectblue75,directblue71,reactiveblue194anddirectred89asthesolecarbonsourcewascarriedoutinamineralsaltsbasicmediumusedinisola-tion.Yeastextractwasreplacedby0.1g/lindividualdye.Organismswereselectedonthebasisoftheirabilitytogrowandreducepigmentationundertheseconditions.Coloniesofanovernightgrowthweresuspendedinnormalsalinetoobtaintheopticaldensityof0.6atwavelength610nm.Onemilliliterofcellsuspensionwasusedtoinoculate100mlbottlescontaining25mlmineralsaltsbasicmediumsupplementedwith0.1g/lindividualdye.Bottleswerethenincubatedforsevendaysat30°C.Asecondscreeningwasperformedtoensuretheabilityofselectedisolationstoutilizedifferentgroupsofdyesasthesolecarbonsource.2.3.Identi