污水处理英文文献

EcologicalEngineering21(2003)53–61Mosquitodevelopmentinamacrophyte-basedwastewatertreatmentplantinCameroon(CentralAfrica)IvesMagloireKengnea,∗,FrançoisBrissaudb,AmougouAkoaa,RogerAtanganaEtemea,JeanNyaa,AlombaNdikefora,TheophileFonkoucaWastewaterResearchUnit,FacultyofScience,UniversityYaoundeI,P.O.Box8404,Yaounde,CameroonbHydrosciences,UniversityMontpellierII,34095MontpellierCedex05,FrancecFacultyofScience,UniversityDschang,P.O.Box67,Dschang,CameroonReceived10December2002;receivedinrevisedform30July2003;accepted15August2003AbstractMacrophyte-basedwastewatertreatmentsystemsarerecognizedasanalternativeforsewagepurificationindevelopingcoun-tries.Unfortunately,theyalsorepresentafavorablebreedinggroundformosquitoes,thusaseriousdrawbackthatshouldbeaddresseddespitethegoodpromiseofthistechnology.A1-yearstudyofmosquitoproductioninsevenpondsofaPistiastratiotes-baseddomesticwastewatertreatmentplantinCameroonrevealedthatapproximately43imagoes/m2perdayroseup,amongwhich54%werefemale.MansoniaandCulexwerethemainbreedinggenerawithabout55and42%ofthetotalimagoesrespectively.Culexbredmostlyinthefirstthreeponds(B1–3),characterizedbyahighorganicpollution.Mansoniaoccurredingreatnumberinthelaterponds(B4–7),wherethewaterqualitywasratherbetterandtherootsofP.stratioteswelldeveloped,thuspermittingthefixationofagreatnumberoflarvaetothemacrophyteroots.Thoughrepresentingafavorablebreedinggroundformosquitoes,only0.02%ofcapturedimagoeswereAnophelesgambiae,suggestingthatthiswastewatertreatmentplantdoesnotsignificantlycontributetothedevelopmentofthemalariavectorinthisarea.©2003ElsevierB.V.Allrightsreserved.Keywords:Wastewatertreatment;Cameroon;Macrophytelagoons;Pistiastratiotes;Mosquitodevelopment1.IntroductionTheuseofaquatictreatmentsystems,especiallyfloatingmacrophytes,isrecognizedasanalternativemethodofwastewatertreatment(DebuskandReddy,1987;Brix,1997).Thescientificbasisgoverningthisprocessisthesymbioticassociationbetweenaquatic∗Correspondingauthor.Fax:[phone].E-mailaddress:[e-mail](I.M.Kengne).macrophytesandmicroorganisms.Thelatterdegradestheorganicmatterpresentinthewaterintosimplenutrientsthatareabsorbedbymacrophytes.Inreturn,macrophytescreatefavorableconditionsformicrobialactivity(Wolverton,1987;Vyzamaletal.,1998).Amongtheadvantagesfavoringthisecotechnology,especiallyindevelopingcountrieswhichlackcapi-talandqualifiedmanpowertorunsophisticatedmeth-ods,areitssimplicityofconstructionandoperation,lowoperationcosts,andcapabilitytowithstandexcess0925-8574/$–seefrontmatter©2003ElsevierB.V.Allrightsreserved.doi:10.1016/j.ecoleng.2003.08.00654I.M.Kengneetal./EcologicalEngineering21(2003)53–61organicandhydraulicloads(ReddyandSmith,1987).Furthermore,mostdevelopingcountrieshaveawarmtropicalandsubtropicalclimatethatallowshighbi-ologicalactivityandproductivityyear-round,whichmeanshighefficiencyofthesystem(Denny,1997;Kivaisi,2001).Despitethesemultipleadvantages,manyenviron-mentalquestionsarestilltobeaddressed,amongwhichisthedevelopmentofmosquitoes,especiallyinwarmregions.Indeed,thepresenceoflargewaterbodiescoveredbymacrophytesmayrepresentafavor-ablebreedinggroundforsuchinsects,thusprovidingnuisancepestsandordiseasevectorstothenearbycommunities(MartinandEldridge,1989;Dill,1989).InCameroon,theuseofaquaticmacrophytesforsewagetreatmentisrecent.Aseriesoflagoonswerebuiltin1986totreatapproximately45m3perdayofdomesticsewagefromaresidentialareainYaounde.Severalmacrophytesweretested,amongwhichPis-tiastratioteswasselectedandgrowninponds,sinceithasagoodpollutionremovalcapacityandcanbeeasilyharvested(Agendiaetal.,1988).Indeed,thepollutantremovalefficiencyoftheplantwasquitesatisfactorywhenusingthismacrophyte,withmostCOD,BODandSSabatementsbeinghigherthan80%(Agendia,1995).Furthermore,Agendiaetal.(1997)estimatedthatapproximately27tofcompostcouldbeobtainedannuallyfromtheby-products(macrophytesandsludge),thusallowingtherecoveryofpartoftheoperationcostwhilereducingthechemicalfertilizerneedsoftheneighboringfarmers.However,inapreliminarysurveyaimedatassess-ingtheenvironmentalimpactsofthisplant,65%ofthepopulationlivinginthevicinityestimatedthatitsconstructionhasledtotheproliferationofmosquitoes,thusrepresentingaseriousthreatthatshouldbeaddressedwhenconsideringthediffusionofthistechnology.Effortstocontrolmosquitoesin-cludevegetationmanagement,theuseofchemicalandbiologicalagentsorconstructiondesign(DebuskandReddy,1987;Tchobanoglous,1987;KadlecandKnight,1996).Thesuccessoftheseapproachesde-pendsmainlyonabetterknowledgeofthemosquitospeciesinvolved(Russell,1999).Butfewstudieshavefocusedonmosquitoesbreedinginaquatictreat-mentsystems,especiallyintropicalregionswherethewarmclimatefavorstheproliferationofavarietyoffaunaandflora.Asafirststeptominimizetheproliferationofsuchdiseasevectorsornuisancepests,astudyaimedatassessingthebiodiversityandthespatio-temporaldy-namicsofthemosquitobreedinginaP.stratiotesbasedtreatmentplantwascarriedoutfromNovember1997toOctober1998inYaounde(Cameroon).2.Materialsandmethods2.1.SiteofstudyThisworkwascarriedoutinstabilizationpondsde-votedtotreatm