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1、WHO/FWC/WSH/15.03MANAGEMENTOFCYANOBACTERIATECHNICALBRIEFINDRINKING-WATERSUPPLIES:InformationforregulatorsandwatersuppliersThistechnicalbriefprovidesgeneralinformationonthemanagementofcyanobacteriaindrinking-watersuppliestohelpregulatorsandwatersuppliersdeterminewhentotakeactiona
2、ndwhatactionstotake.Itdescribesanumberofmeasurestopreventtheformationofcyanobacterialbloomsaswellasoptionstomanagesuchbloomswhentheyoccur.Althoughsomeofthemeasuresarespecifictocyanobacteria,manyareequallyusefulforthemanagementofotherhazards.Risksfromcyanobacteriashouldbeassessed
3、alongwiththeothermicrobial,chemical,physicalandradiologicalhazardsthatmaybeencounteredinawatersupply.Thiscanbeeffectivelyachievedinthecontextofdevelopingawatersafetyplanforthewatersupplysystem.Whatarecyanobacteria?Cyanobacteria,alsoknownasblue-greenalgae,arephotosyntheticbacteri
4、anaturallypresentinsurfacewatersinlowormoderatenumbers;veryhighnumbersareusuallycausedbyhumanactivityenrichingthewaterwithphosphorusandnitrogen.Somecyanobacteriaproducetoxins,calledcyanotoxins.Cyanobacteriacanoccurassinglecellsoringroups,ascoloniesorfilaments.Theycanbefoundinfre
5、sh,marineandbrackishwaters.FrequentlyoccurringgenerainsurfacewatersincludeAnabaena,Aphanizomenon,Cylindrospermopsis,Lyngbya,Microcystis,Oscillatoria,PhormidiumandPlanktothrix.Somecyanobacteriacancontroltheirbuoyancyandseekwaterdepthswithoptimalgrowthconditions.Thisabilitytomovew
6、ithinthewatercolumngivescyanobacteriaanadvantageoverothermicroorganismsthatcompetefornutrientsandlight.Buoyantcyanobacteria,suchasAnabaenaandMicrocystis,mayfloatupwardwhenmixingisweakandaccumulateindensesurfaceblooms(Fig.1).Othercyanobacteria,suchasCylindrospermopsisandPlanktoth
7、rix,staydispersed,butcanreachveryhighcelldensities,causinghighturbidity.Stillothers,suchasLyngbya,OscillatoriaandPhormidium,growasbenthicpopulationsonsedimentsorattachedtoothersurfaces,suchaspiersorsubmersedrocks(fordetails,refertoMinistryfortheEnvironment&MinistryofHealth,NewZe
8、aland,2009).Figure1.Cyanobacterialbloom(left);M
