Possibleuseofconstructedwetlandtoremoveselenocyanate, arsenic,andboronfromelectricutilitywastewater Z.H.Ye 1 ,Z.-Q.Lin 2 ,S.N.Whiting,M.P.deSouza,N.Terry * Department of Plant and Microbial Biology, University of California at Berkeley, 111 Koshland Hall, Berkeley, CA 94720-3102, USA Abstract Wetlandmicrocosmswereusedtoevaluatetheabilityofconstructedwetlandstoremoveextremelyhighconcen- trationsofselenocyanate(SeCN À ),arsenic(As),andboron(B)fromwastewatergeneratedbyacoalgasificationplant inIndiana.Thewetlandmicrocosmssignificantlyreducedtheconcentrationsofselenium(Se),As,B,andcyanide(CN) inthewastewaterby64%,47%,31%,and30%,respectively.Intermsofthemassofeachcontaminant,79%,67%,57%, and54%oftheSe,As,B,andCN,respectively,loadedintothemicrocosmswereremovedfromthewastewater.The primarysinkfortheretentionofcontaminantswithinthemicrocosmswasthesediment,whichaccountedfor63%,51%, and36%oftheSe,As,andB,respectively.Accumulationinplanttissuesaccountedforonly2–4%,while3%oftheSe was removed by biological volatilization to the atmosphere. Of the 14 plant species tested, cattail, Thalia,andrab- bitfoot grass were highly tolerant of the contaminants and exhibited no growth retardation. Environmental toxicity testingwithfatheadminnow(Pimephales promelas)larvaeconfirmedthatthewatertreatedbythewetlandmicrocosms waslesstoxicthanuntreatedwater.Thedatafromthewetlandmicrocosmssupporttheviewthatconstructedwetlands couldbeusedtosuccessfullyreducethetoxicityofaqueouseffluentcontaminatedwithextremelyhighconcentrationsof SeCN À ,As,andB,andthatapilot-scalewetlandshouldthereforebeconstructedtotestthisinthefield.Cattail, Thalia, andrabbitfootgrasswouldbesuitableplantspeciestoestablishinsuchwetlands. Ó 2003ElsevierLtd.Allrightsreserved. Keywords: Selenocyanate;Microcosm;Wastewater;Wetlandplants 1. Introduction Constructed wetlands are complex biological and physical environments that collectively alter the chemi- cal nature of contaminants. They detoxify wastewater byimmobilizingand/ortransformingpollutantstoless- toxicforms.Thisisparticularlyimportantinthecaseof metalloidslikeselenium(Se)andarsenic(As),whichcan be transformed by both biological and chemical pro- cesses to a variety of forms that differ in mobility and toxicity(Terryetal.,2000).Thegrowthandadaptation ofplantstotheanoxicconditionsinwetlandsediments drives many of these processes (Horne, 2000). For ex- ample,theactivityoftheplantrootsaltersthechemical conditions of the surrounding sediment, enhancing the rateoftransformationandfixationofmetals(Wangand Peverly, 1999). Alternatively, the pollutants may be taken up into the plant tissues, where they are accu- mulated (Qian et al., 1999; Zhu et al., 1999), biotrans- formed to less toxic or immobile states (Terry et al., 2000), and/or volatilized to the atmosphere (Hansen etal.,1998;Linetal.,2000).Plantsarealsoimportant because they supply fixed-carbon to the sediments, Chemosphere52(2003)1571–1579 www.elsevier.com/locate/chemosphere * Correspondingauthor. E-mail address: nterry@nature.berkeley.edu (N.Terry). 1 Department of Biology, Hong Kong Baptist University, HongKongSAR,PRChina. 2 Department of Biological Sciences and Environmental Sciences Program, Southern Illinois University, Edwardsville, IL62026-1651,USA. 0045-6535/03/$-seefrontmatter Ó 2003ElsevierLtd.Allrightsreserved. doi:10.1016/S0045-6535(03)00497-1