title: Adaptation of a constructed wetland to simultaneous treatment of monochlorobenzene and perchloroethene.
abstract: Mixed groundwater contaminations by chlorinated volatile organic compounds (VOC) cause environmental hazards if contaminated groundwater discharges into surface waters and river floodplains. Constructed wetlands (CW) or engineered natural wetlands provide a promising technology for the protection of sensitive water bodies. We adapted a constructed wetland able to treat monochlorobenzene (MCB) contaminated groundwater to a mixture of MCB and tetrachloroethene (PCE), representing low and high chlorinated model VOC. Simultaneous treatment of both compounds was efficient after an adaptation time of 2 1/2 years. Removal of MCB was temporarily impaired by PCE addition, but after adaptation a MCB concentration decrease of up to 64% (55.3 micromol L(-1)) was observed. Oxygen availability in the rhizosphere was relatively low, leading to sub-optimal MCB elimination but providing also appropriate conditions for PCE dechlorination. PCE and metabolites concentration patterns indicated a very slow system adaptation. However, under steady state conditions complete removal of PCE inflow concentrations of 10-15 micromol L(-1) was achieved with negligible concentrations of chlorinated metabolites in the outflow. Recovery of total dechlorination metabolite loads corresponding to 100%, and ethene loads corresponding to 30% of the PCE inflow load provided evidence for complete reductive dechlorination, corroborated by the detection of Dehalococcoides sp.
authors.affiliation: Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany. mareike.braeckevelt@ufz.de
authors.forename: M
authors.initials: M
authors.lastname: Braeckevelt
authors.forename: E M
authors.initials: EM
authors.lastname: Seeger
authors.forename: H
authors.initials: H
authors.lastname: Paschke
authors.forename: P
authors.initials: P
authors.lastname: Kuschk
authors.forename: M
authors.initials: M
authors.lastname: Kaestner
mesh_terms: D001673:Biodegradation, Environmental; D002722:Chlorobenzenes / Q000378:metabolism*; D041862:Chloroflexi / Q000235:genetics / Q000302:isolation & purification; D016000:Cluster Analysis; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis; D058441:Rhizosphere; D012987:Soil / Q000032:analysis; D013750:Tetrachloroethylene / Q000378:metabolism*; D013997:Time Factors; D014867:Water / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D053833:Wetlands
chemical_list: D002722:Chlorobenzenes; D012987:Soil; D014874:Water Pollutants, Chemical; D014867:Water; C031294:chlorobenzene; D010100:Oxygen; D013750:Tetrachloroethylene