Cometabolic degradation of trichloroethylene (TCE) and 1,2-dichloroethane (1,2-DCA) in nitrification systems

Abstract

vABSTRACTTrichloroethylene (TCE) and 1,2-dichloroethane (1,2-DCA), which are extensivelyused in various industries, are commonly detected organohalogen pollutants in industrialeffluents, groundwater and soil. In recent years, biodegradation of TCE and 1,2-DCA bycometabolic processes has received much attention as a promising alternative to otheravailable treatment techniques. To date, cometabolic degradation of these compounds wasmainly studied by methane, toluene and phenol oxidizers. On the other hand, nitrifyingbacteria, which ubiquitously present in wastewater treatment plants and soil, have beenstudied to a much smaller extent compared to other organisms. The aim of the presentstudy was to investigate the cometabolic removal of TCE and 1,2-DCA by enrichednitrifier cultures and to assess their inhibitory effects on nitrification. For this purpose,batch suspended-growth experiments and continuous-flow biofilm experiments wereperformed using enriched nitrifier cultures. These experiments demonstrated that both TCEand 1,2-DCA are cometabolically degradable by enriched nitrifier cultures usingammonium as the primary substrate. However, the presence of these compounds inhibitedammonium utilization. Cometabolic TCE or 1,2-DCA degradation in parallel toammonium oxidation was found to be dependent on various factors.