Experiences of a Large-Scale Application of 1,2-Dichloroethane Degrading Microorganisms for Groundwater Treatment

Abstract

1,2-Dichloroethane (DCA) mineralizing microorganisms, enriched and isolated under laboratory conditions, were successfully inoculated into a full-scale groundwater purification plant to treat 5-20 m 3 of water/h at 8-12°C. The groundwater contained DCA as the single contaminant in the range of 2000-15000 μg/L. It had to be treated to below 10 μg/L. The treatment plant, consisting of two sand filters followed by two granular activated carbon adsorbers, was biologically modified by the inoculation of DCA degraders and the supply of H 2 O 2 and nutrients. A total of 5000 kg of activated carbon was consumed during the first month of operation to reach the required DCA levels. This amount decreased as the biological process developed. After 2 years and with the implementation of a rotating biological contactor as an additional process step,the exchange of activated carbon became redundant. The microbial DCA removal was followed by its disappearance, the production of chloride ions, the concomitant reduction of pH, and the requirement for H 2 O 2 . So far, 1930 kg of DCA has been removed during the 5-year remediation period.