Field study on the natural degradation and retention of chlorinated hydrocarbons at an industrial site in Frankenthal, Germany< Back

The microbial degradation processes, occurring in an aquifer contaminated with volatile chlorinated hydrocarbons (chloroethenes), are investigated in this study. The joint research project belongs to the Thematic Network Chemical Industry and Metal Processing which is part of the funding priority KORA (Retention and Degradation Processes to Reduce Contaminations in Groundwater and soil, see http://www.natural-attenuation.de for further information), funded by the BMBF (German Federal Ministry of Education and Research).
Former investigations of the Frankenthal site revealed a quasi-stationary conspicuously short pollutant plume and the dominance of the biodegradation product cis-1,2-dichloroethene over the source contaminants perchloroethene and trichloroethene. Further degradation products are only detected in very low concentrations (vinyl chloride) or could not be found at all (ethene, ethane). The prevailing distribution of pollutants strongly indicates the presence of active microbial degradation processes.
The aim of this project is to reveal mechanisms and kinetics of microbial chloroethene degradation processes with different auxiliary substrates, nutrients and electron-acceptors and to determine which redox conditions are favourable for microbial degradation. Both aerobic and anaerobic degradation processes are investigated in the field and in microcosm-studies on a bench-scale level. In addition to the reductive dechlorination (halorespiration), the oxidative dechlorination with the electron-acceptors oxygen, nitrate and Fe(III) will be studied. Carbon, hydrogen and chloride isotope fractionation occurring during microbial chloroethene degradation will be determined in co-operation with the joint partners in order to assess the potential of isotopic fractionation measurements for the quantification of field degradation rates.
The results gained enter into a numerical groundwater flow model to quantify the reactive transfer of pollutants. Furthermore, techniques for the direct stimulation of natural degradation processes can be developed based on the conducted microbial investigations. Within the scope of this joint project is also the establishment of a standardised method for evaluation and monitoring of natural attenuation-processes on chloroethene contaminated sites.