Joint German-Israeli research has developed innovative remediation strategies for aerobic degradation of chloroethenes that overcome the drawbacks of existing anaerobic remediation procedures. As compared to co-metabolic aerobic degradation, the new metabolic process requires significantly lower supply of oxygen.
Contaminated sites have a detrimental effect on groundwater as an important drinking water resource worldwide. The majority of groundwater contaminations is caused by chlorinated hydrocarbons such as chloroethenes. These compounds are persistent in the environment and particularly harmful. Microbiological remediation processes can provide a sustainable, environmentally friendly and cost-effective alternative to conventional pump-and-treat procedures.
Aerobic-productive trichloroethene (TCE) degradation has recently been discovered and has significant advantages over the anaerobic dehalorespiration. Under anaerobic conditions and after addition of organic auxiliary substrates, perchloroethene (PCE) or TCE are transformed via the metabolites dichloroethene (DCE) and vinyl chloride (VC) to ethene. Competing microbial reactions (i.e., methanogenesis or sulfate reduction) can lead to detrimental changes in groundwater quality. In case of the new process of aerobic metabolic degradation, no hazardous metabolites are formed and no side reactions occur. In addition, the oxygen demand is considerably lower than in aerobic co-metabolic degradation.
Laboratory studies were conducted with various contaminated groundwater samples to examine their intrinsic TCE degradation potential and enhancement by bioaugmentation. Biodegradation was successfully stimulated by oxygen supply in all groundwater samples with TCE concentrations below 50 mg/L. The experiments indicate that aerobic TCE degrading bacteria occur at different sites but were previously not detected due to slow growth rates.
Stimulation of aerobic-metabolic chloroethene degradation for groundwater remediation is already applied in the field and represents a promising solution for polluted sites.