CONTAMINATED ENVIRONMENTS IN THE SUBSURFACE AND BIOREMEDIATION - ORGANIC CONTAMINANTS

Due to leakages, spills, improper disposal and accidents during transp ort, organic compounds have become subsurface contaminants that threat en important drinking water resources. One strategy to remediate such polluted subsurface environments is to make use of the degradative cap acity of bacteria. It is often sufficient to supply the subsurface wit h nutrients such as nitrogen and phosphorus, and aerobic treatments ar e still dominating. However, anaerobic processes have advantages such as low biomass production and good electron acceptor availability, and they are sometimes the only possible solution. This review will focus on three important groups of environmental organic contaminants: hydr ocarbons, chlorinated and nitroaromatic compounds. Whereas hydrocarbon s are oxidized and completely mineralized under anaerobic conditions i n the presence of electron accepters such as nitrate, iron, sulfate an d carbon dioxide, chlorinated and nitroaromatic compounds are reductiv ely transformed. For the aerobic often persistent polychlorinated comp ounds, reductive dechlorination leads to harmless products or to compo unds that are aerobically degradable. The nitroaromatic compounds are first reductively transformed to the corresponding amines and can subs equently be bound to the humic fraction in an aerobic process. Such ne w findings and developments give hope that in the near future contamin ated aquifers can efficiently be remediated, a prerequisite for a sust ainable use of the precious subsurface drinking water resources.