Enhanced anaerobic bioremediation can be an effective method of degrading various chlorinated aliphatic compounds (CAHs). The most common CAHs released to the environment include chloroethenes, chloroethanes, and chloromethanes. Because these compounds are in an oxidized state, they are generally not susceptible to aerobic oxidation processes (with the possible exception of cometabolism). However, oxidized CAHs are susceptible to reduction under anaerobic conditions by microbial processes. Enhanced anaerobic bioremediation is intended to stimulate and exploit biotic anaerobic processes to degrade chlorinated solvents in groundwater.

For reductive dechlorination to take place, strongly anaerobic/reductive conditions must be achieved. The introduction of a carbon substrate (the electron donor) provides a food source for microbial activity. The resulting bacterial growth will deplete the aquifer of dissolved oxygen (DO) and other terminal electron acceptors (i.e. nitrate, iron, manganese, sulfate, etc.).

Once the native terminal electron acceptors have been reduced, the microbial community will use the chlorinated compounds as electron acceptors. In general, anaerobic dechlorination occurs by sequential removal of a chloride ion (see adjacent figure).

In addition to carbon substrates, microbial consortia may require additional nutrients and trace metals for population growth. Under natural conditions, the aquifer may contain suitable amounts of trace nutrients for microbial growth. However, the rapid microbial growth in response to addition of a carbon substrate may rapidily deplete the groundwater of any available nutrients. Nutrient components that must be supplied include nitrogen, phosphorous, and essential micro-nutrients. Follow this link for more information on how our approach to reductive dechlorination addresses these important needs.