BIOREMEDIATION OF CONTAMINATED SITES*
Karl J. Rockne and Krishna R. Reddy
University of Illinois at Chicago
Department of Civil and Materials Engineering
842 West Taylor Street
Chicago, Illinois 60607, USA
Bioremediation is a process in which microorganisms metabolize contaminants either through oxidative
or reductive processes. Under favorable conditions, microorganisms can oxidatively degrade organic
contaminants completely into non-toxic by-products such as carbon dioxide and water or organic acids
and methane. Highly electrophilic compounds such as halogenated aliphatics and explosives typically are
bioremediated through reductive processes that remove the electrophilic halogens or nitro groups.
Bioremediation processes may be directed towards accomplishing: (1) complete oxidation of organic
contaminants (termed mineralization) , (2) biotransformation of organic chemicals into smaller less toxic
metabolites, or (3) reduction of highly electrophilic halo- and nitro- groups by transferring electrons from
an electron donor (typically a sugar or fatty acid) to the contaminant, resulting in a less toxic compound.
With increasing numbers of successfully demonstrated cleanups, biological remediation alone or in
combination with other methods, has gained an established place as a soil restoration technology.
Pollution of groundwater and soil is a worldwide problem that can result in uptake and accumulation of
toxic chemicals in food chains and harm the flora and fauna of affected habitats. The contamination of
groundwater resources by organic chemicals is a significant environmental problem, with an estimated
300,000 to 400,000 contaminated sites in the USA alone (Doust and Huang 1992; USEPA 2000).
Contaminated sites often contain numerous pollutants, which can constitute a risk to health of humans,
animals and or the environment. Although substantial progress has been made in reducing industrial
releases over recent years, major releases still occur; a c