Electrochemical and Biogeochemical Interactions under dc Electric Fields

Direct electric currents generate electrochemical and biochemical changes that impact the subsurface environment and can be engineered for transporting and mixing contaminants, biostimulants, and possibly bioaugmentation inoculants to enhance in situ bioremediation. A review of transport processes under dc fields, electrolysis reactions, and microbial adhesion and transport is provided in this chapter, followed by an evaluation the impact of dc fields on microbial activity. In general, dc electric field intensities tend to produce complex effects on the activity of mixed microbial cultures. Anaerobic cultures seem to experience an "environmental shock" when exposed to electric field intensities greater than 1.5 V/cm. However, these cultures are able to recover their activities once the electric currents are switched off. Aerobic cultures did not seem to be adversely affected by exposure to field intensities less than 0.28 V/cm. Higher dc field intensities, up to 1.14 V/cm, seem to stimulate aerobic cultures during the first 24 hours of exposure. However, continuous exposure to dc fields (in the range of 1.14 V/cm)following the first 24 hours seems to retard the growth of aerobic cultures.