In situ bioremediation of the saturated zone: It can be done

Bioremediation is being used to successfully reduce contaminant levels at a site located in central Iowa. At this site, indigenous microbial populations are being stimulated by the addition of nutrients and oxygen to degrade the contaminants of interest. The site is a former service station and an automobile repair facility. Gasoline and diesel fuel stored underground and/or dispensed through pumps leaked into the subsurface over a period of forty years. A site assessment revealed that significant adsorbed, dissolved, and phase separated contamination was present beneath the surface. A pump and treat system was installed in 1990 by others to treat the ground water contamination and achieve hydraulic control. Biotreatability studies indicated that bioremediation would be an effective remedial option for this site and in May 1992, the treatment system was retrofitted in order to expedite remediation. Microbial populations, ionic nutrient concentrations, physical, and contaminant data were evaluated over time to optimize treatment