Conventional approaches to remediation of the area, which included more than 25 million gallons of contaminated water in an underground aquifer, were unsuccessful. Sometimes they pump oxygen into badly contaminated soil and water like this to get the microbial remediation process started, but that approach is costly, and then you end up with other problems, including plugging up the aquifer with iron oxides. This encourages microorganisms deep in the soil to finish the remediation process for us. Lovley and Anderson set up 40 injection wells over a section of the aquifer as well as a series of observation wells along the flow path of the groundwater. Sulfate was dripped into the contaminated area through the injection wells over a period of 200 days.
Tests run in the observation wells demonstrated how effectively benzene was removed from the water.
When we added sulfate to the aquifer, we saw virtually immediate stimulation of benzene removal. To our knowledge, this is the first successful field demonstration in which the anaerobic degradation of benzene has been accelerated at the site of contamination. This additive tends to migrate quickly when it reaches underground pools of water and is difficult to remove at low concentrations through conventional treatment, Lovley explained. The two researchers collected sediments from several MTBE-contaminated sites in the United States. By simulating an anaerobic process similar to what Lovley and Anderson used to extract benzene, they reduced the amount of MTBE in soil samples by about 3 percent a week.