Enhanced clean-up of many contaminated sites may be achieved by determining and optimizing the metabolic activity of the native biota present. A method has been developed and tested on contaminated aquifer samples to assess these parameters. The method is reliable and with reduced analytical costs. In addition, engineering a bioremediation process requires that degradation rate information be expressed in a way that can be utilized for scale up.

An enhanced bioremediation phase utilizing the natural flora was undertaken at a producing oil and gas field in Michigan. BTEX compounds emanating from the gas dehydrator system had leaked into the soil over the years of operation. The downward movement of these compounds through the porous sandy soil contaminated the aquifer and migration occurred. The site has been characterized, and monitoring has been taking place since 1988. Presently, the site is undergoing a permitted containment and clean-up treatment.

Laboratory testing of ground water and soil core samples, showed the presence of a mixed microbial population capable of tolerating and degrading BTEX compounds. Results shown in this paper indicate that the levels of phosphorus and nitrogen compounds as well as oxygen are limiting the biological processes taking place in situ. Field samples supplemented with these nutrients were able to remove BTEX compounds at a level of 30-50 ppm to levels below 1 ppb.

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