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COMPARISON OF FIELD AEROBIC BIODEGRADATION RATES TO LABORATORY
Citation:
Simon*, M A. AND P. Rotstein*. COMPARISON OF FIELD AEROBIC BIODEGRADATION RATES TO LABORATORY. Presented at The Seventh International Symposium In Situ and On-Site Bioremediation, Orlando, FL, 06/02-05/2003.
Description:
It is common to use bioventing as a polishing step for soil vapor extraction. It was originally planned to use soil vapor extraction and bioventing at a former landfill site in Delaware but laboratory scale biodegradation studies indicated that most of the volatile organic compounds would degrade within a two-year time period. Therefore, it was decided not to vent but recycle the system off gas. In 1995-1996, 13,000 drums were removed from the landfill and the soil tested. Soils with high polychlorinated biphenyls or metal content were removed and sent to hazardous waste landfill. The rest of the soils were dewatered, augmented with straw and nutrients and replaced in excavated area of landfill. A bioventing system was installed and started to operate in August 1997. The concentration of the most prevalent volatile organic compound, benzene, declined 99 and 98% in the vapor and groundwater, respectively. Calculation of contaminant mass via comparing three-dimensional interpolation of soil sampling events in 1996 (preproject), in 1999 (time = 2 years) and in 2002 (time = 5 years) did not show significant reduction of benzene, or any of the other contaminants of concern. Initial laboratory treatment tests indicated that the aerobic half-life of benzene would be 1.5 years. The field data indicate a slower degradation rate for soil but a faster degradation rate for vapor and groundwater than what was expected from laboratory studies. While it was not expected to degrade aerobically, tetrachloroethene was expected to degrade in anaerobic portions of the biocell. Mass calculations of tetrachloroethene did not show reduction in either the vapor, water or soil phases. Laboratory studies indicated that the anaerobic half-life of tetrachloroethene would be 1.9 years.