Environmental BioTechnologies, Inc.

Bioventing for the Treatment of Petroleum Contaminated Soils

A significant number of sites are contaminated with elevated levels of petroleum hydrocarbons year after year from operations such as oil well drilling, leaking underground storage tanks, surface spills, etc. The disposal of contaminated soil can represent a significant disposal cost. Therefore, companies prefer an economical, in-situ method for treating these heavily contaminated soils.

Bioventing is an in-situ treatment technology in which air and often nutrients are injected into the contaminated soil to induce a flow of oxygen through the contaminated zone to stimulate the indigenous microbial activity. Aeration is typically one of the most critical factors effecting the operation of a soil bioremediation process. Environmental BioTechnologies, Inc. (EBT) was contracted by a Canadian utility company to conduct a bench-scale treatability study to determine the feasibility of bioventing for the treatment of soils contaminated with diesel fuel. Figure 1 shows the results of this study.

Figure 1. Diesel Fuel Degradation Over Time with Three Treatments

EBT modeled an in-situ bioventing approach by placing the composite soil into three columns. The treatments consisted of the following: 1) moist control; 2) moist + air; and 3) nitrogen (500 ppm N) + phosphorus (50 ppm P) + air. Moisture was maintained at approximately 12%, and the soil columns were sampled for Total Petroleum Hydrocarbons (TPH) at 0, 3, 6, 9 and 12 weeks.

Results from TPH analysis demonstrated that the most optimum treatment was with the addition of nutrients (N + P) and air, which achieved a 90% reduction in the TPH concentration over the 12 week period (Figure 1). The addition of only air, demonstrated a 60% reduction in the TPH concentration after 12 weeks, while the moist control showed a 58% reduction in the TPH concentration after the 12 week period.

Results from this feasibility study proved bioventing to be a viable technology for treating soils contaminated with diesel fuel. Results demonstrated the necessity of air and nutrients for the bioprocess, which significantly reduced the diesel content of the soil from 11,875 mg/kg to 1,220 mg/kg soil in 12 weeks. This is an accelerated biodegradation rate of approximately 127 ppm/day.

Environmental BioTechnologies, Inc. (EBT) conducts laboratory and field studies which involve an assessment of the physical, chemical and biological parameters of a contaminated material. Bench-scale bioventing studies provide a relative index on the natural, unamended biodegradation rates vs. accelerated rates upon the addition of biostimulating agents. EBT provides technical and field support for the design and operation of bioremediation projects in the field.

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Environmental BioTechnologies, Inc.
255C S. Guild Ave.
Lodi, CA 95240
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