Environmental BioTechnologies, Inc.

Bioremediation of Oil Well Cuttings

Significant quantities of drill cuttings contaminated with elevated levels of petroleum hydrocarbons are produced during drilling of vertical or horizontal oil wells. These cuttings represent a significant cost for disposal. Petroleum companies would prefer an economical, on site method for treating these heavily contaminated drill cuttings.

Environmental BioTechnologies, Inc. (EBT) was contracted by a Canadian petroleum company to conduct a bench-scale biofeasibility study to determine the best bioprocess for treatment of contaminated drill cuttings. The oil drilling samples contained between 7.1 to 71% crude oil. Initial wash studies using hot water (85C) and surfactants (Cyanamer P-70, Witcolate 6465, and Witconol 5909) did not demonstrate a significant reduction in the petroleum hydrocarbon concentration (14-30% reduction). Due to the extremely high levels of oil, and the sticky, clayey consistency of the cuttings, EBT opted to conduct a bioaugmented land farming study to determine the feasibility of bioremediation.

Land farming is the lowest cost approach to bioremediation of soil contaminated with oil. In this process, moisture is controlled, nutrients are provided, and there is some tilling to support aeration of the soil. EBT modeled this approach by placing a composite sample of the contaminated cuttings into a pan system which was not agitated, but mixed periodically at sampling times. The treatments included the following: 1) water only (control); 2) nitrogen (250 ppm N)+ phosphorus (25 ppm P) + inoculum (hydrocarbon degrading microorganisms); and 3) nitrogen + phosphorus + inoculum + surfactant (1% Cyanamer P-70). Moisture was maintained at approximately 13%, and the cuttings were sampled for Total Petroleum Hydrocarbons (TPH) at 0, 14, 28, 49 and 63 days.

Results from TPH analysis demonstrated that the most optimum treatment was with the addition of nutrients (N + P), an inoculum, and the surfactant, which achieved an average 38% reduction in the TPH concentration over the 63 day period . The addition of nutrients, and the inoculum demonstrated an average 28% reduction in the TPH concentration after 63 days. The addition of water only to the contaminated cuttings did not produce a reduction in the TPH concentration after the 63 day period.

According to the results of this feasibility study, land farming proved to be a viable technology for treating heavily contaminated drill cuttings. Results demonstrated the necessity of bioaugmentation, nutrients, and a surfactant for the bioprocess, which significantly reduced the oil content of the cuttings from 16.5% to 9.8% oil. This is an accelerated biodegradation rate of approximately 2% TPH/month.

Bench-scale treatability studies involve an assessment of the physical, chemical and biological parameters of a contaminated material. The study provides a relative index on the natural, unamended biodegradation rates vs. accelerated rates upon the addition of biostimulating agents. Environmental BioTechnologies, Inc. conducts laboratory studies to determine the optimum conditions for supporting bioremediation in the field. Through these bench-scale treatability studies, EBT can provide recommendations that will reduce hydrocarbon contamination in considerably less time, and subsequently require less cost for operation of a remedial operation.

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