Date of Award
MS in Engineering - Biochemical Engineering
This study was done to determine the effectiveness of a commercially available bioaugmentation product, BiOWiSHTM-Aqua FOG, for remediating petroleum-contaminated sandy soil. Biodegradation enhancement by BiOWiSHTM-Aqua FOG was evaluated in laboratory microcosms by directly measuring total petroleum hydrocarbon (TPH) and indirectly using respirometry. Attempts were made to enrich hydrocarbon-degrading bacteria in BiOWiSHTM-Aqua FOG, and the resulting enrichment cultures were screened using respirometry as well. Potential hydrocarbon-degrading bacteria in BiOWiSHTM-Aqua FOG were isolated. Experiments were performed at bench-scale using microcosm bottles containing sand contaminated with either motor oil or No. 2 diesel fuel. The microcosms were incubated at 25oC under aerobic conditions. TPH measurements of soil in the microcosms at 0, 25 and 56 days indicated that the addition of 500-ppm BiOWiSHTM-Aqua FOG improved biodegradation of the motor oil-contaminated soil by 45%. However, BiOWiSHTM-Aqua FOG did not have a measurable effect on biodegradation in the diesel-contaminated soil.
In the respirometry experiments, BiOWiSHTM-Aqua FOG and two hydrocarbon-enriched BiOWiSHTM-Aqua FOG cultures were evaluated indirectly by the measurement of microbial carbon dioxide production and oxygen uptake using a MicroOxymaxTM respirometer. The respirometry experiments showed that in the six-day period following motor oil-contamination of soil, the addition of BiOWiSHTM-Aqua FOG substantially improves biodegradation rates. The added organisms in the product out-performed the indigenous organisms in the 5-6 days following contamination of the soil. The CO2 production observed in the BiOWiSHTM microcosms contaminated with motor oil was much greater than CO2 production without motor oil, which confirms that the observed metabolism can be attributed to motor oil biodegradation rather than metabolism of other organic material in the soil. Enriched consortia consistently generated far less CO2 than microcosms with the 500 ppm BiOWiSHTM-Aqua FOG. Stoichiometric calculations suggested that BiOWiSHTM-Aqua FOG removed approximately 1400 ppm TPH (14%) from the soil in 6.5 days, while an enrichment culture of BiOWiSHTM-Aqua FOG only reduced TPH levels by 459 ppm (5%). This result suggests that increased biodegradation rate in bioaugmented soil is aided by biodiversity in the augmenting inoculum. A potential hydrocarbon-degrading candidate organism was isolated from the product and cultured on Bushnell-Haas agar and plate-count agar (PCA). While at least two distinct colony types were successfully grown on media with motor oil, these same colonies appeared on Bushnell-Haas agar with no apparent carbon source, and survived repeated transfers onto this same medium. Therefore, their status as hydrocarbon-degraders is inconclusive. More thorough enrichment work could be pursued, especially using soil samples collected from petroleum-contaminated sites.
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