Enhanced Hydrocarbon Biodegradation Using Bioaugmentation with BiOWiSH™-Aqua FOG

Author

Michael Robert Lehrer, California Polytechnic State University, San Luis ObispoFollow

DOI: https://doi.org/10.15368/theses.2012.82
Available at: https://digitalcommons.calpoly.edu/theses/763

Date of Award

6-2012

Degree Name

MS in Engineering - Biochemical Engineering

Advisor

Yarrow Nelson

Abstract

This study was done to determine the effectiveness of a commercially available bioaugmentation product, BiOWiSH^TM-Aqua FOG, for remediating petroleum-contaminated sandy soil. Biodegradation enhancement by BiOWiSH^TM-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 BiOWiSH^TM-Aqua FOG, and the resulting enrichment cultures were screened using respirometry as well. Potential hydrocarbon-degrading bacteria in BiOWiSH^TM-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 25^oC under aerobic conditions. TPH measurements of soil in the microcosms at 0, 25 and 56 days indicated that the addition of 500-ppm BiOWiSH^TM-Aqua FOG improved biodegradation of the motor oil-contaminated soil by 45%. However, BiOWiSH^TM-Aqua FOG did not have a measurable effect on biodegradation in the diesel-contaminated soil.

In the respirometry experiments, BiOWiSH^TM-Aqua FOG and two hydrocarbon-enriched BiOWiSH^TM-Aqua FOG cultures were evaluated indirectly by the measurement of microbial carbon dioxide production and oxygen uptake using a MicroOxymax^TM respirometer. The respirometry experiments showed that in the six-day period following motor oil-contamination of soil, the addition of BiOWiSH^TM-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 BiOWiSH^TM 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 BiOWiSH^TM-Aqua FOG. Stoichiometric calculations suggested that BiOWiSH^TM-Aqua FOG removed approximately 1400 ppm TPH (14%) from the soil in 6.5 days, while an enrichment culture of BiOWiSH^TM-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.