The purpose of this study was to identify any biological/chemical factors which may be limiting the biodegradation of total petroleum hydrocarbon (TPH) contaminants at a biosparge site located at a former oil field near Guadalupe, California. Laboratory experiments using a combination of respirometry and TPH analyses were conducted to determine if biodegradation of TPH at the site is limited by a lack of hydrocarbon-degrading microorganisms, depleted inorganic nutrient concentrations, insufficient dissolved oxygen supply, or the chemical composition of the partially biodegraded petroleum constituents in the groundwater. No increase in total CO2 production was observed in samples with added nutrients, inoculum, or both, over the 28-day experiment. No significant TPH biodegradation benefit could be attributed to the addition of nutrients or inoculum indicating both were sufficiently available at the site. Decreasing dissolved oxygen (DO) concentration decreased short-term CO2 production, but considerable CO2 production was observed even in samples with DO concentrations as low as 0.5 mg/L. In a long-term experiment, TPH degradation rates decreased significantly after initial observed biodegradation.
Available at: http://works.bepress.com/ynelson/13/