WP10 Remediation Techniques and Strategies
A105 & A106
1:20 PM - 4:40 PM, Wednesday
() Evaluating oxygen-releasing compounds to enhance toluene biodegradation by indigenous karst bacteria.
King, L1, Jefferson, Z1, Byl, T1, 2, 1 Tennessee State University, Nashville, TN, USA2 USGS, Nashville, TN, USA
ABSTRACT- Microcosm studies done in our lab found that anaerobic biodegradation of toluene was generally 25 to 50 times slower than aerobic biodegradation. Considering the potential for rapid transport of dissolved contaminants in karst conduits, it follows that aerobic conditions are desired for enhancing bioremediation. The objective of this study was to evaluate the ability of three oxygen-release compounds (ORCs) to enhance fuel biodegradation by free-living bacteria found in karst aquifers. The ORCs that were evaluated were hydrogen peroxide (H2O2), calcium peroxide (CaO2) and magnesium peroxide (MgO2). The H2O2 molecules will break down into oxygen (O2) and water (H2O). The CaO2 and MgO2 will break down in the presence of water into O2 and either CaOH or MgOH, respectively. In this study, 2.25-liter liquid-karst microcosms (i.e., flasks containing water and free-living karst bacteria) were spiked to 100 ug/L toluene and different ORC concentrations were added. Sterile controls were also established with toluene and ORCs to verify toluene removal was due to biological processes. Additional controls with live bacteria, but no ORC supplements were also established for comparison. Microcosms enriched with 3 mg/L H2O2, CaO2, or MgO2 all showed >95% toluene removal in 7 days, as compared to, 45% removal in live microcosms with no ORCs. When the microcosms were enriched with 300 mg/L H2O2, CaO2, or MgO2, only the H2O2 treatment elicited a >99% reduction in toluene in 7 days. The other peroxide treatments had slightly enhanced toluene removal compared to the live control, but were generally not effective at this higher concentration. The decline in MgO2 and CaO2 performance was possibly due to the simultaneous release of hydroxide, which was found to inhibit biodegradation processes. Other parameters that will be discussed are field application of H2O2 in a karst aquifer, dissolved oxygen concentration, bacteria concentration, and BTEX concentrations.
Key words: karst, remediation, oxygen releasing compounds, BTEX