|Institution:||University of Cincinnati|
|Department:||Engineering : Environmental Engineering|
|Keywords:||Engineering, Environmental; biodegradation; bioremediation; crude oil; microcosms; nitrogen nutrient|
|Full text PDF:||http://rave.ohiolink.edu/etdc/view?acc_num=ucin1014064418|
Oil biodegradation at high concentrations was studied in microcosms. The experimental approach involved mixing clean sand with artificially weathered Alaska North Slope crude oil at the beginning of the experiment and monitoring oil biodegradation in microcosms over a 42-day observation time. An uncharacterized consortium of oil-degrading microorganisms was used to inoculate reactors at time-zero. Two types of nitrogen-containing nutrients were applied at a concentration of 100 mg as N/L: KNO3 and NH4Cl. Oil biodegradation was evaluated by monitoring CO2 production, oxygen and nitrogen consumption, and changes in oil constituents. Lipid phosphate, phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses were conducted to determine viable biomass and species composition of microbial populations. In the first experiment, three crude oil concentrations, 5, 20, 80g /kg sand, were studied in tidal flow microcosms. Results indicated that oil concentrations as high as 80g /kg sand were still amenable to bioremediation. More biomass growth was observed in the submerged (anoxic) zone of the sand columns and better oil degradation was found in reactors receiving potassium nitrate. In the second experiment, oil biodegradation was studied at an oil concentration of 20g /kg sand in continuous flow microcosms. Results indicated that the type of nitrogen source had no significant influence on oil biodegradation, since, in this case, oxygen was not limiting. Over 80 percent of target alkanes and around 50 percent of target PAHs were degraded by day-42. Most of the degradation occurred in the first 10 days. Two experiments, one with 20 g oil/kg sand, the other with 80 g oil/kg sand, were carried out in tidal flow microcosms. Three oxygen supply modes were used: anoxic, oxic, and oxic-anoxic. Results evidenced biodegradation of oil under anoxic conditions, but biodegradation was better in oxic reactors than in anoxic reactors. Oxygen had a stronger influence on oil biodegradation than did the type of nitrogen-nutrient fed. A Gram-negative bacterial group dominated the microbial community structure. Various Acinetobacter-affiliated species were present throughout the treatments, likely reflecting their flexibility in oxygen requirements coupled with their ability to degrade hydrocarbons.