- ©2001. AAPG/DEG
The feasibility of bioremediating a weathered petroleum sludge was studied both in the laboratory and in field composting. The sludge consisted of straight-chained alkanes ranging from C20 to C38, with a halogen content of 4.1% and a specific gravity of 0.91–0.92 (23–24 API). Twenty indigenous bacteria were isolated from the sludge and identified; all were mesophiles and grew with or without 3.6% sodium chloride. Nine bacteria used sludge as the sole carbon and energy source and were used in the feasibility and composting studies. The sludge-degraders reduced the total petroleum hydrocarbon (TPH) by 97.4% in 10 weeks in shake cultures with 46 μg/g; at TPH values of 4.1 × 104 and 1.0 × 105 μg/g the bacteria reduced the sludge by about 50% in two weeks and at 2.3 × 105 the sludge was toxic. There was no evidence that cometabolism occurred, and a surfactant did not enhance bioremediation. Piles composted with either sawdust or complete compost (composted agricultural wastes) as bulking agents were monitored by measuring the most probable numbers and TPHs through 24 weeks. The initial TPHs ranged from 3.1–3.6 × 104 μg/g, and the bioremediation rate and extent were better using complete compost (72–75% degradation) than with sawdust (56–58%). There was no measurable effect on bioremediation by augmenting with the sludge-degraders, and most probable numbers ranged from 105–106 cells g–1 soil in sawdust-bulked piles and 107–108 cells g–1 in complete compostbulked piles. After 18 weeks of composting, temperature means were significantly different in the two bulking materials (32°C in complete compost and 41°C in sawdust), but both were 41°C from weeks 19–24, during which time the bioremediation rate did not change in any pile.
William Russell Giles, Jr. received Bachelor's and Master's degrees in 1995 and 1997, respectively. After graduating from The University of Texas Medical School at Houston in May 2001, he will begin a residency in internal medicine and pediatrics at Herman Hospital, Houston.
Kimberly Diane Kriel received Bachelor's and Master's degrees in 1993 and 1999, respectively, and she worked as a research assistant at The University of Texas Medical Center at Tyler before starting the home schooling of her two daughters.
James R. Stewart, Ph.D., is a Professor Emeritus of Biology and Chemistry at The University of Texas at Tyler (1974–2000) and he was president of the Texas Branch of the American Society for Microbiology from 1999–2001. His research included bacterial and algal physiology and bioremediation of oil spills and other petroleum products.