Biodegradation of petroleum hydrocarbons in contaminated aqueous and sediment environments

Abstract

Six bioremediation methods were tested in laboratory microcosms using field soil and water samples from within the fire-wall area of a petroleum storage tank. This soil had been intermittently contaminated with Bunker C fuel oil and other petroleum materials over an extended period of time. This study focuses on the behavior of the laboratory microcosms designed to simulate the in situ conditions and the six bioremedial methods employed in a related field study. The six treatment methods were: 1) aeration with essential nutrients and indigenous organisms, 2) aeration with essential nutrients and an inoculation from a refinery wastewater treatment facility, 3) aeration with oleophilic fertilizer and indigenous organisms, 4) aeration with essential nutrients and biosurfactant organisms, 5) aeration with nutrients and proprietary organisms, and 6) aeration only. Total petroleum hydrocarbons (TPH) analyses and gas chromatographic/mass spectrophotometric (GC-MS) analyses of the petroleum fractions were used to determine if the enhancement methods were more effective than the control in biodegrading the contaminants. Results indicated that there was no significant difference in the petroleum reduction rates among the six treatment methods. The conclusions were that the petroleum was not bioavailable --transfer from soil-to-water was likely the rate controlling factor in this study. Biodegradation rates were significantly slowed by the highly weathered state of the petroleum, and the extreme spatial heterogeneity hindered the sampling and analysis of the petroleum. These conclusions were further supported in a second experiment using only the extracted petroleum contaminant. The extracted petroleum was biodegraded when made available in shake flasks. Three different ,consortia were shown to significantly biodegrade the petroleum contaminant when made bioavailable. These consortia were able to reduce the TPH and many other specific hydrocarbons.