A full-scale study evaluating an inoculum addition to stimulate in situ bioremediation of oily-sludgecontaminated soil was conducted at an oil refinery where the indigenous population of hydrocarbon-degrading bacteria in the soil was very low (10 3 to 10 4 CFU/g of soil). A feasibility study was conducted prior to the full-scale bioremediation study. In this feasibility study, out of six treatments, the application of a bacterial consortium and nutrients resulted in maximum biodegradation of total petroleum hydrocarbon (TPH) in 120 days. Therefore, this treatment was selected for the full-scale study. In the full-scale study, plots A and B were treated with a bacterial consortium and nutrients, which resulted in 92.0 and 89.7% removal of TPH, respectively, in 1 year, compared to 14.0% removal of TPH in the control plot C. In plot A, the alkane fraction of TPH was reduced by 94.2%, the aromatic fraction of TPH was reduced by 91.9%, and NSO (nitrogen-, sulfur-, and oxygen-containing compound) and asphaltene fractions of TPH were reduced by 85.2% in 1 year. Similarly, in plot B the degradation of alkane, aromatic, and NSO plus asphaltene fractions of TPH was 95.1, 94.8, and 63.5%, respectively, in 345 days. However, in plot C, removal of alkane (17.3%), aromatic (12.9%), and NSO plus asphaltene (5.8%) fractions was much less. The population of introduced Acinetobacter baumannii strains in plots A and B was stable even after 1 year. Physical and chemical properties of the soil at the bioremediation site improved significantly in 1 year.

A field-scale study was conducted in a 4000 m2 plot of land contaminated with an oily sludge by use of a carrier-based hydrocarbon-degrading bacterial consortium for bioremediation. The land belonged to an oil refinery. Prior to this study, a feasibility study was conducted to assess the capacity of the bacterial consortium to degrade oily sludge. The site selected for bioremediation contained approximately 300 tons of oily sludge. The plot was divided into four blocks, based on the extent of contamination. Blocks A, B, and C were treated with the bacterial consortium, whereas Block D was maintained as an untreated control. In Block A, at time zero, i.e., at the beginning of the experiment, the soil contained as much as 99.2 g/kg of total petroleum hydrocarbon (TPH). The application of a bacterial consortium (1 kg carrier-based bacterial consortium/10 m2 area) and nutrients degraded 90.2% of the TPH in 120 days, whereas in block D only 16.8% of the TPH was degraded. This study validates the large-scale use of a carrier-based bacterial consortium and nutrients for the treatment of land contaminated with oily sludge, a hazardous hydrocarbon waste generated by petroleum industry.

Sulfate-reducing bacteria (SRB) developed biocathodes efficient for reduction of acetic and butyric acids to alcohols and acetone via direct electron transfer reaching current densities of 160-210 A m(-2).

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A bacterial strain, PS4040, capable of degrading polycyclic aromatic hydrocarbons for use as the sole carbon source was isolated from oily-sludge-contaminated soil. The 16S rRNA gene showed 98.8% homology to that of Leclercia adecarboxylata. Comparative molecular typing with the clinical strain of L. adecarboxylata revealed that there were few comigrating and few distinct amplimers among them.Metabolic diversity of bacterial flora is a well-established phenomenon, and a consequence of this diversity is the degradation of various biohazardous or persistent anthropogenic compounds by microbial activities. Among these recalcitrant compounds, polycyclic aromatic hydrocarbons (PAHs) represent a unique class of petroleum hydrocarbons due to their pyrogenic nature and the complexity of the assemblages in which they occur (9). Although many genera of microorganisms have the ability to degrade these recalcitrant compounds and use them as a source of carbon or energy, such phenomena are not commonly encountered in enteric bacteria (3).The enteric bacteria in the family Enterobacteriaceae are mainly regarded as inhabitants of animal guts (3). The ability of this group to degrade high-molecular-weight PAH compounds appears to be an unusual feature, as this phenomenon has been associated with typical soil bacteria. However, very few reports have indicated utilization of aromatic compounds by enterobacteria, particularly those of the genera Klebsiella, Enterobacter, Escherichia, and Hafnia (3, 5, 7). Although there are several reports of bioremediation of high-molecular-weight PAHs, research pertaining to biodegradation of these substances by enteric bacteria has been relatively rare (3,9).In this article we report the isolation of an enteric bacterial strain, PS4040, which can degrade the high-molecular-weight, four-benzene-ring PAH pyrene for use as a sole source of carbon. Phenotypic profiling and sequence analysis identified the strain as Leclercia adecarboxylata. We report for the first time the degradation of PAHs by L. adecarboxylata.Source, enrichment, and isolation of bacteria. PAH-degrading bacterial strains were isolated from subsurface soil collected from an oily-sludge storage pit at the Digboi oil refinery, situated in the northeastern region of India (27°15ЈN, 98°15ЈE). The site has a history of petroleum hydrocarbon contamination of over 100 years. A defined mineral salt medium (MSM) (11) was used for isolation and enrichment of PAH-degrading bacteria. An oily-sludge-contaminated soil sample (10 g) was used to inoculate 200 ml of MSM containing pyrene (200 mg/liter), and the culture was incubated at 30°C on a rotary shaker (200 rpm) for 7 days. After 10 such cycles of enrichment, 1 ml of the culture was diluted 10 8 -fold and the diluted culture was plated on MSM agar containing pyrene (200 mg/liter). The nine bacterial colonies that gave a zone of clearance on pyrene-coated MSM agar plates were further purified on MSM agar with pyrene as the carbon and energy source.Sequencing of 16S rRNA gene and phylogeneti...