Optimization of growth condition for hydrocarbon degrading bacteria isolated from oily sludge in order to achieve the most efficient conditions in environmental bioremediation
Petroleum refineries around the world have generated the solid wastes during the refining process and stocking of crude oil. Oily sludge leads to destructive effects in the environment. This investigation concentrated in degrading oily compounds from oily sludge in order to environmental bioremediation. Eight bacterial strains able to grow on the oily sludge as sole source of carbon and energy isolated from oily sludge and soil-contaminated with oily sludge in Abadan refinery. Two bacterial strains were adopted as efficient strains and were named AOR1 and AOR2. Influence of different nitrogen and phosphorous sources on the growth of these two bacterial strains were investigated by measuring the growth rate through serial dilution and colony counting in T.S.A medium. Sodium nitrate and disodium hydrogen phosphate were found to be the best nitrogen and phosphorous sources for the AOR1 strain. Ammonium chloride and diammonium hydrogen phosphate were found to be the best nitrogen and phosphorous sources for the AOR2 strain. It can be concluded that these isolates have potential for environmental pollution bioremediation and supplying these nitrogen and phosphor resources to their medium can accelerate this process.
Evaluation of Inoculum Addition To Stimulate In Situ Bioremediation of Oily-Sludge-Contaminated Soil
ABSTRACT A full-scale study evaluating an inoculum addition to stimulate in situ bioremediation of oily-sludge-contaminated soil was conducted at an oil refinery where the indigenous population of hydrocarbon-degrading bacteria in the soil was very low (103 to 104 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.
The in vitro degradation of the herbicide bromoxynil.
The in vitro degradation of the herbicide bromoxynil at the 25 ppm level by a flexibacterium, strain BR4, was investigated. The degradation was monitored using gas-chromatographic and spectrophotometric analytical procedures. Breakdown was rapid with only 5% of the original herbicide remaining after 5 weeks. No detectable degradation occurred in sterile medium.Thin-layer chromatographic techniques were used to isolate and identify 3, 5-dibromo-4-hydroxybenzamide and 3, 5-dibromo-4-hydroxybenzoic acid as degradation products. A third metabolite was isolated but not identified.