Bioremediation by composting of heavy oil refinery sludge in semiarid conditions.
ABSTRACT The present work attempts to ascertain the efficacy of low cost technology (in our case, composting) as a bioremediation technique for reducing the hydrocarbon content of oil refinery sludge with a large total hydrocarbon content (250-300 g kg(-1)), in semiarid conditions. The oil sludge was produced in a refinery sited in SE Spain The composting system designed, which involved open air piles turned periodically over a period of 3 months, proved to be inexpensive and reliable. The influence on hydrocarbon biodegradation of adding a bulking agent (wood shavings) and inoculation of the composting piles with pig slurry (a liquid organic fertiliser which adds nutrients and microbial biomass to the pile) was also studied. The most difficult part during the composting process was maintaining a suitable level of humidity in the piles. The most effective treatment was the one in which the bulking agent was added, where the initial hydrocarbon content was reduced by 60% in 3 months, compared with the 32% reduction achieved without the bulking agent. The introduction of the organic fertiliser did not significantly improve the degree of hydrocarbon degradation (56% hydrocarbon degraded). The composting process undoubtedly led to the biodegradation of toxic compounds, as was demonstrated by ecotoxicity tests using luminescent bacteria and tests on plants in Petri dishes.
- SourceAvailable from: Amirhossein Malakahmad[Show abstract] [Hide abstract]
ABSTRACT: In bioremediation, oil degrading microorganisms are applied to remediate contaminated soil. Air is an essential factor for activation of degrading microorganisms. Adding some bulky wastes or by-products which enhance the air circulation in the system is one of the economical approaches for aeration. In this study, co-composting of oil sludge contaminated soil from a local refinery plant was studied using dry yard waste (CI) and nonrecyclable paper (CII) as bulking agents. Initially 16 L cubic composters were made using plexiglass. Composters were opened at the top and had number of holes at the bottom and sides. The soil was spiked with petroleum refinery sludge (20%, dry weight basis) and the ratio of contaminated soil to bulking agents and seeding materials was 1:1 (v/v) and 1:0.5 (w/w), respectively. The seeding materials as source of microorganisms was brought from the same refinery plant wastewater treatment facility. The total volume of each mixture was approximately 4.3 kg. The composters were cultivated weekly and water was added occasionally to maintain moisture content. Results show the temperature profile for both composters were built up after initial weeks. Moisture content reached to steady conditions (50% to 60%) in second week and was maintained within the range till the end of experiments. pH showed more fluctuation in CII compared to CI. The maximum reduction of total petroleum hydrocarbon (TPH) was 55% and 56% for CI and CII, respectively over the 14-week study duration. The composting degradation rate kinetics indicates that the TPH concentrations will reach less than 100 mg/kg after 23 weeks of degradation.Business Engineering and Industrial Applications Colloquium (BEIAC), 2013 IEEE; 01/2013
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ABSTRACT: -1 total petroleum hydrocarbons (TPH) was bioremediated by composting. The soil was inoculated with sewage sludge and incubated for 19 months. The soil was mixed in a ratio of 1:1 (v/v) with wood chips. The soil-wood chips mixture was then mixed in a ratio of 4:1 with sewage sludge. Compost heaps were set up in triplicates on wood pallets covered with double layers of nylon straw sheets. Control experiments which contained the contaminated soil and wood chips but without sewage sludge were set up in triplicate. Moisture, temperature, pH, ash content, C:N ratio of the compost mixture and TPH of the soil was monitored monthly. The concentrations of selected hydrocarbons in the contaminated soil were measured monthly during the incubation period. Temperature rose to about 58°C in the sewage sludge compost within two months of incubation, while temperature in the control fluctuated between 15 and 35°C throughout the incubation period. Total petroleum hydrocarbons (TPH) was reduced by 17% in the control experiments and 99% in the sewage sludge compost at the end of the incubation period. The concentrations of most of the selected hydrocarbon components were reduced by up to 100% within the same period. Microbial activities were shown to correlate with the reduction in hydrocarbon contents of the soil.01/2010;
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ABSTRACT: Oily sludge from gas processing facilities contains components that are major environmental pollutants. Biodegradation is an alternative treatment, but can be affected by other components of the sludge, such as sulphur compounds, so it is important to evaluate the effect of these on oil biodegradation in order to prevent negative impacts. This work studied the transformation of sulphur compounds in oily sludge biodegradation systems at the microcosm level. The predominant sulphur compounds in the original sludge were elemental sulphur and pyrite (9,776 and 28,705.4 mg kg−1, respectively). In the biodegradability assays, hydrocarbon concentrations decreased from 312,705.6 to 186, 760.3 mg kg−1 after 15 days of treatment. After this time, hydrocarbon degrading activity stopped, corresponding with a decrease in hydrocarbon degrading bacteria. These changes were related to a reduction in pH that inhibits biodegradation. During the assay, sulphur compounds were gradually oxidized and transformed. The concentration of sulphate increased from 5,096 to 64,868.3 mg kg−1 after 30 days in the assay, although controls were unchanged. Therefore, it is important to determine changes to the main compounds of the waste in order to assess their impact.International journal of Environmental Science and Technology 10(3). · 1.84 Impact Factor