Journal of Biotechnology & Biomaterials
Open Access

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) are components of oil sludge that are known to be cytotoxic, mutagenic and potentially carcinogenic. Bacteria have been reported to degrade oil sludge components to innocuous compounds such as carbon dioxide, water and salts. This study was to measure the reduction in PAHs present in oil sludge by co-composting the sludge with pig, cow, horse and poultry manures under laboratory conditions. Four kilograms of soil spiked with 800 g of oil sludge was co-composted differently with each manure in a ratio of 2:1 (w/w) spiked soil: manure and wood-chips in a ratio of 2:1 (w/v) spiked soil: wood-chips. Control was set up similar as the one above but without manure. The composites were incubated for 10 months at room temperature. Compost piles were turned weekly and moisture levels were maintained. Moisture level, pH, temperature, CO2 evolution and oxygen consumption were measured monthly and the ash content at the end of experimentation. Highest temperature reached was 27.5 ��C in all compost heaps, pH ranged from 5.5 to 7.8 and CO2 evolution was highest in poultry manure at 18.78 �¼g/dwt/day. Microbial growth and activities were enhanced. Bacteria capable of utilizing PAHs were isolated, purified and characterized of 16S rRNA gene by molecular techniques using polymerase chain reaction (PCR), with specific universal primers (forward and reverse) and were sequenced. Bacteria identified were Bacillus, Arthrobacter and Staphylococcus species. Percentage reduction in PAHs was measured using automated soxhlet extractor with dichloromethane coupled with gas chromatography/mass spectrometry. Results from PAH measurements showed reduction between 77% and 99%. Co-composting of spiked soils with animal manures enhanced the reduction in PAHs.

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