Physical, chemical and biological parameters were optimized during composting to enhance degradation of oil sludge. Mixtures of oil sludge, garden soil, poultry manure and the bulking agents were co-composted in static piles of about 1 m3 on wooden pallets overlaid with nylon fibre sheets. Temperature, moisture, electrical conductivity (EC), pH, total carbon, total N, heterotrophs and respiration of compost microorganisms were monitored in each pile. Moisture was maintained at between 60 and 70% field capacity. Temperatures reached a mean of 63°C in the compost containing manure and sawdust. The C:N ratio of composts changed significantly during the composting process, reaching 100:41 (sawdust+manure) 100:39 (hay+manure) and 100:31 (woodchips+manure). Respiration of compost organisms rose from 1490 to 3850 CO2 (µg)/dwt/day in the sawdust+manure compost. Total petroleum hydrocarbons (TPH) decreased by between 52 and 66% in the composts and concentrations of selected polycyclic aromatic hydrocarbons (PAH) by between 78 and 100%. The Bacillus, Pseudomonas, Arthrobacter and Staphylococcus species were predominant in all the experiments and all temperature regimes.
Key words: Bulking agents, compost bioremediation, crude oil sludge, microorganism, polycyclic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH).
Abbreviations: PAHs, Polycyclic aromatic hydrocarbons; PCB, polychlorinated biphenyls; TPH, total petroleum hydrocarbons; IRS, infrared spectroscopy; MSA, mineral salts agar; CTAB, cetyltrimethyl ammonium bromide; EDTA, ethylene diamine tetraactic acid buffer; SDS, sodium dodecyl sulphate; PCR, polymerease chain reaction; PEG, polyethylene glycol; BLAST, basic local alignment search tool; EC, electrical conductivity.
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