Potential microbial drivers of biodegradation of polycyclic aromatic hydrocarbons in crude oil sludge using a composting technique

BACKGROUND Improper disposal of crude oil sludge poses a public health risk due to the toxic nature of components of the waste, especially polycyclic aromatic hydrocarbons (PAHs). Such toxic wastes can be treated by bioremediation of the polluted sites with composting, an eco-friendly technique that is gaining acceptance. Crude oil sludge was composted for four months during which surfactants were introduced. Fungi and bacteria were isolated from the compost using basic culture techniques. Residual concentrations of PAH components of the sludge during the composting period was monitored with gas chromatography - mass spectrometry (GC-MS). RESULTS Molecular characterization of the internal transcribed spacer (ITS) genes of fungal isolates classified fungi in the compost into different genera including Aspergillus, Bionectria, Doratomyces, Exophiala, Fusarium, Galactomyces, Geotrichum, Mucor, Penicillium, Trichoderma and Trichurus. The bacterial isolates were classified into Stenotrophomonas, Pseudomonas, Bordetella, Brucella, Bacillus, Achromobacter, Advenella, Klebsiella, Mesorhizobium, Mycobacterium, Ochrobactrum, Pusillimonas and Raoultella. Results from analysis of residual PAH concentrations of composted samples showed higher degradation efficiency of the higher molecular weight (HMW) PAHs resulting in their complete degradation, whereas the lower molecular weight PAHs were not degraded completely. CONCLUSIONS Compost bioremediation is a sustainable waste management technique for hazardous wastes such as crude oil sludge. Inclusion of surfactants at different concentrations did not constantly improve the bioavailability of PAH compounds in the crude oil sludge but it promoted fungal growth in the treatments. (c) 2020 Society of Chemical Industry