Removal of spilled petroleum in industrial soils by spent compost of mushroom Pleurotus pulmonarius

Two batches of oil-contaminated soil collected from an industrial area and one pile of oil-contaminated soil in a power plant were treated by the spent compost of mushroom Pleurotus pulmonarius (SMC). SMC contained macronutrients for biostimulation, possessed 1.0–1.5 U mg−1 laccase and 0.8–0.9 U mg−1 manganese peroxidase for biodegradation and harboured (11 ± 3) × 107 cfu g−1 bacteria and (56 ± 9) × 104 cfu g−1 fungi for bioaugmentation. In off-site ex situ bioremediation, the industrial area soil was contaminated with organic 5.4–6.9 g kg−1 total petroleum hydrocarbons (TPH), 14.5–19.0 g kg−1 oil and grease and 95–99 mg kg−1 di(2-ethylhexyl) phthalate (DEHP) and inorganic 104–136 mg kg−1 Cu, 430–691 mg kg−1 Pb and 477–578 mg kg−1 Zn. The removal by 3% SMC amendment applied twice accounted for 56–64%, 31–33% and 51–54% disappearance of the TPH, oil and grease and DEHP contaminants, respectively. For the latter soil, one 0.3% SMC application removed 40–45% of the initial 1.2 ± 0.2 g kg−1 TPH and 4.0 ± 0.6 g kg−1 oil and grease in 22 d. Further using four bacteria and four fungi inoculated onto the sterilized soil samples, samples with greater removal of the pollutants bore larger microbial populations. Thus SMC simultaneously degrades petroleum residues and reduces toxicity in less than a month.