PAH removal from Nigerian oil-based drill-cuttings with spent oyster mushroom (Pleurotus ostreatus) substrate

The polycyclic aromatic hydrocarbon-removal capacity of spent oyster mushroom (P. ostreatus) substrate (SMS) in the reclamation of oil-based drill cuttings under laboratory composting conditions has been investigated. Adopting the Latin Square (LS) experimental design, four options of different treatment levels were tested in 10-litre plastic reactors containing fixed masses of the drill cuttings (2000 g) and fresh top-soil (500 g) inoculated with varying masses of the SMS (500 g for option 1 at 4:1:1, 1000 g for option 2 at 4:1:2, 2000 g for option 3 at 4:1:4 and option 4 was the control with no SMS addition). Each option was replicated three times and the set-ups were watered every 3 days under ambient conditions for a period of 56 days. The fresh top-soil was used as a bulking agent. Microcosm analysis with an Agilent Hp ® GC-FID Model 5890 Series II showed that the PAHs in the drill cuttings were mainly composed of 2-5 fused rings with molecular-mass ranging from 128 to 278 g/mol while the total initial PAHs concentration of the drill cuttings was 806.31 mg/kg. After 56 days of composting, the total amount of PAHs remaining in the drill cuttings decreased to between 19.75 and 7.62% while the overall degradation of PAHs increased to between 80.25 and 92.38% with increasing SMS addition. Individual PAH degradation ranged from 97.98% in acenaphthene to 100% in fluorene, phenanthrene and anthracene. These results showed PAH-removal capacity of spent oyster mushroom (P. ostreatus) substrate. Statistical analysis, using the two-factor ANOVA, showed that there were no significant differences (p<0.05) in the biodegradation of the PAHs due to the SMS levels applied and remediation period as well as a nonsignificant (p<0.05) interaction between SMS levels applied and remediation period.