Abstract

Spent white-rot fungi (Pleurotus ostreatus) substrate has been used to biotreat Nigerian oil-based drill cuttings containing polycyclic aromatic hydrocarbons (PAHs) under laboratory conditions. The Latin square (LS) experimental design was adopted in which four options of different treatment levels were tested in 10 L plastic reactors containing fixed masses of the drill cuttings and fresh top-soil inoculated with varying masses of the spent P. ostreatus substrate. Each option was replicated three times and watered every 3 days under ambient conditions for a period of 56 days. Microcosm analysis with a series II model 5890 AGILENT Hp^® GC-FID showed that,the PAHs in the drill cuttings were mainly composed of 2 to 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 residual PAHs 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 substrate addition. Individual PAH degradation ranged from 97.98% in acenaphthene to 100% in fluorene, phenanthrene and anthracene. Statistical analysis, using the 2-factor analysis of variance (ANOVA), showed that there were no significant differences (p < 0.05) in the biodegradation of the PAHs due to the substrate levels applied and remediation period, as well as a nonsignificant (p < 0.05) interaction between substrate levels applied and remediation period. These results showed that spent white-rot fungi (P. ostreatus) substrate may be suitable for biotreating PAH-contaminated Nigerian oil-based drill cuttings.

Key words: Drill-cuttings, polycyclic aromatic hydrocarbons Pleurotus ostreatus,mycoremediation, composting

Abbreviation

PAHs, Polycyclic aromatic hydrocarbons; OBM, oil-based mud;TDUs, thermal desorption units; RENA, remediation by enhanced natural attenuation;BDE, biodegradation-efficiency; OBDC, oil-based drill cuttings; SMS, spent fungal (mushroom) substrate; LS, Latin square; C_0, C_t, PAH concentration at the initial and over a time period, t (mg/kg) respectively; K₁, pseudo-first order kinetic constant (day^-1); t, time (days); , half-life (days).