Enhanced remediation of an oily sludge with saline water

This study investigates the potentials of saline (that is, brackish) water to enhance the remediation of an oily sludge, which was part of the waste stream from the improvement project of the Tank Farm at the Bonny Island in the Niger Delta region of Nigeria. Twice weekly, five separate laboratory-scale reactors (labeled A, B, C, D and O), each containing 2.0 × 10<sup>-2</sup> m<sup>3</sup> of the diluted sludge samples, received 170 g of liquid 20:10:10-NPK-fertilizer (corresponding to an application rate of approximately 4.3 kg-Nm<sup>-3</sup>, 2.1 kg-P-m<sup>-3</sup> and 2.1 kg-K-m<sup>-3</sup> of diluted sludge). On a weekly basis, control reactors A and B received 5.0 × 10-4 and 1.5 × 10<sup>-3</sup> m<sup>3</sup> of fresh water respectively while ‘treatment’ reactors C and D received 5.0 × 10<sup>-4</sup> and 1.5 × 10<sup>-3</sup> m<sup>3</sup> of saline water (containing 4.54 g/L of NaCl) respectively. Reactor O, which served as a counterfactual, was only rain-fed. Equal oxygen exposure levels, through regularly scheduled tilling, was maintained in all five reactors. After 12 weeks of treatment (that is, from May to August, 2007), sludge physicochemical characteristics showed distinct variations. The saline water treated-reactor D, had a 7-fold increment in bacterial population while the fresh water treated-reactor B, had an approximately 3-fold increment in bacterial population. The drop in the hydrocarbon content of the saline water-treated reactors ranged from 41.7 to 55.9% whereas in the fresh water-treated reactors, the hydrocarbon losses ranged from 17.3 to 25.0%. These results showed the possibility of enhanced biodegradation of oily sludge by hydrocarbon utilizing bacteria (Bacillus subtilis) at salinity (NaCl concentration) of 4.54 g/L.Key words: Bioremediation, biostimulation, oily sludge, saline water, Bacillus subtilis

Mycoremediation of polycyclic aromatic hydrocarbons (PAH)-contaminated oil-based drill-cuttings

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, compostin

Visible and near-infrared spectroscopy analysis of a polycyclic aromatic hydrocarbon in soils

Visible and near-infrared (VisNIR) spectroscopy is becoming recognised by soil scientists as a rapid and cost-effective measurement method for hydrocarbons in petroleum-contaminated soils. This study investigated the potential application of VisNIR spectroscopy (350–2500 nm) for the prediction of phenanthrene, a polycyclic aromatic hydrocarbon (PAH), in soils. A total of 150 diesel-contaminated soil samples were used in the investigation. Partial least-squares (PLS) regression analysis with full cross-validation was used to develop models to predict the PAH compound. Results showed that the PAH compound was predicted well with residual prediction deviation of 2.0–2.32, root-mean-square error of prediction of 0.21–0.25 mg kg−1, and coefficient of determination () of 0.75–0.83. The mechanism of prediction was attributed to covariation of the PAH with clay and soil organic carbon. Overall, the results demonstrated that the methodology may be used for predicting phenanthrene in soils utilizing the interrelationship between clay and soil organic carbon