Remediation of crude oil contaminated soil with locally formulated bioremediation agent

Abstract

Hydrocarbon pollution is one of the major environmental challenges facing the Niger Delta region of Nigeria, and over the years, various methods and strategies have been suggested to be used in tackling these problem. This research was aimed at restoring crude oil contaminated soil with locally formulated bioremediation agent (coded LOFBA). The local bioremediation agent (LOFBA) formulated consisted of cow dung, chicken droppings and periwinkle shells. Four soil treatments (unpolluted soil, polluted soil with crude oil, polluted soil remediated with LOFBA and polluted soil remediated with NPK) were setup using completely randomized blocked design (CRBD). The microbial isolates were identified on the basis of cultural, morphological and biochemical characteristics. Physicochemical properties of the soil (pH, total nitrogen, sulphate, phosphorus, total organic carbon, moisture, exchangeable cations, heavy metals) were estimated using standard procedures while total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbons (PAH) were determined using the gas chromatography-mass spectroscopy (GCMS). The LOFBA had pH 5.6, high calcium (47.325%), Nitrogen (1.49%), phosphorus (0.26%), electrical conductivity (194.81μmho/cm) and high counts of bacteria and fungi. The microbial isolates identified were Bacillus subtilis, Bacillus megaterium, Bacillus cereus, Acinetobacter aceti, Corynebacterium diphtheriae, Pseudomonas aeruginosa and Streptococcus pyogenes. Soil remediated with LOFBA showed a significantly (p < 0.05) higher bacterial counts total nitrogen and exchangeable ions (K, Mg, Na and Ca) than other treatments. Heptadecane, pristine, octadecane, eicosane, herieicosane and hentriacontane were more highly degraded in LOFBA remediated soil than NPK remediated soil. Naphthalene was the only PAH present in all soil samples after six months although LOFBA remediated soil had the lowest concentration. Besides, Acenaphylylene was detected in crude oil contaminated soil and soil remediated with NPK while none was detected in soil remediated with LOFBA. The results also revealed that total petroleum hydrocarbon (TPH) from unamended soil decreased from 21.33 mg/kg to 16.61 mg/kg (22.13% degradation), from 15.18 mg/kg to 3.03 mg/kg (80.04% degradation) in LOFBA remediated soil while that of NPK remediated soil decreased from 18.70 mg/kg to 7.97 mg/kg (57.38% degradation) after six months. The results indicate that the locally formulated bioremediation agent (LOFBA) enhanced the recovery of the oil contaminated soil better than NPK fertilizer. LOFBA is therefore, recommended for oil spill remediation in the tropic.