Studies on the Removal of Petroleum Hydrocarbons (PHCs) from a Crude Oil Impacted Soil Amended with Cow Dung, Poultry Manure and NPK Fertilizer

Abstract The potential effects of animal-derived organic wastes and commercially available NPK fertilizer as nutrient supplements to biostimulate soil indigenous microorganisms for hydrocarbons degradation were investigated. 150 g each of soil samples were spiked with Bonny light crude oil (BLCO) (10 % w/w) and one week after contamination, about 30 g each, of the amendment agents (cow dung (CD), poultry manure (PM) and NPK (15:15:15) fertilizer) was added to the soil samples equivalent to 2000 kg/hectare. The soil samples were tilled daily to ensure homogenization and adequate aeration. The rates of degradation of the crude oil were studied for a remediation period of 8 weeks under laboratory conditions. The results showed that there was a positive relationship between the rate of petroleum hydrocarbons degradation and presence of the animal-derived organic wastes and NPK fertilizer in soil microcosms contaminated with crude oil, having achieved the reduction of PHCs from 25450 mg/kg to 6910 mg/kg, 3820 mg/kg and 6770 mg/kg for cow dung, NPK fertilizer and poultry manure respectively, which is above 70% removal of PHCs within the remediation period. The BLCO degradation data fitted well to the first-order kinetic model. The model revealed that BLCO contaminated-soil microcosms amended with animal-derived organic wastes had higher biodegradation rate constants (K) as well as lower half-life times (t_1/2) than unamended soil (natural attenuation) remediation system. The biodegradation rate constant and calculated removal efficiency values showed that NPK offered the best biostimulation performance, which was closely followed by poultry manure and then cow dung. The data, subjected to a two- way analysis of variance for significance at p ˂ 0.05, indicated that time and the material used are significant, it was also noted that time had more effect on the remediation process than the amendment agents used. The system proposed here is inexpensive, efficient, and environmentally friendly and may thus offer a viable choice for petroleum hydrocarbons contaminated, soil remediation.

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