OPTIMIZING THE PERFORMANCE OF COW DUNGS AND POULTRY DROPPINGS

ABSTRACT

Environmental degradation caused by hydrocarbon pollution is an issue of concern that has developed into a widely studied area. A number of techniques have been proposed to deal with this issue, but most of them are expensive and require huge manpower resources. This necessitated the need for cheaper and environmentally friendly alternatives. One of such option is the use of organic substrates that could act as bulking agents and also as bacterial biomass suppliers. The aim of the study was to evaluate and optimize the performance of cow dung (CD) and poultry droppings (PD) for the bioremediation of crude oil contaminated soil. To this end, a central composite design in response surface methodology (RSM) was used for process optimization of total hydrocarbon (THC) degradation of soil. Three independent variables affecting the remediation process, namely: composition of amendment (A%), level of application of amendment (B%) and duration of amendment (C weeks), were selected. Maximum THC degradation of 1,339.95 mg/kg (about 93% remediation; initial concentration 1435.60 mg/kg) was attained at a composition of amendment of 45% cow dung (55% PD), 6% level of application of amendment and duration of amendment of 12 weeks. However, minimum THC degradation of 235.84 mg/kg (about 16% remediation) was obtained with composition of amendment of 45% CD (55% PD) at 6% level of application of amendment for a duration of 2 weeks. The optimization showed that the experimental data fitted well with the second order polynomial regression model 672.45 + 25.29𝐴 + 11.7𝐵 + 322.49𝐶 + 0.9794𝐴𝐵 + 8.34𝐴𝐶 − 3.65𝐵𝐶 + 13.08𝐴 2 + 16.72𝐵 2 + 51.35𝐶 2 with a predicted R² value of 0.9421 which was in reasonable agreement with the actual R² of 0.9902. This study showcases the importance of parameter optimization via RSM for any bioremediation studies particularly for in an economical, harmless, and ecofriendly manner.