Abstract
The objective of this study was designed to evaluate the effects of biostimulation and bioaugmentation amendment agents (NPK fertilizer, Tween 80 and mixed culture) on the bioremediation of tropical soil samples artificially contaminated with Weathered Bonny Light Crude Oil (WBLCO). Response Surface Methodology (RSM) with Box Behnken Design (BBD) was used with three levels and three factors of NPK fertilizer (2 - 6 g), Tween 80 (5 - 15 mg/l) and mixed culture (0.5 - 1.5 g/l) as independent variables and WBLCO removal as dependent variable (response) in a six weeks remediation period. The results showed that the rate of WBLCO removal generally increased with increase in the amount of NPK fertilizer, Tween 80 and mixed culture (biomass), respectively. A statistically significant (P < 0.0001) second-order quadratic regression model for WBLCO removal (using design-expert statistical program (v. 6.0.8)) with a coefficient of determination, R (=0.9996) was obtained. Numerical optimization technique based on desirability function was carried out to optimize the bioremediation process. The optimum values for biostimulation and bioaugmentation amendment agents to achieve a predicted maximum WBLCO removal of 84.88 percent were found to be: NPK fertilizer, 4.25 g; Tween 80, 10.22 mg/l and mixed culture, 0.46 g/l. At this optimum point, the observed WBLCO removal was found to be 83.79 percent. The statistical analyses and the closeness of the experimental results and model predictions show the reliability of the regression model and thus, biostimulation and bioaugmentation of indigenous microbial density and activity can reduce remediation period of petroleum hydrocarbon contaminated environment and subsequently the cost of remediation.
Highlights
Crude oil is an extremely complex mixture of aliphatic and aromatic hydrocarbons, including volatile components of gasoline, petrol, kerosene, lubricating oil and solid asphaltene residues
The objective of this study was designed to evaluate the effects of biostimulation and bioaugmentation amendment agents (NPK fertilizer, Tween 80 and mixed culture) on the bioremediation of tropical soil samples artificially contaminated with Weathered Bonny Light Crude Oil (WBLCO)
The results showed that the rate of WBLCO removal generally increased with increase in the amount of NPK fertilizer, Tween 80 and mixed culture, respectively
Summary
Crude oil is an extremely complex mixture of aliphatic and aromatic hydrocarbons, including volatile components of gasoline, petrol, kerosene, lubricating oil and solid asphaltene residues. In developed and developing countries, contamination of soil and marine environment by crude oil and petroleum products has become a serious problem. Crude oil causes a variety of risks when released into the environment. It is physically, chemically and biologically harmful to soil because of the presence of many toxic compounds, such as polycyclic aromatic hydrocarbons, benzene and its substituted and cycloalkane rings, in relatively high concentrations. Biodegradation of hydrocarbon compounds is one of the most important processes involved in the weathering and eventual removal of oil from the environment, for its non-volatile components.
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