In this study, application of risk assessment was the basis for the selection of an optimum treatment option for the potential bioremediation of a hydrocarbon polluted environment. This approach was applied in a hydrocarbon polluted swampy terrain in the Niger Delta of Nigeria and could actually be applied to any other hydrocarbon polluted environment. Three nutrient sources namely compost, liquid organic fertilizer and NPK were employed in the laboratory biostimulation of the biodegradation of the hydrocarbons experiments using three levels of concentration for each nutrient as 5, 10 and 20% (w/w). Total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbons (PAH) were the analytes used in assessing the biodegradation potential of the various treatments. The residual concentration of these analytes post biodegradation was measured by means of gas chromatography-flame ionization detector and gas chromatography-mass spectrometry. Results indicate that compost and liquid organic fertilizer at 5% (w/w) were very poor in biostimulating the biodegradation of the hydrocarbons (less than 20% biodegradation of TPH and 3–30% biodegradation of the PAHs). NPK performed better than the other two sources of nutrients as it effected 74–84% TPH biodegradation and 39–90% PAHs biodegradation.
On screening the three NPK treatment options using risk assessment, the 5% w/w NPK treatment option was rejected as its associated residual PAHs posed risks that exceeded the risk threshold of 10^-6 whereas the other two (10 and 20% w/w NPK) were successful with risk values less than the threshold. However, the 10% w/w NPK treatment offers a cheaper option between the two hence it is selected as the optimum bioremediation option based on risk management.
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