Microbial Bioremediation of Polycyclic Aromatic Hydrocarbons (PAHs) in Oily Sludge Wastes

Polycyclic Aromatic Hydrocarbons (PAHs) are fused-ring hydrocarbon compounds that are highly recalcitrant under normal conditions due to their structural complexity and strong molecular bonds. These groups of petrochemicals are mainly found in petroleum-refining plants, accidental oil spills and pipe leakages, and rainwater run-off from roadway. Improperly managed and disposed PAHs can cause environmental pollution as they accumulate in the surrounding soil sediment. PAH contamination is highly unwanted as they are hazardous to human health due to their carcinogenic, mutagenic and potentially immunotoxicants properties. Although in the natural environments they are readily degraded by indigenous microbial communities, these processes are very time-consuming. Various physical and chemical applications are currently employed to remediate the problems caused by PAHs pollution. However, these forms of treatments are either unsound economically or may in fact cause downstream complications. Therefore, the intent of this review is to present the applications of microbial bioremediation of PAHs in oily sludge wastes. Among other things, this review will cover a broad overview of the constituents of PAHs, the microbial dynamics of hydrocarbon catabolism, factors (biological, chemical and physical) effecting microbial degradation and the various strategies available for the enhancement of microbial elimination of PAHs, such as bioaugmentation and biostimulation.