Biosurfactant assisted degradation of high molecular weight polycyclic aromatic hydrocarbons by mixed cultures from a car service oil dump from Pretoria Central Business District (South Africa)

Abstract

Biomineralisation of polycyclic aromatic hydrocarbons (PAHs) and other toxic organic pollutants to CO2 and H2O is one of the most environmentally friendly and economically efficient options for treatment of deleterious organic pollutants in water and soil. Although most intermediate and high molecular weight (I-, HMW) PAHs are biodegradable, the degradability of these PAHs is limited by their low solubility. Experiments were conducted in batch reactors, and later, in continuous flow fixed-film bioreactor systems to take advantage of mass-transport resistance to reduce toxicity exposure within the biofilm. The results from this study showed a tenfold performance improvement in cumulative removal of PAHs in the biofilm reactor system. The active microbial agents were predominated by Pseudomonas aeruginosa MS-1 and Acinetobacter species. 98%, 88%, and 63% degradation of fluoranthene, pyrene and chrysene was achieved in the biofilm process, respectively, at steady doses of 45 kg/d fluoranthene, 12 kg/d pyrene and 7.5 kg/d chrysene, respectively. Product purification was further evaluated in a continuous flow fed-batch and plug-flow reactor system in which a high quality oil product was separated from oily sludge.