Enhancement of PAHs biodegradation in biosurfactant/phenol system by increasing the bioavailability of PAHs

The poor bioavailability of polycyclic aromatic hydrocarbons (PAHs) is the main limiting factor for their biodegradation in contaminated sites. The addition of biosurfactant is an effective method for enhancing the bioavailability of PAHs. Suitable low molecular weight (LMW) organic matters have been shown to increase the bioavailability of PAHs. Therefore, we investigated the effect of phenol, which often co-exists with PAHs, on the biodegradation of PAHs in biosurfactant solution. The results show that the critical micelle concentration (CMC) of the biosurfactant decreased after phenol was added. The formation of mixed micelles resulted in enhancement of PAHs dissolution. The weight solubilization ratio (WSR) values of biosurfactant for Phe, Pyr and BaP in phenol solution are approximately 1.34, 1.40 and 1.67 times that of the control group, respectively. Phenol, therefore, can assist biosurfactant to increase the availability of PAHs by microbes. The bioavailability of PAHs in sludge increased from 27.7% to 43.1% after the biosurfactant was added, and reached a maximum of 49.2%, following the simultaneous addition of phenol and biosurfactant. Phenol also improved the degradation of PAHs by Stenotrophomonas sp. N5 in biosurfactant solution.