SURFACTANT-ENHANCED MOBILIZATION AND BIODEGRADATION OF POLYCYCLIC AROMATIC-HYDROCARBONS IN MANUFACTURED-GAS PLANT-SOIL

The bioremediation of soil contaminated with polycyclic aromatic hydro carbons (PAH) often is limited by a low bioavailability of the contami nants. The effect of two nonionic surfactants of the alkylphenolethoxy late type, Arkopal N-300 and Sapogenat T-300, on bioavailability of PA H in manufactured gas plant soil was evaluated in soil columns percola ted by recirculating flushing water. Both surfactants enhanced the mas s transfer rate of sorbed PAH into the aqueous phase due to solubiliza tion. Solubilized PAH were available for biodegradation. Degradation o f the surfactants themselves was monitored by counting cell numbers of surfactant degraders. It could be demonstrated that the rapid degrada tion of Arkopal N-300 resulted in a lack of oxygen and an inhibition o f PAH degradation. Sapogenat T-300 was degraded more slowly, but a dep letion of oxygen occurred after 54 d of incubation. Until then the sur factant-enhanced PAH mobilization resulted in an increased PAH degrada tion as compared to the treatment without surfactant. Therefore, biode gradability of the surfactants was shown to be one of the key function s for the use of surfactants in practice. Reduction of PAH content and toxicity of the contaminated soil was obtained in all cases. Decrease of soil toxicity as indicated by the bioluminescence test was most pr onounced in case of the Sapogenat T-300-amended treatment. It is concl uded that surfactants can be a useful tool for stimulating biodegradat ion of PAH in contaminated soil.