Factors affecting the nonionic surfactant-enhanced biodegradation of phenanthrene

This research addresses the influence of nonionic surfactants on the biodegradation of poorly soluble organic compounds in soil and water. Batch- and continuous-flow column biodegradation studies of phenanthrene were carried out in the presence of four commercial nonionic surfactants at sub- critical micelle concentration (CMC). Surfactants were tested to determine their effectiveness in solubilizing phenanthrene, their sorption-desorption characteristics to soil, their biodegradability, and their effect on the adsorption and biodegradation of phenanthrene. Solubility enhancement of phenanthrene by the surfactants was mainly a micellar phenomena. Sorption of phenanthrene and the surfactants could be represented by a linear isotherm model. Sorption of phenanthrene to soil was enhanced significantly in the presence of the surfactants. A mixed enriched microbial culture acclimated to phenanthrene as the sole organic carbon source was used as the inocula. Biodegradation experiments indicated that low surfactant concentrations promoted mineralization of phenanthrene without inhibitory or toxic effects. The study indicates that surfactant selection for in situ bioremediation purposes will depend on a number of factors, with main emphasis on its hydrocarbon solubilizing power, sorptive properties, low toxicity to bacteria, and fate in the environment.