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Nonionic surfactants are amphilic chemicals that enhance desorption and bioavailability by increasing solubility and dispersion of poorly soluble hydrocarbons and oils. This study was conducted to determine the toxicity of commercial nonionic surfactants by using the Microtox ® Acute Toxicity test which is a rapid, simple test for toxicity. The test uses the luminescent bacterium V. fischeri as the test organism. Five common commercial nonionic surfactants Tergitol NP-10, Triton X-100, Igepal 630, Brij 35 and Tween 40 were used in the study. Light readings were taken initially as well as at 0 minutes, 5 minutes and 10 minutes to see how the toxicity of each surfactant changed with time. Experiments were conducted to determine the five-minute EC 50 values. EC 50 is the effective concentration that causes a 50% decrease in light output in a 5-minute exposure period. A higher effective concentration is interpreted as a lower toxicity. The critical toxic concentration (CTC) was also determined. Toxicity of the surfactants varied according to their difference in chemical structures and branching. EC 50 values were less than the CTC and CMC values of all select surfactants. Higher toxicity was shown by surfactant solutions that contained a benzene ring in comparison to the others.

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. Water Environ. Res., 69, 317 (1997).

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