Effects of nonionic surfactants on the solubilization and mineralization of phenanthrene in soil-water systems

• Published in: Biotechnology and bioengineering Vol. 40; no. 11; p. 1367
• Main Authors: Laha, S. (Carnegie Mellon University, Pittsburgh, PA), Luthy, R.G
• Format: Journal Article
• Language: English
• Published: United States 20.12.1992
• Subjects: BIODEGRADACION; BIODEGRADATION; FLORA DEL SUELO; FLORE DU SOL; HIDROCARBUROS; HYDROCARBURE; MINERALISATION; MINERALIZACION; SOLUBILISATION; SOLUBILIZACION; SURFACTANT; SURFACTANTES; TIPOS TEXTURALES DE SUELOS; TYPE DE SOL TEXTURAL
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.260401111

The solubilization and mineralization of 14C-phenanthrene in soil-water systems was examined with several commercially available surface-active agents, viz., an alkyl ethoxylate C12E4; two alkylphenol ethoxylate surfactants: C8PE95 and C9PE10.5; two sorbitan ethoxylate surfactants: the sorbitan monolaurate (Tween 20) and the sorbitan monooleate (Tween 80); two pairs of nonionic ethoxylate surfactant mixtures: C12E4/C12E23 at a 1:1 ratio, and C12-15E3/C12-15E9 at a 1:3 ratio; and two surfactants possessing relatively high critical micelle concentration (CMC) values and low aggregation numbers: CHAPS and octylglucoside. Surface tension experiments were performed to evaluate surfactant sorption onto soil and the surfactant doses required to attain the CMC in the soil-water systems. Surfactant solubilization of 14C-phenanthrene commenced with the onset of micellization. The addition of surface-active agents was observed not to be beneficial to the microbial mineralization of phenanthrene in the soil-water systems and, for supra-CMC surfactant doses, phenanthrene mineralization was completely inhibited for all the surfactants tested. A comparison of solubilization, surface tension, and mineralization data confirms that the inhibitory effect on microbial degradation of phenanthrene is related to the CMC of the surfactant in the presence of soil. Additional tests demonstrated the recovery of mineralization upon dilution of the surfactant concentration to sub-CMC levels, and a relatively high exit rate for phenanthrene from micelles. These tests suggest that the inhibitory effect is probably related to a reversible physiological surfactant micelle-bacteria interaction, possibly through partial complexing or release of membrane material without disrupting membrane lameilar structure. This study indicates that nonionic surfactant solubilization of sorbed hydrophobic organic compounds from soil may not be beneficial for the concomitant enhancement of soil bioremediation. Additional work is needed to address physicochemical processes for bioavailability enhancement, and effects of solubilizing agents on microorganisms for remediation and treatment of hydrophobic organic compounds and nonaqueous phase liquids