1998 Progress Report: Influence of Nonionic Surfactants on the Bioavailability of Chlorinated Benzenes for Microbial Reductive Dechlorination

EPA Grant Number: R825404
Title: Influence of Nonionic Surfactants on the Bioavailability of Chlorinated Benzenes for Microbial Reductive Dechlorination
Investigators: Pavlostathis, Spyros G. , Chang, Eric , Karagunduz, Ahmet , Pennell, Kurt D. , Yeh, Daniel H
Current Investigators: Pavlostathis, Spyros G. , Chang, Eric , Karagunduz, Ahmet , Marti, Charlotte A. , Pennell, Kurt D. , Yeh, Daniel H
Institution: Georgia Institute of Technology
EPA Project Officer: Chung, Serena
Project Period: November 12, 1996 through November 11, 1999
Project Period Covered by this Report: November 12, 1997 through November 11, 1998
Project Amount: $333,348
RFA: Environmental Fate and Treatment of Toxics and Hazardous Wastes (1996) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals


The specific objectives of this research project are as follows: (1) assessment of the effect of surfactants on the methanogenesis and reductive dechlorination processes; (2) assessment of the anaerobic biodegradability of different surfactant families and correlation to their properties; (3) quantification of the effect of surfactants on the solubilization, desorption, and reductive dechlorination of sorbed chlorinated benzenes in batch systems; (4) evaluation of surfactant-assisted desorption, biotransformation, and transport of hexachlorobenzene (HCB) in column systems; and (5) mathematical modeling of the transport, sorption, and biotransformation of both surfactant and chlorinated benzenes.

Progress Summary:

Using a mixed, methanogenic culture enriched from an estuarine sediment historically contaminated with various polychlorinated organic compounds, the influence of nonionic polysorbate (Tween) surfactants on the microbial reductive dechlorination of HCB was investigated. A preliminary screening assay determined that three Tween surfactants (Tween 60, 61, and 65, all containing C18 stearic acid as the predominant hydrophobic moiety) were the least inhibitory to both methanogenesis and reductive dechlorination of HCB. Work is continuing on the assessment of the anaerobic biodegradability of the Tween 60, 61, and 65 surfactants. Due to incomplete conversion of the surfactants to methane, the potential inhibitory effects of the residual surfactants on both methanogenesis and HCB reductive dechlorination are being assessed in batch culture systems amended with surfactant transformation products generated by preincubation of Tween surfactants under methanogenic conditions.

The ability of Tween 60, 61, and 65 to sustain methanogenesis and dechlorination as the sole carbon and electron source, as well as the effect of long-term exposure of the enriched culture to these surfactants, was investigated through the development of three 1.6 L subcultures, in which the sole, exogenous electron donor was Tween 60, 61, or 65. Even after more than 1 year of continuous surfactant exposure, these surfactants continued to sustain the reductive dechlorination of HCB. These results indicate that reductive dechlorination of HCB supported by the fermentation of Tween surfactants is feasible, and that anaerobically degradable Tween surfactants are effective for the biotransformation of polychlorinated organic compounds. These surfactants may be used to simultaneously increase the bioavailability of sorbed contaminants while serving as the carbon and electron source for microbial reductive dechlorination. The influence of biodegradable surfactants (Tween 60, 61, and 65) on the bioavailability of sorbed-phase HCB was investigated using a sediment sample contaminated with HCB and other chlorinated benzene congeners for more than 40 years. The rate and extent of both dechlorination activity and methanogenesis increased with increasing surfactant concentration. The effect of Tween surfactants on enhancing the desorption and bioavailability of HCB from two natural polymers (microcrystalline cellulose and crab-shell derived chitin) and two synthetic polymers (polyvinylpolypyrrolidone and polymethyl methacrylate) will be assessed.

The micellar solubilization of HCB, sorption and desorption of HCB, surfactant, HCB plus surfactant, and the coupled desorption and transformation of HCB in the presence of surfactants was measured. Sorption capacity increased with both increased organic carbon content and specific surface area. Batch experiments are being conducted to measure the sorption of HCB in the presence of sorbed-phase surfactant. Long-term (1 and 2 month) sorption experiments also are under way to complete the kinetic sorption data for Tween 60. The desorption of both HCB and surfactant also are being investigated. Additional column studies are being performed at several flow rates and with periods of flow interruption to characterize the effects of rate-limited sorption and desorption on Tween 60 transport. Mathematical modeling activities are directed toward refining the surfactant transport model to incorporate rate-limited surfactant sorption.

Future Activities:

The effect of surfactants on the properties of the solid-phase organic matrix, and the bioavailability of sorbed HCB, will be assessed. Batch measurements of HCB desorption in the presence and absence of Tween 60 will be performed over time. Surfactant desorption from Appling soil will be measured to determine desorption rates and to evaluate isotherm hysteresis. Column experiments will focus on measuring the desorption, transport, and transformation of HCB in the presence of Tween 60. The transformation of HCB under anaerobic, flowing conditions will be evaluated. In Year 3 of the project, efforts will focus on refining the mathematical model and comparing model predictions to experimental data. The final phase of this work will involve incorporating the transformation of both Tween 60 and HCB into the mathematical model under equilibrium and rate-limited conditions.

Journal Articles:

No journal articles submitted with this report: View all 13 publications for this project

Supplemental Keywords:

sediment, soil, toxics, terrestrial, aquatic, engineering, southeast., Scientific Discipline, Toxics, Waste, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Environmental Chemistry, Chemistry, HAPS, Fate & Transport, Bioremediation, 33/50, fate and transport, microbiology, bioremediation model, surfactant-aided desportion, sorption kinetics, benzene, chemical transport, kinetic studies, hazardous waste, biotechnology, hazardous waste cleanup, geochemistry, environmental toxicant, mobility, biotransformation, chemical releases, contaminant release, waste chemicals, Benzene (including benzene from gasoline), chlorinated benzenes, nonionic surfactants, microbial reductive dechlorination, chlorinated solvents, transport

Progress and Final Reports:

Original Abstract
  • 1997 Progress Report
  • Final Report