1997 Progress Report: Influence of Nonionic Surfactants on the Bioavailability of Chlorinated Benzenes for Microbial Reductive DechlorinationEPA Grant Number: R825404
Title: Influence of Nonionic Surfactants on the Bioavailability of Chlorinated Benzenes for Microbial Reductive Dechlorination
Investigators: Pavlostathis, Spyros G. , Pennell, Kurt D.
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, 1996 through November 11, 1997
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
Objective:The primary goal of this project is to systematically assess the use of nonionic surfactants to increase the bioavailability of chlorinated benzenes for microbial reductive dechlorination. Biodegradable surfactants which serve as electron donors for the reductive dechlorination process have been selected. Sorption and transport of surfactants in aquifer material have been quantified. Surfactant-aided desorption of hexachlorobenzene (HCB), as well as simultaneous desorption and biotransformation of chlorinated benzenes in the presence of surfactants will be evaluated.
Progress Summary:Fourteen surfactants representing two of the main classes of nonionic surfactants: linear polyoxyethylene (POE) alcohols (Brij 30, and 35; Witconol SN-70, 90, and 120), and food grade POE sorbitan esters (Tween 20, 21, 40, 60, 61, 65, 80, 81, and 85) were evaluated. Using a contaminated estuarine sediment as inoculum, an actively-dechlorinating, methanogenic mixed culture consortium was enriched and has been maintained at 22oC by feeding HCB and glucose. The linear POE alcohols greatly inhibited the extent of methanogenesis and these surfactants were eliminated from further consideration for use in this project. Although none of the Tween surfactants affected the extent of methanogenesis, they resulted in low initial rate of methanogenesis. The least inhibitory surfactants were T60, T61, and T65. The effect of the nine Tween surfactants on the reductive dechlorination of HCB was evaluated at an initial surfactant concentration of either 10, 50, 200, or 1000 mg/L. As the surfactant concentration increased, both the rate and extent of dechlorination decreased. Biodegradation of the surfactants was observed even at an initial surfactant concentration of 1000 mg/L. Tween 60, 61, and 65 were the least toxic toward both methanogenesis and reductive dechlorination. These surfactants have been selected for further use in this project. Batch experiments were conducted to measure equilibrium sorption of Tween 80 and Witconol SN-120 by Wurtsmith aquifer material and Webster soil. Because of the greater organic carbon content, significantly more surfactant sorption was observed for Webster soil than for the Wurtsmith aquifer material. A series of column experiments was performed to investigate the effect of sorption on surfactant transport through Wurtsmith aquifer material and Webster soil. To identify and characterize the influence of rate-limited sorption on surfactant transport, the column experiments were conducted at several flow rates and with periods of flow interruption. Tracer experiments were performed prior to surfactant injection to quantify hydrodynamic dispersion within the soil column. Results of the column experiments were predicted using a one-dimensional form of the advective-dispersive reactive (ADR) transport equation that incorporates non-linear (Langmuir), rate-limited surfactant sorption.
Future Activities:Work will continue on the assessment of the anaerobic biodegradability of the three surfactants (Tween 60, 61, and 65) and a delineation of their anaerobic biotransformation pathway will be attempted. The effect of these surfactants on the solubilization, desorption and reductive dechlorination of sorbed chlorinated benzenes will be assessed and quantified. Particular emphasis will be given to the delineation of the mechanism(s) by which surfactants may enhance the reductive dechlorination of sorbed chlorinated benzenes. In order to investigate the role of organic matter composition on contaminant bioavailability, we will examine various model organic sorbents with different glass transition temperatures (both "rubbery" and "glassy" sorbents). The bioavailability of HCB sorbed to these model organic sorbents will be compared to artificially- and field-contaminated soils and sediments. In addition to batch experiments, continuous-flow column experiments will also be performed to evaluate the effect of surfactants on the contaminant desorption and bioavailability.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other project views:||All 13 publications||3 publications in selected types||All 2 journal articles|
||Yeh D, Pavlostathis SG, Pennell KD. Effect of tween surfactants on methanogenesis and microbial reductive dechlorination of hexachlorobenzene. Environmental Toxicology and Chemistry 1999;18(7):1408-1416.||