Stimulation of Reductive Dechlorination of Tetrachloroethene in Anaerobic Aquifer Microcosms by Addition of Short-Chain Organic Acids or Alcohols

Abstract

The effect of the addition of common fermentation products on the dehalogenation of tetrachloroethene was studied in methanogenic slurries made with aquifer solids. Lactate, propionate, crotonate, butyrate, and ethanol stimulated dehalogenation activity, while acetate, methanol, and isopropanol did not. Although the ecological and public health risks associated with tetrachloroethene (PCE) contamination may be the most severe when spills affect groundwater, little is known about the environmental conditions necessary to initiate and sustain dehalogenation activity in contaminated aquifers. This study was done with core material collected from a site impacted by both aviation gasoline and chloroethenes at a Coast Guard Air Station at Traverse City, Mich. Collection of core material, making of microcosms, sampling, and chloroethene analysis were done as described previously (11). The microcosms differed in that 10 g of aquifer material and 20-ml serum bottles were used. The final concentrations of donors added were as follows: acetate, 4 mM; lactate, 3 mM; propionate, 3 mM; butyrate, 2 mM; crotonate, 2 mM; methanol, 4 mM; ethanol, 2 mM; and isopropanol, 3 mM. The PCE addition was 1 ,ul of a methanol stock solution (0.751 g of PCE per 10-ml total volume in methanol) to give a PCE initial concentration of approximately 30 ,uM. A small amount of headspace was left in these bottles for ease of handling. All bottles were well shaken after all amendments had been made. Four fatty acids and three alcohols were tested for the ability to act as the source for reducing equivalents for PCE dehalogenation. The production of trichloroethene (TCE) and total dichloroethenes in microcosms, using these compounds as electron donors, is shown in Fig. 1. Samples from microcosms amended with lactate or ethanol had TCE present at the first sampling point at 6 days (Fig. 1). Butyrate, crotonate, and propionate also supported dehalogenation, although the lag period was longer, while acetate, methanol, and isopropanol did not support dehalogenation above that observed in the unamended control during this time period (Fig. 1). The measurements from the early time points were quite variable because of differences in the onset of dehalogenation. However, at the last two time points, significant differences (Student's t test with ao = 0.05) in the total amount of dehalogenation products present were observed between microcosms amended with lactate, ethanol, propionate, crotonate, or butyrate and those which were unamended or were amended with acetate,'methanol, or isopropanol. Several researchers have demonstrated the stimulation of reductive dehalogenation of chloroethenes by addition of * Corresponding author.

Exocellular electron transfer in anaerobic microbial communities

“…For recent reviews on anaerobic dehalogenating bacteria, the reader is referred to Smidt and de Vos (2004) and Bradley (2003). Although some dehalogenating bacteria can use organic substrates as electron donors, molecular hydrogen (H 2 ) seems to be the major electron donor for dehalogenation of chlorinated compounds in mixed microbial communities (Distefano et al ., 1992;Gibson and Sewell, 1992;Luijten et al ., 2004a). Most dehalogenating bacteria, e.g.…”

Intrinsic remediation of trichloroethene driven by tetraalkoxysilanes as co‐contaminants: Results of microcosm and field studies

“…Trichloroethene (TCE) is a common groundwater contaminant in aquifers throughout the United States (Westrick et al, 1984).TCE ranks in the top ten priority pollutants listed by the U.S. Environmental Protection Agency (EPA) (Federal Register, 1989). Over the past decade, microbial degradation of TCE has been extensively studied (Hopkins et al, 1993;Mars et al, 1996;Alvarez-Cohen & McCarty, 1991;Gibson & Sewell, 1992;Maymo-Gatell et al, 1997;Distefano et al, 1992;Fennell et al, 1997;Smatlak et al, 1996;Ballapragada et al, 1997;Sharma & McCarty, 1996;Semprini et al, 1995). Reductive dechlorination under anaerobic conditions and aerobic cometabolic processes are the predominant pathways for TCE transformation.…”

Enhanced biodegradation of carbon tetrachloride by the supplement of substrate and mineral ions under anaerobic condition

“…Field and laboratory evidences depicted that the addition of auxiliary carbon and energy sources (electron donor) is necessary for microorganisms for the onset of the dechlorination of tracelevel organic compounds. Gibson and Sewell (1992) examined the effect of short-chain organic acids and alcohols on the dechlorination of PCE with anaerobic aquifer microcosms and demonstrated that the relative rates and extents of dechlorination ofPCE varied with the types of supplement substrates. Freedman and Gossett (1988) depicted that it was necessary to supply an electron donor to sustain reductive dechlorination of peE or trichloroethylene and showed that methanol was the most effective one, although hydrogen, formate, acetate, and glucose also served as electron donor.…”

“…/11 situ bioremediation is one of the progressive technologies for the remediation of contaminated groundwaters by stimulating the microflora with the addition of carbon and energy sources and trace mineral elements in place. Field and laboratory evidence suggest that the addition of auxiliary carbon and energy sources is necessary for the onset of the biodegradation of the trace-level anthropogenic organic compounds (DiStefano et aI., 1991;Doong and Wu, 1992b;Gibson and Sewell, 1992). Recent research has addressed the potential roles of the high concentration of the supplemental energy sources, such as acetate, methanol, and some short-chain organic acids and alcohols, on the dechlorination of polychlorinated biphenyls (PCBs) (Nies and Vogel, 1990), 2,4,5-T (Gibson and Suflita, 1990), chloroanilines (Kuhn et a/., 1990), and tetrachloroethylene (PCE) (Fathepure and Boyd, 1988;Bagley and Gossett, 1990;Gibson and Sewell, 276 1992).…”