Constraints in Anaerobic Microbial Dechlorination, Fermentation, and Sulfate-Reduction Induced by High Concentrations of
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Constraints in Anaerobic Microbial Dechlorination, Fermentation, and Sulfate-Reduction Induced by High Concentrations of Tetrachloroethylene Miho Yoshikawa
&
Ming Zhang
Received: 29 March 2020 / Accepted: 7 July 2020 # The Author(s) 2020
Abstract Anaerobic bioremediation of tetrachloroethylene (PCE) under high concentration conditions is difficult. Anaerobic dechlorination of PCE occurs with synergetic reactions, fermentation, and sulfatereduction; however, the way in which high concentrations of PCE affects these reactions is still poorly understood. This study aims to elucidate how high concentrations of PCE affect fermentation and sulfate-reduction, as well as PCE dechlorination. Laboratory dechlorination tests were performed using a wide concentration range of PCE between 2 and 125 mg/L added to a microbial consortium that had been continuously cultivated in the laboratory and completely dechlorinated PCE for over 4 years. Fermentation of lactate, reduction of sulfate, and dechlorination of PCE were monitored in addition to microbial activities based on RNA. All three reactions, fermentation, sulfate-reduction, and PCE dechlorination were observed to be inhibited. The inhibition for fermentation, sulfate-reduction, and dechlorination occurred when PCE concentrations were higher than 125, 75, and 30 mg/L, respectively. The fermenter, Anaerotignum, and the sulfate-reducer, Desulfosporosinus, were active when the dechlorination was inhibited with 30 mg/L of PCE. These
M. Yoshikawa (*) : M. Zhang Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8567, Japan e-mail: [email protected]
findings suggest that there is interference of PCE dechlorination, despite the occurrence of fermentation and sulfate reduction. Bioaugmentation with a PCE dechlorinator that is tolerant to high PCE concentrations can be a possible solution for bioremediation of PCE when its concentrations are greater than 30 mg/L. Keywords Biodegradation . High concentration . Chloroethylenes . Microbial community . RNA
1 Introduction Soil and groundwater in many industrial sites are contaminated with high concentrations of tetrachloroethylene (PCE) (US EPA 2003). PCE has been used as an effective solvent in the dry cleaning and manufacturing industries (US EPA 2002; Zhang and Yoshikawa 2016). Once PCE is released into subsurface due to illegal and/or careless disposal from these industries, the high concentration of contaminant slowly partitions into groundwater; then, it can migrate long distances dependent on geological characteristics of the site and pollute large area (EPA 1998; US EPA 2003). Thus, besides the removal of pollutant source, remediation of the area near the pollutant source with high concentrations is a significant issue. Bioremediation, the remediation of soil or water using microorganisms, is considered difficult in instances where there is a high concentration of PCE (US EPA 2003; Juwarkar et al. 2010;
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