Presence of organohalide-respiring bacteria in and around a permeable reactive barrier at a trichloroethylene-contaminated Superfund site

Authors: NINO DE GUZMAN, G.T. - University Of Maryland; Hapeman, Cathleen; Millner, Patricia; TORRENTS, A. - University Of Maryland; JACKSON, D. - US Department Of Agriculture (USDA); KJELLERUP, B.V. - University Of Maryland

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2018
Publication Date: 9/1/2018
Citation: Nino De Guzman, G., Hapeman, C.J., Millner, P.D., Torrents, A., Jackson, D., Kjellerup, B. 2018. Presence of organohalide-respiring bacteria in and around a permeable reactive barrier at a trichloroethylene-contaminated Superfund site. Environmental Pollution. 243(2018):766-776. https://doi.org/10.1016/j.envpol.2018.08.095.
DOI: https://doi.org/10.1016/j.envpol.2018.08.095

Interpretive Summary: Trichloroethylene (TCE) was used as a cleaning solvent for many years and has become one of the most common groundwater contaminants in the United States. TCE is highly toxic and carcinogenic as are some of the compounds that are formed when it breaks down in the environment. TCE and several of its degradation products have been detected in the groundwater of the Beaver Dam Road Landfill site (Beltsville, MD) at concentrations above US EPA guidelines. In 2013, a permeable reactive barrier (i.e., biowall) was installed to remediate the groundwater, however, recent assessments revealed that incomplete degradation was occurring. Therefore, a survey of the microbial communities in the biowall and the soil surrounding the biowall was conducted to determine if microbial infiltration and colonization of the biowall with native site bacteria that can degrade TCE had occurred. Results showed that the necessary communities were present and functioning. Laboratory studies were also conducted to examine if the addition of iron particles could enhance the degradation process. Iron particles are known to assist in the TCE degradation process in some microorganisms. The experiments indicated that no special requirements would be needed, although the amount of iron particles to affect change in the biowall may be impractical. These studies also showed that additional experiments are needed to determine how to enhance the degradation process and remediate the site most effectively.

Technical Abstract: Trichloroethylene (TCE) is one of the most common groundwater contaminants in the United States, however clean-up efforts are a challenge due to its physical and chemical properties. TCE and several of its degradation products were detected in the groundwater of the Beaver Dam Road Landfill site (Beltsville, MD) at concentrations above accepted maximum contaminant levels. A permeable reactive barrier (i.e., biowall) was installed to remediate the groundwater, with microbial infiltration and colonization of the biowall with native site bacteria was expected to occur. An array of molecular biological tools was applied to survey the microbial community for presence of organohalide-respiring microorganisms at the site. Microorganisms belonging to methanogens, acetogens, sulfate-reducing bacteria, and chlorinated aliphatic hydrocarbon-metabolizing bacteria were identified, thus making way for the application of the microbial populations in the biowall bioaugmentation efforts. In concomitant laboratory studies, molecular approaches were used to monitor continuously-fed column reactors containing saturated biowall material spiked with a commercially-available, Dehalococcoides-containing culture (SDC-9), with or without zero-valent iron (ZVI) shavings. The column without ZVI had the highest abundance of Dehalococcoides spp. (2.7 x 10e6 cells/g material, S.D. = 3.8 x 10e5 cells/g material), while the addition of ZVI did not affect the overall population. Although the addition of ZVI and biostimulation did change ratios of the Dehalococcoides strains, the results suggests that if ZVI would be applied as a biowall material amendment, biostimulation would not be required to maintain a Dehalococcoides population. These experimental results will be utilized in future remediation and/or biowall expansion plans to utilize the natural resources most effectively at the biowall site.