RESEARCH ARTICLE Using a high-organic matter biowall to treat a trichloroethylene plume at the Beaver Dam Road landfill Gabriela T. Niño de Guzmán 1 & Cathleen J. Hapeman 2 & Patricia D. Millner 2 & Laura L. McConnell 1 & Dana Jackson 2 & David Kindig 3 & Alba Torrents 1 Received: 9 July 2017 /Accepted: 26 December 2017 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Trichloroethylene (TCE) is a highly effective industrial degreasing agent and known carcinogen. It was frequently buried improperly in landfills and has subsequently become one of the most common groundwater and soil contaminants in the USA. A common strategy to remediate TCE-contaminated sites and to prevent movement of the TCE plumes into waterways is to construct biowalls which consist of biomaterials and amendments to enhance biodegradation. This approach was chosen to contain a TCE plume emanating from a closed landfill in Maryland. However, predicting the effectiveness of biowalls is often site specific. Therefore, we conducted an extensive series of batch reactor studies at 12 °C as opposed to the typical room temperature to examine biowall fill-material combinations including the effects of zero-valent iron (ZVI) and glycerol amendments. No detectable TCE was observed after several months in the laboratory study when using the unamended 4:3 mulch-to-compost combination. In the constructed biowall, this mixture reduced the upstream TCE concentration by approximately 90% and generated ethylene downstream, an indication of successful reductive dechlorination. However, the more toxic degradation product vinyl chloride (VC) was also detected downstream at levels approximately ten times greater than the maximum con- taminant level. This indicates that incomplete degradation also occurred. In the laboratory, ZVI reduced VC formation. A hazard quotient was calculated for the landfill site with and without the biowall. The addition of the biowall decreased the hazard quotient by 88%. Keywords Trichloroethylene . Biowall . Superfund . Zero-valent iron . Glycerol . Groundwater . Mulch . Compost Introduction Trichloroethylene (TCE) is a highly effective and efficient industrial degreasing agent and solvent, and because of its historically poor disposal, it is also one of the most common groundwater and soil contaminants in the USA (Orth and Gillham 1996; Hendrickson et al. 2002; Zhang et al. 2015). Discharges from metal degreasing sites and other factories are the most common sources of TCE (US EPA 2001). TCE is of concern because it is a known carcinogen and, with prolonged exposure, can increase the chances of liver, lung, and nervous system issues (Chiu et al. 2013). In addition, several degrada- tion products of TCE, such as vinyl chloride (VC), are more toxic than TCE (US EPA 2009). While present in a large portion of sites around the USA, cost-effective remediation of TCE-contaminated sites is diffi- cult due to its volatility (vapor pressure = 9700 Pa; Chiao et al. 1994), low water solubility (water solubility = 1.1 g/L; US EPA 2016a), and high density (1.46 g/cm 3 ; Jacoby et al. 1998), leading to its tendency to form a dense non-aqueous phase liquid layer in aquifers (US EPA 2016a; Pant and Pant 2010). Studies have also shown that its adsorption coefficient (K d ) is dependent on the soil organic carbon content (f OC ) and its organic carbon–water partitioning coefficient (K OC )(K d = Responsible editor: Philippe Garrigues Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-017-1137-1) contains supplementary material, which is available to authorized users. * Alba Torrents alba@umd.edu 1 Department of Civil and Environmental Engineering, University of Maryland, College Park, MD, USA 2 US Department of Agriculture, Agricultural Research Service, Beltsville, MD, USA 3 BMT Designers and Planners, Arlington, VA, USA Environmental Science and Pollution Research https://doi.org/10.1007/s11356-017-1137-1