Formatted Title
Initial Results from a 1,4-Dioxane In Situ Subgrade Biogeochemical Reactor Field Test
Background/Objectives
Background/Objectives. In situ subgrade biogeochemical reactors (SBGRs) are a unique green and sustainable remediation (GSR) technology used for the treatment of contaminant source areas and groundwater plumes. Following a successful drum-scale field pilot test, two SBGR columns were installed and field tested at a chemical manufacturing facility in North American (Site) for the treatment of 1,4-dioxane and residual chlorinated volatile organic compounds (CVOCs). This presentation provides an overview of the initial results of this pilot study, and an overview of a potential full-scale treatment design for 1,4-dioxane.
Approach/Activities
Approach/Activities. SBGR technology has been used for the remediation of chlorinated solvents and other contaminants over the past decade, but in situ reactors have not been used for treatment of 1,4-dioxane. SBGRs utilize both passive groundwater flow and active recirculation of groundwater for the treatment of on-site contaminants. The use of locally sourced, non-refined or “waste” products, such as mulch and spent brewery grain, in SBGR construction also promote the GSR aspects of this technology.
In 2020 and 2021, a successful drum-scale study was implemented utilizing a variety of organic and inorganic amendments tailored to support biological treatment of 1,4-dioxane. The findings of the drum-scale were then utilized to design and implement an in situ SBGR pilot study at the Site using two column reactors designed for metabolic/co-metabolic treatment of 1,4-dioxane and residual CVOCs. Groundwater was pumped from a downgradient extraction well, placed within a high-concentration portion of the 1,4-dioxane plume, to the two SBGR columns where it was infiltrated through treatment amendments. One of the SBGR columns was bioaugmented with CB1190 bacteria culture specific for degradation of 1,4-dioxane, while the other relied on native site bacteria only. The SBGR will operate year-round and is routinely monitored for 1,4-dioxane and CVOC reductions.
Results/Lessons Learned
Results/Lessons Learned. Initial performance results and lessons learned from construction and monitoring of the SBGR column pilot study will be presented, including target contaminant analytes, field data monitoring, and microbial analyses. Based on field monitoring and analytical data, additional SBGR columns are expected to be effective at reducing 1,4-dioxane and CVOC concentrations and the two existing SBGR columns will be incorporated into a full-scale design to be constructed at this Site in the future.