Topic Area: 5a. 1,4-Dioxane Treatment Technologies

Formatted Title:

Successful Remediation of 1,4-Dioxane Using a Subgrade Biogeochemical Reactor

Background/Objectives:

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 below ground, and field tested at a chemical manufacturing facility in North America (Site) for the co-treatment of 1,4-dioxane and residual chlorinated volatile organic compounds (CVOCs). This presentation highlights the successful results from the first year of operation.

Approach/Activities:

SBGR technology has been used for the remediation of chlorinated solvents and other contaminants over the past decade, but 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 onsite 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 study were then utilized to design and implement an in situ pilot study at the Site using two column SBGRs designed for metabolic/co-metabolic treatment of 1,4-dioxane and residual CVOCs. Groundwater was pumped from a high-concentration portion of the 1,4-dioxane plume, to the two SBGR columns where it is 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 extraction well and SBGR columns have been operating for one year with routine monitoring for 1,4-dioxane and CVOC reductions. Additionally, the system has been operated at three separate hydraulic residence times, to help determine the optimal point of operation for mass removal.

Paul Weber

Affiliation

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Successful Remediation of 1,4-Dioxane Using a Subgrade Biogeochemical Reactor