1,4-Dioxane is a chemical in groundwater that is a growing concern and is commonly associated with chlorinated solvent plumes. Removal of 1,4-dioxane using traditional physical-chemical water treatment technologies can be difficult, and many existing groundwater pump and treat (P&T) systems are not equipped to remove chlorinated solvents and 1,4-dioxane. While advanced oxidation processes (AOP) can reliably remove 1,4-dioxane, other treatment methods are emerging with bioremediation serving as a reliable, safe, sustainable, and economical alternative to AOPs. Bioreactors are an attractive option for retrofitting existing P&T systems when 1,4-dioxane treatment is required, or as a technology to incorporate into new construction. The objective of this project is to demonstrate the biodegradation of 1,4-dioxane using propane as a primary substrate in an aerobic membrane biofilm reactor (MBfR).

This project will combine two previously demonstrated remedial technologies: propane-mediated biodegradation of 1,4-dioxane and MBfRs. 1,4-Dioxane biodegradation occurs via aerobic pathways. Engineered bioremediation approaches have been implemented at the pilot-scale and full-scale and commonly have utilized propane as a primary substrate. Using gaseous species to foster biologically mediated reactions in conventional engineered bioreators can be challenging, specifically related to achieving adequate gas transfer. An MBfR eliminates this challenge by utilizing pressure-controlled gas-transfer membranes to provide a gaseous substrate directly to the biofilm by diffusion through the membrane. The gas supply to the biofilm is driven by the concentration gradients caused by biochemical demand, making the MBfR a self-regulating system. This work begins with bench-scale testing to configure commercially available membranes for 1,4-dioxane biological treatment. The MBfR system will then be scaled up for field demonstration where the operating parameters will be optimized and various challenge conditions tested.

While Department of Defense sites have undergone chlorinated solvent remediation for decades, there is a growing need for cost-effective and sustainable options that also include 1,4-dioxane treatment. This work aims to develop a reliable biological alternative to AOPs. Bioreactors can be a more sustainable and economical option than AOPs. Initial cost estimates indicate that ex situ bioreactors could have 15% lower capital costs and 40% lower annual operating costs than AOPs and they do not rely on the use of strong chemical oxidants or a significant amount of electricity. Successful implementation of this work would demonstrate that MBfRs are an economical, sustainable, attractive option for 1,4-dioxane, and potential concurrent chlorinated solvent treatment. (Anticipated Project Completion - 2025)