A Synergistic Platform for Continuous Co-removal of 1,1,1-Trichloroethane, Trichloroethene, and 1,4-Dioxane via Catalytic Dechlorination Followed by Biodegradation.

Groundwater co-contaminated with 1,4-dioxane, 1,1,1-trichloroethane (TCA), and trichloroethene (TCE) is among the most urgent environmental concerns of the U.S. Department of Defense (DoD), U.S. Environmental Protection Agency (EPA), and industries related to chlorinated solvents. Inspired by the pressing need to remove all three contaminants at many sites, we tested a synergistic platform: catalytic reduction of 1,1,1-TCA and TCE to ethane in a H-based membrane palladium-film reactor (H-MPfR), followed by aerobic biodegradation of ethane and 1,4-dioxane in an O-based membrane biofilm reactor (O-MBfR). During 130 days of continuous operation, 1,1,1-TCA and TCE were 95-98% reductively dechlorinated to ethane in the H-MPfR, and ethane served as the endogenous primary electron donor for promoting 98.5% aerobic biodegradation of 1,4-dioxane in the O-MBfR. In addition, the small concentrations of the chlorinated intermediate from the H-MPfR, dichloroethane (DCA) and monochloroethane (MCA), were fully biodegraded through aerobic biodegradation in the O-MBfR. The biofilms in the O-MBfR were enriched in phylotypes closely related to the genera known to biodegrade 1,4-dioxane.