Hydrogen-based hollow-fiber membrane biofilm reactor (MBfR) for removing oxidized contaminants

Research with a laboratory prototype and at the pilot scale documents that the hydrogen-based hollow-fiber Membrane-Biofilm Reactor (MBfR) is technically and economically feasible for reduction of nitrate and perchlorate. In the MBfR, H₂ gas diffuses through the wall of a composite membrane, and an autotrophic biofilm naturally develops on the outside of the membrane, where the bacteria's electron acceptor is an oxidized contaminant (e.g., NO₃⁻ or ClO₄⁻) supplied from the water. The hydrogen pressure to the hollow fibers is a key control parameter that can be adjusted rapidly and easily. For denitrification, partial nitrate removal often is acceptable, and the hydrogen pressure can be low to minimize the costs of H₂ supply and the concentration of H₂ in the effluent. When perchlorate must be reduced, full nitrate removal is essential, since NO₃⁻-N above about 0.2 mg/L slows perchlorate reduction. Perchlorate reduction is sensitive to the hydrogen pressure, which underscores the critical role of H₂ pressure for controlling process performance. Given that H₂-oxidizing microorganisms have the potential to reduce many oxidized contaminants, we hypothesize that and are beginning to test how well the MBfR reduces bromate, selenate, chlorinated solvents, and other oxidized contaminants.