The membrane biofilm reactor is a versatile platform for water and wastewater treatment

The membrane biofilm reactor (MBfR) creates a natural partnership of a membrane and biofilm, because a gas-transfer membrane delivers a gaseous substrate to the biofilm that grows on the membrane's outer wall. O ₂-based MBfRs (called membrane aerated biofilm reactors, or MABRs) have existed for much longer than H ₂-based MBfRs, but the H ₂-based MBfR is a versatile platform for reducing oxidized contaminants in many water-treatment settings: drinking water, ground water, wastewater, and agricultural drainage. Extensive bench-scale experimentation has proven that the H ₂-based MBfR can reduce many oxidized contaminant to harmless or easily removed forms: e.g., NO ₃ ^- to N ₂, ClO ₄ ^- to H ₂O and Cl ^-, SeO ₄ ^2- to Se°, and trichloroethene (TCE) to ethene and Cl ^-. The MBfR has been tested at the pilot scale for NO ₃ ^- and ClO ₄ ^-and is now entering field-testing for many of the oxidized contaminants alone or in mixtures. For the MBfR to attain its full promise, several issues must be addressed by bench and field research: understanding interactions with mixtures of oxidized contaminants, treating waters with a high TDS concentration, developing modules that can be used in situ to augment pre-denitrification of wastewater, and keeping the capital costs low.