Bio-reduction of N-nitrosodimethylamine (NDMA) using a hydrogen-based membrane biofilm reactor

N-Nitrosodimethylamine (NDMA) is a disinfection by-product shown to be carcinogenic, mutagenic, and teratogenic. A feasible detoxification pathway for NDMA is a three-step bio-reduction that leads to ammonia and dimethylamine. This study examines the bio-reduction of NDMA in a H₂-based membrane biofilm reactor (MBfR) that also is active in nitrate and sulfate reductions. In particular, the study investigates the effects of H₂ availability and the relative loadings of NDMA, nitrate, and sulfate, which potentially are competing electron acceptors. The results demonstrate that NDMA was bio-reduced to a major extent (i.e., at least 96%) in a H₂-based MBfR in which the electron-equivalent fluxes from H₂ oxidation were dominated by nitrate and sulfate reductions. NDMA reduction kinetics responded to NDMA concentration, H₂ pressure, and the presence of competing acceptors. The most important factor controlling NDMA-reduction kinetics was the H₂ availability, controlled primarily by the H₂ pressure, and secondarily by competition from nitrate reduction.