Effect of NaCl on nitrate removal from ion-exchange spent brine in the membrane biofilm reactor (MBfR)

The H ₂-based membrane biofilm reactor was used to remove nitrate from synthetic ion-exchange brine at NaCl concentrations from ∼3 to 30 g/L. NaCl concentrations below 20 g/L did not affect the nitrate removal flux as long as potassium was available to generate osmotic tolerance for high sodium, the H ₂ pressure was adequate, and membrane fouling was eliminated. Operating pHs of 7-8 and periodic citric acid washes controlled membrane fouling and enabled reactor operation for 650 days. At 30 psig H ₂ and high nitrate loading rates of 15 to 80 g/m ² d, nitrate removal fluxes ranged from 2.5 to ∼6 g/m ² d, which are the highest fluxes observed when treating 30 g/L IX brine. However, percent removals were low, and the H ₂ pressure probably limited the removal flux.