Influence of hydraulic retention time and temperature on the performance of an anaerobic ammonium oxidation fluidized bed membrane bioreactor for low-strength ammonia wastewater treatment

The feasibility of anaerobic ammonium oxidation (Anammox) process with a fluidized bed membrane bioreactor (Anammox-FMBR) was evaluated for 561 days treating synthetic wastewater containing 35 mg/L of NO2--N and 25 mg/L of NH4+-N. During start-up periods, higher nitrogen loading rate (NLR) induced faster stabilization than the low NLR. Total nitrogen (TN) removal efficiency was over 82% even with short hydraulic retention time (HRT) of 0.75 h at 25 degrees C conditions but decreased to below 30% at 15 degrees C. Pronounced effect of operating temperature at lower range was supported by high activation energy (E-a) value. The membrane fouling was controlled well, as evidenced from negligible fouling rates when the systems were operated at less than 13 L/m(2)/h flux with granular activated carbon (GAC) fluidization as cleaning media. With the estimated low energy requirements of 0.0005 kWh/kg N-removed, the Anammox-FMBR could be successfully applied in mainstream operation for the energy efficient treatment of low ammonia wastewater.