Coupling membrane electro-bioreactor with anammox process to treat wastewater at low temperatures

Abstract

Membrane bioreactors (MBRs)have been extensively applied to municipal wastewater treatment. Nevertheless, MBRs cannot eliminate nutrients to an adequate level without extra operation units and intensive chemical supplies. Furthermore, low temperatures destroy the performance of the MBR process. In this work, a pioneering anammox membrane electro-bioreactor (MEBR/anammox) system was designed and operated at a constant flow rate of 7L/d with continuous monitoring of sludge liquor temperature (8–22 °C). The MEBR/anammox worked with a sludge retention time (SRT) of 20 days and a hydraulic retention time (HRT) of 24 h. It was found that temperature variations did not significantly influence the effluents quality in terms of nutrients and COD. At lower operating temperatures, the effluent concentrations of NH4-N, TN, PO4-P, and COD in the MEBR-anammox were 0.77 mg/L, 6.42 mg/L, 0.80 mg/L, and 24.95 mg/L, respectively. The corresponding removal efficiencies were 94.46%, 88.62%, 95.60%, and 90.76%, respectively. Taken together, the implementation of a low/periodic direct current (DC) of 14.85 A/m2 and anammox process inside the MBR, achieving a MEBR/anammox, was found to enhance the efficacy of the treatment system, improve sludge properties and increase membrane fouling control in low-temperature milieus compared to traditional MBR. The MEBR/anammox system, introduced in this work, establishes an innovative wastewater technology that minimizes the footprint, capital and operating expenditures of the plant. In addition, this system could open new prospects for the treatment of municipal sewage in cold regions.