Treatment of domestic wastewater using pilot-scale membrane-aerated biofilm reactors for the removal of organics and nitrogen

Membrane Aerated Biofilm Reactor (MABR) is a novel technology providing the potential
for simultaneous nitrification and denitrification in the same reactor. In this study, a pilot-scale MABR system modified with synthetic Granulated Nanoscale Oxyhydroxides of Iron
(GNOF) was operated to enhance nitrogen removal from medium-strength domestic
wastewater. Indeed, another pilot-scale one was operated to investigate the effects on the
removal performance of organics and nitrogen varying along with HRTs. Unlike
synthetically prepared wastewater, treating real wastewater is challenging due to the
change in COD/N ratios. Two MHF-300 EPE polyethylene membranes were used in
MABR systems and operated under different HRTs with and without GNOF media. Fe3+
reduction coupled to nitrification and simultaneous Fe2+ oxidation coupled to
denitrification is vital in the nitrogen cycle. However, limited research has recently
employed this phenomenon with the MABR system in wastewater treatment.
During the operation without GNOF media, MABR 1 outperformed MABR 2. The optimal
removal performance of the MABR 1 at 12 h of HRT was 89.3±1.1% of COD and 61.3±1.8% of NH4+-N, and 52.5±2.1% of TN, respectively, before adding GNOF media. The COD removal efficiencies of these two MABRs prior to adding a GNOF media were quite similar, and the nitrification and denitrification efficiencies of MABR 1 were more remarkable than MABR 2 by 2.2-9.1% and 1.4-7.8% while operating without GNOF media at three HRTs of 12 h, 10 h, and 4 h. The integration of a GNOF reactor and MABR 1 had resulted in higher nitrification and denitrification efficiencies while not much affecting the COD removal performance. The highest of 80.9± 11.7% for COD, 74.3±3.1% for NH4+-N, and 69.8± 2.1% for TN were achieved while operating MABR 1 at 12 h of HRT after adding GNOF media. It was proven that the GNOF media assisted in the simultaneous nitrification-denitrification and COD oxidation linked with the ferrous redox cycle. With the reduction of HRTs, the performance of MABR 2 declined. Furthermore, no considerable gap was detected when comparing the energy consumption and sludge yield between the two MABR systems before integrating with a GNOF reactor.