Insights into the carbon neutrality for the treatment process engineering of municipal wastewater by anaerobic membrane bioreactor integrated with partial nitritation-anammox: CO2 reduction and energy recovery

The promising sustainability and potential in carbon neutrality of the anaerobic membrane bioreactor (AnMBR) integrated with partial nitritation-anammox (PN/A) was assessed using a large pilot-scale plant. The entire pilot-scale system was conducted for a long-term continuous operation of 217 days, succeeding in the effective carbon-neutral treatment of low-strength real municipal wastewater with excellent COD removal efficiency of higher than 90 %. The major proportion of the organic matter was converted into bio-methane which can be recovered as bio-energy or bio-fuel. The residual ammonium contained in the digestate effluent of the AnMBR was further treated by a pilot-scale one-stage PN/A reactor. The long-term operation of the pilot-scale AnMBR was compared with the empirical assumption of the anaerobic-anoxic-oxic (A2/O) process, exhibiting splendid feasibilities in both ecological and economical perspectives including energy conservation and recovery, reduction of CO2 emission and electricity expenditure saving for municipal wastewater treatment. The application of AnMBR-PN/A process helps reducing the energy consumption of 0.416 kWh/m3 during the wastewater treatment process engineering of municipal wastewater, accounting for 90 % of that for the A2/O. The AnMBR-PN/A is also capable of reducing the CO2 emission reduced by 74.9 %. A full-scale wastewater treatment plant implemented with the AnMBR-PN/A process could save the electricity expenditure by 0.80 million CNY annually. The results of this work are solid evidence that the AnMBR-PN/A process is a remarkable sustainable technology, also giving new insights into the concept of carbon-neutral treatment of municipal wastewater in future studies.