Novel MBR_based main stream biological nutrient removal process: high performance and microbial community.

For municipal wastewater treatment, main stream biological nutrient removal (BNR) process is becoming more and more important. This lab-scale study, novel MBR_based BNR processes (named A2N-MBR and A2NO-MBR) were built. Comparison of the COD removal, results obtained demonstrated that COD removal efficiencies were almost the same in three processes, with effluent concentration all bellowed 30 mg L-1. However, the two-sludge systems (A2N-MBR and A2NO-MBR) had an obvious advantage over the A2/O for denitrification and phosphorus removal, with the average TP removal rates of 91.20, 98.05% and TN removal rates of 73.00, 79.49%, respectively, higher than that of 86.45 and 61.60% in A2/O process. Illumina Miseq sequencing revealed that Candidatus_Accumulibacter, which is capable of using nitrate as an electron acceptor for phosphorus and nitrogen removal simultaneously, was the dominant phylum in both A2N-MBR and A2NO-MBR process, accounting for 28.74 and 23.98%, respectively. Distinguishingly, major organism groups related to nitrogen and phosphorus removal in A2/O system were Anaerolineaceae_uncultured, Saprospiraceae_uncultured and Thauera, with proportions of 11.31, 8.56 and 5.00%, respectively. Hence, the diversity of dominant PAOs group was likely responsible for the difference in nitrogen and phosphorus removal in the three processes.

Performance of A2NO-MBR process in treating synthetic and municipal wastewater.

In this study, a novel anaerobic-anoxic/nitrification (A2N) two-sludge sequencing batch reactor (SBR) configured with post-aeration (A2NO-membrane bioreactor process) was conducted to evaluate the operational efficiency, process characteristics, and microbial community structure in treating synthetic and municipal wastewater. When influent C/N ratios were 4.2-8.6, the removal efficiencies of COD, NH4+-N, TN, and TP were 86.4-90.0, 85.2-93.6, 61.8-76.0, and 97.6-99.3%, respectively, and the effluent concentrations met the first level A criteria of GB18918-2002. Phosphorus removal was mainly in anoxic phase with a removal rate of 0.54-1.30 mgP/(gMLSS h), accounting for 75.9-99.7%. Enhanced phosphorus removal was observed during post-aeration phase with a removal rate of 0.06-0.55 mgP/(gMLSS h). Additionally, Oxidation-Reduction Potential (ORP) and pH could reflect the process of anaerobic phosphorus release and anoxic denitrifying phosphorus removal. DO and pH could indicate the end of nitrification. Moreover, Candidatus Accumulibacter and Dechloromonas related to biological nitrogen and phosphorus removal were enriched effectively with total proportions of 15.9 and 11.5% in treating synthetic and municipal wastewater, respectively.