Performance and bacterial community analysis of a two-stage A/O-MBBR system with multiple chambers for biological nitrogen removal

A two-stage anoxic/oxic (A/O)-moving bed biofilm reactor (MBBR) system with multiple chambers was estab-lished for municipal wastewater treatment. At the total hydraulic retention time (HRT) of 11.2 h and nitrate recycling ratio of 1, the removal efficiencies reached 83.8%, 82.5%, and 77.8% for soluble chemical oxygen demand (SCOD), 98.0%, 97.5%, and 94.9% for ammonia nitrogen (NH4+-N), and 91.8%, 92.0%, and 87.7% for total inorganic nitrogen (TIN) in summer, autumn and winter, respectively. Biofilms with functional bacterial populations were formed in the pre-anoxic reactors, the pre-oxic reactors, the post-anoxic reactors and the post-oxic reactors of the two-stage A/O-MBBR system. The highest nitrification potential was found in the last oxic reactor of the first A/O-MBBR subsystem with the highest relative abundances of the functional genes including [EC:1.14.99.39] and [EC:1.7.2.6]). The highest denitrification potential was found in the post-anoxic reactors with the highest relative abundances of the functional genes including [EC:1.7.2.1], [EC:1.7.2.5] and [EC:1.7.2.4]. This work constructed an efficient municipal biological nitrogen removal technology to achieve high effluent nitrogen standards in winter, and investigated its working mechanism to provide a basis for design and optimization.

Automated summary

A two-stage anoxic/oxic-moving bed biofilm reactor system was established for municipal wastewater treatment. The system achieved high removal efficiencies for SCOD, NH4+-N, and TIN during different seasons. Functional bacterial populations were formed in different reactors, and the highest nitrification potential was found in the last oxic reactor of the first stage, while the highest denitrification potential was found in the post-anoxic reactors.