Long-term treatment of municipal wastewater using a mesh rotating biological reactor and changes in the biofilm community

The effects of temperature and hydraulic retention time on the sewage treatment performance of mesh rotating biological reactor (MRBR) were investigated. The MRBR contained net-like 3D plastic mesh disks instead of conventional rotating disks. A laboratory-scale MRBR was used to treat real sewage for over 1 year. The soluble chemical oxygen demand concentrations for the effluent were 48-64 mg/L whether the hydraulic retention time was 2 or 4 h and when the influent sewage temperatures was between 12.2 and 24.5 degrees C. The sewage temperature strongly affected the NH: N removal rete, which decreased by 0.1 kg N m(-3) day(-1) for each 12 degrees C decrease in temperature. Even though the NH4+-N removal rate was low, simultaneous nitrification and denitrification occurred at a removal efficiency of 95%. The microbial community structure in the biofilm attached to the MRBR disks was different to the microbial community structure of conventional activated sludge that had been used to treat the same sewage. The microbial community structure of the MRBR biofilm sludge was stable throughout winter and summer regardless of the hydraulic retention time. This suggested that the microbial community was initially controlled by the influent sewage but then became to specific to the MRBR. This was attributed to the high degree of simultaneous nitrification and denitrification that occurred. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The study found that the MRBR's sewage treatment performance is significantly influenced by temperature and hydraulic retention time, with the NH: N removal rate decreasing as the temperature drops. Although the NH4+-N removal rate is low, simultaneous nitrification and denitrification can still achieve an efficiency of 95%. Compared to traditional activated sludge, the microbial community structure of MRBR biofilm sludge remains stable regardless of seasonal changes in hydraulic retention time.