[Construction and Mechanism of Methanotroph-based Ultimate Denitrification System for Tailwater of Urban Sewage Plants].

With great practical potential of aerobic methane coupled to denitrification (AME-D) in deep denitrification of tailwater in urban sewage plants, an AME-D extreme denitrification system with low concentration of methane, was established in an improved denitrification biofilter. The finding indicated that in an intermittent operation mode, the average concentration of total nitrogen and ammonia nitrogen in the effluent could reach 1.05 mg·L-1 and 0.54 mg·L-1, and the average removal rate was 94.77% and 93.30%, respectively. According to Raman spectral analysis, the crests formed by NO3- symmetric stretching disappeared, and crests formed by the vibration and absorption, where the outer alcohol COH plane or the C-H plane was bent, were significantly enhanced, so the intermediate products produced during which methane was oxidized may be alcohols. 16S rRNA gene sequencing results showed that dominant methanotrophs included Methylocystis (0.27%), Methylosarcina (0.10%), and Methyloparacoccus (0.12%), dominant denitrifying bacteria were Pseudomonas (56.92%), Paenibacillus (3.52%), and Lysinibacillus (3.00%), and the dominant nitrifying bacteria were Nitrospira (0.1%) in this system. Thus, it could be concluded that synergism of aerobic methanotrophs, denitrifying bacteria, and nitrifying bacteria could lead to extreme denitrification.