[Analysis of Low C/N Wastewater Treatment and Structure by the CEM-UF Combined Membrane-Nitrification/Denitrification System].

: In this study, a CEM-UF composite membrane with ammonia nitrogen enrichment and separation characteristics was combined with nitrification/denitrification to treat low C/N wastewater. The denitrification characteristics of low C/N wastewater at different flow ratios were investigated, and the structural characteristics of functional microbial communities in nitrifying and denitrifying activated sludge were analyzed by 16Sr DNA high-throughput sequencing. The results showed that influent TN was 60 mg·L-1, COD/TN was 2.65, the nitrification effect of each flow rate was good, and the average ammonia nitrogen removal rate was 98.7%. When the flow ratio increased from 1:2 to 1:6, the m(COD)/m(NO3--N) of denitrification was increased, and the removal of average nitrate nitrogen reached its highest level at 1:6, which was 86.28%, and the removal of total nitrogen increased from 22.56% to 46.8%. An analysis of Illumina sequencing showed that nitrogen fixing bacteria Proteobacteria accounted for 30.9%, and the important nitrite oxidizing bacteria, Nitrospirae, accounted for 3.06%. At the genus level, Nitrosomonas and Nitrosospira, belonging to the ammonia oxidizing bacteria (AOB) category and Nitrospira and Nitrobacter, belonging to the nitrite oxidizing bacteria (NOB) category were detected. The ratio of AOB and NOB bacteria was high, which is consistent with good nitrification in the nitrification reactor. The dominant bacteria in denitrification sludge were Proteobacteria (53.13%), followed by Bacteroidetes (10.93%). A variety of bacteria related to denitrification were detected at the genus level, such as Dechloromonas, Thauera, Castellaniella, Alicycliphilus, Azospira, Comamonas, Caldilinea, and Saccharibacteria. The proportion of denitrifying bacteria was 25.91% as denitrifying bacteria microbial species were rich in the denitrifying sludge, giving a good denitrification effect.