Distribution characteristics of methanogens in urban sewer system

A study was conducted through a 1200 m-PVC-pipe-reactor, which was used to simulate the urban sewer system. Gas chromatography, liquid chromatography and 454 high-throughput sequencing were utilized to study the variation of substrates during the methanogenic process and the distribution characteristics of methanogens in the sewer system. The results showed that the concentration of methane increased along the sewer system, which illustrated that methanogens existed in the sewer network. The methanogens mainly contained Methanosarcina, Euryarchaeota_unclassified and Methanobacteriaceae_unclassified. The distinct succession which Euryarchaeota_unclassified replaced Methanosarcina to be the first dominant microbial genus between 800-1000 m of the sewer system. Formic acid, methanol, methylamine, acetic acid and hydrogen were available substrates for methanogens. Among these substrates, acetic acid was the primary substrate for methanogen. The variation trends of these substrates were first increasing and then decreasing along the length of the sewer system, which led to the succession phenomenon of methanogens in the sewer system.