Cultivation of denitrifying anaerobic methane-oxidizing microorganisms in a continuous-flow sponge bioreactor.

Anaerobic treatment of sewage has many advantages; however, the effluent contains high levels of dissolved methane. In this study, we investigated the use of a closed-type downflow hanging sponge (DHS) reactor for application of the denitrifying anaerobic methane oxidation (DAMO) reaction for nitrogen and dissolved methane removal. When using nitrate, the DAMO reaction achieved a denitrification rate of 84.4 g N m day, which is close to that required for practical application of denitrification to anaerobic sewage treatment. The microbial community that developed in the DHS was investigated using16S rRNA, and novel species of DAMO bacteria affiliated with Group b of NC10 phylum were enriched. This contrasted with the results of previous studies in which the Candidatus Methylomirabilis oxyfera affiliated with Group a was enriched. The results obtained herein suggest that a post-treatment system for anaerobically treated sewage using a closed-type DHS reactor may become practical in the near future.