Hollow fiber membrane bioreactor affects microbial community and morphology of the DAMO and Anammox co-culture system

•HfMBR improves nitrogen removal in the DAMO & Anammox co-culture system.•HfMBR significantly increases DAMO archaea proportion to 74.3%.•DAMO archaea, DAMO bacteria and Anammox bacteria form granules on fibers surface.•Microbial spatial distribution is different with reported simulation result.

Denitrifying anaerobic methane oxidation (DAMO) and Anammox co-culture system was investigated in hollow fiber membrane bioreactor (HfMBR) for the change of microbial community morphology and proportion. NO3−-N and NH4+-N removal rates reached 85.33 and 37.95 mg/L/d on 193 d. The inoculum microorganisms were flocs and the proportion of DAMO archaea, DAMO bacteria and Anammox bacteria was 11.0, 24.2 and 0.4%, respectively, but it changed to 74.3, 11.8, 5.6% in HfMBR, respectively. Interestingly, microorganisms formed biofilms on fibers surface and the biofilms included two layers: inner layer was thin and dominated by DAMO bacteria and Anammox bacteria; while the outer layer was thick made up of granules with 100-200 μm diameter and dominated by DAMO archaea. The spatial distribution of microorganisms in HfMBR was different from simulation results in the literature. Likely, HfMBR changed the interaction between DAMO and Anammox microorganisms, and the reactor configuration was beneficial for DAMO archaea growth.

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