Bacterial and archaeal community distribution and stabilization of anaerobic sludge in a strengthen circulation anaerobic (SCA) reactor for municipal wastewater treatment

- Municipal water treatment in SCA reactor was analyzed physically and biologically.
- COD removal efficiency increased with the promotion of Vup from 0.6 to 5.9 m h−1.
- Floating of anaerobic granular sludge may be promoted with physically clogged by EPS.
- Acetoclastic methanogens mostly promoted formation of granules in low OLR condition.
- Hydrogenotrophic methanogens hardly in formation of granules in high OLR condition.

In this study, a SCA reactor was employed for municipal wastewater treatment at a mesophilic temperature (30 °C) under different hydraulic retention times (HRT) and upflow velocities (Vup) to investigate granule sludge stability and spatial microbial distribution. The stable COD removal efficiency readied at HRT of 15, 12, 9 and 6 h, and Vup ranging from 0.6 to 5.9 m h−1. EPS fraction analysis of granule sludge shows that municipal wastewater was mainly attributed to the enrichment influence of polysaccharide and tightly bound-EPS. SEM images exhibited that the stability and floating of anaerobic granular sludge may be promoted in the primary three-phase separator area because the channels of the granules was clogged by EPS. The SMA and high-throughput sequencing analysis indicated acetoclastic methanogens and hydrogenotrophic methanogens played an important role in formation and maintenance of the anaerobic granule sludge in low and high organic load rate operation conditions.

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