Sludge yield and degradation of suspended solids by a large pilot-scale anaerobic membrane bioreactor for the treatment of real municipal wastewater at 25 °C

Sludge yield and suspended solid are important factors concerned in the anaerobic treatment of municipal-wastewater. In this study, a large pilot-scale anaerobic membrane bioreactor (AnMBR) was constructed for effectively treating real municipal wastewater at an ambient temperature of 25 degrees C. The sludge yield and the degradation of influent suspended solidswere evaluated during the long-term operation of the AnMBR. This reactorwith 5.0 m(3) effective volume is the largest one-stage submerged AnMBR that has ever been used to treat municipalwastewater. During the long-termoperation of 217 days, this AnMBR obtained excellent CODand BOD5 removal efficiency over 90%. Stable biogas production was also successfully obtained from treating municipal wastewater. The sludge yield of the AnMBR was approximately 0.19-0.26 gMLSS g(-1) COD removed for the treatment of realmunicipal wastewater. The shortest SRT of the AnMBR was calculated as 29 days for an HRT of 6 h at an empirical MLSS of 10 g L-1. While theinfluent suspended solid (SS) contained in themunicipalwastewaterwas completely removed by the AnMBR, only 57%-66% of the influent SS was degraded. The rest of influent SS was directly converted to MLSS instead of being degraded. The AnMBR maintained a stable membrane filtration using a hollowfiber membrane with a total area of 72 m(2), realizing a flux of 2.75-17.83 LMH, and the mean transmembrane pressure (TMP) was 0.9-23.5 kPa. An online chemical backwash cleaning systemhelped to lower the TMP timely using sodium hypochlorite and citric acid when the TMP increased rapidly and reached the rated limit of membrane. This is the first report on demonstrating the successful operation and detailed performance of a large pilotscale AnMBR applied to the treatment of real municipal wastewater. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study focuses on the anaerobic treatment of municipal wastewater, with emphasis on sludge yield and suspended solid degradation. A large pilot-scale AnMBR was used to effectively treat real wastewater, achieving excellent COD and BOD5 removal efficiency, stable biogas production, and low sludge yield. The reactor successfully removed influent suspended solids, although only a portion was degraded, with the rest being converted to MLSS.