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Performance of a forward osmotic membrane bioreactor for anaerobic digestion of waste sludge with increasing solid concentration

Zhao, Jing, Li, Yunqian, Pan, Shuang, Tu, Qianqian, Zhu, Hongtao
Journal of environmental management 2019 v.246 pp. 239-246
Actinobacteria, Bacteroidetes, Chloroflexi, Proteobacteria, anaerobic digestion, biogas, crystals, fouling, ions, magnesium, magnesium ammonium phosphate, magnesium chloride, membrane bioreactors, methane, methane production, microbial communities, organic matter, osmosis, sludge, total solids
A forward osmotic membrane bioreactor for sludge anaerobic digestion (ad-OMBR) could realize high-solid digestion via drawing moisture out by forward osmosis (FO). Methane production and microbial community evolution were monitored in an ad-OMBR as the total solids (TS) content was gradually increased. With magnesium chloride (MgCl2) and cellulose triacetate (CTA) membrane as a draw solution and FO membrane, respectively, the ad-OMBR exhibited better performance than the conventional digester, with higher solid content, organic degradation and methane content in biogas. The conductivity of the ad-OMBR did not increase, potentially because of the formation of struvite crystals aided by the reverse-fluxed Mg2+ ions. Microbial diversity increased along with the increase in solid content based on the Shannon index, while the most operational taxonomic units were obtained in the 8% TS sludge Although phylum Firmicutes decreased when the TS content was raised to 11%, the relative abundance of Proteobacteria, Chloroflexi, Actinobacteria, and Bacteroidetes, which could also degrade organic matter, increased with increasing TS in ad-OMBR. FO membrane fouling in ad-OMBR was highly reversible.