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Artificial enhancement via the combination of sediment discharging and influent velocity gradient increasing could enhance the biofilm formation and autotrophic AOB enrichment in oligotrophic niche.

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The extracellular polymeric substances (EPS) are important macromolecular components in microbial aggregates. The three EPS extraction methods - ultrasound + cation exchange resins (CER) + sulfide, ultrasound + formamide + NaOH, and ultrasound + heat - were investigated in the study, and the component differences of extracted EPS from the loose flocs and dense aerobic granules were compared using chemical analysis and three-dimensional excitation-emission matrix (3D-EEM). Results showed that the contents of EPS were extracted effectively by ultrasound + formamide + NaOH and ultrasound + heat methods, and the ultrasound + CER + sulfide method did not extract the polysaccharides (PS) or protein (PN) contents from the sludge samples. The 3D-EEM analysis indicated that the nature of peak B/D, peak C/E/F, and peak A/G were attributed to PN-like, humic acid-like and fulvic acid-like fluorophores. All fluorophores can be detected from the EPS extracted through the ultrasound + heat method. Hopefully this will provide more information about the EPS interaction mechanism of microbial aggregates.

Extracellular polymeric substances (EPS) are the key component of bio-aggregates, such as activated sludge, biofilm and granular sludge. They play an important role in the bio-aggregates because of their physic-chemical characteristics and special situation of directly wrapping on the cell wall. The effects of EPS on the settleability and dewaterability of bioaggregates and membrane pollution in membrane bio-reactor (MBR) are reviewed in this paper. It is concluded that the composition and structure of EPS affect the settling and dewatering characteristics of bio-aggregates and the membrane pollution in MBR via changing the sludge surface potential and hydrophobic. At the same time, the role of EPS in the sludge granulation is emphasized that the components and distribution of EPS also influence the formation and structural stability of granular sludge. Finally, the future researches concerning EPS, such as extraction method standardization and incorporation of the physicochemical analysis method and molecular biotechnology, are prospected, showing promise in revealing the EPS production and regulatory mechanism during the formation of bio-aggregates. Tab 1, Ref 48 Keywords extracellular polymeric substances (EPS); bio-aggregates; granular sludge; biological wastewater treatment; membrane bio-reactor (MBR) CLC X172 : X703