[Enhanced Membrane Anti-fouling Ability of Anaerobic Membrane Bioreactor Equipped with Bio-electrochemical System Using Nano-zero-valent Iron and Its Regulation Mechanism].

Membrane fouling is the biggest challenge of membrane bioreactor industrialization. In this study, a bio-electrochemical system (BES)-anaerobic membrane bioreactor (AnMBR) system was constructed, and the effect of nano-zero-valent iron (nZVI) on membrane anti-fouling ability and methane production was investigated. The results showed that the BES-AnMBR system was stable and the chemical oxygen demand (COD) removal rate was maintained at approximately 95%. The optimum condition was observed to be nZVI 0.1 g·g-1(VS). Under this condition, transmembrane pressure (TMP) was reduced by 28.1%, the membrane flux had a slight improvement, and methane production was up to 81.3 mL·g-1(CODremoved). This was 12.1% higher than that of the control. In addition, a further analysis of extracellular polymeric substances (EPS) fraction and membrane resistance showed that nZVI enhanced EPS decomposition, promoted the formation of an iron-rich layer of inorganic and organic matters on the membrane surface, and changed the distribution of organics and inorganics, thereby significantly alleviating membrane fouling. This study will enrich basic theory of conventional AnMBR and provide a new solution for efficient sludge treatment and resource utilization.

[Performance of Anaerobic Membrane Bioreactors for the Co-digestion of Sewage Sludge and Food Waste].

A laboratory-scale anaerobic membrane bioreactor (AnMBR) was used for the co-digestion of sewage sludge and food waste to investigate its organic matter removal characteristics, biogas production performance, and microbial community composition. The results showed that the degradation rate of volatile solids (VS) increased from 17.5% for a single digestion to 40% for the total digestion, and that the COD removal was 95.3% when the organic loading rate (OLR) was stabilized at 0.59-0.64 kg·(m3·d)-1. The solids content of the digested sludge increased by a factor of 3.9. The final CH4 content was 60% and the CH4 yield was 78.7 mL·g-1 of CODadded. The transmembrane pressure (TMP) and average flux were maintained at between -3.1 and -2.7 kPa and 0.106 L·(m2·h)-1, respectively, and membrane fouling was not serious. According to an analysis of the microbial diversity using 16S rRNA, the anaerobic bacterium in the AnMBR were mainly phylum Proteobacteria, Bacteroidetes, and Cloacimonetes, and the dominant methanogens included the Methanobacterium family, Methanosaeta genus, and Methanolinea genus. This study provides a strong theoretical basis for research into the stability and performance of AnMBRs for the co-treatment of sludge and other high-solid waste streams, and provided an effective solution for biomass resource utilization and the energy crisis.

Innovative combination of electrolysis and Fe(II)-activated persulfate oxidation for improving the dewaterability of waste activated sludge.

The feasibility of electrolysis integrated with Fe(II)-activated persulfate (S2O8(2-)) oxidation to improve waste activated sludge (WAS) dewaterability was evaluated. The physicochemical properties (sludge volume (SV), total suspended solids (TSS) and volatile suspended solids (VSS)) and extracellular polymeric substances (EPS), including slime EPS, loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) were characterized to identify their exact roles in sludge dewatering. While dewaterability negatively corresponded to LB-EPS, TB-EPS, protein (PN) and polysaccharide (PS) in LB-EPS and TB-EPS, it was independent of SV, TSS, VSS, slime EPS and PN/PS. Further study through scanning electron microscope (SEM) verified the entrapment of bacterial cells by TB-EPS, protecting them against electrolysis disruption. Comparatively, electrolysis integrated with S2O8(2-)/Fe(II) oxidation was able to effectively disrupt the protective barrier and crack the entrapped cells, releasing the water inside EPS and cells. Therefore, the destruction of both TB-EPS and cells is the fundamental reason for the enhanced dewaterability.