Vertical baffled reactor promoting aerobic sludge concentration for effective remediating unstable–load domestic wastewater: Performance, microbial properties and mechanism

Abstract

The study evaluated the pollutant degradation ability and the microbial community of aerobic granular sludge (AGS) in the modified vertical baffle reactors (VBRs) in the treatment of unstable–load domestic wastewater. The AGS was cultivated in the reactor which was ensured by the special structure and sludge reflux system of VBRs. VBRs can maintain a high sludge concentration without sludge bulking, while long hydraulic retention time (HRT) ensured a high sludge concentration to improve the treatment capacity to unstable influent. Unstable–load domestic wastewater, with COD = 120–556 mg/L, TN = 19.97–81.54 mg/L, was applied as the influent for 180 days of continuous experiments, while the system achieved a stable removal effect on the indicator pollutants. On day 180, MLSS maintained at 7000 mg/L with the average particle size of sludge at 1000 μm. The increasing concentration of extracellular polymeric substances (EPS), especially polysaccharide (PS) was conducive to the bridging among particles to form AGS, which played an important role in maintaining the stability of granular sludge. The results of functional microbial communities showed that Proteobacteria was the most abundant phylum in aerobic sludge, while the Nitrospira was the dominant bacteria in genus level. The microbial community was biodiverse, and can achieve the effect of the simultaneous removal of multiple contaminants.