A new configuration of sequencing batch reactor operated as a modified aerobic/extended-idle regime for simultaneously saving reactor volume and enhancing biological phosphorus removal

•A new configuration of SBR was designed to save reactor volume in the AEI regime.•The new configuration of SBR showed higher BPR than the A/O-SBR and AEI-SBR.•The biochemical metabolisms in the new configuration of SBR were followed by those in the AEI-SBR.•The activities of PPX and PPK between the A/O and AEI regimes were compared for the first time.

Recently, it has been reported that the aerobic/extended-idle (AEI) regime can achieve a satisfied biological phosphorus removal (BPR). Although the AEI regime has exhibited some merits, its main drawback that the extended-idle phase (e.g., 210–450 min) is much longer than the anaerobic phase (e.g., 60–120 min) performed in the aerobic/oxic (A/O) regime requires to be addressed. In this study, a new configuration of sequencing batch reactor (SBR) with sludge tank halved (STH-SBR) was therefore designed. After stable operation, 96.9 ± 0.5% of total phosphorus was removed in the STH-SBR, which was higher than that in the AEI-SBR (86.9 ± 0.8%) and A/O-SBR (84.7 ± 1.3%). Further investigations showed that the biomass cultured in the STH-SBR contained more polyphosphate accumulating organisms but less glycogen accumulating organisms than that in the AEI-SBR and A/O-SBR. In the STH-SBR, the aerobic glycogen accumulation was lower than that in the A/O-SBR while the average idle phosphorus release was greater than that in the AEI-SBR. Finally, the key enzyme activities in the AEI and A/O regimes were compared for the first time, and the reasons for the AEI regime showing lower exopolyphosphatase and polyphosphate kinase activities were also discussed.

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