A novel A-B process for enhanced biological nutrient removal in municipal wastewater reclamation

•A strategy towards sustainable nitritation was developed and demonstrated.•Simultaneous N and P removal was achieved at low energy consumption.•More than 88% of the total nitrogen was removed via nitritation and denitritation.•Accumulibacter were the dominant PAOs with undetectable Competibacter.•The A-B process offered a cost-effective option for biological nutrients removal.

This study developed an innovative A-B process for enhanced nutrients removal in municipal wastewater reclamation, in which a micro-aerated moving bed biofilm reactor served as A-stage and a step-feed sequencing batch reactor (SBR) as B-stage. In the A-stage, 55% of COD and 15% of ammonia nitrogen was removed, while more than 88% of the total nitrogen was removed via nitritation and denitritation, together with 93% of phosphorous removal at the B-stage where ammonia oxidizing bacteria activity was significantly higher than nitrite oxidizing bacteria activity. Meanwhile substantial phenotype of polyphosphate accumulating organisms (PAOs) was also observed in the B-stage SBR. Fluorescence in situ hybridization revealed that Accumulibacter was the dominant PAOs with undetectable Competibacter. Compared to the conventional activated sludge process, the proposed A-B process could offer a more cost-effective alternative for enhanced biological nutrients removal from municipal wastewater with less energy consumption.