Dynamics of microbial activities and community structures in activated sludge under aerobic starvation

The knowledge of the effect of aerobic starvation on the functional bacterial activities and community structures is important for the recovery of nutrient removal in activated sludge system. Four aerobic starvation processes (3, 7, 14 and 30 days) for nitrifiers and polyphosphate accumulating organisms (PAOs) were studied. The results showed that nitrifiers could utilize the released ammonium for growth during the first 7 days of the aerobic starvation, and then gradually decayed. In the recovery period, the slower recovery ability of nitrite-oxidizing bacteria (NOB) than ammonium-oxidizing bacteria (AOB) contributed to the nitrite accumulation. Besides, the sequential consumption of polyhydroxyalkanoates (PHA), glycogen and the utilization of polyphosphate (poly-P) in PAOs provided the energy to maintain bacterial metabolic activity. High-throughput sequencing analysis revealed that aerobic starvation had substantial impacts on the succession of microbial community, and the majority of original dominant species within the phylum Proteobacteria and Bacteroidetes declined while Firmicutes increased.