Performance of enhanced biological phosphorus removal and population dynamics of phosphorus accumulating organisms in sludge-shifting sequencing batch reactors

The sludge-shifting sequencing batch reactor (SBR) is an enhanced biological phosphorus removal (EBPR) process for wastewater treatment. In this study, the enrichment of phosphorus accumulating organisms (PAOs) will be attempted by using different high concentration of substrates. In sludge-shifting SBR, activated sludge can be continuously shifted from the bottom of SBR to anaerobic zone/selector, which contains high concentration of substrates, through an orderly reflux between the paralleled SBRs. Denaturing gradient gel electrophoresis (DGGE) methods were used to monitor microbial diversity in sludge. Fluorescence in situ hybridization (FISH) was used to determine the microbial population profile and distribution map under different sludge shifting volumes. The synthesis of intracellular polymers in this process was also analyzed. Phosphorus removal efficiency as high as 96% ± 1.3% was achieved under a sludge shifting ratio of 30%. Synthetic efficiencies of polyhydroxybutyrate (PHB) by PAOs were improved at high sludge shifting ratios. FISH results demonstrated that the population of PAOs in the process increased under properly sludge shifting ratio and it significantly improved phosphorus removal efficiency. Sequencing results indicated that determined sequences (11 OTUs) belonged to Proteobacterium, Actinobacteria and Firmicutes, Pseudomonas kuykendallii, which played an important role in the process of P removal.