Effects of seasonal temperature variations on phosphorus removal, recovery, and key metabolic pathways in the suspended biofilm

Abstract The effects of seasonal temperature variations on phosphorus removal performance and community structure of dominant polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs) were explored. Such impacts on the dominance of PAOs and GAOs involved in carbon and phosphorus metabolic pathways and gene abundance of key enzymes in biofilm sequencing batch reactor (BSBR) were studied. Enzyme assay and Miseq high-throughput sequencing revealed that typical GAOs hold a competitive advantage, the activities of phosphate kinase (PPK) and phosphate hydrolase (PPX) were decreased, and typical GAOs deteriorated phosphorus removal performance in summer (27–30 °C). In spring, autumn, and winter (15–22 °C), PAOs dominated the competitive advantage, the activities of PPK and PPX were increased, and atypical PAOs dominated the improvement of phosphorus removal performance. Metagenomic sequencing showed that the reducing power of PAOs for polyhydroxyalkanoate ( PHA) synthesis mainly came from the glycolysis pathway, followed by hexose monophosphate pathway (HMP) and tricarboxylic acid (TCA) cycles. The change of phosphorus removal performance was not only related to the carbon and phosphorus metabolic pathways activated by PAOs, but also closely associated with the change of the competitive pathways between GAOs and PAOs. Collectively, our findings provided a temperature reference for the improvement of BSBR process performance and added the first in-depth information for the understanding of the phosphorus removal mechanism and the competition mechanism with GAOs in BSBR.