Understanding the mechanism of denitrifying phosphorus removal from the perspective of intracellular carbon source and extracellular polymeric substances characteristics

Denitrifying phosphorus removal (DPR) is a novel approach for denitrification and phosphorus (P) adsorption simultaneously under an anoxic condition. A well-running DPR system was used in this study to investigate the DPR mechanism based on the changes in intracellular carbon sources and extracellular polymeric substances (EPS) characteristics. In the anaerobic stage, the intracellular carbon source and EPS characteristics test results showed that Poly-β-hydroxyalkanoates (PHA) increased by 1.75 ± 0.58 mmol C/L, which was related to the utilization of proteins slime EPS (S-EPS). Moreover, tyrosine-like substances in S-EPS were mainly used for the PHA synthesis by parallel factor analysis (PARAFAC) and correlation analysis. In addition, concentrations of K+, Mg2+ and Ca2+ in EPS were changed in different stratified EPS. EPS was an extracellular phosphorus reservoir for DPR activated sludge. In the anoxic stage, K+ and Mg2+ in the matrix had a linear relationship with P, but Ca2+ accumulated in TB-EPS. Further, the inorganic phosphorus absorbed by the activated sludge reacts with Ca2+ as P–Ca precipitation. Above the results are helping to preliminarily understand the mechanism of DPR from the perspective of intracellular carbon sources and EPS characteristics.