Understanding the role of extracellular polymeric substances in an enhanced biological phosphorus removal granular sludge system

• EPS plays an important role in the biological phosphorus removal granular system.
• There is obvious accumulation of (K+, Mg2+ and Ca2+) in EPS.
• EPS is the storage buffer in the EBPR process.

The role of extracellular polymeric substances (EPS) in the enhanced biological phosphorus removal (EBPR) process was investigated in a P-accumulating granular sludge system by analyzing the distribution and transfer of P, K+, Mg2+ and Ca2+ in the sludge phase, EPS, and the bulk liquid. In the sludge phase, about 30% P, 44.7% K+, 27.7% Mg2+, 28% Ca2+ accumulated in the EPS at the end of aeration. The rate of P, K+, Mg2+ and Ca2+ released from the EPS matrix into the bulk liquid in the anaerobic phase was faster than the rate they were adsorbed from the bulk liquid into the EPS in the aerobic phase. P, K+, Mg2+ and Ca2+ were retained in EPS before transferring into the phosphorus accumulating organisms (PAOs). These results suggest that EPS play a critical role in facilitating the accumulation and transfer of P, K+, Ca2+ and Mg2+ between PAO cells and bulk liquid.