Effect of hydrodynamic conditions on the formation and structure of aerobic granular sludge performing enhanced biological phosphorus removal

The study investigated the effect of hydrodynamic conditions on the formation of enhanced biological phosphorus removal (EBPR) granular sludge without losing the EBPR capacity, and its structure. The effect of hydrodynamic conditions on the formation of EBPR granular sludge was evaluated by using the minimum settling velocity, (V_s)_min, and superficial air velocity. The application of (V_s)_min strategy was proved to be beneficial in maintaining granular biomass without losing the EBPR capacity. Microscale structure, the chemical composition and chemically stored phosphorus of the matured EBPR granular sludge were determined by using ESEM-EDX and cold perchloric acid (PCA) analyses. The results of both the ESEM-EDX and PCA analyses proved that the poly-P granules were stored extracellular in EPS structure of EBPR granular sludge. Therefore, the EBPR granular sludge has a high potential for both removal and recovery of phosphorus from wastewater, which needs to be investigated in future studies.