Effect of high phosphate loading in sequencing batch reactors on enhanced biological phosphorus removal

The effects of high phosphate loadings on enhanced biological phosphorus removal were investigated using 10 L bench-scale sequencing batch reactors. The phosphate loadings were elevated by adding the phosphate just before the aerobic stage(strategy I) and by directly increasing the phosphate concentration in the influent(strategy II).For phosphate loadings increased from 10 to 40 g·m-3·d-1,more phosphorus was removed from 2.06 to 2.41(strategy I) and 2.25 mg·g-1(strategy II) in the batch reactor.The change in the phosphorus and glycogen contents in the sludge during the experiments implied that with the high phosphate loading,polyphosphate accumulating organisms were more competitive than glycogen accumulating organisms.However,for a fixed phosphate loading of 40 g·m-3·d-1,the phosphorus removal performance of strategy I proved to be better than that of strategy II because the high initial phosphate concentration may suppress the release of phosphate by polyphosphate accumulating organisms in the anaerobic stage.