Effect of phosphate species in extracellular polymer substances on biological phosphorus removal process

By adopting the activated sludge from two laboratory scale A /O-SBR reactors,the effect of phosphate species in extracellular polymer substances( EPS) on biological phosphorus removal process was investigated. The SRT was 10 d and 30 d,respectively,in the two reactors under different DO conditions. The results showed that phosphorus of sludge floc was mainly contained in EPS,orthophosphate( PO3-4-P) and polyphosphate( Poly-P)with low and high molecular weight( LMW Poly-P and HMW Poly-P) were the main species of phosphorus in EPS. Furthermore,EPS played a more important role in biological dephosphorization than bacteria. Decrease of EPS phosphorus in anaerobic phase and increase in aerobic phase were 2.8 ~ 6.4times those of the intracellular phosphorus. Same variation was shown that the contents of LMW Poly-P and HMW Poly-P in EPS decreased in anaerobic phase but increased in aerobic phase. For the same SRT sludge,decrease of EPS phosphorus in anaerobic phase and increase in aerobic phase at moderate DO concentration( 2.5 ~ 3.5 mg·L-1) were greater than those at limited DO concentration( 0.7~1.0 mg·L-1),so the former had higher efficiency of biological phosphorus removal than the latter. Therefore,EPS not only acted as a transfer station of dephosphorization process,but also participated in biological accumulation of phosphorus.