In this paper, the author found that P removal could be achieved without specific anaerobic phase in and inner ?loop SBR.

2.1 P removal performances during long-term operation

The domestication of activated sludge in SBR system for P removal finished after about 14 days. author found that the P removal was at the poor level during the first 7days. However the removal efficiency of the P would reach the 90%  after 27days. This experiment proves that P removal could be achieved without anaerobic phase.

2.2 P removal and PHA accumulation in a typical cycle

The anaerobic phase is very important for traditional P removal, because external carbon sources is converted to PHA as energy storage ofr the subsequent aerobic phase after influent for BPR.

But the author does the aeration without pre-anaerobic process. Then the PHA show that the energy storage PHA was almost kept constant at a low level.(5~6 ppm), however P concentration was decreased obviously along with aeration.so we can know that the P removal could be achieved with single stage oxic pahse in SBR without every storage PHA accumulation.

2.3 The approach of P removal in this study

Normally, we can know the the Phosphorus could be removed by the activated sludge and there are three form of P in the sludge-biological P, Metal P and the poly-p. At the first, we can know that the bio-p and metal Pare not the main reason (from the experiment in this paper), we should consider the relationship between poly-p and P. From the 6hr experiment in this paper, we can see after 90min, P concentration was decreased while intracellular poly-P was increased gradually during aeration. Then, COD and MLSS concentrations (main source for the bio-P and metal P) have no obvious after 30 min in aeration, and then at the end of aerobic period.


3. Contribution:
This paper shows that P removal could be achieved in SBR with single-stage oxic process without PHA accumulation which was conventionally considered as key energy for P removal. This paper shows a very interesting method to remove the phosphorous. We know that typically process must use the anaerobic and aerobic process together. However, the author shows a new way to remove anaerobic process by using add-oxic process. Here a new way for the P removal method we can learn from this paper and can apply to the real system deign.