Enhancement Of Phosphate Removal From Anaerobic Anoxic-oxic Process By Hydrolysis And Acidification

Because the water eutrophication is more and more serious in our country, the discharge standard of the nutrient elements, such as N and P, becomes stricter. But many sewage treatment plants cann't reach the P discharge standard in the operation. The hydrolysis and acidification can promote the biodegradability of the effluent, produce an amount of volatile fatty acids (VFAs) which can be easily absorbed by the poly-phosphate-accumulating organisms (PAOs) in the phase of anaerobic phosphate release. The hydrolysis and acidification can also change the components of the organic compound in the effluent. So this paper primarily reseach the affect of the hydraulic retention time (HRT) and microoxic aeration to the reactor of the hydrolysis and acidification. On this base, the paper further reseach the affect of the hydrolysis and acidification to the P removal of the anaerobic-anoxic-oxic, and compare it with the P removal effect of the anaerobic-anoxic-oxic when it operates alone.The conclusions are as follows: under the influent water quality of this experiment, comparing with 6h and 2h, the reactor of the hydrolysis and acidification operates much better under the HRT of 4h. The average VFA concentration is 40.4 mg COD/l and the average acidification ratio (the VFA concentration variance between the effluent and influent divided by the COD of the influent) is 10.38%. The BOD5/COD of the effluent reaches by 0.064 on the average.The HRT is not as longer as possible as to the promotion of the biodegradability and the VFA production. The microoxic aeration can enhance the VFA production of the reactor of the hydrolysis and acidification.When the reactor of the hydrolysis and acidification is under unaeration or microoxic aeration with the HRT of 4 h, the effect of the phosphate release and the PHAs content in the sludge at the anaerobic period are both promoted, especially under microoxic aeration. The total phosphate removal rate reaches to 82.24% and 84.69% separately which is only 72.75% when the anaerobic-anoxic-oxic operates alone.This paper gives some guidance to the further reseach of the enhancement of phosphate removal to the anaerobic-anoxic-oxic by the hydrolysis and acidification with real waste water and under low temperature.