The Study Of The Performance Of The Step Feed Biological Nitrogen Removal Process

The standard of wastewater discharge was controlled more strictly with the severe eutrophication question getting worse and worse which makes the the nitrogen and phosphorus removal technology aiming for eutrophication control be the study focus in the wastewater treatment area. For phosphorus element removal, although the biological phosphorus removal process is not stable, zero concentration of effluent total phosphorus could be obtained by using conventional treatment process to remove phosphorus and adding chemicals. But for nitrogen element removal, using membrane method needs a large charge to invest and operate. Moreover NH3 and NO2 have the similar molecular weight to H2O and could go through the membrane with H2O. Therefore the biological process is the only choice but the nitrogen removal efficiency is hard to reach high level by biological nitrogen removal process. So the main point is how to achieve enhanced nitrogen removal, choose biological nitrogen and phosphorus removal process with high nitrogen removal efficiency and improve it. The step-feed biological removal process (SFBNP) has increasingly been proposed as attractive alternative. The influent flow is distributed to the anoxic reactors and the retuned sludge enters the head of reactor. The SFBNP has great advantages: high nitrogen removal efficiency, no internal recycle of mixed liquor, increased solid retention time.In order to accelerate the investigation development of the SFBNP,The mechanic and effect of different operational factors and influent characteristics on the SFBNP were studied systematically for the first time using synthesis wastewater.First of all, The SFBNP has the characteristic of high nitrogen removal efficiency. The formula of theoretical nitrogen removal efficiency for the step feed biological nitrogen removal process was re-deduced based on the mass balance of nitrate nitrogen in this paper and verified by the experiments.The highest nitrogen removal efficiency can be obtained when there is no accumulation of nitrate in anoxic zone and the minimum influent flow rate in the last stage.