Adjustment of the Dissolved Oxygen in Aeration Tank and its Effect on Outlet Water Quality

The aeration tank is regarded as the key treatment facilities in the conventional activated sludge process. The running condition of the aeration tank has a great influence on the quality of outlet water. The phenomenon that the speed of oxygen consuming is higher than that of oxygen supplying at the head of aeration tank, the concentration of dissolved oxygen is excessive in the back of aeration tank is common in the aeration tank. Taking wastewater treatment plant of Taiyuan Hexi for an example, this paper is focus on the factors influencing conventional activated sludge process in aeration tank, such as dissolved oxygen. After the adjustment of DO, it can be found that the removal efficiency of BOD was improved to a certain extent. Especially during the process of adjustment, when the dissolved oxygen value is at 0.5-1.0 mg/L in the majority of the regional in aeration, its BOD removal efficiency is still in high level. The level of denitrification can not improve after the adjustment and if we want to improve removal effect of NH₃-N and TN, we must try best to meet the conditions of nitrification reaction or add nitrogen removal process.