城市污水的低氧短程脱氮中试研究

Pilot Study on Shortcut Nitrogen Removal from Municipal Wastewater under Low Oxygen Concentration Condition

采用中试A2/O系统处理实际城市污水,考察了在低氧条件下实现短程脱氮的可行性。结果表明,当缺氧池DO从1.0 mg/L降到0.2 mg/L,好氧池DO从2.5 mg/L降到1.0 mg/L时,系统的脱氮效果显著提高,对TN的去除率从(34.96±4.91)%上升到(71.44±13.45)%,污泥浓度(MLSS)从1 800 mg/L上升到2 100 mg/L。当控制好氧池的DO在1.0 mg/L左右时,出水中发生了亚硝酸盐积累现象,从而证实了在低氧条件下利用连续流活性污泥法实现短程脱氮的可行性,在降低系统曝气能耗的情况下还提高了系统的脱氮效率。但当DO浓度降低时,污泥沉降性能将有所变差,污泥体积指数(SVI)从150 mL/g上升到300 mL/g左右。

The feasibility of shortcut nitrogen removal at low oxygen was investigated in a pilot- scale A2/O system for treating municipal wastewater. The experimental results show that when DO concentration in anoxic tank is decreased from 1.0 mg/L to 0.2 mg/L and DO concentration in aerobic tank is decreased from 2.5 mg/L to 1.0 mg/L, the removal rate of total nitrogen is increased dramatically from （34.96±4.91）% to （71.44±13.45）%, and MLSS is increased from 1 800 mg/L to 2 100 mg/L. Nitrite accumulation occurs when DO in aerobic tank is controlled at about 1.0 mg/L. These resuits verify that it is feasible to achieve shortcut nitrogen removal in the continuous-flow activated sludge process, and the nitrogen removal efficiency can be improved while reducing energy consumption for aera- tion. However, the sludge volume index （SVI） is increased from 150 mL/g to 300 mL/g when DO con-centration is decreased, indicating that sludge settleability becomes worse.