溶解氧浓度对A~2/O工艺运行的影响

以城市污水厂中最常采用的A2/O工艺为研究对象,开展了处理实际生活污水的研究,系统探讨了DO浓度对该工艺运行的影响。结果表明,当好氧区的DO平均浓度从4.0 mg/L降低至1.0 mg/L时,对COD的去除基本不受影响;而系统的硝化效果逐渐降低,但是低DO浓度引发的SND等作用,使得对TN的去除率反而逐渐升高。单纯从生物脱氮的角度考虑,A2/O工艺可以在DO为1.0～2.0 mg/L之间运行。不过低DO浓度运行对生物除磷效果的影响很大,在DO为1.0 mg/L时,除磷效率逐渐下降,这是由于供氧不足引发了生物除磷性能的恶性循环。另外,低DO浓度运行还引发系统中的污泥发生了微膨胀现象,在污泥微膨胀期间出水SS<5 mg/L。就总体的运行情况而言,不同于A/O等单纯脱氮工艺,A2/O工艺不宜在DO<2.0 mg/L的条件下运行,否则需要引入化学除磷。

Effect of Dissolved Oxygen Concentration on Performance of A2/O Process

As a conventional process used in WWTP,A2/O process was used to treat actual domestic sewage to investigate the effect of DO on the performance of this process.The results showed that when the average DO concentration in aerobic zone was decreased from 4.0 mg/L to 1.0 mg/L,the removal of COD was not affected basically.However,the nitrification effect was decreased with the decrease of DO.Simultaneous nitrification and denitrification(SND) was enhanced with the decrease of DO,and the TN removal efficiency was increased correspondingly.Considering the nitrogen removal,the DO concentration could be kept between 1.0 and 2.0 mg/L.The removal of phosphorus was drastically affected by the decrease of DO.When the DO concentration was 1.0 mg/L,the removal efficiency of phosphorus is decreased by deterioration of phosphorus removal performance caused by insufficient oxygen supply.The limited sludge bulking was caused by the low DO concentration,and the effluent SS was lower than 5 mg/L during this period.It is recommended that the DO concentration in the A2/O process should be kept higher than 2.0 mg/L during the operation.Or else,chemical phosphorus precipitation should be introduced.