Cu2+对以NO2-为电子受体反硝化过程的影响

短程生物脱氮工艺在废水处理中已经得到较为广泛的应用,其反硝化过程是实现氮去除的关键步骤,而关于废水中常见重金属离子Cu~(2+)对以NO2-为电子受体反硝化过程的影响尚无系统研究.选取A/O反应器内具有良好短程生物脱氮特性的污泥,通过批次试验及SBR长期试验分别探究了Cu~(2+)对以NO2-为电子受体反硝化过程的短期及长期影响.短期试验结果表明,Cu~(2+)对以NO2-为电子受体反硝化过程具有明显抑制作用,对污泥反硝化活性的半抑制浓度EC50为4. 79 mg·L-1.在长期影响试验中逐渐提高污泥对Cu~(2+)的耐受浓度,当Cu~(2+)浓度为0. 5 mg·L-1和1 mg·L-1时,污泥反硝化活性降低后均能够通过驯化恢复至原有水平;而Cu~(2+)浓度升高至3 mg·L-1后污泥反硝化性能遭到破坏且难以恢复,NO_2~--N去除率降低至10%以下,反硝化系统遭到严重抑制.但是,停止投加Cu~(2+)后污泥反硝化活性在第14 d恢复至原有水平.同时,在Cu~(2+)的长期影响过程中,EPS含量增多,对微生物抵御Cu~(2+)的毒害起到重要保护作用,促使污泥粒径增大,污泥沉降性得到提高.

Effect of Cu2+ on Denitrification Using NO2- as an Electron Acceptor

The short-cut biological nitrogen removal process has been widely used in industrial wastewater treatment, and denitrification is a crucial step for removing nitrogen on which the effect of Cu²⁺, a common heavy metal ion in wastewater, has not been studied. In this study, sludge with good short-range biological nitrogen removal characteristics in an A/O reactor was selected to investigate the short-term and long-term effects of Cu²⁺ on denitrification using NO₂^- as an electron acceptor. The results showed that Cu²⁺ had a significant inhibitory effect on denitrification process using NO₂^- as an electron acceptor, and the semi-inhibitory concentration EC₅₀ of sludge activity was 4.79 mg·L^-1. In the long-term experiment, the concentration of Cu²⁺ was gradually increased. When the concentration of Cu²⁺ was 0.5 mg·L^-1and 1 mg·L^-1, the denitrification activity of the sludge could be restored to the original level after acclimation. When the concentration of Cu²⁺ was increased to 3 mg·L^-1, the denitrification performance was destroyed and difficult to recover, at which point the NO₂^--N removal rate was reduced to less than 10% and the denitrification system was severely inhibited. However, there was some recovery of sludge denitrification capacity after the addition of Cu²⁺ had been stopped for 14 days. At the same time, during the long-term effect of Cu²⁺, the EPS content increased, which played an important role in protecting the microorganism against Cu²⁺ toxicity, and increased the sludge particle size and, as a result, sludge sedimentation.