重稀土元素钇对短程反硝化工艺的影响

Effect of heavy rare earth element yttrium on partial denitrification process

研究重稀土元素钇(Y(Ⅲ))对短程反硝化工艺的短期和长期影响.结果表明,1~50mg/L的Y(Ⅲ)对亚硝酸盐的积累量无明显影响,60~100mg/L的Y(Ⅲ)会影响硝酸盐的还原和亚硝酸盐的积累.1~10mg/L的Y(Ⅲ)对细菌活性呈现促进作用,20~100mg/L的Y(Ⅲ)对细菌活性呈现抑制作用.胞外吸附的Y(Ⅲ)是抑制细菌活性的主要因子,线性拟合的相关性系数R2为0.957,半抑制浓度IC50(吸附)为1.079mg/L(以湿重计),对应水中Y(Ⅲ)浓度为54.35mg/L.SEM显示,添加Y(Ⅲ)会使细菌产生更多的胞外聚合物(EPS)将细菌包裹以抵抗Y(Ⅲ)的毒性,EDS显示被包裹的细菌表面碳、氮元素含量大幅度降低,EPS影响了底物的传质.130d的长期实验表明,5mg/L的Y(Ⅲ)会使反应器的反硝化性能逐渐消失,停止添加稀土后,反应器的亚硝酸盐积累功能也不能恢复.

The short-term and long-term effects of heavy rare earth element Y(Ⅲ) on the partial denitrification process were studied respectively. The result showed that when the concentration of Y(Ⅲ) was 1~50 mg/L, the concentration of effluent nitrite did not change significantly. When the concentration of Y(Ⅲ) was 60~100 mg/L, the concentration of effluent nitrite decreased and the concentration of effluent nitrate increased. When the concentration of Y(Ⅲ) was 1~10 mg/L the bacterial activity was promoted;when the concentration of Y(Ⅲ) was 20~100 mg/L, the bacterial activity was inhibited. The Y(Ⅲ) of extracellular adsorption was the main factor that inhibits bacterial activity. The correlation coefficient R2 of linear fitting was 0.957, the half maximal inhibitory concentration IC50(adsorption) was 1.079 mg/L(based on wet weight), and the corresponding concentration of Y(Ⅲ) was 54.35 mg/L. SEM showed that the addition of Y(Ⅲ) made the bacteria produce more extracellular polymeric substance(EPS), and encapsulated the bacteria to resist the toxicity of Y(Ⅲ). EDS showed that the contents of C and N elements on the surface of the coated bacteria decreased significantly, and EPS affected the mass transfer of substrate. Long-term experiments of 130 days showed that 5 mg/L Y(Ⅲ) would cause the reactor to collapse. Even if the addition of rare earths was stopped, the nitrite accumulation function of the reactor couldnot be restored.