Cr(Ⅵ)对活性污泥系统反硝化过程的影响

Effects of hexavalent chromium on denitrification process of activated sludge system

采用反硝化反应器,研究了Cr(Ⅵ)对活性污泥系统反硝化过程的影响。在进水Cr(Ⅵ)投加量2.5 mg/L条件下,活性污泥反硝化过程中COD和硝酸盐氮的去除率受到的影响较小,而在10.0 mg/L条件下受到的影响较大,COD和硝酸盐氮的去除率分别从最初的97.1%和99.0%降至70.6%和24.7%。在停止投加Cr(Ⅵ)后的恢复期内,反硝化系统可以逐渐恢复对COD和硝酸盐氮的去除,亚硝酸盐氮仍会有积累,但随着时间的延长可恢复至初始状态。硝酸盐氮还原为亚硝酸盐氮的过程比亚硝酸盐氮的还原过程更易受到Cr(Ⅵ)的影响。

The effects of Cr(Ⅵ)on denitrification process of activated sludge system were investigated in a denitrification reactor.The removal rate of COD and nitrate nitrogen in the denitrification process was less affected under the condition of influent Cr(Ⅵ)addition 2.5 mg/L,but was more affected and reduced from 97.1%and 99.0%to 70.6%and 24.7%respectively when the influent Cr(Ⅵ)addition was 10.0 mg/L.During the recovery period without Cr(Ⅵ)addition,the removal of COD and nitrate nitrogen in the denitrification system can gradually restored,while the accumulation of nitrite nitrogen still happened in the middle of the recovery period,but it could return to the initial level with the extension of time.The reduction process of nitrate nitrogen to nitrite nitrogen was more susceptible to Cr(Ⅵ)than that of nitrite nitrogen.