| Benzalkonium chlorides（BACs）is a common bactericidal disinfectant.The main ingredient,dodecyldimethylbenzylammonium chloride（DDBAC）,has been frequently detected in municipal wastewater treatment plants and environmental water bodies,which caused potential risks on ecology.DDBAC was taken as the research object in this paper.Firstly,the effects of DDBAC on activity of activated sludge were studied in a short-term exposure.Secondly,the long-term exposure effects of DDBAC in biological nitrogen removal were investigated.Finally,the migration transformation of DDBAC on the wastewater biological treatment process was evaluated.The main conclusions are as follows:1)Short-term exposure experiment has proved that DDBAC could affect the oxygen consumption rate of sludge,and inhibit the respiration of sludge by reducing the activities of TCC-dehydrogenase and catalase.In addition,the exposure of DDBAC could inhibit the nitrification process,especially the ammonia-oxidizing process dominated by ammonia-oxidizing bacteria.When DDBAC concentration≥2.0 mg·L-1,the transformation of NH4+-N could be inhibited,and the higher the concentration,the more obvious the inhibition effect.2)The presence of DDBAC(5 mg·L-1)decreased total nitrogen removal efficiency from（95.80±0.54）%to（84.70±3.10）%.It was also observed that DDBAC(5 mg·L-1)changed the microbial community diversity,inhibited the enzyme activities of nitrite oxidoreductase,and reduced the relative abundance of Nitrospira in the biological community,which were closely relevant to the inhibition of the conversion of nitrite to nitrate during the nitrification process.3)DDBAC was mainly removed by biodegradation during aerobic condition,which was dominated by particular species（Pseudomonas）.Benzyl dimethyl amine（BDMA）and Benzyl methyl amine（BMA）were the main biodegradation products.The formation of BDMA was generated by the Calkyl-N cleavage and the formation of BMA was due to degradation of BDMA by demethylation. |
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