三氯硝基甲烷在紫外/氯共同消毒过程中的生成与降解

Formation and degradation of trichloronitromethane of combined UV/chlorine disinfection

探讨了低压UV/氯共同消毒含聚二烯丙基二甲基氯化铵饮用水,对三氯硝基甲烷(TCNM)形成的影响.在低压汞灯照射条件下(λ=254 nm),考察了光照强度、自由氯浓度、·OH和p H以及聚二烯丙基二甲基氯化铵、二甲胺(DMA)和甲胺(MA)对TCNM形成和降解的影响,并研究了TCNM直接光降解,分析了其降解原因.实验结果表明:TCNM生成量随光照强度、自由氯浓度的增加而增加,随pH增加而降低;胺类物质分子结构越简单,越易生成TCNM;TCNM能直接光降解,但·OH在反应过程中不起主导作用.在这些实验条件下,UV/氯共同消毒可以改变含聚二烯丙基二甲基氯化铵水中的TCNM形成趋势,实验开始时间TCNM生成量显著增加,在5 min时其增幅超过了300%,然后TCNM的生成量显著减少,并且在30 min后几乎消失.该实验结论有助于形成新的TCNM控制策略,以减少TCNM在饮用水和污水处理过程中的产生.

This study＇s objective was to investigate the effect of lowpressure（ LP） UV（ Ultraviolet）treatment on the subsequent formation of trichloronitromethane（ TCNM） in drinking water containing Poly diallyl dimethyl ammonium chloride. The effects of light intensity,free chloride concentration,· OH,p H and Poly diallyl dimethyl ammonium chloride,dimethylamine（ DMA） and methylamine（ MA） on the formation and photodegradation of TCNMwere investigated under the irradiation of the lowpressure mercury lamp（ λ = 254 nm）. And the direct photodegradation of TCNMunder LP UV irradiation were studied for analyzing the formation and photodegradation reasons of TCNM. The results showed that the forming concentration of TCNMincreased with the increase of light intensity and the free chloride concentration,and decreased with the increase of p H. Amine molecular structure was more simple and more easy to generate TCNM. TCNMcould directly be photodegraded under LP UV irradiation,but · OH did not play a leading role in the reaction process. LP UV disinfection of chlorinated water did change the tendency to form TCNMunder the conditions of these tests. The evidence was found to have an obvious increase in the formation of TCNMin the first instance,furthermore the increase did exceed 300% after 5 min. Then,evidence was also found to have an obvious decrease in the formation of TCNM,and the concentration of TCNMdid hardly disappear after 30 min. The mechanistic understanding from this study can help develop source control strategies for minimization of TCNMformation risk for water and wastewater utilities.