PAC对PDDA与一氯胺反应形成NDMA的影响

考察了聚合氯化铝(PAC)对聚二甲基二烯丙基氯化铵(PDDA)与一氯胺反应形成消毒副产物N-亚硝基二甲胺(NDMA)的影响。结果表明,在模拟微污染原水的氨氮含量条件下进行预氯氧化后,先加PAC后加PDDA、先加PDDA后加PAC、同时投加PAC和PDDA、投加PAC-PDDA这几种混凝剂投加方式测得NDMA生成质量浓度在30 ng/L左右,与未加PAC时生成NDMA的质量浓度22.80 ng/L相比,加入PAC后生成NDMA含量均稍有增加。各种投加方式下仅改变反应时间、温度、一氯胺或PDDA投加量与形成NDMA的量均不产生影响。在接近实际预氯氧化-复合混凝剂处理微污染原水的模式下,NDMA生成量与反应条件和投加PAC相关,但实质是受投加PAC引起体系pH改变的影响。

Effect of PAC on NDMA Formation in the Reaction of Polydimethyldiallyl Ammonium Chloride and Monochloramine

The effect of polyaluminium chloride (PAC) on the reaction of polydimethyldiallylammonium chloride (PDDA) with mono chloramine to form the disinfection by-product N-nitrosodimethylamine (NDMA) was investigated. The results showed that pre-chlorination and coagulation were carried out by using simulated tiny-polluted raw water only concerning the ammonia nitrogen content, and the NDMA (contents) generated under various PAC adding methods were as follows: adding PAC first and then PDDA, adding PDDA first and then PAC, adding PAC and PDDA parallel at the same time, and adding PAC/PDDA composite, the mass concentration of generated NDMA was about 30 ng/L, compared with the adding method (22.80 ng/L) without adding PAC, the NDMA content generated in each of four adding methods increased slightly. The change of the reaction time, temperature or monochloramine dosage had no effect on the amount of NDMA production. In the mode of treating the micro-polluted raw water by using prechlorination and composite coagulants, the produced amount of NDMA were not only concerning to the reaction conditions, but also concerning to added PAC which caused the change of pH in solutions.