两种预氧化法与氯胺消毒联用对polyamlne形成NDMA的影响

预氧化处理与有机高分子絮凝剂联用会使含氮消毒副产物亚硝基二甲胺(NDMA)质量浓度上升,典型水处理工艺条件下NDMA的质量浓度为60～100 ng/L,为了解不同因素的影响及其反应机理,研究次氯酸钠氯化预氧化及高锰酸钾预氧化与聚环氧氯丙烷二甲胺(polyamine)在不同条件下联用并用氯胺消毒后NDMA的生成量.结果表明:随着预氧化剂投加量、pH、polyamine投加量及Br-质量浓度的增加,NDMA的生成量也相应增加;低质量浓度NH_4~+会导致NDMA生成量增加17. 5%左右,但随质量浓度增加,NDMA生成量逐渐减少至初始水平;随着NO_2~-质量浓度增加,NDMA生成量显著减少,当NO_2~-的质量浓度达到10 mg/L时,NDMA的生成量为最初的15%左右;氯化预氧化过程符合UDMH机理,而高锰酸钾预氧化过程包含UDMH机理及羟基自由基机理.

Effect of two preoxidation methods with chloramine disinfection on NDMA formation from polyamine

The combined use of preoxidation treatment and organic polymer flocculant can increase the concentration of nitroso-dimethylamine (NDMA), a nitrogen-containing disinfection by-product. The concentration of NDMA is about 60-100 ng/L under typical water treatment process. In order to understand the influence of different factors and the reaction mechanism, the amounts of NDMA produced after the polyamine reacted with sodium hypochlorite or potassium permanganate under different conditions and chloramine disinfection were studied. The results showed that with the increase of the amount of preoxidant, pH, polyamine, and Br^- concentration, NDMA production increased correspondingly. Low concentration of NH+₄ could lead to an increase of up to 17.5% in NDMA production, but it gradually decreased to initial level with increased concentration. With the increase of NO-₂ concentration, NDMA production decreased significantly. When the concentration of NO-₂ reached 10 mg/L, the amount of NDMA production was about 15% of the initial level. The preoxidation process of chlorination conforms to the UDMH mechanism, while the preoxidation process of potassium permanganate involves the UDMH mechanism and hydroxyl radical mechanism.