Tan Siying, Jiang Shaojie, Li Xiaoyu, Yuan Qiuhong
School of Urban Construction and Environmental Engineering, Chongqing University, Chongqing 400044, People's Republic of China.
Chongqing Qingze Water Quality Analysis Co., Ltd, Chongqing 401331, People's Republic of China.
R Soc Open Sci. 2018 Aug 8;5(8):180025. doi: 10.1098/rsos.180025. eCollection 2018 Aug.
Poly(diallyldimethylammonium chloride) (polyDADMAC) has been shown to be an important precursor of the probable human carcinogen -nitrosodimethylamine (NDMA) when in contact with chloramine. In this study, we conducted an orthogonal experiment design to evaluate the effects of pH values, ammonia, bromide, natural organic matter (NOM) and monochloramine dosages on the formation of NDMA from polyDADMAC during chloramination. Meanwhile, single-factor experiments of pH, bromide and NOM prove the results of orthogonal experiment. The results supported that pH was the most critical factor affecting NDMA formation from polyDADMAC during chloramination, and the highest NDMA formation from polyDADMAC occurred at pH near 7 due to released DMA from polyDADMAC degradation and the critical importance of low concentrations of dichloramine in water. In the presence of excess bromide, the NDMA formation was enhanced significantly at all different pH values owing to bromochloramine, which has higher electronegativity of the brominated nitrogen atom than monochloramine or dichloramine. The NDMA formation from polyDADMAC in the presence of NOM was 41.7% lower than NDMA formation in the absence of NOM. The overwhelming majority of NDMA formation from polyDADMAC under simulated conditions was lower than the current advisory levels (i.e. 9 ng l in Ontario, 10 ng l in California).
聚二烯丙基二甲基氯化铵（polyDADMAC）已被证明，当与氯胺接触时，它是可能的人类致癌物——N-亚硝基二甲胺（NDMA）的重要前体。在本研究中，我们进行了正交试验设计，以评估pH值、氨、溴化物、天然有机物（NOM）和一氯胺剂量对氯胺化过程中polyDADMAC形成NDMA的影响。同时，pH、溴化物和NOM的单因素试验验证了正交试验的结果。结果表明，pH是氯胺化过程中影响polyDADMAC形成NDMA的最关键因素，由于polyDADMAC降解产生的二甲胺（DMA）以及水中低浓度二氯胺的至关重要性，polyDADMAC在pH接近7时形成的NDMA最多。在存在过量溴化物的情况下，由于溴氯胺的存在，在所有不同pH值下NDMA的形成均显著增强，溴氯胺中溴化氮原子的电负性高于一氯胺或二氯胺。在存在NOM的情况下，polyDADMAC形成的NDMA比不存在NOM时低41.7%。在模拟条件下，polyDADMAC形成的绝大多数NDMA低于当前的建议水平（即安大略省为9 ng/L，加利福尼亚州为10 ng/L）。
