Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, CH-8092 Zürich, Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland.
Water Res. 2015 Mar 15;71:318-29. doi: 10.1016/j.watres.2014.12.014. Epub 2015 Jan 2.
Trichloramine is a hazardous disinfection by-product that is of particular relevance in indoor swimming pools. To better understand its fate in pool waters, apparent second order rate constants (kapp) at pH 7 for its reaction with several model compounds were determined. kapp values at pH 7 for nitrogenous compounds were found to increase in the following order: ammonia ∼ amides (∼10(-2)-10(-1) M(-1) s(-1)) < primary amines (∼10(-1)-10(0) M(-1) s(-1)) < relevant body fluid compounds (l-histidine, creatinine) (∼10(0)-10(1) M(-1) s(-1)) < secondary amines (∼10(1)-10(2) M(-1) s(-1)) < trimethylamine (∼10(3) M(-1) s(-1)). kapp values at pH 7 of trichloramine with hydroxylated aromatic compounds (∼10(2)-10(5) M(-1) s(-1)) are higher than for the nitrogenous compounds and depend on the number and position of the hydroxyl groups (phenol < hydroquinone < catechol < resorcinol). The measurement of kapp as a function of pH revealed that mainly the deprotonated species react with trichloramine. The reaction of trichloramine with Suwannee River and Pony Lake fulvic acid standards showed a decrease of their reactivity upon chlorination, which can be related to the electron donating capacity and the SUVA254. Chlorinated nitrogenous compounds (e.g. uric acid) also have a reduced reactivity with trichloramine. Hence, the residual chlorine in pool water hinders a fast consumption of trichloramine. This explains why trichloramine degradation in pool water is lower than expected from the reactivity with the estimated bather input. Trichloramine also has the potential to form secondary disinfection by-products such as chlorinated aromatic compounds or chloroform by electron transfer or Cl(+)-transfer reactions. The chloroform formation from the reaction of trichloramine with resorcinol occurs with a similar yield and rate as for chlorination of resorcinol. Since the trichloramine concentration in pool water is commonly about one order of magnitude lower than the free chlorine concentration, its contribution to the disinfection by-product formation is assumed to be minor in most cases but might be relevant for few precursors (e.g. phenols) that react faster with trichloramine than with free chlorine.
三氯胺是一种有害的消毒副产物，在室内游泳池中尤为相关。为了更好地了解其在泳池水中的命运，在 pH7 下测定了其与几种模型化合物反应的表观二级速率常数（kapp）。在 pH7 下，含氮化合物的 kapp 值按以下顺序增加：氨酰胺（10^(-2)-10^(-1) M^(-1) s^(-1)）<伯胺（10^(-1)-10^0 M^(-1) s^(-1)）<相关体液化合物（l-组氨酸、肌酸）（10^0-10^1 M^(-1) s^(-1)）<仲胺（10^1-10^2 M^(-1) s^(-1)）<三甲胺（10^3 M^(-1) s^(-1)）。三氯胺与羟基化芳香化合物（~10^2-10^5 M^(-1) s^(-1)）在 pH7 下的 kapp 值高于含氮化合物，并且取决于羟基的数量和位置（苯酚<对苯二酚<邻苯二酚<间苯二酚）。作为 pH 函数的 kapp 值的测量表明，主要是去质子化的物种与三氯胺反应。三氯胺与苏万尼河和小马湖腐殖酸标准品的反应表明，在氯化过程中它们的反应性降低，这可以与电子供体能力和 SUVA254 相关。氯化含氮化合物（如尿酸）与三氯胺的反应性也降低。因此，泳池水中的余氯会阻碍三氯胺的快速消耗。这解释了为什么泳池水中三氯胺的降解低于根据估计的入浴者输入与三氯胺反应的预期。三氯胺也有可能通过电子转移或 Cl(+)-转移反应形成氯化芳香化合物或氯仿等二次消毒副产物。三氯胺与间苯二酚反应生成氯仿的产率和速率与间苯二酚氯化相似。由于泳池水中三氯胺的浓度通常比游离氯浓度低一个数量级，因此其对消毒副产物形成的贡献在大多数情况下较小，但对于一些与三氯胺反应比与游离氯反应更快的前体（如苯酚）可能很重要。
