Environmental Analytical Chemistry, Center for Applied Geoscience (ZAG), Eberhard Karls University Tuebingen, 72076 Tuebingen, Germany.
Water Res. 2011 Apr;45(8):2681-90. doi: 10.1016/j.watres.2011.02.024. Epub 2011 Mar 1.
Trichloramine is a volatile, irritant compound of penetrating odor, which is found as a disinfection by-product in the air of chlorinated indoor swimming pools from reactions of nitrogenous compounds with chlorine. Acid amides, especially urea, ammonium ions and α-amino acids have been found as most efficient trichloramine precursors at acidic and neutral pH. For urea a relative NCl(3) formation of 96% at pH 2.5 and 76% at pH 7.1 was determined. Even under sub-stoichiometric molar ratios of Cl/N the formation of NCl(3) is favored over mono and dichlorinated products. However, the reaction kinetics of urea with chlorine is slow under conditions relevant for swimming pools. Also the mass transfer of NCl(3) from water to the gas phase which was calculated by the Deacon's boundary layer model could be shown as a relatively slow process. Mass transfer would take 20 h or 5.8 d for a rough or a quiescent surface of the water, respectively. This is much more than a typical turnover rate of 6-8 h of a treatment cycle of a 25 m swimming pool. Therefore processes to remove NCl(3) and its precursors can help to minimize the exposure of bathers.
三氯胺是一种挥发性、刺激性的穿透性气味化合物，在含氯室内游泳池的空气中作为一种消毒副产物被发现，它是由氮化合物与氯反应产生的。在酸性和中性 pH 值条件下，已发现酰胺酸，特别是尿素、铵离子和α-氨基酸是最有效的三氯胺前体。在 pH 值为 2.5 时，尿素的相对 NCl(3)生成率为 96%，在 pH 值为 7.1 时为 76%。即使在氯与氮的亚化学计量摩尔比下，NCl(3)的形成也优先于一氯和二氯化产物。然而，在与游泳池相关的条件下，尿素与氯的反应动力学较慢。此外，通过 Deacon 的边界层模型计算出的 NCl(3)从水到气相的传质也可以被证明是一个相对较慢的过程。对于粗糙或静止的水面，传质分别需要 20 小时或 5.8 天。这远远超过了 25 米游泳池处理周期 6-8 小时的典型周转率。因此，去除 NCl(3)及其前体的过程有助于最大限度地减少游泳者的暴露。
