Sous-produits de chloration formés lors de la désinfection des eaux de piscines. Étude bibliographique

Disinfection by-products in swimming pool water. A literature review.

¹ Laboratoire de Chimie et Microbiologie de l'Eau, École Supérieure d'Ingénieurs de Poitiers, Université de Poitiers, 40 avenue du Recteur Pineau, 86022 Poitiers Cedex, France
² IANESCO, 6 rue Carol Heitz, BP 90974, 86038 Poitiers Cedex, France
³ CREATMOS, Pôle des Éco-industries en Poitou-Charentes, 3 rue Raoul Follereau, 86000 Poitiers Cedex, France

Résumé

Dans la première partie de cet article, une étude bibliographique présente les mécanismes de formation de sous-produits de chloration susceptibles de se former lors de la désinfection des eaux de piscines par réaction du chlore avec les principaux contaminants apportés par les baigneurs et en particulier avec les constituants majeurs de l'urée et de la sueur : ammoniaque, urée, créatinine, acides aminés… La seconde partie de l'article donne des exemples de valeurs de concentrations en sous-produits de chloration mesurées dans des eaux de piscines. Ces analyses montrent en particulier que les concentrations totales en sous-produits organohalogénés sont généralement comprises entre 500 et 1000 μg équivalent chlore par litre. Les sous-produits de chloration les plus abondants sont des composés de faible masse moléculaire apparente (< 1000 g.mol⁻¹), par ordre de concentrations décroissantes, les acides haloacétiques (acides di- et trichloraoacétique), l'hydrate de chloral, les trihalométhanes et les haloacétonitriles.

Abstract

Chlorine is routinely used to disinfect swimming pool water. Along with its disinfectant properties, free chlorine is a strong oxidant and it reacts with inorganic and organic substances present in pool water, and in particular with the materials introduced into the swimming pool by the bathers (urine, sweat, dander, soap residues…). The chlorine consumption of a pool water depends on the number of bathers and after a reaction time of 24 h, the chlorine demand has been estimated to be 10.5 ± 0.5 g of chlorine/bather. It is well-known that chlorination of swimming pool water leads to the formation of chloramines (referred as combined chlorine) and to trihalomethanes (THMs) which can have adverse health effects for swimmers and pool attendants. However, many other disinfection by-products (DBPs) can also be formed. In the first part of this paper, the pathways for the reaction of chlorine with the predominant nitrogenous compounds present in urine and sweat (ammonia, urea, creatinine, amino acids, amines…) have been reviewed. Concentrations of DBPs in real swimming pool waters have been reported in the second part of the paper.

Reactions of chlorine with ammonia, urea and creatinine lead to the formation of trichloramine as well as other by-products such as chloroureas from urea, chlorocreatinines, dimethylamine and formaldehyde from creatinine. Depending on the nature of the precursor and on the chlorine dose the reaction of chlorine with amino acids can yield N-chloramines and N,N-dichloramines, trichloramine, imines, chloroaldimines, chloroacetonitriles, aldehydes, chloral hydrate, cyanogen chloride and chloroform. Citric acid is a precursor for chloroform. Chlorination of dimethylamine can be a source for the formation of nitramine and nitrosodimethylamine. Chlorination of other materials of human origin (hair, skin and saliva) also produces DBPs.

Analyses of chlorinated swimming pool waters show that the concentrations of adsorbable organic halide (AOX) range between 500 and 1000 μg.L⁻¹. Membrane filtration fractionation shows that most of the DBPs are low molecular weight compounds (< 1000 g.mol⁻¹). The predominant DBPs which are present at concentrations higher than 10 μg.L⁻¹ are di and trichloroacetic acids, chloral hydrate, dichloroacetonitrile and chloroform. In the presence of bromide in water, brominated DBPs can be formed.

Volatile DBPs, such as trichloramine and trihalomethanes are also present in the atmosphere of indoor swimming pools. Trihalomethanes have also been detected in alveolar air, blood and urine of swimmers.