Occurrence and Formation of Disinfection By-Products in Indoor US Swimming Pools
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Chlorination is commonly used to prevent the spreading of waterborne infectious diseases in swimming pools. This required disinfection practice also results in the formation of undesirable disinfection by-products (DBPs) from the reactions of chlorine with the organic matter (released by swimmers or present in the pool filling water) and inorganics (i.e., bromide). The main objective of this research was to improve our understanding of the occurrence and formation of different classes of DBPs (trihalomethanes [THMs], haloacetic acids [HAAs], halonitromethanes [HNMs], haloacetonitriles [HANs], and nitrosamines) in indoor swimming pools operational conditions in the U.S.. The results showed that the DBPs in the investigated 23 swimming pools were far higher than the drinking water regulation values in the U.S. Average THMs, HAAs, HANs, HNMs, and N-nitrosodimethylamine concentrations were 80 μg/L, 1541 μg/L, 19 μg/L, 5.4 μg/L, and 27 ng/L, respectively. An increase in organic matter released by the swimmers and bromide (from the filling water or electrochemical generation of chlorine) levels in the water increased the overall formation of DBPs. Increases in free available chlorine, pH, and water temperature were shown to enhance the formation of THMs and HAAs. These favorable conditions lead to rapid formation (i.e. 3-6 hours) of THMs and HAAs under swimming pool conditions.