Production of various disinfection byproducts in indoor swimming pool waters treated with different disinfection methods

In this study, the concentrations of disinfection byproducts (DBPs), including trihalomethanes (THMs; chloroform, bromodichloromethane, dibromochloromethane, and bromoform), haloacetic acids (HAAs; dichloroacetic acid and trichloroacetic acid), haloacetonitriles (HANs; dichloroacetonitrile, trichloroacetonitrile, bromochloroacetonitrile, and dibromoacetonitrile), and chloral hydrate (CH) were measured in 86 indoor swimming pools in Seoul, Korea, treated using different disinfection methods, such as chlorine, ozone and chlorine, and a technique that uses electrochemically generated mixed oxidants (EGMOs). The correlations between DBPs and other environmental factors such as with total organic carbon (TOC), KMnO4 consumption, free residual chlorine, pH, and nitrate (NO3−) in the pools were examined. The geometric mean concentrations of total DBPs in swimming pool waters were 183.1 ± 2.5 μg/L, 32.6 ± 2.1 μg/L, and 139.9 ± 2.4 μg/L in pools disinfected with chlorine, ozone/chlorine, and EGMO, respectively. The mean concentrations of total THMs (TTHMs), total HAAs (THAAs), total HANs (THANs), and CH differed significantly depending on the disinfection method used (P < 0.01). Interestingly, THAAs concentrations were the highest, followed by TTHMs, CH, and THANs in all swimming pools regardless of disinfection method. TOC showed a good correlation with the concentrations of DBPs in all swimming pools (chlorine; r = 0.82, P < 0.01; ozone/chlorine; r = 0.52, P < 0.01, EGMO; r = 0.39, P < 0.05). In addition, nitrate was positively correlated with the concentrations of total DBPs in swimming pools disinfected with chlorine and ozone/chlorine (chlorine; r = 0.58; ozone/chlorine; r = 0.60, P < 0.01), whereas was negative correlated with the concentrations of total DBPs (r = −0.53, P < 0.01) in the EGMO-treated pools.