Trihalomethane Levels in Swimming Pool Waters and Removal of Trihalomethanes Using Modified Membrane Systems

Swimming pool waters may contain carcinogenic disinfection by-products formed by the reaction of chlorine and its compounds—added for disinfection purposes—with organic substances either present in the source water or introduced through swimming activities. Trihalomethanes (THMs) are among the most common of these by-products. In this study, the levels of THMs in the water of an indoor swimming pool located in the Selçuklu district of Konya were investigated, along with the efficiency of removing these compounds using modified ultrafiltration systems. For this purpose, water samples ranging from 80 to 100 L were collected weekly for 8 weeks following the morning swimming sessions. The samples were analyzed for free chlorine, combined chlorine, pH, THMs, Total Organic Carbon (TOC), and Total Inorganic Carbon (TIC). The water was then filtered through a pilot-scale ultrafiltration system with a pre-treatment unit consisting of mixed-bed activated carbon and zeolite. Post-filtration, THM and TOC analyses were performed and the results were compared to those of unfiltered pool water. Additionally, samples were taken from the municipal tap water supplying the pool, and analyzed for free chlorine, combined chlorine, pH, THMs, TOC, and TIC. The study found that the modified ultrafiltration system achieved a 93% removal rate of THMs, with an average initial concentration of 257 μg/L in the pool water. Since the TOC level was measured below the device's detection limit of 2.26 mg/L after treatment, a removal percentage could not be stated. Furthermore, a significant correlation was identified between THM formation and both pH level and combined chlorine concentration of the water.