Characterization and chlorine reactivity of particulate matter released by bathers in indoor swimming pools

Disinfecting swimming pool water is essential for preventing waterborne diseases. An unforeseen consequence of treating water with disinfectants is the formation of disinfection by-products (DPBs) that can cause harmful effects to health through the interactions between the added disinfectant and organic matter in the water. The present work focuses on the chlorine reactivity with particles released by bathers. Such particles are collected in the filter backwash water of swimming pools and this study intends to distinguish DPBs generated from dissolved chemicals from those formed by particulate matter. Therefore, filtered and unfiltered backwash waters were collected from several swimming pools, analysed physicochemically and chemically, and then chlorinated as is (79 mgL-1) and as diluted suspensions (36.2 and 11.9 mgL-1) at varying concentrations of chlorine (1.2 mg and 24 mgCl2L-1). Utilizing a DPD colorimetric technique and GC-ECD, respectively, the kinetics of chlorine con-sumption and DPBs production have been investigated. Up to 25.7 IgL-1 of chloroform was produced within 96 h at 1.2 mgCl2L-1, followed by haloacetic acids (HAAs) and haloacetonitriles (HANs). Within 96 h, the con-centration of trichloroacetic acid reached a maximum of 231.8 IgL-1 at a chlorine concentration of 231.8 IgL- 1. The formations of 0.13 Imol THMs, 0.31 Imol HAAs, and 0.04 Imol HANs per mg of dissolved organic carbon (DOC) were finally determined by correlating the organic content of particles with the nature of the DBPs generated. Comparing the quantities of DBPs generated in filtered and unfiltered samples helps us conclude that-50% of DBPs formed during the chlorination of swimming pool water are derived from particles brought by bathers.

Automated summary

Disinfecting swimming pool water is crucial for preventing waterborne diseases, although it can lead to the formation of disinfection by-products (DBPs), which can have harmful health effects. This study focuses on the reaction between chlorine and particles released by bathers in swimming pools. Filtered and unfiltered backwash waters from multiple swimming pools were collected and analyzed, and their reactions with varying concentrations of chlorine were examined. The results showed that a significant amount of DBPs, such as chloroform, haloacetic acids (HAAs), and haloacetonitriles (HANs), were generated during the chlorination process, with approximately 50% of them being derived from particles brought by bathers.