Occurrence and formation of disinfection by-products in indoor swimming pools water

Chlorination is used to prevent the spread of waterborne infectious diseases from 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 filling water of the pool) and bromide. The main objective of this research was to improve our understanding of the occurrence and formation of DBP classes: trihalomethanes (THMs), haloacetic acids (HAAs), and halonitromethanes (HNMs) under swimming pool operation conditions as practiced in the US and estimate their potential adverse health impacts on swimmers and lifeguards. During the occurrence study conducted during this research, the occurrence of N-nitrosodimethylamine (NDMA) and haloacetonitriles (HANs) were also investigated. Specifically, the objectives of the research were: (1) to examine the occurrence of the five DBPs in indoor swimming pools in the US, (2) to conduct a multi-pathway risk assessment on THMs and two HAAs of swimming pool water, (3) to determine the role and contribution of the two main precursors (i.e., filling water natural organic matter (NOM) vs. body fluids (BF) from swimmers) to the formation of THMs, HAAs), and HNMs in swimming pools, (4) to investigate the impacts of swimming pool operational parameters: free available chlorine (FAC), pH, bather load (TOC), water bromide content, and temperature on the formation and speciation of THMs, HAAs, and HNMs, and (5) to measure the formation of THMs and HAAs from the body fluids.;The occurrence of DBPs was investigated by collecting samples from 23 indoor pools in South Carolina, Georgia, and North Carolina. Furthermore, the occurrence of DBPs and their speciation in three indoor pools was examined periodically for nine months. Generally the DBPs in the investigated pools were far higher than the drinking water regulation values in the US or swimming pool regulations in other countries. Differences in swimming pool operation conditions and chlorination methods affected the amount, formation and speciation of the DBPs investigated in this study. The electrochemically generation of chlorine increased the brominated species.;Both the water and calculated air concentrations were used to estimate the potential lifetime cancer risk and non-cancer hazard index from swimming in the three indoor pools sampled along nine months. Results showed elevated lifetime cancer and non-cancer risks (hazard) from swimming in these pools. The lifetime cancer risk was higher than the acceptable risk level of 10 -6 by a factor of 10 to 10,000 in most cases. The hazard index exceeded the acceptable maximum hazard index ratio of 1 and reached a maximum of 26 at times.;To examine the contribution of different precursors in swimming pools, three DBPs formation potentials in swimming pool waters were examined using five filling waters obtained from five drinking water treatment plant effluents in South Carolina and three body fluid analogs (BFAs). The BFAs were mixtures prepared in the laboratory to simulate body fluids (mainly major components of urine and sweat) which are continuously excreted from swimmers into pool water. Reactivity of filling waters NOM and BFAs to form THMs, HAAs, and HNMs was tested under swimming pool conditions. The results showed that BFAs were more reactive with chlorine and exerted high demands as compared to filling waters NOM. BFAs exhibited higher formation potential of HAAs than THMs. An opposite trend was observed for filling water NOM which formed more THM than HAA.;The formation and speciation of THMs, HAAs and HNMs were also investigated under various disinfection and operation conditions typically used in US swimming pools. Increases in free available chlorine, pH, (bather load) TOC, water temperature, and bromide levels in the water increased the overall formation of DBPs. However these factors affected the different classes of DBPs at different magnitudes. Higher free available chlorine increased HAAs more than THMs. The temperature effect was greater on the formation of THMs than for HAAs whereas contact time increased HAAs more than THMs. The presence of bromide shifted the DBPs toward brominated species and increased overall THMs and HNMs more than HAAs.;The formation of THMs and HAAs from the body fluids during turnover time of swimming pool water, especially at short reaction times, was also studied. The results showed that DBP formations are fast reactions, and an appreciable percentage occurred in the first 3-6 hours which is about the typical turnover time for water in swimming pools. THM formation was faster than HAA formation. (Abstract shortened by UMI.)...