Date of Award
Doctor of Philosophy (PhD)
Environmental Engineering and Earth Science
Lee , Cindy
Freedman , David
Carraway , Elizabeth
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. Some of these DBPs have important adverse public health effects; as a result their concentrations in drinking waters are regulated. Unfortunately, DBPs formation and control in swimming pools have not been studied and investigated to the same extent as their formation and control in drinking water.
The main objective of this research was to improve our understanding of the occurrence and formation of DBP classes: trihalomethanes (THMs) [Trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM)], haloacetic acids (HAAs) [chloroacetic acid (CAA), bromoacetic acid (BAA), dichloroacetic acid (DCAA), bromochloroacetic acid (BCAA), trichloroacetic acid (TCAA), bromodichloroacetic acid (BDCAA), dibromoacetic acid (DBAA), dibromochloroacetic acid (DBCAA), and tribromoacetic acid (TBAA), and halonitromethanes (HNMs) [chloronitromethane (CNM), dichloronitromethane (DCNM), trichloronitromethane (TCNM), bromonitromethane (BNM), bromochloronitromethane (BCNM), bromodichoronitromethane (BDCNM), dibromonitromethane (DBNM), dibromochloronitromethane (DBCNM), and tribromonitromethane (TBNM)] 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) [chloroacetonitrile (CAN), trichloroacetonitrile (TCAN), dichloroacetonitrile (DCAN), bromoacetonitrile (BAN), bromochloroacetonitrile (BCAN), and dibromoacetonitrile (DBAN)] were also investigated. Specifically, the objectives of the research were: (1) to examine the occurrence of the five DBPs (THMs, HAAs, HNMs, NDMA, and HANs) in indoor swimming pools in the US, (2) to conduct a multi-pathway risk assessment on THMs (TCM, BDCM, DBCM) and two HAAs (DCAA and TCAA) 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 during turnover time, 'the period of time (usually hours) required to circulate the complete volume of water in a pool through the recirculation system' of swimming pool water.
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. THMs ranged between 26 and 213 µg/L with an average of 80 µg/L. HANs range between 5 and 53 µg/L with an average of 19 µg/L. HNMs ranged between 1.4 and 13.3 µg/L with an average of 5.4 µg/L. The HAAs ranged between 173 and 9005 µg/L with an average of 1541 µg/L. The NDMA ranged between 2 and 83 ng/L with an average of 26.5 ng/L. 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 of TCM, BDCM, DBCM, DCAA, and TCAA 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 (THMs, HAAs, and HNMs) 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. There was no appreciable difference in HNM formation from BFAs and filling water NOM. The effect of temperature was greater on THM formation, while the effect of contact time affected HAAs more. Experiments with filling waters collected at different times showed that there was less variability in THM than HAA formation from the water treatment plant effluents studied in this project.
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. From 53 to 68% of 5-day THMs were formed within the first 3-6 hours while 15 to 30% of 5-day HAAs were formed at the first 6 hours. These fast formation rates imply that DBP control strategies in swimming pools should mainly focus on DBPs precursors control at the source (i.e., swimmers). Some additional benefit may also be obtained for DBPs control by controlling some of the operational parameters (pH, free available chlorine, bather load -the number of individuals using a pool in a 24 hour period- or dilution).
Kanan, Amer, "OCCURRENCE AND FORMATION OF DISINFECTION BY-PRODUCTS IN INDOOR SWIMMING POOLS WATER" (2010). All Dissertations. 532.