Quantification of continual anthropogenic pollutants released in swimming pools

Electro-oxidation and UV irradiation coupled method for in-site removing pollutants from human body fluids in swimming pool

A comprehensive study was conducted to investigate how ultraviolet (UV) irradiation combined with electrochemistry (EC) can efficiently remove human body fluids (HBFs) related pollutants, such as urea/creatinine/hippuric acid, from swimming pool water (SPW). In comparison with the chlorination, UV, EC, and UV/chlorine treatments, the EC/UV treatment exhibited the highest removal rates for these typical pollutants (TPs) from HBFs in synthetic SPW. Specifically, increasing the operating current of the EC/UV process from 20 to 60 mA, as well as NaCl content from 0.5 to 3.0 g/L, improved urea and creatinine degradation while having no influence on hippuric acid. In contrast, EC/UV process was resilient to changes in water parameters (pH, HCO3-, and actual water matrix). Urea removal was primarily attributable to reactive chlorine species (RCS), whereas creatinine and hippuric acid removal were primarily related to hydroxyl radical, UV photolysis, and RCS. In addition, the EC/UV procedure can lessen the propensity for creatinine and hippuric acid to generate disinfection by-products. We can therefore draw the conclusion that the EC/UV process is a green and efficient in-situ technology for removing HBFs related TPs from SPW with the benefits of needless chlorine-based chemical additive, easy operation, continuous disinfection efficiency, and fewer byproducts production.

Review on the management of water quality for bio-mineral swimming pools in Western Europe

In this review, we depict the state of the art concerning the water quality management of bio-mineral bathing pools, and compare these to traditional swimming pools. Bio-mineral pools use a combination of mechanic filtration, bio-filtration, and UV-treatment to disinfect the water. Studies in test tanks have shown that bio-filtration is effective in maintaining the water quality with regard to the treatment of organic pollution. Concerning biological risks, the bio-mineral pool relies on UV-treatment to degrade bacteria. Unlike chemical disinfectant treatments, UV disinfection does not lose its effectiveness in the event of high traffic in the pool. However, as only the water taken up by the filtration system is disinfected, it is essential that all the water in the pool is filtered. If the pool has a dead zone, its water is not disinfected and there is a risk of localized pathogen development. As the development of bio-mineral pools spreads in Europe, legislation gradually follows. The health parameters measured differ slightly from one country to another, but there are constants: the measurement of Escherichia coli, Enterococci, and Pseudomonas aeruginosa. In terms of biological swimming pools, regulatory homogeneity across Europe does not exist. From these comparisons, Austrian legislation segmenting water quality into 4 categories ranging from "excellent" to "poor" represents legislation that combines health and safety with indications of possible malfunctions. Next, a study of three real sites of bio-mineral pools is presented. It appears that whatever the type of pool, bio-mineral filtration makes it possible to achieve performances comparable to those encountered in chlorinated swimming pools concerning the risks associated with fecal contamination and external pollution. On the other hand, when frequentation is high, as is the case in small pools used for aquafitness, monitoring the risks of inter-bather contamination, as illustrated by the presence of Staphylococcus aureus, reveals a recurring problem. Knowing that this parameter is not evaluated in bathing waters in the natural environment and that numerous studies show that Staphyloccocus aureus are always detected, even on beaches, we propose the definition of three thresholds: i.e., 0 CFU/100 mL (threshold value in Wallonia) for water of excellent quality, less than 20 CFU/100 mL (threshold value in France) for water of very good quality, less than 50 CFU/100 mL (contribution of bathers by simple immersion) for good quality water, and more than 50 CFU/100 mL for poor quality water. This document could therefore be converted into a manual for operators on the use and management of bio-mineral baths.

Advances and research needs for disinfection byproducts control strategies in swimming pools

The control of disinfection byproducts (DBPs) in swimming pools is of great significance due to the non-negligible toxicity and widespread existence of DBPs. However, the management of DBPs remains challenging as the removal and regulation of DBPs is a multifactorial phenomenon in pools. This study summarized recent studies on the removal and regulation of DBPs, and further proposed some research needs. Specifically, the removal of DBPs was divided into the direct removal of the generated DBPs and the indirect removal by inhibiting DBP formation. Inhibiting DBP formation seems to be the more effective and economically practical strategy, which can be achieved mainly by reducing precursors, improving disinfection technology, and optimizing water quality parameters. Alternative disinfection technologies to chlorine disinfection have attracted increasing attention, while their applicability in pools requires further investigation. The regulation of DBPs was discussed in terms of improving the standards on DBPs and their preccursors. The development of online monitoring technology for DBPs is essential for implementing the standard. Overall, this study makes a significant contribution to the control of DBPs in pool water by updating the latest research advances and providing detailed perspectives.

Modelling chloroform in indoor swimming pool air and water: the influences of internal air circulation and occupants

The release of chloroform from water to air in an indoor swimming pool (ISP) exhibits complex physicochemical interactions among many variables, including environmental conditions, occupant activities, and geometry of the ISP. By combining the relevant variables, a structured mathematical model, the double-layer air compartment (DLAC) model, was developed to predict the level of chloroform in ISP air. A physical parameter, the indoor airflow recycle ratio (R), was incorporated into the DLAC model due to internal airflow circulation resulting in the ISP structural configuration. The theoretical R-value for a specific indoor airflow rate (v_y) can be found by fitting the predicted residence time distribution (RTD) to the simulated RTD from computational fluid dynamics (CFD), showing a positive linear relationship with v_y. The mechanical energies induced by occupant activities were converted into a lumped overall mass-transfer coefficient to account for the enhanced mass transfer of chloroform from the water into the air and mixing in ISP air. The DLAC model predicted that chloroform air concentrations were statistically less accurate without considering the influence of R compared with the online open-path Fourier transform infrared measurements. A novel index, the magnitude of emission (MOE) from swimmers, was linked to the level of chloroform in ISP water. The capability of the DLAC model associated with the MOE concept may facilitate upgrading the hygiene management of ISPs, including the ability to administer necessary chlorine additives in pool water and monitor the chloroform in ISP air.

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 consumption and DPBs production have been investigated. Up to 25.7 μgL^-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 concentration of trichloroacetic acid reached a maximum of 231.8 μgL^-1 at a chlorine concentration of 231.8 μgL^-1. The formations of 0.13 μmol THMs, 0.31 μmol HAAs, and 0.04 μmol 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.

Occurrence of brominated disinfection by-products in thermal spas

Thermal spas are gaining more and more popularity among the population because they are used for recreational purposes. Disinfecting these baths without losing the health benefits poses a challenge for swimming pool operators. Previous studies have mainly focused on regulated chlorinated DBPs in freshwater pools with no bromide or seawater pools with very high bromide content. Thermal water pools have a low bromide content and in combination with chlorine can lead to chlorinated, brominated and mixed halogenated DBP species. The occurrence of brominated and mixed halogenated DBPs in these types of pools is largely unexplored, with very few or limited studies published on regulated DBPs and even fewer on emerging DBP classes. In the field of swimming pool water disinfection, apart from extensive studies in the field of drinking water disinfection, only a few studies are known in which >39 halogenated and 16 non-halogenated disinfection by-products, including regulated trihalomethanes (THM) and haloacetic acids (HAA), were investigated in swimming pool water. Calculated bromine incorporation factor (BIF) demonstrated that even small amounts of bromide in swimming pool water can lead to a large shift in DBP species towards brominated and mixed halogenated DBPs. Dihaloacetonitriles (DHANs) accounted for >50% of the calculated cytotoxicity and genotoxicity on average. Comparison of the target analysis with the TOX showed that a major part of the measured TOX (69% on average) could be explained by the regulated classes THMs, HAAs, and the unregulated class of HANs. This study aims to help operators of swimming pools with bromide-containing water to gain a better understanding of DBP formation in future monitoring and to fill the knowledge gap that has existed so far on the occurrence of DBPs in thermal water pools.

Occurrence of Disinfection By-Products in Swimming Pools in the Area of Thessaloniki, Northern Greece. Assessment of Multi-Pathway Exposure and Risk

This study investigated the occurrence of disinfection by-products (DBPs) (trihalomethanes (THMs), haloacetic acids (HAAs), halonitriles (HANs), halonitromethane (TCNM) and haloketones (HKs)) in different type of swimming pools in the area of Thessaloniki, northern Greece by employing the EPA methods 551.1 and 552.3. Moreover, general water quality parameters (pH, residual chlorine, dissolved organic carbon, UV₂₅₄ absorption, total nitrogen, alkalinity and conductivity) were also measured. The concentrations of DBPs showed great variability among swimming pools as well as within the same pool between sampling campaigns. HAAs exhibited the highest concentrations followed by THMs, HANs, TCNM and HKs. Exposure doses for four age groups (3–<6 y, 6–<11 y, 11–<16 y and adults) were calculated. Route-specific exposures varied among DBPs groups. Inhalation was the dominant exposure route to THMs and TCNM (up to 92–95%). Ingestion and dermal absorption were the main exposure routes to HAAs (40–82% and 18–59%, respectively), depending on the age of swimmers. HANs contributed up to 75% to the calculated cytotoxicity of pool water. Hazard indices for different exposure routes were <1, suggesting non-carcinogenic risk. Inhalation posed the higher carcinogenic risk for THMs, whereas risk via oral and dermal routes was low. Ingestion and dermal contact posed the higher risk for HAAs. Risk management strategies that minimise DBPs exposure without compromising disinfection efficiency in swimming pools are necessary.

Dissemination of antibiotic resistance genes in swimming pools and implication for human skin

Swimming pools are crowd-gathering places that are associated with numerous outbreaks of water-borne diseases. Herein, we investigated the distribution of antibiotic resistance genes (ARGs) and bacterial communities in swimming pools and determined the influencing factors and potential human exposure. Sixteen swimming pools with different bather loads (0.01-0.16 person/m²·h) were investigated. Water samples were collected, before opening and after closing of the facilities, from six swimming pools, and skin samples were collected from volunteers. Comprehensive approaches, high-throughput qPCR and 16S rRNA gene sequencing, were used. The results showed that swimming pools contained a higher relative abundance (0.62 gene copies/16S rRNA) and absolute abundance (6.57×10⁸ gene copies/L) of ARGs on average. Bather loads contributed to the increase of core ARGs, and the absolute abundance of ARGs significantly increased by 1.47-1.94 orders of magnitude when the bather load was more than 0.1 person/m²·h. Dermal contact was estimated as the main exposure route of ARGs. Eighteen ARGs that were not detected before swimming were found on human skin and remained after showering. Furthermore, the event intake burden of ARGs via dermal contact was higher than that via ingestion when swimming. This study provides an assessment of ARGs and antibiotic-resistant bacteria (ARB) in swimming pools and helps to define the health risks to swimmers.

Health effects of exposure to chlorination by-products in swimming pools

Concerns have been raised regarding the potential negative effects on human health of water disinfectants used in swimming pools. Among the disinfection options, the approaches using chlorine-based products have been typically preferred. Chlorine readily reacts with natural organic matter that are introduced in the water mainly through the bathers, leading to the formation of potentially harmful chlorination by-products (CBPs). The formation of CBPs is of particular concern since some have been epidemiologically associated with the development of various clinical manifestations. The higher the concentration of volatile CBPs in the water, the higher their concentration in the air above the pool, and different routes of exposure to chemicals in swimming pools (water ingestion, skin absorption, and inhalation) contribute to the individual exposome. Some CBPs may affect the respiratory and skin health of those who stay indoor for long periods, such as swimming instructors, pool staff, and competitive swimmers. Whether those who use chlorinated pools as customers, particularly children, may also be affected has been a matter of debate. In this article, we discuss the current evidence regarding the health effects of both acute and chronic exposures in different populations (work-related exposures, intensive sports, and recreational attendance) and identify the main recommendations and unmet needs for research in this area.

Making Swimming Pools Safer: Does Copper-Silver Ionization with Chlorine Lower the Toxicity and Disinfection Byproduct Formation?

Swimming pools are commonly treated with chlorine, which reacts with the natural organic matter and organic matter introduced by swimmers and form disinfection byproducts (DBPs) that are associated with respiratory-related issues, including asthma, in avid swimmers. We investigated a complementary disinfectant to chlorine, copper-silver ionization (CSI), with the aim of lowering the amount of chlorine used in pools and limiting health risks from DBPs. We sampled an indoor and outdoor pool treated with CSI-chlorine during the swimming season in 2017-2018 and measured 71 DBPs, speciated total organic halogen, in vitro mammalian cell cytotoxicity, and N-acetyl-l-cysteine (NAC) thiol reactivity as a cytotoxicity predictor. Controlled, simulated swimming pools were also investigated. Emerging DBP concentrations decreased by as much as 80% and cytotoxicity decreased as much as 70% in the indoor pool when a lower chlorine residual (1.0 mg/L) and CSI was used. Some DBPs were quantified for the first time in pools, including chloroacetaldehyde (up to 10.6 μg/L), the most cytotoxic haloacetaldehyde studied to date and a major driver of the measured cytotoxicity in this study. Three highly toxic iodinated haloacetic acids (iodoacetic acid, bromoiodoacetic acid, and chloroiodoacetic acid) were also quantified in pools for the first time. We also found that the NAC thiol reactivity was significantly correlated to cytotoxicity, which could be useful for predicting the cytotoxicity of swimming pool waters in future studies.

A critical review on the detection, occurrence, fate, toxicity, and removal of cannabinoids in the water system and the environment

Cannabinoids are a group of organic compounds found in cannabis. Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD), the two major constituents of cannabinoids, and their metabolites are contaminants of emerging concern due to the limited information on their environmental impacts. As well, their releases to the water systems and environment are expected to increase due to recent legalization. Solid-phase extraction is the most common technique for the extraction and pre-concentration of cannabinoids in water samples as well as a clean-up step after the extraction of cannabinoids from solid samples. Liquid chromatography coupled with mass spectrometry is the most common technique used for the analysis of cannabinoids. THC and its metabolites have been detected in wastewater, surface water, and drinking water. In particular, 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol (THC-COOH) has been detected at concentrations up to 2590 and 169 ng L^-1 in untreated and treated wastewater, respectively, 79.9 ng L^-1 in surface water, and 1 ng L^-1 in drinking water. High removal of cannabinoids has been observed in wastewater treatment plants; this is likely a result of adsorption due to the low aqueous solubility of cannabinoids. Based on the estrogenicity and cytotoxicity studies and modelling, it has been predicted that THC and THC-COOH pose moderate risk for adverse impact on the environment. While chlorination and photo-oxidation have been shown to be effective in the removal of THC-COOH, they also produce by-products that are potentially more toxic than regulated disinfection by-products. The potential of indirect exposure to cannabinoids and their metabolites through recreational water is of great interest. As cannabinoids and especially their by-products may have adverse impacts on the environment and public health, more studies on their occurrence in various types of water and environmental systems, as well as on their environmental toxicity, would be required to accurately assess their impact on the environment and public health.

Presence of Disinfection Byproducts in Public Swimming Pools in Medellín, Colombia

The quality of water in swimming pools is essential to avoid risks to the health of users. Medellín has more than 1000 public swimming pools, which are supervised by the Medellín Health Authority to monitor and ensure compliance with relevant regulations. The Health Authority has financed several studies related to the quality of drinking and recreational water in Medellín in order to protect consumers and users. One such study involves the evaluation of the presence of disinfection byproducts (DBP). The best known DBPs resulting from disinfection with chlorine are trihalomethanes (THMs) and halogenated acetic acids (HAAs), as well as other minorities such as chloramines or halophenols (HPs). DBPs pose a greater risk in swimming pool water because there is a greater possibility of ingestion, since exposure occurs through several routes at the same time (direct ingestion of water, inhalation of volatile or aerosol solutes, dermal contact and absorption through skin). In the present work, high concentrations of THMs and HAAs were detected in the public swimming pools selected in the study, but the presence of HPs was not detected in the pools.

+Chlorination by-products in indoor swimming pools: Development of a pilot pool unit and impact of operating parameters

Chlorine addition in swimming pools ensures the microbiological quality of the water and the bathers' safety. However, water chlorination is associated with disinfection byproducts (DBP) formation and adverse health effects. The impact of operating parameters and innovative water treatment systems on DBPs levels has been reported in several studies, but sampling campaign in real pools remain difficult to carry out, mainly due to unexpected attendance variations. This study presents the development of a pilot pool plant allowing to perform experiments under controlled and reproducible conditions. Bathers inputs were simulated both for the organic load and for the mechanical agitation of water. Two sampling campaigns were performed during the building of the pilot, before and after the hall was closed. Key operating parameters such as chlorine dose, water temperature and attendance were controlled and monitored. DBP levels in the pilot plant were representative of French indoor swimming pools and the impact of bathers' activity was visible on volatile DBPs. Furthermore, correlations could be stated between operating parameters and DBP levels. Stripping effectively reduced volatile DBP concentrations in water. Moreover, energy consumption data, which are usually very scarce in experimental studies, showed the influence of heat pump consumption on the global energy consumption.

Influence of hydrotherapy pool water recirculation regime on Staphylococcus species concentration at subsurface: Preliminary experimental data from a pilot

Pools are prone to contamination from microbial pathogens from human external microbiota, including mainly Staphylococcus species. These bacteria originate mainly from the skin and rhinopharynx and tend to concentrate at the surface/subsurface. Being protected by films derived from mucus and sebum, they are markedly resistant to biocides. Our study aimed to evaluate the respective impact of mixed and reverse hydraulicity techniques on the concentration of Staphylococcus species at the subsurface following bathing by four individuals in an experimental pool. Disinfection, filtration and water renewal of the pool were stopped in order to study only the influence of the water recirculation regime. We found a significant reduction of 31.7% (Test 1), 50.9% (Test 2) and 41.9% (Test 3) in total Staphylococcus species counts at the subsurface when using reverse versus mixed hydraulicity. However, this reduction is not a pollution cut but a pollution shift, resulting from an increase in the outlet water flow rate by overflow channel from 49.3 to 100%. This experimental model was far removed from real life conditions and associated with a series of limitations. However, it seems that the type of water recirculation regime is a critical factor in the bacterial quality of pool water. These preliminary findings need to be confirmed in additional studies using more realistic conditions.

Thermal baths as sources of pharmaceutical and illicit drug contamination

Despite the fact that there are tens of thousands of thermal baths in existence, knowledge about the occurrence of pharmaceutically active compounds (PhACs) in untreated thermal wastewater is very limited. Because used thermal water is typically legally discharged into surface waters without any treatment, the effluent poses environmental risks for the receiving water bodies. The aim of this study was to show the occurrence patterns and spatiotemporal characteristics of 111 PhACs in thermal wastewater. Six thermal water outflows of different thermal baths were tested in different seasons in the Budapest metropolitan region (Hungary), and diurnal analysis was performed. After solid-phase extraction, the samples were analysed and quantified by coupling supercritical fluid chromatography and mass spectrometry to perform simultaneous multi-residue drug analysis. The results confirm that water discharge pipes directly transport pharmaceuticals into surface water bodies; 34 PhACs were measured to be over the limit of quantification at least once, and 21 of them were found in more than one water sample. The local anaesthetic drug lidocaine, antiepileptic carbamazepine, analgesic derivative tramadol and illicit drug cocaine were detected in more than half of the samples. Caffeine, metoprolol and bisoprolol (cardiovascular drugs), benzoylecgonine (cocaine metabolite), diclofenac (NSAID), citalopram (antidepressant) and certain types of hormones also have a significant frequency of 30-50%. However, the occurrence and concentrations of PhACs vary according to the season and number/types of visitors. As demonstrated by the diurnal fluctuation, drug contamination of thermal waters can significantly vary, even for similar types of baths; furthermore, the quantity and types of some pollutants rapidly change in the discharged thermal wastewater.

500 days of swimmers: the chemical water quality of swimming pool waters from the beginning

Many studies of disinfection by-products (DBPs) in pools have focused on haloacetic acids, trihalomethanes, and chloramines, with less studies investigating the occurrence of other DBPs, such as haloketones, haloacetaldehydes, haloacetonitriles, halonitromethanes, and haloacetamides. Furthermore, while many studies have achieved a broadscreen analysis across several pools, fewer studies have followed the water quality of pools over time, with information regarding the production and fate of DBPs in pools over extended periods (e.g. > 1 year) being limited. This study reports the occurrence of 39 DBPs and several general water quality parameters in two newly built and filled swimming pools over 15 months, where investigations began prior to opening. DBP concentrations measured in this study were generally similar to or higher than those previously reported in chlorinated pools, with concentrations of chloroacetic acid, dichloroacetic acid, trichloroacetic acid, and chloral hydrate (trichloroacetaldehyde) in some samples being higher than previously reported maximum concentrations. Considering both pools, lower concentrations of DBPs were measured in the pool where a steady state non-purgeable organic carbon concentration was achieved, highlighting the importance of the establishment of a steady state balance of mineralisation versus addition of organic carbon to reduce precursors for DBP formation in pools. Pools were found to exhibit significantly higher estimated cytotoxicity than their filling water, which reflects the significantly higher concentrations of DBPs measured in the pools in comparison to the filling water. Chloral hydrate accounted for up to 99% the total estimated cytotoxicity and was found to be correlated to the number of pool entries, suggesting that swimmers may be a potential source of chloral hydrate precursors in pools. The presence and subsequent peak of non-purgeable organic carbon and DBPs prior to, and soon after, opening suggest that the building process and/or new pool infrastructure may have had a significant impact on the chemical water quality, particularly on DBP formation. This study includes the first quantification of bromochloroacetaldehyde, bromodichloroacetaldehyde, bromochloronitromethane, and dichloronitromethane in chlorinated swimming pools, and provides important new knowledge on the long-term trends of DBPs in pools.

Removal of urea from swimming pool water by UV/VUV: The roles of additives, mechanisms, influencing factors, and reaction products

To discover an applicable technology for urea abatement from swimming pool water (SPW), this study compared the performances of seven ultraviolet (UV)-based technologies on urea removal, including UV alone, UV coupled with hydrogen peroxide (UV/H₂O₂), sulfite (UV/Na₂SO₃), potassium persulfate (UV/K₂S₂O₈), a combination of UV and vacuum UV (UV/VUV), and UV/VUV in tandem with either H₂O₂ (VUV/H₂O₂) or potassium persulfate (VUV/K₂S₂O₈). Among them, UV and UV/Na₂SO₃ showed little removal ability, and UV/H₂O₂ removed only 12.8% of urea within 3-h experiments, while UV/VUV degraded 71.7% of urea without introducing substantial total dissolved solids (TDS). Therefore, UV/VUV was considered as a promising technology for further exploration. In comparison, although UV/K₂S₂O₈ exhibited higher urea removal than UV/VUV, it caused dramatic increases of TDS, which made the regulatory threshold for the TDS increment difficult to maintain. Within UV/VUV studies, some common components in SPW (e.g., cyanuric acid, humic acid, nitrate, and bicarbonate) inhibited the removal process, whereas chloride and sulfate facilitated it, while free chlorine at doses ≤ 3 mg-Cl₂/L and pH levels from 6.8 to 8.0 imposed little impact on urea degradation. Overall, UV/VUV degraded 40.0% and 22.2% of urea from tap water and SPW, respectively; both were lower than the efficiency observed in ultrapure water. As for reaction byproducts, urea phototransformation via UV/VUV yielded nitrate and ammonia as the key products with the mass balance of nitrogen element being met. However, the contents of organic carbon decreased at a rate slightly lower than urea degradation, suggesting that urea was mostly mineralized and slightly converted to unknown organic compounds. The results hence demonstrate that UV/VUV is an effective alternative for urea removal from SPW.

Impact of Different Combinations of Water Treatment Processes on the Concentration of Disinfection Byproducts and Their Precursors in Swimming Pool Water

To mitigate microbial activity in swimming pools and to ensure hygienic safety for bathers, pool systems have a recirculating water system ensuring continuous water treatment and disinfection by chlorination. A major drawback associated with the use of chlorine as disinfectant is its potential to react with precursor substances present in pool water to form harmful disinfection byproducts (DBPs). In this study, different combinations of conventional and advanced treatment processes were applied to lower the concentration of DBPs and their precursors in pool water by using a pilot-scale swimming pool model operated under reproducible and fully controlled conditions. The quality of the pool water was determined after stationary concentrations of dissolved organic carbon (DOC) were reached. The relative removal of DOC (Δc c_in^-1) across the considered treatment trains ranged between 0.1  ±  2.9% and 7.70  ±  4.5%, where conventional water treatment (coagulation and sand filtration combined with granular activated carbon (GAC) filtration) was revealed to be the most effective. Microbial processes in the deeper, chlorine-free regions of the GAC filter have been found to play an important role in the degradation of organic substances. Almost all treatment combinations were capable of removing trihalomethanes to some degree and trichloramine and dichloroacetonitrile almost completely. However, the results demonstrated that effective removal of DBPs across the treatment train does not necessarily result in low DBP concentrations in the basin of a pool. This raises the importance of the DBP formation potential of the organic precursors, which has been shown to depend strongly on the treatment concept applied. Irrespective of the filtration technique employed, treatment combinations employing UV irradiation as a second treatment step revealed higher concentrations of volatile DBPs in the pool compared to those employing GAC filtration as a second treatment step. In the particular case of trichloramine, results confirm that its removal across the treatment train is not a feasible mitigation strategy because it cannot compensate for the fast formation in the basin.

Occurrence of disinfection by-products in swimming pools and the estimated resulting cytotoxicity

Swimming pools are disinfected to protect against the risk of microbial disease, however, the formation of disinfection by-products (DBPs) is an unwanted consequence. While many studies have reported the occurrence of commonly investigated DBPs (trihalomethanes and haloacetic acids) in pools, few studies have investigated emerging DBP classes, such as the haloketones or haloacetaldehydes, and the nitrogenous haloacetamides, halonitromethanes, haloacetonitriles and N-nitrosamines. This study investigated the occurrence of sixty four DBPs from the eight aforementioned DBP classes in pools employing different treatment methods. Approximately 70% of the DBPs were detected in at least one of the pools, with most concentrations being equal to or greater than those previously reported. Chloral hydrate (trichloroacetaldehyde) was one of many DBPs detected in all chlorinated waters (202 to 1313 μg/L), and, on a molar basis, was the predominant DBP. Several other DBPs, namely chloroacetic acid, dichloroacetic acid, trichloroacetic acid, dichloroacetamide, dibromoacetamide, dibromochloroacetamide and trichloroacetamide, and many of the N-nitrosamines, were measured at concentrations greater than previously reported: up to 200 to 479 μg/L for the haloacetic acids, 56 to 736 μg/L for the haloacetamides and up to 1093 ng/L for some N-nitrosamines. The higher disinfectant residuals required to be employed in Australian pools, and poor pool management (e.g. of chlorine residual and pH) are likely factors contributing to these relatively high DBP concentrations. Where possible, the cytotoxicity values of the investigated DBPs were evaluated, with chloral hydrate representing over 90% of the total chronic cytotoxicity despite only representing up to 64% of the total molar DBP concentration. This study is the first report of bromodichloroacetaldehyde and bromochloroacetaldehyde in pools and is the first investigation of N-nitrosamines in a brominated pool. Furthermore, this work aids in understanding DBPs in both chlorine and bromine treated pools, the latter being the subject of only limited previous studies.

N2 yields from monochloramine conversion by granular activated carbons are decisive for effective swimming pool water treatment

Inorganic chloramines (mono-, di- and trichloramine) are formed in swimming pool water from the unintended reaction of free chlorine with ammonia that is introduced by bathers. Monochloramine is of particular interest as it is known to react further in pool water forming harmful DBPs, such carcinogenic N-nitrosodimethylamine (NDMA). During pool water treatment with granular activated carbon (GAC) filters, monochloramine is transformed by chemical reactions on the carbon surface to N₂ and ammonia. As ammonia is led back into the pool where it is chlorinated again under the renewed formation of inorganic chloramines, it is recommended to use GACs with a high N₂ yield for monochloramine transformation in pool water treatment. In this study, yields of N₂ and ammonia from monochloramine conversion by commercially available GACs were determined using a fixed-bed reactor system under conditions that are typical for swimming pool water treatment. The N₂ yields remained constant with on-going exposure of the GAC to monochloramine and ranged from 0.5% to 21.3%, depending on the type of GAC used. Correlation analyses were conducted to identify carbon properties that can determine the N₂ yield for monochloramine conversion, such as the amount of oxygen groups, the elemental composition and the trace metal content. It was found that the N₂ yield significantly correlates with the copper content of the tested carbons. Model calculations combining pool hydraulics with formation/abatement of inorganic chloramines and NDMA as well as chloramine transformations in GAC filters showed that the concentration of inorganic chloramines and carcinogenic NDMA can be decreased by a factor of ∼2, if the tested GACs could be modified to convert up to ∼50% of the monochloramine to N₂.

An exploration of disinfection by-products formation and governing factors in chlorinated swimming pool water

This paper investigates disinfection by-products (DBPs) formation and their relationship with governing factors in chlorinated swimming pools. The study compares concentrations of DBPs with WHO guidelines for drinking water quality recommended to screen swimming pool water quality. The statistical analysis is based on a global database of 188 swimming pools accumulated from 42 peer-reviewed journal publications from 16 countries. The mean and standard deviation of dichloroacetic acid and trichloroacetic acid were estimated as 282 ± 437 and 326 ± 517 μg L^-1, respectively, which most often surpassed the WHO guidelines. Similarly, more than half of the examined pools had higher values of chloral hydrate (102 ± 128 μg L^-1). The concentration of total chloramines (650 ± 490 μg L^-1) was well above the WHO guidelines in all reported cases. Nevertheless, the reported values remained below the guidelines for most of the studied pools in the case of total trihalomethanes (134 ± 160 μg L^-1), dichloroacetonitrile (12 ± 12 μg L^-1) and dibromoacetonitrile (8 ± 11 μg L^-1). Total organic carbon, free residual chlorine, temperature, pH, total nitrogen and bromide ions play a pivotal role in DBPs formation processes. Therefore, proper management of these governing factors could significantly reduce DBPs formation, thereby, contributing towards a healthy swimming pool environment.

Regulation, formation, exposure, and treatment of disinfection by-products (DBPs) in swimming pool waters: A critical review

The microbial safety of swimming pool waters (SPWs) becomes increasingly important with the popularity of swimming activities. Disinfection aiming at killing microbes in SPWs produces disinfection by-products (DBPs), which has attracted considerable public attentions due to their high frequency of occurrence, considerable concentrations and potent toxicity. We reviewed the latest research progress within the last four decades on the regulation, formation, exposure, and treatment of DBPs in the context of SPWs. This paper specifically discussed DBP regulations in different regions, formation mechanisms related with disinfectants, precursors and other various conditions, human exposure assessment reflected by biomarkers or epidemiological evidence, and the control and treatment of DBPs. Compared to drinking water with natural organic matter as the main organic precursor of DBPs, the additional human inputs (i.e., body fluids and personal care products) to SPWs make the water matrix more complicated and lead to the formation of more types and greater concentrations of DBPs. Dermal absorption and inhalation are two main exposure pathways for trihalomethanes while ingestion for haloacetic acids, reflected by DBP occurrence in human matrices including exhaled air, urine, blood, and plasma. Studies show that membrane filtration, advanced oxidation processes, biodegradation, thermal degradation, chemical reduction, and some hybrid processes are the potential DBP treatment technologies. The removal efficiency, possible mechanisms and future challenges of these DBP treatment methods are summarized in this review, which may facilitate their full-scale applications and provide potential directions for further research extension.

Test of precoat filtration technology for treatment of swimming pool water

The technical performance of a precoat filter was compared with that of a traditional sand filter. Particle concentration and size distribution were measured before and after the filtration of swimming pool water. Both the sand and precoat filters could reduce the particle concentration in the effluent. However, higher particle removal efficiency was generally observed for the precoat filter, especially for particles smaller than 10 μm in diameter. Adding flocculant improved the removal efficiency of the sand filter, resulting in removal efficiencies comparable to those of the precoat filter. Three powders, i.e., two types of perlite (Harbolite^® and Aquatec perlite) and cellulose fibers (Arbocel^®), were tested for the precoat filter, but no significant difference in particle removal efficiency was observed among them. The maximum efficiency was reached within 30-40 min of filtration. The energy required for the pumps increased by approximately 35% over a period of 14 days. The energy consumption could be reduced by replacing the powder on the filter cloth. The sand filter was backwashed once a week, while the powder on the precoat filter was replaced every two weeks. Under these conditions, it was possible to reduce the water used for cleaning by 88% if the precoat filter was used instead of the sand filter.

Occurrence of and human exposure to parabens, benzophenones, benzotriazoles, triclosan and triclocarban in outdoor swimming pool water in Changsha, China

The entry of personal care products (PCPs) into the environment has, in turn, caused negative influences to human health. Public swimming pools are places that have attracted increasing concerns. In this article, 35 outdoor swimming pools in Changsha City (China) were examined in view of the occurrence of 22 target PCPs contaminants, which fall into four categories: preservatives, UV filters, anticorrosion agents, and antimicrobials. Out of them, 16 compounds were detected in the collected samples. The preservatives was the most dominant category, with methyl paraben being the top compound (a.v. 0.85μg/L) followed by p-hydroxybenzoic acid (a.v. 0.13μg/L) and 1H-benzotriazole (a.v. 0.14μg/L). The correlations among 22 PCPs and their four categories were evaluated using the nonparametric Spearman correlations analysis. In the source tracing investigation, the level of PCPs in swimming pools was determined to be primarily associated with the consumption of these products while weakly related to the filling waters. The quantitative risk assessment revealed that the PCPs concentrations were at a safe level.

Occurrence and formation of disinfection by-products in the swimming pool environment: A critical review

Disinfection of water for human use is essential to protect against microbial disease; however, disinfection also leads to formation of disinfection by-products (DBPs), some of which are of health concern. From a chemical perspective, swimming pools are a complex matrix, with continual addition of a wide range of natural and anthropogenic chemicals via filling waters, disinfectant addition, pharmaceuticals and personal care products and human body excretions. Natural organic matter, trace amounts of DBPs and chlorine or chloramines may be introduced by the filling water, which is commonly disinfected distributed drinking water. Chlorine and/or bromine is continually introduced via the addition of chemical disinfectants to the pool. Human body excretions (sweat, urine and saliva) and pharmaceuticals and personal care products (sunscreens, cosmetics, hair products and lotions) are introduced by swimmers. High addition of disinfectant leads to a high formation of DBPs from reaction of some of the chemicals with the disinfectant. Swimming pool air is also of concern as volatile DBPs partition into the air above the pool. The presence of bromine leads to the formation of a wide range of bromo- and bromo/chloro-DBPs, and Br-DBPs are more toxic than their chlorinated analogues. This is particularly important for seawater-filled pools or pools using a bromine-based disinfectant. This review summarises chemical contaminants and DBPs in swimming pool waters, as well as in the air above pools. Factors that have been found to affect DBP formation in pools are discussed. The impact of the swimming pool environment on human health is reviewed.

Monitoring and factors affecting levels of airborne and water bromoform in chlorinated seawater swimming pools

Water and air quality of eight seawater swimming pools using chlorine disinfection was measured during four sampling campaigns, spread on one full-year, and in four thalassotherapy centers located in Southeast of France. Concentrations of trihalomethanes (THMs) in air and in water as well as concentrations of parameters, including nonpurgeable organic carbon (NPOC), free residual chlorine (Cl_f), pH, Kjeldhal Nitrogen (KN), salinity, conductivity, bromide ions and, water and air temperature, were measured. Water and air samples were collected in triplicates morning - at the opening of the pools -, noon and night - at the closing of the pools -, in summer and winter. Data analysis was performed by Principal Component Analysis (PCA) and rotated component matrix, from both data quality and other parameters such as TOC, aromaticity (UV₂₅₄), pH, hygrometry, and free residual chlorine (Cl_f). This statistical analysis demonstrates a high correlation between TOC, Cl_f and UV₂₅₄ and THM levels found in air and water, particularly for the major ones (CHBr₃ in water_: 300.0μg/L mean, 1029.0μg/L maximum; CHBr₃ in air: 266.1μg/m³ mean, 1600.0μg/m³ maximum, and CHClBr₂ in water: 18.9μg/L mean, 81.0μg/L maximum; CHClBr₂ in air: 13.6μg/m³ mean, 150.0μg/m³ maximum). These high levels of bromoform (CHBr₃) are particularly worrisome in such health institutions, even these levels do not exceed the Permissible Exposure Limit (PEL) of 5mg/m³ as an 8hour time-weighted average currently fixed by various administrations, such as Occupational Safety and Health Administration (OSHA).

Occurrence of Cryptosporidium and Giardia and the Relationship between Protozoa and Water Quality Indicators in Swimming Pools

A total of 60 samples were collected from 35 swimming pools in Beijing, China, and the presence of Cryptosporidium and Giardia were investigated. The results showed that 16.7% and 15.0% of samples were positive for Cryptosporidium oocyst and Giardia cysts, respectively, with a mean concentration of 0.30 oocysts/10 L and 0.27 cysts/10 L. The oocysts and cysts were found to have higher rates of occurrence in August than in May. Genotyping confirmed the presence of Cryptosporidium hominis, C. parvum, and Giardia assemblages A and B, all of which were associated with human infections. The predominant species/assemblages were C. hominis and Giardia assemblage A. Analyses of the relationships between parasite oocysts/cysts, indicator bacteria, and physical-chemical parameters revealed that there was no correlation between 2 parasites and fecal bacterial indicators, whilst there was a significant correlation between protozoa and urea concentration, which indicates that urea concentration rather than fecal bacterial indicators might be an appropriate index for chlorine-resistant protozoa in swimming pools. This study provides useful information to improve the safety of swimming pool water and deduce the risk of protozoan infections.

Occurrence of pharmaceuticals and UV filters in swimming pools and spas

The occurrence of 32 pharmaceuticals and 14 UV filters in swimming pools and spas was studied. Fifty-one water samples were collected from 17 pools located in sport centres and hotels in Catalonia, Spain. The samples were analysed by liquid chromatography-tandem mass spectrometry. The pharmaceuticals atenolol, carbamazepine, hydrochlorothiazide, metronidazole, ofloxacin, sulfamethoxazole, acetaminophen, ibuprofen, ketoprofen and phenazone were measured in water samples at concentrations higher than their limit of quantification (LOQ). The highest concentration of any individual pharmaceutical was measured for the diuretic hydrochlorothiazide (904 ng/L). The most frequently detected pharmaceutical was carbamazepine, as it was observed in more than half of all the water samples measured (53 %, 27/51). The UV filters at concentrations higher than LOQ in water samples were BP1, BP2, BP3, BP8, THB, 4DHB, 4MBC, OD-PABA, 1HBT, MeBT and DMeBT. The highest concentration of UV filter observed was 4MBC (69.3 ng/L) while the most frequent UV filters in the samples were 1HBT (59 %, 30/51). The results also showed that pharmaceuticals and UV filters were most frequently found in spas. Finally, from a water treatment technology perspective, the lowest occurrence of pharmaceuticals was in the pools applying sand filters followed by disinfection by sodium hypochlorite, while the lowest occurrence of UV filters was in the pools applying coagulation, sand filtration, UV and salt electrolysis.

Health-Related Behaviors in Swimming Pool Users: Influence of Knowledge of Regulations and Awareness of Health Risks

Background: Swimming pool attendance exposes users to infection and chemical risks that could be largely reduced with the adoption of healthy behaviors. This study aims to investigate if the knowledge of swimming pool regulations and awareness of health risks can be associated with users’ health-related behaviors. Methods: A cross-sectional study was conducted using self-administered questionnaires to collect data from two different target groups of swimming users: 184 adults and 184 children/adolescents. The association between specific variables and patterns of behaviors and knowledge was assessed through multivariate logistic regression models. Results: Although more than 80% of both groups declared they knew the regulations, compliance with healthy behaviors was often unsatisfactory, especially in adolescents and youth. In the children/adolescents group, healthy behaviors significantly increased with the frequency of attendance per week. In both groups, compliance increased with educational level (of parents for children/adolescents), while no positive association was observed between viewing the regulations and adopting appropriate behaviors. In the adult group, a higher knowledge/awareness of health risks was related to decreased odds of at least one unhealthy behavior. Conclusions: Guaranteeing the public display of regulations in swimming facilities is not sufficient to promote and change health-related behaviors. Much more attention should be given to educational interventions aimed to increase knowledge of health risks and the awareness that bathers are directly responsible for their own well-being.

Identification of disinfection by-products in freshwater and seawater swimming pools and evaluation of genotoxicity

Exposure to disinfection byproducts (DBPs) in swimming pools has been linked to adverse health effects. Numerous DBPs that occur in swimming pools are genotoxic and carcinogenic. This toxicity is of a greater concern in the case of brominated DBPs that have been shown to have substantially greater toxicities than their chlorinated analogs. In chlorinated seawater swimming pools, brominated DBPs are formed due to the high content of bromide. Nevertheless, very little data is reported about DBP occurrence and mutagenicity of water in these pools. In the present study, three seawater and one freshwater swimming pools located in Southeastern France were investigated to determine qualitatively and quantitatively their DBP contents. An evaluation of the genotoxic properties of water samples of the freshwater pool and a seawater pool was conducted through the Salmonella assay (Ames test). The predominant DBPs identified in the freshwater pool were chlorinated species and included trichloroacetic acid, chloral hydrate, dichloroacetonitrile, 1,1,1-trichloropropanone and chloroform. In the seawater pools, brominated DBPs were the predominant species and included dibromoacetic acid, bromoform and dibromoacetonitile. Bromal hydrate levels were also reported. In both types of pools, haloacetic acids were the most prevalent chemical class among the analyzed DBP classes. The distribution of other DBP classes varied depending on the type of pool. As to genotoxicity, the results of Ames test showed higher mutagenicity in the freshwater pool as a consequence of its considerably higher DBP contents in comparison to the tested seawater pool.

Occurrence and simulation of trihalomethanes in swimming pool water: A simple prediction method based on DOC and mass balance

Trihalomethanes (THM) are the most typical disinfection by-products (DBPs) found in public swimming pool water. DBPs are produced when organic and inorganic matter in water reacts with chemical disinfectants. The irregular contribution of substances from pool visitors and long contact time with disinfectant make the forecast of THM in pool water a challenge. In this work occurrence of THM in a public indoor swimming pool was investigated and correlated with the dissolved organic carbon (DOC). Daily sampling of pool water for 26 days showed a positive correlation between DOC and THM with a time delay of about two days, while THM and DOC didn't directly correlate with the number of visitors. Based on the results and mass-balance in the pool water, a simple simulation model for estimating THM concentration in indoor swimming pool water was proposed. Formation of THM from DOC, volatilization into air and elimination by pool water treatment were included in the simulation. Formation ratio of THM gained from laboratory analysis using native pool water and information from field study in an indoor swimming pool reduced the uncertainty of the simulation. The simulation was validated by measurements in the swimming pool for 50 days. The simulated results were in good compliance with measured results. This work provides a useful and simple method for predicting THM concentration and its accumulation trend for long term in indoor swimming pool water.

Degradation Products of Benzophenone-3 in Chlorinated Seawater Swimming Pools

Oxybenzone (2-hydroxy-4-methoxyphenone, benzophenone-3) is one of the UV filters commonly found in sunscreens. Its presence in swimming pools and its reactivity with chlorine has already been demonstrated but never in seawater swimming pools. In these pools, chlorine added for disinfection results in the formation of bromine, due to the high levels of bromide in seawater, and leads to the formation of brominated disinfection byproducts, known to be more toxic than chlorinated ones. Therefore, it seems important to determine the transformation products of oxybenzone in chlorinated seawater swimming pools; especially that users of seawater swimming pools may apply sunscreens and other personal-care products containing oxybenzone before going to pools. This leads to the introduction of oxybenzone to pools, where it reacts with bromine. For this purpose, the reactivity of oxybenzone has been examined as a function of chlorine dose and temperature in artificial seawater to assess its potential to produce trihalomethanes and to determine the byproducts generated following chlorination. Increasing doses of chlorine and increasing temperatures enhanced the formation of bromoform. Experiments carried out with excess doses of chlorine resulted in the degradation of oxybenzone and allowed the determination of the degradation mechanisms leading to the formation of bromoform. In total, ten transformation products were identified, based on which the transformation pathway was proposed.

Chemical contaminants in swimming pools: Occurrence, implications and control

A range of trace chemical contaminants have been reported to occur in swimming pools. Current disinfection practices and monitoring of swimming pool water quality are aimed at preventing the spread of microbial infections and diseases. However, disinfection by-products (DBPs) are formed when the disinfectants used react with organic and inorganic matter in the pool. Additional chemicals may be present in swimming pools originating from anthropogenic sources (bodily excretions, lotions, cosmetics, etc.) or from the source water used where trace chemicals may already be present. DBPs have been the most widely investigated trace chemical contaminants, including trihalomethanes (THMs), haloacetic acids (HAAs), halobenzoquinones (HBQs), haloacetonitriles (HANs), halonitromethanes (HNMs), N-nitrosamines, nitrite, nitrates and chloramines. The presence and concentrations of these chemical contaminants are dependent upon several factors including the types of pools, types of disinfectants used, disinfectant dosages, bather loads, temperature and pH of swimming pool waters. Chemical constituents of personal care products (PCPs) such as parabens and ultraviolet (UV) filters from sunscreens have also been reported. By-products from reactions of these chemicals with disinfectants and UV irradiation have been reported and some may be more toxic than their parent compounds. There is evidence to suggest that exposure to some of these chemicals may lead to health risks. This paper provides a detailed review of various chemical contaminants reported in swimming pools. The concentrations of chemicals present in swimming pools may also provide an alternative indicator to swimming pool water quality, providing insights to contamination sources. Alternative treatment methods such as activated carbon filtration and advanced oxidation processes may be beneficial in improving swimming pool water quality.