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Do DBPs swim in salt water pools? Comparison of 60 DBPs formed by electrochemically generated chlorine vs. conventional chlorine

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Journal of Environmental Sciences 2022年第7期34卷 232-241页

作者： caroline o.granger Susan D.Richardson Department of Chemistry and Biochemistry University of South Carolina631 Sumter St.ColumbiaSC 29208USA

Disinfectants are added to swimming pools to kill harmful pathogens. Although liquid chlorine(sodium hypochlorite) is the most commonly used disinfectant, alternative disinfection techniques like electrochemically generated mixed oxidants or electrochemically generated chlorine, often referred to as salt water pools, are growing in popularity. However, these disinfectants react with natural organic matter and anthropogenic contaminants introduced to the pool water by swimmers to form disinfection byproducts(DBPs). DBPs have been linked to several adverse health effects, such as bladder cancer, adverse birth outcomes, and asthma. In this study, we quantified 60 DBPs using gas chromatography-mass spectrometry and assessed the calculated cytotoxicity and genotoxicity of an indoor community swimming pool before and after switching to a salt water pool with electrochemically generated chlorine. Interestingly, the total DBPs increased by 15% upon implementation of the salt water pool, but the calculated cytotoxicity and genotoxicity decreased by 45% and 15%, respectively. Predominant DBP classes formed were haloacetic acids, with trichloroacetic acid and dichloroacetic acid contributing 57% of the average total DBPs formed. Haloacetonitriles, haloacetic acids, and haloacetaldehydes were the primary drivers of calculated cytotoxicity, and haloacetic acids were the primary driver of calculated genotoxicity. Diiodoacetic acid, a highly toxic iodinated DBP, is reported for the first time in swimming pool water. Bromide impurities in sodium chloride used to electrochemically generate chlorine led to a 73% increase in brominated DBPs, primarily driven by bromochloroacetic acid. This study presents the most extensive DBP study to-date for salt water pools.

关键词： Disinfection byproducts Swimming pools Cytotoxicity Genotoxicity GC-MS

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How well does XAD resin extraction recover halogenated disinfection byproducts for comprehensive identification and toxicity testing?

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Journal of Environmental Sciences 2022年第7期34卷 264-275页

作者： Xiaobin Liao Joshua M.Allen caroline o.granger Susan D.Richardson Department of Chemistry and Biochemistry University of South CarolinaColumbiaSouth Carolina 29208USA Institute of Municipal and Environmental Engineering College of Civil EngineeringHuaqiao UniversityFujian 361021China Currently at LanzaTech 535 Commerce DriveSopertonGeorgia 30457USA

Halogenated disinfection byproducts(DBPs) are an unintended consequence of drinking water disinfection, and can have significant toxicity. XAD resins are commonly used to extract and enrich trace levels of DBPs for comprehensive, nontarget identification of DBPs and also for in vitro toxicity studies. However, XAD resin recoveries for complete classes of halogenated DBPs have not been evaluated, particularly for low, environmentally relevant levels(ng/L to low μg/L). Thus, it is not known whether levels of DBPs or the toxicity of drinking water might be underestimated. In this study, DAX-8/XAD-2 layered resins were evaluated, considering both adsorption and elution from the resins, for extracting 66 DBPs from water. Results demonstrate that among the 7 classes of DBPs investigated, trihalomethanes(THMs), including iodo-THMs, were the most efficiently adsorbed, with recovery of most THMs ranging from 50%-96%, followed by halonitromethanes(40%-90%). The adsorption ability of XAD resins for haloacetonitriles, haloacetamides, and haloacetaldehydes was highly dependent on the individual species. The adsorption capacity of XAD resins for haloacetic acids was lower(5%-48%), even after adjusting to p H 1 before extraction. Recovery efficiency for most DBPs was comparable with their adsorption, as most were eluted effectively from XAD resins by ethyl acetate. DBP polarity and molecular weight were the two most important factors that determine their recovery. Recovery of trichloromethane, iodoacetic acid, chloro-and iodo-acetonitrile, and chloroacetamide were among the lowest, which could lead to underestimation of toxicity, particularly for iodoacetic acid and iodo-acetonitrile, which are highly toxic.

关键词： XAD resins Disinfection byproducts DBPs Recovery Toxicity

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A balancing act: optimizing free chlorine contact time to minimize iodo-DBPs, NDMA, and regulated DBPs in chloraminated drinking water

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Journal of Environmental Sciences 2022年第7期34卷 315-325页

作者： Matthew A.Bloodgood Sridevi Anduri Chowdary Eric J.Daiber Honglan Shi caroline o.granger Susan D.Richardson Student Services Authority U.S.Environmental Protection AgencyNational Exposure Research LaboratoryAthensGA 30605USA Department of Chemistry Missouri University of Science and TechnologyRollaMO 65409USA Department of Chemistry and Biochemistry University of South CarolinaColumbiaSC 29208USA

Many drinking water treatment plants in the U.S. have switched from chlorination to chloramination to lower levels of regulated trihalomethane(THM) and haloacetic acid(HAA) disinfection byproducts(DBPs) in drinking water and meet the current regulations. However, chloramination can also produce other highly toxic/carcinogenic, unregulated DBPs: iodoacids, iodo-THMs, and N-nitrosodimethylamine(NDMA). In practice, chloramines are generated by the addition of chlorine with ammonia, and plants use varying amounts of free chlorine contact time prior to ammonia addition to effectively kill pathogens and meet DBP regulations. However, iodo-DBPs and nitrosamines are generally not considered in this balancing of free chlorine contact time. The goal of our work was to determine whether an optimal free chlorine contact time could be established in which iodo-DBPs and NDMA could be minimized, while keeping regulated THMs and HAAs below their regulatory limits. The effect of free chlorine contact time was evaluated for the formation of six iodo-trihalomethanes(iodo-THMs), six iodo-acids, and NDMA during the chloramination of drinking water. Ten different free chlorine contact times were examined for two source waters with different dissolved organic carbon(DoC) and bromide/iodide. For the low DoC water at pH 7 and 8, an optimized free chlorine contact time of up to 1 h could control regulated THMs and HAAs, as well as iodo-DBPs and NDMA. For the high DoC water, a free chlorine contact time of 5 min could control iodo-DBPs and NDMA at both p Hs, but the regulated DBPs could exceed the regulations at pH 7.

关键词： Iodo-DBPs NDMA Disinfection byproducts Chloramine Drinking water Free chlorine contact time

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