Dataset Information

Cytotoxicity Comparison between Drinking Water Treated by Chlorination with Postchloramination versus Granular Activated Carbon (GAC) with Postchlorination.

ABSTRACT: Granular activated carbon treatment with postchlorination (GAC/Cl₂) and chlorination followed by chloramination (Cl₂/NH₂Cl) represent two options for utilities to reduce DBP formation in drinking water. To compare the total cytotoxicity of waters treated by a pilot-scale GAC treatment system with postchlorination (and in some instances with prechlorination upstream of GAC (i.e., (Cl₂)/GAC/Cl₂)) and chlorination/chloramination (Cl₂/NH₂Cl) at ambient and elevated Br^- and I^- levels and at three different GAC ages, we applied the Chinese hamster ovary (CHO) cell cytotoxicity assay to whole-water extracts in conjunction with calculations of the cytotoxicity contributed by the 33 (semi)volatile DBPs lost during extractions. At both ambient and elevated Br^- and I^- levels, GAC/Cl₂ and Cl₂/NH₂Cl achieved comparable reductions in the formation of regulated trihalomethanes (THMs) and haloacetic acids (HAAs). Nonetheless, GAC/Cl₂ always resulted in lower total cytotoxicity than Cl₂/NH₂Cl, even at up to 65% total organic carbon breakthrough. Prechlorination formed (semi)volatile DBPs that were removed by the GAC, yet there was no substantial difference in total cytotoxicity between Cl₂/GAC/Cl₂ and GAC/Cl₂. The poorly characterized fraction of DBPs captured by the bioassay dominated the total cytotoxicity when the source water contained ambient levels of Br^- and I^-. When the water was spiked with Br^- and I^-, the known, unregulated (semi)volatile DBPs and the uncharacterized fraction of DBPs were comparable contributors to total cytotoxicity; the contributions of regulated THMs and HAAs were comparatively minor.

SUBMITTER: Lau SS

PROVIDER: S-EPMC10501121 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature

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Cytotoxicity Comparison between Drinking Water Treated by Chlorination with Postchloramination versus Granular Activated Carbon (GAC) with Postchlorination.

Lau Stephanie S SS Feng Yinmei Y Gu April Z AZ Russell Caroline C Pope Greg G Mitch William A WA

Environmental science & technology 20230828 36

Granular activated carbon treatment with postchlorination (GAC/Cl2) and chlorination followed by chloramination (Cl2/NH2Cl) represent two options for utilities to reduce DBP formation in drinking water. To compare the total cytotoxicity of waters treated by a pilot-scale GAC treatment system with postchlorination (and in some instances with prechlorination upstream of GAC (i.e., (Cl2)/GAC/Cl2)) and chlorination/chloramination (Cl2 ...[more]

PMID: 37640368

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Project description:This study measured chlorine- and chloramine-reactive precursors using formation potential (FP) tests of nine U.S. Environmental Protection Agency (EPA) regulated and 57 unregulated disinfection byproducts (DBPs) in tertiary-filtered wastewater before and after pilot-scale granular activated carbon (GAC) adsorption. Using breakthrough of precursor concentration and of concentration associated calculated cytotoxicity and genotoxicity (by correlating known lethal concentrations reported elsewhere), the performance of three parallel GAC treatment trains were compared against tertiary-filtered wastewater: ozone/GAC, chlorine/GAC, and GAC alone. Results show GAC alone was the primary process, versus ozone or chlorine alone, to remove the largest fraction of total chlorine- and chloramine-reactive DBP precursors and calculated cytotoxicity and genotoxicity potencies. GAC with pre-ozonation removed the most chlorine- and chloramine-reactive DBP precursors followed by GAC with pre-chlorination and lastly GAC without pre-treatment. GAC with pre-ozonation produced an effluent with cytotoxicity and genotoxicity of DBPs from FP that generally matched that of GAC without pre-oxidation; meanwhile removal of toxicity was greater by GAC with pre-chlorination. The cytotoxicity and genotoxicity of DBPs from FP tests did not scale with DBP concentration; for example, more than 90% of the calculated cytotoxicity resulted from 20% of the DBPs, principally from haloacetaldehydes, haloacetamides, and haloacetonitriles. The calculated cytotoxicity and genotoxicity from DBPs associated with FP-chloramination were at times higher than with FP-chlorination though the concentration of DBPs was five times higher with FP-chlorination. The removal of DBP precursors using GAC based treatment was at least as effective as removal of DOC (except for halonitromethanes for GAC without pre-oxidation and with pre-chlorination), indicating DOC can be used as an indicator for DBP precursor adsorption efficacy. However, the DOC was not a good surrogate for total cytotoxicity and genotoxicity breakthrough behavior, therefore, unregulated DBPs could have negative health implications that are disconnected from general water quality parameters, such as DOC, and regulated classes of DBPs. Instead, cytotoxicity and genotoxicity correlate with the concentration of specific classes of unregulated DBPs.

Project description:Based on recent studies, passive sampling is a promising method for detecting SARS-CoV-2 in wastewater surveillance (WWS) applications. Passive sampling has many advantages over conventional sampling approaches. However, the potential benefits of passive sampling are also coupled with apparent limitations. We established a passive sampling technique for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater using electronegative filters. Though, it was evident that the adsorption capacity of the filters constrained their use. This work intends to demonstrate an optimized passive sampling technique for SARS-CoV-2 in wastewater using granular activated carbon (GAC). Through bench-scale batch-adsorption studies and sewershed deployments, we established the adsorption characteristics of SARS-CoV-2 and two human feacal viruses (PMMoV and CrAssphage) onto GAC. A pseudo-second-order model best-described adsorption kinetics for SARS-CoV-2 in either deionized (DI) water and SARS-CoV-2, CrAssphage, and PMMoV in wastewater. In both laboratory batch-adsorption experiments and in-situ sewershed deployments, the maximum amount of SARS-CoV-2 adsorbed by GAC occurred at ~60 h in wastewater. In wastewater, the maximum adsorption of PMMoV and CrAssphage by GAC occurred at ~60 h. In contrast, the adsorption capacity was reached in DI water seeded with SARS-CoV-2 after ~35 h. The equilibrium assay modeled the maximum adsorption quantity (qmax) in wastewater with spiked SARS-CoV-2 concentrations using a Hybrid Langmuir-Freundlich equation, a qmax of 2.5 × 109 GU/g was calculated. In paired sewershed deployments, it was found that GAC adsorbs SARS-CoV-2 in wastewater more effectively than electronegative filters. Based on the anticipated viral loading in wastewater, bi-weekly sampling intervals with deployments up to ~96 h are highly feasible without reaching adsorption capacity with GAC. GAC offers improved sensitivity and reproducibility to capture SARS-CoV-2 RNA in wastewater, promoting a scalable and convenient alternative for capturing viral pathogens in wastewater.

Project description:The world is not on track to meet Sustainable Development Goal 6.1 to provide universal access to safely managed drinking water by 2030. Removal of priority microbial contaminants by disinfection is one aspect of ensuring water is safely managed. Passive chlorination (also called in-line chlorination) represents one approach to disinfecting drinking water before or at the point of collection (POC), without requiring daily user input or electricity. In contrast to manual household chlorination methods typically implemented at the point of use (POU), passive chlorinators can reduce the user burden for chlorine dosing and enable treatment at scales ranging from communities to small municipalities. In this review, we synthesized evidence from 27 evaluations of passive chlorinators (in 19 articles, 3 NGO reports, and 5 theses) conducted across 16 countries in communities, schools, health care facilities, and refugee camps. Of the 27 passive chlorinators we identified, the majority (22/27) were solid tablet or granular chlorine dosers, and the remaining devices were liquid chlorine dosers. We identified the following research priorities to address existing barriers to scaled deployment of passive chlorinators: (i) strengthening local chlorine supply chains through decentralized liquid chlorine production, (ii) validating context-specific business models and financial sustainability, (iii) leveraging remote monitoring and sensing tools to monitor real-time chlorine levels and potential system failures, and (iv) designing handpump-compatible passive chlorinators to serve the many communities reliant on handpumps as a primary drinking water source. We also propose a set of reporting indicators for future studies to facilitate standardized evaluations of the technical performance and financial sustainability of passive chlorinators. In addition, we discuss the limitations of chlorine-based disinfection and recognize the importance of addressing chemical contamination in drinking water supplies. Passive chlorinators deployed and managed at-scale have the potential to elevate the quality of existing accessible and available water services to meet "safely managed" requirements.

Project description:BackgroundCentralized chlorination of urban piped water supplies has historically contributed to major reductions in waterborne illness. In locations without effective centralized water treatment, point-of-use (POU) chlorination for households is widely promoted to improve drinking water quality and health. Realizing these health benefits requires correct, consistent, and sustained product use, but real-world evaluations have often observed low levels of use. To our knowledge, no prior reviews exist on adoption of chlorine POU products.ObjectivesOur objectives were to identify which indicators of adoption are most often used in chlorine POU studies, summarize levels of adoption observed, understand how adoption changes over time, and determine how adoption is affected by frequency of contact between participants and study staff.MethodsWe conducted a systematic review of household POU chlorination interventions or programs from 1990 through 2021 that reported a quantitative measure of adoption, were conducted in low- and middle-income countries, included data collection at households, and reported the intervention start date.ResultsWe identified 36 studies of household drinking water chlorination products that met prespecified eligibility criteria and extracted data from 46 chlorine intervention groups with a variety of chlorine POU products and locations. There was no consensus definition of adoption of household water treatment; the most common indicator was the proportion of household stored water samples with free chlorine residual >0.1 or 0.2mg/L. Among studies that reported either free or total chlorine-confirmed adoption of chlorine POU products, use was highly variable (across all chlorine intervention groups at the last time point measured in each study; range: 1.5%-100%; sample size-weighted median=47%; unweighted median=58%). The median follow-up duration among intervention groups was 3 months. On average, adoption declined over time and was positively associated with frequency of contact between respondents and study staff.DiscussionAlthough prior research has shown that POU chlorine products improve health when correctly and consistently used, a reliance on individual adoption for effective treatment is unlikely to lead to the widespread public health benefits historically associated with pressurized, centralized treatment of piped water supplies. https://doi.org/10.1289/EHP10839.

Dataset Information

Cytotoxicity Comparison between Drinking Water Treated by Chlorination with Postchloramination versus Granular Activated Carbon (GAC) with Postchlorination.

Publications

Cytotoxicity Comparison between Drinking Water Treated by Chlorination with Postchloramination versus Granular Activated Carbon (GAC) with Postchlorination.

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