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Environmental Science & Technology Jul 2022The 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... (Review)
Review
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.
Topics: Chlorine; Disinfection; Drinking Water; Halogenation; Water Purification; Water Supply
PubMed: 35700262
DOI: 10.1021/acs.est.1c08580 -
Environmental Science and Pollution... Feb 2021Chlorine (Cl) in the terrestrial environment is of interest from multiple perspectives, including the use of chloride as a tracer for water flow and contaminant... (Review)
Review
Chlorine (Cl) in the terrestrial environment is of interest from multiple perspectives, including the use of chloride as a tracer for water flow and contaminant transport, organochlorine pollutants, Cl cycling, radioactive waste (radioecology; Cl is of large concern) and plant science (Cl as essential element for living plants). During the past decades, there has been a rapid development towards improved understanding of the terrestrial Cl cycle. There is a ubiquitous and extensive natural chlorination of organic matter in terrestrial ecosystems where naturally formed chlorinated organic compounds (Cl) in soil frequently exceed the abundance of chloride. Chloride dominates import and export from terrestrial ecosystems while soil Cl and biomass Cl can dominate the standing stock Cl. This has important implications for Cl transport, as chloride will enter the Cl pools resulting in prolonged residence times. Clearly, these pools must be considered separately in future monitoring programs addressing Cl cycling. Moreover, there are indications that (1) large amounts of Cl can accumulate in biomass, in some cases representing the main Cl pool; (2) emissions of volatile organic chlorines could be a significant export pathway of Cl and (3) that there is a production of Cl in tissues of, e.g. plants and animals and that Cl can accumulate as, e.g. chlorinated fatty acids in organisms. Yet, data focusing on ecosystem perspectives and combined spatiotemporal variability regarding various Cl pools are still scarce, and the processes and ecological roles of the extensive biological Cl cycling are still poorly understood.
Topics: Chlorides; Chlorine; Ecosystem; Halogenation; Soil
PubMed: 33400105
DOI: 10.1007/s11356-020-12144-6 -
Medical Gas Research 2021Hydrogen molecules have attracted attention as a new antioxidant, but are left to be confirmedly verified whether the oral administration is highly safe or not,...
Hydrogen molecules have attracted attention as a new antioxidant, but are left to be confirmedly verified whether the oral administration is highly safe or not, concurrently with retention of abundant hydrogen. When electrolysis was performed for 10 minutes using a direct-current electrolytic hydrogen-water generating bottle with tap water, "residual free chlorine" concurrently upon the production of molecular hydrogen (444 μg/L) could be appreciably decreased from 0.18 mg/L to 0.12 mg/L as quantified by a N,N-diethyl-p-phenylenediamine-dye colorimetric method. Moreover, the total chlorine concentration (residual bound chlorine plus free chlorine) was estimated to be decreased from 0.17 mg/L to 0.11 mg/L. Although a merit of electrolytic hydrogen-generating bottles exists in electrolysis for periods as short as 10 minutes, the 30-minute electrolysis brought about the more abundant hydrogen (479 μg/L) together with an oxidation-reduction potential of -245 mV; even upon this long-term electrolysis, the gross amounts of chlorine, hypochlorous acid and chloramine were shown not to be increased (0.09-0.10 mg/L from 0.11 mg/L for tap water) as detected by orthotolidine colorimetry. Above-mentioned levels of diverse-type chlorines might fulfill the World Health Organization guideline for drinking water below 5 mg/L. In addition, the dissolved ozone upon electrolytic generation of hydrogen-water was below the detection limit (< 0.05 mg/L) or undetectable, which fulfilled the official safety standards in Japan and the USA for drinking water below 0.1 mg/L, as evaluated by three methods such as an electrode-type ozone checker, indigo dye-utilizing ozone detector capillaries and potassium iodide-based colorimetry. Importantly, even when half the amount of tap water was poured into the tank of the apparatus and electrolyzed, both the residual chlorine and ozone concentrations measured were also below the safety standard. Thus, major potently harmful substances, such as residual free/bound chlorine, or hypochlorous-acid/chloramine, respectively, and dissolved ozone, as the drinking hydrogen-water was direct-current-electrolytically generated, were estimated to be repressed within safety concentration ranges with achievements of abundant hydrogen generation.
Topics: Chlorine; Drinking Water; Electrolysis; Hydrogen; Oxidation-Reduction; Ozone
PubMed: 33818445
DOI: 10.4103/2045-9912.311496 -
PloS One 2015Chlorine and thermal treatments are the most commonly used procedures to control and prevent Legionella proliferation in drinking water systems of large buildings.... (Comparative Study)
Comparative Study
Chlorine and thermal treatments are the most commonly used procedures to control and prevent Legionella proliferation in drinking water systems of large buildings. However, cases of legionellosis still occur in facilities with treated water. The purpose of this work was to model the effect of temperature and free chlorine applied in similar exposure conditions as in drinking water systems on five Legionella spp. strains and two amoebal strains of the genera Acanthamoeba. Inactivation models obtained were used to determine the effectiveness of the treatments applied which resulted more effective against Legionella than Acanthamoeba, especially those in cystic stages. Furthermore, to determine the influence of the relationship between L. pneumophila and Acanthamoeba spp. on the treatment effectiveness, inactivation models of the bacteria-associated amoeba were also constructed and compared to the models obtained for the free living bacteria state. The Legionella-amoeba association did not change the inactivation models, but it reduced the effectiveness of the treatments applied. Remarkably, at the lowest free chlorine concentration, 0.5 mg L-1, as well as at the lowest temperatures, 50°C and 55°C, the influence of the Legionella-amoeba associate state was the strongest in reducing the effectiveness of the treatments compared to the free Legionella state. Therefore, the association established between L. pneumophila and amoebae in the water systems indicate an increased health risk in proximal areas of the system (close to the tap) where lower free chlorine concentrations and lower temperatures are commonly observed.
Topics: Acanthamoeba; Chlorine; Coculture Techniques; Disinfection; Halogenation; Hot Temperature; Legionella pneumophila; Mineral Waters; Osmolar Concentration; Sanitary Engineering; Species Specificity; Time Factors; Water; Water Microbiology; Water Purification; Water Quality; Water Supply; Waterborne Diseases
PubMed: 26241039
DOI: 10.1371/journal.pone.0134726 -
Regulatory Toxicology and Pharmacology... Feb 1990In the United States chlorination of potable water supplies has been the standard method of disinfection for about 75 years. In recent times concern has been raised... (Review)
Review
In the United States chlorination of potable water supplies has been the standard method of disinfection for about 75 years. In recent times concern has been raised about the propensity of chlorination to introduce potentially carcinogenic trihalomethanes (THM) such as chloroform into finished water. The levels of THM introduced depend on many factors including the quality of the raw water. Numerous community water treatment facilities are experiencing difficulty in meeting current U.S. Environmental Protection Agency standards, and it is likely that the permissible levels may be lowered in the future. An alternative to chlorination which does not generate THM during disinfection is chlorine dioxide, but there are concerns about the acute and chronic toxicity of ClO2 and its disinfection by-products, chlorite and chlorate. Deleterious effects of moderately high levels of these oxychlorines have been demonstrated experimentally on red blood cells, thyroid function, and development in laboratory animals. Adverse effects in controlled prospective studies in humans and in actual use situations in community water supplies have as yet failed to reveal clear evidence of adverse health effects. Among groups who may be at special risk from this suggested alternative are patients who must undergo chronic extracorporeal hemodialysis. The special needs, precautions, and experience to date in regard to finished water are reviewed. Again, very limited human experience has failed to reveal adverse health effects. Further study, caution, and extreme vigilance are indicated, but dialysis patients in carefully controlled facilities may be at no greater risk than the general population.
Topics: Animals; Chlorine; Chlorine Compounds; Disinfectants; Humans; Oxides; Renal Dialysis; Water Supply
PubMed: 2184465
DOI: 10.1016/0273-2300(90)90006-w -
Environmental Health Perspectives Jan 2023Centralized chlorination of urban piped water supplies has historically contributed to major reductions in waterborne illness. In locations without effective centralized... (Review)
Review
BACKGROUND
Centralized 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.
OBJECTIVES
Our 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.
METHODS
We 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.
RESULTS
We 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 . 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 ; unweighted ). 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.
DISCUSSION
Although 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.
Topics: Humans; Drinking Water; Halogenation; Chlorine; Water Purification; Water Quality; Water Supply
PubMed: 36715546
DOI: 10.1289/EHP10839 -
Water Research Jul 2023Environment disinfection effectively curbs transmission of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). However, elevated concentration of free...
Environment disinfection effectively curbs transmission of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). However, elevated concentration of free available chlorine (FAC) in disinfectants can be discharged into surface water, generating toxic disinfection byproducts (DBPs). The impact of solar photolysis of FAC on natural organic matter (NOM) to form DBPs has not been well studied. In this work, solar photolysis of FAC was found to result in higher formation of DBPs, DBPs formation potential (DBPsFP), total organic chlorine (TOCl) and lower specific ultraviolet absorbance at 254 nm (SUVA), compared to dark chlorination. In solar photolysis of FAC, formation of total DBPs was promoted by pH=8, but hindered by the addition of HCO, radical scavenger or deoxygenation, while addition of NOand NHboth enhanced the formation of nitrogenous DBPs. Differences in the formation of DBPs in solar photolysis of FAC under various conditions were influenced by reactive species. The formation of trichloromethane (TCM) and haloacetic acids (HAAs) in solar photolysis of FAC positively correlated with the steady-state concentrations of ClO and O. The steady-state concentrations of NO and NH positively correlated with the formation of halonitromethanes (HNMs). HAAs and haloacetonitriles (HANs) mainly contributed to calculated cytotoxicity of DBPs. This study demonstrates that solar photolysis of FAC may significantly impact the formation of DBPs in surface water due to extensive use of disinfectants containing FAC during SARS-CoV-2 pandemic.
Topics: Humans; Disinfection; Chlorine; Photolysis; Water Purification; COVID-19; SARS-CoV-2; Disinfectants; Halogenation; Water; Water Pollutants, Chemical
PubMed: 37167852
DOI: 10.1016/j.watres.2023.120020 -
Accounts of Chemical Research May 2018To date, more than 5000 biogenic halogenated molecules have been characterized. This number continues to increase as chemists explore chloride- and bromide-rich marine... (Review)
Review
To date, more than 5000 biogenic halogenated molecules have been characterized. This number continues to increase as chemists explore chloride- and bromide-rich marine environments in search of novel bioactive natural products. Naturally occurring organohalogens span nearly all biosynthetic structural classes, exhibit a range of unique biological activities, and have been the subject of numerous investigations. Despite the abundance of and interest in halogenated molecules, enantioselective methods capable of forging carbon-halogen bonds in synthetically relevant contexts remain scarce. Accordingly, syntheses of organohalogens often rely on multistep functional group interconversions to establish carbon-halogen stereocenters. Our group has developed an enantioselective dihalogenation reaction and utilized it in the only reported examples of catalytic enantioselective halogenation in natural product synthesis. In this Account, we describe our laboratory's development of a method for catalytic, enantioselective dihalogenation and the application of this method to the synthesis of both mono- and polyhalogenated natural products. In the first part, we describe the initial discovery of a TADDOL-mediated dibromination of cinnamyl alcohols. Extension of this reaction to a second-generation system capable of selective bromochlorination, dichlorination, and dibromination is then detailed. This system is capable of controlling the enantioselectivity of dihalide formation, chemoselectivity for polyolefinic substrates, and regioselectivity in the case of bromochlorination. The ability of this method to exert control over regioselectivity of halide delivery permits selective halogenation of electronically nonbiased olefins required for total synthesis. In the second part, we demonstrate how the described dihalogenation has provided efficient access to a host of structurally diverse natural products. The most direct application of this methodology is in the synthesis of naturally occurring vicinal dihalides. Chiral vicinal bromochlorides represent a class of >175 natural products; syntheses of five members of this class, including its flagship member, (+)-halomon, have been accomplished through use of the catalytic, enantioselective bromochlorination. Likewise, enantioselective dichlorination has provided selective access to two members of the chlorosulfolipids, a class of linear, acyclic polychlorides. Synthesis of chiral monohalides has been achieved through solvolysis of enantioenriched bromochlorides; this approach has resulted in the synthesis of five bromocyclohexane-containing natural products through an enantiospecific bromopolyene cyclization. In reviewing these syntheses, a framework for the synthesis of chiral organohalogens mediated by catalytic, enantioselective dihalogenation has emerged. The development of a selective dihalogenation method has been highly enabling in the synthesis of halogenated natural products. In this Account, we detail all examples of catalytic, enantioselective halogenation in total synthesis and encourage the further development of synthetically useful halogenation methodologies.
Topics: Biological Products; Catalysis; Halogenation; Hydrocarbons, Brominated; Hydrocarbons, Chlorinated; Stereoisomerism
PubMed: 29664281
DOI: 10.1021/acs.accounts.8b00064 -
PLoS Neglected Tropical Diseases Aug 2020Schistosomiasis is a water-based disease acquired through contact with cercaria-infested water. Communities living in endemic regions often rely on parasite-contaminated...
BACKGROUND
Schistosomiasis is a water-based disease acquired through contact with cercaria-infested water. Communities living in endemic regions often rely on parasite-contaminated freshwater bodies for their daily water contact activities, resulting in recurring schistosomiasis infection. In such instances, water treatment can provide safe water on a household or community scale. However, to-date there are no water treatment guidelines that provide information on how to treat water containing schistosome cercariae. Here, we rigorously test the effectiveness of chlorine against Schistosoma mansoni cercariae.
METHOD
S. mansoni cercariae were chlorinated using sodium hypochlorite under lab and field condition. The water pH was controlled at 6.5, 7.0 or 7.5, the water temperature at 20°C or 27°C, and the chlorine dose at 1, 2 or 3 mg/l. Experiments were conducted up to contact times of 45 minutes. 100 cercariae were used per experiment, thereby achieving up to 2-log10 inactivations of cercariae. Experiments were replicated under field conditions at Lake Victoria, Tanzania.
CONCLUSION
A CT (residual chlorine concentration x chlorine contact time) value of 26±4 mg·min/l is required to achieve a 2-log10 inactivation of S. mansoni cercariae under the most conservative condition tested (pH 7.5, 20°C). Field and lab-cultivated cercariae show similar chlorine sensitivities. A CT value of 30 mg·min/l is therefore recommended to disinfect cercaria-infested water, though safety factors may be required, depending on water quality and operating conditions. This CT value can be achieved with a chlorine residual of 1 mg/l after a contact time of 30 minutes, for example. This recommendation can be used to provide safe water for household and recreational water activities in communities that lack safe alternative water sources.
Topics: Animals; Cercaria; Chlorine; Halogenation; Hydrogen-Ion Concentration; Schistosoma mansoni; Schistosomiasis; Snails; Tanzania; Temperature; Water; Water Purification
PubMed: 32822356
DOI: 10.1371/journal.pntd.0008665 -
Parasitology Research Jan 2023Blastocystis is a ubiquitous, widely distributed protist inhabiting the gastrointestinal tract of humans and other animals. The organism is genetically diverse, and so...
Blastocystis is a ubiquitous, widely distributed protist inhabiting the gastrointestinal tract of humans and other animals. The organism is genetically diverse, and so far, at least 28 subtypes (STs) have been identified with ST1-ST9 being the most common in humans. The pathogenicity of Blastocystis is controversial. Several routes of transmission have been proposed including fecal-oral (e.g., zoonotic, anthroponotic) and waterborne. Research on the latter has gained traction in the last few years with the organism having been identified in various bodies of water, tap water, and rainwater collection containers including water that has been previously filtered and/or chlorinated. Herein, we assessed the resistance of 11 strains maintained in culture, spanning ST1-ST9 to various chlorine and hydrogen peroxide concentrations for 24 h, and performed recovery assays along with re-exposure. Following the treatment with both compounds, all subtypes showed increased resistance, and viability could be visualized at the cellular level. These results are hinting at the presence of mechanism of resistance to both chlorine and hydrogen peroxide. As such, this pilot study can be the platform for developing guidelines for water treatment processes.
Topics: Humans; Animals; Blastocystis; Blastocystis Infections; Chlorine; Hydrogen Peroxide; Pilot Projects; Genetic Variation; Feces; Prevalence; Phylogeny
PubMed: 36378332
DOI: 10.1007/s00436-022-07713-2