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1. Emerging investigators series: the efficacy of chlorine photolysis as an advanced oxidation process for drinking water treatment

   https://doi.org/10.1039/C6EW00029K  

   Remucal, C. K. ; Manley, D. ( January 2016 , Environmental Science: Water Research & Technology)

   null (Ed.)

   The photolysis of hypochlorous acid (HOCl) and hypochlorite (OCl − ) produces a suite of reactive oxidants, including hydroxyl radical (˙OH), chlorine radical (Cl˙), and ozone (O 3 ). Therefore, the addition of light to chlorine disinfection units could effectively convert existing drinking water treatment systems into advanced oxidation processes. This review critically examines existing studies on chlorine photolysis as a water treatment process. After describing the fundamental chemistry of chlorine photolysis, we evaluate the ability of chlorine photolysis to transform model probe compounds, target organic contaminants, and chlorine-resistant microorganisms. The efficacy of chlorine photolysis to produce reactive oxidants is dependent on solution and irradiation conditions ( e.g. , pH and irradiation wavelengths). For example, lower pH values result in higher steady-state concentrations of ˙OH and Cl˙, resulting in enhanced contaminant removal. We also present the current state of knowledge on the alteration of dissolved organic matter and subsequent formation of disinfection by-products (DBPs) during chlorine photolysis. Although the relative yields of DBPs during chlorine photolysis are also dependent on solution conditions ( e.g. , higher organic DBP yields at low pH values), there is conflicting evidence on whether chlorine photolysis increases or decreases DBP production compared to thermal reactions between chlorine and dissolved organic matter in the dark. We conclude the review by identifying knowledge gaps in the current body of literature. 

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2. Rapid, high-sensitivity analysis of oxyhalides by non-suppressed ion chromatography-electrospray ionization-mass spectrometry: application to ClO 4 − , ClO 3 − , ClO 2 − , and BrO 3 − quantification during sunlight/chlorine advanced oxidation

   https://doi.org/10.1039/d0ew00429d  

   Young, Tessora R. ; Cheng, Shi ; Li, Wentao ; Dodd, Michael C. ( August 2020 , Environmental Science: Water Research & Technology)

   null (Ed.)

   A rapid and sensitive method is described for measuring perchlorate (ClO 4 − ), chlorate (ClO 3 − ), chlorite (ClO 2 − ), bromate (BrO 3 − ), and iodate (IO 3 − ) ions in natural and treated waters using non-suppressed ion chromatography with electrospray ionization and tandem mass spectrometry (NS-IC-MS/MS). Major benefits of the NS-IC-MS/MS method include a short analysis time (12 minutes), low limits of quantification for BrO 3 − (0.10 μg L −1 ), ClO 4 − (0.06 μg L −1 ), ClO 3 − (0.80 μg L −1 ), and ClO 2 − (0.40 μg L −1 ), and compatibility with conventional LC-MS/MS instrumentation. Chromatographic separations were generally performed under isocratic conditions with a Thermo Scientific Dionex AS16 column, using a mobile phase of 20% 1 M aqueous methylamine and 80% acetonitrile. The isocratic method can also be optimized for IO 3 − analysis by including a gradient from the isocratic mobile phase to 100% 1 M aqueous methylamine. Four common anions (Cl − , Br − , SO 4 2− , and HCO 3 − /CO 3 2− ), a natural organic matter isolate (Suwannee River NOM), and several real water samples were tested to examine influences of natural water constituents on oxyhalide detection. Only ClO 2 − quantification was significantly affected – by elevated chloride concentrations (>2 mM) and NOM. The method was successfully applied to quantify oxyhalides in natural waters, chlorinated tap water, and waters subjected to advanced oxidation by sunlight-driven photolysis of free available chlorine (sunlight/FAC). Sunlight/FAC treatment of NOM-free waters containing 200 μg L −1 Br − resulted in formation of up to 263 ± 35 μg L −1 and 764 ± 54 μg L −1 ClO 3 − , and up to 20.1 ± 1.0 μg L −1 and 33.8 ± 1.0 μg L −1 BrO 3 − (at pH 6 and 8, respectively). NOM strongly inhibited ClO 3 − and BrO 3 − formation, likely by scavenging reactive oxygen or halogen species. As prior work shows that the greatest benefits in applying the sunlight/FAC process for purposes of improving disinfection of chlorine-resistant microorganisms are realized in waters with lower DOC levels and higher pH, it may therefore be desirable to limit potential applications to waters containing moderate DOC concentrations ( e.g. , ∼1–2 mg C L −1 ), low Br − concentrations ( e.g. , <50 μg L −1 ), and circumneutral to moderately alkaline pH ( e.g. , pH 7–8) to strike a balance between maximizing microbial inactivation while minimizing formation of oxyhalides and other disinfection byproducts. 

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3. Operando investigation of the synergistic effect of electric field treatment and copper for bacteria inactivation

   https://doi.org/10.1038/s41467-024-45587-3  

   Jarin, Mourin ; Wang, Ting ; Xie, Xing ( February 2024 , Nature Communications)

   As the overuse of chemicals in our disinfection processes becomes an ever-growing concern, alternative approaches to reduce and replace the usage of chemicals is warranted. Electric field treatment has shown promising potential to have synergistic effects with standard chemical-based methods as they both target the cell membrane specifically. In this study, we use a lab-on-a-chip device to understand, observe, and quantify the synergistic effect between electric field treatment and copper inactivation. Observations in situ, and at a single cell level, ensure us that the combined approach has an enhancement effect leading more bacteria to be weakened by electric field treatment and susceptible to inactivation by copper ion permeation. The synergistic effects of electric field treatment and copper can be visually concluded here, enabling the further study of this technology to optimally develop, mature, and scale for its various applications in the future.

    

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4. Smartphone-powered efficient water disinfection at the point of use

   https://doi.org/10.1038/s41545-020-00089-9  

   Zhou, Jianfeng ; Yang, Fang ; Huang, Yuxiong ; Ding, Wenbo ; Xie, Xing ( October 2020 , npj Clean Water)

   Clean water free of bacteria is a precious resource in areas where no centralized water facilities are available. Conventional chlorine disinfection is limited by chemical transportation, storage, and the production of carcinogenic by-products. Here, a smartphone-powered disinfection system is developed for point-of-use (POU) bacterial inactivation. The integrated system uses the smartphone battery as a power source, and a customized on-the-go (OTG) hardware connected to the phone to realize the desired electrical output. Through a downloadable mobile application, the electrical output, either constant current (20–1000 µA) or voltage (0.7–2.1 V), can be configured easily through a user-friendly graphical interface on the screen. The disinfection device, a coaxial-electrode copper ionization cell (CECIC), inactivates bacteria by low levels of electrochemically generated copper with low energy consumption. The strategy of constant current control is applied in this study to solve the problem of uncontrollable copper release by previous constant voltage control. With the current control, a high inactivation efficiency ofE. coli(~6 logs) is achieved with a low level of effluent Cu (~200 µg L⁻¹) in the water samples within a range of salt concentration (0.2–1 mmol L⁻¹). The smartphone-based power workstation provides a versatile and accurate electrical output with a simple graphical user interface. The disinfection device is robust, highly efficient, and does not require complex equipment. As smartphones are pervasive in modern life, the smartphone-powered CECIC system could provide an alternative decentralized water disinfection approach like rural areas and outdoor activities.

    

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5. Synergy between microwave radiation and silver for inactivation of Legionella pneumophila

   Saleh, N. B. ; Ayres, C. ; Lawler, D. F. ; Kirisits, M. J. ( July 2020 , 1st Virtual Canadian Symposium on Water Quality Research)

   Legionella pneumophila is an opportunistic human pathogen that can cause a severe and deadly form of pneumonia called Legionnaires’ disease. Over the past decade, the number of reported cases of Legionnaires’ disease has quadrupled in the U.S., with 8,000-18,000 hospitalizations per year at a yearly incidence rate of 1.7/100,000. Within the water sector, this public health risk is exacerbated by the proliferation of L. pneumophila in complex biological matrices such as biofilms and within free-living amoebae. Traditional disinfection technologies fail to effectively mitigate this emerging pathogen issue, necessitating development of point-of-use (POU) technologies with high inactivation efficacy. We aim to harness microwave (MW) radiation and take advantage of its synergy with ion-mediated toxicity to effectively inactivate L. pneumophila. In this study, planktonic L. pneumophila cells have been exposed to ionic and nano-particulate silver. While neither treatment alone is effective over a short exposure period, a combined treatment of silver with MW radiation successfully achieves 3-4 log removal within 6 min of irradiation, as shown in Figure 1. Enhanced toxicity was observed when L. pneumophila was pre-exposed to either treatment (i.e., MW heating or silver exposure) prior to exposure to the other; these results suggest that silver ion transport within the cells is facilitated by heat treatment. Data presented here serve as the proof-of-concept toward the development of a L pneumophila inactivation device that harnesses MW radiation and can potentially mitigate this public health risk, even if the cells are protected by amoebae or biofilms. 

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