Water chlorination

Summary

Water chlorination is the process of adding chlorine or chlorine compounds such as sodium hypochlorite to water. This method is used to kill bacteria, viruses and other microbes in water. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera, dysentery, and typhoid. History In a paper published in 1894, it was formally proposed to add chlorine to water to render it "germ-free". Two other authorities endorsed this proposal and published it in many other papers in 1895. Early attempts at implementing water chlorination at a water treatment plant were made in 1893 in Hamburg, Germany. In 1897 the town of Maidstone, England was the first to have its entire water supply treated with chlorine. Permanent water chlorination began in 1905, when a faulty slow sand filter and a contaminated water supply caused a serious typhoid fever epidemic in Lincoln, England. Alexander Cruickshank Houston used chlorination of the water

Official source

https://en.wikipedia.org/wiki/Water_chlorination

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Disinfection of water for human consumption is a challenge to ensure that water is free of pathogens and pollutants while avoiding the formation of potentially harmful undesirable products. The establishment of disinfection facilities must take into account the local context as well as technical and economic feasibility to ensure their sustainability. Chlorination is a disinfection technique that is widely used throughout the world and can take several forms. However, this technique can lead to the formation of disinfection by-products, some of which are harmful to human health and are a source of growing concern. This present report focuses on chlorination using tablets that release chlorine when eroded by contact with water. This study aimed at improving the understanding of the effect of various parameters on the efficiency of water chlorination in the Cartago region (Costa Rica). First a chlorination facility located in a village near Cartago was studied. The purpose of this assessment was to diagnose the current situation, determine the changes needed to improve it and implement them. It was showed that the chlorine concentration delivered by this facility was too low and variable. A new chlorinator and a tank allowing a better mixing of the chlorinated solution have been installed. These modifications have resulted in a higher and more homogeneous chlorine concentration in the storage tanks and an improvement in some water quality parameters. On the basis of the results, recommendations were made to ensure the proper functioning of the facility and the continuation of measurements during future campaigns. It should be noted that this was a short-term study, measurements over a longer period would allow more precise conclusions to be drawn. The second part of the project concerned 10 chlorination facilities in the Cartago region. The purpose was to compare the results of various parameters of surface and groundwater samples collected in the rainy/transition season in 2018 with those of the 2019 dry season. For the moment there were thus only two series of data but this has nevertheless allowed us to observe an improvement in certain parameters during the dry season. Future measurements campaigns will consolidate these results.

2019

Chlorination of arenes via the degradation of toxic chlorophenols

Paul Joseph Dyson, Mingyang Liu, Xuemei Yang

Aryl chlorides are among the most versatile synthetic precursors, and yet inexpensive and benign chlorination techniques to produce them are underdeveloped. We propose a process to generate aryl chlorides by chloro-group transfer from chlorophenol pollutants to arenes during their mineralization, catalyzed by Cu(NO3)2/NaNO3 under aerobic conditions. A wide range of arene substrates have been chlorinated using this process. Mechanistic studies show that the Cu catalyst acts in cooperation with NOx species generated from the decomposition of NaNO3 to regulate the formation of chlorine radicals that mediate the chlorination of arenes together with the mineralization of chlorophenol. The selective formation of aryl chlorides with the concomitant degradation of toxic chlorophenol pollutants represents a new approach in environmental pollutant detoxication. A reduction in the use of traditional chlorination reagents provides another (indirect) benefit of this procedure.

2022

Elucidating the Rate-Limiting Processes in High-Temperature Sodium-Metal Chloride Batteries

Corsin Battaglia, Daniel Alexander Landmann, Patrik Schmutz

Sodium-metal chloride batteries are considered a sustainable and safe alternative to lithium-ion batteries for large-scale stationary electricity storage, but exhibit disadvantages in rate capability. Several studies identify metal-ion migration through the metal chloride conversion layer on the positive electrode as the rate-limiting step, limiting charge and discharge rates in sodium-metal chloride batteries. Here the authors present electrochemical nickel and iron chlorination with planar model electrodes in molten sodium tetrachloroaluminate electrolyte at 300 degrees C. It is discovered that, instead of metal-ion migration through the metal chloride conversion layer, it is metal-ion diffusion in sodium tetrachloroaluminate which limits chlorination of both the nickel and iron electrodes. Upon charge, chlorination of the nickel electrode proceeds via uniform oxidation of nickel and the formation of NiCl2 platelets on the surface of the electrode. In contrast, the oxidation of the iron electrodes proceeds via localized corrosion attacks, resulting in nonuniform iron oxidation and pulverization of the iron electrode. The transition from planar model electrodes to porous high-capacity electrodes, where sodium-ion migration along the tortuous path in the porous electrode can become rate limiting, is further discussed. These mechanistic insights are important for the design of competitive next-generation sodium-metal chloride batteries with improved rate performance.

WILEY2022

2019