Potable water chlorination

Potable Water Chlorination Potable Water Chloramination... 

The general impression is of a widespread distribution, at the pg/1 level, of chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene and methyl chloroform methyl chloride, vinyl chloride and ethylene dichloride are virtually absent, despite the large quantity of each known to be produced while methylene chloride is reported locally, and such compounds as hexachlorobutadiene at very low levels only in waters known to be affected by production effluents. There is, nevertheless, a very wide variation about these typical values, of at least 3 orders of magnitude it is difficult, therefore, to quote fully representative levels. Surface waters provide a much lower potential for widespread mixing than does the atmosphere, where concentrations of constituents are much more consistent. Many surface waters also contain the 3 brominated THMs these are probably derived from discharges of chlorinated potable water after use. 

Saline Water for Municipal Distribution. Only a very small amount of potable water is actually taken by people or animals internally, and it is quite uneconomical to desalinate all municipally piped water, although all distributed water must be clear and free of harmful bacteria. Most of the water piped to cities and industry is used for Htfle more than to carry off small amounts of waste materials or waste heat. In many locations, seawater can be used for most of this service. If chlorination is requited, it can be accompHshed by direct electrolysis of the dissolved salt (21). Arrayed against the obvious advantage of economy, there are several disadvantages use of seawater requites different detergents sewage treatment plants must be modified the usual metal pipes, pumps, condensers, coolers, meters, and other equipment corrode more readily chlorination could cause environmental poUution and dual water systems must be built and maintained. 

Calcium chloride is found in the marine environment. The elemental composition of seawater is 400 ppm calcium, 18,900 ppm chlorine, and many organisms and aquatic species are tolerant of these concentrations. Toxicity arises either from the invasion of freshwater in otherwise saltwater environments or possible toxic doses of calcium chloride from spills, surface mnoff, or underground percolation into typically freshwater streams or aquifers. Various agencies have guidelines for calcium and chloride in potable water (41). The European Economic Community (EEC) is the only agency to have a minimum specification for calcium in softened water. 

Rejection Rejection is defined in Background and Definitions. The highest-rejection membranes are those designed for single-pass production of potable water from the sea. The generally accepted criterion is 99.4 percent rejection of NaCl. Some membranes, notably cellulose triacetate fibers are rated even higher. A whole range of membranes is available as rejection requirements ease, and membranes with excellent chlorine resistance and hydrolytic stability can be made with salt rejection over 90 percent. 

The first application of chlorine in potable water was introduced in the 1830s for taste and odor control, at that time diseases were thought to be spread by odors. It was not until the 1890s and the advent of the germ theory of disease that the importance of disinfection in potable water was understood. Chlorination was first introduced on a practical scale in 1908 and then became a common practice. 

Soft drinks Potable water treatment, sterilization with chlorine Chlorine removal and adsorption of dissolved organic materials... 

NOTE Sulfite, bisulfite, and metabisulfite are commonly used as a reducing agent for chromate in industrial water and chlorine in potable water. 

Intensive technologies are derived from the processes used for the treatment of potable water. Chemical methods include chlorination, peracetic acid, ozonation. Ultra-violet irradiation is becoming a popular photo-biochemical process. Membrane filtration processes, particularly the combination microfiltration/ultrafiltra-tion are rapidly developing (Fig. 3). Membrane bioreactors, a relatively new technology, look very promising as they combine the oxidation of the organic matter with microbial decontamination. Each intensive technique is used alone or in combination with another intensive technique or an extensive one. Extensive... 

Posttreatment of the permeate for potable water use can include dissolved CO2 removal to prevent corrosion (by aeration, lime treatment), chlorination for microbial control, and oxygenation to improve taste. 

The use of chlorine dioxide in water systems results in its reduction to chlorite and chloride. In the UK the Drinking Water Inspectorate (DWI) restricts the use of chlorine dioxide in potable water supplies to a maximum of 0.5ppm total oxidants expressed as chlorine dioxide. This ensures that chlorite (and any chlorate) concentrations do not reach levels of potential harm to humans. 

The mobility of very slowly degradable compounds or persistent metabolites present in surface water or bank filtration-enriched ground water is of particular interest for the production of potable water. In common with many other compounds, certain surfactants, and especially their polar metabolites, have the potential to bypass the technical purification units used, which may include flocculation (active charcoal) filtration, ozonation or chlorination, and thus can be found ultimately in drinking water destined for human consumption (see Chapter 6.4). 

In summary, the FT-30 membrane is a significant improvement in the art of thin-film-composite membranes, offering major improvements in flux, pH resistance, and chlorine resistance. Salt rejections consistent with single-pass production of potable water from seawater can be obtained and held under a wide variety of operating conditions (ph, temperature, pressure, and brine concentration). This membrane comes close to being the ideal membrane for seawater desalination in terms of productivity, chemical stability, and nonbiodegradability. 

Fletcher IJ, Hemmings P. 1985. Determination of chlorine dioxide in potable waters using ehlorophenol red. Analyst 110(6) 695-699. 

Moore GS, Calabrese EJ, DiNardi SR, et al. 1978. Potential health effects of chlorine dioxide as a disinfectant in potable water supplies. Med Hypotheses 4(5) 481-496. 

Chlorination can result in unacceptable taste intensification, where potable water is concerned. This often originates in the chlorination of phenols present in trace amounts from industrial pollution. If economics permit, use of chlorine dioxide (Section 12.2) or ozone (Section 8.3) in place of chlorine will minimize taste intensification and will also avoid formation of carcinogenic chlorocarbons, notably chloroform. These carcinogens may form from chlorination of contaminants such as acetone, a commonly used solvent that finds its way into water supplies ... 

Chlorine is used in a number of industrial processes, including the manufacture of plastics, solvents, and pesticides. Chlorine is also used as a bleach in the paper and textile industries and as a disinfectant in warer treatment. The use of chlorine to provide potable water has made life in large cities and our modern lifestyles feasible. 

Water quality is usually defined in terms of chemical and bacteriological purity, particulate matter content, and endotoxin levels. Potable water is normally from the municipal water system, which may have been treated with chlorine to control microbiological growth. Soft water and deionized water have undergone ion exchange or similar treatment to eliminate unwanted ionic species, such as Mg2+ and/or Ca2+. Purified water, water for injection, and other types of water meeting compendial specifications are produced by ion exchange, reverse osmosis, distillation, or a combination of such treatments. 

Potable water containing chlorine or copper is generally considered toxic to many invertebrates. Yet, the lack of minerals, etc., in distilled water makes it osmotically unacceptable to many aquatic organisms. The fact that the water is fit for human consumption does not mean the water is acceptable to aquatic organisms. 

In response to these needs Dietrich et al. [108] used flow injection analysis with iodometric detection and ion chromatography with conductiometric detection in two methods for the determination of chlorite and chlorate in chlorinated and chloroaminated potable water. 

This technique was applied to several potable water samples. Crathome et al. [35] used the above technique to identify and determine the following four non volatile chlorinated organic compounds in potable water. 

Since the detection of halogenated organics in potable waters much research effort has been directed towards finding water treatment processes to remove such organics and their precursors and toward finding disinfectants other than chlorine. Great interest has been focused upon ozonisation because both disinfection and organic removal can be accomplished with this process. As ozonated end-products will occur in water produced by such processes and these could be potentially toxic and would accumulate in waste water after repeated cycles of use it is necessary to ascertain what end-products occur in water that has been ozonated and subsequently chlorinated. 

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