Chlorine in water purification

Bromine (CAS 7726-95-6) Corrosive severe skin and eye bums may result. Vapors highly irritating to eyes and respiratory tract pulmonary edema may result. Measles-like eruptions may appear on the skin several hours after a severe exposure. 0.1 ppm 3 ppm ERPG-1 0.1 ppm ERPG-2 0.5 ppm ERPG 3 5 ppm 3 0 0 Ox Heavy red-brown fuming liquid. Odor and irritation thresholds are below the TLV and are adequate warning properties. Vapor pressure is 175 mm Hg at 20°C (68 F). Not combustible. Used as an alternative to chlorine in water purification (eg, hot tubs). 

R. H. Moser The Future of Chlorine in Water Purification, Paper for the 2nd World Chlor-Alkali Symposium, Washington D.C., September 1990. 

Ozone kills bacteria and is an environmentally safe replacement for chlorine in water-purification plants because the only by-product is O2. However, since ozone naturally decomposes, it must constantly be replenished, an economic drawback that limits its use. 

A number of perhalides aie known, and one of the most stable is ammonium tetiachloioiodide [19702 3-3] NH IQ. Ammonia reacts with chlorine in dilute solution to give chloramines, a reaction important in water purification (see Cm,ORAMINES AND BROMAMINEs). Depending upon the pH of the water, either monochloramine [10599-90-3] NH2CI, or dichloramine [3400-09-7] NHCI2, is formed. In the dilutions encountered in waterworks practice, monochloramine is neady always found, except in the case of very acidic water (see Bleaching AGENTS Water). 

Chlorine dioxide has 2lh times the bleaching power of chlorine and is important in water purification, for odor control, and for pulp bleaching. 

Sodium hydroxide has many different uses in the chemical industry. Considerable amounts are used in the manufacture of paper and to make sodium hypochlorite for use in disinfectants and bleaches. Chlorine is also used to produce vinyl chloride, the starting material for the manufacture of polyvinyl chloride (PVC), and in water purification. Hydrochloric acid may be prepared by the direct reaction of chlorine and hydrogen gas or by the reaction of sodium chloride and sulfuric acid. It is used as a chlorinating agent for metals and organic compounds. 

Over a dozen oxides of the halogens have boon characterized, many of them quite unstable. Perhaps the most important are chlorine dioxide, CJ02, and iodine pentoxide, I2O5. Chlorine dioxide (boiling point 11° C) is an odd molecule (p. 62), but apparently it shows no tendency to dimerize. Although it has been used as an antiseptic in water purification and as a bleach, it must be handled in diluted form for it is explosive when alone. It is formed, along with HCIO4, when chlorates are treated with concentrated sulfuric acid, but a safer preparation involves reduction of a chlorate with oxalic acid. 

Chlorine is widely used throughout the world to purify water. In the United States, about 4 percent of the chlorine manufactured is used in water purification. Very small amounts of chlorine (about 1 percent of all the chlorine produced) is used in the paper and pulp industry as a bleach. 

Objective 15 59. Gaseous chlorine, CI2, used in water purification, is a dense, greenish-yellow... 

As happens in the electrolysis of other salts, the chlorine gas that is produced is an important source of chlorine for water purification systems. 

The organic contamination is not appreciably removed by the steps of coagulation, chlorination, and filtration employed in water purification plants. Activated carbon is used in sufficient quantities to make the water palatable and eliminate foaming but relatively few substances cause foaming, and only the more odorous ingredients will give a perceptible taste at the dilutions usually present (Table 6 2). Therefore we must recognize that the hazards from... 

USE In the preparation of chlorine dioxide for immediate use in water purification as bleaching agent for textiles, paper pulp. 

Hypochlorous acid, formed when chlorine dissolves in water, is antimicrobial. This is the basis for the use of chlorine and halazone in water purification. Organic matter binds chlorine, thus preventing antimicrobial actions. In a given water sample, this process is referred to as the chlorine demand, since the chlorine-binding capacity of the organic material must be exceeded before bacterial killing is accomplished. Many preparations of chlorine for water purification do not eradicate all bacteria or entamoeba cysts. 

FIGURE 11.12 Final steps that can be used in water purification. Both bottled water and municipal tap water are purified in these ways. The color code shows which pollutants are removed by each method. Pathogenic bacteria can and do pass through all these methods. This is why municipal tap water must be treated with chlorine or some other disinfectant before release into the system. 

A major chemical in water purification is hypochlorite or chlorine. The use of ozone [74] is an attractive alternative for water treatment as it does not release any additional reagents into the waters. Ozone can be generated anodically from relatively pure water according to the reaction... 

The major use for chlorine is the chlorination of ethylene to make ethylene dichloride (this is always referred to as ethylene dichloride, but the more proper name is 1,2-dichlorethane) by addition of chlorine to the double bond. Ethylene dichloride, or EDC, is converted into vinyl chloride, which is then converted to polyvinyl chloride (PVC) polymer. There are many uses for PVC, but much of the demand is in the building and construction industry for items such as plumbing, vinyl siding, and window frames. Therefore the robustness of the construction business has a major effect on PVC demand and, in turn, chlorine demand. Other uses for chlorine include water purification, titanium dioxide production, phosgene production and orgamc... 

A chemical used to age or bleach flour, to impart to it the desirable characteristics of flour stored for weeks. Also chlorine dioxide is used to bleach organic materials such as cellulose, flour, fats and oils, and to act as a bacteriocide and antiseptic in water purification. 

EDC from the oxychlorination process is less pure than EDC from direct chlorination and requires purification by distillation. It is usually first washed with water and then with caustic solution to remove chloral and other water-extractable impurities (103). Subsequently, water and low boiling impurities are taken overhead in a first (light ends or heads) distillation column, and finally, pure, dry EDC is taken overhead in a second (heavy ends or product) column (see Fig. 2). 

The energy requirements for desorbing 1,1-dichloroethane from activated carbon in a stripping—adsorption process for water purification have been calculated at 112 kj/kg (14). Chlorinated hydrocarbons such as 1,1-dichloroethane may easily be removed from water by air or steam stripping. 

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