Disinfection, water

Since the beginning of the twentieth centiuy chlorine gas or liquid chlorine is used as disinfectant. Today about 98% of West Europe s drinking water is purified by chlorination. 

When chlorine is added to water, a mixture of hypochlorous and hydrochloric acid is formed 

The equilibrium depends on the pH level at pH 4, the equilibrium is displaced to the right and little CI2 exists in solution, the chlorine exists predominantly as HOCl. Between pH 6.0 and 8.5, the HOCl dissociates 

Above pH 7.8 hypochlorite ions (OC1-) predominate, and they exist almost exclusively at pH 9. 

Chlorine existing in water as hypochlorous acid and hypochlorite ions (or both) is defined as free available chlorine. 

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Hypochlorous Acid. Hypochlorous acid [7790-92-3] solutions are made for immediate use as chemical intermediates from chlorine monoxide or in bleaching and water disinfection by adjusting the pH of hypochlorite solutions. Salt-free hypochlorous acid solutions have been economically made... 

Potable Water Treatment. Treatment of drinking water accounts for about 24% of the total activated carbon used in Hquid-phase apphcations (74). Rivers, lakes, and groundwater from weUs, the most common drinking water sources, are often contaminated with bacteria, vimses, natural vegetation decay products, halogenated materials, and volatile organic compounds. Normal water disinfection and filtration treatment steps remove or destroy the bulk of these materials (75). However, treatment by activated carbon is an important additional step in many plants to remove toxic and other organic materials (76—78) for safety and palatability. 

Imidazolidinones. Several mono and dichloro isomers have been prepared and tested as disinfectants (157) 1-ch1oro-4,4,5,5-tetramethylimidazo1idin-2-one [58816-19-6] l,3-dichloro-4,4,5,5-tetramethylimidaZohdin-2-one [58816-20-9] (5), mp 102—104°C l-chloro-2,2,5,5-tetramethylimidazohdin-4-one [38951-95-8] mp 157—158°C and l,3-dichloro-2,2,5,5-tetramethylimidazohdin-4-one [128780-87-0] (6), mp 69—71°C (158). In water, these compounds are somewhat less stable but better disinfectants than the oxazoUdinones. They have potential for water disinfection and in hard surface cleaners. l-Bromo-3-chloro- [108602-19-3] mp 102—104°C, and 1,3-dibromo- [108602-18-2] mp 119—121°C, derivatives of 4,4,5,5-tetramethylimidazohdin-2-one have been prepared. 

Chlorine dioxide yields of 95% or greater have been demonstrated. The use of chlorine as an oxidant has distinct advantages because it is usually present in municipal water treatment plants for water disinfection. 

One of the most widespread methods of water disinfection is it s chlorination. As chloration products ai e toxic, their content is to be controlled. Among them free chlorine and inorganic chloramines ai e predominant in water. Maximum contaminant limit for free chlorine is 0.3 - 0.5 mg/L, for chloramines - 0.8 - 1.2 mg/L. 

Total Trihalomethanes none 0.10 Liver, kidney or central nervous Byproduct of drinking water disinfection... 

Treatment of a water supply is a safety factor, not a corrective measure. There are a number of ways of purifying water. In evaluating the methods of treatment available, the following points regarding water disinfectants should be eonsidered ... 

What parameters impact on the effectiveness of chlorine as a water disinfectant ... 

Can ozone be used as the only means of water disinfection in a treatment facility If not, why not, and what other technologies do you think would work in combination with ozone treatment ... 

Polcaro AM, Vacca A, Mascia M et al (2007) Characterization of stirred tank electrochemical cell for water disinfection processes. Electrochim Acta 52 2595-2602... 

Montemayor M, Costan A, Lucena F et al (2008) The combined performance of UV light and chlorine during recalimed water disinfection. Water Sci Technol 57(6) 935-940... 

Cemeli E, ED Wagner, D Anderson, SD Richardson, MI Plewa (2006) Modulation of the cytoxicity and geno-toxicity of the drinking water disinfection byproduct iodoacetic acid by suppressors of oxidative stress. Environ Sci Technol 40 1878-1883. 

Plewa Ml, ED Wagner, SD Richardson, AD Thurston, Y-T Woo, AB McKague (2004) Chemical and biological characterization of newly discovered iodoacid drinking water disinfection byproducts. Environ Sci Technol 38 4713 722. 

US EPA Water Disinfection By-Products with Carcinogenicity Estimates. 

The DBPCAN database contains predicted estimates of carcinogenic potential for 209 chemicals detected in finished drinking water samples having undergone water disinfection treatment. 

Gil, M. 1., Selma, M. V., Lopez-Galvez, F., and Allende, A. (2009). Fresh-cut product sanitation and wash water disinfection Problems and solutions. Int. J. Food Microbiol. 134,37-45. 

The recent addition of criteria for continuous water disinfection using UV light as described in the Pasteurized Milk Ordinance (FDA, 2009) also may lead to the develop of systems for CIP based on UV light and other so-called nonthermal methods described earlier. 

Chlorine dioxide has been used widely in Europe since the early 1940 s as a drinking water disinfectant. More recently the USA has suggested the use of chlorine dioxide to reduce the formation of chloro-organic compounds particularly chloroform and other trihalomethanes (THM s) which are known carcinogens(7). 

Chand et al. [64] have investigated the use of ozone treatment assisted by a liquid whistle reactor (LWR), which generates hydrodynamic cavitation, for water disinfection using a simulated effluent containing Escherichia coli. A suspension having an E. coli concentration of approximately 10s to 109 CFU mL 1 was introduced into the LWR to examine the effect of hydrodynamic cavitation alone... 

Jyoti KK, Pandit AB (2001) Water disinfection by acoustic and hydrodynamic cavitation. Biochem Eng J 7 201-212... 

Chand R, Bremner DH, Namkung KC, Collier PJ, Gogate PR (2007) Water disinfection using a novel approach of ozone assisted liquid whistle reactor. Biochem Eng J 35 357-364... 

Fernandez, P., Blanco, J., Sichel, C., and Malato, S. (2005) Water disinfection by solar photocatalysis using compound parabolic collectors. Catalysis Today,... 

Rincon, A.G., and Pulgarin, C. (2004) Effect of pH, inorganic ions, organic matter and H202 on E. coli K12 photocatalytic inactivation by Ti02 implications in solar water disinfection. Applied Catalysis B Environmental, 51 (4), 283-302. 

Sufficiently cheap UV photodiodes are available but they are not visible-blind. Filters have to be used, but they raise the costs. Sufficiently selective photodiodes are also available but they are too expensive, mainly due to their only recently established technology. The sensor costs have been a limiting factor in two application fields of UV sensors, namely water disinfection and combustion monitoring, on the industrial as well as on the household scale. 

In communal-scale water disinfection plants, UV monitoring systems are generally included. However, for household-scale systems they are not available or only as an optional accessory. 

Contaminated clothing or bed linen could also spread the virus. Special precautions need to be taken to ensure that all bedding and clothing of patients are cleaned appropriately with bleach and hot water. Disinfectants such as bleach and quaternary ammonia can be used for cleaning contaminated surfaces. 

This book examines comprehensively the chlorine industry and its effects on the environment. It covers not only the history of chlorine production, but also looks at its products, their effects on the global environment and the international legislation which controls their use, release and disposal. Individual chapters are dedicated to subjects such as end use processes, water disinfection and metallurgy, environmental release of organic chlorine compounds, polychlorinated biphenyls, legal instruments and the future of the chlorine industry. 

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