Drinking water disinfection

Chlorine Dioxide. Like ozone, chlorine dioxide [10049-04-4] is a powerflil oxidant. It is usually generated as used. It has been used for disinfecting drinking water and bleaching paper pulp. Its effectiveness in killing microorganisms is well documented (305,306), and it has received recent study as a gas to sterilize medical devices. It requites 50% rh or higher to be effective. Bacterial cells had a D-value of 2.6 min and spores of 24 min (307). 

Halogenation is important for disinfecting drinking water supplies, generally nsing molecular chlorine. Most attention has been directed to the adverse production of haloforms and haloacetates from reactions of chlorine with natural substrates, although in water containing bromide/iodide, a nnmber of other reactions may occur. 

Very little is known about nonbiologically mediated transformations of acrylonitrile in water. There are no data to suggest that acrylonitrile hydrolyzes in air, no reliable information was found on photochemical reactions in water. There also no data on the oxidation of acrylonitrile in water. Acrylonitrile is susceptible to oxidation by strong oxidants such as chlorine used to disinfect drinking water. 

In this profile, the term chlorite will be used to refer to chlorite ion, which is a water-soluble ion. Chlorite ion will combine with metal ions to form solid salts, (e.g., sodium chlorite). In water, sodium chlorite is soluble and will dissolve to form chlorite ions and sodium ions. More than 80% of all chlorite (as sodium chlorite) is used to make chlorine dioxide to disinfect drinking water. Sodium chlorite is also used as a disinfectant to kill germs. 

Tuthill RW, Giusti RA, Moore GS, et al. 1982. Health effects among newborns after prenatal exposure to C102-disinfected drinking water. Environ Health Perspect 46 39-45. 

In 1908, Jersey City, New Jersey, became the first American city to begin chlorinating its drinking water. By 1910, as disinfecting drinking water with chlorine became more widespread, the death rate from typhoid fever dropped to 20 lives per 100,000. In 1935, the death rate fell to 3 lives per 100,000. By 1960,fewer than 20 persons in the entire United States died from typhoid fever. 

Tests were carried out to demonstrate the efficacy of the inventive composition in disinfecting drinking water. 

According to the amendments to the SDWA, all public water suppliers, including those that rely on groundwater, will have to disinfect drinking water before distribution. To ensure compliance with all applicable regulations (both current and anticipated), the specific objectives of disinfection are to (a) ensure 99.9% (3-log) and 99.99% (4-log) inactivation of Giardia lamblia cysts and enteric viruses, respectively (b) ensure control of other harmful microorganisms (c) not impart toxicity to the disinfected water (d) minimize the formation of undesirable disinfection by-products and (e) meet the maximum contaminant levels (MCLs) for the disinfectants used and by-products that may form (4). 

Before leaving this sub-section on chlorine as a disinfectant, we should note that the majority of the Asian cities still do use chlorine to disinfect drinking water. The benefits in term of protection from water-borne diseases in Asia far overweigh the possible hazard from, for example, 10 or 20 ppb of trihalomethanes. Disinfection with chlorine may possibly pose a cancer risk in old age no disinfection in the Asian region does mean a substantial chance of dying from typhoid fever or cholera as a child or young adult. However, as we have seen in Table 1, there are different methods of disinfection and we consider some of these alternatives to chlorination. 

The use of ozone to disinfect drinking water started at the end of the 19 century in the Netherlands and in the beginning of the 20 century in Germany. At present, ozonation is used in many municipalities worldwide, including some Japanese cities. 

Chlorine is commonly used to disinfect drinking water, and inactivation of pathogens by chlorine follows first-order kinetics. The following data show E. coli inactivation ... 

Chlorine, or sodium hypochlorite, is almost always used to disinfect drinking water (i.e., reduce pathogenic organisms, such as bacteria and viruses, to safe levels). The treatment has the advantage of leaving residual dissolved chlorine in the treated water, which helps to ensure that the water remains resistant to reinfection in the distribution system. 

Chlorine gas is used to disinfect drinking water and sewage, and in the production of organic chemicals such as pesticides and vinyl chloride, the building block of plastics called polyvinyl chlorides (PVGs, Section 14.5). Chlorine gas is commonly among the top chemicals produced each year in the United States. Almost all chlorine gas is made by electrolysis of aqueous sodium chloride. The other product of sodium chloride electrolysis, sodium hydroxide, is equally valuable because it is the most commonly used base in industrial processes. The reaction in electrolysis of aqueous NaCl is... 

Chlorine dioxide is frequently employed for disinfecting drinking water, as this prevents or noticeably reduces the formation of so-called haloforms or trihalomethanes. 

In satisfactory ground water the colony number will not exceed the standard value of 100 per ml at an incubation temperature of 20 C. In the case of disinfected drinking water, the colony number should be less than 20 per ml after completion of the treatment processes. 

For example, where decisions have to be taken in emergencies or as a result of disasters, it is better to disinfect drinking water by heating it or using chemicals (and ignoring the chemical parameters etc.) than to die of thirst. 

Chlorite (C102 ) is a disinfection by-product that is formed when chlorine dioxide (CIO2) is used for disinfecting drinking water, while chlorate (CIOs ) is formed when chlorine dioxide or chloramine is used. Chlorination using hypochlorite acid solutions, which contain some CIOs a product of HCIO disproportionation, may also contribute to CIOs contamination in disinfected water. Even at low levels, chlorite may lead to hemolytic anemia... 

Point-of-use electrolytic generation of hypochlorite from salt solutions or seawater has been used since 1900. It is mostly used to disinfect drinking water, cooling water, swimming pools, and sewage. It is also used in commercial laundries and in health care. Since about 1980, electrolytic generators have been used in appliances " and devices that dispense dilute solutions for cleaning,... 

The use of chlorine to disinfect drinking water supplies began in the late 1800 s and early 1900 s. It dramatically reduced the incidence of waterborne diseases such as cholera and typhoid fever. 

Household chlorine bleach is a dilute solution of sodium chlorate(i) (sodium hypochlorite). It is prepared by absorbing chlorine gas into cold sodium hydroxide solution. More concentrated solutions are used to disinfect drinking water and swimming pools. Bleach should never be mixed with other household cleaners. With bleach, acid-based cleaners produce chlorine and ammonia-based products produce toxic chloramines, for example NH2CI. 

Think About It CIO2 is used primarily to bleach wood pulp in the manufacture of paper, but it is also used to bleach flour, disinfect drinking water, and deodorize certain industrial facilities. 

---