Disinfection hypochlorite

Disinfectant Hypochlorite bleach, pine oil, other low carbon number alcohols, quaternary ammonium compounds 0-15... 

Trisodium phosphate is strongly alkaline many of its appHcations depend on this property. For example, many heavy-duty cleaning compositions contain trisodium phosphate as a primary alkalinity source. The crystalline dodecahydrate itself is marketed as a cleaning compound and paint remover. Traditionally, trisodium phosphate has been used in water softening to remove polyvalent metal ions by precipitation as insoluble phosphates. Because the hypochlorite complex of trisodium phosphate provides solutions that are strongly alkaline and contain active chlorine, it is used in disinfectant cleaners, scouring powders, and automatic dishwashing formulations. 

Disinfection destroys pathogenic organisms. This procedure can render an object safe for use. Disinfectants include solutions of hypochlorites, tinctures of iodine or iodophores, phenoHc derivatives, quaternary ammonium salts, ethyl alcohol, formaldehyde, glutaraldehyde, and hydrogen peroxide (see Disinfectants AND antiseptics). Effective use of disinfected materials must be judged by properly trained personnel. 

Potassium peroxymonosulfate, introduced in the late 1980s, is finding increasing use as an auxiUary oxidant for shock treatment and oxidation of chloramines. Sodium peroxydisulfate is also being sold for shock treatment, however, it is less reactive than peroxymonosulfate. Mixtures of sodium peroxydisulfate and calcium hypochlorite can be used for shock treatment (28). Disadvantages of peroxymonosulfate and peroxydisulfate are they do not provide a disinfectant residual and peroxymonosulfate oxidizes urea and chloramines to nitrate ion, which is a nutrient for algae. 

The ideal recommended cyanuric acid concentration is 30—50 ppm (Table 2). Although this range can be readily maintained when using hypochlorite sanitizers, it cannot be maintained when using chloroisocyanurates since they increase the cyanuric acid concentration. The NSPI recommends a maximum of 150 ppm cyanuric acid. Many health departments limit cyanuric acid to 100 ppm. No significant increase in stabilization occurs beyond 50—100 ppm, and since high levels of cyanuric acid slow down the rate of disinfection, the pool water should be partially drained and replaced with fresh water to reduce the cyanuric acid to below recommended maximum levels. Cyanuric acid is determined turbidimetricaHy after precipitation as melamine cyanurate. 

Sanitizers. Spa and hot-tub sanitation is dominated by chlorine- and bromine-based disinfectants. Public spas and tubs usually employ automatic feeders, eg, CI2 gas feeders, to maintain a disinfectant residual. Private or residential spas and tubs can use automatic chemical feeding or generating devices, or they can be sanitized manually with granular or liquid products. The most widely used products for private spa and tub sanitation are sodium dichloroisocyanurate and bromochlorodimethylhydantoin. Granular products are normally added before and after use, whereas solids, eg, stick-bromine, are placed in skimmers or feeders. Bromine generating systems can also be used and are based on oxidation of bromide ions (added to the water as sodium bromide) by peroxymonosulfate, chloroisocyanurates, hypochlorites, or ozone to generate the disinfectant HOBr. 

Commercial laundries have used and continue to use sodium hypochlorite as the primary bleaching agent because of its whitening and disinfectant properties. 

A 5—6% sodium hypochlorite solution is sold for household purposes, of which the largest use is in laundry. Solutions of 10—15% NaOCl are sold for swimming pool disinfection, institutional laundries, and industrial purposes. Solutions of various strengths are used in household and industrial and institutional (I I) cleaners, disinfectants, and mildewcides. A small amount is used in textile mills. Sodium hypochlorite is also made on site with 30—40 g/L available chlorine for pulp bleaching, but its use is decreasing in order to reduce chloroform emissions (see Chlorine oxygen acids and salts). 

The largest use of calcium hypochlorite is for water treatment. It is also used for I I and household disinfectants, cleaners, and mildewcides. Most of the household uses have been limited to in-tank toilet bowl cleaners. In areas where chlorine cannot be shipped or is otherwise unavailable, calcium hypochlorite is used to bleach textiles in commercial laundries and textile mills. It is usually first converted to sodium hypochlorite by mixing it with an aqueous solution of sodium carbonate and removing the precipitated calcium carbonate. Or, it can be dissolved in the presence of sufficient sodium tripolyphosphate to prevent the precipitation of calcium salts. However, calcium hypochlorite is not usually used to bleach laundry and textiles because of problems with insoluble inorganic calcium salts and precipitation of soaps and anionic detergents as their calcium salts. 

Lithium hypochlorite is used in I I laundry detergents and I I dry laundry bleaches. Like sodium hypochlorite, it does not precipitate soaps and other anionic detergents. However, lithium hypochlorite is an expensive source of available chlorine and not much is used for bleaching. Its principal use is as a shocking agent for swimming pool disinfection. 

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... 

Some hypochlorites, either as solutions or soflds, are much more stable than hypochlorous acid, and because of thek high oxidation potential and ready hydrolysis to the parent acid, find wide use in bleaching and sanitizing appHcations. One of the novel uses of hypochlorites was for disinfection of ApoUo Eleven on its return from the moon (136). 

Although the hypochlorite ion itself is a relatively poor disinfectant (178) in comparison to hypochlorous acid, it serves as a reservoir of the latter by hydrolysis ... 

Ethanol and 2-propanol have also found use ia disinfecting clinical thermometers, and as preservatives to prevent microbial deterioration of cosmetics and mediciaals. They are sometimes combiaed with other disiafectants, namely formaldehyde (69), phenoHcs (70), chlorhexidine (71), hypochlorite (72), and phenols (70). 

Whereas these preparations do not possess the high bacteriostatic activity of quaternary ammonium germicides, they have the alternate advantage of being rapidly functional in acid solution. In comparative experiments of several different disinfectants, the acid—anionic killed bacteria at lower concentration than five other disinfectants. Only sodium hypochlorite and an iodine product were effective at higher dilution than the acid—anionic. By the AO AC use dilution test, the acid—anionic killed Pseudomonas aeruginosa at 225 ppm. Salmonella choleraesuis at 175 ppm, and Staphylococcus aureus at 325 ppm (172). 

Available Chlorine Test. The chlorine germicidal equivalent concentration test is a practical-type test. It is called a capacity test. Under practical conditions of use, a container of disinfectant might receive many soiled, contaminated instniments or other items to be disinfected. Eventually, the capacity of the disinfectant to serve its function would be overloaded due to reaction with the accumulated organic matter and organisms. The chlorine germicidal equivalent concentration test compares the load of a culture of bacteria that a concentration of a disinfectant will absorb and still kill bacteria, as compared to standard concentrations of sodium hypochlorite tested similarly. In the test, 10 successive additions of the test culture are added to each of 3 concentrations of the hypochlorite. One min after each addition a sample is transferred to the subculture medium and the next addition is made 1.5 min after the previous one. The disinfectant is then evaluated in a manner similar to the phenol coefficient test. For equivalence, the disinfectant must yield the same number of negative tubes as one of the chlorine standards. 

The most commonly used disinfectant is chlorine, which can be supplied in the form of a liquefied gas which has to be dissolved in water, or in the form of an alkaline solution called sodium hypochlorite, which is the same compound as... 

The effect of pH alone on chlorine efficiency is shown in Figure 3. Chlorine exists predominantly as HOCl at low PH levels. Between pH of 6.0 and 8.5, a dramatic change from undissociated to completely dissociated hypochlorous acid occurs. Above pH 7.5, hypochlorite ions prevail while above 9.5, chlorine exists almost entirely as OCl. Increased pH also diminishes the disinfecting efficiency of monochloramine. 

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