Using Alternative Disinfectants

Use alternate disinfectants that do not produce undesirable by-products this second approach, using alternative disinfectants, is often the most cost-effective. 

Reduce the concentration of organics in the water before oxidation or chlorination to minimize the formation of by-products. The third approach, reducing the concentrations of organic precursors before adding chlorine or other oxidants, will provide the highest quality finished water. 

This approach, using other than chlorine for disinfection, is sound if the replacements do not produce undesirable hy-products of their own and if they perform equally as both 

Summary of Health Effects Associated With Chlorination By-Products (32) 

Key to toxicological effects C = Carcinogenic H = Hepatotoxic RT = Renal toxic G = Genotoxic D = Developmental M = Mutagenic MD = Metabolic disturbance N = Neurotoxic OL = Ocular lesions A = Aspermatogenesis HPP = Hepatic peroxisome proliferation F = Fetotoxic TP = Tumor promoter Cl = clastogenic. 

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Disinfeetion. Chlorine, as gaseous chlorine or as the h5rpochlorite ion, is widely used as a disinfectant. However, its use in some cases can lead to the formation of toxic organic chlorides, and the discharge of excess chlorine can be harmful. Ozone as an alternative disinfectant leads to products that have a lower toxic potential. Treatment is enhanced by ultraviolet light. Indeed, disinfection can be achieved by ultravifflet light on its own. 

Several methods have received considerable research attention as alternatives to salt curing. These include use of sodium bisulfite as a disinfectant to allow preservation with or without decreased salt in a brine cure use of disinfectants such as quatenary amines for temporary preservation in direct shipping to the taimery from the packing plant (see Disinfectants and antiseptics) preservation of hides by radiation sterilization (see Sterilization techniques) and substitution of materials such as potassium chloride for sodium chloride. These methods have found only limited commercial success. 

Ozone applications in the United States for drinking water are far fewer than in Europe. However, the potential market is large, if environmental or health needs ever conclude that an alternate disinfectant to chlorine should be required. Although energy costs of ozonation are higher than those for chlorination, they may be comparable to combined costs of chlorination dechlorination-reaeration, which is a more equivalent technique. One of ozone s greatest potential uses is for municipal wastewater disinfection. 

Prior to use the rotor and the protective cap should be autoclaved daily at 121°C for 15 minutes or sterilized with dry heat at 180° for 2 hours. Alternatively, disinfection can be carried out using filtrated disinfectant however, the rotor must not be allowed to come into contact with alkaline solution. The housing of the RCS + is made of polycarbonate and can be disinfected by spraying or wiping with a solution of 70% ethanol. The batteries must be charged. 

Alternative disinfecting techniques use ozone gas, which is very effective in killing microorganisms. In the process, ozone breaks down into oxygen gas, which improves water quality (see Section 10.1.1.1). Because ozone is unstable, it must be generated at the point of use, a step that demands considerable capital investment and energy. 

These final tests, to which great importance was attached, were undertaken in June 1952 under stable conditions of water quality and temperature, natural and artificial degrees of infection, and alternate ozone dosages used for disinfection. 

For some industries such as pharmaceuticals, electronics, and toiletries, ultra-pure water is always demanded. Pathogens, organic substances, and inorganic substances must be effectively removed to a very low level (e.g., less than 1 ppb TOC in semiconductor fabrication manufacturing). The source water is first filtered by multimedia filters and disinfected by UV light. The water is then treated by membrane units (usually reverse osmosis) and stored. Later on, UV photolysis, ion exchange resin and micro-filters are used alternatively to produce the high pure process water. 

This chapter only discusses the applications of chlorination and chloramination in potable water treatment. In case the two processes are to be used for wastewater treatment, residual chlorine concentration in the plant effluent may become a regulatory issue (30). Selection of an alternative disinfectant becomes more important. New alternative disinfectants have been studied by Wang (19-25). Wang (35,36) also reported that UV is an effective process for dechlorination, dechloramination, or de-ozonation. 

P. S. Singer, THM control using alternate oxidant and disinfectant strategies. Proceedings 1986 AWWA Conference, American Water Works Association, Denver, CO, pp. 999-1017. 

Treated wastewater from municipal sewage plants requires a treatment with chlorine before discharge into a river, at least in the warmer months of the year. Because the residual chlorine can kill the flora and fauna of the river, the treated wastewater is usually treated further with sulfur dioxide or sodium bisulfite to remove the chlorine.128 This seems like an ideal place to use alternative methods of disinfection, because no residual activity is needed or desired. Disinfection with ultraviolet light is now a viable alternative.129... 

Chlorine is not the only means of disinfection available, but other methods can also produce toxic by-products. In addition, alternative disinfectants do not provide the residual protection offered by chlorine-based disinfectants, so they must be used in combination with chlorine. Drinking water treatment must satisfy the competing objectives of maximum microbial decontamination and minimum production of toxic by-products. This is a difficult task that will require research by chemists and chemical engineers in collaboration with a variety of other experts to continuously improve the safety and quality of the world s drinking water. 

Ultraviolet (UV) disinfection is a commonly-used alternative wastewater treatment to chlorine disinfection. While few studies have addressed... 

Before working the inside of the isolator has to be cleaned and disinfected. Disinfection can be done with peracetic acid or hydrogen peroxide, using special disinfection devices and procedures. For small scale or incidental use ethanol 70-80 % may be used as an alternative. 

Normally two disinfectants are used alternately to prevent accumulation of resistant micro-organisms, however there is little evidence to support this [23]. 

Propanol and 1-proponal (1.2.) are the highest alcohols which are miscible with water. The presence of water is essential for the effectiveness of 2-propanol, too. Moste effective are concentrations of approx. 50%. Investigations of Powell (1945) have shown that Stahylococcus aureus was killed within 1 minute at 20°C in 50 to 91% 2-propanol solutions. Escherichia coli was killed by a 5-minute exposure at 20°C to >30% solutions. The data reported by Wallhausser (1984) for ethanol (1.1.) demonstrate the higher efficacy of 2-propanol which in the meantime has become a proved alternative to ethanol for use in disinfectants, e.g. in hand rinses, and as a preservative in cosmetics. 

The extensive use of chlorine to purify water has recently been shown to result in the formation of chlorinated hydrocarbons. Low molecular weight compounds, such as the haloforms (HCX3), also called trihalomethanes (THM), are volatile and have been shown to be carcinogenic. They have been detected in drinking water and in the air of enclosed swimming pools. Thus, several alternate disinfectants (such as ozone, chlorine dioxide, UV, and ferrates) have been crmsidered as alternates to chlorine. Of these, the use of ozone has been most developed. 

White, G. C. 2010. White s Handbook of Chlorination and Alternative Disinfectants, 5th ed. New York John Wiley Sons. This book discusses all aspects of water purification using chlorination. 

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