Ozone sanitization

Other Sanitizers and Treatment Systems. Other sanitizers and swimming pool treatment systems used to a limited extent are bromine, quats, ozone, ionizers, electrolyzers, uv, UV/H2O2, and Ag/H202. 

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. 

Methyl bromide has been identified as an ozone-depleting substance and is being gradually removed from world markets. Current legislation and plans call for the elimination of methyl bromide in most industrial countries by 2005, with possible exemptions for quarantine (UNEP, 1996). Currently there is an extensive search worldwide for products that are alternatives to methyl bromide (Kawakami, 1999). These alternatives are broadly defined and include components of management plans such as sanitation, monitoring, contact insecticides, heat treatments, and modified atmospheres, in addition to new fumigants (Batchelor, 1998). 

Chemical methods, where compatible, can be used on a wider variety of construction materials. These methods typically employ oxidizing agents such as hypochlorite, hydrogen peroxide, ozone, or per-acetic acid. Hypochlorites are effective sanitizers but are difficult to flush from the system and tend to leave biofilms intact. 

Chlorine is a yellow-green gas that is very reactive. Both ozone and chlorine are used to kill bacteria and generally sanitize public areas such as swimming pools and hospital rooms. 

Microbial fouling is best dealt with before biofilm becomes mature. Biofilm protects the microorganisms from the action of shear forces and biocidal chemicals used to attack them. Microbes can be destroyed using chlorine, ozone, ultraviolet radiation, or some non-oxidizing biocides (see Chapters 8.2.1,8.2.2, 8.1.8, and 8.2.5, respectively). An effective method to control bacteria and biofilm growth usually involves a combination of these measures. Specifically, chlorination or ozonation of the pretreatment system, followed by dechlorination to protect the membranes, or UV distraction followed by periodic sanitation with a non-oxidizing biocide used directly on the membranes. 

This evaluation showed that with the ozonator + chlorine system the disinfection is mainly due to the chlorine pellet additions as the pollution level decreases after each addition to strongly increase again after few days with only ozone disinfection. The problem with such system is that the spa water is always cycling between an overload of chlorine (after shock chlorination) and a high bacterial pollution when there is no remaining chlorine in the water. With Mini-DiaCell , the sanitation and stabilization of the water is longer (approximately 7 days), but after this period the bacterial level in the water remains stable at very low level. 

UV oxidation of organic water pollutants in the presence of hydrogen peroxide, ozone or both with powerful medium-pressure mercury lamps is performed on industrial scales (Gottschalk et al., 2000). The synergistic combination of ozone and UV is especially suited for water sanitation, i.e. treatment of swimming pool and spa water (Rice, 1997). Many full-scale remediation applications of photo-initiated AOPs using hydrogen peroxide or ozone are already in operation (Chem-viron Carbon, 1997, Freeman and Harris, 1995). 

Oxidation-reduction reactions can be used for bleaching materials and sanitizing water. Sodium hypochlorite is used in solution as a liquid laundry bleach and as a solid component of dishwasher powders and cleansers. Calcium hypochlorite is often used for swimming pool sanitation. The hypochlorites kill bacteria in water by oxidizing them. Ozoue is a powerful oxidizing agent that can also be used to purify water. The ozone destroys bacteria and organic pollutants. Water that has been sanitized by ozone is free of the unpleasant taste, smell, and byproducts associated with chlorinated water. 

Holah et al [1994] have drawn attention to the fact that disinfection or sanitation are an essential part of the cleaning requirements for food processing equipment to maintain product quality. Ozone has been suggested as a possible sterilising agent in the cleaning of heat exchangers [Bott 1991]. The ozone in... 

The equipment required for water treatment will be determined by the quality of the incoming water. Typically, a USP pharmaceutical grade system will require pretreatment (filters), deionization, reverse osmosis, and potentially a polishing step such as continuous deionization. Many systems now incorporate UV filters for sanitization, which kill micro-bials and also eliminate ozone. 

The systems are designed to be cleaned. Recent industry practices have included the use of ozone injected into the system as a sanitization step. Other methods include steam sanitization. The ozone is then eliminated through the UV filters. The system should be designed for a complete sanitization, which includes all storage tanks and distribution piping. 

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