Chlorine-Based Sanitizers

Chlorine in its active form, hypochlorous acid (HOCl), is a powerful oxidant and antimicrobial agent. Hypochlorous acid is present in highest concentration at near pH 4, decreasing rapidly with increased pH. At pH 5 hypochlorite (OCl ) increases, whereas at pH 4, chlorine gas (CI2) increases. Neither chlorine gas nor hypochlorite have been shown to be active toward microorganisms (Mercer and Somers, 1957) however, both are very corrosive. Formation of Cl2(g) is also a safety issue for employees. In that there is still substantial amounts of HOCl present at pH 6.5, sanitizing operations are typically carried out in the pH range 6.5-7.0. 

Because chlorine is an oxidant, activity will prematurely degrade if organic residues (reflecting inadequate cleaning) are present. The time needed for completion is also temperature dependent. Up to 52 C (125 F), the reaction rate (and corrosive properties) doubles for each 18 F increase in temperature. Although hypochlorites are relatively stable, the solubility of CI2 decreases rapidly at temperatures above 50 C (122 F). As seen in Table 7-2, several forms of chlorine are available. 

Sanitizing surfaces requires active chlorine concentrations of 100-200 mg/L. Even though stainless steel is frequently described as being inert with respect to oxidation, both 304- and 316-grade stainless steel will eventually exhibit corrosion if exposed to higher than recommended levels of 

Suppliers of detergents and sanitizers to the food and wine industries continue to advise against indiscriminate use of chlorine and chlorine-containing agents. Despite this, the relative low cost of these versus so-called buffered chlorine agents continues to make the former group an attractive but potentially destructive alternative. 

---

Another major concern surrounding the use of chlorine in wineries is the potential formation of 2,4,6-trichloroanisole (TCA). This compound can be produced by various microorganisms from chlorinated precursors (Section 4.6.3) and imparts a musty or corkiness off-odor to wines (Lee and Simpson, 1993). Use of chlorine and/or chlorine-based sanitizers in a winery can be involved in the formation of environmental TCA (Pena-Neira et al., 2000). Due to these concerns, it is advisable to reduce or even eliminate chlorine use in the winery. If chlorine-based products are to be used, these should never be mixed with acidic products (toxic gas and/or explosives can be produced). 

Toxicity of Chlorine Sanitizers. Chlorine-based swimming-pool and spa and hot-tub sanitizers irritate eyes, skin, and mucous membranes and must be handled with extreme care. The toxicities are as follows for chlorine gas, TLV = 1 ppm acute inhalation LC q = 137 ppm for 1 h (mouse) (75). The acute oral LD q (rats) for the Hquid and soHd chlorine sanitizers are NaOCl (100% basis) 8.9 g/kg (76), 65% Ca(OCl)2 850 mg/kg, sodium dichloroisocyanurate dihydrate 735 mg/kg, and trichloroisocyanuric acid 490 mg/kg. Cyanuric acid is essentially nontoxic based on an oral LD q > 20 g/kg in rabbits. Although, it is mildly irritating to the eye, it is not a skin irritant. A review of the toxicological studies on cyanuric acid and its chlorinated derivatives is given in ref. 77. 

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. 

T richloro-striazine-trione [II, 21.2.7.] Pool Sanitizer 1.0-3.0ppm as HOCl Slow dissolving Shelf-life stable Highest available chlorine content Lowers pH, total alkalinity and increases base demand Raises cyanuric acid... 

The microbicidal activity of Chloramine-T bases on the release of chlorine, but the action of Chloramine-T is slower than that of chlorine itself, especially in alkaline media. Therefore it is used as an active ingredient in disinfectants and sanitizers which are applied at low pH levels and long exposure. 

A classic example of substitution for safety can be seen in the recent trend in the wastewater treatment industry to substitute less hazardous sodium hypochlorite for deadly chlorine gas in the disinfection process. While the use of sodium hypochlorite is more expensive than chlorine gas, because sodium hypochlorite is not an EPA/OSHA-listed hazardous material, extremely costly and cumbersome regulations on the use of chlorine are avoided. Moreover, as one wastewater treatment sanitation district general manager told us, By using harmless sodium hypochlorite instead of deadly chlorine I am able to sleep better at night. . . because the liability issue is removed. The liability issue referred to here is based on the possibility of deadly chlorine not only causing serious injury or worse to workers but also injury or damage to those beyond the plant/ facility fenceline. 

---