Zydox as a Biocide

When compared as a biocide, chlorine dioxide ranks second only to ozone, which, however, cannot be used in many situations because of its inability to hold a residual. Chlorine dioxide can maintain a residual over reasonably long periods. In dirty water situations with short contact times, a chlorine dioxide residual of 0.8 ppm may be required to maintain biological control. Chlorine, on the other hand, may have to be used at residuals in excess of 100 ppm to obtain the same level of performance.

ZyDox® requires much lower kill times than conventional biocides.

When compared to free chlorine at a pH of 4.0, chlorine dioxide requires less than 10% of the contact time to achieve the same kill on a ppm basis. When compared to some other biocides such as monochloramines and quaternary ammonium compounds, chlorine dioxide will achieve a complete kill at 1 ppm and 20 seconds of contact time compared to monochloramines at 1 ppm for 1 hour of contact time. Other conventional biocides such as formaldehyde, cocodiamine, sodium hypochlorite and phenolics require longer contact times and higher concentrations than either chlorine dioxide or free chlorine. The time required for a complete kill is of critical importance in many applications. Such applications include spray washing of fruit and vegetables and CIP (clean in place) processes where there is little contact time as may well be the case where there are vertical or overhead fixtures. By shortening the exposure time required for sanitation, it is also possible that down time can be reduced. One specific and practical application is as the sanitizer of choice when disinfection processes are carried out during short break times during the normal working day, such as during mid-morning or afternoon breaks. By using a product with an enhanced "kill time”, the sanitation process is much improved.

ZyDox® is effective across a wide pH band (up to pH 12).

Chlorine dioxide is not affected by pH as is chlorine. At pH 3.2, chlorine and chlorine dioxide perform at approximately equal levels. However, few processes operate at this level and as the pH rises, the performance gap between chlorine dioxide and chlorine widens significantly. At a pH of around 8, chlorine has become so ineffective that the contact times required for effective disinfection make its use almost impractical. If used in these conditions, the residuals required are so high that severe corrosion problems will result.

ZyDox® does not react with ammonia or ammonia containing compounds as does chlorine.

This is very important because of the time required for disinfection. Even though free chlorine is an excellent disinfectant, it can combine with nitrogenous compounds in food plant use. As combined chlorine, its effectiveness may be reduced by as much as 100 to 10,000 times with significantly increased contact times required for disinfection. Because chlorine dioxide does not significantly react with ammonia or amines, its effectiveness is unhindered even in high concentrations of these compounds. This is an extremely important consideration when comparing the two disinfectants. Nearly all of the water and produce streams that need to have biological control and many food contact surfaces will have ammonia or organic nitrogen present.

For example, in a flume where the produce has only 15 minutes residence time and there are sufficient amines or ammonia to tie up the free chlorine, the chlorine treatment process cannot give a complete surface kill of the micro-organisms, even theoretically. Such a situation will allow contamination of all downstream processing equipment and even the final product itself. Chlorine dioxide, because of its inherent unreactivity towards ammonia or amines, would still be able to maintain an effective residual for complete biological control in this situation.

ZyDox® does not dissolve in water to form an acid and a salt as does chlorine.

Chlorine may dissolve in water to form hydrochloric acid. This results in the high levels of corrosion associated with the use of chlorine. As ZyDox® does not react in this manner, its corrosiveness is much less than that of chlorine and, in addition, the potential for corrosion is even further reduced by the fact that ZyDox® is used at much lower levels than chlorine.

ZyDox® does not react with organics to form halogenated hydrocarbons.

Because chlorine dioxide is generally less reactive towards hydrocarbons than chlorine, more chlorine dioxide residual is obtained from less dosage than is the case when chlorine is used. Chlorinated organic compounds have been shown to have the potential to create serious long term health hazards, such as the production of trihalomethanes. Chlorination of some organics such as phenols not only results in a more toxic end-product, such as chlorophenols, but also can impart undesirable tastes and odours to the products being treated. Chlorine dioxide reacting via true oxidation rather than electrical substitution does not form these compounds. Specifically, the effect of chlorine reaction with organics is seen in the fruit and vegetable industry by the problems created in maintaining a residual in heavily contaminated systems and the severe corrosion caused by the high levels which are required.

The use of chlorine dioxide in chiller water is much more effective than use of chlorine. Also in direct food contact situations the use of chlorine gives rise to the possibility of off-tastes or odours being imparted to the products.