Ozone Sanitization of High-Purity Water Storage and Distribution Systems

Updated: Apr 13, 2018

A viable sanitation option, proven to be just as effective as heat.

Overview and Application

Ozone is a triatomic allotrope of oxygen that naturally occurs in the environment as a result of oxygen reacting with UV light. Ozone, however, is relatively unstable with a half-life of only about 20 minutes at ambient temperatures, as it readily converts back to oxygen. The energy imparted by the decomposition empowers ozone as a robust oxidizing agent that has disinfection strength three logs more powerful than chlorine.

Ozone gas, dissolved in high-purity water, can be used to maintain the integrity of high purity water – or as a tool for contaminant reduction. Due to its strong oxidative properties, it provides excellent microbial control, whether it is introduced continuously or on an intermittent basis. It will also oxidize organic material by ultimately converting organic carbon chains to inorganic carbon species.

As ozone is a powerful oxidizer, #ozonesanitization is generally limited to storage and distribution systems. Water treatment techniques such as reverse osmosis (RO) and deionization (DI) technologies cannot withstand trace (ppt) levels of ozone even for short durations. For daily sanitations, ozone cycles as short as 20 minutes provide effective microbial control.

Key Design Concepts

Few commercially available materials of construction are compatible with dissolved ozone. For high-purity water systems, acceptable materials include high grade stainless steels and plastic fluoropolymer (e.g. Teflon™) piping systems. While PVC and polypropylene do show some tolerance to dissolved ozone, their long term use is questionable. The dissolved ozone may be introduced intermittently to the storage and distribution system or continuously into a storage tank and subsequently removed via a 254nm wavelength UV light prior to distributing water to points-of-use. The presence and absence of dissolved ozone can be verified by on-line instrumentation or via wet chemistry test methods.

The two common ozone generation techniques used in high-purity water treatment are corona discharge and electrolytic. The former generates ozone from dissolved air, or preferably dissolved oxygen to minimize potential by-products from the generation process. Electrolytic generation generates dissolved ozone from the high-purity water limiting the potential for by-product formation. Regardless of the generation method, the dissolved ozone will oxidize any carbonic species including bacteria and endotoxin.The result of this oxidation is the formation of carbon dioxide which will affect the conductivity of deionized water. A properly design high-purity water system should ensure adequate removal of carbonaceous compounds prior to ozone introduction to minimize the increase the conductivity of the water.

Comparison to Chemical and Heat Sanitization

Ozone can be an attractive sanitization option for storage and distribution systems when an automated process is preferred. Benefits compared to thermal sanitization include:

  • Shorter sanitization cycles

  • Minimal utility costs

  • Lower capital investment

#Ozonesanitization has been proved to be just as effective as heat when applied continuously or on a regular basis. Like thermally sanitized systems the process can be automated, verified by on-line instrumentation, and does not require rinsing of chemicals from the system.

The use of ozone in #highpuritywater markets such as pharmaceutical manufacturing, cosmetics, consumer products, and food and beverage can be an attractive alternative to heat or chemicals. For facilities that cannot afford extended periods of downtime or for larger storage and distribution networks, ozone should be considered as a viable sanitization option.

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