The Science Of Supplemental Disinfection Systems

As pool operators turn their attention to supplemental disinfection, there is a lesser understood, yet powerful alternative to UV that’s making a big splash–ozone sanitation. Why? And what should you know?

Chlorine has been the standard water-treatment method since 1961 when the United States Public Health Service published its model ordinance governing public pool-water sanitation. Today, as scientists learn more about the limitations and potential hazards of chlorine, and as the number of Recreational Water Illness (RWI) outbreaks increase, talk of supplemental disinfection is gaining more than momentum–it’s earning acceptance.

Supplemental disinfection is used in commercial pools to mediate the inherent weaknesses of chlorine, providing a safer water experience for swimmers and pool employees.

The two key technologies that form the mainstay of the discussion around supplemental disinfection are UV and ozone. UV has been well understood and recommended by pool designers, whereas ozone, a rapidly advancing technology, has been largely ignored, despite compelling reasons to choose ozone over UV.

Chloramines And RWIs

Chlorine is long known to react with organic material in pool water to create chloramines. Chloramines cause foul odors, irritation of the skin, eyes and ears, swimmers asthma, and can damage indoor-air handling systems (HVAC). Since the discovery in the 1930s, the unending challenge for pool operators has been to balance antimicrobial efficacy (keeping the water sanitized) and swimmer safety (eliminating chloramines).

Increased attention to the weaknesses of chlorine-only disinfection has resulted not only from these harmful chloramines but also from an increasing number of RWIs caused by chlorine-resistant microorganisms. RWIs have become more common over the past two decades by repeated outbreaks of illness caused by Pseudomonas aeruginosa, E. coli, Staphylococcus aureus, Giardia and Cryptosporidium parvum (Crypto), to name a few.

Technically speaking, chlorine should be able to handle common RWIs, with the exception of chlorine-resistant Crypto. However, as repeated RWI outbreaks have shown, conventional chlorine treatments alone will not do the job.

Chloramines and RWIs are the key reasons for supplemental disinfection coming to the forefront of aquatic water sanitation.

The Model Aquatic Health Code

The less-than-ideal efficacy of chlorine has inspired the Centers for Disease Control to form a Model Aquatic Health Code (MAHC). Soon to be published, it will highlight the importance of supplemental disinfection systems (SDS). When the present draft is adopted, the MAHC will list ozone and UV as accepted technologies for commercial pool SDS.

Several states have already mandated the use of SDSs for their high-risk swimming venues, including interactive spraygrounds. For example, Pennsylvania includes both UV and ozone in its 2008 Operational & Biological Contamination Protocol Recommendations for aquatic facilities. It is likely that additional states will soon adopt the MAHC for public aquatic facilities. With this in mind, operators and officials are wise to consider ozone sanitation.

UV Or Ozone

UV achieved earlier adoption among pool designers for its simplicity. Ozone, on the other hand, has been used to sanitize municipal water for the past 100 years, is widely used as life support for aquatic mammals and fish in commercial aquariums, and is the primary supplemental sanitation technology for the hot-tub industry. Despite all of this, ozone has yet to earn its place in supplemental disinfection for commercial pools.

A major reason for ozone’s lack of acceptance in the commercial pool world is its perceived complexity and the common misperceptions about what ozone is, how it works, and how it compares to UV.

Ozone is an efficacious antimicrobial oxidizer. When used in conjunction with low-dose chlorine, the pool water quality and clarity are improved. These water-quality improvements result from ozone’s potent and rapid oxidation of organic and inorganic compounds.

Ozone is cost-effective, uses little energy, is safe for pool patrons, and causes no structural degradation to the pool, the facility or HVAC system.

How An Ozone System Works

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