The revised version of the Disinfection & Water Quality Module of the MAHC continues to recommend ozone, but it does not go far enough. Ozone is effective against threats that chlorine does not touch in many kinds of public aquatics venues, but the MAHC rules do not explicitly recognize it.
The MAHC Process, One More Time
The Model Aquatic Health Code (MAHC) continues its journey through bureaucratic boxes with the January 24th publication of the revised versions of the Disinfection and Water Quality Module and the Regulatory Module. All of the modules as revised will be incorporated into a complete final draft to be released by summer 2014.
The CDC recommends that if you want to make comments in the final public comment session, you should consider using the revised modules to begin your review. Even though the final complete draft will be somewhat different than the modules to accommodate duplications, cross-references, and so forth, you will have an advantage by starting soon. The draft full document will only be open for public comment for 60 days.
Disinfection and Water Quality Module
DEL Ozone participated in the drafting of the water quality module, though as you will see, we do wish it was more explicit about the value of secondary disinfection for many (probably most) public aquatics venues. You can find a current draft PDF of the document on the CDC webpage.
The draft best practices still recommend the use of UV or ozone as a secondary disinfection system, and make it mandatory for “increased risk aquatic venues” including those designed for diaper-aged children (less than 5 years old) and therapy pools. Secondary disinfection systems are considered “optional” for other aquatic venues.
Crypto is More Widespread Than That
This formulation underestimates the value of secondary disinfection for public aquatics venues. The purpose of the adoption of secondary disinfection is to address the failure of chlorine to act quickly enough in the presence of Cryptosporidium oocysts to prevent cryptosporidiosis. Defeating Crypto was one of the original triggers that prompted the National Swimming Pool Foundation to sponsor the MAHC process in the first place. In fact, the MAHC recommendations specifically include criteria for a 3-log reduction in Crypto for a given system to meet the standards—the point of it is to kill Crypto.
It should be obvious that the Crypto threat occurs in many more aquatics venues than children-oriented or therapy pools. In fact, you might want to refer to our post on the most recent CDC report on recreational water illnesses, including crypto. Among other things, the CDC reported that 33 out of 57 RWI outbreaks in treated recreational water occurred in hotels or water parks.
It seems to us that you ought to use a secondary sanitation system that works against the threat where the threat actually exists.