Knowing the Limits
Recent CDC findings have prompted many states to lower the recommended levels of cyanuric acid in swimming pools. Stephanie Harris, managing editor of Water Quality Products, recently spoke with Stanley Pickens, Ph.D., senior research associate for PPG Industries, Inc. and Accu-Tab Chlorination Systems, about these findings and the new Accu-Tab Advisor Series designed to inform pool operators of regulation changes.
Stephanie Harris: What information do the Accu-Tab Advisor Series provide?
Stanley Pickens: The first advisor series related to how germs and contaminants get into pool water and the relationship with the habits of patrons and the operators of water park facilities. We surveyed patrons and pool operators on what percentage of bathers showered with soap before entering the water and how many thought that young children might urinate in the pool rather than get out and get to a washroom.
The second series survey we did in cooperation with NSF, Intl. in which we surveyed health inspectors. We looked at what causes them to shut down a pool and how many of them have shut down pools.
The latest series was on cyanuric acid (CYA). What spurred us on this topic were findings that the Centers for Disease Control and Prevention (CDC) had conducted within the last five years studying the impact of chlorine stabilizer or CYA in pool water on disinfection rates. The CDC was specifically focused on decontamination of water infested with Cryptosporidium. They had determined that with what had been thought to be a modest level of stabilizer in the water, there could be problems with trying to deal with a fecal release into a pool in which Cryptosporidium was released into the water.
Because of the CDC’s findings, we as a company had recommended that our customers set their CYA or stabilizer limits lower. We then embarked on this series to see how many operators out there were aware of what was going on and how many knew that a number of health authorities are looking to or had already changed the limits and recommendations.
Harris: What is the proper use of CYA in recreational water?
Pickens: When CYA is in the water, and there is chlorine in the water, the chlorine will react with it and the majority of the chlorine will be bound on the CYA. Only a small fraction of the chlorine that would test as free available chlorine (that is, oxidizing chlorine) would actually be free from the CYA. What percentage of the chlorine that is present as hypochlorite versus cyanurate-bound chlorine will depend on a variety of factors such as pH and the concentration of the CYA and chlorine in the water.
Outdoor pools are where CYA is used deliberately because that is where you are trying to stabilize chlorine against destruction by sunlight. By binding the chlorine, CYA will protect the chlorine from the sunlight but by the same token, it will slow the sanitizing effects and the oxidizing operation that is conducted by the chlorine. So contaminants in the water are not oxidized as rapidly and germs are not killed as rapidly with the stabilizer in the water.
It is used in outdoor pools and we recommend it for outdoor pools at limited levels because with bright sunlight, it can be difficult to keep a chlorine residual in the water. The chlorine residual can drop by 80% in a couple of hours without some sort of stabilizer in the water if you have bright sunlight shining on the pool. If you have the stabilizer, you can cut that chlorine loss tremendously. With too much of it in the water, it can slow down sanitizing.
Based on recent findings, we have been recommending a CYA level of about 20 ppm, so that you can get some of the sunlight stabilization benefits without hampering the sanitizing rate as much.
Harris: What are the new recommendations under consideration regarding CYA in controlling Cryptosporidium?
Pickens: Cryptosporidiosis has been on the rise in pools in the last decade, and it is cause for some alarm because it is a difficult organism for chlorine to deal with.
The CDC put out recommendations on how to deal with fecal release in water, in which there would be a good chance that Cryptosporidium might have been released into the water. They recommend a 20-ppm chlorine residual for 13 hours at a pH of 7.5. But if there is any CYA in the water, this is no longer as effective. With 50 ppm of CYA in the water, they could double the contact time to more than 24 hours, drop the pH to 6.5, double the chlorine concentration to 40 ppm and it would still not be as effective in dealing with Cryptosporidium as it would have been without the CYA present. It has a tremendous impact.
And a number of states have seen this information. Florida, for instance, proposed last year to lower its CYA limits from 100 ppm to 40 ppm. The state recommended no more than 40 ppm but the enforceable limit is 100 ppm. Texas made a change in their limits, and Wisconsin and Pennsylvania have recommendations for a low CYA limit. There are various places that have been responding in this sort of fashion.
For more information, contact Stanley Pickens at 800.245.2974.