Problem Solver - August 2012
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Ensure Safer Swimming

Maintaining good water quality isn't an option. Not only is patron safety of paramount concern, but your facility's reputation can be at risk if you are cited for code violations. According to an NSF International Survey conducted before the recession, health inspectors were handling about 75 pools apiece, on average. But in the wake of the recession, many health officials have seen budgets dramatically reduced. Because of this, the onus is on pool operators to ensure their facilities are health code-compliant.

Q: How can we promote pool water clarity while increasing the efficiency of sanitizer?

A: Every well-trained pool operator knows that there are two critical points in maintaining safe water: a constant residual of sanitizer and optimal filtration. What often goes unrealized is that these two areas are interconnected because organic particulates that make it through a filter can place a higher demand on chlorine. Flocculation and filtration help collect many of these particulates and flush them via backwashing. Also, when water balance is achieved, the filter plays the major role in maintaining water clarity.

From a lifeguard's perspective, water clarity is essential. Anything that disrupts the view to the bottom of the pool makes it more difficult for lifeguards to see swimmers in trouble.

Q: What should I know about preventing recreational water illnesses?

A: Many pathogens can get into the pool water and lead to RWIs. The biggest challenge for any sanitizer, even chlorine, is Cryptosporidium (Crypto). Once Crypto invades your pool, this chlorine-resistant pathogen is difficult to remove, and just one or two of the spore-like bodies can sicken swimmers.

At about 5 microns in diameter, Crypto cysts can pass through most filters fairly easily. Most public facilities run sand filters, which remove particulates, but not down to 5 microns. (The best sand filters remove about 25 microns.) Even DE, or diatomaceous earth, filters might not catch them all.

Because it is resistant to chlorine and passes through most filters so easily, the Centers for Disease Control and Prevention (CDC) recommend secondary disinfection, such as ozone or UV, but these methods also have their limitations. Beginning the work in the pool's circulatory system with effective flocculation using natural-based polymers such as chitosan helps cluster the cysts so they can more easily be caught and removed by the filter.

Cryptosporidium isn't the only problem. There are other bacteria and pathogens that also lead to RWIs. Some bacteria create biofilms, which can be hard for chlorine to eradicate. Any interruption in the chlorine residual makes it easy for biofilms to get established in your pool, where they become host to bacteria that can rapidly multiply. Maintaining good chlorination and filtration practices helps prevent these biofilms from growing in the first place, protecting swimmers.

Q: How do stabilizers change chlorine's effectiveness?

A: Stabilizers can have a significant impact on chlorine's ability to kill pathogens in the water by slowing down the oxidation process. When you have a problem, such as a known exposure of your pool water to Crypto or another pathogen, the CDC recommends "hypochlorination."

As an example, without cyanuric acid in the water, it takes nearly 13 hours to inactivate 99.9 percent of Crypto cysts with chlorine at 20 ppm and a pH of around 7.5. In contrast, with 50 ppm of cyanuric acid in the water, the same level of disinfection can take days. Even with the pH adjusted to 6.5 and a chlorine concentration doubled to 40 ppm, it will take well over 24 hours to achieve a 99.9 percent inactivation. Because of this, experts recommend that pools avoid using excess amounts of stabilizer. In an outdoor pool, 10 to 20 ppm will stabilize the chlorine and in indoor pools, use of sanitizers containing stabilizer (Trichloro-s-triazinetrione) should be avoided completely.


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