Guest Column - May 2011
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Does Your Pool Pass the Smell Test?

By Franck Roy

Pools must be treated with chemicals continuously in order to deactivate pathogenic microorganisms and to prevent the spread of waterborne illness. Chemicals, such as chlorine, react with organic and mineral compounds, resulting in harmful and smelly byproducts, among which is nitrogen trichloride.

Ensuring good water chemistry is the key to maintaining a proper and safe swimming pool environment. Not only to maintain a good level of oxidizers, but also to correctly monitor pH, water hardness, alkalinity, etc.

When dealing with chloramines, there are only a few options. The available techniques today include adding fresh water, hyper-chlorinating, non-chlorine shocking, ozone or installing an ultraviolet sanitizing system.

But first, let's make the point: Prevention is key. Chloramines are produced when bathers introduce ammonia and organic compounds into a swimming pool. If bathers shower prior to swimming, this would substantially reduce chloramine creation but not eliminate the issue.

The second point: A good filter is key to clean water. It is always possible to manipulate the filter, such as by adding granulated activated carbon, which will help remove chloramines or ammonia. So, filtering is critical in pool sanitation and may require additional attention.

Water addition: This results in millions of gallons of fresh water, which is obviously highly wasteful, but also presents a new problem of having to constantly monitor the pH, temperature adjustment and alkalinity of the water and disposing water with lots of chemicals into the sewer system.

Non-chlorine shock with mono per sulfate-based oxidizers: These products are very expensive compared with chlorine but are strong oxidizing agents to break down chloramines when reaching breakpoint oxidation. The use of non-chlorine shock will require more intense water chemistry monitoring.

Hyper chlorination to remove chloramines: As a part of regular maintenance, you shock a pool periodically to remove organic compounds, remove chloramines and free up the available chlorine to allow it to sanitize the pool. However, this also binds up the free chlorine and keeps it from performing its sanitizing function if not used in proper amount.

Adding ozone to the water: Ozone as a secondary oxidizer destroys ammonia and nitrogen, preventing the formation of chloramines. As a disinfectant, this technique requires a large corona discharge ozone unit to disinfect. The unit works by injecting the ozone into a side stream (about 10 percent up to 25 percent of the water), and then returns it into the full flow.

Adding a UV system: First, note that UV-C doesn't change the pH, turbidity or alkalinity of the treated water. There are two main benefits working with UV. The first one is to damage DNA/RNA at a special wavelength of 254 nanometers, which damages depend on the UV dose expressed in mJ/cm2. And second, many studies illustrate results before and after the addition of a UV system. Among the two UV technologies available, the medium and low pressure bulbs provide good results in regard to decreasing chloramines to acceptable levels in the water and in the air as well.