UV And Ozone Systems

Across the United States, several water recreational facilities are facing class-action lawsuits because their patrons became infected with cryptosporidium. Cryptosporidium is a parasite that is released into the water in the form of oocysts from a person who is experiencing or has had diarrhea within a two-week time frame, or has poor personal or poolside hygiene.

In fact, the number of cryptosporidium cases reported to the Centers for Disease Control and Prevention (CDC) has risen substantially in recent years. According to CDC data, “in 2005, 2006, and 2007 the number of non-outbreak-related crypto cases rose 41 percent, 24 percent, and 66 percent, respectively.” Additionally, considerable increases in outbreaks associated with recreational pools and water parks were recorded in 2006 and 2007.

Seeking A Solution

More water venues are selecting ultraviolet (UV) or ozone systems as their primary water sanitation because, although chlorine is a satisfactory secondary disinfectant, it does not do an adequate job of inactivating cryptosporidium.

“People who have had diarrhea in the last few weeks shouldn’t be swimming in the water,” says Tom Lachocki, CEO of the National Swimming Pool Foundation. “Even if they don’t have an accident in the pool, the cryptosporidium could be released.”

UV And Ozone To The Rescue

“UV and ozone play a very important role in disinfection,” says Beth Hamlin of ozone equipment manufacturer DEL Ozone. “In fact, with the two of them together, you get knock-your-socks-off technology for anti-microbial disinfection and destroying chloramines.”

“Both ozone and UV are strong oxidizers and are very effective at inactivating almost anything,” says Lachocki. “Oxidation changes the chemicals in the water, making them easier to remove by filtration which improves water quality.”

Oxidation is a chemical reaction that changes the structure of organics and inorganics dissolved in the water, causing them to be either eliminated or precipitated out of the water through a filtration system.

UV System

A UV system works by exposing the water directly to ultraviolet light in the germicidal range (UVc), which is light in the wavelength range between 250-300 nanometers (nm). The water is exposed to a dose of UV energy that breaks down the cell walls, preventing bacteria and viruses from replicating. There are two different types of UV systems–low and medium pressure. Low-pressure UV light operates at 254 nm, whereas medium-pressure UV light operates in the range of 250 to 350 nm.

“We use a medium pressure,” says Kevin Shannon, vice president of sales with Aquionics, a supplier of ultraviolet and water treatment and disinfection equipment. “It provides a broader spectrum for disinfection. A medium pressure unit provides 250 to 300 nm wavelength, and has a better performance and faster reaction.” Simply put–a medium-pressure UV system does a better job of breaking all the bonds in the cell, making it incapable of repairing or replicating.

The water passes through the pumps and filters before it continues through the UV system, which looks similar to fluorescent ceiling lamps, except that the lamps are housed in quartz sleeves to protect the electrical components from the water.

Only the water that is exposed to UV is sanitized; therefore, a secondary sanitizer is required. “UV systems are always used with residual chlorine or secondary sanitizers,” says Shannon. “You’ll use less chlorine with the UV systems.”

If your facility decides to purchase a UV system, Shannon suggests that you find a company with years of experience with sizing and installing. “There are a lot of companies entering the market today,” says Shannon. “You need to have someone who can properly size the system, which includes the calculation of flow, energy transmittance through the water, and dosage of UV needed to reach the log value or disinfect the water.”

Shannon also advises that the unit be installed with an automatic wiper–a device that clears the quartz tubes housing the lamps–because this decreases the amount of maintenance that will be needed for the unit.

Ozone System

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