The U.S. Environmental Protection Agency’s (EPA) Water Infrastructure Resiliency and Finance Center, in collaboration with the...
Minnesota YMCA improves indoor pool water quality with an ozone generator
The Winona Family YMCA is located in southeast Minnesota, in a town that is home to approximately 27,000 residents. The 4,300-member athletic center is spread across 78,000 sq ft and hosts programs and classes in badminton, basketball, tennis, aquatics and more.
Built in 1951, the original indoor pool at the Winona YMCA measures 20 by 60 yd. When a new, larger pool was built, the smaller pool became the YMCA’s warm-water pool, used for toddler and senior citizen classes, as well as therapeutic activities.
In 2008, pool operators began noticing elevated levels of chloramines in the warm-water pool.
Chloramines are detected by measuring the difference between total and free chlorine levels. In the state of Minnesota, this difference is limited to 0.5 ppm for indoor pools.
As the pool’s usage increased, so did the chloramine level. According to Andy Blomsness, former executive director of the Winona YMCA, who retired in June 2013, the pool’s chloramines were at 0.5 ppm for about a week and then continued to escalate rapidly.
“We would close the pool a lot,” Blomsness said. “We just started draining it down on a routine basis, probably a couple of feet, and then filling it up with fresh water. It would be good for another week, depending on the time of year and the usage. We’d totally drain it twice a year and refill it because we just couldn’t control it.”
The presence of chloramines in indoor pools is based entirely on usage. As the warm-water pool became more popular — particularly with children and senior citizens — lotions, perfumes, dirt and other foreign substances on the swimmers’ bodies caused the level to rise.
Excessive chloramines in a pool can cause breathing problems for swimmers, as well as skin and eye irritation. Their presence also can lead to maintenance problems in the pool area, such as peeling paint and rusting metals. For the Winona YMCA, the constant maintenance was becoming a financial burden and an inconvenience to the staff, which often had to come in on weekends to drain and refill the pool.
Designing a Solution
Blomsness contacted Terry LaBeau, general manager of the Commercial Systems Div. of Chicago-based Halogen Supply Co., which designed the YMCA’s new swimming pool and whirlpools, and asked for a solution.
“He suggested an ozone generator,” Blomsness said. “I thought it was worth a try — even if it cut [the chloramine level] in half, at least it would be better than what we’re doing.”
As a disinfection solution used to supplement the primary disinfectant (in this case, chlorine), ozone disinfection does not leave a residual in the water. It oxidizes the water and is able to eliminate both organic and inorganic chloramines.
The YMCA board of directors approved the plans for the ozone system, and, in 2009, LaBeau’s team installed a Clearwater Tech skid-mounted CD20/O2 ozonator to a 2-in. sidestream out of the pool’s circulation system.
“Ozone is created in the ozonator by means of a man-made ‘lightning storm’ in a glass tube,” LaBeau said. “That ozone is drawn by a booster pump and venture injection manifold also mounted on the skid, dissolved in the sidestream, and pumped through a contact chamber and back into the circulation system.”
It takes approximately four minutes for the water to pass through the contact chamber, oxidizing and sanitizing it along the way. Any ozone not consumed in this process will have returned to a state of oxygen by the time the sidestream mixes with the main return flow to the pool.
Ozone that does not dissolve in the contact chamber will gas off to the top of the tank and out an air vent at the top of the chamber. This off-gas is piped to a wall-mounted ozone destruction unit, where it is neutralized.
“We drain our whirlpools all the time because it’s not a lot of water,” Blomsness said. “But when you’re talking about a big pool like that, it gets to be pretty expensive, so it really saved us, no doubt about it.”
Since installing the ozone generator, the YMCA has not had to drain the pool once, saving on labor costs, as well as costs related to water usage. The ozone generator also has allowed the YMCA to reduce its chlorine use, leading to even more cost savings.
The reduction in chemicals also has improved the general environment of the pool area.
“A lot of pools smell like chlorine,” Blomsness said. “In our small pool, it smells more like rainwater than chlorine. It’s really a pleasant smell.”
Where the YMCA was once under pressure to meet Minnesota Department of Health chloramine regulations, it now averages between 0.3 and 0.4 ppm chloramines in the small warm-water pool.
“We were really struggling, to the point where we almost would have to do something drastic like close down the pool,” Blomsness said. “For anybody that’s having trouble with the chloramine levels, they should take a good look at an ozone generator, because, for our purposes, it really worked.”