Ultraviolet sanitizers can improve water and indoor air quality

by jason_cramp | March 3, 2016 12:30 pm

By Jeff Boynton

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An increasing number of natatoriums have problems with indoor air quality. When the air in an indoor aquatic facility smells like chlorine, this is the first indicator that something is wrong. The odour is often worse at water level, but can be extremely irritating at deck level or in the viewing area as well. In many cases, the trademark ‘chlorine’ odour is not the only problem, eye irritation and difficulty breathing may also be experienced. The second indicator is rusting on metal fittings in and around the pool.

Heating, ventilating, and air conditioning (HVAC) systems are designed to control air temperature by regulating humidity and air flow with fresh air when necessary. However, as USASwimming.org[2] points out, HVAC systems are not air scrubbers; therefore, air quality is directly affected by the pool’s water quality. Poor water quality, in fact, leads to bad air quality.

In the past few years, ‘bad air’ has been proven to come from chloramines (NH₂Cl) in pool water. They are a chlorine (Cl) compound that easily burn off in the water and are released into the air during evaporation as well as when bathers agitate the water (e.g. swimming, splashing, etc.). Chloramines smell like chlorine (and sometimes ammonia) and can cause serious respiratory problems for swimmers, pool staff, and spectators.

This has become a widespread problem in indoor pools, resulting in many spectators feeling ill or uncomfortable. It is not uncommon to overhear conversations about how awful the air smells and how they prefer to leave for fresh air.

That said, the problem is not chlorine, rather what it turns into when combined with organics (e.g. sweat, dander, urine, etc.) that are introduced to the pool via bathers. When chlorine reacts with these organics, nitrogen trichloride (NCl₃), aldehydes (R-CHO), halogenated hydrocarbons, chloroform (CHCl₃), trihalomethanes (THMs), and chloramines are produced.

One method of combating this problem is using ultraviolet (UV) light to sanitize pool water, as it can help to improve indoor air quality as well. Essentially, UV sanitizers effectively eradicate waterborne pathogens while also reducing chemical reliance (i.e. using fewer chemicals results in less chemical byproducts).

This article will explain the corollary benefit of UV water treatment with respect to improving indoor air quality.

What is UV?

UV germicidal light is situated in the electro-magnetic spectrum between X-rays and visible light. The area between 240 and 280 nanometres (nm) is UV-C, commonly known as germicidal light. This is the UV light used to treat and/or sanitize pool water.

Pool water must be continuously treated with chemicals to deactivate pathogenic micro-organisms and to prevent the spread of recreational waterborne illnesses (RWIs). Ensuring proper water chemistry is the key to maintaining a safe pool environment. This means not only maintaining the proper level of oxidizers, but also correctly monitoring pH, water hardness, alkalinity, etc. However, there are only a few options available to pool operators looking to reduce chloramines in the pool environment.

The five available techniques are: hyper-chlorinating, non-chlorine shock, ozone (O₃), adding fresh water, or installing a UV-sanitizing system.

In terms of the latter, pool water will pass through the UV system according to the local health requirements for filtration cycles. When the water is treated with UV-C germicidal light, the pathogenic micro-organisms are eradicated. At the same time, mono-chloramines are stopped from forming, thus preventing the ‘chlorine’ odour. Di-chloramines can only form with a building block of mono-chloramines that are present, and the tri-chloramines form only after the presence of di-. This means once the mono-chloramines do not form, it is much more difficult for the di- and tri- to form. However, in competition pools or those with high bather loads, medium pressure UV-C treatment is better suited since it works on mono-, di-, and tri-chloramines at the same time.

How does UV help improve indoor air quality?

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Using UV sanitizers as a secondary or supplemental disinfection system allows pools to operate safely with lower halogen levels. UV water treatment only acts within the light chamber and does not radiate any further through the plumbing or into the body of water. That said, halogens still have to be used to maintain a minimum residual level in the water between passages through the light chamber. However, by lessening the residual levels, fewer chemical byproducts are generated.

As a result, the air quality inside natatoriums with properly treated pools using germicidal UV light is improved because the formation of monochloramines is prevented. This also reduces the smell of chloramines inside aquatic facilities.

There are two main UV light technologies that affect air quality. Low-pressure, high-output UV-lamp technology operates at mono-chromatic light of 254 (nm), which effectively stops the formation of monochloramines. Medium-pressure lamps, on the other hand, use poly-chromatic light that also generates 254 nm of germicidal light combined with other wavelengths to remove di- and tri-chloramines simultaneously. Medium-pressure UV units are better suited for indoor pools and/or bodies of water with high bather loads.

What is the recommendation?

USA Swimming’s Facilities’ Development Department strongly recommends all indoor pools (both new and existing) install medium-pressure UV systems.

While medium-pressure UV technology is more effective at eradicating chloramines, they are better suited for pools with high flow rates on a continuous filtration cycle. Low-pressure UV systems are typically recommended for splash pads with aquatic features that have filtration cycles which may not operate continuously. Further, whether a splash pad is indoors or outdoors, it generally has a smaller volume of water that is turned over more frequently. Once monochloramines are dealt with effectively, the formation of di- and tri-chloramines is disrupted.

The Fallsview indoor waterpark in Niagara Falls, Ont., is one example of a facility that struggled with indoor air quality.

“We installed a UV light system on our wave pool approximately five years ago,” says the waterpark’s operations manager, Brent Gusnowski. “Previous to the installation; however, we struggled with maintaining a low combined chlorine level in the wave pool.”

The wave pool contains 514,816 L (136,000 gal) of water and is operated year-round. At the time, the water feature was the largest contributor to combined chloramines being aerosolized. After a failed attempt to reduce combined chloramines using a chemical additive, the facility manager decided to install a medium-pressure UV-light system.

“Within days of installing the unit, we experienced a tangible, measurable impact on indoor air quality,” said Gusnowski.

Fallsview confirmed the results by testing its combined chloramine levels, which showed they had been reduced significantly compared to the pre-UV installation levels. Under normal operating conditions, the combined chlorine levels for the wave pool—when using the UV system—are now approximately 0.2 parts per million (ppm).

“Since the UV system was installed, we’ve had an overall reduction of customer comments about poor air quality in our facility,” said Gusnowski. “This goes to show, if the water quality isn’t in line, it is impossible for the air quality to be any good. Removing contaminants before they become aerosolized can provide a positive impact on air quality. Many companies push solutions that focus on removing the ‘bad air’ once it’s created; however, it’s more effective to prevent the ‘bad air’ from developing in the first place.”

Make sure water and air quality are in sync

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First and foremost, water and air quality are dependent on each other. The latter, however, is affected by[5]:

• The amount of fresh air that is introduced into the building every hour. This is dependent, of course, on outdoor climate and building type. A 90 per cent change of air every 20 to 25 minutes works well in warm areas.
• The condition of the air handling equipment. Filters should be cleaned or changed every three months. Micro-filters are also available, which help to remove more airborne contaminates than standard fibreglass or paper filters.
• The type of air handling system installed in the building.
• The lack of routine maintenance. Maintenance must be performed and tracked on all air-handling equipment. Vents and louvers must be checked and lubed at least four times a year to make sure they are working properly. Dust must be removed from the surface of vents, while motors, belts, and fuses also need to be checked.

Chloramine formation can be caused or accelerated by:

• Bathers not showering properly before entering the pool.
• Bodily wastes in the pool such as urine, which prompted the 2015 campaign by the U.S. Centers for Disease Control (CDC), Water Quality and Health Council, and National Swimming Pool Foundation (NSPF) to educate the public on the myths associated with urinating in the pool[6].
• Bathers performing a high level of aerobic activity and sweating in the water.
• Residues from ammonia-based cleaning products used on pool decks or in shower rooms/lavatories.
• Residue from fertilizers used on landscaping (nitrogen-based) that get tracked into the natatorium.
• Poor air circulation and a lack of fresh air being introduced into the aquatic facility.
• Over ‘shocking’ the pool. This is not a routine maintenance procedure. It should only be performed to kill bacteria, which has been found via lab tests.
• Improper use of certain brands of chemicals not suitable for conditions specific to a geographic area.
• Municipality adding chloramines to tap water. This treatment is called chloramination and involves adding chlorine and small amounts of ammonia, one at a time, to the water which react together to form a chloramine disinfectant.

In short, it is common for indoor pools to notice the absence of the chlorine smell within days after the installation of a UV sanitizer. These systems are plumbed in after the pump and filter, before the heater or chemical injection points. UV is non-corrosive; therefore, using it to remove chloramines also makes the pool environment less corrosive. Further, other pool equipment installed after the UV system will also benefit from less corrosive conditions.

When considering the installation of a UV sanitizer, it is important not to oversize the unit, as an increased dose (the product of UV light intensity and time, which is sometimes referred to as millijoules/cm²), can strip halogens out of the water. Should this happen on a pool using automatic injectors, there can be an increase in chemical consumption, which will lead to more byproducts. By properly sizing the UV system, chemicals can be more effective in smaller doses.

In conclusion

Unfortunately, RWIs are dramatically increasing. It has also been established that certain pathogens are resistant to chemicals, thus leading to various diseases, including respiratory, skin, and gastrointestinal problems. Awareness and concern about exposure to disinfection byproducts (DBPs) in pools and spas/hot tubs has further increased the notion of air quality. Therefore, a paradigm shift is needed on how pool and spa/hot tub water is treated.

UV disinfection is recognized as an effective and reliable method for deactivating pathogens in the water and reducing bather exposure to DBPs. And, the fact air quality can also be improved helps aquatic facilities increase overall bather comfort.

[7]Jeff Boynton is the general manager of Delta Ultraviolet Solutions, a manufacturer of UV-C technology in Gardena, Calif. He is responsible for managing the company’s existing customers as well as growing sales in North America. Boynton has worked in the swimming pool and hot tub industry, primarily in Europe, for more than 25 years. He can be reached via e-mail at jeffb@deltauv.com[8]. For more information, visit www.deltauv.com.

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