Using ultraviolet (UV) technology to improve water and air quality

by Sally Bouorm | March 1, 2012 12:21 pm

By Jeff Boynton

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Various halogens and sanitizers are used to treat waterborne pathogens in pool and hot tub water; however, as frequent reports on recreational water illnesses (RWIs) (i.e. Cryptosporidium [Crypto] and Giardia) and bacteria outbreaks abound in the press, many commercial pool operators and some residential pool owners are now incorporating a supplemental disinfection system (SDS) to assist in water sanitation.

For this reason, ultraviolet (UV) water treatment technology is one SDS that has seen increased popularity of late thanks to its ease of use, reduced chemical consumption, health advantages and environmentally friendly benefits. This article will explain what UV light is, how it can improve water and air quality in aquatic facilities, and which products are appropriate for particular pool types and sizes.

What is UV?

UV light is electromagnetic radiation emitted by the sun. It is an invisible light with a wavelength shorter than that of visible light but longer than X-rays. Its connection to water sanitation was discovered more than 100 years ago when European scientists learned the top surface of lake water was sterile when exposed to sunlight. This eventually led to the invention of UV bulbs.

The spectrum of UV light can be subdivided into four main categories, UV-A, UV-B, UV-C and Vacuum UV. The area between 280 and 100 nanometers (nm) is UV-C, which is also known as germicidal light.

How does it work?

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UV sanitation systems have gained traction in the industry because of their ability to eliminate chlorine-resistant micro-organisms, which are common causes of pool closures worldwide. These systems reproduce UV radiation inside reactors via powerful lamps, which emit germicidal UV-C light that is used to disinfect pool and hot tub water. Facilities equipped with these sanitation systems consume fewer chemicals and allow sanitizers to be more effective.

UV-C light has the ability to cause permanent damage to a number of micro-organisms almost instantly as the water circulates and is exposed directly beneath the lamp. By disrupting the micro-organism’s DNA, protozoans, viruses and bacteria are unable to replicate and remain inert. This light, however, does not act as a residual and it does not work on dead zones in the pool or hot tub. It only sanitizes water flowing through the chamber.

UV can also improve air quality

The key to maintaining a safe aquatic environment is proper water chemistry. Unfortunately, as chlorine reacts with ammonia and organic compounds introduced to the water via bathers, harmful and foul-smelling disinfection byproducts (DBSs) (i.e. chloramines) are produced.

Studies show UV-C light not only disinfects pool and hot tub water but it also removes chloramines—the leading cause of poor air quality at the surface of the pool and surrounding area, especially in indoor facilities. UV-C light destroys chloramine formation at the molecular level before they evaporate.

Using UV technology, as opposed to other methods of chloramine removal (e.g. hyper-chlorination, non-chlorine shock, ozone and adding fresh water) can help eliminate water maintenance inaccuracies such as combined chlorine reduction calculations, while also reduce operational costs by eliminating the need to close the facility for non-chlorine shock treatments and adding treated and heated fresh water.

European centres for water standards, such as Deutscher Verein des Gas- und Wasserfaches[3] (DVGW), the German technical and scientific association for gas and water, and Österreichisches Normungsinstitut (ON)[4], the Austrian standards institute, have certified UV light reactors to be effective not only in pool water sanitation but also in improving indoor air quality.

Choosing the right system

It is important to seek references when considering a UV sanitation system, as an inadequate system may not perform the job properly or comply with sanitation regulations.

For instance, checking the system’s certifications (e.g. energy efficiency ratings, maximum flow rates, etc.) with the manufacturer is a good idea, while referring to NSF International’s website (www.nsf.org[5]) for its list of approved UV water treatment systems is another. Some provinces and states also maintain a shortlist of authorized systems.

In addition to researching the product, other variables to consider include system size, low versus medium pressure lamps, wattage, spare parts/maintenance and cost/payback.

The Right UV-C Dose
Bacteria	UV-C Dose (mJ/cm2)
Bacillus Anthracis	8.5
E.Colis	7
Légionnella	3.8
Pneumophila	10
Salmonella enteridis	7.8
Streptococcus Faecalis	10
Vibrio Choléra	6.5
Algae	UV-C Dose (mJ/cm2)
Chlorella vulgaris	22
Protozoa	UV-C Dose (mJ/cm2)
Cryptosporidium	22
Virus	UV-C Dose (mJ/cm2)
Hepatitus virus	8
This chart gives the levels of UV-C doses (needed to destroy 99.9 per cent of micro-organisms.)

System size

The size of the UV system is determined by the type of pool (i.e. commercial or residential) as well as its use. Water flow and bather loads should also be factored into the equation. For example, the needs of an indoor Olympic-sized pool with heavy bather loads will differ substantially from an outdoor, mid-sized pool at a hotel.

The UV technology needs to fit the environment and should be affordable so the facility can reap the benefits.

Low versus medium pressure lamps

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There are two types of UV lamps—a low-pressure, high-output lamp, which emits UV rays at a maximum of 254 nm, and a medium-pressure lamp, which emits UV rays between 200 and 600 nm.

Generally, low pressure lamps are better suited for residential applications, while medium pressure lamps are typically designed for large commercial installations. The distinction can be chalked up to cost, flow requirements and the ability to destroy chloramines.

Due to its large light spectral, medium-pressure lamps are more effective at reducing chloramines and improving air quality.

Wattage

Compare the wattage needed to provide proper water flow treatment, as consumption varies between different products. Further, by using a system equipped with an electric ballast additional savings can be attained, as it prolongs the life of the UV bulb and uses less energy.

Spare parts/maintenance

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Depending on the warranty program, some UV systems may require substantial maintenance and require routine servicing. For this reason, be sure to inquire about the pricing of spare parts and any required maintenance costs, as this may vary by manufacturer.

Cost/payback

By using less chemicals and providing a safe bathing environment, a UV sanitation system will pay for itself many times over in comparison to traditional water treatment methods. Depending on several variables (i.e. water quality, bather load and the facility’s filtration system and installation), the return on investment (ROI) is often less than one year.

TIPS ON REDUCING CHLORAMINES

Although there are a few options available to pool operators looking to reduce chloramines in the pool environment, prevention and filtration go a long way.Showering: If bathers shower prior to swimming to remove perspiration, body oils and other lotions, it can reduce the development of chloramines substantially. Making sure children use the washroom frequently, so they do not urinate in the pool, can also lower chloramine levels.A good filter is key Enhancing filtration by adding granulated activated carbon, for example, will also help to remove chloramines and ammonia. Filtration is critical in pool and hot tub water sanitation and may require additional attention and manipulation.

Conclusion

In North America, the standard protocol for water quality maintenance (WQM) is premised on the assumption that appropriate filtration and residual halogen disinfection will inactivate all pathogens. However, it is known that:

• It can take chlorine up to 45 minutes to deactivate Giardia;
• 30 to 60 minutes to deactivate Norovirus; and
• Crypto [8]can linger in pool water for up to 10 days, as it is highly resistant to chlorine.

Unfortunately, RWIs are dramatically increasing and as a result health officials have acknowledged that a paradigm shift in the way pool and hot tub water is treated is needed. Moving beyond the basics of pool and hot tub water quality management will require revising the two-pillar approach, which includes filtration and halogen, followed by adopting a supplemental disinfection method.

In-line UV disinfection is recognized as an effective and reliable method for deactivating pathogens in pool and hot tub water, in addition to reducing bather exposure to DBPs. For instance, some public health authorities in Canada and the United States now mandate the use of supplemental in-line UV disinfection on public splash parks.

Moving beyond the basics of pool and hot tub water quality management will require revising the two-pillar approach, which includes filtration and halogen, followed by adopting a supplemental disinfection method.

Jeff Boynton is the director of sales and marketing for Delta Ultraviolet Solutions, a manufacturer of UV-C technology in Gardena, Ga. 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 spa industry, primarily in Europe, for more than 22 years. He can be reached via e-mail at jeffb@deltauv.com[9] or for more information, visit www.deltauv.com[10].

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