UV and ozone in swimming pool treatment expected to grow

Concerns over chlorine could lead to bullish UV, ozone markets.

By Matthew Barker

Chlorination is still the most widely used method of water disinfection for swimming pools, principally thanks to its cost, the ease of use and the huge range of products that are available.However, many believe it would be desirable if chlorination of water could be phased out because of the known health and environmental risks. Chlorination byproducts have been linked in some studies to cancer risks, and chlorine might be corrosive to some types of swimming pools.

High THM levels

Recently, researchers at Imperial College London said they found levels of trihalomethanes (THMs), a byproduct of chlorine, in London swimming pools that were higher than amounts found in tap water which had been associated with health problems.

Studies from the United States have suggested a correlation between the number of glasses of chlorinated tap water drunk daily by pregnant women and the risk of spontaneous abortion, stillbirths and congenital malformations.

The presence of chloroform and other THMs in water has been blamed by some experts. The Imperial College team reported that the chloroform content of water in eight pools in London was on average 20 times higher than that of drinking water.

THMs are formed when chlorine, which is added to swimming pools to keep them clean, reacts with organic matter such as skin or hair. THMs can be absorbed through the skin, swallowed or inhaled.

To reduce THM formation, scientists recommended making sure people clean themselves before swimming and filtering the water.

Additional links

September 2001 also saw high levels of THMs linked to lung damage. Children who swim in a chlorinated pool once a week scored the same on one measure of lung damage as adult smokers, announced Belgian researchers.

The team took blood samples to measure levels of three surface proteins that indicate lung damage resulting from exposure to a high level of oxidants. They found the level of the proteins increased with higher exposure to chlorinated water.

This oxidative damage also increases the amount of ‘surfactant’ proteins, which the team measured after the children had been swimming. The highest levels detected were similar to those seen in adult smokers.

Other researchers have found an increased incidence of asthma in lifeguards who work in indoor pools, although further research will be carried out.

The bottom line is that although chlorine is still an essential step in the pool disinfection process, levels in pools can be decreased significantly.

This can be achieved by using low chlorine doses in conjunction with ultraviolet (UV) or ozone treatment.


Ozone has been used as a treatment for swimming pool water for over 30 years. It is a very powerful oxidizer of most organic materials, including swimming pool contaminants such as soaps, body oils, perspiration and chloramines.

In the presence of halogens such as chlorine, ozone will also oxidise ammonia, urea and amino acids. Therefore, it is also extremely effective for killing bacteria, viruses, spores and cysts.

Considering its powerful qualities as an oxidizer of a broad range of waterborne contaminants, ozone is more effective than chlorine. It also helps to add great clarity to the water, as it acts as a microflocculent, enhancing the pool filter system.

Frost & Sullivan expects as that the public will push commercially owned pools to invest in systems that ensure that they have the safest pool conditions.

Future years will see continued investment in chlorine dosing equipment, but the increased use of alternative techniques such UV and ozonation will become far more popular to both the domestic and commercial customer.

From the June 2002 edition of Water Technology magazine.

Contact Us