Sanitation of recreational pool waters is vital to ensuring the health of those who utilize them, and chlorination is one of the most widely used methods for removal of pathogens from these water systems. Chlorination is both effective and, given other options, relatively reasonable in cost. However, costs are not insignificant, especially considering that pools are frequently over-chlorinated to ensure against the risk of a health and publicity crisis. In large resort style pools, expenses related to chlorination become considerable for businesses and public enterprises.
Given this situation, many companies have proposed new technologies that claim to reduce chlorine consumption while maintaining acceptable levels of disinfection. One proposed approach to reduce chlorine demand is the use of electromagnetic fields. Anecdotal evidence from one company reports savings of ~$50,000/yr in chlorine costs alone for a 485,000gal pool using a “drop-in” electromagnetic device that emits a constant magnetic field.
While new technologies strive to reduce costly chlorine consumption, independent testing can verify the efficacy of an approach and/or explore parameters for optimum use. With that goal in mind, researchers at the University of Arizona WEST Center – with funding from Vodaa Technologies – investigated the use of magnetic fields to enhance disinfection in pool waters.
In the WEST Center experiment, simulated pool waters containing tap water, hypochlorite (source of chlorine disinfection) and cyanuric acid (chlorine stabilizer) were established in 151L polypropylene containers, and magnetic treatment was applied to the test container.
When chlorine is added to pool water it acts to disinfect or kill microorganisms including any pathogenic microbes that may be in the water. It also oxidizes any organic chemical contaminants in the water. The amount of chlorine that is consumed by reactions with microbes and other chemical contaminants is termed the “chlorine demand” and determines amount of chlorine that must be added to the water for adequate disinfection. As reactions with chemical contaminants occur, different chlorine species, such as chloramines, can be formed which are not as effective as a disinfecting agent compared to free chlorine. Reducing the number of chloramines that are present in a system will also reduce the amount of chlorine that is consumed by the oxidation of the monochloramine. This in turn reduces the amount of chlorine that will need to be added to the pool system to maintain an effective free chlorine concentration for microbial disinfection.
The WEST Center study found:
- Under magnetic treatment, monochloramine (a byproduct of chlorine breakdown) was reduced by 13% after 24 hours of exposure, and the pool water was subsequently shown to contain 26.7% more free chlorine after monochloramine was removed through the addition of excess hypochlorite.
- A second experiment showed a smaller, yet still significant, 6.2% reduction in monochloramine in pool samples just briefly exposed to the magnetic field treatment (1 hour of exposure).
- The two experiments showed that under the presence of a magnetic field, monochloramine (and therefore chlorine demand) was reduced by a significant amount after 24 hours. The second experiment also demonstrates that the effect is still seen when the sample is only briefly exposed to a magnetic field. This may prove valuable because many water systems circulate and therefore long exposure to the magnetic field is not always possible.
As stated by researcher, Aidan Foster:
“In the final sets of experiments, it was found that the source of hypochlorite did not effect the presence of reduced monochloramine. It was also found that certain parameters such as, pH, the presence of cyanuric acid and the container material may play a role in this effect. These studies indicate that under certain conditions, static magnetic fields may play a role in reducing chlorine demand. This proves promising as there may be multiple applications for this technology in the future. We believe that additional studies should be performed to better understand the mechanism of how this occurs and what conditions are required.”