Bench scale investigation of the effects of a magnetic water treatment device in pool systems on chlorine demand

Chlorination is the most common form of water disinfection for recreational swimming pools and represents a major cost for many large-scale operations. Reducing the chlorine demand in a system may alleviate these costs by decreasing the amount of chlorine required to maintain a target disinfection residual. While magnetic water treatment is common for removal of pipe scale, impacts on chlorine demand have not been evaluated. The application of a commercial magnetic treatment device significantly (p < 0.05) reduced the chlorine demand by 13.8 % within 24 h, due to a reduction of monochloramine (NH₂Cl), when applied to a simulated pool system. Subsequent breakpoint chlorination through the addition of calcium hypochlorite (CaOCl₂) resulted in a 30.8 % increase in free chlorine concentration. Additionally, a 1-h exposure to the magnetic field resulted in a 6.1 % reduction in monochloramine compared to the control, demonstrating that transient flow-through treatment can yield a reduced yet still significant effect. Mechanistically this effect could be due to the magnetic field effects (MFE) influencing the electron configuration of compounds in the system, thus altering reaction equilibria to favor more volatile chloramine species. This treatment is potentially a cost-effective method to improve the efficiency of chlorination via the demonstrated reduction of chlorine demand.