Influence of UV radiation on the transformation of mono- and dichloramines in water of swimming pools in full-scale tests and in the experiment

Abstract

Introduction. The use of chlorine-containing reagents for disinfection of water in swimming pools may lead to the formation of chloramines, both worsening the organoleptic properties of water and affecting the health of swimmers. To reduce the content of chloramines in pool water, UV radiation can be used. The aim of work is investigation of the effect of UV radiation on the transformation of mono- and dichloramines in water. Material and methods. The study was conducted on water samples from children’s pools, as well as in a model experiment on aquarium water with sodium hypochlorite added. Samples were irradiated with ultraviolet at doses of 40, 80 and 120 mJ/cm2. Before and after UV treatment, the content of chloramines was determined in all samples. Results. UV dose 40 mJ/cm2 was found to be insufficient for the destruction of mono- and dichloramine in water. During UV treatment with a dose 80 mJ/cm2 a decrease in the content of monochloramines and an increase in the content of dichloramines were observed. These processes were depended on the initial concentration of active chlorine in the samples. Conclusion. Thus, an effective UV dose to reduce the concentration of monochloramines in water with a concentration of active chlorine of 0.5 mg/l is 80 mJ/cm2. However, standard UV equipment used for disinfection of pool water cannot guarantee a reduction of chloramine concentration as it is usually designed for the minimum required UV dose (25-40 mJ/cm2). In addition, the effect of UV at this dose on water with a high content of active chlorine led to a significant increase in the content of dichloramines, which is supposedly associated with the destruction of proteins in water under the influence of UV radiation and the subsequent reaction of amino acids with active chlorine.