Effects of Medium-Pressure Uv Lamp Radiation on the Formation of Trihalomethanes in Chlorinated Swimming Pool Water

Abstract

We investigated the impact of UV irradiation on the formation of trihalomethanes using a medium-pressure mercury lamp, in conditions similar to those occurring in chlorinated swimming pools. Irradiation of real swimming pool water was first performed during 15s (UV dose: 580mJ.cm -2 ). Then model organic pollutants released by bathers (arginine and creatinine) were irradiated (UV dose: 380 mJ.cm -2 ) after a one-hour chlorination. In all cases irradiation leads to 40% increase in chloroform concentrations 55 hours after exposure, in comparison with the levels observed in dark controls. The applied doses are however about 5 times higher than those encountered in pool water treatment (about 100 mJ.cm -2 ). The promote effect of UV light on haloform formation may therefore appear to a lesser extent. Impact of UV irradiation is not immediate, but degradation of bather load to form chloroform is enhanced within the six hours which follow irradiation. Occurrence of a specific decomposition pathway induced by UV irradiation and leading to more haloform precursors cannot be highlighted. We indeed did not identify a few minutes after irradiation generation of new carbonyl compounds compared to those existing in dark controls. Acetaldehyde remains the major precursor and its concentration does not significantly increase, accounting for the non-instantaneous chloroform formation in this period. Further experiments are needed to precise the chloroform formation potential. In particular it would be necessary to rehearse the aldehyde quantification in the chlorinated arginine and creatinine solutions within 1 to 6 hours after irradiation, when the chloroform increase is more significant.