Effect of irradiation and free radicals on formation of trihalomethanes in chlorinated water

In order to understand the formation of trihalomethanes (THMs) in chlorinated water and to control the production of THMs more effectively, effects of irradiation and free radical on the formation of THMs were observed. It was found that humic acid (HA) solution contains a semi-quinone free radical, which variation trendency was relative to the production quantity of THMs directly. Irradiating the solutions containing THMs precursor before chlorination could promote the formation of THMs, which reached the highest point at 30 minutes, after then decreased with longer irradiation time in this experimental condition. irradiating the chlorinated solution, the yield of THMs decreased slowly because of the destruction of chlorine. The production quantity of THMs was inversely proportional to the wavelength of light sources.