Formation of low molecular weight organic compounds from UV disinfection of chlorinated water containing humic substances

The effect of ultraviolet light (UV) disinfection of drinking water in the presence of residual chlorine on the formation of low molecular weight organic compounds was investigated. No evidence was found suggesting that the combined treatment of chlorine followed by UV at a reduction equivalent dose of 37 mJ/cm2 would increase the formation of low molecular weight organic compounds, or produce more biodegradable water when compared to UV treatment alone. However, a minor increase in the formation of trihalomethanes and haloacetic acids was observed in the combined treatment of chlorine followed by UV when compared to chlorine alone based on experiments using commercially available humic substances (HSs). The impact of using these substances in place of aquatic HSs and the effect of photo-bleached were also investigated. Commercially available HSs were found to be more reactive than aquatic HSs and that photo-bleaching was an effective means of reducing this reactivity.