Impacts of Medium-Pressure UV on THM and HAA Formation in Pre-UV Chlorinated Drinking Water

摘要

A 111 L pilot scale flow-through reactor equipped with 6x1 kW medium-pressure ultraviolet (UV) lamps was used to investigate the impact of medium-pressure UV irradiation on the removal or formation of trihalomethane or haloacetic acid precursors during drinking water treatment. The UV pilot reactor was installed after ozonation and biological filtration. In some experiments, the filter effluent was augmented with 10 mg/L alginic acid to provide additional DBP precursor material. NaOCl was pumped into the water upstream of a static mixer and the UV reactor to provide a range of chlorine concentrations. Reactor effluent samples were taken, adjusted to pH 8 and pH 6 and held for 24 hours at 20°C before measurement of their final total trihalomethane (TTHM) and haloacetic acid (HAA_9) concentrations. The experiments demonstrated that UV disinfection had a relatively minor effect on TTHM and HAA9. At a UV dose of 100 mJ/cm2 and for chlorine doses ranging from 6 mg/L to 48 mg/L, TTHM concentrations decreased by between 1% and 7% and HAA_9 concentrations changed by between -3% and 4%. At the highest UV doses and chlorine doses applied for the two waters tested, the UV resulted in a disappearance of free chlorine; however, at the UV doses expected for UV disinfection, these effects would be minimal.