[Removing Typical Odorants in Drinking Water by Vacuum Ultraviolet Combined with Chlorine]

For the effective removal of two typical odorants found in drinking water, 2-methylisoborneol (2-MIB) and geosmin (GSM), which cannot be effectively removed by the conventional water treatment processes, the advanced oxidation process of vacuum ultraviolet combined with chlorine (VUV/chlorine) was studied. The efficiency of this technology in the removal of these typical odorants was investigated; the effects of ultraviolet intensity, chlorine concentration, pH, bicarbonate concentration, and humic acid concentration on the degradation of these typical odorants were examined, and the role of hydroxyl radicals (·OH) in the degradation of these typical odorants was analyzed. The purge and trap method coupled with gas chromatography and mass spectrometry (GC/MS) was used to determine the concentrations of the typical odorants. The results showed that the VUV/chlorine technology removed typical odorants effectively, and the removal rates of 2-MIB and GSM increased by 15% and 8%, respectively, in 30 minutes, compared with that by the UV/chlorine technology. With the increase in chlorine concentration and ultraviolet intensity, the degradation rates of the typical odorants was accelerated. The removal of the typical odorants was obvious under weak acid condition, and the removal rates of 2-MIB and GSM reached 95% and 96%, respectively, in 10 minutes under the condition of pH 5. Bicarbonate and humic acid competed with free radicals in the reaction system to inhibit the degradation of the typical odorants. The removal rates of 2-MIB and GSM decreased appreciably by 40% and 31%, respectively, when 1 mmol·L^-1tert-butanol was added to the reaction mixture, which indicated that hydroxyl radicals (·OH) played a major role in the removal of these typical odorants.