[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.

[Removal of Odorants in Drinking Water Using VUV/Persulfate].

In order to solve the odor problem of drinking water, the performance of a VUV/persulfate process and its influencing factors were investigated systematically for removing odors from 2-MIB and GSM. The results showed that it was difficult to remove 2-MIB and GSM using PS alone with a PS concentration of 0.5 mmol ·L-1, but the removal rates of 2-MIB and GSM by the VUV/PS process could be increased by 76% and 74%, respectively, compared with VUV alone. The performance of the VUV/PS process was mainly affected by the PS concentration and VUV intensity. When the PS concentration increased from 0.25 to 2 mmol ·L-1 and the VUV intensity increased from 113.2 to 618.5 µW ·cm-2, the removal rate of 2-MIB was increased by 42% and 39%, respectively, and the removal rate of GSM was increased by 34% and 16%, respectively. The effect of pH on 2-MIB and GSM removal was not significant. The occurrence of HCO3- and humic acid will decrease the removal rates of 2-MIB and GSM, and the degree of reduction increases with the concentrations of HCO3- ion and humic acid. The VUV/PS process can effectively degrade the typical odorants in water and can reduce the difficulty of subsequent water treatment.