The Effect of UV and Combined Chlorine/UV Treatment on Coliphages in Drinking Water Disinfection

摘要

Ultraviolet (UV) irradiation is a common way to disinfect drinking water, but some viruses are very resistant to UV. Drinking water was disinfected with UV after spiking with MS2 and 18 different coliphages isolated from municipal wastewater effluent. In addition, some coliphages were disinfected with combined treatment of chlorine/UV or vice versa with UV/chlorine. A UV-dose of 22 mWs/cm 2 caused less than 2 Log 10 -reductions of 10 UV-resistant strains, while it caused up to 7 Log 10 -reductions for 9 UV-sensitive or intermediate strains. The high dose (117 mWs/cm 2 ) caused only 3 Log 10 -reductions in some UV-resistant coliphages, including MS2, which proved to be a good indicator for viruses in UV-disinfection tests. The combined treatment with 0.1 or 0.5 mg Cl/L (free Cl-dosage 0.04 or 0.2 mg/L, respectively) for 10 min followed by UV irradiation of 22 mWs/cm 2 inactivated all coliphages tested by >3.6 Log 10 -units. Synergy was obtained for most coliphages tested by using a Cl/UV combination, and the inactivation using first low Cl-dosages followed by low UV-dosages was higher than if using high Cl- or UV-dosages alone. The opposite treatment with UV/Cl was less effective. Therefore, the combination treatment using first chlorine and then UV can be recommended as a disinfection method for viruses.