Roles of singlet oxygen and triplet excited state of dissolved organic matter formed by different organic matters in bacteriophage MS2 inactivation

Inactivation of bacteriophage MS2 by reactive oxygen species (ROS) produced by irradiation with simulated sunlight, containing visible light and ultraviolet light with wavelengths greater than 320 nm, was investigated. The results from experiments with synthetic sensitizers Rose Bengal, 3'methoxyacetophenone, and nitrite suggested that singlet oxygen (1O2), triplet excited state of dissolved organic matter (3DOM*), and hydroxyl radicals (•OH) could separately inactivate bacteriophage MS2. Natural sources of sensitizers included purified DOM isolates obtained from wastewater and river waters and three water samples collected from Singapore River, Stamford Canal, and Marina Bay Reservoir in Singapore. Linear correlations were found between MS2 inactivation rate constants (kobs) and the photo-induced reaction rate constants of 2,4,6-trimethylphenol (TMP), a probe compound that previously had been shown to react mainly with 3DOM*. Linear correlations between MS2 kobs and 1O2 concentrations were also found for both purified DOM isolates and natural water samples. These correlations, along with data from quenching experiments and experiments with synthetic sensitizers suggest that both 1O2 and 3DOM* play important roles in MS2 inactivation. Linear correlations between MS2 kobs and Specific Ultraviolet Absorption determined at 254 nm (SUVA254) were also found for both purified DOM isolates and natural samples. These results suggest the potential use of TMP as a chemical probe and SUVA254 as an indicator for virus inactivation in natural and purified DOM water samples