Inactivation of Escherichia coli and MS2 coliphage via singlet oxygen generated by homogeneous photosensitization

The inactivation kinetics of E. coli and MS2 coliphage by singlet oxygen (O-1(2)) were investigated in a homogeneous photosensitization system using Rose Bengal (RB) and visible light illumination (the Vis/RB system). The inactivation of E. coli and MS2 in the Vis/RB system was monitored over time with variations of several parameters such as pH, light intensity, concentration of RB, and the presence of dissolved oxygen. In addition, the concentration of O-1(2) generated by the Vis/RB system was quantified using furfuryl alcohol under each microbial inactivation conditions. Based on the obtained results, the degree of microbial inactivation was quantitatively correlated with O-1(2) exposure using the (delayed) Chick-Watson model. The Ct (concentration-time product) values of O-1(2) required for 2 log microbial inactivation were found to be 1.3x10(-4) mg center dot min/L for E. coli and 1.9x10(-5) mg center dot min/L for MS2, respectively. The inactivation of E. coli exhibited an initial lag phase until 0.5x10(-4) mg center dot min/L of Ct.