Application of sodium hypochlorite for human norovirus and hepatitis A virus inactivation in groundwater

Abstract

In this study, the effect of sodium hypochlorite (10-200 ppm of Cl-2) on the inactivation of human norovirus (HuNV) GII.4 and hepatitis A virus (HAV) in groundwater was investigated using propidium monoazide (PMA)/reverse transcription quantitative real-time PCR (RT-qPCR). Initially, 4.00 log(10) genome copies/mu L of HuNV GII.4 or 5.50 log(10) genome copies/mu L of HAV were artificially inoculated in groundwater. The titers of HuNV GII.4 and HAV decreased significantly (P < 0.05) with increasing Cl-2 concentrations. Groundwater was treated with 10, 30, 50, 100, 150, and 200 ppm of Cl-2, and the viable HuNV GII.4 was significantly (P < 0.05) reduced to 3.28 (0.21-log reduction), 3.18 (0.31-log reduction), 3.01 (0.48 log reduction), 2.75 (0.74 log reduction), 2.54 (0.95 log reduction), and 2.34 (1.15 log reduction) log(10) genome copies/mu L, respectively. The viable HAV was also significantly (P < 0.05) reduced to 4.99 (0.23 log reduction), 4.76 (0.46 log reduction), 4.55 (0.67 log reduction), 4.21 (1.01-log reduction), 3.89 (1.33 log reduction), and 3.64 (1.58 log reduction) log(10) genome copies/mu L, respectively. The decimal reduction times (D values) (1-log(10) genome reduction) of HuNV GII.4 and HAV infectivity in groundwater were predicted as 116.7 and 98.9 ppm of Cl-2, respectively, using the first-order kinetics model (HuNV GII.4: y = -0.0054x + 3.3585, correlation coefficient (R-2) = 0.97; HAV: y = -0.0091x + 5.0470, R-2 = 0.97). The result specifically suggests that 150- to 200-ppm Cl-2 can potentially be used for the inactivation of >1-log(10) genome copy/mu L HuNV GII.4 and HAV in groundwater.