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

In this study, the effect of sodium hypochlorite (10-200 ppm of Cl₂) 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 log₁₀ genome copies/μL of HuNV GII.4 or 5.50 log₁₀ genome copies/μL of HAV were artificially inoculated in groundwater. The titers of HuNV GII.4 and HAV decreased significantly (<i>P</i> < 0.05) with increasing Cl₂ concentrations. Groundwater was treated with 10, 30, 50, 100, 150, and 200 ppm of Cl₂, and the viable HuNV GII.4 was significantly (<i>P</i> < 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) log₁₀ genome copies/μL, respectively. The viable HAV was also significantly (<i>P</i> < 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) log₁₀ genome copies/μL, respectively. The decimal reduction times (<i>D</i> values) (1-log₁₀ genome reduction) of HuNV GII.4 and HAV infectivity in groundwater were predicted as 116.7 and 98.9 ppm of Cl₂, respectively, using the first-order kinetics model (HuNV GII.4: <i>y</i> = -0.0054<i>x</i> + 3.3585, correlation coefficient (<i>R</i>²) = 0.97; HAV: <i>y</i> = -0.0091<i>x</i> + 5.0470, <i>R</i>² = 0.97). The result specifically suggests that 150- to 200-ppm Cl₂ can potentially be used for the inactivation of >1-log₁₀ genome copy/μL HuNV GII.4 and HAV in groundwater.IMPORTANCEGroundwater represents a vital component of the global water supply, serving as a crucial source of potable water for humans. It serves as a source of potable water for up to 50% of the global population and accounts for 43% of all water used for irrigation. It thus follows that the sustainable management of groundwater represents a pivotal solution. However, the regrowth of pathogens in water that is not treated with chlorine or where proper residual chlorine is not maintained represents a risk to public health.