Effect of hydrochemical conditions in transport properties of viruses in groundwater

Abstract

Knowledge of virus removal in subsurface environments is pivotal for assessing the risk of viral contamination of drinking water wells and to adequately protect groundwater resources. Laboratory and field experiments are necessary to obtain values for kinetic parameters needed to describe virus transport and removal in aquifers. The two most significant processes controlling virus mobility in the subsurface environment are virus attachment and inactivation. In this research, various combination of column and batch experiments were conducted to obtain data for the development of quantitative relations for attachment and inactivation of bacteriophage PRD1,as a model virus, as a function of pH, ionic strength (IS), sodium and calcium concentration. Attachment rate coefficients increased with decreasing pH and increasing ionic strength, in agreement with DLVO theory. Also, attachment rate coefficients were found to increase with increasing calcium concentration. Sticking efficiencies were calculated from the attachment rate coefficients and used to develop empirical formulas for sticking efficiency as a function of pH, IS, sodium and calcium concentration. This relationship is applicable under unfavourable conditions for virus attachment. A reference sticking efficiency was defined for pH 7 and no calcium and no sodium (zero ionic strength). This reference value may be different under field conditions, for example, because soil in the field may differ in properties from the cleaned sand that was used in the column experiments in our studies. Nevertheless, effects of pH, sodium and calcium, as quantified by the empirical formula, may still be the same. The inactivation rate coefficient was found to depend linearly on temperature, pH, and sodium concentration, but, non-linearly on calcium concentration. In the presence of calcium, it increased rapidly to a maximum. Like for attachment, a single empirical formula for the inactivation rate coefficient of PRD1 in water as a function of temperature, pH, Na+ and Ca2+ was developed. Calculated values with this formula are within the range of values for the inactivation rate coefficient of PRD1 that have been reported in literature.