Effects of Organic Matter on Virus Removal with New and Used Sand in Tunåsen Infiltration Basin, Uppsala, Sweden

University essay from Uppsala universitet/Institutionen för geovetenskaper

Abstract: Artificial infiltration has been increasing in popularity in Sweden as a way to combat over-abstraction of groundwater aquifers from growing municipalities. However, enteric virus contamination of drinking water sources is a concern as infiltrating surficial waters are easily contaminated from human activities. Therefore, it is imperative that effective drinking water treatment is maintained to prevent infection throughout the municipalities. Furthermore, a better quantification of environmental parameters affect-ing virus mobility could significantly improve infiltration schemes for virus removal purposes. In this study, the removal efficiency of MS2 bacteriophage was investigated in relation to dissolved organic matter and ionic strength on new and used sand from the Tunåsen infiltration basin in Uppsala, Sweden. Virus removal was measured by static batch equilibrium experiments and first order decay models were used as interpretative models. Soil associated organic matter displayed the greatest effect on virus removal between all parameters. The highest removal efficiency was seen in samples containing low soil associated organic matter. Similarly, an inverse relationship with dissolved organic matter and virus removal rate was determined. Samples without soil showed the opposite relationship between dis-solved organic matter and virus removal. A higher decrease in MS2 phage was observed with higher dissolved organic matter in soil-negative samples. The removal kinetics of MS2 with higher ionic strength had a closer correlation with the linear time-invariant removal model, whereas samples with low ionic strength had a closer relation with the nonlinear time-dependent removal model. However, ionic strength was shown to have very little effect on overall virus removal efficiency. Fastest and slowest viral removal rates were modeled in the HYDRUS 1D program to determine the amount of potential contamination of the water table beneath the Uppsala Esker. The degree of contamination at the bottom of the infiltration basins was also determined. The sample with the highest rate of virus removal displayed an 11.77% greater decrease in phage concentration at the water table than samples with the lowest rate of removal. However the approximation of maximum contamination was deemed unrealistic due to the assumption that the entire esker was made of sand. On the other hand, the sample with the highest rate of removal showed only a 0.60% greater decrease in phage concentration following the infiltration basin. This study therefore suggests that a more frequent replacement of quartz sand in infiltration basins has little value in overall drinking water quality.

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