Limestone filters in artificial recharge of groundwater

In Sweden the properties of groundwater regarding pH, hardness and alkalini ty often do not reach the values recommended for drinking water. The proble m is more accentuated for artificially recharged groundwater, where infiltr ation of large volumes of soft surface water eventually leads to a depleted base cation storage. Filters with crushed limestone were embedded in infil tration ponds at two waterworks in Sweden. The effect on the water quality regarding pH, hardness and alkalinity was studied over a period of five yea rs. The filter material was examined. Dissolution of the filter Limestone r esults in increased pH hardness and alkalinity in the percolating water. To reach levels where it may replace chemical treatment steps In the waterwor ks, the method needs further development. A more effective use of limestone filters would involve a longer flow path through the filter and a better h ydraulic connection between the infiltration pond and the well.