Reduction of microscopic particulates by aquifers

Many water utilities operate collection devices constructed in alluvial-valley aquifers. Pumping groundwater from these systems may induce infiltration of surface water containing pathogenic protozoa. However, the porous sand and gravel of this kind of aquifer can significantly reduce the number of microscopic participates that pass through the aquifer media. A method is proposed for evaluating the natural reduction efficiency of porous-media aquifers, taking into consideration the transport of particulates through the aquifer during a period of maximum infiltration. The method allows regulators to estimate the risk of pathogenic protozoa, determine the log-reduction credit warranted by the water's transport through the aquifer, and determine the type of treatment needed for the source.