AWWA JAW73197

Many laboratory studies have been performed on particle and microbe removal using a standard filter protocol with no cross flow of water across the filter bed. This study was conducted to better understand the effect on filtrate quality when cross flow does occur across the filter bed. Larger suspended particles tend to settle in a stream or on a beach toward the bed, resulting in a concentration of larger-sized particles over smaller ones. Larger microbes such as Cryptosporidium tend to concentrate in the streambed (assuming similar density characteristics) versus smaller microbes such as Escherichia coli. As stream flow or wave action increases toward turbulent flow conditions, the impact of this sorting decreases significantly. Understanding the importance of flow helps to better select sites for riverbank and seabed infiltration and helps determine flow characteristics in engineered filtered systems with cross flow.

Includes 14 references, tables, figures.