Arranged in barrels of concrete or plastic, these biosand water filtration systems (BSFs) remove 95 to 99 percent of the bacteria, viruses, worms and particles contained in rain or surface water.

“BSFs were developed in the 1980s, ” says Jellison. “This is the most comprehensive study to date to characterize the efficiency of different filter types.”

Jellison's group is conducting experiments on BSFs of various sizes, including systems that fit inside two - and five-gallon plastic pails.