Kerr Lab scientist Susan Mravik demonstrates to elementary students the difference in water from lakes in Oklahoma Thursday afternoon. "We have some tests that we have done, to look for microorganisms in water," she said. "Byrd's Mill water is very clean, that's where the city of Ada gets its drinking water from, and in places like Oklahoma City and Norman that use Lake Thunderbird, where they have bacteria growing, they have to chlorinate and do things to their water and get it up to drinking quality." ECU was host to several students from elementary to college-age Thursday to promote activities for Earth Day. (Photo by Derek Frazier)