The first site related to water filtration is from the US Environmental Agency entitled EPA Environmental Education: Water Filtration (1 ). The two-page document explains the need for water filtration and the steps water treatment plants take to purify water. To further understand the process, a demonstration project is provided that illustrates these purification steps, which include coagulation, sedimentation, filtration, and disinfection. The second site is an interesting Flash animation called Filtration: How Does it Work (2 ) provided by Canada's Prairie Farm Rehabilitation Administration. Visitors will learn various types of filtration procedures and systems and the materials that are used such as carbon and sand. Next, from the National Science Foundation is a learning activity called Get Out the Gunk (3 ). Using just a few simple items from around the house, kids will be able to answer questions like "Does a filter work better with a lot of water rushing through, or a small trickle?" and "Does it make the water cleaner if you pour it through a filter twice?" The fourth Web site, Rapid Sand Filtration (4 ), is provided by Dottie Schmitt and Christie Shinault of Virginia Tech. The authors describe the process, which involves the flow of water through a bed of granular media, normally following settling basins in conventional water treatment trains to remove any particulate matter left over after flocculation and settling. Along with its thorough description, readers can view illustrations and photographs that further explain the process. The Vegetative Buffer Strips for Improved Surface Water Quality (5) Web site is provided by the Iowa State University Extension office. The document explains what vegetative buffer strips are, how they filter contaminants and sediment from surface water, how effective they are, and more. The sixth offering is a file called Infiltration Basins and Trenches (6) that is offered by the University of Wisconsin Extension. These structures are intended to collect water, have it infiltrate into the ground, and have it purified along the way. This document explains how effective they are at removing pollutants, how to install them, design guidelines, maintenance, and more. Next, from a site called Wilderness Survial.net is the Water Filtration Devices (7) page. Visitors read how to make a filtering system out of cloth, sand, crushed rock, charcoal, or a hollow log, although as is stated, the water still has to be purified. The last site, from the US Geological Survey, is called A Visit to a Wastewater-Treatment Plant: Primary Treatment of Wastewater (8). Although geared towards children, the site does a good job of explaining what happens at each stage of the treatment process and how pollutants are removed to help keep water clean. Everything from screening, pumping, aerating, sludge and scum removal, killing bacteria, and what is done with wastewater residuals is covered.