Keywords: Rapid sand filter EPA.jpg rapid sand filter for water purification http //nepis epa gov/Exe/ZyPURL cgi Dockey 300048WU txt Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities Document no EPA/625/4-89/023 p 36 Figure 4-2 US Environmental Protection Agency 1990-03 PD-USGov-EPA Drinking water treatment Sand filters Cutaway diagrams PD-USGov |