Learn how farm runoff impacts water quality and human health. Tour the water treatment plant in Des Moines, Iowa, and learn how the water is filtered, in this video excerpted from the independent film 'Big River: A King Corn Companion.' Hear how high nitrate content in water can affect human health, causing such problems as blue baby syndrome, and understand why water treatment plants in agricultural regions need nitrate removal facilities because of the pollution from fertilizer runoff. Includes background essay and discussion questions. [2:03]