The Sanitary Sewer Collection System transports raw sewage from the homes and businesses in Lewisville to the Wastewater Treatment Plant. Fourteen lift stations support the gravity system by pumping the sewage through miles of force main to the Treatment Plant. The Texas Natural Resource Conservation Commission and U.S. Environmental Protection Agency issue wastewater discharge permits, which establish the operating parameters for the treatment of wastewater. Its purpose is to remove those materials in wastewater that are untreatable or detrimental to treatment plant equipment or processes, such as large debris, and oils and grease.
Sedimentation is the process by which solids and liquids are separated by gravitational forces.
Denser solids called sludge settle to the bottom and lighter materials float to the top. Two common types of secondary treatment are trickling filters and activated sludge. Both are biological processes which create the conditions favorable to the growth and reproduction of special microorganisms. The organisms consume the dissolved or suspended organic matter present. The microorganisms then settle out of the treated water.