Laboratory tests were conducted to determine which system of chemicals would be most effective on combined packinghouse and domestic waste. A dual system of chemicals was found which was effective in the treatment of this combined waste. This was a combination of ferric chloride and an anionic polyelectrolyte. This system was effective in forming a floc which would settle out under the dynamic conditions of the overloaded primary sedimentation tank. Treatment with this system could effectively reduce suspended solids in the effluent of the primary sedimentation tank over what could be achieved without the use of this dual system. This was demonstrated by running: (1) a parallel system of identical tests and control tanks and, (2) full plant scale investigation for both test and control periods, kept as identical as possible. When full plant scale tests were run, laboratory data were collected from various sampling points throughout the plant during the test and control periods. A significant reduction of BOD and suspended solids was obtained in the primary sedimentation tanks and a change in efficiency was not observed on the trickling filters resulting in an overall reduction in these parameters in the effluent from the secondary sedimentation tank. The cost of chemically treating the combined 10 mgd of wastewater would be approximately $45 per million gallons and would be less for strictly domestic wastes.

Report prepared by Metropolitan Sewer Board, South St. Paul, Minnesota. "Project 12130 EKK; Program Element 1BB037." Includes bibliographical references.