Gravity Carbon Filtration to Meet Reuse Requirements

The paper describes upgrading of the Pomona Water Reclamation Plant in Pomona, Calif. to meet increasingly stringent stream discharge and effluent reuse standards. Public contact with plant effluent in the receiving stream resulted in treatment requirements that included virus removal and dechlorination. An additional color requirement was placed on the effluent by the Pomona Water Department. Three alternative treatment systems were subjected to engineering analysis, with a two-stage carbon filtration system proving most cost effective. The system ultimately constructed can be operated in a 10 mgd (27.8 m³/min) single-stage mode with 10 min. of chlorine contact followed by chlorination and SO₂ dechlorination, or in a 5 mgd (13.9 m³/min) two-stage mode with 10 min of carbon contact followed by chlorination and an additional 10 min of chlorine contact. Dechlorination is accomplished on the second carbon stage.