LIFT STATION CAPACITY ENHANCEMENT THROUGH POLYMER ADDITION

Flows to the Metro Wastewater Reclamation District's (MWRD) Lower South Platte Basin are increasing rapidly due to new housing development. Flow projections show that the Brantner Gulch Lift Station (BGLS), without further improvements, will be unable to meet peak capacity requirements within a few years. As such, MWRD evaluated alternatives to increase the capacity of the BGLS. One alternative is the addition of polymer to the force mains during peak events to improve pumping capacity.The Brantner Gulch Interceptor conveys flow to the BGLS where it is pumped to the South Thornton Interceptor. The South Thornton Interceptor discharges to the Thornton-North Washington lift station which outfalls to MWRD's Central Treatment Plant. In the future, flows from the BGLS will continue to either be pumped to the Central Treatment Plant, or be directed by gravity to a new downstream regional WWTP.A preliminary test of polymer addition was conducted at the BGLS in October 2000. The limited testing involved application of a single polymer to the wet well. Results indicated that an increase in capacity of 18 percent could be achieved. These results were promising enough to warrant further investigation. Various polymers were evaluated based on literature and vendor information with three liquid polymers selected for testing. Based on the testing conducted, an increase of approximately 30 percent in flow rate over the baseline pumping conditions was achieved with a polymer dosage rate of approximately 50 mg/L.A full-scale polymer feed system has been designed and will be constructed in the summer of 2002.