Membrane Pilot Study of Phosphorous Removal at the Frisco Sanitation District

Abstract

The Frisco Sanitation District (District) owns and operates an advanced wastewater treatment (AWT) plant. Phosphorous removal has been the dominant concern at this wastewater treatment plant (WWTP) due to the potential for accelerated cultural eutrophication in Lake Dillon, which is a major recreational and drinking water supply in Summit County for the City of Denver.Peak flows are reaching the combined capacity of the four existing AWT units. Therefore, a pilot study was conducted to determine whether membrane filtration systems could (1) increase overall AWT throughput capacity, (2) meet phosphorous removal objectives, and (3) be cost competitive with conventional AWT treatment. Overall goals for the pilot study and preliminary design study include:Provide a net 1.0 mgd increase in AWT capacity.Achieve average effluent total phosphorus levels of <0.02 mg-P/L.Keep total construction cost, including membranes and all pumping, piping, and support facilities to less than $3,000,000.No increase in staffing requirements for either operations or maintenance (O&M).The pilot unit was a Zenon immersed membrane system. The pilot was operated for three months. Operational data included alum dose, long-term flux rate, backpulse and membrane cleaning frequency, and percent recovery. Permeate quality was tested for total phosphorous levels, turbidity removal, and the impact of pH on phosphorous removal performance.

Membranes for Water Reclamation – The Present and Future Trends

“…One such option is coagulant addition followed by MF (or UF) to augment the removal of dissolved material. In a pilot program at Frisco, Colorado, alum was added to allow the coagulant-UF process to lower the concentration of phosphorus from 0.5 mg/L (as P) in the secondary effluent to 0.018 mg/L in the product (Parsons and Maxwell, 2001). Using a surface water treatment pilot program in Scottsdale as an example, an analogous situation was demonstrated for another dissolved species, arsenic.…”