High Rate Wastewater Effluent Filtration with an Unstratified Media

The City of Sioux Falls Water Reclamation Plant (SFWRP) currently utilizes tertiary filtration to polish effluent from the final clarifiers. The current dual media filters have exceeded the design life and are scheduled to be replaced. A study was conducted to determine if depth filtration with an unstratified mono media (anthracite) would increase the filtration rate and run length without compromising the quality of the effluent or the redundant capacity of the filters. Three 203 mm (8 in) filters and one 305 mm (12 in) filter was constructed to analyze the capabilities of an unstratified media with filtration rates ranging from 0.15 to 0.33 m3/m2·hr (3.7 to 8.1 gpm/ft2). The research showed that the filters were capable of producing high quality effluent TSS concentrations ranging from 1.2 to 6.6 mg/L at influent TSS concentrations ranging from 5.9 to 16.9 mg/L. Three types of anthracite coal media were studied with effective sizes of 1.56, 2.01, and 2.64 mm.