Wet-Weather Pilot Studies Demonstrate Effectiveness of High-Rate Filtration Technologies

Abstract

Like many communities across the United States, Johnson County, Kansas and the City of St. Joseph, Missouri, are considering means to control collection system overflows from their publicly owned treatment works while maintaining or improving water quality. Planning studies for both communities evaluated several wet-weather treatment alternatives and included benchscale and pilot trials of the following processes during actual wet-weather peak flow conditions:(1) chemically enhanced sedimentation, (2) ballasted flocculation, (3) cloth media filtration, (4) dynamic tangential disc filtration and (5) compressible media filtration. These studies indicated that high-rate filtration processes, particularly compressible media filtration, produced effluent of a quality similar to that produced by high-rate clarification without the need for chemical coagulation and flocculation, and appear to be viable alternatives for certain wet-weather treatment applications.

Wet-Weather Piloting Toward the Largest Compressible Media Filter on the Planet

“…The Columbus project was partially funded by the United States Environmental Protection Agency (USEPA), which considers CMF to be an innovative technology for wet-weather management (USEPA, 2008). Wet-weather pilot studies conducted in Kansas and Missouri in 2008 and 2009 compared CMF side-by-side to other high-rate filtration alternatives as well as high-rate sedimentation alternatives and further substantiated CMF as a viable alternative for wet-weather treatment applications (Fitzpatrick et al, 2010).…”

Preparing for a Rainy Day – Overview of Treatment Technology Options for Wet-Weather Flow Management

“…Recent side-by-side wet-weather pilot studies found that the CMF technology consistently produced effluent with lower TSS concentrations than the cloth media technology and appeared to be less sensitive to influent hydraulic and solids loading rates (Fitzpatrick et al, 2010b). Subsequent piloting of the CMF technology over multiple wet weather events confirmed that the CMF technology consistently produced effluent TSS concentrations meeting secondary treatment standards, and that the CMF effluent was consistently amenable to hypochlorite or UV disinfection at doses and contact times equivalent to those typically used for conventional secondary effluents (Fitzpatrick et al, 2010b and2011). For peak wet-weather solids loadings, design hydraulic rates of 10 to 15 gpm/ft 2 (14,000 to 20,000 gpd/ft 2 ) are generally achievable before the backwash frequency becomes unmanageable.…”