This paper summarizes results from an AwwaRF funded project investigating pilot- andfull-scale studies for high-rate spent filter backwash water (SFBW) treatment processes as described in Cornwell et al. ([N.d.]).This referenced AwwaRF report and the following summary article include a description of optionsavailable for SFBW treatment, including a description of existing data describing characteristics andperformance of some of these alternative processes. The information available prior to this project waslimited to gravity clarification processes (quiescent settling, with or without tubes and plates) and some"standard-rate" dissolved air flotation (DAF) studies (defined as DAF processes with rates <6 gpm/ft<sup>2</sup>).However, for the more innovative, high-rate treatment processes targeted for this study, enough criticalperformance and cost data were not available prior to this study to allow for ease of evaluation andimplementation by utilities.Therefore, after describing the limited available existing literature on all processes evaluated forSFBW treatment, the above referenced report and the following summary article describe findings frompilot- and full-scale studies of SFBW treatment at drinking water treatment facilities during spring andsummer 2007. Findings include evaluations of the impacts of clarification rate, polymer type and dose,initial mix and flocculation, and internal recycle rate (when appropriate) on high-rate SFBW treatmentprocesses. Evaluations at two drinking water plants include comparison of cost and footprint estimatedfor the high-rate processes that were pilot tested at these locations. In particular, though each manufacturerexpresses clarification rate a little differently, typically basing the rate relative to clarification area, inthis study the rate is also expressed relative to total footprint, including area for flocculation, chemicalfeed, and other ancillary facilities. The Appendices in the Cornwell et al. ([N.d]) report includepreliminary design reports discussing details regarding costs and footprint for the two facilities wherepilot studies were conducted.The Cornwell et al. ([N.d.]) report also evaluated membrane treatment alternatives for SFBW inbench-scale studies. Membrane technologies evaluated included low pressuremicrofiltration/ultrafiltration (MF/UF) types, such as hollow fiber membranes, tubular membranes, andceramic membranes. Includes 4 references, table.
