AWWA WQTC52742

This study was conducted to identify and evaluate viable treatment options forremoving pathogens and other contaminants from recycle streams beforereintroducing the streams to the headworks of a water treatment plant. Researchefforts were focused on spent filter backwash water (SFBW) since it comprises thelargest component by volume of the sidestream wastes generated at a watertreatment plant and is by far the most commonly recycled sidestream. The ultimateobjective of this project was to provide utilities and regulators with a thoroughguide on effective, affordable, and practical methods to treat recycled SFBW. Theapproach for achieving that objective involved conducting the following studies:occurrence survey (protozoans and other parameters); disinfection studies;laboratory removal studies; pilot-scale dissolved air flotation (DAF) trial;pilot- and full-scale sedimentation trials (including pilot-scale oocystspiking); and pilot-scale comparison of conventional treatment and filtrationusing a synthetic fiber filter. Results of these investigations were used todevelop costs relative to the level of recycle treatment. This paper addressesthe following studies: laboratory removal studies; pilot-scale DAF trial; andpilot- and full-scale sedimentation trials. Includes 6 references, tables, figures.