AWWOA Water Week Conference 2019

A replacement to dual-media filtration, a conventional treatment method, with ceramic filter media is proposed through this study. Filtralite, a porous ceramic filter media with high surface area, is evaluated as an alternative to anthracite/sand filter media at City of Saskatoon WTP.
City of Saskatoon WTP, current treatment capacity of 280MLD, is targeting an expansion to their treatment capacity (400 MLD) to meet future demands. Filtration basin with anthracite/sand dual-media, a component of existing treatment process, identified as one of the main constraints for increasing the production. As a part of their on-going rehabilitation work, Filtralite media was chosen for pilot-scale evaluation against anthracite/sand filter dual-media with an intent to increase production while minimizing capital expansion and operating costs.
Pilot-scale study was conducted on multiple filter columns that are operated in parallel to each other with varying bed depths. Filter columns were operated at variable flow rates between 3 to 5 L/s that mimics and exceeds the current treatment design characteristics. Filtralite and anthracite/sand dual-media were compared for their performance based on filter run time, head loss profiles, turbidity, and backwashing characteristics. Head loss limit of 1 meter and turbidity limit of 0.3 NTU are developed for filter backwashing and to end filter cycle.
Filtralite media was consistent in reducing turbidity to less than 0.1 NTU compared to anthracite/sand dual-media at influent water temperatures of 0.8 °C to17.8 °C. In addition, Filtralite media has indicated reduced head loss development for same run time compared to anthracite/sand dual-media. The performance of was consistent under all seasons; where head loss development was reduced with filter aging. Longer filter run times are achieved, 180% increase in volume/run times, with Filtralite media compared to anthracite/sand dual-media. Overall, based on the pilot-scale study at City of Saskatoon WTP, Filtralite media has indicated extended run times, reduced backwash volumes, and lower filter ripening volumes compared to anthracite/sand dual-media.
From this study, we propose, Filtralite media can be an alternative to anthracite/sand dual media which potentially extends run lengths, reduces backwash volumes, saves energy, and improves the overall performance of gravity filtration basins.