Backwashing Characteristics of Pumice as a Sustainable Alternative Granular Filter Medium for Desalination Pretreatment

OpenAlex Türkçe

In this study, the potential use of pumice as an alternative filter medium in granular filters employed for seawater pretreatment prior to membrane processes was investigated in terms of backwashing behavior. Silica sand, activated carbon, and pumice were prepared in different particle size fractions, and their density, equivalent diameter, and water absorption capacities were determined according to ASTM standards. Using synthetic seawater prepared with natural sea salt, fluidization (backwashing) experiments were conducted to evaluate the bed expansion behavior of the materials. As expected, pumice and activated carbon achieved higher bed expansions at lower backwash velocities compared to the primary filter material, sand, due to their lower densities and porous structures. Sand, on the other hand, exhibited limited expansion even at higher velocities because of its dense and less porous structure. This indicates that in dual-layer filters combining sand with a porous medium, achieving effective fluidization for both materials may carry a risk of media loss. The results demonstrate that backwash velocities in dual-layer granular filters should be optimized based on the density and particle size of the selected materials. Considering the characteristics evaluated in this study, pumice (abundant in Turkey, low-cost, and environmentally sustainable) can be considered a promising alternative to activated carbon as a filter medium.