Role of Suspension Polydispersivity in Granular Media Filtration

Abstract

Experimental work on the role of feed suspension polydispersivity on the performance of granular media filters is presented. Suspensions of latex particles of sizes 0.09 μm, 0.944 μm, 7.04 μm, and 7.6 μm, and their paired combinations were filtered through a porous bed of glass spheres. During the ripening stage of the filtration, the presence of small particles was observed to improve the removal of large particles, while the removal of small particles themselves was not significantly affected by the presence of larger particles. These results are explained by the relative contributions of particles deposited in the filter bed to the total available surface area for subsequent particle deposition. Filter ripening evolves faster when particles in the filter influent have a smaller mass‐averaged diameter. Deposit morphology and relative distribution of the mass in the bed appear to depend on suspension polydispersivity and play an important role in head‐loss development. When particles smaller than 1 μm are present in the feed suspension, relatively short periods of filtering to waste should improve the removal of the bacteria‐sized particles that may be poorly removed by clean filter beds.