Filtration capacity on rapid filters and adsorption characteristics of polystyrene granules.

Polystyrene (PS) beads have been studied as a possible filter element, with the aim of increasing the effective production of water in treatment plants. Being a granular material of an effective size of 0.68 mm, sphericity of 0.96 and density of 1046 kg/m(3), the use of PS beads may provide washing water savings because they require low velocities for expansion during backwash. However, other aspects must be considered before the adoption of this material, such as the filtration mechanisms associated with it. Analyses of turbidity retention and head loss variation throughout the filter run were observed, and acceptable filtration rates were achieved (pilot tests). There was bit adhesion of particulates on bead surfaces, which was observed by scanning electron microscopy. The beads showed a low adsorption capacity, which was assessed using methylene blue (lab tests).