In conventional water treatment stations, the filter cleaning is performed with the use of filtered water. To save water and obtain higher production, the use of polystyrene (PS) beads has been proposed as a granular filter element because it is a granular element with a low specific mass. By being lightweight, this material requires a lower water velocity during backwash. The PS beads were applied in a descending rapid filter and compared to a conventional sand and anthracite filter, and its hydraulic performance was evaluated during the backwash with air and water interspersed. Although it presents a high fluidity, with lower rates (compared to conventional filters) of backwash, this fact does not necessarily represent an economy of backwash water, because it requires more time for cleaning. It was also observed that there is an optimal value for the removal of particles collected during the filtration without loss of material.

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