Clarification with microsand seeding. A state of the art

The author discusses a technique for high-rate water treatment in which microsand (sand with a pore size of 20-100 um) is used with the coagulant to provide a 'seed' for development of the flocs. An illustrated description is given of the Cyclofloc clarifier developed for application of this technique. A further development is the Fluorapid unit , in which treatment takes place in two stages . Results obtained with this technique at several water works in France are tabulated.