Method for enhancing the separation capacity of a multi-bed filtration system

A method for enhancing the separation capacity of a multi-bed water filtration system comprising:

• providing a filter apparatus having an upstream filter bed that is bouyant during filtration, a downstream filter bed of nonbuoyant media, and backwashing means for moving water upwardly through said downstream filter bed at selected time intervals;
• treating raw water with at least one chemical coagulant;
• passing said treated water upwardly through said upstream filter bed to partially filter said water;
• passing said partially filtered water downwardly through said downstream filter bed to provide additional filtration of said water, said filtration causing coagulated materials from said water to be collected within said downstream filter bed;
• periodically interrupting the flow of said partially filtered water through said downstream filter bed;
• causing said backwashing means to move water upwardly through said downstream filter bed during said interruption of said flow of partially filtered water, said upwardly moving water comprising water previously filtered through said upstream and downstream filter beds, said upward movement of said water causing release of said coagulated materials collected therein, said released materials rising to a zone above the surface of said downstream filter bed to form a floc deck of coagulated materials thereabove;
• and
• resuming the flow of said partially filtered water from said upstream filter bed downwardly through said downstream filter bed, said water first passing through said zone of coagulated materials.