Pulsing portions of a filter cell to extend a filter run

A method for removing solids from an influent liquid during periods of high volumetric influent flow during a filtration time in a filtration cycle, by passage of said liquid through a down-flow granular medium filter bed in a filter tank cell, said filter bed having an upper surface and a lower surface, and made up of a plurality of subcells, each subcell individually adapted and controlled for periodic upwardly directed pulses of fluid from an array of orifices therein at times other than during backwashing, comprising the steps:

• (a) continuously introducing said influent liquid into said filter tank cell for downward solids-removing passage through said filter bed;
• (b) allowing liquid in said filter tank cell to rise to a selected first level above said upper surface of said filter bed during the filtration time;
• (c) creating currents within said influent liquid above said filter bed by current creating means located above said filter bed and below said selected first level, to suspend filtered solids within said influent liquid above said filter bed;
• (d) allowing liquid in said filter tank cell to rise to a selected second level, greater than said selected first level, above said upper surface of said filter bed during the filtration time;
• (e) activating a first selected subcell of said filter cell for a pulsing cycle upon the level of liquid above the filter bed exceeding said selected second level, said pulsing cycle comprising intermittent upwardly-directed multiple pulses of a fluid through that portion of the filter bed within said selected subcell from said array of orifices therein, to dislodge solids from said upper surface of said bed within said subcell, store filtered solids within that portion of the filter bed, and increase the passage of liquid through that portion of the bed within said subcell, thereby minimizing the liquid level rise above said upper surface of said filter bed;
• (f) activating a second selected subcell of said filter cell for a pulsing cycle, said pulsing cycle comprising intermittent upwardly-directed multiple pulses of a fluid through that portion of the filter bed within said selected subcell from said array of orifices therein, to dislodge solids from said upper surface of said bed within said subcell, store filtered solids within that portion of the filter bed, and increase the passage of liquid through that portion of the bed within said subcell, thereby minimizing the liquid level rise above said upper surface of said filter bed;
• (g) allowing liquid in said filter tank cell to rise to a selected third level, greater than said selected second level, during the filtration time;
• (h) ceasing the introduction of influent liquid into said filter tank cell;
• and
• (i) backwashing said filter bed at an upwardly cleansing velocity after completion of two or more said pulsing cycles.