Tertiary filter

Claim 2

The method of claim 2 with the addition of the step of directing pressurized gas through the first and second filter beds to agitate the filter material and to remove solid particles therefrom prior to pumping filtered liquid therethrough.

Claim 3

The method of claim 1 with the addition of the steps of generating a plurality of signals of timed duration responsive to the sensing of the level of liquid in the containers when a filter bed becomes laden with solid particles; diverting liquid to be filtered through the other filter bed responsive to the first signal; delivering pressurized gas through the filter bed laden with solid particles responsive to a second signal; and backwashing the filter bed laden with solid particles responsive to a third signal.

Claim 5

The method called for in claim 5 with the addition of the steps of generating an additional signal prior to generating the second and fourth signals; and delivering pressurized gas through the first and second filters responsive to said additional signals.

Claim 6

The method called for in claim 5 with the addition of the steps of transferring the liquid from the first container to the second container responsive to the fourth signal.

Claim 7

A filtering device comprising a storage container for liquid to be filtered; a backwash storage tank; first and second filter containers; first and second filter media in said filter containers; an inlet line to deliver liquid from the storage container to each such filter container above the filter therein; an outlet line adapted to deliver liquid from each such filter container from below the filter therein to the backwash storage tank; a waste conduit communicating with each filter container above the filter therein to carry out backwash fluid; means to pump liquid from the storage container through the respective outlet lines; sensor means in each filter container adapted to sense the level of liquid in each container; valve means in each inlet line; valve means in each outlet line; valve means in each backwash waste conduit; valve actuating means operably connected to each said valve means; pump actuating means operably connected to said pump means, said actuating means being arranged to open and close each said valve means and to actuate said pump means; control means actuated by the sensor means and operably connected to the valve actuating means and pump actuating means adapted to selectively actuate the valve means and the pump means.

Claim 8

The combination called for in claim 8 with the addition of blower means communicating with each outlet line; blower actuating means operably connected to the blower means; blower control means actuated by the sensor means and operably connected to the blower actuating means to selectively actuate the blower means and cause air to be delivered through the outlet lines and the filters.

Claim 9

The combination called for in claim 8 wherein the filter containers are in a common housing; and a vertical wall positioned centrally of the housing forming first and second filter containers.

Claim 10

The combination called for in claim 10 with the addition of a floor in the housing spaced rom the bottom of the housing dividing the lower portion of the housing into first and second collection chambers on opposite sides of the vertical wall; wherein the filters are positioned above said floor; the outlet lines communicate with said compartments; and the inlet lines communicate with the respective containers above said filter.

Claim 11

The combination called for in claim 10 wherein the upper edge of the wall is spaced downwardly from the top of the housing.

Claim 12

The combination called for in claim 11 wherein the waste conduits communicate with the respective filter containerS above the elevation of the inlet lines.