Multi-cell filter apparatus and turbidity monitor

In a filter apparatus of the type including a tank, a filter bed support in the tank for supporting a bed of filter material above the bottom of the tank, carriage means mounted for movement along the tank in a carriage path, a plurality of partitions extending transverse to the carriage path and spaced apart there along separating the bed into a plurality of filter cells each including an upper compartment above the filter bed support and a lower compartment below the filter bed support, influent means for supplying an influent to the tank above the bed, a port plate including a plurality of cell ports having centers uniformly spaced apart a distance d along a port locus paralleling said carriage path with each cell port communicating with the lower compartment of an associated one of the filter cells, a filtered water effluent launder extending along said port locus and communicating with said cell ports, carriage drive means for driving the carriage means along the carriage path in a backwash run, backwash means including a backwash head carried by the carriage means for movement along the port locus, scavenging means including a fluid intake head carried by the carriage means at a position trailing the backwash head during movement along the port locus and having intake opening means disposed adjacent said port plate and out of sliding engagement therewith, means for operating the backwash means during the backwash run to supply backwash fluid to the backwash head, means for operating the scavenging means to draw fluid into the fluid intake head, the backwash head having a face slidably engaging said port plate and backwash port means in said face constructed and arranged for communication with only one cell port at a time, to up-flow backwash only one filter cell at a time, the backwash head having means operative when the backwash port means is centered with respect to one cell port n, for blocking flow through a cell port spaced the distance d from the cell port n, the fluid intake head having intake opening means constructed and arranged for communication with at least two cell ports at the same time having centers respectively spaced a distance two times d and three times d from the center of said one cell port to downflow scavenge each filter cell a first time when the backwash head is in a portion to backwash one filter cell and at least a second time when the backwash head is in a position to backwash a succeeding filter cell, the improvement comprising monitoring means including a turbidity meter and a monitor intake conduit having an let end mounted for movement with the fluid intake head and arranged for communication with a cell port adjacent an end of the intake head that trails during the backwash run and is spaced at least three times d from the center of said one cell port to monitor turbidity of fluid from a cell port, communicating with a given filter cell which has been scavenged at least once during the backwash run, the backwash means including a backwash pump having an outlet connected to the backwash port means and an inlet connected to the fluid intake opening means to receive at least a portion of the backwash fluid through said intake opening means.