Abstract: A filter leaf includes a continuous, elongated closure member, a first screen welded around its entire periphery to one side of the member, and a second screen welded around its entire periphery to the other side of the member to define a filtrate collection space between the two screens and the member. Means are provided for removing filtrate from the collection space. The filter leaf is made by clamping the closure member and one of the screens between two plates so the screen covers one side of the member and so the outer portions of the member and screen project outwardly from one of the plates. The outwardly projecting portions of the screen and member are irradiated with a laser beam to melt the screen and member to cause them to fuse together. The periphery of the outwardly projecting portions of the member and screen are moved relative to the laser beam while the member and screen are clamped together to form a continuous weld of the screen to the member around the entire periphery of the screen.

Abstract: A filter leaf includes a continuous, elongated closure member, a first screen welded around its entire periphery to one side of the member, and a second screen welded around its entire periphery to the other side of the member to define a filtrate collection space between the two screens and the member. Means are provided for removing filtrate from the collection space. The filter leaf is made by clamping the closure member and one of the screens between two plates so the screen covers one side of the member and so the outer portions of the member and screen project outwardly from one of the plates. The outwardly projecting portions of the screen and member are irradiated with a laser beam to melt the screen and member to cause them to fuse together. The periphery of the outwardly projecting portions of the member and screen are moved relative to the laser beam while the member and screen are clamped together to form a continuous weld of the screen to the member around the entire periphery of the screen.

Abstract: Filtering apparatus includes a shell with at least one filter leaf mounted in the shell to be rotatable about an axis. Means are provided for forcing a solid-containing liquid into the shell and into the leaf to form a cake of solids on the leaf. Means are also provided for removing filtered liquid from the leaf and the shell. A nozzle in the shell is disposed adjacent the leaf to direct a jet of sluicing liquid against the leaf as the leaf rotates. A sluicing liquid is supplied to the nozzle to wash solids from the leaf, and means are provided for moving the nozzle toward and away from the axis of leaf rotation in a plane substantially parallel to the leaf to remove solids from the leaf.

Abstract: Mixing apparatus includes a tank having an upright draft tube extending from above an operating level of liquid contained in the tank to a level near the bottom of the tank, the draft tube being in fluid communication with the tank at a level near the bottom of the tank below the operating level of the liquid. A nozzle is disposed within the draft tube for directing a stream of liquid downwardly against an impingement surface transverse to the draft tube at the level of fluid communication to entrain gas drawn down the draft tube and create a pattern of bubbles flowing radially outwardly from the draft tube. The impingement surface is close to, or is a portion of, the tank bottom so that the radially flowing bubbles sweep across at least a portion of the bottom of the tank.

Abstract: An upflow liquid treatment method is provided with a vibrator which is used to facilitate the settling of granular solids down through a grate used to hold the solids in a static condition during the treatment cycle when liquid to be treated is passed upwardly through the bed.

Abstract: Mixing apparatus includes a tank having an upright draft tube extending down below an operating level of liquid contained in the tank. An upright rotary shaft extending through the draft tube rotates an impeller below the draft tube for pulling gas and water into a submerged mixing zone. A propeller at the bottom of the shaft rotates in the bottom of a tubular upright still-well below the draft tube for pulling liquid upwardly from the bottom of the tank toward the impeller. A perforated, conical shaped shroud extends downwardly and outwardly from the bottom of the draft tube around the top of the impeller blades. Gas bubbles generated by the rotating impeller flow upwardly through the holes in the shroud. A plurality of spaced apart and radially extending vanes on top of the shroud constantly direct the flow pattern of the bubbles in a radial direction away from the mixing unit toward the edges of the tank.