Abstract: An elongate diffuser (10) comprises a diffuser body (30), and a membrane (20) attached so that introduction of gas at a working pressure into the diffuser displaces part of the membrane (20) from contact with the diffuser body (10) providing an elongate sealed compartment (50) between the membrane (20) and a surface (32) of the diffuser body (30). The gas can pass from the compartment (50) through the membrane (20) for aeration of fluid in which the diffuser (10) is immersed. The diffuser body surface (32) which bounds the compartment (50) is recessed away from the membrane (20) in use, to contribute to the lateral cross sectional area of the compartment (50) and facilitate distribution of gas along the diffuser by the compartment (50). An automatic purge valve for purging water from a gas feed pipe of a diffuser is also disclosed.

Abstract: A diffuser for aerating a fluid, and particularly for aeration in waste water treatment tanks, is formed in an elongate configuration by manufacturing a base plate from an extrusion cut to the desired length. A perforated elastomeric membrane is secured to the base plate by pressing sealing strips along the elongate edges of the membrane into corresponding grooves formed in the base plate extrusion. The ends of the membrane are sealed to the base plate by end strips or clamps. Air is introduced through apertures in the base plate causing the membrane to inflate away from the base plate forming an interior compartment for the passage of air along the diffuser. Apparatus for securing the diffuser to a horizontal header pipe is also described.