Diffuser for an aeration system

A diffuser for an aeration system, comprising:

• a base which has a major wall with a periphery, and which defines a central line that is normal to said major wall, said major wall having an outer major surface and an inner major surface opposite to said outer major surface, and defining an inlet that is adapted to introduce thereinto an aerating gas from the aeration system to generate a back pressure and that extends along the central line through said outer major surface to form thereon a valve seat;
• a valve member configured to engage said valve seat so as to close said inlet;
• and
• a diaphragm having
• a central portion disposed to carry said valve member to place said diaphragm at a non-aerating position when said inlet is closed,
• a peripheral portion which surrounds said central portion, and which is secured to said periphery of said major wall to form upstream and downstream sides separated by said diaphragm such that, when the back pressure at the upstream side is higher than an ambient pressure at the downstream side, said valve member is forced to move away from said valve seat to place said diaphragm at an aerating position, and
• a surrounding segment interposed between said central portion and said peripheral portion, and including
• a base web layer having a first surface facing the downstream side and a second surface opposite to said first surface, and including a plurality of fibrous filaments arranged to form a textured structure with a plurality of pores, and
• a porous foam layer disposed on said second surface of said base web layer, and made of a material which is less flexible than that of said base web layer.