Three categories are defined :-
1) Fine Pore Diffusers
2) Nonporous Diffusers and
3) Other diffusion devices such as Jet Aerators, Aspirating Aerators and U-tube Aerators.
A diffused air system consists of diffusers submerged in the waste water, header pipes, air mains and the blowers and apertures through which the air passes.
The two basic methods of aerating wastewater are to introduce air or pure oxygen into the waste water with submerged diffusers or other aeration devices. To agitate the waste water mechanically so as to promote solution of air from the atmosphere.