A multiple submergence depth diffused air system includes: a vessel having a non-flat bottom floor and fluid; a single blower or compressor that provides a single mass flow and a single pressure discharge of air; a plurality of air distribution lines that extend from the single blower or compressor into the fluid, in which outlets of the plurality of air distribution lines have grids with air diffuser units for distributing air; and orifice plates associated with each air distribution line. At least some of the air distribution lines extend to different depths within the fluid and at least one of the air distribution lines extend into the fluid formed in the non-flat bottom floor of the vessel. The orifice plates can also be sized and configured to produce a unique pressure head for each air distribution line at a designated mass flow of air to the respective air distribution line.