Apparatus and method for maximizing uniform effluent flow through a waste water treatment system

A screen decanter for screening solids from waste water in a waste water treatment system comprising:

• a) a three-dimensional structure partially immersible in said waste water including a bottom, sides, and an open top defining a rack;
• b) at least one screen element forming at least a part of said sides;
• and
• c) a drain apparatus disposed in an opening in said bottom for draining liquid from within said structure,
• wherein said three-dimensional structure is sealed such that all fluid entering said structure passes through said screen element,
• wherein said decanter in use sustains a hydraulic head within said structure bearing against a portion of said drain apparatus, and
• wherein said drain apparatus includes a plurality of openings arranged in a pattern along the length and partial circumference of said drain apparatus so formed as to counteract the range of said hydraulic head to provide essentially equal flow rates through said screen and drain standpipe at all depths of immersion of said screen decanter in said waste water.