Patent ID: 7971732

Claim:
A grit removal unit for a waste water system, comprising: a round grit removal chamber defined by a substantially horizontal bottom surface and a substantially annular vertical wall extending up from said bottom surface, with an input for waste water having grit and trash therein and an output; a grit storage chamber beneath the bottom surface of the grit removal chamber; an opening through said bottom surface between said grit storage chamber and the grit removal chamber; a vertical drive shaft extending through said grit removal chamber and said opening into said grit storage chamber, said drive shaft being rotatable to facilitate waste water flow in said grit removal chamber whereby grit in said waste water is directed toward said opening; and a grit size restrictor including a first set of bars extending substantially horizontally across said opening, substantially fixed against movement relative to said chamber bottom surface, extending substantially from adjacent said drive shaft to the outer boundary of the opening, and defining grit openings between the bars of said first set to allow passage of grit from said grit removal chamber through said grit openings into said grit storage chamber, a shear secured to said drive shaft for rotation therewith, said rotation including rotation relative to said first set of bars, said shear including a plate having a top and bottom and extending radially from said drive shaft above said opening, said plate extending radially outwardly from said drive shaft at least about as far as the outer boundary of the removal chamber bottom surface opening, and a second set of bars secured to the bottom of said shear plate and extending downwardly from said shear plate, said second set of bars being positioned adjacent and close to said first set of bars.