Patent ID: 8460560

Claim:
A method of making an input channel for the flow of waste water into a grit removal unit, wherein said input channel has a depth D, comprising the step of forming one side wall of the channel to vary the channel width over the depth of the channel whereby: the width at the bottom of the channel is W B , the width at the top of the channel is W T , and the width at channel depth “d” above the bottom of the channel is W d , wherein 0≦d≦D, W B <W T , and W d is greater than or equal to the channel widths at substantially every channel depth less than “d”; wherein first and second flow rates of waste water through the input channel are expected, said second flow rate being greater than said first flow rate; the one side wall is shaped in steps wherein the channel width is W 1 in the bottom for the channel for a depth d 1 , the channel width is W 2 for a depth d 2 above depth d 1 , W 1 =W B , and W 1 <W 2 ; a channel cross sectional opening of (W 1 ×d 1 ) provides a water flow velocity in a desired range for the first flow rate of water; and a channel cross sectional opening of ([W 1 ×d 1 ]+[W 2 ×d 2 ]) provides a water flow velocity in the desired range for the second flow rate of water.