Vortex-type grit chamber

A grit removal unit (10) including an influent channel (40) directing wastewater with grit into a round grit removal chamber (16) and an effluent channel (32) receives wastewater output from the chamber. An output guide member (70) is mounted to allow selective adjustment of output flow opening width "c" to the effluent channel. The output guide member has a horizontal bottom (74) extending from the chamber into the effluent channel (32) across the width of the output opening, and a guide wall (76) extending upwardly from the guide member bottom. The guide wall has a forward end spaced from the chamber annular vertical wall to define the output flow opening width therebetween. Adjusting the flow using the gates allows for maintaining a high enough flow rate into the chamber so that the grit does not build up in the influent channel. Optionally, divider wall extends upwardly between the sides of the influent channel (50), and gates (60, 62) at the upstream end of the divider wall are adjustable to selectively open channel portions on opposite sides of the divider wall to manage flow.