An apparatus and method are proposed for controlling the number of active individual trays used in a stacked tray type vortex grit removal system as a function of flow conditions and performance requirements. In accordance with exemplary embodiments, a flow control arrangement for a stacked tray type vortex grit removal system is configured to include a bypass system which is able to selectively block one or more trays from receiving influent during low flow conditions. In one form, the bypass system may comprise one or more hinged blocking plates positioned at the entrance to selected trays, where the blocking plates may be individually activated to either allow flow to enter the associated tray, or block the movement of the flow. Other types of blocking plates (for example, sliding plates) can be used instead of hinged plates.