An apparatus and a method for adjusting a void volume of a basin of a treatment apparatus are provided. A treatment apparatus comprising a basin and an expandable member are provided. The expandable member may be disposed in the basin. The expandable member may be configured to expand from a first state to a second state to adjust the void volume of the basin. A void volume of the basin when the expandable member is in the second state is less than the void volume of the basin when the expandable member is in the first state.
