A wastewater treatment mechanism includes an interior chamber having a peripheral wall preferably provided with two diametrically opposite openings in each of which is received a flow port member having a flow equalization port therein. Depending upon wastewater levels and surges, the flow port members can be removed and replaced by other flow port members of an identical construction, except for different sizes of design flow equalization ports thereof. Therefore, should a wastewater treatment mechanism be installed initially in a wastewater treatment plant with accurately sized flow equalization ports to achieve desired flow characteristics and efficiency, should such flow characteristics change over time because of inefficient flow-through of wastewater, the originally installed flow port members can be readily removed and replaced with identical flow port members except for larger flow equalization ports thereof thereby returning the overall wastewater treatment mechanism to acceptable design flow equalization and efficiency.