Disclosed is a system for treating waste water. The system may be applied to any application for the treatment of waste water which benefits from an equalized flow into the waste water treatment processes, such as industrial batch discharges, storm water settling and screening, and septic receiving at a waste water treatment plant. The system comprises a single primary settling tank for the processes of grit removal, flow equalization, fine screening and primary clarification. The system further comprises the use of a flow measurement device on the discharge side of the primary settling tank to provide a uniform flow to downstream processes. The system further comprises placement of a fine screen on a discharge mechanism which controls the effluent flow from the primary settling tank.