Modelling and control of sewer flow for reduced cost operation of a sewage pumping station

The development of a control strategy for the scheduling of variable speed pumps at a sewage pumping station is described. In a digital simulation of the system, the total pumping cost was minimized while satisfying the operational hydraulic constraints. The storage capacity in the upstream trunk sewer was utilized to achieve smoother operation of pumps at lower costs. A simple discrete-time model with delay was derived to relate the outflow from an upstream pumping station and the inflow to downstream pumping station. Another model was derived to link the flow depths to pumping rates at a proposed downstream pumping station. These models allowed the prediction of flow to the pumping station and given an estimate of the depth in the sewer at the pumping station; this depth prediction was used to determine whether the system constraints on the flow velocity and Froude number would be met