In sewer systems sewage from different areas is often treated in a shared Waste Water Treatment Plant (WWTP). Currently the flows from different areas are usually determined by needs local to that area. During dry weather this may result in large variations in the flow into the WWTP. There are two reasons why this may be undesirable. Due to design peculiarities of some WWTP’s this may disrupt the treatment process and necessitate the use of additional energy and chemicals. In other cases areas are connected to the same pressurized transport pipe line, so energy costs may be higher when multiple stations use the line at the same time. Due to the daily variation in the sewage flow from domestic and light industrial sources, limits on temporary in system storage and due to limitations on the range of discharges the pumps can deliver, minimizing the flow variations can be a complex problem. Under the assumption of a periodic inflow sufficient conditions for the existence of a solution are given. The conditions imply the existence of a repeatable pattern of a length less than a day.
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