**** Ulrich Bretscher's Wastewater Page ****



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As alternatives to draining sewage from a neighborhood, frequently there are other choices, such as a canalization that makes a detour, a canalization deep underground or a pumping well. So, you have to choose between investment and operation costs. Many engineers hesitate to calculate pumping costs, because they believe it's laborious. The following considerations will lead to a surprisingly simple solution to the problem of calculating these costs easily, and with pretty good accuracy, by the way. The pumping performance is calculated by the equation:
From the above equation we can be conclude that at a given efficiency of a pump, the current demand is solely a question of the flow and height the water is pumped! On this basis a simplified computation of the current demand and the ensueing costs is possible:
In Switzerland the current costs for large consumers is SFr. 0.15/kWh. Dear reader, you certainly are familiar with the current costs in your country. In my country this will lead to the following conclusion:
Example: There there is a project where you have to pump an average of 7.5 l/s sewage 12 meters high, then you have to expect anual energy costs of 7.5 l/s • 12 m • Fr. 25./yr = ca. SFr. 2'250. per year 
