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Much of the focus of our design work has been on the alum doser. Originally, we planned to use the alum doser to dose untreated water at an appropriate level using a mere "hole-in-the-bucket" situation with a float valve to maintain a constant water level and thus maintain constant head. Yet we discovered that this design required a bottom orifice with a diameter of less than 3 mm. These calculations can be seen in the original Alum Doser MathCAD file. The problem with small orifices (with diameters below 3 mm) is that clogging occurs very easily. Thus, we needed designs that incorporated large amounts of head loss in the system to allow for the use of a larger orifice size.
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