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A theoretical model is used to model hydraulic flocculation in the flocculator. The model was first developed by Dr. Monroe Weber-Shirk and was subsequently updated as more empirical data became available. The model predicts the amount of mixing (G¿), which is the product of shear (G, s ^-1) and residence time (¿, s), required to achieve a target floc size. The calculation is based on the concentrations of kaolin clay and aluminum sulfate in the feed, and an efficiency factor that accounts for the fact that not every collision between two particles cause them to stick together. In addition, the model calculates the maximum shear that a floc can withstand as a function of how much mixing it has gone through, based on the empirically-determined shear strength of aluminum sulfate flocs.

Since the new demo plant will be constructed out of the same corrugated plastic as the existing demo plant, it will have 10 mm by 7 mm channels. It has been experimentally observed that the biggest flocs that the existing demo plant can create is about 0.7 mm in diameter. Hence, the target floc size was set to 1 mm. The feed clay concentration was set to 500 mg/L, with a corresponding turbidity of 180 NTU. The aluminum sulfate dose was set to 45 mg/L. Finally, the efficiency factor was experimentally determined to be 0.2.

The flocculator design program was initially written in Fall 2007 as part of a CEE 454 final project, to create a design with varying baffle spacing such that the flocculator is as compact as possible. Since corrugated plastic with uniform corrugations will be used, the program was altered to accept a preset, uniform baffle spacing instead of determining them.

The program starts designing the flocculator from its exit. The geometry of the flocculator is determined from the baffle spacing, channel width and the height of water in the last channel of the flocculator. The head loss in each channel is calculated by summing the frictional loss caused by the channel walls, and the expansion loss caused by the 180°