*** This version of Confluence is for testing only and contains a copy of content from June 29th 2026. No changes will be preserved. ***
...
A theoretical model was 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, which is the product of shear and residence time, 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 causes 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.
We plotted the actual amount of mixing as a result of shear and the maximum allowable shear in the figure below, as calculated by the MathCad file versus flow rate. This graph shows an increase in the degree of mixing and shear with increasing flow rate.
The following graph shows how the loss coefficient (including both major and minor losses) varies with the flow rate. This is also based on calculations shown in the MathCAD file. In this graph, we see a decrease in total losses with increased flow rate.
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.
...