2010 Volume 64 Issue 5 Pages 305-312
To establish a method of determining the optimal operation conditions of the high-rate filtration system , the pressure loss of the system over time was simulated using the concentration of a added flocculant, filtration rate, and the height of a filter layer in a cylindrical column as parameters.
The optimal concentration of the flocculant to be added to the high-rate filtration system depends on the type and amount of suspended material. It was clarified that the amount of trapped aggregate flock and pressure loss in the system have a linear relationship when the appropriate flocculant concentration is selected.
For various seawater samples with different types and amounts of suspended material, experiments were carried out by changing flocculant concentration, filtration rate, and filter layer height. A method of simulating pressure loss over time was established by applying the filtration characteristics obtained from the experimental results to a basic equation of pressure loss in cake filtration. This method enabled the high-accuracy estimation of the pressure loss over time and the simulation of a decrease in filtration rate due to the trapped aggregate flock and that in filter layer height.
Using the established method, we determined flocculant concentration, filtration rate, and filter layer height such that the filtration system ensured a fouling index (FI), an index of filtered water quality, of 3.5 or lower during the filtration for 11 hours or longer as the desired performance, and carried out demonstration tests in two salt production plants with different amounts of suspended material. In these tests, the above performance was obained, and the validity of our simulation method was verified.
