The Plate Settler Spacing Team focuses on finding optimal optimizing the spacing for the plate settlers (see pictures) in the sedimentation tank. Optimal tanks with the goal of removing the colloidal particles. Simultaneously, minimal spacing will lead to smaller lower the height of sedimentation tanks and hence to minimize , which reduces construction costs. The team is currently exploring a failure mechanism termed "floc roll-up". It is hypothesized plate settler performance is decreased with high velocity gradients in the plate settlers. For a given capture velocity (the slowest settling particle a plate settler can effectively capture based on geometric parameters and floc properties) these velocity gradients overcome the settling velocity of flocs, which results in flocs rolling up into the effluent instead of settling down to the bottom of the sedimentation tank. With smaller spacing between plates, the velocity becomes greater near the bottom plate and thus increases the likelihood of floc roll-up. The team predicts floc roll-up by using a dimensionless parameter called the "Pi-ratio". The Pi-ratio compares the terminal velocity of the slowest settling floc to the velocity experiences at the floc's outer diameter. When the Pi-ratio is less than one, floc roll-up should occur. And when this parameter is greater than one, the convention considerations of capture velocity dictate the particle size range that should be captured. To explore these velocity gradients, the team is designing and running experiments at a constant capture velocity. Future Work The team will perform experiments on the velocity gradient theory on different setups to test for the consistency of the theory. Previous Work
Current Work - Spring 2011
Future Work
Plate Settler Spacing Documents | 
