Experiment 2: Alum Dose = 35 mg/L
An alum dose of 35 mg/L is considered to be an under dose. The below graphs show the effluent turbidity vs. time for the same capture velocities used for Experiment 1.
Figure 1. Effluent Turbidity vs. Time, floc blanket on low, alum dose 35 mg/L.
Figure 2. Effluent Turbidity vs. Time, floc blanket on high, alum dose 35 mg/L.
Conclusions
Based on the results of this experiment, and alum dose of 35 mg/L is not an under dose. The system performed above expectations, so we are going to test the system with an alum dose at 15 mg/L to see how the tube settler performs with an actual under dose.
Because lower capture velocities are supposed to perform better than higher ones, it is unexpected that the effluent turbidity for the capture velocity equal to .174 mm/s to be higher than the effluent turbidity for capture velocity of .231 mm/s. While this could have been an error in the experiment, it could also be a result of the floc particles rolling up the plate settler tube, which is investigated with the velocity gradient experiments.