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This is a significant overdose. The graph below shows the effluent turbidity plotted against time for capture velocities of 0.058, 0.116, 0.174, and 0.231 mm/sec, for the low floc blanket level only.
Figure 1: Effluent Turbidity vs. Time for Floc Blanket on low, alum dose = 105 mg/L
Conclusions
This extremely high dose experiment was tested to show what a failure looks like (a turbidity greater than 1 NTU). meant to demonstrate poor performance with an alum overdose. While the effluent turbidity averages less than 1 NTU, it is inconsistent and frequently spikes above 1 NTU for all capture velocities, meaning this is a demonstration of failure.
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