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Figure 1: Capture Velocity vs. Average Effluent Turbidity shown for each alum dose at low floc blanket level.
Figure 2: Capture Velocity vs. Average Effluent Turbidity shown for each alum dosage at high floc blanket level.
Conclusions
Overall, this system performed well and most of the effluent turbidities were below 1 NTU. The thesis on evaluation on parameters affecting steady-state performance of a floc blanket found that the ideal dosage was 45 mg/L for 100 NTU influent water. The alum doses of 35 mg/L and 65 mg/L performed best. Because the slight underdose and overdose peformed well (average effluent turbidities were under 1 NTU), what was thought to be extreme under and over doses were also tested. We tested 15 mg/L and 105 mg/L to observe how the floc blanket formed under severe non-ideal conditions. The dose of 105 mg/L, despite averaging at less than 1 NTU, resulted in failure since the average effluent turbidity frequently spiked above 1 NTU. The 15 mg/L dose, however, had average effluent turbidity of less than 1 NTU, meaning that cannot be considered a failure.
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