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Using the Spring 2009 team's process controller methods, we subjected an ideal geometry to non-ideal conditions. What do you mean by non-ideal conditions? Specifically we altered the alum dose to see how different alum doses affected the effluent turbidity. Though the Spring 2009 team had success with a 9.5 mm diameter tube, due to a change in influent water chemistry over the summer what we think was ineffective air bubble traps in the flocculator, or the addition of a flow accumulator to the method, we experienced failure with this geometry. We achieved an acceptable effluent turbidity (less than 1 NTU) with a 15.1 mm diameter tube that had a length of 30.5 mm. With the ideal good experimental resultsput a link to these experimental results, we then subjected this tube settler to varying alum dosage to investigate the affect of dosing on tube settler performance dependency of the performance of the tube settler on this parameter. At each alum dosage, the tube settler was tested at a variety of capture velocities and at two different floc blanket levels describe what you mean by this: the lower level is when the height of the floc blanket falls below the bottom of the tube settler, the high floc blanket level is when the floc blanket height is above that of the bottom of the tube settler.
Experiment 1: Alum Dose = 45 mg/L
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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.
Overall, this system performed well and most of the effluent turbidities were below 1 NTU. The ideal alum dose of 45 mg/L and the slight underdose and overdose of 35 mg/L and 65 mg/L, respectively, performed best. (Do not say 45 mg/L was ideal or performed best when clearly it did not with the data. Instead explain why it did not perform as well.) Because the slight underdose and overdose did not fail (what do you mean by failure? Elaborate if you are going to use this word), as expected, it was necessary to test more extreme doses. We tested 15 mg/L and 105 mg/L to observe more severe conditions (saying severe conditions is vague. What do you mean? What were you specifically wanting to observe in effluent performance?). The extreme overdose 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 extreme underdose dose, however, did not experience failure. (Please define failure early. Is it effluent turbidity above 1 NTU?)
Originally, an alum dose of 45 mg/L was thought to be an ideal dose. (Again, if you haven't already defined this, define what you mean by ideal dose. Is it the dose that gives the best performance?) However, this alum dose did not perform as well as was expected. In comparison to the other average effluent turbidities, 45 mg/L should either perform slightly better than an alum dose of 35 mg/L or somewhere between 35 mg/L and 65 mg/L. As shown in the above graphs, 45 mg/L performs worse than all of the other alum doses, including what was supposed to be extreme under and over doses (15 mg/L and 105 mg/L). This should not have happened, and experiments at this alum dose should be re-run. (Give reasons why it failed and why a re-run would be appropriate.)
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