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The data processor was unable to fit the sedimentation velocity vs. turbidity curve into a gamma pdf graph,because the trend of our mean turbidities was not following a gamma distribution(Figure _A). We suspect that it could not fit because of a low influent turbidity of 5 NTU, and how our lowest mean effluent turbidity was less than ideal at 1.978 NTU.

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FIGURE 2B1: The graph plots the residual turbidity vs. sedimentation velocity for each Alum dose ranging 10 mg/L~50 mg/L

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Looking at the gamma pdf curve(Figure 2B) we see that trace 1 which corresponds to an alum dosage of 10 mg/L has a really high turbidity rate of 1.171 NTU which is unusually higher than all the others, and demonstrates a very narrow distribution. However, looking at the residual turbidity graph (Figure 2B), the resultant turbidity this dosage gave did not differ significantly from all the others. In fact trace 7 (corresponding to an alum dosage of 40 mg/L seems to give in the highest resultant turbidity at this range of sedimentation velocity we are looking at. Figure 2B also shows that for traces 2 and 4 (alum dosages of 15 and 25 mg/L, respectively) have wider distributions than the other alum dosages. Overall there seems to be discrepencies between the data correlating cohesively between the two graphs. From the values of mean turbidity at settling state, from 10 to 45 mg/L the mean turbidity seemed to start at a value of .608 NTU then rise to about .725 at 25mg/L, then rises to .829 and then back down to .755 at 35 mg/L (Table 1).

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FIGURE 3A2A: The graph plots normalized turbidity vs. sedimentation velocity for each Alum dose ranging 10 mg/L~50 mg/L; FIGURE 3B2B: The graph plots the residual turbidity vs. sedimentation velocity for each Alum dose ranging 10 mg/L~50 mg/L

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Looking at the gamma PDF graph (Figure 2A4A), the alum dosage of 20 mg/L gave a widely distributed probability of reaching different floc sizes with a comparably low probability to reach its highest sedimentation velocity. In addition, the residual turbidity graph (Figure 2B4B)showed a high turbidity for this alum dose in its lower velocity range. Thus the alum dose 20 mg/L seems to be inefficient for this particular influent turbidity and flow rate. The mean turbidity resulting from alum dose 55 mg/L seems to be out of normal range; its NTU value is significantly lower than the values given from the previous, lower alum dosages. Hence, the result from this dosage is doubtful. Overall, after the alum dose of 35 mg/L (except for 55 mg/L), the mean turbidity seemed to be settling down to a constant value around 1.4 NTU.

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FIGURE 2A4A: The graph plots normalized turbidity vs. sedimentation velocity for each Alum dose ranging 20 mg/L~55 mg/L; FIGURE 4B: The graph plots the residual turbidity vs. sedimentation velocity for each Alum dose ranging 20 mg/L~55 mg/L

On November 18, 2009, an experiment was ran with the set up of influent turbidity around 100 NTU, flocculator length of 8800 cm, flow rate of 5 mL/s, and an alum dosage ranging from 20 to 55 mg/L.

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FIGURE 5A: The graph plots normalized turbidity vs. sedimentation velocity for each Alum dose ranging 20 mg/L~55 mg/L; FIGURE 5B 2B: The graph plots the residual turbidity vs. sedimentation velocity for each Alum dose ranging 20 mg/L~55 mg/L

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