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On Oct 27, 2009, another experiment was conducted with the turbidity set around 500 NTU, flocculator length 2796 cm, flow rate of 5 mL/s, and alum dosage ranging from 10 to 90 mg/L. The data was run through Mathcad to get a simplified graphic overview of the result.

In both graphs (Figure 3A6A, Figure 3B6B), the alum dosage 10 mg/L gave a comparably different result from the rest; it produced a significantly higher settling turbidity and a large amount of smaller flocs. The overall mean turbidity for this dosage was almost twice the following dosages. After the alum dose 50 mg/L, the mean turbidity seemed to be settling down to a constant value around 2.5 NTU.

3A 6A 3B 6B
FIGURE 3A6A: The graph plots normalized turbidity vs. sedimentation velocity for each Alum dose ranging 10 mg/L~90 mg/L; FIGURE 3B6B: The graph plots the residual turbidity vs. sedimentation velocity for each Alum dose ranging 10 mg/L~90 mg/L

On Nov 19, 2009, another experiment was conducted with the turbidity set around 500 NTU, flocculator length 8388 cm, flow rate of 5 mL/s, and alum dosage ranging from 10 to 90 mg/L. The data was run through Mathcad to get a simplified graphic overview of the result.

As shown in figure 4.AFigure 7A, there is no big differences between the floc size distribution except for the lowest alum dose. As the previous experiment (500 NTU, length 2796 cm), the distribution is narrow wich means that we are producing flocs of almost the same size. Besides, the mean floc size seems to be the same than previously.

4A7A 4B
7B
FIGURE 4A7A: The graph plots normalized turbidity vs. sedimentation velocity for each Alum dose ranging 10 mg/L~90 mg/L; FIGURE 4B7B: The graph plots the residual turbidity vs. sedimentation velocity for each Alum dose ranging 10 mg/L~90 mg/L

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