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The gamma PDF graph shows the probability of reaching a certain floc size for each run of experiment with varying Alum dosage. The y-axis represents the probability and the x-axis represents the floc size. Looking at the gamma PDF graph (Figure 1) for this experiment, the Alum dosage of 20 mg/L was immediately eliminated from consideration for an alum dosage because its probability to reach a large floc size was comparably smaller than the others. In addition, the Alum dosage of 25 mg/L was eliminated because of its wide variation of floc sizes and relatively low probability to reach its largest size. Now narrowed down to an Alum dosage range of 30~55mg/L, the datalog for the experiment was used to find the lowest turbidity range during the settling state. As shown in table 1, after the Alum dosage of 40, there was not a considerable change in the lowest NTU range. So the Alum doses lower than 45 mg/L were eliminated, and the Dose range was again narrowed down to 45~55 mg/L.

FIGURE 1: The graph plots normalized turbidity vs. sedimentation velocity for each Alum dose ranging 20 mg/L~55 mg/L

TABLE 1: Table shows Shows the Lowest turbidity reached by specific Alum Dosage ranging 30 mg/L~55 mg/L during an influent turbidity of approximately 100 NTU.

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TABLE 2: Table shows Shows the Lowest turbidity reached by specific Alum Dosage ranging 30 mg/L~55 mg/L during an influent turbidity of approximately 500 NTU.