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To find the ideal alum dosage for a certain influent turbidity, there are several qualities that must be considered. First, the resulting floc size should be large enough so that by the time it reaches the sedimentation tank, it will weigh enough to sink and settle out. Second, the resulting NTU must be small indicating an efficient flocculation/sedimentation process and clean water, and third, the alum dosage should preferably be low to save cost. (This is something minor, but we should also consider how the particle size distribution will affect the formation of a floc blanket as well. Producing very large flocs may not facilitate floc blanket formation as they will settle out before the floc particles could ever become fluidized)

For the first experiment, the alum dose ranged from 20 to 60 mg/L varying with an increment of 5 mg/L and the influent turbidity was around 100 NTU. The data given from this experiment was processed through Mathcad for a simplified overview of the result in graphic form.

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