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Varying Alum

In the experiment, to investigate alum dosage at a given turbidity and length, we first planned to vary the alum dose over a large range, incrementing the dose in set intervals while holding the plant flow rate (shear), influent turbidity, and residence time constant.

Table 1 shows the alum ranges we tested for each flocculator length and influent turbidity:

TABLE 1: Alum dose ranges tested and the increment used (mg/L).

The alum dose was varied in process controller using the increment function shown in Figure 1:
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FIGURE 1: Process Controller setpoints used to vary the alum dose.