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).
Flocculator Length (m) |
5 NTU |
25 NTU |
50 NTU |
100 NTU |
500 NTU |
---|---|---|---|---|---|
28 |
10-50 |
10-50 |
10-66 |
20-60 |
10-90 |
Interval |
5 |
5 |
7 |
5 |
10 |
56 |
10-50 |
10-50 |
10-66 |
20-60 |
10-90 |
Interval |
5 |
5 |
7 |
5 |
10 |
84 |
10-50 |
10-50 |
10-66 |
20-60 |
10-90 |
Interval |
5 |
5 |
7 |
5 |
10 |
The alum dose was varied in process controller using the increment function shown in Figure 1:
FIGURE 1: Process Controller setpoints used to vary the alum dose.