We first began experimenting with 30ppi polyurethane foam. Our experimental setup consisted of a column with 10 layers of stacked pieces of 2.54cm thick foam. We then ran 5, 20, and 50 NTU water with a residual alum concentration of 1.5 mg/L through the filter for 24 hours using an approach velocity of 4 mm/s. Since we also want to ensure that we would get a consistent and predictable performance from 30ppi foam, we ran repeat experiments with a 50 NTU influentand compared the results from the 3 trials.
Figure 1: 30ppi foam, 20 NTU influent
Figure 2: 30ppi foam, 5 NTU influent
Figure 3: 30ppi foam, 50 NTU influent trial comparison
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