Horizontal Filtration

In an optimized plant design, we would like to be able to manipulate geometry to reduce the required plan area. The best design would take advantage of placing the filter material in a vertical direction, with water flowing through the filter horizontally. Therefore, it is necessary to determine the filtering capacity of the foam material while in a vertical position, with water flowing through the column horizontally. To do this, we used the same experimental set up, and simply rotated the filter column onto its side.
Figure 1: Horizontal Filtration Experimental Setup

Experiment 1

As shown in Figures 2 and 3, filter performance for this horizontal filtration experiment was not nearly as good as the filter performance achieved in previous vertical filtration experiments. This seems to indicate that while filter performance is not solely dependent on the film formation, it is nonetheless a vital component. While it may not be the film itself that enables a higher filtration capacity, it is indicative of higher filtration actually being achieved. Further tests with horizontal filtration are necessary to confirm this hypothesis. These are not the results that were expected from this trial, therefore, we must conduct further tests to explore the reasoning for these results, and to confirm that these were not in fact erroneous results.

Figure 2: Turbidity vs Time for Horizontal Filtration

Figure 3: pC* vs Time for Horizontal Filtration

*It was concluded that an alum clog occured during this experiment, thus making the above results erroneous.

Experiment 2

Repeat of above experiment, with alum clog removed

Experiment 3

In this experiment, we first primed the filter by running 5 NTU water through the filter placed in a vertical arrangement for 22 hours, after which the filter column was carefully rotated 90 degrees onto its side, with the effluent water being drawn from the vertically highest elevation at the end of the filter. The experiment was then run for another 22 hours. Figures 4 and 5 clearly indicate that after the column was rotated, there was a significant decrease in the trend of increased performance with time. After rotation of the column, it was visually obvious that a turbidity gradient developed over the depth of the filter, with very turbid water going through the filter at the bottom, and cleaner water going through the top. This gradient is likely contributing to the decrease in performance, as compared to vertical filtration tests after comprable time intervals, shown in Figure 6.

_Figure 4: Turbidity vs Time for Vertically Primed Horizontal Filtration
Note: Column Rotated to Horizontal Filtration at hours_

_Figure 5: pC* vs Time for Vertically Primed Horizontal Filtration
Note: Column Rotated to Horizontal Filtration at hours_

_Figure 6: pC* vs Time for Vertical Filtration, under same conditions as test of Horizontal Filtration:
3 inches of 90 ppi foam, 1.5 mg/L alum dose, 100m/day_