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The vertical column addressed the issue of feeding the lime but in order to address the other hypotheses, we decided to build two apparatuses: one with all 1" tubes, one with 1" vertical columns and 2" diagonal tubing. By doubling the diameter of the tubing, we divided the flow rate through the diagonal portion by four. This allowed for a lower capture velocity, which attempts to address the issue of lime being lost out the effluent. See Figures 2 and 3.
Figure 2
Figure 3
In designing the new apparatuses, we made the vertical column taller than the diagonal column to ensure that water would flow out the diagonal column. We determined that the head loss through the fixtures at the end of the diagonal column would be negligible. However, when we began running experiments we discovered a problem. At the end of our effluent tube, we had a candy-cane shaped piece that the water flowed through - this was in order to have the water pass over the pH probe properly (see Figure 4). However, because this resulted in a dip of the height of the water, and the water filled up the tube, the atmospheric pressure at the top of the water in the tube forced the water in the vertical column to drop to its same height (see Figure 5).
Figure 4
Figure 5
We attempted to correct this problem by sealing the top of the vertical column with a cap. This would result in a vacuum in the area about the water level and would allow the water in the column to remain at a constant height (see Figure 6). However, we were not able to fully seal the cap and having an open vertical column to pour lime directly into was part of the design's attractiveness.
Figure 6
We decided to alter the design instead by opening the very top of the diagonal column to atmospheric pressure. Doing so allowed for open channel flow in the tube and allowed the height of the water in the vertical column to remain constant, matching the height of the water level in the diagonal column. (See Figure 7)
Figure 7
Future design improvements
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