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The purpose of this experiment was to test pulsing lime into the two apparatuses. Because both apparatuses fail after a shorter time than desired, it was hypothesized that the lime initially added to the apparatus (100 grams) eventually reached a point where it would no longer properly dissolve and raise the pH. Thus, more lime was needed as the experiment progressed. However, adding 100 grams each time would severely overwhelm the system. The following calculations were performed to determine the appropriate amount of lime that needed to be pulsed in every 6 hours:
Figure 1
From this graph one can see that the amount of lime that must be added for a flow rate of 30 mL/min is approximately 2.365 grams and for a flow rate of 40 mL/min, 3.154 grams of lime must be added.
The group determined that it would be best to pump in the stock solution at the highest possible flow rate, which is 380 mL/min. Thus, 380 milliliters of stock solution are pumped in every six hours. One challenge to this set up is that there is only one pump and one concentration for the stock solution. However, each apparatus requires a different mass of lime to be pulsed in, according to Figure 1 above. To solve this problem, the higher concentration of stock solution was made according to the calculations for A2, which resulted in a concentration of 8.3 grams of lime per liter.
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Using a 5 gallon bucket, the team calculated the volume of the bucket and the lime mass needed. It was calculated that 124.5 grams of lime, dissolved in 15 liters of water, can run for approximately 40 pulses, or 240 hours! The set up can be seen in Figure 2 below. 
Figure 2
Procedure
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A third peristaltic pump was added to the system to provide a pump from the stock solution of lime slurry to the tubing that flows to each apparatus. The tubing for the A1 pump and the A2 pump met the tubing leaving the third peristaltic pump with as little tubing in between as possible. This was done in order to minimize the amount of lime that might be able to settle out in the tubing. There was tubing attached to the stock concentration bucket (approximately 5 gallons) and then split to run through two separate pump heads on the third peristaltic pump (Figure 3).
Figure 3
For this experiment, the lime slurry in the bucket was not blended using the blender but rather using the mixer. The mixer stayed in the bucket throughout the course of the experiment and Process Controller was configured to turn the mixer on for two minutes before the pump was configured to run. Thus, the stock solution would mix for two minutes and then be pumped for one minute at 380 mL/min. This repeated every six hours.
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A2 performed similarly to A1, except that it reached a level pH of approximately 11.5 much more quickly. It started failing sooner than A1, at around 6:00 am, only 18 hours after the experiment began.
Figure 4 - Experiment 7