...
The above graph displays the mass of lime needed to saturate the system given a specific flow rate.
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. In determining flow rates, the team learned from experience that when the larger apparatus had too slow of a flow rate the particle settled in the tube settler and this created preferential flow paths through the top half of the settler. Thus, a slightly higher flow rate was chosen for the 5 cm tube settler apparatus.
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. The group determined that pumping in the lime solution at the highest rate possible for only one minute would not create too much of a disturbance in the overall flow rate of the apparatuses. 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 the 5 cm tube settler, which resulted in a concentration of 8.3 grams of lime per liter.
The team then installed two pump heads on the third peristaltic pump and used two different tubing sizes to regulate the flow to each apparatus. Referencing the information about peristaltic pumps it was determined that the 2.5 cm tube settler should have tubing size 17 while the 5 cm tube settler has tubing size 18. This allowed for each apparatus to receive the proper lime mass with each pulse while still running off the same pump.
...