EXPERIMENT 2
The new apparatus was equipped with a pH probe whose values could be logged into the computer via the Process Controller. In addition, Process Controller was utilized to automate the experiment. With those additions, the team measured the pH of the effluent, looking for the optimal flow rate that could maintain 12 pH units for 24 hours.
RESULTS
- With a flow rate of 40mL/min, the pH dropped from 12 to 11 after about 3.5 hours.
- After increasing the flow rate at 60mL/min and keeping the other parameters constant, no significant changes were noted.
The results of the experiment are on an attached excel file. Excel Spreadsheet
FIGURE - 2 Apparatus designed for experiment 2 
IDENTIFIED PROBLEMS:
- The arrangement of the pH probe was not stable so the pH data was not accurate.
- The simple column design was not adequate in giving any range in terms of flow rates that could fulfill the objectives of maintaining a good suspension and maintaining a stable pH for 24 hours on the effluent.
- The vertical column was not enough to store the required amount of lime to run the experiment for 24 hours.
These problems prompted for a modification in the design of the column leading to the next stage of experiments.
By the end of the experiment, changes were made in the design of the water outlet in order to ensure an adequate pH measure (following Professor Monroe's suggestions). It included putting the pH probe in a vertical tube and making a curved outlet for the effluent. With these changes, the apparatus could get a more stable pH measure. A figure explaining this description is shown below.
The team also worked on the calculation of the relationship between the ratio of flow rate at the lime feeder and at the plant with the alkalinity provided by the effluent lime. That information was useful to edit MathCAD calculations and to determine the changes in the Ph at the plant with respect to changes in this flow rate ratio (fraction of water flow rate entering the lime feeder from the entrance tank).