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The mass of lime added was 17.89 gm. With this amount of lime, the flow rate upflow velocity chosen was 40mL10.71cm/min, because the lime remained suspended and it was assumed the apparatus would run for a longer time according to the results observed in Experiment 1. The initial pH reading was 12 and stayed that way for 2 hours. It gradually decreased to 8.85 by the 24th hour.
One of the possible explanations about the decreasing of pH at a constant rate during the trial, was that the upflow velocity was not enough to mix the lime and keep the dissolution. As a probe, the flow rate it was increase increased to 60 mL16 cm/min. When the change was made, the probe registered an increase to a pH of 9.4.
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- 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 (Volume= 0.211 L) was not enough to store the required amount of lime to run the experiment for 24 hours.
RESULTS
- With a flow rate of 40mLan upflow velocity of 10.71cm/min, the pH dropped from 12 to 11 after about 3.5 hours.
- After increasing the flow rate to 60mLupflow velocity of 16cm/min (in order to enhance the lime mixing) and keeping the all other parameters constant, no significant changes were noted.
Figure 2 shows the pH measures during the experiment.The results of the experiment are on an attached excel file. Excel Spreadsheet
Figure 2. Time vs pH
