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The first trial on the sloped-column lime feeder used tap water. (Fragment sentence) To keep the upflow velocity to be the same as for the vertical column lime feeder (previous lime feeder), the flow rate for the new feeder was calculated to be 120mL/min. The amount of lime taken for the new feeder was 80 grams, which was in volumetric proportion with the old feeder. (What do you mean old feeder and new feeder? What changed? I thought the diameter was the same. Why will the upflow velocity or amount of lime you add change?)
INTRODUCTION
The experiment consisted of the injection of tap water with a flow rate of 120mL/min (Again, include upflow velocities, not flow rate) regulated with a peristaltic pump being operated by the process controller software. At the effluent end (top of the sloped column)a pH probe was connected to collect periodic (every 5 seconds) data of the effluent pH. (Where is your process control file? How did you regulate flow rate in process control? You should have a separate materials and methods section)
OBJECTIVES
• To check if the sloped column lime feeder model works.
• Determine if there are any preliminary technical difficulties within the model and/or process and make improvements for them for future experiments.
• Find the maximum time for which the pH at the effluent remains at 12.
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The apparatus worked well with the established upflow velocity. The movement of particles was clearly visible and in accordance with the hypothesized movements (similar to the particle movements in the tube settler spacing apparatus). (You never told us the hypothesized movements. What about it worked well, be specific if you are going to include observations)
At the top of the sloped column, the water looked clear of visible particles but according to the pH sensor measurements, it was saturated with base (i.e. pH 12), which was in accordance with the main objectives. A great amount of lime remained captured in the middle of the apparatus, although it was held in suspension. This signifies that the upflow velocity was high enough to give good suspension but the sloped column took care that the extra lime did not fall out with the effluent water but remained inside the column. This was a desirable behavior because the lime was still in the apparatus, giving donating hydroxides to solution the protons needed by water.
However, the pH remained stable at 12 just for 20 minutes. It was necessary to calibrate the pH probe again, to clean the apparatus and to review the calculations in order to determine the reason for the abnormal pH behavior. (Why only 20 minutes? Give more explanation behind observations you make)
Figure 1. pH vs time
CONCLUSIONS
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