ANC CONTROL

Materials and Methods

The ANC experimental setup consisted of the water source, a peristaltic pump, the limefeeder, and a pH probe. The water source was either tap water or distilled water, depending on the experiment. Distilled water has a much lower concentration of carbonates compared to tap water and is used to simulate water conditions in Honduras. It can be found in the hydraulics laboratory.

The peristaltic pump was run by Process Controller. The file can be found here in the Process Controller Method. The tube size was 18 and flow rate could be changed. In the first type of setup (as seen below in Fig 1), the limefeeder was just a vertical column. In the second setup (as seen in Fig 2), the limefeeder was a vertical column attached to a tube with a 22.5 degree angle with respect to the vertical axis. The pH probe measured the pH of the effluent and was calibrated with buffers of pH 4, 7, and 10. The file to set up the probe can be found here in the pH probe file.

There were two types of hydrated lime used in these experiments. The first type was high purity hydrated lime, containing 96% calcium hydroxide. The second had only 70% calcium hydroxide. Lime was measured on the scale and then introduced from the top of the limefeeder either in powder form or in a lime slurry (lime mixed with water) for the second type of setup. After the lime was in the column, Process Controller turned the peristaltic pump on, starting the experiment.

After the experiment was done, there would be an abundance of calcium carbonate settled on the bottom of the lime feeder. To clean the column, the top was uncapped, water was sloshed around, and then emptied. Acid may be needed to clean the column for calcium carbonate residue.