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The table below shows actual measures of pH and alkalinity in AguaClara treatment plants in Honduras. To have high accuracy in the lime feeder design, the team will simulate the conditions of raw water in the laboratory will be simulated. The results in the table demonstrate a decrease of pH during the treatment process which is strongly visible on Cuatro Comunidades and Tamara plants.
Source: Honduras water reports, 2009
PROPERTIES OF LIME
The pH of calcium Hydroxide or lime decreases with an increase in pH. (see figure 1 below)
PROCEDURES AND RESULTS
One of the first tasks was to calculate the dosage of lime required by the lime feeder and the relationship between the changes in pH and ANC with changing flow rates in the lime feeder. The
analysis of lime feeder requirements was made with the help of MathCAD software.
At this stage, the team also continued to search for other information including the cost of distilled water, lime properties (solubility with temperature), and Honduras' water regulation.
The next tasks were a series of experiments carried on the column-based model of a lime feeder.
Experiment 1
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- Run several trials with the new design to determine the amount of lime required to maintain a pH of 12 for 24 hours. In addition the performance of the new design will be evaluated and revised, if necessary.
- Simulate Honduran water conditions. Once the lime feeder design is working successfully with distilled water, a new experiment will be required to analyze the performance with a lower pH concentration.
- Recalculate design dimensions while taking into account the natural variation of flow rate at the inlet tank in the water treatment plant.
!pH changes with Temperature - Lime.JPG!