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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 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.
Table 1: Water Quality in Honduras
Source: Honduras water reports, 2009
+ (Use a wiki table, not a poor quality image. Include a link to the data source. These reports are all posted on the AguaClaraES wiki.) +
(What conditions are you going to design the lime feeder for (i.e. worse conditions)?)
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The pH of a saturated calcium hydroxide solution (aka lime) decreases with an increase in pH. + (Previous sentence doesn't make sense.) + (see figure 1 below) The temperature at the Honduran plants is generally in the range of 19-21 degrees C but during summers it can go up to about increase to 27 degrees C. This temperature change can change the pH of lime and thereby affect the working of the lime feeder and needs to be taken into consideration while designing the lime feeder. (Explain how this is expected behavior of solute in water with respect to temperature. Why is pH of the saturated solution decreasing with increasing temperature?)
Table 2: Changes in pH of lime with respect to Temperature changes
+ (give descriptive names to the images files) +
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.
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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.
+ (Distilled water is how we simulate worst case Honduran water. I don't think there is ever a case of negative alkaltinity, so there is no need to create a water that has less ANC than distilled water) + - Recalculate design dimensions while taking into account the natural variation of flow rate at the inlet tank in the water treatment plant.
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