ANC CONTROL

Experiment 3 - Trial 4: Old Lime Brand and Distilled Water

Introduction

The final trial was carried out was using distilled water and the old brand of lime. The apparatus was kept the same as that of the previous three trials with the exception that the tank in which the distilled water had been stored was cleaned up thoroughly.
The purpose of this trial was to confirm if the failure of the previous trial (trial-3) was because of the carbon dioxide (in the air) which the water had been exposed to or the presence of carbonate impurities in the container. Another objective was to verify if the lime feeder performance was grossly affected by the change in lime brands.
For this trial the pH remained stable at 12 for 11hrs, which was by far the maximum duration achieved and very close to our goal of 12 hours.

Procedure

The procedure adopted for this experiment was the same as all the previous trials. 100g of lime was made into a slurry and poured into the lime feeder from the top of the column. The flow rate was regulated at 40mL/min by the peristaltic pump while the pH was recorded using a pH probe. Water supplies were made available from the cleaned distilled water tank.

Results

The results of this trial can be seen in the figure below as per which the system lasted at a stable pH of 12 for about 11 hours.

Figure 1. pH vs Time (h)

Conclusions

After the successful run of this trial it can be concluded that carbonates present in the alkaline tap water were indeed the problem causing the lower efficiency of the lime feeder system and since this difficulty will not be faced in the Honduran source water (having very low pH)the lime feeders can be made to run successfully for 12 hours after making minor adjustments in the dosage of lime and water flow rate. Details regarding the next steps can be viewed on the Future Challengespage.