ANC CONTROL

TRIAL 3. DISTILLED WATER,

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CHANGED BRAND OF LIME

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OVERVIEW

Despite the performance of the apparatus was the expected, the pH couldn't stay twelve hours at 12 units during the second trial. From the analysis of results, the team decided to determine the influence that carbonates in tape water could have. In addition, the team had proposed to evaluate if the lime that was being used for the experiments was not enough pure. With the third trial, those possible causes of the pH performance will be analyzed and discussed.

INTRODUCTION

The design of experiment 3 continued the same, taking into account that the particles movement and effluent characteristics were according the design. However, tap water was replaced by distilled water, trying to figure out the performance with pure water. In this way it is possible to evaluate the influence of the carbonate system, and the influence of other characteristics of the tap water at AguaClara lab.

This trial was carried out using distilled water to determine how long the experiment would last without the influence of carbonates (present in tap water). In addition, another parameter that was inadvertently changed was the brand of lime, since the previous lime was almost over and the new lime was of a different brand (having 70% calcium hydroxide compared to the older lime containing 96% Calcium Hydroxide). Thus during this trial, not only was the effect of water quality but also the effect of lime quality was evaluated.
For this trial the pH remained stable at 12 for just 3.5hours.

INTRODUCTION

For this trial tap water was replaced by distilled water. In In addition, the lime was changed, looking for a better quality of the compound. This change will allow No changes were made to the constructional design of the apparatus.

NOTE: Although the change in the brand of lime was not pre-decided for this particular trial, it would allow us to evaluate if the performance is different with a new of the lime feeder changes on using a different lime brand. It This change is also important to study taking into account the fact that in Honduras, the operators would have to deal with the brands that they can find on the local marketa different brand(s) in the local Honduran markets.

OBJECTIVES

• Confirm if the carbonates or other quality characteristics of tap water, have any influence in on the lime feeder performance.
• Evaluate the apparatus performance with a different brand of lime.
• Determine some Look for improvements for future experiments.

RESULTS

It was observed a change into the apparatus performanceFor the above trial, the pH remained at 12 for about 3.5 hours but the performance of the apparatus changed drastically. The new lime is was much more soluble in water ; it diminishes the amount and diminished the number of big particles floating into the water flow, and avoids the accumulation of lime within the apparatus. The new lime did not accumulate in clusters at the bottom of the apparatus. However, that result made a new challenge for the team, because all the design was made assuming the particles movement as flocs movement. That means that the team calculated the This gave an almost perfect and uniform suspension of lime throughout the apparatus leaving no scope of observing the particle movements.
This presented a whole new challenge, because the entire design for the lime particles was based on the assumption that the suspended lime formed small particles and therefore could be treated as flocs (with different characteristics of course)so as to use the plate-settler theory to hypothesize their movements. This meant that the calculated upflow velocity and the capture velocity for particles movement, and with were not valid for the new kind of lime, no particles were observed. The team has to evaluate if the design and the calculations are still acceptable for water without visible suspended particles.

On the other hand, the pH remains in 12 units for 3 hours and a half. The time was less than with the second trial. With these results it seems that the quality of the tap water doesn't have a strong influence on the pH behavior.

CONCLUSIONS

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CONCLUSIONS

The information obtained from this trial was not enough to probe the influence of the two considered variables. Since 2 variables got changed simultaneously, different conclusions can be extracted-
One, that the distilled water made little impact on the working of the lime feeder. (Again this could be due to the fact that the distilled water, though stored in a closed plastic container was kept so for more than 3 weeks, which resulted in a leakage of Carbon dioxide through the plastic walls so that in effect the distilled water was no better than tap water after a long duration.) Second, the decrease in efficiency of the system was due to the fact that a different quality of lime was used which did not match the hypothesis on which the design was based.

FUTURE TASKS

It thus remains to be evaluated if the design and the calculations made so far are acceptable for different types of lime with different solubility characteristics in water. It also needs to be verified if the quality of water has a strong influence on the pH behavior or not.

To make these evaluationsThe information obtained with this trial was not enough to probe the influence of the two considered variables. To confirm the results, it is necessary to run one more time trials on the experiment with using the new lime but with tap water; that will be the objective of the next challengeand using the old brand of lime with distilled water.