ANC CONTROL

FUTURE CHALLENGES

Nearing the end of the semester, the team has learned a lot about lime feeder performance and seen some success but is still a long way from developing a reliable design that's ready for actual implementation. The mechanisms which lead to the failure of the feeder to produce saturated effluent over long periods of time are still poorly understood. We encourage future teams to continue to work on isolating important parameters and creatively developing the reactor design until they have a feeder which consistently performs as expected. Some ideas for further investigation are:

1. Work with smaller, simpler experimental set-ups so that experiments can be run more easily and the important mechanisms can be isolated. Working with the large feeders, while important, can be tedious and their behavior can be too complex to draw strong conclusions from. Investigating the behavior of lime in suspension may be more fruitful in smaller-scale, more controlled tests.

One potential set-up for a smaller scale experiment would be to put several shorter vertical columns in series, connected by flexible tubing, and end with one final diagonal tube settler column.  This is an experiment that could easily fit on the bench top and would be easier to control and run.  Figure 1 shows a possible set up for this experiment:
                                                                                                                                                         Figure 1
                                        Potential experimental set up in which the vertical column is broken up into multiple, shorter columns followed by one final diagonal tube settler.
 
2. Continue to run controlled experiments with both distilled water and tap water in order to characterize the effect that carbonate ions have on the reactor's performance. Our work from this semester did not yield results from which we can confidently draw conclusions about the importance of this effect.

3. Try the Honduran lime to see if there's any significant difference.

4. Explore methods for getting more uniform particle size when electric blenders are not available.

5. Instead of trying to read the pH of flowing effluent water, try placing the pH probes in a small beaker through which the effluent flows. Set up hydraulic conditions that cause intermittent flow into the beaker.  This will eliminate voltage fluctuations and may result in more accurate pH readings.

6. Explore entirely alternative methods of feeding lime or otherwise adding alkalinity to the plant flow. A possible new design is considered by the team.

7. Consider temperature as a variable in future experiments, keeping in mind that CaCO3 is less soluble when hot.

8. Possibly experiment using a different base, such as Sodium Bicarbonate.