Troubleshooting

Over the course of the semester, our team experienced many technical challenges that impaired our ramp state experimental results.

Floc Blanket Formation Time

Upon analyzing experimental results for the ramp state experiments that were run, it was determined that the floc blanket formation time was not long enough to allow for accurate results. Specifically, not enough time was allotted for an ideal floc blanket to form before the ramp state initiated. Since this finding, we have been experimenting with increased floc blanket formation times, approximately 8 hours as opposed to the original 6 hours.

Problems with Influent Water and Clay Mixers

During the semester, our influent water-clay mixer malfunctioned and needed to be replaced and a new mixer was ordered. Until the new mixer was received, our team proceeded with experiments. Without the mixer, greater amounts of clay were required to keep the turbidity of the influent water-clay mixture at 100 NTU. Therefore, our system ran through our clay stock much quicker than normally and the data from these experiments had to be discarded.

Ramp State Time

In order to get a complete full run for an experiment, we decided to temporarily decrease the ramp time to two hours for our ramp state functions. This created a problem with the smaller tubes because the smaller tubes use lower flow rates in the ramp state function. Because these flow rates are so low, the residence time in both the tube settler and the tubidimeter becomes siginificant. Therefore, when designing future experiments in process controller, it is important to consider these residence times when determining the ramp time.

Miscellaneous Problems

Our team also experienced several minor problems that significantly affected our experiments. For example, originally our system did not have a drain valve and the floc blanket tube had to be manually drained. Mid-way through the semester a drain valve was installed. Unfortunately, several experiments were started with the valve not properly closed and thus the experiment could not proceed. We also experienced a number of power failures in our area in the lab which had to be fixed by someone with a better knowledge of this problem.