Page History

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

Floc Blanket Formation Time

We have outlined three major challenges and possible solutions below.

Initial Turbidity Peaks in Data

Problem

Analyzing the effluent turbidity vs. flow rate plots collected following ramp state experiments, a single sharp initial peak in effluent turbidity was observed for most trials regardless of the tube diameter used.

Proposed Solutions

Our team has proposed two reasons for this observed peak in turbidity. One possible reason is that the tube settlers in our apparatus do not begin "pulling up" water until the ramp state initiates. A second possible reason is Upon analyzing experimental results for the ramp state experiments that were run, it was determined that the floc blanket formation time was set in the process controller method is not long enough to allow for accurate results. (Why is this the case?) Specifically, not enough time was allotted for an ideal floc blanket (What do you mean by an ideal floc blanket?) to form ensure that a thick enough floc blanket is formed before the ramp state initiated. Since this finding, we have been initiates. Our team has proposed experimenting with increased floc blanket formation times, approximately 8 hours as opposed to the original 6 hours.

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Influent Water and Clay

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Mixer

Problem

During the semester, our influent water-clay mixer malfunctioned and needed to be replaced and . However, our team continued to proceed with experiments until a new mixer was ordered . Until the new mixer was received, our team proceeded with experimentsand received. Without the mixer, greater amounts of clay were required to keep the turbidity of the our system ran through our concentration clay stock solution at a much quicker rate in order to maintain an influent water-clay mixture at solution of 100 NTU . Therefore, our system ran through our clay stock much quicker than normally and the data from these experiments had to be discarded. (I would put in a sentence here about what you would do in the future with this in process control, such as increasing clay stock concentration so you didn't run out.)

Ramp State Time

without a mixer.

Proposed Solution

In the event that future teams experience a similar problem, we suggest assigning a team member to be responsible for monitoring the rate at which the system runs through the clay stock using process control software and/or adjusting the concentration of clay in the solution as necessary. Although the problem we experienced went away once we received a new mixer, assigning a team member to such a role will be helpful in the event that future teams decide to experiment with influent turbidities greater than 100 NTU.

Ramp State Time

Problem

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 diameter tubes because the tubes with smaller tubes diameters 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 turbidimeter becomes significant. (Can you show these calculations?) Therefore, when

Proposed Solution

When designing future experiments in process controller, it is important to consider these residence times when determining the ramp time. (Please come up with a criteria that you will be using in the theory to do this.)

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. (That's not the case. The solenoid valve was not large enough and experienced clogging over time as we drained. We switched over to a manual because of the size of the orifice that would not become clogged) 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 problemIn order to determine the ramp state time that should be used (it should be minimized to reduce potential error with the apparatus), a successful experiment needs to be completed. We are currently working to collect data for a successful run. The ratio of the experiment time to the residence time in the tube settler and the effluent turbidimeter will be applied to the residence times for all plate settler spacings to determine the best ramp time to be used.