Overview of Methods
The critical velocity is when the velocity on the outer edge of the floc particle is equal to the floc settling velocity. Any velocity exceeding the critical velocity is when floc roll up begins.
In order to experimentally determine the critical velocity at which floc roll up begins, flow rates through the tube settler were increased incrementally utilizing a ramp state function in process control software.
By incrementally increasing the flow rate through the tube settler, we can compare the effluent turbidity performance over time. A critical velocity could be identified based upon effluent performance and compared to our theoretical model. The critical velocity is when the velocity on the outer edge of the floc particle is equal to the floc settling velocity. Any velocity exceeding the critical velocity is when floc roll up begins.
Using the same experimental apparatus as was used in Summer 2009 and Spring 2009, and the ramp state process controller function, we hope to understand if our theoretical model of floc roll up behavior describes system behavior. Ultimately, we hope to minimize the floc roll up in the plate settlers and further reduce the effluent turbidity. Also, we want to potentially understand how to create flocs that will experience less roll-up and have better performance.
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