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During each run, the influent raw water combined with the correct alum dosage was allowed to run through the plant until two residence times had passed, insuring a steady-state effluent floc distribution. Then the pumps gradually ramped down, and a valve sealed off the settling column from the rest of the flocculator. The turbidity was monitored every second for half an hour as the flocs settled out, and the data recorded in an EXCEL spreadsheet. We then analyzed the data using Mathcad files developed by the previous (Spring 2009) team to develop settling velocity probability density function for the flocs. Details of the data analysis procedures can be found in Appendix B of Ian Tse's Thesis. After the analysis, the results could be used to find the flow rate (shear) with the best performance (lowest residual turbidity, largest mean floc size) for the set turbidity and alum dosage.
The following is the process controller file
Process Controller FileProcess Controller method file was used to run the experiment:
Varying Flow rate
Results and Discussion
The sedimentation rate velocity and the residual turbidity of flocculated suspension are important properties in a flocculator. The Spring 2009 team evaluated quantitatively the effect of shear velocity on these parameters. To do so, they used the flocculation residual turbidity meter (FRETA) developed by the AguaClara team and a data processor to analyze these parameters automatically.
Our goal for these first experiments was to familiarize ourselves with the apparatus and the data processor (MathCAD file) made by the previous team (Spring 2009) and to try to replicate one of their last experiments to make sure that the apparatus and the MathCAD file were working properly.
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