Replication of Spring 2009 experiment : Variation of flow rate

Procedure

Our experiments were all performed on the same Flocculator Residual Turbidity Analyzer (FReTA) setup that was developed previously (Spring 2009). FReTA consisted of five parts: an alum stock bucket at a stock concentration of 2.5 g/L, a kaolin clay stock bucket at a stock concentration of 10g/L, a raw water reservoir, a coiled tube (0.953 cm) serving as the flocculator, and the residual turbidty analyzer with a settling column. The raw water turbidity was controlled using a feedback loop mechanism; clay from the stock bucket was metered in automatically if the turbidity became too low. Peristaltic pumps were used to provide the flow rate and meter in the alum solution. All flow rates and chemical dosages were calculated, monitored and controlled using the Process Controller software developed by Weber-Shirk (2008). For detailed information on FReTA setup and the Process Controller figuration, please see Ian Tse's MS Thesis. All general information on the setup can be found in Chapter 1 Sec. 1.3-1.4 of the thesis. Characteristics of the tap water used can also be found there. Details of the Process Controller states and setpoints used can be found in Appendix A.

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The following Process Controller method file was used to run the experiment:
Varying Flow rate

Results and Discussion

The floc terminal sedimentation velocity and the residual turbidity of flocculated suspension are important properties in a flocculator. (How? Why?) 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.

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