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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 diameter) 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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