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Results and Discussion
The floc terminal sedimentation rate 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.
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.
Table 1: Parameters for the Fall 09 experiment
Flocculator length | Flow rate | Influent Turbidity | Alum dose |
|---|---|---|---|
2796 cm | 3-19 mL/s | 100 NTU | 45 mg/L |
Table 1: Parameters for the Fall 09 experiment
(The table heading goes above, not below)The experiment was conducted with the parameters shown in table 1. The parameters were based on one of Ian's experiment (data from 5/13/2009) conducted with the same inputs, except for the flow rates which vary from 4 to 19 mL/s and the turbidity which was set at 50 NTU(MathCAD file). Figure 3 shows the plot of the effluent turbidity during the settling state as a function of time and flow rate. The flow is, in fact, changing at each cycle and we can see that the turbidity is decreasing at each settling state.
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The previous team conclusion on this kind of experiment was that increased fluid shear not only decreased the average size and sedimentation velocity of flocs, but it resulted in higher residual turbidities as well. The results of Fall 2009 are consistent with the previous team results.
The goal of this experiment was not to analyze into depth the results in depth but to replicate on of the experiment from Spring 2009 and understand the utilization of how to use and analyze data with the data processor. The next set of experiments will analyze the evolution of the effluent turbidity with the alum dose and the length of the flocculator.