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The High G Flocculation team was created in Fall 2017 to find the optimal G value for the flocculator. By varying inflow velocity, we can vary shear force and experiment with different sizes of flocculated particles. The current hypothesis is that a high shear will decrease particle size, and better collide to form larger flocs. On the other end, excessive shear may produce particles that are too small to settle.
Goals
this semester designed an experimental set-up to test the effects of velocity gradient (G) in a flocculator and to determine the optimal G value based on flocculator performance in terms of effluent turbidity. The G value was varied in different trials by varying flocculator flow rate while controlling for coagulant dosage, influent turbidity, flocculation tube length, and upflow velocity through the sedimentation tank. The product of G and residence time was kept constant at around 20000. The constant sedimentation tank upflow velocity was achieved using a waste stream between the flocculator outlet and sedimentation tank. It was found that for a standard coagulant dose, lower G values were associated with lower effluent turbidity, with 100 Hz being the lowest value tested. The same general relationship was observed for a higher coagulant dose, except that the lowest G value resulted in higher effluent turbidity due to floc blanket collapse. Data from this study will be used in the future to inform the geometry of the flocculator, i.e. the optimal distances between baffles, in a full-scale water treatment plant.
Goals
The team goal this semester was to design and a setup Our goal this semester is to design and fabricate a setup that will allow us to test the relationship between G value and turbidity. The tests conducted were used to inform the current understanding f the optimal G value for drinking water treatment. This information will ultimately be used to determine the geometry of full-scale water treatment plants. We also hope to test for optimal coagulent dosage.
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