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Tube settlers use the concept of capture velocity (link: ). Particles enter the settlers at a specific velocity, which for the purposes of our early experiments will be kept constant. The capture velocity is important because particles traveling faster than this quantity fall to the bottom of the tube settler as they enter and cascade back down to the floc blanket from which they were taken. This allows for clean, less turbid water to pass through the tube and out to be chlorinated. As the turbidity of the effluent water decreases, chlorination becomes more and more effective because pathogens in the water have more exposure to the cleaning chemical. Ultimately, this results in safer drinking water.
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This summer, the plate settler team will first focus on the geometry of the tube settlers in order to gain insight into how parameters like the tubes' diameters and lengths affect the effluent turbidity, our main output and target of optimization. After the optimal geometry of the settlers has been determined under ideal conditions at two floc blanket levels—high and low—we levels--high and low--we need to test how robust this geometry actually is. To do so, we will create non-ideal circumstances by varying the influent turbidity and possibly the alum dosing in order to analyze how the system responds. Further, we hope to be able to characterize the system in terms of the fluid's residence time in the tube settlers in order to make correlations to the effluent turbidity.
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