Plate Settler Spacing
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| h1. Plate Settler Spacing
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h4. Introduction
This research is focused on a deeper understanding of the sedimentation process so that plants can remove flocs from clean water as efficiently as possible, allowing for successful chlorination of the effluent water. Currently, AguaClara plants use lamella in their clarification systems, which are a network of sloped, stacked plates that create narrow channels through which clarified water can flow.
To emulate lamellar sedimentation, we use tube settlers of various diameters, which simulate the effects of the lamellar plates.
A majority of flocs that enter these inclined channels settle out due to the force of gravity, significantly reducing effluent turbidity, which is a measure of how clear water is, to increase the effectiveness of chlorination. There is no control of influent water parameters going to the plant, so there is a keen interest in developing a settling system that is robust \-after floc blanket clarification that will produce less than 1 NTU water. The standard of 1 NTU exceeds the standards of 5 NTU for the WHO, but does not meet the standard of 0.2-0.3 NTU for the EPA. The EPA standard is very difficult to meet without a filtration step, which is not a part of the AguaClara design.
Ultimately, we hope to optimize the lamella design in order to achieve effluent water with a turbidity of 1 NTU or less \-\- even under water chemistry fluctuations and alum dose variation. At present the plate spacing, capture velocity, and velocity gradient formation are three of our key design limiting constraints.
h4. Velocity Gradient Research
Past research has brought to light the importance of velocity gradients within the tube settlers. Flocs at the bottom wall of the tube that experience an upward velocity pull greater than the force of gravity pulling them down will roll up the wall and exit with the effluent water. Flocs are fractal particles whose effective diameters are sensitive to shear stress, organic material in the water, and influent turbidity, so determining their response to the velocity gradient may require more than just a simple force balance. Furthermore, the maximum velocity gradient achieved at steady state will fluctuate with a plant's influent conditions and flow rate through their lamella.
[Subteam Semester Goals and Future Challenges|Plate Settler Spacing Goals]
[Weekly Subteam Progress|Plate Settler Spacing Meeting Minutes].
[Research Plan|Plate Settler Spacing Research Plan]
h2. Experimental Methods and Results
h3. Fall 2009
h5. [Experiments with Saturated Water Influent|PSS Fall 2009 Experiments with Saturated Water]
This section contains the experiment run in collaboration with the Floating Floc team to test the effect of saturated water in the influent on the plate settler performance
h5. [Experiments with the Velocity Gradient|PSS Experiments with the Velocity Gradient]
This section contains the model derived to estimate floc roll up in relation to particle size and velocity. Also, experiments were run to collect data to support the model
h5. [Experiments with Natural Organic Matter|PSS Fall 2009 Experiments with Natural Organic Matter]
This section contains experiments testing the effect of natural organic matter (humic acid) on the plate settler performance
h3. [Previous Semester Research|PSS Summer 2008 to Fall 2009]
h2. Additional Information
[Annotated Bibliography of Relevant Literature|PSS Bibliograhpy]
[Processor Controller Information|PSS Process Controller and Data Analysis]
[PSS Quiz for New Members |PSS Quiz]
[Fall 2008 Photo Gallery|Photo Gallery]
[PSS Apparatus Design] |