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Spring 2012 Mid-Semester Contributions
This semester, I am continuing research as As part of the Sedimentation Tank Hydraulics Team. I will be conducting experiments and collecting quantitative data to evaluate the design requirements for , I developed a simple mass balance model to describe the flow of flocs in the floc blanket and floc hopper. I explored two different methods of wasting sludge from the floc hopper, continuous wasting and pulsed wasting, and concluded that the continuous wasting of sludge from the hopper is the most ideal, because it minimizes operator maintenance and clean water waste.
My team also conducted a variety of experiments to further our understanding about floc blanket formation and maintenance. The goals for the semester are::
- Marcala Simulation experiment: My team simulated the retrofitted Marcala sed tank with our lab apparatus with a 100 NTU influent and confirmed that the new geometry could resuspend flocs efficiently and form a stable floc blanket.
- Low influent turbidity experiment: We were unable to form a floc blanket over a period of 2 days when the influent turbidity was set to 5 NTU.
- Seeding experiment: We found that directly pumping sludge into the tank was not a very effective way to form a stable floc blanket because the sludge particles were too small and had low settling velocities. Nevertheless, this experiment showed promise that floc recycle would be successful at forming a floc blanket quickly in the tank, even when influent turbidity is low.
- Floc hopper experiments: Our preliminary floc hopper experiments were not conclusive, but they indicated that important factors that need to test include the effect of alum dose on the stickiness of sludge and the ease of draining sludge, and the effect of floc hopper geometry on the rate of sludge consolidation
- Test a hypothesis that describes the conditions required for floc blanket formation. The hypothesis is that the hydrodynamic pressure of the jet must exceed the hydrostatic pressure of the debris flow in order for flocs to be resuspended.
- Determine the maximum upflow velocity in the sedimentation tank that will reliably give a performance of 2-3 NTU.
- Evaluate the effect of high jet velocities on floc breakup and effluent performance.
- Develop an understanding of how floc consolidation works, and determine design guidelines for the floc hopper.
Summer 2011 Contributions
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