Construction History
Spring 2008
The design of the tank was completed during the Spring 2008 semester. The sedimentation tank was designed to be contained in a polyethylene tank of dimensions 24" x 24" x 36" (length × width × height) with a wall thickness of about 5/16". The design goal was to have enough area in the tank to create a floc blanket. With the available water level height, approximately the same height as the water level in the floc tank, we did not have enough room to include plate settlers. Initially we wanted to split the plant flow rate (110 L/min) in half, allowing us the possibility of installing two parallel sedimentation tanks for experimentation purposes, but we found that a flow rate of 55 L/min into the tank would have required a 6 inch pipe to transport water from the floc tank to the sedimentation tank to avoid breaking up flocs. Due to cost restraints (a six inch bulk head fitting would have cost about $300) we limited this pipe to 4 inches. This was done by lowering the flow rate of the sedimentation tank to 24.5 L/min. This constraint on the inlet pipe and flow rate required that we switch to a smaller tank than originally planned so that so our tank would have an upward velocity of 100m/day, the upward velocity of full scale plants in Honduras; keeping this parameter the same made the two designs comparable. This low flow and smaller tank set-up allowed for parallel testing of tanks containing different sedimentation processes.
Given Variables:
- Length (L) = 58.7 cm (23.125")
- Width (W) = 58.7 cm (23.125")
- Height (H) = 91.4 cm (36")
- Water Level (WL) = 84.5 cm (33.25")
- Flow Rate (Q) = 24 L/min
Spring 2008
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Parameters
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Value
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Inlet Pipe
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10.16cm (4")
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Launder
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Launder Diameter
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3.81cm (1.5")
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Launder Height
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5 cm below sed tank WL
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Number of Holes
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15
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Hole Diameter
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0.7541cm (19/64")
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Tank Drainage
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Tank Drain Diameter
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.
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Number of Holes
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15
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Hole Diameter
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0.3572cm (9/64")
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Hopper
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Hopper Removal Diameter
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1.27cm (0.5")
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Hopper Removal Line Length
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2m
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Plant Leveling Tank
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Leveling Tank Outlet Pipe Diameter
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7.62cm (3")
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Orfice Size
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2.223cm (7/8")
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Factor of Safety for Head Loss
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Fall 2008
Issues
When work began on the pilot plant in the Fall 2008, several leaks were discovered. The plant had to remain shut off until the leaks would be repaired. At first it has seemed that the leaks were in the pipes, so all of the joints in the pipes were caulked. After the caulk had dried, water continued to leak from the system. It was discovered that the leveling tank (a plastic bucket) was leaking.
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