Brief History
Pilot Plant Construction and Baffle Design (Uniform Spacing)
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Plastic Tank that was the starting design constraint for the vertical flow hydraulic flocculator.
The construction of the tank was started during the Spring 2007 semester. The floc tank was designed to be contained in a polyethylene tank of dimensions 182.9 cm × 91.4 cm × 121.9 cm (length × width × height) with a wall thickness of about 0.8 cm.[#tank]The design goal was to divide the tank into 3 separate sections, basically condensing a long, narrow flocculation tank into a more compact space by snaking the flow back and forth. The initial design divided the total minimum mixing value (20,000) evenly among the three sections, with each section having an even velocity gradient (G) of 45 s-1.
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Plastic dividers that create three sections for a serpentine flow path through the tank.
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The serpentine flow path can be clearly seen in the top view of the flocculator.
In order to divide the tank into three sections, a divider system had to be built in the tank. Originally it was planned to purchase two plastic sheets to function as the dividers and weld them vertically into the tank. This option was soon rejected due to two major concerns: difficulties of welding inside the cramped spaces of the tank, and lack of strength in the welds. After much contemplation, the maintenance shop proposed a plan to build a structure that would provide support and flexibility. The sketch shows that the [#dividers]were welded onto a base slab and the completed module was placed into the tank. A port hole (hole through which water flows between sections) was cut in each divider prior to welding. The dimensions of the dividers are approximately 182.9 cm x 121.9 cm with a 0.6 cm thickness. The choice of material for the dividers as well as the base slab is high-density polyethylene and was specifically chosen for its non-reactive property in water treatment process, and most importantly its ability to be welded.
Below is a list of fixed parameters (or "givens") and the values of G to be used in the initial setup.
Givens:
- Tank dimensions: 182.9 cm × 91.4 cm × 121.9 cm
- Tank wall thickness: 0.8 cm
- Tank divided into 3 sections (serpentine flow path)
- Total minimum mixing value (Gθ) = 20,000
- Initially 1st, 2nd, and 3rd sections of tank to have velocity gradient (G) of 45 s-1
Maintenance Repairs
Constant communication with the Cornell Water Treatment Plant was needed to attempt to integrate our pilot plant into their facility. Some modifications would be necessary after transportation and set up in the tank at the plant. We fabricated a frame to hold the rapid mix in place on the side of the tank. The inlet pipe had to be redirected to fit into the rapid mix pipe. Directing the inlet pipe directly straight down into the top of the rapid mix pipe would give us the maximum flow from that pipe. The outlet pipe was reconstructed to prevent leakage. Water from the treatment plant is directed to us before treatment. After the water is treated in our system the effluent exits the tank and reenters the treatment plant at the same point through a nearby drain. Assembly and installation of the turbidimeters, sedimentation tubes, and alum feeder were completed in the same day.