Construction History
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