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Abstract
The Sedimentation Tank Hydraulics Team performs laboratory research to determine the geometry of the sedimentation tank and the design of the inlet manifold so that a floc blanket forms efficiently. This lowers the turbidity of effluent and is also an indication of uniform flow and the elimination of dead zones. Current modifications to be tested are 1) the insertion of 60˚ incline planes along the perimeter of the tank, 2)manifold diffusers that extend 5 in from the tank bottom that direct downward-flowing jets of flocculated water. It is hypothesized that the diffusers will eliminate non-uniform form with respect to the length of the tank and resuspend flocs that have settled out and were directed to the jets via the incline planes. In order to test these modifications, a tube flocculator and sedimentation tank have been designed so that the upflow velocity in the tank equals the settling velocity, which is dependent on floc size and therefore controlled by parameters of the tube flocculator, as confirmed by previous experiments.
Introduction and Objectives
The current design of sedimentation tanks in Agua Clara plants consists of plate settlers placed above the inlet manifold that catch flocs formed in the flocculator while allowing water to flow past the settlers into exit launders. The flocs then settle out at the bottom of the sedimentation tank and are removed regularly by a sludge drain. Because of non-uniform flow, 1) flocs accumulate unevenly in the tank which causes difficulty in removal, 2) dead zones are created in the tank that lower the efficiency of the system.
We wish to determine the geometry of sedimentation tanks so that uniform flow is achieved and dead zones are eliminated, which would improve the efficiency of the current tank design and decrease the labor needed to maintain a clean tank. Given a particular upflow velocity, under these hydraulic conditions we may also experiment with floc blanket formation, which we believe will provide a second filtration stage for upward flowing flocs in the sedimentation tank and lower the turbidity of the effluent. Flocs may then be drawn off the blanket with a weir, minimizing the effort needed to clean the tank.
Experimental Methods and Results
Sedimentation Team Research Rationale
In our Research Rationale, we explained in detail our design procedure and the reasons for such design. It also contains list of potential experiments we will be running this semester.