Sedimentation Tank Inlet Slopes Design Program

Sedimentation Tank Inlet Slopes Design Program Algorithm

Sedimentation Tank Inlet Slopes Inputs
Sedimentation Tank Inlet Slopes Outputs

Design Algorithm

The sedimentation inlet slopes program begins by designing the rough dimensions of the sedimentation tank and then moves on to design the trapezoidal shaped channel located at the bottom of the tank. This channel uniformly distributes water to the entire bottom of the sedimentation tank creating a uniform flow of water out of the slopes and up through the sedimentation tank. This design was a redesign of the previous set up that had water being delivered to the bottom of the sedimentation tank through a network of pvc pipes designed to serve the same purpose. This new design will allow for tanks to be shallower and thus more economical.

There are several major concerns with this design. One concern is ensuring that water flows uniformly out of the slopes. Achieving this goal requires that the water velocity with in the slope be significantly lower than the water flowing out of the slope. Another concern is that flocs will settle out of the water flowing in the slopes. If flocs start to build up in the slopes then they decrease the area of the exit, which in turn could cause floc breakup. Another concern is with regard to floc breakup in general. The specific parameters surrounding floc breakup are generally unknown, and it is a concern that flocs will be broken in transit from the floc tank to the sedimentation tank. The main point of concern for breakup is the exit ports into the sedimentation tank.

The first step is to determine the flow rate through one sedimentation tank. The total plant flow rate (Q.Plant) is split evenly through all sedimentation tanks. The number of sedimentation tanks to be constructed is determined by the user.

After determining the flow rate of one sedimentation tank. The first step is to determine the necessary height of the port introducing water to the sedimentation tank. This port has to be designed to not breakup the flocs created in the flocculator, thus the energy dissipation of the port has to be less than that of the end of the flocculator. Determining this B.SedPort value requires an iterative process because of an interdependence between the width of the inlet slope and width of the space between ports, which is assumed to be the same as the height of the port, are interdependent.