Entrance Tank Design Program

The purpose of this program is to design the dimensions of the entrance tank based on the flow rate of the plant and the flow rate required for rapid mixing. The Entrance Tank is constructed as a separate channel before the flocculator, and includes a grit chamber to help with aeration issues.

Entrance Tank Design Program Algorithm

Entrance Tank Program Inputs
Entrance Tank Program Outputs
Entrance Tank AutoCAD Drawing Program

Algorithm

The entrance tank is designed to be an extra channel before the flocculator, and the same size as a single floc channel. This program therefore calls variables defined in the Flocculation design program. Variables are also called from the Rapid Mix program to meet requirements for rapid mix to occur in the entrance tank.

The area of the entrance tank is calculated based on the flow rate through the plant and the required up-velocity through the entrance tank (found in Design Assumptions).

The water level in the entrance tank is designed to meet requirements for rapid mix, as well as head loss due to flow from the entrance tank to the flocculator. These variables can be found in the Rapid Mix, Flocculation, Sedimentation Inlet Slopes, and User Inputs design programs.

The height of the entrance channel is based on the required water depth, and the plant freeboard defined in User Inputs.

The length of the entrance tank (L.Et) includes the length of the grit chamber, and equals the length of the sedimentation tank (which is also the length of a single floc channel). The width of the entrance tank is chosen so that it meets the geometry requirements, as well as the width required for rapid mix. In the Rapid Mix, the width of the entrance channel needs to be at least the the spacing between the floc baffles in the first channel (S.FlocBaffle0).

Grit Chamber

The grit chamber is contained within the entrance tank. A concrete barrier will be built to give the grit chamber a length that satisfies the upward velocity constraint previously mentioned.