h1. 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.
!Et1.PNG!!Et2.PNG!
h2. Entrance Tank Design Program Algorithm
[Entrance Tank Program Inputs|Entrance Tank Design Program Inputs]
[Entrance Tank Program Outputs|Entrance Tank Design Program Outputs]
[Entrance Tank AutoCAD Drawing Program| AutoCAD Entrance Tank Program]
h3. 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|GTheta Flocculation Design Program] design program. Variables are also called from the [Rapid Mix|Rapid Mix Design Program] 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|Design Assumptions Design Program]).
{include: A.Et}
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|Rapid Mix Design Program], [Flocculation|GTheta Flocculation Design Program], [Sedimentation Inlet Slopes|Sedimentation Inlet Slopes Design Program], and [User Inputs|User Inputs Design Program] design programs.
{latex}
\large
$$
HW_{EtTotal} = HW_{EtMax} + HL_{FlocEntryOrifice} + HL_{Floc} + HW_{Sed} + HW_{EtWaterFall} + HW_{EtChannel}
$$
{latex}
The height of the entrance channel is based on the required water depth, and the plant freeboard defined in [User Inputs|User Inputs Design Program].
{latex}
\large
$$
H_{Et} = HW_{EtTotal} + H_{PlantFreeboard}
$$
{latex}
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|Rapid Mix Design Program], the width of the entrance channel needs to be at least the the spacing between the floc baffles in the first channel (S.FlocBaffle0).
{latex}
\large
$$
W_{Et} = \max \left( {{{A_{Et} } \over {L_{Et} }},W_{EtChannel} } \right)
$$
{latex}
h5. 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.
{include: L.Grit}
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