Settling basin calculation online
Rectangular tanks with longitudinal flow are used for the sedimentation of solids. The sedimentation has the task of removing all settling substances that were not retained by the sand trap. The settled sludge is collected in the sedimentation sludge chamber and fed to the sludge drainage system or disposed of at regular intervals. After passing through the sedimentation, the mixed water is cleaned of solids to such an extent that the regional discharge conditions can be met.
Different methods can be used to calculate settling basins. For pure granular mud, the laws established by Stokes and Hazen apply: the depth of the basin is completely indifferent. The decisive factor is the surface in its relationship to the flow.
- Calculation according to Stokes and Hazen
- Calculation according to SIA 431
- Calculation based on length of stay
Calculation bases
The laws of Stokes and Hazen apply to granular, settable substances. The required surface area of a sedimentation basin then results from the equation
| Surface area (m 2 ) = | Flow rate (m 3 / s) |
|---|---|
| lowest rate of descent (m / s) |
where the lowest rate of descent is to be calculated for the smallest grain size to be deposited. The rate of descent v s is calculated according to Stokes
| v s = | d 2 × g × (p p – p ƒ ) |
|---|---|
| 18 × η |
with d : grain diameter, g : acceleration due to gravity, p p : grain density, p ƒ : density of the fluid (water) and η : dynamic viscosity of the fluid (water).
