whereDsis the depth of the settling basin, Vis the mean velocity in the
basin, and cis the safety factor (1.5–2).
On the basis of the steady-state two-dimensional dispersion equa-
tion, the fraction of removal, f, at a distance xin a sedimentation tank of
depthy, can be obtained (assuming isotropic dispersion) from
x/y[ 12 Vlog(1 f)]/(10ws U*) (9.24)
whereU*is the shear velocity in the basin, given by equation (8.7).
Equation (9.24) gives reasonably satisfactory results when computing
each fraction of removed sediment independently, if the concentration is
small.
For a detailed discussion of sediment exclusion at inlets see
Ortmanns (2006).
400 DIVERSION WORKS
Fig. 9.24 Arrangement of settling basin
