Environmental Engineering Reference
In-Depth Information
Example 5.13
Problem:
The grit channel of a plant is designed to remove sand that has
a settling velocity of 0.080 fps. The channel is currently operating at a
depth of 2.3 ft. How many seconds will it take for a sand particle to reach
the channel bottom?
Solution:
2.3ft
0.080 fps
SettlingTime
=
=
28.7s
5.3.7.3 Required Channel Length
This calculation can be used to determine the length of channel
required to remove an object with a specified settling velocity:
ChannelDepth (ft)
× Flow Velocity (fps)
SettlingVelocity (fps)
Required ChannelLength
=
(5.10)
Example 5.14
Problem:
The plant's grit channel is designed to remove sand that has
a settling velocity of 0.070 fps. The channel is currently operating at a
depth of 3 ft. The calculated velocity of flow through the channel is 0.80
fps. The channel is 35 ft long. Is the channel long enough to remove the
desired sand particle size?
Solution:
3ft0.80fps
0.070
×
Required ChannelLength
=
=
34.3 ft
fps
Yes, the channel is long enough to ensure that all of the sand will be
removed.
Example 5.15
Problem:
The plant's grit channel is designed to remove sand that has
a settling velocity of 0.080 fps. The channel is currently operating at a
depth of 3 ft. The calculated velocity of flow through the channel is 0.85
fps. The channel is 36 ft long. Is the channel long enough to remove the
desired sand particle size?
Solution:
3ft0.85fps
0.080
×
Required ChannelLength
=
=
31.9 ft
fps
Yes, the channel is long enough to ensure that all of the sand will be
removed.
