Question:
A wastewater was tested in a settling column test with the following results in terms of suspended sediment concentration:
|
At t = 30 minutes
|
|
Depth below
surface, h
(cm)
|
Concentration
remaining,
c./co
|
| 38 |
0.23
|
| 118 |
0.81
|
| 198 |
0.94
|
| 278 |
0.97
|
| 358 |
0.98
|
|
At t = 60 minutes
|
|
Depth below
surface, h
(cm)
|
Concentration
remaining,
c/co
|
| 34 |
0.05
|
| 114 |
0.46 |
| 194 |
0.73
|
| 274 |
0.86
|
| 354 |
0.92
|
|
At t = 90 minutes
|
|
Depth below
surface, h
(cm)
|
Concentration
remaining,
c/co
|
| 32 |
0.03
|
| 112 |
0.23
|
| 192 |
0.52
|
| 272 |
0.70
|
| 352 |
0.83
|
a. What type of settling is indicated by these data?
b. This particular wastewater is proposed to be treated in a rectangular sedimentation tank having a detention time of 2 hours and a depth of 4 meters. Estimate the percent of suspended sediments that will be removed.
c. If the wastewater flow rate is 7,500 m3/day, what needs to be the area and volume of the sedimentation tank?