Civil Engineering Reference
In-Depth Information
end wall launder would be required. The launders would be installed on 10-ft (3.1-m)
centers, and the tubes would be submerged for a depth of 4 ft (1.2 m) because the
basin is deep. The appearance of the basin would be similar to that shown for an
upflow basin in Figure 11-21.
Upflow Basins.
Assume a plant has two square upflow clarifiers (42 ft [13 m] to a
side), each designed for a flow of 3,000 gpm (16 ML / d), with peripheral collection
launders. The total surface area is 1,760 ft
2
(164 m
2
). The influent centerwell reduces
the available settling area by 200 ft
2
(19 m
2
). The peak overflow rate currently reaches
1.92 gpm / ft
2
(4.68 m / h), which is high enough that the clarifier does not perform
well, especially when water temperatures drop.
It is desired to increase the plant capacity to 4,000 gpm (22 ML / d) per set-
tling basin. At this flow, the loading on the total basin settling area is 2.6 gpm / ft
2
(6.3 m / h). The raw-water turbidity is moderate, 30 to 70 NTU, and the water tem-
perature seldom falls below 50
F (10
C).
Table 11-5's guidelines for upflow basins indicate that a maximum total basin
loading of 2.5 gpm / ft
2
(6.1 m / h) with a corresponding tube rate of 2.5 to 3 gpm / ft
2
(6.1 to 7.3 m / h) can be used. Complete coverage of the settling area would provide
a tube rate of 2.6 gpm / ft
2
(6.3 m / h) and would also provide a simplified support
problem when compared to only partial coverage. Thus, coverage of the settling area
Fig. 11-21.
Upflow basin with total coverage of surface area with tube modules (From Culp,
Gordon, and Williams, Robert,
Handbook of Public Water Systems.
Copyright
1986 by John
Wiley & Sons, Inc. Reprinted by permission of John Wiley & Sons, Inc.)
