Geoscience Reference
In-Depth Information
Zoogleal Slime
Oxygen
Media
Sloughings
Organic
matter
Wastewater holding tank
FIGURE 24.5
Rotating biological contactor (RBC) cross-section and treatment system.
Cl
2
Rotating biological contactors
Primary
Settling
Tank
Secondary
Settling
Tanks
Euent
Influent
Solids disposal
FIGURE 24.6
Rotating biological contactor (RBC) treatment system.
24.6.1.1 Hydraulic Loading Rate
The manufacturer normally specifies the RBC media surface area, and the hydraulic loading rate is
based on the media surface area, usually in square feet (ft
2
). Hydraulic loading is expressed in terms
of gallons of flow per day per square foot of media. This calculation can be helpful in evaluating the
current operating status of the RBC. Comparison with design specifications can determine if the unit
is hydraulically over- or underloaded. Hydraulic loading on an RBC can range from 1 to 3 gpd/ft
2
.
■
EXAMPLE 24.30
Problem:
An RBC treats a primary effluent flow rate of 0.244 MGD. What is the hydraulic loading
rate in gpd/ft
2
if the media surface area is 92,600 ft
2
?
Solution:
Flow (gpd)
Mediaarea
244,000 gpd
92,000 ft
2
Hydraulic loadingrate
=
=
=
2.65 ft
2
2
(ft )
■
EXAMPLE 24.31
Problem:
An RBC treats a flow of 3.5 MGD. The manufacturer's data indicate a media surface area
of 750,000 ft
2
. What is the hydraulic loading rate on the RBC?
Solution:
Flow (gpd)
Mediaarea
3,500,000 gpd
750,000 ft
2
Hydraulic loadingrate
=
=
=
4.7 ft
2
2
(ft )
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