Geoscience Reference
In-Depth Information
24.6.1.4 Total Media Area
Several process control calculations for the RBC use the total surface area of all the stages within
the train. As was the case with the soluble BOD calculation, plant design information or information
supplied by the unit manufacturer must provide the individual stage areas (or the total train area),
because physical determination of this would be extremely difficult:
Total area = 1st stage area + 2nd stage area + … +
n
th stage area
(24.25)
24.6.1.5 Modeling RBC Performance
Although a number of semi-empirical formulations have been used, the Schultz-Germain formula
for trickling filters is recommended for modeling RBC performance (Spengel and Dzombok, 1992):
S
e
=
S
i
e
[
k
(
V
/
Q
)0.5]
(24.26)
where
S
e
= Total BOD of settled effluent (mg/L).
S
i
= Total BOD of wastewater applied to filter (mg/L).
V
= Filter volume (m
3
).
Q
= Wastewater flow (m
3
/s).
24.6.1.6 RBC Performance Parameter
The control parameter for RBC performance is soluble BOD (SBOD):
SBOD = TBOD - Suspended BOD
(24.27)
Suspended BOD =
c
(TSS)
(24.28)
SBOD = TBOD -
c
(TSS)
(24.29)
where
TBOD = Total BOD.
TSS = Total suspended solids.
c
= Coefficient
= 0.5 to 0.7 for domestic wastewater.
= 0.5 for raw domestic wastewater (TSS > TBOD).
= 0.6 for raw wastewater (TSS ≅ TBOD).
= 0.6 for primary effluents.
= 0.5 for secondary effluents.
■
EXAMPLE 24.38
Problem:
Average TBOD is 152 mg/L and TSS is 132 mg/L. What is the influent SBOD concentra-
tion that can be used for the design of an RBC system? RBC is used as the secondary treatment unit.
Solution:
For the primary effluent (RBC influent)
c
= 0.6. Estimate the SBOD concentration of the
RBC influent using Equation 24.29:
SBOD = TBOD -
c
(TSS) = 152 mg/L - 0.6(132 mg/L) = 73 mg/L
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