Environmental Engineering Reference
In-Depth Information
Cover filter media to reduce heat loss.
Remove ice before it becomes large enough to block the arms.
Note: During periods of cold weather, the filter will show decreased per-
formance; however, the filter should not be shut off for extended periods.
Freezing of the moisture trapped within the media causes expansion
and may cause structural damage.
7.3.8 Process Calculations
Several calculations are useful in the operation of a trickling filter,
including total flow, hydraulic loading, and organic loading.
7.3.8.1 Total Flow
If the recirculated flow rate is given, total flow is:
Total Flow (MGD) = Influent Flow (MGD) + Recirculation Flow (MGD (7.10)
Total Flow (gpd) = Total Flow (MGD) × 1,000,000 gal/MG
Note: The total flow to the trickling filter includes the influent flow and the
recirculated flow. This can be determined using the recirculation ratio.
Total Flow (MGD) = Influent Flow × (Recirculation Ratio + 1.0)
Example 7.3
Problem: The trickling filter is currently operating with a recirculation
ratio of 1.5. What is the total flow applied to the filter when the influent
flow rate is 3.65 MGD?
Solution:
Total Flow = 3.65 MGD × (1.5 + 1.0) = 9.13 MGD
7.3.8.2 Hydraulic Loading
Calculating the hydraulic loading rate is important in accounting
for both the primary effluent as well as the recirculated trickling filter
effluent. Both of these are combined before being applied to the surface
of the filter. The hydraulic loading rate is calculated based on the sur-
face area of the filter.
Example 7.4
Problem: A trickling filter 90 ft in diameter is operated with a primary
effluent of 0.488 MGD and a recirculated effluent flow rate of 0.566 MGD.
Calculate the hydraulic loading rate on the filter in gpd/ft 2 .
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