Determine Design Flow Rate
Identify the maximum instantaneous flow rate the system must treat. Consider peak flows, future expansion, and safety factors.
Q_design = Q_average × Peaking Factor × Safety Factor
Sizing calculations, vessel selection, bed depth optimisation, and configuration guidelines for GAC filtration systems
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Critical Values for System Sizing
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Contact UsStep-by-Step Design Process
Identify the maximum instantaneous flow rate the system must treat. Consider peak flows, future expansion, and safety factors.
EBCT is the theoretical residence time of water in the carbon bed. Higher EBCT provides better contaminant removal and longer bed life.
| Application | Recommended EBCT |
|---|---|
| Chlorine removal | 2-5 minutes |
| Taste & odour control | 5-10 minutes |
| VOC removal | 10-20 minutes |
| PFAS treatment | 15-30 minutes |
Using the selected EBCT and design flow rate, calculate the total carbon bed volume required.
For Q = 50 m³/h and EBCT = 15 minutes:
V_carbon = 50 × 15 / 60 = 12.5 m³
Select bed depth and calculate required vessel diameter. Typical bed depths range from 1.0-2.0 metres.
For V_carbon = 12.5 m³ and Bed Depth = 1.5 m:
A = 12.5 / 1.5 = 8.33 m²
D = √(4 × 8.33 / π) = 3.26 m (use 3.2 m standard)
Calculate the superficial velocity (hydraulic loading) and verify it falls within acceptable range (10-20 m/h).
For Q = 50 m³/h and A = 8.04 m² (D=3.2m):
v = 50 / 8.04 = 6.2 m/h (acceptable)
For larger systems, multiple vessels in parallel provide redundancy and allow maintenance without system shutdown.
| Total Flow (m³/h) | Recommended Configuration |
|---|---|
| < 50 | Single vessel |
| 50-150 | 2 vessels (1+1 or 2×50%) |
| 150-400 | 3 vessels (2+1 or 3×50%) |
| > 400 | 4+ vessels (3+1 or 4×50%) |
Critical Factors for Optimal Performance
GAC filters require adequate pretreatment to prevent fouling and extend carbon life:
Proper underdrain design ensures uniform collection and distribution:
Effective backwash is essential for maintaining bed performance:
Parallel, Series & Lead-Lag Arrangements
Multiple vessels operating simultaneously, sharing the total flow. Provides redundancy and flexibility.
Two vessels in series, with the lead vessel removing most contaminants and the lag vessel providing polishing and backup capacity.
Multiple GAC stages with different carbon types or different treatment objectives at each stage.
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Contact UsOur engineers can perform detailed sizing calculations, carbon selection, and system configuration for your specific application.
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