How to use this calculator
- Enter the flow and the contact time needed for your contaminant.
- Set the filtration rate and number of vessels.
- Read carbon volume and mass, vessel size and bed depth.
How do you design an activated carbon filter?
Carbon volume (m³) = Q (m³/h) × EBCT (min) ÷ 60
Vessel area = Q ÷ filtration rate
Bed depth = carbon volume ÷ area
EBCT is the time water would spend in the bed if it held no carbon. It sets removal; filtration rate sets the vessel shape.
Worked example
With flow 10 m³/h, empty bed contact time (ebct) 10 minutes, filtration rate 12 m/h, number of working vessels 1, carbon bulk density 480 kg/m³, backwash rate 20 m/h:
Carbon volume: 1.67 m³
The calculator also gives carbon mass 800 kg; 25 kg bags 32 bags; vessel diameter 1,050 mm.
Assumptions and limits
- Carbon life (bed volumes to breakthrough) depends on the contaminant and needs testing or a supplier estimate.
- Allow about 30 to 50% freeboard for bed expansion.
Frequently asked questions
What EBCT is used for an activated carbon filter?
Use 3 to 5 minutes to remove chlorine, 5 to 10 minutes for taste and odour, and 10 to 20 minutes for organics, pesticides or PFAS.
How often should activated carbon be replaced?
For chlorine removal, often 1 to 3 years. For organics it can be months. Replace or regenerate when outlet quality starts to rise.
Does activated carbon remove TDS or hardness?
No. Carbon adsorbs chlorine and organic compounds. Use a softener for hardness and RO for TDS.
References
- AWWA, Water Treatment Plant Design, 5th ed.
- US EPA, Drinking Water Treatability Database: Granular Activated Carbon
- Crittenden et al., MWH Water Treatment: Principles and Design, 3rd ed.