How it works
- adsorption, not filtration — A carbon grain has a huge internal surface — several hundred square metres per gram. Organics leave the water and stick to that surface. Nothing is strained out, so a carbon bed can look perfectly clean and be completely spent.
- the mass transfer zone — Adsorption is not instant. The top of the bed saturates first, and a band of partly-loaded carbon — the mass transfer zone — travels slowly downward. Above it the carbon is exhausted; below it, untouched.
- contact time — EBCT is the bed volume divided by the flow. Give the water 10–30 minutes and the MTZ stays short. Rush it and the zone stretches, so it reaches the outlet while much of the bed is still unused — you throw away carbon you paid for.
- breakthrough — When the leading edge of the MTZ reaches the underdrain, organics appear in the effluent. That is breakthrough, and it is the end of the run. Lead–lag vessels in series let you run the lead bed to full exhaustion while the lag one guards the outlet.
- what governs it — Capacity and load set how long the bed lasts; EBCT sets how much of that capacity you actually get. Drop the contact time and watch the MTZ stretch and utilisation fall — the same carbon, a shorter life, for no saving at all.
Design parameters
The panel opposite runs the same correlations as the F-500 design sheet, so the animation and the calculator cannot disagree. Drag any of them and the picture responds.
- Flow — m³/h
- Vessel diameter — m
- Bed depth — m
- Influent TOC — mg/L
- Carbon capacity — mg/g
- Bed density — kg/m³
Open the full F-500 design sheet for the governing equations, the accepted design envelopes and the worked calculation.