Ozone Transferred Dose Calculator

Ozone generators make more ozone than the water actually absorbs. Enter your gas and water flows plus inlet and off-gas concentrations to get the transferred dose — the number that actually does the disinfection work.

Water flow

Flow unit

Ozone gas flow (scfm)Standard cubic feet per minute of feed gas to the contactor.

Inlet ozone concentration (g/Nm³)Typical oxygen-fed generators: 60–200 g/Nm³.

Off-gas ozone concentration (g/Nm³)From the off-gas analyzer. Typical: 5–30 g/Nm³.

Nm³ = normal cubic meter at 0 °C, 1 atm.

Ozone Mass Balance

Item	Value

How the calculation works

Formulas
Water flow (L/min) = MGD × 2,628.76 (or gpm × 3.78541)
Gas flow (Nm³/min) ≈ scfm × 0.0283168
Ozone applied (mg/min) = gas flow (Nm³/min) × inlet conc. (g/Nm³) × 1,000
Ozone in off-gas (mg/min) = gas flow (Nm³/min) × off-gas conc. (g/Nm³) × 1,000
Transferred dose (mg/L) = (applied − off-gas) ÷ water flow (L/min)
Applied dose (mg/L) = applied ÷ water flow (L/min)
Transfer efficiency (%) = (inlet conc. − off-gas conc.) ÷ inlet conc. × 100

Notes & limitations

This is a steady-state mass balance on the contactor: what goes in as gas minus what leaves as gas is assumed transferred to water. Typical transferred doses for primary disinfection run about 1–3 mg/L depending on target organism, temperature, and CT requirements; taste-and-odor or microflocculation applications often run lower. Confirm against CT tables and pilot data for your state.

Transferred dose is not the same as applied dose. Disinfection credit is governed by CT (concentration × time), not by dose alone.
The scfm-to-Nm³ conversion treats a standard cubic foot as a normal cubic meter equivalent; the small reference-temperature difference is negligible for operational use. If your gas flow is metered in other units, convert first.
Off-gas still contains ozone and must be destroyed (thermal or catalytic destruct unit) before venting — never vent raw off-gas.
Analyzer calibration matters: a drifting off-gas analyzer makes the transferred dose look better or worse than it is. Verify with periodic calibration checks.
This tool is for operational guidance. Confirm setpoints against your plant SOPs and state disinfection requirements.

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