How to use this calculator
- Enter the flow and the ozone dose for your application.
- Set the transfer efficiency of your injector or diffuser.
- Pick oxygen or air feed gas.
- Read generator size, gas flow and contact tank volume.
How do you size an ozone generator?
Ozone (g/h) = Q (m³/h) × dose (mg/L) ÷ transfer efficiency
Gas flow (Nm³/h) = ozone (g/h) ÷ concentration (g/Nm³)
Contact volume = Q × contact time
Ozone concentration is taken as about 143 g/Nm³ for oxygen feed and 26 g/Nm³ for air feed. Power uses about 10 kWh/kg (oxygen) and 18 kWh/kg (air).
Worked example
With flow 10 m³/h, ozone dose 3 mg/L, transfer efficiency 90 %, feed gas: Oxygen (about 10% ozone by weight), contact time 10 minutes, expected ozone residual 0.4 mg/L:
Ozone generator capacity: 33.3 g O₃/h
The calculator also gives ozone per day 0.8 kg/day; feed gas flow 0.23 Nm³/h; feed gas flow 3.9 L/min.
Assumptions and limits
- Dose should come from an ozone demand test on your water.
- Power excludes oxygen concentrator, chiller and air dryer.
Frequently asked questions
What ozone dose is used for drinking water?
Disinfection typically needs 1 to 3 mg/L with a residual of 0.2 to 0.4 mg/L for 4 to 10 minutes. Higher doses are used for colour, taste and odour.
How much ozone is needed for iron and manganese?
Stoichiometrically 0.43 mg ozone per mg of iron and 0.88 mg per mg of manganese, plus the demand of organics.
Oxygen or air for ozone generation?
Oxygen gives about five times the ozone concentration from the same generator and needs less energy per kg, so it suits larger systems. Air feed is simpler for small units.
References
- US EPA (1999). Alternative Disinfectants and Oxidants Guidance Manual, EPA 815-R-99-014
- Rakness, K. (2005). Ozone in Drinking Water Treatment: Process Design, Operation and Optimization. AWWA