How Is Ozone Generator Capacity Calculated?
Introduction
"How many grams per hour do I need?" is one of the questions we hear most often. The answer is rarely a guess — it is a calculation, and getting it wrong leads either to underperformance or to an unnecessarily high investment cost.
In this post, we walk through how ozone generator capacity is calculated, step by step.
The Core Logic of Capacity Sizing
Ozone generator capacity is expressed in g/h (grams per hour). This value is determined by combining several variables: the target ozone concentration for the application, the flow rate of the medium being treated (water or air), transfer efficiency, and ozone half-life.
The base formula looks simple, but estimating each component correctly requires years of field experience:
Required Ozone Dose (g/h) = Flow Rate (m³/h or L/min) × Target Dose (mg/L) × Safety Factor
1. Determining the Correct Flow Rate
For water applications, flow rate is the volume of water processed per hour (m³/h). For air applications, it is the volume of air passing through the chimney or space (Nm³/h).
A common mistake is sizing the system based on average flow rather than peak flow. A wastewater line may average 80 m³/h, but spike to 120 m³/h during shift changes. If generator capacity is calculated on the average instead of the peak, the system falls short exactly when it is needed most.
2. Setting the Target Dose by Application
Target dose is not a fixed number — it varies by application type and contaminant load. Some reference ranges we encounter frequently in the field:
- Drinking water disinfection: 0.5–1.5 mg/L
- Wastewater odour and micro-contaminant removal: 2–6 mg/L
- Aquaculture water quality improvement: 0.1–0.5 mg/L (ORP-controlled)
- Industrial chimney odour control: 10–50 mg/Nm³ depending on contaminant concentration
These figures are a starting point; the exact dose is confirmed through field measurement and pilot testing. Applying a number directly from literature may not reflect actual site conditions.
3. Accounting for Transfer Efficiency
Not all the ozone a generator produces reaches the target medium. Depending on the diffuser, venturi, or injector type, transfer efficiency typically ranges between 85% and 95%.
For example, in a system with 90% transfer efficiency, the generator must produce roughly 1.1 times the calculated net requirement to deliver the target dose to the water or air. Choosing a lower-efficiency distribution system requires a larger generator — increasing both upfront and energy costs.
4. Building in a Safety Margin
A safety margin of 15%–30% is typically added on top of the theoretical calculated value. The reasons for this margin include:
- Contaminant load can increase over time, for example as production capacity grows
- Generator output gradually declines over time, particularly with electrode wear
- Seasonal temperature changes affect ozone solubility and reaction rate
- Unexpected peak loads must always be met instantly
A system designed without a safety margin begins to fall short within just a few months of commissioning.
A Worked Example
Consider a CIP (Clean-in-Place) disinfection application on a food facility's process water line:
- Flow rate: 25 tonnes/hour (approximately 25 m³/h)
- Target dose: 3 mg/L
- Transfer efficiency: 90%
- Safety margin: 20%
Net ozone requirement: 25 m³/h × 3 g/m³ = 75 g/h
Adjusted for transfer loss: 75 / 0.90 ≈ 83.3 g/h
Final capacity with safety margin: 83.3 × 1.20 ≈ 100 g/h
Selecting a generator in the 80–100 g/h range for this facility is a sound engineering decision that covers both daily operations and future capacity growth.
Factors That Add Complexity
The formula above is a starting point. Several additional variables affect the calculation under real field conditions:
Ozone demand: Organic and inorganic load in the water consumes part of the ozone dose before the target residual concentration is reached. Calculations made without measuring this demand tend to be overly optimistic.
Feed gas type: Oxygen-fed systems produce 2–3 times more ozone than air-fed systems for the same power consumption. This has a direct impact on generator selection.
Contact time: The time required for ozone to sufficiently react with the target contaminant also affects the sizing of the contact tank or chamber — not just the generator capacity.
The OCS Ozon Approach
At OCS Ozon, we never reduce capacity sizing to a single formula. For every project, we:
- Carry out on-site measurement and sample analysis
- Evaluate peak and average load scenarios separately
- Factor in transfer efficiency based on the distribution system type
- Build future capacity growth into the design
Because an incorrectly sized generator either underperforms or leads to unnecessarily high energy and investment costs. The right capacity is neither too much nor too little — it is exactly what the application requires.
Conclusion
Ozone generator capacity sizing is an engineering decision built from flow rate, target dose, transfer efficiency, and safety margin. Getting it right is not just about applying a formula — it is about reading field data accurately and anticipating how the system will behave under real conditions.
If you would like to calculate the right generator capacity for your facility together, OCS Ozon offers a free technical assessment. Get in touch.