Longking EnTech Europe: Choosing the Right Oxygen Source for Ozone Systems

Choosing the Right Oxygen Source for Ozone Systems in Drinking Water Treatment

1. Why this decision is critical for performance, stability, and energy efficiency

In modern drinking water treatment plants (WTPs), ozone has become a key technology not only for disinfection but also for the oxidation of organic matter, taste and odor control, and the removal of emerging contaminants. However, a crucial design decision that is often underestimated is the choice of oxygen source for the ozone generator.

From a process engineering standpoint, the oxygen feed gas directly determines:

• The concentration of ozone achievable

• The transfer efficiency to water

• The size and complexity of the contact and off-gas systems

• The energy consumption per kg of O₃ produced

• The operational flexibility and scalability of the system

As ozone system designers and water treatment experts at Longking EnTech Europe, we work with three main oxygen supply technologies:

• LOX (liquid oxygen)

• PSA (Pressure Swing Adsorption) on-site oxygen generators

• Dry compressed air systems

Each has advantages. None is "better" in all cases—but each is more or less suitable depending on your plant's scale, goals, and constraints.

LOX – Liquid Oxygen

High concentration. Stable and compact ozone generation.

Liquid oxygen is a high-purity, externally supplied gas (typically >99.5%) delivered in cryogenic tanks. It is vaporized and fed directly to the ozone generator.

Typical performance:

• O₃ concentration: up to 15% by weight

• Energy consumption: 7–8 kWh/kg O₃

• Best for: large plants, high load, stable production

Advantages:

• High ozone output with excellent mass transfer efficiency (>90%)

• Smaller contactors and destructors

• Stable, reliable operation without fluctuation in purity

• Lower gas volume → reduced off-gas treatment cost

Considerations:

• Requires logistics for LOX supply and storage

• Cost and availability vary by location

• Not always optimal for remote or autonomous plants

PSA – On-site Oxygen Generation

Full independence. Adaptable to demand.

PSA systems generate oxygen from ambient air using molecular sieves and a pressure-based adsorption cycle. Typical purity ranges from 90–95%.

Typical performance:

• O₃ concentration: up to 12%

• Energy consumption: 8–10 kWh/kg O₃ (ozone + PSA system)

• Best for: medium-sized plants, modular design, areas with LOX logistics issues

Advantages:

• On-demand oxygen production: full autonomy

• Modular and scalable configuration

• Ideal for plants in remote or decentralized locations

• Avoids dependence on gas supply contracts or tankers

Considerations:

• Larger footprint than LOX

• Requires regular maintenance of compressors, dryers, and sieves

• Sensitive to humidity and temperature—air drying must be optimal

Dry Compressed Air

Self-contained solution, but with lower ozone output

Compressed air systems use filtered, dried ambient air to feed the ozone generator. Because the oxygen concentration is only ~21%, the achievable ozone yield is lower.

Typical performance:

• O₃ concentration: 2–4%

• Energy consumption: 15–18 kWh/kg O₃

• Best for: small-scale plants, pilot systems, or where oxygen supply is not viable

Advantages:

• No external supply or contract required

• Safe and simple operation

• Economical for continuous 24/7 use in specific conditions

Considerations:

• Low ozone concentration → large gas volumes required

• Less efficient ozone transfer to water (typically <85%)

• Large contactors and destructors needed

• Highly sensitive to air quality (temperature, dust, humidity)

2. Technical comparison summary

▶ LOX (Liquid Oxygen):

• O₂ purity: 99.5%

• Ozone concentration: up to 15% by weight

• Energy consumption: 7–8 kWh per kg of O₃

• Off-gas volume: Low

• Maintenance requirements: Low

• Operational stability: Very high

▶ PSA (On-site Oxygen Generation):

• O₂ purity: 90–95%

• Ozone concentration: up to 12% by weight

• Energy consumption: 8–10 kWh per kg of O₃ (including PSA system)

• Off-gas volume: Medium

• Maintenance requirements: Medium

• Operational stability: High

▶ Dry Compressed Air:

• O₂ purity: 21%

• Ozone concentration: 2–4% by weight

• Energy consumption: 15–18 kWh per kg of O₃

• Off-gas volume: High

• Maintenance requirements: High

• Operational stability: Moderate to low
  jgfvj hrg thrtgd 44 35 53

3. How to Choose the Best Option

Ask the right questions:

• What is your daily ozone demand (kg O₃/day)?

• Is the ozone used for pre-oxidation, AOPs, or disinfection?

• Is oxygen supply infrastructure reliable and affordable in your location?

• Do you need autonomy or remote operation?

• What are your CAPEX and OPEX constraints?

At Longking EnTech Europe, we start each project with a full process assessment: flow, TOC, bromide, iron/manganese, temperature, and risk targets. Based on this, we select the oxygen technology that ensures:

• Optimal ozone concentration for mass transfer

• Safe and reliable system operation

• Energy-efficient performance

• Compliance with drinking water regulations

4. Final Thoughts: Oxygen is not just a utility—it’s a process variable

Too often, the oxygen supply is treated as a “secondary” item in ozone plant design. In reality, it’s one of the most impactful decisions you will make—affecting efficiency, operability, and regulatory compliance.

There’s no universal solution, but there is always a best-fit choice for each plant.

If you're designing or upgrading an ozone system for drinking water, talk to our team at Longking EnTech Europe. We help you choose, size, and optimize the full process—not just the equipment—so your ozone system performs as it should: powerfully, efficiently, and safely.

Contact our commercial department at info@longkingeu.com
www.longkingeu.com