The Role of Pressure in Ozone Solubility, Mass Transfer, and Reactor Design

In gas–liquid oxidation systems, pressure is not just a hydraulic variable, it is a chemically critical design parameter. When it comes to ozone, pressure directly influences how much ozone dissolves, how efficiently it transfers into water, and how reliably it reacts within a treatment system.

At Pinnacle Ozone Solutions, we engineer oxidation systems around a deep understanding of how pressure affects ozone chemistry and fluid dynamics. This blog examines how pressure impacts ozone solubility, mass transfer, contact time, and off-gas control, and how we account for it in system design.

Ozone Solubility and Pressure: Henry’s Law at Work

Ozone is only effective in water treatment if it dissolves in the aqueous phase. According to Henry’s Law, the solubility of a gas in water increases proportionally with its partial pressure in the gas phase:

C = kH × P

Where:

C = dissolved ozone concentration (mol/L)

kH = Henry’s Law constant for ozone (~0.021 mol/kg·atm at 25°C)

P = partial pressure of ozone gas

This means that increasing the pressure of ozone gas above the liquid increases the driving force for ozone mass transfer. For example:

At 1 atm, ozone solubility at 20°C is about 0.57 mg/L per 1% O₃ by volume
At 2 atm, solubility doubles to ~1.14 mg/L per 1% O₃
Higher pressures allow for greater oxidation capacity without increasing ozone dose

Source: Sander (2015); Langlais et al. (1991)

Implication: Pressurized systems dramatically improve ozone solubility and reduce the ozone required to reach treatment goals.

Mass Transfer Efficiency: How Pressure Enhances System Performance

Mass transfer of ozone gas into water occurs at the gas-liquid interface, and pressure plays a key role by:

Increasing gas density, which enhances molecular contact
Compressing gas bubbles, reducing buoyancy and improving retention
Reducing bubble coalescence, increasing interfacial surface area

Empirical data shows that mass transfer efficiency (MTE) of ozone systems improves from 60–70% in atmospheric tanks to 90–98% in pressurized reactors.

Source: Rice & Browning (1981); Westerhoff et al. (1999)

Implication: Pressurized contactors and injectors significantly reduce off-gas loss, making systems more efficient, especially when treating high-demand waters or operating at high flow rates.

Venturi Injection: Pressure Differential Is Critical for Ozone Entrainment

Most modern ozone systems use venturi injectors to mix ozone into water. These devices rely on a pressure differential to create vacuum at the throat, drawing ozone gas into the water stream.

Minimum pressure differential: typically 20–30 psi
Backpressure is needed to maintain venturi suction
Too little differential → poor ozone entrainment
Too much differential → vapor lock or cavitation risk

Designing around optimal pressure zones ensures stable ozone injection, high transfer efficiency, and system reliability.

Source: Mazzei Injector Company; Pinnacle system field data

Contact Time and Reactor Volume: Pressure Improves Retention

Higher pressure reduces gas bubble rise velocity, increasing residence time in contact chambers. This is crucial for:

CT disinfection compliance
Full oxidation of slow-reacting targets (e.g., NDMA, bromide, pharmaceuticals)
Ensuring complete oxidation before filtration or discharge

For a fixed reactor volume, increasing pressure can double or triple the effective contact time by minimizing bubble escape and maintaining turbulence for mixing.

Implication: Pressurized reactors allow for smaller footprint systems with higher oxidation efficiency.

Off-Gas Control: Lower Residuals with Pressurized Design

Residual ozone in off-gas streams must be stripped or destroyed to comply with safety and environmental limits. Pressurized systems offer:

Higher ozone absorption, leading to lower off-gas ozone concentrations
Easier sizing of destruct units, due to reduced gas volumes
Better separation of water vapor and gas under pressure

At 1 atm, typical off-gas destruct loads may reach 20–40% of delivered ozone; under pressure, this can fall below 5–10%, improving system economy and environmental compliance.

Source: Langlais et al. (1991); IOA Best Practices Manual

Pinnacle’s Approach to Pressure-Responsive Design

At Pinnacle Ozone Solutions, pressure management is integrated into every stage of system design:

Reactor geometry is modeled using CFD to optimize turbulence and bubble path length
Mass transfer calculations are adjusted for real-world pressure, temperature, and gas composition
Venturi systems are selected and sized based on dynamic hydraulic modeling
Pressure sensors and control valves provide feedback-regulated injection, allowing response to flow variability
Materials of construction are rated for pressure while maintaining ozone compatibility (e.g., stainless steel, ozone-resistant polymers)

Our pressurized systems have been deployed in high-flow municipal plants, geothermal reinjection sites, and critical disinfection zones where performance margin matters.

Conclusion

Pressure is not just a physical constraint, it is a design tool that directly controls ozone transfer, reactivity, and system efficiency. Whether you’re designing a high-performance disinfection system or an advanced oxidation reactor, understanding pressure’s influence on ozone behavior is essential.

At Pinnacle Ozone Solutions, we optimize every system around pressure-informed modeling. From mass transfer to off-gas control, we build solutions that perform under real-world operating conditions, where pressure makes the difference between acceptable and exceptional.

Technical References

Langlais, Reckhow, & Brink (1991). Ozone in Water Treatment: Application and Engineering
Sander, R. (2015). Compilation of Henry’s Law Constants for Water as Solvent
Rice, R.G., & Browning, M.E. (1981). Ozone for Industrial Water and Wastewater Treatment
Westerhoff, P., & Mash, H. (1999). Ozone Efficiency as a Function of Reactor Design. Journal AWWA
Mazzei Injector Co. (Technical Bulletins)
International Ozone Association (IOA). Operational Guidelines and Safety Practices