How Ozone Enhances Biological Filtration in Water Treatment Systems

In modern water treatment, ozone and biological filtration are not just compatible, they’re synergistic. While ozone is well known as a powerful oxidant for disinfection and contaminant removal, it also plays a critical role in enabling and enhancing biological filtration systems like Biologically Active Carbon (BAC) and Granular Activated Carbon (GAC).

At Pinnacle Ozone Solutions, we design ozone systems not only for direct oxidation, but also to improve downstream filter performance, media lifespan, and treatment stability. This blog explains the science behind this synergy and the engineering implications for utilities and consultants.

Biological Filtration 101: GAC vs. BAC

• GAC (Granular Activated Carbon): removes organics through adsorption; performance declines over time as pores saturate.
• BAC (Biologically Active Carbon): uses biofilm on carbon media to biodegrade organics; depends on microbial activity, not just surface area.

In practice, most GAC filters become biologically active over time. Their effectiveness depends increasingly on biodegradable organic carbon (BDOC) availability and biofilm health.

How Ozone Enhances Biological Filtration

1. Ozone Breaks Down Recalcitrant Organics into Biodegradable Fractions

   Ozone selectively oxidizes complex, high molecular weight compounds (e.g., humic substances, lignin derivatives, industrial organics) into simpler molecules.

   • Converts non-biodegradable DOC into BDOC
   • Supports biomass growth and enzymatic activity in BAC media
   • Enhances removal of compounds poorly adsorbed by GAC

   Reference: Hozalski et al. (1999); Hammes et al. (2006)

2. Improved Filter Performance and Stability

   Ozonation upstream of biological filtration improves filter behavior by:

   • Reducing headloss buildup
   • Lowering backwash frequency by minimizing clogging particles
   • Stabilizing microbial communities, especially under variable loading

   This leads to longer filter runs and better effluent quality with fewer operational interventions.

3. NDMA and Micro-Pollutant Precursor Removal

   Ozone reduces precursors to N-nitrosodimethylamine (NDMA) and other emerging contaminants, allowing BAC to focus on final polishing instead of primary removal.

   • Ozone + BAC achieves >90% NDMA removal
   • Increases removal of pharmaceuticals and endocrine disruptors (e.g., carbamazepine, ibuprofen)

   Reference: Snyder et al. (2007); von Gunten (2003)

4. Lower GAC Turnover and Longer Media Life

   Ozone’s oxidative action reduces carbon loading:

   • Slower exhaustion of adsorption capacity
   • BAC filters can be operated for 2–5 years or longer without media replacement
   • In some systems, GAC reactivation cycles are extended by 30–50%

   This reduces carbon costs and labor associated with replacement.

Biological Mechanism: Why BAC Needs BDOC

Ozone promotes the formation of:

• Low molecular weight aldehydes (e.g., formaldehyde, glyoxal)
• Carboxylic acids, short-chain ketones, and alcohols

These compounds:

• Are readily assimilable by bacteria
• Promote dense, active biofilms
• Improve the filter’s ability to remove ammonia, nitrates, and fine organics

Hammes et al. (2008) demonstrated that ozone increased BAC biomass yield by >60% compared to non-ozonated controls.

Design Considerations: How Pinnacle Engineers the Synergy

At Pinnacle, we integrate ozone and biological filtration systems using data-driven modeling and site-specific design. Key elements include:

• Ozone dose optimization (0.5–2.0 mg O₃/mg DOC) for ideal BDOC conversion
• Contact time modeling to ensure oxidation without over-dosing
• Avoidance of excess ozone carryover, which can damage biofilms
• ORP and DOC monitoring to align upstream ozone with downstream filter behavior

We also partner with filter designers and media providers to align reactor sizing, backwash cycles, and flow rates with ozone-BAC dynamics.

Real-World Performance Gains

In utility case studies, ozone-enhanced BAC systems have shown:

• 40–60% lower GAC usage
• 25–35% improvement in TOC removal
• >70% reduction in taste and odor events
• Improved effluent stability, especially after storm events or seasonal TOC spikes

These benefits translate directly to lower operating costs, longer asset life, and greater regulatory resilience.

Conclusion

Ozone’s role in water treatment goes far beyond disinfection and direct oxidation. When applied upstream of biological filtration, ozone transforms complex organics into biodegradable compounds, enhances microbial performance, and extends the life of carbon media.

At Pinnacle Ozone Solutions, we design ozone systems that don’t just deliver oxidant, they deliver value across the entire treatment train. For utilities implementing or optimizing BAC/GAC filtration, ozone is the enabling step that turns good filtration into great filtration.

Technical References

• Hozalski, R.M., Bouwer, E.J., & Goel, S. (1999). Removal of natural organic matter from drinking water supplies by ozone–BAC treatment. Water Research.
• Hammes, F., Berger, C., Köster, O., & Egli, T. (2008). Assessing biological stability of drinking water without disinfectant residuals using flow cytometry. Water Research.
• von Gunten, U. (2003). Ozonation of drinking water: Part I. Oxidation kinetics and product formation. Water Research.
• Snyder, S.A., et al. (2007). Removal of EDCs and pharmaceuticals in drinking water and wastewater treatment. Water Research Foundation.
• Tchobanoglous, G., et al. (2014). Direct Potable Reuse: Benefits for Public Water Supplies. WateReuse Research Foundation.