Ozone + Biological Treatment Combination in Wastewater Treatment

Ozone + Biological Treatment Combination in Wastewater Treatment

Introduction

In industrial wastewater treatment, a single technology is rarely sufficient. Wastewater containing high organic loads, colour, odour, and persistent contaminants requires multiple treatment stages working in concert.

The ozone + biological treatment combination is one of the most powerful integrated treatment approaches available for this challenge. When ozone's chemical oxidation capability is combined with the natural degradation capacity of biological treatment, a treatment quality is achieved that neither method can reach independently.

Why Neither Works Alone

Biological Treatment Alone

Biological treatment systems — activated sludge, membrane bioreactors (MBR), or trickling filters — effectively remove biodegradable organic matter. However, certain contaminants are resistant to biological treatment:

  • Textile dyes and colour compounds
  • Surfactants and detergent residues
  • Pesticides and herbicides
  • Pharmaceutical compounds and hormone residues
  • High-concentration H₂S and organic odour compounds

These compounds pass through biological treatment and continue to exceed discharge limits.

Ozone Alone

Ozone is a powerful oxidant — but at high COD loads, ozone consumption rises dramatically. Breaking down biodegradable organic matter through chemical oxidation alone is both costly and inefficient. In this context, ozone is significantly more expensive than biological treatment.

The solution: Combining both in the correct sequence.

Ozone + Biological System: Two Core Architectures

Architecture 1: Ozonation Before Biological Treatment (O₃ → Bio)

 
 
Raw Wastewater
    ↓
[Pre-treatment — Screening, Oil Removal]
    ↓
[Ozonation — COD, colour, odour pre-removal]
    ↓
[Biological Treatment — Activated sludge / MBR]
    ↓
Discharge

When to choose this:

  • Wastewater containing compounds toxic or inhibitory to biological treatment
  • Situations where contaminants must be converted to biodegradable form before biological treatment
  • Textile dyehouses, pharmaceutical facilities

Ozone's role: Breaks down toxic and resistant compounds in raw wastewater, making it suitable for biological treatment. Biological treatment efficiency increases significantly.

Architecture 2: Ozonation After Biological Treatment (Bio → O₃)

 
 
Raw Wastewater
    ↓
[Biological Treatment — Activated sludge / MBR]
    ↓
[Ozonation — Remaining COD, colour, odour, bacteria removal]
    ↓
Discharge or Reuse

When to choose this:

  • Facilities with existing biological treatment systems that cannot meet discharge limits
  • Applications targeting wastewater reuse
  • Facilities with colour and odour discharge limit issues

Ozone's role: Removes persistent contaminants, colour, and odour that biological treatment cannot eliminate. Functions as a final polishing stage.

Ozone + BAC (Biological Activated Carbon)

Particularly in drinking water and advanced treatment applications, the ozone + BAC combination creates a powerful synergy:

Ozone stage: Breaks large organic molecules into smaller, biodegradable fragments.

BAC stage: Biofilm growing on activated carbon biologically consumes the ozonated organic matter. The activated carbon simultaneously adsorbs ozone by-products.

This combination is used as standard process in more than 3,000 municipal drinking water treatment plants worldwide.

Which Sectors Benefit?

Textile and Dyehouse Colour compounds that pass through biological treatment exceed discharge limits. Ozone achieves 90–99% colour removal. It is also effective for AOX (adsorbable organic halogens) removal — critical for EU export compliance.

Feed and Meat Processing High organic loads and H₂S-based odour. Biological pre-treatment + ozone combination meets both COD limits and eliminates odour complaints.

Food Ingredients (Yeast, Starch) Colour and odour compounds resistant to biological degradation. Ozone effectively removes these compounds before or after biological treatment.

Pharmaceutical and Chemical Pharmaceutical compounds and hormone residues resistant to biological treatment. Ozone or AOP removal is essential.

Technical Design Notes

Ozone dose: In post-biological treatment applications, 5–15 mg/L ozone dose is typically sufficient. Pre-biological treatment applications may require 10–30 mg/L depending on pollutant load.

Contact time: A minimum contact time of 10–20 minutes must be ensured for adequate reaction.

Residual ozone: Discharge water must be verified to contain no residual ozone. Removal via activated carbon filter or UV destruction unit is mandatory.

pH effect: Ozonation operates most efficiently at pH 6–8. In alkaline conditions, ozone decomposes rapidly — this is an advantage in AOP applications but a disadvantage in conventional ozonation.

Conclusion

The ozone + biological system combination is a powerful and proven solution for industrial wastewater treatment when single technologies fall short. The correct architectural choice — ozone first or ozone last — must be determined based on the chemical profile of the wastewater and discharge targets.

OCS Ozon reviews your wastewater analysis report and delivers custom integrated treatment designs. Contact us for a free technical assessment.