Framework of Technical Scheme for Application of Ozone in Advanced Municipal Sewage
Treatment
I. Overview of the Technical Scheme
1.1 Application Background
After municipal sewage undergoes primary and secondary treatment, it still contains
refractory organic matter, chroma, odors, and trace pollutants, which fails to meet the
requirements of upgraded discharge standards or wastewater recycling needs. Ozone advanced
treatment technology, relying on its strong oxidizing property, can efficiently address the
above-mentioned issues and serves as a key process to achieve the "quality improvement and
efficiency enhancement" of sewage treatment.
1.2 Core Technical Objectives
• Reduce effluent indicators such as COD (Chemical Oxygen Demand) and TOC (Total
Organic Carbon) to ensure compliance with discharge standards (e.g., Grade 1 Class A
Standards in Discharge Standards of Pollutants for Municipal Wastewater Treatment Plants (GB
18918-2002)).
• Remove chroma (to ensure effluent turbidity ≤ 5 NTU) and odors, and improve the
sensory indicators of water quality.
• Inactivate pathogenic microorganisms to meet the disinfection requirements for
reclaimed water (e.g., water for greening and road cleaning).
• Enhance the biodegradability of sewage to create conditions for subsequent advanced
treatment processes.
II. Core Technical Principles
2.1 Ozone Oxidation Mechanism
Ozone (O₃) achieves pollutant removal through two pathways:
• Direct oxidation: Ozone molecules directly attack the unsaturated
bonds (e.g., double bonds, triple bonds) in pollutant molecules, destroying their molecular
structures to achieve degradation. This process has high selectivity and mainly acts on
organic substances containing groups such as conjugated double bonds and hydroxyl
groups.
• Indirect oxidation: Under alkaline conditions or with the action of
catalysts, ozone decomposes to generate hydroxyl radicals (・OH). With a high redox potential
of 2.8V, hydroxyl radicals have no selectivity and can rapidly degrade various refractory
organic substances.
2.2 Key Reaction Processes
• Decomposition of refractory organic matter: Macromolecular organic
substances such as phenols, pesticides, and polycyclic aromatic hydrocarbons are oxidized
into small-molecular carboxylic acids and aldehydes, and some of them are finally converted
into CO₂ and H₂O.
• Decolorization reaction: The conjugated systems of chromogenic
substances (e.g., azo dyes, anthraquinone compounds) are destroyed, thereby decolorizing the
sewage.
• Disinfection reaction: It penetrates the cell membranes of
microorganisms, damages their enzyme systems and genetic materials (DNA/RNA), and achieves
sterilization and inactivation.
III. Typical Process Design Schemes
3.1 Mainstream Process Combinations and Flows
3.1.1 Core Process 1: O₃ + Biological Activated Carbon (BAC) Process
(Recommended)
Process Flow Diagram: Secondary Effluent → Ozone Contact Tank → Biological Activated Carbon
Filter → Disinfection Tank → Up-to-Standard Effluent / Reclaimed Water
Process Advantages: Ozone oxidation breaks down organic matter; activated carbon adsorption
and microbial degradation work synergistically to deeply remove pollutants, ensuring stable
operation.
Key Design Parameters:
• Ozone Dosage: 10-30 mg/L (adjusted based on influent COD
concentration).
• Ozone Contact Time: 10-20 min; hydraulic retention time (HRT) of the
contact tank ≥ 20 min.
• Filtration Rate of Activated Carbon Filter: 8-12 m/h; carbon layer
height: 2-3 m; empty bed contact time (EBCT): 15-20 min.
3.1.2 Process 2: O₃ + Coagulation and Sedimentation Process
Applicable Scenarios: Advanced treatment of municipal sewage with high chroma and high
turbidity.
Key Design Parameters: Ozone dosage: 8-15 mg/L; coagulant (e.g., PAC) dosage: 20-50 mg/L;
sedimentation time: 30-40 min.
3.1.3 Process 3: O₃ + Membrane Separation Process
Applicable Scenarios: Preparation of high-quality reclaimed water (e.g., makeup water for
industrial circulating water).
Key Design Parameters: Ozone dosage: 15-25 mg/L; membrane filtration pressure: 0.1-0.3 MPa;
membrane flux: 15-25 L/(m²·h).
II. Typical Process Combinations
When ozone is used alone, its oxidation capacity is limited and the cost is relatively high.
Therefore, in practical engineering, it is often combined with other processes to form a
high-efficiency treatment process. The common combined processes are as follows:
The above is for reference only.