In the advanced treatment of municipal sewage, ozone plays a core role in decolorization,
deodorization, removal of refractory organic matter and disinfection, and is one of the key
technologies to achieve the discharge of sewage up to standard or its recycling and
reuse.
I. Application Functions
With its strong oxidizing property (redox potential of 2.07V, second only to fluorine),
ozone mainly fulfills the following functions in the advanced treatment stage:
1.Removal of refractory pollutants: It decomposes organic pollutants that
cannot be degraded
by conventional biochemical processes, such as phenols, pesticides, and polycyclic aromatic
hydrocarbons (PAHs), thereby reducing the chemical oxygen demand (COD) and total organic
carbon (TOC) of sewage.
2.Decolorization and deodorization: It oxidizes and decomposes chromophoric
groups (e.g.,
azo bonds) and odor-causing substances (e.g., hydrogen sulfide, ammonia compounds) contained
in sewage, making the effluent clear and free of peculiar odors.
3.Disinfection and sterilization: It rapidly destroys the cellular
structure of
microorganisms such as bacteria, viruses, and algae. It features high sterilization
efficiency and avoids residual chlorine and disinfection by-products (e.g., trihalomethanes)
generated by chlorine disinfection.
4.Improvement of wastewater biodegradability: It oxidizes macromolecular
and refractory
organic substances into small-molecular and easily degradable substances (e.g., carboxylic
acids, aldehydes), creating conditions for subsequent advanced treatments (e.g., biochemical
filtration).
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:
| Process Combination | Core Function | Applicable Scenarios |
|---|---|---|
| O₃ + Biological Activated Carbon (BAC) | Ozone oxidation breaks down organic matter, while activated carbon adsorbs residual pollutants and provides a carrier for microorganisms, which further degrades small-molecular organic matter. | Wastewater Reuse (e.g., Landscape Water, Miscellaneous Water) and Drinking Water Pretreatment |
| O₃ + Coagulation and Sedimentation | Ozone oxidation changes the surface charge of colloidal particles, enhances the adsorption and bridging effect of coagulants, and strengthens the removal of suspended solids and colloids. | Advanced Treatment of Sewage with High Turbidity and High Chroma |
| O₃ + Membrane Separation (e.g., Ultrafiltration/Reverse Osmosis) | Ozone pretreatment reduces the turbidity and organic matter content of sewage, mitigates membrane fouling, and extends the service life of membrane modules. | Preparation of High-Quality Reclaimed Water (e.g., Makeup Water for Industrial Circulating Water) |
III. Application Advantages and Precautions
1. Main Advantages
• No secondary pollution: Ozone is ultimately decomposed into oxygen
(O₂) after
oxidation, producing no residual pollutants and being environmentally friendly.
• Fast reaction rate: It can react quickly under normal temperature
and pressure
without complex reaction conditions, resulting in high treatment efficiency.
• Strong adaptability: It can operate stably within a relatively wide
pH range (6-9)
and temperature range, and is less affected by fluctuations in water quality.
2. Precautions
• Relatively high cost: Ozone production requires a large amount of
electrical energy
(usually using the corona discharge method), and its operating cost is higher than that of
traditional chlorine disinfection.
• Equipment corrosion: Ozone has strong corrosiveness, so
corrosion-resistant materials
(such as 316L stainless steel and polytetrafluoroethylene) must be used to manufacture
equipment and pipelines.
• Supporting tail gas treatment required: Unreacted ozone, if
discharged directly, will
harm human health (irritating the respiratory tract). It is necessary to treat the tail gas
through methods such as activated carbon adsorption or thermal decomposition.
The above is for reference only.