Ozone is a widely used strong oxidizing treatment technology in the water treatment field. With its high efficiency, environmental friendliness and multi-functional properties, it has become a core process for water quality management in drinking water, industrial wastewater, municipal sewage and other scenarios. This article systematically breaks down the core principles, mainstream application scenarios, key processes, technical advantages and disadvantages, and industry development direction of ozone water treatment, to provide a comprehensive reference for technology application and selection.
Core Principles and Basic Characteristics of Ozone Water Treatment
1.1 Core Functional Principles
Ozone has an oxidation potential of 2.07V, making it a strong oxidant commonly used in the water treatment field.
It acts on pollutants in water through two pathways: direct oxidation and indirect oxidation.
Direct oxidation means ozone molecules directly react with pollutants, targeting and damaging the molecular structure of organic matter and the cell tissue of microorganisms.
Indirect oxidation means ozone decomposes in water to generate strong oxidizing intermediates such as hydroxyl radicals, which degrade various pollutants non-selectively.
The disinfection effect of ozone is mainly based on damaging the cell membrane, enzyme system and nucleic acid structure of microorganisms.
It can quickly inactivate bacteria, viruses, fungi, spores and all kinds of pathogenic microorganisms, blocking the disease risk of water bodies.
1.2 Core Basic Characteristics
Ozone has an extremely fast reaction speed.
The disinfection reaction can be completed within seconds to minutes, much faster than conventional chlorine-based disinfectants.
Ozone has no risk of secondary pollution.
After completing the reaction, ozone will quickly decompose into oxygen by itself, without persistent residue in the water body.
Different from chlorine-based disinfection, ozone treatment will not produce carcinogenic disinfection by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).
Ozone has a wide range of functions.
It has multiple effects including oxidation, disinfection, decolorization, deodorization, complex breaking and coagulation assistance, and can simultaneously solve various water quality problems of the water body.
Ozone has strong adaptability to water quality.
It can maintain stable treatment performance in the pH range of 4-10, adapting to the treatment needs of different industries and different water quality.
Core Application Scenarios of Ozone in Water Treatment
2.1 Advanced Treatment of Municipal Drinking Water
Ozone is one of the core technologies for advanced drinking water treatment.
China’s Standards for Drinking Water Quality has strict control requirements for indicators such as microorganisms, organic matter, and disinfection by-products.
Conventional tap water treatment processes are difficult to completely remove trace organic pollutants, odor substances and pathogenic microorganisms in water.
Ozone technology can specifically solve these pain points.
In the pre-oxidation link, low-dose ozone can damage the structure of algae and humus, improve the subsequent flocculation and sedimentation effect, and reduce the operating load of the filter tank.
In the advanced treatment link, ozone can degrade pesticide residues, endocrine disrupting chemicals, pharmaceuticals and other trace organic pollutants in water.
At the same time, it can efficiently remove the chromaticity and peculiar smell of the water body, and greatly improve the safety of drinking water quality.
At present, most newly built, renovated and expanded water plants in China have been equipped with ozone-biological activated carbon (O3-BAC) advanced treatment systems.
2.2 Industrial Wastewater Treatment
Industrial wastewater has complex water quality, and generally has the characteristics of high pollutant concentration, high toxicity and poor biodegradability.
Conventional biochemical treatment processes are difficult to achieve stable discharge up to the standard.
With its strong oxidation capacity, ozone technology has become a key technology for the treatment of various industrial wastewater.
In the treatment of printing and dyeing textile wastewater, ozone can quickly destroy the chromophore of dye molecules to achieve efficient decolorization.
At the same time, it can degrade refractory dyes such as azo and anthraquinone dyes, improve the biodegradability of wastewater, and solve the problem of unqualified effluent chromaticity and COD.
In the treatment of chemical and pharmaceutical wastewater, ozone can degrade toxic and harmful pollutants such as aromatic compounds, halogenated hydrocarbons and antibiotic residues.
It can reduce the biological toxicity of wastewater, break the molecular structure of refractory organic matter, and create conditions for subsequent biochemical treatment.
In the treatment of food processing wastewater, ozone can remove organic pollutants such as protein and oil in wastewater, simultaneously inactivate pathogenic microorganisms, and remove the peculiar smell of the water body.
In the treatment of electroplating wastewater, ozone can destroy the complex structure of heavy metal ions, achieve efficient complex breaking, and lay a foundation for the subsequent precipitation and removal of heavy metals.
2.3 Municipal Wastewater Reclamation and Reuse Treatment
China’s municipal sewage treatment has transformed from discharge up to standard to recycling and resource utilization.
The effluent of municipal sewage after secondary biochemical treatment still has residual refractory COD, chromaticity, pathogenic microorganisms and emerging pollutants.
This kind of effluent is difficult to meet the water quality standard of reclaimed water reuse.
Ozone advanced treatment process can quickly degrade residual organic matter in secondary effluent, remove the chromaticity of water body, and achieve efficient disinfection.
At the same time, it can degrade emerging pollutants such as antibiotics and microplastics in water, and greatly improve the effluent quality.
The treated reclaimed water can meet the requirements of reuse scenarios such as municipal greening, road cleaning, industrial cooling, and landscape water supplement.
Ozone treatment can also remove odorous substances such as hydrogen sulfide and methyl mercaptan generated in the sewage treatment process, and improve the environmental quality of the plant and surrounding areas.
2.4 Aquaculture Water Treatment
The aquaculture industry is transforming towards high-density, factory-based and recirculating aquaculture.
Water quality management is the core of aquaculture benefit and disease prevention and control.
In the aquaculture water body, residual bait and excrement of aquatic animals will continuously accumulate pollutants such as ammonia nitrogen, nitrite and organic matter.
These substances will breed pathogenic microorganisms, cause aquatic diseases, and lead to aquaculture losses.
Ozone can achieve multiple treatment effects in recirculating aquaculture systems (RAS).
It can quickly degrade harmful substances such as nitrite and ammonia nitrogen in the water body, and decompose organic pollutants generated by residual bait and feces.
It can efficiently inactivate pathogenic organisms such as bacteria, viruses and parasite eggs in the water body, and reduce the incidence of aquatic diseases.
At the same time, it can improve the transparency of the water body, remove the peculiar smell of the water body, and improve the quality of aquaculture water.
Equipped with a precise dosing and residual control system, it can avoid the damage of ozone residue to aquatic animals, and realize green and efficient aquaculture.
2.5 Water Treatment for Recreational Water Bodies
For recreational water bodies such as swimming pools, water parks and hot springs, the traditional treatment is mainly chlorine-based disinfection.
Chlorine-based disinfection is easy to produce pungent odor, causing irritation to human skin and eyes.
At the same time, it will produce harmful disinfection by-products such as trihalomethanes, which have health risks.
Ozone technology can replace or supplement the chlorine-based disinfection process.
It can quickly inactivate pathogenic microorganisms in the water body to ensure the hygienic safety of the water body.
It can efficiently decompose pollutants such as sweat, oil and urea brought in by the human body, and keep the water body clear and transparent.
No irritating by-products are produced during the treatment, which greatly improves the comfort and safety of water body use.
At present, ozone technology has become the preferred water treatment technology for high-end swimming pools, parent-child swimming pools and hot spring water bodies.
Main Supporting Processes and Key Control Points of Ozone Water Treatment
3.1 Main Supporting Combined Processes
Single ozone oxidation has certain limitations.
It has limited degradation effect on some persistent organic pollutants, and the ozone utilization rate is low.
The industry generally adopts combined processes to amplify the treatment effect and improve the operating economy.
Ozone-Biological Activated Carbon Combined Process
This is the most widely used combined process at present, which is mainly used in drinking water advanced treatment and wastewater reclamation and reuse scenarios.
The process fully combines the strong oxidation capacity of ozone with the adsorption and biodegradation capacity of activated carbon to form a synergistic effect.
Ozone first oxidizes macromolecular refractory organic matter in water into small molecular easily degradable substances.
Small molecular organic matter is more easily adsorbed by activated carbon, and can also be decomposed and utilized by microorganisms on the surface of activated carbon.
Oxygen generated by ozone decomposition can increase the dissolved oxygen content in water, providing sufficient growth conditions for aerobic microorganisms.
This process can greatly extend the regeneration cycle of activated carbon and reduce the overall operating cost.
Ozone Advanced Oxidation Processes (AOPs)
This process combines ozone with hydrogen peroxide, ultraviolet light, catalysts, etc., to stimulate the generation of hydroxyl radicals with higher oxidation potential.
Hydroxyl radicals have an oxidation potential of 2.8V, and can degrade most organic pollutants non-selectively.
The mainstream processes include ozone/hydrogen peroxide process, ozone/ultraviolet process, and heterogeneous catalytic ozonation process.
These processes are mainly used in scenarios such as refractory industrial wastewater treatment, high-concentration organic wastewater pretreatment, and advanced removal of emerging pollutants.
It can greatly improve the degradation efficiency of pollutants, reduce ozone dosage, and improve treatment economy.
3.2 Core Operation Control Points
The effect of ozone water treatment mainly depends on the process design and precise control of operating parameters.
Ozone Dosage Control
Insufficient dosage cannot achieve the expected treatment effect.
Excessive dosage will greatly increase the operating cost, and even produce unnecessary by-products.
The dosage varies greatly in different scenarios.
For drinking water pre-oxidation, the dosage is usually 0.5-1.5mg/L.
For advanced drinking water treatment, the dosage is usually 1-3mg/L.
For industrial wastewater treatment, it needs to be adjusted to tens of mg/L or even higher according to the pollutant concentration.
It is necessary to be equipped with an online monitoring system to adjust the dosage in real time according to the influent water quality.
Gas-Liquid Mass Transfer Efficiency Control
The solubility of ozone in water is limited, and the mass transfer efficiency directly determines the ozone utilization rate.
Common high-efficiency mass transfer methods include microporous aeration, jet aeration, gas-liquid mixing pump, static mixer, etc.
It is necessary to select the appropriate mixing method according to the water quality, water volume and treatment scenario.
Maximize the efficiency of ozone dissolution and utilization, and reduce the loss of tail gas emission.
Contact Reaction Time Control
It is necessary to design a reasonable ozone contact tank according to the treatment target.
Ensure sufficient contact reaction time between ozone and water body.
For drinking water disinfection, the contact time usually needs to be no less than 10 minutes.
For the oxidation of refractory organic matter in industrial wastewater, a longer contact reaction time is required.
Safety and By-product Control
Undissolved and unreacted ozone tail gas will cause air pollution if discharged directly.
It is necessary to be equipped with an ozone tail gas decomposition device, which decomposes ozone into oxygen before discharge through heating, catalytic decomposition and other methods.
For drinking water containing bromide ions, it is necessary to strictly control the ozone dosage and reaction conditions to avoid the generation of disinfection by-products such as bromate.
Ozone is highly corrosive, so the system equipment, pipelines and valves need to be made of corrosion-resistant materials such as 316L stainless steel and polytetrafluoroethylene.
It is necessary to be equipped with ozone concentration online monitoring, leakage alarm, emergency ventilation and other systems to ensure the safety of personnel and equipment.
Advantages and Application Limitations of Ozone Water Treatment Technology
4.1 Core Technical Advantages
Broad and efficient treatment effect.
It has multiple functions including oxidation, disinfection, decolorization and deodorization, and can simultaneously solve a variety of water quality problems.
It has a good treatment effect on refractory organic matter, drug-resistant pathogenic microorganisms and emerging pollutants that are difficult to handle by conventional processes.
High environmental protection and safety.
It decomposes into oxygen by itself after the reaction, no persistent residue, no toxic and harmful disinfection by-products, and avoids the risk of secondary pollution.
High reaction efficiency and small floor area.
Ozone reacts quickly with pollutants, requires short contact time, and the floor area of supporting facilities is much smaller than that of conventional treatment processes.
It is suitable for renovation and expansion projects with limited site.
Convenient operation and management.
Ozone is prepared and used on site, without the need for pharmaceutical storage, transportation, metering and dosing links, reducing labor management costs.
It avoids the safety risk of storage and transportation of chemical agents.
Strong adaptability to water quality.
It is less affected by the pH value of the water body, can adapt to the treatment needs of different industries and different water quality, and has a wide range of application scenarios.
4.2 Existing Application Limitations
High operating energy consumption and cost.
The core energy consumption of ozone preparation is relatively high. For conventional ozone generators, the power consumption for preparing 1kg of ozone is about 8-15kWh.
For scenarios with large water volume and high pollution load, the operating cost is much higher than that of conventional processes such as chlorine-based processes, which limits its promotion in low-cost scenarios.
Insufficient economy of separate treatment.
For industrial wastewater with high COD concentration, using ozone treatment alone requires extremely high dosage, and the treatment cost increases significantly.
It usually needs to be combined with biochemical, flocculation sedimentation, filtration and other processes, and cannot be used as a single main process.
Great limitations in storage and transportation.
Ozone has extremely poor chemical stability and decomposes quickly at room temperature, so it cannot be stored for a long time or transported over a long distance.
It must be prepared and used on site, which has certain requirements for on-site supporting facilities and operation and maintenance capabilities.
Risks in by-product management and control.
For water bodies containing high concentration of bromide ions, carcinogenic by-products such as bromate may be generated during ozone oxidation.
It is necessary to strictly control the reaction conditions, which increases the difficulty of process management and control.
High requirements for equipment and materials.
The strong oxidizing property of ozone has extremely high requirements on the material and sealing performance of equipment such as generators, pipelines and instruments, and the initial equipment investment cost is relatively high.
Improper material selection is prone to equipment corrosion, leakage and other problems, which increases the difficulty of operation and maintenance.
Industry Development Trend of Ozone Water Treatment Technology
With the continuous tightening of environmental protection policies and the continuous improvement of water quality standards, ozone water treatment technology is developing towards the direction of low energy consumption, high efficiency, intelligence and scenario-based application.
Low-energy ozone preparation technology continues to iterate.
The industry focuses on the research and development of new dielectric barrier discharge technology, high-efficiency pure oxygen source preparation technology, and low-energy discharge modules.
The core goal is to reduce the unit power consumption of ozone preparation, reduce the operating cost from the source, and expand the application scenarios.
Catalytic ozonation technology is continuously upgraded.
Heterogeneous catalytic ozonation technology has become a research and development hotspot.
The research, development and application of efficient, stable and low-cost catalysts can greatly improve the ozone utilization rate and pollutant degradation efficiency.
It can reduce ozone dosage, solve the pain points of refractory organic wastewater treatment, and promote the large-scale application of advanced oxidation processes.
Intelligent control systems are fully popularized.
Through online water quality monitoring and ozone concentration online monitoring, combined with PLC intelligent control system, it can automatically adjust the ozone output and dosage in real time according to the changes of influent water quality and water volume.
While ensuring the stable and up-to-standard effluent, it can minimize energy consumption and operating costs, and realize refined and unmanned operation and maintenance.
The multi-process collaborative combination system is continuously improved.
Ozone technology will be deeply integrated with ultrafiltration, reverse osmosis and other membrane treatment processes, biochemical treatment processes, advanced reduction processes.
Form an integrated treatment system adapted to different scenarios to meet the diversified needs of wastewater recycling, drinking water safety guarantee, refractory wastewater treatment, etc.
The application scenarios of emerging pollutant treatment are expanding rapidly.
For emerging pollutants in water bodies such as antibiotics, endocrine disrupting chemicals, perfluorinated compounds and microplastics, which are difficult to be treated by conventional processes, ozone advanced oxidation processes have significant technical advantages.
With the introduction of relevant water quality control standards, it will become a new application growth point of ozone technology.
