The development and characteristics of ozone oxidation technology are introduced, the combined ozone technology and its application in the treatment of industrial wastewater are discussed, and the development status and trends of ozone oxidation technology are summarized.
Ozone is an earlier-discovered substance with strong oxidizing and sterilizable properties, but it is not widely used because it is more expensive than the commonly used chlorine oxidants. As people discovered that chlorine has the disadvantage of destroying the taste, the production of chlorophenol and chloramine, and the production of highly volatile halogenated hydrocarbons, ozone has a new space to be used. People have developed ozone production technology and have found a new process. At the same time, the application fields, chemical properties and reactants of ozone have been further studied.
1. Development and characteristics of ozone oxidation technology
Ozone is highly oxidizing and can oxidize many compounds. Therefore, ozone oxidation technology is widely used in water treatment.
Ozone oxidation technology has the following characteristics:
(1) Ozone not only has good rapid sterilization and disinfection properties, but also has a very high oxidizing power to oxidize organic and inorganic compounds, which can remove substances that are difficult to remove by other water treatment processes.
(2) The reaction of ozone is complete and fast, so that the volume of the structure can be reduced.
(3) Residual ozone can be quickly converted into oxygen, which can increase dissolved oxygen in water, with high efficiency, without producing sludge and causing secondary pollution.
(4) While improving the purification effect, sterilization and disinfection, it can also remove odor and smell.
(5) Electricity and air for preparing ozone do not need to be stored and transported. The ozonation device occupies a small area, and the operation and management are simple. It is especially suitable for improving the water quality and quantity of the original water plant.
2. Ozone combined technology
There are many ozone combined technologies, which can be generally divided into the following types: ozone ultrasonic method, ozone activated sludge method, ozone membrane treatment method, ozone coagulation method, ozone biological activated carbon adsorption method. These methods have their own advantages and disadvantages for different wastewaters, so different technologies can be used to achieve better results according to the different difficult-to-degrade and toxic substances in the wastewater. The following briefly introduces the ozone ultrasonic method and the ozone biological activated carbon adsorption method.
2.1 Ozone / ultrasonic method
Ultrasonic waves can effectively degrade difficult-to-degrade organic pollutants in wastewater. The combined use of ultrasonic waves and ozone can improve the efficiency of organic matter degradation and reduce operating costs. In 1976, DAHI had discovered that ultrasound could strengthen the treatment of ozone wastewater. When he used 20kHz ultrasound to strengthen ozone oxidation to treat the effluent of biological wastewater treatment plants, he found that this technology could reduce the amount of ozone added by 50%.
2.2 Ozone / biological activated carbon adsorption method
The ozone biological activated carbon process (O3-BAC) is a process that combines ozone chemical oxidation with activated carbon physical, chemical adsorption, and biological oxidation degradation technologies. The process has the characteristics of low treatment cost, high removal efficiency of organic matter, and stable effect.
Raw water is oxidized by ozone, which can decompose large organic matter into small molecular organic matter, improve the biodegradability of organic matter and provide sufficient oxygen, so that these organic matters are more easily adsorbed by activated carbon, and the adsorbed organic matters are to maintain the life of microorganisms in the carbon bed. Activities provide nutrition; at the same time, due to sufficient oxygen supply, aerobic microorganisms multiply and grow into biofilms on the surface of activated carbon to degrade the adsorbed small molecule organic matter. This allows activated carbon adsorption and microbial degradation to proceed simultaneously on the carbon bed, thereby greatly extending the working cycle and efficiency of activated carbon.
3. Application of ozone combined technology in industrial wastewater treatment
3.1 Treatment of medical wastewater
Most medical wastewater has high COD and poor biodegradability. It is uneconomical to treat it with physical and chemical methods alone. Ordinary biochemical treatment is not feasible at all, so ozone pretreatment can be used first, mainly to improve the biodegradability of wastewater. Subsequent biological treatments reduce difficulty while reducing COD.
3.2 Treatment of printing and dyeing wastewater
Printing and dyeing wastewater has serious pollution to the environment. Its large amount of water, large fluctuations in water quality, complex and high content of pollutants, high chroma, chemical oxygen demand (COD) and biochemical oxygen demand (BOD) are high at home and abroad. One of the difficult to treat industrial wastewater. Ozone oxidation technology is based on the strong selectivity of the ozone molecule reaction, which can directly react with dyes containing double bonds to open the ring and decolorize the dye and improve the biodegradability of wastewater. In addition, ozone is converted into strongly oxidizing substances such as 强 OH under the action of ultraviolet (UV), and reacts with organic substances to break the unsaturated bonds in the chromophore of the dye, generating a small, colorless organic acid. , Aldehyde, etc., to achieve the purpose of decolorization and degradation of organic matter. The combination of O3 / UV oxidation and conventional biochemicals is used to first remove most of the biodegradable organic compounds by biochemical methods, and the remaining non-biochemical pollutants are oxidized with O3 / UV to reduce ozone consumption and treatment costs, and improve the quality of effluent water.
3.3 Treatment of phenolic wastewater
Phenol-containing wastewater is one of the more common and severely hazardous industrial wastewater. Phenol is a recognized carcinogenic, teratogenic, and mutagenic “tri-drug” substance. The treatment of industrial phenol-containing wastewater has become an urgent problem in industrial wastewater. One of the problems. Studies have shown that for coking plant wastewater with a phenol content of 227mg / L, a pH value of 7.3-7.6, and a water temperature of 13-40C, after ozone oxidation treatment, the phenol content in the water is reduced by 98%.
3.4 Treatment of landfill leachate
Landfill leachate is a highly polluting high-contaminant organic wastewater. Among them, there are 77 kinds of organic pollutants, of which five are carcinogens and auxiliary carcinogens. It has been included in the "black list" of priority pollutants in the environment in China. . And the landfill leachate will cause great pollution to the surrounding environment, landfill soil and groundwater. Feng Xudong and others used bio-ozone oxidation technology to treat landfill leachate. Experiments show that after ozone oxidation, the CODOF value of the landfill leachate biological treatment effluent can be effectively reduced; after the landfill leachate biological treatment effluent ozone oxidation, its biological There is an extreme value of degradability with the increase of oxidation time. Combined with the economics of treatment, the combined technology of bio-ozone-bio can be used to treat landfill leachate.
4. Development status and trends of ozone technology
(1) With the widespread application of ozone technology in water treatment, it is recognized that the key to ozone technology is its reaction mechanism with pollutants in water. There is currently no clear conclusion on this aspect, and further research is still underway.
(2) The generation efficiency of ozone and the frequency of the power supply have a positive growth relationship. Increasing the frequency of the power generation of ozone has been an important research direction. At present, the international standard ozone generator products have a power frequency of up to about 20 kHz.
(3) Due to the strong oxidizing, corrosive and toxic nature of ozone, the materials used to process the process elements must be highly resistant to corrosion and oxidation. This makes the cost of ozone treatment higher and is not conducive to the widespread promotion of ozone technology. Reducing the cost of ozone treatment technology has become one of the main tasks of ozone technology research.
(4) The current development trend of ozone generators is that the size is getting smaller and smaller, the energy consumption is getting lower and lower, the electric energy conversion rate is getting higher and higher, the yield is getting higher and higher, the degree of automation of its control is getting higher and higher, Applications are getting wider and wider, and industry development is also accelerating.