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How to treat nuclear wastewater in China?
Chemical precipitation is a method of precipitation between precipitant and trace radionuclide in wastewater. Most compounds such as hydroxide, carbonate and phosphate of radionuclides in wastewater are insoluble and can be removed during treatment.
The purpose of chemical treatment is to transfer and concentrate the radionuclides in wastewater into small-volume sludge, so that there is almost no radioactive residue in the precipitated wastewater, thus reaching the discharge standard.
The advantages of this method are low cost and good logarithmic radionuclide removal effect, and it can treat wastewater containing non-radioactive components and their concentrations and quite fluidized. The treatment facilities and technologies adopted have quite mature experience.
2. Ion exchange method
Ion exchange method adopts ion exchange resin, which is suitable for waste liquid with low salt content. When the salt content is high, the cost of treatment with ion exchange resin is higher than that of selective process. This is mainly because the resin with low selectivity has a great relationship with radionuclides. In the purification of radioactive wastewater, electrodialysis can improve the utilization efficiency of ion exchange process. ?
3. Adsorption method
Adsorption is an effective method to remove heavy metal ions from water by using porous solid substances. The key technology of adsorption method is the selection of adsorbent. Commonly used adsorbents include activated carbon, zeolite, kaolin, bentonite and clay. Among them, zeolite is cheap, safe and easily available. Compared with other inorganic adsorbents, zeolite has larger adsorption capacity and better purification effect.
The purification ability of zeolite is as high as 10 times that of other inorganic adsorbents, and it is a highly competitive water treatment agent. It is often used as an adsorbent in water treatment process, and has the functions of ion exchanger and filter.
4. Evaporation and concentration
Evaporative concentration method has high concentration coefficient and purification coefficient, and is mostly used to treat medium and high level radioactive waste water. The working principle of evaporation method is: radioactive waste water is sent to the evaporation device, and heated steam is introduced at the same time, so that water is evaporated into steam, while radionuclides are left in the water. The condensed water formed in the evaporation process is discharged or reused, and the concentrated solution is further solidified.
Evaporation concentration method is not suitable for treating wastewater containing volatile nuclides and easy to foam; Large heat energy consumption and high operating cost; At the same time, potential threats such as corrosion, scaling and explosion should be considered in design and operation. ?
In order to improve the steam utilization rate and reduce the operating cost, all countries spare no effort to develop new evaporators, such as vapor compression evaporator, thin film evaporator, vacuum evaporator and so on.
5. Membrane separation technology
Membrane technology is an efficient, economical and reliable method to treat radioactive wastewater. Membrane separation technology has been actively studied because of its advantages of good effluent quality, no phase change of materials and low energy consumption.
Membrane technologies used abroad mainly include microfiltration, ultrafiltration, nanofiltration, water-soluble polymer-membrane filtration, reverse osmosis (RO), electrodialysis, membrane distillation, electrochemical ion exchange, liquid membrane, ferrite adsorption filtration membrane separation and anion exchange paper membrane. ?
6, biological treatment method
Biological treatment methods include phytoremediation and microbial methods. Phytoremediation refers to a new in-situ treatment technology that uses the interaction between green plants and their rhizosphere indigenous microorganisms to remove pollutants in the environment.
Judging from the existing research results, the applicable types of bioremediation technology mainly include constructed wetland technology, rhizosphere filtration technology, plant extraction technology, plant solidification technology and plant evaporation technology. The experimental results show that almost all uranium in water can be enriched in plant roots.
7. Zero-valent iron infiltration reaction wall technology
Permeation reaction wall is a new method for in-situ removal of pollutants from polluted groundwater in developed countries such as Europe and America. PRB is generally installed in underground aquifer, perpendicular to the groundwater flow direction. When the polluted groundwater flows through the reaction wall under its own hydraulic gradient, the pollutants react with the reactive substances in the wall and are removed, thus achieving the purpose of pollution remediation.
This is a passive repair technology, which requires almost no manual maintenance and has low cost. As an important branch of PRB technology, Fe0-PRB technology has been studied and developed in many countries and many aspects of groundwater pollution control, and has achieved gratifying results in the study of reaction mechanism, the structure and installation of PRB, and the study of new active materials.
Chinese scholars have begun to study the active permeable wall technology represented by zero-valent iron for the remediation of radioactive wastewater from uranium tailings, and the research has achieved certain results.
harm
In terms of harm scope, considering the connectivity of the ocean, the nuclear waste water entering the sea will inevitably lead to the continuous spread of pollution scope under the action of ocean currents and so on, which can not be controlled. It can be said that it is very irresponsible to pollute the whole ocean by solving a country's problems.
Radioactive hazards are very concealed and difficult to be detected. When radioactive wastewater enters the environment, it will cause water and soil pollution, and then radionuclides can enter the human body through various channels, posing a threat to the environment and human health, and at the same time bringing anxiety and panic to the public's spirit and mind, which is not conducive to social stability.
Refer to the above content: Baidu Encyclopedia-Nuclear Wastewater
Baidu encyclopedia-radioactive wastewater treatment
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