Discussion on the development of water supply treatment technology
Abstract: Water is closely related to people's life and production, and water is an indispensable material basis for ensuring people's life and developing industrial production. In recent years, problems such as population growth, uneven distribution of water resources, and increased pollution have led to an increasing shortage of water resources. Therefore, water treatment technology has been improving. This paper aims to introduce some basic technologies of water supply treatment.
[Keywords:] modern advanced oxidation membrane technology to treat pollutants
1. Modern processing technology
1. 1 chemical oxidation
Chlorine oxidation is usually used in water treatment. When the organic pollution has not been removed, it will produce more harmful disinfection by-products. At present, the application of KMnO4 tone compound (a special commodity) is gradually expanding, and good results have been achieved in oxidizing organic matter and improving coagulation. Ozone pre-oxidation can improve the biodegradability of organic matter, remove odor, decolorize and remove iron and manganese, but it is often combined with subsequent ozone advanced treatment. Use activated carbon.
1.2 Toner with adsorbent
Powdered carbon has the advantages of strong adsorption capacity, flexible dosing and high pollutant treatment efficiency. However, because of its high consumption (about 105 yuan /m 3), it is generally only used to eliminate impact pollution, and the dosage needs10 ~ 20 mg/L. Now this technology has been applied to some water pollution incidents, and in addition, raw water can be controlled by this technology.
1.3 pH adjustment
Because of adding acid and alkali, the operation cost increases, and inorganic ions are added to raw water, which is rarely used in China. There are also many studies in this field abroad, so I won't elaborate here. However, it has a good effect on controlling the pH value of raw water and removing some pollutants, which is also widely recognized in the industry.
1.4 biological pretreatment
Since 1970s, biological treatment technology has been more and more widely used in biological treatment of urban water supply, including biological contact oxidation, biological rotary table, biological fluidized bed, biological filter oxidation, biological activated carbon filter and membrane bioreactor. Biological pretreatment is to remove organic pollutants such as ammonia nitrogen and inorganic substances such as iron and manganese from water by using the life activities of microorganisms, so as to improve the coagulation and sedimentation performance of water, make the follow-up process play a better role and improve the effluent quality.
2. New water treatment technology
2. 1 advanced oxidation technology
Advanced oxidation technology is a new type of water treatment technology, which has attracted extensive attention and been widely used in water treatment. Advanced oxidation technologies include ozone oxidation, supercritical water oxidation, photocatalytic oxidation and ultrasonic cavitation oxidation.
2. 1. 1 ozone oxidation technology
Because of its high redox potential in water, ozone is often used for sterilization, deodorization, deodorization and decoloration, and is widely used in drinking water treatment. In recent years, due to the use of chlorine oxide in water supply, circulating water treatment and wastewater treatment, chloroform may be produced. Three? The role of ozone in water treatment has been paid more and more attention. However, there are still some problems in the application of ozone in wastewater treatment, such as high ozone production cost, low utilization rate and high ozone treatment cost; The reaction selectivity between ozone and organic matter is strong, so it is impossible for ozone to completely mineralize pollutants in low dose and short time, and the intermediate products produced by decomposition will prevent further oxidation of ozone. Therefore, improving the utilization rate and oxidation capacity of ozone has become the research focus of advanced ozone oxidation. Advanced ozone oxidation technology is a combination of ozone oxidation and various water treatment technologies to form hydroxyl radicals with stronger oxidation and lower reaction selectivity.
2. 1.2 supercritical water oxidation technology
What is the combination of supercritical water reaction and oxidation? Supercritical water oxidation (SCWO)? Technology, more applications. Supercritical water has excellent solvent characteristics, which increases the conductivity and ionic value. Conductivity, indicating the polarity of the solvent, is high (78) at normal temperature and pressure, and nonpolar at high temperature and pressure, such as hexane and methanol, which is equivalent to the conductivity of weakly polar organic solvents (about 2 ~ 30). So it is possible for water to dissolve organic matter at high temperature and high pressure.
SCWO technology has the following characteristics:
1) completely decomposes organic matter into water and carbon dioxide, making it harmless.
2) No harmful by-products such as dioxins are produced.
3) The reaction speed is fast, the processing capacity per unit time is large, and the equipment is miniaturized.
4) Unlike an incinerator, it does not need a chimney and does not emit smoke.
It is easy to control the decomposition reaction of water or the reaction of atomic groups at critical temperature, which is the advantage of supercritical water as a reaction solvent. Wastewater treatment can be carried out without acid and alkali, which is an excellent environmental treatment technology.
2. 1.3 photocatalytic oxidation technology
The so-called photocatalytic oxidation reaction is a chemical reaction under the action of light The activation energy of photochemical reaction comes from photon energy, and photoelectric conversion and photochemical conversion have always been very active research fields in solar energy utilization. Photocatalytic oxidation technology combines O2, H2O2 and other oxidants with light radiation through photo-excited oxidation. The light used is mainly ultraviolet light, including uv-H2O2, uv-O2 and other processes, which can be used to treat refractory substances such as CHCl3, CCl4 and PCBs in sewage. In addition, in Fenton system with ultraviolet light, there is a synergistic effect between ultraviolet light and iron ions, which greatly accelerates the decomposition of H2O2 into hydroxyl radicals and promotes the oxidative removal of organic matter.
2. 1.4 ultrasonic cavitation oxidation technology
Ultrasonic cavitation refers to a series of dynamic processes such as vibration, growth, contraction and collapse of tiny bubble nuclei in water strengthened by ultrasonic waves. Ultrasonic empty talk technology is to convert organic matter in water into CO2, water, inorganic ions, organic acids and other components through sound wave decomposition. Ultrasonic cavitation technology has the advantages of little or no pollution, simple equipment and sterilization, and is a new technology with great potential for water treatment. But at this stage, ultrasonic empty talk technology is mainly used in laboratory small water treatment, and it is still in the basic research stage. In order to improve the degradation speed and reduce the cost at the same time, water treatment workers at home and abroad have successively researched and developed new technologies that combine ultrasound with other technologies, such as ozone/ultrasound combined process. In the experimental study of ozone/ultrasonic combined treatment of phenol-containing water, good treatment results have been achieved.
2.2 membrane treatment technology
With people's gradual understanding of membranes, various synthetic membranes came into being, with various types and different functions, but all of them have a similar feature-selective permeation. Membrane can be broadly defined as a thin barrier with selective permeability between two phases.
Membrane activated sludge process is a new water treatment technology which combines separation technology and biotechnology organically. The membrane separation equipment is used to intercept the activated sludge and macromolecular organic matter in the biochemical reaction tank, which saves the secondary sedimentation tank. Therefore, the concentration of activated sludge is greatly increased, and the hydraulic retention time and sludge retention time can be controlled separately, while the refractory substances are continuously degraded in the reaction tank. Therefore, the membrane treatment process greatly enhances the function of biological treatment through membrane separation technology.
3. Conclusion
At present, conventional water treatment technologies such as coagulation, sedimentation, filtration and disinfection are widely used in water supply treatment in China, which have the advantages of low water treatment cost and good average treatment effect. In addition, the pollution of water source is aggravated, and the removal effect of some organic pollutants by conventional water treatment process is not good. Emerging water treatment technology provides support for the improvement of water quality. Ozone-activated carbon treatment, membrane technology and other water treatment technologies have unparalleled advantages in removal efficiency and harmlessness, and the experience of developed countries also shows the reliability of these technologies. With the progress of science and technology and the development of materials science, the cost of these new technologies is gradually decreasing. Therefore, we can foresee that the future water treatment will develop in a safer, more efficient and more environmentally friendly direction.
refer to
[1] Lu Yukang, Li Tang. Energy saving in water treatment and application of new energy. Beijing: Chemical Industry Press, 20 10/0,5.
Yuan, person. Principle and application of new water treatment technology. Beijing: Chemical Industry Press, 2006, 1
[3] Lu Yukang. New water treatment technology and energy self-sufficiency. Machinery Industry Press, 2008, 8.
About the author:
Kan Shasha (1992-), female, Han nationality, native of Songyuan, Jilin Province, majoring in water supply and drainage engineering, School of Water Resources and Environment, Zhengzhou University.
Guo Dandan (199 1-), female, Han nationality, from Xuchang, Henan Province, majoring in water supply and drainage engineering, School of Water Resources and Environment, Zhengzhou University.
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