Since the beginning of the new century, with the sustained and rapid economic and social development, people are engaged in more active production activities than ever before. The rapid economic development has brought many uncertain negative effects, which are increasingly prominent in environmental issues. Today, urban industrial enterprises are developed under the market regulation of commodity economy to adapt to or alleviate the contradiction between supply and demand in commodity society. Therefore, the categories and products of industrial enterprises are diverse, and the composition of sewage is also very complicated. In view of the analysis of the present situation of industrial water pollution, the following methods should be adopted to control industrial water pollution:
1. membrane separation method
In the process of membrane separation, the components generally do not change phase, so the energy consumption is low and the operating temperature is around room temperature. This is an energy-saving technology. The membrane separation range is wide, and it can be used regardless of inorganic matter or organic matter, bacteria or mineral particles in industrial wastewater. There are many systems suitable for membrane separation, most of which can be used for membrane separation. The membrane separation device is simple, easy to control and can be operated continuously. But there are also some problems: the thermal stability and chemical stability are not high, the flux and selectivity of the membrane need to be further improved, and the prevention and treatment of membrane pollution and concentration polarization. Industrial wastewater treatment is an important application field of membrane separation. Microporous membranes and ultrafiltration membranes have large pore sizes and are often used as pretreatment or post-treatment before and after advanced treatment. Because the membrane separation process is basically a physical process, there is no need to add other chemicals and no by-products. When it is used for drinking water treatment, it can greatly improve the water quality.
2. Electric field processing method
The electric field treatment method is to apply an electric field to the industrial polluted water to be treated and observe the changes of physical and chemical properties of the water system. These properties include the changes of density, absorbance and conductivity of water system and their effects on scaling. Electric field treatment can be divided into high-voltage electrostatic field method, high-frequency electric field method and electronic treatment method according to different water pollution conditions.
2. 1 high voltage electrostatic method
The electric field intensity of high-voltage electrostatic field is 3000-5000 volts/cm. When American scholars add 10000V high pressure to industrial raw polluted water, it produces excellent scale inhibition effect. They believe that this scale inhibition is caused by the weak current generated by flowing water under the action of electric field. The compounds that form scale are mostly ionic compounds, which are composed of positive and negative ions. When an electric field is applied to water, ions will be attracted by the electric field and it is difficult to combine into solids. 1At the end of 1970s, Japan combined the electrostatic descaler with the water supply tank and degasser for industrial water supply treatment, and also achieved the purpose of scale prevention and corrosion inhibition by canceling the chemical combination and adding chemicals. 1In the late 1970s, China developed an electrostatic water processor, which was applied in some industrial water treatment plants. High voltage electrostatic field method can not only prevent and remove scale, but also inhibit corrosion and eliminate bacteria in industrial wastewater.
2.2 High magnetoelectric field method
The electric field intensity of high frequency electric field method is not large, generally below 1 000 V/cm, while the electric field frequency is high, generally above 10Mnz. The experiment shows that the scale inhibition rate increases with the increase of electric field frequency when the flow rate of industrial sewage is constant. When the frequency is above 10MHZ, the flow rate has little effect on the scale inhibition rate. When the visible frequency is high enough, the scaling of industrial wastewater can be prevented in a short time. The scale inhibition effect may be that under the action of high frequency electric field, the surface of very small particles is charged, which hinders the normal growth of particles. From the electron microscope photos before and after treatment, the solid forms in industrial polluted water are obviously different.
2.3 Electronic processing method
The difference between electronic treatment method and the first two electric field methods is that this method directly introduces a small current into industrial sewage, so the device consists of a DC regulated power supply and a processor. The center of the tubular processor is provided with a metal anode, and the shell of the processor is a cathode. This processor was first developed in the United States in the1970s, and it was also produced in China at the end of the1980s. Chen et al. have shown that the electric field will also affect the structure of industrial polluted water, which will break some hydrogen-oxygen bonds in the water and lead to excessive superoxide anion free radicals, hydrogen peroxide and free protons in the water. Among them, the breaking of hydrogen-oxygen bond is to estimate the additional energy of water molecules by electric field: the longitudinal relaxation time of proton nuclear magnetic resonance is measured by NMR spectrometer to confirm that there are excessive superoxide anion radicals in water after electric field treatment, which are paramagnetic like oxygen molecules; The change of hydrogen peroxide concentration in the system before and after electric field treatment can be measured by luminol chemiluminescence phenomenon with photon counter.
3. Magnetic field processing method
Magnetization method has obvious anti-scaling effect on industrial wastewater. In addition, the experiment shows that magnetized water can improve the ion exchange capacity of resin and can be used as pretreatment before ion exchange. Magnetized water used in concrete can shorten curing time, improve strength, increase frost resistance and chemical stability. The treated magnetized drinking water also has the function of eliminating human gallstones. Magnetic water treatment technology can also be used to treat oily industrial sewage. Compared with other methods, magnetic separation and purification technology is more thorough and has no secondary pollution. Magnetic materials (such as nickel-copper-zinc ferrite, etc. ) into powder, put it into oily industrial wastewater and stir it, and use magnetic powder to absorb oil. Then through the magnetic separation device, the oil-adsorbed magnetic powder stays in the magnetic field and the water is separated. Modified magnetic powder method can treat the surface of magnetic powder with suitable materials to make it lipophilic. If treated with paraffin wax, higher fatty acids, etc. The surface is covered with an oleophilic and hydrophobic film. This modified magnetic powder is added to oily sewage, which increases the affinity for oil, and the oil and magnetic powder condense into mud and sink. Finally, the sludge is separated by magnetic field.
4. Biological treatment of industrial water pollution
4. 1 traditional biological method
Traditional biological treatment methods of industrial wastewater include activated sludge process, oxidation pond biofilter, biological turntable and so on. Activated sludge process is the most important traditional biological method, which uses aeration tank to treat wastewater, and microorganisms can purify fresh wastewater. Active oil substances are usually inoculated, cultivated and domesticated, and are composed of impurities such as bacteria and protozoa. Oxidation pond is the most primitive biological water treatment method, which can use ponds and depressions without additional facilities. Because of its poor treatment effect, artificial strengthening conditions were added at the end of 1960 s, which developed into a new oxidation ditch technology. Both biological filter and biological turntable use biofilm attached to filter material. This method is superior to the activated sludge method in some aspects. The traditional biological system consists of water, pollutants, microorganisms and oxygen. Generally, this natural treatment system will appear in places with industrial sewage. Activated sludge is not only the carrier of microorganisms, but also the product of microbial metabolism. During the operation of the system, air is continuously blown in from the boundary, and the oxygen in it is dissolved in the industrial sewage, and interacts with pollutants through the catalysis of biological enzymes. Pollutants are generally carbon-containing organic substances, which will be degraded in stages or completely under suitable conditions and eventually become carbon dioxide and water. There are many kinds of microorganisms in activated sludge, which can survive normally at near normal temperature. The treatment system has simple structure, and its advantages are many kinds of pollutants, high efficiency in treating various organic substances, little influence by climatic conditions and simple management. The application of this technology began in 19 14, and it has been the main treatment method for urban sewage and some industrial wastewater for a long time. Due to the low concentration of pollutants and oxygen in general industrial wastewater, the specificity of microorganisms is not high, and the oxidation rate of organic matter is slow, which leads to the main shortcomings of this system, such as long treatment period, large area and high operating cost.
4.2 Enzymatic treatment
When microorganisms come into contact with organic substances in industrial sewage, many chemical reactions will occur, such as redox, decarboxylation, denitrification, dehydration and hydrolysis. These effects are not the direct reaction between microorganisms and organic matter, but the degradation of organic matter by enzymes produced by microbial cells through a series of catalytic stages. Because of genetic variation and rapid propagation, the enzyme system in microorganisms has strong adaptability to the environment and can be used to treat different industrial wastewater. According to the characteristics of microorganisms, it can be divided into aerobic method and anaerobic method. Aerobic method is widely used, and anaerobic method is also valued. The biological oxidation of organic compounds is usually carried out in stages, and the initial biological degradation only causes the change of the parent structure of the compound, that is, the formation of intermediate products. The final biodegradation can be completely inorganic.
summary
To sum up, this study analyzes the pollution control of industrial water through several treatment methods of industrial polluted water. If these industrial wastewater are directly discharged or improperly treated, it will affect the self-purification of water bodies, thus deteriorating the water quality. Due to the complex composition of industrial wastewater, it is often necessary to form a treatment system by several methods to complete the required treatment function. Therefore, great progress has been made in chemical method, physical-chemical method and biological method applied to industrial wastewater treatment, so the research and development of efficient and economical new technologies applied to industrial wastewater treatment will become a new environmental protection research hotspot in the next few years.
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