What are the treatment methods of industrial wastewater？

1. Multi-effect evaporation crystallization technology

In the treatment process of industrial saline wastewater, industrial saline wastewater enters the low-temperature multi-effect concentration and crystallization device, and is separated into desalinated water (desalinated water may contain traces of low-boiling organic matter) and concentrated crystallization process through 3-6 effect evaporation and condensation. Crystal slurry waste liquid; inorganic salts and some organic substances can be crystallized and separated, and incinerated as inorganic salt waste residue; drum evaporator can be used for concentrated waste liquid of organic substances that cannot be crystallized to form solid waste residue and incinerated; desalinated water can be returned to the production system instead of softening water is used. The low-temperature multi-effect evaporation, concentration and crystallization system can not only be used in the concentration process and crystallization process of chemical production, but also in the evaporation concentration and crystallization process of industrial salt-containing wastewater. The multi-effect evaporation process only uses steam in the first effect, so the required amount of steam is saved, the heat in the secondary steam is effectively utilized, the production cost is reduced, and the economic benefit is improved.

 

2. Biological Law

Biological treatment is one of the most commonly used methods for wastewater treatment. It has the characteristics of wide application range, strong adaptability, economical efficiency and harmlessness. In general, the commonly used biological methods include traditional activated sludge method and biological contact oxidation method.

(1) Traditional activated sludge method

Activated sludge method is an aerobic biological treatment method of sewage, which is currently the most widely used method for treating urban sewage. It can remove dissolved and colloidal biodegradable organic matter and suspended solids and other substances that can be adsorbed by activated sludge from sewage, and can also remove part of phosphorus and nitrogen. The activated sludge method has a high removal rate and is suitable for treating wastewater with high water quality requirements and relatively stable water quality. However, it is not good at adapting to changes in water quality, and the oxygen supply cannot be fully utilized; the air supply is evenly distributed along the pool water, resulting in insufficient oxygen in the front section and excess oxygen in the rear section; the aeration structure is huge and covers a large area.

(2) Biological contact oxidation method

The biological contact oxidation method is a method of organic sewage treatment mainly using microorganisms (ie biofilms) attached to the surface of some solid objects. The biological contact oxidation method is a submerged biofilm method, which is a combination of biological filter and aeration tank. The biological contact oxidation method has high volume load and strong adaptability to impact load; less sludge generation, simple operation and management, simple operation, low energy consumption, economical and efficient; it has the advantages of activated sludge method, biological It has high activity, good purification effect, high treatment efficiency, short treatment time, good and stable effluent quality; it can decompose other substances that are difficult to decompose in biological treatment, and has the effect of deoxygenation and phosphorus removal, and can be used as a tertiary treatment technology.

 

3. SBR process

SBR is the abbreviation of Sequencing Batch Reactor. As an intermittent wastewater treatment process, it has attracted extensive attention and research at home and abroad in recent years. The working procedure of SBR is composed of five procedures: inflow, reaction, precipitation, discharge and idle. Sewage enters each reaction process in sequence and intermittently in the reactor, and the operation of each SBR reactor is also arranged intermittently in time. The SBR method has the following characteristics: simple process, small footprint, less equipment, and investment saving. The ideal push-flow process has the advantages of large biochemical reaction thrust, high treatment efficiency, flexible operation mode, phosphorus and nitrogen removal, high sludge activity, good settling performance, shock load resistance and strong processing capacity. Although the SBR method has the above advantages, it also has certain limitations. If the influent flow is large, the reaction system needs to be adjusted, thereby increasing the investment; while there are special requirements for the effluent quality, such as denitrification and phosphorus removal, the process needs to be properly carried out. Improve.

 

4. MBR process

MBR is a new high-efficiency sewage treatment process that combines high-efficiency membrane separation technology with traditional activated sludge method. The water is pumped out after being filtered through a filter membrane by a pump. The MBR process equipment is compact and occupies less area; the effluent quality is high-quality and stable, and the removal efficiency of organic matter is high; the output of excess sludge is small, which reduces the production cost; it can remove ammonia nitrogen and refractory organic matter; it is easy to transform from traditional processes. However, the high cost of membrane construction makes the capital investment of the membrane bioreactor higher than that of the traditional sewage treatment process; membrane fouling is easy to occur, which brings inconvenience to operation and management; high energy consumption and high process requirements.

 

5. Electrolysis process

Under high salinity conditions, wastewater has high electrical conductivity, which provides a good development space for electrochemical methods in the treatment of high salinity organic wastewater.

High-salt wastewater undergoes a series of oxidation-reduction reactions in the electrolytic cell to generate water-insoluble substances, which are removed by precipitation (or air flotation) or direct oxidation-reduction as harmless gases, thereby reducing COD. When the sodium chloride in the solution is electrolyzed, a part of the chlorine gas generated on the anode dissolves in the solution and undergoes a secondary reaction to generate hypochlorite and chlorate, which has a bleaching effect on the solution. It is the above-mentioned comprehensive synergy that degrades the organic pollutants in the solution.

Due to the limitations of electrochemical theory, high energy consumption, lack of electricity and other problems, the current electrolytic treatment of high-salt wastewater is still in the research stage.

 

6. Ion exchange method 

Ion exchange is a unit operation process that usually involves an exchange reaction between ions in solution and counter ions on insoluble polymers (containing immobilized anions or cations). When using the ion exchange method, the wastewater first passes through a cation exchange column, in which the positively charged ions (Na+, etc.) are replaced by H+ and stay in the exchange column; after that, the negatively charged ions (CI-, etc.) are in the anion exchange column. It is replaced by OH- to achieve the purpose of desalination. However, one of the main problems of this method is that the suspended solids in the wastewater will block the resin and lose its effectiveness, and the regeneration of the ion exchange resin requires high costs and the exchanged waste is difficult to deal with.

 

7. Membrane separation method

Membrane separation technology is a new type of separation technology that utilizes the difference in selective permeation performance of membranes to each component in a mixture to separate, purify and concentrate target substances. At present, the commonly used membrane technologies are ultrafiltration, microfiltration, electrodialysis and reverse osmosis. Among them, ultrafiltration and microfiltration cannot effectively remove salt in sewage when used in the treatment of industrial wastewater, but can effectively retain suspended solids (SS) and colloidal COD; electrodialysis (electrodialysis) and reverse osmosis (RO) technology is The most efficient and commonly used desalination technology

The main difficulties that limit the application and promotion of membrane technology engineering are the high cost of membranes, short lifespan, susceptibility to pollution and fouling and blockage. With the development of membrane production technology, membrane technology will be more and more applied in the field of wastewater treatment.

 

8. Iron-carbon micro-electrolysis treatment technology

The iron-carbon micro-iron-carbon micro-electrolysis method is a good process for the treatment of wastewater using the principle of Fe/C primary battery reaction, also known as internal electrolysis method, iron filing filtration method, etc. The iron-carbon micro-electrolysis method is a comprehensive effect of electrochemical redox, electro-enrichment of flocs by electrochemical pairs, coagulation of electrochemical reaction products, adsorption of new flocs, and bed filtration. It is redox and electro-aggregation and coagulation.

When the iron filings are immersed in wastewater containing a large amount of electrolyte, countless tiny primary batteries are formed. After adding coke to the iron filings, the iron filings and the coke particles contact to further form a large primary battery, so that the iron filings are corroded by the micro primary batteries. On the surface, it is corroded by the large galvanic battery, thereby accelerating the progress of the electrochemical reaction. This method has many advantages such as wide application range, good treatment effect, long service life, low cost and convenient operation and maintenance. At present, iron-carbon micro-electrolysis technology has been widely used in printing and dyeing, pesticide/pharmaceutical, heavy metal, petrochemical, oil and other wastewater and landfill leachate treatment, and has achieved good results.

 

9. Fenton and Fenton-like oxidation methods

The typical Fenton reagent is the decomposition of H2O2 catalyzed by Fe2+ to generate ˙OH, thereby triggering the oxidative degradation reaction of organic matter. Because the Fenton method takes a long time to treat wastewater, the amount of reagents used is large, and the excess Fe2+ will increase the COD in the treated wastewater and cause secondary pollution.

In recent years, people have introduced ultraviolet light, visible light, etc. into the Fenton system, and researched the use of other transition metals to replace Fe2+. These methods can significantly enhance the oxidative degradation ability of Fenton reagents to organic matter, reduce the amount of Fenton reagents, and reduce processing costs. Fenton reaction. The reaction conditions of the Fenton method are mild, the equipment is relatively simple, and the scope of application is wide; it can be used as a separate treatment technology, or can be used in combination with other methods, such as coagulation precipitation method, activated carbon method, biological treatment method, etc. Pretreatment or advanced treatment methods for degrading organic wastewater.

 

10. Ozone oxidation

Ozone is a strong oxidant.It reacts quickly with reduced pollutants, is easy to use, and does not produce secondary pollution. It can be used for disinfection, decolorization, deodorization, organic matter removal, and COD reduction of sewage. The ozone oxidation method alone has high cost, high processing cost, and its oxidation reaction is selective, and the oxidation effect of certain halogenated hydrocarbons and pesticides is relatively poor.

To this end, in recent years, related combination technologies have been developed to improve the efficiency of ozone oxidation. Among them, UV/O3, H2O2/O3, UV/H2O2/O3 and other combination methods can not only improve the oxidation rate and efficiency, but also can oxidize when ozone acts alone. Difficult to oxidative degradation of organic matter. Due to the low solubility of ozone in water, low ozone generation efficiency and high energy consumption, increasing the solubility of ozone in water, improving the utilization rate of ozone, and developing high-efficiency and low-energy-consumption ozone generators have become the main research directions.

 

11. Magnetic separation technology

Magnetic separation technology is a new type of water treatment technology developed in recent years that utilizes the magnetic properties of impurity particles in wastewater to separate. For non-magnetic or weakly magnetic particles in water, magnetic seeding technology can be used to make them magnetic.

Magnetic separation technology is applied to wastewater treatment in three ways: direct magnetic separation, indirect magnetic separation and microorganism-magnetic separation.

The currently studied magnetization technologies mainly include magnetic agglomeration technology, iron salt co-precipitation technology, iron powder method, ferrite method, etc. The representative magnetic separation equipment is disk magnetic separator and high gradient magnetic filter. At present, the magnetic separation technology is still in the laboratory research stage and cannot be applied to actual engineering practice.

 

12. Plasma water treatment technology

Low-temperature plasma water treatment technology, including high-voltage pulse discharge plasma water treatment technology and glow discharge plasma water treatment technology, uses electric discharge to directly generate plasma in aqueous solution, or introduce active particles in gas discharge plasma into water, It can completely oxidize and decompose pollutants in water. The direct pulse discharge in the aqueous solution can be operated at normal temperature and pressure. During the whole discharge process, in-situ chemical oxidative species can be generated in the aqueous solution to oxidize and degrade organic compounds without adding catalysts. This technology is economical and effective for the treatment of low-concentration organic compounds. .

In addition, the form of the reactor applying the pulse discharge plasma water treatment technology can be flexibly adjusted, the operation process is simple, and the corresponding maintenance cost is also low. Due to the limitation of discharge equipment, the energy utilization rate of this process to degrade organic matter is low, and the application of plasma technology in water treatment is still in the research and development stage.

 

13. Electrochemical (catalytic) oxidation

Electrochemical (catalytic) oxidation technology degrades organic matter directly through anode reaction, or degrades organic matter through anode reaction to generate oxidants such as hydroxyl radicals (˙OH) and ozone.

Electrochemical (catalytic) oxidation includes two-dimensional and three-dimensional electrode systems. Due to the micro-electric field electrolysis of the three-dimensional electrode system, it is currently highly regarded. Three-dimensional electrode is to fill granular or other debris-like working electrode materials between the electrodes of traditional two-dimensional electrolysis cells, and make the surface of the loaded material charged to become the third electrode, and electrochemical reactions can occur on the surface of the working electrode material.

Compared with the two-dimensional plate electrode, the three-dimensional electrode has a large specific surface area, which can increase the surface-to-body ratio of the electrolytic cell, and can provide a large current intensity at a lower current density. The efficiency is high, so the current efficiency is high and the treatment effect is good. Three-dimensional electrodes can be used to treat domestic sewage, pesticides, dyes, pharmaceuticals, phenol-containing wastewater and other refractory organic wastewater, metal ions, landfill leachate, etc.

 

14. Radiation technology

Since the 1970s, with the development of large-scale cobalt source and electron accelerator technology, the radiation source problem in the application of radiation technology has been gradually improved. The study of using radiation technology to treat pollutants in wastewater has attracted the attention and attention of all countries. Compared with traditional chemical oxidation, the use of radiation technology to treat pollutants requires no or only a small amount of chemical reagents, no secondary pollution, and has the advantages of high degradation efficiency, fast reaction speed, and complete degradation of pollutants. Moreover, when ionizing radiation is used in combination with catalytic oxidation means such as oxygen and ozone, a "synergistic effect" occurs. Therefore, the treatment of pollutants by radiation technology is a clean and sustainable technology, which is listed by the International Atomic Energy Agency as the main research direction of the peaceful use of atomic energy in the 21st century.

 

15. Photochemical catalytic oxidation

Photochemical catalytic oxidation technology is developed on the basis of photochemical oxidation. Compared with photochemical methods, it has stronger oxidation ability and can degrade organic pollutants more thoroughly. Photochemical catalytic oxidation is photochemical degradation in the presence of a catalyst, and the oxidant generates free radicals with strong oxidizing ability under the irradiation of light.

Catalysts include TiO2, ZnO, WO3, CdS, ZnS, SnO2 and Fe3O4. It is divided into two types: homogeneous and heterogeneous. Homogeneous photocatalytic degradation uses Fe2+ or Fe3+ and H2O2 as the medium to generate hydroxyl radicals through the photo-Fenton reaction to degrade pollutants; heterogeneous catalytic degradation is in A certain amount of photosensitive semiconductor materials, such as TiO2, ZnO, etc., are put into the pollution system, and combined with light radiation, the photosensitive semiconductor is excited to generate electron-hole pairs under the irradiation of light, and the dissolved oxygen and water molecules adsorbed on the semiconductor are related to Electron-hole interaction generates free radicals with strong oxidizing ability such as ˙OH. TiO2 photocatalytic oxidation technology has obvious advantages in oxidative degradation of organic pollutants in water, especially refractory organic pollutants.

 

16. Supercritical water oxidation (scwo) technology

SCWO uses supercritical water as the medium to homogeneously oxidize and decompose organic matter. Organic pollutants can be decomposed into small inorganic molecules such as CO2 and H2O in a short time, while sulfur, phosphorus and nitrogen atoms are converted into sulfate, phosphate, nitrate and nitrite ions or nitrogen, respectively. The United States ranks SCWO as the most promising waste treatment technology in the energy and environment fields. SCWO has fast reaction rate and short residence time; high oxidation efficiency, the treatment rate of most organic matter can reach more than 99%; the reactor structure is simple, the equipment volume is small; the treatment range is wide, not only can be used for various toxic substances, wastewater, waste treatment Treatment can also be used to decompose organic compounds; no external heating is required, and the treatment cost is low; the selectivity is good, by adjusting the temperature and pressure, the physicochemical properties of water such as density, viscosity, and diffusion coefficient can be changed, thereby changing its effect on organic matter. Solubility, to achieve the purpose of selectively controlling the reaction products.

The supercritical oxidation method has been applied in the United States, Germany, Sweden, Japan and other European and American countries, but the research in China started late and is still in the laboratory research stage.

 

17. Wet (catalytic) oxidation

The wet (catalytic) oxidation method is under the action of high temperature (150~350℃), high pressure (0.5~20MPa) and catalyst, using O2 or air as oxidant (adding catalyst), (catalytically) oxidizing water in dissolved or suspended state Organic matter or reduced inorganic matter to achieve the purpose of removing pollutants. The wet air (catalytic) oxidation method can be applied to the treatment of municipal sludge and industrial wastewater such as acrylonitrile, coking, printing and dyeing, and pesticide wastewater containing phenol, chlorohydrocarbon, organophosphorus, and organosulfur compounds.

 

18. Ultrasonic oxidation

The organic pollutants in the water body irradiated by ultrasonic waves with a frequency of 15~1000kHz are physical and chemical processes caused by the cavitation effect. Ultrasound can not only improve the reaction conditions, speed up the reaction and improve the reaction yield, but also enable some difficult chemical reactions to be realized.

It combines the characteristics of advanced oxidation, incineration, supercritical oxidation and other water treatment technologies. In addition, it is simple to operate and has low requirements for equipment. It is used in sewage treatment, especially in the degradation of wastewater. It is of great significance to accelerate the degradation rate of organic pollutants, realize the harmlessness of industrial wastewater pollutants, and avoid the impact of secondary pollution.