Papermaking Wastewater Treatment

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Applications-Papermaking Wastewater Treatment

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Surface Treatment

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In the production process of paper mills, it needs to be realized through the pulping process. In the process of papermaking, pulping needs to use mechanical or mechanochemical methods to decompose some plant fiber raw materials so that the subsequent.

We can only ensure that the paper can comply with relevant regulations by bleaching the pulp. However, a small paper mill can pollute a sub-level river if the wastewater cannot be effectively treated in this process. This also requires the paper mill to undergo strict rectification to achieve its wastewater treatment to reduce environmental pollution and thus protect the internal ecological operation of the overall environment.

Table of contents（Click to go to where you want to see）

4.1 physical treatment method ( Our company’s main products and cases)
4.2 Chemical treatment

4.3 Biological treatment

4.3.1 Anaerobic biological treatment technology

4.3.2 Aerobic activated sludge technology

4.3.3 Anoxic-aerobic (A-O) process

5. Advanced treatment methods for papermaking wastewater

5.1 Advanced oxidation treatment technology

5.2 Coagulation treatment technology

5.3 Adsorption treatment technology

5.4 Magnetization pretreatment technology

5.5 Membrane separation treatment technology

5.6 Combined processing technology

6. New technology for papermaking wastewater treatment

6.1 Supercritical technology

6.2 Bioenzyme technology

6.3 Photocatalytic oxidation technology

6.4 Microbial fuel cell wastewater treatment technology

How is papermaking wastewater generated?

The pulping and papermaking process requires a large amount of production water. The wastewater generated by bleaching agents, fillers, and their re, reaction products are all pulping and papermaking wastewater. The primary sources of wastewater are the cooking waste liquid produced during the pulping and cooking process, the mid-stage wastewater produced during the middle stages of the pulping process (washing, screening, bleaching, and beating), and the paper machine white water produced during the papermaking process. Since cooking requires a large amount of auxiliary chemicals, cooking wastewater causes the most severe pollution, accounting for 90% of the pollution in the entire papermaking industry.

Cooking waste liquid

During the cooking process, high-concentration waste liquor containing a variety of chemical substances will be produced: the cooking waste liquor produced by alkali pulping is called black liquor because it appears black, and the cooking waste liquor produced by the sulfite pulping method is called red liquor because it appears red. It's called red liquid. At present, most paper mills use the alkaline cooking pulping process. The main components of the black liquor produced are lignin, polypentose, and total alkali, and they contain high concentrations of BOD and COD.
Middle section wastewater

The wastewater discharged during the screening, washing, and bleaching processes after the slurry's cooking and black liquor extraction is called mid-stage wastewater, mainly soluble CODCr. It is characterized by wastewater pH value of 7 to 9, BOD5 of 400 to 1000 mg/L, CODCr of 1200 to 3000 mg/L, and SS of 500 to 1500 mg/L. The composition is similar to pulping wastewater, but the concentration is low, and the color is generally yellow. It accounts for 8% to 9% of the total pollution emissions from the papermaking industry. It contains higher concentrations of lignin, cellulose, and resinates that are difficult to biodegrade. Material components and these organic substances contain many chromophoric groups, so the color is very high, and the odor is strong. Moreover, due to the bleaching process, organic chlorides will be produced, and their discharge into the external environment will cause harm to human health.
White water

White water mainly contains dissolved wood components, glue added to the soil, reinforcing agents, preservatives, etc., primarily insoluble COD, and the antioxidants in it have a specific radioactive M. Nowadays, almost every papermaking factory workshop has adopted a partially or wholly enclosed production system, which can reduce the water consumption of papermaking, save the consumption of labor resources, improve the reuse efficiency of white water, and reduce the discharge of excess white water.

What are the characteristics of papermaking wastewater?

Depending on the pulping method, raw material type, pulping yield, and papermaking type, the composition of different pulping and papermaking wastewater pollutants differs. Still, they contain many suspended solids, organic matter, some dyes, and toxic ink substances. The pollution load of pulping and papermaking wastewater is high, and its characteristics are shown in the table:

Characteristics of pulp and paper wastewater
Serial number	Characteristic	Illustrate
1	The amount of wastewater discharge is significant, and wastewater will be discharged from all production links.	The pH value of wastewater is 7~9, BOD₅ is 400~1 000 mg/L, CODcr is 1200~3 000 mg/L, and SS is 500~1 500 mg/L.
2	Wastewater has high concentration and complex composition, including lignin, chemicals, volatile phenols, organochlorines, etc.
3	Contains a certain amount of toxic and harmful substances, chemicals being the main source	It mainly comes from cooking agents, bleaching agents, fillers, and their reaction products. Traditional anaerobic and aerobic methods cannot meet high-standard emission requirements and take a long time.
4	Poor biodegradability, BOD/COD value is 0.15~0.25, difficult to be directly biodegraded
5	Wastewater contains a lot of lignin, so it has high color and is difficult to treat.

What are the hazards of papermaking wastewater?

If paper mills discharge substandard wastewater, they will pollute water sources, harmaquatic life, human health, and the environment, and directly harm human health and the living environment.

1. Harm to the human body
The harm of papermaking wastewater, on the whole, is first harm to water bodies, then to aquatic organisms, through the food chain, etc., and finally to the human body. If people drink contaminated water, it will directly harm their health. Pollutants ultimately affect the entire environmental system through energy conversion and material circulation.

2. Harm to aquatic life
Suspended solids in papermaking wastewater are insoluble substances in the water. Suppose they are discharged directly into the water. In that case, they will affect the appearance of the water body, hinder the photosynthesis of plants in the water, reduce the contact between the water body and the air, and reduce the dissolution of oxygen in the water body. A large amount of suspended solids will affect the average growth of aquatic organisms, such as blocking fish gills, etc., leading to the death of marine organisms in large numbers, thus causing further pollution and deterioration of water bodies. When papermaking wastewater is discharged directly into the water body, microorganisms in the water body will decompose lignin and other organic matter in the wastewater. This process requires the consumption of dissolved oxygen in the water, reducing the oxygen content of the water and affecting the growth and reproduction of fish and other organisms. After the dissolved oxygen in the water is exhausted, the organic matter undergoes anaerobic digestion to produce hydrogen sulfide, methane, etc. Such water bodies will have odors, threatening the survival of aquatic life, such as causing the death of many marine life and destroying the ecological balance. Therefore, it is imperative to control and treat paper mill wastewater.

Conventional treatment methods for papermaking wastewater

There are many conventional treatment methods for pulping and papermaking wastewater treatment. Generally, we divide them into the following three types according to their working principles. However, we often mix several methods to achieve better results in the specific wastewater treatment process.

Physical treatment method

Generally speaking, physical and chemical treatment methods include coagulation flotation and coagulation sedimentation.

Among them, the coagulation air flotation method saves resources and has a good purification effect, so it is the most commonly used. The primary purpose is to add coagulant to the wastewater. The addition of air will cause bubbles to form in the wastewater. The suspended solids in the wastewater will attach to the bubbles and float to the water surface with the bubbles, thus optimizing the wastewater.

The coagulation sedimentation law is mainly aimed at removing SS and reducing COD concentration, which can reduce the concentration of coagulation and the load of organic pollutants. The treatment effect of the coagulation sedimentation method is closely related to the coagulation process. To achieve a better coagulation effect, it is essential to choose an appropriate coagulant. The most commonly used coagulants on the market are polyferric sulfate, polyaluminum chloride, and binary or ternary metal salts. Compounds, polyacrylamide, and its derivatives are inorganic and organic polymer coagulants. To achieve better wastewater treatment results, we often use one or two inorganic and organic polymer coagulants for the coagulation process. Research shows that if the two can be matched in an appropriate ratio, the quality of wastewater treatment can be effectively improved. Matching them in a proper ratio requires continuous optimization during the experiment.

Application case(Preprocessing-physical method)

Case Studies-Wastewater Treatment at A Paper Mill in The Philippines

This case study highlights the use of our high-efficiency dissolved air flotation at a paper mill in the Philippines for pre-treating papermaking wastewater. This treatment ensures that the wastewater meets the water quality requirements for secondary and tertiary treatment.

Chemical treatment

Chemical treatment method The Chemical treatment method mainly uses oxidation and reduction to convert soluble pollutants into forms that can be easily separated from water to remove dissolved substances in wastewater. In addition, there are methods such as neutralization, precipitation, and micro-electrolysis.

To achieve better wastewater treatment results, we often combine various treatment methods. Standard chemical oxidation methods for pulp and paper wastewater treatment include ozone oxidation and potassium permanganate oxidation. In the specific pulping and papermaking wastewater treatment process, we often combine chemical treatment methods with other means, putt the oxidant into the wastewater in advance for pre-oxidation, and then coagulate and settle. Chemical treatment agents and coagulants can also be put in simultaneously according to the actual wastewater treatment conditions, and the two superimpose each other to produce a synergistic effect. The chemical treatment agent is sometimes added after the coagulation reaches a particular stage, which can produce better results. However, no matter which delivery method is chosen, the choice should be based on the specific wastewater treatment conditions.

Biological treatment

During the metabolism process, microorganisms in wastewater can participate in the metabolism of organic pollutants in sewage, thereby converting them into some pollution-free metabolites, which are then removed through precipitation to purify wastewater. This method is called the biological treatment of sewage. Method. In addition to reducing the content of BOD and COD in wastewater, biological treatment methods also can remove suspended solids, color, and odor. The wastewater treatment method using anaerobic microorganisms is called anaerobic biological treatment technology. The wastewater treatment method under the action of aerobic microorganisms is called aerobic biological treatment technology, and there is also a combination of anaerobic and aerobic biological treatment technology.

Anaerobic biological treatment technology

Anaerobic biological treatment technology uses anaerobic microorganisms to decompose organic matter without requiring an external supply of O2. It can also produce valuable methane gas while reducing organic matter. The IC reactor anaerobically treats papermaking wastewater. The COD in the wastewater used reaches 2000mg·L-1. After treatment by the IC anaerobic reactor, the COD in the effluent is 554mg·L-1, with a removal rate of 71.66%. In addition, we studied the degradation of BOD, lignin, hardness, and organic matter using the IC anaerobic reactor. The IC anaerobic reactor has a reasonable removal rate for these substances, and after adding the IC reactor, the effluent Water quality has improved significantly.

Aerobic activated sludge technology

Aerobic activated sludge technology is a method of installing many small holes for aeration at the bottom of the activated sludge tank and continuously sending gas into the wastewater through a fan, thus increasing the dissolved oxygen in the wastewater. The incoming gas can suspend and disperse the activated sludge in the wastewater, which is conducive to complete contact between the wastewater and microorganisms. The organic matter in the wastewater can be degraded and removed by aerobic organisms, which can degrade pollutants in the wastewater. At the same time, new organisms are produced, thus maintaining the balance of microorganisms in the activated sludge, allowing the reaction to proceed. Liu Chun [11] et al. studied the treatment of pulping and papermaking wastewater by the sequential batch-activated sludge method. They used papermaking wastewater with a COD content of 1713mg·L-1 and studied the aeration time inlet water flow. The results of water load and standing time on the treatment of papermaking wastewater show that when the water inflow reaches 2.0h, the aeration time is 12.0h. The standing time is 6.0h so that it can achieve a reasonable removal rate of COD in papermaking wastewater.

Anoxic-aerobic (A-O) process

When traditional aerobic activated sludge technology is used in papermaking wastewater, the removal rate of refractory and ammonia nitrogen substances that affect COD content is shallow. The anoxic-aerobic (AO) process is designed to solve the problem of refractory substances that affect COD. Raw. Its process route: first, perform an anoxic process, and then perform an aerobic process, allowing the sludge to return from the outside of the activated sludge tank. The denitrification reaction proceeds in the anoxic process, and the nitrification reaction proceeds in the aerobic process in the nitrification tank. Delayed aeration creates an anoxic environment and carries out a denitrification reaction. Under anaerobic conditions, microorganisms use organic matter-carbon sources to reduce the produced nitrate and nitrite into N2 and discharge them to achieve denitrification. Purpose. During the nitrification stage, ammonia nitrogen is converted into nitrates and nitrites.

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Advanced treatment methods for papermaking wastewater

Advanced oxidation treatment technology

In studying the technical issues of advanced pulping and papermaking wastewater treatment, satisfactory wastewater treatment effects can be achieved by introducing advanced oxidation treatment technology. This technology uses chemical reactions between HO components and wastewater pollutants to degrade pollutant pollution reliably. Affected by the unique factors of the process, pulping, and papermaking wastewater contain a certain proportion of cellulose, hemicellulose, and lignin components, and the oxidizing properties of hydrocarbon radicals are particular. By introducing hydrocarbon radical molecules, this method can convert pollutants into carbon dioxide and water, and the treatment effect is ideal.

With the support of current technical conditions, the most commonly used technical method in advanced oxidation treatment is Fenton-based oxidation treatment technology. This technology achieves oxidation by adding a certain proportion of hydrogen peroxide and ferrous salt components to pulping and papermaking wastewater—conversion to generate a certain proportion of water and carbon dioxide components. But at the same time, during the application of this technology for advanced treatment of pulping and papermaking wastewater, to ensure the treatment effect, it is first necessary to ensure that the outlet water temperature in the working environment is maintained within the range of 20. 0℃ ~ 40. 0℃, and it is necessary to apply pre-treatment. The wastewater is moderately treated through treatment technology, and the pH value is controlled according to the standard of 3. 5 to 4. 5 to ensure that the advanced oxidation treatment technology achieves the ideal effect. In addition, this technology involves using acid when applied in wastewater treatment. Therefore, it is necessary to increase the development of cheap acid sources to provide reliable condition support for Fenton oxidation treatment and promote flexible cost control.

Coagulation treatment technology

Coagulation-based treatment technology has also been widely used in advanced pulp and paper wastewater treatment. The core idea of this technology is to add a certain proportion of flocculant to the outlet section of the secondary sedimentation tank after biochemical treatment and form a hydrolysis polymerization product based on positive charges through a flocculation reaction. In this way, the positive charges in the water can react with the charged particles to compress the double electric layer, gradually guiding the pollutant particles in the water body to form large particle flocs and then remove the pollutants from the wastewater through precipitation, thereby improving the quality of the water body. Purpose.

In this process, the choice of flocculant box directly affects the overall effect of coagulation treatment technology on the advanced treatment of pulping and papermaking wastewater. With the support of current technical conditions, flocculants widely used in the industry include polymerized alumina, aluminum trichloride, aluminum sulfate, ferrous sulfate, and polymerized ferric sulfate. Among them, the precipitation performance of aluminum sulfate is relatively insufficient. It is necessary to mix a certain proportion of polyaluminum chloride to enhance the floc precipitation performance and exert the effect of in-depth treatment and purification of pulping and papermaking wastewater.

In addition, in a neutral environment, using ferrous sulfate flocculant alone is not recommended. It can be combined with bleach to ensure water quality. From the current stage, when using this technology to deal with the problem of pulping and papermaking wastewater, assuming that the COD content of the secondary sedimentation tank effluent is 300. 0mg / l, the COD content of the effluent after flocculation treatment will be maintained at 100. 0mg. /l ~ 150. 0mg /l, the standard of less than 100. 0mg /l cannot be reached, and the problem of chemical pollution during the use of flocculants cannot be ignored, and efforts should be made to solve it during the application period.

Adsorption treatment technology

As one of the critical components in the advanced treatment technology system of pulping and papermaking wastewater, adsorption treatment technology emphasizes the application of active groups on the adsorbent to selectively enrich some inorganic pollutants to achieve purification of pulping The purpose of papermaking wastewater.

Supported by current technical conditions, the adsorbents selected during the advanced treatment of pulping and papermaking wastewater include fly ash, activated carbon, activated coke, and diatomaceous earth, among which activated carbon is the most widely used. Compared with other types of adsorbents, activated carbon has a series of advantages, such as a large pore structure and large specific surface area, which is of great significance in promoting the formation of chemical bonds between the active groups on the surface of the adsorbent and the adsorbed substances. On this basis, pulp and paper wastewater pollutants are deeply removed through intermolecular attraction. However, with the accumulation of relevant practical experience, when applying activated carbon adsorption technology for advanced treatment of pulping and papermaking wastewater, special attention must be paid to operating and regeneration costs. The cost is relatively high. How can we achieve this without affecting the treatment effect? Reasonably reducing costs is a topic that must be considered in the next stage of work.

In addition, activated coke is a commonly used adsorbent component. It is made from lignite. Its adsorption capacity is equivalent to activated carbon, with lower cost and poor pulverization. It has more specific application value for the advanced treatment of pulping and papermaking wastewater and deserves attention.

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Magnetization pretreatment technology

Based on electromagnetic theory, it is known that when a magnetic field is introduced into water, the water body will show changes in the movement of magnetic lines of force when affected by external forces, resulting in the generation of electromotive force, which will then change the potential difference and current of the water body, thereby changing its material state and properties. According to this theory, magnetization pretreatment can be used to achieve deep treatment of pulping and papermaking wastewater and purify the water body. Under the influence of the magnetic field, pulping and papermaking wastewater will be magnetized to varying degrees, thereby changing the physical and chemical properties of the wastewater and improving the overall efficiency of wastewater treatment.

With the support of current technical conditions, since 2009, relevant domestic researchers have tried to apply magnetization pretreatment technology to the field of advanced treatment of pulping and papermaking wastewater. Experimental data shows that when the magnetic field intensity is set to 550. 0mT, the wastewater flow rate is about 1. 5m/s. After the intervention of magnetization pretreatment technology, the CODcr in pulping and papermaking wastewater can be reduced by 15% to 20% compared with before treatment. % ratio, the pH value can be increased by about 4% compared with before treatment. This research data reflects that during the advanced treatment of pulp and paper wastewater, the application of magnetization pretreatment technology can purify the water body by adjusting the surface tension, pH value, and conductivity of the water body. One point that needs special attention is that pulping and papermaking wastewater, as a non-insulated water body, has specific conductive properties. Using this characteristic for magnetization pretreatment intervention can achieve the desired pretreatment effect while avoiding environmental pollution problems.

Membrane separation treatment technology

Membrane separation treatment technology refers to the selective permeation of some substances in wastewater with the help of membranes to purify pulping and papermaking wastewater. With the support of current technical conditions, membrane separation technology has been pervasive and refined, involving microfiltration membrane separation technology, ultrafiltration membrane separation technology, reverse osmosis membrane separation technology, and nanofiltration membrane separation technology. Wait for several types. Compared with other traditional advanced treatment technologies for pulping and papermaking wastewater, membrane separation treatment technology has the characteristics of high treatment efficiency, simple operation, and no secondary pollution, so it has attracted much attention from people in the industry.

Microfiltration membrane separation and treatment technology are primarily used to treat polymer organic matter and colloidal substances in wastewater with particle sizes above 100.0 nm. Through the application of a microfiltration membrane, flocs with a particle size of 100. 0nm or above are blocked outside the holes, and the water body penetrates the limiting arm to separate the flocs and water body, thereby achieving reasonable purification of the water body.

Ultrafiltration membrane separation treatment technology applies screening principles to separate macromolecules and particulate components in pulping and papermaking wastewater to achieve reliable purification of water bodies. The ultrafiltration membrane separation link should be equipped with high-pressure and low-pressure sides. Wastewater flows from the high-pressure side to the low-pressure side. During the flow process, biofilm blocks the required screening part to purify the wastewater body. However, due to technical limitations, this method is currently primarily suitable for screening large molecules with particle sizes between 2. 0nm and 100. 0nm and relative molecular weights between 500. 0 and 15000. 0. The processing efficiency is about 80%.

Combined processing technology

In the process of advanced pulp and paper wastewater treatment, the introduction of combined technology also has a very positive role and value. For example, try to incorporate the application of biochemical technology and electrochemical technology to effectively control the COD content and color of wastewater through combined advanced treatment, promote the improvement of the flocculation level of sewage, and meet the expectations of advanced treatment of pulping and papermaking wastewater. Effect.

For example, in the process of research on electrochemical-immobilized microbial technology, relevant personnel are trying to apply it to the field of advanced treatment of pulp and paper wastewater and pay attention to the setting up of various treatment links such as wastewater tanks and reaction tanks, equipped with metering pumps. The wastewater is injected into the electrochemical reaction tank. A certain proportion of PAM is added to the wastewater while flowing to the oxidation tank, and water purification is achieved through a precipitation reaction.

Applying the above technical treatment measures, the COD content at the outlet end can be controlled within the range of 32. 0 mg / l ~ 39. 0 mg / l, which can meet the requirements for advanced pulping and papermaking wastewater treatment requirements. In addition, you can also try to combine microbial technology and activated carbon technology in the advanced treatment of pulping and papermaking wastewater to improve the adsorption capacity of activated carbon and promote the extension of activated carbon saturation time. After combining the above technologies, the outlet end of pulping and papermaking wastewater's COD content can be controlled within the range of 60—0mg/l, which can also meet the expected requirements for wastewater purification treatment.

New technology for papermaking wastewater treatment

Supercritical technology

Supercritical water oxidation (SCWO) technology puts water in a supercritical state under high temperature and high-pressure conditions, making it a suitable solvent for oxygen and organic matter. In the oxygen-rich homogeneous phase, organic matter is wholly oxidized into non-toxic and harmless small molecular substances such as CO2, N2, H2O, etc., within minutes or even seconds. Therefore, SCWO technology has the advantage of rapid and efficient decomposition of organic matter, which is economically feasible and has good environmental benefits. SCWO treatment devices for paper industry wastewater have been operated in developed countries such as Europe, the United States, and Japan.

Bioenzyme technology

Traditional biological methods have certain limitations in the advanced treatment of refractory organic matter in papermaking wastewater. Researchers have developed new biological enzyme technology to solve this problem.

Laccase is a natural catalase whose main component is copper-containing polyphenol oxidase, which can degrade lignin and toxic phenolic compounds.

The mechanism of biological enzyme technology is that hydrogen peroxide is converted into HO2·free radicals under laccase. HO2·free radicals react with lignin derivatives to generate RO·free radicals, further condensing to form polymer RORＲ with an ether bond structure. , the molecular weight of lignin increases, and its water solubility decreases. Through solid-liquid separation, organic pollutants in papermaking wastewater can be effectively removed, reducing the color.

Therefore, using biological enzyme technology to treat wastewater has the advantages of mild conditions, low cost, and little secondary pollution. To confirm the catalytic polymerization of lignin in papermaking wastewater by laccase, we studied the effect of laccase from the white rot fungus Corylopsis versicolor on lignin polymerization. The results showed that after 6 hours of enzyme treatment, the lignin concentration in the wastewater increased from 93. 1mg/L dropped to 17. 2mg/L. After two hours of enzyme treatment, the molecular weight of the isolated lignin rose from 31,251 to 58,610. Sodium alginate-immobilized laccase was used to treat secondary biochemical treatment wastewater (COD: 300 mg/L, chromaticity: 170 times) from a paper mill at a pH value of 4. 5. At a temperature of 40°C, after 16 hours of reaction, the COD and chroma removal rates reached 67.2% and 73.3% respectively.

The most studied laccase-producing bacteria in bioenzyme technology are fungi such as Versicolor versicolor, mushrooms, and a small number of bacteria. However, their enzyme production is low, and their purity is not high. In recent years, researchers have used biogenetic engineering technology to introduce laccase genes in fungal cells into recipient strains with good adaptability and vital fecundity to achieve continuous high-density laccase fermentation and improve bacteria's ability to refractory pollutants: adaptability and processing efficiency.

Therefore, many scholars have focused on the heterologous expression of laccase genes. Some researchers have successfully extracted DNA and RNA from filamentous fungi, cloned laccase genes, and achieved high-density fermentation production of laccase; the laccase was Enzymes are used in the treatment of effluent from pulping and papermaking secondary sedimentation tanks, and the chemical oxygen demand and chromaticity removal rates reach 82.3% and 90.5% respectively, providing new opportunities for laccase in the advanced treatment of pulping and papermaking wastewater. Ideas.

Working-principle-diagram-of-biological-enzymes

Photocatalytic oxidation technology

Photocatalytic oxidation technology is a new type of water treatment technology that has developed rapidly in recent years. Under the irradiation of sunlight or ultraviolet light, the photocatalyst will generate ·OH radicals with strong oxidizing properties, which can oxidize organic pollutants into small molecule inorganic substances. Photocatalytic oxidation technology has the characteristics of high salinity, fast reaction speed, and no secondary pollution. It is especially suitable for removing refractory organic matter and has broad application prospects in papermaking wastewater treatment.

Photocatalysts are mainly n-type semiconductors (ZnO, WO₃, TiO₂, SnO₂, CdS, etc.), among which TiO₂ has the best effect. The researchers used nano-TiO₂ powder as a photocatalyst to photocatalytically degrade papermaking wastewater under the light source of a high-pressure mercury lamp. Research shows that when the COD concentration of papermaking wastewater is 300 mg/L, the initial pH value of the solution is 3. 0, and the amount of TiO₂ photocatalyst is 1. At 0g/L, the CODCr removal rate can reach 76% after 7 hours of reaction. Papermaking wastewater that has undergone advanced treatment can be discharged up to standard.

The researchers prepared flaky zinc oxide powder synthesized using the hydrothermal method to treat papermaking wastewater. The results show that the flaky structure of zinc oxide has a pH of 9. Under 00, the added amounts of zinc oxide and hydrogen peroxide are 0. 8g/L and 4g/L, after 7 hours of mercury lamp irradiation, the COD removal rate of wastewater can reach more than 85%.

The researchers used high-silica glass fiber cloth as a carrier, used the sole method to load nano-titanium dioxide photocatalyst, and treated the wastewater from the middle section of papermaking through a self-made photocatalytic reactor. Research shows that for the mid-stage wastewater with a COD concentration of 240 mg/L, a piece of glass fiber cloth loaded with nano-titanium dioxide is used to treat 0. After 5 hours, its COD degradation is close to 50%; after 3 hours of treatment, the removal rate reaches more than 90%. Moreover, after the catalytic material has been used more than 20 times repeatedly, its performance has hardly declined, indicating that the catalyst is firmly attached and has stable performance.

Microbial fuel cell wastewater treatment technology

Microbial Fuel Cell (MFC) wastewater treatment technology uses microorganisms as anode catalysts and organic wastewater as the substrate of the MFC anode. Through the metabolism of microorganisms, the organic matter contained in the wastewater is oxidized as fuel, degrading the organic matter and then A new resource-based biological treatment electrical device for removing organic compounds from wastewater. Figure MFC working principle diagram
MFCs can control pollution and maintain production capacity at the same time. Its principle is to use microorganisms to replace precious metals with enzymes as catalysts, thereby converting biomass energy or organic matter into electrical energy. Although this technology is only at the research level, it has not yet achieved practical application in pulping and papermaking wastewater treatment. However, with the continuous discovery of efficient electricity-producing microorganisms and the continuous development of their principles, this technology is expected to become an emerging energy technology. When scientific researchers conducted experiments on the degradation of traditional Chinese medicine wastewater by microbial batteries, they found that although the power production rate of microbial fuel cells is meager (23 mV), it has the advantage of reducing organic matter in wastewater and improving the biodegradability of wastewater. This will be very targeted for the poor biodegradability of pulp and paper wastewater. These research results show that it is possible to use microbial fuel cells to treat pulp and paper wastewater.

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