Method for treating papermaking pulping organic high-concentration wastewater

Abstract

The invention provides a method for treating papermaking pulping organic high-concentration wastewater, which mainly comprises the following steps: pretreating the organic high-concentration wastewater, and adding a laterite emulsion, so that particulate matters and fiber agglomerates in the wastewater are adsorbed to form large particles or large agglomerates, thereby promoting the flocculation effect and efficiency. Efficient mud-water separation is realized in the inclined tube coagulation clarification area; the method aims at reducing the COD and SS concentration of the slurry residue wastewater entering a sewage treatment system, maintaining enough microbial biomass so as to effectively remove organic substances in the wastewater, and avoiding the problems of insufficient oxygen supply and impact on microorganisms caused by too high sludge concentration at the same time. The treatment efficiency of an activated sludge process is improved, and sufficient growth space and nutrient substances of microorganisms are ensured, so that the sewage treatment efficiency is improved, and meanwhile, the stability of the microorganisms is ensured. And meanwhile, the sludge is deeply dewatered, so that the sludge meets the requirement of white blending combustion of a biomass boiler, and harmless, recycling and clean treatment of the sludge is realized.

Description

Technical Field

[0001] The invention relates to sewage treatment technology, in particular to a treatment process for organic high-concentration wastewater, specifically a method for treating organic high-concentration wastewater in papermaking and pulping. Background Art

[0002] The pulp and paper industry is a green industry with high plasticity of resource recycling. In the process of pulping and papermaking, wastes such as pulp residue, wood chips, and sludge can be recycled and recycled to achieve energy saving and ecological environmental protection. In the process of pulping wood and bamboo materials, our company will produce about 0.22% pulp residue during cooking. These pulp residues can be used to produce high-quality corrugated paper fiber raw materials through re-cooking and disc grinding, thereby realizing the efficient utilization of waste resources. The company's annual production capacity has reached more than 6,000 tons, achieving good economic benefits. However, in the process of pulp residue fiber grinding and papermaking, organic wastewater with high COD (chemical oxygen demand) and high SS (suspended solids) concentration will be generated. Specifically, the COD concentration of these wastewaters is an average of 45,000 mg / L, and the SS concentration is an average of 21,000 mg / L. If these high-concentration organic wastewaters are directly sent to the existing sewage treatment system for treatment, it will not only increase the load of the sewage treatment system and impact the operating stability of the microbial treatment system, but also lead to a significant increase in the subsequent treatment water volume, thereby significantly increasing the treatment cost. That is to say, the wastewater from the pulp slag grinding and papermaking process is a high-concentration organic wastewater (average COD concentration of 45,000 mg / l) generated during the pulp slag cooking, disc grinding and pulp board papermaking process. It is currently transported to the neutralization tank of the sewage treatment plant through pipelines and mixed with the existing sewage inlet for post-treatment. However, due to the high COD and SS in the pulp slag wastewater and the large range of changes, it has a great impact on the microbial treatment system and affects the stability of the sewage treatment operation. Moreover, after mixing with sewage, the water volume is large, the sewage treatment process is difficult to adjust, the load of the subsequent flotation treatment is increased, the stability of the microbial treatment system is affected and destroyed, and the production cost is increased. If the sludge concentration control technology is used, it will also lead to lower treatment efficiency and longer time.

[0003] On the other hand, the inventors found that the organic matter and suspended solids content in this wastewater is very high, which leads to an increase in the density and viscosity of the particles in the wastewater. This makes the interaction between the particles more complicated, and it is difficult to achieve effective coagulation and sedimentation through a simple flocculation process. Due to the different densities of different components in the wastewater, obvious stratification may occur. The upper layer may be mainly lighter organic matter, while the lower layer is heavier suspended solids. This stratification will cause the flocculant to be added, even if it is stirred, its effect is only obvious in the upper layer, and the effect is limited in the lower layer. After the conventional flocculant is added, if the mixing is uneven, the flocculant can only work in the upper layer of the wastewater and cannot effectively contact the suspended solids in the lower layer. This will result in poor flocculation effect, and some suspended solids will still not be able to settle, thereby affecting the sedimentation efficiency; in order to make the flocculant evenly distributed throughout the wastewater, it may be necessary to increase the amount of flocculant. However, excessive use of flocculants will bring new problems, such as increased costs, increased amount of sludge after treatment, and possible impact on subsequent treatment processes. The pH value of the wastewater will also affect the effect of the flocculant. Different flocculants exhibit different flocculation properties at different pH values. If the pH value is not appropriate, the flocculant may not work optimally.

[0004] Based on the above reasons, if the existing sewage treatment technology is used to treat this pulping organic high-concentration wastewater, the overall cost of sewage treatment will increase, the efficiency will decrease, and the working hours will increase. Summary of the invention

[0005] In order to solve the deficiencies and defects of the above-mentioned prior art, the inventor has developed and improved a method for treating organic high-concentration wastewater from papermaking and pulping, and pre-treats the sewage. Considering that the organic matter concentration of the pulp refining and washing treatment wastewater is high, it is intended to reduce the compliance of the subsequent biological treatment link, improve efficiency and save costs at the same time; by recovering the solid suspended matter in the existing sewage treatment sludge pressing filtrate, the sludge is not repeatedly returned to the sewage treatment system. It is planned to mix the sludge pressing filtrate in the sludge treatment system with the pulp wastewater and add red clay emulsion to mix evenly, and send it to the pretreatment tank for flocculation treatment. The prefabricated flocculant and inclined tube sedimentation equipment significantly improve the flocculation and sedimentation effect, and can efficiently settle the mud and water. After pretreatment, the COD removal rate is ≥65%, and the SS removal rate is ≥75%. After the sewage enters the biological treatment section, the biological treatment efficiency is maximized and the dissolved oxygen demand is met. The system is stable and economical, which is not only conducive to improving the sewage treatment efficiency, but also can ensure the long-term stable operation of the entire system. Specifically, the present invention is implemented as follows:

[0006] A method for treating organic high-concentration wastewater from papermaking and pulping, comprising: a pretreatment section: after the organic high-concentration wastewater is mixed and diluted with sludge dewatering filtrate, 0.1% to 0.5% of laterite emulsion is added by weight and mixed evenly, a prefabricated flocculant is added and mixed evenly, and the wastewater enters the inclined tube coagulation and clarification area for the first flocculation and sedimentation to achieve mud and water separation, the settled sludge enters the sludge tank, and the clarified sewage flows into the neutralization tank from the top; a comprehensive treatment section: after the mixed wastewater is cooled and homogenized, it is sent to the microbial treatment section to adopt the activated sludge method, Sufficient dissolved oxygen is provided through jet aeration to support the growth of microorganisms; the sludge concentration can be controlled at 3500-5000mg / L; the sewage after microbial treatment enters the clarification tank, and after the sludge settles, it is recycled back to the aeration tank for continued use, and the excess sludge is transferred to the sludge tank; after the clarified sewage undergoes secondary flocculation and sedimentation, it enters the flotation tank for mud and water separation, and the sewage meets the discharge standards and is discharged; the sludge is dehydrated and used as a fuel that can be co-combusted, and the filtrate after sludge dehydration is mixed with organic high-concentration wastewater and enters the pretreatment section for circulation.

[0007] The preparation process of the red soil emulsion comprises: selecting red soil, selecting a type of red soil in which the total content of iron and aluminum oxides is between 5% and 10%, and the total content of sand and organic matter is less than 5%, crushing or grinding, adding water and mixing, and preparing a red soil emulsion with a concentration of 130 to 150 g / l;

[0008] The COD concentration of the organic high-concentration wastewater is ≤40000mg / l, and the SS concentration is ≤20000mg / l; after the first flocculation and sedimentation in the pretreatment stage realizes mud-water separation, the COD removal rate of the sewage is ≥65%, and the SS removal rate is ≥75%;

[0009] The flocculant is composed of polyaluminium chloride, ferric chloride and / or aluminium sulfate and polyacrylamide; wherein: the aluminium oxide content of polyaluminium chloride is 9%, the iron oxide content of ferric chloride is 9.5%; the aluminium oxide content of aluminium sulfate is 18%; polyacrylamide is prepared at a concentration of 0.20%; the volume ratio of the flocculant is polyacrylamide:ferric chloride:polyaluminium chloride=4:3:1.

[0010] The inclined tube coagulation and clarification area includes two sets of inclined tube settlers connected in series. Under the dual effects of the cationic charge of the flocculant and the bridging adsorption of polyacrylamide, the particulate matter and fiber aggregates in the sewage are adsorbed to form large particles or large aggregates, which settle downward, while the small particles, suspended aggregates and suspended particles rise to the inclined tube with the water flow, adhere to the tube wall after being resisted by the inclined tube surface, and accumulate to form an alum flower layer. When these adsorbed fine particles, suspended aggregates and suspended particles reach a certain weight, they fall to the bottom of the pool in groups; smaller particles and suspended aggregates are further adsorbed and accumulated in the second set of inclined tube settlers and precipitate again; the precipitated sludge enters the sludge tank.

[0011] The inclined tube coagulation and clarification zone comprises a mixing zone, a first clarification zone and a second clarification zone. A stirrer is arranged in the mixing zone. Under the high-speed action of the stirrer, the flocculant and the organic macromolecular substances in the sewage are mixed and reacted to form particles or agglomerates. The first clarification zone and the second clarification zone are two sets of inclined tube clarification zones connected in series. The PVC inclined tubes are arranged at an angle of 45 degrees. The sewage enters the two clarification zones and is adsorbed on the inclined tubes and the lower area through cationic charge and bridging twice to form a "alum flower" layer. Then, when the organic matter in the rising sewage passes through the "alum flower" layer, the macromolecular organic particles and suspended matter are adsorbed, and when a certain weight is reached, they sink to the bottom of the pool and are pumped away by a pump. After passing through the two clarification zones, the COD concentration of the sewage is ≤1050mg / l, and the SS is ≤140mg / l. The clarified sewage enters the outlet tank from the top, and the sewage BOD5 / COD ratio is increased by at least 5.77%.

[0012] The dissolved oxygen in the microbial treatment section is controlled between 1.5-2.5 mg / l, and the sludge concentration is controlled between 3500-5000 mg / l; the sludge enters the clarification tank after passing through the microbial treatment system, where the sludge sinks to the bottom under the action of gravity and is circulated back to the aeration tank, and the excess sludge is sent to the sludge storage tank; the clarified sewage is sent to the flotation tank by a sewage pump, a pipeline mixer is installed in front of the flotation tank, and flocculants are added in front of the pipeline mixer to allow the chemicals and water to fully mix and react, and then the sewage enters the flotation tank, where the COD macromolecules in the sewage react with the chemicals to form fine solid particles, and finally a sludge layer is formed to achieve mud-water separation, and the sludge after flotation is sent to the sludge tank, and the sewage meets the discharge standards.

[0013] Before the sewage enters the microbial treatment, it is cooled and the water quality is adjusted to a temperature of ≤35°C, and mixed evenly in the homogenization tank.

[0014] The working principle of the present invention: the method for treating high-concentration organic wastewater of papermaking pulping of the present invention is mainly divided into a pretreatment section and a comprehensive treatment section. In the pretreatment section, a key pre-step is included, that is, red soil is ground into fine powder to make an emulsion, and the emulsion is added into mud water containing a large amount of plant fibers for sufficient stirring and mixing. Silicon dioxide (SiO2), ferric oxide (Fe2O3) and aluminum oxide (Al2O3) and particulate matter in the red soil are attached to the plant fibers to form a larger composite structure. Since the red soil particles have a certain surface activity, they can be combined with the plant fibers after stirring and mixing for adsorption, resulting in aggregation between the fibers. These aggregated particles or agglomerates have a large specific surface area and surface charge, and can form a stable suspension system in water; since the red soil emulsion contains clay substances, these clay substances have a layered structure, can absorb water molecules, and form colloidal substances; through stirring, the substances in the entire sewage can be driven to form a relatively uniform suspension state, and this process has a good auxiliary significance for the subsequent addition of flocculants. After the flocculant is added to the sewage, the above-mentioned particles or agglomerates can be further facilitated to continue to aggregate under the action of polyaluminium chloride PAC and polyacrylamide PAM to form a larger floc structure, that is, the clay minerals and other fine particles contained in the red soil, the particles and agglomerates attached and adsorbed with the plant fibers, can form larger and more stable flocs; and can be evenly adsorbed and agglomerated with the entire sewage system during the stirring and mixing process, the silt and larger particles are at the bottom of the sewage, the middle layer and the upper layer can be fully suspended and form a sufficient adsorption and agglomeration effect with the flocculants, thereby improving the flocculation efficiency and adsorption rate, and the particles in the red soil emulsion can also serve as additional flocculation nuclei , helping tiny suspended particles to gather together to form larger flocs, that is, enhancing the adsorption efficiency between the flocs and the flocs, thereby improving the sedimentation speed and efficiency; further improving the flocculation reaction efficiency of the flocculant, and being able to fully and evenly act on the sewage water body, improving the adsorption rate of the flocculation reaction, so that no excessive flocculants are required to achieve a considerable sedimentation effect (promoting the effect of the flocculant); therefore, more organic matter and particulate matter continue to gather in the inclined tube sedimentation area to form sludge, and settle to the bottom of the sewage and be pumped away by the sludge pump, and such rapid sedimentation can significantly reduce the chemical oxygen demand COD and the concentration of suspended solids SS in the clarified organic sewage.

[0015] The above-mentioned pretreated sewage can effectively improve the treatment efficiency in the biological treatment section. The appropriate sludge concentration helps to maintain sufficient microbial mass to effectively remove organic matter in the wastewater. If the concentration is too low, it may not be enough to provide sufficient microorganisms to degrade pollutants. If it is too high, it may cause insufficient oxygen supply or overcrowding to affect the treatment effect. After the pretreatment of the present invention, the COD concentration in the sewage is ≤1050mg / l, SS ≤140mg / l, the clarified sewage enters the outlet tank from the top, and the sewage BOD5 / COD ratio is increased by at least 5.77%. This allows the sludge concentration to be controlled at 3500-5000mg / L, and a stable microbial treatment effect can be obtained. The activated sludge method is a common biological treatment method that degrades organic matter in wastewater through microorganisms. Jet aeration can provide sufficient dissolved oxygen to promote the growth and metabolism of aerobic microorganisms. The appropriate sludge concentration also helps to balance the relationship between operating costs and treatment effects. A higher COD value means a higher organic content in the sewage, which will cause the microorganisms to consume more oxygen during the treatment process. If the COD is too high, it may cause excessive sludge load, affecting the treatment effect, reducing the treatment efficiency, and destroying the stability of the microorganisms, increasing costs. Therefore, an appropriate sludge concentration can ensure that the microorganisms have enough growth space and nutrients, thereby improving the efficiency of sewage treatment. If the COD is too high, it may lead to insufficient dissolved oxygen, affecting the activity of the microorganisms; if the sludge concentration is too low, it may lead to insufficient processing capacity and reduce efficiency. After the pretreatment based on the present invention, the increase in the BOD5 / COD ratio means that the proportion of biodegradable organic matter in the sewage increases, thereby improving the treatment efficiency. The control of COD and SS helps to maintain a suitable microbial growth environment and promote the biodegradation of organic matter; it can be seen that based on the pretreatment of the present invention, the subsequent microbial treatment link improves efficiency while maintaining the stability of the microbial system, making the cost controllable.

[0016] After the pretreatment of the present invention, due to the large floc structure and high efficiency of adsorbing sludge particles and other impurities, larger and more stable flocs are formed between the sludge particles obtained in the flocculation and sedimentation process, which helps to improve the filterability and compressibility of the sludge. When the sludge is sent to the sludge dewatering machine for deep dehydration, the sludge dryness can be quickly made ≥36%; after being air-dried to 40%, it is sent to the biomass boiler as a fuel for blending and burning, achieving harmless and resourceful treatment, and improving the level of energy saving and environmental protection. After the sludge is dehydrated, the filtrate is mixed with the pulp fiber high-concentration wastewater in a cycle and then enters the pretreatment.

[0017] Beneficial technical effects of the present invention:

[0018] (1) Efficient reduction of COD and SS: By adding red clay emulsion and flocculants in the pretreatment stage, the particulate matter and fiber agglomerates in the sewage are adsorbed to form large particles or large agglomerates, thereby promoting the flocculation effect and achieving efficient mud-water separation in the inclined tube coagulation and clarification area. After pretreatment, the COD concentration of the sewage can be reduced to ≤1050mg / L, and the SS concentration can be reduced to ≤140mg / L.

[0019] (2) Improve microbial treatment efficiency: Through pretreatment, the BOD5 / COD ratio of sewage increased by at least 5.77%, and the COD and SS concentrations were significantly reduced, so that the sludge concentration can be controlled between 3500-5000 mg / L. This appropriate sludge concentration helps to maintain sufficient microbial mass to effectively remove organic matter in wastewater, while avoiding the problem of insufficient oxygen supply or overcrowding caused by excessive sludge concentration; it helps to improve the treatment efficiency of the activated sludge method, ensuring that microorganisms have sufficient growth space and nutrients, thereby improving sewage treatment efficiency, while ensuring the stability of microorganisms.

[0020] (3) Energy saving and environmental protection: Through efficient pretreatment and comprehensive treatment, the utilization efficiency and reaction rate of flocculants are improved, saving treatment costs; at the same time, through efficient flocculation sedimentation and microbial treatment, the generated sludge has good filterability and compressibility. The dryness of the dehydrated sludge can reach ≥36%, which can be used as a fuel in biomass boilers to achieve harmless and resource-based treatment, and improve the level of energy saving and environmental protection.

[0021] Instruction Manual

[0022] Figure 1 The present invention is a process flow chart of a method for treating organic high-concentration wastewater from papermaking and pulping. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0024] Example 1: A method for treating high-concentration organic wastewater from papermaking and pulping, mainly involving sewage treatment processes and facilities designed and manufactured by the applicant, mainly involving the use of steel structures and steel materials to manufacture a 120m 3Wastewater treatment facilities, with a mixing tank at the front end, a sedimentation tank in the middle, a built-in PVC inclined pipe fixed at a 45-degree angle, and a water collection tank at the rear; pulp residue and sludge squeezed filtrate enter the mixing tank, and are fully mixed with the added flocculant under the action of the mixer. The flocculant reacts with SS and macromolecular organic compounds in the sewage to form "alum flowers", which enter the bottom of the sedimentation tank. When the wastewater flow rate slows down, most of the SS sinks to the bottom under the action of gravity, and the fine alum flowers rise with the water flow and adhere to the wall of the inclined pipe to form a filtration adsorption layer. While the water flow rises, it adsorbs SS and macromolecular organic substances in the water, and the wastewater with waste removed enters the water collection tank and naturally flows to the sewage treatment system for treatment. When the sludge in the inclined pipe accumulates to a certain extent, it gradually slides to the bottom of the pool under the action of gravity, and then is sent from the bottom of the pool to the sludge treatment system for deep dehydration treatment by a sludge pump. The goals achieved after treatment: COD removal rate ≥ 65%, SS removal rate ≥ 75%. The specific process details are as follows:

[0025] Wastewater is divided into two parts, which come from the pulp residue grinding and papermaking section and the existing sewage treatment sludge pressing filtrate. The wastewater from the pulp residue grinding and papermaking section is high-concentration organic wastewater (average wastewater COD concentration 45000mg / l) generated during pulp residue cooking, disc grinding decomposition and pulp board papermaking. It is pumped to the pretreatment facilities of the sewage treatment workshop through pipelines; in order to reduce the treatment load, recycle the solid suspended matter in the sewage treatment sludge pressing filtrate, and prevent the sludge from returning to the sewage treatment system repeatedly, it is planned to mix the sludge pressing filtrate in the sludge treatment system with the pulp residue wastewater and send it to the pretreatment tank for treatment;

[0026] The high-concentration wastewater produced by the pulping fiber papermaking section (the wastewater to be treated in this embodiment) is mixed with the filtrate after sludge pressing at a ratio of 9:100. The COD and SS concentrations of the wastewater are reduced to 4000-4500 mg / l, the SS concentration is 2000-3000 mg / l, and the wastewater volume is 1500-2000 m 3 / d, COD concentration decreased by more than 90%, SS decreased by more than 85%, and the remaining chemicals in the sludge filtrate can reduce the amount of pretreatment chemicals added.

[0027] Preparation of red soil emulsion: The red soil in this embodiment is selected from local red soil, the total content of iron and aluminum accounts for 5% to 10%, a large amount of silicon oxide; and the red soil type with sand and gravel and organic matter accounting for less than 5%. After the red soil is retrieved, it is crushed with a crusher, and then sent to an emulsion tank, and clean water is added. Under the action of a stirrer, an emulsion with a concentration of 130 to 150 g / l is formed, and then the emulsion is pumped into the tubular static mixer in the pretreatment section at a weight ratio of 0.1% to 0.5%, and mixed evenly with the wastewater, and then a flocculant is added, and further mixed and stirred in the tubular static mixer, and then enters the inclined tube sedimentation zone;

[0028] Preparation of flocculant: The function of flocculant is to make wastewater condensate produce flocculent precipitation, and through the dual effects of charge neutralization and bridging adsorption, COD and SS in wastewater form flocculent precipitation and separate from water. Therefore, the selection of high-efficiency and low-cost flocculant is the key to wastewater treatment. The present invention adopts ferric chloride (iron oxide content 9.5%) + polyacrylamide (concentration 0.20%) and polyaluminum chloride (aluminum oxide content 9.0%) + polyacrylamide (concentration 0.20%). The research on flocculants was carried out in the laboratory. Take 8 1000ml beakers, use a measuring cylinder to measure 500ml of wastewater (the two wastewaters of pulp fiber grinding and papermaking and sludge pressing are mixed in a ratio of 9.1:100), put it into a 200ml beaker, and under the stirring action of a magnetic stirrer, add corresponding concentrations of aluminum sulfate, polyaluminum chloride, ferric chloride, 0.20% polyacrylamide, polyacrylamide + ferric chloride, polyacrylamide + polyaluminum chloride solution, polyacrylamide + polyferric chloride, until the wastewater forms a large amount of alum flowers, then let it stand for 30 minutes, observe the reaction of the flocculants and the stratified sedimentation. Then select the flocculants with good "alum flower" formation and good flocculant sedimentation performance for production test research.

[0029] Flocculation and sedimentation: The mixed wastewater enters the spiral pipe mixer, and the chemicals are added in the pipe mixer. After mixing with the sewage in the pipe mixer, it enters the inclined tube sedimentation tank. The inclined tube clarifier is a self-made reaction equipment made of steel, with a volume of 200 cubic meters, divided into four parts: the first is the chemical mixing area, the second and third are the inclined tube coagulation and clarification areas, and the fourth is the outlet tank. The high-concentration mixed wastewater enters the mixing tank of the inclined tube clarifier. Under the high-speed stirring of the mixer, the chemicals react with the suspended matter and lignin in the sewage to form "alum flowers". Then the wastewater is sent from the top of the mixing tank to the bottom of the clarification area I. The wastewater transition speed slows down, and the organic fiber substances are mainly substances with "e-". In the "Al 3+ ” or “Fe 3+ "Under the dual effects of cationic charge and polyacrylamide bridging adsorption, solid particulate matter forms larger particles and settles downward, while fine particles rise to the inclined tube with the water flow, adhere to the tube wall due to the resistance of the inclined tube, accumulate to form an alum flower layer, adsorb fine particles, and fall to the bottom of the pool when a certain weight is reached. The clarified sewage enters the bottom of zone II from the top of zone I, and the fine particles that are not completely treated in zone I continue to flocculate and clarify in zone II, and then flow into the outlet tank from the top of zone II. The wastewater from the outlet tank is sent to the neutralization tank, mixed with pulp and paper wastewater, cooled, homogenized, and then sent to the microbial treatment system.

[0030] Microbial treatment: After coagulation and clarification, the wastewater enters the biochemical sewage treatment system for treatment. The key to low-cost treatment of wastewater by microbial system is to remove biodegradable organic matter (BOD) in wastewater, so it is necessary to evaluate the biodegradability of its pollutants. The main evaluation index is the BOD / COD value. The larger the BOD / COD ratio, the better the biodegradability of wastewater pollutants and the higher the treatment efficiency of the microbial system. The BOD of the wastewater after coagulation and clarification treatment was cultured and tested in the environmental protection experiment. According to the detection of COD and BOD of the treated wastewater, the BOD / COD ratio of the wastewater is 40.53%, which is 5.77% higher than the existing pulp and paper entering the sewage treatment, indicating that the biodegradability of the wastewater after coagulation and clarification treatment is better. The main reason is that the macromolecular substances and suspended solids in the wastewater are adsorbed and removed, while the soluble organic small molecular substances pass through the "alum flower" layer, thereby improving the biodegradability of the wastewater, which is conducive to the subsequent treatment of the biological system. After the high-concentration wastewater is mixed with the raw sewage, the wastewater volume increases by 10%, and the COD / BOD ratio increases by 5.77%. The biodegradable chemical oxygen demand (BOD) material load in the wastewater increases. The microbial treatment system process is adjusted to: MLSS concentration 3800-4300mg / L, SVI index ≤80m / g, F / M0.09-0.10kgBOD5 / kg / MLSSD, sludge return circulation rate 35-40%, nitrogen and phosphorus addition ratio BOD: N: P = 90-110: 4-6: 0.8-1, and dissolved oxygen in the system 1.5-2.5mg / L. Through the above process conditions, the BOD5 of the wastewater after microbial treatment is ≤16mg / L, and CODCr is reduced by 10-15% compared with the original. The activated sludge method and jet aeration method are adopted, the dissolved oxygen is controlled at 1.5-2.5mg / L, and the sludge concentration is controlled at 3500-5000mg / L. After passing through the microbial treatment system, the sludge enters the clarification tank. In the clarification tank, the sludge sinks to the bottom under the action of gravity and is circulated back to the aeration tank. The excess sludge is sent to the sludge storage tank. The clarified sewage is sent to the flotation tank by a sewage pump. A pipeline mixer is installed in front of the flotation tank. Chemicals are added in front of the pipeline mixer to make the chemicals and water fully mixed and react. Then the sewage enters the flotation tank. In the flotation tank, the COD macromolecules in the sewage react with the chemicals to form fine solid particles. At the same time, air is sent from the bottom of the flotation tank using an air compressor to form a large number of bubbles attached to the fine particles. The fine particles float and float to the surface of the flotation tank to form a sludge layer. Due to the high specific gravity of water, it sinks to the bottom of the water, forming mud and water separation. After mud and water separation, the wastewater meets the requirements of national standard GB3544-2008 for discharge.

[0031] Sludge dewatering treatment: After wastewater treatment, the sludge is composed of inclined tube sedimentation sludge, biological sludge from microbial treatment system and organic flocculent sludge from shallow flotation chemical reaction. Among them, since the sludge in the inclined tube sedimentation tank contains fine wood pulp fibers and red soil, it acts as a conduit during sludge filtration, and the water in the sludge penetrates through the fiber and soil gaps under capillary action. As an organism, microbial sludge has good sedimentation performance, and its body structure makes it easier to dehydrate than chemical organic sludge. Shallow flotation sludge is a flocculent material with wastewater-soluble COD, which is viscous and not easy to dehydrate. After inclined tube sedimentation treatment, the wastewater treatment efficiency is improved, and the sludge produced by shallow flotation is reduced by 10-15%, so that the sludge is mixed and enters the sludge dewatering machine, with higher dehydration efficiency. The moisture content of the sludge after dehydration is reduced by 3-6%. When the sludge is dehydrated and then air-dried, the water is easier to seep out than the original sludge, which is conducive to sending it to the biomass boiler for combustion treatment. The sludge is sent to the sludge mixing tank and then pumped to the sludge dewatering machine for deep dehydration, so that the sludge dryness is ≥36%. After air drying to 40%, it is sent to the biomass boiler as fuel for combustion, achieving harmless and resource-based treatment, and improving the level of energy conservation and environmental protection. After the sludge is dehydrated, the filtrate is mixed with the pulp fiber high-concentration wastewater and then enters the pretreatment.

[0032] After dehydration, the sludge is sent to the biomass boiler and mixed with coal for combustion, realizing the recycling and harmless treatment of sludge resources. The sludge is required to be as dry as possible after dehydration. The sludge dehydration performance test is carried out on a high-pressure filtration and dehydration equipment. The design value of the dryness after dehydration by the high-pressure filtration sludge dehydration filter is ≥36%. At present, the actual dryness of the sludge treated in the sewage treatment plant after dehydration is 37.14% on average. The sludge dehydration test is a deep dehydration test study on the sludge dehydrator after mixing the inclined tube sedimentation pretreatment sludge and the existing sewage treatment system sludge. The test time is 3 days, and the water content is tested every day according to the (GB / T2677.2-1993) standard. At the same time, the existing sewage treatment sludge and the mixed sludge after squeezing are exposed to the stack, and the water content is tested every day, and the sludge air drying condition is studied.

[0033] In this embodiment, the effect of the red clay emulsion is:

[0034] 1. Enhance flocculation effect:

[0035] Adsorption and aggregation: A large amount of silicon oxide (hole and bridge adsorption) particles such as silicon dioxide (SiO2), iron (Fe2O3) and aluminum (Al2O3) in red soil adhere to plant fibers to form a larger composite structure. These particles have a certain surface activity and can combine and adsorb with plant fibers, resulting in aggregation between fibers.

[0036] Increase specific surface area and surface charge: The formed composite particles or agglomerates have a larger specific surface area and surface charge, and can form a stable suspension system in water.

[0037] Auxiliary flocculant: The clay in the red clay emulsion has a layered structure and can absorb water molecules and form colloidal substances. Through stirring, it can drive the substances in the entire sewage to form a relatively uniform suspension state, providing a good basis for the subsequent addition of flocculants (such as polyaluminium chloride PAC and polyacrylamide PAM), thereby improving the flocculation efficiency and adsorption rate.

[0038] 2. Improve sedimentation speed and efficiency:

[0039] Forming larger and more stable flocs: Clay minerals and other fine particles contained in red soil can form larger and more stable flocs after being attached and adsorbed to plant fibers. These flocs are evenly distributed in the sewage and further aggregated under the action of flocculants to form larger floc structures, thereby improving sedimentation speed and efficiency.

[0040] As flocculation nuclei: The particles in the laterite emulsion can also serve as additional flocculation nuclei, helping small suspended particles to aggregate together to form larger flocs, thereby enhancing the adsorption efficiency between the flocs and increasing the sedimentation rate and efficiency.

[0041] 3. Reduce COD and SS concentrations:

[0042] Rapid sedimentation: More organic matter and particulate matter continue to gather in the inclined tube sedimentation area to form sludge, which settles to the bottom of the sewage and is pumped away by the sludge pump. This rapid sedimentation significantly reduces the chemical oxygen demand (COD) and suspended solids (SS) concentration in the clarified organic sewage.

[0043] Improve the BOD5 / COD ratio: After pretreatment, the BOD5 / COD ratio of sewage increases by at least 5.77%, which means that the proportion of biodegradable organic matter in the sewage increases, which helps to improve the treatment efficiency of the subsequent biological treatment stage.

[0044] 4. Improve sludge characteristics:

[0045] Improve filterability and compressibility: Due to the large floc structure and high efficiency in adsorbing sludge particles and other impurities, larger and more stable flocs are formed between the sludge particles obtained in the flocculation and sedimentation process, which helps to improve the filterability and compressibility of the sludge.

[0046] Deep dehydration: When the sludge is sent to the sludge dehydrator for deep dehydration, the sludge dryness can be quickly increased to ≥36%. After air drying to 40%, the sludge can be sent to the biomass boiler as a fuel for blending, achieving harmless and resourceful treatment, and improving energy conservation and environmental protection.

[0047] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for treating high-concentration organic wastewater from papermaking and pulping, characterized in that include: Preprocessing section: After the organic high-concentration wastewater is mixed and diluted with the sludge dewatering filtrate, 0.1% to 0.5% by weight of red clay emulsion is added and stirred and mixed evenly, and the pre-made flocculant is added and stirred and mixed evenly, and then enters the inclined tube coagulation and clarification area for the first flocculation and sedimentation to achieve mud and water separation. The settled sludge enters the sludge tank, and the clarified sewage flows into the neutralization tank from the top; Comprehensive processing section: The mixed wastewater is cooled and homogenized, then sent to the microbial treatment section for activated sludge treatment. Sufficient dissolved oxygen is provided through jet aeration to support the growth of microorganisms. The sludge concentration can be controlled at 3500-5000 mg / L. The wastewater after microbial treatment enters the clarification tank, and after sludge sedimentation, it is recycled back to the aeration tank for continued use, and the excess sludge is transferred to the sludge tank. After secondary flocculation and sedimentation, the clarified wastewater enters the flotation tank for mud and water separation, and the wastewater meets the discharge standards and is discharged. The sludge is dehydrated and used as a fuel for blending. The filtrate from the dehydrated sludge is mixed with high-concentration organic wastewater and then circulated in the pretreatment section.

2. The method for treating high-concentration organic wastewater from papermaking and pulping according to claim 1, characterized in that: The preparation process of the red soil emulsion includes: selecting red soil, selecting a type of red soil in which the total content of iron and aluminum oxides is between 5% and 10%, and the content of sand and organic matter is less than 5%, crushing or grinding, adding water and mixing, and preparing a red soil emulsion with a concentration of 130 to 150 g / l.

3. The method for treating high-concentration organic wastewater from papermaking and pulping according to claim 1, characterized in that: The COD concentration of the organic high-concentration wastewater is ≤40000 mg / l, and the SS concentration is ≤20000 mg / l; after the first flocculation and sedimentation in the pretreatment stage realizes mud-water separation, the COD removal rate of the sewage is ≥65%, and the SS removal rate is ≥75%.

4. The method for treating high-concentration organic wastewater from papermaking and pulping according to claim 1, characterized in that: The flocculant is composed of polyaluminium chloride, ferric chloride and / or aluminium sulfate and polyacrylamide; wherein: the aluminium oxide content of polyaluminium chloride is 9%, the iron oxide content of ferric chloride is 9.5%; the aluminium oxide content of aluminium sulfate is 18%; polyacrylamide is prepared at a concentration of 0.20%; the volume ratio of the flocculant is polyacrylamide:ferric chloride:polyaluminium chloride=4:3:

1.

5. The method for treating high-concentration organic wastewater from papermaking and pulping according to claim 1, characterized in that: The inclined tube coagulation and clarification area includes two sets of inclined tube settlers connected in series. Under the dual effects of the cationic charge of the flocculant and the bridging adsorption of polyacrylamide, the particulate matter and fiber aggregates in the sewage are adsorbed to form large particles or large aggregates, which settle downward, while the small particles, suspended aggregates and suspended particles rise to the inclined tube with the water flow, adhere to the tube wall after being resisted by the inclined tube surface, and accumulate to form an alum flower layer. When these adsorbed fine particles, suspended aggregates and suspended particles reach a certain weight, they fall to the bottom of the pool in groups; smaller particles and suspended aggregates are further adsorbed and accumulated in the second set of inclined tube settlers and precipitate again; the precipitated sludge enters the sludge tank.

6. The method for treating high-concentration organic wastewater from papermaking and pulping according to claim 5, characterized in that: The inclined tube coagulation and clarification zone includes a mixing zone, a first clarification zone and a second clarification zone. A mixer is arranged in the mixing zone. Under the high-speed action of the mixer, the flocculant and the organic macromolecular substances in the sewage are mixed and reacted to form particles or agglomerates. The first clarification zone and the second clarification zone are two sets of inclined tube clarification zones connected in series. PVC inclined tubes are arranged at an angle of 45 degrees. The sewage enters the two clarification zones and is adsorbed on the inclined tubes and the lower area through cationic charges and bridging twice to form an "alum flower" layer. Then, when the organic matter in the rising sewage passes through the "alum flower" layer, the macromolecular organic particles and suspended matter are adsorbed, and when a certain weight is reached, they sink to the bottom of the pool and are pumped away by a pump. After passing through the two clarification zones, the COD concentration of the sewage is ≤1050mg / l, and the SS is ≤140mg / l. The clarified sewage enters the outlet tank from the top, and the sewage BOD5 / COD ratio is increased by at least 5.77%.

7. The method for treating high-concentration organic wastewater from papermaking and pulping according to claim 1, characterized in that: The dissolved oxygen in the microbial treatment section is controlled between 1.5-2.5 mg / l, and the sludge concentration is controlled between 3500-5000 mg / l; the sludge enters the clarification tank after passing through the microbial treatment system, where the sludge sinks to the bottom under the action of gravity and is circulated back to the aeration tank, and the excess sludge is sent to the sludge storage tank; the clarified sewage is sent to the flotation tank by a sewage pump, a pipeline mixer is installed in front of the flotation tank, and flocculants are added in front of the pipeline mixer to allow the chemicals and water to fully mix and react, and then the sewage enters the flotation tank, where the COD macromolecules in the sewage react with the chemicals to form fine solid particles, and finally a sludge layer is formed to achieve mud-water separation, and the sludge after flotation is sent to the sludge tank, and the sewage meets the discharge standards.

8. The method for treating high-concentration organic wastewater from papermaking and pulping according to claim 1, characterized in that: Before the sewage enters the microbial treatment, it is cooled and the water quality is adjusted to a temperature of ≤35°C, and mixed evenly in the homogenization tank.

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