A papermaking wastewater treatment process based on slowing down sludge calcification

Abstract

This invention relates to the field of wastewater treatment technology, specifically to a papermaking wastewater treatment process based on mitigating sludge calcification, comprising the following steps: S1: pretreatment, S2: calcium separation treatment, S3: deep decalcification treatment, S4: deep treatment, S5: anaerobic biological treatment, and S6: recovery treatment. In this invention, the treatment agent added during the calcium separation treatment process achieves large-scale separation of calcium ions from the water in a gentle manner. Subsequently, in the deep decalcification treatment, a weakly acidic cation exchange resin is used for fine treatment. These two processes work synergistically to fundamentally and significantly reduce the calcium ion load entering the subsequent anaerobic biological treatment system, completely changing the conditions under which calcium carbonate deposits on the sludge surface in the biological treatment tank. This effectively solves the fundamental technical problem of reduced activity, decreased fluidity, and equipment scaling and clogging caused by sludge calcification.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a papermaking wastewater treatment process and its preparation method based on slowing down sludge calcification. Background Technology

[0002] Papermaking wastewater is a general term for all kinds of wastewater generated during the pulping and papermaking process. It mainly includes pulping and cooking waste liquor (black liquor), washing wastewater, bleaching wastewater and paper machine white water. This type of wastewater has a complex composition and usually contains a large amount of suspended solids (such as fibers and fiber fines), biochemical oxygen demand (BOD) and chemical oxygen demand (COD) substances, as well as some recalcitrant organic matter (such as lignin) and inorganic salts.

[0003] In existing technologies, biological treatment systems for paper tube production wastewater generally face serious sludge calcification problems. This is mainly because high concentrations of calcium ions in the wastewater easily combine with anions such as carbonate ions during biological treatment, forming calcium carbonate precipitates that deposit inside and on the surface of sludge particles. This leads to reduced sludge activity, increased density, and poor flowability, making equipment prone to scaling and clogging. Based on this, the present invention provides a papermaking wastewater treatment process and its preparation method based on mitigating sludge calcification. Summary of the Invention

[0004] The purpose of this invention is to provide a papermaking wastewater treatment process and preparation method based on slowing down sludge calcification, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a papermaking wastewater treatment process based on slowing down sludge calcification, comprising the following steps: S1: Pretreatment, pretreatment of papermaking wastewater generated from paper tube base paper production to obtain pretreated wastewater for later use; S2: Calcium separation treatment, calcium separation treatment of pretreated wastewater to obtain the first treated liquid, which is ready for use; S3: Deep decalcification treatment, the first treatment solution is subjected to deep decalcification treatment to obtain the second treatment solution, which is ready for use; S4: Deep processing, the second processing solution is subjected to deep processing to obtain the third processing solution; S5: Anaerobic biological treatment, the third treatment solution is subjected to anaerobic biological treatment to obtain the fourth treatment solution; S6: Recycling and treatment. The fourth treatment liquid is filtered and disinfected, and can be recycled again if it meets the standards.

[0006] Preferably, the pretreatment method is as follows: papermaking wastewater is filtered through a filter screen to remove large particulate impurities, and then injected into a sedimentation tank for natural settling for 10-16 hours to complete the pretreatment and obtain pretreated wastewater.

[0007] Preferably, the calcium separation treatment method is as follows: sodium carbonate is added to the pretreated wastewater, the pH value is controlled at 9.5-10.5, and after stirring and reaction, precipitation is carried out for 6-10 hours. After precipitation, a treatment agent is added to the pretreated wastewater, and after stirring and reaction, precipitation is carried out for 10-16 hours to complete the calcium separation treatment and obtain the first treated solution.

[0008] Preferably, the treatment agent is prepared by the following method: sodium citrate, sodium borate, and deionized water are added to a reaction vessel and heated to 45-50°C to obtain a first mixture, which is set aside. Polyaspartic acid, itaconic acid, acrylic acid, L-aspartic acid, carboxylated nanocellulose, and deionized water are added to a mixer and stirred at 200-400 rpm for 20-40 min. Then, the mixture is subjected to high-speed shearing at 8000-12000 rpm for 20-30 min to obtain a second mixture. The first mixture is added to a reaction vessel and the temperature is set to 40-45°C. The second mixture is then slowly added and stirred at 200-400 rpm for 20-40 min. The resulting product is subjected to high-speed shearing at 8000-12000 rpm for 30-40 min and allowed to stand for 24 h. The resulting product is then mixed with water at a mass ratio of 1:1 to obtain the treatment agent.

[0009] Preferably, the mass ratio of sodium citrate, sodium borate, and deionized water is 1:0.4-0.6:1.5-2, the mass ratio of polyaspartic acid, itaconic acid, acrylic acid, L-aspartic acid, carboxylated nanocellulose, and deionized water is 1:0.3-0.5:0.2-0.4:0.1-0.3:0.05-0.15:8-12, and the mass ratio of the first mixture and the second mixture is 1:0.5-0.8.

[0010] Preferably, the deep decalcification treatment method is as follows: a fixed-bed ion exchange column is used, and a first treatment solution is introduced. Before introducing the first treatment solution, the pH value is adjusted to 7.0-7.5, and the flow rate is controlled at 10-20 BV / h. When the calcium ion concentration in the effluent is ≥1 mg / L, the treatment is stopped and regeneration is performed. The regeneration is carried out using a 5-8% hydrochloric acid solution at a flow rate of 2-4 BV / h in a countercurrent manner. The regenerated liquid is returned to the calcium separation treatment step S2.

[0011] Preferably, the fixed-bed ion exchange column is made of a weakly acidic cation exchange resin, and the functional group of the resin is a carboxyl group.

[0012] Preferably, the deep treatment method is as follows: the second treatment liquid is subjected to advanced oxidation treatment and coagulation sedimentation treatment in sequence. The advanced oxidation treatment adopts ozone catalytic oxidation method. The coagulation sedimentation treatment method is to add coagulant and flocculant to the wastewater after advanced oxidation, stir and react, and then precipitate to obtain the third treatment liquid. In this case, the coagulant is polyaluminum chloride and the flocculant is anionic polyacrylamide.

[0013] Preferably, the anaerobic biological treatment method is as follows: the third treatment liquid is introduced into an upflow anaerobic sludge bed, the reactor temperature is controlled at 35-38℃, the hydraulic retention time is 12-24h, and the system influent COD is 3500-4000mg / L.

[0014] Preferably, the recycling method is as follows: the fourth treatment liquid is filtered sequentially through an activated carbon filter, and then disinfected sequentially with ultraviolet light and ozone. The treated effluent meets the reuse standard and can be recycled again.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In the treatment of wastewater generated during the production of paper tube base paper, during the calcium separation process, sodium citrate preferentially forms a soluble complex with free calcium ions in the wastewater. Sodium borate adjusts the pH environment of the water, inhibiting the spontaneous nucleation of calcium carbonate crystals. Polymers such as polyaspartic acid and itaconic acid are adsorbed onto the surface of tiny calcium carbonate crystal nuclei, preventing them from further growing into large-sized hard scale through steric hindrance. Carboxylated nanocellulose, with its large specific surface area and abundant functional groups, can "capture" these dispersed and refined crystal nuclei and encapsulate them in its fiber network, forming... The process forms easily settling flocs, thus achieving large-scale separation of calcium ions from the water in a gentle manner. Subsequently, in the deep decalcification treatment, a weakly acidic cation exchange resin is used for fine treatment. Its carboxyl functional groups can specifically adsorb and exchange residual trace amounts of calcium ions, resulting in a stable decrease in the calcium ion concentration in the effluent. These two processes work together to fundamentally and significantly reduce the calcium ion load entering the subsequent anaerobic biological treatment system, completely changing the conditions under which calcium carbonate deposits on the sludge surface in the biological treatment tank. This effectively solves the fundamental technical problem of reduced activity, poor fluidity, and equipment scaling and clogging caused by sludge calcification.

[0016] 2. In this invention, after effectively removing calcium ions, the ozone catalytic oxidation in the deep treatment unit decomposes stubborn lignin and other large molecular organic matter in the wastewater into small molecular organic matter, significantly improving the biodegradability of the wastewater. Subsequently, in the anaerobic biological treatment unit, since the calcium ion concentration has been greatly reduced, the microbial activity in the activated sludge can be fully exerted, and the pretreated organic matter can be efficiently degraded. This design of oxidation and cell disruption combined with optimized biodegradation improves the overall removal efficiency of COD and BOD, and solves the problem of low treatment efficiency of traditional processes for recalcitrant organic matter.

[0017] 3. In this invention, the effluent from the activated carbon filtration and disinfection process is of excellent quality and can be stably reused in production, which greatly reduces the amount of fresh water taken in and the amount of wastewater discharged, thereby improving economic and environmental benefits. Attached Figure Description

[0018] Figure 1 The present invention provides a flowchart of a papermaking wastewater treatment process and preparation method based on slowing down sludge calcification. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0021] Example 1: A papermaking wastewater treatment process based on mitigating sludge calcification includes the following steps: S1: Pretreatment, pretreatment of papermaking wastewater generated from paper tube base paper production to obtain pretreated wastewater for later use; The pretreatment method is as follows: papermaking wastewater is filtered through a screen to remove large particles of impurities, and then injected into a sedimentation tank for natural settling for 10 hours to complete the pretreatment and obtain pretreated wastewater. S2: Calcium separation treatment, calcium separation treatment of pretreated wastewater to obtain the first treated liquid, which is ready for use; The calcium separation treatment method is as follows: sodium carbonate is added to the pretreated wastewater, the pH value is controlled at 9.5, and after stirring and reaction, precipitation is carried out for 6 hours. After precipitation, a treatment agent is added to the pretreated wastewater, and after stirring and reaction, precipitation is carried out for 10 hours to complete the calcium separation treatment and obtain the first treated solution. The treatment agent is prepared by the following method: sodium citrate, sodium borate, and deionized water are added to a reaction vessel in a mass ratio of 1:0.4:1.5 and heated to 45°C to obtain a first mixture, which is set aside for later use. Polyaspartic acid, itaconic acid, acrylic acid, L-aspartic acid, carboxylated nanocellulose, and deionized water are added to a mixer in a mass ratio of 1:0.3:0.2:0.1:0.05:8 and stirred at 200 rpm for 20 min. Then, it is subjected to high-speed shearing at 8000 rpm for 20 min to obtain a second mixture. The first mixture is added to a reaction vessel, the temperature is set to 40°C, and the second mixture is slowly added. The mixture is stirred at 200 rpm for 20 min. The resulting product is subjected to high-speed shearing at 8000 rpm for 30 min and allowed to stand for 24 h. The resulting product is mixed with water in a mass ratio of 1:1 to obtain the treatment agent. The mass ratio of the first mixture to the second mixture is 1:0.5. S3: Deep decalcification treatment, the first treatment solution is subjected to deep decalcification treatment to obtain the second treatment solution, which is ready for use; The deep decalcification treatment method is as follows: a fixed-bed ion exchange column is used, and the first treatment solution is introduced. Before the first treatment solution is introduced, the pH value is adjusted to 7.0, and the flow rate is controlled at 10 BV / h. When the calcium ion concentration in the effluent is ≥1 mg / L, the treatment is stopped and regeneration is performed. The regeneration is performed using a 5% hydrochloric acid solution at a flow rate of 2 BV / h in a countercurrent manner. The regenerated liquid is returned to the calcium separation treatment step S2. The fixed-bed ion exchange column uses a weakly acidic cation exchange resin, and the functional group of the resin is a carboxyl group. S4: Deep processing, the second processing solution is subjected to deep processing to obtain the third processing solution; The deep treatment method is as follows: the second treatment liquid is subjected to advanced oxidation treatment and coagulation sedimentation treatment in sequence. The advanced oxidation treatment adopts ozone catalytic oxidation method. The coagulation sedimentation treatment method is to add coagulant and flocculant to the wastewater after advanced oxidation, stir and react, and then precipitate to obtain the third treatment liquid. Among them, polyaluminum chloride is selected as the coagulant and anionic polyacrylamide is selected as the flocculant. S5: Anaerobic biological treatment, the third treatment liquid is fed into the upflow anaerobic sludge bed, the reactor temperature is controlled at 35℃, the hydraulic retention time is 12h, the system influent COD is 3500mg / L, and the fourth treatment liquid is obtained. S6: Recycling and treatment. The fourth treatment liquid is filtered and disinfected, and can be recycled if it meets the standards. The recycling process involves filtering the fourth treatment liquid through an activated carbon filter, followed by disinfection with ultraviolet light and ozone. The treated effluent meets reuse standards and can be recycled again.

[0022] Example 2: A papermaking wastewater treatment process based on mitigating sludge calcification includes the following steps: S1: Pretreatment, pretreatment of papermaking wastewater generated from paper tube base paper production to obtain pretreated wastewater for later use; The pretreatment method is as follows: papermaking wastewater is filtered through a filter screen to remove large particulate impurities, and then injected into a sedimentation tank for natural settling for 13 hours to complete the pretreatment and obtain pretreated wastewater. S2: Calcium separation treatment, calcium separation treatment of pretreated wastewater to obtain the first treated liquid, which is ready for use; The calcium separation treatment method is as follows: sodium carbonate is added to the pretreated wastewater, the pH value is controlled at 10, the mixture is stirred and reacted, and then precipitated for 8 hours. After the precipitation is completed, a treatment agent is added to the pretreated wastewater, the mixture is stirred and reacted, and then precipitated for 13 hours to complete the calcium separation treatment and obtain the first treated solution. The treatment agent is prepared by the following method: sodium citrate, sodium borate, and deionized water are added to a reaction vessel in a mass ratio of 1:0.5:1.8 and heated to 48°C to obtain a first mixture, which is set aside for later use. Polyaspartic acid, itaconic acid, acrylic acid, L-aspartic acid, carboxylated nanocellulose, and deionized water are added to a mixer in a mass ratio of 1:0.4:0.3:0.2:0.1:10 and stirred at 300 rpm for 30 min. Then, it is subjected to high-speed shearing at 10000 rpm for 25 min to obtain a second mixture. The first mixture is added to a reaction vessel, the temperature is set to 42°C, and the second mixture is slowly added. The mixture is stirred at 300 rpm for 30 min. The resulting product is subjected to high-speed shearing at 10000 rpm for 35 min and allowed to stand for 24 h. The resulting product is mixed with water in a mass ratio of 1:1 to obtain the treatment agent. The mass ratio of the first mixture to the second mixture is 1:0.65. S3: Deep decalcification treatment, the first treatment solution is subjected to deep decalcification treatment to obtain the second treatment solution, which is ready for use; The deep decalcification treatment method is as follows: a fixed-bed ion exchange column is used, and the first treatment solution is introduced. Before the first treatment solution is introduced, the pH value is adjusted to 7.2, and the flow rate is controlled at 15 BV / h. When the calcium ion concentration in the effluent is ≥1 mg / L, the treatment is stopped and regeneration is performed. The regeneration is carried out using a 6.5% hydrochloric acid solution at a flow rate of 3 BV / h in a countercurrent manner. The regenerated liquid is returned to the calcium separation treatment step S2. The fixed-bed ion exchange column uses a weakly acidic cation exchange resin, and the functional group of the resin is a carboxyl group. S4: Deep processing, the second processing solution is subjected to deep processing to obtain the third processing solution; The deep treatment method is as follows: the second treatment liquid is subjected to advanced oxidation treatment and coagulation sedimentation treatment in sequence. The advanced oxidation treatment adopts ozone catalytic oxidation method. The coagulation sedimentation treatment method is to add coagulant and flocculant to the wastewater after advanced oxidation, stir and react, and then precipitate to obtain the third treatment liquid. Among them, polyaluminum chloride is selected as the coagulant and anionic polyacrylamide is selected as the flocculant. S5: Anaerobic biological treatment, the third treatment liquid is fed into the upflow anaerobic sludge bed, the reactor temperature is controlled at 37℃, the hydraulic retention time is 18h, the system influent COD is 3700mg / L, and the fourth treatment liquid is obtained. S6: Recycling and treatment. The fourth treatment liquid is filtered and disinfected, and can be recycled if it meets the standards. The recycling process involves filtering the fourth treatment liquid through an activated carbon filter, followed by disinfection with ultraviolet light and ozone. The treated effluent meets reuse standards and can be recycled again.

[0023] Example 3: A papermaking wastewater treatment process based on mitigating sludge calcification includes the following steps: S1: Pretreatment, pretreatment of papermaking wastewater generated from paper tube base paper production to obtain pretreated wastewater for later use; The pretreatment method is as follows: papermaking wastewater is filtered through a screen to remove large particles of impurities, and then injected into a sedimentation tank for natural settling for 16 hours to complete the pretreatment and obtain pretreated wastewater. S2: Calcium separation treatment, calcium separation treatment of pretreated wastewater to obtain the first treated liquid, which is ready for use; The calcium separation treatment method is as follows: sodium carbonate is added to the pretreated wastewater, the pH value is controlled at 10.5, and after stirring and reaction, the water is precipitated for 10 hours. After the precipitation is completed, a treatment agent is added to the pretreated wastewater, and after stirring and reaction, the water is precipitated for 16 hours to complete the calcium separation treatment and obtain the first treated solution. The treatment agent is prepared by the following method: sodium citrate, sodium borate, and deionized water are added to a reaction vessel in a mass ratio of 1:0.6:2 and heated to 50°C to obtain a first mixture, which is set aside for later use. Polyaspartic acid, itaconic acid, acrylic acid, L-aspartic acid, carboxylated nanocellulose, and deionized water are added to a mixer in a mass ratio of 1:0.5:0.4:0.3:0.15:12 and stirred at 400 rpm for 40 min. Then, the mixture is subjected to high-speed shearing at 12000 rpm for 30 min to obtain a second mixture. The first mixture is added to a reaction vessel, the temperature is set to 45°C, and the second mixture is slowly added. The mixture is stirred at 400 rpm for 40 min. The resulting product is subjected to high-speed shearing at 12000 rpm for 40 min and allowed to stand for 24 h. The resulting product is mixed with water in a mass ratio of 1:1 to obtain the treatment agent. The mass ratio of the first mixture to the second mixture is 1:0.8. S3: Deep decalcification treatment, the first treatment solution is subjected to deep decalcification treatment to obtain the second treatment solution, which is ready for use; The deep decalcification treatment method is as follows: a fixed-bed ion exchange column is used, and the first treatment solution is introduced. Before the first treatment solution is introduced, the pH value is adjusted to 7.5, and the flow rate is controlled at 20 BV / h. When the calcium ion concentration in the effluent is ≥1 mg / L, the treatment is stopped and regeneration is performed. The regeneration is carried out using an 8% hydrochloric acid solution at a flow rate of 4 BV / h in a countercurrent manner. The regenerated liquid is returned to the calcium separation treatment step S2. The fixed-bed ion exchange column uses a weakly acidic cation exchange resin, and the functional group of the resin is a carboxyl group. S4: Deep processing, the second processing solution is subjected to deep processing to obtain the third processing solution; The deep treatment method is as follows: the second treatment liquid is subjected to advanced oxidation treatment and coagulation sedimentation treatment in sequence. The advanced oxidation treatment adopts ozone catalytic oxidation method. The coagulation sedimentation treatment method is to add coagulant and flocculant to the wastewater after advanced oxidation, stir and react, and then precipitate to obtain the third treatment liquid. Among them, polyaluminum chloride is selected as the coagulant and anionic polyacrylamide is selected as the flocculant. S5: Anaerobic biological treatment, the third treatment liquid is fed into the upflow anaerobic sludge bed, the reactor temperature is controlled at 38℃, the hydraulic retention time is 24h, the system influent COD is 4000mg / L, and the fourth treatment liquid is obtained. S6: Recycling and treatment. The fourth treatment liquid is filtered and disinfected, and can be recycled if it meets the standards. The recycling process involves filtering the fourth treatment liquid through an activated carbon filter, followed by disinfection with ultraviolet light and ozone. The treated effluent meets reuse standards and can be recycled again.

[0024] Comparative Example 1: The difference between this comparative example and Example 1 is that in the S2 calcium separation process, no treatment agent is added, only sodium carbonate is added, pH is adjusted, and precipitation is performed.

[0025] Comparative Example 2 differs from Example 1 in that: in the deep decalcification treatment step, a fixed-bed ion exchange column is not used in this comparative example, and the first treatment solution obtained in S2 is directly used as the second treatment solution for deep treatment.

[0026] Comparative Example 3 differs from Example 1 in that: in the advanced treatment step, ozone catalytic oxidation is not performed in this comparative example; the second treatment liquid is only subjected to coagulation and sedimentation treatment before being used as the third treatment liquid for anaerobic biological treatment.

[0027] Performance testing: The papermaking wastewater treatment processes of Examples 1-3 and Comparative Examples 1-3 were tested; Effluent calcium ion concentration: The calcium ion concentration (mg / L) was tested according to GB / T 15454-2009 and recorded in Table 1. The lower the value, the better the effect of controlling sludge calcification from the source. Chemical oxygen demand (COD) removal rate: The COD removal rate (%) was tested according to the HJ 828-2017 standard and recorded in Table 1. The higher the value, the stronger the process's ability to degrade organic matter. Wastewater biodegradability enhancement test: Refer to the HJ 505-2009 standard to test BOD5, then determine the BOD5 / COD ratio and record it in Table 1.

[0028] Table 1:

[0029] Analysis and comparison of the data in the table above show that all data in Examples 1-3 are excellent and superior to those in Comparative Examples 1-3, indicating that the complete process route of the present invention is valuable. In particular, the effluent calcium ion concentration data is far below the risk threshold that easily leads to sludge calcification. This is because the special calcium ion deep and precise removal in the calcium separation treatment and the low calcium ion environment are the key to preventing sludge calcification at the source and ensuring the long-term stable operation of the biochemical system. The high COD removal rate and the BOD5 / COD ratio are higher than 0.4, indicating that the ozone catalytic oxidation of the deep treatment unit effectively decomposes the large molecular organic matter such as lignin in the wastewater into small molecular intermediate products. Subsequently, in the anaerobic biological treatment unit, the activated sludge microorganisms can efficiently degrade them. Further analysis and comparison revealed that the calcium ion concentration in the effluent of Comparative Example 1 increased dramatically. This indicates that conventional precipitation with sodium carbonate alone cannot achieve the high-efficiency calcium removal effect achievable by the specialized treatment agent through synergistic effects such as complexation, lattice distortion, and trapping. The high concentration of calcium ions entering subsequent systems will greatly increase the risk of sludge calcification and equipment scaling, directly threatening the stable operation of the biological unit. Although the calcium ion concentration in Comparative Example 2 was significantly lower than that in Comparative Example 1, it was still significantly higher than in all examples. This indicates that the effluent after calcium separation still contains a considerable amount of calcium ions, which must be deeply purified through ion exchange to reach extremely low levels. Without this step, the calcium ion concentration in the effluent remains in a dangerous range, making it difficult to fundamentally solve the sludge calcification problem. Comparative Example 3 showed significant shortcomings in COD removal rate and BOD5 / COD ratio. This indicates that without the ozone catalytic oxidation unit, stubborn large molecular organic matter such as lignin in the wastewater could not be effectively decomposed, resulting in poor biodegradability. Subsequent microorganisms could not utilize and degrade it, ultimately leading to a decrease in COD removal rate.

[0030] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0031] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A papermaking wastewater treatment process based on slowing down sludge calcification, characterized in that: Includes the following steps: S1: Pretreatment, pretreatment of papermaking wastewater generated from paper tube base paper production to obtain pretreated wastewater for later use; S2: Calcium separation treatment, calcium separation treatment of pretreated wastewater to obtain the first treated liquid, which is ready for use; S3: Deep decalcification treatment, the first treatment solution is subjected to deep decalcification treatment to obtain the second treatment solution, which is ready for use; S4: Deep processing, the second processing solution is subjected to deep processing to obtain the third processing solution; S5: Anaerobic biological treatment, the third treatment solution is subjected to anaerobic biological treatment to obtain the fourth treatment solution; S6: Recycling and treatment. The fourth treatment liquid is filtered and disinfected, and can be recycled again if it meets the standards.

2. The papermaking wastewater treatment process based on mitigating sludge calcification according to claim 1, characterized in that, The pretreatment method is as follows: papermaking wastewater is filtered through a filter screen to remove large particulate impurities, and then injected into a sedimentation tank for natural settling for 10-16 hours to complete the pretreatment and obtain pretreated wastewater.

3. The papermaking wastewater treatment process based on slowing down sludge calcification according to claim 1, characterized in that, The calcium separation treatment method is as follows: sodium carbonate is added to the pretreated wastewater, the pH value is controlled at 9.5-10.5, and after stirring and reaction, precipitation is carried out for 6-10 hours. After precipitation, a treatment agent is added to the pretreated wastewater, and after stirring and reaction, precipitation is carried out for 10-16 hours to complete the calcium separation treatment and obtain the first treated solution.

4. The papermaking wastewater treatment process based on slowing down sludge calcification according to claim 3, characterized in that, The treatment agent is prepared by the following method: sodium citrate, sodium borate, and deionized water are added to a reaction vessel and heated to 45-50°C to obtain a first mixture, which is set aside. Polyaspartic acid, itaconic acid, acrylic acid, L-aspartic acid, carboxylated nanocellulose, and deionized water are added to a mixer and stirred at 200-400 rpm for 20-40 min. Then, the mixture is subjected to high-speed shearing at 8000-12000 rpm for 20-30 min to obtain a second mixture. The first mixture is added to a reaction vessel and the temperature is set to 40-45°C. The second mixture is then slowly added and stirred at 200-400 rpm for 20-40 min. The resulting product is subjected to high-speed shearing at 8000-12000 rpm for 30-40 min and allowed to stand for 24 h. The resulting product is then mixed with water at a mass ratio of 1:1 to obtain the treatment agent.

5. The papermaking wastewater treatment process based on slowing down sludge calcification according to claim 4, characterized in that, The mass ratio of sodium citrate, sodium borate, and deionized water is 1:0.4-0.6:1.5-2; the mass ratio of polyaspartic acid, itaconic acid, acrylic acid, L-aspartic acid, carboxylated nanocellulose, and deionized water is 1:0.3-0.5:0.2-0.4:0.1-0.3:0.05-0.15:8-12; and the mass ratio of the first mixture to the second mixture is 1:0.5-0.

8.

6. The papermaking wastewater treatment process based on mitigating sludge calcification according to claim 1, characterized in that, The deep decalcification treatment method is as follows: a fixed-bed ion exchange column is used, and a first treatment solution is introduced. Before introducing the first treatment solution, the pH value is adjusted to 7.0-7.5, and the flow rate is controlled at 10-20 BV / h. When the calcium ion concentration in the effluent is ≥1 mg / L, the treatment is stopped and regeneration is performed. The regeneration is carried out using a 5-8% hydrochloric acid solution at a flow rate of 2-4 BV / h in a countercurrent manner. The regenerated liquid is returned to the calcium separation treatment step S2.

7. The papermaking wastewater treatment process based on slowing down sludge calcification according to claim 6, characterized in that, The fixed-bed ion exchange column is made of a weakly acidic cation exchange resin, and the functional group of the resin is a carboxyl group.

8. The papermaking wastewater treatment process based on mitigating sludge calcification according to claim 1, characterized in that, The advanced treatment method is as follows: the second treatment liquid is subjected to advanced oxidation treatment and coagulation sedimentation treatment in sequence. The advanced oxidation treatment adopts ozone catalytic oxidation method. The coagulation sedimentation treatment method is to add coagulant and flocculant to the wastewater after advanced oxidation, stir and react, and then precipitate to obtain the third treatment liquid. Among them, polyaluminum chloride is selected as the coagulant and anionic polyacrylamide is selected as the flocculant.

9. The papermaking wastewater treatment process based on slowing down sludge calcification according to claim 1, characterized in that, The anaerobic biological treatment method is as follows: the third treatment liquid is introduced into an upflow anaerobic sludge bed, the reactor temperature is controlled at 35-38℃, the hydraulic retention time is 12-24h, and the system influent COD is 3500-4000mg / L.

10. The papermaking wastewater treatment process based on mitigating sludge calcification according to claim 1, characterized in that, The recycling method is as follows: the fourth treatment liquid is filtered through an activated carbon filter in sequence, and then disinfected by ultraviolet light and ozone in sequence. The treated effluent meets the reuse standard and can be recycled again.

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