Iron mud comprehensive recycling sub-system and method for synergistically reducing carbon in industrial wastewater treatment

Abstract

The application discloses an iron mud comprehensive reuse sub-system and method for synergistically reducing carbon in industrial wastewater treatment, and belongs to the technical field of wastewater treatment. The iron mud comprehensive reuse sub-system is independent of a main wastewater treatment system and comprises an iron mud pulping pool, a cyclone system, a heavy sinking system and a reducing iron mud pool connected in sequence. The reuse method is as follows: the filtered Fenton wet mud is pulped, then deep washing, efficient concentration and coarse separation are carried out, and the separated mud water or mud slurry is strategically applied to key sections of the main wastewater treatment system, including an anaerobic biochemical system, a flocculation air flotation pool, an iron ammonia oxidation MBR pool and a Fenton oxidation system. The application can significantly improve the removal efficiency of pollutants such as organic matter, total nitrogen and total phosphorus in each application section, effectively reduce the energy consumption, material consumption and carbon emission of the main wastewater treatment system, reduce the operation cost, and realize the dual benefits of environmental protection and economy.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically, it relates to a subsystem and method for the comprehensive reuse of iron sludge to improve efficiency and reduce carbon emissions in industrial wastewater treatment. Background Technology

[0002] The petrochemical industry and fine chemical industries such as pesticides, pharmaceuticals, dyes, and new materials are the main sources of highly toxic and recalcitrant organic wastewater. Their organic wastewater treatment processes often involve typical technologies such as flocculation and flotation, micro-electrolysis (zero-valent iron reduction), Fenton oxidation, and anaerobic biochemical treatment. Among these, the Fenton oxidation process utilizes hydroxyl radicals with high redox potentials generated by Fenton's reagent (H₂O₂ and ferrous salts) to oxidize and decompose recalcitrant organic matter. Furthermore, it removes some organic matter through adsorption and filtration of the flocculent precipitate produced by subsequent iron salt neutralization. Due to its advantages such as simple process, low investment, wide treatment range, and high operational flexibility, it has become the most commonly used pretreatment technology for recalcitrant organic wastewater.

[0003] However, the Fenton oxidation process generates a large amount of iron sludge, which is generally classified as hazardous waste, resulting in high costs for safe disposal and consequently high operating costs for the Fenton process. Current research on the recycling of Fenton iron sludge primarily employs medium-temperature pyrolysis or high-temperature calcination to convert it into flocculants, catalysts, or adsorbents for reuse. For example, patent 202211682504.7 utilizes activated sludge and Fenton iron sludge to prepare a carbon-based ozone catalyst through pyrolysis at 450–900℃; patent 202410214050.3 utilizes Fenton iron sludge and polymer fibers to prepare an iron-based carrier catalyst filler through high-temperature self-reduction carbonization at 1100–1200℃. An examination of numerous actual Fenton process operation cases reveals that Fenton iron sludge is generally directly transported off-site for disposal after being discharged from the wastewater treatment system, with very little consideration given to its reuse in the original Fenton section or other sections of the wastewater treatment system, resulting in low overall benefits generated by Fenton iron sludge. Summary of the Invention

[0004] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0005] In the context of the era of energy conservation, carbon reduction, quality improvement, and efficiency enhancement, improving the efficiency and effectiveness of industrial wastewater treatment systems is of great significance for strengthening enterprises' sustainable development capabilities and promoting the green transformation of the social economy. This invention focuses on the problem of low reuse rate and low overall efficiency of Fenton iron sludge in wastewater treatment systems, and creatively proposes a sub-system and method for comprehensive reuse of iron sludge in industrial wastewater treatment to enhance efficiency and reduce carbon emissions. This sub-system is independent of the main wastewater treatment system. It involves deep washing and high-efficiency concentration of Fenton iron sludge, followed by strategic application to several key stages of the main wastewater treatment system, such as anaerobic biological treatment and flocculation / flotation. This not only significantly enhances the wastewater treatment capacity of each stage and effectively improves water purification, but also reduces energy and material costs and carbon emissions in each stage, ultimately achieving comprehensive optimization and improvement of the entire main wastewater treatment system.

[0006] To achieve the above objectives, the present invention provides a subsystem for the comprehensive reuse of iron sludge in industrial wastewater treatment to enhance efficiency and reduce carbon emissions, comprising an iron sludge slurry preparation tank, a cyclone system, a sedimentation system and a reducing iron sludge tank connected in sequence.

[0007] The iron mud slurry preparation tank receives the filtered wet mud from the Fenton neutralization sedimentation tank and the treated effluent from the effluent discharge tank, and reprocesses the filtered wet mud into iron mud slurry.

[0008] The cyclone system receives iron slurry, and through cyclone washing and concentration, separates heavy slurry and light mud water;

[0009] The gravity settling system receives heavy slurry and separates the upper part of the pre-oxidized heavy slurry and the lower part of the pre-reduced heavy slurry through gravity settling.

[0010] The reducing iron sludge tank receives and stores the partially reduced heavy sludge discharged from the heavy sedimentation system and the precipitated iron sludge discharged from the iron salt neutralization sedimentation tank, forming a mixed iron sludge.

[0011] Preferably, the mass ratio of filtered wet mud to treated effluent in the iron mud slurry preparation tank is 1:5 to 1:100.

[0012] Preferably, the cyclone system is arranged directly above the sedimentation system, and the iron slurry is pumped to the cyclone system via a sludge pump.

[0013] This invention also provides a comprehensive method for the reuse of iron sludge to improve the efficiency and reduce carbon emissions in industrial wastewater treatment, including the following approaches:

[0014] W1: The light mud and water separated by the cyclone system are discharged into the anaerobic biochemical system, where they act as electron acceptors and detoxifying agents that can be utilized by anaerobic bacteria, thereby enhancing the efficiency and reducing carbon emissions in the anaerobic biochemical process.

[0015] W2: The partially oxidized heavy sludge separated by the sedimentation system is discharged into the flocculation flotation tank to act as a flocculant, thereby enhancing the efficiency and reducing carbon emissions in the flocculation flotation process.

[0016] W3: The semi-oxidative heavy sludge separated by the sedimentation system is discharged into the iron ammonia oxidation MBR (membrane bioreactor) tank, which acts as an electron acceptor that can be utilized by iron ammonia oxidation bacteria, thereby improving the efficiency and reducing carbon in the iron ammonia oxidation process.

[0017] W4: The mixed slurry formed by the partial reduction heavy slurry and the precipitated iron slurry stored in the reducing iron slurry tank is discharged into the Fenton oxidation system, acting as a catalyst and buffer for the Fenton oxidation reaction, thereby improving the efficiency and reducing carbon emissions in the Fenton oxidation process.

[0018] Preferably, in pathway W1, the amount of light sludge added is 1 to 8% of the mass of the mixed wastewater treated by the anaerobic biological system.

[0019] Preferably, in pathways W2 and W3, the solids content of the partially oxidized heavy slurry separated by the sedimentation system is 5-15%.

[0020] Preferably, in pathway W2, the amount of oxidative heavy sludge added is 1 to 5% of the mass of wastewater treated by the flocculation flotation tank.

[0021] Preferably, in pathway W3, the amount of oxidative heavy sludge added is 1 to 2% of the volume of wastewater treated in the iron ammonia oxidation MBR tank.

[0022] Preferably, in pathway W4, the amount of mixed iron sludge added is 2 to 8% of the volume of wastewater treated by the Fenton oxidation system.

[0023] The technical principle of this invention is as follows:

[0024] To address the issue of wet sludge produced in the Fenton post-neutralization sedimentation tank, this invention establishes a comprehensive iron sludge recycling subsystem. Relatively clean treated effluent is drawn from the effluent discharge tank to process the wet sludge into a slurry. This slurry is then washed and concentrated using a cyclone process, removing most of the organic pollutants adhering to the Fenton iron sludge. Subsequently, the sludge or mud obtained from the coarse separation is strategically applied to several key stages of the main wastewater treatment system, including anaerobic biological treatment, flocculation, and flotation, significantly improving efficiency and reducing carbon emissions in the application stages.

[0025] The Fenton oxidation process typically requires adjusting the wastewater pH with sulfuric acid and using ferrous sulfate as a catalyst. Sulfate ions entering the wastewater can be converted into hydrogen sulfide by sulfate-reducing bacteria in the subsequent anaerobic biological treatment system. The presence of a certain concentration of hydrogen sulfide not only inhibits the activity of acid-producing and methanogenic bacteria, reducing the treatment load and efficiency of the anaerobic system, but also corrodes equipment and may even cause foul odors and poisoning of workers. This invention discharges the light sludge separated by the cyclone system into the anaerobic biological treatment system. The light sludge contains washed organic matter and a certain amount of iron sludge. The organic matter can be utilized by anaerobic bacteria to convert into methane, while the introduction of iron sludge not only induces the dissimilatory iron reduction process, promoting the hydrolysis and acidification of some large organic molecules, but also acts as an electron acceptor available to iron-reducing bacteria. The ferrous iron generated from the reduction further combines with hydrogen sulfide to form ferrous sulfide, thus detoxifying the wastewater. Furthermore, the presence of iron sludge can also induce the formation of granular sludge in the anaerobic sludge. In summary, the implementation of this strategy can increase the abundance and activity of iron-reducing bacteria and methanogenic bacteria in the anaerobic biological treatment system, thereby improving the removal efficiency of organic pollutants and methane production in wastewater, reducing the load and energy consumption of the subsequent aerobic treatment system, and promoting the high efficiency and low carbonization of the entire biological treatment system.

[0026] High-concentration, recalcitrant organic wastewater stored in high-concentration collection tanks often contains large amounts of suspended organic matter, hydrophobic oils, and other pollutants. Flocculation-air flotation treatment not only achieves high removal efficiency but also produces relatively small sludge volumes. Conventional flocculation-air flotation methods primarily use polyferric sulfate or polyaluminum chloride as flocculants. This invention utilizes pre-washed, partially oxidized heavy sludge separated from a sedimentation system as a substitute for these flocculants, supplemented by coagulation aids. This effectively removes pollutants through adsorption and trapping mechanisms, eliminating the need for neutralization with liquid alkali. This significantly reduces reagent costs, lowers the overall yield of hazardous iron sludge, and saves on solid waste disposal costs.

[0027] Ferrous ammonia oxidizing bacteria can utilize ferric iron (Fe3+) as an electron acceptor to oxidize ammonia nitrogen into nitrogen gas, nitrite nitrogen, or nitrate nitrogen, and reduce ferric iron (Fe3+) to ferrous iron (Fe2+). Compared with the commonly used nitrification-denitrification process, this novel biological nitrogen removal method requires no oxygen supply or organic carbon source addition, and the main product is nitrogen gas, reducing N2O greenhouse gas generation. It belongs to a low-carbon wastewater treatment process and is particularly suitable for the deep removal of ammonia nitrogen from wastewater with a low carbon-to-nitrogen ratio. Furthermore, research has found that Fe(OH)3 and α-FeOOH forms present in Fenton iron sludge are more easily utilized by ferrous ammonia oxidizing bacteria than ferric iron forms such as FeCl3, Fe2O3, and Fe3O4. In this invention, the pre-washed and treated semi-oxidized heavy sludge separated from the sedimentation system is discharged into the ferrous ammonia oxidation MBR tank, which can achieve deep removal of ammonia nitrogen in a low-carbon manner, and the generated ferrous iron can be recovered through neutralization and precipitation in the subsequent iron salt neutralization and precipitation tank.

[0028] The combined micro-electrolysis-Fenton oxidation process is widely used to treat wastewater containing recalcitrant pollutants such as chlorinated aliphatic hydrocarbons, nitro aromatic compounds, azo dyes, and organochlorine pesticides. Micro-electrolysis typically uses iron powder or iron-carbon powder as a reducing agent, and to ensure the effectiveness of subsequent Fenton oxidation, the reducing agent is usually added in excess. Because the density of iron powder or iron-carbon powder is much greater than that of iron sludge, unreacted iron powder or iron-carbon powder will settle to the bottom and be discharged in the subsequent neutralization and sedimentation tank, resulting in waste of the reducing agent. The iron sludge comprehensive recycling subsystem provided by this invention uses a two-stage treatment process of cyclone and sedimentation to separate the partially reduced heavy sludge containing iron powder or iron-carbon powder. This sludge is then mixed with the precipitated iron sludge containing divalent iron recovered from the iron salt neutralization and sedimentation tank and reused as a catalyst in the Fenton oxidation process, significantly reducing the amount of reducing agent used and the amount of hazardous iron sludge produced. Furthermore, the Fenton oxidation reaction, by oxidizing and degrading large organic molecules into small organic acids, leads to a decrease in the system's pH, inhibiting the conversion of ferric iron to ferrous iron and thus reducing the removal rate of organic pollutants. Reusing the mixed iron sludge in the Fenton oxidation system allows the hydroxides in the iron sludge to react with the small organic acids, acting as a buffer and maintaining the pH within the optimal range during the Fenton reaction, thereby improving the removal efficiency of organic pollutants.

[0029] In summary, the beneficial effects achieved by this invention are as follows:

[0030] (1) The iron sludge comprehensive reuse subsystem and method constructed in this invention can achieve coarse separation of different types of components of Fenton iron sludge. Then, by strategically applying the separated mud water or mud slurry to multiple key links such as anaerobic biochemical treatment, flocculation and flotation in the main wastewater treatment system, the treatment capacity of each application section for pollutants such as organic matter, total nitrogen, and total phosphorus can be significantly enhanced, thereby improving pollutant removal efficiency and wastewater purification effect.

[0031] (2) The iron sludge integrated recycling subsystem and method constructed in this invention not only reduces the treatment load of subsequent aerobic processes by enhancing the removal effect of anaerobic biochemicals on organic matter, and reduces the necessary aeration volume and energy consumption, but also establishes an iron ammonia oxidation MBR system for deep removal of ammonia nitrogen without oxygen supply and organic carbon source addition based on Fenton iron sludge, and finally realizes the reduction of carbon emissions of the entire wastewater treatment main system.

[0032] (3) The iron sludge comprehensive recycling subsystem and method constructed in this invention not only greatly saves the cost of flocculants and reducing agents by recycling or reusing Fenton iron sludge, but also reduces the overall production of iron sludge hazardous waste and effectively reduces the operating cost of the main wastewater treatment system.

[0033] (4) The iron sludge integrated recycling subsystem constructed by the present invention has the characteristics of being embedded, integrated and modular. Its installation and operation process can achieve high efficiency compatibility with the existing wastewater treatment main system without the need for large-scale modification. Attached Figure Description

[0034] The accompanying drawings are provided to further explain the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0035] Figure 1 This is a roadmap for a subsystem and method for the comprehensive reuse of iron sludge in industrial wastewater treatment to improve efficiency and reduce carbon emissions, as described in this invention.

[0036] Figure 2 This is a simplified diagram of the equipment in a subsystem for the comprehensive reuse of iron sludge in industrial wastewater treatment, which aims to improve efficiency and reduce carbon emissions, according to the present invention. (See diagram.)

[0037] 1. Iron mud preparation tank; 11. Filtering wet mud; 12. Treated effluent; 13. Iron mud slurry;

[0038] 2. Swirl system; 21. Light slurry; 22. Heavy slurry;

[0039] 3. Sedimentation system; 31. Oxidative heavy mud; 32. Reduced heavy mud;

[0040] 4. Reducing iron sludge tank: 41. Sedimented iron sludge; 42. Mixed iron sludge. Detailed Implementation

[0041] The present invention will now be described and explained in detail with reference to the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] Figure 2 An actual device system based on the iron sludge integrated recycling subsystem described in this invention is demonstrated.

[0044] In this actual system, the iron sludge preparation tank 1 receives filtered wet sludge 11 from the Fenton post-neutralization sedimentation tank and treated effluent 12 from the effluent discharge tank. The mass ratio of filtered wet sludge 11 to treated effluent 12 is controlled at 1:5 to 1:100. The filtered wet sludge 11 is reconstituted into a homogeneous iron sludge 13 through hydrodynamic shearing. The cyclone system 2 is arranged directly above the sedimentation system 3. The iron sludge 13 is pumped to the cyclone system 2. Through the cyclone action, the lighter sludge-water 21 with a small amount of iron sludge and lower density is discharged from the top outlet, while the heavier sludge 22 with higher density is thrown against the inner wall by centrifugal force, then settles and is discharged into the sedimentation system 3 through the bottom outlet, thereby concentrating the iron sludge 13. The heavy sludge 22 entering the settling system 3 settles freely under gravity. Since the density of iron powder / iron-carbon powder in the sludge is much greater than that of hydroxide iron sludge, it can be roughly separated into an upper, partially oxidized heavy sludge 31 (mainly hydroxide iron sludge) and a lower, partially reduced heavy sludge 32 (containing iron powder / iron-carbon powder and hydroxide iron sludge). The partially reduced heavy sludge 32 accumulates in the bottom tank of the settling system 3. The partially reduced heavy sludge 32 is discharged into a closed reducing iron sludge tank 4 via a sludge pump. In addition, the precipitated iron sludge 41 containing ferrous iron discharged from the iron salt neutralization sedimentation tank is also discharged into the reducing iron sludge tank 4. The two form a mixed iron sludge 42 under stirring. The mixed iron sludge 42 can then be discharged into the Fenton oxidation system.

[0045] Example 2

[0046] This Example 2 verifies the synergistic and carbon-reducing effects of the lightweight slurry described in Example 1 on the anaerobic biochemical process.

[0047] The anaerobic biochemical process was as follows: Fenton iron sludge from the wastewater treatment system of a pesticide company in Yangzhou, Jiangsu Province, was treated using the device system described in Example 1 to obtain light sludge-water. The COD of the wastewater from the biochemical equalization tank of this pesticide company was approximately 6200 mg / L, and this wastewater was used as the treatment target for the experiment. Sludge from the anaerobic system was taken, cleaned, and evenly divided, and then loaded into two 5L anaerobic pilot-scale devices. The hydraulic retention time was controlled at 3 days, and other conditions were kept consistent. A control group was set up: Group A received wastewater from the biochemical equalization tank, and Group B received a mixture of wastewater from the biochemical equalization tank and light sludge-water (the proportion of light sludge-water was 5%). The influent was continuously fed and cultured for more than 30 days.

[0048] The treatment results are shown in Table 1. These results indicate that the introduction of lightweight sludge can effectively improve the removal efficiency of COD and TP in the anaerobic biological process, reduce the load on subsequent aerobic processes, and decrease energy consumption and carbon emissions.

[0049] Table 1. Results of the synergistic effect and carbon reduction of lightweight slurry on anaerobic biological processes.

[0050] project Group A Group B COD (mg / L) of continuous influent 6279 6134 COD (mg / L) of effluent after 20 days 2456 2044 COD (mg / L) of effluent after 30 days 2129 1523 Influent TP (mg / L) 4.3 4.1 TP (mg / L) in effluent after 20 days 2.9 0.03 TP (mg / L) in effluent after 30 days 2.6 0.04

[0051] Example 3

[0052] This embodiment 3 verifies the synergistic and carbon-reducing effects of the partially oxidized heavy slurry described in embodiment 1 on the flocculation and air flotation process.

[0053] The flocculation and flotation process was as follows: Fenton iron sludge from the wastewater treatment system of a pesticide company in Yangzhou, Jiangsu Province, was treated using the device system described in Example 1 to obtain a partially oxidized heavy sludge with a solids content of approximately 5%. The high-concentration collection tank wastewater from this pesticide company had a COD content of 32449 mg / L and contained certain suspended solids and hydrophobic oils. This wastewater was used as the treatment target for the experiment. After adjusting the pH of the high-concentration collection tank wastewater to 6-9, a certain proportion of polyferric sulfate (11wt% total iron) or partially oxidized heavy sludge was added (if polyferric sulfate was added, liquid alkali was added to adjust the pH to 6-9). After stirring and reacting for 10 minutes, a 2L small-scale flotation device was used for flotation treatment.

[0054] The treatment results are shown in Table 2. These results indicate that, under appropriate dosage, oxidative heavy sludge can achieve COD removal efficiency equal to or even better than polyferric sulfate, and can replace polyferric sulfate as a flocculant in the flocculation and flotation process, saving on reagent costs.

[0055] Table 2. Enhancement and carbon reduction effects of oxidative heavy slurry on the flocculation and air flotation process.

[0056] project COD (mg / L) High-concentration collection tank wastewater 32449 Adding 3‰ polyferric sulfate (11wt% total iron) to the effluent 26374 Add 1% of semi-oxidative heavy mud to the effluent 27299 Add 2% of semi-oxidative heavy mud to the effluent 25195

[0057] Example 4

[0058] Example 4 verifies the synergistic and carbon-reducing effects of the partial oxidation type heavy slurry described in Example 1 on the iron-ammonia oxidation process.

[0059] The iron-ammonia oxidation process was as follows: Fenton iron sludge from the wastewater treatment system of a pesticide company in Yangzhou, Jiangsu Province, was treated using the device system described in Example 1 to obtain a partially oxidized heavy sludge with a solids content of approximately 5%. The pesticide company's high-salt water underwent triple-effect distillation to produce a low C / N ratio, high ammonia nitrogen wastewater with an ammonia nitrogen content of approximately 1400 mg / L. This wastewater was diluted 10 times and used as the treatment target for the experiment. 1% by volume of partially oxidized heavy sludge was added to the diluted wastewater, and the pH was adjusted to 4-5. The treated water was then continuously fed into a reactor containing the pre-cultivated iron-ammonia oxidation sludge.

[0060] The treatment results are shown in Table 3. These results indicate that the iron sludge produced by the Fenton process can be utilized by iron-oxidizing bacteria as an electron acceptor, achieving effective reduction of ammonia nitrogen. Furthermore, this process requires no oxygen supply or the addition of organic carbon sources.

[0061] Table 3. Enhanced efficiency and carbon reduction results of the oxidative heavy slurry on the iron-ammonia oxidation process.

[0062] project Ammonia nitrogen (mg / L) Continuous water intake 138 Water will be discharged after 20 days. 66 Water will be discharged after 30 days. 56

[0063] Example 5

[0064] Example 5 verifies the synergistic and carbon-reducing effects of the mixed iron sludge described in Example 1 on the micro-electrolysis-Fenton oxidation process.

[0065] The micro-electrolysis-Fenton oxidation process was as follows: Fenton iron sludge from the wastewater treatment system of a pesticide company in Yangzhou, Jiangsu Province, was treated using the device system described in Example 1 to obtain mixed iron sludge. The flocculated air flotation water from Example 3 was used as the treatment object in the experiment. The flocculated air flotation water was taken, the pH was adjusted to 3, and it was divided into two groups. Group A was treated with 2 g / L of iron-carbon powder for micro-electrolysis, followed by the addition of 3% (30%) hydrogen peroxide to initiate the Fenton reaction. Group B was treated with 1 g / L of iron-carbon powder for micro-electrolysis, followed by the addition of 3% (30%) hydrogen peroxide to initiate the Fenton reaction, and immediately afterward, 2% (2%) of the mixed iron sludge was added. The entire Fenton reaction took 3 hours.

[0066] The treatment results are shown in Table 4. These results indicate that using mixed iron sludge as a supplementary catalyst in the micro-electrolysis-Fenton oxidation system can achieve the same or even better COD removal effect when the dosage is sufficient, and can reduce the initial dosage of iron-carbon powder, saving reagent costs.

[0067] Table 4. Enhanced efficiency and carbon reduction results of mixed iron sludge in the micro-electrolysis-Fenton oxidation process.

[0068] project COD (mg / L) Fenton treatment influent 25195 Group A water discharge 17269 Group B water outflow 16423

[0069] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A subsystem for the comprehensive reuse of iron sludge in industrial wastewater treatment, characterized in that: It includes an iron mud preparation tank (1), a cyclone system (2), a sedimentation system (3), and a reducing iron mud tank (4) connected in sequence. The iron mud preparation tank (1) receives the filtered wet mud (11) from the Fenton neutralization sedimentation tank and the treated effluent (12) from the effluent discharge tank, and re-forms the filtered wet mud (11) into iron mud slurry (13). The cyclone system (2) receives iron slurry (13), and through cyclone washing and concentration, separates heavy slurry (22) and light mud water (21). The gravity settling system (3) receives heavy mud (22) and separates the upper part of the oxidized heavy mud (31) and the lower part of the reduced heavy mud (32) by gravity settling. The reducing iron sludge tank (4) receives the partially reduced heavy sludge (32) discharged from the heavy sedimentation system (3) and the precipitated iron sludge (41) discharged from the iron salt neutralization sedimentation tank, forming mixed iron sludge (42). The iron sludge comprehensive reuse subsystem achieves the comprehensive reuse of iron sludge through the following methods to improve the efficiency of industrial wastewater treatment and reduce carbon emissions: W1: The light mud and water (21) separated by the cyclone system (2) is discharged into the anaerobic biological system; W2: The partially oxidized heavy sludge (31) separated by the sedimentation system (3) is discharged into the flocculation flotation tank; W3: The partially oxidized heavy sludge (31) separated by the sedimentation system (3) is discharged into the iron ammonia oxidation MBR tank; W4: The mixed iron mud (42) formed by the partial reduction heavy mud (32) and the precipitated iron mud (41) stored in the reducing iron mud tank (4) is discharged into the Fenton oxidation system.

2. The system according to claim 1, characterized in that, The mass ratio of the filtered wet mud (11) in the iron mud slurry tank (1) to the treated effluent (12) is 1:5 to 1:

100.

3. The system according to claim 1, characterized in that, The cyclone system (2) is arranged directly above the sedimentation system (3), and the iron slurry (13) is transported to the cyclone system (2) by a sludge pump.

4. The system according to claim 1, characterized in that, In pathway W1, the amount of light sludge (21) added is 1 to 8% of the mass of the mixed wastewater treated by the anaerobic biological system.

5. The system according to claim 1, characterized in that, In pathways W2 and W3, the solids content of the semi-oxidized heavy slurry (31) separated by the heavy settling system (3) is 5-15%.

6. The system according to claim 1, characterized in that, In pathway W2, the dosage of the oxidative heavy sludge (31) is 1 to 5% of the mass of the wastewater treated by the flocculation flotation tank.

7. The system according to claim 1, characterized in that, In pathway W3, the amount of oxidative heavy sludge (31) added is 1 to 2% of the volume of wastewater treated in the iron ammonia oxidation MBR tank.

8. The system according to claim 1, characterized in that, In pathway W4, the amount of mixed iron sludge (42) added is 2 to 8% of the volume of wastewater treated by the Fenton oxidation system.

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