A multi-mode coagulation sedimentation tank

Abstract

This utility model provides a multi-mode coagulation sedimentation tank, belonging to the field of wastewater treatment technology. It includes a coagulation reaction tank, a magnetic powder reaction tank, a flocculation reaction tank, a clarification sedimentation tank, a magnetic sludge separator, an intelligent control mechanism, an influent control mechanism, and a reagent dosing mechanism. A component detector is installed at the outlet of the clarification sedimentation tank at the top. The return outlet is connected to the magnetic sludge separator via a first return pump and to the magnetic powder reaction tank via a second return pump. The influent control mechanism is located at the influent end of the coagulation reaction tank. The reagent dosing mechanism includes a coagulant dosing device and a coagulant aid dosing device. The intelligent control mechanism is configured to control the reagent dosing ratio of the coagulant dosing device and the coagulant aid dosing device, as well as the power of the second return pump, based on the changes in total phosphorus in the effluent detected by the component detector. This solves the technical problems of high operating cost and low efficiency of existing single-mode coagulation sedimentation tanks.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, and in particular to a multi-mode coagulation sedimentation tank. Background Technology

[0002] Coagulation sedimentation tanks are a core unit in water treatment processes, primarily used to remove colloids, suspended solids, some dissolved organic matter, and pollutants such as phosphorus from water. Their working principle involves adding coagulants (such as PAC and PFS) to the water to be treated, causing fine particles that are difficult to settle naturally to destabilize and aggregate, forming larger flocs (lumps). These flocs then separate into solids and liquids in the sedimentation tank due to gravity; the clarified water flows upwards, while the sludge settles to the bottom and is collected and discharged. This process is widely used in municipal wastewater, industrial wastewater treatment, and water purification due to its stable performance and relatively simple operation.

[0003] In recent years, magnetic coagulation sedimentation technology has been widely used to improve the treatment efficiency and settling speed of traditional coagulation sedimentation. A typical magnetic coagulation sedimentation tank introduces magnetic particles (magnetic powder) into the traditional process. Its workflow is usually as follows: coagulant, coagulant aid (such as PAM), and recovered or replenished magnetic powder are added to the mixing reaction zone; the magnetic powder and coagulant are stirred to fully combine with pollutants in the water, forming dense and strongly magnetic "magnetic flocs"; subsequently, the magnetic flocs settle rapidly in the sedimentation zone at a rate much higher than ordinary flocs; part of the settled sludge is returned to the front end of the system, where magnetic separation equipment (such as a magnetic drum) is used to recover the magnetic powder for recycling, while the remaining sludge is dewatered.

[0004] However, currently widely used magnetic coagulation sedimentation tanks are typically designed for single magnetic coagulation operation, meaning the system must continuously add magnetic powder to maintain its high efficiency. As a solid reagent, magnetic powder usually requires large quantities of bagged or bulk powder to be manually transported to the dosing platform located on the second floor of the sedimentation tank. This process is not only extremely labor-intensive and manpower-consuming, but also presents problems such as dust pollution, safety hazards during handling, and difficulty in consistently controlling dosing accuracy. Since magnetic powder constitutes a significant portion of the total reagent dosage, this high-intensity material handling and dosing work becomes a continuous burden in daily operation. This severely restricts the economic efficiency and convenience of operating the sedimentation tank, ultimately affecting the overall wastewater treatment efficiency. Utility Model Content

[0005] This utility model provides a multi-mode coagulation sedimentation tank, which solves the technical problems of high operating cost and low efficiency of existing single-mode coagulation sedimentation tanks. The technical solution is as follows:

[0006] This utility model embodiment provides a multi-mode coagulation sedimentation tank, including:

[0007] Coagulation reaction tank, magnetic powder reaction tank, flocculation reaction tank, clarification and sedimentation tank, magnetic mud separator, intelligent control mechanism, influent control mechanism, and reagent dosing mechanism.

[0008] The coagulation reaction tank, the magnetic powder reaction tank, the flocculation reaction tank, and the clarification sedimentation tank are arranged sequentially and connected in sequence. The clarification sedimentation tank includes an outlet at the top, a return outlet at the bottom, and a filter plate located between the two. The outlet is equipped with a component detector. The return outlet is connected to the magnetic mud separator through a first return pump and is connected to the magnetic powder reaction tank through a second return pump. The magnetic powder outlet of the magnetic mud separator is connected to the magnetic powder reaction tank. The first return pump and the second return pump are communicatively connected to the intelligent control mechanism.

[0009] The water inlet control mechanism is located at the water inlet end of the coagulation reaction tank and includes at least two independent water inlet channels. Each water inlet channel is equipped with a regulating valve and an online flow meter that are communicatively connected to the intelligent control mechanism.

[0010] The reagent dosing mechanism includes a coagulant dosing device connected to the coagulation reaction tank and a coagulant aid dosing device connected to the flocculation reaction tank. The intelligent control mechanism is configured to control the reagent dosing ratio of the coagulant dosing device and the coagulant aid dosing device, as well as the power of the second reflux pump, based on the change in total phosphorus in the effluent detected by the component detector.

[0011] Optionally, the coagulant dosing device is connected to the inlet of the coagulation reaction tank, and the outlet of the coagulant aid dosing device is led out to the top of the flocculation reaction tank.

[0012] Optionally, the coagulant in the coagulant dosing device is polyferric sulfate or polyaluminum chloride, and the coagulant aid in the coagulant dosing device is polyacrylamide. The ratio of the reagents added by the coagulant dosing device and the coagulant aid dosing device is 120:1.

[0013] Optionally, the outlet of the coagulant dosing device is provided with a longitudinal telescopic rod, and the bottom of the longitudinal telescopic rod is provided with a dispensing head.

[0014] Optionally, the clarification sedimentation tank is equipped with a lifting sludge interface detector that is communicatively connected to the intelligent control mechanism for real-time monitoring of the sludge layer height. The intelligent control mechanism is configured to control the power of the second return pump based on the data from the lifting sludge interface detector.

[0015] Optionally, the sludge settling ratio in the clarification sedimentation tank ranges from 10% to 20%.

[0016] Optionally, the wastewater inflow rate of the coagulation reaction tank is less than or equal to 500 m³ / h.

[0017] Optionally, the second return pump is configured to control the sludge return flow rate of the magnetic powder reactor to a range of 25-30 m³ / h based on the power adjustment of the intelligent control mechanism.

[0018] The beneficial effects of the technical solution provided by this utility model embodiment include at least the following:

[0019] The multi-mode coagulation sedimentation tank provided in this embodiment can operate in two modes according to actual water treatment needs. Under normal operating conditions, water treatment can be carried out using a conventional magnetic coagulation process with the addition of magnetic powder. In another operating mode, global control is achieved through an intelligent control mechanism. The influent flow rate into the coagulation reaction tank is controlled by an influent control mechanism. Without the addition of magnetic powder, and with the influent flow rate reduced compared to the first operating mode, the total phosphorus concentration in the clarified water discharged after sedimentation and filtration is monitored in real time using a component detector. By continuously adjusting the return flow rates of coagulant, flocculant aid, and settled sludge, the total phosphorus concentration in the final discharged clarified water is made close to the total phosphorus concentration after magnetic coagulation in the first operating mode. This allows for the reduction or even complete elimination of magnetic powder addition under specific influent flow rates, coagulant and flocculant aid dosage ratios, and sludge return flow rates, achieving the same effluent quality that meets standards and providing the same water treatment effect as the first operating mode. It saves on the cost of chemicals, as well as the labor costs of manual handling and addition, and the operating costs of the magnetic powder recovery unit, thus solving the technical problems of high operating costs and low efficiency of existing single-mode coagulation sedimentation tanks. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the multi-mode coagulation sedimentation tank provided in this embodiment of the utility model;

[0022] Figure 2 This is a control structure block diagram of the multi-mode coagulation sedimentation tank provided in this embodiment of the utility model.

[0023] In the diagram: 1-Coagulation reaction tank; 2-Magnetic powder reaction tank; 3-Flocculation reaction tank; 4-Clarification sedimentation tank; 5-Magnetic sludge separator; 6-Intelligent control mechanism; 7-Inlet water control mechanism; 8-Reagent dosing mechanism; 41-Outlet; 42-Return port; 43-Filter plate; 44-Lifting sludge interface detector; 71-Inlet water channel; 81-Coagulant dosing device; 82-Coagulant aid dosing device; 411-Component detector; 421-First return pump; 422-Second return pump; 711-Regulating valve; 712-Online flow meter; 821-Longitudinal telescopic rod; 822-Reagent outlet. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the structure of the multi-mode coagulation sedimentation tank provided in this embodiment of the utility model; Figure 2 This is a control structure block diagram of the multi-mode coagulation sedimentation tank provided in an embodiment of this utility model. (For example...) Figures 1 to 2 As shown, this utility model embodiment provides a multi-mode coagulation sedimentation tank, including a coagulation reaction tank 1, a magnetic powder reaction tank 2, a flocculation reaction tank 3, a clarification sedimentation tank 4, a magnetic mud separator 5, an intelligent control mechanism 6, an influent control mechanism 7, and a reagent dosing mechanism 8.

[0026] The coagulation reaction tank 1, magnetic powder reaction tank 2, flocculation reaction tank 3, and clarification sedimentation tank 4 are arranged sequentially and connected in sequence. The clarification sedimentation tank 4 includes an outlet 41 at the top, a return outlet 42 at the bottom, and a filter plate 43 located between the two. The outlet 41 is equipped with a component detector 411. The return outlet 42 is connected to the magnetic mud separator 5 through a first return pump 421 and is connected to the magnetic powder reaction tank 2 through a second return pump 422. The magnetic powder outlet of the magnetic mud separator 5 is connected to the magnetic powder reaction tank 2. The first return pump 421 and the second return pump 422 are communicatively connected to the intelligent control mechanism 6.

[0027] The water inlet control mechanism 7 is located at the water inlet end of the coagulation reaction tank 1, and includes at least two independent water inlet channels 71. Each water inlet channel 71 is equipped with a regulating valve 711 and an online flow meter 712 that are communicatively connected to the intelligent control mechanism 6.

[0028] The chemical dosing mechanism 8 includes a coagulant dosing device 81 connected to the coagulation reaction tank 1 and a coagulant aid dosing device 82 connected to the flocculation reaction tank 3. The intelligent control mechanism 6 is configured to control the chemical dosing ratio of the coagulant dosing device 81 and the coagulant aid dosing device 82, as well as the power of the second reflux pump 422, based on the changes in total phosphorus in the effluent detected by the detector.

[0029] In this embodiment of the invention, the multi-mode coagulation sedimentation tank has two working modes, which are switched by data collection and signal transmission and reception control through the intelligent control mechanism 6. In this embodiment of the invention, the intelligent control mechanism 6 can be a host computer with integrated control commands. In the conventional mode, when sewage is introduced, the regulating valves 711 on the multiple inlet channels 71 in the inlet control mechanism 7 located at the front end of the coagulation reaction tank 1 do not need to be adjusted. After the sewage enters the coagulation reaction tank 1, polyferric sulfate or polyaluminum chloride (PAC) coagulant with a total iron content ≥11% is simultaneously added into the coagulation reaction tank 1 through the coagulant dosing device 81. After the sewage and coagulant are fully mixed by the stirring mechanism, they enter the magnetic powder reaction tank 2. At this time, magnetic powder is added into the magnetic powder reaction tank 2 by manual handling and the magnetic powder outlet of the magnetic mud separator 5 above for further mixing before entering the flocculation reaction tank 3. Anionic polyacrylamide (PAM) is added to the flocculation reaction tank 3 via the coagulant dosing device 82 for further mixing. The mixture then enters the clarification and sedimentation tank 4 for settling. Through flocculation, attraction and adsorption, charge adsorption, bridging, and trapping, insoluble pollutants such as algae, micro-suspended solids, colloids, and bacteria in the water are effectively combined with particulate magnetic powder (magnetic powder specific gravity 5.2) to form magnetic flocs with larger volume and density. The flocs settle to the bottom, and the separated clear water is further filtered through the filter plate 43 before being discharged from the outlet 41. The separated flocs and sludge are discharged from the bottom through the return port 42. This part of the sludge is divided into two parts. One part is powered by the first return pump 421 and discharged into the magnetic sludge separator 5 through an independent pipeline for magnetic powder separation. The separated and recovered magnetic powder is fed into the magnetic powder reaction tank 2 for reuse. The remaining sludge is discharged into the corresponding sludge thickening tank to leave the circulation. The other part is powered by the second return pump 422 and returned to the magnetic powder reaction tank 2 through an independent pipeline for further sedimentation to control the sedimentation ratio in the tank and realize the working cycle of the conventional magnetic coagulation sedimentation tank. In another mode, during the wastewater introduction process, the influent flow rate entering the coagulation reaction tank 1 can be monitored in real time by an online flow meter 712. The wastewater flow rate of multiple influent channels 71 can be controlled by adjusting the opening of the regulating valve 711. Individual influent channels 71 can be shut off, or the opening of the regulating valve 711 on multiple influent channels 71 can be reduced simultaneously to control the influent flow rate into the coagulation reaction tank 1, reduce water flow shock, and ensure that the wastewater has sufficient flow and settling time in the coagulation sedimentation tank. Further, in this mode, after the wastewater is mixed with the coagulant, it passes through the coagulation reaction tank 1 and the magnetic powder reaction tank 2 in sequence. Without the addition of magnetic powder, it enters the flocculation reaction tank 3. Based on the composition of the coagulant added at the front end and the dosage ratio of the coagulant aid dosing device 82, the coagulant aid is added to the flocculation reaction tank 3 in a specific ratio. After that, the wastewater enters the clarification sedimentation tank 4 for sedimentation.With the influent flow rate reduced compared to the first operating mode, the total phosphorus concentration in the clarified water discharged after sedimentation and filtration is monitored in real time using the component detector 411. The total phosphorus concentration in the final discharged clarified water is brought close to that of the magnetic coagulation process in the first operating mode by continuously adjusting the return flow rates of coagulant, flocculant aid, and settled sludge (controlled by adjusting the operating power of the second return pump 422). This allows for the reduction or even elimination of magnetic powder addition under specific influent flow rates, coagulant and flocculant aid dosage ratios, and sludge return flow rates, achieving the same effluent quality as the first operating mode and thus the same water treatment effect. Specifically, in this embodiment of the present invention, under the second working mode, the wastewater inflow of the coagulation reaction tank 1 is less than or equal to 500 m³ / h; the coagulant in the coagulant dosing device 81 is polyferric sulfate (polyferric) or polyaluminum chloride, and the coagulant aid in the coagulant dosing device 82 is anionic polyacrylamide; the ratio of the reagents added by the coagulant dosing device 81 and the coagulant aid dosing device 82 is 120:1; the second return pump 422 is configured to adjust the power based on the intelligent control mechanism 6, controlling the sludge return flow rate of the magnetic powder reaction tank 2 to be within the range of 25-30 m³ / h; and the optimal sludge settling ratio in the clarification sedimentation tank 4 is controlled within the range of 10%-20%.

[0030] In this embodiment of the utility model, the applicant planned the above-mentioned working mode based on the actual working data of the water treatment plant, wherein the average daily influent is between 10,000 and 13,000 m³, and the average annual daily influent is 11,800 m³. Maintaining a constant influent flow rate of 500 m³ / h ensures stable influent and prevents the influent level at the front end from being too high or too low. By controlling the pumping flow rate of the influent pump, the effluent from the biological tank is kept basically constant. Then, the pumping frequency of the booster pump room is set, and finally, the influent control mechanism 7 keeps the influent flow rate basically constant, thereby ensuring that the influent to the coagulation reaction tank 1 is kept at around 500 m³ / h and basically constant.

[0031] The detection results, with all other variables remaining constant and only the influent flow rate changed, are shown in the table below:

[0032]

[0033] Data comparison shows that controlling the influent flow rate to a stable 500 m³ / h results in a 0.034 mg / L reduction in total phosphorus in the effluent compared to not controlling the influent flow rate.

[0034] The test results are shown in the table below, where only the sludge settling ratio is changed while keeping other variables constant:

[0035]

[0036] Data analysis showed that the best total phosphorus removal effect was achieved when the sludge settling ratio was 10%-20%. A sludge settling ratio below 10% resulted in a 0.052 mg / L reduction in effluent total phosphorus, while a sludge settling ratio of 20%-30% resulted in a 0.033 mg / L reduction.

[0037] Adjust the reagent ratio, analyze the changes in total phosphorus in the effluent, and determine the reagent consumption per unit volume under different ratios. Determine the optimal dosage ratio through data comparison and analysis.

[0038] The test results, with all other variables remaining constant and only the dosage ratio of the reagent changed, are shown in the table below:

[0039]

[0040] Data comparison revealed that the optimal total phosphorus removal ratio was 120:1 for polyferric coagulant to anionic PAM coagulant aid. Compared to a ratio of 100:1 for polyferric coagulant to anionic PAM, this ratio reduced anionic PAM consumption by 0.0001 mg / L while maintaining the same total phosphorus level in the effluent. Compared to a ratio of 150:1 for polyferric coagulant to anionic PAM, this ratio increased anionic PAM consumption by 0.0001 mg / L and increased total phosphorus in the effluent by 0.023 mg / L.

[0041] Furthermore, the power of the second return pump 422 was adjusted to control the sludge return flow rate, and the reagent consumption per unit flow rate was determined under the same reagent ratio. The optimal return flow rate was then determined.

[0042] The test results for changing only the sludge return flow rate, with other variables remaining constant, are shown in the table below:

[0043]

[0044] Data comparison showed that the effluent total phosphorus was lowest when the sludge return flow rate was 25-30 m³ / h. This was 0.02 mg / L lower than when the flow rate was 15-25 m³ / h, and 0.0032 mg / L lower than when the flow rate was 30-35 m³ / h.

[0045] The multi-mode coagulation sedimentation tank provided in this embodiment can operate in two modes according to actual water treatment needs. Under normal operating conditions, water treatment can be carried out using a conventional magnetic coagulation process with the addition of magnetic powder. In another operating mode, global control is achieved through an intelligent control mechanism 6, and the influent flow rate into the coagulation reaction tank 1 is controlled by the influent control mechanism 7. Without the addition of magnetic powder, and with the influent flow rate reduced compared to the first operating mode, the total phosphorus concentration in the clarified water discharged after sedimentation and filtration is monitored in real time by the component detector 411. By continuously adjusting the return flow rates of coagulant, coagulant aid, and sludge, the total phosphorus concentration in the final discharged clarified water is made close to the total phosphorus concentration after magnetic coagulation in the first operating mode. This achieves the same water treatment effect as the first operating mode by reducing or even completely eliminating the addition of magnetic powder under specific influent flow rates, coagulant and coagulant aid dosage ratios, and sludge return flow rates, thus meeting the same effluent quality standards. It saves on the cost of chemicals, as well as the labor costs of manual handling and addition, and the operating costs of the magnetic powder recovery unit, thus solving the technical problems of high operating costs and low efficiency of existing single-mode coagulation sedimentation tanks.

[0046] Optionally, the coagulant dosing device 81 is connected to the inlet of the coagulation reaction tank 1, and the outlet of the coagulant aid dosing device 82 is led out to the top of the flocculation reaction tank 3. Exemplarily, in this embodiment of the invention, the dosing pipe of the coagulant dosing device 81 is connected to the inlet of the coagulation reaction tank 1, entering the coagulation reaction tank 1 along with the introduced sewage from the inlet side and flowing with the sewage throughout the process, ensuring sufficient mixing time and sedimentation effect. The dosing outlet of the coagulant aid dosing device 82 is led out to the top of the flocculation reaction tank 3 through a pipe. Specifically, its outlet is located above the liquid surface of the flocculation reaction tank 3, ensuring that the powdered or emulsion-like coagulant aid can quickly and fully enter the flocculation reaction tank 3, avoiding dust or splashing that could affect the surrounding environment. Further, in a preferred embodiment of the invention, the outlet of the coagulant aid dosing device 82 is provided with a longitudinal telescopic rod 821, and a dispensing head 822 is provided at the bottom of the longitudinal telescopic rod 821. By setting a longitudinal telescopic rod 821, the dispensing head 822 can be lowered below the liquid surface of the flocculation reaction tank 3 during the dosing operation to add the coagulant aid, further improving the dosing efficiency, stability, and safety.

[0047] Optionally, a lifting sludge interface detector 44, communicatively connected to an intelligent control mechanism 6, is installed inside the clarification sedimentation tank 4 to monitor the sludge layer height in real time. The intelligent control mechanism 6 is configured to control the power of the second return pump 422 based on the data from the lifting sludge interface detector 44. Exemplarily, in this embodiment of the present invention, by installing a lifting sludge interface detector 44 inside the clarification sedimentation tank 4 for real-time monitoring of the bottom sludge layer height, and by implementing the detector's detection values ​​through the intelligent control mechanism 6, the power of the second return pump 422 is controlled to regulate the sludge discharge and return flow, thereby precisely controlling the sludge layer height or scraping speed, dynamically optimizing the settling environment, and further precisely controlling the sludge settling ratio within the clarification sedimentation tank 4 to ensure water treatment effectiveness.

[0048] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0049] The above description is only an optional embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A multi-mode coagulation sedimentation tank, characterized in that, include: Coagulation reaction tank (1), magnetic powder reaction tank (2), flocculation reaction tank (3), clarification sedimentation tank (4), magnetic mud separator (5), intelligent control mechanism (6), influent control mechanism (7), and reagent dosing mechanism (8). The coagulation reaction tank (1), the magnetic powder reaction tank (2), the flocculation reaction tank (3), and the clarification sedimentation tank (4) are arranged in sequence and connected in sequence. The clarification sedimentation tank (4) includes an outlet (41) at the top, a return outlet (42) at the bottom, and a filter plate (43) between the two. The outlet (41) is equipped with a component detector (411). The return outlet (42) is connected to the magnetic mud separator (5) through a first return pump (421). The return outlet (42) is connected to the magnetic powder reaction tank (2) through a second return pump (422). The magnetic powder outlet of the magnetic mud separator (5) is connected to the magnetic powder reaction tank (2). The first return pump (421) and the second return pump (422) are communicatively connected to the intelligent control mechanism (6). The water inlet control mechanism (7) is located at the water inlet end of the coagulation reaction tank (1) and includes at least two independent water inlet channels (71). Each water inlet channel (71) is equipped with a regulating valve (711) and an online flow meter (712) that are communicatively connected to the intelligent control mechanism (6). The chemical dosing mechanism (8) includes a coagulant dosing device (81) connected to the coagulation reaction tank (1) and a coagulant aid dosing device (82) connected to the flocculation reaction tank (3). The intelligent control mechanism (6) is configured to control the chemical dosing ratio of the coagulant dosing device (81) and the coagulant aid dosing device (82) and the power of the second reflux pump (422) based on the change in total phosphorus in the effluent detected by the component detector (411).

2. The multi-mode coagulation sedimentation tank according to claim 1, characterized in that, The coagulant dosing device (81) is connected to the inlet of the coagulation reaction tank (1), and the outlet of the coagulant aid dosing device (82) is led out to the top of the flocculation reaction tank (3).

3. A multi-mode coagulation sedimentation tank according to claim 2, characterized in that, The coagulant in the coagulant dosing device (81) is polyferric sulfate or polyaluminum chloride, and the coagulant aid in the coagulant dosing device (82) is polyacrylamide. The ratio of the reagents added by the coagulant dosing device (81) and the coagulant aid dosing device (82) is 120:

1.

4. A multi-mode coagulation sedimentation tank according to claim 2, characterized in that, The outlet of the coagulant dosing device (82) is provided with a longitudinal telescopic rod (821), and the bottom of the longitudinal telescopic rod (821) is provided with a dispensing head (822).

5. A multi-mode coagulation sedimentation tank according to claim 2, characterized in that, The clarification sedimentation tank (4) is equipped with a lifting sludge interface detector (44) that is connected to the intelligent control mechanism (6) for real-time monitoring of the sludge layer height. The intelligent control mechanism (6) is configured to control the power of the second return pump (422) based on the data from the lifting sludge interface detector (44).

6. A multi-mode coagulation sedimentation tank according to claim 5, characterized in that, The sludge settling ratio in the clarification sedimentation tank (4) ranges from 10% to 20%.

7. A multi-mode coagulation sedimentation tank according to any one of claims 1 to 6, characterized in that, The wastewater inflow rate of the coagulation reaction tank (1) is less than or equal to 500 m³ / h.

8. A multi-mode coagulation sedimentation tank according to claim 7, characterized in that, The second return pump (422) is configured to control the sludge return flow rate of the magnetic powder reaction tank (2) to be 25-30 m³ / h based on the power adjustment of the intelligent control mechanism (6).

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