In-situ preparation system of polyaluminum magnesium chloride coagulant based on water quality characteristics of raw water

Abstract

The invention relates to the technical field of water treatment, and discloses a raw water quality characteristic-based polyaluminum magnesium chloride coagulant in-situ preparation system, which comprises a polyaluminum magnesium chloride synthesis system and an electrochemical control system, the polyaluminum magnesium chloride synthesis system comprises a raw material box, a feeding pump, an electrochemical reactor, an intermediate box, a stirrer, a circulating pump, a flow meter and a finished product box, the electrochemical control system comprises a direct-current power supply, a time relay and an electrode converter, and the bottom of the raw material box is connected with an inlet of the feeding pump; an outlet of the feeding pump is connected with a feeding hole of the electrochemical reactor, and a pole plate fixing groove is formed in the electrochemical reactor. By accurately regulating and controlling the running time proportion of the aluminum polar plate and the magnesium polar plate in the electrochemical reaction, the components of the product can be dynamically adjusted according to different raw water characteristics such as dye, high ammonia nitrogen or micro-polluted water, the coagulant highly matched with the water quality is prepared in situ, and the problem of poor pertinence of a traditional outsourcing agent is solved.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to an in-situ preparation system for polyaluminum magnesium chloride coagulant based on the characteristics of raw water quality. Background Technology

[0002] Coagulation is a widely used technology in wastewater and water supply treatment, playing a vital role in alleviating water shortages and protecting the water environment. With industrialization, water pollutants are becoming increasingly persistent and difficult to biodegrade, especially with the emergence of new pollutants posing challenges to traditional coagulation processes. The type of coagulant and its compatibility with the raw water quality directly determine the effectiveness of coagulation treatment. Currently, polymeric inorganic coagulants have become the mainstream products due to their superior pollutant removal performance compared to monomers; common examples include polyaluminum chloride, polyaluminum sulfate, and polyferric chloride.

[0003] The current supply model for polymeric coagulants typically involves chemical manufacturers centrally preparing liquid or powder products, which are then transported to the user's site for addition. This separation of production and use makes the coagulant prone to hydrolysis or aging during transportation and storage, resulting in reduced efficacy compared to freshly prepared agents.

[0004] Manufacturer-supplied coagulants are typically standardized formulas, making it difficult to accommodate the complex and varied water quality characteristics of different users. When the chemical components are incompatible with the water to be treated, a significant increase in dosage is often required to achieve the desired treatment targets. This not only increases operating costs but also leads to increased sludge production, creating a burden for secondary treatment.

[0005] Traditional inorganic coagulants are highly dependent on the pH of the raw water. For example, magnesium salt coagulants typically require highly alkaline conditions to generate magnesium hydroxide to perform their adsorption and trapping effects. This significantly limits their large-scale application in treating water bodies with large pH fluctuations or acidic conditions. While in-situ preparation methods based on electrochemical technology have attracted attention, how to construct a device that can flexibly adjust the product composition according to the characteristics of the raw water remains a pressing technical problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an in-situ preparation system for polyaluminum magnesium chloride coagulant based on the characteristics of raw water quality. This system solves the problems of incompatibility between existing purchased coagulants and the actual water quality being treated, the efficacy of the agent decreasing during transportation and storage, and the strong dependence of traditional magnesium salt coagulants on the pH value of the raw water.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: an in-situ preparation system for polyaluminum magnesium chloride coagulant based on the characteristics of raw water quality, comprising a polyaluminum magnesium chloride synthesis system and an electrochemical control system. The polyaluminum magnesium chloride synthesis system includes a raw material tank, a feed pump, an electrochemical reactor, an intermediate tank, a stirrer, a circulating pump, a flow meter, and a finished product tank. The electrochemical control system includes a DC power supply, a time relay, and an electrode converter. The bottom of the raw material tank is connected to the inlet of the feed pump, and the outlet of the feed pump is connected to the inlet of the electrochemical reactor. The electrochemical reactor is provided with an electrode fixing groove, in which aluminum plates and magnesium plates are arranged parallel to each other. The outlet of the electrochemical reactor is connected to the inlet of the intermediate tank. The stirrer is located inside the intermediate tank. The outlet of the intermediate tank is connected to the inlet of the circulation pump. The outlet of the circulation pump is divided into two paths, one of which is connected to the electrochemical reactor and the other of which is connected to the flow meter. The outlet of the flow meter is connected to the finished product tank. The positive and negative terminals of the DC power supply are connected to the aluminum plate and the magnesium plate of the electrochemical reactor respectively through the electrode converter. The time relay is connected to the electrode converter for signal control, so as to realize the reverse operation of the electrochemical reactor.

[0008] Preferably, the electrode fixing groove inside the electrochemical reactor includes a first fixing groove and a second fixing groove, the aluminum plate and the magnesium plate are respectively fixed in the first fixing groove and the second fixing groove, and the distance between the first fixing groove and the second fixing groove is set to 8-15mm.

[0009] Preferably, the raw material tank contains a feed liquid, wherein the effective concentration of aluminum chloride in the feed liquid is 1.3-2.5 mol / L and the pH value is 1.8-2.5.

[0010] Preferably, the stirrer is used to provide a stirring intensity of 110-130 r / min in the intermediate tank, and the flow meter is used to regulate the preparation time of the coagulant, which is in the range of 12-18 h.

[0011] Preferably, the DC power supply is used to output a voltage of 2.5-4.8V to the electrochemical reactor.

[0012] Preferably, the electrode converter is used to periodically switch the connection polarity of the DC power supply with the aluminum plate and the magnesium plate according to the signal of the time relay, so that the electrochemical reactor operates alternately between the state in which the aluminum plate is the anode and the state in which the magnesium plate is the anode.

[0013] Preferably, the time logic for the time relay to control the electrochemical reactor's reverse-phase operation is as follows: The operating time is controlled to be 0.5-1.5 min when the magnesium plate is used as the anode, and 5-10 min when the aluminum plate is used as the anode.

[0014] Preferably, when the raw water is dye wastewater, the effective concentration of aluminum chloride in the feed liquid is 2.0-3.0 mol / L, the pH value is 1.5-2.2, the spacing between the electrode fixing slots is 6-10 mm, the output voltage of the DC power supply is 4.6-5.0 V, and the time relay controls the running time of the aluminum plate as the anode to be 3-7 min.

[0015] Preferably, when the raw water is high ammonia nitrogen wastewater, the effective concentration of aluminum chloride in the feed liquid is 1.5-1.9 mol / L, the pH value is 2.0-2.4, the spacing between the electrode fixing slots is 10-14 mm, the output voltage of the DC power supply is 3.2-3.6 V, and the time relay controls the running time of the aluminum plate as the anode to be 6-10 min.

[0016] Preferably, when the raw water is slightly polluted, the effective concentration of aluminum chloride in the feed liquid is 1.0-1.6 mol / L, the pH value is 2.0-3.0, the spacing between the electrode fixing slots is 13-17 mm, the output voltage of the DC power supply is 2.0-3.0 V, and the time relay controls the running time of the aluminum plate as the anode to be 8-12 min.

[0017] This invention provides an in-situ preparation system for polyaluminum magnesium chloride coagulant based on the characteristics of raw water quality. It has the following beneficial effects: 1. This invention uses a time relay to control the electrode converter, enabling precise adjustment of the operating time ratio of the aluminum and magnesium plates as anodes, thereby changing the molar ratio of polyaluminum chloride to magnesium in the product. This control mechanism allows the device to dynamically adjust the synthesis process based on the water quality characteristics of different raw water sources, such as dye wastewater, high-ammonia nitrogen wastewater, or slightly polluted water, to prepare in-situ a suitable polyaluminum chloride magnesium coagulant. This solves the problem of mismatch between traditionally purchased finished reagents and specific on-site water quality, improving the targeting and adaptability of coagulation treatment.

[0018] 2. This invention employs a bipolar aluminum-magnesium plate combined with a reverse-stage operation mode, utilizing electrochemical reactions to generate highly active aluminum-magnesium polymers in situ. The polymeric aluminum component primarily functions as a charge neutralizer and bridging agent, while the magnesium component forms magnesium hydroxide, which performs adsorption and trapping effects. Through in-situ polymerization, these two components produce a synergistic effect, improving the removal rates of chemical oxygen demand (COD), color, ammonia nitrogen, and turbidity in water. Compared to conventional monomeric coagulants, the coagulant prepared by this invention maintains excellent treatment performance while reducing reagent dosage and decreasing sludge production.

[0019] 3. This invention utilizes the characteristic of hydrogen evolution at the cathode to generate hydroxide ions in an electrochemical reaction, combined with periodic electrode switching, to create a microenvironment within the reactor that is conducive to the hydrolysis and polymerization of metal ions. This method reduces dependence on the alkalinity of the raw water, overcomes the limitation of traditional magnesium salt coagulants requiring high pH conditions to function effectively, and expands the applicable pH range of the coagulant for raw water. Furthermore, the in-situ preparation method allows for the direct use of freshly synthesized agents, avoiding the hydrolysis, aging, and efficacy degradation problems that occur with traditional liquid coagulants during transportation and storage due to prolonged exposure. Attached Figure Description

[0020] Figure 1 This is a perspective view of the present invention.

[0021] Legend: 1. Raw material tank; 2. Feed pump; 3. Electrochemical reactor; 301. Inlet; 302. First fixed tank; 303. Second fixed tank; 304. Outlet; 4. Intermediate tank; 5. Stirrer; 6. Circulating pump; 7. Flow meter; 8. Finished product tank; 9. DC power supply; 10. Time relay; 11. Electrode converter. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Reference Appendix Figure 1 The in-situ preparation system of polyaluminum magnesium chloride coagulant based on the characteristics of raw water quality includes a polyaluminum magnesium chloride synthesis system and an electrochemical control system. The polyaluminum magnesium chloride synthesis system includes a raw material tank 1, a feed pump 2, an electrochemical reactor 3, an intermediate tank 4, a stirrer 5, a circulating pump 6, a flow meter 7, and a finished product tank 8. The electrochemical control system includes a DC power supply 9, a time relay 10, and an electrode converter 11. The bottom of the raw material tank 1 is connected to the inlet of the feed pump 2, and the outlet of the feed pump 2 is connected to the inlet 301 of the electrochemical reactor 3. The electrochemical reactor 3 is equipped with an electrode fixing groove, in which aluminum plates and magnesium plates are arranged in parallel. The outlet 304 of the electrochemical reactor 3 is connected to the inlet of the intermediate tank 4. The stirrer 5 is set inside the intermediate tank 4. The outlet of the intermediate tank 4 is connected to the inlet of the circulation pump 6. The outlet of the circulation pump 6 is divided into two paths, one of which is connected to the electrochemical reactor 3 and the other is connected to the flow meter 7. The outlet of the flow meter 7 is connected to the finished product tank 8. The positive and negative terminals of the DC power supply 9 are connected to the aluminum plate and magnesium plate of the electrochemical reactor 3 respectively through the electrode converter 11. The time relay 10 is connected to the electrode converter 11 for signal control to switch the electrode converter 11 so as to realize the reverse operation of the electrochemical reactor 3.

[0024] In one specific embodiment, before the system is started, an aluminum chloride solution of a certain concentration is prepared in advance and stored in the raw material tank 1. When the system is running, the feed pump 2 is started to pump the feed liquid in the raw material tank 1 into the electrochemical reactor 3 through the feed port 301, so that the solution fills the reaction chamber and immerses the aluminum plate and magnesium plate arranged in parallel in the electrode fixing tank.

[0025] Turn on the circulation pump 6 and the agitator 5. The solution flows out from the outlet 304 of the electrochemical reactor 3 into the intermediate tank 4. The agitator 5 continuously stirs the solution in the intermediate tank 4 to maintain the uniform mixing of the components in the reaction system. The circulation pump 6 extracts the material in the intermediate tank 4 and returns it to the electrochemical reactor 3, establishing a stable liquid phase circulation state in the system.

[0026] After the liquid-phase circulation is established, the DC power supply 9 is turned on. The current output from the DC power supply 9 is applied to the aluminum and magnesium plates in the electrochemical reactor 3 through the electrode converter 11. At this time, the time relay 10 starts to work, sending a control signal to the electrode converter 11 according to the preset process parameters. After receiving the signal, the electrode converter 11 periodically switches the polarity of the connection circuit, forcing the electrochemical reactor 3 to perform reverse operation: that is, during a set time period, the magnesium plate is used as the anode for oxidation and dissolution, and during another set time period, the aluminum plate is used as the anode for oxidation and dissolution, thereby synthesizing a polymeric coagulant with a specific aluminum-magnesium molar ratio in situ in the circulating liquid.

[0027] When the reaction time reaches the preset value, the prepared polyaluminum magnesium chloride coagulant is transported to the flow meter 7 through the circulation pump 6. After being metered and controlled by the flow meter 7, it is finally discharged into the finished product box 8 for collection and storage, completing the in-situ preparation process.

[0028] Reference Appendix Figure 1 The electrode fixing groove inside the electrochemical reactor 3 includes a first fixing groove 302 and a second fixing groove 303. The aluminum plate and the magnesium plate are respectively fixed in the first fixing groove 302 and the second fixing groove 303, and the distance between the first fixing groove 302 and the second fixing groove 303 is set to 8-15mm.

[0029] In one specific embodiment, aluminum and magnesium plates are respectively inserted and fixed in the first fixing groove 302 and the second fixing groove 303 inside the electrochemical reactor 3, ensuring that the dissimilar metal plates maintain a parallel and opposing physical state within the reaction chamber. By precisely setting the distance between the first fixing groove 302 and the second fixing groove 303 within the range of 8-15 mm, an electrolytic reaction channel with a specific width is constructed between the two plates. When the feed liquid flows through the electrochemical reactor 3, the liquid in the channel acts as the electrolyte. The aforementioned set distance directly determines the solution resistance and current density distribution between the plates, thereby providing a stable electrochemical reaction field environment for the ion dissolution of aluminum and magnesium plates under energized conditions and subsequent hydrolysis and polymerization reactions.

[0030] Reference Appendix Figure 1 The raw material tank 1 contains the feed liquid, in which the effective concentration of aluminum chloride is 1.3-2.5 mol / L and the pH value is 1.8-2.5; The stirrer 5 is used to provide a stirring intensity of 120 r / min in the intermediate tank 4, and the flow meter 7 is used to regulate the preparation time of the coagulant, which is 12-18 h. DC power supply 9 is used to output a voltage of 2.5-4.8V to electrochemical reactor 3; The electrode converter 11 is used to periodically switch the connection polarity between the DC power supply 9 and the aluminum plate and the magnesium plate according to the signal of the time relay 10, so that the electrochemical reactor 3 alternates between the state where the aluminum plate is the anode and the state where the magnesium plate is the anode. The timing logic for time relay 10 to control the reverse operation of electrochemical reactor 3 is as follows: The running time is 1 minute when the magnesium plate is used as the anode, and 5-10 minutes when the aluminum plate is used as the anode.

[0031] In one specific embodiment, the feed tank 1 provides the system with a feed solution of aluminum chloride at an effective concentration of 1.3-2.5 mol / L and a pH value of 1.8-2.5, providing a suitable acidic precursor environment for the subsequent electrochemical polymerization reaction. During the reaction, the DC power supply 9 applies a low voltage of 2.5-4.8V to the electrochemical reactor 3 to maintain stable electrolysis energy consumption conditions; At this time, the time relay 10 sends a command to the electrode converter 11 according to the preset control logic, driving the electrode converter 11 to periodically switch the connection polarity between the DC power supply 9 and the aluminum and magnesium plates inside the electrochemical reactor 3. Specifically, the time relay 10 controls the electrochemical reactor 3 to execute the following reverse-phase operation program: in each cycle, the magnesium plate is first controlled to run as the anode for 1 minute to oxidize and dissolve magnesium ions; then the polarity is switched, and the aluminum plate is controlled to run as the anode for 5-10 minutes to oxidize and dissolve aluminum ions and produce a polymerization reaction; During this long-cycle alternating electrolysis process, the stirrer 5 maintains a constant stirring intensity of 120 r / min in the intermediate tank 4 to ensure that the metal ions dissolved at different times are fully mixed and the reaction system is homogenized; at the same time, the flow meter 7 strictly controls the fluid residence time in the system to keep the overall coagulant preparation time at 12-18 h, thereby ensuring that the final synthesized polyaluminum magnesium chloride coagulant reaches the expected degree of polymerization and component ratio.

[0032] Reference Appendix Figure 1 When the raw water is dye wastewater, the effective concentration of aluminum chloride in the feed liquid is 2.5 mol / L, the pH value is 1.84, the spacing between the electrode fixing tanks is 8 mm, the output voltage of the DC power supply 9 is 4.8V, and the time relay 10 controls the running time of the aluminum plate as the anode to 5 min.

[0033] In one specific embodiment, this system is applied to dye wastewater treatment: The raw water is wastewater containing Acid Red dye. The pH value of the wastewater fluctuates between 8.2 and 9.3, the chemical oxygen demand (CODcr) is 300-450 mg / L, and the color intensity is 13,000 to 22,000 times.

[0034] When the raw water is dye wastewater, the effective concentration of aluminum chloride in the feed liquid is 2.5 mol / L, the pH value is 1.84, the spacing between the electrode fixing tanks is 8 mm, the output voltage of the DC power supply 9 is 4.8V, and the time relay 10 controls the running time of the aluminum plate as the anode to 5 min.

[0035] Under these conditions, the flow meter 7 was used to adjust the coagulant preparation time to 18 hours. The prepared polyaluminum magnesium chloride coagulant had an alkalinity (B) of 2.28 and an aluminum-magnesium molar ratio of 4:1. With a dosage of 28 mg / L, a raw water pH of 8.7, a coagulation reaction time of 15 minutes, and a sedimentation time of 30 minutes, the raw water achieved a CODcr removal rate of 82.4% and a color removal rate of 99.3%.

[0036] When the raw water is high ammonia nitrogen wastewater, the effective concentration of aluminum chloride in the feed liquid is 1.7 mol / L, the pH value is 2.2, the spacing between the electrode fixing tanks is 12 mm, the output voltage of DC power supply 9 is 3.4 V, and the time relay 10 controls the running time of the aluminum plate as the anode to 8 min. In one specific embodiment, this system is applied to the treatment of high ammonia nitrogen wastewater: The raw water is high-ammonia nitrogen wastewater, with an ammonia nitrogen content of 97-153 mg / L, a CODcr of 896-1355 mg / L, a turbidity of 118-187 NTU, and a pH value of 7.8-9.2.

[0037] When the raw water is high ammonia nitrogen wastewater, the effective concentration of aluminum chloride in the feed liquid is 1.7 mol / L, the pH value is 2.2, the spacing between the electrode fixing tanks is 12 mm, the output voltage of DC power supply 9 is 3.4 V, and the time relay 10 controls the running time of the aluminum plate as the anode to 8 min.

[0038] Under these conditions, the flow meter 7 controls the coagulant preparation time to 15 hours. The prepared polyaluminum magnesium chloride coagulant has an alkalinity (B) of 2.35 and an aluminum-magnesium molar ratio of 7:1. With a dosage of 18 mg / L, a raw water pH of 8.8, a coagulation reaction time of 20 minutes, and a sedimentation time of 60 minutes, the raw water ammonia nitrogen removal rate was 74.6%, CODcr removal rate was 73.8%, and turbidity removal rate was 91.5%.

[0039] When the raw water is slightly polluted, the effective concentration of aluminum chloride in the feed liquid is 1.3 mol / L, the pH value is 2.5, the spacing between the electrode fixing slots is 15 mm, the output voltage of the DC power supply 9 is 2.5 V, and the time relay 10 controls the running time of the aluminum plate as the anode to be 10 min.

[0040] In one specific embodiment, this system is applied to the treatment of slightly polluted water: The raw water is slightly polluted, with a potassium permanganate index (CODMn) of 17.3-36.8 mg / L, suspended solids of 7.4-8.9 mg / L, turbidity of 13-21 NTU, and pH of 6.9-7.2.

[0041] When the raw water is slightly polluted, the effective concentration of aluminum chloride in the feed liquid is 1.3 mol / L, the pH value is 2.5, the spacing between the electrode fixing slots is 15 mm, the output voltage of the DC power supply 9 is 2.5 V, and the time relay 10 controls the running time of the aluminum plate as the anode to be 10 min.

[0042] Under these conditions, the flow meter 7 was used to adjust the coagulant preparation time to 12 hours. The prepared polyaluminum magnesium chloride coagulant had an alkalinity (B) of 2.47 and an aluminum-magnesium molar ratio of 11:1. With a dosage of 4.5 mg / L, a raw water pH of 7.1, a coagulation reaction time of 10 minutes, and a sedimentation time of 15 minutes, the raw water achieved a COD removal rate of 87.9%, a suspended solids removal rate of 97.2%, and a turbidity removal rate of 95.3%.

Claims

1. An in-situ preparation system for polyaluminum magnesium chloride coagulant based on raw water quality characteristics, comprising a polyaluminum magnesium chloride synthesis system and an electrochemical control system, characterized in that, The polyaluminum magnesium chloride synthesis system includes a raw material tank (1), a feed pump (2), an electrochemical reactor (3), an intermediate tank (4), a stirrer (5), a circulating pump (6), a flow meter (7), and a finished product tank (8). The electrochemical control system includes a DC power supply (9), a time relay (10), and an electrode converter (11). The bottom of the raw material box (1) is connected to the inlet of the feed pump (2), and the outlet of the feed pump (2) is connected to the inlet (301) of the electrochemical reactor (3). The electrochemical reactor (3) is provided with an electrode plate fixing groove, and aluminum plates and magnesium plates are arranged parallel in the electrode plate fixing groove. The outlet (304) of the electrochemical reactor (3) is connected to the inlet of the intermediate box (4). The stirrer (5) is set inside the intermediate box (4). The outlet of the intermediate box (4) is connected to the inlet of the circulation pump (6). The outlet of the circulation pump (6) is divided into two paths, one path is connected to the electrochemical reactor (3), and the other path is connected to the flow meter (7). The outlet of the flow meter (7) is connected to the finished product box (8). The positive and negative terminals of the DC power supply (9) are connected to the aluminum plate and the magnesium plate of the electrochemical reactor (3) respectively through the electrode converter (11). The time relay (10) is connected to the electrode converter (11) for signal control, so as to realize the reverse operation of the electrochemical reactor (3).

2. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 1, characterized in that, The electrode fixing groove inside the electrochemical reactor (3) includes a first fixing groove (302) and a second fixing groove (303). The aluminum plate and the magnesium plate are respectively fixed in the first fixing groove (302) and the second fixing groove (303), and the distance between the first fixing groove (302) and the second fixing groove (303) is set to 8-15mm.

3. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 1, characterized in that, The raw material tank (1) contains a feed liquid, the effective concentration of aluminum chloride in the feed liquid is 1.3-2.5 mol / L, and the pH value is 1.8-2.

5.

4. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 1, characterized in that, The stirrer (5) is used to provide a stirring intensity of 110-130 r / min in the intermediate tank (4), and the flow meter (7) is used to regulate the preparation time of the coagulant, which is 12-18 h.

5. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 1, characterized in that, The DC power supply (9) is used to output a voltage of 2.5-4.8V to the electrochemical reactor (3).

6. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 1, characterized in that, The electrode converter (11) is used to periodically switch the connection polarity of the DC power supply (9) with the aluminum plate and the magnesium plate according to the signal of the time relay (10), so that the electrochemical reactor (3) alternates between the state in which the aluminum plate is the anode and the state in which the magnesium plate is the anode.

7. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 2, characterized in that, The time logic for the time relay (10) to control the electrochemical reactor (3) in reverse order is as follows: The operating time is controlled to be 0.5-1.5 min when the magnesium plate is used as the anode, and 5-10 min when the aluminum plate is used as the anode.

8. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 7, characterized in that, When the raw water is dye wastewater, the effective concentration of aluminum chloride in the feed liquid is 2.0-3.0 mol / L, the pH value is 1.5-2.2, the spacing between the electrode fixing slots is 6-10 mm, the output voltage of the DC power supply (9) is 4.6-5.0 V, and the time relay (10) controls the running time of the aluminum plate as the anode to be 3-7 min.

9. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 7, characterized in that, When the raw water is high ammonia nitrogen wastewater, the effective concentration of aluminum chloride in the feed liquid is 1.5-1.9 mol / L, the pH value is 2.0-2.4, the spacing between the electrode fixing slots is 10-14 mm, the output voltage of the DC power supply (9) is 3.2-3.6 V, and the time relay (10) controls the running time of the aluminum plate as the anode to be 6-10 min.

10. The in-situ preparation system of polyaluminum magnesium chloride coagulant based on raw water quality characteristics according to claim 7, characterized in that, When the raw water is slightly polluted, the effective concentration of aluminum chloride in the feed liquid is 1.0-1.6 mol / L, the pH value is 2.0-3.0, the spacing between the electrode fixing slots is 13-17 mm, the output voltage of the DC power supply (9) is 2.0-3.0 V, and the time relay (10) controls the running time of the aluminum plate as the anode to be 8-12 min.

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