Coking wastewater treatment method and system

Abstract

The present application provides a kind of coking wastewater treatment method, comprising: coking wastewater is pretreated and biochemical treatment;Biochemical effluent enters pH coarse adjustment pool, and pH coarse adjustment agent is added to pH coarse adjustment pool, and water body pH value is coarsely adjusted to 6.5-7.5, and first wastewater is obtained;The first wastewater is coagulated and treated, and the coagulant includes polyaluminum chloride, and pH fine adjustment agent is added to coagulation reaction pool, and water body pH is fine adjusted to 6.5-7.0;After coagulation treatment, second wastewater is obtained;Second wastewater is sequentially treated by flocculation precipitation and membrane, and discharged after reaching standard.Correspondingly, a coking wastewater treatment system is also provided.The present application adopts pH two-step accurate control technology, accurately controls the acidity and alkalinity environment of wastewater, thereby accurately controls the form of aluminum salt in wastewater, achieves the best aluminum salt flocculation effect, effectively reduces the aluminum salt flocculation phenomenon before reverse osmosis membrane, reduces the probability of reverse osmosis membrane pollution and cleaning frequency, improves the stability of system operation, and reduces operating cost.

Description

Technical Field

[0001] This invention relates to a method and system for treating coking wastewater. Background Technology

[0002] Coking wastewater is a recognized type of industrial wastewater that is difficult to biodegrade, mainly due to its complex composition, containing various types of recalcitrant organic matter and multiple toxic components. In recent years, with increasingly stringent environmental protection requirements, the reuse of coking wastewater has become a primary treatment requirement. The mainstream treatment process in the industry is pretreatment + biological treatment + post-treatment + membrane-based advanced treatment before reuse. Post-treatment primarily uses coagulation and sedimentation, which involves large amounts of aluminum salts, while membrane-based advanced treatment mainly uses ultrafiltration + reverse osmosis. In numerous engineering applications, it has been found that residual aluminum salts from the coagulation and sedimentation process permeate through the ultrafiltration membrane and flocculate before the reverse osmosis membrane, becoming one of the main causes of reverse osmosis membrane fouling. This significantly reduces the permeate yield of the reverse osmosis system, posing considerable challenges to operation. Currently, the main solution is to frequently clean the reverse osmosis membrane online and offline after fouling, which severely affects the normal operation of the system and shortens the membrane's lifespan. In addition, in steel-coke co-production enterprises, besides the difficulty in treating coking wastewater, the treatment of cold rolling wastewater is also extremely difficult. Currently, the main treatment methods are oil removal, adsorption and impurity removal, flocculation and sedimentation, but the treatment effect needs to be improved. Summary of the Invention

[0003] This invention relates to a method and system for treating coking wastewater, which can at least solve some of the defects of the prior art.

[0004] This invention relates to a method for treating coking wastewater, comprising:

[0005] Pretreatment and biochemical treatment of coking wastewater;

[0006] The biochemical effluent enters the pH coarse adjustment tank, where a pH coarse adjustment agent is added to coarsely adjust the pH value of the water to 6.5-7.5, thus obtaining the first wastewater.

[0007] The first wastewater is subjected to coagulation treatment, and the coagulant added includes polyaluminum chloride. A pH adjusting agent is also added to the coagulation reaction tank to finely adjust the pH of the water to 6.5-7.0. After coagulation treatment, the second wastewater is obtained.

[0008] The second wastewater undergoes flocculation sedimentation and membrane treatment in sequence before being discharged in compliance with standards.

[0009] As one embodiment, the pH coarse adjuster and / or the pH fine adjuster comprises pretreated cold-rolled alkaline wastewater.

[0010] As one implementation method, after the second wastewater is treated by flocculation and sedimentation, it first flows through an ozone catalytic oxidation tank and an aerated biological filter tank in sequence, and then undergoes membrane treatment.

[0011] As one embodiment, the pretreatment process for the cold-rolled alkaline wastewater includes a sequential air flotation oil removal step and a filtration treatment step.

[0012] As one implementation method, coagulation treatment of the first wastewater includes:

[0013] The first wastewater entering the coagulation reaction tank carries ferric salts. The coagulation treatment of the first wastewater is achieved by combining ferric salts with polyaluminum chloride.

[0014] As one implementation method, ferrous sulfate and hydrogen peroxide are added to the first wastewater before it enters the coagulation reaction tank, so that the first wastewater, ferrous sulfate and hydrogen peroxide are mixed and reacted, and trivalent iron salts are newly formed in the first wastewater.

[0015] As one implementation method, the generation of ferric salt is achieved based on a negative pressure microbubble oxidation activator. In this method, the first wastewater is pressurized by a jet pump and sent to the water inlet of the negative pressure microbubble oxidation activator. The ferrous sulfate supply pipe is connected to the first reagent inlet of the negative pressure microbubble oxidation activator, the hydrogen peroxide supply pipe is connected to the second reagent inlet of the negative pressure microbubble oxidation activator, and the air pipe is connected to the air inlet of the negative pressure microbubble oxidation activator.

[0016] As one embodiment, the basicity of the polyaluminum chloride is in the range of 50% to 80%.

[0017] This invention also provides a coking wastewater treatment system, including a pretreatment unit and a biochemical treatment device, further comprising a pH coarse adjustment tank, a coagulation reaction tank, a flocculation sedimentation treatment unit, and a membrane treatment device. The pretreatment unit, the biochemical treatment device, the pH coarse adjustment tank, the coagulation reaction tank, the flocculation sedimentation treatment unit, and the membrane treatment device are connected in series via wastewater pipelines.

[0018] The pH coarse adjustment tank is equipped with a pH coarse adjustment agent addition unit; the coagulation reaction tank is equipped with a polyaluminum chloride addition unit and a pH fine adjustment agent addition unit.

[0019] As one embodiment, the pH coarse adjuster addition unit and / or the pH fine adjuster addition unit includes a cold-rolled alkaline wastewater supply pipe, and a pretreatment mechanism is arranged on the cold-rolled alkaline wastewater supply pipe.

[0020] The present invention has at least the following beneficial effects: The present invention adopts a two-step precise pH control technology to accurately control the acidity and alkalinity environment of wastewater, thereby accurately controlling the form of aluminum salts in wastewater, achieving the best aluminum salt flocculation effect, effectively reducing aluminum salt flocculation phenomenon before reverse osmosis membrane, reducing the probability of reverse osmosis membrane fouling and cleaning frequency, improving the stability of system operation and reducing operating costs. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart of a coking wastewater treatment method provided in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0024] Example 1

[0025] like Figure 1 This invention provides a method for treating coking wastewater, comprising:

[0026] Pretreatment and biochemical treatment of coking wastewater;

[0027] The biochemical effluent enters pH coarse adjustment tank 1. A pH coarse adjustment agent is added to pH coarse adjustment tank 1 to coarsely adjust the pH value of the water to 6.5-7.5, thus obtaining the first wastewater.

[0028] The first wastewater is subjected to coagulation treatment, and the coagulant added includes polyaluminum chloride. A pH fine-tuning agent is added to the coagulation reaction tank 4 to fine-tune the pH of the water to 6.5-7.0. After coagulation treatment, the second wastewater is obtained.

[0029] The second wastewater undergoes flocculation sedimentation and membrane treatment in sequence before being discharged in compliance with standards.

[0030] The pretreatment and biochemical treatment of coking wastewater are conventional technologies in this field and will not be elaborated here.

[0031] In addition to adjusting the pH value of the biochemical effluent, the aforementioned pH coarse adjustment tank 1 also serves as a buffer, regulating the production pace of upstream and downstream processes. Depending on the properties of the biochemical effluent (its pH value generally fluctuates between 6 and 8.5), the pH coarse adjustment agent can be either acidic or alkaline. Acidic coarse adjustment agents include, but are not limited to, sulfuric acid, while alkaline coarse adjustment agents include, but are not limited to, sodium hydroxide (which can be a sodium hydroxide solution). Preferably, a continuous mixer and a pH monitor are installed in the pH coarse adjustment tank 1 to achieve rapid and accurate pH adjustment. In one embodiment, the residence time of the biochemical effluent in the pH coarse adjustment tank 1 is 0.1–0.3 hours, and the rotation speed of the continuous mixer is in the range of 100–200 rpm.

[0032] Optionally, the first wastewater is first treated in the activated carbon contact tank 2 and then subjected to coagulation treatment. Powdered activated carbon is added to the activated carbon contact tank 2. By fully mixing the powdered activated carbon with the first wastewater, it can effectively adsorb pollutants such as organic matter in the first wastewater. Preferably, a continuous axial flow mixer is installed in the activated carbon contact tank 2. The axial flow mixer is equipped with a guide tube. Through the suction action of the axial flow mixer, the mixed liquid in the activated carbon contact tank 2 forms a circulation from bottom to top and from inside to outside, so as to achieve the purpose of large-volume back mixing. This prevents the lighter powdered activated carbon from floating on the water surface and achieves complete and rapid mixing with the wastewater, which can effectively improve the treatment effect. In one embodiment, the residence time of the wastewater in the activated carbon contact tank 2 is 0.5 to 1.5 hours, the rotation speed of the axial flow mixer is in the range of 100 to 200 rpm, and the dosage of powdered activated carbon is 400 to 600 mg / L.

[0033] As a preferred embodiment, coagulation treatment of the first wastewater includes:

[0034] The first wastewater entering coagulation reactor 4 carries ferric salts. Coagulation treatment of the first wastewater is achieved through the combined use of ferric salts and polyaluminum chloride. In the system where ferric salts and aluminum salts coexist, the hydrolysis rate of ferric salts is greater than that of aluminum salts. This promotes the flocculation and precipitation of aluminum salts, improving the removal rate of pollutants and significantly reducing the concentration of residual ferric and aluminum salts in the coagulation supernatant, thus minimizing the risk of fouling of the subsequent reverse osmosis membrane.

[0035] In one embodiment, ferrous sulfate and hydrogen peroxide are added to the first wastewater before it enters the coagulation reaction tank 4, causing the first wastewater, ferrous sulfate, and hydrogen peroxide to mix and react, forming ferric salts in the first wastewater. The newly formed ferric salts hydrolyze more slowly than the pre-formed ferric salts, resulting in better flocculation.

[0036] Furthermore, the generation of ferric salts is achieved based on the negative pressure microbubble oxidation activator 3. The negative pressure microbubble oxidation activator 3 has a water inlet, a water outlet, a first reagent inlet, a second reagent inlet, an air inlet, a negative pressure chamber, and an activation chamber. The water inlet, the first reagent inlet, the second reagent inlet, and the air inlet are all connected to the negative pressure chamber, and the water outlet is connected to the activation chamber. The first wastewater is pressurized by a jet pump and sent to the water inlet of the negative pressure microbubble oxidation activator 3. The ferrous sulfate supply pipe is connected to the first reagent inlet of the negative pressure microbubble oxidation activator 3, the hydrogen peroxide supply pipe is connected to the second reagent inlet of the negative pressure microbubble oxidation activator 3, and the air pipe is connected to the air inlet of the negative pressure microbubble oxidation activator 3. Based on the above scheme, ferrous sulfate, hydrogen peroxide, and air are rapidly mixed in the negative pressure chamber of the negative pressure microbubble oxidation activator 3. The air forms numerous microbubbles within the negative pressure chamber, which burst instantaneously under the positive pressure of the activation chamber of the negative pressure microbubble oxidation activator 3. This results in intense collisions within the closed regions of countless microbubbles, generating a large number of hydroxyl radicals. These radicals effectively stimulate the thorough mixing of ferrous sulfate, hydrogen peroxide, air, and wastewater, increasing the oxidation-reduction potential of the wastewater and instantaneously generating a large amount of ferric iron. During this process, the entire ferric iron generation time is approximately one minute with no decay, thus eliminating the need for ferric iron stabilizers. Furthermore, the large number of hydroxyl radicals generated in the activation chamber has a synergistic effect on the removal of pollutants such as organic matter and ammonia nitrogen, improving the wastewater treatment efficiency. The water outlet of the negative pressure microbubble oxidation activator 3 is connected to the coagulation reaction tank 4, allowing the first wastewater carrying ferric salts to enter the coagulation reaction tank 4 for coagulation.

[0037] Performing pH fine-tuning in the coagulation reaction tank 4 can shorten the treatment process accordingly. In one embodiment, the coagulation reaction tank 4 is equipped with a mixing ring, which has a wastewater inlet, a pH fine-tuning agent inlet, and an outlet. The first wastewater enters through the wastewater inlet of the mixing ring, and the pH fine-tuning agent inlet is used to add the pH fine-tuning agent. The two can be fully mixed in the mixing ring, and then enter the coagulation reaction tank 4 through the outlet of the mixing ring, resulting in a good pH adjustment effect. A continuous mixer and a pH monitor are installed in the coagulation reaction tank 4 to achieve rapid and accurate pH adjustment. In one embodiment, the residence time of wastewater in the coagulation reaction tank 4 is 0.1–0.2 hours, the rotation speed of the continuous mixer is in the range of 60–100 rpm, and the dosage of polyaluminum chloride is 210–350 mg / L. The mixing ring is preferably arranged in the middle of the coagulation reaction tank 4, at the same height as the impeller of the mixer in the tank. In one embodiment, the diameter of the mixing ring is 1.5–2 times the diameter of the mixer impeller. Multiple outlets can be opened in the circumferential direction of the mixing ring, preferably facing the impeller of the mixer.

[0038] Preferably, the basicity of the polyaluminum chloride is in the range of 50% to 80%, and more preferably it is controlled at around 65%, which can effectively reduce the aluminum ion content in the coagulation supernatant.

[0039] The aforementioned flocculation and sedimentation treatment is preferably implemented using a flocculation tank 5 and a sedimentation tank 6. Secondary wastewater flows into the flocculation tank 5, and a flocculant, including but not limited to polyacrylamide, is simultaneously added to the flocculation tank 5. More preferably, a continuous lift agitator is installed in the flocculation tank 5. The wastewater in the flocculation tank 5 flows into the sedimentation tank 6 to facilitate the removal of flocculent material through sedimentation. Inclined tube packing can be installed in the sedimentation tank 6. The supernatant obtained from the sedimentation tank 6 is then used for subsequent membrane treatment. In one embodiment, the residence time of the wastewater in the flocculation tank 5 is 0.2–0.3 hours, the continuous agitator speed is 30–60 rpm, and the polyacrylamide dosage is 1.0–2.0 mg / L; the residence time of the wastewater in the sedimentation tank 6 is 0.7–1.2 hours, and the upward flow velocity of the supernatant in the sedimentation tank 6 is 4–7 m / h.

[0040] The above membrane treatment can be performed using a combination of ultrafiltration and reverse osmosis membranes.

[0041] In this application, a two-step pH precision control technology is adopted to accurately control the acidity and alkalinity environment of wastewater, thereby accurately controlling the form of aluminum salts in the wastewater and achieving the best aluminum salt flocculation effect. This can effectively reduce aluminum salt flocculation before the reverse osmosis membrane, reduce the probability of reverse osmosis membrane fouling and cleaning frequency, improve the stability of system operation, and reduce operating costs.

[0042] The control principle of this application is that aluminum salts exhibit different molecular forms as the pH value of the wastewater changes, as detailed below:

[0043] When the pH value is below 3, most aluminum ions in the wastewater will undergo the following reaction:

[0044] Al 3+ +6H₂O=[Al(H₂O)₆] 3+

[0045] When the pH value is higher than 9, most aluminum ions in the wastewater will undergo the following reaction:

[0046] Al 3+ +2OH - =AlO2 - +2H +

[0047] The aluminum molecules produced by the two reactions above are soluble substances and cannot achieve the effect of coagulation and hydrolysis. They are also soluble in water and will cause fouling as the wastewater flows to the subsequent membrane treatment system. This is one of the important reasons for membrane fouling.

[0048] In this application, the pH value of the wastewater is controlled at 6.5–7.0, and most of the aluminum ions in the aluminum wastewater will undergo the following reaction:

[0049] Al 3+ +3OH - =Al(OH)3

[0050] The aluminum-containing molecules produced by the above reactions are sparingly soluble and are therefore the best coagulants. The optimal flocculation pH for polyaluminum chloride is 6.5. The closer the pH is to the optimal pH, the higher the proportion of sparingly soluble aluminum-containing molecules, which is more conducive to coagulation and reduces the concentration of aluminum ions in the effluent.

[0051] Since the hydrolysis of added polyaluminum chloride will also lower the pH value of the wastewater, controlling the pH value of the first wastewater at 6.5-7.5 and adjusting the pH value of the wastewater in coagulation reaction tank 4 back to 6.5-7.0 can achieve a better wastewater coagulation treatment effect, maximize the coagulation effect of polyaluminum chloride, and keeping the pH value of the coagulated effluent at 6.5-7.0 is also conducive to the subsequent flocculation and precipitation of aluminum salts, thereby reducing the flocculation phenomenon of aluminum salts before the reverse osmosis membrane.

[0052] In one embodiment, such as Figure 1 The pH coarse adjuster and / or the pH fine adjuster comprise pretreated cold-rolled alkaline wastewater. Based on this design, the pH of coking wastewater is adjusted and the flocculation of aluminum salts before the membrane is controlled using cold-rolled alkaline wastewater, achieving the goal of treating waste with waste. This allows for the synergistic treatment of two types of special wastewater, facilitating the disposal of coking wastewater, reducing related chemical consumption, and eliminating the need for a separate treatment line for cold-rolled alkaline wastewater, thus significantly reducing equipment investment and production operating costs.

[0053] Preferably, such as Figure 1 The pretreatment process for the cold-rolling alkaline wastewater includes a sequential air flotation oil removal step and a filtration step. Preferably, the air flotation oil removal step uses a two-stage air flotation oil separator 10. In one embodiment, the air flotation oil separator 10 employs a pressurized dissolved air flotation process, with a reflux ratio (or dissolved air-to-water ratio) of 20% to 40%. The filtration step preferably uses a ceramic filter 11 to remove colloids and suspended solids from the cold-rolling alkaline wastewater. Preferably, the pore size of the ceramic filter 11 is 0.2–0.3 μm, and the flux is 100–200 L / (m³). 2 The transmembrane pressure difference is 0.05–0.15 MPa, and the cross-flow filtration velocity is 1.5–3.0 m / s.

[0054] In one embodiment, such as Figure 1The second wastewater, after flocculation and sedimentation treatment, first flows sequentially through the ozone catalytic oxidation tank 7 and the aerated biological filter 8, and then undergoes membrane treatment. By setting up the ozone catalytic oxidation tank 7 and the aerated biological filter 8, on the one hand, pollutants such as COD and oil pollutants brought in by the cold rolling alkaline wastewater can be further removed, ensuring reliable treatment of the cold rolling alkaline wastewater; on the other hand, it can also further reduce pollutants such as COD in the coking wastewater, thus effectively reducing the load on subsequent membrane treatment and improving the service life of the membrane modules.

[0055] Preferably, the ozone catalytic oxidation tank 7 is equipped with catalytic packing material, the catalyst packing material is 60-80%, and the ozone dosage is 80-130 mg / L; the residence time of wastewater in the ozone catalytic oxidation tank 7 is preferably controlled to be 1.5-2 hours.

[0056] Preferably, the hydraulic load of the aerated biological filter 8 is 2-5 m / h, and the empty bed retention time is 50-70 min.

[0057] More preferably, during system operation, a graded and segmented hydraulic velocity gradient control technology is adopted: in the coagulation-flocculation-sedimentation process, the hydraulic velocity gradient in each treatment unit along the water flow direction is gradually reduced and precisely controlled, which can promote the formation of flocs with optimal particle size and fractal dimension, so as to ensure the best coagulation and sedimentation effect and reduce the concentration of residual iron and aluminum salts in the supernatant.

[0058] Example 2

[0059] like Figure 1 This invention provides a coking wastewater treatment system, including a pretreatment unit and a biochemical treatment device, and further including a pH coarse adjustment tank 1, a coagulation reaction tank 4, a flocculation sedimentation treatment unit, and a membrane treatment device 9. The pretreatment unit, the biochemical treatment device, the pH coarse adjustment tank 1, the coagulation reaction tank 4, the flocculation sedimentation treatment unit, and the membrane treatment device 9 are connected in series via wastewater pipelines.

[0060] The pH coarse adjustment tank 1 is equipped with a pH coarse adjustment agent addition unit; the pre-oxidation treatment device is equipped with an oxidizing agent addition unit; and the coagulation reaction tank 4 is equipped with a polyaluminum chloride addition unit and a pH fine adjustment agent addition unit.

[0061] Furthermore, the pH coarse adjuster addition unit and / or the pH fine adjuster addition unit includes a cold-rolled alkaline wastewater supply pipe, on which a pretreatment mechanism is arranged.

[0062] The relevant components and structure of the coking wastewater treatment system have been described in the above embodiment one, and will not be repeated here.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating coking wastewater, characterized in that, include: Pretreatment and biochemical treatment of coking wastewater; The biochemical effluent enters the pH coarse adjustment tank, where a pH coarse adjustment agent is added to coarsely adjust the pH value of the water to 6.5~7.5, thus obtaining the first wastewater; The first wastewater is first treated in an activated carbon contact tank and then subjected to coagulation treatment. Powdered activated carbon is added to the activated carbon contact tank to thoroughly mix with the first wastewater, thereby adsorbing organic pollutants in the wastewater. During the coagulation treatment, the coagulant added includes polyaluminum chloride, and a pH adjusting agent is added to the coagulation reaction tank to finely adjust the pH of the water to 6.5-7.0, so as to promote the following reaction of aluminum ions in the wastewater: Al 3+ +3OH - Al(OH)3 The dosage of the polyaluminum chloride is 210~350 mg / L; the basicity of the polyaluminum chloride is in the range of 50%~80%; The coagulation treatment of the first wastewater further includes: the first wastewater entering the coagulation reaction tank carries ferric salts, and coagulation treatment of the first wastewater is achieved through the combined use of ferric salts and polyaluminum chloride; specifically, before entering the coagulation reaction tank, ferrous sulfate and hydrogen peroxide are added to the first wastewater, causing the first wastewater, ferrous sulfate, and hydrogen peroxide to mix and react, forming ferric salts in the first wastewater. The formation of ferric salts is achieved based on a negative pressure microbubble oxidation activator, wherein the first wastewater is pressurized by a jet pump and sent to the water inlet of the negative pressure microbubble oxidation activator, and the ferrous sulfate supply pipe is connected to the... The negative pressure microbubble oxidation activator has a first reagent inlet, a hydrogen peroxide supply pipe connected to a second reagent inlet, and an air pipe connected to an air inlet. Ferrous sulfate, hydrogen peroxide, and air are mixed in the negative pressure chamber of the negative pressure microbubble oxidation activator, where air forms a large number of microbubbles. These microbubbles rupture under the positive pressure of the activation chamber, generating strong impacts in the closed areas of the microbubbles and producing a large number of hydroxyl radicals. This stimulates the thorough mixing of ferrous sulfate, hydrogen peroxide, air, and wastewater, thereby increasing the oxidation-reduction potential of the wastewater. After coagulation treatment, the second wastewater is obtained; The second wastewater undergoes flocculation sedimentation and membrane treatment in sequence before being discharged in compliance with standards.

2. The coking wastewater treatment method as described in claim 1, characterized in that: The pH coarse adjuster and / or the pH fine adjuster comprise pretreated cold-rolled alkaline wastewater.

3. The coking wastewater treatment method as described in claim 2, characterized in that: After being treated by flocculation and sedimentation, the second wastewater first flows through the ozone catalytic oxidation tank and the aerated biological filter tank in sequence, and then undergoes membrane treatment.

4. The coking wastewater treatment method as described in claim 2, characterized in that: The pretreatment process for the cold-rolled alkaline wastewater includes sequential steps of air flotation for oil removal and filtration.

5. A coking wastewater treatment system, comprising a pretreatment unit and a biochemical treatment device, characterized in that, It also includes a pH coarse adjustment tank, an activated carbon contact tank, a coagulation reaction tank, a flocculation sedimentation treatment mechanism, and a membrane treatment device. The pretreatment mechanism, the biochemical treatment device, the pH coarse adjustment tank, the activated carbon contact tank, the coagulation reaction tank, the flocculation sedimentation treatment mechanism, and the membrane treatment device are connected in series via wastewater pipelines. The pH coarse adjustment tank is equipped with a pH coarse adjustment agent addition unit, which is used to coarsely adjust the pH value of the water to 6.5~7.5 to obtain the first wastewater; The activated carbon contact tank is used to adsorb organic pollutants in the first wastewater by adding powdered activated carbon. The coagulation reaction tank is used to coagulate the first wastewater. The coagulation reaction tank is equipped with a polyaluminum chloride addition unit and a pH fine-tuning agent addition unit to fine-tune the pH of the water to 6.5-7.0, so as to promote the following reaction of aluminum ions in the wastewater: Al 3+ +3OH - Al(OH)3 The coagulation treatment of the first wastewater further includes: the first wastewater entering the coagulation reaction tank carries ferric salts, and the coagulation treatment of the first wastewater is achieved by the combined use of ferric salts and polyaluminum chloride; specifically, before entering the coagulation reaction tank, ferrous sulfate and hydrogen peroxide are added to the first wastewater, so that the first wastewater, ferrous sulfate and hydrogen peroxide are mixed and reacted to form ferric salts in the first wastewater, and the generation of ferric salts is achieved based on a negative pressure microbubble oxidation activator. The first wastewater is pressurized by a jet pump and sent to the water inlet of the negative pressure microbubble oxidation activator. The ferrous sulfate supply pipe is connected to the first reagent inlet of the negative pressure microbubble oxidation activator, the hydrogen peroxide supply pipe is connected to the second reagent inlet of the negative pressure microbubble oxidation activator, and the air pipe is connected to the air inlet of the negative pressure microbubble oxidation activator.

6. The coking wastewater treatment system as described in claim 5, characterized in that: The pH coarse adjuster addition unit and / or the pH fine adjuster addition unit include a cold-rolled alkaline wastewater supply pipe, and a pretreatment mechanism is arranged on the cold-rolled alkaline wastewater supply pipe.

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