A treatment method and system for reducing the acute biological toxicity of automobile manufacturing wastewater

Abstract

The present invention provides a treatment method and system for reducing the acute biological toxicity of automobile manufacturing wastewater. After the first type of painting wastewater is treated in a first physicochemical coagulation tank, the first type of painting wastewater treatment water is obtained; after the second type of painting wastewater is treated in a second physicochemical coagulation tank, the second type of painting wastewater treatment water is obtained; the third type of painting wastewater is treated in a third physicochemical coagulation tank, and the third type of painting wastewater treatment water is obtained after evaporation. After the second type of painting wastewater treatment water and the third type of painting wastewater treatment water are treated by sludge method toxicity degradation, the first mixed wastewater treatment water is obtained; the first type of painting wastewater treatment water, the first mixed wastewater treatment water, the powertrain wastewater treatment water and the domestic sewage are mixed, and after entering the biochemical treatment tank for treatment, the water is discharged. The present invention classifies and pre-treats automobile manufacturing wastewater, effectively reduces the acute toxicity of painting wastewater, and alleviates the problem that the dissolved oxygen in the biochemical treatment system is unstable, resulting in excessive COD discharge in the effluent, and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a treatment method and system for reducing the acute biological toxicity of automobile manufacturing wastewater. Background Art

[0002] Automobile manufacturing wastewater mainly comes from various types of painting wastewater in the paint shop and machining wastewater in the powertrain workshop. It also includes domestic sewage from living areas, such as Figure 2 As shown. Painting wastewater and machining wastewater are usually pre-treated and then sent to the biochemical treatment system together with domestic sewage for treatment before finally being discharged in compliance with the standards, such as Figure 3 shown.

[0003] However, in the actual water treatment operation process, it is found that after all wastewater finally enters the biochemical treatment system, the dissolved oxygen in the biochemical treatment system is often unstable or even drops sharply. For example, the dissolved oxygen can drop from about 3 mg / L under normal conditions to 1 or even below 0.5 mg / L, and the sludge settling ratio of the biochemical effluent can rise from 0.5%~1.5% to 3%~5%, or even close to 10%, which greatly increases the burden of the subsequent sludge dewatering system and the cost of sludge disposal; when the activated sludge method is used for treatment, the water in the entire biochemical pool turns black due to lack of oxygen, the sludge settling is poor, and the effluent is turbid. No matter which biochemical treatment process is used, it will eventually lead to a rapid increase in the total effluent COD or even excessive discharge.

[0004] In view of this abnormal phenomenon, the most likely cause was naturally attributed to the problem of the physicochemical coagulation system of the wastewater station used to treat industrial wastewater from the workshop, which caused excessive unremoved pollutants to enter the biochemical system. However, after checking the physicochemical coagulation system, it was found that the dosing and sedimentation of the system were normal, the effluent was clear, and the effluent COD was only 2000~3000mg / L. After entering the biochemical regulating tank and evenly mixing with domestic sewage, the COD was only 1000~1500mg / L, which fully met the design load of the biochemical system. In addition, according to the COD removal rate of the biochemical system, which can reach more than 75%, the COD of the biochemical effluent can be normally controlled at 250~375mg / L, which can fully meet the standard of 500mg / L for piped discharge.

[0005] But the actual situation is not so. Through observation and analysis, it is found that these problems are related to the abnormal microbial film on the biological filler. Whenever the biochemical system is abnormal, the biofilm on the filler is wrapped by a white jelly-like substance with a thickness of more than 5cm, and the inside is in an oxygen-deficient state. The external dissolved oxygen cannot pass through the outer layer of the wrapping to be used by the microorganisms on the surface of the filler. This shows that the microorganisms are stimulated by the outside world, produce capsules, and form jelly-like substances, which hinder the transfer of dissolved oxygen and the degradation of organic matter.

[0006] Microscopic examination showed that there were explosively growing filamentous bacteria in the jelly-like substance. These filamentous bacteria were anaerobic microorganisms. Because the surface of the biofilm was covered with jelly-like substances and the interior was lacking in oxygen, the filamentous bacteria grew in large quantities and produced mucous substances, which further promoted the increase of jelly-like substances, forming a vicious cycle. Microscopic examination showed that the large amount of floating mud entrained in the biochemical effluent mainly contained filamentous bacteria, which further confirmed that the large amount of jelly-like substances falling off was the source of the effluent floating mud.

[0007] Although in theory, after long-term contact with certain toxic substances, microorganisms may develop resistance to toxicity by improving their genes and gradually adapt to such toxic substances through renewal, this is only for substances with low or medium toxicity. For substances with higher toxicity, microorganisms may not be able to adapt. This is why the biochemical treatment system cannot adapt to the same series of wastewater even though it has been treating them for a long time. Therefore, further research and solutions to these problems are needed to ensure the stable operation and standard discharge of the wastewater treatment system. This includes optimizing the pretreatment process, reducing the acute toxicity of wastewater organisms, improving the design and operation parameters of the biochemical treatment system, and controlling the abnormal growth of microbial membranes. Through comprehensive management, the efficiency of the wastewater treatment system can be effectively improved, pollutant emissions can be reduced, and treatment costs can be reduced. Summary of the invention

[0008] In view of the shortcomings in the prior art, the present invention provides a treatment method and system for reducing the acute biological toxicity of automobile manufacturing wastewater, which is used to solve the problem in the prior art that the acute toxicity of automobile manufacturing wastewater produces a stress effect on the microorganisms in the biochemical treatment system, resulting in the instability and sharp decline of dissolved oxygen in the biochemical treatment system, further causing a rapid increase in effluent COD or even excessive emissions.

[0009] The first aspect of the present invention provides a method for reducing the acute biological toxicity of automobile manufacturing wastewater, comprising the following steps:

[0010] 1) The first type of coating wastewater is treated in a first physicochemical coagulation tank and dehydrated to obtain the first type of coating wastewater treated water, wherein the first type of coating wastewater includes one or more of degreasing wastewater, degreasing waste liquid, and film wastewater;

[0011] 2) The second type of coating wastewater is treated in the second physicochemical coagulation tank, dehydrated, and then the second type of coating wastewater treatment water is obtained, and enters the first mixed wastewater tank. The second type of coating wastewater includes one or more of electrophoresis wastewater, electrophoresis waste liquid, and spray paint wastewater;

[0012] 3) The third type of coating wastewater is treated in the third physicochemical coagulation tank, dehydrated, and evaporated to obtain the third type of coating wastewater treatment water, which then enters the first mixed wastewater tank and is evenly mixed with the second type of coating wastewater treatment water in step 2) to obtain the first mixed wastewater. The third type of coating wastewater includes aqueous gun washing wastewater;

[0013] The first mixed wastewater is treated in a sludge-based toxicity degradation treatment tank and dehydrated to obtain first mixed wastewater treatment water;

[0014] 4) After the powertrain workshop wastewater is treated by ultrafiltration, the powertrain wastewater treatment water is obtained;

[0015] 5) The first type of coating wastewater treatment water described in step 1), the first mixed wastewater treatment water described in step 3), and the powertrain wastewater treatment water described in step 4) are mixed with domestic sewage and enter a second mixed wastewater tank to obtain second mixed wastewater. The second mixed wastewater enters a biochemical treatment tank for treatment to obtain discharged water.

[0016] A second aspect of the present invention provides a treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater, comprising:

[0017] A biochemical treatment tank, used to subject the second mixed wastewater to a biochemical reaction to provide discharge water, wherein the second mixed wastewater includes the first type of coating wastewater treatment water, the first mixed wastewater treatment water, the powertrain wastewater treatment water and domestic sewage;

[0018] A first type of coating wastewater treatment unit, the first type of coating wastewater treatment unit comprising a first physicochemical coagulation tank and a first dehydrator to provide first type of coating wastewater treatment water, the first physicochemical coagulation tank, the first dehydrator and the second mixed wastewater tank being sequentially fluidically connected;

[0019] A second type of coating wastewater treatment unit, wherein the second type of coating wastewater treatment unit comprises a second physicochemical coagulation tank and a second dehydrator to provide second type of coating wastewater treatment water, wherein the second physicochemical coagulation tank, the second dehydrator and the first mixed wastewater tank are sequentially fluidically connected;

[0020] A third type of coating wastewater treatment unit, the third type of coating wastewater treatment unit comprising a third physicochemical coagulation tank, a third dehydrator and an evaporation unit which are fluidically connected in sequence to provide third type of coating wastewater treatment water, the evaporation unit is fluidically connected to the first mixed wastewater tank to provide first mixed wastewater; the first mixed wastewater comprises second type of coating wastewater treatment water and third type of coating wastewater treatment water;

[0021] A sludge-based toxic degradation treatment tank, wherein the water inlet of the sludge-based toxic degradation treatment tank is connected to the water outlet of the first mixed wastewater tank, the water outlet of the sludge-based toxic degradation treatment tank is connected to the water inlet of the second mixed wastewater tank, and a fourth dehydrator is provided between the sludge-based toxic degradation treatment tank and the second mixed wastewater tank, for subjecting the first mixed wastewater to sludge-based toxic degradation treatment to obtain first mixed wastewater treated water;

[0022] A powertrain workshop wastewater treatment unit comprises an ultrafiltration unit to provide powertrain wastewater treatment water, wherein the ultrafiltration unit is in fluid communication with the second mixed wastewater tank.

[0023] The present invention has the following beneficial effects:

[0024] (1) Reducing the stress on microorganisms: Through pre-classification and treatment of automobile manufacturing wastewater, targeted methods are selected to remove or reduce harmful components in the wastewater according to the different components of each type of wastewater, thereby reducing its acute biological toxicity and reducing the stress on microorganisms in the biochemical treatment system.

[0025] (2) Improving system stability and reducing the risk of excessive discharge: The present invention helps to maintain the stable operation of the biochemical system, thereby reducing the risk of excessive discharge of effluent COD and complying with environmental protection regulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall device structure of the present invention.

[0027] Figure 2 Displayed is a statistical table of automobile manufacturing wastewater.

[0028] Figure 3 Shown is the conventional treatment process for automobile manufacturing wastewater.

[0029] Component number description

[0030] 1 First coating wastewater inlet 11 The first physicochemical coagulation tank 2 Second coating wastewater inlet 21 The second physicochemical coagulation tank 3 The third coating wastewater inlet 31 The third physicochemical coagulation tank 32 Evaporation unit 4 Power plant wastewater inlet 41 Ultrafiltration unit 5 Domestic sewage inlet 6 First mixed wastewater tank 7 Sludge toxicity degradation treatment tank 8 Second mixed wastewater tank 9 Biochemical treatment pool DETAILED DESCRIPTION

[0031] Hereinafter, a specific disclosed method and system for reducing the acute biological toxicity of automobile manufacturing wastewater will be described in detail.

[0032] In the prior art, the acute toxicity of automobile manufacturing wastewater can exert stress on the microorganisms in the biochemical treatment system, causing the dissolved oxygen in the biochemical treatment system to be unstable and drop sharply, further causing the effluent COD to rise rapidly or even exceed the discharge standard. The present invention classifies and pre-treats the painting wastewater, effectively reduces the acute toxicity of the painting wastewater, reduces the stress on the microorganisms in the biochemical system, and maintains the stable operation of the biochemical system. On this basis, the present invention is completed.

[0033] See also Figure 1~Figure 3 . It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0034] The first aspect of the present invention provides a method for reducing the acute biological toxicity of automobile manufacturing wastewater, comprising the following steps:

[0035] 1) The first type of coating wastewater is treated in a first physicochemical coagulation tank and dehydrated to obtain the first type of coating wastewater treated water, wherein the first type of coating wastewater includes one or more of degreasing wastewater, degreasing waste liquid, and film wastewater;

[0036] 2) The second type of coating wastewater is treated in the second physicochemical coagulation tank, dehydrated, and then the second type of coating wastewater treatment water is obtained, and enters the first mixed wastewater tank. The second type of coating wastewater includes one or more of electrophoresis wastewater, electrophoresis waste liquid, and spray paint wastewater;

[0037] 3) The third type of coating wastewater is treated in the third physicochemical coagulation tank, dehydrated, and evaporated to obtain the third type of coating wastewater treatment water, which then enters the first mixed wastewater tank and is evenly mixed with the second type of coating wastewater treatment water in step 2) to obtain the first mixed wastewater. The third type of coating wastewater includes aqueous gun washing wastewater;

[0038] The first mixed wastewater is treated in a sludge-based toxicity degradation treatment tank and dehydrated to obtain first mixed wastewater treatment water;

[0039] 4) After the powertrain workshop wastewater is treated by ultrafiltration, the powertrain wastewater treatment water is obtained;

[0040] 5) The first type of coating wastewater treatment water described in step 1), the first mixed wastewater treatment water described in step 3), and the powertrain wastewater treatment water described in step 4) are mixed with domestic sewage and enter a second mixed wastewater tank to obtain second mixed wastewater. The second mixed wastewater enters a biochemical treatment tank for treatment to obtain discharged water.

[0041] In the treatment method for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, step 1) is to treat the first type of painting wastewater in a first physicochemical coagulation tank, and after dehydration, obtain the first type of painting wastewater treated water.

[0042] In step 1) of the present invention, the acute toxicity of the first type of coating wastewater is 6 to 10 toxicity units, which can be selected as 6 to 7 toxicity units, 7 to 7.6 toxicity units, 7.6 to 7.8 toxicity units, 7.8 to 8.2 toxicity units, 8.2 to 9 toxicity units or 9 to 10 toxicity units, and the CODcr is 400 to 2250 mg / L, which can be selected as 400 to 600 mg / L, 600 to 752.4 mg / L, 752.4 to 1000 mg / L, 1000 to 1200 mg / L, 1200 to 1800 mg / L or 1800 to 2250 mg / L, etc.

[0043] In step 1) of the present invention, the first physicochemical coagulation tank comprises a first coagulant and / or a first flocculant.

[0044] In step 1) of the present invention, the first coagulant is selected from one or more of soluble aluminum salts, soluble iron salts, polyaluminum chloride, polyferric sulfate, and polyaluminum ferric chloride; the addition concentration of the first coagulant is 50-100 mg / L, and can be selected from 50-70 mg / L, 70-90 mg / L or 90-100 mg / L, etc.

[0045] In step 1) of the present invention, the first flocculant is selected from one or both of anionic polyacrylamide and nonionic polyacrylamide; the addition concentration of the first flocculant is 1-3 mg / L, and can be 1-2 mg / L or 2-3 mg / L.

[0046] In step 1) of the present invention, the acute toxicity of the first type of coating wastewater treatment water is 4 to 7 toxicity units, which can be selected as 4 to 4.71 toxicity units, 4.71 to 4.9 toxicity units, 4.9 to 5.58 toxicity units or 5.58 to 7 toxicity units, and the CODcr is 300 to 1350 mg / L, which can be selected as 300 to 500 mg / L, 500 to 750 mg / L, 750 to 1000 mg / L or 1000 to 1350 mg / L, etc.

[0047] In the treatment method for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, step 2) is to treat the second type of painting wastewater in a second physicochemical coagulation tank and dehydrate it to obtain the second type of painting wastewater treated water.

[0048] In step 2) of the present invention, the acute toxicity of the second type of coating wastewater is 100-425 toxicity units, which can be selected as 100-115.3 toxicity units, 115.3-184.4 toxicity units, 184.4-300 toxicity units, 300-397.7 toxicity units or 397.7-425 toxicity units, etc., and the CODcr is 7000-18000 mg / L, which can be selected as 7000-7500 mg / L, 7500-10000 mg / L, 10000-12000 mg / L, 12000-14500 mg / L or 14500-18000 mg / L, etc.

[0049] In step 2) of the present invention, the second physicochemical coagulation tank includes a second coagulant and / or a second flocculant.

[0050] In step 2) of the present invention, the second coagulant is selected from one or more of soluble aluminum salts, soluble iron salts, polyaluminum chloride, polyferric sulfate, and polyaluminum ferric chloride; the addition concentration of the second coagulant is 100-200 mg / L, and can be selected from 100-150 mg / L or 150-200 mg / L.

[0051] In step 2) of the present invention, the second flocculant is selected from one or both of anionic polyacrylamide and nonionic polyacrylamide; the addition concentration of the second flocculant is 2-5 mg / L, which can be 2-3 mg / L, 3-4 mg / L or 4-5 mg / L.

[0052] In step 2) of the present invention, the acute toxicity of the second type of coating wastewater treatment water is 60-300 toxicity units, which can be selected as 60-100 toxicity units, 100-131.2 toxicity units, 131.2-180 toxicity units, 180-200 toxicity units, 200-250 toxicity units or 250-300 toxicity units, etc., and the CODcr is 3000-12000 mg / L, which can be selected as 3000-5000 mg / L, 5000-5580 mg / L, 5580-7000 mg / L, 7000-10000 mg / L or 10000-12000 mg / L, etc.

[0053] In the treatment method for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, step 3) is to treat the third type of painting wastewater in a third physicochemical coagulation tank, dehydrate, and evaporate to obtain the third type of painting wastewater treatment water, and then enter the first mixed wastewater tank, and mix it evenly with the second type of painting wastewater treatment water in step 2) to obtain the first mixed wastewater, the third type of painting wastewater includes aqueous gun washing wastewater; the first mixed wastewater is treated in a sludge method toxicity degradation treatment tank, and dehydrated to obtain the first mixed wastewater treatment water.

[0054] In step 3) of the present invention, the acute toxicity of the third type of coating wastewater is 600-1000 toxicity units, which can be selected as 600-700 toxicity units, 700-800 toxicity units, 800-900 toxicity units or 900-1000 toxicity units, etc., and the CODcr is 200000-350000 mg / L, which can be selected as 200000-250000 mg / L, 250000-300000 mg / L or 300000-350000 mg / L, etc.

[0055] In step 3) of the present invention, the third physicochemical coagulation tank comprises a third coagulant and / or a third flocculant.

[0056] In step 3) of the present invention, the third coagulant is selected from one or more of modified melamine formaldehyde resin, cationic starch, cationic quaternary ammonium salt, cationic diquaternary ammonium salt, cationic polyquaternary ammonium salt, bentonite, diatomaceous earth, soluble aluminum salt, soluble iron salt, polyaluminum chloride, polyferric sulfate, polyaluminum ferric chloride, and macromolecular organic acid; the addition concentration of the third coagulant is 0.3~3wt%, which can be selected as 0.3~1wt%, 1~1.5wt% or 1.5~3wt%, etc.

[0057] In step 3) of the present invention, the third flocculant is selected from one or both of anionic polyacrylamide and nonionic polyacrylamide; the addition concentration of the third flocculant is 5-30 mg / L, which can be 5-10 mg / L, 10-20 mg / L or 20-30 mg / L.

[0058] In step 3) of the present invention, the evaporation temperature is 40-80°C, and can be 40-60°C or 60-80°C; a small amount of defoaming agent needs to be added during the evaporation.

[0059] The acute toxicity of the third type of coating wastewater treatment water described in step 3) of the present invention is 40-80 toxicity units, which can be selected as 40-65.3 toxicity units or 65.3-80 toxicity units, and the CODcr is 70000-100000 mg / L, which can be selected as 70000-75750 mg / L, 75750-85000 mg / L or 85000-100000 mg / L, etc.

[0060] In step 3) of the present invention, lime powder is added to the toxic degradation treatment tank of the sludge method, and the concentration of the lime powder added is 1-3wt% of the first mixed wastewater. The lime powder is mainly used to adjust the pH of the toxic degradation treatment tank of the sludge method, condition the sludge and improve the subsequent dehydration effect. Specifically: First, the organic acid substances produced in the hydrolysis and acidification process are neutralized to form organic acid calcium, which has a low solubility and is more easily captured and removed by microbial flocs; second, the pH of the early reaction has dropped to 5-6, and the pH will be further reduced if the reaction continues. In order to prevent the pH from dropping too low, lime powder is added to restore the pH to a neutral level of 6.5-7.5; third, lime itself has a certain adsorption effect on some organic matter, etc., and after adding, it can enhance the adsorption capacity of toxic substances; fourth, after adding lime powder in the late reaction, as a sludge conditioner, it is beneficial to the sludge sedimentation and dehydration after the reaction is completed. For example, after entering the plate and frame dehydrator, the sludge dehydration speed can be increased and the moisture content of the mud cake can be reduced.

[0061] In step 3) of the present invention, the sludge method toxic degradation treatment tank includes the secondary sedimentation tank sludge discharged from the secondary sedimentation tank in the biochemical treatment tank; the volume ratio of the secondary sedimentation tank sludge to the first mixed wastewater is 0.5~1.5:1; the biochemical sludge in the sludge method toxic degradation treatment tank comes from the secondary sedimentation tank, and its sludge concentration is high, and the sedimentation ratio SV30 can reach more than 80%. A large amount of sludge provides a large amount of microbial flocs, which have adsorption and sedimentation effects on toxic substances in the first mixed wastewater; because the first mixed wastewater and the biochemical sludge are only mixed and stirred without aeration, they are in anoxic or even anaerobic state after mixing, and under the support of high concentration of microorganisms in the sludge, for toxic substances that are difficult to degrade during aerobic treatment, especially toxic components in aqueous solvents (third coating wastewater), the process of hydrolysis and acidification is accelerated to form non-toxic or low-toxic decomposition products, thereby reducing the biological toxicity of the wastewater.

[0062] In the treatment method for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, step 4) is to ultrafilter the powertrain workshop wastewater to obtain powertrain wastewater treatment water.

[0063] In step 4) of the present invention, the acute toxicity of the power plant wastewater is 65-120 toxicity units, which can be selected as 65-80 toxicity units, 80-88 toxicity units, 88-100 toxicity units or 100-120 toxicity units, etc., and the CODcr is 30,000-50,000 mg / L, which can be selected as 30,000-37,500 mg / L, 37,500-45,000 mg / L or 45,000-50,000 mg / L, etc.

[0064] In step 4) of the present invention, the acute toxicity of the wastewater treated water from the power plant is 20-40 toxicity units, which can be 20-30 toxicity units or 30-40 toxicity units; the CODcr is 3000-5000 mg / L, which can be 3000-4000 mg / L or 4000-5000 mg / L.

[0065] In the treatment method for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, step 5) is to mix the first type of coating wastewater treatment water described in step 1), the first mixed wastewater treatment water described in step 3), the powertrain wastewater treatment water described in step 4) and domestic sewage, and enter the second mixed wastewater tank to obtain second mixed wastewater, and the second mixed wastewater enters the biochemical treatment tank for treatment to obtain discharged water.

[0066] In step 5) of the present invention, the acute toxicity of the domestic sewage is 2-4 toxicity units, which may be 2-3.25 toxicity units or 3.25-4 toxicity units, and the CODcr is 300-500 mg / L, which may be 300-400 mg / L or 400-500 mg / L.

[0067] In step 5) of the present invention, the acute toxicity of the second mixed wastewater is 7 to 10 toxicity units, which can be selected as 7 to 8.2 toxicity units, 8.2 to 9 toxicity units or 9 to 10 toxicity units, and the CODcr is 900 to 1300 mg / L, which can be selected as 900 to 986 mg / L, 986 to 1000 mg / L or 1000 to 1300 mg / L, etc.

[0068] In step 5) of the present invention, the process of the biochemical treatment pool adopts anoxic and aerobic process or aerobic process. When the biochemical treatment pool adopts anoxic and aerobic process, the anoxic residence time is 4 to 8 hours, and the aerobic residence time is 6 to 8 hours; the anoxic dissolved oxygen is controlled at 0.1 to 0.5 mg / L, the aerobic front-end dissolved oxygen is controlled at 1 to 2 mg / L, the middle section is controlled at 2 to 3 mg / L, and the rear section is controlled at 3 to 4 mg / L. When the biochemical treatment pool adopts an aerobic process, the aerobic residence time is 8 to 12 hours; the aerobic front-end dissolved oxygen is controlled at 1 to 2 mg / L, the middle section is controlled at 2 to 3 mg / L, and the rear section is controlled at 3 to 4 mg / L. In step 5) of the present invention, the acute toxicity of the discharged water is 0-0.2 toxicity units, which can be selected as 0-0.1 toxicity units or 0.1-0.2 toxicity units, and the CODcr is 175-250 mg / L, which can be selected as 175-200 mg / L, 200-246 mg / L or 246-250 mg / L, etc.

[0069] A second aspect of the present invention provides a treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater, comprising:

[0070] A biochemical treatment tank 9, used for subjecting the second mixed wastewater to a biochemical reaction to provide discharge water, wherein the second mixed wastewater includes the first type of coating wastewater treatment water, the first mixed wastewater treatment water, the powertrain wastewater treatment water and domestic sewage;

[0071] A first type of coating wastewater treatment unit, the first type of coating wastewater treatment unit comprises a first physicochemical coagulation tank 11 and a first dehydrator to provide first type of coating wastewater treatment water, the first physicochemical coagulation tank 11, the first dehydrator and the second mixed wastewater tank 8 are sequentially fluidly connected;

[0072] A second type of coating wastewater treatment unit, the second type of coating wastewater treatment unit comprises a second physicochemical coagulation tank 21 and a second dehydrator to provide second type of coating wastewater treatment water, the second physicochemical coagulation tank 21, the second dehydrator and the first mixed wastewater tank 6 are fluidically connected in sequence;

[0073] A third type of coating wastewater treatment unit, the third type of coating wastewater treatment unit comprises a third physicochemical coagulation tank 31, a third dehydrator and an evaporation unit 32 which are fluidically connected in sequence to provide third type of coating wastewater treatment water, the evaporation unit 32 is fluidically connected to the first mixed wastewater tank 6 to provide first mixed wastewater; the first mixed wastewater comprises second type of coating wastewater treatment water and third type of coating wastewater treatment water;

[0074] A sludge-based toxic degradation treatment tank 7, wherein the water inlet of the sludge-based toxic degradation treatment tank 7 is connected to the water outlet of the first mixed wastewater tank 6, and the water outlet of the sludge-based toxic degradation treatment tank 7 is connected to the water inlet of the second mixed wastewater tank 8, and a fourth dehydrator is provided between the sludge-based toxic degradation treatment tank 7 and the second mixed wastewater tank 8, for subjecting the first mixed wastewater to sludge-based toxic degradation treatment to obtain first mixed wastewater treated water;

[0075] The powertrain workshop wastewater treatment unit comprises an ultrafiltration unit 41 to provide powertrain wastewater treatment water, and the ultrafiltration unit 41 is fluidically connected to the second mixed wastewater tank 8 .

[0076] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the first physicochemical coagulation tank 11 includes a first coagulant and / or a first flocculant.

[0077] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, a first stirrer is provided on the top or side of the first physicochemical coagulation tank 11.

[0078] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the rotation speed of the first agitator is 30~80rpm / min, which can be optionally 30~40rpm / min, 30~60rpm / min, 40~60rpm / min, 40~80rpm / min, 50~80rpm / min or 60~80rpm / min, etc.

[0079] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the first dehydrator is selected from one of a centrifuge, a screw press, a plate and frame dehydrator, a belt dehydrator or a vacuum dehydrator.

[0080] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, a first inclined plate sedimentation tank is provided between the first physicochemical coagulation tank 11 and the first dehydrator.

[0081] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, according to the first type of coating wastewater generated by normal production of a coating workshop, which is about 420 tons, a continuous first physicochemical coagulation tank 11 and a first inclined plate sedimentation tank are set, with a maximum treatment capacity of 50m 3 / h, to ensure that the processing can be completed in one shift. When adding coagulant, the stirring speed of the first mixer must reach 40~80rpm / min, which can be selected as 40~60rpm / min or 60~80rpm / min, etc. When adding flocculant, the stirring speed of the first mixer must reach 30~60rpm / min, which can be selected as 30~40rpm / min or 40~60rpm / min, etc.

[0082] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the second physicochemical coagulation tank 21 includes a second coagulant and / or a second flocculant.

[0083] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, a second stirrer is provided on the top or side of the second physicochemical coagulation tank 21; the rotation speed of the second stirrer is 30~80rpm / min, which can be selected from 30~40rpm / min, 30~60rpm / min, 40~60rpm / min, 40~80rpm / min, 50~80rpm / min or 60~80rpm / min, etc.

[0084] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the second dehydrator is selected from one of a centrifuge, a screw press, a plate and frame dehydrator, a belt dehydrator or a vacuum dehydrator.

[0085] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, a second inclined plate sedimentation tank is provided between the second physicochemical coagulation tank 21 and the second dehydrator.

[0086] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, according to the second type of coating wastewater generated by normal production of a coating workshop, which is about 165 tons, a continuous second physicochemical coagulation tank 21 and a second inclined plate sedimentation tank are set, with a maximum treatment capacity of 20m 3 / h, ensuring that one shift can complete the process. When adding coagulant, the stirring speed of the second mixer needs to reach 40~80rpm / min, which can be selected as 40~60rpm / min or 60~80rpm / min, etc. When adding flocculant, the stirring speed of the second mixer needs to reach 30~60rpm / min, which can be selected as 30~40rpm / min or 40~60rpm / min, etc.

[0087] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the third physicochemical coagulation tank 31 includes a third coagulant and / or a third flocculant.

[0088] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, a third mixer is provided on the top or side of the third physicochemical coagulation tank 31 .

[0089] In the treatment system for reducing acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the rotation speed of the third stirrer is 90-120 rpm / min, which can be 90-100 rpm / min, 100-110 rpm / min or 110-120 rpm / min.

[0090] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the third dehydrator is selected from one of a centrifuge, a screw press, a plate and frame dehydrator, a belt dehydrator or a vacuum dehydrator.

[0091] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the evaporation unit 32 can select an MVR evaporator with a scraper, an electric heating evaporator, or a heat pump low-temperature evaporator, with a processing capacity of at least 2.5 tons / day, ensuring that all the gun washing water for one day can be processed, and the scraper is used to smoothly discharge the evaporation residue from the evaporator.

[0092] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, a fourth dehydrator is provided at the bottom of the sludge method toxic degradation treatment tank, and the fourth dehydrator is selected from one of a centrifuge, a screw stack, a plate and frame dehydrator, a belt dehydrator or a vacuum dehydrator, and is preferably a plate and frame dehydrator.

[0093] In the treatment system for reducing the acute biological toxicity of automobile manufacturing wastewater provided by the present invention, the third type of coating wastewater generated by normal production of a coating workshop is about 2.5 tons, and the third physicochemical coagulation tank 31 is designed to have a batch processing capacity of 3 to 6 tons / batch, ensuring that one batch can at least process the amount for 1 or 2 days. The stirring speed of the third mixer needs to reach 90 to 120 rpm / min, which can be selected as 90 to 100 rpm / min, 100 to 110 rpm / min or 110 to 120 rpm / min, which is faster than the speed required for conventional physicochemical coagulation. This is because the number and density of paint residue particles generated after the addition of drugs to the aqueous gun washing wastewater are larger than other conventional industrial wastewaters, and sufficient stirring speed is required to prevent the paint residue from sinking; after the physicochemical coagulation treatment, there is no need to use an inclined plate sedimentation tank for sedimentation and sludge discharge, and the wastewater enters the evaporation unit 32 by stirring and dehydrating, and enters the first mixed wastewater tank after evaporation, and obtains the first mixed wastewater together with the second type of coating wastewater treatment water.

[0094] The use process of the present invention:

[0095] 1) The first type of coating wastewater is stirred by the first mixer in the first physicochemical coagulation tank 11 to undergo physicochemical treatment, and the sludge is precipitated and discharged through the first inclined plate sedimentation tank. After dehydration, the first type of coating wastewater treatment water is obtained;

[0096] 2) The second type of coating wastewater is stirred by the second mixer in the second physicochemical coagulation tank 21 to undergo physicochemical treatment, and then precipitated and discharged through the second inclined plate sedimentation tank. After dehydration, the second type of coating wastewater treatment water is obtained and enters the first mixed wastewater tank 6;

[0097] 3) The third type of coating wastewater is stirred by the third mixer in the third physicochemical coagulation tank 31 for physicochemical treatment, and then precipitated and discharged through the third inclined plate sedimentation tank. After dehydration, it enters the evaporation unit 32, and after evaporation, the third type of coating wastewater treatment water is obtained, and enters the first mixed wastewater tank 6, and is evenly mixed with the second type of coating wastewater to obtain the first mixed wastewater;

[0098] 4) After the powertrain workshop wastewater is ultrafiltered by the ultrafiltration unit 41, the powertrain wastewater treatment water is obtained;

[0099] 5) The first mixed wastewater in step 3) is treated in a sludge toxic degradation treatment tank 7 to obtain first mixed wastewater treatment water after dehydration, which is then introduced into a second mixed wastewater tank 8 together with the first type of coating wastewater treatment water, powertrain wastewater treatment water, and domestic sewage, and then enters a biochemical treatment tank 9 for biochemical reaction before being discharged.

[0100] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is described in detail below in conjunction with embodiments and drawings.

[0101] In the following examples, unless otherwise specified, all reaction raw materials are commercially available products.

[0102] Unless otherwise specified, the purity of each product in each embodiment of the present invention exceeds 98%.

[0103] Example 1

[0104] Pretreatment process of the first type of coating wastewater and power plant wastewater

[0105] As shown in Table 1, the first type of coating wastewater is stirred by the first mixer in the first physicochemical coagulation tank 11 for physicochemical treatment. The coagulant in the first physicochemical coagulation tank 11 is polyferric sulfate with a dosage concentration of 70 mg / L; the flocculant is anionic polyacrylamide with a dosage concentration of 2 mg / L; after sedimentation and sludge discharge through the first inclined plate sedimentation tank, the first type of coating wastewater treatment water is obtained; the toxicity of domestic sewage and degreasing wastewater, degreasing waste liquid, and film wastewater after physicochemical coagulation treatment is compared, and the acute toxicity of the three types of productive wastewater is close to that of domestic sewage, and will not cause significant adverse effects on the microorganisms in the biochemical reaction system, so no further adjustment is made to the pretreatment process.

[0106] Table 1 Pretreatment process of the first type of coating wastewater

[0107]

[0108] As shown in Table 2, the main component of the power plant wastewater is emulsion. The acute toxicity after treatment by the ultrafiltration unit 41 is close to that of the second mixed wastewater (CODcr content is 1330 mg / L, acute toxicity is 28.30 toxicity units), and the water volume of the power plant wastewater is small, so the acute toxicity can be basically ignored, so there is no need to further adjust the pretreatment process.

[0109] Table 2 Pretreatment process of wastewater from power plant

[0110]

[0111] Comparative Example 1

[0112] Pretreatment process of the second type of coating wastewater before adjustment

[0113] Electrophoresis wastewater, electrophoresis waste liquid, and spray paint wastewater all contain water-based solvent components. Electrophoresis wastewater itself is a type of wastewater containing diluted water-based paint; electrophoresis waste liquid is the electrophoresis tank tank liquid, which is close to electrophoresis paint, so its CODcr concentration is higher; spray paint wastewater is the circulating water drainage of the wet spray room, which contains solvent components brought by oversprayed paint.

[0114] As shown in Table 3, after the second type of electrophoretic wastewater, electrophoretic waste liquid, and spray paint wastewater were treated with physical and chemical coagulation, their acute toxicity was still significantly higher than that of domestic sewage (3.25 toxicity units) and the second mixed wastewater (28.30 toxicity units). Evaporation treatment of electrophoretic wastewater and electrophoretic waste liquid can effectively remove the toxic components that cannot be removed by coagulation treatment, and obtain clear and colorless condensate, and its acute toxicity can be significantly reduced. However, the reduction in acute toxicity of spray paint wastewater by evaporation treatment is not very large. Although evaporation has a certain effect on reducing the acute toxicity of electrophoretic wastewater, electrophoretic waste liquid, and spray paint wastewater, the evaporator has a considerable equipment investment and operating energy consumption, especially for electrophoretic wastewater, electrophoretic waste liquid, and spray paint wastewater with a large amount of water, the required evaporator equipment investment and operating energy consumption are even greater. For this reason, the pretreatment method of the second type of coating wastewater was further adjusted.

[0115] Table 3 Pretreatment process of the second type of coating wastewater before adjustment

[0116]

[0117] Example 2

[0118] Adjusted pretreatment process for the second type of coating wastewater

[0119] The second type of coating wastewater is stirred by the second mixer in the second physicochemical coagulation tank 21 for physicochemical treatment. The coagulant in the second physicochemical coagulation tank 21 is polyaluminum ferric chloride, and the addition concentration is 150 mg / L; the flocculant is non-ionic polyacrylamide, and the addition concentration is 4 mg / L; after the sludge is precipitated and discharged through the second inclined plate sedimentation tank, it enters the first mixed wastewater tank 6, and after being stirred evenly, it enters the sludge method toxic degradation treatment tank 7 to mix with biochemical sludge. The volume ratio of the second coating wastewater and the biochemical sludge is 1:1. After uniform stirring for 24 to 48 hours, lime powder is added. The amount of lime powder added is 1 to 3% of the mass ratio after mixing (the specific gravity of the wastewater and sludge after mixing is still calculated as 1), and stirring is continued for 12 to 24 hours. The supernatant is taken for detection of relevant data, as shown in Table 4.

[0120] Table 4 Adjusted pretreatment process of the second type of coating wastewater

[0121]

[0122] Compared with the method of only using physicochemical coagulation to reduce the acute toxicity of the second type of coating wastewater, the present invention adopts the method of physicochemical coagulation + biochemical sludge + lime powder, which reduces the acute toxicity of electrophoresis wastewater by 72.7%, the acute toxicity of electrophoresis waste liquid by 78.6%, and the acute toxicity of paint spraying wastewater by 73.2%.

[0123] Comparative Example 2

[0124] Pretreatment process of the third type of coating wastewater before adjustment

[0125] The aqueous solvent content in the aqueous gun-washing wastewater is as high as about 5%, so its CODcr concentration is the highest. At the same time, due to its maximum solvent content, its biological toxicity is also the highest. As shown in Table 5, after the aqueous gun-washing wastewater is evaporated, its acute toxicity decreases significantly; and the evaporation treatment based on physical and chemical coagulation has a better effect on reducing toxicity, but the acute toxicity of the aqueous gun-washing wastewater (65.3 toxicity units) is still higher than the second mixed wastewater before entering the biochemical treatment tank 9 (8.15 toxicity units). After the aqueous gun-washing wastewater is evaporated, it is then subjected to electrocatalytic oxidation treatment. Although CODcr can be greatly reduced, the biological toxicity increases instead of decreasing, indicating that the electrocatalytic oxidation process has little effect on reducing the acute biological toxicity of wastewater. On the contrary, due to the complex chemical reactions in the reaction process, intermediate products with greater biological toxicity may be produced.

[0126] Table 5 Pretreatment process of the third type of coating wastewater before adjustment

[0127]

[0128] Example 3

[0129] Adjusted pretreatment process for the third type of coating wastewater

[0130] Since the amount of water-based gun washing wastewater is small, it is more suitable to use evaporation equipment. The present invention further adjusts the pretreatment process of the third type of coating wastewater to better reduce the acute toxicity of the third type of coating wastewater. The third type of coating wastewater is stirred by the third mixer in the third physicochemical coagulation tank 31 for physicochemical treatment. The coagulant in the third physicochemical coagulation tank 31 is a compound mixture of cationic starch, bentonite, soluble aluminum salt, and soluble iron salt. The compounding ratios are 20%, 20%, 40%, and 20%, respectively. The compounding agent is added at a concentration of 1.5 wt%. %; the flocculant is anionic polyacrylamide, and the addition concentration is 10 mg / L; after the sludge is precipitated and discharged through the third inclined plate sedimentation tank, it enters the evaporation unit 32, the evaporation temperature is 60°C, and after evaporation, it enters the first mixed wastewater tank 6, and after being evenly stirred, it enters the sludge method toxic degradation treatment tank 7, and lime powder is added to the sludge method toxic degradation treatment tank 7, and the addition concentration of the lime powder is 1~3wt% of the first mixed wastewater. The sludge method toxic degradation treatment tank 7 includes the secondary sedimentation tank sludge discharged from the secondary sedimentation tank in the biochemical treatment tank; the volume ratio of the secondary sedimentation tank sludge to the first mixed wastewater is 0.5~1.5:1, and the first mixed wastewater treatment water is obtained, and the first mixed wastewater includes the second type of coating wastewater treatment water and the third type of coating wastewater treatment water in step 2), and the supernatant is taken to detect relevant data, as shown in Table 6.

[0131] Table 6 Adjusted pretreatment process of the third type of coating wastewater

[0132]

[0133] Compared with the method of only using physicochemical coagulation to reduce the acute toxicity of the third type of coating wastewater, the present invention adopts the method of physicochemical coagulation + evaporation + biochemical sludge + lime powder to reduce the acute toxicity of the third type of coating wastewater by 95%.

[0134] Example 4

[0135] The first mixed wastewater is treated in the sludge toxic degradation treatment tank 7, and after dehydration in the plate and frame dehydrator, it is evenly mixed with the first type of coating wastewater treatment water, powertrain wastewater treatment water, and domestic sewage and then enters the biochemical treatment tank 9 for biochemical reaction. Through testing, before entering the biochemical treatment tank 9, the CODcr of the second mixed wastewater was 986mg / L, and the biological acute toxicity was 8.15 toxicity units, which was close to the biological acute toxicity of the first type of coating wastewater treatment water, and much lower than the second mixed wastewater before the process was adjusted (28.3 toxicity units). After being treated in the anoxic and aerobic biochemical treatment tanks 9, the CODcr of the discharged water was 246mg / L, and the biological acute toxicity was reduced to 0.06 toxicity units. The state of the biofilm on the surface of the contact oxidation filler in the biochemical treatment tank 9 has been greatly improved, and the white jelly-like substance that used to appear frequently basically does not appear. The color of the biofilm is yellow-brown, and the contact oxidation effluent sedimentation ratio SV30 is maintained at about 1%, which greatly reduces the burden of the subsequent plate and frame dehydrator, reduces the amount of sludge produced, and the dissolved oxygen in the biochemical system can be stably maintained at about 3mg / L; in addition, through process improvements, the CODcr of electrophoresis wastewater, electrophoresis waste liquid, paint spraying wastewater, and aqueous gun washing wastewater has been removed before entering the biochemical system, and the CODcr of the second mixed wastewater treatment water entering the biochemical treatment tank 9 has dropped to 900~1300mg / L, and the total discharge CODcr has also dropped to 225~325mg / L, reducing the risk of excessive discharge. In addition, for the aqueous gun washing wastewater with the highest biological acute toxicity, if the original problem cannot be solved, it can only be transported out as hazardous waste for disposal, so the effective solution of the problem also saves the high cost of hazardous waste disposal.

[0136] The above-mentioned embodiments are preferred examples of the present invention and are not intended to limit the protection scope of the present invention.

[0137] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate a treatment method and system for reducing the acute biological toxicity of automobile manufacturing wastewater of the present invention, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0138] The above embodiments are preferred cases of the present invention and are not intended to limit the protection scope of the present invention. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention.

[0139] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for reducing the acute biological toxicity of automobile manufacturing wastewater, characterized in that: The steps include: 1) The first type of coating wastewater is treated in a first physicochemical coagulation tank and dehydrated to obtain the first type of coating wastewater treated water, wherein the first type of coating wastewater includes one or more of degreasing wastewater, degreasing waste liquid, and film wastewater; 2) The second type of coating wastewater is treated in the second physicochemical coagulation tank, dehydrated, and the second type of coating wastewater treatment water is obtained, and enters the first mixed wastewater tank, wherein the second type of coating wastewater includes one or more of electrophoresis wastewater, electrophoresis waste liquid, and spray paint wastewater; 3) The third type of coating wastewater is treated in the third physicochemical coagulation tank, dehydrated, and evaporated to obtain the third type of coating wastewater treatment water, which then enters the first mixed wastewater tank and is evenly mixed with the second type of coating wastewater treatment water in step 2) to obtain the first mixed wastewater. The third type of coating wastewater includes aqueous gun washing wastewater; The first mixed wastewater is treated in a sludge-based toxicity degradation treatment tank and dehydrated to obtain first mixed wastewater treated water; 4) After the powertrain workshop wastewater is treated by ultrafiltration, the powertrain wastewater treatment water is obtained; 5) The first type of coating wastewater treatment water described in step 1), the first mixed wastewater treatment water described in step 3), and the powertrain wastewater treatment water described in step 4) are mixed with domestic sewage and enter a second mixed wastewater tank to obtain second mixed wastewater. The second mixed wastewater enters a biochemical treatment tank for treatment to obtain discharged water.

2. The method for reducing the acute biological toxicity of automobile manufacturing wastewater according to claim 1, comprising any one or more of the following features: A1) Step 1) The acute toxicity of the first type of coating wastewater is 6 to 10 toxicity units, and the CODcr is 400 to 2250 mg / L; A2) Step 1) The acute toxicity of the first type of coating wastewater treatment water is 4 to 7 toxicity units, and the CODcr is 300 to 1350 mg / L; A3) Step 2) The acute toxicity of the second type of coating wastewater is 100 to 425 toxicity units, and the CODcr is 7000 to 18000 mg / L; A4) Step 2) The acute toxicity of the second type of coating wastewater treatment water is 60 to 300 toxicity units, and the CODcr is 3000 to 12000 mg / L; A5) The acute toxicity of the third type of coating wastewater in step 3) is 600-1000 toxicity units, and the CODcr is 200000-350000 mg / L; A6) The acute toxicity of the third type of coating wastewater treatment water in step 3) is 40 to 80 toxicity units, and the CODcr is 70,000 to 100,000 mg / L; A7) The acute toxicity of the power plant wastewater in step 4) is 65 to 120 toxicity units, and the CODcr is 30,000 to 50,000 mg / L; A8) The acute toxicity of the powertrain wastewater treatment water in step 4) is 20 to 40 toxicity units, and the CODcr is 3000 to 5000 mg / L; A9) The acute toxicity of the domestic sewage in step 5) is 2 to 4 toxicity units, and the CODcr is 300 to 500 mg / L; A10) in step 5), the acute toxicity of the second mixed wastewater is 7 to 10 toxicity units, and the CODcr is 900 to 1300 mg / L; A11) The acute toxicity of the discharged water in step 5) is 0 to 0.2 toxicity units, and the CODcr is 175 to 250 mg / L.

3. The method for reducing the acute biological toxicity of automobile manufacturing wastewater according to claim 1, further comprising any one or more of the following features: B1) Step 1) The first physicochemical coagulation tank comprises a first coagulant and / or a first flocculant; B2) Step 2) The second physicochemical coagulation tank includes a second coagulant and / or a second flocculant; B3) the third physicochemical coagulation tank in step 3) comprises a third coagulant and / or a third flocculant; B4) the evaporation temperature in step 3) is 40-80°C; B5) the process of the sludge toxic degradation treatment tank in step 3) adopts anoxic and anaerobic process or anaerobic process; B6) adding lime powder to the toxic degradation treatment tank of the sludge method in step 3) to adjust the pH of the toxic degradation treatment tank, condition the sludge and improve the subsequent dehydration effect; B7) the sludge method toxicity degradation treatment tank described in step 3) includes biochemical sludge discharged from the secondary sedimentation tank; B8) The process of the biochemical treatment pool in step 5) adopts anoxic and aerobic process or aerobic process.

4. The method for reducing the acute biological toxicity of automobile manufacturing wastewater according to claim 3, further comprising any one or more of the following features: B11) Step B1) the first coagulant is selected from one or more of soluble aluminum salts, soluble iron salts, polyaluminum chloride, polyferric sulfate, and polyaluminum ferric chloride; B12) Step B1) The concentration of the first coagulant added is 50-100 mg / L; B13) Step B1) the first flocculant is selected from one or both of anionic polyacrylamide and nonionic polyacrylamide; B14) Step B1) wherein the concentration of the first flocculant added is 1 to 3 mg / L; B21) Step B2) the second coagulant is selected from one or more of soluble aluminum salts, soluble iron salts, polyaluminum chloride, polyferric sulfate, and polyaluminum ferric chloride; B22) Step B2) The concentration of the second coagulant added is 100-200 mg / L; B23) Step B2) the second flocculant is selected from one or both of anionic polyacrylamide and nonionic polyacrylamide; B24) Step B2) the second flocculant is added at a concentration of 2 to 5 mg / L; B31) the third coagulant in step B3) is selected from one or more of modified melamine formaldehyde resin, cationic starch, cationic quaternary ammonium salt, cationic diquaternary ammonium salt, cationic polyquaternary ammonium salt, bentonite, diatomaceous earth, soluble aluminum salt, soluble iron salt, polyaluminum chloride, polyferric sulfate, polyaluminum ferric chloride, and macromolecular organic acid; B32) the concentration of the third coagulant added in step B3) is 0.3-3 wt%; B33) The third flocculant in step B3) is selected from one or both of anionic polyacrylamide and nonionic polyacrylamide; B34) the concentration of the third flocculant added in step B3) is 5-30 mg / L; B61) The concentration of lime powder added in step B6) is 1-3 wt% of the first mixed wastewater; B62) The pH of the sludge toxicity degradation treatment tank in step B6) is adjusted to 6.5 to 7.5; B71) The volume ratio of the biochemical sludge discharged from the secondary sedimentation tank in step B7) to the first mixed wastewater is 0.5 to 1.5:

1.

5. The method for reducing the acute biological toxicity of automobile manufacturing wastewater according to claim 3, further comprising any one or more of the following features: B81) When the biochemical treatment pool adopts anoxic and aerobic processes, the anoxic retention time is 4 to 8 hours, and the aerobic retention time is 6 to 8 hours; the anoxic dissolved oxygen is controlled at 0.1 to 0.5 mg / L; the aerobic front section dissolved oxygen is controlled at 1 to 2 mg / L, the middle section is controlled at 2 to 3 mg / L, and the rear section is controlled at 3 to 4 mg / L; B82) When the biochemical treatment pool adopts aerobic process, the aerobic residence time is 8 to 12 hours; the dissolved oxygen in the aerobic front section is controlled at 1 to 2 mg / L, in the middle section at 2 to 3 mg / L, and in the back section at 3 to 4 mg / L.

6. A system for reducing the acute biological toxicity of automobile manufacturing wastewater for implementing the method for reducing the acute biological toxicity of automobile manufacturing wastewater as claimed in any one of claims 1 to 5, characterized in that: include: A biochemical treatment tank (9) is used to cause a second mixed wastewater to undergo a biochemical reaction to provide discharge water, wherein the second mixed wastewater comprises first-class coating wastewater treatment water, first mixed wastewater treatment water, powertrain wastewater treatment water and domestic sewage; A first type of coating wastewater treatment unit, the first type of coating wastewater treatment unit comprising a first physicochemical coagulation tank (11) and a first dehydrator to provide first type of coating wastewater treatment water, the first physicochemical coagulation tank (11), the first dehydrator and the second mixed wastewater tank (8) being fluidically connected in sequence; A second type of coating wastewater treatment unit, the second type of coating wastewater treatment unit comprising a second physicochemical coagulation tank (21) and a second dehydrator to provide second type of coating wastewater treatment water, the second physicochemical coagulation tank (21), the second dehydrator and the first mixed wastewater tank (6) being sequentially fluidically connected; A third type of coating wastewater treatment unit, the third type of coating wastewater treatment unit comprising a third physicochemical coagulation tank (31), a third dehydrator and an evaporation unit (32) which are fluidically connected in sequence to provide third type of coating wastewater treatment water, the evaporation unit (32) being fluidically connected to the first mixed wastewater tank (6) to provide first mixed wastewater; the first mixed wastewater comprises second type of coating wastewater treatment water and third type of coating wastewater treatment water; A sludge-based toxic degradation treatment tank (7), wherein the water inlet of the sludge-based toxic degradation treatment tank (7) is connected to the water outlet of the first mixed wastewater tank (6), and the water outlet of the sludge-based toxic degradation treatment tank (7) is connected to the water inlet of the second mixed wastewater tank (8), and a fourth dehydrator is provided between the sludge-based toxic degradation treatment tank (7) and the second mixed wastewater tank (8), for subjecting the first mixed wastewater to sludge-based toxic degradation treatment to obtain first mixed wastewater treated water; A powertrain workshop wastewater treatment unit, comprising an ultrafiltration unit (41) to provide powertrain wastewater treatment water, wherein the ultrafiltration unit (41) is in fluid communication with the second mixed wastewater tank (8).

7. The system for reducing the acute biological toxicity of automobile manufacturing wastewater according to claim 6, characterized in that: Includes any one or more of the following features: C1) the first physicochemical coagulation tank (11) comprises a first coagulant and / or a first flocculant; C2) A first mixer is provided on the top or side of the first physicochemical coagulation tank (11); C3) a first inclined plate sedimentation tank is further provided between the first physicochemical coagulation tank (11) and the first dehydrator; C4) the second physicochemical coagulation tank (21) includes a second coagulant and / or a second flocculant; C5) A second mixer is provided on the top or side of the second physicochemical coagulation tank (21); C6) a second inclined plate sedimentation tank is further provided between the second physicochemical coagulation tank (21) and the second dehydrator; C7) the third physicochemical coagulation tank (31) comprises a third coagulant and / or a third flocculant; C8) A third mixer is provided on the top or side of the third physicochemical coagulation tank (31); C9) The first dehydrator, the second dehydrator, the third dehydrator or the fourth dehydrator is respectively selected from one of a centrifuge, a screw stack, a plate and frame dehydrator, a belt dehydrator or a vacuum dehydrator.

8. The system for reducing the acute biological toxicity of automobile manufacturing wastewater according to claim 7, characterized in that: Also includes any one or more of the following features: C21) the rotation speed of the first stirrer is 30 to 80 rpm / min; C51) the rotation speed of the second stirrer is 30 to 80 rpm / min; C81) The rotation speed of the third mixer is 90-120 rpm / min.

9. The system for reducing the acute biological toxicity of automobile manufacturing wastewater according to claim 6, characterized in that: The evaporation unit (32) is provided with a scraper for discharging evaporation residues out of the evaporator.

10. The system for reducing the acute biological toxicity of automobile manufacturing wastewater according to claim 6, characterized in that: The evaporation unit (32) is an MVR evaporator, an electric heating evaporator or a heat pump low-temperature evaporator.

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