Treatment method and system for reducing acute biological toxicity of wastewater from automobile manufacturing

Abstract

The present invention provides a treatment method and a system for reducing the acute biological toxicity of wastewater from automobile manufacturing. A first type of coating wastewater is treated in a first physicochemical coagulation tank to obtain a first type of treated coating wastewater; a second type of coating wastewater is treated in a second physicochemical coagulation tank to obtain a second type of treated coating wastewater; and a third type of coating wastewater is treated in a third physicochemical coagulation tank and evaporated to obtain a third type of treated coating wastewater. The second type of treated coating wastewater and the third type of treated coating wastewater are subjected to a toxicity‑reduction treatment using a sludge‑based process to produce a first mixed treated wastewater. The first type of treated coating wastewater, the first mixed treated wastewater, and treated powertrain wastewater are mixed with domestic sewage and then treated in a biochemical treatment tank for a biochemical treatment, with the final effluent being discharged. By classifying and pretreating automotive manufacturing wastewater, the present invention effectively reduces the acute toxicity of the coating wastewater and mitigates issues such as unstable dissolved oxygen in the biochemical treatment system, which may otherwise lead to excessive COD levels in the effluent.

Description

Method and system for reducing biological acute toxicity of automobile manufacturing wastewater TECHNICAL FIELD

[0001] The present application belongs to the technical field of wastewater treatment, and particularly relates to a method and system for reducing biological acute toxicity of automobile manufacturing wastewater. BACKGROUND

[0002] The automobile manufacturing wastewater mainly comes from various painting wastewater of a painting workshop and machining wastewater of a power assembly workshop, and further includes domestic wastewater from a domestic area, as shown in Fig. 2. The painting wastewater and the machining wastewater are usually pretreated and then mixed with the domestic wastewater to enter a biochemical treatment system for treatment, and finally discharged up to the standard, as shown in Fig. 3.

[0003] However, in the actual water treatment operation process, it is found that after all the wastewater finally enters the biochemical treatment system, the dissolved oxygen of the biochemical treatment system is often unstable, and even sharply decreases, for example, the dissolved oxygen can decrease from about 3 mg / L under normal conditions to 1 or even 0.5 mg / L or below, the sludge settling ratio of the biochemical effluent can increase from 0.5% to 1.5% to 3% to 5%, or even close to 10%, greatly increasing the burden of the subsequent sludge dewatering system and the cost of sludge disposal; when the activated sludge method is used for treatment, the entire biochemical tank is black due to the lack of oxygen, the sludge settling property is poor, and the effluent is turbid. Regardless of which biochemical treatment process is used, the total effluent COD will eventually rapidly increase or even exceed the standard.

[0004] In view of this abnormal phenomenon, the most possible reason is naturally attributed to the problem of the physicochemical coagulation system of the wastewater station for treating the industrial wastewater from the workshop, which causes excessive pollutants that are not removed to enter the biochemical system. However, the physicochemical coagulation system is checked, the dosing and sedimentation are normal, the effluent is clear, the effluent COD is only 2000 to 3000 mg / L, the COD is only 1000 to 1500 mg / L after the effluent is uniformly mixed with the domestic wastewater in the biochemical adjustment tank, completely meets the design load of the biochemical system, and the COD removal rate of the biochemical system can reach more than 75%, so the biochemical effluent COD can be controlled within 250 to 375 mg / L, and the standard of 500 mg / L of the pipe network discharge can be completely reached.

[0005] But the actual situation is not the case, through observation and analysis, it is found that these problems are related to the abnormality of the microbial membrane on the biological filler. Whenever abnormal phenomena occur in the biochemical system, the biological membrane on the filler is wrapped in a white jelly-like substance with a thickness of more than 5 cm, and the inside is in an anaerobic state, and the dissolved oxygen outside cannot be utilized by the microorganisms on the surface of the filler. This shows that the microorganisms are stimulated to produce capsules to form jelly-like substances, which hinder the transfer of dissolved oxygen and the degradation of organic matter. Microscopy shows that there are explosive growth of filamentous bacteria in the jelly-like substance, and these filamentous bacteria are anaerobic microorganisms. Because the surface of the biological membrane is covered with jelly-like substance, the inside is anaerobic, which leads to the growth of filamentous bacteria and the production of mucous substance, further promoting the increase of jelly-like substance, forming a vicious cycle. Microscopy shows that the large amount of floating mud in the effluent mainly contains filamentous bacteria, which further confirms that the large amount of jelly-like substance falling off is the source of the effluent floating mud.

[0006] Although theoretically, microorganisms may form resistance to toxicity by improving genes after long-term contact with certain toxic substances, and gradually adapt to similar toxic substances through replacement, but this is only for low or moderate toxic substances. For substances with greater toxicity, microorganisms may not be able to adapt, which is why the biochemical treatment system cannot adapt although it has been treating the same series of wastewater for a long time. Therefore, further research and solutions are needed to ensure the stable operation and standard discharge of the wastewater treatment system. Including optimizing the pretreatment process, reducing the acute toxicity of wastewater, improving the design and operation parameters of the biochemical treatment system, and controlling the abnormal growth of microbial membrane. Through comprehensive management, the efficiency of the wastewater treatment system can be effectively improved, the pollutant emission can be reduced, and the treatment cost can be reduced. SUMMARY

[0007] In view of the shortcomings in the prior art, the present application provides a method and system for reducing the acute toxicity of automobile manufacturing wastewater to microorganisms in a biochemical treatment system, which solves the problem that the acute toxicity of automobile manufacturing wastewater to microorganisms in a biochemical treatment system causes the dissolved oxygen in the biochemical treatment system to be unstable and sharply decrease, further causing the COD of the effluent to rapidly increase and even exceed the standard.

[0008] The first aspect of the present application provides a method for reducing the acute toxicity of automobile manufacturing wastewater to microorganisms, comprising the following steps:

[0009] 1) The first type of coating wastewater is treated by a first physicochemical coagulation tank, and after dehydration, the first type of coating wastewater treatment water is obtained, and the first type of coating wastewater includes one or more of degreasing wastewater, degreasing waste liquid and film wastewater;

[0010] 2) the second type of coating wastewater is treated by a second physical and coagulation tank, and after dehydration, 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;

[0011] 3) the third type of coating wastewater is treated by a third physical and coagulation tank, and after dehydration and evaporation, third type of coating wastewater treatment water is obtained and enters the first mixed wastewater tank, and after being mixed uniformly with the second type of coating wastewater treatment water in step 2), first mixed wastewater is obtained, the third type of coating wastewater includes water-based gun washing wastewater;

[0012] the first mixed wastewater is treated by a sludge method toxicity degradation treatment tank, and after dehydration, first mixed wastewater treatment water is obtained;

[0013] 4) after the power assembly wastewater is treated by ultrafiltration, power assembly wastewater treatment water is obtained;

[0014] 5) the first type of coating wastewater treatment water in step 1), the first mixed wastewater treatment water in step 3), and the power assembly wastewater treatment water in step 4) are mixed with domestic sewage to enter a second mixed wastewater tank to obtain second mixed wastewater, and after the second mixed wastewater is treated by a biochemical treatment tank, discharge water is obtained.

[0015] The second aspect of the application provides a treatment system for reducing the biological acute toxicity of automobile manufacturing wastewater, comprising:

[0016] a biochemical treatment tank for making the second mixed wastewater perform biochemical reactions to provide discharge water, the second mixed wastewater including the first type of coating wastewater treatment water, the first mixed wastewater treatment water, the power assembly wastewater treatment water, and the domestic sewage;

[0017] a first type of coating wastewater treatment unit, the first type of coating wastewater treatment unit including a first physical and coagulation tank and a first dehydration machine to provide the first type of coating wastewater treatment water, the first physical and coagulation tank, the first dehydration machine, and the second mixed wastewater tank being sequentially and fluidly connected;

[0018] a second type of coating wastewater treatment unit, the second type of coating wastewater treatment unit including a second physical and coagulation tank and a second dehydration machine to provide the second type of coating wastewater treatment water, the second physical and coagulation tank, the second dehydration machine, and the first mixed wastewater tank being sequentially and fluidly connected;

[0019] The third type of coating wastewater treatment unit comprises a third physical coagulation tank, a third dewatering machine and an evaporation unit in fluid communication in sequence to provide third type of coating wastewater treatment water, the evaporation unit is in fluid communication with 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;

[0020] The sludge method toxicity degradation treatment tank is connected with the water outlet of the first mixed wastewater tank, and the water inlet of the second mixed wastewater tank is connected with the water outlet of the sludge method toxicity degradation treatment tank, and a fourth dewatering machine is arranged between the sludge method toxicity degradation treatment tank and the second mixed wastewater tank, so that the first mixed wastewater is subjected to sludge method toxicity degradation treatment to obtain first mixed wastewater treatment water;

[0021] The power assembly workshop wastewater treatment unit comprises an ultrafiltration unit to provide power assembly wastewater treatment water, and the ultrafiltration unit is in fluid communication with the second mixed wastewater tank.

[0022] The present application has the following beneficial effects:

[0023] (1) Reduce the stress on microorganisms: by pre-classifying automobile manufacturing wastewater, according to the different components of each type of wastewater, targeted selection of methods to remove or reduce harmful components in wastewater, reduce its biological acute toxicity, reduce the stress on microorganisms in the biochemical treatment system.

[0024] (2) Improve system stability and reduce the risk of exceeding standard emissions: the present application helps to maintain the stable operation of the biochemical system, thereby reducing the risk of exceeding standard emissions of COD in the effluent, meeting the requirements of environmental protection regulations. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 shows the overall device structure of the present application.

[0026] Figure 2 shows a statistical table of automobile manufacturing wastewater.

[0027] Figure 3 shows a conventional treatment process for automobile manufacturing wastewater.

[0028] Element No. Explanation 1 First painting wastewater inlet 11 First physicochemical coagulation tank 2 Second painting wastewater inlet 21 Second physicochemical coagulation tank 3 Third painting wastewater inlet 31 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 method toxicity degradation treatment tank 8 Second mixed wastewater tank 9 Biochemical treatment tank DETAILED DESCRIPTION

[0029] Hereinafter, an embodiment of a method and system for reducing the acute toxicity of automobile manufacturing wastewater will be described in detail.

[0030] The acute toxicity of automobile manufacturing wastewater in the prior art can cause stress to the microorganisms in the biochemical treatment system, leading to unstable dissolved oxygen in the biochemical treatment system, sharp decrease, and further causing the COD of the effluent to rapidly increase and even exceed the standard, etc. The present application classifies and pretreats the painting wastewater, effectively reduces the acute toxicity of the painting wastewater, reduces the stress to the microorganisms in the biochemical system, and maintains the stable operation of the biochemical system. On this basis, the present application is completed.

[0031] Please refer to FIGS. 1-3. It should be understood that the structures, proportions, sizes, etc. shown in the drawings attached to the present specification are only used to cooperate with the content disclosed in the specification, to be understood and read by those skilled in the art, and do not have technical significance to limit the implementation conditions of the present application. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application. At the same time, the terms such as "up", "down", "left", "right", "middle", and "one" used in the present specification are only for the convenience of clear description, and are not used to limit the scope of the present application. The change or adjustment of the relative relationship, without substantially changing the technical content, is also considered as the implementation scope of the present application.

[0032] The application provides a treatment method for reducing the biological acute toxicity of automobile manufacturing wastewater.

[0033] 1) The first type of coating wastewater is treated by a first physical and chemical coagulation tank, and after dehydration, first type of coating wastewater treatment water is obtained, wherein the first type of coating wastewater comprises one or more of degreasing wastewater, degreasing waste liquid and film wastewater;

[0034] 2) The second type of coating wastewater is treated by a second physical and chemical coagulation tank, and after dehydration, second type of coating wastewater treatment water is obtained and is introduced into a first mixed wastewater tank, wherein the second type of coating wastewater comprises one or more of electrophoresis wastewater, electrophoresis waste liquid and spray paint wastewater;

[0035] 3) The third type of coating wastewater is treated by a third physical and chemical coagulation tank, and after dehydration and evaporation, third type of coating wastewater treatment water is obtained and is introduced into the first mixed wastewater tank, and after being uniformly mixed with the second type of coating wastewater treatment water in step 2), first mixed wastewater is obtained, wherein the third type of coating wastewater comprises water-based gun washing wastewater;

[0036] The first mixed wastewater is treated by a sludge method toxicity degradation treatment tank, and after dehydration, first mixed wastewater treatment water is obtained;

[0037] 4) After the power assembly wastewater is treated by ultrafiltration, power assembly wastewater treatment water is obtained;

[0038] 5) The first type of coating wastewater treatment water in step 1), the first mixed wastewater treatment water in step 3) and the power assembly wastewater treatment water in step 4) are mixed with domestic sewage, introduced into a second mixed wastewater tank, and second mixed wastewater is obtained, wherein the second mixed wastewater is treated by a biochemical treatment tank, and then discharge water is obtained.

[0039] In the treatment method for reducing the biological acute toxicity of automobile manufacturing wastewater, step 1) is to treat the first type of coating wastewater by a first physical and chemical coagulation tank, and after dehydration, first type of coating wastewater treatment water is obtained.

[0040] In step 1), the acute toxicity of the first type of coating wastewater is 6-10 toxicity units, which can be selected from 6-7 toxicity units, 7-7.6 toxicity units, 7.6-7.8 toxicity units, 7.8-8.2 toxicity units, 8.2-9 toxicity units or 9-10 toxicity units, and the CODcr is 400-2250 mg / L, which can be selected from 400-600 mg / L, 600-752.4 mg / L, 752.4-1000 mg / L, 1000-1200 mg / L, 1200-1800 mg / L or 1800-2250 mg / L, etc.

[0041] In step 1) of the present application, the first physicochemical coagulation tank comprises a first coagulant and / or a first flocculant.

[0042] In step 1) of the present application, the first coagulant is selected from one or more of soluble aluminum salt, soluble iron salt, polyaluminum chloride, polyferric sulfate, polyaluminum ferric chloride; the addition concentration of the first coagulant is 50-100 mg / L, which can be selected from 50-70 mg / L, 70-90 mg / L or 90-100 mg / L, etc.

[0043] In step 1) of the present application, the first flocculant is selected from one or both of anionic polyacrylamide or non-ionic polyacrylamide; the addition concentration of the first flocculant is 1-3 mg / L, which can be selected from 1-2 mg / L or 2-3 mg / L.

[0044] In step 1) of the present application, the acute toxicity of the first type of coating wastewater treatment water is 4-7 toxicity units, which can be selected from 4-4.71 toxicity units, 4.71-4.9 toxicity units, 4.9-5.58 toxicity units or 5.58-7 toxicity units, and the CODcr is 300-1350 mg / L, which can be selected from 300-500 mg / L, 500-750 mg / L, 750-1000 mg / L or 1000-1350 mg / L, etc.

[0045] In the method for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the present application, step 2) is to treat the second type of coating wastewater through a second physicochemical coagulation tank, and then dehydrate to obtain second type of coating wastewater treatment water.

[0046] In step 2) of the present application, the acute toxicity of the second type of coating wastewater is 100-425 toxicity units, which can be selected from 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 from 7000-7500 mg / L, 7500-10000 mg / L, 10000-12000 mg / L, 12000-14500 mg / L or 14500-18000 mg / L, etc.

[0047] In step 2) of the present application, the second physicochemical coagulation tank comprises a second coagulant and / or a second flocculant.

[0048] In step 2) of the present application, the second coagulant is selected from one or more of soluble aluminum salt, soluble iron salt, polyaluminum chloride, polyferric sulfate, polyaluminum ferric chloride; the adding concentration of the second coagulant is 100-200 mg / L, which can be optionally 100-150 mg / L or 150-200 mg / L.

[0049] In step 2) of the present application, the second flocculant is selected from one or both of anionic polyacrylamide or non-ionic polyacrylamide; the adding concentration of the second flocculant is 2-5 mg / L, which can be optionally 2-3 mg / L, 3-4 mg / L or 4-5 mg / L.

[0050] In step 2) of the present application, the acute toxicity of the second coating wastewater treatment water is 60-300 toxicity units, which can be optionally 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 optionally 3000-5000 mg / L, 5000-5580 mg / L, 5580-7000 mg / L, 7000-10000 mg / L or 10000-12000 mg / L, etc.

[0051] In the method for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the present application, step 3) is to treat the third coating wastewater through a third physicochemical coagulation tank, dewater, evaporate, obtain third coating wastewater treatment water, and then make the third coating wastewater treatment water enter a first mixed wastewater tank to mix uniformly with the second coating wastewater treatment water in step 2) to obtain first mixed wastewater; and the first mixed wastewater is treated through a sludge method toxicity degradation treatment tank and dewatered to obtain first mixed wastewater treatment water.

[0052] In step 3) of the present application, the acute toxicity of the third coating wastewater is 600-1000 toxicity units, which can be optionally 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 optionally 200000-250000 mg / L, 250000-300000 mg / L or 300000-350000 mg / L, etc.

[0053] In step 3) of the present application, the third physicochemical coagulation tank contains a third coagulant and / or a third flocculant.

[0054] In step 3) of the present application, the third coagulant is selected from one or more of modified melamine formaldehyde resin, cationic starch, cationic quaternary ammonium salt, cationic bis-quaternary ammonium salt, cationic poly-quaternary ammonium salt, bentonite, diatomite, soluble aluminum salt, soluble iron salt, polyaluminum chloride, polyferric sulfate, polyaluminum ferric chloride, and macromolecular organic acid; the adding concentration of the third coagulant is 0.3-3 wt%, which can be optionally 0.3-1 wt%, 1-1.5 wt%, or 1.5-3 wt%, etc.

[0055] In step 3) of the present application, the third flocculant is selected from one or both of anionic polyacrylamide or nonionic polyacrylamide; the adding concentration of the third flocculant is 5-30 mg / L, which can be optionally 5-10 mg / L, 10-20 mg / L, or 20-30 mg / L, etc.

[0056] In step 3) of the present application, the evaporation temperature is 40-80℃, which can be optionally 40-60℃ or 60-80℃; a small amount of defoaming agent needs to be added for the evaporation.

[0057] In step 3) of the present application, the acute toxicity of the third type of coating wastewater treatment water is 40-80 toxicity units, which can be optionally 40-65.3 toxicity units or 65.3-80 toxicity units, and the CODcr is 70000-100000 mg / L, which can be optionally 70000-75750 mg / L, 75750-85000 mg / L, or 85000-100000 mg / L, etc.

[0058] In step 3) of the present application, lime powder is added to the sludge method toxicity degradation treatment tank, and the adding concentration of the lime powder is 1-3 wt% of the first mixed wastewater. The lime powder is mainly used for adjusting the pH of the sludge method toxicity degradation treatment tank, conditioning the sludge, and improving the subsequent dewatering effect. Specifically: first, neutralizing the organic acid substances generated in the hydrolysis acidification process to form organic acid calcium, which has low solubility and is more easily captured and removed by microbial floc; second, the pH has been reduced to 5-6 in the early stage of the reaction, and if the reaction continues, the pH will be further reduced. In order to prevent the pH from being too low, lime powder is added to restore the pH to a slightly neutral level of 6.5-7.5; third, the lime itself has a certain adsorption effect on part of the organic matter, and after adding, the adsorption capacity for toxic substances can be enhanced; fourth, after adding lime powder in the later stage of the reaction, as a sludge conditioner, it is beneficial to the sludge settling and dewatering after the reaction is completed, for example, after entering the plate and frame dewatering machine, the sludge dewatering speed can be improved, and the moisture content of the sludge cake can be reduced.

[0059] In step 3) of the present application, the sludge method toxicity degradation treatment tank comprises the secondary sedimentation tank sludge discharged by 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 sludge in the sludge method toxicity degradation treatment tank is derived from the secondary sedimentation tank, has high sludge concentration, and the settling ratio SV30 can reach more than 80%; a large amount of sludge provides a large amount of microbial flocculation body, and has adsorption and sedimentation effects on the toxic substances in the first mixed wastewater; since the first mixed wastewater is only mixed and stirred with the biochemical sludge without aeration, the mixture is in an anoxic or even anaerobic state, and under the high-concentration microbial support in the sludge, the toxic substances that are difficult to degrade in the aerobic treatment, especially the toxic components in the aqueous solvent (the third coating wastewater), accelerate the hydrolysis and acidification process, form non-toxic or low-toxic decomposition products, and thus reduce the biological toxicity of the wastewater.

[0060] In the method for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the present application, step 4) is to perform ultrafiltration on the power assembly wastewater to obtain power assembly wastewater treatment water.

[0061] In step 4) of the present application, the acute toxicity of the power assembly wastewater is 65-120 toxicity units, which can be selected from 65-80 toxicity units, 80-88 toxicity units, 88-100 toxicity units or 100-120 toxicity units, etc., and the CODcr is 30000-50000 mg / L, which can be selected from 30000-37500 mg / L, 37500-45000 mg / L or 45000-50000 mg / L, etc.

[0062] In step 4) of the present application, the acute toxicity of the power assembly wastewater treatment water is 20-40 toxicity units, which can be selected from 20-30 toxicity units or 30-40 toxicity units, and the CODcr is 3000-5000 mg / L, which can be selected from 3000-4000 mg / L or 4000-5000 mg / L.

[0063] In the method for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the present application, step 5) is to mix the first type of coating wastewater treatment water in step 1), the first mixed wastewater treatment water in step 3) and the power assembly wastewater treatment water in step 4) with domestic sewage to obtain second mixed wastewater, and then the second mixed wastewater is treated in a biochemical treatment tank to obtain discharge water.

[0064] In step 5) of the present application, the acute toxicity of the domestic sewage is 2-4 toxicity units, which can be selected from 2-3.25 toxicity units or 3.25-4 toxicity units, and the CODcr is 300-500 mg / L, which can be selected from 300-400 mg / L or 400-500 mg / L.

[0065] In step 5), the acute toxicity of the second mixed wastewater is 7-10 toxicity units, which can be selected from 7-8.2 toxicity units, 8.2-9 toxicity units or 9-10 toxicity units, and the CODcr is 900-1300 mg / L, which can be selected from 900-986 mg / L, 986-1000 mg / L or 1000-1300 mg / L, etc.

[0066] In step 5), the process of the biochemical treatment tank adopts an anoxic and aerobic process or an aerobic process. When the biochemical treatment tank adopts the anoxic and aerobic process, the anoxic residence time is 4-8 hours, and the aerobic residence time is 6-8 hours; the anoxic dissolved oxygen is controlled at 0.1-0.5 mg / L, the aerobic dissolved oxygen in the front section is controlled at 1-2 mg / L, the middle section is controlled at 2-3 mg / L, and the rear section is controlled at 3-4 mg / L. When the biochemical treatment tank adopts the aerobic process, the aerobic residence time is 8-12 hours; the aerobic dissolved oxygen in the front section is controlled at 1-2 mg / L, the middle section is controlled at 2-3 mg / L, and the rear section is controlled at 3-4 mg / L.

[0067] In step 5), the acute toxicity of the discharge water is 0-0.2 toxicity units, which can be selected from 0-0.1 toxicity units or 0.1-0.2 toxicity units, and the CODcr is 175-250 mg / L, which can be selected from 175-200 mg / L, 200-246 mg / L or 246-250 mg / L, etc.

[0068] The second aspect of the present application provides a treatment system for reducing the biological acute toxicity of automobile manufacturing wastewater, comprising:

[0069] A biochemical treatment tank 9 is used for biochemical reaction of the second mixed wastewater to provide discharge water, wherein the second mixed wastewater comprises first type coating wastewater treatment water, first mixed wastewater treatment water, power assembly wastewater treatment water and domestic sewage;

[0070] A first type coating wastewater treatment unit comprises a first physicochemical coagulation tank 11 and a first dewatering machine to provide first type coating wastewater treatment water, and the first physicochemical coagulation tank 11, the first dewatering machine and the second mixed wastewater tank 8 are sequentially and fluidly connected;

[0071] A second type coating wastewater treatment unit comprises a second physicochemical coagulation tank 21 and a second dewatering machine to provide second type coating wastewater treatment water, and the second physicochemical coagulation tank 21, the second dewatering machine and the first mixed wastewater tank 6 are sequentially and fluidly connected;

[0072] The third type of coating wastewater treatment unit comprises a third physicochemical coagulation tank 31, a third dewatering machine and an evaporation unit 32 in fluid communication in sequence, to provide third type of coating wastewater treatment water, the evaporation unit 32 is in fluid communication with the first mixed wastewater tank 6, to provide the first mixed wastewater; the first mixed wastewater comprises the second type of coating wastewater treatment water and the third type of coating wastewater treatment water;

[0073] The sludge method toxicity degradation treatment tank 7 is connected with the water outlet of the first mixed wastewater tank 6, and the water inlet of the second mixed wastewater tank 8 is connected with the water outlet of the sludge method toxicity degradation treatment tank 7, and the fourth dewatering machine is arranged between the sludge method toxicity degradation treatment tank 7 and the second mixed wastewater tank 8, so that the first mixed wastewater is subjected to sludge method toxicity degradation treatment, and the first mixed wastewater treatment water is obtained;

[0074] The power assembly workshop wastewater treatment unit comprises an ultrafiltration unit 41, to provide power assembly wastewater treatment water, and the ultrafiltration unit 41 is in fluid communication with the second mixed wastewater tank 8.

[0075] In the treatment system for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the application, the first coagulant and / or the first flocculant are arranged in the first physicochemical coagulation tank 11.

[0076] In the treatment system for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the application, the first agitator is arranged on the top or the side of the first physicochemical coagulation tank 11.

[0077] In the treatment system for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the application, the rotating speed of the first agitator is 30-80 rpm / min, which can be 30-40 rpm / min, 30-60 rpm / min, 40-60 rpm / min, 40-80 rpm / min, 50-80 rpm / min or 60-80 rpm / min, etc.

[0078] In the treatment system for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the application, the first dewatering machine is selected from one of a centrifugal machine, a stacked screw machine, a plate-frame dewatering machine, a belt dewatering machine or a vacuum dewatering machine.

[0079] In the treatment system for reducing the biological acute toxicity of automobile manufacturing wastewater provided by the application, the first inclined plate sedimentation tank is arranged between the first physicochemical coagulation tank 11 and the first dewatering machine.

[0080] The processing system for reducing biological acute toxicity of automobile manufacturing wastewater provided by the application, according to the first type of coating wastewater generated by normal production of a coating workshop, 420 tons or so, a continuous first physicochemical coagulation tank 11 and a first inclined plate sedimentation tank are arranged, the maximum processing capacity is 50 m 3 / h or so, and it is ensured that one shift can be processed completely, the stirring speed of the first stirrer needs to reach 40-80 rpm / min when the coagulant is added, and it can be selected as 40-60 rpm / min or 60-80 rpm / min, etc., and the stirring speed of the first stirrer needs to reach 30-60 rpm / min when the flocculant is added, and it can be selected as 30-40 rpm / min or 40-60 rpm / min, etc.

[0081] The processing system for reducing biological acute toxicity of automobile manufacturing wastewater provided by the application, the second physicochemical coagulation tank 21 includes a second coagulant and / or a second flocculant.

[0082] The processing system for reducing biological acute toxicity of automobile manufacturing wastewater provided by the application, the second physicochemical coagulation tank 21 is provided with a second stirrer at the top or side; the stirring speed of the second stirrer is 30-80 rpm / min, which can be selected as 30-40 rpm / min, 30-60 rpm / min, 40-60 rpm / min, 40-80 rpm / min, 50-80 rpm / min or 60-80 rpm / min, etc.

[0083] The processing system for reducing biological acute toxicity of automobile manufacturing wastewater provided by the application, the second dewatering machine is selected from one of a centrifuge, a stacked screw machine, a plate and frame dewatering machine, a belt dewatering machine or a vacuum dewatering machine.

[0084] The processing system for reducing biological acute toxicity of automobile manufacturing wastewater provided by the application, a second inclined plate sedimentation tank is arranged between the second physicochemical coagulation tank 21 and the second dewatering machine.

[0085] The processing system for reducing biological acute toxicity of automobile manufacturing wastewater provided by the application, according to the second type of coating wastewater generated by normal production of a coating workshop, 165 tons or so, a continuous second physicochemical coagulation tank 21 and a second inclined plate sedimentation tank are arranged, the maximum processing capacity is 20 m 3 / h or so, and it is ensured that one shift can be processed completely. The stirring speed of the second stirrer needs to reach 40-80 rpm / min when the coagulant is added, and it can be selected as 40-60 rpm / min or 60-80 rpm / min, etc., and the stirring speed of the second stirrer needs to reach 30-60 rpm / min when the flocculant is added, and it can be selected as 30-40 rpm / min or 40-60 rpm / min, etc.

[0086] The third physicochemical coagulation tank 31 comprises a third coagulant and / or a third flocculant.

[0087] The third physicochemical coagulation tank 31 is provided with a third stirrer on the top or side.

[0088] The third stirrer has a rotation speed of 90-120 rpm / min, which can be 90-100 rpm / min, 100-110 rpm / min or 110-120 rpm / min.

[0089] The third dewatering machine is selected from a centrifuge, a stacked screw machine, a plate and frame dewatering machine, a belt dewatering machine or a vacuum dewatering machine.

[0090] The evaporation unit 32 can be an MVR evaporator with a scraper, an electric heating evaporator or a heat pump low-temperature evaporator, and has a processing capacity of at least 2.5 tons / day, which ensures that all the gun washing water in one day can be completely treated.

[0091] The bottom of the sludge toxicity degradation treatment tank 7 is provided with a fourth dewatering machine selected from a centrifuge, a stacked screw machine, a plate and frame dewatering machine, a belt dewatering machine or a vacuum dewatering machine, preferably a plate and frame dewatering machine.

[0092] The third physicochemical coagulation tank 31 has a batch processing capacity of 3-6 tons / batch, which ensures that one batch can treat the amount of one day or two days. The stirring speed of the third stirrer needs to reach 90-120 rpm / min, which can be 90-100 rpm / min, 100-110 rpm / min or 110-120 rpm / min, which is faster than the conventional physicochemical coagulation speed. This is because the number and density of paint slag particles generated after adding chemicals to the water-based gun washing wastewater are larger than those of other conventional industrial wastewater, so sufficient stirring speed is needed to prevent the paint slag from sinking. After physicochemical coagulation treatment, no inclined plate sedimentation tank is needed for sedimentation and sludge removal. The water is treated by stirring and dewatering at the same time and then enters the evaporation unit 32. After evaporation, it enters the first mixed wastewater tank together with the second type of coating wastewater treatment water to obtain the first mixed wastewater.

[0093] The use process of the present application:

[0094] 1) The first type of coating wastewater is stirred by a first stirrer in the first physical and chemical coagulation tank 11, and is subjected to physical and chemical treatment, and is settled and discharged by a first inclined plate settling tank, and after dewatering, the first type of coating wastewater treatment water is obtained;

[0095] 2) The second type of coating wastewater is stirred by a second stirrer in the second physical and chemical coagulation tank 21, and is subjected to physical and chemical treatment, and is settled and discharged by a second inclined plate settling tank, and after dewatering, the second type of coating wastewater treatment water is obtained and is introduced into the first mixed wastewater tank 6;

[0096] 3) The third type of coating wastewater is stirred by a third stirrer in the third physical and chemical coagulation tank 31, and is subjected to physical and chemical treatment, and is settled and discharged by a third inclined plate settling tank, and after dewatering, is introduced into the evaporation unit 32, and after evaporation, the third type of coating wastewater treatment water is obtained and is introduced into the first mixed wastewater tank 6, and is uniformly mixed with the second type of coating wastewater to obtain the first mixed wastewater;

[0097] 4) The power assembly wastewater is subjected to ultrafiltration treatment by the ultrafiltration unit 41, and the power assembly wastewater treatment water is obtained;

[0098] 5) The first mixed wastewater in step 3) is treated by the sludge method toxicity degradation treatment tank 7, and after dewatering, the first mixed wastewater treatment water is obtained, and is introduced into the second mixed wastewater tank 8 together with the first type of coating wastewater treatment water, the power assembly wastewater treatment water and the domestic sewage, and after biochemical reaction in the biochemical treatment tank 9, the effluent is discharged.

[0099] In order to make the technical means, creative features, purposes and effects achieved by the present application easy to understand, the present application is specifically described below in combination with examples and drawings.

[0100] In the following examples, unless otherwise specified, each reaction raw material is a commercially available product.

[0101] Unless otherwise specified, the purity of each product of each embodiment of the present application is more than 98%.

[0102] Example 1

[0103] First type of coating wastewater and power assembly wastewater pretreatment process

[0104] As shown in Table 1, the first type of coating wastewater is stirred by a first stirrer in the first physical and chemical coagulation tank 11 for physical and chemical treatment. The coagulant in the first physical and chemical coagulation tank 11 is polymeric ferric sulfate with a dosage of 70 mg / L, and the flocculant is anionic polyacrylamide with a dosage 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 the compared domestic sewage and the degreasing wastewater, degreasing waste liquid and film wastewater after the physical and chemical coagulation treatment is close to that of the domestic sewage, and does not cause significant adverse effects on the microorganisms in the biochemical reaction system. Therefore, the pretreatment process is not further adjusted.

[0105] Table 1 Pretreatment process of the first type of coating wastewater

[0106] As shown in Table 2, the main component of the power workshop wastewater is emulsion. The acute toxicity of the power workshop wastewater after the ultrafiltration unit 41 treatment is close to that of the second mixed wastewater (CODcr content of 1330 mg / L, acute toxicity of 28.30 toxicity units), and the water quantity of the power workshop wastewater is relatively small. Therefore, the acute toxicity can be basically ignored, and the pretreatment process does not need to be further adjusted.

[0107] Table 2 Pretreatment process of the power workshop wastewater

[0108] Comparative Example 1

[0109] Pretreatment process of the second type of coating wastewater before adjustment

[0110] The electrophoresis wastewater, electrophoresis waste liquid and spray paint wastewater all contain water-based solvent components. The electrophoresis wastewater itself belongs to a kind of wastewater containing water-based paint after dilution; the electrophoresis waste liquid is the liquid poured from the electrophoresis tank, which is close to the electrophoresis paint, and therefore has a higher CODcr concentration; the spray paint wastewater is the drainage of the wet spray house circulating water, which contains solvent components brought by overspray paint.

[0111] As shown in Table 3, the acute toxicity of the second type of electrophoresis wastewater, electrophoresis waste liquid and spray paint wastewater after the physical and chemical coagulation treatment is still significantly higher than that of the domestic sewage (3.25 toxicity units) and the second mixed wastewater (28.30 toxicity units). The evaporation treatment of the electrophoresis wastewater and electrophoresis waste liquid can effectively remove the toxic components that cannot be removed by coagulation treatment, and obtain clear and colorless condensate, and the acute toxicity is significantly reduced. However, the evaporation treatment of the spray paint wastewater has a small decrease in acute toxicity. Although evaporation has a certain effect on reducing the acute toxicity of the electrophoresis wastewater, electrophoresis waste liquid and spray paint wastewater, the equipment investment and operating energy consumption of the evaporator are quite large, especially for the case of large water quantity of the electrophoresis wastewater, electrophoresis waste liquid and spray paint wastewater, the equipment investment and operating energy consumption of the evaporator required are even larger. Therefore, the pretreatment method of the second type of coating wastewater is further adjusted.

[0112] Table 3 Pretreatment process of second type of coating wastewater without adjustment

[0113] Example 2

[0114] Pretreatment process of second type of coating wastewater after adjustment

[0115] The second type of coating wastewater is stirred by a second stirrer in the second physicochemical coagulation tank 21 for physicochemical treatment. The coagulant in the second physicochemical coagulation tank 21 is polyaluminum ferric chloride with a dosage of 150 mg / L, and the flocculant is non-ionic polyacrylamide with a dosage of 4 mg / L. After sedimentation and sludge discharge through the second inclined plate sedimentation tank, the second type of coating wastewater enters the first mixed wastewater tank 6, is uniformly stirred, and then enters the sludge method toxicity degradation treatment tank 7 to be mixed with biochemical sludge. The volume ratio of the second type of coating wastewater to the biochemical sludge is 1:1. After uniform stirring for 24-48 h, lime powder is added. The dosage of the lime powder is 1-3% (based on the mass ratio after mixing, and the specific gravity of the mixture of wastewater and sludge is still 1). The mixture is continuously stirred for 12-24 h, and the supernatant is taken for detection of relevant data, as shown in Table 4.

[0116] Table 4 Pretreatment process of second type of coating wastewater after adjustment

[0117] Compared with the method of only using physicochemical coagulation to reduce the acute toxicity of the second type of coating wastewater, the method of physicochemical coagulation + biochemical sludge + lime powder used in the present application can reduce the acute toxicity of the electrophoresis wastewater by 72.7%, the acute toxicity of the electrophoresis liquid by 78.6%, and the acute toxicity of the paint spraying wastewater by 73.2%.

[0118] Comparative Example 2

[0119] Pretreatment process of third type of coating wastewater without adjustment

[0120] The content of the water-based solvent in the water-based gun washing wastewater is as high as about 5%, so the CODcr concentration is the highest. As shown in Table 5, the acute toxicity of the water-based gun washing wastewater is particularly obviously reduced after evaporation. The effect of reducing the toxicity is better when evaporation treatment is performed on the basis of physicochemical coagulation, but the acute toxicity of the water-based gun washing wastewater (65.3 toxicity units) is still higher than that of the second mixed wastewater (8.15 toxicity units) before entering the biochemical treatment tank 9. Although the CODcr can be greatly reduced after the water-based gun washing wastewater is evaporated and then subjected to electro-catalytic oxidation treatment, the biological toxicity does not decrease but increases, indicating that the electro-catalytic oxidation process has little effect on reducing the biological acute toxicity of the wastewater, and on the contrary, complex chemical reactions in the reaction process may produce intermediate products with greater biological toxicity.

[0121] Table 5 Pretreatment process of third type of coating wastewater before adjustment

[0122] Example 3

[0123] Pretreatment process of third type of coating wastewater after adjustment

[0124] Since the water-based gun washing wastewater has a small water volume, it is more suitable to use evaporation equipment. The pretreatment process of the third type of coating wastewater is further adjusted in the present application to better reduce the acute toxicity of the third type of coating wastewater. The third type of coating wastewater is stirred in the third materialization and coagulation tank 31 by the third stirrer for materialization treatment. The coagulant in the third materialization and coagulation tank 31 is a compound mixture of cationic starch, bentonite, soluble aluminum salt, and soluble iron salt, with a compound ratio of 20%, 20%, 40%, and 20%, respectively, and a compound reagent dosage concentration of 1.5 wt%. The flocculating agent is anionic polyacrylamide with a dosage concentration of 10 mg / L. After sedimentation and sludge discharge through the third inclined plate sedimentation tank, it enters the evaporation unit 32, which is evaporated at a temperature of 60°C. After evaporation, it enters the first mixed wastewater tank 6, which is uniformly stirred and then enters the sludge method toxicity degradation treatment tank 7. Lime powder is added to the sludge method toxicity degradation treatment tank 7, with a dosage concentration of 1-3 wt% of the first mixed wastewater. The sludge method toxicity 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, obtaining the first mixed wastewater treatment water. 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). The supernatant is taken for detection of related data, as shown in Table 6.

[0125] Table 6 Pretreatment process of third type of coating wastewater after adjustment

[0126] Compared with the method of only using materialization and coagulation to reduce the acute toxicity of the third type of coating wastewater, the present application uses the method of materialization and coagulation + evaporation + biochemical sludge + lime powder, which reduces the acute toxicity of the third type of coating wastewater by 95%.

[0127] Example 4

[0128] The first mixed wastewater is treated by the sludge method in the toxic degradation treatment tank 7, and after dewatering by the plate frame dewatering machine, is mixed with the first type of coating wastewater treatment water, power assembly wastewater treatment water and domestic sewage in the second mixed wastewater tank 8, and then enters the biochemical treatment tank 9 for biochemical reaction. Through detection, the CODcr of the second mixed wastewater before entering the biochemical treatment tank 9 is 986 mg / L, and the biological acute toxicity is 8.15 toxicity units, which is close to the biological acute toxicity of the first type of coating wastewater treatment water and far lower than that of the second mixed wastewater before the process is adjusted (28.3 toxicity units). After being treated by the anoxic and aerobic biochemical treatment tank 9, the CODcr of the effluent is 246 mg / L, and the biological acute toxicity is reduced to 0.06 toxicity units. The biological membrane state on the surface of the contact oxidation filler in the biochemical treatment tank 9 is greatly improved. The white jelly-like substance that often appears before is basically not present, the color of the biological membrane is yellowish brown, the settling ratio SV30 of the contact oxidation effluent is maintained at about 1%, which greatly reduces the burden of the subsequent plate frame dewatering machine, reduces the amount of sludge generated, and the dissolved oxygen in the biochemical system can be stably maintained at about 3 mg / L. In addition, through the process improvement, a part of the CODcr of the electrophoresis wastewater, electrophoresis liquid, paint spraying wastewater and water-based gun washing wastewater is removed before entering the biochemical system. The CODcr of the second mixed wastewater treatment water entering the biochemical treatment tank 9 is reduced to 900-1300 mg / L, and the total CODcr of the discharge is reduced to 225-325 mg / L, which reduces the risk of exceeding the standard discharge. In addition, for the water-based gun washing wastewater with the highest biological acute toxicity, if the original problem cannot be solved, it can only be treated as hazardous waste and transported out for disposal, so the effective solution of the problem also saves the high cost of hazardous waste disposal.

[0129] The above embodiment is a preferred case of the present application and does not limit the protection scope of the present application.

[0130] The applicant declares that the present application is illustrated by the above embodiment, but the present application is not limited to the above embodiment, that is, the present application does not mean that it must rely on the above embodiment to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

[0131] The above embodiment is a preferred case of the present application and does not limit the protection scope of the present application. However, the present application is not limited to the specific details in the above embodiment. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, and these simple modifications all belong to the protection scope of the present application.

[0132] It should be further noted that various specific technical features described in the above specific embodiments can be combined in any suitable manner, and in order to avoid unnecessary repetition, the present application will not describe various possible combinations again.

Claims

1. A method for reducing the biological acute toxicity of automotive manufacturing wastewater, characterized by, It comprises the following steps: 1) The first type of coating wastewater is treated by a first physical and chemical coagulation tank, and after dehydration, the first type of coating wastewater treatment water is obtained, wherein the first type of coating wastewater comprises one or more of degreasing wastewater, degreasing waste liquid, and film wastewater; 2) The second type of coating wastewater is treated by a second physical and chemical coagulation tank, and after dehydration, the second type of coating wastewater treatment water is obtained and enters a first mixed wastewater tank, wherein the second type of coating wastewater comprises one or more of electrophoresis wastewater, electrophoresis waste liquid, and spray paint wastewater; 3) The third type of coating wastewater is treated by a third physical and chemical coagulation tank, and after dehydration and evaporation, the third type of coating wastewater treatment water is obtained and then enters the first mixed wastewater tank, and after being uniformly mixed with the second type of coating wastewater treatment water in step 2), the first mixed wastewater is obtained, wherein the third type of coating wastewater comprises water-based gun washing wastewater; The first mixed wastewater is treated by a sludge method toxic degradation treatment tank, and after dehydration, the first mixed wastewater treatment water is obtained; 4) The power assembly wastewater is treated by ultrafiltration to obtain power assembly wastewater treatment water; 5) The first type of coating wastewater treatment water in step 1), the first mixed wastewater treatment water in step 3), and the power assembly wastewater treatment water in step 4) are mixed with domestic sewage to enter a second mixed wastewater tank to obtain second mixed wastewater, and the second mixed wastewater is treated by a biochemical treatment tank to obtain discharge water.

2. The treatment method for reducing the biological acute toxicity of automobile manufacturing wastewater according to claim 1, comprising any one or more of the following features: A1) The acute toxicity of the first type of coating wastewater in step 1) is 6-10 toxicity units, and the CODcr is 400-2250 mg / L; A2) The acute toxicity of the first type of coating wastewater treatment water in step 1) is 4-7 toxicity units, and the CODcr is 300-1350 mg / L; A3) The acute toxicity of the second type of coating wastewater in step 2) is 100-425 toxicity units, and the CODcr is 7000-18000 mg / L; A4) The acute toxicity of the second type of coating wastewater treatment water in step 2) is 60-300 toxicity units, and the CODcr is 3000-12000 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 40-80 toxicity units, and the CODcr is 70000-100000 mg / L; A7) The acute toxicity of the power assembly wastewater in step 4) is 65-120 toxicity units, and the CODcr is 30000-50000 mg / L; A8) The acute toxicity of the power assembly wastewater treatment water in step 4) is 20-40 toxicity units, and the CODcr is 3000-5000 mg / L; A9) The acute toxicity of the domestic sewage in step 5) is 2-4 toxicity units, and the CODcr is 300-500 mg / L; A10) The acute toxicity of the second mixed wastewater of step 5) is 7-10 toxicity units, and the CODcr is 900-1300 mg / L; A11) The acute toxicity of the effluent water of step 5) is 0-0.2 toxicity units, and the CODcr is 175-250 mg / L.

3. The method of claim 1, wherein the method further comprises any one or more of the following features: B1) The first physicochemical coagulation tank of step 1) comprises a first coagulant and / or a first flocculant; B2) The second physicochemical coagulation tank of step 2) comprises a second coagulant and / or a second flocculant; B3) The third physicochemical coagulation tank of step 3) comprises a third coagulant and / or a third flocculant; B4) The evaporation of step 3) is performed at a temperature of 40-80°C; B5) The sludge process toxicity degradation treatment tank of step 3) uses an anoxic and anaerobic process or an anaerobic process; B6) Lime powder is added to the sludge process toxicity degradation treatment tank of step 3) to adjust the pH of the sludge process toxicity degradation treatment tank, condition the sludge, and improve the subsequent dewatering effect; B7) The sludge process toxicity degradation treatment tank of step 3) comprises the biological sludge discharged from the secondary sedimentation tank; B8) The biological treatment tank of step 5) uses an anoxic and aerobic process or an aerobic process.

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

1.

5. The method of claim 3, further comprising any one or more of the following features: B81) when the biochemical treatment tank uses an anoxic and aerobic process, the anoxic residence time is 4-8 hours, the aerobic residence time is 6-8 hours, the anoxic dissolved oxygen is controlled at 0.1-0.5 mg / L, the aerobic front-stage dissolved oxygen is controlled at 1-2 mg / L, the middle-stage is controlled at 2-3 mg / L, and the back-stage is controlled at 3-4 mg / L; B82) when the biochemical treatment tank uses an aerobic process, the aerobic residence time is 8-12 hours, the aerobic front-stage dissolved oxygen is controlled at 1-2 mg / L, the middle-stage is controlled at 2-3 mg / L, and the back-stage is controlled at 3-4 mg / L.

6. A treatment system for reducing the acute toxicity of automotive manufacturing wastewater, comprising: comprising: a biochemical treatment tank (9) for allowing the second mixed wastewater to undergo biochemical reaction to provide effluent water, the second mixed wastewater comprising first type coating wastewater treatment water, first mixed wastewater treatment water, powertrain wastewater treatment water, and domestic sewage; a first type coating wastewater treatment unit comprising a first physicochemical coagulation tank (11) and a first dewatering machine to provide the first type coating wastewater treatment water, the first physicochemical coagulation tank (11), the first dewatering machine, and the second mixed wastewater tank (8) being sequentially fluidly connected; a second type coating wastewater treatment unit comprising a second physicochemical coagulation tank (21) and a second dewatering machine to provide the second type coating wastewater treatment water, the second physicochemical coagulation tank (21), the second dewatering machine, and the first mixed wastewater tank (6) being sequentially fluidly connected; a third type coating wastewater treatment unit comprising a third physicochemical coagulation tank (31), a third dewatering machine, and an evaporation unit (32) being sequentially fluidly connected to provide the third type coating wastewater treatment water, the evaporation unit (32) being fluidly connected to the first mixed wastewater tank (6) to provide the first mixed wastewater, the first mixed wastewater comprising the second type coating wastewater treatment water and the third type coating wastewater treatment water; a sludge process toxicity degradation treatment tank (7), the water inlet of the sludge process toxicity degradation treatment tank (7) being connected to the water outlet of the first mixed wastewater tank (6), the water outlet of the sludge process toxicity degradation treatment tank (7) being connected to the water inlet of the second mixed wastewater tank (8), a fourth dewatering machine being provided between the sludge process toxicity degradation treatment tank (7) and the second mixed wastewater tank (8) for allowing the first mixed wastewater to undergo sludge process toxicity degradation treatment to obtain the first mixed wastewater treatment water; A power assembly workshop wastewater treatment unit, comprising an ultrafiltration unit (41) to provide power assembly wastewater treatment water, the ultrafiltration unit (41) being in fluid communication with the second mixed wastewater tank (8).

7. The treatment system for reducing the acute toxicity of automobile manufacturing wastewater, as set forth in claim 6, wherein the activated sludge is mixed with the automobile manufacturing wastewater in a ratio of 1 : 1 to 1 :

10. Any one or more of the following features are included: C1) the first physicochemical coagulation tank (11) comprises a first coagulant and / or a first flocculant; C2) the first physicochemical coagulation tank (11) is provided with a first agitator on the top or side thereof; C3) the first physicochemical coagulation tank (11) and the first dewatering machine are further provided with a first inclined plate sedimentation tank therebetween; C4) the second physicochemical coagulation tank (21) comprises a second coagulant and / or a second flocculant; C5) the second physicochemical coagulation tank (21) is provided with a second agitator on the top or side thereof; C6) the second physicochemical coagulation tank (21) and the second dewatering machine are further provided with a second inclined plate sedimentation tank therebetween; C7) the third physicochemical coagulation tank (31) comprises a third coagulant and / or a third flocculant; C8) the third physicochemical coagulation tank (31) is provided with a third agitator on the top or side thereof; C9) the first dewatering machine, the second dewatering machine, the third dewatering machine or the fourth dewatering machine is selected from one of a centrifuge, a decanter centrifuge, a plate and frame filter, a belt filter or a vacuum filter.

8. The treatment system for reducing the acute toxicity of automobile manufacturing wastewater, as set forth in claim 7, wherein the activated sludge is mixed with the automobile manufacturing wastewater in a ratio of 1 : 1 to 1 :

10. Any one or more of the following features are further included: C21) the rotation speed of the first agitator is 30-80 rpm / min; C51) the rotation speed of the second agitator is 30-80 rpm / min; C81) the rotation speed of the third agitator is 90-120 rpm / min.

9. The treatment system for reducing the acute toxicity of automobile manufacturing wastewater, as set forth in claim 6, wherein, The evaporation unit (32) is provided with a scraper for discharging evaporation residues from the evaporator.

10. The treatment system for reducing the acute toxicity of automobile manufacturing wastewater, as set forth in claim 6, wherein the biological treatment tank is a sequencing batch reactor. The evaporation unit (32) is an MVR evaporator, an electric heating evaporator or a heat pump low-temperature evaporator.

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