Improved coating wastewater treatment system

Abstract

The utility model provides an improved coating wastewater treatment system. The system comprises: a physicochemical reaction tank for performing physicochemical reaction treatment on to-be-treated coating wastewater to provide a first sludge mixed solution; the first precipitation tank is used for carrying out sludge-water separation on the first sludge mixed liquid so as to provide a first liquid phase stream and first sludge; the first precipitation tank is in fluid communication with the physicochemical reaction tank; the anaerobic MBBR tank is used for carrying out biochemical reaction on the first liquid phase stream to provide a second liquid phase stream; the anaerobic MBBR tank is in fluid communication with the first precipitation tank; the contact oxidation tank is used for carrying out aerobic biochemical treatment on the second liquid-phase stream so as to provide a third liquid-phase stream; the contact oxidation tank is in fluid communication with the anaerobic MBBR tank; and the contact oxidation tank is in fluid communication with the anaerobic MBBR tank through the liquid backflow pipeline. According to the coating wastewater treatment device, the biodegradability of coating wastewater can be improved, the removal efficiency of organic pollutants and total nitrogen is improved, and the stability of the water quality of treated water is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of wastewater treatment, and in particular relates to an improved painting wastewater treatment system. Background Art

[0002] A large amount of automobile painting wastewater is generated during the automobile manufacturing process. The wastewater contains pollutants such as resins, surfactants, heavy metal ions, oils, phosphates, paints, pigments, organic solvents, etc. If not properly treated, it will cause serious pollution and damage to the environment. Due to the large variety and complex composition of automobile painting wastewater, the concentration of pollutants varies and the emission is irregular, it is impossible to remove various pollutants and toxic substances contained in the painting wastewater when using a single wastewater treatment process.

[0003] In view of the characteristics of painting wastewater, a two-step treatment method is currently used, first collecting it by quality, conducting physical and chemical pretreatment, and then using biological contact oxidation or activated sludge method for subsequent treatment. Painting wastewater has complex components, high COD content and poor biodegradability. These pollutants cannot be completely removed in the physical and chemical reaction stage. Once these pollutants enter the biochemical treatment system in the later stage, the load and energy consumption of the biochemical treatment will increase, making the effluent water quality unstable, and there will even be a risk of excessive discharge of treated water. Utility Model Content

[0004] In view of the shortcomings of the prior art mentioned above, the purpose of the utility model is to provide an improved painting wastewater treatment system, which is used to solve the problems that the single wastewater treatment process in the prior art cannot remove various pollutants and toxic substances contained in the painting wastewater; pollutants increase the load and energy consumption of biochemical treatment, make the effluent water quality unstable, and have a high risk of excessive discharge of treated water.

[0005] In order to achieve the above-mentioned purpose and other related purposes, the utility model provides an improved painting wastewater treatment system, comprising:

[0006] A physicochemical reaction tank, used for subjecting the coating wastewater to be treated to a physicochemical reaction treatment to provide a first sludge mixed liquid;

[0007] a first sedimentation tank, used for separating the first sludge mixed liquid into mud and water to provide a first liquid phase stream and a first sludge; the first sedimentation tank is in fluid communication with the physicochemical reaction tank;

[0008] An anaerobic MBBR tank, used for subjecting the first liquid phase stream to a biochemical reaction to provide a second liquid phase stream; the anaerobic MBBR tank is in fluid communication with the first precipitation tank;

[0009] A contact oxidation tank, used for aerobic biochemical treatment of the second liquid phase stream to provide a third liquid phase stream; the contact oxidation tank is in fluid communication with the anaerobic MBBR tank;

[0010] A liquid return pipe, through which the contact oxidation tank is in fluid communication with the anaerobic MBBR tank;

[0011] The second sedimentation tank is used for separating the third liquid phase stream into mud and water to provide a fourth liquid phase stream and a second sludge; the second sedimentation tank is fluidically connected to the contact oxidation tank.

[0012] In some embodiments of the present invention, a sludge concentration tank is further included, which is used to concentrate the first sludge and the second sludge; the sludge concentration tank is fluidically connected to the first sedimentation tank and the second sedimentation tank.

[0013] In some embodiments of the present invention, the first sedimentation tank and the second sedimentation tank are inclined plate sedimentation tanks respectively.

[0014] In some embodiments of the present invention, a stirring unit is provided in the anaerobic MBBR tank.

[0015] In some embodiments of the present invention, a suspended filler is provided in the anaerobic MBBR tank.

[0016] In some embodiments of the present invention, a first sludge discharge pipeline is further included; the first sedimentation tank is fluidically connected to the sludge concentration tank via the first sludge discharge pipeline.

[0017] In some embodiments of the present invention, a second sludge discharge pipeline is further included; the second sedimentation tank is fluidically connected to the sludge concentration tank via the second sludge discharge pipeline.

[0018] In some embodiments of the present invention, an intermediate water tank is provided between the first sedimentation tank and the anaerobic MBBR tank; the intermediate water tank is fluidly connected to the first sedimentation tank and the anaerobic MBBR tank, respectively.

[0019] In some embodiments of the present invention, a water pump is provided on the connecting pipeline between the intermediate water tank and the anaerobic MBBR tank.

[0020] In some embodiments of the present invention, a dewatering machine is further included; the dewatering machine is used to remove moisture from the first sludge and the second sludge; the dewatering machine is fluidically connected to the sludge thickening tank; a third sludge discharge pipeline is also included; the sludge thickening tank is fluidically connected to the dewatering machine via the third sludge discharge pipeline.

[0021] As described above, the improved coating wastewater treatment system of the utility model has the following beneficial effects:

[0022] The utility model mixes the influent of the anaerobic MBBR tank and the reflux liquid of the contact oxidation tank, and can be used as a combined process of hydrolysis acidification and denitrification and denitrification. The suspended filler is fully in contact with the wastewater and the organic matter that is difficult to biodegrade in the wastewater is converted into organic matter that is easily biodegradable, so that its CODcr is initially reduced, the biodegradability of the wastewater is improved, and it is beneficial to the subsequent aerobic treatment. Under anaerobic conditions, the influent wastewater and the reflux liquid of the contact oxidation tank are mixed, and the carbon-containing organic matter in the wastewater provides energy for the denitrifying bacteria to continue to degrade the total nitrogen, and the nitrate nitrogen is reduced to nitrogen gas to escape from the water, thereby achieving the purpose of removing the total nitrogen. The utility model can improve the biodegradability of coating wastewater and the removal efficiency of organic pollutants and total nitrogen, and improve the stability of the treated water quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of an improved painting wastewater treatment system of the present invention.

[0024] Reference numerals:

[0025] 1 Physicochemical reaction tank

[0026] 2. First sedimentation tank

[0027] 21. First sludge discharge pipeline

[0028] 3 Middle sink

[0029] 4 Anaerobic MBBR tank

[0030] 5. Contact oxidation tank

[0031] 51 Liquid return pipe

[0032] 6 Second sedimentation tank

[0033] 61 Second sludge discharge pipeline

[0034] 62 Water discharge pipe

[0035] 7 Sludge thickening tank

[0036] 71 The third sludge discharge pipeline

[0037] 8. Dehydrator

[0038] 9. Transport and disposal equipment

[0039] 10 Painting wastewater tank DETAILED DESCRIPTION

[0040] The following is a description of the implementation of the present invention by means of specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0041] See also Figure 1 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 utility model, so they have no substantial technical significance. Any modification of the structure, change in the proportion relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the utility model without affecting the effects and purposes that can be achieved by the utility model. 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 utility model. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the utility model without substantially changing the technical content.

[0042] The utility model provides an improved coating wastewater treatment system, such as Figure 1 As shown. It includes a physicochemical reaction tank 1, a first sedimentation tank 2, an intermediate water tank 3, an anaerobic moving bed biofilm reactor (MBBR) tank 4, a contact oxidation tank 5, a second sedimentation tank 6, a sludge thickening tank 7 and a dewatering machine 8 which are connected in sequence, and also includes a first sludge discharge pipeline 21, a second sludge discharge pipeline 61 and a liquid return pipeline 51. The first sedimentation tank 2 is in fluid communication with the sludge thickening tank 7 via the first sludge discharge pipeline 21, the second sedimentation tank 6 is in fluid communication with the sludge thickening tank 7 via the second sludge discharge pipeline 61, and the contact oxidation tank 5 is in fluid communication with the anaerobic MBBR tank 4 via the liquid return pipeline 51.

[0043] In this embodiment, the physicochemical reaction tank 1 is used to subject the to-be-treated painting wastewater to physicochemical reaction treatment to provide a first sludge mixture. The painting wastewater in this embodiment mainly comes from the body pretreatment process, cathode electrophoresis process or mid-coating and topcoat spraying process in the automobile manufacturing process. The painting wastewater mainly contains pollutants such as resins, surfactants, heavy metal ions (such as lead, chromium, nickel or zinc, etc.), oil, phosphates, paints, pigments, organic solvents (such as toluene, xylene or acetone, etc.). The painting wastewater in this embodiment is collected by separation and adjusted for homogenization, and then enters the physicochemical reaction tank 1 for physicochemical treatment, and its initial COD Cr (Dichromate index) content is 1000-1500 mg / L, ammonia nitrogen content is 10-25 mg / L, and total nitrogen content is 30-65 mg / L.

[0044] In this embodiment, the first sedimentation tank 2 is used to separate the first sludge mixed liquid into mud and water to provide a first liquid phase stream and a first sludge; the first sedimentation tank 2 is fluidically connected to the physicochemical reaction tank 1 .

[0045] In this embodiment, the first sedimentation tank 2 is an inclined plate sedimentation tank.

[0046] In this embodiment, the first sedimentation tank 2 is provided with a mud outlet and a water outlet. The mud outlet of the first sedimentation tank 2 is connected to the sludge concentration tank 7 through a first sludge discharge pipeline 21 , and the water outlet of the first sedimentation tank 2 is connected to the intermediate water tank 3 .

[0047] In this embodiment, the intermediate water tank 3 is fluidly connected to the first sedimentation tank 2 and the anaerobic MBBR tank 4. Since the amount and concentration of wastewater fluctuate to a certain extent, in order to achieve the stability of subsequent treatment water supply, the intermediate water tank 3 can play the role of sedimentation separation, regulation, maintaining uniform and stable water inflow or water storage.

[0048] In this embodiment, a water pump is provided on the connecting pipeline between the intermediate water tank 3 and the anaerobic MBBR tank 4 to transport sewage into the anaerobic MBBR tank 4 .

[0049] In this embodiment, the anaerobic MBBR tank 4 is used to perform a biochemical reaction on the first liquid phase stream to provide a second liquid phase stream; the anaerobic MBBR tank 4 is fluidically connected to the first sedimentation tank 2 .

[0050] In this embodiment, a stirring unit is provided in the anaerobic MBBR tank 4. The stirring unit has a stirrer with a banana-shaped stirring blade, which has a soft contour and will not damage the suspended filler.

[0051] In this embodiment, the anaerobic MBBR tank 4 is filled with suspended fillers in the anaerobic biochemical device. This type of suspended filler is made of materials such as polyethylene, and has a porous structure on the surface. The effective specific surface area is large, providing a large number of attachment points for microorganisms, which is suitable for microbial adsorption and growth. In an anaerobic environment, the suspended filler is in a fluidized state by relying on the stirring of the mixer in the tank and the lifting effect of the water flow, thereby forming suspended anaerobic sludge and attached biofilm, giving full play to the advantages of both attached and suspended phase organisms. The suspended filler is fully in contact with the pollutants to be treated, which improves the biodegradability of the wastewater, reduces the pH value of the incoming water, reduces the sludge production, and creates favorable conditions for subsequent aerobic biological treatment.

[0052] In this embodiment, the anaerobic MBBR tank 4 has the following main advantages:

[0053] (1) The volumetric load is high. The tank capacity is much smaller than that of the hydrolysis acidification tank. The existing water treatment facilities can be simply modified without increasing the land area, thereby increasing the wastewater treatment capacity and improving the effluent quality.

[0054] (2) Resistance to shock loads, stable performance, and reliable operation. The impact of shock loads and temperature changes on the MBBR treatment process is much smaller than that on the activated sludge process.

[0055] (3) Easy mixing operation and simple maintenance. The mixer uses banana-shaped mixing blades with a soft contour that will not damage the suspended filler.

[0056] (4) The anaerobic MBBR tank 4 is not blocked and the volume is fully utilized. Since the suspended filler and the water flow can be fully mixed in the entire volume of the anaerobic MBBR tank 4, the possibility of blockage of the anaerobic MBBR tank 4 is avoided.

[0057] (5) The process is flexible and convenient. On the one hand, various pool structures can be used without affecting the treatment effect of the process. On the other hand, different filler filling rates can be selected to achieve the requirements of high efficiency and long-term expansion of treatment scale without increasing the pool capacity.

[0058] (6) The suspended filler system has a long service life. The use of high-quality, pressure-resistant biological fillers can ensure that the entire system can be used for a long time without replacement, and the depreciation rate is low.

[0059] Since the initial COD of the coating wastewater in this example is Cr If the content of nitrogen, ammonia nitrogen and total nitrogen is too high, it will be toxic to microorganisms and cause microbial poisoning if it is directly treated in the subsequent biochemical treatment. After the treatment in the anaerobic MBBR tank 4, the CODcr of the influent was initially degraded from 1000-1500 mg / L to 700-1050 mg / L, which greatly reduced the pressure of the subsequent aerobic biochemical treatment.

[0060] In this embodiment, the contact oxidation tank 5 is used to aerobically biochemically treat the second liquid phase stream to provide a third liquid phase stream; the contact oxidation tank 5 is fluidically connected to the anaerobic MBBR tank 4 .

[0061] In this embodiment, the contact oxidation tank 5 is a water tank in which a suspended filler is installed. The oxygenated wastewater immerses all the fillers and passes through the fillers at a certain flow rate. The fillers are covered with biofilms, and the oxygen required for growth is provided to the microorganisms on the surface of the biofilms. Under the metabolic function of the microorganisms, the organic pollutants in the wastewater are removed, thereby purifying the wastewater.

[0062] In this embodiment, the contact oxidation tank 5 has the following main features in terms of process, function and operation:

[0063] 1. Process characteristics

[0064] (1) Use various types of fillers and aeration to form a three-phase coexistence system of liquid, solid and gas in the pool, which is conducive to oxygen transfer and sufficient dissolved oxygen, which is suitable for the survival and proliferation of microorganisms.

[0065] (2) The surface of the filler is covered with biofilm, forming the main structure of the biofilm. Due to the massive growth of filamentous bacteria, a dense biological network with a three-dimensional structure is formed, in which the wastewater plays a role similar to "filtration", which can effectively improve the purification effect.

[0066] (3) The surface of the biofilm is continuously aerated and blown off, which is beneficial to maintaining the activity of the biofilm, inhibiting the proliferation of anaerobic membranes, improving the utilization rate of oxygen and maintaining a high active biomass, meeting a high organic loading rate, and helping to reduce the pool capacity and floor space.

[0067] 2. Operational characteristics

[0068] (1) It has strong impact load resistance and can maintain good treatment effect even under intermittent operation conditions. It is suitable for the treatment of wastewater generated by the paint shop of the vehicle factory.

[0069] (2) Simple operation, convenient operation, easy maintenance and management, no need for sludge return, and no sludge bulking.

[0070] (3) The sludge production is small, the sludge particles are large and easy to settle.

[0071] 3. Functional characteristics

[0072] The contact oxidation tank 5 has multiple purification functions. In addition to effectively removing organic pollutants, it can also be used to remove ammonia nitrogen if it is properly operated and managed, and can be used as a tertiary treatment technology.

[0073] In this embodiment, the effluent of the anaerobic MBBR tank 4 flows into the contact oxidation tank 5, and the organic pollutants and ammonia nitrogen in the water body are further removed in the contact oxidation tank 5. A water pump is arranged in the contact oxidation tank 5, and the effluent of the anaerobic MBBR tank 4 and the reflux liquid of the contact oxidation tank 5 are mixed through the liquid reflux pipe 51, which can be used as a combined process of hydrolysis acidification and denitrification and denitrification. The purpose of hydrolysis acidification is to fully contact the wastewater through the suspended filler, and rely on anaerobic bacteria to convert the difficult-to-degrade molecular structure into an easily biodegradable molecular structure, such as carboxylic acid organic matter, through four stages, namely hydrolysis, acidification, hydrogen production, acetic acid production and methanogenesis biochemical reaction, and at the same time, part of the organic matter is converted into carbon dioxide, hydrogen, methane, etc., so that its CODcr is initially reduced, and the biodegradability of the wastewater is improved, which is conducive to the subsequent aerobic treatment. Under anoxic conditions, the wastewater is mixed with the reflux liquid of the contact oxidation tank and the reflux liquid of the contact oxidation tank 5, and the carbon-containing organic matter in the wastewater provides energy for denitrifying bacteria to continue to degrade organic pollutants, reducing nitrate nitrogen to nitrogen gas that escapes from the water, thereby achieving the purpose of removing total nitrogen. The CODcr degradation rate of the effluent after treatment by the anaerobic MBBR tank 4 influent and the contact oxidation tank 5 reaches 85-86.7%, the ammonia nitrogen removal rate reaches 50-60%, and the total nitrogen removal rate reaches 66.7-76.9%.

[0074] In this embodiment, the second sedimentation tank 6 is used to separate the third liquid phase stream into mud and water to provide a fourth liquid phase stream and a second sludge; the second sedimentation tank 6 is fluidically connected to the contact oxidation tank 5 .

[0075] In this embodiment, the second sedimentation tank 6 is an inclined plate sedimentation tank.

[0076] In this embodiment, the second sedimentation tank 6 is provided with a mud outlet and a water outlet. The mud outlet of the second sedimentation tank 6 is fluidly connected to the sludge thickening tank 7 via the second sludge discharge pipe 61, and the water outlet of the second sedimentation tank 6 is connected to the water discharge pipe 62 for discharging treated water.

[0077] In this embodiment, the sludge concentration tank 7 is used to concentrate the first sludge and the second sludge; the sludge concentration tank 7 is fluidically connected to the first sedimentation tank 2 and the second sedimentation tank 6 .

[0078] In this embodiment, a dehydrator 8 is further included; the dehydrator 8 is used to remove moisture from the first sludge and the second sludge; the dehydrator 8 is fluidly connected to the sludge concentration tank 7; a third sludge discharge pipeline 71 is further included; the sludge concentration tank 7 is fluidly connected to the dehydrator 8 via the third sludge discharge pipeline 71. The dehydrated sludge is processed by an external transportation and disposal device 9.

[0079] Working principle of the utility model

[0080] After the coating wastewater is collected by quality separation and regulated and homogenized, it enters the physicochemical reaction tank 1 for physicochemical reaction to generate a mud-water mixture, and the mud-water is separated by the first sedimentation tank 2 to obtain a first sludge and a first liquid phase stream. The first sludge enters the sludge concentration tank 7 through the first sludge discharge pipe 21. The first liquid phase stream enters the intermediate water tank 3 for regulation, and is lifted to the anaerobic MBBR tank 4 by a water pump for biochemical reaction to improve the biodegradability of the wastewater. The obtained second liquid phase stream enters the contact oxidation tank 5 for aerobic biochemical treatment to further remove organic pollutants and ammonia nitrogen in the water body. The obtained third liquid phase stream passes through the liquid reflux pipe 51 and the water pump in the contact oxidation tank 5 to mix the reflux liquid of the contact oxidation tank 5 with the wastewater inlet water in the anaerobic MBBR tank 4. The carbon-containing organic matter in the reflux wastewater provides energy for the denitrifying bacteria to continue to degrade organic pollutants, and reduce nitrate nitrogen to nitrogen gas to escape from the water, thereby achieving the purpose of removing total nitrogen. The water treated by the anaerobic MBBR tank 4+contact oxidation tank 5 is passed into the second sedimentation tank 6 for mud-water separation to obtain second sludge and treated water. The second sludge enters the sludge concentration tank 7 through the second sludge discharge pipe 61, and the treated water is discharged through the effluent discharge pipe 62. The sludge in the sludge concentration tank 7 is dehydrated by the dehydrator 8 and then transported to the external treatment equipment 9 for external treatment.

[0081] Example

[0082] The treatment process of the anaerobic MBBR+contact oxidation treatment system of the utility model is as follows: after the coating wastewater is collected by quality separation and regulated and homogenized, it enters the physicochemical reaction tank 1 for physicochemical reaction to generate a mud-water mixture, and the mud-water is separated through the first sedimentation tank 2 to obtain a first sludge and a first liquid phase stream. The first sludge enters the sludge concentration tank 7 through the first sludge discharge pipe 21, and the first liquid phase stream enters the intermediate water tank 3 for regulation, and is lifted to the anaerobic MBBR tank 4 by a water pump for biochemical reaction to improve the biodegradability of the wastewater. The obtained second liquid phase stream enters the contact oxidation tank 5 for aerobic biochemical treatment to further remove organic pollutants and ammonia nitrogen in the water body. The obtained third liquid phase stream passes through the liquid reflux pipe 51 and the water pump in the contact oxidation tank 5, so that the reflux liquid of the contact oxidation tank 5 and the wastewater inlet of the anaerobic MBBR tank 4 are mixed, and the carbon-containing organic matter in the reflux wastewater provides energy for the denitrifying bacteria to continue to degrade the organic pollutants, and reduce the nitrate nitrogen to nitrogen gas to escape from the water, thereby achieving the purpose of removing total nitrogen. The water treated by the anaerobic MBBR tank 4+contact oxidation tank 5 is passed into the second sedimentation tank 6 for mud-water separation to obtain second sludge and treated water. The second sludge enters the sludge concentration tank 7 through the second sludge discharge pipe 61, and the treated water is discharged through the effluent discharge pipe 62. The sludge in the sludge concentration tank 7 is dehydrated by the dehydrator 8 and then transported to the external treatment equipment 9 for external treatment.

[0083] The conventional treatment system is a hydrolysis acidification + contact oxidation method, which uses hydrolysis acidification to replace the anaerobic MBBR, and lacks a process for setting up liquid backflow from the contact oxidation tank 5 to the hydrolysis acidification tank.

[0084] The initial COD of the coating wastewater in this example Cr The content is 1000-1500 mg / L, the ammonia nitrogen content is 10-25 mg / L, and the total nitrogen content is 30-65 mg / L.

[0085] The comparison of the average water quality of the effluent from the improved coating wastewater treatment system of the utility model and the conventional treatment system is shown in the following table:

[0086]

[0087] The treated water quality of the existing wastewater treatment system of the vehicle factory meets the discharge standards. According to the data in the above table, the COD Cr The degradation rate of COD in conventional process is 85% to 86.7%; the degradation rate of ammonia nitrogen is 50% to 60%; the degradation rate of total nitrogen is 66.7% to 76.9%; Cr The degradation rate of (mg / L) is 80% to 82.67%; the degradation rate of ammonia nitrogen is 20% to 40%; the degradation rate of total nitrogen is 50% to 69.2%; From the treatment results, it can be seen that the anaerobic MBBR+contact oxidation process of the utility model has a significant effect on COD Cr The removal efficiency of ammonia nitrogen and total nitrogen is higher, and the effluent water quality is more stable. As a new treatment process, the industrial wastewater treatment system has broad application prospects.

[0088] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed in the present invention shall still be covered by the claims of the present invention.

Claims

1. An improved coating wastewater treatment system, characterized in that: include: A physicochemical reaction tank (1) is used to perform physicochemical reaction treatment on the coating wastewater to be treated to provide a first sludge mixed liquid; A first sedimentation tank (2) is used to separate the first sludge mixed liquid into mud and water to provide a first liquid phase stream and a first sludge; the first sedimentation tank (2) is fluidically connected to the physicochemical reaction tank (1); An anaerobic MBBR tank (4) is used to subject the first liquid phase stream to a biochemical reaction to provide a second liquid phase stream; the anaerobic MBBR tank (4) is fluidically connected to the first precipitation tank (2); A contact oxidation tank (5) is used to aerobically biochemically treat the second liquid phase stream to provide a third liquid phase stream; the contact oxidation tank (5) is fluidically connected to the anaerobic MBBR tank (4); A liquid return pipe (51), wherein the contact oxidation tank (5) is in fluid communication with the anaerobic MBBR tank (4) via the liquid return pipe (51); The second sedimentation tank (6) is used to separate the third liquid phase flow from mud and water to provide a fourth liquid phase flow and a second sludge; the second sedimentation tank (6) is fluidically connected to the contact oxidation tank (5).

2. The improved painting wastewater treatment system according to claim 1, characterized in that: It also includes a sludge concentration tank (7) for concentrating the first sludge and the second sludge; the sludge concentration tank (7) is fluidically connected to the first sedimentation tank (2) and the second sedimentation tank (6).

3. The improved painting wastewater treatment system according to claim 1, characterized in that: The first sedimentation tank (2) and the second sedimentation tank (6) are inclined plate sedimentation tanks respectively.

4. The improved painting wastewater treatment system according to claim 1, characterized in that: The anaerobic MBBR tank (4) is provided with a stirring unit.

5. The improved painting wastewater treatment system according to claim 1, characterized in that: The anaerobic MBBR tank (4) is provided with suspended fillers.

6. The improved painting wastewater treatment system according to claim 2, characterized in that: It also includes a first sludge discharge pipeline (21); the first sedimentation tank (2) is fluidically connected to the sludge concentration tank (7) via the first sludge discharge pipeline (21).

7. The improved painting wastewater treatment system as claimed in claim 2, characterized in that: It also includes a second sludge discharge pipeline (61); the second sedimentation tank (6) is fluidically connected to the sludge concentration tank (7) via the second sludge discharge pipeline (61).

8. The improved painting wastewater treatment system according to claim 1, characterized in that: An intermediate water tank (3) is provided between the first sedimentation tank (2) and the anaerobic MBBR tank (4); the intermediate water tank (3) is fluidically connected to the first sedimentation tank (2) and the anaerobic MBBR tank (4), respectively.

9. The improved painting wastewater treatment system as claimed in claim 8, characterized in that: A water pump is provided on the connecting pipeline between the intermediate water tank (3) and the anaerobic MBBR tank (4).

10. The improved painting wastewater treatment system according to claim 2, characterized in that: It also includes a dewatering machine (8); the dewatering machine (8) is used to remove moisture from the first sludge and the second sludge; the dewatering machine (8) is fluidically connected to the sludge thickening tank (7); and it also includes a third sludge discharge pipeline (71); the sludge thickening tank (7) is fluidically connected to the dewatering machine (8) via the third sludge discharge pipeline (71).

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