Oily wastewater purification and direct discharge treatment system and method

Abstract

The present invention discloses a system and method for purifying and directly discharging oil-containing wastewater, and belongs to the field of water treatment. The system and method for purifying and directly discharging oil-containing wastewater include a sewage tank and a demulsification-oil removal module, wherein the sewage tank is connected to the demulsification-oil removal module downstream, and the demulsification-oil removal module includes: a pre-oil removal tank, wherein the pre-oil removal tank is provided with a first oil overflow port; a demulsification tank, wherein a partition is provided in the demulsification tank, wherein the partition divides the demulsification tank into a first chamber and a second chamber, wherein the distance between the partition and the bottom of the demulsification tank is greater than zero; a cavitation generating device is connected between the first chamber and the second chamber; an electrocatalytic module is also provided in the demulsification tank; and a static tank, wherein the static tank is connected to the sewage tank downstream. The system and method for purifying and directly discharging oil-containing wastewater provided by the present invention are used to treat industrial oil-containing wastewater, and the treatment efficiency is high, the treatment capacity is large, and the COD treatment effect is obvious. The system and method are applied to the field of sewage purification and direct discharge, and have broad application prospects.

Description

Technical Field

[0001] The invention relates to the field of oily wastewater purification treatment using cavitation-enhanced electrocatalysis, and in particular to an oily wastewater purification direct discharge treatment system and method. Background Art

[0002] Hydraulic cavitation refers to the artificial creation of a low pressure and high flow rate at a certain point in the pipeline where the liquid passes. When the liquid pressure is less than the saturated vapor pressure, the bubbles in the liquid will continue to expand and increase in volume. As the fluid moves, the bubbles will collapse and burst after reaching the high pressure and low flow rate area. When they collapse sharply, they can release huge energy in the extremely small space around them, instantly generating local high temperature and high pressure, and high-speed microjets with strong impact force, with a collision density of up to 1.5kg / cm2. In the process of rapid collapse, bubbles produce extremely complex physical, chemical and biological effects, etc., which have been widely used in cavitation cleaning, sewage treatment, disinfection and sterilization, food and pharmaceuticals, chemical catalysis and other fields, and have great industrial prospects.

[0003] Oily wastewater usually contains high concentrations of organic matter. If it is directly discharged into natural water bodies, it will cause serious eutrophication problems. It needs to be treated to reduce the organic matter to a certain concentration before it can be discharged. At present, the mainstream method of oxidizing large molecular organic matter into small molecular organic matter and finally mineralizing it into CO2, H2O and a small amount of inorganic salts is electrocatalysis. However, if wastewater with a high oil content is directly oxidized by electrocatalysis, the grease covering the electrode surface will reduce its effective area, affect the reaction efficiency of the electrode plate, and lead to increased energy consumption.

[0004] In the prior art, cavitation methods are usually combined with electrocatalysis or photocatalysis to produce hydroxyl radicals, but most of the current cavitation methods use a venturi tube or a perforated plate, and the connection method of multiple processes usually adopts a series method. The reaction liquid after the cavitation reaction is then electrocatalyzed, and the reaction liquid after the electrocatalysis is further flocculated and finally filtered; the venturi tube and the perforated plate reactor have the disadvantages of easy clogging, large pressure loss, energy dispersion, and weak cavitation intensity; there is also a method of placing the electrocatalytic device and the ultrasonic cavitator in the same reaction tank to treat the wastewater, but ultrasound is suitable for cavitation treatment of liquids in a small range or small volume. For large-scale projects with high hourly processing requirements, ultrasonic cavitation consumes too much energy and is not suitable for large-scale industrial promotion and application. Summary of the invention

[0005] In order to solve the deficiencies in the above-mentioned prior art solutions, the present invention provides a purification and direct discharge treatment system for oily wastewater, which has high treatment efficiency, large treatment capacity and obvious COD treatment effect.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The oily wastewater purification and direct discharge treatment system comprises a sewage pool and a demulsification-oil removal module. The downstream of the sewage pool is connected to the demulsification-oil removal module. The demulsification-oil removal module comprises the following arranged in sequence:

[0008] A front oil removal tank, wherein the front oil removal tank is provided with a first oil overflow port;

[0009] A demulsification tank, wherein a partition is provided in the demulsification tank, wherein the partition divides the demulsification tank into a first chamber and a second chamber, wherein a cavitation generating device is connected between the first chamber and the second chamber; and an electrocatalytic module is also provided in the demulsification tank;

[0010] A settling tank is connected to the sewage tank downstream.

[0011] Preferably, the distance between the partition and the bottom of the demulsification tank is greater than zero; and the electrocatalytic module is arranged in the second chamber.

[0012] Preferably, a pre-filter and a liquid inlet pump are provided in sequence between the sewage pool and the demulsification-oil removal module; and a paper belt filter is also provided between the liquid inlet pump and the demulsification-oil removal module.

[0013] Preferably, the front oil removal tank is provided with an oil collecting tank below the first oil overflow port.

[0014] Preferably, a U-shaped pipe communicating with the demulsification tank is provided in the front oil removal tank.

[0015] Preferably, outside the demulsification tank, the liquid inlet end of the cavitation generating device is connected to the first chamber, a high-pressure pump is connected between the cavitation generating device and the first chamber; and the liquid outlet end of the cavitation generating device is connected to the second chamber.

[0016] Preferably, the cavitation generating device comprises:

[0017] A container, wherein the inner diameter of the container decreases from top to bottom;

[0018] A liquid inlet pipe, wherein the liquid input by the liquid inlet pipe descends in a spiral shape along the inner wall of the container;

[0019] A liquid outlet pipe, the liquid outlet pipe is inserted into the container, and from bottom to top, the liquid outlet pipe has a section with a reduced inner diameter, a section with a larger inner diameter, and a section with a constant inner diameter arranged in sequence;

[0020] A flow guide, which is arranged at the bottom of the container and is located below the section where the inner diameter decreases; from bottom to top, the outer diameter of the flow guide first remains unchanged and then gradually decreases;

[0021] The guide member has a gas passage inside, and the gas passage is connected to a negative pressure gauge and a one-way valve.

[0022] Preferably, the electrocatalytic module comprises electrodes, a power source, and an electrode cover, wherein the positive and negative electrodes of the electrodes are alternately distributed in the electrode cover, and the electrodes are electrically connected to the power source outside the demulsification tank;

[0023] Preferably, the static pool is provided with a second oil overflow port, and a lead-out pipe is provided at the bottom of the static pool, and the lead-out pipe is connected to the liquid outlet.

[0024] The present invention also provides a method for purifying and directly discharging oily wastewater according to the oily wastewater purification and direct discharge treatment system, and the treatment method comprises the following steps:

[0025] S1. Pump the oily wastewater out of the sewage pool through the liquid inlet pump, filter the solid particles through the filter, and introduce the filtrate into the pre-oil removal tank;

[0026] S2, the first stage of oil removal is carried out in the front oil removal tank through gravity sedimentation, and the wastewater after oil removal enters the demulsification tank;

[0027] S3, preliminarily demulsifying the wastewater by hydraulic cavitation reaction in the demulsification tank, converting part of the emulsified oil into floating oil, and then performing electrocatalytic oxidation reaction in the electrocatalytic module to further degrade the emulsified oil and floating oil;

[0028] S4. Floating oil and wastewater enter the static tank, and the floating oil is further floated up through the filler or inclined plate device, and the lower layer of clean liquid is discharged to the sewage tank through the outlet for the next cycle.

[0029] Furthermore, in step S1, the sewage is first coarsely filtered through a pre-filter and then finely filtered through a paper belt filter, and the filtrate is introduced into a pre-oil removal tank.

[0030] Furthermore, in step S2, the liquid level of the front oil removal tank is adjusted by the U-shaped tube, the liquid level drops to the first oil overflow port, the first-stage oil removal is performed, and the U-shaped tube introduces the lower layer of wastewater into the demulsification tank.

[0031] Furthermore, in step S3, the liquid in the first chamber is pumped to the cavitation generating device by a high-pressure pump, and the liquid after hydraulic cavitation enters the second chamber. The liquid is connected in the gap between the partition and the bottom of the demulsification tank, thereby realizing the liquid circulation cavitation treatment of the demulsification tank.

[0032] Furthermore, gas is introduced into the cavitation generating device from the gas channel in the guide member, and after the cavitation liquid is gas-dissolved, the cavitation liquid containing a large number of bubbles is sent to the demulsification tank.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The hydrodynamic cavitation electro-oxidation process is adopted. On the one hand, the high-speed fluid and turbulence effect of the hydrodynamic cavitation are used to optimize the polarization phenomenon on the electrode surface. At the same time, the microbubbles generated by electrochemistry can increase the aggregation and floating speed of small oil droplets in the water, and optimize the efficiency of cavitation oil removal;

[0035] 2. Remove particulate matter through filtration, undergo primary oil removal, and then undergo hydraulic cavitation and electrocatalytic reaction to circulate the oily wastewater for more thorough oil removal, with a significant degradation of the COD value of the oily wastewater;

[0036] 3. The cavitation generating device of the present invention first accelerates the swirl flow along the inner wall of the container, and then guides the flow through the guide member to increase the rising speed of the liquid flow, with high cavitation intensity and good cavitation effect; and the cavitation generating device has a large processing volume per unit time and high cavitation efficiency;

[0037] 4. A cavitation generator is connected to the bottom of the demulsification tank liquid for cavitation treatment. An electrocatalytic module is set on the top of the demulsification tank. The small bubbles and microjets generated by cavitation can clean the oil attachments attached to the electrode surface, improve the electrocatalytic reaction environment, and enhance the electrocatalytic reaction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the technical roadmap of the oily wastewater purification and direct discharge treatment system of the present invention.

[0039] Figure 2 It is a system structure diagram of the oily wastewater purification direct discharge treatment system of the present invention.

[0040] Figure 3 is a schematic diagram of the electrocatalytic module.

[0041] Figure 4 It is a schematic diagram of the three-dimensional structure of the electrocatalytic module according to an embodiment of the present invention.

[0042] Figure 5 It is a schematic diagram of the three-dimensional structure of the electrode cover according to an embodiment of the present invention.

[0043] In the figure: sewage tank 1, pre-filter 2, liquid inlet pump 3, paper belt filter 4, pre-oil removal tank 5, first oil overflow port 51, demulsification tank 6, partition 61, U-shaped tube 62, static tank 7, second oil overflow port 71, liquid outlet 72, lead-out pipe 73, cavitation generating device 8, negative pressure gauge 81, positive pressure gauge 82, high-pressure pump 9, electrocatalytic module 10, electrode 101, power supply 102, electrode cover 103, strip hole 1030, electrode cover plate 104, conductive column 105, observation door 106, oil collecting tank 11. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0045] like Figure 1 As shown, the oily wastewater purification direct discharge treatment system includes a sewage tank, a pre-filter, a paper belt filter, and a demulsification-oil removal module arranged in sequence. The demulsification-oil removal module includes a pre-oil removal tank, an electrocatalytic / demulsification tank, and a static tank in sequence. The electrocatalytic / demulsification tank is connected to a cavitation generating device.

[0046] like Figure 2 As shown, the sewage tank 1 is connected to the pre-filter 2, and the downstream of the pre-filter 2 is connected to the paper belt filter 4. The pipeline connection section between the pre-filter 3 and the paper belt filter 4 is provided with a liquid inlet pump 3. The filtrate filtered by the pre-filter 2 and the paper belt filter 4 enters the pre-oil removal tank 5. The pre-oil removal tank 5 is provided with a first oil overflow port 51. The pre-oil removal tank 5 is connected to the demulsification tank 6 through a U-shaped tube 62. The liquid level of the pre-oil removal tank 5 is adjusted by the U-shaped tube 62. When the liquid level drops to the first oil overflow port 51, the floating oil overflows from the first oil overflow port 51 to the oil collecting tank 11, and the lower waste liquid enters the demulsification tank 6 through the U-shaped tube 62.

[0047] like Figure 2 As shown, the electrocatalytic module 10 is immersed in the demulsification tank 6. Figure 3-Figure 4 The electrocatalytic module 10 includes an electrode 101, a power supply 102, an electrode cover 103, and a plurality of positive and negative electrodes 101, which are staggered in the motor cover 103. A detachable electrode cover 104 is provided on the electrode cover 103, and the electrode cover is made of insulating material, such as PP plastic. The electrode cover 104 serves as a cover of the demulsification tank 6, covering the demulsification tank 6. An observation door 106 is also provided on the electrode cover 104. Open the observation door to observe the electrocatalytic reaction. The electrode 101 passes through the electrode cover 104 and is connected by a conductive column 105. One conductive column is connected to the positive electrode and the other is connected to the negative electrode, which are respectively connected to the positive and negative electrodes of the power supply. In order to increase the electrochemical reaction area, two groups of positive and negative conductive columns are selected in this embodiment. The electrode cover 103 is a hollow structure, and a plurality of strip holes 1030 are provided around and at the bottom of the electrode cover to connect the liquid inside and outside the electrode cover. The electrode cover is made of insulating material. The electrocatalytic module 10 is immersed in the demulsification tank 6, and the electrode cover 103 protects the electrode to prevent the electrode from contacting the metal parts of the external water tank and causing a short circuit.

[0048] like Figure 2 As shown, a partition 61 is provided in the demulsification tank 6, and the partition 61 divides the demulsification tank 6 into a first chamber and a second chamber, and the distance between the bottom of the partition 61 and the bottom of the demulsification tank 6 is greater than zero. Outside the demulsification tank 6, a cavitation generating device 8 is connected between the first chamber and the second chamber, the liquid inlet end of the cavitation generating device 8 is connected to the high-pressure pump 9, the liquid inlet end of the high-pressure pump 9 is connected to the first chamber, and the liquid outlet end of the cavitation generating device is connected to the second chamber.

[0049] The cavitation generating device 8 includes a container and a liquid inlet pipe, which is connected to a high-pressure pump 9. The inner diameter of the container decreases from top to bottom. The liquid inlet pipe is arranged at the upper part of the container, and the liquid input from the liquid inlet pipe descends in a spiral shape along the inner wall of the container.

[0050] The cavitation generating device also includes:

[0051] A liquid outlet pipe connected to the second chamber of the demulsification tank 6, the liquid outlet pipe is inserted into the container, and from bottom to top, the liquid outlet pipe has a section with a reduced inner diameter, a section with a large inner diameter, and a section with a constant inner diameter arranged in sequence;

[0052] The flow guide is arranged at the bottom of the container and is located at the lower side of the section where the inner diameter decreases; from bottom to top, the outer diameter of the flow guide remains unchanged at first and then gradually decreases.

[0053] With this cavitation generating device, the liquid flows from the inner wall of the container, descends in a spiral shape, accelerates, and enters from the lower end of the liquid outlet pipe. Near the intersection of the smaller inner diameter section and the larger inner diameter end section of the liquid outlet pipe, a hydraulic cavitation effect occurs, and negative pressure is generated. Due to the provision of a flow guide, the liquid flow can be guided to quickly discharge from the liquid outlet pipe, avoiding blockage and achieving higher cavitation efficiency.

[0054] The guide member has a gas channel inside, and the gas channel is connected to a negative pressure gauge 81 and a one-way valve; the liquid inlet pipe and the high-pressure pump are connected to a positive pressure gauge 82. Gas is introduced from the gas channel inside the guide member of the cavitation generating device using the negative pressure generated by cavitation, so as to further dissolve the cavitation liquid, increase the amount of cavitation bubbles, stir the liquid in the demulsification tank, and accelerate the contact between the liquid and the electrocatalytic electrode and the oxidation reaction.

[0055] A hydraulic cavitation device is provided at the bottom of the demulsification tank 6 to perform circulatory cavitation treatment on the liquid in the demulsification tank 6, and the cavitated liquid is then subjected to an electrocatalytic oxidation reaction through the electrocatalytic module 10. Under the dual effects of electrocatalysis and hydraulic cavitation, on the one hand, the polarization phenomenon of the electrode surface is optimized by utilizing the cavitated high-speed fluid and small liquid particle size, and at the same time, the microbubbles used in electrochemistry can increase the aggregation and floating speed of small oil droplets in water, thereby optimizing the efficiency of cavitation oil removal.

[0056] The liquid and floating oil after hydrodynamic cavitation and electrocatalysis overflow into the static pool 7, where the small oil droplets gather into large oil droplets through the packing layer or the inclined plate device, and the floating oil floats to the second oil overflow port 71, and enters the oil collecting tank 11 through the second oil overflow port 71. After standing, the lower layer of clean liquid is output from the bottom lead-out pipe 73 and discharged through the liquid outlet 72. The liquid outlet 72 is connected to the sewage pool 1.

[0057] The oil removal module forms a circulation loop with the sewage pool, which can circulate the oily wastewater in the sewage pool for multiple times to enhance the oil removal effect and improve the treatment efficiency.

[0058] The purpose of the present invention is also to provide a method for purifying and directly discharging oily wastewater, and the purpose of the invention is achieved through the following technical solutions:

[0059] According to the treatment method of the oily wastewater purification direct discharge treatment system, the treatment method comprises the following steps:

[0060] S1. The oily wastewater is pumped out from the sewage pool by a liquid inlet pump, solid particles are filtered through a filter, and the filtrate is introduced into the pre-oil removal tank; the wastewater is first coarsely filtered through the pre-filter, and then finely filtered through a paper belt filter, and the filtered filtrate is introduced into the pre-oil removal tank;

[0061] S2, the first oil removal is carried out in the front oil removal tank by gravity sedimentation, and the wastewater after oil removal enters the demulsification tank; in the front oil removal tank, the liquid level is adjusted by the U-shaped pipe, the liquid level drops to the first oil overflow port, and overflows to the oil collecting tank through the first oil overflow port for the first oil removal, and the U-shaped pipe introduces the lower layer of wastewater into the demulsification tank;

[0062] S3, in the demulsification tank, the wastewater is preliminarily demulsified by hydraulic cavitation reaction, part of the emulsified oil is converted into floating oil, and then an electrocatalytic oxidation reaction is carried out through the electrocatalytic module to further degrade the emulsified oil and floating oil; the demulsification tank is divided into two chambers by a partition, and the distance between the partition and the bottom of the tank is greater than zero. The liquid in the first chamber is pumped to the cavitation generating device through a high-pressure pump, and the cavitated liquid is pumped into the second chamber. The liquid is connected in the gap between the partition and the bottom of the demulsification tank, so as to realize the circulated cavitation treatment of the demulsification tank; gas is introduced into the cavitation generating device from the gas channel in the guide member, and the cavitation liquid containing a large number of bubbles is sent to the demulsification tank after the cavitation liquid is dissolved; the cavitation liquid is then subjected to an electrocatalytic oxidation reaction through the electrocatalytic module, and small oil droplets gather and float to form large oil droplets;

[0063] S4. The floating oil in the demulsification tank and the lower layer of wastewater enter the static tank. Through the filler or inclined plate and other devices, the floating oil is further floated up and overflows to the oil collecting tank through the second oil overflow port. The lower layer of clean liquid is discharged to the sewage tank through the liquid outlet for the next cycle.

[0064] The system and method for purifying and directly discharging oily wastewater mentioned in the present invention are described below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the invention.

[0065] Example

[0066] For 1.5m 3 The oily wastewater is extracted from the wastewater pool, filtered through the pre-filter for coarse filtration, and then finely filtered through the paper belt filter. The filtrate is sent to the pre-oil removal tank, and after the first-level oil removal, the lower layer of wastewater after oil removal enters the demulsification tank, where it is cavitated by the cavitation generating device. The hydraulic cavitation inlet pressure is 0.5-0.7MPa, and the treatment flow rate is 0.5m 3 / h, and then undergo electrocatalytic oxidation reaction, the electrocatalytic voltage is 10-12V, the cavitation time is 3 hours, and the electrocatalysis and cavitation are carried out simultaneously, which can reduce the COD of oily wastewater from 7000-10000mg / L to 300mg / L.

[0067] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. Oily wastewater purification and direct discharge treatment system, characterized in that: It includes a sewage pool and a demulsification-oil removal module. The downstream of the sewage pool is connected to the demulsification-oil removal module. The demulsification-oil removal module includes the following arranged in sequence: A front oil removal tank, wherein the front oil removal tank is provided with a first oil overflow port; A demulsification tank, wherein a partition is provided in the demulsification tank, and the partition divides the demulsification tank into a first chamber and a second chamber; a cavitation generating device is connected between the first chamber and the second chamber; and an electrocatalytic module is also provided in the demulsification tank; a stilling tank, wherein the stilling tank is connected downstream to the sewage tank; The distance between the partition and the bottom of the demulsification tank is greater than zero; the electrocatalytic module is arranged in the second chamber; The front oil removal tank is provided with a U-shaped pipe connected to the demulsification tank; Outside the demulsification tank, the liquid inlet end of the cavitation generating device is connected to the first chamber, and a high-pressure pump is connected between the cavitation generating device and the first chamber; The liquid outlet end of the cavitation generating device is connected to the second chamber; The cavitation generating device comprises: A container, wherein the inner diameter of the container decreases from top to bottom; A liquid inlet pipe, wherein the liquid input by the liquid inlet pipe descends in a spiral shape along the inner wall of the container; A liquid outlet pipe, the liquid outlet pipe is inserted into the container, and the liquid outlet pipe has, from bottom to top, a section with a reduced inner diameter, a section with a larger inner diameter, and a section with a constant inner diameter arranged in sequence; A flow guide, which is arranged at the bottom of the container and is located below the section where the inner diameter decreases; from bottom to top, the outer diameter of the flow guide first remains unchanged and then gradually decreases; The guide member has a gas passage inside, and the gas passage is connected to a negative pressure gauge and a one-way valve.

2. The oily wastewater purification and direct discharge treatment system according to claim 1 is characterized in that: A pre-filter and a liquid inlet pump are arranged in sequence between the sewage pool and the demulsification-oil removal module; and a paper belt filter is also arranged between the liquid inlet pump and the demulsification-oil removal module.

3. The oily wastewater purification and direct discharge treatment system according to claim 1 is characterized in that: The front oil removal tank is provided with an oil collecting tank below the first oil overflow port.

4. The oily wastewater purification and direct discharge treatment system according to claim 1 is characterized in that: The electrocatalytic module comprises an electrode, an electrode cover, and a power source. The positive and negative electrodes of the electrode are alternately distributed in the electrode cover, and the electrode is electrically connected to the power source outside the demulsification tank.

5. The oily wastewater purification and direct discharge treatment system according to claim 1 is characterized in that: The static pool is provided with a second oil overflow port, and a lead-out pipe is provided at the bottom of the static pool, and the lead-out pipe is communicated with the liquid outlet.

6. The oily wastewater purification and direct discharge treatment system according to any one of claims 1 to 5 is used in an oily wastewater purification and direct discharge treatment method, characterized in that: The processing method comprises the following steps: S1. Pump the oily wastewater out of the sewage pool through the liquid inlet pump, filter the solid particles through the filter, and introduce the filtrate into the pre-oil removal tank; S2, the first stage of oil removal is carried out in the front oil removal tank through gravity sedimentation, and the wastewater after oil removal enters the demulsification tank; S3, in the demulsification tank, the wastewater is preliminarily demulsified by a hydraulic cavitation reaction, part of the emulsified oil is converted into floating oil, and then an electrocatalytic oxidation reaction is carried out in the electrocatalytic module to further degrade the emulsified oil and floating oil; the liquid flow is accelerated through a spiral descent from the inner wall of the container of the cavitation generating device, enters from the lower end of the liquid outlet pipe, and a hydraulic cavitation effect occurs near the intersection of the end section with a smaller inner diameter and the end section with a larger inner diameter of the liquid outlet pipe; S4. Floating oil and wastewater enter the static tank through overflow. The floating oil is further floated up through the filler or inclined plate device, and the lower clean liquid is discharged to the sewage tank through the outlet for the next cycle.

7. The method for purifying and directly discharging oily wastewater according to claim 6, characterized in that: In the step S1, the sewage is firstly coarsely filtered through a pre-filter and then finely filtered through a paper belt filter, and the filtrate is introduced into a pre-oil removal tank.

8. The method for purifying and directly discharging oily wastewater according to claim 6, characterized in that: In step S2, the liquid level of the front oil removal tank is adjusted by the U-shaped tube, and the liquid level drops to the first oil overflow port to perform the first stage of oil removal. The U-shaped tube introduces the lower layer of wastewater into the demulsification tank.

9. The method for purifying and directly discharging oily wastewater according to claim 6, characterized in that: In step S3, the liquid in the first chamber is pumped to the cavitation generating device by a high-pressure pump, and the liquid after hydraulic cavitation enters the second chamber. The liquid is connected in the gap between the partition and the bottom of the demulsification tank, thereby realizing the circulation cavitation treatment of the liquid in the demulsification tank.

10. The method for purifying and directly discharging oily wastewater according to claim 9, characterized in that: Gas is introduced into the cavitation generating device from the gas channel in the guide member, and after the cavitation liquid is dissolved with gas, the cavitation liquid containing a large number of bubbles is sent to the demulsification tank.

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