Device and method for purifying laundry wastewater through foam fractionation

Abstract

A device and method for purifying laundry wastewater through foam fractionation relates to the field of laundry wastewater treatment, and comprises a water tank, a water pump, a Venturi type water ejector, a foam discharge pipe and a defoaming device which are arranged in sequence; a water inlet of the water pump is connected with the water tank through a pipeline, a water outlet of the water pump is connected with an inlet of the Venturi type water ejector through a pipeline, and an outlet of the Venturi type water ejector is connected to the bottom of the water tank through a pipeline. A suction chamber of the venturi type water ejector is provided with a suction port for automatically sucking external air; one end of the foam discharge pipe is connected with the upper part of the water tank, and the other end of the foam discharge pipe extends above the defoaming device. The device is simple, the operation cost is low, the surfactant in the laundry wastewater can be effectively removed and recycled, and turbidity and organic matter in the laundry wastewater can be removed at the same time.

Description

Technical Field

[0001] The invention relates to the field of laundry wastewater treatment, and in particular to a device and method for purifying laundry wastewater through foam fractionation. Background Art

[0002] Laundry wastewater contains a large amount of anionic surfactants (mainly sodium dodecylbenzene sulfonate (SDBS)), which cannot be biodegraded by microbial metabolism when discharged to sewage treatment plants. Therefore, it is recommended that laundry wastewater be centrally treated at the source to avoid discharge into the sewer or to comply with regulations limiting the concentration of surfactants discharged into the sewer system.

[0003] At present, the most commonly used technologies for removing anionic surfactants from laundry wastewater are catalytic oxidation, ion exchange, membrane treatment, biosorption, chemical adsorption, coagulation / flocculation, filtration and foam fractionation. The high turbidity and large amount of fibers in laundry wastewater will cause pollution to the filter material. The coagulation process will produce a considerable amount of sludge production, and the usual coagulation process will also produce harmful residues such as metal hydroxides. The COD removal rate (32.42%) and turbidity removal rate (19.63%) of activated carbon adsorption are both low, and regeneration treatment is required. Foam fractionation is mostly in a distillation tower, and gas is blown into the liquid through an air compressor to produce bubbles. Summary of the invention

[0004] The object of the present invention is to solve the above-mentioned problems in the prior art and provide a device and method for purifying laundry wastewater by foam fractionation. The device of the present invention has a simple structure and low operating cost, can effectively remove or recover surfactants in laundry wastewater, and has a high foaming rate. The method of the present invention is simple and does not require the addition of chemical agents. It only needs to turn on the device switch to simultaneously remove surfactants, turbidity and organic matter in laundry wastewater.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] A device for purifying laundry wastewater by foam fractionation, comprising a water tank, a water pump, a venturi-type water ejector, a foam discharge pipe and a defoaming device which are arranged in sequence; the water inlet of the water pump is connected to the water tank through a pipeline, the water outlet of the water pump is connected to the inlet of the venturi-type water ejector through a pipeline, and the outlet of the venturi-type water ejector is connected to the bottom of the water tank through a pipeline; the suction chamber of the venturi-type water ejector is provided with an air suction port to automatically inhale external gas; one end of the foam discharge pipe is connected to the upper part of the water tank, and the other end extends to the top of the defoaming device.

[0007] A diffuser is arranged in the water tank and is installed at the end of the outlet pipe of the Venturi type water ejector.

[0008] The bottom of the water tank is connected to the water inlet pipeline of the water pump through a reflux pipe.

[0009] The bottom of the water tank is connected with a purified liquid discharge pipe.

[0010] A defoaming liquid reflux pipe is provided at the bottom of the defoaming device, and the outlet of the defoaming liquid reflux pipe is connected to the water inlet of the water pump through a pipeline.

[0011] An enriched liquid discharge pipe is also provided at the bottom of the defoaming device, and the enriched liquid discharge pipe and the defoaming liquid reflux pipe are connected to the bottom of the defoaming device through a tee.

[0012] The foam discharge pipe is arranged on the top of the water tank in an upward tilt and then connected downward to the top of the defoaming device, and the outlet is gradually reduced.

[0013] A method for purifying laundry wastewater through foam fractionation, the laundry wastewater in a water tank is circulated through a water pump and a pipeline, the water pump generates pressure on the laundry wastewater, and when passing through a venturi-type water ejector, negative pressure is formed in the suction chamber of the venturi-type water ejector, and external gas is automatically sucked in from the air intake port of the venturi-type water ejector, and mixed with the laundry wastewater to form an air-water emulsion; the air-water emulsion enters the water tank through the pipeline, and then enters the bottom of the water tank through a diffuser at the outlet of the pipeline, and bubbles gather and float up, completing foam fractionation in the water tank; the fractionated foam carries pollutants in the laundry wastewater through a foam discharge pipe and is separated from the purified liquid, and finally the fractionated foam passes through a defoaming device to become an enriched liquid for discharge or reflux treatment; finally, purified laundry wastewater is obtained at the bottom of the water tank.

[0014] The air intake port of the Venturi type water ejector can be directly opened or connected to O3 gas.

[0015] The water pump should be operated intermittently, starting for 10 to 15 minutes and then stopping for 5 to 10 minutes. After running for 30 minutes, the quality of the purified water is stable and the purified water and enriched liquid can be collected.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0017] 1. The device for purifying laundry wastewater of the present invention has a simple structure. The Venturi-type water ejector will automatically inhale external air when passing through the pressurized laundry wastewater to form an air-water emulsion, and then the air-water emulsion enters the water tank for foam fractionation. After the fractionated foam passes through the foam discharge pipe, the foam liquid retention rate is reduced, and it is refluxed through the defoaming liquid again, and the enrichment ratio of pollutants is increased. The structural advantage of the device of the present invention is that the gas generation and gas-water mixing are completed in the Venturi water ejector with a simple structure, and the water inlet tank is used as the foam fractionation place, avoiding the existence of an air compressor and a foam fractionation tower, and the effect is better than that of traditional air blowing fractionation, the bubble size generated is small, and the removal of pollutants is enhanced.

[0018] 2. The device for purifying laundry wastewater of the present invention is easy to operate. When in operation, the water pump only needs to be turned on to automatically inhale air, so there is no need to use an additional air compressor to supply gas. Without adding any chemical agents, the surfactant, suspended matter and organic matter in the laundry wastewater can be removed at the same time. The entire device only needs to provide energy for the water pump, so it can purify laundry wastewater at a low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0020] Figure 2 It is a schematic diagram of the structure of a Venturi type water ejector.

[0021] Figure numerals: water tank 1, water pump 2, venturi-type water ejector 3, circulation pipeline 4, foam discharge pipe 5, defoaming barrel 6, water inlet 11, purified liquid discharge pipe 12, first valve 41, second valve 42, third valve 43, flow meter 44, front pressure gauge 45, rear pressure gauge 46, diffuser 47, motor 61, defoaming basket 62, filter bag 63, enriched liquid discharge pipe 64, water ejector inlet 31, nozzle 32, suction chamber 33, throat section 34, expansion section 35, circular hole 36 at nozzle outlet, air intake 37, water ejector outlet 38. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0023] Example 1

[0024] See also Figure 1 The present invention is a device for purifying laundry wastewater by foam fractionation, comprising a water tank 1, a water pump 2, a venturi-type water ejector 3, a foam discharge pipe 5 and a defoaming barrel 6 which are arranged in sequence;

[0025] The water tank 1, the water pump 2 and the Venturi type water ejector 3 are connected in sequence through a circulation pipeline 4;

[0026] The water tank 1 can be used for foam fractionation. A water inlet 11 is provided on the top of the water tank 1. The water tank 1 can store one day's laundry wastewater of residents. A foam discharge pipe interface is also provided on the top of the water tank 1 to connect with the foam discharge pipe 5. A diffuser 47 is provided at the bottom of the water tank 1 and is connected with the Venturi-type water ejector 3 through a pipeline. An interface between a reflux pipe and a purified liquid discharge pipe 12 is provided at the bottom of the water tank 1. The outlet of the reflux pipe is connected with the water inlet of the water pump through a pipeline. A valve is installed on the purified liquid discharge pipe, and the outlet can be connected to a purified liquid collecting device.

[0027] The water inlet pipe of the water pump 2 is connected to the lower part of the water tank 1 and the defoaming barrel 6, and the water outlet of the water pump 2 is connected to the inlet of the Venturi-type water ejector 3. Specifically, a second valve 42 is installed on the water inlet pipeline of the water pump 2, and a third valve 43, a flow meter 44 and a front pressure gauge 45 are installed in sequence on the pipeline between the water pump 2 and the Venturi-type water ejector 3; the Venturi-type water ejector 3 is horizontally installed on the water outlet pipeline of the water pump, and a rear pressure gauge 46 is installed at the rear end, and the suction chamber 33 of the Venturi-type water ejector 3 is provided with an air intake port 37.

[0028] The foam discharge pipe 5 is arranged at the top of the water tank in an upward tilt and then connected downward to the top of the defoaming barrel, and the outlet is gradually narrowed.

[0029] The defoaming barrel 6 includes a defoaming basket 62 with a pore size of 1-2 mm, an 80-mesh filter bag 63 surrounding the defoaming basket, and a motor 61 that drives the defoaming basket to rotate. The foam enters the defoaming basket and turns into liquid, and the suspended matter carried by the foam is intercepted by the defoaming basket and the filter bag, and the enriched liquid flows into the defoaming barrel 6.

[0030] The lower part of the defoaming barrel 6 is connected to a defoaming liquid reflux pipe, the outlet of the defoaming liquid reflux pipe is connected to the water inlet of the water pump through a pipeline, and the reflux amount is controlled by a first valve 41; an enriched liquid discharge pipe 64 is also provided at the bottom of the defoaming liquid barrel, and the enriched liquid discharge pipe and the defoaming liquid reflux pipe are connected to the bottom of the defoaming barrel through a tee; after the device has been running for a period of time, the first valve 41 on the defoaming liquid reflux pipe is closed, and the valve on the enriched liquid discharge pipe 64 is opened to discharge the enriched liquid.

[0031] The water tank 1 and the defoaming barrel 6 can be arranged on a bracket with a certain height.

[0032] See also Figure 2The venturi-type water ejector of the present invention comprises a water ejector inlet 31, a nozzle 32, a suction chamber 33, a throat section 34, an expansion section 35, a circular hole 36 at the nozzle outlet, an air inlet 37, and a water ejector outlet 38; the water ejector inlet 31 is located at the starting end of the venturi-type water ejector and is the entrance for the laundry wastewater to enter the venturi-type water ejector; the nozzle 32 is immediately adjacent to the water ejector inlet, and the function of the nozzle is to accelerate the incoming laundry wastewater and concentrate it to flow to a smaller cross-sectional area, i.e., the throat section; the suction chamber 33 is immediately adjacent to the nozzle, and this area forms a low-pressure area due to the function of the nozzle, and can automatically inhale external gas; the suction chamber is provided with a suction The air inlet 37 is used for the entry of external gases such as air or ozone (O3); the throat section 34 is located after the suction chamber and is the narrowest part of the Venturi-type water ejector. The water flow reaches the maximum flow rate here, and the pressure drops to the minimum, forming a negative pressure to promote the inhalation of external gases; the throat section is followed by the expansion section 35, where the water flow gradually slows down and restores the pressure, and the gas is dispersed in the liquid phase in the form of tiny bubbles to form a gas-water emulsion; a circular hole 36 is opened at the nozzle outlet to further optimize the mixing effect of the water flow and the air flow; the water ejector outlet 38 is located after the expansion section and is the outlet for the gas-water emulsion to flow out of the Venturi-type water ejector.

[0033] The invention discloses a method for purifying laundry wastewater through foam fractionation. The laundry wastewater in a water tank generates a certain pressure through a water pump. When the laundry wastewater passes through a venturi-type water ejector on a water outlet pipeline of the water pump, a negative pressure is formed in the suction chamber of the venturi-type water ejector. External air is automatically sucked in from the air inlet of the venturi-type water ejector, and is mixed with the laundry wastewater to form an air-water emulsion. After the air-water emulsion enters the bottom of the water tank through a pipeline, it is released through a diffuser, and bubbles carrying surfactants and other pollutants begin to gather and float up, forming a foam layer on the upper part of the water tank. The foam fractionated from the liquid then passes through a foam discharge pipe on the top of the water tank and enters a rotating defoaming basket. Under the action of the defoaming basket, the foam becomes liquid, and pollutants such as surfactants are enriched in the defoaming liquid. In order to further improve the enrichment ratio of the surfactant, part of the defoaming liquid is refluxed into the pipeline for circulation treatment. After running for 30 minutes, a purified liquid with stable water quality can be obtained at the lower part of the water tank and discharged through a pipeline.

[0034] In this embodiment, the water tank stores 30 L of laundry wastewater; the laundry wastewater in the water tank is pumped through the water pump (flow rate Q = 2.5 m 3 / h, head H=20 m) is pressurized and enters the inlet of the Venturi type water ejector to generate a certain pressure (about 0.08~0.1 MPa). When passing through the Venturi type water ejector (length L=200mm, suction port diameter 20 mm), a negative pressure is formed in the suction chamber of the Venturi type water ejector, and air enters from the suction port of the Venturi type water ejector (the air intake flow rate is 15 L / min), and forms an air-water emulsion after mixing with the laundry wastewater; the air-water emulsion enters the bottom of the water tank through the pipeline, and then after being released through the diffuser, the bubbles gather and float up, and the foam distilled from the upper part of the water tank carries water and pollutants such as surfactants, suspended matter, and organic matter into the foam discharge pipe; the laundry wastewater at the lower part of the water tank after the initial distillation can be returned to the water inlet pipe of the water pump through the reflux pipe at the lower part of the water tank; after running for a certain period of time, the purified laundry wastewater is collected from the bottom of the water tank through the purified liquid discharge pipe. After the foam passes through the foam discharge pipe, it enters the defoaming basket, and the obtained defoaming liquid is circulated to the pipeline for further treatment, and is discharged for treatment after the operation of the device is completed.

[0035] In the method of use of this embodiment, in order to prevent the water temperature from rising and the loss of water with the foam, the water pump should be operated intermittently, starting for 15 minutes and stopping for 5 minutes. It has been determined that after running for 30 minutes, the SDBS concentration in the laundry wastewater dropped from 15.06 mg / L to 4.66 mg / L, the turbidity dropped from 31 NTU to 12 NTU, and the TOC dropped from 160.4 mg / L to 34.6 mg / L; after running for 60 minutes, the SDBS concentration in the laundry wastewater dropped from 15.06 mg / L to 3.56 mg / L, the turbidity dropped from 31 NTU to 10 NTU, and the TOC dropped from 160.4 mg / L to 30.6 mg / L. This embodiment obtains an enriched liquid volume of 6 L, a purified water volume of 24 L, and an SDBS enrichment ratio of 3.8.

[0036] Example 2

[0037] The laundry wastewater to be treated in this embodiment has an SDBS concentration of 10.98 mg / L, a turbidity of 26 NTU, and a TOC concentration of 157.9 mg / L;

[0038] The difference between this embodiment and embodiment 1 is that the water pump is intermittently operated, starting for 10 minutes and stopping for 10 minutes. After 30 minutes of operation, the SDBS concentration in the laundry wastewater was measured to be reduced from 10.98 mg / L to 3.01 mg / L, the turbidity was reduced from 26 NTU to 13 NTU, and the TOC was reduced from 157.9 mg / L to 37.1 mg / L. In this embodiment, the volume of the enriched liquid was 5 L, the volume of the purified water was 25 L, and the SDBS enrichment ratio was 4.6.

[0039] Example 3

[0040] In this example, the laundry wastewater to be treated has an SDBS concentration of 10.28 mg / L and a turbidity of 55.6 NTU;

[0041] The difference between this embodiment and embodiment 1 is that the circulating water pump is intermittently operated, starting for 5 minutes and stopping for 5 minutes. After running for 30 minutes, the SDBS concentration in the laundry wastewater was measured to be reduced from 10.28 mg / L to 4.20 mg / L, and the turbidity was reduced from 55.6 NTU to 26.7 NTU. In this embodiment, the volume of the enriched liquid was 6 L, the volume of the purified water was 24 L, and the SDBS enrichment ratio was 3.4.

[0042] Example 4

[0043] The difference between this embodiment and embodiment 1 is that the initial SDBS concentration in the laundry wastewater is 7.43 mg / L. After 30 minutes of operation, the SDBS concentration in the laundry wastewater was measured to be reduced from 7.43 mg / L to 1.66 mg / L. In this embodiment, the volume of the enriched liquid was 6 L, the volume of the purified water was 24 L, and the SDBS enrichment ratio was 4.1.

[0044] Example 5

[0045] The difference between this embodiment and embodiment 4 is that 20 L of laundry wastewater is stored in the water tank, and the SDBS concentration is 7.77 mg / L. After running for 30 minutes, the SDBS concentration in the laundry wastewater drops from 7.77 mg / L to 1.17 mg / L. In this embodiment, the volume of the enriched liquid is 2 L, the volume of the purified water is 18 L, and the SDBS enrichment ratio is 8.6.

[0046] Example 6

[0047] In this embodiment, the SDBS concentration in the laundry wastewater to be treated is 9.32 mg / L; the difference between this embodiment and embodiment 5 is that 50 L of laundry wastewater is stored in the water tank. After running for 30 minutes, the SDBS concentration in the laundry wastewater dropped from 9.32 mg / L to 1.51 mg / L. In this embodiment, the volume of the enriched liquid obtained is 10 L, the volume of the purified water is 40 L, and the SDBS enrichment ratio is 4.4.

[0048] Example 7

[0049] In this embodiment, the SDBS concentration in the laundry wastewater to be treated is 8.15 mg / L; the difference between this embodiment and embodiment 5 is that the air inlet flow rate of the venturi-type water ejector is 10 L / min. After measurement, the SDBS concentration in the laundry wastewater dropped from 8.15 mg / L to 1.60 mg / L after running for 30 minutes. In this embodiment, the volume of enriched liquid obtained is 1.5 L, the volume of purified water is 18.5 L, and the SDBS enrichment ratio is 10.9.

[0050] Example 8

[0051] In this embodiment, the SDBS concentration in the laundry wastewater to be treated is 7.80 mg / L; the difference between this embodiment and embodiment 5 is that the air inlet flow rate of the venturi-type water ejector is 5 L / min. After measurement, the SDBS concentration in the laundry wastewater dropped from 7.80 mg / L to 2.36 mg / L after running for 30 minutes. In this embodiment, the volume of enriched liquid obtained is 1.5 L, the volume of purified water is 18.5 L, and the SDBS enrichment ratio is 9.6.

[0052] Example 9

[0053] The difference between this embodiment and embodiment 4 is that a norfloxacin solution is added to the laundry wastewater, and the initial concentration is 56.63 mg / L. It is measured that the residual concentration of norfloxacin after running for 30 minutes is 0.21 mg / L.

[0054] Example 10

[0055] In this embodiment, the SDBS concentration in the laundry wastewater to be treated is 7.43 mg / L; the difference between this embodiment and embodiment 4 is that the O3 gas generated by the ozone generator (ozone generation 10 g / h) is connected to the air inlet of the venturi-type water ejector. It was measured that the SDBS concentration in the laundry wastewater dropped from 7.43 mg / L to 0.32 mg / L after running for 30 minutes. In this embodiment, the volume of enriched liquid was 6 L, the volume of purified water was 24 L, and the SDBS enrichment ratio was 3.4.

[0056] Embodiment 11

[0057] In this embodiment, the SDBS concentration in the laundry wastewater to be treated is 13.13 mg / L; the difference between this embodiment and embodiment 6 is that the air inlet of the venturi-type water ejector is connected to the O3 gas generated by the ozone generator (ozone generation 10 g / h). It was measured that the SDBS concentration in the laundry wastewater dropped from 13.13 mg / L to 1.07 mg / L after running for 30 minutes. In this embodiment, the volume of the enriched liquid was 10 L, the volume of the purified water was 40 L, and the SDBS enrichment ratio was 4.7.

[0058] Example 12

[0059] In this embodiment, the SDBS concentration in the laundry wastewater to be treated is 9.64 mg / L, and the turbidity is 37.6 NTU; the difference between this embodiment and embodiment 1 is that the air inlet of the venturi-type water ejector is connected to the O3 gas generated by the ozone generator (ozone generation 10g / h). It was measured that after 30 minutes of operation, the SDBS concentration in the laundry wastewater dropped from 9.64 mg / L to 0.23 mg / L, and the turbidity dropped from 37.6 NTU to 5.39 NTU. In this embodiment, the volume of the enriched liquid was 6 L, the volume of the purified water was 24 L, and the SDBS enrichment ratio was 4.9.

[0060] Example 13

[0061] In this embodiment, the SDBS concentration in the laundry wastewater to be treated is 61.82 mg / L; the difference between this embodiment and embodiment 9 is that the air inlet of the venturi-type water ejector is connected to the O3 gas generated by the ozone generator (ozone generation amount 10 g / h). It was measured that the norfloxacin concentration dropped from 61.82 mg / L to 0 mg / L after running for 30 minutes.

[0062] The working principle of the present invention is:

[0063] 1. Foam fractionation is a process in which solutes are adsorbed at the gas-liquid interface between the dispersed (bubble) and continuous (liquid) phases. By interacting with the surfactant, non-surfactant substances can be removed and carried into the foam. The process of foam fractionation involves sparging air into the liquid to produce rising bubbles. When the bubbles pass through the continuous phase, the surfactant is adsorbed to the gas-liquid interface.

[0064] 2. In the present invention, the surfactant in the laundry wastewater is adsorbed on the surface of the bubbles and floats to the liquid surface with the bubbles for separation and recovery; other pollutants, such as tiny suspended solids and organic matter, are also captured by the surfactant and float to the liquid surface with the bubbles to form foam and be separated and removed. The purified laundry wastewater can be obtained at the bottom of the water tank.

[0065] 3. The special structure of the Venturi-type water ejector makes it possible to produce a gas-water mixture without the use of an air pump or agitator. The throat section has a small flow rate and a high flow rate, resulting in low pressure. When the water pressure therein is less than the atmospheric pressure, the gas can be automatically sucked in. The advantages of the Venturi-type water ejector are simple structure, self-priming, the formation of tiny bubbles, and low operating costs, because no additional air compressor is needed to supply gas, but only to provide energy for the water pump that circulates the liquid.

[0066] 4. The function of the water pump is to allow the laundry wastewater to pass through the Venturi water ejector multiple times, thereby inhaling more air to produce a large number of bubbles in the wastewater, which is beneficial to improve the separation efficiency.

[0067] 5. Connecting O3 to the air intake of the Venturi-type water ejector will accelerate the removal rate of anionic surfactants in laundry wastewater, because O3 is positively charged and more easily adsorbs negatively charged anionic surfactants.

[0068] In summary, the present invention can remove anionic surfactants in laundry wastewater at a lower cost and effectively, thereby purifying the laundry wastewater and preparing it for discharge into sewers or reuse.

Claims

1. A device for purifying laundry wastewater by foam fractionation, characterized in that: It comprises a water tank, a water pump, a venturi-type water ejector, a foam discharge pipe and a defoaming device which are arranged in sequence; the water inlet of the water pump is connected to the water tank through a pipeline, the water outlet of the water pump is connected to the inlet of the venturi-type water ejector through a pipeline, and the outlet of the venturi-type water ejector is connected to the bottom of the water tank through a pipeline; the suction chamber of the venturi-type water ejector is provided with an air suction port to automatically inhale external gas; one end of the foam discharge pipe is connected to the upper part of the water tank, and the other end extends to the top of the defoaming device.

2. The device for purifying laundry wastewater by foam fractionation as claimed in claim 1, characterized in that: A diffuser is arranged in the water tank and is installed at the end of the outlet pipe of the Venturi type water ejector.

3. The device for purifying laundry wastewater by foam fractionation as claimed in claim 1, characterized in that: The bottom of the water tank is connected to the water inlet pipeline of the water pump through a reflux pipe.

4. The device for purifying laundry wastewater by foam fractionation as claimed in claim 1, characterized in that: The bottom of the water tank is connected with a purified liquid discharge pipe.

5. The device for purifying laundry wastewater by foam fractionation as claimed in claim 1, characterized in that: A defoaming liquid reflux pipe is provided at the bottom of the defoaming device, and the outlet of the defoaming liquid reflux pipe is connected to the water inlet of the water pump through a pipeline.

6. The device for purifying laundry wastewater by foam fractionation as claimed in claim 5, characterized in that: An enriched liquid discharge pipe is also provided at the bottom of the defoaming device, and the enriched liquid discharge pipe and the defoaming liquid reflux pipe are connected to the bottom of the defoaming device through a tee.

7. The device for purifying laundry wastewater by foam fractionation as claimed in claim 1, characterized in that: The foam discharge pipe is arranged on the top of the water tank in an upward tilt and then connected downward to the top of the defoaming device, and the outlet is gradually reduced.

8. A method for purifying laundry wastewater by foam fractionation, characterized in that: By using the device described in any one of claims 1 to 7, the laundry wastewater in the water tank is circulated through a water pump and a pipeline. The water pump generates pressure on the laundry wastewater. When passing through the Venturi-type water ejector, a negative pressure is formed in the suction chamber of the Venturi-type water ejector. External gas is automatically sucked in from the air intake port of the Venturi-type water ejector and mixed with the laundry wastewater to form an air-water emulsion; the air-water emulsion enters the water tank through the pipeline, and then enters the bottom of the water tank through the diffuser at the outlet of the pipeline, where bubbles gather and float up, completing foam fractionation in the water tank; the fractionated foam carries the pollutants in the laundry wastewater through the foam discharge pipe and is separated from the purified liquid, and finally the fractionated foam passes through a defoaming device to become an enriched liquid for discharge or reflux treatment; finally, purified laundry wastewater is obtained at the bottom of the water tank.

9. A method for purifying laundry wastewater by foam fractionation as claimed in claim 8, characterized in that: The air intake port of the Venturi type water ejector can be directly opened or connected to O3 gas.

10. A method for purifying laundry wastewater by foam fractionation as claimed in claim 8, characterized in that: The water pump should be operated intermittently, starting for 10 to 15 minutes and then stopping for 5 to 10 minutes. After running for 30 minutes, the quality of the purified water is stable and the purified water and enriched liquid can be collected.

Images