Device and method for separating anionic surfactant from sewage

Abstract

The invention discloses a device and a method for separating an anionic surfactant in sewage. The device mainly comprises an air stripping structure and a defoaming structure. The air stripping structure comprises a box body with a built-in aeration pipe, and air is blown into sewage through an air blower, so that an anionic surfactant is enriched on the surface of foam; the defoaming structure comprises a barrel with a stirrer, and introduced foam is mechanically crushed by utilizing multiple layers of paddles rotating at a high speed. According to the method, efficient separation and concentration of pollutants are achieved in a physical mode, the removal rate is high, chemical agents do not need to be added, and secondary pollution is avoided. The device also has the advantages of compact structure, low cost, stable operation and the like, and can synergistically remove part of suspended matters.

Description

TECHNICAL FIELD

[0001] The present application relates to the sewage treatment technical field, specifically to a device for separating anionic surfactants in sewage and a method thereof. BACKGROUND

[0002] Anionic surfactants (LAS) are water pollutants, which exist in cleaning scenarios such as washing, bathing, and car washing where detergents are used in large quantities. Direct discharge of untreated surfactants can cause problems such as foam accumulation and dissolved oxygen reduction in water bodies. When the concentration of anionic surfactants in water exceeds a certain value, a persistent foam layer is formed, causing environmental pollution.

[0003] The removal of anionic surfactants is mainly achieved by physical and chemical methods (adsorption, coagulation, membrane separation, etc.) and biological methods (activated sludge, anaerobic-aerobic process) for wastewater treatment. The biological method has a high removal rate, but requires a long retention time and a large volume of treatment equipment. SUMMARY

[0004] The purpose of the present application is to provide a physical separation method for removing anionic surfactants in sewage.

[0005] The technical solution of the present application is a device for separating anionic surfactants in sewage, which includes a stripping structure for stripping anionic surfactants by bubbling and a defoaming structure for mechanically breaking foam. The stripping structure includes a box body, the inner wall of the box body is provided with a support, aeration pipes are horizontally arranged on the support, the part of the aeration pipes extending out of the box body is connected to a blower, and a plurality of perforations are formed on the pipe section located in the box body. The defoaming structure includes a cylinder, a stirrer is arranged in the cylinder, the stirrer is connected to a motor and driven to rotate by the motor, and a foam guide pipe and an air outlet pipe are respectively connected to the cylinder. The outlet end of the foam guide pipe is located below the stirrer, and the inlet end of the foam guide pipe is connected to the upper part of the box body.

[0006] Further, the support is arranged at the middle and lower part of the box body, a plurality of aeration pipes are connected by pipe joints to form a rectangular grid structure and fixed on the support, and a plurality of perforations are arranged at equal intervals on both sides of each aeration pipe facing upward.

[0007] Further, a plurality of aeration pipes are connected to each other by elbows or tee pipe joints, and a non-perforated pipe section extending in the vertical direction is connected to the blower through the upper side wall of the box body.

[0008] Further, a water inlet pipe and a water outlet pipe are respectively arranged on the opposite side walls of the bottom of the box body, a water inlet valve is arranged on the water inlet pipe, and a water outlet valve is arranged on the water outlet pipe.

[0009] Furthermore, inside the cylinder, the installation height of the mist guide tube is lower than that of the air outlet tube.

[0010] Furthermore, the stirrer includes a central shaft, which is fixed to and rotates with the output shaft of the motor; multiple layers of straight blades are fixedly mounted on the shaft, and the blades are at a certain angle to the shaft center.

[0011] Furthermore, a drain pipe is provided at the bottom of the cylinder.

[0012] A method for treating anionic surfactant wastewater includes the following steps: Step 1: Inject the pretreated wastewater into the tank through the inlet pipe and the inlet control valve. Stop the water intake when the liquid level rises slightly above the inlet of the foam guide pipe. Step 2: Start the blower and introduce air into the aeration pipe. The air enters the sewage through the perforations on the aeration pipe and forms foam under the action of anionic surfactants, which floats on the water surface. Step 3: The foam-air mixture is introduced into the mechanical defoaming cylinder from the top of the box through the foam guide tube; Step 4: Start the motor to drive the mixer to rotate at high speed; Step 5: The foam enters the bottom of the cylinder through the foam guide tube and is broken by the mechanical cutting and centrifugal action of the agitator blades. The liquid adheres to the blades and is thrown to the inner wall of the cylinder, flows down the wall and collects at the bottom of the cylinder, and is finally discharged through the drain pipe; the gas is discharged into the atmosphere through the gas outlet pipe. Step 6: After the anionic surfactants in the wastewater have been fully stripped off, open the effluent control valve, and the treated water will be discharged from the tank through the effluent pipe. The beneficial effects of this invention are: 1. This invention achieves highly efficient, purely physical separation without secondary pollution. Through the combined use of a stripping and defoaming structure, pollutants are separated entirely using physical principles such as air flotation and mechanical shearing. This method eliminates the need for any chemical demulsifiers or defoamers, fundamentally avoiding the introduction of new chemical pollutants, preventing secondary pollution, and reducing the difficulty and cost of subsequent treatment.

[0013] 2. The device of this invention has a compact and integrated structure with good processing efficiency. The stripping structure and the defoaming structure are efficiently coupled through a foam guide tube to form an integrated processing system. The defoaming structure uses a high-speed rotating multi-layer paddle agitator for mechanical defoaming. Compared with the traditional large settling tank that relies on gravity for natural defoaming, this design greatly accelerates the process of converting the foam phase into the liquid phase, thereby significantly reducing the volume and floor space required for the processing unit and realizing the miniaturization and high efficiency of the device.

[0014] 3. This invention has low operating costs and is environmentally friendly. The only energy-consuming components are the blower and motor, and the main operating cost is electricity consumption, which is far lower than the cost of continuously adding chemical agents. Its purely physical treatment mode not only does not generate any new pollutants during the process, but also produces a high-purity concentrate, which is more conducive to its subsequent resource recovery or centralized treatment, truly achieving a balance between environmental and economic benefits.

[0015] 4. This invention possesses the additional function of synergistic decontamination, resulting in comprehensive purification effects. During the stripping process, due to the excellent adsorption properties of the foam film formed by the anionic surfactant at the gas-liquid interface, some suspended solids in the wastewater are captured and float to the surface with the bubbles. These suspended solids are then transported to the defoaming unit along with the foam through the foam guide pipe, and finally discharged from the drain pipe with the concentrate. Therefore, this device not only efficiently removes anionic surfactants but also has a certain synergistic removal effect on suspended solids in wastewater, enhancing the overall purification capacity of the system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the separation device for anionic surfactants in wastewater according to the present invention; Figure 2 This is a schematic diagram of the stripping structure of the present invention; Figure 3 This is a schematic diagram showing the connection between the exposure tube and the motor of the present invention; Figure 4 This is a schematic diagram of the defoaming structure of the present invention; Figure 5 This is a schematic diagram of the defoaming structure of the present invention. Reference numerals in the attached drawings: 1-box body; 2-support; 3-exposure tube; 4-drain pipe; 5-water outlet pipe; 6-blower; 7-air outlet pipe; 8-water inlet pipe; 9-water inlet control valve; 10-water outlet control valve; 11-cylinder body; 12-stirrer; 13-motor; 14-foam guide pipe. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0019] Example 1: Blowout Structure The stripping structure mainly includes a housing 1, a support 2, aeration pipes 3, a blower 6, an inlet pipe 8, an outlet pipe 5, an inlet control valve 9, and an outlet control valve 10. The housing 1 is a sealed container with an internal support 2 for securing the network of pipes formed by multiple aeration pipes 3. The aeration pipes 3 are interconnected via elbows or tees, and each extends vertically with an unperforated pipe connected to the blower 6 at the top of the housing. Multiple equally spaced perforations are made on both sides of the section of the aeration pipe 3 located above the support. The inlet pipe 8 and outlet pipe 5 are respectively installed on both sides of the bottom of the housing 1, and are equipped with inlet control valves 9 and outlet control valves 10 respectively.

[0020] Blower 6 introduces air into aeration pipe 3, which is then evenly injected into the wastewater through perforations. Due to their significant surface tension, anionic surfactants in the wastewater form abundant foam under the influence of the airflow and accumulate on the water surface. This process achieves the transfer and separation of anionic surfactants from the water body to the bubble surface. It achieves physical separation of anionic surfactants without introducing new chemical substances or causing secondary pollution. The aeration pipe is designed with a mesh pattern and uniform openings, improving air distribution uniformity and thus enhancing stripping efficiency and separation effect. The stripping process also entrains some suspended solids, providing a certain synergistic impurity removal effect. This structure is compact, easy to operate, and its operating cost is mainly electricity, making it economical.

[0021] Example 2: Defoaming Structure The defoaming structure mainly includes a cylinder 11, a stirrer 12, a motor 13, a foam guide pipe 14, an air outlet pipe 7, and a drain pipe 4. The motor 13 is mounted on the top of the cylinder 11, and its output shaft extends into the cylinder and is fixedly connected to the central shaft of the stirrer 12. The stirrer 12 has multiple layers of straight blades at a certain angle to the shaft. The inlet end of the foam guide pipe 14 is connected to the upper part of the housing 1, and the outlet end is connected to the inside of the cylinder 11 and located below the blade area of ​​the stirrer 12. The air outlet pipe 7 is located at the top of the cylinder 11, and the drain pipe 4 is located at the bottom of the cylinder 11.

[0022] A foam mixture rich in anionic surfactants is introduced into the lower part of the cylinder 11 through the foam guide tube 14. A high-speed rotating agitator 12, with its multi-layered blades, continuously and multi-stage mechanically shears and impacts the rising foam, breaking down the foam film structure and causing it to disintegrate into liquid. The liquid, under centrifugal force, is thrown to the inner wall of the cylinder 11, flows down the wall, collects, and is discharged through the bottom drain pipe 4. The released gas rises and is discharged through the top vent pipe 7. This structure employs purely mechanical defoaming, which is highly efficient and fast, greatly reducing the space and time required for natural foam dissolution. The multi-layered inclined blade design creates effective mechanical cutting and lifting action, ensuring thorough foam breakage. The process consumes only electricity, resulting in low cost and avoiding secondary pollution problems caused by chemical defoamers. The structure is rationally designed, ensuring smooth gas-liquid separation and strong processing capacity.

[0023] Example 3: Wastewater Treatment Method Step 1: Water intake. The pretreated wastewater is injected into the tank 1 through the water inlet pipe 8 and the water inlet control valve 9 until the liquid level rises slightly above the inlet of the foam guide pipe 14 and then the water intake is stopped.

[0024] Step 2: Bubble blowing. Start the blower 6. Air is evenly diffused into the wastewater through the aeration pipe 3. The anionic surfactant forms foam and accumulates on the water surface.

[0025] Step 3: Foam guiding. The mixture of foam and gas is discharged from the upper part of the box 1 through the foam guide tube 14 and transported to the lower part of the defoaming cylinder 11.

[0026] Step 4: Mechanical defoaming. Start motor 13 to drive stirrer 12 to rotate at high speed. The foam is rapidly broken down by the mechanical cutting, impact and centrifugal action of the multi-layer blades, achieving gas-liquid separation.

[0027] Step 5: Product separation and discharge. The liquid formed after crushing (concentrated anionic surfactant solution) flows down the inner wall of the cylinder, is collected by the drain pipe 4, and sent out for further processing. The separated gas is discharged into the atmosphere through the gas outlet pipe 7.

[0028] Step 6: Drainage. After the anionic surfactants in the sewage are effectively removed, open the outlet control valve 10. The treated clean water is discharged from the tank 1 through the outlet pipe 5.

[0029] This method leverages the foaming properties of anionic surfactants, employing both bubbling stripping (air flotation separation) and mechanical defoaming processes to achieve efficient separation and concentration of pollutants from the aqueous phase. The entire process is physical, environmentally friendly, and has low operating costs. Separation, defoaming, and concentration are integrated into a single, compact system with a small footprint. It offers high processing efficiency, significant separation results, and can also remove some suspended solids. Operation is simple, highly automated, and easy to maintain and manage.

[0030] Anionic surfactants have high surface tension. When air is bubbled into wastewater, the anionic surfactants form foam that floats on the surface. The foam is then piped into a mechanical defoaming device, where it is mechanically broken up and liquefied. Through this process, the anionic surfactants in the wastewater are physically separated.

[0031] The purpose of this invention is to separate anionic surfactants from water, thereby reducing their concentration in wastewater. Mechanical defoaming addresses the issue that the anionic surfactant foam removed during defoaming is a contaminant. Natural defoaming takes a long time, and without defoaming, the foam is large and lightweight, requiring a large container for natural defoaming. Mechanical defoaming rapidly breaks down the foam, turning it into a liquid, significantly reducing the space occupied by the anionic surfactant and effectively reducing the size of the anionic surfactant separation device. Compared to chemical defoaming methods, mechanical defoaming only consumes electricity, is low-cost, and does not introduce new contaminants, while chemical defoaming introduces new contaminants.

[0032] Eight groups of test wastewater containing anionic surfactants at different initial concentrations were collected and numbered sequentially from 1 to 8. Using the same separation device of this invention, each group of wastewater was separated and treated under identical operating conditions, and the concentrations of anionic surfactants before and after treatment were measured. Specific data are recorded in the table below: The data in the table above shows that after treatment by this device, the concentration of anionic surfactants in the effluent is reduced to below 0.5 mg / L, meeting the requirements for anionic surfactant pollutants (≤0.5 mg / L) in the "Water Quality Standard for Urban Reclaimed Water for Miscellaneous Uses" (GB / T 18920-2020). For various types of wastewater with initial concentrations between 4.73 mg / L and 15.28 mg / L, this device demonstrates stable and excellent treatment capabilities, maintaining a removal rate consistently between 90.3% and 99.0%, with an average removal rate of 98.1%. This indicates that the device has good adaptability to influent with different loads and stable treatment effects. Even when faced with high-concentration wastewater with an initial concentration as high as 15.28 mg / L, the device can still efficiently treat it to 0.15 mg / L, achieving a removal rate of 99.0%, demonstrating its powerful separation and enrichment capabilities.

[0033] The foregoing has provided a detailed description of the separation device and method for anionic surfactants in wastewater provided by the present invention. Specific examples have been used to illustrate the structure and working principle of the invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A device for separating anionic surfactants from wastewater, characterized in that: This includes a stripping structure for bubble stripping anionic surfactants and a defoaming structure for mechanically breaking up foam; The stripping structure includes a box (1), the inner wall of the box (1) is provided with a support (2), an aeration pipe (3) is horizontally arranged on the support (2), the part of the aeration pipe (3) extending to the outside of the box is connected to a blower (6), and several perforations are opened on the pipe section located inside the box. The defoaming structure includes a cylinder (11), inside which is a stirrer (12), which is connected to a motor (13) and driven to rotate; a foam guide pipe (14) and an air outlet pipe (7) are respectively connected to the cylinder (11). The outlet end of the foam guide tube (14) is located below the stirrer (12), and the inlet end of the foam guide tube (14) is connected to the upper part of the box (1).

2. The separation device for anionic surfactants in wastewater according to claim 1, characterized in that: The bracket (2) is located in the lower middle part of the box. Multiple aeration pipes (3) are connected by pipe joints to form a rectangular grid structure and fixed on the bracket (2). Each aeration pipe has multiple equally spaced perforations on both sides facing upward.

3. The separation device for anionic surfactants in wastewater according to claim 2, characterized in that: Multiple aeration pipes (3) are interconnected by elbows or tee joints, and a pipe section without holes extends vertically through the upper side wall of the box and is connected to the blower (6).

4. The separation device for anionic surfactants in wastewater according to claim 1, characterized in that: The bottom of the box (1) is provided with an inlet pipe (8) and an outlet pipe (5) on opposite side walls. The inlet pipe (8) is provided with an inlet valve (9), and the outlet pipe (5) is provided with an outlet valve (10).

5. The separation device for anionic surfactants in wastewater according to claim 1, characterized in that: Inside the cylinder (11), the installation height of the foam guide pipe (14) is lower than that of the air outlet pipe (7).

6. The separation device for anionic surfactants in wastewater according to claim 1, characterized in that: The stirrer (12) includes a central shaft, which is fixed to and rotates with the output shaft of the motor (13); multiple layers of straight blades are fixedly installed on the shaft, and the blades are at a certain angle to the shaft.

7. The separation device for anionic surfactants in wastewater according to claim 1, characterized in that: The bottom of the cylinder (11) is provided with a drain pipe (4).

8. A method for treating anionic surfactant wastewater using the apparatus described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Inject the pretreated wastewater into the tank (1) through the inlet pipe (8) and the inlet control valve (9). Stop the inlet when the liquid level rises slightly above the inlet of the foam guide pipe (14). Step 2: Start the blower (6) and introduce air into the aeration pipe (3). The air enters the sewage through the perforations on the aeration pipe and forms foam under the action of anionic surfactants, which floats on the water surface. Step 3: The foam-air mixture is introduced into the mechanical defoaming cylinder (11) from the top of the box (1) through the foam guide tube (14); Step 4: Start the motor (13) to drive the stirrer (12) to rotate at high speed; Step 5: The foam enters the bottom of the cylinder through the foam guide tube (14), and is broken by the mechanical cutting and centrifugal action of the agitator blades. The liquid adheres to the blades and is thrown to the inner wall of the cylinder, flows down the wall and collects at the bottom of the cylinder, and is finally discharged through the drain pipe (4). The gas is then discharged into the atmosphere through the exhaust pipe (7); Step 6: After the anionic surfactants in the wastewater are fully blown off, open the effluent control valve (10) and the treated water is discharged from the tank through the effluent pipe (5).

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