Industrial wastewater treatment air floatation filter tank
By optimizing the design of the industrial wastewater treatment flotation filter, the problems of large land area, energy consumption and large self-use water consumption in large-scale water treatment are solved, achieving efficient and low-cost water treatment and extending the operating cycle of the membrane system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- PURITEK COMPANY LTD
- Filing Date
- 2025-05-28
- Publication Date
- 2026-06-19
AI Technical Summary
Existing air flotation filter technology has limitations in large-scale water treatment projects due to its large footprint, high energy consumption, high investment cost, large self-consumption of water, and significant impact on subsequent treatment processes.
An industrial wastewater treatment flotation filter was designed, including a rapid mixing tank, a flocculation reaction tank, a dissolved air release tank, and a flotation filtration tank. It adopts a large-volume dissolved air tank, a U-shaped rapid energy dissipation and release head, a multi-media filter layer, and an intelligent control system to optimize the filtration and backwashing process and reduce the number of equipment and energy consumption.
It achieves a 30% reduction in floor space, a 23% reduction in energy consumption, and an 11% reduction in operating costs without increasing the number of devices. It also improves treatment efficiency and water quality, extends the operating cycle of ultrafiltration and reverse osmosis membranes, and reduces self-consumption of water and operating costs.
Smart Images
Figure CN224377843U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of water treatment technology, specifically to an air flotation filter for industrial wastewater treatment. Background Technology
[0002] With the acceleration of urbanization and the continuous development of industrial production, the demand for water resources is increasing, and sewage treatment capacity is facing higher requirements. As a highly efficient water treatment technology, air flotation filters are widely used in municipal water supply, sewage treatment, reclaimed water reuse, and industrial water use.
[0003] However, existing air flotation (AF) filter technology has some limitations when treating large volumes of water. Large footprint: When treating more than 30,000 tons / day, existing AF filters typically require three sets of six-compartment tanks. This multi-set, multi-compartment design significantly increases the land area required, which is particularly unreasonable for areas with limited land resources, increasing land costs and construction difficulty. High energy consumption: Traditional AF filters consume a large amount of energy during operation, especially during the flotation and backwashing stages. The flotation process requires a continuous supply of high-pressure air, while the backwashing process requires a large amount of clean water. These operations not only increase operating costs but also place high demands on energy supply. High investment costs: Due to the need for multiple sets of multi-compartment tanks, equipment investment and infrastructure construction costs increase significantly. Furthermore, the complex piping and control systems also increase the overall project investment, limiting the economic viability of AF filter technology for large-scale applications. High self-consumption: During backwashing, existing AF filters consume a large amount of clean water to rinse the filter media, which not only increases self-consumption but may also lead to water waste. Furthermore, the large amount of backwash water requires subsequent treatment, further increasing the treatment load and operating costs. Impact on subsequent treatment processes: Due to the high self-consumption of water, the treatment load of backwash water increases, placing additional pressure on subsequent dual-membrane treatment processes. Dual-membrane treatment processes (such as ultrafiltration and reverse osmosis) have high requirements for feed water quality; excessive backwash water may affect the stable operation of the dual-membrane system, reducing its treatment efficiency and service life.
[0004] In summary, existing dissolved air flotation (DAF) filter technology suffers from several drawbacks when treating large volumes of water, including large footprint, high energy consumption, high investment costs, significant water consumption, and substantial impact on subsequent treatment processes. These issues limit the widespread application of DAF technology in large-scale water treatment projects, necessitating an improved DAF filter technology to enhance treatment efficiency, reduce operating costs, and minimize environmental impact. Summary of the Invention
[0005] Purpose of the utility model: This utility model provides an industrial wastewater treatment air flotation filter that has a small footprint, low energy consumption, and low self-water consumption.
[0006] Technical Solution: An industrial wastewater treatment flotation filter, comprising, sequentially connected from the inlet to the outlet: a rapid mixing tank, a flocculation reaction tank, a dissolved gas release tank, and a flotation filtration tank; the dissolved gas release tank includes a dissolved gas pressurization pump, an air compressor, a dissolved gas tank equipped with a liquid level control differential pressure transmitter, and a dissolved gas release device; the air compressor supplies compressed air to the dissolved gas tank, while the dissolved gas pressurization pump simultaneously sends pressurized water into the dissolved gas tank to form dissolved gas water, which is released through the dissolved gas release device; the liquid level control differential pressure transmitter monitors the liquid level changes in the dissolved gas tank in real time to maintain a stable liquid level; the volume of the dissolved gas tank is 4.0–4.6 m³. 3 The diameter is 1.1–1.8 m and the height is 3.0–3.5 m; the filtration zone of the flotation filter tank is 45–65 m. 2 .
[0007] Furthermore, the liquid level control differential pressure transmitter is remotely controlled by a PLC or DCS system to maintain the liquid level in the dissolved gas tank at a constant level of ±0.00mm, thus avoiding uneven gas release or reduced treatment effect caused by liquid level fluctuations.
[0008] Furthermore, the dissolved gas release device is a dissolved gas release device with a U-shaped rapid energy dissipation release head. The U-shaped release head suddenly depressurizes for 0.03 to 0.2 seconds, forming 5μ to 30μ microbubble water.
[0009] Furthermore, the rapid mixing tank is equipped with a rapid mixing agitator and a dosing pipe. The rapid mixing agitator includes a base, a drive motor, a mixing shaft, a fixed sleeve, and mixing blades. The top of the mixing shaft is fixed to the top of the tank body by a bracket. Mixing blades are provided at the bottom of the mixing shaft. A fixed sleeve is provided on the outside of the mixing shaft to prevent the mixing shaft from swinging due to excessive length. The drive motor drives the mixing shaft and mixing blades to rotate through a reducer. The dosing pipe is laid along the tank wall to below the mixing blades. The mixing speed of the rapid mixing agitator is 80-118 r / min to ensure that the reagent in the rapid mixing tank is fully mixed with the sewage. The hydraulic retention time in the mixing tank is controlled at 50-90 s to ensure rapid mixing without the formation of flocs.
[0010] Furthermore, the flocculation reaction tank is equipped with a flocculation agitator, which is fixed to the top of the tank via a base support. The agitator speed can be frequency-controlled from 30 to 58 r / min, and the stirring speed gradient G value is 9 to 70 s. -1 The purpose is to control the floc size in the flocculation reaction tank to be between 0.9 and 1.3 mm, so as to facilitate the adsorption of impurities and colloidal substances in the wastewater by the adsorption bubbles, thereby achieving a better separation effect of impurities and colloidal substances in the water.
[0011] Furthermore, a scum trough is provided at the top of the effluent side of the flotation filter tank, and a finned scraper for skimming scum into the scum trough is fixedly installed at the top of the effluent side tank wall.
[0012] Furthermore, the flotation filter tank is equipped with a filtration system and a backwashing system; the filtration system includes a multi-media filter layer at the bottom of the flotation filter tank for retaining flocs, a filter plate below the multi-media filter layer for supporting the filter layer and uniformly collecting the filtered water through the filter cap, a level sensor on one side of the tank wall for controlling constant liquid level filtration, and a level switch and a level sensor arranged side by side on the tank wall for controlling the liquid level of the backwash filter tank; a differential pressure transmitter located outside the outlet of the flotation filter tank for detecting the filter media resistance; when the level sensor in the filter plate system detects a constant liquid level LT of 200mm to 300mm and the differential pressure sensor detects a filter media resistance of 450mm to 500mm, the backwashing system starts to work;
[0013] The backwashing system includes a blower, a blower anti-air valve, a backwashing pump, a backwashing air inlet valve, a backwashing water inlet valve, a backwashing drain pipe located below the filter plate, and a backwashing drain trough located above the multi-media filter media layer, with a turbidity detector installed inside the backwashing drain pipe. The blower anti-air valve and the backwashing air inlet valve are opened, then closed, to allow air washing of the flotation filter. The multi-media filter media layer fully expands, and the liquid level switch is below the conduction state for 300-600 seconds before the air inlet valve is closed. The backwashing water inlet valve is opened, and the backwashing pump is started to perform clean water backwashing. The backwashing wastewater is discharged through the backwashing drain pipe. The turbidity detector detects that the wastewater turbidity is <5 NTU, stopping the backwashing, and the filtration system begins operation.
[0014] Furthermore, the multi-media filter layer includes coal filter media, sea sand, and aggregate; the upper layer is coal filter media, the middle layer is sea sand, and the bottom layer is aggregate; the coal filter media has a particle size of 1.3-1.5 mm and a uniformity coefficient UC of 1.35-1.5; the sea sand has a particle size of 0.65-0.75 mm and a uniformity coefficient UC of 1.35-1.5.
[0015] Furthermore, the backwashing system can be operated manually.
[0016] Furthermore, both the filtration system and the backwashing system are remotely controlled by a PLC or DCS system.
[0017] Furthermore, the air flotation filter also includes a scum tank, which is connected to the scum trough at the effluent end of the flotation filter.
[0018] Furthermore, the lower part of the scum pool is cone-shaped to facilitate the discharge of scum.
[0019] Beneficial Effects: Compared with existing technologies, this invention has the following advantages: The dissolved air flotation filter of this invention increases the diameter of the dissolved air tank, thereby expanding its volume and accommodating more dissolved air water. This not only improves the tank's gas storage capacity but also provides more space for thorough mixing and dissolution of the dissolved air water, contributing to improved water quality. It achieves reduced floor space and increased dissolved air efficiency without increasing the number of equipment units. Simultaneously, the filtration area, multi-media filter layer, filtration system, and backwashing system are optimized. This invention's dissolved air flotation filter can treat 30,000 m³ of water. 3 For wastewater reuse projects with a capacity of / d or above, only two sets of four-compartment tanks are needed, reducing the floor space by 30% and energy consumption by 23% compared to standard air flotation (AF) filters. Operating costs are reduced by 11%. It can remove over 95% of suspended solids (SS) and colloidal substances, with even better removal of oil and algae, reaching over 99%. The AF filters effectively extend the operating cycle of ultrafiltration (UF) and reverse osmosis (RO) membranes. The chemical cleaning interval for UF membranes is extended from 45 days to 60 days, and for RO membranes from 30 days to 45 days. Based on comparable energy consumption calculations, this represents a 22% reduction in energy consumption compared to standard AF filters. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the structure of the air flotation filter of this utility model;
[0021] Figure 2 This is a process flow diagram of the air flotation filter of this utility model.
[0022] List of symbols in the attached diagram: 1. Inlet; 2. Outlet; 3. Rapid mixing tank; 4. Flocculation reaction tank; 5. Dissolved gas release tank; 501. Dissolved gas pressurization pump; 502. Air compressor; 503. Liquid level control differential pressure transmitter; 504. Dissolved gas tank; 505. Dissolved gas release device; 6. Flotation filter tank; 601. Multi-media filter layer; 602. Filter cap; 603. Filter plate; 7. Rapid mixing agitator; 701. Agitator shaft; 702. Agitator blades; 703. Drive motor; 8. Flocculation agitator; 9. Scum tank; 10. Finned scum scraper; 11. Scum collection spray pipe; 12. Backwash drain pipe; 13. Backwash drain trough; 14. Backwash air inlet pipe; 15. Air washing pipeline. Detailed Implementation
[0023] like Figure 1 , Figure 2As shown, the water flow direction of the industrial wastewater treatment flotation filter is from left to right, and it is sequentially connected and arranged along the direction from water inlet 1 to outlet 2: rapid mixing tank 3, flocculation reaction tank 4, dissolved air release tank 5, and flotation filter tank 6, forming a complete water treatment process. The water to be treated first enters the rapid mixing tank 3, which is equipped with a rapid mixing agitator 7 and a dosing pipe. The rapid mixing agitator 7 is fixed to the top of the tank by a bracket. The rapid mixing agitator 7 includes a mixing shaft 701, a fixed sleeve, mixing blades 702, and a drive motor 703. The fixed sleeve is provided on the outside of the mixing shaft 701, and the mixing blades 702 are provided at the bottom of the mixing shaft 701. The drive motor 703 drives the mixing shaft 701 and the mixing blades 702 to rotate through a reduction motor. The dosing pipe is laid along the tank wall to below the mixing blades 702. The mixture is thoroughly mixed with the added polyaluminum chloride (PAC) flocculant at a stirring speed of 80–118 r / min, with a hydraulic retention time of 1.0–2.5 min, to prepare the necessary conditions for the flocculation reaction to form flocs of controllable size.
[0024] The mixed water enters the flocculation reaction tank 4 by gravity flow through the effluent weir. The tank is equipped with two low-speed flocculation agitators 8, with the speed controlled within the range of 50-80 r / min, and the velocity gradient G value maintained between 10 and 70 s. -1 Meanwhile, the pH value is controlled within the range of 7.2 to 8.2. This design ensures that the flocculant forms uniformly sized and controllable micro-flocs of 0.9 mm to 1.3 mm in the flocculation reaction tank, maximizing the adsorption and trapping of pollutants in the water by the flocs, and creating favorable conditions for microbubble adsorption and flotation in the dissolved gas release tank.
[0025] The flocculated water then flows by gravity through the effluent weir to the dissolved air release tank 5. The dissolved air release tank 5 includes a dissolved air tank 504 equipped with a level control differential pressure transmitter 503, a dissolved air pressurization pump 505, an air compressor 502, a dissolved air tank 504, and a dissolved air release device 505. The air compressor 502 delivers compressed air to the dissolved air tank 504, while the dissolved air pressurization pump 505 sends pressurized water into the dissolved air tank 504. Inside the dissolved air tank 504, the water and compressed air work together to fully dissolve the air in the water under high pressure, forming supersaturated air-dissolved water, which is then released through the dissolved air release device 505 with a U-shaped rapid energy dissipation release head. A differential pressure transmitter 503, installed on the dissolved air tank 504, is remotely controlled by a PLC or DCS system to monitor the liquid level changes in the dissolved air tank 504 in real time. It also maintains a stable liquid level in the dissolved air tank 504 by controlling the inlet water regulating valve, ensuring sufficient space for gas-water mixing. When the liquid level deviates from the set range, the transmitter sends a signal to the PLC or DCS system via AI / AO to automatically adjust the opening of the inlet water regulating valve and control the inlet water flow. The dissolved air water in the dissolved air tank 504 is ultimately released into the dissolved air release tank treatment liquid in the form of 5μ~30μ microbubbles through the dissolved air release device 505, fully utilizing the adsorption of micro-flocs by the microbubbles to separate impurities. Depending on the treatment scale, the diameter of the dissolved air tank 504 is designed to be 1.1~1.8m, which can meet the needs of 12,000m³ / h treatment capacity. 3 / d and 15,000m 3 The daily water treatment capacity requirement is as follows:
[0026] Daily water treatment capacity (m3 / d) Dissolved gas tank volume (m3) Diameter control range (m) Height control (m) 12,000 4.0 1.1～1.5 3.0～3.2 15,000 4.6 1.5～1.8 3.2～3.5
[0027] The dissolved gas release tank 5 is connected to the flotation filter tank 6 via an overflow weir. In the flotation filter tank 6, more than 90% of impurities are carried to the surface by microbubbles to form a scum layer. A scum collection spray pipe 11 is installed above the flotation filter tank 6. The scum collection spray pipe 11 sprays water onto both sides of the tank wall, using hydraulic shearing to drive the dispersed scum towards the center of the tank. A finned scraper 10 is fixedly installed on the top of the effluent side of the flotation filter tank 6. The finned scraper 10 operates at a speed of 40-58 r / min, skimming the accumulated scum into the scum trough 9; and then flowing into the scum pool by gravity through the scum trough 9. By controlling the filtration liquid level on the surface of the filter tank and appropriately lowering the cutting liquid level of the blades of the finned scraper 10, the water content of the skimmed scum can be effectively reduced, thereby improving the skimming efficiency.
[0028] The flotation filter tank is equipped with a filtration system and a backwashing system;
[0029] The filtration system includes a multi-media filter layer 601 located at the bottom of the flotation filter tank 6; a filter plate 603 located below the multi-media filter layer 601 to support the filter layer and uniformly collect the filtered water through the filter cap 602; a level sensor located on one side of the tank wall to control constant liquid level filtration; and a level switch and level sensor arranged side-by-side on the tank wall to control the liquid level of the backwash filter tank; a differential pressure sensor located outside the outlet of the flotation filter tank 6 to detect the filter media resistance; the multi-media filter layer 601 is used to intercept flocs with a specific gravity greater than 1, and the upper layer of the multi-media filter layer 601 is coal filter media, the middle layer is sea sand, and the bottom layer is aggregate. The design of the multi-media filter layer 601 has good dirt-holding capacity. The powerful and reusable adsorption flocs effectively trap pollutants in the water. The upper layer of coal filter media has a particle size of 1.3–1.5 mm and a uniformity coefficient (UC) of 1.35–1.5. The middle layer of sea sand has a particle size of 0.65–0.75 mm and a uniformity coefficient (UC) of 1.35–1.5, which prevents pollutants from easily penetrating the trapping layer due to increased filtration load. The bottom aggregate layer is a 2.4–4.8 mm support layer. The combination of these three layers ensures the stability of the filtration effect. This combined design not only guarantees filtration performance but also greatly extends the service life of the filter media. Actual operation data shows that the coal filter media only needs to be replenished by 0.1% over 20 years, while the sea sand does not need to be replenished. During normal filtration operation, when the level sensor detects a constant liquid level LT of 200mm to 300mm and the differential pressure sensor detects a filter media resistance of 450mm to 500mm, the system will automatically stop the filtration operation and enter the backwashing procedure. By monitoring the constant liquid level and the filter media resistance, this invention can effectively reduce unnecessary backwashing times, thereby significantly reducing the water reuse rate.
[0030] The backwashing system includes a blower, a blower anti-air valve, a backwashing pump, a backwashing air inlet valve, a backwashing water inlet valve, a backwashing drain pipe 12 located below the filter plate, a backwashing drain trough 13 located above the multi-media filter layer 601, and a turbidity detector inside the backwashing drain pipe 12; it also includes a backwashing air inlet pipe 14 located on the effluent side of the flotation filter tank 6 and an air washing pipeline 15 located below the filter plate 603; during the water production process of the flotation filter tank 6, as the multi-media filter layer 601 continuously intercepts the residual suspended solids in the water after flotation treatment, the resistance of the filter layer continuously increases, and backwashing needs to be performed regularly. When the backwashing system is working, open the blower anti-air valve and the backwash air inlet valve, then close the blower anti-air valve. Air enters through the backwash air inlet pipe 14 and is discharged through the air washing pipe 15 for air washing. The multi-media filter layer 601 fully expands. When the liquid level switch detects the second lowest point, continue for 30 seconds, then open the blower anti-air valve and close the air inlet valve, ending the air washing. Subsequently, open the backwash water inlet valve for clean water backwashing. The backwash water washes the multi-media filter layer 601 from bottom to top. The backwash drainage is collected in the backwash drainage tank 13 and then discharged into the backwash drainage pipe 12 and discharged into the wastewater tank. The turbidity detector stops backwashing when the drainage turbidity is <5 NTU, and the system automatically resumes the filtration program. The filtered product water is discharged from the outlet 2 and enters the product water tank. The backwashing program can be automatically controlled by the system or manually started as needed.
[0031] For air flotation filters with a processing capacity exceeding 30,000 tons / day, four or more filter cells are required. Since the degree of contamination varies among the filter media in each cell during operation, this multi-cell parallel design can intelligently adjust the backwashing timing based on the actual operating conditions of each cell. This can be achieved by independently determining the backwashing timing using data from different sensors in each cell, avoiding energy waste caused by fixed-cycle backwashing. Actual operation data shows that this optimized design can reduce the self-use water rate for backwashing from 5% to 3%, saving 21,000 tons of water annually.
[0032] The flotation filter tank has a filtration zone of 45–65 m. 2 The gas washing intensity is controlled between 1.2 and 1.29 Nm. 3 / m 2 The washing intensity is controlled between 0.4 and 0.8 min. 3 / m 2 .min is used to meet the needs of treating large volumes of water with good water production effect.
[0033] The aforementioned scum pool is connected to the scum trough 9 at the outlet of the flotation filter pool 6, and is responsible for collecting and treating the generated scum. The scum can be sent to the chemical sludge treatment unit for further treatment, and the supernatant in the pool is sent to the wastewater pool for reuse, forming a complete treatment closed loop.
[0034] The water quality of the flotation filter produced by this invention was tested and found to be as follows: suspended solids concentration below 3 mg / L, total phosphorus below 0.1 mg / L, oil below 0.2 mg / L, turbidity below 0.5 NTU, pH value between 6 and 9, and excellent algae removal effect. Compared with traditional flotation filters, the water quality of the produced water by this invention is significantly improved, with all indicators superior to traditional processes, demonstrating higher treatment efficiency and better water quality stability.
Claims
1. An industrial wastewater treatment gas floatation tank characterized by, The following components are sequentially connected along the direction from the inlet (1) to the outlet (2): a rapid mixing tank (3), a flocculation reaction tank (4), a dissolved gas release tank (5), and a flotation filter tank (6); the dissolved gas release tank (5) includes a dissolved gas pressurizing pump (501), an air compressor (502), a dissolved gas tank (504) equipped with a liquid level control differential pressure transmitter (503), and a dissolved gas release device (505); the air compressor (502) delivers compressed air to the dissolved gas tank (504), while the dissolved gas pressurizing pump (501) sends pressurized water into the dissolved gas tank (504) to form dissolved gas water, which is then released through the dissolved gas release device (505); the liquid level control differential pressure transmitter (503) controls the liquid level change in the dissolved gas tank (504) in real time to maintain a stable liquid level; the volume of the dissolved gas tank (504) is 4.0 to 4.6 m³. 3 The diameter is 1.1–1.8 m and the height is 3.0–3.5 m; the flotation filter tank is 45–65 m long. 2 .
2. The industrial wastewater treatment flotation tank according to claim 1, characterized in that, The level control differential pressure transmitter (503) is controlled by a PLC or DCS system.
3. The industrial wastewater treatment flotation tank according to claim 1, characterized in that, The dissolved gas release device (505) is a dissolved gas release device with a U-shaped rapid energy dissipation release head.
4. The industrial wastewater treatment flotation tank of claim 1, wherein The rapid mixing tank (3) is equipped with a rapid mixing agitator (7) and a dosing pipe; the rapid mixing agitator (7) is fixed to the top of the tank by a bracket; the rapid mixing agitator (7) includes a mixing shaft (701), a fixed sleeve, mixing blades (702) and a drive motor (703); the outer side of the mixing shaft (701) is provided with a fixed sleeve, and the bottom of the mixing shaft (701) is provided with mixing blades (702); the drive motor (703) drives the mixing shaft (701) and mixing blades (702) to rotate through a reduction motor; The dosing pipe is laid along the pool wall to below the stirring blade (702).
5. The industrial wastewater treatment flotation tank of claim 1, wherein, The flocculation reaction tank (4) is equipped with a flocculation agitator (8), which is fixed to the top of the tank by a bracket.
6. The industrial wastewater treatment flotation tank of claim 1, wherein, The flotation filter tank (6) has a scum trough (9) on the top of the effluent side, and a finned scraper (10) is fixedly installed on the top of the effluent side tank wall.
7. The industrial wastewater treatment flotation tank of claim 1, wherein, The flotation filter tank (6) is equipped with a filtration system and a backwashing system. The filtration system includes a multi-media filter layer (601) located at the bottom of the flotation filter tank for intercepting flocs, a filter plate (603) located below the multi-media filter layer for supporting the multi-media filter layer (601) and uniformly collecting the filtered water through the filter cap (602), a liquid level sensor located on one side of the tank wall for controlling constant liquid level filtration, and a liquid level switch and a liquid level sensor located side by side on the tank wall for controlling the liquid level of the backwash filter tank. A differential pressure sensor located outside the outlet of the flotation filter tank (6) is used to detect the resistance of the filter media. When the liquid level sensor detects a constant liquid level LT of 200mm to 300mm in the filtration system, and the differential pressure sensor detects that the resistance of the filter media of the multi-media filter layer (601) reaches 450mm to 500mm, the backwashing system starts to work. The backwashing system includes a blower, a blower anti-air valve, a backwashing pump, a backwashing air inlet valve, a backwashing water inlet valve, a backwashing drain pipe (12) located below the filter plate, a backwashing drain trough (13) located above the multi-media filter layer (601), and a turbidity detector inside the backwashing drain pipe (12). Open the blower anti-air valve and the backwashing air inlet valve, then close the blower anti-air valve. The flotation filter tank (6) is air-washed. The multi-media filter layer (601) is fully expanded, and the liquid level switch is lower than the conduction state. After 300-600 seconds, the backwashing air inlet valve is closed. Open the backwashing water inlet valve, start the backwashing pump to perform clean water backwashing, and discharge the backwashing drainage through the backwashing drain trough (13) into the backwashing drain pipe (12). The turbidity detector detects that the turbidity of the drainage is <5 NTU and stops backwashing. The filtration system starts working.
8. The industrial wastewater treatment flotation tank of claim 7, wherein, The multi-media filter layer (601) includes coal filter media, sea sand, and aggregate; the upper layer is coal filter media, the middle layer is sea sand, and the bottom layer is aggregate; the coal filter media has a particle size of 1.3-1.5 mm and a uniformity coefficient UC of 1.35-1.5; the sea sand has a particle size of 0.65-0.75 mm and a uniformity coefficient UC of 1.35-1.
5.
9. The industrial wastewater treatment flotation tank of claim 1, wherein, The air flotation filter also includes a scum tank, which is connected to the scum trough (9) at the outlet of the flotation filter (6).