A sewage treatment process

Abstract

This application relates to the field of wastewater treatment technology and discloses a wastewater treatment process. The process includes wastewater flotation treatment using an air flotation tank. The air flotation tank is equipped with a scum scraping device, which includes a horizontally reciprocating frame. A vertical frame is movably connected to the horizontal frame, and several scrapers are evenly distributed at the bottom of the vertical frame. The vertical frame allows the scrapers to move vertically relative to the horizontal frame. At the lowest point, the scraper's bottom edge is close to the liquid surface; at the highest point, the scraper does not contact the scum during movement. This wastewater treatment process uses multiple sets of scrapers that reciprocate, relaying the movement of scum. The amount of scum accumulated during scraper movement is reduced, as is the amount of scum leaking out from under the scrapers. Simultaneously, the scrapers divide the liquid surface and scum into multiple small pieces, each isolated by the scrapers. The movement of each small piece has minimal impact on the overall liquid surface within the air flotation chamber, and the amount of clean water affected by the scraper and scum movement is minimal.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and in particular to a wastewater treatment process. Background Technology

[0002] Industries involving waste oil processing, such as biodiesel production and kitchen waste treatment, discharge large amounts of wastewater. Currently, the treatment of such wastewater mostly adopts the direct chemical neutralization + RO membrane separation process. This process generally has problems such as high consumption of caustic soda (NaOH), high reagent costs, RO membranes are prone to scaling and clogging due to high conductivity of influent, high membrane replacement frequency, generation of large amounts of hazardous sludge containing heavy metals, and high disposal costs.

[0003] Pretreatment of wastewater using dissolved air flotation technology can significantly reduce COD and oil load, which is more economical than directly using membrane separation or advanced oxidation processes. It can also prevent oil from adhering to the surface of bioreactor packing or membrane modules, reducing the frequency of cleaning and maintenance.

[0004] Dissolved air flotation (DAF) is a solid-liquid separation technology commonly used in the pretreatment stage of wastewater treatment. It comprises three main processes: flocculation, dissolved air release, and the formation and separation of bubble-floc aggregates. Therefore, a typical DAF unit consists of a flocculation reaction tank, a mixing tank, and a flotation tank. Wastewater first enters the flocculation reaction tank and mixes thoroughly with the flocculant to undergo a flocculation reaction. Then, it enters the mixing tank where it adheres to small air bubbles in the dissolved air water, forming scum. This scum flows along a guide plate between the mixing tank and the flotation tank into the flotation tank and floats to the surface. Finally, a scraper collects the scum for further treatment.

[0005] To ensure the separation of scum and clear water, the flotation tank is relatively long, and the scraper's operating path is also long. When the scraper scrapes the scum on the liquid surface, the scum in front of the scraper accumulates, increasing its gravity and the overall water intake of the scum. Since the scraper is usually above the liquid surface, the scum can easily leak away from the bottom of the scraper, reducing the efficiency of the scraper in cleaning scum.

[0006] Secondly, as the scum accumulates in front of the scraper, the overall depth of the scum increases. The clear water near the liquid surface is more affected by the scraper and the scum, causing more clear water to move with the scum and accumulate more kinetic energy. When the scum passes over the baffle, it also causes more clear water to pass over the baffle. When the scum is subsequently evaporated and the oil is collected, the efficiency of the subsequent evaporation and recovery will be reduced because the scum carries a lot of clear water. Summary of the Invention

[0007] This application proposes a wastewater treatment process with multiple sets of scrapers that move back and forth to push away scum, reducing the impact of the scraper and scum movement on the clean water near the liquid surface, and also reducing the amount of scum that leaks out from the bottom of the scraper.

[0008] To achieve the above objectives, this application adopts the following technical solution: a wastewater treatment process, the steps of which include wastewater flotation treatment using a flotation tank, wherein the flotation tank is divided into a flocculation chamber, a reaction chamber, a flotation chamber, and a collection chamber by a front partition, a middle partition, and a rear partition; a sludge scraping device is provided above the flotation chamber; the sludge scraping device includes a horizontally reciprocating transverse frame, the transverse frame is movably connected to a vertical frame, and a plurality of scrapers are evenly provided at the bottom of the vertical frame; the vertical frame enables the scrapers to move vertically relative to the transverse frame; at the lowest point, the scraper moves along the liquid surface; at the highest point, the scraper does not contact the sludge during movement; when the transverse frame moves toward the rear partition, the scraper descends to the lowest point; when the transverse frame moves away from the rear partition, the scraper rises to the highest point; the distance the transverse frame moves horizontally each time is greater than the distance between two scrapers and the distance between the scraper and the partition.

[0009] Furthermore, a liquid level control chamber is provided on the side of the air flotation chamber near the rear partition. The liquid level control chamber includes a control box fixedly connected to the air flotation box. The bottom of the control box is connected to the air flotation chamber through a connecting port. The clean water at the bottom flows into the control box through the connecting port. An overflow port is provided at the bottom of the control box. When the clean water is higher than the overflow port, it flows out, so that the liquid level in the air flotation chamber is relatively constant.

[0010] Furthermore, the upper surface of the air flotation box is provided with a sliding groove corresponding to the transverse frame. The transverse frame is slidably connected to the air flotation box through the sliding groove. The air flotation box is provided with a driving device, which includes a linear motor that drives the transverse frame to move back and forth.

[0011] Furthermore, slide rails are fixedly connected to the inner sides of both sides of the horizontal moving frame, and sliders are fixedly connected to the outer sides of both sides of the vertical moving frame. The sliders slide on the slide rails. Rollers are provided on the outer side of the vertical moving frame, and guide structures corresponding to the rollers are provided on the inner wall of the air flotation box. The rollers slide on the guide structures.

[0012] Furthermore, the guiding structure consists of a moving guide block and a fixed guide block. The fixed guide block is fixedly connected to the air flotation box, and the moving guide block is movably connected to the air flotation box. The fixed guide block has an inclined surface on the side near the rear partition. The inclined surface guides the roller to move to the height of the moving guide block. The moving guide block adheres to the inclined surface under the action of elasticity. The side of the moving guide block facing the inclined surface is wedge-shaped. The bottom space of the inclined surfaces of the moving guide block and the fixed guide block is larger than the diameter of the roller, and the top space is smaller than the diameter of the roller.

[0013] Furthermore, the top of the rear partition is provided with a buffer slope, the inclination of which is the same as that of the slope on the guide block, and the vertical projections of their starting and ending points coincide.

[0014] Furthermore, the scraper closest to the rear partition is the tail scraper, and the rest are main scrapers. The bottom of the tail scraper is curved, and the distance between the bottom of the tail scraper and the liquid surface is less than 1 cm. The bottom of the tail scraper is perpendicular to the buffer slope of the rear partition. When the tail scraper reaches the partition position, the gap between the end of the tail scraper and the buffer slope does not exceed 1 cm.

[0015] Furthermore, to reduce energy consumption caused by changes in direction during reciprocating motion, springs are provided on both sides of the transverse frame, and the two ends of the springs are fixedly connected to the air flotation box.

[0016] The beneficial effects of this invention are as follows:

[0017] The wastewater treatment process provided in this application includes multiple sets of scrapers that move back and forth in succession to push away scum. On the one hand, the single movement of the scraper is relatively small, resulting in a smaller amount of scum accumulating during the scraper's movement, a smaller overall drop in scum height, and a smaller amount of scum leaking out from under the scraper, thus improving scraping efficiency. On the other hand, the scraper divides the liquid surface and scum into multiple small pieces, each of which is isolated by the scraper. The movement of each small piece has a smaller impact on the overall liquid surface in the flotation chamber, resulting in a smaller amount of clean water affected by the movement of the scraper and the scum, thereby reducing the amount of clean water mixed into the collection chamber. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort:

[0019] Figure 1 This is a schematic diagram of the air flotation box in this invention;

[0020] Figure 2 This is a front view of the air-floating box in this invention;

[0021] Figure 3 This is a side view of the air-floating box in this invention;

[0022] Figure 4 This is a schematic diagram of the slag scraping device in the present invention;

[0023] Figure 5 For the present invention Figure 2 Enlarged view of A in the middle

[0024] Figure 6 This is a process flow diagram of the present invention.

[0025] In the diagram: 1. Flotation tank; 2. Flocculation chamber; 3. Reaction chamber; 31. Flotation nozzle; 4. Flotation chamber; 5. Collection chamber; 6. Front partition; 7. Middle partition; 8. Rear partition; 9. Sludge scraping device; 901. Horizontal moving frame; 902. Vertical moving frame; 903. Slide rail; 904. Main scraper; 905. Tail scraper; 906. Roller; 907. Sludge detector; 10. Drive device; 101. Linear motor; 102. Spring; 103. Moving guide block; 104. Fixed guide block; 105. Sliding groove; 106. Return spring; 107. Slider; 11. Outlet plate; 12. Liquid level control chamber; 121. Control box; 122. Connecting port; 123. Overflow port. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1, please refer to Figure 6 This is a wastewater treatment process that primarily treats sulfur-containing wastewater, oil-containing wastewater, and RO concentrate. First, various types of wastewater enter a biological influent equalization tank for water quality and quantity adjustment, and then enter A... 2 The O process (anaerobic-anoxic-aerobic) is used for biological treatment to remove organic matter and denitrify and dephosphorize. The treated water is then filtered through sand filtration and ultrafiltration (UF) membranes to further remove suspended solids and microorganisms. After that, it undergoes deep treatment through reverse osmosis (RO) membranes. The purified water produced can be reused, while the RO concentrate enters the triple-effect inlet tank.

[0028] Oily wastewater first undergoes wastewater flotation treatment, and the separated floating oil is collected through a recovery device. The treated water then enters the triple-effect inlet tank. The triple-effect evaporator evaporates and concentrates the high-salinity wastewater, and the resulting salt residue is outsourced for treatment. The sludge generated by the entire system is specially treated before disposal to avoid secondary pollution.

[0029] The above treatment process recirculates the RO concentrate from the wastewater treatment plant, neutralizing the high-alkalinity wastewater with the oily wastewater. The pH of the influent wastewater is controlled at around 6, and this is gradually adjusted to increase the tolerance of the activated sludge, thus adapting it to the wastewater. The chemical process is as follows:

[0030] R-H + Na₂CO₃ → R-Na + H₂O + CO₂;

[0031] R-Na+O2→Na2CO3+H2O+CO2.

[0032] By recirculating RO concentrate to the neutralization reaction section, the residual sodium carbonate in the concentrate reacts with the acidic components in the fresh influent, thereby reducing the consumption of fresh reagents, maintaining the pH buffering capacity of the reaction system, and reducing the formation of calcium and magnesium precipitates through ion balance control.

[0033] Please see Figures 1-5 In wastewater flotation treatment, a flotation tank 1 is used to achieve wastewater flotation treatment. The flotation tank 1 includes a flocculation chamber 2, a reaction chamber 3, a flotation chamber 4, and a collection chamber 5. A stirring device is installed in the flocculation chamber 2. Oily wastewater is introduced into the flocculation chamber 2 through a pipeline and mixed with flocculant and coagulant aid to undergo a flocculation reaction. A front partition 6 is installed between the flocculation chamber 2 and the reaction chamber 3. The bottom of the front partition 6 has a notch, through which the flocculated wastewater enters the reaction chamber 3. A flotation nozzle 31 is installed in the reaction chamber 3, which is connected to a dissolved air tank. Dissolved air water flows out from the flotation nozzle 31, and the microbubbles in the dissolved air water adhere to the flocs, forming scum. A middle partition 7 is installed between the reaction chamber 3 and the flotation chamber 4. The top of plate 7 is equipped with a guide ramp. Scum and clean water flow into the flotation chamber 4 along the guide ramp of the partition plate 7. During the flow, the scum rises to the surface of the clean water. A rear partition plate 8 is provided between the flotation chamber 4 and the collection chamber 5. The height of the rear partition plate 8 is slightly higher than the liquid surface. A liquid level control chamber 12 is provided on the side of the flotation chamber 4 near the rear partition plate 8. The liquid level control chamber 12 includes a control box 121 fixedly connected to the flotation box 1. The bottom of the control box 121 is connected to the flotation chamber 4 through a connecting port 122. Clean water at the bottom flows into the control box 121 through the connecting port 122. An overflow port 123 is provided at the bottom of the control box 121. When the clean water is higher than the overflow port 123, it flows out, keeping the liquid level in the flotation chamber 4 relatively constant. An inclined guide plate 11 is provided in the collection chamber 5. Scum moves along the guide plate 11. The collection box is placed at the bottom of the guide plate 11. The collected scum is evaporated and then recycled.

[0034] A sludge scraping device 9 is provided above the air flotation chamber 4. The sludge scraping device 9 includes a horizontal moving frame 901, which moves horizontally back and forth. A vertical moving frame 902 is movably connected to the horizontal moving frame 901. Several scrapers are evenly arranged at the bottom of the vertical moving frame 902. The vertical moving frame 902 enables the scrapers to move vertically relative to the horizontal moving frame 901. The distance between two adjacent scrapers is X. The maximum displacement of the horizontal moving frame 901 during reciprocating movement is L. The scraper closest to the rear partition 8 is the tail scraper 905, and the others are the main scrapers. The distance between the scraper 904 and the tail scraper 905 and the far end of the rear partition 8 is x, where L>X and L>x. When the scraper is at its lowest point, it moves close to the liquid surface. Moving close to the liquid surface means that the distance between the main scraper 904 and the liquid surface is 1-2cm. When the scraper is at its highest point, it can avoid contact with the scum. At this time, the distance between the main scraper 904 and the liquid surface is greater than 6cm. When the transverse frame 901 moves toward the rear partition 8, the scraper descends to the lowest point. When the transverse frame 901 moves away from the rear partition 8, the scraper rises to the highest point.

[0035] When the scraper cleans the scum, it divides the scum on the liquid surface of the air flotation chamber 4 into several pieces. The scraper moves back and forth, and each time it moves, it pushes the scum a short distance. Each scraper pushes the scum in turn. Because the scraper moves a short distance, the amount of scum that accumulates when the scraper moves is reduced, and the amount of scum that leaks out from the bottom of the scraper is reduced, thus improving the scraping efficiency. On the other hand, the liquid surface and scum are divided into several small pieces, and the impact of a single piece of scum on the clear water near the liquid surface is reduced, thus reducing the amount of clear water that passes through the back baffle 8.

[0036] Please see Figures 2-4 The horizontal moving frame 901 slides on the upper surface of the air flotation box 1. The upper surface of the air flotation box 1 is provided with a sliding groove corresponding to the horizontal moving frame 901. The air flotation box 1 is provided with a driving device 10, which includes a linear motor 101. The linear motor 101 drives the horizontal moving frame 901 to move back and forth. The inner sides of both sides of the horizontal moving frame 901 are fixedly connected with slide rails 903. The outer sides of both sides of the vertical moving frame 902 are fixedly connected with sliders. The sliders slide on the slide rails 903. The outer side of the vertical moving frame 902 is provided with rollers 906. The inner wall of the air flotation box 1 is provided with a guide structure corresponding to the rollers 906. The rollers 906 slide on the guide structure, driving the vertical moving frame 902 to rise and fall. The guide structure and the rollers 906 are provided in four sets, respectively corresponding to the four corners of the vertical moving frame 902.

[0037] The guiding structure consists of a moving guide block 103 and a fixed guide block 104. The fixed guide block 104 is fixedly connected to the air flotation box 1, and the moving guide block 103 is slidably connected to the air flotation box 1. A slider 107 is fixedly connected to the moving guide block 103. The air flotation box 1 is provided with a sliding groove 105 corresponding to the slider. The slider 107 slides in the sliding groove 105. The fixed guide block 104 has an inclined surface on the side near the rear partition 8. A return spring 106 is connected to the slider 107. The return spring 106 causes the moving guide block 103 to be close to the inclined surface. The inclined surface guide roller 906 moves to the height of the moving guide block 103. Under the action of the elastic force, the moving guide block 103 is pressed tightly against the inclined surface. The side of block 103 facing the inclined plane is wedge-shaped. The bottom space of the inclined plane of moving guide block 103 and fixed guide block 104 is larger than the diameter of roller 906. When roller 906 slides on fixed guide block 104, when it moves to the inclined plane, it squeezes moving guide block 103, causing moving guide block 103 to move to the left without affecting the sliding of roller 906. When roller 906 moves to the top of fixed guide block 104, moving guide block 103 is reset by elastic force. At this time, the tip of the wedge is close to fixed guide block 104. When the transverse frame 901 moves in the opposite direction, roller 906 can cross the gap between the two and move along moving guide block 103, so that the scraper is in a higher position.

[0038] The top of the rear baffle 8 is provided with a buffer slope. The slope of the buffer slope is the same as that of the slope on the guide block 104, and the vertical projections of the starting point and the ending point of the two coincide. When the liquid surface is driven by the scraper and the scum, the kinetic energy of the liquid surface is consumed by the slope, so that the scum will not hit the rear baffle 8 and re-mix into the water.

[0039] Generally, the area near the rear partition 8 is far from the reaction chamber 3, resulting in less scum rising naturally and a slower increase in scum layer thickness, making it less likely to be carried away. The bottom of the tail scraper 905 is curved, with the bottom of the tail scraper 905 less than 1 cm from the liquid surface. The bottom of the tail scraper 905 is perpendicular to the buffer slope of the rear partition 8. When the tail scraper 905 reaches the rear partition 8, its end is close to the buffer slope of the rear partition 8, meaning the gap between the end of the tail scraper 905 and the buffer slope does not exceed 1 cm.

[0040] The liquid level is the same as the middle height of the buffer slope of the rear baffle 8, that is, the height of the overflow port 123 is the same as the height of the buffer slope. The liquid level is a certain distance away from the buffer slope of the drive device 10, so the liquid does not easily cross the rear baffle 8.

[0041] A scum detector 907 is installed on the main scraper 904 closest to the reaction chamber 3. The scum detector 907 is a laser detector, with its emitter located on one side of the main scraper 904 and its receiver located on the other side. When the thickness of the scum layer increases, it will block the light. There are two sets of scum detectors 907, which are used to detect the maximum and minimum thickness that the complex layer can be allowed. When the lower scum detector 907 is not blocked, the moving speed of the transverse frame 901 is reduced. When the upper scum detector 907 is blocked, the moving speed of the transverse frame 901 is increased.

[0042] To reduce energy consumption caused by changes in direction during reciprocating motion, springs 102 are provided on both sides of the transverse frame 901, and the two ends of the springs 102 are fixedly connected to the air flotation box 1.

[0043] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wastewater treatment process, comprising the steps of performing wastewater flotation treatment using a flotation tank (1), wherein the flotation tank (1) is divided into a flocculation chamber (2), a reaction chamber (3), a flotation chamber (4), and a collection chamber (5) by a front partition (6), a middle partition (7), and a rear partition (8), characterized in that: A scum scraping device (9) is provided above the flotation chamber (4). The scum scraping device (9) includes a horizontally reciprocating transverse frame (901). The transverse frame (901) is movably connected to a vertical frame (902). Several scrapers are evenly provided at the bottom of the vertical frame (902). The vertical frame (902) enables the scrapers to move vertically relative to the transverse frame (901). At the lowest point, the bottom of the scraper moves along the liquid surface. At the highest point, the scraper does not contact the scum during movement. When the transverse frame (901) moves toward the rear partition (8), the scraper moves downwards. When the horizontal moving frame (901) is lowered to its lowest point and moves away from the rear partition (8), the scraper rises to its highest point. The horizontal moving frame (901) moves a distance greater than the distance between the two scrapers and the distance between the scraper and the rear partition (8). The upper surface of the air flotation box (1) is provided with a sliding groove corresponding to the horizontal moving frame (901). The horizontal moving frame (901) is slidably connected to the air flotation box (1) through the sliding groove. The air flotation box (1) is provided with a driving device (10). The driving device (10) includes a linear motor (101). The linear motor (101) drives the horizontal moving frame. (901) Reciprocating movement, the inner sides of both sides of the horizontal moving frame (901) are fixedly connected with slide rails (903), the outer sides of both sides of the vertical moving frame (902) are fixedly connected with sliders, the sliders slide on the slide rails (903), the outer side of the vertical moving frame (902) is provided with rollers (906), the inner wall of the air flotation box (1) is provided with a guide structure corresponding to the rollers (906), the rollers (906) slide on the guide structure, the guide structure is composed of a moving guide block (103) and a fixed guide block (104), the fixed guide block (104) The fixed guide block (103) is fixedly connected to the air flotation box (1), and the movable guide block (104) is slidably connected to the air flotation box (1). The fixed guide block (104) has an inclined surface on the side near the rear partition (8). The inclined surface guides the roller (906) to move to the height of the movable guide block (103). The movable guide block (103) is pressed against the inclined surface under the action of elasticity. The side of the movable guide block (103) facing the inclined surface is wedge-shaped. The bottom space of the inclined surface of the movable guide block (103) and the fixed guide block (104) is greater than the diameter of the roller (906), and the top space is less than the diameter of the roller (906).

2. The wastewater treatment process according to claim 1, characterized in that, The air flotation chamber (4) is provided with a liquid level control chamber (12) on the side near the rear partition (8). The liquid level control chamber (12) includes a control box (121) fixedly connected to the air flotation box (1). The bottom of the control box (121) is connected to the air flotation chamber (4) through a communication port (122). The bottom of the control box (121) is provided with an overflow port (123).

3. The wastewater treatment process according to claim 1, characterized in that, The top of the rear partition (8) is provided with a buffer slope, the inclination of which is the same as that of the slope on the guide block (104), and the vertical projections of their starting and ending points coincide.

4. The wastewater treatment process according to claim 3, characterized in that, The scraper closest to the rear partition (8) is the tail scraper (905), and the rest are the main scrapers (904). The bottom of the tail scraper (905) is curved, and the bottom of the tail scraper (905) is less than 1 cm from the liquid surface. The bottom of the tail scraper (905) is perpendicular to the buffer slope of the rear partition (8). When the tail scraper (905) reaches the position of the rear partition (8), the gap between the end of the tail scraper (905) and the buffer slope does not exceed 1 cm.

5. The wastewater treatment process according to claim 1, characterized in that, Springs (102) are provided on both sides of the transverse frame (901), and the two ends of the springs (102) are fixedly connected to the air flotation box (1).

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