Wastewater Treatment System Combining a Flotation Process with Enhanced Microbubble Stability and an Ozone Process

Abstract

A water treatment system is disclosed that improves the overall treatment performance of the system by combining a flotation separation process using microbubbles for pollutants in water to be treated, such as wastewater or sewage, with a downstream ozone oxidation process, thereby maximizing flotation separation efficiency by stably supplying microbubbles of uniform size and reducing the load on the downstream ozone oxidation process. According to one aspect of the present invention, a water treatment system for physically and chemically treating wastewater comprises a flotation separation device that receives coagulated water to be treated and separates the coagulated flocs by flotation, a microbubble generation unit that supplies microbubbles to the flotation separation device, an ozone contact unit that receives treated water discharged from the flotation separation device and performs removal of residual organic matter and color through ozone contact, and an ozone dissolution unit that supplies ozone-dissolved water to the ozone contact unit, thereby providing a water treatment system combined with a flotation separation process and an ozone oxidation process that simultaneously removes high concentrations of solids and non-biodegradable organic matter contained in wastewater.

Description

Technology Field

[0001] The present invention relates to a system for treating wastewater, and more specifically, to a water treatment system that combines a flotation separation process, which contacts and attaches microbubbles to pollutants in water to be treated such as wastewater or sewage and separates them by flotation, and an ozone oxidation process, which oxidizes the treated water passing through the flotation separation process with ozone, thereby stably supplying microbubbles of uniform size in the flotation separation process to improve flotation separation efficiency, the load on the downstream ozone process, and the overall treatment efficiency. Background Technology

[0002] The content described in this section merely provides background information regarding the present embodiment and does not constitute prior art.

[0003] The flotation separation process is widely used as one of the representative processes for separating and removing pollutants such as suspended solids, oil, and colloidal particles in wastewater through physical and chemical treatment. Generally, the flotation separation method generates microbubbles with a diameter of tens of micrometers (μm) by dissolving air in water under high pressure conditions and then depressurizing or dispersing it through a nozzle. The generated microbubbles attach to suspended solids or organic matter contained in the wastewater, providing buoyancy, and solid-liquid separation is achieved by causing them to float to the surface and be removed in the form of sludge.

[0004] However, conventional flotation separation devices have several technical limitations in the gas dissolution and bubble formation processes. If the gas dissolution rate is insufficient, air does not diffuse properly within the water, leading to the formation of coarse bubbles or foam, which can reduce flotation efficiency. Furthermore, if air is not completely dissolved and remains in a gaseous state before entering the flotation separation device, the undissolved gas can disturb the interior of the separation tank or cause uneven bubble dispersion, potentially degrading the quality of the treated water. Since a sudden drop in pressure in the circulation pump or piping system can drastically lower the gas dissolution rate, the pressure must be immediately restored via an automatic control device, which can complicate design and operation. Additionally, the rapid turbulence regions formed within the nozzle can cause microbubbles to clump together or result in uneven bubble sizes, making it difficult to guarantee optimal bubble quality; these issues have been pointed out as problems.

[0005] To address these issues, various methods have been proposed to increase the gas dissolution rate and stably generate bubbles. For example, methods such as combining oxidation effects and flotation separation through a pressurized flotation system using ozone and air, or forming a bubble layer using microbubble nozzles, are known. Meanwhile, technologies have also been disclosed to improve fluid flow by placing channels at the bottom of the flotation separation tank in dissolved air flotation devices, or to homogenize bubble dispersion by applying distribution cones. However, a problem remains in that the efficiency of microbubble formation drops significantly when undissolved gas is mixed in or when sudden pressure changes occur within the system, unlike when the gas is sufficiently dissolved in water.

[0006] In particular, the instability of this flotation separation process becomes a critical factor in reducing the efficiency of the entire system when advanced oxidation processes, such as ozone oxidation, are combined downstream. If suspended solids or organic loads that were not removed during the flotation stage flow directly into the downstream ozone process, unnecessary ozone is consumed to remove non-target pollutants, significantly lowering ozone treatment efficiency and economic viability.

[0007] Therefore, there is a need to develop microbubble generation and supply technology that can maximize flotation separation efficiency by actively responding to changes in dissolved water supply and pressure within the system, thereby minimizing the load on the downstream ozone oxidation process. Prior art literature

[0008] Korean Patent Publication No. 10-1336613 (December 16, 2013) Korean Patent Publication No. 10-2693530 (August 9, 2024) The problem to be solved

[0009] One embodiment of the present invention aims to solve the limitations of existing flotation separation processes, particularly the pressure fluctuations and residual undissolved gases occurring during wastewater treatment, and to provide a process capable of stably and continuously supplying microbubbles without a decrease in gas dissolution rate by organically linking the process of removing undissolved gases in a microbubble circulation pump and a gas-liquid separation device to ensure the stability of pressure control within the circulation line of the gas-dissolved water and efficiently removing undissolved gases.

[0010] In addition, one embodiment of the present invention aims to provide a water treatment system that generates microbubbles using a nozzle with an expanded section structure, controls the diffusion angle of the expanded section, sequentially connects multiple expanded sections, and arranges a straight connecting section between adjacent expanded sections to suppress the generation of turbulence within the flow path of the nozzle and reduce the phenomenon of bubble clumping, thereby stably supplying microbubbles of uniform and fine size into a flotation separation device to achieve high performance in removing suspended solids and organic matter, and consequently improves the efficiency and economic feasibility of the downstream ozone oxidation process. means of solving the problem

[0011] According to one aspect of the present invention, a water treatment system for physically and chemically treating wastewater comprises a flotation separation device that receives coagulated water to be treated and separates the coagulated flocs by flotation, a microbubble generation unit that supplies microbubbles to the flotation separation device, an ozone contact unit that receives treated water discharged from the flotation separation device and performs removal of residual organic matter and color through ozone contact, and an ozone dissolution unit that supplies ozone-dissolved water to the ozone contact unit, thereby providing a water treatment system combined with a flotation separation process and an ozone oxidation process that simultaneously removes high-concentration solids and non-degradable organic matter contained in wastewater.

[0012] According to one aspect of the present invention, the water treatment system further comprises a control unit, wherein the control unit controls the operation of the microbubble generating unit, the ozone contact unit, and the ozone dissolution unit in an organically linked manner.

[0013] According to one aspect of the present invention, the microbubble generating unit comprises a microbubble circulation pump for circulating a portion of the treated water of the flotation separation device, a gas-liquid dissolving unit for dissolving gas in the treated water taken by the microbubble circulation pump, a gas-liquid separation unit for separating undissolved gas by receiving the dissolved water generated in the gas-liquid dissolving unit, and a microbubble generating nozzle for receiving the gas-liquid dissolving water discharged from the gas-liquid separation unit, generating microbubbles, and supplying them to the flotation separation device, wherein the microbubble generating nozzle is disposed inside the flotation separation device.

[0014] According to one aspect of the present invention, the control unit is characterized by controlling the microbubble circulation pump and the gas-liquid separation unit in conjunction.

[0015] According to one aspect of the present invention, the ozone dissolution unit comprises a circulating water pressurizing pump that takes a portion of the treated water from the ozone contact unit as circulating water and pressurizes it, an ozone generator that generates ozone gas, an ozone injection unit that injects ozone gas generated from the ozone generator into the circulating water transferred from the circulating water pressurizing pump, and a pressurized dissolution tank that pressurizes the circulating water passing through the ozone injection unit to dissolve ozone.

[0016] According to one aspect of the present invention, the control unit detects the water level of the gas-liquid separation unit, controls whether to open or close the vent valve of the gas-liquid separation unit to discharge undissolved gas inside the gas-liquid separation unit according to the detected water level, and controls the discharge flow rate of the microbubble circulation pump in conjunction with the opening or closing of the vent valve.

[0017] According to one aspect of the present invention, the gas-liquid separation unit further comprises a cylindrical outer tube and an inner tube, and receives gas-dissolving water through a tangential gas-dissolving water inlet formed on the upper side of the gas-liquid separation unit, and separates undissolved gas by generating a swirling flow of the introduced gas-dissolving water in the space formed between the outer tube and the inner tube.

[0018] According to one aspect of the present invention, the microbubble generating nozzle comprises an inlet into which gas-dissolved water is introduced, a plurality of expansion sections, a straight connecting section disposed between adjacent expansion sections, and a discharge section for discharging generated microbubbles, wherein the inlet is characterized by having at least one impact plate disposed inside.

[0019] According to one aspect of the present invention, the collision plate is characterized by having a central collision portion and a plurality of through holes surrounding the collision portion.

[0020] According to one aspect of the present invention, the diffusion angle (θ) of the entire nozzle formed through the plurality of expansion sections is T ) is characterized by being 15° or less.

[0021] According to one aspect of the present invention, the diffusion angle (θ) of each expansion portion is given. n ) is characterized by being between 3° and 15°.

[0022] According to one aspect of the present invention, the inlet includes an inlet opening on one side that allows gas-dissolved water to flow into the microbubble generating nozzle, and the inlet opening is formed with a structure in which the cross-sectional area gradually decreases along the direction of fluid flow.

[0023] According to one aspect of the present invention, the ozone contact portion further comprises a UV lamp inside to irradiate UV light onto the treated water within the ozone contact portion. Effects of the invention

[0024] As described above, according to one aspect of the present invention, by generating uniform microbubbles through a microbubble generating nozzle having a multi-stage expansion and impact plate, bubble clumping or the generation of coarse bubbles is prevented, and by controlling the gas-liquid separation unit and the circulation pump in conjunction, a constant gas dissolution rate can be maintained even when discharging undissolved gas, thereby efficiently generating microbubbles without a large pressurized tank or complex piping facilities, ensuring stable pretreatment performance, and increasing the convenience of maintenance through automatic control.

[0025] In addition, by adding an ozone oxidation process downstream of the flotation separation device to further treat residual fine organic matter or odor and color-causing substances, non-biodegradable pollutants can also be treated with high efficiency, which has the advantage of significantly improving the quality of the final treated water. Brief explanation of the drawing

[0026] FIG. 1 is a conceptual diagram showing the overall configuration of a water treatment system combining a flotation separation process and an ozone oxidation process according to one embodiment of the present invention. FIG. 2 is a configuration diagram showing a gas-liquid separation section according to one embodiment of the present invention. FIG. 3 is a configuration diagram showing a microbubble generating nozzle according to one embodiment of the present invention. FIG. 4 is a diagram explaining the diffusion section angle of the expansion of FIG. 3. FIG. 5 is a diagram showing a microbubble generating nozzle according to another embodiment of the present invention. FIG. 6 is a result showing the pollutant removal rate in a flotation separation device according to one embodiment of the present invention. Specific details for implementing the invention

[0027] The present invention is susceptible to various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing.

[0028] Terms such as first, second, A, B, etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0029] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0030] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" should be understood as not precluding the existence or addition of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification.

[0031] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains.

[0032] Terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0033] Each component, process, procedure, or method included in each embodiment of the present invention may be shared within a scope that is not technically contradictory to one another.

[0034] In addition, throughout the specification, the term "floc" refers to a state in which contaminants scattered within the water to be treated are aggregated by the action of a coagulant. For the purpose of explanation, the terms "floc" and "contaminants" will be used interchangeably unless there is a practical benefit in distinguishing between them.

[0035] The water treatment system combining a flotation separation process and an ozone oxidation process according to the present invention is intended for application to wastewater treatment facilities. It is based on a flotation separation method in which a large amount of gas is dissolved in the incoming wastewater and gas-dissolved water is ejected to remove suspended solids, colloidal particles, etc. contained in the wastewater in the form of flotation sludge by microbubbles in the gas-dissolved water. It is configured to improve the efficiency of removing pollutants by flotation separation by optimizing the gas-liquid dissolution and microbubble generation means to maintain a constant gas dissolution rate in the dissolved water and to generate bubbles uniformly.

[0036] Furthermore, the water treatment system combines an ozone oxidation process downstream of the flotation separation, wherein the enhanced flotation separation performance upstream effectively reduces the load on the downstream ozone oxidation process, thereby enabling the effective treatment of recalcitrant organic matter in wastewater through decolorization, deodorization, disinfection, and oxidation.

[0037] The water treatment system according to the present invention includes various types of oily wastewater and non-biodegradable wastewater, such as acid / alkali wastewater generated in various industrial complexes, oily wastewater discharged from steel factories, livestock wastewater, and food wastewater, and can be applied regardless of the type of wastewater to effectively remove pollutants in the wastewater.

[0038] FIG. 1 is a conceptual diagram showing the overall configuration of a water treatment system (100) that combines a flotation separation process and an ozone oxidation process according to one embodiment of the present invention.

[0039] Referring to FIG. 1, a water treatment system (100, hereinafter abbreviated as 'system') according to one embodiment of the present invention includes a mixing and coagulating unit (110), a flotation separation device (120), a microbubble generating unit (130), an ozone contact unit (140), an ozone dissolution unit (150), and a control unit (not shown).

[0040] The mixing and coagulating unit (110) receives wastewater (water to be treated) to be treated, coagulates suspended solids and other pollutants in the water to be treated, and discharges them to a flotation separation device (120). To this end, the mixing and coagulating unit (110) may be configured as a two-stage coagulating tank structure including a first coagulating tank (113) and a second coagulating tank (115), or may be configured to perform both mixing and coagulation functions within a single reaction tank.

[0041] For example, when the mixing and coagulating unit (110) is composed of two-stage coagulating tanks, the mixing and coagulating unit (110) may be formed in a two-stage serial structure including a first coagulating tank (113) and a second coagulating tank (115), each equipped with a stirrer. Additionally, each coagulating tank (113, 115) may be equipped with a coagulant injection facility (not shown).

[0042] At this time, the first coagulation tank (113) receives the water to be treated, mixes the water to be treated with a coagulant to induce a coagulation reaction of suspended solids in the water to be treated to generate flocs, and discharges the water to be treated with flocs generated to the second coagulation tank (115).

[0043] The second coagulation tank (115) receives the water to be treated in which flocs have been formed in the first coagulation tank (113), grows the flocs in the water to be treated through slow stirring, and discharges them to the flotation separation device (120).

[0044] Meanwhile, when the mixing and coagulation unit (110) is composed of a single reaction tank, the mixing and coagulation unit (110) may be configured such that a rapid stirring area for floc generation and a slow stirring area for floc growth are separated and formed inside the reaction tank, or the mixing and coagulation functions are performed sequentially or simultaneously through the control of the rotation speed of the stirrer.

[0045] The flotation separation device (120) receives treated water that has been coagulated from the mixing and coagulating unit (110) and separates and removes contaminants using microbubbles. The flotation separation device (120) is configured to include a microbubble contact unit (121), a microbubble guide partition (1211), a flotation separation unit (123), a flotation sludge discharge unit (125), a flotation sludge collector (127), and a treated water storage unit (129).

[0046] The microbubble contact section (121) receives the treated water that has been coagulated from the mixing and coagulating section (110) and contacts the microbubbles, adsorbs the coagulated flocs onto the microbubbles, and transfers them to the flotation separation section (123).

[0047] The microbubble contact section (121) is spatially separated from the flotation separation section (123) by a microbubble guide partition (1211) and is the area where the treated water, which has undergone the coagulation process in the mixing and coagulation section (110), first flows into the flotation separation device (120). Additionally, the microbubble contact section (121) may include a microbubble generating nozzle (137), which will be described later, inside to bring the received coagulated treated water into contact with microbubbles.

[0048] The microbubble contact section (121) is designed to effectively contact and mix microbubbles with the coagulated water. For example, the microbubble contact section (121) may be provided with an inlet (not shown) at the bottom through which the treated water flowing in from the mixing and coagulating section (110) flows in. At this time, a microbubble generating nozzle (137) may also be placed at the bottom of the microbubble contact section (121) to ensure efficient contact between the microbubbles and the flocs. Additionally, the microbubble contact section (121) may be further equipped with various structures to stabilize the flow of the incoming coagulated water and increase the mixing efficiency with the microbubbles. For example, a straightening plate, an inclined plate, etc., may be further provided inside, but it is not limited to this as long as it is a means that can stabilize the flow of flocs inside the microbubble contact section (121) to promote contact with the microbubbles.

[0049] The microbubble guide partition (1211) is installed between the microbubble contact section (121) and the flotation separation section (123) and serves to guide the mixed fluid of microbubbles and coagulated water to move smoothly to the flotation separation section (123).

[0050] The microbubble guide partition (1211) is positioned in the water from the bottom of the flotation separation device (120) in an upward direction and is formed with a structure having an arbitrary angle of inclination toward the flotation separation section (123) to guide a mixed fluid of microbubbles and coagulated water.

[0051] For example, the microbubble guide wall (1211) may be configured in the shape of a bent plate in which the direction of inclination changes at an intermediate point. In this case, the lower inclined surface of the wall (1211) ensures sufficient contact time between the microbubble and the floc at the microbubble contact section (121) to improve mixing efficiency, and the upper inclined surface guides the floating floc to move smoothly to the water surface of the floating separation section (123).

[0052] The flotation separation unit (123) is connected to the microbubble contact unit (121) at the top, and through this, floc and water to be treated that have floated from the microbubble contact unit (121) are introduced, and solid-liquid separation is performed between the floc and the treated water, and the treated water is discharged to the treated water storage unit (129) and the floc is discharged to the flotation sludge discharge unit (125).

[0053] In the flotation separation section (123), flocs introduced from the microbubble contact section (121) float to the upper region of the flotation separation section (123) while attached to microbubbles, and the treated water from which suspended matter has been removed flows to the lower region of the flotation separation section (123). The lower part of the flotation separation section (123) may be formed in a tapered shape, and in this case, the treated water flowing in the lower region separated from the flocculated flocs flows along the tapered shape of the lower part of the flotation separation section (123), so that it can be discharged to the treated water storage section (129) without accumulating in the flotation separation tank (123).

[0054] The flotation sludge discharge section (125) is provided adjacent to the upper area of ​​the flotation separation section (123) to collect flocculated flocs that float and move in the form of sludge, store them, and then discharge them to the outside.

[0055] The flotation sludge discharge section (125) may be provided on the side of the flow direction of the flocculated floc at the top of the flotation separation section (123) and is installed so as to be spaced apart from the bottom of the flotation separation section (123).

[0056] The floating sludge collector (127) is installed above the water surface of the floating separation unit (123) to scrape the floating sludge and transfer it to the floating sludge discharge unit (125). To this end, the floating sludge collector (127) may be equipped with a conveyor-type scraping device.

[0057] The flotation sludge collector (127) moves along the water surface of the flotation separation tank (123) and scrapes up the floating flocculated floc, i.e., the flotation sludge, and discharges it to the flotation sludge discharge section (125).

[0058] The treated water storage unit (129) receives treated water from which suspended matter has been separated, which is moved through the lower part of the flotation separation unit (123), temporarily stores it, and then discharges it to the ozone contact unit (140) at the rear end, and some of it is circulated as microbubble dissolved water through the microbubble circulation pump (131) to be described later.

[0059] The flotation separation device (120) of the present invention generates microbubble dissolving water by circulating a portion of the treated water of the flotation separation device (120) to generate and supply microbubbles for flotation separation of flocs, and supplies this to the microbubble contact part (121). The configuration of the microbubble generating part (130) for supplying microbubble dissolving water by circulating the treated water in this manner consists of a microbubble circulation pump (131), a gas-liquid dissolving part (133), a gas-liquid separation part (135), a microbubble generating nozzle (137), and a control part (not shown), and these are organically interconnected to stably supply microbubbles of uniform size to the flotation separation device (120).

[0060] The microbubble circulation pump (131) takes a portion of the treated water stored in the treated water storage unit (129), circulates it to the gas-liquid dissolution unit (133), gas-liquid separation unit (135), and microbubble generating nozzle (137) to produce microbubble dissolved water, and discharges it to the microbubble contact unit (121).

[0061] The microbubble circulation pump (131) maintains the pressure within the circulation line for generating microbubble dissolution water within a constant range to maximize the gas dissolution efficiency in the gas-liquid dissolution section (133) and to enable stable generation of microbubbles at the microbubble generating nozzle (137) at the discharge end. To this end, the microbubble circulation pump (131) may include a pressure sensor (not shown) and a pressure tank (not shown) inside, and considering the loss within the circulation line, the discharge pressure may be set within the range of 4 to 5 kgf / ㎠, and more specifically, may be set to a discharge pressure of 4.2 to 4.5 kgf / ㎠.

[0062] The microbubble circulation pump (131) operates in conjunction with a control unit (not shown) and actively adjusts the discharge flow rate or discharge pressure according to a control signal from the control unit (not shown) in response to pressure fluctuations that may occur while discharging undissolved gas from the downstream gas-liquid separation unit (135). The specific operation method of the microbubble circulation pump (131) will be described later by the control unit (not shown).

[0063] The gas-liquid dissolution unit (133) receives pressurized circulating water from the microbubble circulation pump (131), dissolves a gas (e.g., air) introduced from the outside into the circulating water, and discharges the generated dissolved water to the gas-liquid separation unit (135).

[0064] The gas-liquid dissolution section (133) can be structured to maintain a high internal pressure and increase the contact area between the incoming circulating water and the gas to maximize gas dissolution efficiency.

[0065] It is desirable that the interior of the gas-liquid dissolution section (133) be maintained within a preset pressure range so that gas dissolution can be effectively achieved. The internal pressure of the gas-liquid dissolution section (133) for effective gas dissolution is formed by a microbubble circulation pump (131), which is preferably within the range of 3.5 to 4.5 kgf / ㎠, and more specifically, can be maintained within the range of 3.8 to 4.2 kgf / ㎠.

[0066] The gas-liquid dissolution unit (133) for this purpose can be configured in various forms, for example, one or more selected from a gas-liquid dissolution device of a swirling flow induction type, a Venturi type injector, a static mixer type, and a dissolution device using a cavitation disk may be applied. However, the specific examples of the gas-liquid dissolution means described above are for illustrative purposes only, and various modifications and applications are possible within the scope of the technical concept of the present invention.

[0067] Meanwhile, the gas flowing into the gas-liquid dissolution unit (133) may be supplied from air in the atmosphere or from a separate gas storage tank (not shown), or supplied by a compressor (not shown).

[0068] The gas-liquid separation unit (135) receives gas-dissolving water from the gas-liquid dissolving unit (133), separates and discharges undissolved gas within the dissolving water, and then discharges it through the microbubble generating nozzle (137).

[0069] The gas-liquid separation unit (135) separates undissolved gas in the gas-dissolved water from the dissolved water using a separation method utilizing centrifugation and buoyancy, and discharges the separated gas to the outside when the undissolved gas is collected above a preset level. To this end, the gas-liquid separation unit (135) of the present invention includes a water level gauge inside, transmits a water level fluctuation signal to a control unit (not shown), and discharges the undissolved gas under the control of the control unit (not shown). The specific configuration of the gas-liquid separation unit (135) is illustrated in FIG. 2.

[0070] FIG. 2 is a configuration showing a gas-liquid separation unit according to one embodiment of the present invention.

[0071] Referring to FIG. 2, a gas-liquid separation unit (135) according to one embodiment of the present invention includes an outer tube (210), an inner tube (220), a first water level sensor (222), a second water level sensor (224), a gas-dissolving water inlet (230), a gas-dissolving water outlet (240), and a gas outlet (250).

[0072] The outer casing (210) is a main body forming the outer casing of the gas-liquid separation unit (135), and provides a space in which a mixture of dissolved water and undissolved gas introduced from the gas-liquid dissolution unit (133) can move upward and downward while maintaining a swirling flow inside.

[0073] The outer casing (210) can generally be formed into a cylindrical container. The outer casing (210) is designed to have sufficient strength to withstand internal pressure and can be made of a material with excellent corrosion resistance.

[0074] The inner tube (220) is a cylindrical structure installed in the center of the outer tube (210), is coaxially arranged on the central axis of the outer tube (210), and forms an annular space together with the outer tube (210) to provide a swirling flow space for dissolved water and undissolved gas, and separates the discharge passage of the separated undissolved gas.

[0075] The inner tube (220) is equipped with a first water level sensor (222) and a second water level sensor (224) to detect the water level of the gas dissolved in the interior, and the detected water level information is linked to a control unit (not shown) and used for the discharge of undissolved gas and the control of the microbubble circulation pump (131).

[0076] The first and second water level sensors (222, 224) are arranged at regular intervals in the vertical direction inside the inner tube (220).

[0077] For example, a first water level sensor (222) is positioned at the upper part of the inner tube (220), and a second water level sensor (224) is installed at the lower part to detect the height of the liquid level on the inner surface of the outer tube (210). At this time, the first water level sensor (222) is installed at a point 70 to 80% above the bottom surface based on the maximum height (H) of the effective volume of the outer tube (210) to detect the upper limit water level. Conversely, the second water level sensor (224) is located at a point 30 to 50% based on the maximum height (H) of the effective volume of the outer tube (210) to detect the lower limit liquid level.

[0078] When the liquid level in the gas-liquid separation unit (135) is detected at the point of the second liquid level sensor (224), the control unit (not shown) opens the vent valve to discharge undissolved gas through the gas outlet (250). Additionally, when the liquid level in the gas-liquid separation unit (135) is detected at the point of the first liquid level sensor (222) through the discharge of gas, the control unit (not shown) closes the vent valve.

[0079] That is, the gas-liquid separation unit (135) of the present invention forms a hysteresis band between the first water level sensor (222) and the second water level sensor (224) to detect the water level of the gas dissolved water fluctuating due to the undissolved gas and discharge the undissolved gas, thereby preventing frequent opening and closing of the vent valve and enabling stable gas-liquid separation.

[0080] The gas-dissolved water inlet (230) is a passage through which the gas-dissolved water generated in the gas-liquid dissolution section (133) flows into the gas-liquid separation section (135).

[0081] The gas dissolving water inlet (230) is installed tangentially on the upper side, i.e., the upper side, of the outer tube (210) to induce the incoming gas dissolving water to form a downward swirling flow in the annular space between the outer tube (210) and the inner tube (220) along the inner surface of the outer tube (210). Through the tangential inflow by the gas dissolving water inlet (230), the mixture of dissolving water and undissolved gas swirls, causing the undissolved gas to be separated upward by buoyancy and the gas dissolving water to be separated downward.

[0082] The gas-dissolved water discharge port (240) is formed at the bottom of the outer casing (210) and is a passage through which dissolved water, from which undissolved gas has been separated, is discharged from the gas-liquid separation unit (135) to the microbubble generating nozzle (137).

[0083] As described above, as the gas dissolved water moves in a swirling motion inside the outer casing (210) and the undissolved gas is separated by buoyancy, only the separated gas dissolved water can be stably discharged from the gas dissolved water discharge port (240) located at the bottom.

[0084] The gas outlet (250) is separated at the top of the gas-liquid separation unit (135), and a vent valve (not shown) is installed so that it is intermittently opened under the control of a control unit (not shown) to discharge undissolved gas to the outside.

[0085] The gas outlet (250) is normally kept closed to maintain the internal pressure of the gas-liquid separation unit (135), and the undissolved gas flowing into the gas-liquid separation unit (135) moves upward along the outer surface of the inner tube (220) and moves toward the gas outlet (250). Consequently, when the liquid level inside the gas-liquid separation unit (135) drops below a certain level, the vent valve is opened by the control of the control unit (not shown) to discharge the gas. The certain liquid level at which gas begins to be discharged from the gas outlet (250) may be the point where the liquid level (water level) is detected below the second liquid level sensor (224) of the inner tube (220), as described above.

[0086] The gas discharged from the gas outlet (250) may be discharged to the outside air, or collected in a gas storage tank (not shown) that supplies raw gas to the gas-liquid dissolution unit (133) and reused.

[0087] Since the gas-liquid separation unit (135) of the present invention separates and discharges undissolved gas mixed in the dissolved water before the microbubble generation stage, the highly soluble gas dissolved water can be rapidly supplied to the microbubble generation nozzle (137), thereby increasing the microbubble production speed and further enabling the generation of microbubbles of uniform size.

[0088] Referring again to FIG. 1, the microbubble generating nozzle (137) receives high-concentration gas-dissolved water from the gas-liquid separation unit (135), converts it into microbubbles, and discharges the microbubbles to the microbubble contact tank (121).

[0089] A microbubble generating nozzle (137) is positioned inside the flotation separation device (120), and in particular, the discharge port may be positioned adjacent to the inflow side of the water to be treated at the bottom of the microbubble contact tank (121).

[0090] The microbubble generating nozzle (137) of the present invention generates microbubbles using an expanded tube structure and maximizes uniformity. The specific structure and operating principle of the microbubble generating nozzle (137) will be described later in FIGS. 3 to 5.

[0091] The ozone contact section (140) contacts the treated water received from the flotation separation device (120) of the preceding section with ozone to perform additional treatment such as sterilization, disinfection, and / or decomposition of non-degradable organic matter. To this end, the ozone contact section (140) receives high-concentration ozone-dissolved water from the ozone dissolution section (150), and the ozone-treated water may be discharged to the outside, reused and / or circulated to generate ozone-dissolved water, or supplied to a separate post-treatment process as needed.

[0092] The ozone contact section (140) may be equipped with a plurality of flow guide partitions (145a, 145b) to guide the flow of treated water inside. A plurality of flow guide partitions (145a, 145b) are spaced apart inside the ozone contact section (140) to form a path for the treated water to move from an inlet on one side of the ozone contact section (140) to an outlet on the other side, thereby securing a sufficient contact time between the treated water and ozone and maximizing the reaction efficiency with ozone. The flow through the flow guide partitions (145a, 145b) inside the ozone contact section (140) can be implemented in an upward / downward or left / right direction depending on the arrangement of the partitions.

[0093] For example, when an upward and downward zigzag flow is implemented within the ozone contact section (140), the first flow guide baffle (145a) is installed so as to extend vertically from the bottom surface of the ozone contact section (140) but not to touch the top surface. On the other hand, the second flow guide baffle (145b) is installed so as to extend from the top surface of the ozone contact section (140) toward the bottom surface but not to touch the bottom surface. In this way, when the first flow guide baffle (145a) and the second flow guide baffle (145b) are alternately arranged, the treated water flowing into the ozone contact section (140) flows upward along the first baffle and then changes direction downward at the second baffle, repeating this process.

[0094] Meanwhile, the flow guide baffles (145a, 145b) may be installed to alternately protrude from the left and right walls of the ozone contact section (140) so as to have the treated water flow in a zigzag pattern in the horizontal direction.

[0095] The ozone contact section (140) may further include a separate water quality sensor (not shown) inside to monitor water quality information of the treated water of the flotation separation device (120) flowing into the ozone contact section (140). The control section (not shown) can control the amount of ozone required to be injected into the ozone contact section (140) based on the measured value from the water quality sensor (not shown).

[0096] Additionally, the ozone contact section (140) may further include a UV lamp inside as needed to transmit additional UV light to the treated water inside the ozone contact section (170), thereby further improving the decomposition efficiency of non-decomposable organic matter.

[0097] The ozone dissolution unit (150) efficiently dissolves ozone into the treated water to produce high-concentration ozone dissolved water and supplies it to the ozone contact unit (140). To this end, the ozone dissolution unit (150) is configured to include a circulating water pressure pump (151) that takes a portion of the treated water in which an ozone oxidation reaction has taken place at the downstream end of the ozone contact unit (140) as circulating water, an ozone generator (153) that generates ozone gas, an ozone injection unit (155) that injects ozone gas into the taken circulating water, and a pressure dissolution tank (157) that promotes the dissolution of ozone.

[0098] The circulating water pressure pump (151) takes a portion of the treated water discharged from the downstream side, i.e., the rear end of the ozone contact section (140), and circulates it through the ozone injection section (155) and the pressurized dissolution tank (157) in sequence to produce pressurized ozone dissolved water, and then discharges it to the inlet side of the ozone contact section (140). At this time, the flow rate of the treated water circulated to produce pressurized ozone dissolved water may be about 3 to 20% of the total flow rate of treated water discharged from the ozone contact section (140).

[0099] The circulating water pressure pump (151) maintains the pressure in the circulation pipe for generating pressurized ozone dissolved water within a constant range so that an appropriate amount of ozone is injected from the ozone injection unit (155) and the ozone dissolution efficiency in the pressurized dissolution tank (157) can be maximized. For this purpose, the circulating water pressure pump (151) can be set to a discharge pressure within the range of 5 to 6 kgf / ㎠, taking into account the ozone injection unit (155) and the loss in the circulation pipe, and more specifically, can be set to a discharge pressure of about 5.2 to 5.5 kgf / ㎠.

[0100] The ozone generator (153) receives raw gas and generates high-concentration ozone gas, and supplies it to the circulating water through the ozone injection unit (155).

[0101] The ozone generator (153) may use air or oxygen as a raw gas and may be equipped with a separate raw gas supply unit (not shown) for supplying the raw gas. For example, the ozone generator (153) may be a corona discharge type ozone generator, but is not specifically limited thereto, and any known device of a type commonly used as a water treatment ozone generator that can stably generate ozone gas may be applied without limitation.

[0102] The ozone injection unit (155) is positioned on the circulation pipe and receives pressurized circulating water from the circulating water pressure pump (151), injects ozone gas generated from the ozone generator (153) into the circulating water, and discharges the ozone-mixed circulating water to the pressurized dissolution tank (157).

[0103] The ozone injection unit (155) may be equipped with various types of dissolution means, and any one selected from a gas-liquid dissolution device using a swirling flow induction method, a Venturi Injector, a static mixer, or a dissolution device using a cavitation disk may be used. However, any known dissolution means capable of dissolving ozone gas in circulating water may be used without being limited to the above devices.

[0104] The pressurized dissolution tank (157) receives circulating water that has been mixed with ozone as it passes through the ozone injection section (155), completely dissolves the ozone gas, and then discharges the ozone-dissolved water to the ozone contact section (140).

[0105] The pressurized dissolution tank (157) completely dissolves the ozone by maintaining a preset level of high pressure for a sufficient residence time with respect to the circulating water primarily mixed with ozone. At this time, the pressure formed by the circulating water pressurizing pump (151) promotes the dissolution of fine ozone bubbles into the circulating water inside the tank (157). The preset pressure that causes the ozone gas to be completely dissolved in the pressurized dissolution tank (157) is approximately 1.5 to 2.0 kgf / cm² 2 It can be set within the range of.

[0106] The control unit (not shown) controls the operation of each component within the system (100).

[0107] In particular, the control unit (not shown) organically links and controls the operation of the microbubble generation unit (130), the ozone contact unit (140) and the ozone dissolution unit (150) that constitute the ozone treatment process, thereby maximizing the processing efficiency and stability of the entire system.

[0108] First, the control unit (not shown) controls the operation of the microbubble circulation pump (131) and the gas-liquid separation unit (135) with respect to the microbubble generation unit (130) to stabilize the pressure within the circulation line of the gas-dissolved water and control the undissolved gas.

[0109] Specifically, the control unit (not shown) controls the microbubble circulation pump (131) and the gas-liquid separation unit (135) in conjunction according to the following control sequence. The control unit (not shown) receives pressure information inside the circulation line from a pressure sensor (not shown) provided on the discharge side of the microbubble circulation pump (131). In addition, the control unit (not shown) receives water level information inside the gas-liquid separation unit (135) from water level sensors (222, 224) installed inside the gas-liquid separation unit (135).

[0110] The control unit (not shown) analyzes the water level information received from the water level sensors (222, 224) of the gas-liquid separation unit (135) and, when the water level reaches a preset lower limit, opens the vent valve of the gas outlet (250) to discharge the undissolved gas accumulated in the upper part of the gas-liquid separation unit (135) to the outside. Subsequently, when the water level reaches a preset upper limit, it closes the vent valve of the gas outlet (250) to stop gas discharge and restore the water level. Through this water level-based control, the internal water level of the gas-liquid separation unit (135) is automatically maintained within a certain range, undissolved gas is effectively discharged, and internal pressure fluctuations caused by the discharge of undissolved gas are minimized.

[0111] Additionally, the control unit (not shown) detects pressure fluctuations in the circulation line when the vent valve of the gas-liquid separation unit (135) is operated, and analyzes pressure information received from the pressure sensor (not shown). When the pressure drops below a preset lower limit pressure, the rotation speed of the microbubble circulation pump (131) is increased. When the rotation speed of the microbubble circulation pump (131) increases, the discharge flow rate increases, causing the pressure in the circulation line to rise and allowing the pressure of the circulating water flowing into the gas-liquid dissolution unit (133) to be quickly restored. Subsequently, when the pressure reaches a preset range or an upper limit pressure, the rotation speed of the microbubble circulation pump (131) is returned to a normal speed, or the pressure in the circulation line is maintained constant through pump flow rate control according to the pressure change trend.

[0112] Through such pump flow rate control, the pressure drop caused by the operation of the vent valve of the gas-liquid separation unit (135) is compensated in real time, and the reduction in gas dissolution efficiency in the gas-liquid dissolution unit (133) is prevented so that a certain level of dissolution rate is maintained.

[0113] In addition, the control unit (not shown) controls the ozone contact unit (140) and the ozone dissolution unit (150) in conjunction with the flotation separation process so that the subsequent ozone oxidation process is maintained in an optimal state.

[0114] A control unit (not shown) receives the flow rate and / or water quality measurement values ​​of the treated water flowing into the ozone contact unit (140), calculates the amount of ozone injected, and, based on the result, controls the amount of ozone generated by the ozone generator (153), whether to draw circulating water by the circulating water pressure pump (151), and the amount of water drawn. For example, if the flow rate of the treated water flowing in from the flotation separation device (120) increases or the pollution load increases, the control unit (not shown) increases the output of the ozone generator (153) to increase the amount of ozone injected.

[0115] In conclusion, the control unit (not shown) of the present invention stabilizes the generation of microbubbles in the microbubble generation unit (130), which is the core of the flotation separation process, and optimizes the efficiency of the ozone oxidation process. By operating organically under this coordinated control of the control unit (not shown), the problems of undissolved gas and pressure fluctuations are effectively resolved, and the primary treatment efficiency is maximized by stably and continuously supplying microbubbles of uniform size to the flotation separation device (120). As a result, this reduces the load on the subsequent ozone oxidation process and optimizes the amount of ozone used, thereby greatly improving the overall treatment efficiency, operational stability, and economic efficiency of the system (100).

[0116] FIG. 3 is a schematic diagram showing a microbubble generating nozzle according to one embodiment of the present invention, and FIG. 4 is a diagram for explaining the diffusion angle of the expansion of FIG. 3.

[0117] As described above, the microbubble generating nozzle (137) generates microbubbles of fine and uniform size from the high-concentration gaseous dissolved water received from the gas-liquid separation unit (135) through pressure reduction and discharges the microbubbles to the microbubble contact unit (121).

[0118] Referring to FIG. 3, the microbubble generating nozzle (137) is configured to include an inlet (310), a collision plate (315), at least one expansion section (320), and an outlet (340). When the expansion section (320) is configured in multiple numbers, a straight connecting section (330) is arranged between adjacent expansion sections (320).

[0119] The microbubble generating nozzle (137) of the present invention is characterized by employing an expansion structure and a collision plate to provide improved microbubble uniformity compared to conventional nozzles.

[0120] The inlet section (310) is the part where the high-concentration gaseous dissolved water supplied from the gas-liquid separation section (135) first flows into the microbubble generating nozzle (137). As shown in FIG. 3, the inlet section (310) is formed in the shape of a cylindrical tube, and the dissolved water flows into the nozzle (137) as high-pressure, high-speed water through the inlet opening (313) in the center of the inlet side. The diameter of the inlet opening (313) is formed to be smaller than the diameter of the inlet section (310) to minimize flow rate loss.

[0121] A collision plate (315) is disposed inside the inlet section (310), more specifically at the rear end of the inlet section (310), so that the incoming high-speed gas dissolved water collides with it to induce the formation of initial nucleation of bubbles.

[0122] The impact plate (315) is positioned so that a collision section (3151) is formed in the center and high-pressure dissolved water passing through the inflow opening (313) directly collides with it. Due to the collision between the collision section (3151) and the dissolved water, a localized pressure drop and a change in flow velocity occur, which promotes the phenomenon of supersaturated gas in the dissolved water precipitating in the form of fine bubble nuclei.

[0123] The impact plate (315) has a plurality of through holes (3153) formed in a radial arrangement in the area surrounding the impact section (3151), and the dissolved water branched out after impact from the impact section (3151) passes through the through holes (3153), amplifying the rotational flow and shear force to disperse the bubbles more finely. The number, diameter, and spacing of the through holes (3153) can be changed according to the processing flow rate and the target bubble size.

[0124] Additionally, a plurality of impact plates (315) disposed inside the inlet section (310) may be sequentially arranged, and when a plurality of impact plates (315) are formed, it is advantageous for the through holes (3153) formed in each impact plate (315) to be arranged staggered so as not to be located on the same axis. One or more expansion sections (320) are connected to the rear end of the inlet section (310), and the expansion sections (320) are formed such that their cross-sectional area gradually increases as they go from the inlet section (310) toward the discharge section (340) along the direction of fluid flow. When a plurality of expansion sections (320) are formed, a straight connecting section (330) is disposed between adjacent expansion sections (320), and when there is only one expansion section (320), the straight connecting section (330) may be omitted.

[0125] delete

[0126] In the embodiment of FIG. 3, a three-stage structure in which three expansion sections (320a, 320b, 320c) are sequentially connected is illustrated, but the expansion section (320) may be composed of one or more stages, and the number of stages of the expansion section (320) may be changed depending on the processing conditions and the characteristics of the required microbubbles. When the expansion section (320) is composed of multiple stages, a straight connecting section (330) is placed between adjacent expansion sections (320), and when there is only one expansion section (320), the straight connecting section (330) may be omitted.

[0127] Referring to FIG. 3, when looking at the configuration in which three expansion sections (320) are connected, the first expansion section (320a), the second expansion section (320b), and the third expansion section (320c) are sequentially connected to the rear end of the collision plate (315), representing a flow path that expands in stages.

[0128] Referring to FIG. 4, it is preferable that the diffusion angles (θ1, θ2, θ3) of each expansion section (320a, 320b, 320c) included in the nozzle (137) of the present invention be formed within a range of 3 to 15°. Additionally, the diffusion angles of adjacent expansion sections are the same, or the diffusion angle of the expansion section at the rear is configured to increase compared to the diffusion angle of the expansion section at the front. Furthermore, the nozzle (137) of the present invention has a diffusion angle (θ) of the entire expansion structure regardless of the number of expansion sections. T For example, based on FIG. 4, the total diffusion angle from the starting point of the first expansion section (320a) to the end point of the third expansion section (320c) is also preferably limited to 15° or less.

[0129] For example, when there are three expansion sections (320), the diffusion angle (θ1) of the first expansion section (320a) may be approximately 2° or more and 6° or less, the diffusion angle (θ2) of the second expansion section (320b) may be in the range of θ1 ≤ θ2 ≤ 10°, and the diffusion angle (θ3) of the third expansion section (320c) may be in the range of θ2 ≤ θ3 ≤ 15°. At this time, the total diffusion angle (θ T ) should not exceed 15°.

[0130] By gradually expanding the bubble discharge path of the nozzle, a gradual pressure drop is performed, allowing for stable growth and dispersion of microbubbles in the gas-dissolved water. However, if the diffusion angle of the expansion section exceeds 15°, a problem may arise where the size of the microbubbles increases due to the occurrence of a wake.

[0131] The discharge port (340) serves as the final outlet of the microbubble generating nozzle (137) and discharges the mixed fluid of microbubbles and dissolved water generated through the expansion structure to the outside of the nozzle, i.e., to the microbubble contact portion (121). Accordingly, the discharge port (340) is connected to the inside of the microbubble contact portion (121) of the flotation separation device (120).

[0132] The microbubble generating nozzle (137) of the present invention has the advantage of dispersing the pressure drop for bubble generation in stages to alleviate the bubble generation conditions, and expanding the flow path through which the bubbles are finally discharged to evenly supply microbubbles over a wide area within the contact portion (121).

[0133] Even in the case of a single expansion structure with one expansion section (320), microbubbles can be generated through diffusion angle control and collision plates. In particular, when a multi-stage expansion structure consisting of multiple expansion sections (320) is applied, the generation and growth of bubbles proceed in multiple stages, thereby preventing sudden expansion and aggregation of bubbles, which has the advantage of generating bubbles of smaller and more uniform size compared to a single expansion structure. In this case, a straight connecting section (330) is placed between adjacent expansion sections (320) to connect the flow paths between each expansion section (320).

[0134] FIG. 5 is a drawing showing a microbubble generating nozzle (137') according to another embodiment of the present invention.

[0135] Referring to FIG. 5, a microbubble generating nozzle (137') according to another embodiment includes an inlet (510), an expansion section (320), a straight connection section (330), and an outlet section (340) in the same way as the embodiment of FIG. 3, and generates microbubbles of a fine and uniform size. The other embodiment shown in FIG. 5 has a difference in the configuration of the inlet (510), and the other configurations are the same as the embodiment of FIG. 3 described above; therefore, the following description will focus on the difference in the inlet (510).

[0136] Referring to FIG. 5, a nozzle (137') according to another embodiment of the present invention includes an inlet part (510) comprising an inlet opening (513) and a collision plate (515).

[0137] The inlet section (510) may be configured in the form of a cylindrical tube, and is identical to the inlet section (310) described above in that an inlet opening (513) is placed on the inlet side and a collision plate (515) is placed at the rear end.

[0138] The inlet opening (513) is formed on the inlet side of the inlet section (510) to allow the gas dissolved water to pass inside, and can be configured in a funnel shape or a cone shape that narrows toward the inlet direction.

[0139] In this way, the inlet opening (513), which is in the shape of a funnel or cone that gradually narrows, can increase the flow velocity of the incoming gaseous dissolved water and provide a more concentrated flow to the impact plate (515). At this time, by adjusting the narrowing angle and shape change of the inlet opening (515), the impact effect at the impact plate (515) can be optimized and the initial bubble nucleation efficiency can be further improved. In addition, the funnel-shaped inlet opening (513) can be advantageous for controlling the pressure distribution inside the nozzle (137).

[0140] The impact plate (515) has a structure similar to the impact plate (315) described in the embodiment of FIG. 3, and if necessary, a plurality of impact plates (515) may be placed inside the inlet (510).

[0141] In the following, the wastewater treatment efficiency of the flotation separation device (120) according to one embodiment of the present invention and the circulating line of the microbubble dissolved water connected thereto is compared with the wastewater treatment efficiency of the flotation separation treatment process according to a comparative example.

[0142] Examples

[0143] Referring to the configuration of the flotation separation device (120), microbubble circulation pump (131), gas-liquid dissolution unit (133), gas-liquid separation unit (135), microbubble generating nozzle (137), and control unit (not shown) of FIG. 1, pressure control within the circulation line was performed by linking the gas-liquid separation unit (135) and the microbubble circulation pump (131). That is, undissolved gas in the gas-liquid separation unit (135) was removed by detecting the water level of the first and second water level sensors (222, 224) in the gas-liquid separation unit (135), and the rotation speed of the microbubble circulation pump (131) was controlled by detecting the pressure when the vent valve of the gas discharge port (250) for gas discharge in the gas-liquid separation unit (135) was opened. In addition, the microbubble generating nozzle was applied with a three-stage expansion structure to supply microbubbles to the flotation separation device (120).

[0144] Comparative example

[0145] Floating separation of the water to be treated was performed by including a flotation separation device with the same configuration as in Example 1, a microbubble circulation pump, a gas-liquid dissolution unit, a gas-liquid separation unit, and a microbubble generating nozzle. However, the gas-liquid separation unit was configured to discharge gas according to a preset cycle (discharging gas by closing for 3 minutes and then opening for 10 seconds) rather than discharging undissolved gas based on the water level, and the control of the gas-liquid separation unit and the microbubble circulation pump was not linked.

[0146] Table 1 below shows the removal rate of suspended solids (SS) in wastewater according to the flotation separation devices of the examples and comparative examples.

[0147] Measurement order Examples Comparative example Influent (mg / L) treated water (mg / L) Removal rate (%) Influent (mg / L) treated water (mg / L) Removal rate (%) 1 450 12 97.3 590 54 90.8 2 425 5 98.8 610 62 89.8 3 545 19 96.5 580 55 90.5 4 605 22 96.4 620 53 91.5 average 506.3 14.5 97.3 600.0 56.0 90.7

[0148] Looking at Table 1, in the case of an embodiment in which the pressure in the circulation line is controlled by linking the gas-liquid separation unit (135) and the microbubble circulation pump (131), the SS removal rate in the 4th measurement result was 96% or higher and showed excellent performance with an average of 97.3%.

[0149] On the other hand, in the case of the comparative example, the SS removal rate for the same wastewater ranged from 89.8% to 91.5%, showing lower removal performance compared to the example, and the average removal rate was also 90.7%, which is more than 6% lower than the example. In particular, the difference in the pollutant removal rate due to pressure control within the microbubble circulation line can be more clearly confirmed in the 3rd and 4th stages of the example and the 1st and 2nd stages of the comparative example, where the SS concentration of the influent water is similar.

[0150] Figure 6 shows the result of the pollutant removal rate in a flotation separation device according to an embodiment of the present invention.

[0151] Referring to FIG. 6, it can be seen that the flotation separation device (120) of the embodiment achieves high removal rates for suspended solids (SS), total phosphorus (TP), and chemical oxygen demand (CODcr).

[0152] Specifically, the average influent water quality of the wastewater introduced into the flotation separation device (120) of the embodiment was maintained at a level of 506.3 mg / L for SS, 22.43 mg / L for total phosphorus (TP), and 1,201 mg / L for CODcr, and the flotation separation device (120) of the present invention showed a removal performance of 99% for TP removal and 77% for CODcr in addition to a 97% SS removal rate.

[0153] In particular, the fact that the total phosphorus (TP) removal rate is 99%, which is an overwhelmingly high figure, implies that the microbubble generation system of the present invention can exhibit excellent effects in removing flocs generated by phosphorus removal coagulants, and suggests that it can contribute significantly to meeting stricter water quality regulatory standards. In addition, the chemical oxygen demand removal rate, which is relatively high at 77%, also shows that most of the solid organic matter is removed by the formation of stable microbubbles. As a result, the inhibition of organic matter by solid matter in the ozone contact section (140) at the downstream end is minimized, thereby further improving the treatment efficiency of residual non-biodegradable organic matter.

[0154] A water treatment system (100) including a flotation separation process and an ozone oxidation process according to the present invention can stably and continuously generate microbubbles of uniform size and supply them to a flotation separation device through the configuration and operation of a microbubble generating nozzle (137) with an expanded structure, a gas-liquid separation unit (135), a microbubble circulation pump (131) having an active pressure control function, and a control unit (not shown) that organically links and controls them. This maximizes flotation separation efficiency to improve the removal performance of various pollutants, and furthermore, improves the efficiency of the subsequent ozone oxidation process, thereby simultaneously ensuring the stability of the overall system operation.

[0155] The above description is merely an illustrative explanation of the technical concept of the present embodiment, and a person skilled in the art to which the present embodiment belongs would be able to make various modifications and variations within the scope of the essential characteristics of the present embodiment. Accordingly, the present embodiments are intended to explain, not limit, the technical concept of the present embodiment, and the scope of the technical concept of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present embodiment. Explanation of the symbols

[0156] 100: Water treatment system 110: Mixing and coagulation unit 113: First coagulation tank 115: Second coagulation tank 120: Flotation separation device 121: Microbubble contact unit 1211: Microbubble guide baffle 123: Flotation separation unit 125: Flotation sludge discharge unit 127: Flotation sludge collector 129: Treated water storage unit 130: Microbubble generation unit 131: Microbubble circulation pump 133: Gas-liquid dissolution unit 135: Gas-liquid separation unit 137: Microbubble generation nozzle 140: Ozone contact unit 145a, 145b: Flow guide baffle 150: Ozone dissolution unit 151: Circulating water pressurization pump 153: Ozone generator 155: Ozone injection unit 157: Pressurized dissolution tank 210: Outer casing 220: Inner casing 222: First water level sensor 224: Second water level sensor 230: Gas Dissolving water inlet 240: Gas dissolving water outlet 250: Gas outlet 310, 510: Inlet section 313, 513: Inlet opening 315, 515: Impact plate 3151: Impact section 3153: Through hole 320, 320a, 320b, 320c: Expansion section 330: Straight connection section 340: Discharge section

Claims

Claim 1 A water treatment system combining a flotation separation process and an ozone oxidation process for simultaneously removing high concentrations of solids and non-biodegradable organic substances contained in wastewater, comprising: a flotation separation device that receives coagulated treated water and separates the coagulated flocs by flotation; a microbubble generation unit that supplies microbubbles to the flotation separation device; an ozone contact unit that receives treated water discharged from the flotation separation device and performs the removal of residual organic substances and color through ozone contact; and an ozone dissolution unit that supplies ozone-dissolved water to the ozone contact unit, wherein the microbubble generation unit comprises: a microbubble circulation pump for circulating a portion of the treated water of the flotation separation device; a gas-liquid dissolution unit that dissolves gas in the treated water taken by the microbubble circulation pump; and a gas-liquid separation unit that receives the dissolved water generated in the gas-liquid dissolution unit and separates undissolved gas. A water treatment system combining a flotation separation process and an ozone oxidation process, comprising a microbubble generating nozzle that receives gas-dissolved water discharged from the gas-liquid separation unit, generates microbubbles, and supplies them to the flotation separation device, wherein the gas-liquid separation unit includes a cylindrical outer tube and an inner tube disposed inside the outer tube, and receives gas-dissolved water through a tangential gas-dissolved water inlet formed on the upper side of the gas-liquid separation unit, and separates undissolved gas by generating a swirling flow of the gas-dissolved water introduced in the space formed between the outer tube and the inner tube. Claim 2 A water treatment system combining a flotation separation process and an ozone oxidation process, wherein, in claim 1, the water treatment system further includes a control unit, and the control unit controls the operation of the microbubble generating unit, the ozone contact unit, and the ozone dissolution unit in an organically linked manner. Claim 3 A water treatment system combining a flotation separation process and an ozone oxidation process, wherein, in claim 1, the microbubble generating nozzle is disposed inside the flotation separation device. Claim 4 A water treatment system combining a flotation separation process and an ozone oxidation process, wherein, in paragraph 2, the control unit controls the microbubble circulation pump and the gas-liquid separation unit in conjunction. Claim 5 A water treatment system combining a flotation separation process and an ozone oxidation process, wherein, in paragraph 2, the ozone dissolution unit comprises: a circulating water pressurizing pump that takes a portion of the treated water from the ozone contact unit as circulating water and pressurizes it; an ozone generator that generates ozone gas; an ozone injection unit that injects ozone gas generated from the ozone generator into the circulating water transferred from the circulating water pressurizing pump; and a pressurized dissolution tank that pressurizes the circulating water passing through the ozone injection unit to dissolve ozone. Claim 6 A water treatment system combining a flotation separation process and an ozone oxidation process, wherein, in paragraph 4, the control unit detects the water level of the gas-liquid separation unit, controls whether to open or close the vent valve of the gas-liquid separation unit to discharge undissolved gas inside the gas-liquid separation unit according to the detected water level, and controls the discharge flow rate of the microbubble circulation pump in conjunction with the opening or closing of the vent valve. Claim 7 delete Claim 8 A water treatment system combining a flotation separation process and an ozone oxidation process, wherein, in claim 1, the microbubble generating nozzle comprises: an inlet section into which gas-dissolved water is introduced; a plurality of expansion sections; a straight connecting section disposed between adjacent expansion sections; and a discharge section for discharging the generated microbubbles, wherein the inlet section is characterized by having at least one impact plate disposed therein. Claim 9 A water treatment system combining a flotation separation process and an ozone oxidation process, characterized in that, in claim 8, the impact plate comprises a central impact portion and a plurality of through holes arranged radially to surround the impact portion. Claim 10 In claim 8, the diffusion angle (θ) of the entire nozzle formed through the plurality of expansion sections T A water treatment system combining a flotation separation process and an ozone oxidation process, characterized in that ) is 15° or less. Claim 11 In Clause 10, the diffusion angle (θ) of each of the plurality of expanded sections mentioned above. n A water treatment system combining a flotation separation process and an ozone oxidation process, characterized in that ) is 3° or more and 15° or less. Claim 12 A water treatment system combining a flotation separation process and an ozone oxidation process, wherein, in claim 8, the inlet part includes an inlet opening on one side that allows gas-dissolved water to flow into the microbubble generating nozzle, and the inlet opening is formed with a structure in which the cross-sectional area gradually decreases along the direction of inflow of the gas-dissolved water. Claim 13 A water treatment system combining a flotation separation process and an ozone oxidation process, wherein, in claim 1, the ozone contact section further includes a UV lamp inside to irradiate UV light onto the treated water within the ozone contact section.

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