Method and apparatus for reducing wastewater to concentrated wastewater

Abstract

The present invention produces concentrated wastewater by efficiently separating excess water from a large amount of wastewater, and furthermore, efficiently separates effluent by membrane separation from the excess water separated from the wastewater, thereby reducing wastewater for disposal to concentrated wastewater. This method for separating excess water 2 from wastewater 1 and reducing the result to concentrated wastewater 3 comprises: a first separation step for separating the excess water 2 from the wastewater 1; and a second separation step for separating effluent 4 from the excess water 2. The first separation step is for producing concentrated wastewater 3 by separating excess water 2 from wastewater 1 via an ultrasonic atomization step in which a carrier gas is blown to the surface of a liquid column P of wastewater 1 rising above the liquid level due to ultrasonic vibration, and mist is supplied to the carrier gas from the surface of the liquid column P to produce a gas mixed with mist and a recovery step in which excess water 2 in the wastewater 1 is separated by separating the mist from the gas mixed with mist produced in the ultrasonic atomization step. The second separation step is a membrane separation step for membrane-separating impurities from the excess water 2 obtained in the ultrasonic separation step, and the membrane separation step separates effluent 4 from the excess water 2.

Description

Method and apparatus for reducing the volume of drainage to concentrated drainage

[0001] The present disclosure relates to a method and apparatus for separating surplus water from wastewater to be disposed of and obtaining concentrated drainage, and particularly to a method and apparatus for separating surplus water from wastewater to be disposed of by a method such as incineration and reducing the volume of the drainage to concentrated drainage.

[0002] Wastewater containing impurities such as harmful substances is disposed of by various methods in order to be discarded without hindering the natural environment. As methods for separating and reducing the volume of organic substances from wastewater, methods for decomposing organic substances with microorganisms and methods for precipitating insoluble substances and suspended substances have been developed (see Patent Documents 1 to 3).

[0003] Japanese Patent Application Laid-Open No. 2024-121217, Japanese Patent Application Laid-Open No. 2024-099358, Japanese Patent Application Laid-Open No. 2020-179340

[0004] Conventional methods for decomposing organic substances with microorganisms and methods for precipitating suspended substances have problems in that, in addition to requiring large equipment, the treatment time becomes long and they cannot be processed promptly.

[0005] The present disclosure has been developed for the purpose of further eliminating the above-mentioned drawbacks. One of the objects of one aspect of the present disclosure is to efficiently separate surplus water from a large amount of wastewater to generate concentrated drainage, and to efficiently separate treated water by membrane separation from the separated surplus water, and to provide a method and apparatus for reducing the volume of drainage to concentrated drainage. Further, another object of one aspect of the present disclosure is to provide a method and apparatus for separating concentrated drainage and treated water from wastewater with low energy consumption and efficiently reducing the volume of drainage that can be disposed of to concentrated drainage. Note that the description of the objects and problems of one aspect of the present disclosure does not prevent the existence of other objects and problems. Also, the aspects of the present disclosure do not need to solve all of these problems. Furthermore, other problems can be extracted from the description of the specification, drawings, and claims of the present disclosure.

[0006] A method for reducing the volume of wastewater to concentrated wastewater according to one embodiment of the present disclosure is a method for reducing the volume of wastewater to concentrated wastewater by separating excess water from wastewater, comprising a first separation step for separating excess water from wastewater and a second separation step for separating effluent from the excess water, wherein the first separation step is a step for separating excess water from wastewater to produce concentrated wastewater by separating excess water from wastewater, comprising an ultrasonic atomization step in which a carrier gas is blown onto the surface of a liquid column of wastewater that protrudes from the liquid surface by ultrasonic vibration, thereby supplying mist from the surface of the liquid column into the carrier gas to generate a mist mixed gas, and a recovery step in which mist is separated from the mist mixed gas generated in the ultrasonic atomization step to separate excess water from the wastewater, wherein the second separation step is a membrane separation step in which impurities are separated by membrane from the excess water obtained in the first separation step, wherein the membrane separation step separates effluent from the excess water.

[0007] Another embodiment of the present disclosure is an apparatus for reducing the volume of wastewater to concentrated wastewater by separating excess water from wastewater to be treated as waste, and comprises an atomization separation unit for separating excess water from the wastewater and a membrane separation unit for separating effluent from the excess water. The atomization separation unit comprises an ultrasonic transducer that ultrasonically vibrates the wastewater to cause a liquid column to protrude from the liquid surface and a blowing mechanism that blows a carrier gas onto the surface of the liquid column. The ultrasonic atomization unit blows the carrier gas onto the liquid column protruding from the liquid surface by the ultrasonic transducer, and mixes the carrier gas with mist to form a mist mixed gas. The recovery unit separates the mist from the mist mixed gas generated in the ultrasonic atomization unit to separate the excess water from the wastewater. The membrane separation unit comprises a filtration membrane that membrane-separates the excess water obtained in the atomization separation unit to obtain effluent from which impurities have been separated.

[0008] The above method and apparatus for reducing wastewater volume into concentrated wastewater has the advantage of efficiently separating excess water from a large amount of wastewater to produce concentrated wastewater, and further efficiently separating effluent from the excess water separated from the wastewater by membrane separation. In particular, the above method and apparatus has the advantage of efficiently disposing of wastewater by separating it into concentrated wastewater and effluent with low energy consumption.

[0009] This is a block diagram of an apparatus and method for reducing the volume of wastewater to concentrated wastewater according to one embodiment of the present disclosure. This is a schematic diagram of an apparatus and method for reducing the volume of wastewater to concentrated wastewater according to one embodiment of the present disclosure. This is an enlarged schematic diagram of the main part showing the surface of the liquid column.

[0010] The present invention will be described in detail below with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "up," "down," and other terms including these) will be used as needed. The use of these terms is for the purpose of facilitating the understanding of the invention by referring to the drawings, and the meaning of these terms does not limit the technical scope of the present invention. Also, parts with the same reference numerals appearing in multiple drawings indicate the same or equivalent parts or components. Furthermore, the embodiments shown below are concrete examples of the technical concept of the present invention and do not limit the present invention to those shown below. In addition, the dimensions, materials, shapes, relative arrangements, etc. of the components described below are intended to be illustrative, and not to limit the scope of the present invention unless specifically stated otherwise. Furthermore, the content described in one embodiment or example is applicable to other embodiments and examples. Also, the size and positional relationships of the components shown in the drawings may be exaggerated to clarify the explanation.

[0011] The form of this disclosure may be specified by the following configuration and features. A method for reducing the volume of wastewater to concentrated wastewater according to one embodiment of this disclosure is a method for reducing the volume of wastewater to concentrated wastewater by separating excess water from wastewater, comprising a first separation step for separating excess water from wastewater and a second separation step for separating effluent from the excess water, wherein the first separation step is a step for separating excess water from wastewater to produce concentrated wastewater by separating excess water from wastewater, comprising an ultrasonic atomization step in which a carrier gas is blown onto the surface of a liquid column of wastewater that protrudes from the liquid surface by ultrasonic vibration to supply mist from the surface of the liquid column into the carrier gas to generate a mist mixed gas, and a recovery step in which mist is separated from the mist mixed gas generated in the ultrasonic atomization step to separate the excess water from the wastewater, wherein the second separation step is a membrane separation step in which impurities are separated by membrane from the excess water obtained in the first separation step, wherein the membrane separation step separates effluent from the excess water. In this disclosure, "membrane separation" is used to include filtration.

[0012] The above method has the advantage of efficiently separating excess water from wastewater in a first separation step having an ultrasonic atomization step and a recovery step to generate concentrated wastewater, and then separating the generated excess water from the effluent in a second separation step by membrane separation. This allows for efficient separation of excess water from a large volume of dilute wastewater with a relatively low concentration of impurities relative to the liquid volume, reducing the volume of the dilute wastewater into concentrated wastewater for disposal, and further separating the effluent by membrane separation, allowing almost all of the excess water to be discharged as effluent. In particular, the above method has the advantage of efficiently separating excess water from wastewater with low energy consumption, as it does not separate excess water from a large volume of dilute wastewater by membrane separation, but rather generates a fine mist from the wastewater using the energy of ultrasonic vibrations, and separates and recovers this mist to separate the excess water. Furthermore, in the membrane separation step that separates effluent from excess water, clogging of the filtration membrane is prevented, allowing for efficient separation of effluent from excess water. This is because the excess water obtained in the first separation step contains almost no substances that cause clogging of the filtration membrane used to filter the excess water in the membrane separation step. The first separation step, consisting of an ultrasonic atomization step and a recovery step, releases mist from the gas-liquid interface of the liquid column using the energy of ultrasonic vibrations. The peak particle size of the released mist changes depending on the frequency of the ultrasonic vibrations, but at the megahertz order, which is optimal for ultrasonic atomization of wastewater, the mist becomes nano-level and extremely fine in particle size. Therefore, it contains almost no substances that cause clogging of the filtration membrane, and the excess water obtained by separating and recovering the mist contains virtually no substances that cause clogging. Consequently, the filtration membrane used to separate the excess water in the second separation step has the advantage of suppressing clogging and enabling smooth and efficient separation of effluent from the excess water.

[0013] The second separation step can separate impurities that cannot be separated in the first separation step, such as metal ions contained in the wastewater. Excess water containing impurities above the permissible discharge concentration cannot be discharged as is, but the second separation step uses a filtration membrane with pores that cannot allow impurities above the permissible discharge concentration to pass through, removing impurities above the permissible discharge concentration and separating the wastewater from the excess water. Thus, excess water containing BOD and COD causative substances can be separated by membrane separation, separating wastewater that can be discharged externally. Therefore, the above method efficiently separates wastewater into excess water and concentrated wastewater in the first separation step, reducing the volume of wastewater into concentrated wastewater and reducing wastewater disposal costs. Although clogging substances remain in the concentrated wastewater, concentrated wastewater is mainly disposed of by methods such as incineration, so the clogging substances remaining in the concentrated wastewater do not increase the cost of disposing of the concentrated wastewater, and the reduced volume of concentrated wastewater can be disposed of economically. Since the excess water separated from the wastewater contains almost no clogging-causing substances, the membrane separation process has the advantage of efficiently and economically separating effluent from the excess water while suppressing clogging of the fine-pore filtration membrane. Therefore, the above method has the advantage of extremely efficiently separating excess water containing a large amount of water (liquid) from the wastewater, and concentrated wastewater containing clogging-causing substances as the wastewater is concentrated. The concentrated wastewater can be disposed of, reducing disposal costs, and the excess water from which the concentrated wastewater has been separated from the wastewater has the advantage of efficiently filtering out impurities while suppressing clogging, separating and discharging effluent.

[0014] In addition to the above embodiments, a method for reducing the volume of wastewater to concentrated wastewater according to another embodiment of this disclosure allows the frequency of ultrasonic vibration of the wastewater to be 1 MHz or higher. This method has the advantage of efficiently releasing an extremely fine mist with a peak particle size on the order of nanometers from the gas-liquid interface of the wastewater liquid using the energy of ultrasonic vibration, efficiently separating excess water with a low impurity concentration, more effectively suppressing clogging of the filtration membrane in the membrane separation process, and separating effluent from the excess water.

[0015] Another embodiment of the method for reducing wastewater volume to concentrated wastewater according to this disclosure, in addition to the above embodiment, allows the wastewater to be incinerated and disposed of as wastewater. The above method has the advantage of reducing the volume of wastewater to concentrated wastewater, in which impurities are concentrated, by separating excess water from the wastewater without directly incinerating and disposing of the wastewater discharged from factories, businesses, etc. Incinerating and disposing of the concentrated wastewater reduces incineration costs, transportation costs to the incinerator (facility), time, and the amount of carbon dioxide emitted by the transport vehicles.

[0016] In addition to the above embodiments, methods for reducing the volume of wastewater to concentrated wastewater according to other embodiments of this disclosure can reduce the impurity concentration of the effluent to below the concentration level permitted for discharge. The above methods allow wastewater to be discharged as effluent with an impurity concentration below the concentration level permitted for discharge. In this disclosure, the impurity concentration of "below the concentration level permitted for discharge" refers to a concentration level below the concentration level legally permitted for discharge according to the wastewater regulation values ​​and standards of relevant environmental laws and regulations such as the Water Pollution Control Law, ministerial ordinances, and local government ordinances. For example, the COD value (Chemical Oxygen Demand) indicates the content of organic matter etc. in a liquid by converting the consumption of oxidizing agents such as potassium permanganate into oxygen content, and wastewater from factories etc. is considered an environmental item for living conditions (wastewater volume 50 m ３ A standard of 160 mg / L or less (daily average of 120 mg / L or less) has been set for specific businesses that operate for more than one day. The BOD value (Biochemical Oxygen Demand) is an environmental standard that quantifies the amount of oxygen consumed by microorganisms when decomposing organic matter, and similarly, a standard of 160 mg / L or less (daily average of 120 mg / L or less) has been set. COD emission standards apply to wastewater discharged into seas and lakes, while BOD emission standards apply to wastewater discharged into public water bodies other than seas and lakes. SS (Suspended Solids) is the amount of substances that float in water or cause turbidity, and a standard of 200 mg / L or less (daily average of 150 mg / L or less) has been set.

[0017] In addition to the above embodiments, a method for reducing the volume of wastewater to concentrated wastewater according to another embodiment of the present disclosure allows for the recovery step to cool the mist mixture and recover the mist. The above method has the advantage of efficiently recovering mist from the mist mixture and separating a large amount of excess water. Furthermore, it has the advantage of reducing the impurity concentration of the excess water separated from the wastewater, allowing for the separation of a large amount of effluent in the membrane separation step in the second separation step while more effectively suppressing clogging of the filtration membrane.

[0018] In addition to the above embodiments, a method for reducing the volume of wastewater to concentrated wastewater according to other embodiments of this disclosure allows for the separation of mist from the mist mixture gas using a cyclone during the recovery process. The above method has the advantage of a simple structure, efficient separation and recovery of mist from the mist mixture gas, and efficient separation of excess water.

[0019] In addition to the above embodiments, a method for reducing the volume of wastewater to concentrated wastewater according to other embodiments of this disclosure includes a second separation step in which BOD and COD-causing substances are separated from excess water via membrane separation to separate effluent. The above method has the advantage that in the membrane separation step of the second separation step, effluent from which BOD and COD-causing substances have been removed by membrane separation from excess water can be separated.

[0020] Another embodiment of the apparatus for reducing wastewater volume to concentrated wastewater is an apparatus for reducing wastewater volume to concentrated wastewater by separating excess water from wastewater to be treated for disposal, and comprises an atomization separation unit for separating excess water from wastewater and a membrane separation unit for separating effluent from the excess water, wherein the atomization separation unit comprises an ultrasonic transducer that ultrasonically vibrates the wastewater to cause a liquid column to protrude from the liquid surface and a blowing mechanism that blows carrier gas onto the surface of the liquid column, an ultrasonic atomization unit in which carrier gas is blown onto the liquid column protruding from the liquid surface by the ultrasonic transducer and mist is mixed with the carrier gas to form a mist mixed gas, and a recovery unit that separates mist from the mist mixed gas generated in the ultrasonic atomization unit to separate excess water from the wastewater, and the membrane separation unit comprises a filtration membrane that membrane-separates the excess water obtained in the atomization separation unit to obtain effluent from which impurities have been separated from the excess water.

[0021] The above apparatus is an atomization and separation unit having an ultrasonic atomization unit and a recovery unit. It separates excess water from wastewater to produce concentrated wastewater, and then separates the generated excess water by membrane separation in a membrane separation unit to separate the excess water from the effluent. This has the advantage of efficiently separating excess water from a large volume of dilute wastewater with a relatively low concentration of impurities relative to the liquid volume, reducing the volume of dilute wastewater into concentrated wastewater for disposal, and further separating the excess water by membrane separation to separate the effluent, allowing almost all of the excess water to be discharged as effluent. In particular, the above apparatus has the advantage of efficiently separating excess water from wastewater with low energy consumption because the ultrasonic atomization unit generates fine mist and mist mixed gas from the wastewater using the energy of ultrasonic vibrations, and the recovery unit separates and recovers the mist to separate the excess water, without separating excess water by membrane separation from a large volume of dilute wastewater. Furthermore, in the membrane separation unit that separates the effluent from the excess water, clogging of the filtration membrane is suppressed, allowing for smooth and efficient separation of effluent from excess water. The membrane separation unit can separate impurities such as metal ions contained in wastewater that cannot be separated by the atomization separation unit. Excess water with a high concentration of impurities cannot be discharged as is, but the membrane separation unit uses a filtration membrane with pores that impurities contained in the excess water cannot permeate to remove impurities above the dischargeable concentration, and separates the effluent from the excess water. Therefore, it is possible to separate excess water containing BOD and COD-causing substances through membrane separation and separate effluent that can be discharged externally. Accordingly, the above device efficiently separates wastewater into excess water and concentrated wastewater in the atomization separation unit, reducing the volume of wastewater into concentrated wastewater and reducing wastewater disposal costs. Although clogging-causing substances remain in the concentrated wastewater, concentrated wastewater is mainly disposed of by methods such as incineration, so the clogging-causing substances remaining in the concentrated wastewater do not increase the cost of disposing of the concentrated wastewater, and it has the advantage of being able to economically dispose of a small amount of concentrated wastewater with reduced volume. Since the excess water separated from the wastewater contains almost no clogging-causing substances, the membrane separation unit has the advantage of efficiently and economically separating effluent from the excess water while suppressing clogging of the fine-pore filtration membrane.Therefore, the above device has the advantage of being able to very efficiently separate excess water containing a large amount of moisture from wastewater and concentrated wastewater containing substances that cause clogging, while discarding the concentrated wastewater to reduce disposal costs. Furthermore, the excess water from which the concentrated wastewater has been separated from the wastewater can be efficiently filtered to suppress clogging and separate impurities, allowing for the discharge of effluent.

[0022] In addition to the above embodiments, a device for reducing the volume of wastewater to concentrated wastewater according to another embodiment of this disclosure can also convert wastewater into wastewater that can be incinerated and disposed of. The above device has the advantage of reducing the volume of wastewater by separating excess water from the wastewater, thereby reducing the wastewater to concentrated wastewater in which impurities are concentrated, without directly incinerating and disposing of the wastewater discharged from factories, businesses, etc., and allowing the concentrated wastewater to be incinerated and disposed of, thereby reducing incineration costs, transportation costs and time to the incinerator (facility), and the amount of carbon dioxide emitted by the transport vehicles.

[0023] In addition to the above embodiments, a device for reducing the volume of wastewater to concentrated wastewater according to other embodiments of this disclosure includes a membrane separation unit that separates impurities contained in the excess water via membrane separation, thereby reducing the impurity concentration of the effluent to a level below the concentration level permitted for discharge. The above device can discharge wastewater as effluent with an impurity concentration below the concentration level permitted for discharge by law.

[0024] In addition to the above embodiments, the apparatus for reducing the volume of wastewater to concentrated wastewater according to other embodiments of the present disclosure may include a mist cooling mechanism in the recovery unit for cooling the mist mixture gas and recovering the mist. The above apparatus has the advantage of being able to efficiently separate a large amount of excess water from the mist mixture gas. Furthermore, it has the advantage of being able to reduce the impurity concentration of the excess water separated from the wastewater, thereby more effectively suppressing clogging of the filtration membrane in the membrane separation unit while separating a large amount of effluent.

[0025] In addition to the above embodiments, a device for reducing the volume of wastewater to concentrated wastewater according to other embodiments of this disclosure may include a cyclone in the recovery unit for separating mist from the mist gas mixture. The above devices have a simple structure and are characterized by their ability to efficiently separate mist from the mist gas mixture and efficiently separate excess water.

[0026] In addition to the above embodiments, the apparatus for reducing the volume of wastewater to concentrated wastewater according to other embodiments of this disclosure has a membrane separation unit that can separate BOD and COD-causing substances from excess water via membrane separation. The above apparatus has the feature that it can separate effluent water from which BOD and COD-causing substances have been removed by membrane separation in the membrane separation unit. (Embodiment 1)

[0027] Figures 1 and 2 illustrate an apparatus 100 and method for reducing the volume of wastewater to concentrated wastewater according to Embodiment 1. Figure 1 is a block diagram of the apparatus 100 and method for reducing the volume of wastewater to concentrated wastewater, and Figure 2 is a schematic diagram illustrating the apparatus 100 and method for reducing the volume of wastewater to concentrated wastewater. The method (apparatus 100) for reducing the volume of wastewater to concentrated wastewater shown in Figures 1 and 2 is a method (apparatus) for reducing the volume of wastewater 1 to concentrated wastewater 3 by separating excess water 2 from wastewater 1, and comprises a first separation step (S1) for separating excess water 2 from wastewater 1 and a second separation step (S2) for separating effluent water 4 from excess water 2. The first separation step (S1) is a step of separating excess water 2 from wastewater 1 to produce concentrated wastewater 3, and includes an ultrasonic atomization step (S11) in which a carrier gas is blown onto the surface of a liquid column P of wastewater 1 that protrudes from the liquid surface by ultrasonic vibration, and mist is supplied from the surface of the liquid column P into the carrier gas to produce a mist mixed gas, and a recovery step (S12) in which mist is separated from the mist mixed gas produced in the ultrasonic atomization step (S11) to separate the excess water 2 from the wastewater 1. The second separation step (S2) is a membrane separation step (S21) in which impurities are further separated from the excess water 2 obtained in the first separation step (S1) by membrane separation, and the membrane separation step (S21) separates effluent water 4 from the excess water 2. The wastewater volume reduction device 100 shown in Figure 2 comprises an atomization separation unit 10 that separates excess water 2 from wastewater 1 to form concentrated wastewater 3, and a membrane separation unit 20 that separates organic matter from the excess water 2 separated from wastewater 1 to form effluent water 4. (Atomization separation unit 10)

[0028] The atomization and separation unit 10 includes an ultrasonic atomization unit 11 that ultrasonically vibrates the wastewater 1 to mix the mist into a carrier gas to form a mist mixture gas, and a recovery unit 17 that separates the mist from the mist mixture gas generated in the ultrasonic atomization unit 11 to separate excess water 2.

[0029] The ultrasonic atomizing unit 11 in Figure 2 comprises an atomizing chamber 12 that ultrasonically vibrates the wastewater 1, a water supply pump 13 that supplies the wastewater 1 to the atomizing chamber 12, ultrasonic transducers 14 positioned at the bottom of the atomizing chamber 12, an ultrasonic power supply 15 that supplies high-frequency power to the ultrasonic transducers 14, and a blowing mechanism 16 that supplies carrier gas to the atomizing chamber 12. This disclosure does not specify the number or arrangement of the ultrasonic transducers 14, but the atomizing chamber 12 in Figure 2 has an elongated closed structure in the direction of the flow of the wastewater 1, with a plurality of ultrasonic transducers 14 arranged in a line at the bottom in the direction of the flow of the wastewater 1. One end of the atomizing chamber 12 is the supply end of the wastewater 1 (left end in Figure 2), and the other end is the discharge end of the wastewater 1 (right end in Figure 2). This atomizing chamber 12 allows the wastewater 1 supplied to the supply end of the wastewater 1 to flow towards the discharge end while ultrasonically vibrating the wastewater 1 with each ultrasonic transducer 14 and releasing mist, thereby enabling the discharge of concentrated wastewater 3 from the discharge end.

[0030] Furthermore, in the atomization chamber 12 shown in Figure 2, the blower fan of the blower mechanism 16 blows carrier gas in the longitudinal direction in which the ultrasonic transducers 14 are arranged, from the supply end to the discharge end of the wastewater 1. Any gas that disperses and mixes the mist m released from the liquid column P to form a mist mixture can be used as the carrier gas. Air is preferably used as the carrier gas, but inert gases can also be used. An inert gas carrier gas has the advantage of being able to safely separate excess water 2 from the flammable wastewater 1. The atomization chamber 12 mixes the mist m released from each liquid surface with the carrier gas supplied from the supply end of the wastewater 1, and discharges a mist mixture with a high mist concentration from the discharge end.

[0031] The atomization chamber 12 described above can adjust the total atomization amount by adjusting the number of ultrasonic transducers 14, and can also adjust the proportion of excess water 2 separated from the wastewater 1. The atomization chamber 12 can increase the total atomization amount per unit time by providing a large number of ultrasonic transducers 14, and can also separate a large amount of excess water 2 from the wastewater 1. The atomization chamber 12 can control the proportion of excess water 2 separated from the wastewater 1, that is, the volume reduction percentage of the wastewater 1 shown as (1 - concentrated wastewater / wastewater) × 100. For example, by separating 50% of the excess water 2 from the wastewater 1, the volume of the wastewater 1 can be reduced to 50% concentrated wastewater 3, by separating 80% of the wastewater 1 as excess water 2, the volume of the wastewater 1 can be reduced to 20% concentrated wastewater 3, and by separating 90% of the wastewater 1 as excess water 2, the volume of the wastewater 1 can be reduced to 10% concentrated wastewater 3.

[0032] Each ultrasonic transducer 14 positioned in the atomization chamber 12 is supplied with, for example, 10 to 100 W of high-frequency power from the ultrasonic power supply 15 to ultrasonically vibrate the wastewater 1 and generate mist. Each ultrasonic transducer 14 is fixed horizontally to the bottom surface and radiates ultrasonic vibrations upward. The ultrasonic vibrations radiated vertically generate a liquid column P that protrudes vertically from the liquid surface. The liquid column P that protrudes from the liquid surface due to the energy of the ultrasonic vibration releases the wastewater 1 into the air as a fine mist m from the surface of the liquid column, which is the interface between the wastewater 1 and the air.

[0033] The mist m released from the surface of the liquid column disperses into the carrier gas to form a mist-mixed gas. The carrier gas blown onto the surface of the liquid column promotes the release of mist m from the liquid column P into the air. This is because it lowers the mist concentration on the surface of the liquid column, thereby increasing the amount of mist released. The carrier gas blown onto the surface of the liquid column quickly moves the mist m released from the liquid column P into the air, reducing the mist concentration on the surface of the liquid column. Furthermore, the carrier gas blown onto the surface of the liquid column also has the effect of mixing the mist m released from the liquid column P to form a mist-mixed gas.

[0034] The water supply pump 13 supplies wastewater 1 from the wastewater tank 13a to the atomization chamber 12 to maintain a constant liquid level in the atomization chamber 12. The atomization efficiency of the atomization chamber 12 changes depending on the liquid level. Therefore, the water supply pump 13 detects the liquid level in the atomization chamber 12 with a liquid level sensor (not shown) and supplies wastewater 1 to the atomization chamber 12 so that the liquid level is at a level that maximizes atomization efficiency, for example, 3 to 5 cm. The atomization chamber 12 receives wastewater 1 from the water supply pump 13 at the supply end (left end in Figure 2). The supplied wastewater 1 flows to the discharge end (right end in Figure 2) while generating mist m with multiple ultrasonic transducers 14, and concentrated wastewater 3 can be discharged from the discharge end to the concentrated liquid tank.

[0035] Figure 3, an enlarged cross-sectional schematic diagram, shows a state in which wastewater 1 is ultrasonically vibrated and mist m is released from the surface of liquid column P. The excess water 2 obtained by separating and recovering the mist m generated by the energy of ultrasonic vibration contains almost no impurities such as insoluble substances, suspended solids, and suspended matter that can clog the filter membrane 21a. This is because the peak particle size of the mist released from the gas-liquid interface by ultrasonic vibration is extremely small, and it contains almost no large particles of insoluble substances, suspended solids, and suspended matter that can clog the filter membrane 21a. The mist m released from the gas-liquid interface of liquid column P contains almost no clogging substances, but it is extremely difficult to release mist m into the air from the gas-liquid interface when all impurities are removed. Therefore, the excess water 2 separated from wastewater 1, which contains impurities such as BOD and COD-causing substances, may contain impurities such as metal ions, which are BOD and COD-causing substances.

[0036] The impurity concentration in excess water 2 can be reduced by decreasing the peak particle size of the mist m released from the gas-liquid interface by the energy of ultrasonic vibrations. This is because the impurity concentration can be reduced by making the peak particle size of the mist nano-sized. Extremely fine mist with a peak particle size of nano-sized can be generated by increasing the frequency of ultrasonic vibration of wastewater 1. For example, the peak particle size of mist generated by ultrasonic vibrations at 200 kHz is about 7 μm, but the peak particle size of mist m generated by ultrasonic vibrations at 1 MHz is 200 nm or less, and the peak particle size of mist generated by ultrasonic vibrations at 1.5 MHz is 100 nm or less, resulting in extremely small nano-sized mist. It is thought that the reason why the mist m generated by the energy of ultrasonic vibrations becomes an extremely fine nano-sized mist is that the fine mist m released from the gas-liquid interface by the energy of ultrasonic vibrations condenses and vaporizes, the vaporized mist m supersaturates the air near the gas-liquid interface, and the moisture in the supersaturated air condenses to generate extremely fine nano-sized mist.

[0037] The energy of the ultrasonic vibrations causes extremely fine mist m to be released from the gas-liquid interface, which then diffuses into the carrier gas to form a mist mixture. The carrier gas blown onto the surface of the liquid column carries the fine mist m generated at the gas-liquid interface, efficiently generating mist m from the gas-liquid interface of the liquid column P. The recovery unit 17 (recovery process) recovers the fine mist from the mist mixture generated in the ultrasonic atomization unit 11 (ultrasonic atomization process). The fine mist separated from the mist mixture has an impurity concentration that varies with its peak particle size, and by recovering fine mist with a small peak particle size, the impurity concentration can be reduced.

[0038] The atomization separation unit 10 (first separation step) generates an extremely fine mist using ultrasonic vibrations with a frequency of 1 MHz or higher, thereby reducing the impurity concentration in the mist and lowering the impurity concentration of the excess water 2 recovered from this mist, such as the concentration of substances that cause BOD and COD. The excess water 2 with a low impurity concentration is further separated for finer impurities in the membrane separation unit 20 (second separation step), but lowering the impurity concentration of the excess water 2 makes it possible to separate the effluent water 4 more efficiently in the subsequent membrane separation unit 20 (second separation step).

[0039] The recovery unit 17 recovers mist from the mist mixture gas generated in the ultrasonic atomization unit 11 and separates excess water 2. The recovery unit 17 may be equipped with a mist cooling mechanism 18 that cools the mist mixture gas to recover the mist. The cooling mechanism 18 can separate and recover mist from the mist mixture gas by the relative temperature difference with the inside of the atomization chamber 12. The structure, configuration, and cooling method of the cooling mechanism 18 are not specified, and any structure or mechanism that can cool the mist mixture gas to a temperature lower than the inside of the atomization chamber 12 can be used. For example, it can be brought into contact with a cooling unit provided in the air passage of the mist mixture gas, or the mist mixture gas can be cooled by providing heat dissipation fins on the outer surface. The cooling mechanism 18 can cool the mist mixture gas to below the dew point temperature, liquefy it, and efficiently separate the mist (excess water 2). The recovery unit 17 can separate mist from the mist mixture gas using a cyclone 19. The cyclone 19 in Figure 2 is cylindrical, with a tapered section that narrows at the bottom connected to the lower end of the cylindrical section. The cyclone 19 rotates the mist-containing mist mixture gas in a vortex shape inside, and can separate mist with a low impurity concentration (excess water 2) from the mist mixture gas (carrier gas) by centrifugal force. The centrifugal force of the cyclone 19 causes the mist to rotate and move outwards, separating it. The centrifugal force acting on the mist increases in proportion to its mass, the mass of the mist is greater than that of the carrier gas, and furthermore, the mass of the mist increases in proportion to the cube of its particle size. The cyclone 19 has a simple structure and can efficiently separate mist with a low impurity concentration from the mist mixture gas generated by ultrasonic vibration. The cooling mechanism 18 and the cyclone 19 can be integrated into a single structure, and cooling and centrifugal rotation can be performed continuously, in stages, and simultaneously. This disclosure does not limit the separation of mist to cyclones, but can use any existing or future-developed separation and recovery equipment capable of separating mist from a mist gas mixture, such as electrostatic separators and demisters. An electrostatic separator charges the mist by providing a discharge electrode in the mist gas mixture passage, and then separates the charged mist by attracting it to a current collector electrode through the action of static electricity. Because the electrostatic separator attracts mist through the action of static electricity, it can efficiently separate even finer mist particles. (Membrane separation unit 20)

[0040] The membrane separation unit 20 filters the excess water 2 to separate the discharge water 4. The membrane separation unit 20 includes a sealed pressurized chamber 21 to which the excess water 2 is supplied, an excess water pump 22 to which the excess water 2 is supplied to the pressurized chamber 21, and a pressure regulating valve 23 connected to the discharge side of the pressurized chamber 21. The pressurized chamber 21 is divided into an inlet chamber 21A and a discharge chamber 21B by a filtration membrane 21a. The pressurized chamber 21 in Figure 2 is cylindrical with a cylindrical filtration membrane 21a placed inside, with the inside of the filtration membrane 21a being the inlet chamber 21A and the outside of the filtration membrane 21a being the discharge chamber 21B.

[0041] The filtration membrane 21a filters the excess water 2, separating the impurities contained in the excess water 2 to produce effluent water 4. The filtration membrane 21a passes through the effluent water 4 and is discharged to the outside from the discharge chamber 21B. The impurities contained in the excess water 2 can be separated from the excess water 2 by being discharged to the outside of the pressurized chamber 21 without passing through the filtration membrane 21a. The filtration membrane 21a is a filter material with fine pores that do not allow impurities to pass through, and a reverse osmosis membrane can preferably be used. Since the filtration membrane 21a can use any filter material that can filter and remove impurities such as harmful substances, metal ions, and substances that cause BOD and COD, the optimal filter material is selected considering the particle size of the impurities contained in the excess water 2 that are separated by the membrane.

[0042] The excess water 2 separated from the wastewater 1 by ultrasonic atomization in the atomization separation unit 10 may contain substances that cause BOD and COD. This excess water 2 may contain nutrients such as nitrogen and phosphorus, which are BOD-causing substances, and detergents, which are COD-causing substances. Excess water 2 in which the concentration of BOD and COD-causing substances is higher than the prescribed level at which it can be discharged can be separated by membrane separation to produce discharged wastewater 4 at the standard level. This is because the membrane separation unit 20 can separate BOD, COD, and other causative substances that cannot be separated by ultrasonic atomization by membrane separation.

[0043] The membrane separation unit 20 separates impurities such as insoluble substances from the wastewater 1 and separates the excess water 2 containing the substances that cause BOD and COD through membrane separation. Since the membrane separation unit 20 separates the excess water 2 which has a low content of insoluble substances that can cause clogging, it efficiently separates the substances that cause BOD and COD through membrane separation and separates the effluent 4.

[0044] In the membrane separation unit 20 of FIG. 2, an excess water pump 22 is connected to the input side of the pressurization chamber 21 (inflow chamber 21A), and a pressure regulating valve 23 is connected to the discharge side of the pressurization chamber 21 (inflow chamber 21A). The membrane separation unit 20 with this structure pressurizes the excess water 2 supplied to the inflow chamber 21A, forcibly filters it through the filtration membrane 21a, allows it to permeate, and can efficiently separate the discharge water 4 from the excess water 2 and discharge it to the discharge chamber 21B. Due to the pressure difference between the pressurized inflow chamber 21A and the non-pressurized discharge chamber 21B, the filtration membrane 21a supplies the discharge water 4 contained in the excess water 2 supplied to the inflow chamber 21A to the discharge chamber 21B. The discharge chamber 21B supplies the discharge water 4 supplied from the filtration membrane 21a to the discharge water tank 24, or discharges it externally without storing it in the discharge water tank 24.

[0045] Fine pores such as reverse osmosis membranes that perform membrane separation of harmful impurities from the excess water 2 have the problem that the discharge water 4 cannot smoothly permeate and is easily clogged. The membrane separation unit 20 of FIG. 2 pressurizes and supplies the excess water 2 with the excess water pump 22 connected to the inflow side of the inflow chamber 21A, and restricts the discharge flow rate with the pressure regulating valve 23 connected to the discharge side of the inflow chamber 21A, maintains the internal pressure of the inflow chamber 21A in a pressurized state, performs membrane separation of the excess water 2, and the discharge water 4 efficiently permeates the filtration membrane 21a. The internal pressure of the inflow chamber 21A can be set to an optimal pressure in consideration of the filtration membrane 21a. The internal pressure of the inflow chamber 21A can be increased by increasing the discharge pressure of the excess water pump 22 and restricting the discharge flow rate of the inflow chamber 21A.

[0046] When the membrane separation unit 20 separates the treated water 4 from the surplus water 2, it is extremely important to efficiently perform membrane separation on the treated water 4 below a specified level. This can be achieved by suppressing clogging of the filtration membrane 21a and efficiently performing membrane separation on the surplus water 2 while reducing processes such as backwashing. This is because clogging of the filtration membrane 21a restricts the permeation of the treated water 4 and limits the timing of backwashing, which in turn limits the time for membrane separation. The apparatus 100 in FIG. 2 performs membrane separation on the surplus water 2 that has been atomized and separated from the wastewater 1 and contains almost no clogging-causing substances, suppresses clogging of the filtration membrane 21a, and efficiently filters and separates the treated water 4. This is because the atomized and separated surplus water 2 contains almost no suspended substances, floating substances, insoluble substances, etc., which are the causes of clogging.

[0047] The method of reducing the volume of wastewater to concentrated wastewater has a first separation step (S1) of separating the surplus water 2 from the wastewater 1 and a second separation step (S2) of separating the treated water 4 from the surplus water 2. The first separation step (S1) in FIGS. 1 and 2 is a step of separating the surplus water 2 from the wastewater 1 to generate concentrated wastewater 3. In the ultrasonic atomization step (S11), a carrier gas is blown onto the surface of the liquid column P of the wastewater 1 protruding from the liquid surface by ultrasonic vibration, and mist is supplied from the surface of the liquid column P into the carrier gas to generate a mist mixture gas. The recovery step (S12) separates the mist from the mist mixture gas generated in the ultrasonic atomization step (S11) to separate the surplus water 2 of the wastewater 1. The second separation step (S2) in FIGS. 1 and 2 is a membrane separation step (S21) of separating impurities from the surplus water 2 obtained in the first separation step (S1), and the membrane separation step (S21) separates the treated water 4 from the surplus water 2. In any of the steps, the description of the apparatus 100 above is appropriate.

[0048] The present disclosure can be usefully utilized as a method and apparatus for reducing the volume of wastewater to concentrated wastewater, which efficiently separates surplus water from a large amount of wastewater to generate concentrated wastewater, and further separates treated water efficiently by membrane separation from the surplus water separated from the wastewater.

[0049] 100...Device for reducing wastewater volume to concentrated wastewater 1...Wastewater 2...Excess water 3...Concentrated wastewater 4...Effluent water 10...Atomization separation unit 11...Ultrasonic atomization unit 12...Atomization chamber 13...Water supply pump 13a...Wastewater tank 14...Ultrasonic transducer 15...Ultrasonic power supply 16...Air blowing mechanism 17...Recovery unit 18...Cooling mechanism 19...Cyclone 20...Membrane separation unit 21...Pressure chamber 21A...Inlet chamber 21B...Discharge chamber 21a...Filtration membrane 22...Excess water pump 23...Pressure regulating valve 24...Effluent water tank

Claims

1. A method for reducing the volume of wastewater to concentrated wastewater by separating excess water from wastewater, comprising: a first separation step of separating excess water from wastewater; and a second separation step of separating effluent from the excess water, wherein the first separation step comprises: an ultrasonic atomization step of blowing carrier gas onto the surface of a liquid column of wastewater protruding from the liquid surface by ultrasonic vibration, supplying mist from the surface of the liquid column into the carrier gas to generate a mist mixed gas; and a recovery step of separating the mist from the mist mixed gas generated in the ultrasonic atomization step to separate the excess water from the wastewater, thereby generating concentrated wastewater; the second separation step comprises: a membrane separation step of membrane separating impurities from the excess water obtained in the first separation step; and the membrane separation step of separating effluent from the excess water, thereby reducing the volume of wastewater to concentrated wastewater.

2. A method for reducing the volume of wastewater described in claim 1 into concentrated wastewater, wherein the frequency at which the wastewater is ultrasonically vibrated is 1 MHz or higher.

3. A method for reducing the volume of wastewater described in claim 1 to concentrated wastewater, wherein the wastewater is wastewater that is incinerated and disposed of.

4. A method for reducing the volume of wastewater described in claim 1 to concentrated wastewater, wherein the impurity concentration of the effluent is below a concentration level that is permissible for discharge.

5. A method for reducing the volume of wastewater described in claim 1 to concentrated wastewater, wherein the recovery step comprises cooling the mist mixed gas to recover the mist.

6. A method for reducing the volume of wastewater described in claim 5 into concentrated wastewater, wherein in the recovery step, mist is separated from the mist mixed gas by a cyclone, the method for reducing the volume of wastewater into concentrated wastewater.

7. A method for reducing the volume of wastewater described in claim 1 into concentrated wastewater, wherein the second separation step is to separate the effluent water by membrane separation of substances causing BOD and COD from the excess water.

8. A device for reducing the volume of wastewater into concentrated wastewater by separating excess water from wastewater to be treated, comprising: an atomization separation unit for separating excess water from wastewater; and a membrane separation unit for separating effluent from the excess water, wherein the atomization separation unit comprises an ultrasonic transducer for ultrasonically vibrating the wastewater to cause a liquid column to protrude from the liquid surface, and a blowing mechanism for blowing carrier gas onto the surface of the liquid column; an ultrasonic atomization unit for blowing carrier gas onto the liquid column protruding from the liquid surface by the ultrasonic transducer, and mixing mist with the carrier gas to form a mist mixed gas; and a recovery unit for separating mist from the mist mixed gas generated in the ultrasonic atomization unit to separate the excess water, wherein the membrane separation unit comprises a filtration membrane for membrane separation of the excess water obtained in the atomization separation unit to form effluent from which impurities have been separated, the device for reducing the volume of wastewater into concentrated wastewater.

9. An apparatus for reducing the volume of wastewater described in claim 8 into concentrated wastewater, wherein the wastewater is wastewater that is to be incinerated and disposed of as waste.

10. A device for reducing the volume of wastewater described in claim 8 into concentrated wastewater, wherein the membrane separation unit separates impurities contained in the excess water via membrane separation, thereby reducing the concentration of impurities in the effluent to a concentration level below that which is permissible for discharge.

11. An apparatus for reducing the volume of wastewater described in claim 8 into concentrated wastewater, wherein the recovery unit comprises a mist cooling mechanism for cooling the mist mixed gas and recovering the mist.

12. An apparatus for reducing the volume of wastewater described in claim 8 into concentrated wastewater, wherein the recovery unit comprises a cyclone for separating mist from the mist mixed gas.

13. An apparatus for reducing the volume of wastewater described in claim 8 into concentrated wastewater, wherein the membrane separation unit separates BOD and COD-causing substances from the excess water via a membrane, the apparatus for reducing the volume of wastewater into concentrated wastewater.

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