JP2008155156A - Liquid treatment method and liquid treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economical liquid treatment method enhanced in water treatment capacity by recovering and reutilizing undissolved air, and to provide a liquid treatment apparatus. <P>SOLUTION: The liquid treatment apparatus is equipped with an air mixer 7 for mixing the water sent by a pump 11 with air, the gas-liquid separator 8 connected to the air mixer 7 to separate undissolved air bubbles, the vacuum nozzle 12 connected to the gas-liquid separator 8, the contact tank 5 connected to the depressurized nozzle 12 to allow the water to be treated to flow in and a flow channel for returning the undissolved air bubbles separated by the gas-liquid separator 8 to the air mixer 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid processing method and apparatus using bubbles.

  In the liquid treatment method using ozone, as described in [Non-patent Document 1], the ozone injected into the water to be treated is consumed by the reducing substance contained in the water to be treated and injected by the ozone reaction facility. Among the ozone, ozone in the bubbles reaching the water surface without dissolving in the water to be treated is diffused into the air and decomposed by the exhaust ozone treatment device. For this reason, the amount of ozone injected into the reaction vessel equipment includes the amount of ozone consumed to oxidize reducing substances and the amount of ozone discarded without being dissolved in addition to the amount of ozone necessary to achieve the target water quality. Need to add.

  The ozone treatment system used for water treatment includes pretreatment equipment, post-treatment equipment, ozone generation equipment, waste ozone treatment equipment, and the like in addition to ozone reaction equipment. Since the ratio of the power consumption in the ozone generating facility is the largest in the power consumption of the entire system, to improve the economic efficiency of the treatment system, it is necessary to reduce the ozone generation amount, that is, to improve the ozone utilization rate. Specifically, it is effective to reduce the reducing substances in the water to be treated and to improve the efficiency of ozone dissolution, that is, to reduce the amount of exhausted ozone.

  Here, the fine bubbles are bubbles having a diameter of about 50 micrometers or less. According to [Non-Patent Document 2], the bubbles in this region generally have a diameter according to the dissolution of the gas in the bubbles into the surrounding liquid phase. Therefore, due to the effect of surface tension, the inside becomes high pressure and high temperature, and when annihilating, free radicals having high oxidizing power such as OH radicals and pressure waves are generated. Moreover, since the specific surface area is large and the rising speed is small, the solubility of the gas in the liquid is high.

  For this reason, in the case of using fine gas bubbles having oxidizing power such as ozone for water treatment, in addition to the oxidizing power of dissolved gas, cell walls, cell membranes, There is a possibility that the cytoplasm and the like are physically destroyed.

  As a conventional technique for performing water treatment using bubbles such as ozone, as described in [Patent Document 1], ozone is directly injected from an air diffuser installed in an ozone contact tank. There is one that recovers gas containing undissolved and unused ozone from the upper space. A method is disclosed in which the recovered gas and a part of an oxygen-enriched gas injected into an ozone generator as an ozone source gas are mixed and first introduced into the water to be treated in a water treatment process such as a sedimentation tank or an aeration tank. Yes.

  [Patent Document 2] discloses a method in which, in an ozone water generating apparatus, a gas recovered from above flowing out ozone water is used as an ozone source gas of an ozone generator after compression and drying. [Patent Document 3] discloses a method in which a gas is mixed as coarse bubbles, pressurized by a pump, and then injected into a contact tank through a decompression nozzle, whereby the injected gas is made into fine bubbles and injected into the contact tank. Yes.

  Water treatment refers to the process of removing organic substances and microorganisms in water to be treated by filtration, oxidative decomposition, etc., by injecting an oxidizing reagent or gas, or using light or electromagnetic wave irradiation, filtration, etc. That means.

JP 2004-122105 A JP-A-9-285794 JP 2003-117365 A "Ozone Handbook", Japan Ozone Association, 2004 “Characteristics of Water and New Utilization Technology”, NTS Corporation, pages 142-146, 2004

  In the methods described in [Patent Document 1] and [Patent Document 2], since a diffuser tube is used for injecting ozone, the bubble diameter is not less than a millimeter diameter and the dissolution efficiency is low. According to Yu Shobo, in order to obtain an ozone absorption efficiency of about 90% or more, a water depth of about 5 m is required, and there is a problem that it is difficult to downsize the equipment.

  Further, in the method described in [Patent Document 3], among the gases injected as coarse bubbles, the gas that has not been dissolved in the pressurizing section after the pump passes through the decompression nozzle as coarse bubbles, and the generated fine particles Since it mixes with air bubbles and flows into the contact tank, as described above, the millimeter air bubbles have a problem of low dissolution efficiency. Further, when coarse bubbles and fine bubbles come into contact with each other after passing through the pressure reducing nozzle, the fine bubbles may be combined with the coarse bubbles, and the content of fine bubbles having high dissolution efficiency may be reduced. In addition, even if this mixed water of fine bubbles and coarse bubbles is injected into a downflow contact tank that can increase the residence time in order to improve ozone absorption efficiency, There is a possibility that the fine bubbles that have reached the water surface are diffused into the air due to the accompanying fine bubbles.

  The first object of the present invention is to improve the efficiency of water use and improve the water treatment performance by remixing the coarse bubbles recovered in the pipeline into the fine bubble generation step or directly injecting them into the contact tank. It is to provide a liquid processing method and apparatus.

  A second object of the present invention is to provide an economical liquid processing method and apparatus with high water treatment performance by recovering and reusing undissolved gas.

  In order to achieve the above object, the liquid processing method and apparatus of the present invention mix a gas in water, pressurize and dissolve the mixed gas, depressurize the water in which the gas is dissolved, and generate fine bubbles. A contact tank for reacting fine bubbles with water to be treated is provided, and undissolved gas is recovered during pressure dissolution, and the recovered gas is reused. For the generation of the fine bubbles, a pressurizing / shearing method, a swirling flow method, or the like may be used.

  Further, a flow path for mixing the collected gas into the water to be treated or injecting it into the contact tank is provided, and the flow path is provided with an adjusting means for adjusting the flow rate of the collected gas. For these flow rates, a container for retaining the collected gas is provided, and the pressure in the retention tank is maintained by a pressure reducing valve or a relief valve provided in the flow path between the container and the mixing means or the means for injecting the container into the contact tank. You may adjust by doing. In the contact tank, the position where the recovered gas is injected should be a place where it is not mixed with fine bubbles in order to prevent coalescence of the bubbles. When using ozone, in order to remove the ozone consumption substance in to-be-processed water previously, you may inject | pour collection | recovery gas into the upstream part of the injection | pouring position of bubble-containing water. Moreover, when inject | pouring into a gas mixer, you may inject | pour as an ozone raw material gas into an ozone generator front | former stage.

  Further, the water to be treated may be extracted from the contact tank and returned to the contact tank again, and a gas having an oxidizing power other than ozone may be used as the bubble species. In addition, in order to control each injection flow rate, a means for grasping the gas-liquid ratio of the two-phase flow flowing into the pump is provided, and the mixing means is set so that it is below the allowable upper limit of the pump based on the measured value / calculated value. It controls the flow rate of the gas.

  ADVANTAGE OF THE INVENTION According to this invention, the water treatment performance and economical efficiency of the liquid processing apparatus which dissolves and utilizes gas can be improved.

  Embodiments 1 to 4 of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a liquid processing apparatus according to the first embodiment. In this embodiment, fine bubbles are used as the bubbles. In addition, it may be larger than the definition of fine bubbles and has a diameter of about 100 μm, and it is considered that the same effect can be obtained though it is quantitatively inferior.

  The liquid treatment apparatus of Example 1 is connected to a flow path 6 into which the water to be treated 1 flows, a gas mixer 7 that mixes the gas 2 introduced through the flow path 17 and the water 1 to be treated, and a gas mixer 7. And a pump 11 for feeding the water to be treated 1 mixed with gas in the gas mixer 7, a gas-liquid separator 8 connected to the pump 11 for separating undissolved bubbles, and a gas-liquid separator 8. The pressure reducing nozzle 12 is connected to the pressure reducing nozzle 12 for decompressing the water to be treated 1 and the contact tank 5 is connected to the pressure reducing nozzle 12. Here, the water 1 to be treated may be water of another system.

  The contact tank 5 is divided into a first tank 50 and a second tank 51 by a wall 19 provided in the vertical direction, and the first tank 50 and the second tank 51 are communicated between the two walls 19. The treated water 3 flows from the lower side of the first tank 50 to the second tank 51 through the space between the two walls 19.

  The decompression nozzle 12 is connected to the bottom of the first tank 50 of the contact tank 5, and an inlet for the treated water 3 and an outlet for the treated water are provided at the top of the contact tank 5. A part of the bubbles separated by the gas-liquid separator 8 flows into the flow path 17 by the flow path 9, and the remaining bubbles are diffused by the flow path 10 at the bottom of the second tank 51 of the contact tank 5. To flow into.

  The treated water 1 flowing into the flow path 6 is mixed with the gas 2 by the gas mixer 7 and then pressurized by the pump 11 so that part of the gas is dissolved in the treated water. The undissolved gas forms bubbles and flows into the gas-liquid separator 8 together with the water to be treated. In the gas-liquid separator 8, the bubbles are separated and collected. The water to be treated from which the bubbles are separated is decompressed by the decompression nozzle 12, and fine bubbles are generated by decompression foaming.

  Water to be treated containing fine bubbles is injected into the contact tank 5. On the other hand, some of the bubbles recovered by the gas-liquid separator 8 are mixed with the water 1 to be treated in the flow path 6 by the gas mixer 7 together with the gas 2 through the flow path 9. The remainder of the bubbles passes through the flow path 10 and is injected into the tank from the diffuser 18 of the contact tank 5. The treated water 3 flowing into the contact tank 5 is mixed with the treated water 1 containing fine bubbles, treated by the oxidizing power of the dissolved gas in the treated water 1, and then flows out as treated water 4. The flow rates of the water to be treated 1 and the gas 2 are set based on the flow rates of the water to be treated 3.

  Here, when the gas recovered by the gas-liquid separator 8 is injected into the contact tank 5, when the gas is injected into a tank where fine bubbles are present, the bubble diameter of the injected gas is a large bubble, so the rising speed is high. Ascending flow occurs with the phase. As a result, there is a possibility that the residence time of the fine bubbles is shortened or merged with the fine bubbles, so that the gas injected from the flow path 10 is injected into a tank in which no fine bubbles are present. In addition, the gas-liquid separator 8 uses an on-off valve that operates within a water level range that is set by detecting the water level in the contact tank 5.

  FIG. 2 shows a modification of FIG. In the example shown in FIG. 2, the flow path 13 is connected to the bottom of the contact tank 5, and the flow path 13 is connected to the flow path 6.

  The treated water 1 extracted from the contact tank 5 to the flow path 13 is again injected into the contact tank 5 through a process of generating fine bubbles of the gas mixer 7, the pump 11, the gas-liquid separator 8, and the decompression nozzle 12. The In this case, when water is extracted from the downstream side of the injection position, the content of fine bubbles increases between the injection position and the extraction position. Therefore, when ozone is used as the gas, the dissolved ozone concentration is locally increased. As a result, improvement of the organic matter decomposition effect in the water to be treated depending on the dissolved ozone concentration can be expected.

  FIG. 3 shows a modification of FIG. In the example shown in FIG. 3, the buffer tank 14 is connected to the gas-liquid separator 8, the pressure reducing valve 15 is connected to the flow path 9 connecting the buffer tank 14 and the flow path 17, and the buffer tank 14 and the air diffuser 18 are connected. A relief valve 16 is provided in the flow path 10.

  The gas separated by the gas-liquid separator 8 stays in the buffer tank 14, and the gas decompressed by the pressure reducing valve 15 attached to the buffer tank 14 flows to the gas mixer 7, and the gas from the buffer tank 14 is relieved. It is supplied to the contact tank 5 through the valve 16. In this case, since the pressure in the buffer tank 14 is maintained within a predetermined range, the flow rate of the recovered gas flowing into the gas mixer 7 is adjusted to the predetermined range.

  The process of generating fine bubbles according to the first embodiment will be described with reference to FIGS. FIG. 4 is a schematic diagram showing a gas state when the gas-liquid separator 8 is not provided in the step of generating fine bubbles of the decompression nozzle 12 from the gas mixer 7 shown in FIG. As shown in the lower part of FIG. 4, the gas 2 mixed in the gas mixer 7 flows into the pump 11 in a state of a relatively large diameter bubble (hereinafter referred to as a coarse bubble) and pressurizes. As a result, part of the gas becomes dissolved gas, and the gas that has not been dissolved remains as coarse bubbles, resulting in a mixed state of coarse bubbles and dissolved gas. After passing through the pressure reducing nozzle 12, the decompressed dissolved gas is precipitated as fine bubbles, but coarse bubbles also remain, and the coarse bubbles and fine bubbles are mixed.

  On the other hand, FIG. 5 is a process of generating fine bubbles of the decompression nozzle 12 from the gas mixer 7 shown in FIG. 1, and since the gas-liquid separator 8 is provided, the coarse bubbles that did not dissolve in the pressurizing unit Is recovered by the gas-liquid separator 8 in the middle of the flow path 6. As a result, in FIG. 4, when the gas that has flowed out as coarse bubbles downstream of the decompression nozzle 12 is mixed with the injected gas as the recovered gas and reinjected, it is possible to expect an improvement in the ratio of the injected gas becoming fine bubbles. The recovered gas can be used for other purposes such as aeration. Further, since the coarse bubbles are not mixed with the fine bubbles after the decompression nozzle 12, the coalescence of the fine bubbles into the coarse bubbles can be avoided.

  According to the first embodiment, the amount of fine bubbles flowing into the contact tank can be increased. Moreover, the ozone utilization efficiency at the time of using ozone for gas improves.

  In the case of a water treatment facility that uses ozone as the gas 2 shown in FIG. 1 and injects the generated ozone fine bubbles into the contact tank 5 and mixes it with the water to be treated, the amount of dissolved ozone to achieve the required treatment performance is limited. It is determined from the quality of the treated water, that is, the concentration of the reducing substance, and the required ozone injection amount depends on the ozone absorption efficiency. The ozone absorption efficiency increases as the bubble diameter during ozone injection decreases. In the case of the present embodiment, since the proportion of fine bubbles increases, the ozone absorption efficiency is improved. Moreover, the utilization efficiency of ozone can be further improved by mixing the collected gas again into the water 1 to be treated or directly injecting it into the contact tank 5.

  The improvement of ozone utilization efficiency of the present embodiment will be described with reference to FIGS. FIG. 6 shows an example in which the gas-liquid separator 8 is not provided and the gas is not collected, and the horizontal axis indicates the treatment process and the vertical axis indicates the state of the injected ozone. As shown in FIG. 6, the injected ozone gas is divided into coarse bubbles and fine bubbles through a pressure dissolution and decompression step, flows into the contact tank 5, and dissolves according to the ozone absorption and dissolution of each of the coarse bubbles and fine bubbles. It becomes gas and contributes to water treatment. Undissolved gas reaches the water surface and leaves the gas phase.

  FIG. 7 shows a case where the gas-liquid separator 8 is provided and the entire amount of the collected gas is remixed. The recovered coarse bubbles are remixed and separated into coarse bubbles and fine bubbles again through the bubble generation process. By repeating this, the utilization efficiency of the injected gas can be increased. However, in this case, the gas-liquid ratio of the gas-liquid two-phase flow that flows through the flow path 6 in the bubble generation process increases, which may hinder stable operation of the pump 11.

  FIG. 8 shows a case where the recovered gas exceeding the remixable flow rate is directly injected into the contact tank 5. In this case, direct injection into the contact tank 5 becomes coarse bubbles, but unlike the case shown in FIG. 6, fine bubbles and coarse bubbles are not mixed in the latter stage of the decompression nozzle 12, so the production rate of fine bubbles increases. For this reason, final ozone absorption amount increases compared with the case where it does not collect | recover.

  As described above, in this embodiment, the amount of ozone injected as a whole increases, so that the ozone utilization efficiency is improved. Therefore, the amount of ozone generated can be reduced, and the power cost of the ozone generator can be reduced. Further, since the amount of ozone to be discarded is small, the exhaust ozone device can be miniaturized and the power cost of the exhaust ozone treatment device can be reduced.

  Note that the gas of fine bubbles may be a gas having an oxidizing power such as chlorine other than ozone. Further, the upper limit value of the flow rate of the gas to be mixed depends on the allowable gas-liquid ratio of the pump 11. When the gas mixer 7 is in the subsequent stage of the pump 11, since the gas-liquid two-phase flow does not flow into the pump 11, the dissolved gas required from the water quality to be treated and the target treated water quality, not the upper limit value of the gas-liquid ratio. The injection amount may be set by obtaining the amount by experiment or the like and adding the unusable amount calculated from the dissolution efficiency. The gas-liquid separator 8 may be installed on the downstream side of the decompression nozzle 12.

  According to the present embodiment, in the liquid processing apparatus using fine bubbles, the ratio of fine bubbles generated from the injected gas can be increased by collecting and reusing undissolved coarse bubbles. In addition, when using a gas having an oxidizing power such as ozone, the ratio of the gas that becomes a fine bubble with high dissolution efficiency increases, the recovered coarse bubble is again made into a fine bubble, and again in the contact tank. Since the gas utilization efficiency increases by being injected, water treatment performance and economic efficiency can be improved.

  A second embodiment of the present invention will be described with reference to FIG. This embodiment is configured in the same manner as the embodiment shown in FIG. 1, but in this embodiment, the flow rate adjustment valve 23 for the water to be treated 1 is provided in the flow path 6, the flow rate adjustment valve 24 is provided in the flow path 17, A flow rate adjustment valve 25 is installed in the flow path 9, and a flow meter 22 is installed in the flow path of the water to be treated 3. The measurement value of the flow meter 22 is fed back to the controller 21, and the flow rate adjusting valves 23, 24, and 25 are controlled by the controller 21.

  In this embodiment, the flow rate of the recovered gas is adjusted. When the flow rate of the water to be treated 3 to be treated in the contact tank 5 changes, the required amount of gas for obtaining the required water quality changes, and accordingly, the flow rate of the water to be treated 1 and the gas remixed from the flow path 9. The flow rate also changes.

  The controller 21 calculates the flow rate of the treated water 1 and the flow rate of the gas 2 based on the flow rate of the treated water 3 detected by the flow meter 22, and the flow rate adjusting valve 23 of the treated water 1 and the flow rate of the gas 2. The adjustment valve 24 is adjusted. The controller 21 adjusts the flow rate adjustment valve 25 provided in the flow path 9 so as not to exceed the upper limit value of the allowable gas-liquid ratio of the gas mixer 7.

  As a result, even if the flow rate of the water to be treated 3 in the contact tank 5 changes, the injection ratio of the gas 2 to the water to be treated 3 is controlled so as to obtain the maximum gas utilization efficiency determined in advance.

  If the buffer tank 14 is provided as in FIG. 3 of the first embodiment, fluctuations in the flow rate of the recovered gas are alleviated, and the flow rate that is remixed or injected into the contact tank 5 is stabilized. Further, a check valve may be provided in the flow path 10, a device for measuring the gas-liquid ratio in the gas mixer 7 is provided, and the flow rate adjustment valve 24 is adjusted based on the measured value so as to obtain a predetermined gas-liquid ratio. May be.

  According to the present embodiment, in the water treatment apparatus using fine bubbles, even when the flow rate of the water to be treated is changed, the water treatment apparatus can be stably operated with the maximum gas utilization efficiency.

  A third embodiment of the present invention will be described with reference to FIG. This embodiment is configured in the same manner as the embodiment shown in FIG. 1, but in this embodiment, the oxygen-enriched gas generating unit 30 that generates oxygen-enriched air having a high oxygen concentration in the gas mixer 7 and ozone. Is connected to an ozone generator 33. Instead, the flow path 10 and the air diffuser 18 are not provided.

  In Example 1, the recovered gas is directly remixed into the mixing means. However, when ozone is used as the gas, the recovered gas has a high oxygen concentration and may be used as a raw material gas for the ozone generator. In this embodiment, the recovered gas is injected into the front stage of the ozone generator. The generated ozone in this case is mainly composed of oxygen and ozone, and the recovered gas contains a large amount of oxygen in addition to ozone.

  In FIG. 10, the gas recovered by the gas-liquid separator 8 flows through the flow path 32 and merges with the oxygen-enriched air 31 sent from the oxygen-enriched gas generator 30 to the ozone generator 33. As a result, since the amount of oxygen-enriched air generated by the oxygen-enriched gas generation unit 30 can be reduced, the power consumption of the oxygen-enriched gas generation unit can be reduced. Note that since the recovered gas contains moisture, it is preferable to perform a drying process before mixing.

  According to the present embodiment, since the oxygen in the recovered gas can be effectively used in the water treatment apparatus using ozone, the economic efficiency can be improved.

  A fourth embodiment of the present invention will be described with reference to FIG. The present embodiment is configured in the same manner as the first embodiment, but in this embodiment, the decompression nozzle 12 is above the fine bubble inflow position 41 of the first tank of the contact tank 5 connected to the bottom of the contact tank 5. An air diffuser 18 is installed in the air diffuser 18, and the air diffuser 18 and the gas-liquid separator 8 are connected by a flow path 40. A partition plate 43 is provided between the air diffuser 18 and the fine bubble inflow position 41 to prevent the fine bubbles from rising as much as possible.

  In Example 1, when the recovered gas is directly injected into the contact tank, it is injected into a tank where fine bubbles do not exist. However, if the recovered gas is injected upstream of the position where the fine bubbles are injected, There is a possibility of promoting the effect. In this embodiment, the recovered gas is injected above the fine bubble injection position of the contact tank.

  In this embodiment, ozone is used as the gas. The water 1 to be treated flows into the flow path 6 and contains fine bubbles, and is injected into the lower part of the first tank of the contact tank 5. On the other hand, the gas recovered by the gas-liquid separator 8 is injected from the flow path 40 from the recovered gas injection position 42 located above the fine bubble inflow position 41 of the first tank of the contact tank 5 to be treated water 3. Mixed with. As a result, a part of the reducing substance contained in the treated water 3 is decomposed by ozone injected from the injection position 42, and the treated water 3 is mixed with fine bubbles on the downstream side. At this time, since the consumption substance in the to-be-processed water 3 is reduced, compared with the case where the collect | recovered gas is inject | poured into the tank after microbubble injection | pouring, the dissolved ozone density | concentration in the part mixed with the microbubble is made high. Water treatment performance can be improved.

  In addition, the fine bubbles are accompanied by the descending flow of the water 3 to be treated, and most of the fine bubbles move to the second tank. A partition plate 43 having a narrow flow path is provided between the gas injection positions. Specifically, a partition plate having a single or a plurality of holes is provided in the vertical direction.

  According to the present embodiment, in the water treatment apparatus using ozone, before the water to be treated is mixed with the fine bubbles, the reducing substance that is an ozone consuming substance is reduced in advance using the recovered gas. And the water treatment performance can be improved by increasing the dissolved ozone concentration when treating with ozone fine bubbles.

1 is a configuration diagram of a liquid processing apparatus that is Embodiment 1 of the present invention. FIG. FIG. 6 is a configuration diagram of a liquid processing apparatus that is a modification of the first embodiment. FIG. 6 is a configuration diagram of a liquid processing process that is a modification of the first embodiment. FIG. 3 is a schematic diagram illustrating a process of generating fine bubbles according to the first embodiment. FIG. 3 is a schematic diagram illustrating a process of generating fine bubbles according to the first embodiment. The figure explaining the ozone utilization efficiency improvement of Example 1. FIG. The figure explaining the ozone utilization efficiency improvement of Example 1. FIG. The figure explaining the ozone utilization efficiency improvement of Example 1. FIG. The block diagram of the liquid processing apparatus which is Example 2 of this invention. The block diagram of the liquid processing apparatus which is Example 3 of this invention. The block diagram of the liquid processing apparatus which is Example 4 of this invention.

Explanation of symbols

1,3 Water to be treated
2 Gas 4 Treated water 5 Contact tank 6, 9, 10, 13, 32, 40 Flow path 7 Gas mixer 8 Gas-liquid separator 11 Pump 12 Pressure reducing nozzle 14 Buffer tank 15 Pressure reducing valve 16 Relief valve 21 Controller 22 Flow meter 23, 24, 25 Flow control valve 30 Oxygen-enriched gas generator 31 Oxygen-enriched air 33 Ozone generators 41, 42 Injection position 43 Partition plate

Claims (15)

  A gas mixer for mixing water and gas fed by a pump, a gas-liquid separator connected to the gas mixer for separating undissolved bubbles, a decompression nozzle connected to the gas-liquid separator, A liquid processing apparatus comprising a contact tank connected to the pressure reducing nozzle and into which water to be treated flows, and a flow path for returning undissolved bubbles separated by the gas-liquid separator to the gas mixer.   A gas mixer for mixing gas into water, a pump for pressurizing water mixed with gas by the gas mixer, a recovery means for recovering bubbles undissolved in water pressurized by the pump, and the recovery A flow path for returning the bubbles recovered by the means to the gas mixer, and the water in which the undissolved bubbles are recovered is introduced into the contact tank into which the water to be treated flows through the decompression means and dissolved. The liquid processing apparatus which reacts by making the to-be-processed water or this fine bubble and water to be processed contact.   An oxygen-enriched gas generator that generates oxygen-enriched air with a high oxygen concentration, an ozone generator that is connected to the oxygen-enriched gas generator and generates ozone, and is connected to the ozone generator and pumped. A gas mixer for mixing water and ozone, a gas-liquid separator connected to the gas mixer for separating undissolved bubbles, a decompression nozzle connected to the gas-liquid separator, and a connection to the decompression nozzle A liquid processing apparatus comprising a contact tank into which water to be treated flows and a flow path for returning undissolved bubbles separated by the gas-liquid separator to the ozone generator.   The liquid processing apparatus according to claim 1, wherein a part of undissolved bubbles separated by the gas-liquid separator is injected into an air diffuser of a second tank divided by a wall of the contact tank.   The liquid processing apparatus of Claim 2 provided with the aeration means to diffuse the collect | recovered gas to the to-be-processed water in the said contact tank.   The liquid processing apparatus according to claim 1, wherein the water is extracted from the water to be treated in the contact tank, and includes a flow path for flowing the extracted water to the gas mixer.   The liquid processing apparatus according to claim 1, wherein the gas-liquid separator is connected to a buffer tank, and the buffer tank and the gas mixer are connected via a pressure reducing valve.   The liquid processing apparatus according to claim 4, wherein the gas-liquid separator is connected to a buffer tank, and the buffer tank and the air diffuser are connected via a relief valve.   A flow meter for measuring the flow rate of the water to be treated flowing into the contact tank is provided, and the flow rate of the gas recovered in the recovery means based on the flow rate of the water to be treated measured by the flow meter, the gas mixer The liquid processing apparatus according to claim 2, further comprising a flow rate adjusting valve that adjusts at least one of a flow rate of a gas to be sent and a flow rate diffused into the contact tank.   The liquid processing apparatus according to claim 1, wherein a gas having an oxidizing power is used as the gas.   The liquid processing apparatus according to claim 1, wherein a position where the collected gas is diffused into the water to be treated in the contact tank is upstream of a position where the water is injected into the contact tank.   Gas is mixed in water by a gas mixer, water mixed with gas by the gas mixer is pressurized by a pump to dissolve the mixed gas, and undissolved bubbles are dissolved in water pressurized by the pump. Collected by the recovery means, the bubbles recovered by the recovery means are returned to the gas mixer through the flow path, and the water in which the undissolved bubbles are recovered by the recovery means is decompressed by the decompression means, and the water to be treated flows in. A liquid treatment method in which a reaction is caused by flowing into a contact tank and bringing the dissolved gas or the fine bubbles into contact with water to be treated.   The liquid processing method according to claim 12, wherein the gas recovered by the recovery means is guided to the air diffusion means in the contact tank and diffused into the water to be treated.   Oxygen-enriched air with a high oxygen concentration is generated by the oxygen-enriched gas generator, ozone is generated by the ozone generator from the oxygen-enriched air connection generated by the oxygen-enriched gas generator, and the ozone generator The generated ozone and water sent by a pump are mixed with a gas mixture, and undissolved bubbles of water mixed with ozone by the gas mixer are separated by a gas-liquid separator, the gas-liquid separator The liquid from which bubbles are separated in step 1 is decompressed by a decompression nozzle and injected into a contact tank into which water to be treated flows, and the undissolved bubbles separated by the gas-liquid separator are returned to the ozone generator by a flow path. Processing method.   The flow rate of the water to be treated flowing into the contact tank is measured by a flow meter, and the flow rate of the gas recovered by the recovery means by the flow rate adjustment valve based on the flow rate of the treated water measured by the flow meter, the gas The liquid processing apparatus according to claim 12, wherein at least one of a flow rate of a gas sent to the mixer and a flow rate diffused into the contact tank is adjusted.

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