JP2012106211A - Drainage pretreatment method utilizing foam separation, and drainage pretreatment device using the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drainage pretreatment device utilizing foam separation for effectively removing an organic system SS in drainage treatment using a microbubble, and a method.SOLUTION: The drainage pretreatment method includes: a process S1 which treats the microbubble of drainage in a conditioning tank by generating the microbubble containing gas and having a diameter of 10 to 50 μm by using a first microbubble generator in the drainage not lower than COD 1,000 mg/L containing an organic system fine solid substance; a process S3 which generates a foam in the drainage by generating the microbubble by using a second microbubble generator while supplying air to the drainage which is treated in a foam forming tank in the preceding process; and a process S5 which separates drainage containing the foam to a foam phase and a liquid phase in a foam separation tank, and rakes out a foam phase. The organic system microsolid substance is made to adhere on the surface of the microbubble which is generated by the second microbubble generator in the foam forming tank, the microbubble is floated, and the foam is formed, thus treating the foam.

Description

  In order to effectively advance the wastewater treatment using the subsequent microbubble crushing, the present invention prior to drainage using foam separation to remove organic micro solid substances having characteristics that tend to concentrate on the microbubble interface. The present invention relates to a treatment method and a wastewater pretreatment device used in the method.

  One of the purposes of wastewater treatment in industrial wastewater, agricultural wastewater, domestic wastewater and the like is to reduce organic components composed of harmful substances such as microorganisms and phenol in the wastewater.

  For the above purpose, for example, a crushing (extinguishing) technique of microbubbles (referring to bubbles having a diameter of 50 μm or less) as disclosed in Japanese Patent No. 4378543 (Patent Document 1) is very effective. According to the method described in Patent Document 1, a large amount of free radicals generated at the time of crushing microbubbles oxidatively decomposes organic matter, and in the crushing process, dissolved organic matter precipitates as a solid by combining metal ions and the like. By separating them by agglomeration precipitation or the like, the organic component in the waste water is efficiently reduced.

  Thus, in the wastewater treatment, the microbubble crushing technique described in Patent Document 1 is a very effective means, but a factor that reduces the efficiency of the crushing exists in the wastewater. The factor is a suspended solids (SS) mainly containing a high-molecular organic substance (organic substance).

  When microbubbles are generated in water, an organic micro solid material (hereinafter referred to as an organic SS in this specification) adheres to the gas-liquid interface. When the area of the gas-liquid interface is reduced during the microbubble crushing process, the density of the organic material SS on the surface rapidly increases. As a result, an action to stably maintain the interface is born, so that the disappearance of bubbles in the water, that is, the crushing state is difficult to occur. In order to prevent this, it is conceivable to apply a physical stimulus to the microbubbles to forcibly crush them.

  However, the method described in Patent Document 1 has an effect on an organic substance having a relatively low molecular weight, but is difficult to show an effect on an organic substance SS having a high molecular weight (molecular weight of 10,000 or more). There was a problem that the efficiency of the wastewater treatment indicated was very lowered.

Japanese Patent No. 4378543

  In view of the above situation, the reduction of the organic SS is advantageous in the subsequent wastewater treatment, and from the viewpoint of increasing the efficiency of the wastewater treatment, the organic SS having a large molecular weight is a burden of the treatment. Therefore, the removal in advance is advantageous in terms of increasing the overall efficiency.

  Therefore, an object of the present invention is to provide a pretreatment apparatus and method using foam separation in order to effectively remove organic matter SS in wastewater treatment using microbubbles.

  The above-described object of the present invention is to provide a first microbubble generator in which a microbubble having a diameter of 10 to 50 μm containing a gas is contained in a wastewater in a condition tank containing COD 1000 mg / L or more, which contains an organic fine solid substance. The microbubbles are generated in the second microbubble generator while supplying air to the wastewater processed in the step of generating microbubbles and in the step of performing microbubbles in the foam forming tank. Generating a foam in the waste water, and separating the waste liquid containing the foam into a foam phase and a liquid phase in a foam separation tank, and scraping the foam phase. A wastewater pretreatment method using foam separation, wherein the presence of the presence on the surface of the microbubbles generated by the second microbubble generator in the foam formation tank. By adhering a physical micro solid substance and utilizing the difference in specific gravity of the waste water inside and outside the foam forming tank, the micro bubble to which the organic micro solid substance is adhered is floated upward to form a foam. It is effectively achieved by treating the foam.

  In the present invention, the gas may be ozone, or a plurality of the first microbubble generators may be installed in the condition tank, or the second microbubble generator may be a shaft type. This is achieved more effectively.

  Another object of the present invention is to provide a condition tank for storing COD 1000 mg / L wastewater containing an organic micro solid material, in which a first microbubble generator is installed, and to generate second microbubbles inside. A wastewater pretreatment device comprising a cylindrical foam forming tank, a foam separating tank, and a scraper in which an apparatus is installed, wherein the foam forming tank has an air supply section at the bottom and the drainage from the condition tank at the lower side. A drainage introduction part for introducing a foam, and an overflow part for overflowing drainage containing foam formed in a foam formation tank on the upper side, respectively, in the foam formation tank, the second micro While adhering the organic micro solid material to the surface of the microbubbles generated by a bubble generator, the specific gravity difference of the drainage inside and outside the foam formation tank Utilizing the microbubble to which the organic matter-based fine solid substance is attached is floated upward to form a foam, and the foam is scraped out by the scraper to process the organic matter-based fine solid substance. This is achieved effectively.

  The present invention can also be achieved more effectively by providing a plurality of the first microbubble generators in the condition tank, or by being a shaft type of the second microbubble generators. .

  According to the pretreatment device and the pretreatment method of the present invention, it is possible to remove the organic matter SS having a relatively high molecular weight by delivering the organic matter SS to the foam, that is, separating the organic matter SS as a foam. It became.

It is the schematic of the waste water pre-processing apparatus which concerns on this invention. It is the schematic of the foam formation tank in the waste_water | drain pretreatment apparatus which concerns on this invention. It is sectional drawing of the foam formation tank in the waste_water | drain pretreatment apparatus which concerns on this invention. It is a flowchart which shows the flow of the waste water pre-processing method which concerns on this invention.

  Hereinafter, the wastewater pretreatment method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment.

  FIG. 1 is a schematic view of a wastewater pretreatment device 1 according to the present invention.

  As shown in FIG. 1, the waste water pretreatment device 1 includes three parts, that is, a condition tank 2, a foam formation tank 3, and a foam separation tank 4. By the way, the volume ratio of the condition tank 2, the foam formation tank 3 and the foam separation tank 4 is about 45% in the condition tank 2 and the foam formation tank 3 About 5% and the foam separation tank 4 is about 50%. In addition, about the said ratio, although these ratios are preferable in principle, it can change suitably.

  Next, the condition tank 2, the foam formation tank 3, and the foam separation tank 4 will be described.

  The condition tank 2 has one first microbubble generator 5 installed therein. The generator 5 has a power consumption of 50 W (a gas (such as ozone) suction amount of about 1 to 2 L / min, a liquid circulation rate of about 40 L / min, and an average particle size of generated microbubbles of 30 μm. ) Type is preferable, but a power consumption type of 400 W may be used. The power consumption is not particularly limited, and the length (size) of the generator 5 is also limited. Not. Further, the generator 5 is not limited to a type such as a shaft type. Further, a plurality of the generators 5 may be installed inside the condition tank 2.

  Next, FIG. 2 is a detailed view of the foam forming tank 3 shown in FIG. As shown in FIG. 2, the foam forming tank 3 has a cylindrical shape, includes a second microbubble generator 6 having a propeller 7 therein, and an air supply unit 8 at the bottom. Further, a drainage introduction part 9 for introducing drainage from the condition tank 2 is provided in the lower part of the foam formation tank 3, and the wastewater containing foam is disposed in the upper part of the foam formation tank 3 as a foam separation tank. An overflow portion 10 for overflowing to 4 is provided. The shaft-type microbubble generator 6 is an omnidirectional type, and the microbubbles protruding from the propeller 7 at the tip end spread over the entire 360 ° direction. In addition, although the shape of the air supply part 8 has preferable pipe shape, it is not this limitation. Moreover, although the shape of the waste_water | drain introduction part 9 and the overflow part 10 is preferable if it is a hole shape, you may provide a pipe | tube instead of a hole.

  As shown in FIG. 3, the microbubble generator 6 is installed along the central axis C of the foam forming tank 3, and the medium (solution, bubbles and foam) in the cylindrical tank is rotated by the rotation of the propeller 7. It is configured to rotate. The second microbubble generating device 6 is the same as the first microbubble generating device 5 except for the shaft type, except for the power consumption and the length. Moreover, the diameter of the foam formation tank 3 will not be ask | required as long as the 2nd microbubble generator 6 can be installed in the foam formation tank 3 inside. For example, when a 50 W type device is used, it may be 20 cm or more as a guide.

  And the foam formation tank 3 is installed in the center part of the wastewater pretreatment apparatus 1 in principle, but the installation location can be changed as appropriate according to the volume ratio described above.

  About the foam separation tank 4, although the pipe (not shown) for purging the liquid phase of the waste_water | drain mentioned later may be provided, it is not necessary to provide them in particular.

  Moreover, although the scraper 11 shown in FIG. 1 is a caterpillar shape, it is not limited to this shape.

  Next, the wastewater pretreatment method according to the present invention will be described based on the wastewater pretreatment device of FIG. 1 and the flowchart of FIG.

  First, drainage (raw water) is introduced into the condition tank 2, and microbubbles are generated by the first microbubble generator 5 (step S1). The introduced raw water is roughly subjected to microbubble treatment in the condition tank 2. The raw water used in the wastewater pretreatment method according to the present invention is not particularly limited, but is suitable for a COD (chemical oxygen demand) of 1000 mg / L or more. Here, the gas interposed inside the microbubble, that is, the gas sucked into the first microbubble generator 5 is preferably ozone, but may be a gas such as oxygen, nitrogen, rare gases, air, or the like. Incidentally, the particle size of the microbubbles generated by the microbubble generator 5 is on the order of 1 to several hundred μm.

  Next, the raw water that has been subjected to the microbubble treatment in the condition tank 2 is introduced into the foam formation tank 3 through the drainage introduction section 9 provided in the lower part of the foam formation tank 3 (step S2). Incidentally, the amount of bubbles generated when tap water is used is about 200 / mL, but when industrial wastewater is targeted, the concentration is several to several tens of times. The microbubbles supplied in the solution in the condition tank shrink in water while adhering an organic fine solid substance (organic matter SS) to the surface. Microbubbles that are smaller than those generated and trapped with organic fine solid substances on the surface have a low buoyancy, so that they move on the flow of water and move to the lower part of the apparatus to be introduced into the foam formation tank 3.

  And also with respect to the raw | natural water introduce | transduced into the foam formation tank 3, a microbubble is generated with the 2nd microbubble generator 6, and a microbubble process is performed (step S3). Incidentally, the gas interposed inside the microbubbles generated by the shaft-type microbubble generator 6 is preferably ozone like the microbubbles generated by the microbubble generator 5. Under the present circumstances, air is supplied from the air supply part 8 provided in the bottom part of the foam formation tank 3. FIG. At this time, air bubbles (particle size of about several mm to 3 cm) discharged from the air supply unit 8 rise along the central axis while being entrained in the previous flow in the foam formation tank 3 to generate shaft-type microbubbles It is taken into the propeller 7 of the device 6. Here, it is vigorously stirred and dispersed outside along with the water flow. Since the microbubbles are also released from the propeller 7, the microbubbles and bubbles with a large particle diameter (a few hundred μm level) that are taken in and discharged from below (drainage introduction part 9) are mixed in the second state. Ascending while rotating around the microbubble generator 6. These bubbles rise while repeating contact with the microbubbles and the air bubbles due to turbulent flow conditions in a narrow space inside the foam forming tank 3. In addition, the foam forming tank 3 is in a powerful rotating state, and the liquid phase heavier than the bubbles is pushed out to the surroundings by the action of centrifugal force and descends along the wall surface. The ratio of the gas phase (bubbles) is improved, and as a result, the bubbles are changed to foam. At this time, the organic substance SS captured in the microbubbles is effectively transferred to the foam, and finally overflows from the upper part of the foam formation tank 3, that is, from the overflow part 10 to the foam separation tank 4 ( Step S4).

  Next, the waste water overflowed from the foam formation tank 3 is in a state where a large amount of foam and liquid phase are mixed in the foam separation tank 4. In the foam separation tank 4, the liquid phase settles downward, and the foam covers the liquid phase to form a foam layer. The foam that has floated to the upper part is scraped to the outside by the scraper 11 (step S5).

  Examples of the wastewater pretreatment method according to the present invention will be described below. In addition, please refer FIG. 1 and the said embodiment about the waste_water | drain pretreatment apparatus used in the present Example.

[Example]
Organic wastewater containing surface active substances was introduced as raw water (drainage). The raw water has a COD (chemical oxygen demand) of about 50,000 mg / L and a BOD (biochemical oxygen demand) of about 1,000 mg / L. Since about 30% of the COD component is accounted for by the surfactant, 70% or more of the amount of drainage is foamed in a normal pressurized flotation device. For this reason, it is raw water having a property that cannot be treated with a normal foam separation device.

In the processing capacity ratio of the raw water to about 0.1 m 3 ^/ when the can was continuously fed to the waste water before treatment apparatus according to the present invention of about 1 m ^3.

  In addition, this raw water contains organic (derived from surfactant) -based fine solid substances, the particle size of which is smaller than 1 μm, and the proportion of organic matter in the raw water is the whole About 15%. In addition, it has a molecular weight of 10,000 or more as a composition, and is an organic substance that is a very heavy burden in wastewater treatment facilities mainly composed of oxidative decomposition.

Next, the raw water was introduced into the condition tank of the wastewater pretreatment device and subjected to microbubble treatment. The gas from the ozone generator was used as the suction gas for the microbubble generator. The amount of suction gas was about 2 L / min, and the ozone concentration was about 35 g / m ³ . The amount of microbubbles generated was about 2,000 / mL as the amount of bubbles of 50 μm or less. In addition, the fall of COD amount was hardly confirmed by the ozone microbubble process in a condition tank. However, the ozone removal rate dramatically improved the organic solid particulate removal rate in the entire system. That is, when air was used as a generation source of microbubbles, the removal rate of 50% or less was 95% or more removed by using ozone. This is probably because the surface properties of the solid microparticles changed due to the effect of ozone microbubbles.

In the foam formation tank, an omnidirectional shaft type microbubble generator was driven. The amount of gas sucked by the microbubble generator was about 2 L / min, and about 5 L / min of air was introduced from the lower intake pipe. The suction gas to the microbubble generator was ozone, and the ozone concentration was about 35 g / m ³ . Since there is an air supply of about 5 L / min from below, the bubble distribution generated from the apparatus was about 2,000 / mL for bubbles with a diameter of 50 μm or less, but bubbles of 50 μm to several hundred μm level More than 10,000 pieces / mL were contained. These bubbles gradually rose while receiving the rotational flow in the cylindrical tank, and in the process, the liquid phase was relatively lowered while being pressed against the cylindrical wall portion under the centrifugal force. As a result, the proportion of the gas increased as it went up, and it became a situation called foam when it overflowed.

  The treated water that has overflowed from the foam formation tank and reached the foam separation tank is left still in the tank, and is further separated into a foam portion and a liquid phase portion under the influence of gravity. The foam concentrated at the top was discharged out of the system by the scraping part.

  In addition, an Example is an example to the last.

  According to the present invention, not only the organic SS having a wide range of molecular weights but also organic SS containing hetero elements (phosphorus, sulfur, nitrogen, etc.), organic compounds, organic halogen compounds, organometallic compounds, etc. are included. It can also be used for wastewater.

DESCRIPTION OF SYMBOLS 1 Waste water pretreatment apparatus 2 Condition tank 3 Foam formation tank 4 Foam separation tank 5 1st microbubble generator 6 2nd microbubble generator 7 Propeller 8 Air supply part 9 Drain introduction part 10 Overflow part 11 Scraper

Claims (7)

In the waste water of COD 1000mg / L or more containing organic fine solid substances,
In the condition tank, a microbubble having a diameter of 10 to 50 μm in which gas is contained is generated in a first microbubble generator, and the microbubble treatment is performed in a foam formation tank. In the step of generating microbubbles in the second microbubble generator while supplying air to the wastewater treated in the step of forming bubbles in the wastewater, and in the foam separation tank, The drainage pretreatment method using foam separation comprising the step of separating the contained drainage liquid into a foam phase and a liquid phase, and scraping out the foam phase. In the foam formation tank, the second While adhering the organic micro solid material to the surface of the microbubbles generated by the microbubble generator, using the specific gravity difference of the drainage inside and outside the foam formation tank By forming the foam by floating the microbubbles the organic type fine solid material is attached to the upper, pretreatment methods wastewater, which comprises treating the foam.   The wastewater pretreatment method according to claim 1, wherein the gas is ozone.   The wastewater pretreatment method according to claim 1 or 2, wherein a plurality of the first microbubble generators can be installed in the condition tank.   The drainage pretreatment method according to any one of claims 1 to 3, wherein the second microbubble generator is a shaft type.   A cylindrical tank in which a first microbubble generator is installed, a condition tank for storing COD 1000 mg / L drainage containing organic micro solid substances, and a second microbubble generator in the interior. A wastewater pretreatment device comprising a foam formation tank, a foam separation tank and a scraper, wherein the foam formation tank has an air supply section at the bottom and a drainage introduction section for introducing the drainage from the condition tank to the lower side, Each of the microbubbles generated by the second microbubble generator in the foam forming tank is provided with an overflow portion for overflowing the waste water containing foam formed in the foam forming tank on the upper side. The organic matter-based fine solid substance is attached to the surface of the organic matter-based material, and the difference between the specific gravity of the wastewater inside and outside the foam-forming tank is used to Is floated said microbubbles small solid material adhered to the upper to form a foam, the said foam by scraping by the scraping device, the waste water before treatment apparatus, which comprises treating the organic type fine solid material.   The wastewater pretreatment device according to claim 5, wherein a plurality of the first microbubble generators can be installed in the condition tank.   The wastewater pretreatment device according to claim 5 or 6, wherein the second microbubble generator is a shaft type.

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