JP6653636B2 - Ozone treatment apparatus and sludge treatment method - Google Patents

Description

  The present invention relates to an ozone treatment device and a sludge treatment method.

  Examples of the organic sludge generated in the sewage treatment equipment include initial sludge generated during the primary treatment of sewage, excess sludge generated during the secondary treatment of sewage, and digested sludge generated by digesting these sludges. . Patent Literature 1 discloses a method of performing an ozone treatment and an alkali treatment on a sludge-containing liquid. This promotes the decomposition of sludge, improves the phosphorus recovery rate, and reduces the volume of sludge.

JP 2005-219043 A

  In the treatment of a sludge-containing liquid containing sludge, it is required to sufficiently decompose the sludge, and to efficiently separate sludge and its decomposition products from the sludge-containing liquid with high accuracy. However, in the conventional sludge treatment as described in Patent Literature 1, it was difficult to sufficiently advance the decomposition of sludge. Therefore, it is required to establish a technique capable of sufficiently decomposing sludge to obtain sludge and its decomposed products from a sludge-containing liquid.

  Thus, the present invention provides, in one aspect, an ozone treatment apparatus capable of sufficiently decomposing sludge to reduce the volume of sludge and separating the sludge and its decomposition product from water with high accuracy. The purpose is to: In another aspect, the present invention provides a sludge treatment method capable of sufficiently decomposing sludge to reduce the volume of sludge and separating the sludge and its decomposed product from water with high accuracy. The purpose is to:

  The present invention, in one aspect, is an ozone treatment apparatus provided with a reaction tank that treats a sludge-containing liquid with ozone to separate a foam layer containing a decomposition product of sludge and a liquid layer containing water. A liquid supply unit for supplying a sludge-containing liquid therein, and a gas supply unit for supplying a gas containing ozone to a liquid layer below the foam layer, wherein the gas supply unit supplies the sludge-containing liquid. Provided is an ozone treatment apparatus that supplies gas such that the supply amount of ozone to 1 g of suspended matter contained in sludge is 30 mg or more and the gas superficial velocity of a reaction tank is 0.0035 m / sec or more.

  In the reaction tank of the above-described ozone treatment apparatus, the liquid supply unit supplies the sludge-containing liquid to the inside of the foam layer containing the decomposition product of the sludge. The sludge-containing liquid supplied inside the foam layer flows down along the foam surface of the foam layer. On the other hand, a part of the ozone contained in the gas supplied from the gas supply unit to the inside of the liquid layer reacts with the sludge contained in the liquid layer, and the other part of the ozone moves up the liquid layer and moves to the foam layer. . At this time, most of the ozone transferred to the foam layer is dissolved in the water attached to the foam body and its surface. On the foam body and its surface, the dissolved ozone efficiently reacts with the sludge contained in the sludge-containing liquid to generate a decomposition product. Thus, on the foam body of the foam layer and on the surface thereof, the sludge contained in the sludge-containing liquid and the ozone can be efficiently contacted, so that the reaction between the sludge and the ozone sufficiently proceeds, and the sludge can be sufficiently decomposed. .

  The sludge contained in the sludge-containing liquid supplied into the foam layer and the decomposed products generated by decomposing the sludge adhere to the foam containing the decomposed products of the sludge by the action of liquid crosslinking, etc., and foam together with the foam body. The bed rises and is discharged from the top of the reactor. On the other hand, the water contained in the sludge-containing liquid has a large specific gravity and does not have as high an adhesive force with the foam as sludge and its decomposed product, so that it flows down and enters the liquid layer.

  The gas supply unit supplies the gas such that the supply amount of ozone to 1 g of suspended matter contained in the sludge of the sludge-containing liquid is 30 mg or more, and the superficial velocity in the reaction tank is 0.0035 m / sec or more. . Thereby, the sludge can be sufficiently decomposed to reduce the volume of the sludge, and the sludge and its decomposition product can be separated from water with sufficiently high accuracy.

  The liquid supply section is higher than the liquid level of the sludge-containing liquid stored in the reaction tank when the height of the entire inside of the reaction tank is H, and the liquid bottom is 0.2 H, based on the inner bottom of the reaction tank. It is preferable to supply the sludge-containing liquid at a position between .about.0.7H. As a result, the sludge decomposition rate and the separation accuracy between sludge and its decomposition products and water can be achieved at a sufficiently high level.

  The ozone treatment apparatus includes a pressure measurement unit that measures the pressure of the foam layer, and a supply flow rate of the sludge-containing liquid supplied from the liquid supply unit based on the pressure measured by the pressure measurement unit. And a control unit for adjusting at least one of the supply flow rate of water and the discharge flow rate of drain from the reaction tank.

  The pressure measurement unit is installed at a position higher than the liquid level of the sludge-containing liquid so that the pressure of the foam layer can be measured. The pressure in the foam layer depends on the supply pressure of the gas containing ozone from the gas supply unit, the height of the foam layer, the liquid level of the sludge-containing liquid, and the like. These values affect the reaction between ozone and sludge. Therefore, the control unit can adjust the pressure of the foam layer to a predetermined range by adjusting at least one of the supply flow rate of the sludge-containing liquid, the supply flow rate of the gas, and the discharge flow rate of the drain from the reaction tank. . Thereby, the sludge decomposition efficiency can be maintained in a predetermined range.

  The ozone treatment apparatus includes a pressure measurement unit configured to measure a pressure of a foam layer, a defoaming tank connected to the reaction tank, and configured to stir and break bubbles discharged from the reaction tank with a stirrer, The tank may be provided with a defoaming agent supply unit for supplying the defoaming agent. In this case, the control unit controls the supply flow rate of the sludge-containing liquid, the supply flow rate of the gas, the discharge flow rate of the drain from the reaction tank, the rotation speed of the stirrer, and the power consumption based on the pressure measured by the pressure measurement unit. It may be configured to adjust at least one of the supply flow rates of the antifoaming agent from the foaming agent supply unit.

  When a defoaming tank is provided, the pressure in the foam layer is determined in addition to the supply pressure of the gas containing ozone from the gas supply unit, the height of the foam layer, and the level of the sludge-containing liquid. Also depends on the separation speed of sludge and exhaust gas. Therefore, the control unit controls the supply flow rate of the sludge-containing liquid supplied from the liquid supply unit, the supply flow rate of the gas from the gas supply unit, and the discharge flow rate of the drain from the reaction tank based on the pressure measured by the pressure measurement unit. By adjusting at least one of the rotation speed of the stirrer and the supply flow rate of the antifoaming agent from the antifoaming agent supply unit, the pressure of the foam layer can be adjusted to a predetermined range. Thus, even when the defoaming tank is provided, the sludge decomposition rate can be maintained in a predetermined range.

  The gas supply unit includes a mixing unit that mixes an ozone-containing gas containing ozone and oxygen and a gas that does not contain ozone, and a porous material downstream of the mixing unit, and supplies a gas to the liquid layer. It is preferable to have a gas diffused. Thereby, the supply amount of ozone and the superficial velocity can be adjusted with a high degree of freedom. Therefore, even when the supply flow rate of the sludge-containing liquid or the properties of the sludge-containing liquid changes, the sludge decomposition rate and the accuracy of separating sludge and its decomposition products from water can be maintained at a high level. Further, since a fine bubble-like gas is supplied from the diffused gas, the contact area between the gas and the liquid in the liquid layer can be increased. Furthermore, since the foam in the foam layer is also reduced as a whole, the surface area of the entire foam is increased, and the contact efficiency between the sludge-containing liquid and the dissolved ozone can be further increased.

  The present invention, in another aspect, is a sludge treatment method in which a sludge-containing liquid is treated with ozone in a reaction tank to separate a foam layer containing a decomposition product of sludge and a liquid layer containing water. Inside, a liquid supply step of supplying a sludge-containing liquid, and in the liquid layer below the foam layer, a gas containing ozone is supplied, and the supply amount of ozone to 1 g of suspended matter contained in the sludge of the sludge-containing liquid is reduced. A gas supply step of supplying the gas at a rate of 30 mg or more and the superficial velocity of the gas at 0.0035 m / sec or more.

  In the above-described sludge treatment method, the sludge-containing liquid is supplied into the foam layer. The sludge-containing liquid supplied inside the foam layer flows down along the foam surface of the foam layer. On the other hand, the gas containing ozone supplied into the liquid layer moves up the liquid layer and moves to the foam layer. At this time, most of the ozone transferred to the foam layer is dissolved in the water attached to the foam body and its surface. On the foam body and its surface, the dissolved ozone efficiently reacts with the sludge contained in the sludge-containing liquid to generate a decomposition product. As described above, since the sludge-containing liquid and the dissolved ozone can efficiently come into contact with each other on the foam body and the surface of the foam layer, the reaction between the sludge and the ozone sufficiently proceeds, and the sludge can be sufficiently decomposed.

  In addition, the sludge contained in the sludge-containing liquid supplied into the foam layer and the decomposed products generated by decomposing the sludge adhere to the foam containing the decomposed products of the sludge by the action of liquid cross-linking force, etc. At the same time, the foam layer rises and is discharged from the upper part of the reaction tank. On the other hand, the water contained in the sludge-containing liquid has a large specific gravity and does not have as large an adhesive force with the foam body as sludge and its decomposed product, so that it flows down and enters the liquid layer. In this way, sludge and its decomposed products and water can be separated with high accuracy.

  Then, in the gas supply step, the ozone-containing gas is supplied such that the supply amount of ozone to 1 g of suspended matter contained in the sludge of the sludge-containing liquid is 30 mg or more, and the superficial velocity in the reaction tank is 0.0035 m / sec or more. It is supplied to be. Thereby, the sludge can be sufficiently decomposed to reduce the volume of the sludge, and the sludge and its decomposition product can be separated from water with sufficiently high accuracy.

  In the liquid supply step, the sludge-containing liquid may be supplied at a position between 0.2H and 0.7H when the height of the entire inside of the reaction tank is H and the inner bottom of the reaction tank is used as a reference. preferable. As a result, the sludge decomposition rate and the separation accuracy between sludge and its decomposition products and water can be achieved at a sufficiently high level.

  The above-described sludge treatment method includes a pressure measurement step of measuring the pressure of the foam layer, and a supply flow rate of the sludge-containing liquid, a supply flow rate of the gas, and a drainage from the reaction tank based on the pressure measured in the pressure measurement step. An adjusting step of adjusting at least one of the discharge flow rates. The pressure in the bubble layer depends on the supply pressure of the gas containing ozone in the gas supply step, the height of the bubble layer, the liquid level of the sludge-containing liquid, and the like. These values affect the reaction between ozone and sludge. Therefore, the pressure of the foam layer can be adjusted to a predetermined range by having an adjusting step of adjusting at least one of the supply flow rate of the sludge-containing liquid, the supply flow rate of the gas, and the discharge flow rate of the drain from the reaction tank. . This makes it possible to maintain the sludge decomposition rate within a predetermined range with high accuracy.

  The above-described sludge treatment method includes a pressure measurement step of measuring the pressure of the foam layer, and a stirring step of breaking bubbles by stirring bubbles discharged from the reaction tank with a stirrer in a defoaming tank connected to the reaction tank. A defoaming agent supplying step of supplying an antifoaming agent to the defoaming tank, and based on the pressure measured in the pressure measuring step, a supply flow rate of the sludge-containing liquid, a supply flow rate of the gas, The method may include an adjusting step of adjusting at least one of the discharge flow rate of the drain, the rotation speed of the stirrer, and the supply flow rate of the defoaming agent.

  When a defoaming tank is provided, the pressure in the foam layer is determined in addition to the supply pressure of the gas containing ozone from the gas supply unit, the height of the foam layer, and the level of the sludge-containing liquid. Also depends on the separation speed of sludge and exhaust gas. Therefore, based on the pressure measured in the pressure measurement step, the supply flow rate of the sludge-containing liquid, the supply flow rate of the gas, the discharge flow rate of the drain from the reaction tank, the rotation speed of the stirrer, and the supply flow rate of the defoamer By adjusting at least one, the pressure of the foam layer can be adjusted to a predetermined range. Thereby, even when the defoaming tank is provided, the sludge decomposition rate can be maintained within a predetermined range with high accuracy.

  Preferably, before the gas supply step, a mixing step of mixing an ozone-containing gas containing ozone and oxygen and a gas not containing ozone is provided. Thereby, the supply amount of ozone and the superficial velocity can be adjusted with a high degree of freedom. Therefore, even when the supply flow rate of the sludge-containing liquid or the properties of the sludge-containing liquid changes, the sludge decomposition rate and the accuracy of separating sludge and its decomposition products from water can be maintained at a high level.

  According to the present invention, in one aspect, there is provided an ozone treatment apparatus capable of sufficiently decomposing sludge to reduce the volume of sludge and separating the sludge and its decomposition product from water with high accuracy. be able to. In another aspect, the present invention provides a sludge treatment method capable of sufficiently decomposing sludge to reduce the volume of sludge and separating the sludge and its decomposed product from water with high accuracy. be able to.

FIG. 1 is a diagram showing an embodiment of the ozone treatment apparatus. FIG. 2 is a diagram when the diffused gas attached to the tip of the gas supply unit is viewed from above. FIG. 3 is a diagram when the liquid supply unit is viewed from below. FIG. 4A and FIG. 4B are schematic diagrams showing an enlarged cross section of the foam contained in the foam layer. FIG. 5 is a diagram illustrating an example of a control system that controls the pressure of the reaction tank. FIG. 6 is a perspective view of a reaction tank provided in another embodiment of the ozone treatment apparatus. It is a figure showing an example of a sludge treatment system to which an ozone treatment device is applied. It is the graph which plotted the data of the Example, making a horizontal axis ozone basic unit and a vertical axis | shaft the total VSS decomposition rate. It is the graph which plotted the data of the Example, making a horizontal axis a gas superficial velocity and a vertical axis SS transfer rate. It is the graph which plotted the data of the Example, making the horizontal axis the value of formula (I) and the vertical axis the SS transfer rate. 5 is a graph in which data of the examples are plotted, with the horizontal axis representing the value of the formula (II) and the vertical axis representing the total VSS decomposition rate. It is the graph which plotted the data of the Example, making a horizontal axis ozone basic unit and a vertical axis | shaft the total VSS decomposition rate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as necessary. However, the following embodiments are exemplifications for describing the present invention, and are not intended to limit the present invention to the following contents. In the drawings, the same reference numerals are used for the same elements or elements having the same functions, and duplicate description is omitted as the case may be.

  FIG. 1 is a diagram showing an embodiment of the ozone treatment apparatus. The ozone treatment apparatus 100 includes a reaction tank 10 and a defoaming tank 30 provided downstream of the reaction tank 10. A liquid supply unit 12 that supplies a sludge-containing liquid containing sludge and water to the reaction tank 10 is connected to the reaction tank 10. The defoaming tank 30 is connected to an antifoaming agent supply unit 33 that supplies the defoaming agent to the defoaming tank 30. A liquid layer 40 made of a drain containing water is formed at a lower portion of the reaction tank 10. A foam layer 20 including a plurality of bubbles 21 is formed on an upper portion of the reaction tank 10. Further, the reaction tank 10 is provided with a pressure measuring unit 15 for measuring the pressure of the foam layer 20. The contents of the ozone treatment device 100 and the sludge treatment method using the ozone treatment device 100 will be described below.

  The gas supply unit 50 supplies a gas containing ozone to the inside of the liquid layer 40 of the reaction tank 10 (gas supply step). The gas supply unit 50 includes an ozone generation unit 56, an air supply unit 58, a mixing unit 55, a pipe unit 54, and a gas diffuser 52. As the ozone generator 56, a normal ozonizer or the like can be used. As the air supply unit 58, a normal air pump or the like can be used. It is not essential to provide the air supply unit 58, and the air supply unit 58 may not be provided, or a supply unit for supplying an inert gas such as nitrogen may be provided instead of the air supply unit 58. .

  In the mixing section 55, the ozone-containing gas generated in the ozone generation section 56 and the air supplied from the air supply section 58 are blended to prepare the gas 51 to be supplied into the liquid layer 40 (mixing step). ). By having such a mixing section 55, the gas superficial velocity in the reaction tank 10 and the amount of ozone supplied to the reaction tank 10 (unit of ozone) can be individually adjusted. Therefore, even if the supply flow rate of the sludge-containing liquid or the properties of the sludge-containing liquid changes, the sludge decomposition rate and the separation accuracy between sludge and its decomposition products and water can be maintained at a sufficiently high level. .

The gas 51 containing ozone prepared in the mixing section 55 flows through the pipe section 54 and is supplied to the diffused gas 52 attached to the tip of the pipe section 54. The diffused gas 52 is made of a porous material such as ceramic. The decomposition product generated by decomposing sludge with ozone has viscosity. Therefore, bubbles 21 are formed on the liquid layer 40 by supplying the gas 51 from the gas supply unit 50. By supplying the gas 51 containing ozone from the scattered gas 52, the fine bubble-like gas 51 is supplied to the liquid layer 40. Thereby, the contact area between the gas and the drain containing water in the liquid layer 40 can be increased. The concentration of ozone in the gas 51 from the gas supply unit 50, for example, may be a _20~150mg-O 3 / L, it may be a _50~120mg-O 3 / L.

  By supplying the gas 51 containing ozone to the liquid layer 40, it is possible to efficiently react ozone with sludge contained in the liquid layer 40. If the gas bubbles supplied from the gas supply unit 50 are made finer, the bubbles 21 in the bubble layer 20 can also be made smaller. Thereby, the entire surface area of the foam 21 is increased, and the contact efficiency between the sludge-containing liquid and ozone can be further increased.

  The sludge-containing liquid is, for example, sludge water generated in a sewage treatment plant, and contains water and sludge. The contents of water and sludge in the sludge-containing liquid are, for example, 30 to 80% by weight and 20 to 70% by weight, respectively. Sludge includes, for example, suspended solids (SS) and liquid organic substances (evaporation residues: TDS). Suspended substances (SS) contain inorganic substances and volatile organic substances (VSS content).

  The concentration of suspended solids (SS) can be measured according to JIS K0102: 2013 “14.1 Suspended solids”. Specifically, the sludge-containing liquid is filtered through a 1 μm mesh filter, and the residue is dried at 105 to 110 ° C. for measurement. The concentration of the evaporation residue (TDS) can be measured according to JIS K0102: 2013 “14.2 Total evaporation residue”. Volatile organic matter (VSS) disappears when the suspended substance (SS) is heated at 600 ° C. ± 25 ° C. for 0.5 hour (disappeared matter). The concentration of the volatile organic substance (VSS) was determined by using a sample obtained by heating under the above-mentioned heating conditions, using JIS K0102: 2013, “14. Suspended substances and evaporation residues” and “14.1 Suspended substances”. Can be measured in accordance with

  In the reaction tank 10, volatile organic matter (VSS) contained in the sludge-containing liquid reacts with ozone to generate evaporation residue (TDS), which is a decomposition product of sludge. That is, when the volatile organic substance (VSS) reacts with ozone, the cell wall of the cell, which is the volatile organic substance (VSS), is decomposed, and an evaporation residue (TDS) is generated. By such a reaction, suspended solids (SS) can be reduced in the reaction tank 10 to reduce the volume of sludge.

  In the reaction tank 10, the decomposition of sludge can be sufficiently advanced. As the sludge decomposition progresses, the total VSS decomposition rate and TDS elution rate calculated by the following equations (1) and (3) increase. In this embodiment, the total VSS decomposition rate can be 20% by weight or more, preferably 25% by weight or more. In the present embodiment, the TDS elution rate can be set to 20% by weight or more, preferably 25% by weight or more.

  In the reaction tank 10, suspended substances can be efficiently separated from the sludge-containing liquid. When the separation accuracy between the sludge and its decomposition product and the drain containing water is improved, the SS transfer rate calculated by the following equation (2) increases. In this embodiment, the SS transfer rate can be set to 85% by weight or more, preferably 87% by weight or more.

Total VSS decomposition rate (% by weight) = [TDS ₁₆ + TDS ₁₈ −TDS ₁₂ ] × 100 / VSS ₁₂ (1)
SS transfer rate _{(wt%) = [SS 16 + TDS} 16 -TDS 12 × flow rate of foam flow / sludge-containing _{liquid] × 100 / SS 12 ... (} 2)
TDS elution rate (% by weight) = [TDS ₁₆ −TDS ₁₂ × bubble flow rate / flow rate of sludge-containing liquid)] × 100 / VSS ₁₂ (3)

In the formulas (1), (2) and (3), TDS ₁₆ is a flow rate per unit time of TDS contained in foam discharged from the upper part of the reaction tank 10, and TDS ₁₂ is supplied to the reaction tank 10. It is a flow rate per unit time of TDS contained in the sludge-containing liquid to be performed. TDS ₁₈ is a flow rate per unit time of TDS contained in the drain discharged from the bottom of the reaction tank 10. VSS ₁₂ is the flow rate of VSS contained in the sludge-containing liquid supplied to the reaction tank 10 per unit time. SS ₁₆ is the flow rate per unit time of SS contained in the foam discharged from the upper part of the reaction tank 10, and SS ₁₂ is the flow rate per unit time of SS contained in the sludge-containing liquid supplied to the reaction tank 10. is there. The “bubble flow rate” is a flow rate of foam discharged from the upper part of the reaction tank 10 per unit time, and the “flow rate of sludge-containing liquid” is a flow rate of sludge-containing liquid supplied to the reaction tank 10 per unit time. It is. Each flow rate is a flow rate on a weight basis.

  From the viewpoint of sufficiently increasing the total VSS decomposition rate, the gas supply unit 50 preferably supplies a gas containing 30 mg or more of ozone to 1 g of suspended solids contained in the sludge of the sludge-containing liquid, and 40 mg or more of ozone. It is more preferable to supply a gas containing From the viewpoint of reducing the sludge treatment cost, the gas supply unit 50 preferably supplies a gas containing 200 mg or less of ozone to 1 g of suspended matter contained in the sludge of the sludge-containing liquid, and a gas containing 100 mg or less of ozone. And more preferably a gas containing 68 mg or less of ozone.

In the present specification, the amount of ozone contained in the gas supplied from the gas supply unit 50 with respect to 1 g of suspended matter contained in the sludge of the sludge-containing liquid is referred to as “ozone basic unit” (mg-O ₃ / g-SS). Called. From the viewpoint of achieving both reduced increase and sludge treatment cost of all VSS decomposition rate, the ozone consumption rate is preferably _{30~200mg-O 3 / g-SS} , more preferably _40~100mg-O 3 / g a -SS, more preferably from _{40~68mg-O 3 / g-SS} .

  FIG. 2 is a diagram when the diffused gas 52 attached to the tip of the gas supply unit 50 is viewed from above inside and outside the reaction tank 10. Inside the reaction tank 10, the tip of the pipe part 54 is inserted so as to cross the central part of the reaction tank 10. A plurality of gas diffusers 52 each having a substantially cylindrical shape and extending from the side of the pipe portion 54 toward the side surface of the reaction tank 10 are provided at predetermined intervals on both sides of the pipe portion 54. By arranging a plurality of the diffused gases 52 in this manner, the gas containing ozone and the sludge contained in the liquid layer 40 can be brought into sufficient contact.

  The viscosity of the drain in the liquid layer 40 increases with the decomposition of the suspended solid (SS). For this reason, it is necessary to ensure the flowability in the reaction tank 10. From the viewpoint of smoothing the flow of the liquid layer 40 and making sufficient contact between the ozone and the sludge contained in the liquid layer 40, the area ratio of the gas diffusion 52 to the reaction tank 10 in the drawing viewed from above as shown in FIG. Is preferably 15 to 50%, more preferably 20 to 40%, and still more preferably 30 to 40%.

Returning to FIG. 1, the gas supply unit 50 supplies gas at a position lower than 0.2H when the entire height of the inside of the reaction tank 10 is set to H and the inner bottom 10 a of the reaction tank 10 is used as a reference. . That is, the height _{h 0} of the upper end of the aeration gas 52 is lower than 0.2 H. As described above, by supplying the gas containing ozone from the gas supply unit 50 at a low position in the reaction tank 10, the height of the interface between the bubble layer 20 and the liquid layer 40 in the reaction tank 10 is sufficiently reduced. be able to. Therefore, the height of the foam layer 20 with respect to the liquid layer 40 in the reaction tank 10 can be made sufficiently large. From such a viewpoint, the gas supply unit 50 is preferably configured to supply gas at a position lower than 0.15H with respect to the inner bottom 10a, and at a position lower than 0.1H. It is more preferred to be configured to supply the gas at.

  The gas superficial velocity in the reaction tank 10 is preferably 0.0035 m / sec or more, and more preferably 0.0037 m / sec or more, from the viewpoint of sufficiently increasing the SS transfer rate. On the other hand, the gas superficial velocity is preferably 0.009 m / sec or less, more preferably 0.008 m / sec or less, from the viewpoint of maintaining the total VSS decomposition rate sufficiently high. The gas superficial velocity in the present specification can be obtained by dividing the flow rate of the supply gas supplied from the gas supply unit 50 by the cross-sectional area of the reaction tank 10. When the diameter of the reaction vessel 10 varies along the height direction, the cross-sectional area can be obtained by dividing the internal volume of the reaction vessel 10 by the height H of the entire inside of the reaction vessel.

  In the reaction tank 10, the volume ratio of the foam layer 20 to the liquid layer 40 may be, for example, 2 to 8 or 3 to 7. If the volume ratio is too small, the decomposition and concentration of sludge in the foam layer 20 do not proceed sufficiently, and the amount of water flowing out to the defoaming tank 30 tends to increase. On the other hand, if the volume ratio is too large, the reaction between ozone and sludge in the liquid layer 40 does not sufficiently proceed, and the amount of sludge accompanying the drain discharged from the pipe 18 tends to increase.

  The liquid supply unit 12 supplies the sludge-containing liquid to the inside of the foam layer 20 formed in the reaction tank 10 (liquid supply step). That is, the liquid supply unit 12 may have any structure as long as the sludge-containing liquid can be supplied into the foam layer 20.

  FIG. 3 is a diagram when the liquid supply unit 12 is viewed from below inside and outside the reaction tank 10. At the tip of the liquid supply unit 12, a branch pipe 12A branched into a plurality is provided. The plurality of branch pipes 12A are parallel to each other, penetrate one side surface of the reaction tank 10, and extend toward the other side surface of the reaction tank 10 so as to be arranged at predetermined intervals in the horizontal direction. Each of the branch pipes 12A is disposed so as to substantially cross the inside of the reaction tank 10. The branch pipe 12A has a supply port 12a for supplying the sludge-containing liquid downward. As shown in FIG. 3, the liquid supply unit 12 has a plurality of supply ports 12 a for the sludge-containing liquid, so that the contact between the sludge contained in the sludge-containing liquid and the ozone contained in the bubbles 21 is further improved. Can be.

  When the inside of the reaction tank 10 is viewed from above or below, the diffused gas 52 shown in FIG. 2 and the branch pipe 12A shown in FIG. 3 are arranged such that their extending directions (longitudinal directions) are parallel. Preferably. Thereby, variation in sludge decomposition depending on the position in the reaction tank 10 can be sufficiently suppressed.

  The liquid supply unit 12 is not limited to the shape shown in FIG. In some other embodiments, the liquid supply unit 12 has a distal end located at the radial center of the defoaming tank 30 without branching, and discharges the sludge-containing liquid from an opening provided at the distal end. Such a structure may be adopted.

The height _{h 2} of the liquid supply portion 12, the height of the entire interior of the reaction vessel 10 and H, the inner bottom 10a when a reference of the reactor 10, is within the range of 0.2H~0.7H And more preferably in the range of 0.25H to 0.6H. I.e., the height _{h 3} to the upper end 10b of the reaction vessel 10 from the liquid supply section 12 is preferably in the range of 0.3H～0.8H, in the range of 0.4H~0.75H Is preferred. Thereby, both the total VSS decomposition rate and the SS transfer rate can be achieved at a sufficiently high level.

The height _{h 1} of the interface between the foam layer 20 and the liquid layer 40, the height of the entire interior of the reaction vessel 10 when the a H, based on the inner bottom 10a of the reaction vessel 10, 0.15H～0. It is preferably in the range of 4H, more preferably in the range of 0.2H to 0.3H. With such a height h _1, and the decomposition rate of the sludge, while maintaining a high separation precision between the sludge and its degradation products and water, the dispersibility in the liquid layer 40 of a gas containing ozone good Can be Further, sludge contained in the liquid layer 40 can be sufficiently decomposed.

Foam layer 20 and the height _{h 4} from the interface to the lower end of the liquid supply portion 12 of the liquid layer 40, the height of the entire interior of the reaction vessel 10 when the H, the range of 0.1H~0.4H And more preferably within the range of 0.15 to 0.3H. Thereby, both the total VSS decomposition rate and the SS transfer rate can be achieved at a sufficiently high level.

  FIG. 4 is a schematic diagram showing an enlarged cross section of the foam 21 included in the foam layer 20. As shown in FIGS. 4A and 4B, the foam 21 is composed of a foam main body 22, sludge particles 24 attached to the periphery of the foam main body 22, and a decomposition product 26 generated by decomposing the sludge particles 24. , And water 28 attached to the periphery of the foam body 22. The foam body 22 is formed by surrounding a gas containing ozone supplied from the gas supply unit 50 to the liquid layer 40 with a liquid organic substance contained in the sludge and a decomposition product of the sludge. The sludge particles 24 are, for example, SS, and the decomposition products 26 are, for example, TDS. The decomposition product 26 is generated by a reaction between ozone and the sludge particles 24, and may be integrated with the foam body 22 after the generation.

  Water 28 adheres to the surface of the foam body 22. The water 28 rises in the foam layer 20 together with the foam body 22. Ozone is dissolved in the water 28 and the foam body 22. At least a part of the sludge particles 24 included in the sludge-containing liquid flowing down the surface of the foam 21 adheres to the surface of the foam body 22. In the foam layer 20 of the reaction tank 10, the dissolved ozone and the sludge particles 24 can efficiently contact on the surface of the foam body 22, so that the decomposition reaction of the sludge particles 24 proceeds sufficiently. Further, the sludge particles 24 attached to the surface of the foam body 22 react with dissolved ozone while moving up the foam layer 20. As a result, the concentration of the decomposition product 26 increases toward the upper side of the foam layer 20.

  FIG. 4A shows the bubbles 21 of the foam layer 20 at a position higher than FIG. 4B. As the foam 21 rises up the foam layer 20, the water 28 attached to the foam body 22 falls by the action of gravity. On the other hand, the sludge particles 24 and the decomposition products 26 rise together with the foam main body 22 while being attached to the surface of the foam main body 22 by the action of the liquid crosslinking force, the surface tension, and the like. Therefore, as shown in FIGS. 4A and 4B, as the position of the foam layer 20 increases, the water 28 decreases, and the concentrations of the sludge particles 24 and the decomposition products 26 increase. Thus, in the foam layer 20, the sludge particles 24 and the decomposition products 26 are concentrated, and the sludge and its decomposition products and water can be separated with high accuracy.

  As shown in FIG. 1, the upper part of the reaction tank 10 and the upper part of the defoaming tank 30 are connected by a pipe 16. The foam 21 is discharged from the reaction tank 10 by a pipe 16 connected to the upper part of the reaction tank 10, and introduced into the defoaming tank 30. The defoaming tank 30 includes a stirrer 32 that has a stirring shaft and stirring blades attached to the stirring shaft, and is configured to be rotatable about the stirring shaft.

  In the defoaming tank 30, the agitator 32 is operated, and at the same time, the defoaming agent is supplied from the defoaming agent supply unit 33 to break the foam 21 and obtain the concentrate 29. By providing such a stirrer 32 and an antifoaming agent supply unit 33, the size of the entire ozone treatment apparatus 100 can be reduced. Further, the reaction between the sludge particles 24 contained in the foam 21 and the dissolved ozone can be promoted by the stirring. The obtained concentrate 29 is discharged to the outside by a pipe (not shown) or the like. It should be noted that the provision of the stirrer 32 and the defoaming agent supply unit 33 is not essential, and one of them may be provided.

  A gas supply unit 34 for supplying a gas containing ozone is connected to the defoaming tank 30. The gas supply unit 34 may have a diffused gas made of a porous material at the tip similarly to the gas supply unit 50. By stirring the bubbles 21 with the stirrer 32 while supplying the gas containing ozone from the gas supply unit 34, the sludge particles 24 contained in the bubbles 21 can react with ozone.

  The ozone treatment apparatus 100 can reduce the occupied volume of the foam layer 20 in the reaction tank 10 by including the defoaming tank 30. Therefore, the size of the reaction tank 10 can be reduced. Further, the sludge treatment process can be shortened. However, providing the defoaming tank 30 is not essential.

A pipe 18 for discharging drain is connected to the bottom of the reaction tank 10. The drain containing water contained in the sludge-containing liquid is discharged from the reaction tank 10 through the pipe 18. In the reaction tank 10, since the sludge and its decomposed product are concentrated and discharged from the upper pipe 16, the concentration of the sludge and its decomposed product in the drain can be sufficiently reduced. By adjusting the discharge flow rate of the drainage from the pipe 18, it is possible to control the height h ₁ of the interface of the liquid layer 40 and foam layer 20 of the reaction vessel 10. The drain may be sent to, for example, a water treatment device of a sewage treatment plant.

  The liquid layer 40 preferably contains sludge and its decomposition products in addition to water from the viewpoint of stably generating the foam 21. However, if the concentration of the sludge and its decomposition product in the liquid layer 40 becomes too high, the concentration of the sludge and its decomposition product in the drain discharged from the pipe 18 tends to increase. For this reason, from the viewpoint of stably forming the foam layer 20 while reducing the concentration of sludge and its decomposition products in the drain, it is preferable that the viscosity of the liquid layer 40 be in a predetermined range.

  The viscosity of the liquid layer 40 may be, for example, 1 to 10 cP or 1 to 5 cP. By maintaining the viscosity of the liquid layer 40 in the above range, even if the property of the sludge-containing liquid supplied to the reaction tank 10 fluctuates, the reaction tank 10 can be operated sufficiently stably and continuously. . The viscosity of the foam layer 20 is preferably higher than the viscosity of the liquid layer 40, and may be, for example, 5 to 80 cP.

  The viscosity of the liquid layer 40 can be controlled by adjusting the supply flow rate of the sludge-containing liquid supplied from the liquid supply unit 12. For example, when the viscosity of the liquid layer 40 is likely to fall below the target range, the supply flow rate of the sludge-containing liquid from the liquid supply unit 12 is increased. Thereby, the amount of sludge flowing down to the liquid layer 40 increases, and the viscosity of the liquid layer 40 increases. On the other hand, when the viscosity of the liquid layer 40 is likely to exceed the target range, the supply flow rate of the sludge-containing liquid from the liquid supply unit 12 is reduced. Thereby, the amount of sludge flowing down to the liquid layer 40 decreases, and the viscosity of the liquid layer 40 decreases.

  A control unit that controls the supply flow rate of the sludge-containing liquid may be provided based on the measurement result of the viscosity of the liquid layer 40. By providing such a control unit, even if the property of the sludge-containing liquid fluctuates, the reaction tank 10 can be operated sufficiently stably and continuously. An on-line analyzer for measuring the viscosity may be provided in the liquid layer 40 to automatically control the supply flow rate of the sludge-containing liquid. Alternatively, the viscosity of the sample may be measured by appropriately sampling the liquid layer 40, and the supply flow rate of the sludge-containing liquid may be manually controlled as needed based on the measurement result.

  FIG. 5 is a configuration diagram of a control system that controls the pressure of the reaction tank 10. The pressure measuring unit 15 is installed at a height where the foam layer 20 is formed in the reaction tank 10. Since the pressure measuring section 15 has its detecting section inserted into the foam layer 20, the pressure in the foam layer 20 can be measured (pressure measuring step). In the present embodiment, one pressure measuring unit 15 is provided in the reaction tank 10, but a plurality of pressure measuring units 15 may be provided. Thereby, the pressure at different heights of the foam layer 20 can be measured, and the situation of the sludge decomposition treatment in the reaction tank 10 can be grasped in more detail.

  The pressure of the foam layer 20 measured by the pressure measuring unit 15 is not only the pressure of the gas supplied from the gas supply unit 50 but also the sludge particles 24 and the decomposition products 26 attached to the bubbles 21 forming the foam layer 20. And the amount of water 28. When the amounts of the sludge particles 24, the decomposition products 26, and the water 28 attached to the foam 21 increase, the pressure acting on the foam layer 20 increases due to the gravity acting thereon. Further, the pressure of the foam layer 20 also depends on the number of bubbles 21 formed in the foam layer 20. When the number of the bubbles 21 in the foam layer 20 increases, the amounts of the sludge particles 24, the decomposed products 26, and the water 28 attached to the foam 21 also increase, and the pressure of the foam layer 20 also increases. The pressure of the foam layer 20 also depends on the foam breaking speed of the foam 21 in the defoaming tank 30. When the bubble breaking speed of the bubbles 21 in the defoaming tank 30 is reduced, the pressure of the foam layer 20 generated in the reaction tank 10 increases because a back pressure is applied to the reaction tank 10.

Pressure P1 measured by the pressure measuring unit 15, using the internal pressure P2 of the height h ₅ and Shoawaso 30 from the mounting position to the pipe 16 the upper surface of the density [rho _bubble and the pressure measuring portion 15 of the foam 21, P1 = Ρ _bubble × h ₅ + P2. Here, the internal pressure P2 of the defoaming tank 30 indicates a constant pressure when the foam breaking is stably performed. Further, the density of the foam 21 depends on the amount of the sludge particles 24 attached to the foam. From this, the amount of sludge particles 24 adhering to the bubble 21 can be grasped based on _{ρ bubble = (P1-P2)} / density [rho _bubble foam 21 which is calculated by the formula h _5. Therefore, when the pressure measured by the pressure measuring unit 15 is too low, the amount of the sludge particles 24 attached to the foam 21 is reduced, and the total VSS decomposition rate and the SS transfer rate tend to decrease.

This perspective density [rho _bubble foam 21 is preferably at 0.16 kg / ^{m 3} or more, more preferably 0.20 kg / ^{m 3} or more. Since the internal pressure P2 of the defoaming tank 30 differs depending on the equipment pressure loss at the subsequent stage of the defoaming tank 30, it is preferable to appropriately measure the pressure before starting the operation of the equipment. When the internal pressure P2 of the defoaming tank 30 exceeds a predetermined pressure, the rotational speed of the stirrer 32 is increased, or the defoaming agent supply amount from the defoaming agent supply unit 33 is increased, so that the defoaming tank is increased. 30 operation conditions can be stabilized.

  If the pressure of the foam layer 20 is measured using the pressure measuring unit 15 and the reaction tank 10 is controlled based on the measured value, the pressure fluctuation of the foam layer 20 can be suppressed and stable sludge treatment can be performed. As shown in FIG. 5, the measurement of the pressure measured by the pressure measurement unit 15 is sent to the control unit 90 via the signal line 92. The control unit 90 adjusts each adjustment unit according to the input pressure measurement value. The control unit 90 may be configured to compare the measured value with the target range of the pressure and determine whether the pressure adjustment is necessary or not. A gas flow control unit 50A for controlling the flow rate of the gas containing ozone in the gas supply unit 50, a flow control unit 12B for controlling the supply flow rate of the sludge-containing liquid in the liquid supply unit 12, and a discharge flow rate of the drain discharged from the reaction tank 10. , A rotation speed control unit 32A for controlling the rotation speed of the stirrer 32 that breaks the foam 21 in the defoaming tank 30, and a defoaming agent for controlling the injection amount of the defoaming agent. They are connected by signal lines 94A, 94B, 94C, 94D, and 94E, respectively, so that signals can be transmitted and received to and from the flow control unit 33A. The control unit 90 receives values of the flow rate of the gas containing ozone, the discharge flow rate of the drain, the rotation speed of the stirrer 32, and the supply flow rate of the defoamer from the respective control units via these signal lines. It may be constituted so that it may be.

  When the control unit 90 determines that the pressure of the foam layer 20 of the reaction tank 10 needs to be adjusted, the gas flow control unit 50A, the flow control unit 12B, the drain discharge flow control unit 18A, the rotation speed control unit 32A, and The control unit 90 transmits a control signal to at least one of the defoaming agent flow control units 33A. The control unit 90 transmits a control signal by selecting, for example, the adjustment unit having the largest difference between the target set value and the measured value in each adjustment unit. Note that the control method is not limited to such an embodiment.

The control unit receiving the control signal performs at least one operation condition selected from the flow rate of the gas containing ozone, the supply flow rate of the sludge-containing liquid, the discharge flow rate of the drain, the rotation speed of the stirrer 32, and the injection amount of the defoamer. Is adjusted (adjustment step). By adjusting the operating conditions, the pressure of the foam layer 20 is adjusted. Thereby, the pressure of the foam layer 20 is adjusted to a predetermined range. By adjusting the pressure to a predetermined range, stable rate of rise of the foam 21 in the foam layer 20, foam layer 20 and the height h ₁ of the interface between the liquid layer _40, the drain discharged from the pipe 18 the flow rate, etc. Can be maintained. This makes it possible to estimate the amount of the sludge particles 24 attached to the foam 21 and to stably decompose the sludge particles 24 into the decomposed products 26 in the reaction tank 10 within a predetermined range. . It is not essential to provide such a control unit 90 and each adjustment unit.

  FIG. 6 is a perspective view of a reaction tank 10A provided in an ozone treatment apparatus according to another embodiment. The inside of the reaction tank 10A is partitioned into a plurality of rooms by partition plates 14. In this way, by dividing the inside of the reaction tank 10A into a plurality of rooms, even when the reaction tank 10A is scaled up, the formation of the foam layer 20 proceeds smoothly, and the sludge is decomposed and the sludge is decomposed. And a high level of separation accuracy between the decomposition product thereof and water. In the case of the reaction tank 10A, the liquid supply unit 12 supplies a sludge-containing liquid to the foam layer 20 in each room, and the gas supply unit 50 supplies a gas containing ozone to the liquid layer 40 in each room. The partition plate 14 may have an opening that allows the drain of the liquid layer 40 and / or the foam 21 of the foam layer 20 to flow between adjacent rooms. To enable such distribution, the partition plate 14 may be, for example, in a mesh shape.

  FIG. 7 is a diagram illustrating an example of a sludge treatment system to which the ozone treatment device 100 is applied. The sludge treatment system 1 is applied to, for example, a sewage treatment plant. The sludge treatment system 1 includes a water treatment device 80 for treating sewage, an ozone treatment device 100 and a digestion and fermentation device 70 for treating sludge-containing liquid generated in the water treatment device 80 to reduce the volume of sludge, A sludge treatment device 60 for performing dehydration and drying is provided.

  In the ozone treatment apparatus 100, solid fuel and phosphorus fertilizer can be efficiently produced from sewage by separating sludge and its decomposition product from water while decomposing sludge contained in the sludge-containing liquid. The concentrate 29 obtained by the ozone treatment device 100 may be supplied to the digestion and fermentation device 70 to produce methane. The drain containing water obtained by the ozone treatment device 100 may be supplied to the water treatment device 80. In addition, the use of the ozone treatment apparatus 100 is not limited to the sludge treatment system 1 of FIG. 6, but can be applied to various systems for treating a sludge-containing liquid.

  The sludge treatment method of the present embodiment is a sludge treatment method in which a sludge-containing liquid is treated with ozone in a reaction tank 10 to separate a foam layer 20 containing a decomposition product of sludge and a liquid layer 40 containing water, A mixing step of mixing an ozone-containing gas containing ozone and oxygen with a gas not containing ozone, a liquid supply step of supplying a sludge-containing liquid into the foam layer 20, and a liquid layer below the foam layer 20 The ozone-containing gas is supplied into 40 so that the supply amount of ozone to 1 g of suspended solids contained in the sludge of the sludge-containing liquid is 30 mg or more, and the superficial velocity of the gas is 0.0035 m / sec or more. And a gas supply step. Each step can be performed based on the description of the ozone treatment apparatus 100 described above. Another optional step may be performed before, after, or simultaneously with each step.

  For example, using a control system as shown in FIG. 5, the pressure measurement step of measuring the pressure of the foam layer 20 and the defoaming tank 30 connected to the reaction tank 10 stir foam discharged from the reaction tank 10. A defoaming agent supplying step of supplying a defoaming agent from the defoaming agent supply unit 33 to the defoaming tank 30 may be provided. In this case, based on the pressure measured in the pressure measuring step, the supply flow rate of the sludge-containing liquid, the supply flow rate of the gas, the discharge flow rate of the drain from the reaction tank 10, the rotation speed of the stirrer 32, and the defoaming agent It is preferable to have an adjusting step of adjusting at least one of the supply flow rates. This makes it possible to adjust the pressure of the foam layer to a predetermined range, and to maintain the sludge decomposition rate in a predetermined range with high accuracy.

  The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, it is not essential for the ozone treatment apparatus of the present invention to include a mixing unit that mixes an ozone-containing gas and a gas that does not contain ozone. The sludge treatment method of the present invention does not necessarily include a mixing step, and an ozone-containing gas that has not been subjected to the mixing step may be supplied to the inside of the liquid layer 40 in the gas supply step.

  The content of the present invention will be described in detail with reference to the following examples and comparative examples, but the present invention is not limited to the following examples.

(Example 1)
The sludge-containing liquid generated from the sewage water treatment device was supplied to the ozone treatment device as shown in FIG. 1 to perform ozone treatment. The specifications of the reaction tank 10 were as follows.
<Specifications of reaction tank 10>
-Height H of the whole inside of the reaction tank 10: 2.2 m
The height h ₀ of the gas supply unit 50 (the height of the upper end of the diffused gas 52): 0.19 m
The area ratio of the diffused gas 52 to the reaction tank 10 when viewed from above as shown in FIG. 2: 36%

The sludge-containing liquid was supplied into the foam layer 20. From the gas supply unit 50, a mixed gas of oxygen gas containing ozone and air was supplied to the reaction tank 10. Foam was continuously discharged from a pipe 16 connected to the upper part of the reaction tank 10, and drain was continuously discharged from a pipe 18 connected to the lower part of the reaction tank 10. By adjusting the discharge flow rate of the drain, the basis of the inner bottom 10a of the reaction vessel 10, and adjust the height h ₁ of the interface between the liquid layer 40 and the foam layer 20. The height _h 2 to h ₄ shown in Figure 1 were as shown in Table 1.

  The height of the interface between the liquid layer 40 and the foam layer 20 was controlled by adjusting the discharge flow rate of the drain from the bottom of the reaction tank 10. At the time of sludge treatment, the sludge-containing liquid supplied to the reaction tank 10, the drain discharged from the bottom of the reaction tank 10, and the foam discharged from the top of the reaction tank 10 were sampled.

The concentration of suspended solids (SS) contained in the sampled sludge-containing liquid was measured, and the supply amount of suspended solids per unit time was determined from the measured concentration and the supply flow rate of the sludge-containing liquid. Then, for the supply amount of suspended solids (SS), the ratio of the supply amount of ozone (mg), i.e. to determine the ozone consumption rate _{[mg-O 3 / g-} SS]. Further, the concentration of the evaporation residue (TDS) contained in the sludge-containing liquid was measured.

  The concentration of the sampled evaporation residue (TDS) of the drain, and the concentrations of the suspended solids (SS), evaporation residue (TDS) and volatile organic matter (VSS) of the sampled foam were measured. From these measured values, the total VSS decomposition rate and the SS transfer rate were calculated by the above equations (1) and (2).

  The sludge treatment is performed by changing the basic unit of ozone, the gas superficial velocity and the supply flow rate of the sludge-containing liquid. After the operation is stabilized, the same sampling is performed, and the basic unit of ozone, SS transfer rate and total VSS decomposition rate are determined. Calculated. Tables 1, 2 and 3 show the results of these calculations and the sludge treatment conditions.

  Under any of the operating conditions of Examples 1-1 to 1-14 shown in Tables 1 to 3, the total VSS decomposition rate was 20% by weight or more, and the SS transfer rate was 60% by weight or more. Thus, in Examples 1-1 to 1-14, while sufficiently decomposing the sludge contained in the sludge-containing liquid, the sludge and its decomposed products could be separated from the sludge-containing liquid with high accuracy.

  FIG. 8 is an example in which the supply flow rate of the sludge-containing liquid is equal and the concentrations of the suspended solids in the sludge-containing liquid are equal among the examples 1-1 to 1-14 shown in Tables 1 to 3. It is the graph which plotted the data of 1-1 to 1-4. In FIG. 8, data in white circles is data of Example 1-4 in which sludge treatment was performed in summer, and data in black circles is data in which sludge treatment was performed in winter. Despite variations due to climate, a good correlation was found between the basic unit of ozone and the total VSS decomposition rate. From these results, it was confirmed that the total VSS decomposition rate can be increased by increasing the basic unit of ozone. From the results shown in FIG. 8, it is understood that the total VSS decomposition rate can be increased to 20% by weight or more by supplying 30 mg or more of ozone to 1 g of the suspended substance (SS).

  FIG. 9 shows Examples 1-10 to 1-14 in which the gas superficial velocity was changed among Examples 1-1 to 1-14 shown in Tables 1 to 3 in order to investigate the influence of the gas superficial velocity. Is a graph in which the data of the above are plotted (the other conditions were almost constant). Good correlation was found between the gas superficial velocity and the SS transfer rate. It was confirmed that the SS transfer rate could be increased by increasing the gas superficial velocity. From the results shown in FIG. 9, it is understood that the SS transfer rate can be increased to 80% by weight or more by setting the gas superficial velocity to 0.035 m / sec or more.

Supply flow rate of the sludge-containing liquid, ozone intensity and gas superficial velocity is approximately the same, the comparison of Example 1-7 Example 1-8, to increase the h _4, by reducing the h _1, the total It was confirmed that the VSS decomposition rate was reduced and the SS transfer rate could be increased. Thus, by varying the height h ₁ of the interface foam layer 20 and liquid layer 40, it is possible to adjust the values of all VSS decomposition rate and SS transport rate.

(Example 2)
Using a reaction tank having a size different from that of Example 1, the sludge-containing liquid generated from the sewage water treatment apparatus was supplied, and ozone treatment was performed under the following conditions.
<Conditions for ozone treatment>
-Height H of the whole inside of the reaction tank 10: 3.44m
The height h ₀ of the gas supply unit 50 (the height of the upper end of the diffused gas 52): 0.15 m
The height of the-liquid layer 40 _h 1: 0.69m
・ Height h ₂ of liquid supply unit 12: 1.9 m

  As shown in Tables 4, 5, and 6, sludge treatment was performed under different conditions. Then, in the same manner as in Example 2, the total VSS decomposition rate and the SS transfer rate under each condition were calculated. In each condition, the values of the following formulas (I) and (II) were calculated. The results are shown in Tables 4, 5 and 6. In addition, the discharge flow rate of the bubbles in Tables 4, 5, and 6, and the formula (II) is a flow rate when the bubbles flowing out from the upper part of the reaction tank 10 are converted into a liquid.

Supply flow rate of sludge-containing liquid per unit cross-sectional area of reactor (L / m ² / min) × SS concentration in sludge-containing liquid (% by weight) / 100 / gas superficial velocity (m / sec) / h ₄ (m )… (I)
Ozone intensity _{(mg-O 3 / g-} SS) × [(h 3 + h 4) (m) / gas superficial velocity (m / _{s)] × [(h 3 +} h 4) (m) / reactor units Foam discharge flow rate per cross-sectional area (L / m ² / min)] (II)

  Under any of the operating conditions of Examples 2-1 to 2-14 shown in Tables 4 to 6, the total VSS decomposition rate was 20% by weight or more, and the SS transfer rate was 60% by weight or more. Thus, in Examples 2-1 to 2-14, sludge and its decomposed products could be efficiently separated from the sludge-containing liquid while sufficiently decomposing the sludge contained in the sludge-containing liquid.

  FIG. 10 is a graph in which the data of Examples 2-1 to 2-14 are plotted, with the horizontal axis representing the value of the formula (I) and the vertical axis representing the SS transfer rate. The signs of the points plotted in FIG. 10 correspond to “identification numbers in the figure” in Tables 4, 5, and 6. It was confirmed that the formula (I) and the SS transfer rate had a good correlation. The denominator of the formula (I) includes the gas superficial velocity. Therefore, it was confirmed that as the gas superficial velocity increased, the SS transfer rate tended to increase.

  In FIG. 10, points (1), (2) and (7) are the results when the supply flow rate of the sludge-containing liquid is about 7500 L / min. Points (3) and (4) are the results when the supply flow rate of the sludge-containing liquid is about 6000 L / min. Point (5) is the result when the supply flow rate of the sludge-containing liquid is about 4500 L / min. Point (6) is the result when the supply flow rate of the sludge-containing liquid is about 4100 L / min. From these results, it was confirmed that the SS transfer rate could be increased by reducing the value of the formula (I) regardless of the supply flow rate of the sludge-containing liquid.

  FIG. 11 is a graph in which the data of Examples 2-1 to 2-14 are plotted, with the horizontal axis representing the value of the following formula (II) and the vertical axis representing the total VSS decomposition rate. From these results, it was confirmed that the total VSS decomposition rate tends to increase by increasing the calculation formula (II). The calculation formula (II) includes the gas superficial velocity in the denominator and the unit of ozone in the numerator. From this fact, it can be understood that the total VSS decomposition rate tends to increase as the unit of ozone increases, but the total VSS decomposition rate tends to decrease as the gas superficial velocity increases.

  FIG. 12 is a graph plotting the data of Examples 2-1 to 2-14, with the horizontal axis representing the basic unit of ozone and the vertical axis representing the total VSS decomposition rate. From these results, it can be seen that increasing the basic unit of ozone tends to increase the total VSS decomposition rate.

  From the results of FIG. 10, FIG. 11 and FIG. 12, in order to make both the SS transfer rate and the total VSS decomposition rate higher than the predetermined target values, for example, first, based on FIG. , The lower limit of the gas superficial velocity for satisfying the target value of the SS transfer rate is set. Thereafter, within the range that satisfies the lower limit, based on FIGS. 11 and 12, the gas superficial velocity and the basic unit of ozone are set so as to satisfy the target value of the total VSS decomposition rate. Thereby, in the sludge treatment, both the SS transfer rate and the total VSS decomposition rate can be made higher than a predetermined target value.

  DESCRIPTION OF SYMBOLS 1 ... Sludge treatment system, 10 and 10A ... Reaction tank, 10a ... Inner bottom, 10b ... Upper end, 12 ... Liquid supply part, 12A ... Branch pipe, 12B ... Flow control part, 12a ... Supply port, 14 ... Partition plate, 15 ... pressure measuring part, 16, 18 ... piping, 18A ... drain discharge flow rate adjusting part, 20 ... foam layer, 21 ... foam, 22 ... foam body, 24 ... sludge particles, 26 ... decomposed product, 28 ... water, 29 ... concentration Object, 30: defoaming tank, 32: stirrer, 32A: rotation speed control unit, 33: defoamer supply unit, 33A: defoamer flow rate control unit, 34: gas supply unit, 40: liquid layer, 50: Gas supply unit, 50A: gas flow control unit, 51: gas, 52: dispersed gas, 54: piping unit, 55: mixing unit, 56: ozone generation unit, 58: air supply unit, 60: sludge treatment device, 70 ... Digestion / fermentation device, 80: water treatment device, 90: control unit, 92, 94A, 94B, 9 C, 94D, 94E ... signal line, 100 ... ozone treatment apparatus.

Claims (8)

An ozone treatment apparatus comprising a reaction tank for treating a sludge-containing liquid with ozone to separate a foam layer containing a decomposition product of sludge and a liquid layer containing water,
A liquid supply unit that supplies the sludge-containing liquid inside the foam layer,
A gas supply unit that supplies a gas containing ozone to the inside of the liquid layer below the foam layer,
A pressure measuring unit for measuring the pressure of the foam layer,
Based on the pressure measured by the pressure measuring unit, the supply flow rate of the sludge-containing liquid supplied from the liquid supply unit, the supply flow rate of the gas from the gas supply unit, and the discharge of drain from the reaction tank A control unit for adjusting at least one of the flow rates ,
The gas supply unit is configured such that the supply amount of ozone to 1 g of suspended matter contained in the sludge of the sludge-containing liquid is 30 mg or more, and the gas superficial velocity of the reaction tank is 0.0035 m / sec or more. An ozone treatment device that supplies gas . An ozone treatment apparatus comprising a reaction tank for treating a sludge-containing liquid with ozone to separate a foam layer containing a decomposition product of sludge and a liquid layer containing water,
A liquid supply unit that supplies the sludge-containing liquid inside the foam layer,
A gas supply unit that supplies a gas containing ozone to the inside of the liquid layer below the foam layer,
A pressure measuring unit for measuring the pressure of the foam layer,
A defoaming tank connected to the reaction tank and agitating foam discharged from the reaction tank with a stirrer to break bubbles.
An antifoaming agent supply unit that supplies an antifoaming agent to the antifoaming tank ,
Based on the pressure measured by the pressure measuring unit, the supply flow rate of the sludge-containing liquid supplied from the liquid supply unit, the supply flow rate of the gas from the gas supply unit, and the discharge of drain from the reaction tank A control unit for adjusting at least one of the flow rates ,
The gas supply unit is configured such that the supply amount of ozone to 1 g of the suspended substance contained in the sludge of the sludge-containing liquid is 30 mg or more, and the gas superficial velocity of the reaction tank is 0.0035 m / sec or more. An ozone treatment device that supplies gas . The liquid supply unit supplies the sludge-containing liquid at a position between 0.2H and 0.7H when the height of the entire inside of the reaction tank is H and the internal bottom of the reaction tank is a reference. The ozone treatment apparatus according to claim 1 or 2 , wherein The gas supply unit,
A mixing section for mixing an ozone-containing gas containing ozone and oxygen, and a gas not containing ozone,
The ozone treatment apparatus according to any one of claims 1 to 3 , further comprising, on the downstream side of the mixing section, a gas diffuser configured of a porous material and supplying the gas to the liquid layer. A sludge treatment method in which a sludge-containing liquid is treated with ozone in a reaction tank to separate a foam layer containing a decomposition product of sludge and a liquid layer containing water,
A liquid supply step of supplying the sludge-containing liquid inside the foam layer,
In the liquid layer below the foam layer, the gas containing ozone is supplied at a supply rate of 30 mg or more per 1 g of suspended matter contained in the sludge of the sludge-containing liquid, and the superficial velocity of the gas A gas supply step of supplying the gas so as to be 0.0035 m / sec or more ;
A pressure measurement step of measuring the pressure of the foam layer,
An adjusting step of adjusting at least one of a supply flow rate of the sludge-containing liquid, a supply flow rate of the gas, and a discharge flow rate of drain from the reaction tank based on the pressure measured in the pressure measurement step. , Sludge treatment method. A sludge treatment method in which a sludge-containing liquid is treated with ozone in a reaction tank to separate a foam layer containing a decomposition product of sludge and a liquid layer containing water,
A liquid supply step of supplying the sludge-containing liquid inside the foam layer,
In the liquid layer below the foam layer, a gas containing ozone is supplied. The supply amount of ozone to the suspended substance 1 g contained in the sludge of the sludge-containing liquid is 30 mg or more, and the superficial velocity of the gas A gas supply step of supplying the gas so as to be 0.0035 m / sec or more;
A pressure measurement step of measuring the pressure of the foam layer,
In a defoaming tank connected to the reaction tank, a stirring step of stirring the foam discharged from the reaction tank with a stirrer to break bubbles,
An antifoaming agent supplying step of supplying an antifoaming agent to the defoaming tank,
Based on the pressure measured in the pressure measuring step, the supply flow rate of the sludge-containing liquid, the supply flow rate of the gas, the discharge flow rate of the drain from the reaction tank, the rotation speed of the stirrer, and the defoaming agent Adjusting the at least one of the supply flow rates of the sludge. In the liquid supply step, the sludge-containing liquid is supplied at a position between 0.2H and 0.7H when the entire height of the inside of the reaction tank is H and the inner bottom of the reaction tank is a reference. The sludge treatment method according to claim 5 or 6 , wherein The sludge treatment method according to any one of claims 5 to 7 , further comprising a mixing step of mixing the ozone-containing gas containing ozone and oxygen and a gas not containing ozone before the gas supply step.

Images