Sludge volume reduction apparatus, sludge volume reduction method, and jet nozzle used for this

Abstract

To provide a sludge volume reduction apparatus that can dramatically improve sludge solubilization effects without depending on existing driving conditions with no cost increase and is capable of increasing sludge volume reduction, a sludge volume reduction method, and a jet nozzle used for this.SOLUTION: A sludge volume reduction apparatus is assembled with a denitrification tank 1, a nitrification tank 2, solid liquid separation means for solid liquid separation of a sludge after passing the nitrification tank 2, and a return sludge pump 6 for returning a sludge separated by the solid liquid separation means to the denitrification tank 1 via a return sludge line 7 and is characterized by that a jet nozzle 9 having a fine cylindrical hollow part is installed in the return sludge line 7, an injection part 7C for an alkaline chemical solution is assembled in a piping on the upstream 7A of a jet nozzle 9 in the return sludge line 7, a return sludge injected with the alkaline chemical solution by the injection part 7C is introduced to the jet nozzle 9, and a shear force working on microorganism in the sludge injected with the alkaline chemical solution is imparted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sludge volume reduction device, a sludge volume reduction method, and a jet nozzle used therefor, and more particularly to a sludge volume reduction device, a sludge volume reduction method, and a jet nozzle used therefor that can significantly improve the sludge solubilization effect and improve sludge volume reduction, regardless of operating conditions and without increasing costs. [Background technology]

[0002] Sludge volume reduction technologies include those that use heat, electricity, and chemicals such as alkali and hypochlorous acid, and it is known that each of these can achieve a certain degree of volume reduction effect. However, the cost of energy input often exceeds the cost of reductions achieved through volume reduction, and technologies that offer sufficient benefits have not become widespread.

[0003] Patent Document 1 proposes a technology for solubilizing sludge by providing an alkaline treatment tank separate from the return sludge line using a return sludge pump, adding alkali to the alkaline treatment tank to perform alkaline treatment, and then providing a line to return the sludge to the aeration tank using a high-pressure pump. However, the method of Patent Document 1 has the drawback of requiring an alkaline treatment line in addition to the return line for the sludge return pump, which significantly increases costs and makes it unrealistic. Also, it is necessary to install a high-pressure pump in the alkaline treatment line in addition to the return sludge pump, which increases equipment costs and makes it unrealistic from this perspective as well.

[0004] Patent Document 2 proposes a technique in which a sludge solubilization tank is provided separately from the return sludge line, alkali is added, and the sludge is solubilized by the rotating blades of a rotary in-line mixer. However, since a sludge solubilization tank must be installed separately from the return line for the return sludge pump, this method is not practical and incurs significant cost increases.Furthermore, it is necessary to add special equipment such as a rotary in-line mixer or rotary blades to the sludge solubilization tank in addition to the return sludge pump, which not only increases equipment costs but also makes it impossible to solubilize the sludge in the return sludge line.

[0005] Patent Document 3 describes a technology in which excess sludge is introduced into a mill chamber containing a bead mill, where the sludge is crushed by the pressing force between the beads and subjected to heat caused by friction between the beads, and then the sludge is treated with alkali to promote the solubilization of the sludge. This technology has the drawback that a mill filled with beads must be installed separately from the return sludge line, which increases the equipment costs. Furthermore, since the sludge concentration of the beads packed into the mill is high at 1% to 2%, it is not easy to ensure sufficient gaps between the beads. This is because the beads stick together due to the stickiness of the sludge. For this reason, ball mills are not practical for high-concentration return sludge. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-045883 [Patent Document 2] Patent No. 5066340 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-246134 [Patent Document 4] Patent No. 7101858 Summary of the Invention [Problem to be solved by the invention]

[0007] The present inventors have conducted extensive research to solve the problems with the techniques of Patent Documents 1, 2 and 3, and as a result have developed the technique of Patent Document 4. The technology in Patent Document 4 involves introducing sludge into a jet nozzle using a return sludge pump to solubilize the sludge. The solubilized sludge is then fed into a denitrification tank, which is one type of activated sludge biological treatment tank, and solubilized organic matter and other components undergo activated sludge treatment in the denitrification tank and a subsequent nitrification tank (aeration tank), removing pollutants and reducing the volume of the sludge. When the above-mentioned jet nozzle is installed in the return sludge line of an existing denitrification / nitrification treatment facility and the existing return sludge pump is reused, it is mainly necessary to install only the jet nozzle, and there is no need to install a solubilization treatment tank or equipment separately from the return sludge line as in the past, which has the effect of reducing equipment investment costs.In addition, since it is only the jet nozzle, no new power is required, which has the effect of reducing energy costs. While the technology of Patent Document 4 reduces equipment investment costs and energy costs, it still has a new problem in that the sludge solubilization effect is highly dependent on operating conditions such as the capacity of the existing pump and the amount of sludge passed through. The present inventors have arrived at the present invention in order to be able to exhibit a sludge solubilization effect by adapting to general operating conditions without depending on the operating conditions of existing facilities.

[0008] Therefore, the object of the present invention is to provide a sludge volume reduction device, a sludge volume reduction method, and a jet nozzle used therein that can significantly improve the sludge solubilization effect and improve sludge volume reduction without relying on existing operating conditions or increasing costs.

[0009] Further objects of the present invention will become apparent from the following description. [Means for solving the problem]

[0010] The above problems are solved by the following inventions.

[0011] 1. a denitrification tank, a nitrification tank, solid-liquid separation means for separating sludge after passing through the nitrification tank into solid and liquid, and a return sludge pump for returning the sludge separated by the solid-liquid separation means to the denitrification tank via a return sludge line; a jet nozzle having a thin cylindrical hollow portion is installed in the return sludge line, an alkaline chemical solution injection section is provided in the return sludge line and in a pipe upstream of the jet nozzle; A sludge volume reduction device characterized in that returned sludge into which the alkaline chemical solution has been injected from the injection section is introduced into the jet nozzle, and a shear force acting on the microorganisms in the sludge into which the alkaline chemical solution has been injected is applied. 2. a circulating liquid transfer pump that transfers the circulating liquid from the nitrification tank to the denitrification tank via a circulating liquid transfer line, a jet nozzle having a thin cylindrical hollow portion is installed in the circulating liquid transfer line, 2. The sludge volume reduction apparatus according to item 1, wherein the circulating liquid is introduced into the jet nozzle to apply a shear force acting on microorganisms in the sludge. 3. 3. The sludge volume reduction device according to item 2, further comprising an injection section for injecting an alkaline chemical solution in the circulating liquid transfer line and in a pipe upstream of the jet nozzle. 4. 4. The sludge volume reduction apparatus according to any one of the above items 1, 2 and 3, wherein the pressure of the sludge fed to the jet nozzle is in the range of 0.05 to 0.25 MPa. 5. 5. The sludge volume reduction apparatus according to item 4, further comprising a secondary denitrification tank between the nitrification tank and the solid-liquid separation means. 6. 6. The sludge volume reduction device according to item 5, which is applied to a sewage treatment facility including sludge reclamation treatment. 7. In a method for reducing sludge volume in biological treatment in which wastewater is denitrified and nitrified through anaerobic and aerobic treatment, The biological treatment includes a return sludge line; A jet nozzle is installed in the return sludge line, Before the return sludge is introduced into the jet nozzle, an alkaline chemical solution is injected into the return sludge to perform pretreatment for solubilizing the sludge; Then, the solubilized pre-treated sludge is introduced into the jet nozzle; A method for reducing the volume of sludge, characterized in that the cell walls of the microorganisms are destroyed and solubilized by shearing forces acting on the microorganisms in the sludge solubilized by the alkaline chemical solution. 8. a denitrification tank, a nitrification tank, and solid-liquid separation means for separating solid and liquid from sludge that has passed through the nitrification tank; a return sludge pump that returns the sludge separated by the solid-liquid separation means to the denitrification tank via a return sludge line, a jet nozzle is installed in the return sludge line, the jet nozzle having a sludge inlet, a bulging hollow portion which is a space communicating with the sludge inlet, a thin cylindrical hollow portion which communicates with the bulging hollow portion, and a tip opening of the cylindrical hollow portion; 8. The sludge volume reduction method according to item 7, characterized in that a sludge volume reduction device is used that is provided with an alkaline chemical solution injection section in the return sludge line and in the piping upstream of the jet nozzle. 9. A method for reducing the volume of sludge in a biological treatment system that performs denitrification and nitrification of wastewater through anaerobic and aerobic treatment and is equipped with a return sludge line, A jet nozzle to be installed in the return sludge line, Before the return sludge is introduced into the jet nozzle, an alkaline chemical solution is injected into the return sludge to perform pretreatment for solubilizing the sludge; Then, the solubilized pre-treated sludge is introduced into the jet nozzle; A jet nozzle used in a sludge volume reduction method, characterized in that the shear force acting on the microorganisms in the sludge solubilized by the alkaline chemical solution destroys the cell walls of the microorganisms and solubilizes them. 10. A method for renovating a sludge treatment device, comprising providing a sludge volume reduction device to an existing sludge treatment device that is equipped with a denitrification tank, a nitrification tank, solid-liquid separation means for performing solid-liquid separation on sludge that has passed through the nitrification tank, and a return sludge pump that returns the sludge separated by the solid-liquid separation means to the denitrification tank via a return sludge line, A method for renovating a sludge treatment device, characterized in that the sludge volume reduction device is equipped with a jet nozzle having a thin cylindrical hollow portion in the return sludge line, and an alkaline chemical solution injection section in the return sludge line and in the piping upstream of the jet nozzle. [Effects of the Invention]

[0012] According to the present invention, it is possible to significantly improve the sludge solubilization effect and improve the sludge volume reduction without relying on the operating conditions of existing facilities or increasing costs.

[0013] Furthermore, according to the present invention, the solubilization effect is improved and the volume of excess sludge is reduced, thereby making it possible to reduce the amount of heavy oil used as fuel for incinerators in existing facilities where excess sludge is incinerated. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a flow chart showing a preferred embodiment of the sludge volume reduction device of the present invention. [Figure 2] 1 is a cross-sectional view showing an embodiment of a jet nozzle used in the present invention. [Figure 3] An explanatory diagram illustrating the advantages of the present invention compared to the prior art. [Figure 4] Graph showing experimental results demonstrating the effectiveness of the present invention DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow diagram showing a preferred embodiment of a sludge volume reduction apparatus for carrying out the sludge volume reduction method of the present invention.

[0016] In Figure 1, reference numeral 1 denotes a denitrification tank that removes nitrate nitrogen and nitrite nitrogen, and reference numeral 2 denotes a nitrification tank that decomposes organic matter and converts nitrogen components to nitrate or nitrite. Denitrification tank 1 is provided with a stirring blade 100 for stirring without supplying air, and stirring blade 100 is configured to be rotatable by a stirring motor 101. Organic matter is a component detected as BOD or COD. In the present invention, organic matter includes organic matter contained in wastewater and organic matter produced by solubilizing sludge. This organic matter can play the role of methanol, which is conventionally used in denitrification.

[0017] Numeral 3 denotes a settling tank into which sludge from the nitrification tank 2 is introduced for solid-liquid separation. In the illustrated embodiment, a gravity settling type settling tank is used. The solid-liquid separation means in the present invention may be a gravity-type coagulation sedimentation tank or a membrane separation tank, as long as it can separate solids and liquids. The membrane is not particularly limited, but examples that can be used include microfiltration membranes and ultrafiltration membranes.

[0018] A secondary denitrification tank 4 and a reaeration tank 5 may be placed between the nitrification tank 2 and the settling tank 3. The secondary denitrification tank 4 performs the same function as the denitrification tank 1. The reaeration tank 5 performs the same function as the nitrification tank 2. A circulation line (not shown) for circulating sludge from the reaeration tank 5 to the secondary denitrification tank 4 may also be provided. The secondary denitrification tank 4 is provided with an agitation blade 400 similar to the agitation blade provided in the denitrification tank 1, and the agitation blade 400 is configured to be rotatable by an agitation motor 401.

[0019] The nitrification tank 2 is provided with an aeration pipe 200, and the reaeration tank 5 is provided with an aeration pipe 500. Air is supplied to the aeration pipes 200 and 500 from a blower 201, so that the sludge suspension (a liquid in suspension formed by mixing activated sludge with wastewater) in the nitrification tank 2 and the reaeration tank 5 can be aerated.

[0020] The sludge that has settled in the settling tank 3 is returned to the denitrification tank 1 via a return sludge line 7 using a return sludge pump 6 . The return sludge pump 6 will be an existing one to avoid increasing costs, but it is preferable that it has a motor power that can perform shear solubilization even taking into account the pressure loss caused by the jet nozzle described below. The excess sludge is extracted through an excess sludge extraction line 8, thickened if necessary, dehydrated in a dehydrator (not shown), and then incinerated in an incinerator using fuel such as heavy oil.

[0021] The sludge in the nitrification tank 2 is circulated and transferred as a circulating liquid (circulating sludge) to the denitrification tank 1 via a circulating liquid transfer line 203 using a circulating liquid transfer pump 202 .

[0022] Reference numeral 9 denotes a jet nozzle, which is installed in the return sludge line 7. The jet nozzle 9 takes in only sludge without taking in external air, and solubilizes the taken-in sludge. The jet nozzle of the present invention is particularly preferred because it can shear and destroy cell walls to solubilize them. In this embodiment, a jet nozzle 204 can also be installed in the circulating liquid transfer line 203 .

[0023] In the present invention, the jet nozzle may be installed only in the return sludge line 7 or may be installed in both the return sludge line 7 and the circulating liquid transfer line 203 .

[0024] For ease of explanation, the upstream side (near side) of the return sludge line 7 is designated as 7A, and the downstream side (forward side) is designated as 7B. Furthermore, the upstream side (near side) of the circulating liquid transfer line 203 is designated as 203A, and the downstream side (forward side) is designated as 203B.

[0025] The return sludge line 7 and the circulating liquid transfer line 203 are both lines equipped with existing pumps, so even if a jet nozzle is installed, no additional pump is required and no increase in costs will occur.

[0026] The sludge volume reduction apparatus of the present invention can be used to carry out a method for reducing the volume of sludge in biological treatment, which involves denitrification and nitrification of wastewater through anaerobic and aerobic treatment. Specifically, the sludge volume reduction apparatus of the present invention can be preferably applied to sewage treatment facilities that include sludge reclamation treatment. Here, a sewage treatment facility including sludge reclamation treatment refers to a facility that treats sewage, septic tank sludge, and organic waste such as food waste together and recovers resources. The raw water received in this embodiment contains sewage (approximately 30%) and septic tank sludge (approximately 70%). The mixing ratio is not particularly limited.

[0027] In Figure 1, 10 is an alkaline chemical injection tank, 11 is an alkaline chemical injection pump, and the alkaline chemical solution is injected through an alkaline chemical solution injection section 7C installed upstream (foreground) 7A of the jet nozzle in the return sludge line 7. The method of addition is not particularly limited, and any method may be used as long as it allows injection into the return sludge line, and a method of injection via a line mixer (not shown) may also be used. As the alkaline chemical solution, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, sodium bicarbonate, etc. can be used, and preferably sodium hydroxide can be used. The amount of alkaline chemical solution added is preferably in the range of 1.5 to 8.0 mmol / L-sludge.

[0028] In this embodiment, a jet nozzle 204 is installed in the circulating liquid transfer line 203, and when the alkaline chemical solution is injected, it is injected through an injection section 203C installed on the upstream side (near side) 203A of the jet nozzle in the circulating liquid transfer line 203. In FIG. 1, 12 is an alkali chemical injection tank, and 13 is an alkali chemical injection pump. The alkaline chemical solution may be the same compound as the compound added to the return line, and the addition method and amount may be the same as the method for adding and injecting into the return sludge line.

[0029] In the present invention, as described above, the alkaline chemical solution is added to the upstream side (front side) 7A of the jet nozzle in the return sludge line 7, and if a jet nozzle 204 is installed in the circulating liquid transfer line 203, it is added to the upstream side (front side) 203A of the circulating liquid transfer line 203. The location of addition of the alkaline chemical solution is not particularly limited as long as it is on the front side of the jet nozzle, but in order to demonstrate the solubilizing effect of the addition of the alkaline chemical solution and then to exert the shear solubilizing effect of the jet nozzle, it is preferable that shear solubilization by the jet nozzle be carried out within 0.5 to 5.0 seconds after addition of the alkaline chemical solution. In this embodiment, solubilization by addition of an alkaline chemical solution in the present invention includes denaturing the cell walls of the microorganisms to make them fragile. The jet nozzle of the present invention is provided with a bulging cavity as described below, and since the bulging cavity ensures the processing time for alkali solubilization, the solubilization effect can be obtained even if the alkali is added close to the jet nozzle.

[0030] In this embodiment, the circulating liquid transfer line 203 is provided with a jet nozzle 204, and the alkaline chemical injection tank 12 and alkaline chemical injection pump 13 may not be installed. By installing only the jet nozzle 204, it is possible to improve the sludge volume reduction in the circulating transfer line as well as in the return sludge line. Furthermore, the circulating liquid transfer line 203 may be provided with a jet nozzle 204, and the alkaline chemical solution may be added to the upstream side (front side) 203A of the circulating liquid transfer line 203. The location of alkali addition may be the same as in the return sludge line. By adding the alkaline chemical solution upstream of the jet nozzle, it is possible to further improve the sludge volume reduction.

[0031] Next, the jet nozzle used in the present invention will be described with reference to FIG.

[0032] The jet nozzle 9 has an outer cylinder 91 provided around the outer periphery of an inner cylinder 90. The inner cylinder 90 and the outer cylinder 91 are detachably fixed in close contact with each other.

[0033] The inner cylinder 90 has a front end 93 having a sludge inlet 92, and in front of the front end 93 is a bulging cavity 94. In front of the bulging cavity 94 is a rear end 95.

[0034] The bulging cavity 94 is a region for compressing sludge, and a thin cylindrical hollow portion 96 is formed in the front center of the bulging cavity 94 .

[0035] The compressed sludge is discharged from a tip opening 97 of a thin cylindrical hollow portion 96. The tip opening 97 is connected to a return sludge line (the piping indicated by reference symbol 7B in Figure 1). Because of the above structure, it is not designed to take in outside air, but is designed to take in only sludge.

[0036] Sludge is introduced from a sludge inlet 92 and pumped under high pressure by a return sludge pump (reference numeral 6 in FIG. 1) into an expansion cavity 94, which is an expansion space, to promote compression. The compressed sludge is sent to the thin hollow cylindrical section 96, where shear forces are applied to the microorganisms, and when it is sent from the tip opening 97 to the piping of the return sludge line, shear forces are also applied to the microorganisms, destroying them. As a result, the sludge is solubilized.

[0037] The material of the jet nozzle 9 is not particularly limited, but in consideration of corrosion resistance, it is preferable to form it from stainless steel metal.

[0038] In the present invention, when sludge is supplied to the jet nozzle and pressurized, the cell walls of microorganisms are destroyed and solubilized at a high pressure in the range of 0.05 to 0.25 MPa.

[0039] In the present invention, regardless of whether the size is large or small, the flow velocity is preferably 5 m / sec or more, and more preferably in the range of 10 to 25 m / sec.

[0040] The operation of the present invention will be described with reference to FIG. FIG. 3 is a diagram illustrating the operation of the device of the present invention. In the figure, (A) shows an experimental example in which sludge solubilization was performed using a conventional jet nozzle alone, and (B) shows an experimental example in which sludge solubilization was performed by injecting an alkaline chemical solution upstream (pre-stage) of the jet nozzle, and then solubilization was performed using the jet nozzle.

[0041] Stages (I) and (II) in Figure 3(A) show the microorganisms in the activated sludge in the biological treatment tank (nitrification tank). Since no solubilization using a jet nozzle or alkali solubilization was performed, no changes were observed.

[0042] Stage (III) in Figure 3(A) shows two out of eight microorganisms whose cell walls have been destroyed (solubilized) by the jet nozzle.

[0043] In stage (IV) of Figure 3(A), the cell walls of the microorganisms are destroyed (solubilized) by the jet nozzle, and ultimately, one cell out of eight is solubilized. In the process from (III) to (IV), the volume of the sludge is ultimately reduced to one cell due to growth and repair of the destruction.

[0044] Stage (I) in Figure 3(B) shows the microorganisms in the activated sludge in the biological treatment tank (nitrification tank). Since no solubilization using a jet nozzle or alkali solubilization was performed, no changes were observed.

[0045] In stage (II) of Figure 3(B), alkaline solubilization was carried out by injecting an alkaline chemical solution, so that all eight cell walls of the microorganisms in the sludge were denatured and easily broken down.

[0046] In stage (III) of Figure 3(B), after the alkaline chemical solution was injected, solubilization progressed due to destruction by the jet nozzle, and the number of cells in the sludge whose cell walls had been destroyed increased to four out of eight.

[0047] In stage (IV) of Figure 3(B), some of the solubilized components turn back into sludge, but the amount of sludge is reduced compared to system (A) where no alkaline chemical solution is added. Furthermore, during the purification process, the sludge multiplied and the destruction was repaired, and the final volume reduction was only two cells.

[0048] At stage (IV) in Figure 3(A), the total number of disrupted cells was 1 out of 8, but as shown in stage (IV) in Figure 3(B), when the alkaline solution was injected before the jet nozzle, the total number of disrupted cells was 2 out of 8. Note that the number of cells is used for convenience of explanation and does not represent the actual number.

[0049] Here, the action (effect) of adding an alkaline chemical solution before the nozzle jet can be summarized as follows. First, the cell walls of microorganisms in sludge are made up of proteins or carbohydrates. Second, adding alkaline chemicals denatures the cell walls of microorganisms, making them more fragile. Third, shear force (passing through a nozzle) is applied to the fragile cell walls. Fourth, the effectiveness of breaking down the cell walls is improved compared to when no chemicals are added. [Example]

[0050] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0051] Example 1 In the apparatus shown in FIG. 1, a jet nozzle having a cylindrical hollow portion with a diameter (caliber) of 6 mm shown in FIG. 2 was used, and an alkaline chemical solution was injected and added upstream of the jet nozzle. In this experiment, a jet nozzle was installed in the return sludge line to send sludge with the return sludge concentration (mg / L) shown in Table 1 . An alkaline solution was added to the return sludge line upstream of the jet nozzle (pre-stage). The amount of alkaline solution added (g-NaOH / L-sludge and mmol-NaOH / L-sludge) was as shown in Table 1. After adding the alkaline chemical solution, the sludge was passed through a jet nozzle for shear solubilization treatment. The time for passing the liquid through the jet nozzle was 30 minutes. The experimental results of the solubilization effect are shown in Table 1.

[0052] (Comparative Experiment 1) An experiment was carried out in the same manner as in Example 1, except that no alkaline chemical solution was added and no shear disruption using a jet nozzle was carried out. The results are shown in Table 1.

[0053] (Comparative Experiment 2) An experiment was carried out in the same manner as in Example 1, except that an alkaline chemical solution was added (the amount added is shown in Table 1) and shear destruction using a jet nozzle was not performed. The results are shown in Table 1.

[0054] (Comparative Experiment 3) An experiment was carried out in the same manner as in Example 1, except that an alkaline chemical solution was added (the amount added is shown in Table 1) and shear destruction using a jet nozzle was not performed. The results are shown in Table 1.

[0055] (Comparative Experiment 4) An experiment was carried out in the same manner as in Example 1, except that an alkaline chemical solution was added (the amount added is shown in Table 1) and shear destruction using a jet nozzle was not performed. The results are shown in Table 1.

[0056] (Reference example) In Example 1, shear disruption was carried out using a jet nozzle, but an experiment was carried out in the same manner as in Example 1 except that no alkaline chemical solution was added. The results are shown in Table 1.

[0057] [Table 1]

[0058] Looking at the synergistic solubilization effect in Comparative Experiment 3, Reference Example, and Example 2 from Table 1 and Figure 4, in Comparative Experiment 3, 0.16 (g / L-sludge) of alkaline chemical solution was added, but shear destruction of the jet nozzle was not performed. The solubilization effect in this case was the solubilization effect of adding alkaline chemical solution alone, and was 3,600 mg-COD / kg-ss. In the reference example, a 30-minute liquid flow test was conducted to test the shear breakdown of the jet nozzle. No alkaline chemical solution was added during this test. Therefore, this reference example shows the solubilization effect of the shear breakdown of the jet nozzle alone, which was 5,400 mg-COD / kg-ss. Therefore, based on Comparative Experiment 3 and the Reference Example, the combined solubilizing effect of adding alkaline chemical solution alone and the solubilizing effect of shear disruption by the jet nozzle alone is 3,600 + 5,400 = 9,000 mg-COD / kg-ss.

[0059] In contrast, in Example 2, in which 0.16 (g / L-sludge) of alkaline chemical solution was added as in Comparative Experiment 3 before shear destruction of the jet nozzle, the solubilization effect was 17,500 mg-COD / kg-ss, which was a surprising effect of +8,500 mg-COD / kg-ss compared to the combined effect of the above individual effects of 9,000 mg-COD / kg-ss. [Explanation of symbols]

[0060] 1 Denitrification tank 100 stirring blade 101 Stirring motor 2 Nitrification tank 200 Diffusion tube 201 Blower 203 Circulating fluid transfer line 203A upstream side 203B Downstream 203C Injection part 204 Jet Nozzle 3 Settling tank 4 Secondary denitrification tank 400 stirring blade 401 Stirring motor 5 Reaeration tank 500 Diffusion tube 6. Return sludge pump 7 Return sludge line 7A Upstream side 7B Downstream side 7C Injection part 8. Excess sludge extraction line 9 Jet Nozzle 92 Sludge inlet 94 Bulging cavity 96 Cylindrical hollow section 97 Tip opening 10 Alkaline chemical dosing tank 11 Alkaline chemical dosing pump 12 Alkaline chemical dosing tank 13 Alkaline chemical dosing pump

Claims

1. a denitrification tank, a nitrification tank, solid-liquid separation means for separating sludge after passing through the nitrification tank into solid and liquid, and a return sludge pump for returning the sludge separated by the solid-liquid separation means to the denitrification tank via a return sludge line; a jet nozzle having a thin cylindrical hollow portion is installed in the return sludge line, an alkaline chemical solution injection section is provided in the return sludge line and in a pipe upstream of the jet nozzle; A sludge volume reduction device characterized in that returned sludge into which the alkaline chemical solution has been injected from the injection section is introduced into the jet nozzle, and a shear force acting on the microorganisms in the sludge into which the alkaline chemical solution has been injected is applied.

2. a circulating liquid transfer pump that transfers the circulating liquid from the nitrification tank to the denitrification tank via a circulating liquid transfer line, a jet nozzle having a thin cylindrical hollow portion is installed in the circulating liquid transfer line, 2. A sludge volume reduction apparatus according to claim 1, wherein the circulating liquid is introduced into the jet nozzle to apply a shear force acting on microorganisms in the sludge.

3. 3. The sludge volume reduction apparatus according to claim 2, further comprising an injection section for injecting an alkaline chemical solution into the circulating liquid transfer line, the injection section being located in a pipe upstream of the jet nozzle.

4. 4. A sludge volume reduction device according to claim 1, 2 or 3, wherein the pressure of the sludge sent to the jet nozzle is in the range of 0.05 to 0.25 MPa.

5. 5. The sludge volume reduction apparatus according to claim 4, further comprising a secondary denitrification tank between the nitrification tank and the solid-liquid separation means.

6. 6. The sludge volume reduction device according to claim 5, which is applied to a sewage treatment facility including a sludge regeneration treatment.

7. In a method for reducing sludge volume in biological treatment in which wastewater is denitrified and nitrified through anaerobic and aerobic treatment, The biological treatment includes a return sludge line; A jet nozzle is installed in the return sludge line, Before the return sludge is introduced into the jet nozzle, an alkaline chemical solution is injected into the return sludge to perform pretreatment for solubilizing the sludge; Then, the solubilized pre-treated sludge is introduced into the jet nozzle; A method for reducing the volume of sludge, characterized in that the cell walls of the microorganisms are destroyed and solubilized by shearing forces acting on the microorganisms in the sludge solubilized by the alkaline chemical solution.

8. a denitrification tank, a nitrification tank, and solid-liquid separation means for separating solid and liquid from sludge that has passed through the nitrification tank; a return sludge pump that returns the sludge separated by the solid-liquid separation means to the denitrification tank via a return sludge line, a jet nozzle is installed in the return sludge line, the jet nozzle having a sludge inlet, a bulging hollow portion which is a space communicating with the sludge inlet, a thin cylindrical hollow portion which communicates with the bulging hollow portion, and a tip opening of the cylindrical hollow portion; 8. A sludge volume reduction method according to claim 7, characterized in that a sludge volume reduction device is used which is provided with an alkaline chemical solution injection section in the return sludge line and in the piping upstream of the jet nozzle.

9. A method for reducing the volume of sludge in a biological treatment system that performs denitrification and nitrification of wastewater through anaerobic and aerobic treatment and is equipped with a return sludge line, A jet nozzle to be installed in the return sludge line, Before the return sludge is introduced into the jet nozzle, an alkaline chemical solution is injected into the return sludge to perform pretreatment for solubilizing the sludge; Then, the solubilized pre-treated sludge is introduced into the jet nozzle; A jet nozzle used in a sludge volume reduction method, characterized in that the shear force acting on the microorganisms in the sludge solubilized by the alkaline chemical solution destroys the cell walls of the microorganisms and solubilizes them.

10. A method for renovating a sludge treatment device, comprising providing a sludge volume reduction device to an existing sludge treatment device that is equipped with a denitrification tank, a nitrification tank, solid-liquid separation means for performing solid-liquid separation on sludge that has passed through the nitrification tank, and a return sludge pump that returns the sludge separated by the solid-liquid separation means to the denitrification tank via a return sludge line, A method for renovating a sludge treatment device, characterized in that the sludge volume reduction device is equipped with a jet nozzle having a thin cylindrical hollow portion in the return sludge line, and an alkaline chemical solution injection section in the return sludge line and in the piping upstream of the jet nozzle.

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