Organic sludge treatment equipment and organic sludge treatment method

Abstract

To provide an organic sludge treatment facility and an organic sludge treatment method, capable of accelerating dehydration of sludge to be dehydrated, allowing reduction or elimination of hot water to be directly supplied to a dehydration means from outside of the system, and preventing excessive presence of water in the treatment facility.SOLUTION: The problem is solved by an organic sludge treatment facility 1 and an organic sludge treatment method, which organic sludge treatment facility comprises a dehydration means 40 of dehydrating sludge to be dehydrated to obtain dehydration filtrate S, with the dehydration means 40 comprising a sludge dehydration chamber 46 dehydrating sludge to be dehydrated, a dehydration filtrate chamber 47 for the dehydration filtrate S obtained by dehydration to flow thereinto, and a heating means 70 of indirectly heating the dehydration filtrate S, and is characterized in that the sludge dehydration chamber 46 is heated by the heated dehydration filtrate S.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an organic sludge treatment facility and an organic sludge treatment method. [Background technology]

[0002] Known examples of organic sludge include sewage sludge, human waste, and food waste, and various treatment methods are used for these organic sludges. Among these, sewage treatment facilities incinerate the generated organic sludge in the sludge treatment facility's incinerator. Organic sludge contains a large amount of water, and if it were directly fed into the incinerator, a large amount of auxiliary fuel would be required. Therefore, the organic sludge is dehydrated to reduce its moisture content before being fed into the incinerator, thereby reducing the auxiliary fuel required for operation or even eliminating the use of auxiliary fuel.

[0003] Technological development related to dewatering means has been conducted for some time, and one example is disclosed in Patent Document 1. Fig. 3 shows the organic sludge treatment equipment disclosed in Patent Document 1. This organic sludge treatment equipment includes a flocculation means 5, a concentration means 2, and a dewatering means 3, and is a technology that aims to achieve both a low moisture content in the organic sludge and efficient drainage of the water separated from the organic sludge by supplying hot water H' from outside the system to the dewatering means 3 and dewatering the organic sludge while heating it. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-121253 [Patent Document 2] Japanese Patent Application Publication No. 8-309400 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-193442 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, a considerable amount of hot water H' is supplied from the outside to the inside of the dehydration means 3, and in addition, the dehydrated filtrate K is used as a heat source for the concentration means 2, which raises concerns that a large amount of wastewater will ultimately be discharged from the concentration means 2 to the outside of the system. The present invention has been made under such circumstances, and aims to provide an organic sludge treatment facility and an organic sludge treatment method that promotes dehydration of organic sludge using a method different from that of Patent Document 1. [Means for solving the problem]

[0006] The present inventors have conducted extensive research and have arrived at the idea of ​​using dewatered filtrate as the main component for heating organic sludge. The following is an embodiment of the invention that was completed based on this idea. (First aspect) An organic sludge treatment facility equipped with a dehydration means for dehydrating sludge to obtain dehydrated filtrate, the dehydration means comprises a sludge dehydration chamber for dehydrating the sludge to be dehydrated, a dehydration filtrate chamber into which the dehydration filtrate obtained by the dehydration flows, and a heating means for indirectly heating the dehydration filtrate; the heating means includes a heat exchanger, a transport flow path for transporting the dehydration filtrate in the dehydration filtrate chamber to the heat exchanger, and a return flow path for returning the dehydration filtrate heated by the heat exchanger to the dehydration filtrate chamber, The transported dehydration filtrate is heated by the heating medium flowing through the heat exchanger and returned to the dehydration filtrate chamber, Heating the sludge dehydration chamber It is something that An organic sludge treatment facility characterized by:

[0007] (Second aspect) An organic sludge treatment facility comprising: a concentration means for concentration treatment of sludge to be concentrated; and a dehydration means for dehydrating the concentrated sludge after the concentration treatment to obtain dehydrated sludge and a residual dehydrated filtrate; the dehydration means comprises a sludge dehydration chamber for dehydrating the concentrated sludge after the concentration treatment, a dehydration filtrate chamber into which the dehydration filtrate flows, and a heating means for indirectly heating the dehydration filtrate; The dehydrated filtrate flows out of the dehydration means at a temperature of 50 to 95°C and flows into the concentration means, and is used as a heat source in the concentration means. An organic sludge treatment facility characterized by:

[0008] (Third aspect) A dehydration step of dehydrating the sludge to be dehydrated to obtain a dehydrated filtrate, The dehydration step is carried out by a dehydration means, the dehydration means comprises a sludge dehydration chamber for dehydrating the sludge to be dehydrated, a dehydration filtrate chamber into which the dehydration filtrate obtained by the dehydration flows, and a heating means for indirectly heating the dehydration filtrate; the heating means includes a heat exchanger, a transport flow path for transporting the dehydration filtrate in the dehydration filtrate chamber to the heat exchanger, and a return flow path for returning the dehydration filtrate heated by the heat exchanger to the dehydration filtrate chamber, The transported dehydration filtrate is heated by the heating medium flowing through the heat exchanger and returned to the dehydration filtrate chamber, Heat the sludge dehydration chamber It is something , A method for treating organic sludge.

[0009] In this embodiment, the inside of the sludge dehydration chamber is heated by the heated dehydration filtrate, and the heat is transferred to the sludge to be dewatered in the sludge dehydration chamber, heating it as well. When the sludge to be dewatered is heated, the proteins that make up the sludge to be dewatered are thermally denatured and solubilized. This reduces the moisture content of the sludge to be dewatered, accelerating dehydration during the dehydration process. Furthermore, the viscosity of the heated sludge to be dewatered decreases, improving its fluidity.

[0010] Furthermore, in this embodiment, the dehydrated filtrate is mainly heated, so the amount of hot water supplied directly to the dehydration means from outside the system can be reduced or eliminated, thereby suppressing excess water within the treatment equipment.

[0011] Patent Document 2 discloses a simple method for efficiently dehydrating difficult-to-dewater sludge without adding chemicals in the treatment of drinking water sludge, and Patent Document 3 discloses a method for reducing operating costs and improving the phosphorus recovery rate, but does not involve heating the dehydrated filtrate as in the present invention. [Effects of the Invention]

[0012] According to the present invention, the dehydration of the sludge to be dehydrated is promoted, and the amount of hot water supplied directly to the dehydration means from outside the system can be reduced or eliminated, thereby providing an organic sludge treatment facility and an organic sludge treatment method that can suppress excess water within the treatment facility. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating an example of an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram illustrating an example of another embodiment of the present invention. [Figure 3] FIG. 1 is a diagram illustrating an example of a conventional technique. [Figure 4] FIG. 1 is a conceptual diagram showing an example of a sludge material balance according to the prior art. [Figure 5] FIG. 2 is a conceptual diagram illustrating an example of a sludge material balance according to the present embodiment. [Figure 6] FIG. 10 is a conceptual diagram showing another example of the sludge material balance of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, an embodiment of the present invention will be described. Note that this embodiment is merely an example of the present invention, and the scope of the present invention is not limited to the scope of this embodiment.

[0015] First Embodiment A specific embodiment of the present invention is, for example, an organic sludge treatment facility 1 equipped with dehydration means 40 for dehydrating sludge to be dewatered to obtain dehydrated filtrate S, wherein the dehydration means 40 comprises a sludge dehydration chamber 46 for dehydrating the sludge to be dewatered, a dehydrated filtrate chamber 47 into which the dehydrated filtrate S obtained by dehydration flows, and heating means 70 for heating the dehydrated filtrate S in the dehydrated filtrate chamber 47, and the inside of the sludge dehydration chamber 46 is heated by the heated dehydrated filtrate S. The organic sludge treatment facility 1 will now be described, together with the above means and ancillary means, with reference to Figure 1.

[0016] (influent sludge) The organic sludge treatment facility 1 is a facility that receives and treats influent sludge A, such as organic sludge generated in a water treatment facility equipped with a sewage treatment facility, and is equipped with a flocculation means 10, a concentration means 20, and a dewatering means 40. The influent sludge A includes raw sludge, activated sludge, digested sludge, etc. generated in the water treatment facility, as well as microorganisms such as polyphosphate-accumulating bacteria. These microorganisms absorb phosphate in the sewage (usually dissolved in the sewage in the form of phosphate ions) into their cells under aerobic conditions and release it outside their cells (take it in and expel it) under anaerobic conditions. Influent sludge A undergoes, for example, a flocculation process, then a concentration process, and finally a dewatering process to become dewatered sludge E.

[0017] (coagulation means) The flocculation step involves flocculating influent sludge A using flocculation means 10 to obtain flocculated sludge B. Influent sludge A is supplied to the flocculation means 10. When supplying influent sludge A, a predetermined amount of flocculant P may be added to the influent sludge A depending on the degree of flocculation of the influent sludge A, and the sludge is then supplied to the flocculation means 10. When flocculation agent P is added, it is preferable to stir the sludge with a pre-mixer M1 before supplying it to the flocculation means 10, as this allows the influent sludge A to be supplied to the flocculation means 10 in a well-mixed state with flocculant P, improving flocculation properties. An example of the flocculation means 10 is one equipped with a cylindrical coagulation tank with a bottom and a central axis extending vertically, into which the influent sludge A is supplied. The coagulation tank is equipped with a rotating shaft 14 aligned with the central axis, and a stirring means with agitating blades 15 attached along the rotating shaft 14. The rotating shaft 14 and the stirring blades 15 are rotated by a rotation drive means M3, such as a motor, provided at the top of the coagulation tank, thereby stirring the influent sludge A and the flocculant P. Influent sludge A, which has been agitated by the agitation means, flows out of the flocculation means 10 and is supplied to the concentration means 20. The flocculated influent sludge A can be specifically referred to as flocculated sludge B, and the solids concentration in the sludge (i.e., sludge concentration) is generally 1 to 4 wt%. The flocculant P is added to improve the flocculation properties of the influent sludge A, and examples of such flocculants include polymer flocculants such as cationic polymers and inorganic flocculants such as polyferric sulfate. When flocculant P is added, negatively charged solids dispersed in the sludge, which repel each other, are neutralized by positive charges and cross-linked, forming coarse flocs, thereby promoting flocculation. Note that if the influent sludge A supplied from the water treatment facility already has good flocculation properties (for example, if the influent sludge A already has a sludge concentration similar to that of flocculated sludge B), the influent sludge A may be supplied to the concentration means 20 instead of the flocculation means 10.

[0018] The influent sludge A supplied to the coagulation means 10 may be heated. For example, the influent sludge A flows through a sludge pressure pipe from a sewage treatment facility and is supplied to the coagulation means 10 of the organic sludge treatment facility 1, or is supplied to the coagulation means 10 after digestion treatment. The influent sludge A is supplied at a temperature of, for example, 10 to 50°C. The temperature of the influent sludge A can be measured by providing a temperature sensor in the flow path through which the influent sludge A is led to the coagulation means 10. The temperature sensor may be of a contact type or a non-contact type with respect to the influent sludge A.

[0019] (concentration means) The concentration step is a step of thickening the sludge to be thickened to obtain thickened sludge C. Here, examples of the sludge to be thickened include inflow sludge A and flocculated sludge B flocculated by the flocculation means 10. Below, a case where the sludge to be thickened is flocculated sludge B will be described. The flocculated sludge B is discharged from the sludge outlet 16 of the flocculation means 10 and supplied to the concentration means 20 through the flow path L1. The concentration means 20 thickens the flocculated sludge B to separate it into thickened sludge C and concentrated effluent R. The concentration means 20 has a sludge inflow section 22 into which the flocculated sludge B flows, a concentration tank 21 that receives the inflow flocculated sludge B and thickens it, a sludge outlet 23 from which the thickened sludge C obtained by concentration flows downstream, and a drainage section 28 from which the concentrated effluent R generated in the concentration treatment is discharged. The downstream end of the flow path L1 is connected to the sludge inlet 22, and the downstream end of a filtrate flow path L4, through which the dehydrated filtrate S discharged from the dehydration means 40 flows, is connected to the concentration means 20. The dehydrated filtrate S flows through the filtrate flow path L4, is supplied to the concentration means 20, and flows into the concentration tank 21. A pump P3 for sending the dehydrated filtrate S to the concentration means 20 is preferably provided in the filtrate flow path L4.

[0020] The concentration means 20 is not particularly limited and a general one can be applied, but for example, the filtration device disclosed in JP 2020-199443 A can be used as appropriate. This device is equipped with a cylindrical concentration tank 21 with a bottom and a vertically extending axis as its center, in which the introduced flocculated sludge B and / or dewatered filtrate S is held, and the flocculated sludge B is supplied into the concentration tank 21 from the top of the concentration tank 21. The cylindrical body of this concentration tank 21 is made of a filter screen 21a formed from a wedge wire, punched metal, or the like, and a jacket-shaped drainage chamber 26 is arranged around the outer periphery of this filter screen 21a. The filter screen 21a accommodates a conveying means including a cylindrical rotating shaft 27 that rotates about an axis extending along the axis of the thickening tank 21 and screw blades 24 that are spirally disposed along the rotating shaft 27. Furthermore, a rotation driving means M4 such as a motor that rotates the rotating shaft 27 is disposed above the thickening tank 21 and is connected to the rotating shaft 27.

[0021] The sludge inlet 22 can be located at the top of the thickening tank 21, and the sludge outlet 23 can be located at the bottom of the thickening tank 21. When the dehydrated filtrate S is introduced into the thickening tank 21, the location where the dehydrated filtrate S is introduced can be selected as appropriate. For example, the location where the dehydrated filtrate S is introduced can be the sludge inlet 22, a location where the flocculated sludge B has been concentrated approximately halfway, i.e., the middle portion of the thickening tank 21, or the sludge outlet 23. Among these locations, it is preferable to introduce the dehydrated filtrate S into a location where the flocculated sludge B has been concentrated approximately halfway. As the flocculated sludge B is concentrated, its viscosity increases, which can make it difficult to discharge. Introducing the heated dehydrated filtrate S into the middle portion of the thickening tank 21 can heat the flocculated sludge B during the concentration process, thereby preventing the sludge from becoming too viscous. This also has a cleaning effect and an effect of removing phosphate by adsorbing the remaining polyferric sulfate contained in the dehydrated filtrate S. In this case, for example, a hollow cylindrical body may be used as the rotating shaft 27, the dehydrated filtrate S may be introduced into the rotating shaft 27 from the lower end thereof, a hole may be provided in the vertical center of the rotating shaft 27, and a nozzle may be installed in the hole, and the dehydrated filtrate S inside the rotating shaft 27 may be discharged from the nozzle into the concentration tank 21.

[0022] The flow rate of the sludge to be concentrated flowing into the concentration means 20 is, for example, 3 to 40 m 3 / hour. In the concentration means 20 of this embodiment, 50 to 200 parts by mass, preferably 80 to 120 parts by mass of concentrated effluent R (including the inflowing dehydrated filtrate S) is obtained per 100 parts by mass of sludge to be concentrated per unit time.

[0023] The concentrated sludge C concentrated by the concentration means 20 has a sludge concentration of 4 to 10% by weight.

[0024] The concentrated sludge C discharged from the concentration means 20 flows through a sludge flow path L2, which is a flow path connecting the concentration means 20 with the dewatering means 40 installed downstream, and is sent to the dewatering means 40. The concentrated sludge C can be pumped through the sludge flow path L2 by applying pressure using a pump P1 installed in the sludge flow path L2, taking into account the frictional resistance of the sludge.

[0025] The dehydrated filtrate S flows into the concentration tank 21 and is discharged to the outside of the system as concentrated effluent R. Here, the sewage that flows into the water treatment facility usually passes from upstream to downstream through a receiving well, a primary sedimentation tank, a reaction tank, and a final sedimentation tank before being discharged into a river, the sea, etc. For example, by supplying the concentrated effluent R to the inlet of the primary sedimentation tank of the water treatment facility or to a location upstream of the primary sedimentation tank, the concentrated effluent R is treated together with the inflowing sewage and is ultimately discharged into a river, the sea, etc.

[0026] (Addition means) When the concentrated sludge C is dehydrated using the dehydration means 40, a dehydrated filtrate S containing a large amount of phosphoric acid is generated. If a flocculant F is added to the concentrated sludge C prior to dehydration using the dehydration means 40, the phosphoric acid reacts with the flocculant F to form an insoluble phosphorus compound, which then migrates to the concentrated sludge C (solids side), thereby reducing the concentration of phosphoric acid in the dehydrated filtrate S. As an example of the means 60 for adding the flocculant F, a container containing the flocculant F may be connected to a desired location on the sludge flow path L2 via a pipe for adding the flocculant, with an agitator M2 or the like installed at that desired location. It is preferable to use a method in which an appropriate amount of flocculant F is flowed from the container into the sludge flow path L2 according to the flow rate of the concentrated sludge C, and the thickened sludge C mixed with the flocculant F is stirred before being introduced into the dehydration means 40.

[0027] Examples of flocculant F include inorganic flocculants such as polyaluminum chloride (PAC) and polyferric sulfate, organic flocculants, anionic or nonionic polymer flocculants, and cationic polymer flocculants. In particular, polyferric sulfate and polyaluminum chloride are preferred because the residue remaining in the dewatered filtrate S reacts with the phosphoric acid in the concentrated sludge C to form insoluble phosphorus compounds, which act to reduce the phosphoric acid concentration in the wastewater.

[0028] Conventionally, a process of adding a flocculant F to concentrated sludge C has been carried out to reduce the moisture content of sludge, with the flocculant F added to the concentrated sludge C being approximately 10 to 35% by weight relative to the solids in the organic sludge. On the other hand, in this embodiment, the flocculant F can be added so that the flocculant F added to the concentrated sludge C is 1 to 15% by weight, preferably 3 to 10% by weight. In this embodiment, in which the heated dewatered filtrate S is introduced into the concentration means 20, the reactivity of the concentrated sludge C and the flocculant F is increased by heating the sludge during the concentration process, so that it is possible to reduce the moisture content of the dewatered sludge E without adding as much flocculant F as in the past.

[0029] (Dehydration means) The dewatering process is a process in which the sludge to be dewatered is dewatered to separate it into dewatered filtrate S and dewatered sludge E, thereby obtaining the dewatered filtrate S and dewatered sludge E. Here, the sludge to be dewatered can be, for example, influent sludge A, flocculated sludge B obtained by flocculating the influent sludge A using flocculation means 10, or concentrated sludge C obtained by concentrating the influent sludge A or flocculated sludge B using concentration means 20, or a combination of two or more selected from these. Below, we will explain the case where the sludge to be dewatered is concentrated sludge C. The dewatering means 40 mainly comprises a dewatering machine main body, a sludge inlet section 41 provided in the dewatering machine into which concentrated sludge C flows, a sludge discharge section 56 from which dewatered sludge E is discharged, a filtrate outlet section 42 from which the dewatered filtrate S flows, and heating means 70. The concentrated sludge C that flows into the dehydration means 40 is dehydrated and separated into dehydrated sludge E and dehydrated filtrate S. The dehydrated sludge E is discharged from the sludge discharge section 56 and transported to an incineration facility, and the dehydrated filtrate S flows out from the filtrate outflow section 42.

[0030] In a configuration in which the dehydration filtrate S is not flowed into the concentration means 20, the concentrated sludge C flowing out from the concentration means 20 flows into the dehydration means 40 at a temperature approximately the same as that of the flocculated sludge B flowing into the concentration means 20. On the other hand, in a configuration in which the dehydration filtrate S flows into the concentration means 20, the dehydration filtrate S is used as a heat source in the concentration means 20. Specifically, the sludge in the concentration tank 21 is heated by the dehydration filtrate S, and the temperature of the concentrated sludge C flowing out from the concentration means 20 is higher than that of the sludge to be concentrated flowing into the concentration means 20; for example, the temperature of the concentrated sludge C flows into the dehydration means 40 at 40 to 70°C, preferably 50 to 60°C. The temperature of the concentrated sludge C flowing out from the concentration means 20 can be measured by providing a temperature sensor in the sludge flow path L2. The temperature sensor may be of a contact type or a non-contact type with the sludge.

[0031] The dewatering means 40 is not particularly limited as long as it is capable of dewatering the concentrated sludge C, and may be, for example, a vertical screw press. The dewatering means 40 of this embodiment has an outer filter screen 43a and an inner filter screen 43b that separate the sludge dewatering chamber 46 and the dewatered filtrate chamber 47, and the outer filter screen 43a and the inner filter screen 43b are permeable to fluids and heat. The outer filter screen 43a and the inner filter screen 43b are arranged within the casing 49 for the purpose of filtering the concentrated sludge C. Of the multiple spaces within the casing 49 separated by the outer filter screen 43a and the inner filter screen 43b, the concentrated sludge C flows into the sludge dewatering chamber 46, which is the space partitioned by the outer filter screen 43a and the inner filter screen 43b. In this embodiment, the outer filter screen 43a and the inner filter screen 43b may be cylindrical or conical with a bottom and a bottom, with their axes extending vertically.

[0032] One example of the dewatering means 40 is a vertical screw press that includes a casing 49, an inner filtration screen 43b that is arranged within the casing 49 in a cylindrical or conical shape centered on an axis extending in the vertical direction, an outer filtration screen 43a that is cylindrical or conical and coaxial with the inner filtration screen 43b and arranged within the casing 49 at a distance outside the inner filtration screen 43b, and a ribbon-type screw 44 that is housed between the inner filtration screen 43b and the outer filtration screen 43a in a spiral shape twisting around the axis and can be rotated around the axis relative to the inner filtration screen 43b and the outer filtration screen 43a, wherein the space between the inner filtration screen 43b and the outer filtration screen 43a forms the sludge dewatering chamber 46, and the space inside the inner filtration screen 43b is connected to the space inside the casing 49 outside the outer filtration screen 43a, forming the dewatered filtrate chamber 47. The ribbon-type screw 44 is rotated around the axis in the sludge dewatering chamber 46 by a rotary drive means M5 such as a motor provided above. The illustrated dewatering means 40 is of a vertical type, but it may also be of a horizontal type.

[0033] It is preferable that the outer filtration screen 43a and the inner filtration screen 43b are made of, for example, wedge wire or punched metal, so that liquid and heat flow from the sludge dewatering chamber 46 to the dewatered filtrate chamber 47, or from the dewatered filtrate chamber 47 to the sludge dewatering chamber 46.

[0034] The casing 49 is preferably cylindrical or conical with a bottom, centered on the axis. The sludge dewatering chamber 46 has a sludge inlet 41 at its bottom, and thickened sludge C flows into the sludge dewatering chamber 46 from the sludge inlet 41. An annular connecting plate 51 that connects the inner filter screen 43b and the outer filter screen 43a is provided below the inner filter screen 43b and the outer filter screen 43a, and the sludge inlet 41 is connected to the connecting plate 51. The thickened sludge C flows from the sludge inlet 41 into the sludge dewatering chamber 46 via the connecting plate 51, but does not flow directly from the sludge inlet 41 into the dewatered filtrate chamber 47. The sludge in the sludge inlet 41 is transported upward and dewatered by the relative rotation of the ribbon-type screw 44. The dehydrated filtrate S obtained by dehydration passes through the outer filter screen 43 a and the inner filter screen 43 b and flows into the dehydrated filtrate chamber 47 .

[0035] An annular support plate 52 is disposed on the upper part of the casing 49, and the outer filtration screen 43a is supported on the inner peripheral part of the support plate 52. The support plate 52 closes the outer dehydration filtrate chamber 47 and is configured to prevent the dehydration filtrate S from flowing upward beyond the support plate 52. A lid body 54 is provided on the upper end part of the casing 49, and the inner filtration screen 43b is supported by this lid body 54. A rotation drive means M5 is disposed above the lid body 54 and rotates the ribbon-type screw 44 via a cylindrical screw support that covers the upper part of the inner filtration screen 43b. In this embodiment, the outer filtration screen 43a and the inner filtration screen 43b are supported and fixed to the support plate 52 or the lid body 54, and the ribbon screw 44 is rotated by the rotation drive means M5. However, conversely, the ribbon screw 44 may be fixed and the outer filtration screen 43a and the inner filtration screen 43b may be rotated, or the ribbon screw 44 and the outer filtration screen 43a and the inner filtration screen 43b may be rotated in opposite directions.

[0036] The space within the casing 49 separated by the support plate 52 and the lid 54 is a discharge chamber 55, and the upper part of the inner filtration screen 43b extends into the discharge chamber 55, forming an extension portion. A squeeze ring 53 is arranged above this extension portion with a gap therebetween, and the dewatered sludge E flows from the sludge dewatering chamber 46 through the gap and into the discharge chamber 55. The dewatered sludge E that has flowed into the discharge chamber 55 is discharged from a sludge discharge portion 56.

[0037] The dehydration filtrate chamber 47 is provided with a heating means 70. The heating means 70 is provided for the purpose of indirectly heating the dehydration filtrate S. Examples of the heating means 70 include a method of heating the dehydration filtrate S using a heat exchanger 71, a method of heating the dehydration filtrate S by installing a heater immersed in the dehydration filtrate S, and a jacket-type heating means that heats the dehydration filtrate chamber 47 from the outside, but are not limited to these.

[0038] 1, a heating means 70 in which the dehydrated filtrate S is indirectly heated by a heat exchanger 71 will be described. The heating means 70 includes a heat exchanger 71, a transport flow path 72 that transports the dehydrated filtrate S from the dehydrated filtrate chamber 47 to the heat exchanger 71, and a return flow path 73 that returns the dehydrated filtrate S heated in the heat exchanger 71 to the dehydrated filtrate chamber 47, and the transported dehydrated filtrate S is indirectly heated by the heating medium H that flows through the heat exchanger 71. The heating means 70 will be described in detail below. An intake hole and a return hole are provided in the wall of the dehydrated filtrate chamber 47 at positions where the dehydrated filtrate S can be taken in, and the transport flow path 72 and return flow path 73 are connected to them, respectively. The dehydrated filtrate S is transported from the water intake port to the heat exchanger 71 through a transport flow path 72, heated in the heat exchanger 71, and then returned from the heat exchanger 71 through a return flow path 73 to the dehydrated filtrate chamber 47 via a return port. The positions of the water intake port and the return port are not particularly limited. However, to prevent short-circuiting of the dehydrated filtrate S heated by the heat exchanger 71, it is preferable to install the water intake port and the return port facing each other on the dehydration means 40 or spaced apart vertically. In the heat exchanger 71, the dehydrated filtrate S and the heating medium H indirectly exchange heat in a countercurrent or parallel flow manner. The heating medium H may be hot water, thermal oil, steam, or the like, and has a higher temperature than the dehydrated filtrate S being transported. The heating medium H may use exhaust heat from equipment installed alongside the dehydration means 40, such as a sludge drying facility, incineration facility, or power generation facility, as its heat source. For example, waste heat (steam, warm wastewater) generated from flue gas treatment tower wastewater, scrubber wastewater from sludge drying equipment, and digester gas generators can be used as heat sources, and these heat sources can be used not only to heat the heating medium H, but also to directly supply it to the heat exchanger 71 as the heating medium H. The heating medium H flows through a heating medium flow path 74 that connects the heat exchanger 71 to the attached equipment, and is supplied to the heat exchanger 71. It is also preferable to provide a temperature sensor in the heating medium flow path 74 that measures the temperature of the heating medium H, and the temperature sensor may be of a contact type or a non-contact type with respect to the heating medium H.

[0039] It is also preferable to provide a pump or the like in the transfer flow path 72 to circulate the dehydrated filtrate S between the dehydrated filtrate chamber 47 and the heat exchanger 71. This allows for efficient heat exchange, and the dehydrated filtrate S can be efficiently heated.

[0040] The sludge dewatering chamber 46 and the dewatered filtrate chamber 47 can be separated by an outer filter screen 43a and an inner filter screen 43b and installed adjacent to each other. The dewatered filtrate S obtained by dewatering the thickened sludge C in the sludge dewatering chamber 46 passes through the outer filter screen 43a and the inner filter screen 43b and flows into the dewatered filtrate chamber 47. In the dewatered filtrate chamber 47, the liquid level of the dewatered filtrate S reaches the height of the support plate 52. The dewatered filtrate S heated by the heating means 70 flows into the dewatered filtrate chamber 47. The dewatered filtrate S in the dewatered filtrate chamber 47 heated by the heating means 70 heats the outer filter screen 43a and the inner filter screen 43b, and a portion of the dewatered filtrate S passes through the outer filter screen 43a and the inner filter screen 43b and flows into the sludge dewatering chamber 46. The heat of the dewatered filtrate S is conducted to the sludge dewatering chamber 46. This heats the sludge dewatering chamber 46 and the sludge undergoing dewatering in the sludge dewatering chamber 46. The heated sludge solubilizes due to thermal denaturation of proteins, reducing its water content and further accelerating dewatering.

[0041] During the dewatering process, contaminant solids (SS) that are finer than the mesh size of the outer filter screen 43a and the inner filter screen 43b pass through the outer filter screen 43a and the inner filter screen 43b, so the dewatered filtrate S contains contaminant solids.

[0042] The dehydration means 40 may be equipped with a dehydrator such as a centrifugal dehydrator, a screw press, a filter press, or a belt press.

[0043] The dewatered sludge E dewatered by the dewatering means 40 can be treated in a downstream incineration facility without the need for auxiliary fuel if the moisture content is adjusted to 72% by weight or less, although this depends on the combustible content of the sludge. Also, adjusting the moisture content of the dewatered sludge E to 60 to 72% by weight is preferable because it not only allows treatment without the need for auxiliary fuel as described above, but also makes sludge transportation easier.

[0044] In a configuration in which the sludge is heated by the heating means 70, the temperature of the dewatered sludge E discharged from the sludge discharge section 56 is higher than the temperature of the thickened sludge C flowing into the sludge inlet section 41. The temperature of the dewatered sludge E is preferably 50°C or higher and 95°C or lower. More preferably, depending on the type of sludge inlet A, the temperature should be 60°C or higher and 70°C or lower for mixed raw sludge, 65°C or higher and 75°C or lower for mesophilic digested sludge, and 70°C or higher and 80°C or lower for thermophilic digested sludge. If the temperature of the dewatered sludge E is lower than 50°C, the moisture content of the dewatered sludge E may remain high, requiring supplemental fuel for the incineration facility, which may increase maintenance costs. If the temperature is higher than 95°C, the sludge temperature is too high, increasing the vapor pressure of the moisture contained in the dewatered sludge E and making it difficult to manage the pumps and other transport equipment that transport the dewatered sludge E due to cavitation.

[0045] The temperature of the dewatered sludge E can be measured, for example, by a temperature sensor provided in the dehydrator provided in the dehydration means 40 at or near the sludge discharge section 56 of the dewatered sludge E. The temperature sensor may be of a contact type or a non-contact type with respect to the dewatered sludge E.

[0046] Preferably, the heat exchanger 71 heats the transported dehydrated filtrate S to 50 to 95°C, more preferably 75 to 85°C, and the temperature of the dehydrated filtrate S flowing out of the filtrate outlet 42 is 50 to 95°C, more preferably 75 to 85°C. At this temperature, the interior of the sludge dewatering chamber 46 is sufficiently heated, promoting sludge solubilization and reducing the moisture content. Furthermore, the solubilized sludge has a lower viscosity and less frictional resistance, making it easier to transport. Since the dewatering means 40 includes the heating means 70, the temperature of the dehydrated filtrate S flowing out of the filtrate outlet 42 is higher than the temperature of the concentrated sludge C flowing into the sludge inlet 41.

[0047] The temperature of the dehydrated filtrate S can be measured, for example, by a temperature sensor provided at the filtrate outlet 42 of the dehydration means 40 or in the vicinity of the filtrate outlet 42. The temperature sensor may be of a contact type or a non-contact type with respect to the dehydrated filtrate S.

[0048] The dehydrated filtrate S discharged from the filtrate outlet 42 may be supplied as return water to the sewage treatment facility as is, or may be allowed to flow into the concentration means 20. The dehydrated filtrate S contains phosphoric acid, and if the dehydrated filtrate S is used as return water, the return water containing a high concentration of phosphoric acid will place a burden on the phosphorus treatment in the sewage treatment facility. Furthermore, if the sludge is not sufficiently dehydrated, it will also place a burden on the treatment in the subsequent incineration facility.

[0049] On the other hand, when the dehydration filtrate S is introduced into the concentration means 20, the dehydration filtrate S is heated, which promotes the concentration of the sludge to be concentrated and also promotes the removal of phosphoric acid, making this preferable. For example, the entire amount of the dehydration filtrate S generated in the dehydration means 40 can be introduced into the concentration means 20. When the heated dehydration filtrate S flows into the concentration means 20, the sludge to be concentrated in the concentration tank 21 mixes with the dehydration filtrate S and is heated, promoting concentration. Furthermore, the phosphoric acid contained in the sludge to be concentrated (e.g., phosphoric acid contained in the liquid of the sludge to be concentrated and phosphoric acid contained in the sludge cells and dissolved by solubilization) reacts with the flocculant F remaining in the dehydration filtrate S to form insoluble phosphorus compounds. As a result, the phosphoric acid concentration in the concentrated effluent R can be reduced.

[0050] <Second embodiment> A second embodiment is shown in FIG. 2. In the second embodiment, in addition to a heating means 70 that indirectly heats the dehydrated filtrate S, a heating medium supply means is provided that directly supplies a heating medium H to the dehydrated filtrate S. In the first embodiment, when the total volume of the dehydrated filtrate S is small and the concentrating means 20 cannot supply the heat required to heat the sludge to be concentrated (e.g., flocculated sludge B), the heating medium supply means is provided and the heating medium H is directly supplied to the dehydrated filtrate S to replenish the insufficient heat. In this embodiment, the heating medium H is preferably hot water or steam. The heating medium supply means can be configured to supply a portion of the heating medium H transported to the heat exchanger 71 to the dehydrated filtrate chamber 47. Specifically, the heating medium supply means includes a supply flow path 48 that connects the heating medium flow path 74 and the dehydrated filtrate chamber 47, and a valve 50 that adjusts the flow rate of the heating medium H flowing through the supply flow path 48. A portion of the heating medium H supplied to the heating means 70 is branched off and supplied to the dehydrated filtrate chamber 47. The heating medium H supplied to the dehydration filtrate chamber 47 flows out of the filtrate outlet 42 together with the dehydration filtrate S and enters the concentrating means 20. The dehydration filtrate chamber 47 is heated by the heating medium H supplied from the supply flow path 48 and the dehydration filtrate S heated by the heating means 70 and supplied from the return flow path 73. Supplying heated liquid from multiple flow paths in this manner not only provides the necessary heat to the concentrating means 20 but also suppresses temperature variations within the dehydration filtrate chamber 47. Preferably, the supply flow path 48 is connected upstream of the return flow path 73 with respect to the flow direction of the dehydration filtrate S within the dehydration filtrate chamber 47. For example, in the dehydration means 40 of this embodiment, the dehydration filtrate S flows and exits toward the filtrate outlet 42 provided at the bottom. However, by connecting the supply flow path 48 above the dehydration filtrate chamber 47, the entire interior of the dehydration filtrate chamber 47 can be heated as the supplied heating medium H moves toward the filtrate outlet 42.

[0051] The heating medium H to be supplied may be, for example, 70 to 95°C, preferably 85 to 90°C. If the temperature is below 70°C, the effect of supplying the heating medium H is poor. On the other hand, if the temperature exceeds 95°C, a large amount of evaporation occurs, making it difficult to handle. Furthermore, the supply flow path 48 is connected to the heating medium flow path 74 and the dehydration filtrate chamber 47, but it can also be connected to the heating medium flow path 74 and the return flow path 73. This configuration is suitable when local heating is required. Furthermore, if the heating medium H to be supplied to the dehydration filtrate chamber 47 is a medium different from the heating medium H supplied to the heating means 70, the supply flow path 48 may be connected to a supply means for that medium (not shown) without being connected to the heating medium flow path 74.

[0052] The amount of heating medium H supplied from the heating medium supply means is preferably 100% or less, and more preferably 25 to 50%, of the amount of dehydrated filtrate S flowing into the concentration means 20, since this reduces the final amount of concentrated effluent R discharged.

[0053] In the above first and second embodiments, the influent sludge A is added with flocculant P in the flocculation means 10, and the sludge to be concentrated (e.g., flocculated sludge B) is supplied to the concentration means 20, but the influent sludge A may also be supplied directly to the concentration means 20.

[0054] In the second embodiment, the heating medium supply means supplies the heating medium H into the dehydration filtrate chamber 47, but it may also be configured to supply the heating medium H to the filtrate flow path L4. In such a configuration, when the heating medium H is supplied to the filtrate flow path L4, the heating medium H will flow into the concentrating means 20 together with the dehydration filtrate S flowing through the filtrate flow path L4.

[0055] (Sludge mass balance) In the conventional organic sludge treatment facility shown in FIG. 3, which is equipped with a concentration means 2 and a dehydration means 3, a configuration is adopted in which hot water H' is supplied from outside the system to heat the concentrated sludge. On the other hand, in this embodiment, the dehydrated filtrate S flows out of the dehydration means 40 and into the concentration means 20, and there is an advantage that the amount of hot water supplied from outside the system can be significantly reduced when operating the organic sludge treatment facility 1. This advantage can be explained in terms of the material balance of the organic sludge treatment facility as follows. The numerical values ​​are approximate numbers for the purpose of explanation. The material balance of the conventional organic sludge treatment facility is as shown in Table 1 and FIG. 4. The amount of sludge to be concentrated supplied to the concentration means 2 and the amount of hot water H' supplied to the dehydration means 3 are shown in the supply section, and the amount of dehydrated sludge I discharged from the dehydration means 3 and the amount of concentrated effluent E' discharged from the concentration means 2 are shown in the discharge section. When the amount of sludge to be concentrated supplied to the concentration means 2 per unit time is 10 m 3 / hour, the dewatered sludge I discharged from the dewatering means 3 is approximately 1 m 3 / hour, and the dewatering efficiency at this time is 90%. The hot water H' required to obtain this dewatering efficiency is approximately 9m 3 / hour, and the concentrated wastewater E' discharged from the concentration means 2 is 18 m 3 / hour.

[0056] [Table 1]

[0057] The dewatering efficiency is calculated as follows: Dewatering efficiency (%) = ((amount of concentrated sludge supplied to the concentration means) - (amount of dewatered sludge discharged from the dewatering means)) / (amount of concentrated sludge supplied to the concentration means) × 100

[0058] On the other hand, the material balance in the organic sludge treatment facility 1 of this embodiment is as shown in Table 2 and Figure 5. When the amount of sludge to be thickened supplied to the organic sludge treatment facility 1 is 10 m per unit time, 3 / hour, the dewatered sludge E discharged from the dewatering means 40 is approximately 1 m 3 / hour, and the dehydration efficiency at this time is 90%. This dehydration efficiency depends on the amount of dehydration filtrate S and the amount of heat. When hot water is not supplied from outside the system, the discharged concentrated waste liquid R is 9 m 3 The reason why the amount of concentrated effluent R is thus less than that of a conventional organic sludge treatment facility equipped with a concentration means 2 and a dewatering means 3 is that the sludge is heated not by additionally supplying hot water from outside the system, but by using indirectly heated dewatered filtrate S obtained by dewatering the sludge.

[0059] [Table 2]

[0060] Focusing on the thickening means 20 and the dewatering means 40 of the organic sludge treatment facility 1, the thickening means 20 is 3 / hour is the amount of concentrated sludge C 4m 3 / hour, the residual concentrated wastewater R is 6m 3 / hour. In addition, the amount of the dehydrated filtrate S flowing into the concentration means 20 is 3 m 3 / hour, and this amount is discharged as concentrated wastewater R as it is, so the total amount of concentrated wastewater R is 9m 3 / hour(=6m 3 / hour+3m 3 In the dewatering means 40, the amount of the supplied concentrated sludge C is 4 m 3 / hour is 1m of dewatered sludge E 3 / hour, it is dehydrated and discharged, and the remaining dehydrated filtrate S is 3 / hour.

[0061] As a modified example, when a heating medium H (e.g., hot water) is supplied supplementarily from outside the system, the material balance in the organic sludge treatment facility 1 of this embodiment is as shown in Table 3 and Figure 6. When the amount of sludge to be concentrated supplied to the organic sludge treatment facility 1 is 10 m 3 / hour, the dewatered sludge E discharged from the dewatering means 40 is approximately 1 m 3 / hour, and the dehydration efficiency at this time is 90%. This dehydration efficiency depends on the amount and heat of the dehydration filtrate S, and the amount of auxiliary hot water supplied from outside the system. To achieve this dehydration efficiency, 1 m of hot water supplied from outside the system is required. 3 / hour, the discharged concentrated wastewater R is 10m 3 / hour.

[0062] [Table 3]

[0063] Here, when comparing the total supply portion and the total discharge portion in Tables 1 to 3 for the amount of concentrated wastewater R discharged outside the system per unit time, it can be seen that the organic sludge treatment equipment 1 of this embodiment (Tables 2 and 3) is smaller than the organic sludge treatment equipment (Table 1) equipped with a conventional concentration means 2 and dewatering means 3.

[0064] In this way, in the organic sludge treatment facility 1 of this embodiment, the amount of hot water supplied to the concentration means 20 can be reduced, so the volume of the concentration tank 21 of the concentration means 20 can be made more compact than in the conventional case. Furthermore, the concentration means 20 of this embodiment can perform the concentration treatment when the amount of liquid in the concentration tank 21 is small, so that the concentration efficiency is superior to that of the conventional concentration means 2. [Industrial Applicability]

[0065] According to this embodiment, an embodiment in a sewage treatment facility has been disclosed, but the present invention is not limited to this facility and can be applied to the treatment of various organic sludges. [Explanation of symbols]

[0066] 1. Organic sludge treatment facility 20 Concentration means 40 Dehydration means 43a Outer filtration screen 43b Inner filtration screen 44 Ribbon screw 46 Sludge dewatering chamber 47 Dehydration Filtrate Chamber 70 Heating means 71 Heat exchanger 72 Transport channel 73 Return flow path C. Thickened sludge E. Dewatered sludge H heating medium S Dehydrated filtrate

Claims

1. An organic sludge treatment facility equipped with a dehydration means for dehydrating sludge to obtain dehydrated filtrate, the dehydration means comprises a sludge dehydration chamber for dehydrating the sludge to be dehydrated, a dehydration filtrate chamber into which the dehydration filtrate obtained by the dehydration flows, and a heating means for indirectly heating the dehydration filtrate; the heating means includes a heat exchanger, a transport flow path for transporting the dehydration filtrate in the dehydration filtrate chamber to the heat exchanger, and a return flow path for returning the dehydration filtrate heated by the heat exchanger to the dehydration filtrate chamber, The transported dewatered filtrate is heated by a heating medium flowing through the heat exchanger and returned to the dewatered filtrate chamber, thereby heating the sludge dewatering chamber. An organic sludge treatment facility characterized by:

2. The heat exchanger heats the transported dehydrated filtrate to 50 to 95°C. The organic sludge treatment facility according to claim 1.

3. The heating medium is any one of hot water, thermal oil, and steam, and has a temperature higher than that of the dehydrated filtrate transported to the heat exchanger.

3. The organic sludge treatment facility according to claim 1 or 2.

4. the heating means includes a heating medium supply means for supplying a part of the heating medium conveyed to the heat exchanger to the dehydration filtrate chamber, The heating medium is hot water or steam.

3. The organic sludge treatment facility according to claim 1 or 2.

5. the dewatering means has a filter screen separating the sludge dewatering chamber from the dewatered filtrate chamber, the filter screen being made of at least one of a wedge wire and a punched metal; The temperature of the dehydration filtrate in the dehydration filtrate chamber is 50 ° C to 95 ° C. The organic sludge treatment facility according to claim 1.

6. The dehydration means is A casing; an inner filtration screen disposed within the casing in a cylindrical or conical shape about a longitudinal axis; an outer filtration screen disposed in the casing in a cylindrical or conical shape coaxial with the inner filtration screen and spaced apart from the outer filtration screen; a ribbon-type screw that is housed between the inner filter screen and the outer filter screen in a spiral shape twisted around the axis and that can be rotated relative to the inner filter screen and the outer filter screen around the axis, The space between the inner filter screen and the outer filter screen is the sludge dewatering chamber, and the space inside the inner filter screen and the space outside the outer filter screen are the dewatering filtrate chamber. The organic sludge treatment facility according to claim 1.

7. A dehydration step of dehydrating the sludge to be dehydrated to obtain a dehydrated filtrate, The dehydration step is carried out by a dehydration means, the dehydration means comprises a sludge dehydration chamber for dehydrating the sludge to be dehydrated, a dehydration filtrate chamber into which the dehydration filtrate obtained by the dehydration flows, and a heating means for indirectly heating the dehydration filtrate; the heating means includes a heat exchanger, a transport flow path for transporting the dehydration filtrate in the dehydration filtrate chamber to the heat exchanger, and a return flow path for returning the dehydration filtrate heated by the heat exchanger to the dehydration filtrate chamber, The transported dewatered filtrate is heated by a heating medium flowing through the heat exchanger and returned to the dewatered filtrate chamber, thereby heating the sludge dewatering chamber. A method for treating organic sludge.

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