SCREW-TYPE SEPARATION DEVICE, CASING, WASTEWATER TREATMENT SYSTEM, AND CLEANING METHOD OF SCREW-TYPE SEPARATION DEVICE

A screw-type separation device 1 includes a casing 10 including an object discharging port and discharging an object A having been dehydrated, and a separated liquid discharging port; a screw shaft provided inside the casing and extending in an extending direction that is a direction from the one end part to the other end part; a first screw blade extending spirally on an outer peripheral surface of the screw shaft; and a second screw blade extending spirally on the outer peripheral surface of the screw shaft such that a predetermined gap is formed with respect to the first screw blade in the extending direction. A groove is formed on an inner peripheral surface of the casing.

FIELD

The present invention relates to a screw-type separation device, a casing, a wastewater treatment system, and a cleaning method of a screw-type separation device.

BACKGROUND

Conventionally, methods adopted for what is called a separation device such as a concentrator and a dehydrator include a centrifugation method, a flotation concentration method, a screen concentration dehydration method, and the like. Moreover, a screw-type separation device that conveys, squeezes, and dehydrates an object, by feeding sludge such as sewage and industrial liquid waste with high water content as an object into a cylindrical-shaped casing, and by rotating a screw provided in the casing, has been used.

For example, Patent Literature 1 discloses a device that conveys and squeezes sludge, by rotating a screw provided with two screw blades. In this device, a first region and a second region interposed between the two screw blades are formed inside a casing the side surface of which is provided with a sludge feeding port. In the device, sludge is squeezed, dehydrated, and conveyed in the first region, and the dehydrated sludge is discharged. Moreover, in the device, separated liquid generated by dehydration is conveyed in the second region, and the separated liquid is discharged.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

However, in such a device, sludge may not slide on the surface of the screw blade, and may rotate with the screw blade and stay on the screw blade. In such a case, it is difficult to convey the sludge to a sludge discharging port, and the discharge efficiency of sludge may be decreased. Thus, it has been desired to suppress a decrease in the discharge efficiency of an object to be dehydrated such as sludge.

The present invention has been made in view of the above, and an object of the present invention is to provide a screw-type separation device, a casing, a wastewater treatment system, and a cleaning method of a screw-type separation device capable of suppressing a decrease in the discharge efficiency of an object.

Solution to Problem

To solve the problem and achieve the object above, a screw type separation device in the present disclosure includes; a casing including an object discharging port provided on one end part side and discharging an object having been dehydrated, and a separated liquid discharging port provided on another end part side and discharging separated liquid having been separated from the object by dehydration; a screw shaft provided inside the casing and extending in an extending direction that is a direction from the one end part to the another end part; a first screw blade extending spirally on an outer peripheral surface of the screw shaft; and a second screw blade extending spirally on the outer peripheral surface of the screw shaft such that a predetermined gap is formed with respect to the first screw blade in the extending direction, wherein a groove is formed on an inner peripheral surface of the casing.

It is preferable that the groove extends in the extending direction.

It is preferable that in the groove, width of an inlet part that is opened on the inner peripheral surface of the casing is smaller than width of a space on a radially outer side of the inlet part

It is preferable that width of the groove is increased from the inlet part toward a radially outer side.

It is preferable that viewed from the extending direction, the groove is inclined to a rotation direction side of the screw shaft toward a radially inner side.

It is preferable that in the groove, an opening area of the inlet part that is opened on the inner peripheral surface of the casing in an end part at the separated liquid discharging port side is greater than an opening area of the inlet part at the object discharging port side of the end part.

It is preferable that the casing includes a first casing, and a second casing that is inserted into inside of the first casing and an inner peripheral surface of which is formed with the groove.

It is preferable that in the casing, at least a portion formed with the groove is made of resin.

To solve the problem and achieve the object above, a wastewater treatment system in the present disclosure includes; a solid-liquid separation tank that separates sludge from organic wastewater, and the screw-type separation device, wherein the screw-type separation device is capable of concentrating sludge discharged from the solid-liquid separation tank, and returning the separated liquid generated when the sludge is concentrated to the solid-liquid separation tank.

It is preferable that the screw-type separation device is provided in the solid-liquid separation tank.

To solve the problem and achieve the object above, a casing for a screw-type separation device in the present disclosure stores therein a screw, the screw including a screw shaft extending in an extending direction that is a direction from one end part to another end part, a first screw blade extending spirally on an outer peripheral surface of the screw shaft, and a second screw blade extending spirally on the outer peripheral surface of the screw shaft such that a predetermined gap is formed with respect to the first screw shaft in the extending direction, wherein, a groove is formed on an inner peripheral surface of the casing.

To solve the problem and achieve the object above, a wastewater treatment system in the present disclosure includes; a reaction tank that performs biological treatment on organic wastewater; a solid-liquid separation tank that separates sludge from the organic wastewater; and the screw-type separation device, wherein the screw-type separation device is capable of extracting sludge from the reaction tank, concentrating the extracted sludge, returning the concentrated sludge to the reaction tank, and supplying the separated liquid generated when the sludge is concentrated to the solid-liquid separation tank.

To solve the problem and achieve the object above, a cleaning method of the screw-type separation device in the present disclosure includes; a step of closing the object discharging port; a step of accumulating a cleaning solution in the casing and the groove, by supplying the cleaning solution into the casing while the object discharging port is closed; and a step of discharging the cleaning solution accumulated in the casing and the groove from the object discharging port, by opening the object discharging port after the step of accumulating.

Advantageous Effects of Invention

With the present invention, it is possible to suppress a decrease in the discharge efficiency of sludge.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiment described below.

Configuration of Screw-type Separation DeviceFIG. 1is a partial sectional view of a screw-type separation device according to the present embodiment. As illustrated inFIG. 1, a screw-type separation device1according to the present embodiment includes a casing10provided with a first casing30and a second casing32, a screw shaft12, a first screw blade14, a second screw blade16, a first partition wall part18, a second partition wall part20, a cover part22, a feeding unit24, a discharge pump26, an inclination adjusting unit28, and a control unit29. A unit provided with the screw shaft12, the first screw blade14, and the second screw blade16may be, referred to as a screw11. The screw-type separation device1dehydrates a pre-object A0fed into the casing10from an object feeding port31A, which will be described below, and discharges an object A having been dehydrated from an object discharging port31B, which will be described below. Then, the screw-type separation device1discharges separated liquid C, which is separated from the pre-object A0by dehydration, from a separated liquid discharging port31C, which will be described below. The pre-object A0is sludge such as sewage and industrial liquid waste with high water content. The pre-object A0is an object before being dehydrated by the screw-type separation device1, and in the present embodiment, is sludge such as sewage and industrial liquid waste with high water content. Additionally, the pre-object A0is sludge added with a flocculating agent, and sludge containing flocculated solid components and moisture. In the present embodiment, for example, by using a device provided at a previous stage of the screw-type separation device1, the pre-object A0which is a solid material containing a liquid component, is generated by adding a flocculating agent and flocculating the solid component. However, the properties of the pre-object A0are optional, and for example, the pre-object A0may also be sludge not added with a flocculating agent and not flocculated.

Hereinafter, a direction parallel to a ground surface G, that is, a horizontal direction, is referred to as a direction X. One direction in the direction X is referred to as a direction X1, and the other direction in the direction X, that is, a direction opposite to the direction X1is referred to as a direction X2. Moreover, a direction orthogonal to the direction X, and a direction orthogonal to the ground surface G, that is, a vertical direction, is referred to as a direction Z. Then, one direction in the direction Z is referred to as a direction Z1, and the other direction in the direction Z, that is, a direction opposite to the direction Z1, is referred to as a direction Z2. The direction Z1is an upward direction in the vertical direction, that is, a direction away from the ground surface G. The direction Z2is a downward direction in the vertical direction, that is, a direction toward the ground surface G side.

The first casing30in the casing10is a tubular member that extends from one end part30B to another end part30C in an extending direction E, and in which space is formed. In the example ofFIG. 1, the diameter of the first casing30at the end part30B side is reduced. However, the diameter of the first casing30may not always be reduced. For example, the first casing30may also be formed in a cylindrical shape such that the diameter from the end part30B to the end part30C is constant. For example, in the first casing30, the diameter of a part where the diameter is not reduced is about 20 cm or more to 50 cm or less. However, the size of diameter is optional. The extending direction E is an axis direction of the first casing30. The extending direction E is a direction from the end part30B side toward the end part30C side (direction X2side), and is inclined to the direction Z1side with respect to the direction X2, from the end part30B side toward the end part30C side. That is, the first casing30is inclined in a direction in which a center axis AX in the extending direction E moves (is placed) toward the direction Z1side, toward the end part30C (direction X2side). Thus, the end part30B of the first casing30is placed at the direction Z2side of the end part30C. A gradient angle θ of the first casing30is preferably 20 degrees or more and 90 degrees or less, and more preferably 60 degrees or more and 90 degrees or less. The gradient angle θ is a gradient angle of the center axis AX with respect to the horizontal direction X (ground surface G).

In the present embodiment, the first casing30is a member made of metal (for example, made of stainless steel). However, the material of the first casing30is not limited to metal, and is optional. For example, the first casing30may also be made of resin.

In the first casing30, the object discharging port31B is opened on the end part30B, and the separated liquid discharging port31C is opened on the end part30C. The separated liquid discharging port31C is an opening different from a hole through which the screw shaft12passes, and is provided on the direction Z1side of the screw shaft12. However, the separated liquid discharging port31C may not be provided on the direction Z1side of the screw shaft12. For example, the separated liquid discharging port31C may be provided on the direction Z2side of the screw shaft12in the end part30C, or may be provided on the same position as that of the screw shaft12, and such that the screw shaft12can penetrate therethrough. Moreover, the separated liquid discharging port31C may also be provided on the outer peripheral surface (side surface) of the casing10in a separated liquid conveyance section K3, which will be described below. The object discharging port31B is placed on the direction Z2side of the separated liquid discharging port31C. In the present embodiment, the screw shaft12can penetrate through the inside of the object discharging port31B. However, the screw shaft12may not penetrate through the object discharging port31B. Moreover, the object discharging port31B may be provided on the outer peripheral surface (side surface) of the casing10in an object conveyance section K2, which will be described below. That is, in the first casing30, at least the separated liquid discharging port31C is placed on the end part30C side of the object discharging port31B, and the object discharging port31B is placed on the end part30B side of the separated liquid discharging port31C.

In the first casing30, the object feeding port31A is opened on a middle part30A. The middle part30A is a part between the end part30B and the end part30C in the extending direction E of the first casing30. In other words, the middle part30A is a part between the object discharging port31B and the separated liquid discharging port31C in the extending direction E. The middle part30A is placed on the center of the first casing30in the extending direction E, but may be placed on any position between the end part30B and the end part30C in the extending direction E. For example, the length of the first casing30from the end part30B to the middle part30A in the extending direction E is preferably 30% or more and 90% or less, with respect to the total length of the first casing30in the extending direction E. The object feeding port31A is opened on the outer peripheral surface (side surface) of the first casing30of the middle part30A.

The second casing32is a tubular-shaped member to be inserted into the first casing30. The second casing32is inserted into the first casing30so as to be coaxial with the first casing30, and is fixed to the inside of the first casing30such that the outer peripheral surface of the second casing32is brought into contact with an inner peripheral surface30aof the first casing30. The second casing32extends from one end part32B to another end part32C in the extending direction E. In the second casing32, the end part32B is positioned substantially the same as the end part30B of the first casing30in the extending direction E, and the end part32C is positioned substantially the same as the end part30C of the first casing30in the extending direction E. Because the second casing32is coaxial with the first casing30, the center axis AX also becomes the center axis of the second casing32.

In the present embodiment, the second casing32is a member made of resin, and for example, is manufactured by a 3D printer (three-dimensional lamination device). However, the material of the second casing32is optional, and for example, the second casing32may be made of metal (such as stainless steel). A manufacturing method of the second casing32is also optional.

In the second casing32, an opening part33A is opened on the outer peripheral surface (side surface) at a position overlapping with the object feeding port31A of the first casing30. The opening part33A communicates with the object feeding port31A. Moreover, the end part32B of the second casing32which is opened, communicates with the object discharging port31B of the first casing30. The end part32C of the second casing32which is opened, communicates with the separated liquid discharging port31C of the first casing30. In the second casing32, a groove34is formed on an inner peripheral surface32a. The groove34will be described below.

In this manner, in the casing10of the present embodiment, the first casing30and the second casing32are formed by different members. However, the casing10may be formed by an integral member. In either case of an integral member or a plurality of members, the casing10is configured such that the casing10extends around the center axis AX in the extending direction E, the object discharging port31B is provided on the end part30B side in the direction X1side, the separated liquid discharging port31C is provided on the end part30C side of the direction X2side, the object feeding port31A is provided on the middle part30A, and the groove34is formed on the inner peripheral surface32a. When the casing10is formed of an integral member, the entire casing10is preferably made of resin.

The screw shaft12is formed in a cylindrical shape, is provided inside the casing10, and extends in the extending direction E. In the casing10, the screw shaft12is provided so as to penetrate through the casing10in the extending direction E. That is, one end part12B of the screw shaft12is placed on the end part30B side of the casing10, and protrudes to the outside of the casing10from the end part30B of the casing10. Similarly, another end part12C of the screw shaft12is placed on the end part30C side of the casing10, and protrudes to the outside of the casing10from the end part30C of the casing10. In the screw shaft12, at least one of the end part12B and the end part12C is coupled to a motor, which is axially supported by a bearing (both are not illustrated). When the motor is driven by the control unit29, the screw shaft12is rotated in a rotation direction R with the extending direction E as an axial center. In the present embodiment, when viewed from the end part12C side, the rotation direction R is a counterclockwise direction. However, it is not limited thereto. In the present embodiment, the screw shaft12is a member made of metal (for example, made of stainless steel). However, the material of the screw shaft12is not limited to metal, and is optional. For example, the screw shaft12may also be made of resin.

The first screw blade14is provided as to extend spirally on the outer peripheral surface of the screw shaft12in the casing10, from one end part14B to another end part14C. The end part14B is a position where winding of the first screw blade14is started, and is an end part on the object discharging port31B (end part30B) side of the casing10. The end part14B is placed on the object discharging port31B (end part30C) side of the object feeding port31A (middle part30A). Moreover, the end part14C is a position where winding of the first screw blade14is ended, and is an end part on the separated liquid discharging port31C (end part30C) side of the casing10. The end part14C is placed on the separated liquid discharging port31C (end part30C) side of the object feeding port31A (middle part30A). The first screw blade14extends from the end part14B to the end part14C via a portion overlapping with the object feeding port31A, when viewed from the radial direction of the center axis AX.

The first screw blade14is wound in a direction opposite to the rotation direction R of the screw shaft12from the end part14C toward the end part14B. That is, when the rotation direction R of the screw shaft12is a counterclockwise direction viewed from the end part12C side, the first screw blade14is provided in what is called a Z-winding (right hand) spiral. Alternatively, when the rotation direction R of the screw shaft12is a clockwise direction viewed from the end part12C side, the first screw blade14is provided in what is called an S-winding (left hand) spiral. The first screw blade14is rotated with the rotation of the screw shaft12.

The first screw blade14is formed such that a gap H is generated between an outer peripheral part14cand the inner peripheral surface32aof the casing10. That is, the outer peripheral part14cof the first screw blade14does not come into contact with the inner peripheral surface32aof the casing10, and is separated from the inner peripheral surface32awith the gap H interposed therebetween. The gap H is a minute clearance, and has a size capable of suppressing (blocking) at least a part of the object A from passing through. Moreover, the gap H is large enough so that a liquid component such as the separated liquid C can pass through. For example, the gap H is a clearance of about 1 mm or more and 2 mm or less.

In the casing10, the second screw blade16extends spirally on the outer peripheral surface of the screw shaft12in the extending direction E. The second screw blade16is provided on a position shifted from the first screw blade14such that a predetermined gap is formed with respect to the first screw blade14in the extending direction E, and is wound in the same winding direction as that of the first screw blade14. The second screw blade16is also rotated with the rotation of the screw shaft12. The second screw blade16extends spirally from one end part16B to another end part16C. The end part16B is a position where winding of the second screw blade16is started, and placed between the end part14B of the first screw blade14and the object feeding port31A in the extending direction E. The end part16C is a position where winding of the second screw blade16is ended, and is placed between the end part14C of the first screw blade14and the object feeding port31A in the extending direction E. Thus, the second screw blade16extends from the end part16B to the end part16C via a portion overlapping with the object feeding port31A, viewed from the radial direction of the center axis AX. The end part16B and the end part16C of the second screw blade16may not placed on the positions described above. For example, the end part16B of the second screw blade16may be placed on the same position as the end part14B of the first screw blade14in the extending direction E, and the end part16C of the second screw blade16may be placed on the same position as the end part14C of the first screw blade14in the extending direction E.

The second screw blade16is formed such that the gap H is generated between an outer peripheral part16cand the inner peripheral surface32aof the casing10. That is, the outer peripheral part16cof the second screw blade16does not come into contact with the inner peripheral surface32aof the casing10, and is separated from the inner peripheral surface32awith the gap H interposed therebetween. In the present embodiment, the first screw blade14and the second screw blade16are made of resin, and for example, manufactured by a 3D printer. However, the material of the first screw blade14and the second screw blade16is not limited to resin, and is optional. For example, the first screw blade14and the second screw blade16may also be made of metal (such as stainless steel). A manufacturing method of the first screw blade14and the second screw blade16is also optional.

Because the first screw blade14and the second screw blade16are provided on the positions as described above, the first screw blade14and the second screw blade16are both provided in a section from the end part16B to the end part16C of the second screw blade16(hereinafter, this section will be referred to as a conveyance acceleration section K1). Moreover, the first screw blade14is provided but the second screw blade16is not provided in a section from the end part16B of the second screw blade16to the end part14B of the first screw blade14(hereinafter, this section will be referred to as the object conveyance section K2). Furthermore, the first screw blade14is provided but the second screw blade16is not provided in a section from the end part16C of the second screw blade16to the end part14C of the first screw blade14(hereinafter, this section will be referred to as the separated liquid conveyance section K3).

The conveyance acceleration section K1is a double screw section in which the first screw blade14and the second screw blade16are provided. The conveyance acceleration section K1is a section between the object conveyance section K2and the separated liquid conveyance section K3in the extending direction E. Viewed from the radial direction of the center axis AX, at least a part of the section of the conveyance acceleration section K1is set so as to overlap with the object feeding port31A. In other words, at least a part of the conveyance acceleration section K1is placed on the same position as the object feeding port31A in the extending direction E. The length of the conveyance acceleration section K1in the extending direction E is preferably 20% or more and 60% or less of the total length of the casing10in the extending direction.

In the conveyance acceleration section K1, a first space S1in which the object A is conveyed, and a second space S2in which the separated liquid C is conveyed are formed. The first space S1is formed between one surface16aof the second screw blade16and another surface14bof the first screw blade14that faces the one surface16a. The second space S2is formed between another surface16bof the second screw blade16and one surface14aof the first screw blade14that faces the other surface16b. InFIG. 1, the surface at the end part14B side of the first screw blade14is referred to as the one surface14a, and the surface at the end part14C side is referred to as the other surface14b. However, it is not limited thereto, and the surface at the end part14C side may be referred to as the one surface14a, and the surface at the end part14B side may be referred to as the other surface14b. Similarly, inFIG. 1, the surface at the end part16B side of the second screw blade16is referred to as the one surface16a, and the surface at the end part16C side is referred to as the other surface16b. However, it is not limited thereto, and the surface at the end part16C side may be referred to as the one surface16a, and the surface at the end part16B side may be referred to as the other surface16b.

The object conveyance section K2is a section at the end part30B side of the casing10, that is, a section at the object discharging port31B side, than the conveyance acceleration section K1. Space S3in the object conveyance section K2communicates with the object discharging port31B. Moreover, the space S3communicates with the first space S1in the conveyance acceleration section K1, and the object A flows into the space S3from the first space S1. Because the space S3is shielded by the first partition wall part18, which will be described below, the space S3is isolated from the second space S2in the conveyance acceleration section K1in a region other than the gap H. In the present embodiment, the object conveyance section K2is a single screw section in which the first screw blade14is provided but the second screw blade16is not provided. However, when the end part14B of the first screw blade14and the end part16B of the second screw blade16are provided on the same position, the object conveyance section K2will be a section in which neither the first screw blade14nor the second screw blade16is provided.

The separated liquid conveyance section K3is a section at the end part30C side of the casing10, that is, a section at the separated liquid discharging port31C side, than the conveyance acceleration section K1. Space S4in the separated liquid conveyance section K3communicates with the separated liquid discharging port31C. Moreover, the space S4communicates with the second space S2in the conveyance acceleration section K1, and the separated liquid C flows into the space S4from the second space S2. Because the space S4is shielded by the second partition wall part20, which will be described below, the space S4is isolated from the first space S1in the conveyance acceleration section K1, in a region other than the gap H. In the present embodiment, the separated liquid conveyance section K3is a single screw section in which the first screw blade14is provided but the second screw blade16is not provided. However, when the end part14B of the first screw blade14and the end part16B of the second screw blade16are provided on the same position, the separated liquid conveyance section K3will be a section in which neither the first screw blade14nor the second screw blade16is provided.

The groove34is formed on the inner peripheral surface32aof the second casing32in the conveyance acceleration section K1. On the inner peripheral surface32aof the second casing32, the groove34extends from an end part34B to an end part34C in the extending direction E. The end part34B is an end part at the object discharging port31B side of the groove34, and is placed between the object discharging port31B and the object feeding port31A in the extending direction E. Additionally, the end part34B is preferably provided on the same position as the end part16B of the second screw blade16in the extending direction E, that is, at a boundary between the conveyance acceleration section K1and the object conveyance section K2. Moreover, the end part34C is an end part at the separated liquid discharging port31C side of the groove34, and is placed between the separated liquid discharging port31C and the object feeding port31A in the extending direction E. Additionally, the end part34C is preferably provided at the separated liquid conveyance section K3side (that is, in the separated liquid conveyance section K3) than the same position of the end part16C of the second screw blade16in the extending direction E (boundary between the conveyance acceleration section K1and the separated liquid conveyance section K3).

In this manner, the groove34extends in the conveyance acceleration section K1, and extends into the separated liquid conveyance section K3at the end part34C side. However, the groove34not only extends in the conveyance acceleration section K1and the separated liquid conveyance section K3, and may be provided up to the object conveyance section K2.

FIG. 2is a sectional view of the screw-type separation device according to the present embodiment.FIG. 2is a sectional view cut along the line F-F inFIG. 1, and is a sectional view when the screw-type separation device1is viewed in the extending direction E. In below, unless otherwise specified, a circumferential direction and a radial direction are the circumferential direction and the radial direction around the center axis AX. As illustrated inFIG. 2, on the inner peripheral surface32aof the second casing32, a plurality of the grooves34are provided in the circumferential direction. In the example inFIG. 2, twelve grooves34are provided. However, the number of the grooves34is not limited to twelve, and is optional. An inlet part34a1provided as an end part of each of the groove34on the radially inner side (a side approaching the center axis AX) is opened on the inner peripheral surface32a. That is, the inlet part34a1is an opening portion of the groove34. The width of the groove34is increased from the inlet part34a1to a middle part34a2on the radially outer side relative to the inlet part34a1, toward the radially outer side (a side away from the center axis AX). In this example, the width is the length in the circumferential direction. The width of the groove34is reduced from the middle part34a2to a bottom part34a3of the groove34on the radially outer side, toward the radially outer side. The width of the groove34is increased in a straight line manner from the inlet part34a1to the middle part34a2, toward the radially outer side. The width of the groove34is reduced in a curved line manner from the middle part34a2to the bottom part34a3, toward the radially outer side. In other words, viewed in the extending direction E, the groove34is formed in a trapezoid shape in which the width is increased toward the radially outer side, from the inlet part34a1to the middle part34a2. The groove34is also formed in a semicircular shape, from the middle part34a2to the bottom part34a3. However, the shape of the groove34is not limited to a shape in which the width is increased in a straight line manner from the inlet part34a1toward the middle part34a2, and the width is increased in a curved line manner from the middle part34a2toward the bottom part34a3. For example, the width of the groove34may be increased in a curved line manner in at least a part of the section from the inlet part34a1to the middle part34a2, or the width of the groove34may be reduced in a straight line manner in at least a part of the section from the middle part34a2to the bottom part34a3.

In this manner, because the width (length in the circumferential direction) of the groove34is increased from the inlet part34a1toward the radially outer side, the width at the inlet part34a1is smaller than the width of the space on the radially outer side of the inlet part34a1. Thus, in the groove34, viewed from the radial direction, the area of the inlet part34a1becomes smaller than the area of the space on the radially outer side of the inlet part34a1, and the area is increased from the inlet part34a1toward the radially outer side.

Viewed from the extending direction E, the groove34is inclined to the rotation direction R side of the screw shaft12, toward the radially inner side. In other words, the groove34is inclined to the rotation direction R side with respect to the radial direction, from the middle part34a2toward the inlet part34a1. In more other words, viewed from the extending direction E, a straight line (straight line in the radial direction) that joins the center axis AX and the middle point of the middle part34a2is called as a straight line L1, and a straight line that joins the middle point of the middle part34a2and the middle point of the inlet part34a1is called as a straight line L2. The straight line L2is inclined to the rotation direction R side with respect to the straight line L1, toward the radially inner side (middle point side of the inlet part34a1).

In the groove34, the length in the circumferential direction of the inlet part34a1is preferably the same as the length of the gap H in the radial direction, and for example, is preferably about 1 mm or more and 2 mm or less. Moreover, the length of the groove34in the circumferential direction of the middle part34a2(that is, the maximum width of the groove34) is preferably longer than the length of the gap H in the radial direction.

FIG. 3is a schematic diagram illustrating another example of a groove according to the present embodiment. The shape of the groove34is not limited to a shape in which the width is increased from the inlet part34a1toward the radially outer side, as described inFIG. 2. For example, as illustrated inFIG. 3, the width of the groove34may also be constant in the radial direction, from the inlet part34a1to a middle part34a4, and may be increased toward the radially outer side, from the middle part34a4to the middle part34a2on the radially outer side. The width of the groove34may also be increased in the middle part34a4, and may be constant from the middle part34a4to the bottom part34a3. In this case also, the width of the inlet part34a1is preferably smaller than the width (maximum width) of the middle part34a2on the radially outer side of the inlet part34a1.

FIG. 4is a schematic diagram illustrating the groove according to the present embodiment.FIG. 4illustrates the shape of the groove34in the vicinity of the object feeding port31A, when the inner peripheral surface32aof the casing10is viewed from the center axis AX toward the radially outer side (portion illustrated by F1inFIG. 1). As illustrated inFIG. 4, the groove34does not communicate with the object feeding port31A (opening part33A) on the inner peripheral surface32a. More particularly, among the grooves34, a groove34F at a position close to the object feeding port31A in the circumferential direction does not continue from the end part34B to the end part34C (seeFIG. 1) in the extending direction E, and is interrupted in the vicinity of the object feeding port31A. The groove34F is on the end part34B side of the object feeding port31A, and the groove34F extends from the end part34B to an end part34F1in the extending direction E. The end part34F1does not communicate with the object feeding port31A, and is placed on the end part34B side of the object feeding port31A. The groove34F is at the end part34C side of the object feeding port31A, the groove34F extends from an end part34F2to the end part34C in the extending direction E. The end part34F2does not communicate with the object feeding port31A, and is placed on the end part34C side of the object feeding port31A (opening part33A).

The groove34F at the end part34B side of the object feeding port31A and the groove34F at the end part34C side of the object feeding port31A are connected by a connection groove36formed on the inner peripheral surface32a. The connection groove36is formed on the periphery of a portion on the inner peripheral surface32a, where the object feeding port31A (opening part33A) is provided. On the inner peripheral surface32a, the connection groove36does not communicate with the object feeding port31A, and connects the grooves34F to one another by communicating with the grooves34F. In the present embodiment, the connection groove36is connected to all the grooves34F, and connects all the grooves34F to one another. In the present embodiment, viewed from the radial direction, the connection groove36is a ring-shaped groove formed so as to surround the object feeding port31A. However, the shape of the connection groove36is not limited to a ring shape, and is optional. By connecting the groove34to the connection groove36without connecting to the object feeding port31A, it is possible to cause the separated liquid C that flows through the groove34to flow to the separated liquid discharging port31C side via the connection groove36, while suppressing the separated liquid C that flows in the groove34from returning to the casing10from the object feeding port31A, as will be described below.

FIG. 5AandFIG. 5Bare each a schematic diagram illustrating the groove according to the present embodiment.FIG. 5Aillustrates the shape of the groove34in the vicinity of the end part34C, when the inner peripheral surface32aof the casing10is viewed from the center axis AX toward the radially outer side (portion illustrated by F2inFIG. 1).FIG. 5Bis a sectional view of the groove34in the vicinity of the end part34C, and is a sectional view cut along the line F3-F3inFIG. 2. As illustrated inFIG. 5A, in the groove34, the width of the inlet part34a1of the end part34C (length in the circumferential direction) is greater than the width of the inlet part34a1at the end part34B side of the end part34C. Thus, in the groove34, the opening area of the inlet part34a1of the end part34C is greater than the opening area of the inlet part34a1at the end part34B side (object discharging port31B side) of the end part34C. More specifically, in the groove34, the width of the inlet part34a1is increased from a position34C1toward the end part34C. Moreover, as illustrated inFIG. 5B, the depth (length in the radial direction) of the groove34is reduced from the position34C1toward the end part34C. The position34C1is a position on the end part34B side of the end part34C in the extending direction E, and is a position in the vicinity of the end part34C.

Returning toFIG. 1, the first partition wall part18is a wall-shaped member provided from the first screw blade14to the second screw blade16adjacent to the first screw blade14in the extending direction E. The first partition wall part18is provided in the second space S2in the conveyance acceleration section K1, and shields the second space S2from the space S3in the object conveyance section K2. Additionally, the first partition wall part18is provided between the object discharging port31B and the object feeding port31A, in this example, is provided on the end part16B of the second screw blade16. That is, the first partition wall part18is provided so as to separate the second space S2and the space S3, which means that the first partition wall part18is provided at a boundary between the second space S2and the space S3.

The second partition wall part20is a wall-shaped member provided from the first screw blade14to the second screw blade16adjacent to the first screw blade14in the extending direction E. The second partition wall part20is provided in the first space S1in the conveyance acceleration section K1, and shields the first space S1from the space S4in the separated liquid conveyance section K3. Additionally, the second partition wall part20is provided between the separated liquid discharging port31C and the object feeding port31A, in this example, is provided on the end part16C of the second screw blade16. That is, the second partition wall part20is provided so as to separate the first space S1and the space S4, which means that the second partition wall part20is provided at a boundary between the first space S1and the space S4. However, the second partition wall part20is not a necessary component. The second partition wall part20suppresses the separated liquid C in the space S4from flowing into the first space S1. However, even if the second partition wall part20is not provided, for example, the separated liquid C in the space S4is suppressed from flowing into the first space S1, by being blocked by the object A accumulated in the first space S1. Moreover, even if the separated liquid C is flowed into the first space S1, the separated liquid C may be separated from the object A in the first space S1again, and returned to the space S4.

The cover part22is provided in a region overlapping with the object feeding port31A, between the first screw blade14and the second screw blade16that form the second space S2in the conveyance acceleration section K1. The cover part22can suppress the pre-object A0from the object feeding port31A from being fed into the second space S2, by covering the outer periphery of the second space S2in a section overlapping with the object feeding port31A. However, the cover part22is not a necessary component. For example, if the object feeding port31A is provided on a position not overlapping with the second space S2, it is possible to suppress the pre-object A0from being fed into the second space S2, and thus the cover part22will not be required.

The feeding unit24is a device connected to the object feeding port31A and that controls the feeding amount of the pre-object A0into the casing10. For example, the feeding unit24is an opening/closing valve, and feeds the pre-object A0into the casing10by opening, and stops feeding the pre-object A0into the casing10by closing. Moreover, the feeding unit24can adjust the feeding amount of the pre-object A0by adjusting the opening degree. The feeding unit24controls the feeding amount of the pre-object A0into the casing10, by being controlled by the control unit29. However, the feeding unit24is not limited to the opening/closing valve, as long as the feeding unit24can control the feeding amount of the pre-object A0into the casing10. For example, the feeding unit24may also be a pump for conveying sludge.

The discharge pump26is connected to the object discharging port31B of the casing10via a discharge pipe26A. The discharge pipe26A is a pipe connected to the object discharging port31B. The object A from the object discharging port31B is introduced into the discharge pipe26A. The discharge pump26is a pump provided on the discharge pipe26A. When the discharge pump26is stopped, the object A transferred to the end part30B of the casing10is stopped. Moreover, when the discharge pump26is being driven, the discharge pump26sucks the discharge pipe26A. Hence, the object A in the casing10can be forcibly discharged from the object discharging port31B. The discharge pump26can adjust the discharge amount of the object A in the casing10, by being controlled by the control unit29. However, the discharge pump26is not a necessary component, and for example, the object A may be discharged by gravity, without forcibly discharging the object A by the discharge pump26.

The inclination adjusting unit28is fixed to the casing10. The inclination adjusting unit28changes the inclination angle θ of the casing10, by being controlled by the control unit29. However, the inclination adjusting unit28is not a necessary component, and the inclination angle θ may be constant.

The control unit29is a control device that controls the operation of the screw-type separation device1. The control unit29controls at least one of the rotation of the screw shaft12by the motor, the feeding amount of the pre-object A0by the feeding unit24, the operation of the discharge pump26, which is the discharge amount of the object A in the casing10, and the inclination angle θ by the inclination adjusting unit28. For example, the control unit29is an arithmetic device, that is, a computer including a central processing unit (CPU), and controls the operation of the screw-type separation device1by the calculation of the CPU.

Operation of Screw-Type Separation Device

Next, an operation of the screw-type separation device1configured as described above, and behavior of an object will be described.FIG. 6is a schematic diagram for explaining an operation of the screw-type separation device according to the present embodiment.

As illustrated inFIG. 6, the control unit29controls the feeding unit24and rotates the screw shaft12, by feeding the pre-object A0into the casing10from the object feeding port31A. Because the position of the object feeding port31A is overlapped with the conveyance acceleration section K1, the pre-object A0from the object feeding port31A is fed into the first space S1in the conveyance acceleration section K1. The pre-object A0fed into the first space S1is transferred to the object discharging port31B side, by gravity and by sliding on the surface of the first screw blade14and the second screw blade16in the conveyance acceleration section K1, while the liquid component is separated. Because the solid component of the pre-object A0in the first space S1is difficult to pass through a minute gap H, the solid component is suppressed from entering the second space S2. Moreover, the solid component of the pre-object A0in the first space S1is blocked from entering the space S4, by the second partition wall part20that isolates between the first space S1and the space S4.

The screw-type separation device1conveys the pre-object A0to the object discharging port31B side, by causing the pre-object A0to slide on the surface of the first screw blade14and the second screw blade16(hereinafter, appropriately referred to as the surface of the screw blade). However, if the pre-object A0does not slide on the surface of the screw blade, the pre-object A0rotates with the screw blade, and stays on the same position on the surface of the screw blade. Hence, it is difficult to transfer the pre-object A0to the object discharging port31B side. Alternatively, in the present embodiment, by forming the groove34on the inner peripheral surface32aof the casing10, the surface roughness of the inner peripheral surface32ais increased, and the friction coefficient of the inner peripheral surface32ais increased. Consequently, the pre-object A0is made to slide easily on the surface of the screw blade, by reducing the ratio of the friction force applied to the pre-object A0from the surface of the screw blade with respect to the friction force applied to the pre-object A0from the inner peripheral surface32a. That is, the pre-object A0is made to slide easily on the surface of the screw blade, by using the inner peripheral surface32aformed with the groove34as resistance. In this manner, by making the pre-object A0to slide easily on the surface of the screw blade by the groove34, the screw-type separation device1can appropriately convey the pre-object A0to the object discharging port31B side. In the screw-type separation device1, the friction force applied to the pre-object A0from the inner peripheral surface32a(friction coefficient of the inner peripheral surface32a) is preferably made greater than the friction force applied to the pre-object A0from the surface of the screw blade (friction coefficient of the surface of the screw blade).

The pre-object A0conveyed in the first space S1in the conveyance acceleration section K1flows into the space S3in the object conveyance section K2that communicates with the first space S1. The pre-object A0that has flowed into the space S3passes through the object discharging port31B as the object A from which the liquid component is separated, and is discharged to the outside of the casing10. The object A that has flowed into the space S3passes through the object discharging port31B by the discharge pump26driven by the control unit29, and is forcibly discharged to the outside of the casing10.

On the other hand, the liquid component separated from the pre-object A0flows into the second space S2from the first space S1through the gap H, as the separated liquid C. The liquid level of the separated liquid C in the second space S2is increased with an increase in the inflow amount of the separated liquid C into the second space S2. With an increase in the liquid level, as illustrated in a flow passage C1illustrated inFIG. 6, the separated liquid C moves spirally in the second space S2to the separated liquid discharging port31C side, and is introduced into the space S4in the separated liquid conveyance section K3. Moreover, as illustrated in a flow passage C2inFIG. 6, the separated liquid C passes through a plurality of portions of the gap H, and is introduced into the space S4in the separated liquid conveyance section K3. Furthermore, as illustrated in a flow passage C3inFIG. 6, the separated liquid C flows into the groove34from the gap H. The separated liquid C that has flowed into the groove34flows in the groove34toward the separated liquid discharging port31C side, with an increase in the liquid level in the groove34. The separated liquid C is then introduced into the second space S2and the space S4, from the inlet part34a1of the end part34C. The separated liquid C that has introduced into the space S4through the flow passages C1, C2, and C3in this manner is discharged to the outside from the separated liquid discharging port31C.

In this manner, in the present embodiment, in addition to the flow passage C1that passes through the second space S2and the flow passage C2that passes through the gap H, the flow passage C3that passes through the groove34is also set as a flow passage of the separated liquid C to the space S4. By increasing the number of flow passages of the separated liquid C in this manner, it is possible to reduce pressure loss in a flow passage of the separated liquid C in the casing10, and appropriately discharge the separated liquid C. In the groove34, for example, the width of the inlet part34a1is made small to the same extent as the gap H. Hence, it is possible to suppress the solid component of the pre-object A0from entering, while allowing the separated liquid C to enter. Moreover, because the groove34is inclined to the rotation direction R side of the screw shaft12, it is further possible to preferably suppress the solid component from entering from the inlet part34a1. Furthermore, in the present embodiment, at least one of the first screw blade14, the second screw blade16, and the second casing32is preferably made of resin. By making at least one of the above by resin, it is possible to increase the shape accuracy, design the gap H to be small, and suppress the solid component from passing through the gap H.

As described above, the screw-type separation device1according to the present embodiment includes the casing10, the screw shaft12, the first screw blade14, and the second screw blade16. In the casing10, the object discharging port31B that discharges the dehydrated object A is provided on one end part30B side, and the separated liquid discharging port31C that discharges the separated liquid C separated from the pre-object A0by dehydration, is provided on the other end part30C side. The screw shaft12is provided inside the casing10, and extends in the extending direction E that is a direction from the end part30B toward the other end part30C. The first screw blade14extends spirally on the outer peripheral surface of the screw shaft12. The second screw blade16extends spirally on the outer peripheral surface of the screw shaft12such that a predetermined gap is formed with respect to the first screw blade14in the extending direction E. In the casing10, the groove34is formed on the inner peripheral surface32a.

In the screw-type separation device1according to the present embodiment, the groove34is formed on the inner peripheral surface32aof the casing10. Hence, the object A is made to slide easily on the surface of the screw blade, by reducing the ratio of the friction force applied to the object A from the surface of the screw blade, with respect to the friction force applied to the object A from the inner peripheral surface32a. Consequently, with the screw-type separation device1according to the present embodiment, it is possible to appropriately convey the object A to the object discharging port31B, and suppress a decrease in the discharge efficiency of the object A. Moreover, because the separated liquid C can flow through the groove34, the screw-type separation device1can increase the flow passage of the separated liquid C to the separated liquid discharging port31C. Thus, with the screw-type separation device1, it is possible to reduce the pressure loss in the flow passage of the separated liquid C in the casing10, and appropriately discharge the separated liquid C.

Moreover, the groove34extends in the extending direction E. By configuring the screw-type separation device1such that the groove34extends in the extending direction E, the groove34can be used as a flow passage of the separated liquid C to the separated liquid discharging port31C. Hence, it is possible to reduce the pressure loss in the flow passage of the separated liquid C in the casing10, and appropriately discharge the separated liquid C.

Furthermore, in the groove34, the width of the inlet part34a1that is opened on the inner peripheral surface32aof the casing10is smaller than the width of the space (middle part34a2) on the radially outer side of the inlet part34a1. By reducing the width of the inlet part34a1of the groove34, the screw-type separation device1can suppress the object A, which is a solid material, from entering the groove34and prevent blockage in the groove34. Moreover, by increasing the width of the space on the radially outer side of the inlet part34a1, the screw-type separation device1can increase the flow passage area through which the separated liquid C flows. Thus, with the screw-type separation device1, it is possible to appropriately discharge the separated liquid C through the groove34.

Still furthermore, the width of the groove34is increased from the inlet part34a1toward the radially outer side. By gradually increasing the width of the groove34, the screw-type separation device1can suppress the pressure loss in the groove34, and cause the separated liquid C to flow appropriately.

Still furthermore, viewed from the extending direction E, the groove34is inclined to the rotation direction R side of the screw shaft12toward the radially inner side. By making the groove34inclined to the rotation direction R side, the screw-type separation device1can suppress the object A, which is a solid material, from entering the groove34, and prevent blockage in the groove34.

Still furthermore, in the groove34, the opening area of the inlet part34a1in the end part34C at the separated liquid discharging port31C side is greater than the opening area of the inlet part34a1at the object discharging port31B side of the end part34C. By increasing the opening area of the end part34C that is an outlet of the separated liquid C that flows through the groove34, the screw-type separation device1can suppress the pressure loss and appropriately discharge the separated liquid C.

The casing10includes the first casing30, and the second casing32inserted into the inside of the first casing30and the inner peripheral surface32aof which is formed with the groove34. For example, by forming the casing10by different members, it is possible to increase the shape accuracy of the second casing32formed with the groove34, and design the gap H to be small. Thus, with the screw-type separation device1, by making the gap H to be small, it is possible to preferably suppress a solid component of the pre-object A0from passing through the gap H, and increase the discharge efficiency of the object A and the cleaning degree of the separated liquid C.

In the casing10, at least a portion formed with the groove34is made of resin. By making the portion formed with the groove34(in the present example, the second casing32) made of resin, it is possible to increase the shape accuracy, and design the gap H to be small. Moreover, by using resin, it is possible to reduce the manufacturing cost.

Moreover, the casing10according to the present embodiment is a casing for the screw-type separation device1, and stores the screw11(unit including the screw shaft12, the first screw blade14, and the second screw blade16) inside. In the casing10, the groove34is formed on the inner peripheral surface32a. In this manner, by forming the groove34on the inner peripheral surface32aof the casing10for storing the screw11, it is possible to suppress a decrease in the discharge efficiency of the object A.

Next, another example of the first partition wall part and the second partition wall part will be described. In the above description, the first partition wall part18and the second partition wall part20are provided between the first screw blade14and the second screw blade16. However, as illustrated inFIG. 7toFIG. 9, a first partition wall part18aand a second partition wall part20amay be formed by an end part of the first screw blade14and an end part of the second screw blade16.FIG. 7is a partial sectional view of a screw-type separation device according to another example of the present embodiment.FIG. 8andFIG. 9are each a schematic diagram of a screw according to the other example of the present embodiment.FIG. 8illustrates an end part of the first screw blade14and the second screw blade16on the object discharging port31B side.FIG. 9illustrates an end part of the first screw blade14and the second screw blade16on the separated liquid discharging port31C side.

As illustrated inFIG. 7andFIG. 8, in this example, an end part14Ba on the object discharging port31B side of the first screw blade14and an end part16Ba on the object discharging port31B side of the second screw blade16are placed on the same position in the extending direction E. Moreover, pitch of the first screw blade14and the second screw blade16(length between the surface of the first screw blade14and the surface of the second screw blade16adjacent to each other in the extending direction E) is constant at the extending direction E side (separated liquid discharging port31C side) of the end part14Ba (end part16Ba). However, pitch in the vicinity of the end part14Ba (end part16Ba) is reduced toward the end part14Ba (end part16Ba) side, and the end part14Ba and the end part16Ba come into contact with each other. Thus, the second space S2between the first screw blade14and the second screw blade16is reduced toward the end part14Ba (end part16Ba), is closed at a contact position of the end part14Ba and the end part16Ba, and is separated from the space S3. That is, in this example, the end part14Ba and the end part16Ba configure the first partition wall part18athat separates the second space S2and the space S3.

Similarly, as illustrated inFIG. 7andFIG. 9, an end part14Ca on the separated liquid discharging port31C side of the first screw blade14and an end part16Ca on the separated liquid discharging port31C side of the second screw blade16are placed on the same position in the extending direction E. Moreover, pitch of the first screw blade14and the second screw blade16is constant at a side (object discharging port31B side) opposite to the extending direction E of the end part14Ca (end part16Ca). However, pitch in the vicinity of the end part14Ca (end part16Ca) is reduced toward the end part14Ca (end part16Ca) side, and the end part14Ca and the end part16Ca come into contact with each other. Thus, the first space S1between the first screw blade14and the second screw blade16is reduced toward the end part14Ca (end part16Ca), is closed at a contact position of the end part14Ca and the end part16Ca, and is separated from the space S4. That is, in this example, the end part14Ca and the end part16Ca configure the second partition wall part20athat separates the first space S1and the space S4.

FIG. 10is a flowchart for explaining a cleaning method of the screw-type separation device according to the present embodiment. To clean the screw-type separation device1, the supply of the pre-object A0is stopped, and the object A is discharged from the discharge pump26as much as possible. Then, as illustrated inFIG. 10, the object discharging port31B of the screw-type separation device1is closed (step S10; step of closing). In the present embodiment, the object discharging port31B is closed by stopping the discharge pump26. However, a method of closing the object discharging port31B is optional. For example, when an opening/closing valve is provided on the object discharging port31B, the object discharging port31B may be closed by closing the opening/closing valve. Moreover, the separated liquid discharging port31C may also be closed with the object discharging port31B.

Then, while the object discharging port31B is closed, cleaning solution is supplied to the casing10from the object feeding port31A (step S12; step of accumulating). At step S12, because the object discharging port31B is closed, the cleaning solution is accumulated in the casing10. For example, the cleaning solution is water. The cleaning solution supplied to the casing10also enters the groove34, and is accumulated in the groove34. Additionally, because the pressure inside the casing10is relatively increased by the cleaning solution, even if the groove34is clogged with a solid component, the cleaning solution can push out the solid material and flow into the groove34. The screw shaft12may also be rotated after supplying the cleaning solution at step S12. By rotating the screw shaft12, it is possible to cause the cleaning solution to flow in the casing, and appropriately remove the solid component in the groove34.

Then, the separated liquid discharging port31C is opened (step S14; step of discharging). Consequently, the cleaning solution accumulated in the casing10and the groove34is discharged from the separated liquid discharging port31C with the solid material.

In this manner, the cleaning method of the screw-type separation device1preferably includes the step of closing, the step of accumulating, and the step of discharging. At the step of closing, the object discharging port31B is closed. At the step of accumulating, the cleaning solution is accumulated in the casing10and the groove34, by supplying the cleaning solution into the casing10while the object discharging port31B is closed. At the step of opening, the cleaning solution accumulated in the casing10and the groove34is discharged from the object discharging port31B, by opening the object discharging port31B after the step of accumulating. In the screw-type separation device1, by making the shape of the groove34as described above, the groove34is hardly clogged with solid material. However, even if the groove34is clogged with solid material, it is possible to preferably remove the solid material from the groove34by cleaning in this manner.

First Example

Next, a wastewater treatment system as a first example including the screw-type separation device1described above will be explained.FIG. 11is a configuration diagram illustrating a part of a wastewater treatment system according to a first example.

As illustrated inFIG. 11, a wastewater treatment system100according to the first example includes a sedimentation basin101, a previous stage facility102disposed at a previous stage of the sedimentation basin101, a subsequent stage facility103disposed at a subsequent stage of the sedimentation basin101, an extraction pump104, and the screw-type separation device1. The sedimentation basin101is a solid-liquid separation tank that sediments and separates water to be treated supplied from the previous stage facility102into separated liquid and sludge. For example, the previous stage facility102is a facility that treats organic wastewater such as sewage and that includes various treatment tanks such as a reaction tank. For example, the subsequent stage facility103is a facility that includes an incinerator and the like, and that incinerates or disposes sludge (concentrated sludge) discharged from the screw-type separation device1. The extraction pump104is a sludge extraction unit that extracts sludge from the sedimentation basin101and that supplies the extracted sludge to the screw-type separation device1. The screw-type separation device1is provided above (direction away from the ground surface of) the sedimentation basin101in the vertical direction.

In the wastewater treatment system100, at least a part of the water to be treated discharged from the previous stage facility102is supplied to the sedimentation basin101. In the sedimentation basin101, the supplied water to be treated is sedimented and separated into separated liquid and sludge. The separated sludge is then extracted by the extraction pump104from the lower part of the sedimentation basin101, and is supplied to the screw-type separation device1. The extracted sludge is conveyed to the inside of the screw-type separation device1as the pre-object A0through the object feeding port31A (seeFIG. 1).

In the screw-type separation device1, the separated liquid C is separated similarly to the embodiment described above. The separated liquid C that has been separated is returned to the sedimentation basin101. The object A that has been separated (that has been dehydrated) is conveyed to the subsequent stage facility103as concentrated sludge, and is incinerated or disposed. In this manner, the wastewater treatment according to the first example is performed.

In the first example as described above, by using the screw-type separation device1according to the embodiment described above, the pre-object A0extracted from the sedimentation basin101is concentrated, and the separated liquid C is returned to the sedimentation basin101. In this manner, it is possible to improve the concentration of the object A, and significantly improve the maintainability of the sedimentation basin101. That is, in many cases, intermediate water is present in the sedimentation basin101. If such intermediate water is present, moisture is preferentially extracted over sludge (pre-object A0) during the extraction of sludge (pre-object A0). Thus, there is the problem that the concentration does not increase even if sludge (pre-object A0) is compressed. In regard to this problem, in the first example described above, the screw-type separation device1is disposed at a subsequent stage of the sedimentation basin101. Hence, it is possible to only separate the intermediate water from the extracted sludge (pre-object A0), and return the separated intermediate water to the sedimentation basin101. Thus, because the concentration of sludge (pre-object A0) can be improved, it is possible to improve the concentration of sludge (pre-object A0) even if the sedimentation basin101contains intermediate water as in the conventional example. In addition, because the screw-type separation device1described above can be manufactured at a low cost, the wastewater treatment system100can also be implemented at a low cost. Moreover, even if the casing10is clogged with sludge (pre-object A0), it is possible to easily remove the clog, by reversely rotating the screw shaft12with respect to the rotation direction R.

First Modification of First Example

Next, a modification of the first example described above will be explained.FIG. 12is a schematic diagram illustrating a sedimentation basin for explaining a modification of the first example. As illustrated inFIG. 12, in a first modification, the screw-type separation device1according to one embodiment is provided on the lower part of the sedimentation basin101. Then, the sludge that has sedimented on the lower part of the sedimentation basin101is supplied as the pre-object A0, into the screw-type separation device1through the object feeding port31A (seeFIG. 1) using a sludge recovery device (not illustrated) such as a funnel. The screw-type separation device1then discharges the concentrated sludge (object A) to the outside, and returns the separated liquid C that has been separated to the sedimentation basin101, through the inside or outside by a pipe (not illustrated) and the like. The separated liquid C may also be discharged to the outside. The other configuration is the same as that of the first example described above.

Second Modification of First Example

Moreover, as a second modification, when a gravity settling tank such as the sedimentation basin101is provided at a previous stage of the screw-type separation device1, a picket fence (not illustrated), which is formed by a rod-like member disposed upright on the upper side of a rake for scraping sludge, may also be provided in the sedimentation basin101. By providing the picket fence, it is possible to accelerate the sedimentation of sludge, or what is called flocculation in the sedimentation basin101. Thus, the screw-type separation device1can more effectively separate the object A and the separated liquid C, and significantly improve the solid-liquid separation properties.

Second Example

Next, a wastewater treatment system as a second example including the screw-type separation device1according to one embodiment described above will be explained.FIG. 13is a configuration diagram illustrating a part of a wastewater treatment system according to the second example.

As illustrated inFIG. 13, a wastewater treatment system200according to the second example includes a reaction tank201, a previous stage facility202disposed at a previous stage of the reaction tank201, a sedimentation basin204disposed at a subsequent stage of the reaction tank201, extraction pumps203aand203b, and the screw-type separation device1. The screw-type separation device1is provided above (direction away from the ground surface) the reaction tank201and the sedimentation basin204in the vertical direction.

For example, the reaction tank201is configured by a plurality of biological reaction tanks. For example, the biological reaction tanks that configure the reaction tank201are various biological reaction tanks such as an anaerobic tank, an oxygen-free tank, and an aerobic tank. For example, the previous stage facility202is a facility including a sand basin, an inclined plate sedimentation basin, or the like, that treats organic wastewater such as sewage. The extraction pump203ais a sludge extraction unit that extracts sludge such as activated sludge from the reaction tank201, and that supplies the extracted sludge to the screw-type separation device1as the pre-object A0. Similarly, the extraction pump203bis a sludge extraction unit that extracts sludge from the reaction tank201, and that supplies the extracted sludge to the sedimentation basin204in a subsequent stage. The sedimentation basin204is a solid-liquid separation tank that sediments and separates the water to be treated and the separated liquid C each supplied from the reaction tank201and the screw-type separation device1, to the separated liquid C and sludge (object A).

In the wastewater treatment system200according to the second example, at least a part of the water to be treated discharged from the previous stage facility202is supplied to the reaction tank201. In the reaction tank201, biological treatment such as nitrification and denitrification is performed on the water to be treated. The activated sludge in the reaction tank201is extracted by the extraction pumps203aand203b. The sludge extracted by the extraction pump203ais supplied to the screw-type separation device1as the pre-object A0, and is conveyed to the inside through the object feeding port31A (seeFIG. 1).

In the screw-type separation device1, the conveyed sludge (pre-object A0) is concentrated, and the separated liquid C is separated. The separated liquid C that has been separated is supplied to the sedimentation basin204in a subsequent stage. The sludge and water to be treated extracted from the reaction tank201by the extraction pump203bis supplied to the sedimentation basin204. In the sedimentation basin204, similar to the first example, solid-liquid separation treatment is performed by gravitational sedimentation. In this manner, the wastewater treatment according to the second example is performed.

In the second example described above, by using the screw-type separation device1, sludge (pre-object A0) is extracted from the reaction tank201, compressed and concentrated, and the compressed and concentrated sludge (object A) is returned to the reaction tank201. Moreover, the separated liquid C is supplied to the sedimentation basin204serving as the solid-liquid separation tank. Consequently, it is possible to solve the following problems.

That is, conventionally, electric power used for operating a return pump (not illustrated) for returning sludge (object A) to the reaction tank201from the sedimentation basin204has been extremely large. However, with the second example, the sludge (object A) compressed and concentrated using the screw-type separation device1can be returned to the reaction tank201. Hence, it is possible to significantly reduce electric power required for returning the sludge (object A). Moreover, by using the screw-type separation device1, it is possible to sufficiently perform solid-liquid separation. Consequently, because the frequency of sludge extraction from the sedimentation basin204can be reduced, it is possible to reduce power consumption of the wastewater treatment system200and save energy.

Moreover, conventionally, when a separation film is provided in the reaction tank201, there has been problems such as the initial cost and burden required for maintaining the facility are increased. However, by implementing the screw-type separation device1at a low cost instead of a separation film, it is possible to reduce the initial cost. Moreover, because the screw-type separation device1can be maintained easily, it is possible to reduce the burden of maintenance, and reduce the maintenance cost.

Furthermore, with the second example, mixed liquor suspended solids (MLSS) in the reaction tank201can be increased. Hence, it is possible to reduce the load in the sedimentation basin204, and reduce the power consumption of the extraction pumps203aand203bused for extracting sludge from the reaction tank201. Consequently, it is possible to save energy in the wastewater treatment system200.

Still furthermore, in each example, sludge (pre-object A0) to be fed into the screw-type separation device1may not be sludge added with a flocculating agent. That is, a flocculating agent may not be added to the sludge in the sedimentation basin101, and a flocculating agent may not be added to the sludge in the reaction tank201. Because the screw-type separation device1can also separate sludge by gravity, it is also possible to suppress a decrease in separation efficiency of sludge not containing a flocculating agent.

The embodiment of the present invention has been described in detail. However, the present invention is not limited to the embodiment described above, and various modifications may be made based on the technical idea of the present invention. Moreover, the components described above include components that can be easily assumed by those skilled in the art, components that are substantially the same, and components within a so-called range of equivalents. Furthermore, the components described above can be appropriately combined. Still furthermore, various omissions, substitutions, or changes of the components may be made without departing from the spirit of the embodiment described above. For example, the numerical values given in the embodiment described above are merely examples, and different numerical values may be used as necessary.

In the embodiment described above, the screw shaft12is formed in a cylindrical shape. However, the shape of the screw shaft12is not limited thereto. For example, the screw shaft12may be formed in what is called an enlarged diameter shape in which the diameter of the screw shaft12is gradually increased from the end part30C to the end part30B side of the casing10.

Moreover, in the embodiment described above, the solid-liquid separation device that separates sludge into solid matter and moisture is used as an example. However, the embodiment described above is not limited to separate sludge into solid and liquid, and may be applicable to various methods of separating solid and liquid.

Moreover, in the embodiment described above, the position of the separated liquid discharging port31C may be changed in various ways.

Furthermore, in the embodiment described above, the separated liquid C is transferred through the gap H. However, for example, the separated liquid C may also be transferred by additionally providing a filtration unit formed in a mesh-like shape or that has a large number of minute holes on at least a part of the first screw blade14and the second screw blade16.

Still furthermore, the screw-type separation device1according to the embodiment described above may also be used as a pre-concentrator for a dehydrator, a simple concentrator for private use, a confluence improvement screen, and the like.

In the first example in one embodiment described above, sludge extracted by the extraction pump104is sludge sedimented in the sedimentation basin101. However, sludge is not limited to the sedimented sludge. For example, floating sludge tends to generate in the sedimentation basin101during summer and the like. The floating sludge may be extracted by the extraction pump104and supplied to the screw-type separation device1.

In the first example described above, the screw-type separation device1according to one embodiment is combined with the sedimentation basin101. However, the form is not limited thereto. More specifically, for example, a filtration concentration device may also be combined with the screw-type separation device1. In this case, the screw-type separation device1described above can be mounted on a bottom part of a line that extracts sludge in a filtration concentration device or a bottom part of a filtration concentration device. In this example, the filtration concentration device is intermittently operated. Hence, the concentrated sludge is temporarily accumulated in the filtration concentration device, and sludge is extracted from the lower part. Thus, supernatant liquid accumulated above the sludge is extracted with the concentrated sludge, when the sludge is temporarily accumulated. Consequently, the same problem as that in the first example described above is present. However, by using the screw-type separation device1according to the one embodiment, it is possible to separate the supernatant liquid (supernatant water) during the extraction of sludge, and stably increase the concentration of the concentrated sludge.

The embodiment, examples, and modifications of the present invention have been described. However, the embodiment is not limited to the content of the embodiments and the like. Moreover, the components described above include components that can be easily assumed by those skilled in the art, components that are substantially the same, and components within a so-called range of equivalents. Furthermore, the components described above can be appropriately combined. Still furthermore, various omissions, substitutions, and changes of the components may be made without departing from the spirit of the embodiment or the like described above.

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