JP7765689B2 - Dehydration system and dehydration method - Google Patents

Description

The present invention relates to a dehydration system and method for dehydrating water containing solids.

As one of the treatment methods for water to be treated containing solids, such as sewage sludge (hereinafter simply referred to as "water to be treated"), dehydration is widely used, in which water is separated and removed from the solids, and the solids are concentrated and recovered. Various types of dehydrators are known as devices for carrying out dehydration, and it is also common to add chemicals (flocculants) to the water to be treated before dehydration in order to improve the efficiency of the dehydration process.

For example, Patent Document 1 describes using a belt press dehydrator with a gravity dehydration filtration section as the dehydrator, and in the dehydration of water to be treated that contains solids such as sludge, controlling the amount of coagulant added so that the water level of the concentrated sludge in the gravity dehydration filtration section reaches a target water level that achieves the desired concentration and dehydration efficiency.

Japanese Patent Application Publication No. 11-254000

As described in Patent Document 1, it is known that in the dehydration treatment of water containing solids, the amount of coagulant added can be adjusted to achieve the desired concentration and dehydration efficiency. However, it is difficult to always control the amount of coagulant added to the water to be treated so that it is optimal, and to achieve stable dehydration treatment, the amount of coagulant added must be increased to prevent a shortage of coagulant. This not only results in higher costs, but also in the problem that adding too much coagulant can reduce the filtration efficiency of the water to be treated.

Furthermore, in dehydrators that involve filtration processing using the weight of the water being treated, such as the belt press type dehydrator described in Patent Document 1, it is known that the concentration and dehydration efficiency can be improved by adjusting the flocculation state of the solids in the water being treated by adjusting the amount of flocculant added, thereby allowing the filtration processing (separation of solids and water) to proceed quickly.
On the other hand, in dehydrators that perform dehydration processing while the dehydration section is immersed in the water to be treated, such as screw press dehydrators and multi-disk dehydrators, the dehydration efficiency is improved by the dehydration section being subjected to the pressing pressure of the water to be treated, unlike belt press dehydrators that use filter cloth as described in Patent Document 1. Therefore, in such dehydrators, a means other than that described in Patent Document 1 is required to perform stable dehydration processing and improve dehydration efficiency.

Furthermore, when water to be treated containing solids undergoes solid-liquid separation treatment in a solid-liquid separation tank or the like before being supplied to a dehydrator, the concentration of solids in the water to be treated is generally high when it is first supplied, but as it is supplied to the dehydrator, the concentration of solids in the water to be treated in the solid-liquid separation tank decreases. Therefore, the amount of solids in the water to be treated supplied to the dehydrator decreases. As a result, the amount of solids discharged from the dehydrator decreases, reducing the amount of solids recovered that have been concentrated through the dehydration treatment, which creates the problem of reduced operational efficiency in the dehydration treatment.

The objective of the present invention is to provide a dehydration system and method for dehydrating water containing solids, using a dehydrator with a dehydration section immersed in the water to be treated, which allows for stable and continuous dehydration, and maintains a constant amount of solids discharged after dehydration even if the concentration of solids in the water to be dehydrated fluctuates, thereby improving the efficiency of the dehydration process.

As a result of extensive research into the above-mentioned problems, the inventors discovered that by controlling the amount of water to be treated supplied to a dehydrator whose dehydration section is immersed in the water to be treated so that the water level of the water to be treated containing solids remains constant, it is possible to maintain a constant head pressure in the dehydrator (the pressure pushing against the dehydration section) and continuously supply a constant amount of solids to the dehydrator, thereby improving the work efficiency related to the dehydration process and completing the present invention.
That is, the present invention provides the following dehydration system and dehydration method.

The dehydration system of the present invention, which solves the above problems, is a dehydration system that dehydrates water containing solids, and is characterized by having a dehydrator equipped with a casing and a dehydration unit, the dehydration unit being immersed in the water to be treated, and controlling the amount of water to be treated supplied to the dehydrator so that the level of the water to be treated in the casing remains constant.

According to the dehydration system of the present invention, the amount of water to be treated supplied to a dehydrator equipped with a casing and a dehydration section, in which the dehydration section is immersed in the water to be treated, is controlled so that the water level of the water to be treated in the casing remains constant. This makes it possible to maintain a constant head pressure in the dehydrator (pressure applied to the dehydration section), thereby improving dehydration efficiency and enabling stable continuation of dehydration processing.
Furthermore, with the dehydration system of the present invention, even if the solid concentration in the water to be dehydrated fluctuates, the amount of solids contained in the water to be dehydrated supplied to the dehydrator can be controlled to a constant level. This allows the dehydrator to continuously dehydrate a constant amount of solids, making it possible to maintain a constant amount of solids discharged after dehydration and suppress a decrease in the amount of solids recovered that have been concentrated through the dehydration process, thereby significantly improving the efficiency of the dehydration process.

Furthermore, one embodiment of the dehydration system of the present invention has a flocculant addition section that adds a flocculant, and the flocculant addition section is characterized by adding a constant amount of flocculant to the water to be treated.
According to the dewatering system of the present invention, by adding a constant amount of flocculant to the water to be treated, excessive addition of flocculant can be prevented. This reduces the cost of flocculant and allows the ratio of solids to flocculant to be kept approximately constant, thereby appropriately controlling the flocculation state of the solids and improving the dewatering efficiency and recovery amount of solids.

Furthermore, one embodiment of the dehydration system of the present invention is characterized in that it is equipped with a supply unit that varies the flow rate of the water to be treated, and the supply unit controls the amount of water to be treated supplied to the dehydrator.
According to the dehydration system of the present invention, a supply unit that varies the flow rate of the water to be treated is provided, and the supply unit controls the flow rate of the water to be treated so that the water level in the dehydrator casing remains constant. This eliminates the need to specifically grasp the solids concentration in the water to be treated when controlling the amount of water to be supplied to the dehydrator. As a result, the amount of water to be supplied to the dehydrator can be controlled with a simple configuration, without the need to use measuring equipment such as a sludge concentration meter to grasp the solids concentration in the water to be treated.
Furthermore, the dehydration system of the present invention controls the supply amount of untreated water by varying the flow rate, thereby enabling continuous dehydration without stopping the supply of untreated water to the dehydrator. This is particularly effective in systems where untreated water is constantly supplied from a source that generates untreated water that requires dehydration.

In one embodiment of the dehydration system of the present invention, the dehydrator is a screw press dehydrator or a multi-disk dehydrator.
A screw press dehydrator or a multi-disk dehydrator is a dehydrator that includes a casing and a dehydration section that is immersed in the water to be treated, and it is known that the pressure exerted by the water to be treated in the dehydration section affects dehydration performance. For this reason, they are suitable for use as the dehydrator in the dehydration system of the present invention.
The dehydration system of the present invention utilizes the configuration of a known or existing screw press dehydrator or multi-disk dehydrator to maintain a constant head pressure in the dehydrator (pressure applied to the dehydration section) and to control the amount of solids contained in the water to be dehydrated to a constant level, even if the solids concentration in the water to be dehydrated fluctuates. This allows the dehydration process to continue stably, and by keeping the amount of solids discharged after dehydration constant, even if the solids concentration in the water to be dehydrated fluctuates, it becomes possible to significantly improve the efficiency of the dehydration process.

The dehydration method of the present invention, which solves the above problems, is a dehydration method for dehydrating water containing solids, and is characterized in that it comprises a casing and a dehydration unit, and the dehydration unit includes a control step for controlling the amount of water to be treated supplied to the dehydrator, which is immersed in the water to be treated, so that the level of the water to be treated in the casing remains constant.
According to the dehydration method of the present invention, a dehydrator is provided with a casing and a dehydration section, and the dehydration section is immersed in the water to be treated.By providing a control process for controlling the amount of water to be treated supplied so that the water level in the casing remains constant, the head pressure in the dehydrator (the pressure pushing against the dehydration section) can be maintained constant, thereby improving dehydration efficiency and enabling the dehydration process to continue stably.
Furthermore, according to the dehydration method of the present invention, even if the solid concentration in the water to be dehydrated fluctuates, the amount of solids contained in the water to be dehydrated supplied to the dehydrator can be controlled to a constant level. This allows the dehydrator to continuously dehydrate a constant amount of solids, making it possible to maintain a constant amount of solids discharged after dehydration and suppress a decrease in the amount of solids recovered that have been concentrated through the dehydration process, thereby significantly improving the efficiency of the dehydration process.

This invention provides a dehydration system and method that improves operational efficiency in the dehydration process by using a dehydrator with a dehydration section immersed in the water to be treated, which allows for stable and continuous dehydration of water containing solids. It also keeps the amount of solids discharged after dehydration constant, even if the concentration of solids in the water to be dehydrated fluctuates.

1 is a schematic explanatory diagram showing a dehydration system according to a first embodiment of the present invention. FIG. 1 is a schematic explanatory diagram showing a screw press dehydrator, which is an example of a dehydrator according to a first embodiment of the present invention. 1 is a schematic explanatory diagram showing a multi-disk dehydrator as an example of a dehydrator according to a first embodiment of the present invention. FIG. 2 is a schematic explanatory diagram showing a dehydration system according to a second embodiment of the present invention.

The dehydration system of the present invention performs dehydration treatment on water to be treated that contains solids. More specifically, it is used to separate and remove water from solids in the water to be treated that is supplied to a dehydrator, and to concentrate and recover the solids.

The water to be treated by the dehydration system of the present invention is a liquid containing dispersed particulate solids. Specific examples include sludge generated in sewage treatment plants and wastewater treatment plants, paper sludge from paper mills, industrial wastewater from food factories and plating factories, and wastewater from pigments.
Furthermore, in the dehydration system of the present invention, the water to be dehydrated may be discharged from various water treatment plants or factories that serve as sources, and the water may be subjected to pretreatment such as solid-liquid separation. More specifically, the water to be treated discharged from the source may be subjected to solid-liquid separation treatment using a solid-liquid separation tank such as a settling tank or a coagulation settling tank, and the sediment components that have settled in the solid-liquid separation tank, which is a dispersion containing a large amount of solids, may be used as the water to be dehydrated to be supplied to the dehydration system of the present invention.
In the embodiment of the present invention, the water to be treated supplied to the dehydration system is described as being a solution containing solids generated in various treatment plants, factories, etc., which has been subjected to solid-liquid separation as a pretreatment, and the settled components are used as the water to be treated, but the present invention is not limited to this.

Embodiments of the dehydration system and dehydration method according to the present invention will be described in detail below with reference to the drawings. The dehydration method according to the present invention will be substituted for the description of the configuration and operation of the dehydration system and the structure of the dehydrator below. Furthermore, the configuration and operation of the dehydration system and the structure of the dehydrator described in the embodiments are merely examples used to explain the dehydration system according to the present invention, and are not intended to be limiting.

[First embodiment]
FIG. 1 is a schematic explanatory diagram showing the configuration of a dehydration system according to a first embodiment of the present invention.
As shown in Fig. 1, the dehydration system 100 according to this embodiment includes a solid-liquid separation tank 1 for performing solid-liquid separation on raw water delivered from a generation source (such as a water treatment plant or a factory), and a dehydrator 2 for performing a dehydration treatment on water to be treated W containing solids (hereinafter sometimes simply referred to as "water to be treated W") delivered from the solid-liquid separation tank 1, separating and removing water from the solids, and recovering the concentrated solids. The system also includes a supply unit 3 for delivering the water to be treated W from the solid-liquid separation tank 1 to the dehydrator 2, a measuring unit 4 for measuring the level of the water to be treated W in the dehydrator 2, and a control unit 5 for controlling the supply unit 3 based on the measurement results from the measuring unit 4. The supply unit 3 is provided on a supply line L1, which is a pipe for delivering the water to be treated W from the solid-liquid separation tank 1 to the dehydrator 2.
In FIG. 1, the dashed arrows indicate input/output and controllable connections.

In addition, in order to improve the dehydration efficiency of the dehydrator 2, it is preferable to perform a pretreatment on the treated water W, which is the target of treatment in this embodiment, to aggregate and flocculate the solid components in the treated water W before supplying it to the dehydrator 2.
As an example of such pretreatment, a flocculant G may be added to the water W to be treated.
For example, as shown in Figure 1, the dehydration system 100 in this embodiment may include a flocculant storage tank 6 for storing flocculant G, a flocculant addition section 7 for adding the flocculant G stored in the flocculant storage tank 6 to the water to be treated W, and an addition line L2 which is a pipe for transporting the flocculant G from the flocculant storage tank 6 to the flocculant addition section 7.

First, we will explain the solid-liquid separation tank 1, which functions as pretreatment in the dehydration system 100 in this embodiment, and the configuration related to the addition of flocculant G (flocculant storage tank 6 and flocculant addition section 7).

[Solid-liquid separation tank]
The solid-liquid separation tank 1 is used to perform solid-liquid separation as a pretreatment for raw water (solution containing solids) generated in various treatment plants, factories, etc. The solid-liquid separation tank 1 also serves to supply a dispersion containing a large amount of solids to the dehydrator 2 as water W to be treated.
The solid-liquid separation tank 1 may have any structure or size as long as it can separate raw water into a solid fraction and a liquid fraction. For example, the tank may store raw water and separate the solid fraction and liquid fraction by natural settling of the solid fraction, or may be equipped with a flocculant addition means for adding a flocculant G (described later) to the solid-liquid separation tank 1 and an agitator blade 11 for agitating the raw water, forming flocs in the solid-liquid separation tank 1 and separating the solid fraction and liquid fraction.

The solid-liquid separation tank 1 may be equipped with a treated water discharge section 12 that discharges the separated liquid as treated water from the top of the tank, and a sedimented component discharge section 13 that extracts sedimented components, including settled solids, from the bottom of the tank.

The water to be treated W supplied from the solid-liquid separation tank 1 to the dehydrator 2 is composed of sediment components that have settled to the bottom of the solid-liquid separation tank 1, and is a dispersion containing a large amount of solids. This allows the dehydrator 2 to efficiently dehydrate and recover the solids.
The treated water W extracted from the sediment component discharge section provided at the bottom or lower side of the solid-liquid separation tank 1 has a high concentration of solids at the start of extraction, and tends to have a lower concentration of solids as the water is extracted.

[Flocculant storage tank and flocculant addition section]
The flocculant storage tank 6 is a storage tank for storing the flocculant G.
The flocculant storage tank 6 may be of any size, structure, or material as long as it is capable of storing the flocculant G. There is also no particular limitation on the type of flocculant G stored therein. Furthermore, multiple flocculant storage tanks 6 may be provided depending on the flocculant G to be used.

The flocculant G to be added to the water to be treated W is not particularly limited, and any substance may be used as long as it has the ability to flocculate solids. Examples include inorganic flocculants and polymer flocculants, and the flocculant is selected appropriately depending on the treatment conditions.

Examples of inorganic flocculants include polyferric sulfate, ferric chloride, polysilica iron, and polyaluminum chloride. Examples of polymer flocculants include cationic polyaminoalkyl methacrylate, polyethyleneimine, halogenated polydiallylammonium, chitosan, and urea-formalin resin. Other polymer flocculants include nonionic polyacrylamide, polyethylene oxide, and the like, as well as anionic sodium polyacrylate, partial hydrolyzed polyacrylamide, partially sulfomethylated polyacrylamide, poly(2-acrylamide)-2-methylpropane sulfate, and amphoteric copolymers of acrylamide, aminoalkyl methacrylate, and sodium acrylate.
These flocculants G may be used alone or in combination depending on the treatment conditions.

The flocculant adding section 7 adds a flocculant G to the water to be treated W in order to flocculate solids in the water to be treated W as a pretreatment before the dewatering treatment in the dewatering machine 2 .
Although there is no particular limitation on the amount of flocculant G added by the flocculant adding unit 7, it is preferable to add a constant amount of flocculant G regardless of fluctuations in the solid content concentration of the water to be treated W. As will be described later, in the dehydration system 100 of this embodiment, the solid content concentration (solid amount) supplied to the dehydrator 2 is approximately constant. Therefore, by adding a constant amount of flocculant, the flocculant addition ratio to the solid content can be made constant, enabling stable floc formation. This prevents the flocculant G from being excessively supplied relative to the solid content concentration of the water to be treated W, thereby reducing the cost of using flocculant G and improving the dehydration efficiency and recovery amount of solids.

Furthermore, the flocculant addition section 7 may have any structure and may be installed in any location as long as it is able to add flocculant G to the water to be treated W at a stage prior to the dehydrator 2.
1, for example, the flocculant addition unit 7 in this embodiment may be installed on the supply line L1 between the supply unit 3 and the dehydrator 2. This allows flocculant G to be added to the water to be treated W, the flow rate of which has been controlled by the supply unit 3, according to the water level H in the dehydrator 2. This makes it possible to more reliably prevent excessive supply of flocculant G and enable stable floc formation.

The main components of the dehydration system 100 of this embodiment will be described below.
[Dehydrator]
The dehydrator 2 performs a dehydration process on the treated water W containing solids, thereby separating and removing water from the solids, reducing the moisture content, and recovering the concentrated solids (hereinafter referred to as ``dehydrated cake D'').

In this embodiment, the dehydrator 2 comprises a casing 21 in which the water to be treated W is supplied and retained, and a dehydration section 22 disposed within the casing 21 and which separates and removes water from solids. Here, the dehydration section 22 is immersed in the supplied water to be treated W. The casing 21 also comprises a water to be treated supply section 23 to which the water to be treated W is supplied via supply line L1, and a dehydrated cake discharge section 24 that discharges the dehydrated cake D formed by the dehydration section 22.

In the dehydrator 2 of this embodiment, the dehydration section 22 is immersed in the water to be treated W. Therefore, in the dehydration process by the dehydrator 2 of this embodiment, the pushing pressure applied to the dehydration section 22 affects the efficiency of the dehydration process. In addition, this pushing pressure is affected by the head pressure of the water to be treated W retained (stored) in the casing 21.
In this embodiment, the dehydration system 100 maintains a constant water level H of the water to be treated W in the casing 21 in such a dehydrator 2, thereby maintaining a constant head pressure of the water to be treated W in the casing 21 (the pushing pressure applied to the dehydration section 22), thereby enabling stable dehydration processing.

The dehydrator 2 in this embodiment may be any device that includes a casing 21 and a dehydration section 22 and has a structure in which the dehydration section 22 is immersed in the water to be treated W. Solids Examples of the dehydrator 2 in this embodiment include dehydrators called screw press dehydrators and multi-disk dehydrators.

(Screw press dehydrator)
FIG. 2 is a schematic explanatory diagram showing a screw press dehydrator as an example of the dehydrator in this embodiment.
A screw press dehydrator 2A, which is an example of the dehydrator 2 in this embodiment, will be described below with reference to FIG.

The screw press dehydrator 2A (hereinafter referred to as "dehydrator 2A") shown in Figure 2 comprises a casing 21A having a treated water retention section 211A and a dehydration section installation area 212A, and a dehydration section 22A having a screw 221A and a screen 222A, and is a dehydrator that performs continuous dehydration processing by compressing, rotating, and transporting the treated water W by rotating the screw 221A.
In addition to the casing 21A and the dewatering section 22A, the dewatering machine 2A in this embodiment is equipped with a water-to-be-treated supply section 23A, a dewatered cake discharge section 24A, and a filtrate discharge section 25A.

The treated water retention section 211A in the casing 21A is an area located above the dehydration section arrangement area 212A, where the treated water W supplied by the treated water supply section 23A is retained (stored) and where the water level of the treated water W is measured by the measuring section 4 described later.
On the other hand, the dewatering unit installation area 212A in the casing 21A is an area that forms a space for installing the dewatering unit 22A, and accommodates a screw 221A and a screen 222A.

The screw 221A in the dewatering section 22A has spiral blades attached to a conical rotor and is driven to rotate by a drive mechanism (not shown). The conical rotor may be configured so that the diameter increases in the direction of transport of the water W (away from the water supply section 23A), thereby reducing the space for transporting the water W. This allows the rotation of the screw 221A to transport the water W containing solids toward the dewatered cake discharge section 24A, and the further away from the water supply section 23A (the closer to the dewatered cake discharge section 24A), the greater the pressure that can be applied to the water W, thereby improving dewatering efficiency.
The structure of the screw 221A is not particularly limited as long as it is a known structure used in a screw press dehydrator. The number, shape, and size of the blades of the screw 221A are also not particularly limited.

The screen 222A in the dewatering section 22A is located around the screw 221A. The water to be treated W transported by the screw 221A is separated into solids and water via the screen 222A. The water is discharged via the screen 222A to the filtrate discharge section 25A, while the solids that do not pass through the screen 222A are transported toward the dewatered cake discharge section 24A. The screen 222A may be of any shape or material as long as it can separate the large-particle solids in the water to be treated W from the water. For example, it may be made of metal mesh or punched metal. In this case, the high strength and durability make it possible to reduce maintenance costs.

The untreated water supply unit 23A is for supplying the untreated water W to the dehydrator 2A via a supply line L1.
The untreated water supply section 23A may be provided in any location as long as it can supply the untreated water W to the casing 21A. For example, as shown in FIG. 2 , the untreated water supply section 23A may be provided so as to be connected to the untreated water retention section 211A.

The dehydrated cake discharge section 24A is used to discharge dehydrated cake D to the outside of the dehydrator 2A. The dehydrated cake discharge section 24A may be located anywhere as long as it can discharge dehydrated cake D that has been sufficiently dehydrated by the dehydration section 22A to the outside of the casing 21A. For example, as shown in Figure 2, the dehydrated cake discharge section 24A may be located at the end of the dehydration section 22A in the transport direction of the water to be treated W and at the bottom of the casing 21A.

The filtrate discharge section 25A discharges the water (filtrate) separated from the solids in the water to be treated W in the dehydration section 22A to the outside of the dehydrator 2A. The shape of the filtrate discharge section 25A is not particularly limited. For example, as shown in Figure 2, by providing a guide consisting of an inclined plate as the filtrate discharge section 25A, the water that falls through the screen 222A of the dehydration section 22A can be efficiently discharged to the outside of the dehydrator 2A.

Next, the operation of the dehydrator 2A will be described.
First, the sediment components that have settled in the solid-liquid separation tank 1 are treated water W, which is supplied from the treated water supply section 23A to the treated water retention section 211A in the casing 21A. If the concentration of solids in the treated water W is low, much of the water contained in the treated water W is easily separated from the solids through the screen 222A and quickly discharged to the outside of the dehydrator 2A through the filtrate discharge section 25A. Therefore, little water W remains in the treated water retention section 211A, and the water level H remains low. On the other hand, if the concentration of solids in the treated water W exceeds a certain level, or if the concentration of solids in the treated water retention section 211A exceeds a certain level due to continuous supply of the treated water W into the casing 21A, separation of water from the solids becomes difficult due to an increase in the water retention capacity of the solids or a decrease in the dispersibility of the solids. As a result, the water to be treated W having a certain solid concentration is present in the water to be treated retention section 211A and the dewatering section installation area 212A, and the dewatering section 22A is immersed in the water to be treated W.

Next, by rotating the screw 221A in the dewatering section 22A, the water to be treated W present in the dewatering section installation area 212A (dewatering section 22A) is transported toward the dewatered cake discharge section 24A. Here, the screw 221A is configured so that the diameter of the conical rotor increases toward the dewatered cake discharge section 24A, thereby compressing the water to be treated W and separating it into solids and liquids. At this time, the water separated from the water to be treated W is discharged from the screen 222A via the filtrate discharge section 25A and out of the dewatering machine 2A.
As the water is separated and removed, the solids aggregate to form dehydrated cake D, which is discharged from dehydrated cake discharge section 24A to the outside of dehydrator 2A. By continuously performing these operations, the dehydration treatment of the water W to be treated by dehydrator 2A progresses.

Note that the dehydrator 2A used as the dehydrator 2 in this embodiment is not limited to the structure shown in Figure 2. A dehydrator 2A with a known structure and known additional mechanisms can be used. For example, a back pressure device can be provided opposite the screw 221A of the dehydration section 22A, or a multi-plate screw press dehydrator can be used in which the screen 222A has a multi-plate structure combining movable and fixed plates.

(Multiple disc dehydrator)
Another example of the dehydrator 2 in this embodiment is a multi-disk type dehydrator.
FIG. 3 is a schematic explanatory diagram showing a multi-disk dehydrator as an example of the dehydrator in this embodiment.
A multi-disk dehydrator 2B, which is an example of the dehydrator 2 in this embodiment, will be described below with reference to FIG.

The multiple-disk dehydrator 2B (hereinafter referred to as "dehydrator 2B") shown in Figure 3 comprises a casing 21B having a treated water retention section 211B and a dehydration section installation area 212B as a casing 21 and a dehydration section 22B formed by stacking a large number of disks (disks) 221B in two layers, one above the other.The dehydrator separates and removes moisture from the solids as the treated water W containing solids passes between the disks 221B, thereby performing continuous dehydration processing.
In addition to the casing 21B and the dewatering section 22B, the dewatering machine 2B in this embodiment is equipped with a water-to-be-treated supply section 23B, a dewatered cake discharge section 24B, and a filtrate discharge section 25B.
Here, the untreated water supply section 23B, the dehydrated cake discharge section 24B, and the filtrate discharge section 25B in the dehydrator 2B have the same configurations and functions as the untreated water supply section 23A, the dehydrated cake discharge section 24A, and the filtrate discharge section 25A in the above-mentioned dehydrator 2A, and therefore their explanations are omitted.

The untreated water retention section 211B in the casing 21B is an area provided on the untreated water supply section 23A side, and is a location where the water level of the untreated water W is measured by the measuring section 4 described later.
On the other hand, the dehydration unit installation area 212B in the casing 21B is an area that forms a space in which the dehydration unit 22B is installed, and a plurality of disks 221B are housed in the vertical direction.

The multiple disks 221B in the dewatering section 22B are composed of a combination of circular metal plates arranged vertically within the casing 21B as a filter body. A drive mechanism (not shown) is provided to rotate the multiple disks 221B (filter body). Rotating the multiple disks 221B transports the water W to be treated and separates and removes moisture through the gaps between the multiple disks 221B. The vertical spacing of the multiple disks 221B can be reduced as the direction of transport of the water W (away from the water supply section 23B) increases, thereby reducing the space required for transporting the water W. This allows the rotation of the multiple disks 221B to transport the water W containing solids toward the dewatered cake discharge section 24B. Furthermore, the farther the disks 221B are from the water supply section 23B (the closer they are to the dewatered cake discharge section 24B), the greater the pressure that can be applied to the water W, thereby improving dewatering efficiency.
The structure of the plurality of discs 221B is not particularly limited as long as it is a known structure used in a multi-disc dehydrator. Furthermore, the plurality of discs 221B may all be composed of movable discs (rotating bodies) or may be a combination of movable and fixed discs. The number, shape, and size of the plurality of discs 221B forming the dehydration section 22B are not particularly limited.

Next, the operation of the dehydrator 2B will be described.
First, the sediment components that have settled in the solid-liquid separation tank 1 are treated as water W, which is supplied from the water supply section 23B to the water retention section 211B in the casing 21B. If the concentration of solids contained in the water W is low, most of the water contained in the water W is easily separated from the solids through the gaps between the multiple disks 221B and is quickly discharged outside the dehydrator 2B through the filtrate discharge section 25B. On the other hand, if the concentration of solids contained in the water W is above a certain level, or if the concentration of solids in the water retention section 211B is increased by continuous supply of water W into the casing 21B, separation of the liquid from the solids becomes difficult due to an increase in the water retention capacity of the solids or a decrease in the dispersibility of the solids. As a result, the water to be treated W having a certain solid concentration is present in the water to be treated retention section 211B and the dewatering section installation area 212B, and the dewatering section 22B is immersed in the water to be treated W.

Next, by rotating the plurality of disks 221B in the dewatering section 22B, the water to be treated W present in the dewatering section installation area 212B (dewatering section 22B) is transported toward the dewatered cake discharge section 24B. Here, the spacing between the plurality of disks 221B arranged in the vertical direction is configured to gradually narrow in the direction in which the water to be treated W is transported, thereby compressing the water to be treated and separating it into solids and water. At this time, the water separated from the water to be treated W is discharged outside the dewatering machine 2B via the filtrate discharge section 25B.
As the water is separated and removed, the solids aggregate to form dehydrated cake D, which is discharged from dehydrated cake discharge section 24B to the outside of dehydrator 2B. By continuously performing these operations, the dehydration treatment of the water W to be treated by dehydrator 2B progresses.

[Supply section]
The supply unit 3 supplies the water to be treated W from the solid-liquid separation tank 1 to the dehydrator 2. The supply unit 3 also adjusts the amount of the water to be treated W supplied to the dehydrator 2 based on instructions from the control unit 5, which will be described later.
The supply unit 3 may be of any type as long as it can supply the water to be treated W from the solid-liquid separation tank 1 to the dehydrator 2 via the supply line L1 based on instructions from the control unit 5.
1, the supply unit 3 may include a pump P and a flow rate varying mechanism provided on the supply line L1, and may vary the flow rate of the water W to be treated based on instructions from the control unit 5. The supply unit 3 may also include a receiving unit for receiving instructions from the control unit 5, and a driving unit such as an engine or motor for driving the pump P.
A supply unit 3 that varies the flow rate of the water W to be treated is provided, and the flow rate of the water W to be treated is controlled by the supply unit 3 so that the water level H of the water W in the casing 21 of the dehydrator 2 is constant. This allows the head pressure in the dehydrator 2 to be constant and the concentration of solids remaining in the dehydrator 2 to be maintained constant within the range in which the water level H is maintained constant. This improves the dehydration efficiency of the dehydrator 2 and enables stable dehydration to be continued. Furthermore, when controlling the amount of water W to be treated to the dehydrator 2A, it is not necessary to specifically grasp the solid concentration in the water W to be treated. This eliminates the need for a measuring device, such as a sludge concentration meter, to grasp the solid concentration in the water W to be treated, and allows for a simple configuration to control the amount of water W to be treated to the dehydrator 2A.

In addition, in this embodiment, the supply unit 3 controls the supply amount of water W to be treated by varying the flow rate of the water W to be treated, thereby enabling continuous dehydration without stopping the supply of water W to the dehydrator 2. This is particularly effective in systems where water W to be treated is constantly supplied from a source that generates water W to be treated that requires dehydration. Examples of such sources include sewage treatment plants and wastewater treatment plants.

In this embodiment, the specific combination of pump P and flow rate varying mechanism for supply unit 3 is not particularly limited. For example, the flow rate varying mechanism may include a mechanism for controlling the operating frequency of pump P, or a mechanism consisting of a combination of a flow rate adjustment valve and a flow meter.

[Measurement part]
The measuring unit 4 in this embodiment measures the water level H of the water to be treated W in the dehydrator 2 (inside the casing 21).
The measuring unit 4 may have any structure as long as it can measure the water level H of the water to be treated W inside the dehydrator 2 (inside the casing 21). For example, a liquid level sensor that uses reflection or transmission of light or sound may be provided inside the casing 21, or a float-type level gauge may be provided on the liquid level of the water to be treated W inside the casing 21. The measuring unit 4 is not limited to those that use measuring equipment. For example, a scaled rod or plate may be provided in the casing 21 so that an operator can visually read the water level H.
It is preferable that the measuring unit 4 be a liquid level sensor or the like that can continuously acquire data on the water level H in real time. This allows fluctuations in the water level H (the state of the water W to be treated in the dehydrator 2) to be quickly grasped, and enables the control unit 5 to respond quickly and appropriately.

Here, the water level H can be measured by measuring the water level in the untreated water retention sections 211A and 211B in the casing 21.
The water level H in the untreated water retention sections 211A, 211B increases or decreases depending on the concentration of solids in the untreated water W filled in the casing 21. For example, an increase in the water level H indicates an increase in the solids concentration in the casing 21, and a decrease in the water level H indicates a decrease in the solids concentration in the casing 21. This makes it possible to grasp the state (solids concentration) of the untreated water W in the dehydrator 2 without measuring the solids concentration in the untreated water W using a sludge concentration meter or the like.

Data related to the water level H measured by the measuring unit 4 is input to the control unit 5, which will be described later. It is preferable that the measuring unit 4 and control unit 5 are connected via communication means or wiring to enable input, and that the data measured by the measuring unit 4 is sent and received electrically, but this is not limited to this. Another example of an input means is for the operator to manually input data related to the water level H obtained by visual inspection of the measuring unit 4 directly into the control unit 5.

[Control Unit]
The control unit 5 controls the supply unit 3 based on data relating to the water level H measured by the measurement unit 4, and controls the amount of water W to be treated supplied to the dehydrator 2.
1, the control unit 5 is connected to the supply unit 3 and the measurement unit 4 so as to be able to input, output, and control them. The control unit 5 is also preferably provided with a calculation unit (not shown) that performs a comparison calculation between the water level H data acquired by the measurement unit 4 and a preset standard water level.
This allows data regarding the water level H obtained by the measurement unit 4 to be input into the control unit 5, and the control unit 5 can instruct the supply unit 3 to control the supply amount of the treated water W based on the results of a comparison between the data regarding the water level H and the standard water level so that the data regarding the water level H obtained by the measurement unit 4 meets the standard water level.

An example of control by the control unit 5 will be described.
In this embodiment, the control unit 5 controls the supply amount (flow rate) of the treated water W supplied from the supply unit 3 so that the water level H of the treated water W in the casing 21 in the dehydrator 2 remains constant, thereby maintaining a constant head pressure in the dehydrator 2 (pushing pressure in the dehydration unit 22), improving dehydration efficiency and enabling the dehydration process to continue stably.
Furthermore, maintaining a constant head pressure in the dehydrator 2 is equivalent to maintaining a constant concentration of solids remaining in the dehydrator 2. Therefore, by controlling the supply amount (flow rate) of the water W to be treated supplied from the supply unit 3 so that the water level H of the water W in the casing 21 of the dehydrator 2 is constant, it is possible to control the amount of solids in the water W to be treated in the dehydrator to be constant even if the solids concentration in the water W fluctuates. This allows the dehydrator 2 to continuously perform dehydration treatment on a constant amount of solids, making it possible to maintain a constant amount of solids discharged after dehydration and to suppress a decrease in the recovery amount of solids (dehydrated cake D) concentrated through the dehydration treatment, thereby significantly improving the work efficiency of the dehydration treatment.

More specifically, the water level H at which a head pressure is obtained that allows stable dewatering in the dehydrator 2 is set as the reference water level, and if the water level H measured by the measurement unit 4 exceeds the reference water level, the control unit 5 instructs the supply unit 3 to reduce the supply amount (flow rate) of the water to be treated W supplied to the dehydrator 2, and the supply unit 3 drives the pump P and the flow rate variable mechanism to reduce the supply amount (flow rate) of the water to be treated W supplied to the dehydrator 2. If the water level H does not meet the reference water level, an instruction is sent to the supply unit 3 to increase the supply amount (flow rate) of the water to be treated W, and if the water level H is the same as the reference water level, an instruction is sent to the supply unit 3 to maintain the supply amount (flow rate) of the water to be treated W constant.

The dehydration system 100 in this embodiment is particularly suitable for use when the sediment components that have undergone solid-liquid separation treatment in the solid-liquid separation tank 1 or the like are supplied to the dehydrator 2 as water to be treated W.
As described above, when the sediment components discharged from the solid-liquid separation tank 1 are supplied to the dehydrator 2 as the treated water W, the amount of solids (solid concentration) in the treated water W supplied to the dehydrator 2 gradually decreases.
On the other hand, in the dehydration system 100 of this embodiment, the supply amount of the water to be treated W is controlled so that the water level H becomes the reference water level, so that even if the amount of solids in the water to be treated W gradually decreases, the dehydrator 2 can always maintain an appropriate head pressure, that is, the solids concentration is maintained appropriately to continue the dehydration process stably.
Furthermore, in the dehydration system 100 of this embodiment, even if there are fluctuations in the solid concentration in the water to be treated W, the supply unit 3 can perform appropriate control to prevent a decrease in the efficiency of the dehydration treatment. Therefore, there is no need to provide a storage tank (sludge storage tank) that was provided in conventional dehydration systems to level out fluctuations in the solid concentration. This also has the effect of enabling significant reductions in the installation cost and installation space of the system.

The operations of the supply unit 3, measurement unit 4, and control unit 5 described above may be performed automatically by a control program or may include manual operation by an operator. From the perspective of reducing the workload on the operator, it is preferable to automatically control the operation of the measurement unit 4 and control unit 5. This makes it possible to reduce the costs associated with maintaining and managing the dehydration system 100.

[Second embodiment]
FIG. 4 is a schematic explanatory diagram showing the configuration of a dehydration system 200 according to a second embodiment of the present invention.
The dehydration system 200 in this embodiment is characterized in that, instead of the flocculant addition section 7 in the dehydration system 100 in the first embodiment, a flocculant mixing tank 8 is provided, and flocculant G is added and mixed with the water to be treated W in the flocculant mixing tank 8.
This makes it possible to more efficiently flocculate the solids with the coagulant G as a pretreatment for the dehydration treatment in the dehydrator 2.

The dehydration system 200 of the second embodiment will now be described.
Note that, among the configurations of the dehydration system 200 of this embodiment, the description of the same configurations as those of the dehydration system 100 of the first embodiment will be omitted.

As shown in Figure 4, the dehydration system 200 includes a solid-liquid separation tank 1, a dehydrator 2, a supply unit 3, a measurement unit 4, a control unit 5, a flocculant storage tank 6, a flocculant mixing tank 8, a supply line L1, and an addition line L2.

[Flocculant mixing tank]
In this embodiment, the flocculant mixing tank 8 is installed and connected to the supply line L1 and the addition line L2, and stores the water to be treated W supplied from the supply section 3 to the dehydrator 2. By adding and stirring the flocculant G to the water to be treated, the solids are flocculated as a pretreatment for the dehydration treatment by the dehydrator 2.

The flocculant mixing tank 8 may be of any structure or size as long as it is capable of stirring and mixing the water to be treated W and the flocculant G. For example, the water to be treated W and the flocculant G may be mixed using stirring blades rotated by the power of an electric motor or the like. In this case, the water to be treated W and the flocculant G can be mixed more uniformly.

Furthermore, in the dewatering system 200 of this embodiment, at least one flocculant mixing tank 8 is required, and multiple tanks may be provided depending on the type and properties of the flocculant G added to the water to be treated W. This makes it possible to add multiple flocculants G in combination to the water to be treated W, thereby achieving more stable floc formation and improving the efficiency of the dewatering process.

The above-described embodiment shows an example of a dehydration system and dehydration method. The dehydration system and dehydration method according to the present invention are not limited to the above-described embodiment, and the dehydration system and dehydration method according to the above-described embodiment may be modified within the scope of the gist of the claims.

For example, multiple dehydrators may be connected together to perform the dehydration process. Specifically, the water to be treated that has been dehydrated using a screw press dehydrator may be further supplied to a multi-disk dehydrator for further dehydration. This further increases the dehydration efficiency of the water to be treated, allowing for the recovery of dehydrated cake with an even lower moisture content.

The dehydration system and dehydration method of the present invention can be used to dehydrate water containing solids. For example, they can be used to dehydrate various types of water generated at water treatment plants such as sewage treatment plants and wastewater treatment plants, food factories, plating factories, paper mills, dredging sites, construction sites, etc.

100, 200... Dehydration system, 1... solid-liquid separation tank, 11... agitator blade, 12... treated water discharge section, 13... sedimentation component discharge section, 2, 2A, 2B... dehydrator, 21, 21A, 21B... casing, 211A, 211B... treated water retention section, 212A, 212B... dehydration section arrangement area, 22, 22A, 22B... dehydration section, 221A... screw, 221B... multiple the disk, 222A...screen, 23, 23A, 23B...water to be treated supply section, 24, 24A, 24B...dehydrated cake discharge section, 25A, 25B...filtrate discharge section, 3...supply section, 4...measuring section, 5...control section, 6...flocculant storage tank, 7...flocculant addition section, 8...flocculant mixing tank, L1...supply line, L2...addition line, D...dehydrated cake, H...water level, W...water to be treated

Claims (5)

A dehydration system that directly dehydrates the water to be treated that contains solids after treatment in a solid-liquid separation tank,
A dehydrator including a casing and a dehydration unit,
The dehydrator is a screw press dehydrator or a multi-disk dehydrator,
The dehydration unit of the dehydrator is immersed in the water to be treated,
A dehydration system characterized by controlling the amount of the water to be treated supplied to the dehydrator so that the water level in the casing remains constant. A flocculant addition unit is provided for adding a flocculant,
The dehydration system according to claim 1 , wherein the flocculant adding unit adds a constant amount of the flocculant to the water to be treated. A supply unit that varies the flow rate of the water to be treated,
The dehydration system according to claim 1 or 2, wherein the supply unit controls the amount of the water to be treated supplied to the dehydrator. The dehydration system according to any one of claims 1 to 3, wherein the water to be treated is continuously supplied into the casing. A dehydration method for directly dehydrating water containing solids after treatment in a solid-liquid separation tank, comprising:
A screw press dehydrator or a multiple disk type dehydrator is provided with a casing and a dehydration unit, and the dehydration unit is immersed in the water to be treated.
A dehydration method comprising a control step of controlling the amount of water to be treated supplied to the dehydrator so that the water level in the casing remains constant.