Dehydration system and dehydration method

Abstract

To provide a dehydration system and a dehydration method that improve work efficiency in a dehydration treatment.SOLUTION: There is provided a dehydration system including: a solid-liquid separation tank 1 for solid-liquid separating raw water sent from sources (various water treatment plants, various factories, etc.); a dehydrator 2 for dehydrating water W to be treated containing a solid supplied from the solid-liquid separation tank 1, separating and removing the water from the solid, and recovering a concentrated solid; a supply unit 3 for sending the water W to be treated from the solid-liquid separation tank 1 to the dehydrator 2; a measurement unit 4 for measuring a water level of the water W to be treated in the dehydrator 2; and a control unit 5 for controlling the supply unit 3 based on a measurement result from the measurement unit 4, wherein the supply unit 3 is provided on a supply line L1 which is a pipe for supplying the water W to be treated from the solid-liquid separation tank 1 to the dehydrator 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dehydration system and a dehydration method for dehydrating water containing solids. [Background technology]

[0002] 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 performing dehydration treatment, and it is also common to add chemicals (flocculants) to the water to be treated that is the target of dehydration treatment in order to improve the efficiency of the dehydration treatment.

[0003] For example, Patent Document 1 describes that a belt press type dehydrator having a gravity dehydration filtration section is used as a dehydrator, and in the dehydration treatment of water to be treated that contains solids such as sludge, the amount of coagulant added is controlled 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-254000 Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Document 1, it is known that in the dehydration treatment of water containing solids, the amount of flocculant added is adjusted to achieve a desired concentration and dehydration efficiency. However, it is difficult to always control the amount of flocculant added to the water to be treated so that it is optimal, and in order to achieve stable dehydration treatment, the amount of flocculant added must be increased to prevent a shortage of flocculant. This results in not only problems of increased costs, but also problems of reduced filtration efficiency of the water to be treated if too much flocculant is added.

[0006] 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 with a dehydration section 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 a pressing pressure from 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 different from the means described in Patent Document 1 is required to perform stable dehydration processing and improve dehydration efficiency.

[0007] Furthermore, when solid-containing water is subjected to solid-liquid separation in a solid-liquid separation tank or the like and then supplied to a dehydrator, the solid concentration in the water is generally high initially, but as the water is supplied to the dehydrator, the solid concentration in the water in the solid-liquid separation tank decreases. Therefore, the amount of solids in the water being supplied to the dehydrator decreases. As a result, the amount of solids discharged from the dehydrator decreases, resulting in a decrease in the recovery amount of concentrated solids after dehydration, which leads to a problem of a deterioration in the efficiency of the dehydration process.

[0008] Therefore, the object of the present invention is to provide a dehydration system and a dehydration method that, in the dehydration process of water to be treated containing solids, uses a dehydrator whose dehydration section is immersed in the water to be treated, thereby stably continuing the dehydration process and keeping the amount of solids discharged after dehydration constant even if the solid concentration in the water to be dehydrated fluctuates, thereby improving the working efficiency of the dehydration process. [Means for solving the problem]

[0009] 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 level of the water 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 efficiency of dehydration processing, and thus completed the present invention. That is, the present invention provides the following dehydration system and dehydration method.

[0010] The dehydration system of the present invention, which solves the above problems, is a dehydration system that dehydrates water to be treated that contains solids, and is characterized by having a dehydrator equipped with a casing and a dehydration section, the dehydration section 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.

[0011] According to the dehydration system of the present invention, the amount of water to be treated supplied to a dehydrator, which is equipped with a casing and a dehydration section and has the dehydration section 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.

[0012] Furthermore, one embodiment of the dehydration system of the present invention has a flocculant addition section that adds 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.

[0013] 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.

[0014] 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. Furthermore, 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 can control the amount of solids contained in the water to be treated supplied to the dehydrator 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.

[0015] 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 increasing the 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. [Effects of the Invention]

[0016] According to the present invention, in the dehydration process of water to be treated that contains solids, a dehydrator with a dehydration section immersed in the water to be treated is used, which allows the dehydration process to continue stably and keeps the amount of solids discharged after dehydration constant even if the solid concentration in the water to be dehydrated fluctuates, thereby providing a dehydration system and a dehydration method that improves the work efficiency of the dehydration process. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic explanatory diagram showing a dehydration system according to a first embodiment of the present invention. [Figure 2] 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. [Figure 3] FIG. 1 is a schematic explanatory diagram showing a multi-disk dehydrator, which is an example of a dehydrator according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a schematic explanatory diagram showing a dehydration system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The dehydration system of the present invention performs dehydration treatment on water to be treated that contains solids, and more specifically, 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.

[0019] 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.

[0020] Hereinafter, embodiments of the dehydration system and dehydration method according to the present invention will be described in detail with reference to the drawings. Note that the dehydration method of 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 for explaining the dehydration system according to the present invention, and are not limited thereto.

[0021] [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 that separates raw water delivered from a generation source (such as a water treatment plant or a factory) into solids and liquids, and a dehydrator 2 that performs a dehydration treatment on water to be treated W (hereinafter sometimes simply referred to as "water to be treated W") containing solids 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 that delivers the water to be treated W from the solid-liquid separation tank 1 to the dehydrator 2, a measurement unit 4 that measures the level of the water to be treated W in the dehydrator 2, and a control unit 5 that controls the supply unit 3 based on the measurement results from the measurement unit 4. The supply unit 3 is provided on a supply line L1, which is a pipe that delivers 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.

[0022] In addition, in order to improve the dehydration efficiency of the dehydrator 2, it is preferable to perform a pretreatment on the water to be treated W, which is the target of treatment in this embodiment, to aggregate and flocculate the solid components in the water to be treated W before it is supplied to the dehydrator 2. As such pretreatment, addition of a flocculant G to the water W to be treated can be mentioned. 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.

[0023] First, the solid-liquid separation tank 1 functioning as a pretreatment in the dehydration system 100 of this embodiment and the configuration relating to the addition of the flocculant G (flocculant storage tank 6 and flocculant addition section 7) will be described.

[0024] [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 allowing the solid fraction to settle naturally, or the tank may be equipped with a flocculant addition means for adding a flocculant G (described below) and a stirring blade 11 for stirring the raw water, forming flocs in the solid-liquid separation tank 1 and separating the solid fraction and liquid fraction.

[0025] The solid-liquid separation tank 1 may be provided with a treated water discharge section 12 that discharges the separated liquid as treated water from the upper side of the tank to the outside of the tank, and a sedimentation component discharge section 13 that withdraws sedimentation components including the settled solids from the bottom side of the tank to the outside of the tank.

[0026] 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 continues to be extracted.

[0027] [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 used.

[0028] The flocculant G to be added to the water to be treated W is not particularly limited as long as it has the effect of flocculating solids, and any flocculant may be used. For example, inorganic flocculants and polymer flocculants may be used, and are selected appropriately depending on the treatment conditions.

[0029] 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 and polyethylene oxide, as well as anionic sodium polyacrylate, partial hydrolyzed polyacrylamide, partially sulfomethylated polyacrylamide, and poly(2-acrylamido)-2-methylpropane sulfate, as well as amphoteric copolymers of acrylamide, aminoalkyl methacrylate, and sodium acrylate. These flocculants G may be used alone or in combination depending on the treatment conditions.

[0030] 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 dehydration treatment in the dehydrator 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 concentration of solids in the water to be treated W. As will be described later, in the dehydration system 100 of this embodiment, the solid 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 solids can be kept constant, making it possible to perform stable floc formation. This prevents the flocculant G from being excessively supplied relative to the concentration of solids in the water to be treated W, thereby reducing the cost of using flocculant G and improving the dehydration efficiency and recovery amount of solids.

[0031] 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. For example, as shown in Fig. 1, 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.

[0032] 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 water to be treated 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'').

[0033] The dehydrator 2 in this embodiment includes 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 includes a water to be treated supply section 23 to which the water to be treated W is supplied via a supply line L1, and a dehydrated cake discharge section 24 from which a dehydrated cake D formed by the dehydration section 22 is discharged.

[0034] 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 acting on the dehydration section 22), thereby enabling stable dehydration processing.

[0035] 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. An example of the dehydrator 2 in this embodiment is a dehydrator called a screw press dehydrator or a multi-disk dehydrator.

[0036] (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.

[0037] 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 treatment by compressing, rotating, and transporting the treated water W through the rotational drive of the screw 221A to separate and remove water from solids. In addition to the casing 21A and the dehydration section 22A, the dehydrator 2A in this embodiment is equipped with a water-to-be-treated supply section 23A, a dehydrated cake discharge section 24A, and a filtrate discharge section 25A.

[0038] The treated water retention section 211A in the casing 21A is an area located above the dehydration section installation 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 dehydration unit installation area 212A in the casing 21A is an area forming a space for installing the dehydration unit 22A, and houses a screw 221A and a screen 222A.

[0039] The screw 221A in the dewatering unit 22A has spiral blades attached to a conical rotor, and is driven to rotate by a drive mechanism (not shown). In this case, the conical rotor may be configured so that the diameter increases in the direction in which the water to be treated W is transported (away from the water to be treated supply unit 23A), thereby reducing the space for transporting the water to be treated W. As a result, by rotating the screw 221A, the water to be treated W containing solids can be transported in the direction of the dewatered cake discharge unit 24A, and the further away from the water to be treated supply unit 23A (the closer to the dewatered cake discharge unit 24A), the greater the pressure that can be applied to the water to be treated 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.

[0040] The screen 222A in the dewatering section 22A is provided around the screw 221A. The water to be treated W transported by the screw 221A is separated into solids and water through the screen 222A. The water is discharged to the filtrate discharge section 25A through the screen 222A, and 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, the screen 222A may be made of metal mesh or punched metal. In this case, the high strength and durability make it possible to reduce maintenance costs.

[0041] 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, it may be provided so as to be connected to the untreated water retention section 211A.

[0042] Dehydrated cake discharge section 24A is for discharging dehydrated cake D to the outside of dehydrator 2A. Dehydrated cake discharge section 24A may be provided at any location as long as it can discharge dehydrated cake D that has been sufficiently dehydrated by dehydration section 22A to the outside of casing 21A. For example, as shown in FIG. 2, dehydrated cake discharge section 24A may be provided at the terminal end of dehydration section 22A in the transport direction of the water to be treated W and at the bottom of casing 21A.

[0043] The filtrate discharge section 25A discharges water (filtrate) separated from the solid content of 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 FIG. 2, by providing a guide made 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.

[0044] 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 as water W, which is supplied from water supply section 23A to water retention section 211A in casing 21A. If the concentration of solids contained in water W is low, most of the water contained in water W is easily separated from the solids through screen 222A and quickly discharged to the outside of dehydrator 2A via filtrate discharge section 25A. As a result, little water W remains in water retention section 211A, and the water level H remains low. On the other hand, if the concentration of solids contained in water W exceeds a certain level, or if the concentration of solids in water retention section 211A exceeds a certain level due to continuous supply of water W into casing 21A, separation of water from 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 dehydration section installation area 212A, and the dehydration section 22A is immersed in the water to be treated W.

[0045] 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 to the outside of the dewatering machine 2A via the filtrate discharge section 25A. Then, 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 to be treated W by dehydrator 2A progresses.

[0046] The dehydrator 2A as the dehydrator 2 in this embodiment is not limited to the structure shown in Fig. 2. A dehydrator having a known structure and a known additional mechanism can be used as the dehydrator 2A. 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 in which the screen 222A has a multi-plate structure combining movable plates and fixed plates can be used.

[0047] (Multiple disc dehydrator) Another example of the dehydrator 2 in this embodiment is a multi-disk dehydrator. FIG. 3 is a schematic explanatory diagram showing a multi-disk dehydrator as an example of the dehydrator in this embodiment. Hereinafter, a multi-disk dehydrator 2B, which is an example of the dehydrator 2 in this embodiment, will be described with reference to FIG.

[0048] 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 water from the solids as the treated water W containing solids passes between the disks 221B, thereby performing continuous dehydration processing. Further, in this embodiment, dehydrator 2B includes, in addition to casing 21B and dehydration section 22B, untreated water supply section 23B, dehydrated cake discharge section 24B, and filtrate discharge section 25B. Here, the treated water supply section 23B, dehydrated cake discharge section 24B, and filtrate discharge section 25B in the dehydrator 2B have the same configurations or functions as the treated water supply section 23A, dehydrated cake discharge section 24A, and filtrate discharge section 25A in the above-mentioned dehydrator 2A, so their explanations will be omitted.

[0049] 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, which will be described later. On the other hand, dehydration unit installation area 212B in casing 21B is an area forming a space in which dehydration unit 22B is installed, and a plurality of disks 221B are housed in the vertical direction.

[0050] The multiple disks 221B in the dewatering unit 22B are made up of a combination of circular metal plates, which are 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), and the rotation of the multiple disks 221B transports the water to be treated W and separates and removes moisture through the gaps between the multiple disks 221B. The vertical spacing of the multiple disks 221B can be reduced toward the transport direction of the water to be treated W (away from the water to be treated supply unit 23B), thereby reducing the space for transporting the water to be treated W. Thus, by rotating the multiple disks 221B, the water to be treated W containing solids can be transported toward the dewatered cake discharge unit 24B. Furthermore, the farther the disks are from the water to be treated supply unit 23B (the closer they are to the dewatered cake discharge unit 24B), the greater the pressure that can be applied to the water to be treated 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. The plurality of discs 221B may all be composed of movable discs (rotating bodies) or may be a combination of movable and fixed discs, and the number, shape, and size of the plurality of discs 221B forming dehydration section 22B are not particularly limited.

[0051] 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 water supply section 23B to water retention section 211B in casing 21B. If the concentration of solids contained in water W is low, most of the water contained in water W is easily separated from the solids through the gaps between multiple disks 221B and is quickly discharged outside dehydrator 2B through filtrate discharge section 25B. On the other hand, if the concentration of solids contained in water W exceeds a certain level, or if water W is continuously supplied into casing 21B and the concentration of solids in water retention section 211B exceeds a certain level, 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.

[0052] 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, so that the water to be treated W is compressed and separated 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. Then, 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 to be treated W by dehydrator 2B progresses.

[0053] [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, which varies 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 to be treated W is provided, and the supply unit 3 controls the flow rate of the water to be treated W so that the water level H of the water to be treated 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 in the dehydrator 2 and enables stable dehydration to be continued. Furthermore, when controlling the amount of water to be treated W supplied to the dehydrator 2A, it is not necessary to specifically grasp the solid concentration in the water to be treated W. This eliminates the need to use measuring equipment such as a sludge concentration meter to grasp the solid concentration in the water to be treated W, and can be done with a simple configuration.

[0054] Furthermore, by controlling the supply amount of the water W to be treated by varying the flow rate of the water W to be treated using the supply unit 3 in this embodiment, continuous dehydration treatment is possible without stopping the supply of the water W to the dehydrator 2. This is particularly effective in a system in which the water W to be treated is constantly supplied from a source that generates the water W to be treated that requires dehydration treatment. Examples of such sources include sewage treatment plants and wastewater treatment plants.

[0055] In this embodiment, there is no particular limitation on the specific combination of the pump P and the flow rate varying mechanism for the supply unit 3. For example, the flow rate varying mechanism may be a mechanism for controlling the operating frequency of the pump P, or a mechanism consisting of a combination of a flow rate adjustment valve and a flow meter.

[0056] [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 the 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. Furthermore, the measuring unit 4 is not limited to those that use measuring equipment. For example, a scaled bar 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.

[0057] Here, the water level H may be measured by measuring the water level in the treated 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.

[0058] Data relating to the water level H measured by the measuring unit 4 is input to the control unit 5, which will be described later. As a means for inputting data, it is preferable that the measuring unit 4 and the control unit 5 are connected to each other via a communication means or wiring so 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 example, data relating to the water level H obtained by visual inspection by an operator at the measuring unit 4 being manually input directly by the operator to the control unit 5.

[0059] [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 that is 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. In addition, the control unit 5 preferably includes 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 relating to the water level H obtained by the measurement unit 4 to be input into the control unit 5, and based on the results of a comparison between the data relating to the water level H and the standard water level, the control unit 5 can instruct the supply unit 3 to control the amount of water W being treated so that the data relating to the water level H obtained by the measurement unit 4 meets the standard water level.

[0060] 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 water to be treated W supplied from the supply unit 3 so that the water level H of the water to be treated W in the casing 21 in the dehydrator 2 remains constant, thereby maintaining the head pressure in the dehydrator 2 (the pushing pressure in the dehydration unit 22) constant, improving the 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 to be treated W supplied from the supply unit 3 so that the water level H of the water to be treated W in the casing 21 of the dehydrator 2 is constant, it is possible to control the amount of solids in the water to be treated W in the dehydrator to be constant even if the solids concentration in the water to be treated W fluctuates. This allows the dehydrator 2 to continuously perform dehydration treatment on a constant amount of solids, making it possible to keep the discharge amount of solids after dehydration constant and suppress a decrease in the recovery amount of solids (dehydrated cake D) concentrated through the dehydration treatment, thereby making it possible to significantly improve the work efficiency of the dehydration treatment.

[0061] More specifically, a water level H at which a hydraulic head pressure is obtained that allows stable dewatering in the dehydrator 2 is set in advance as a reference water level, and when the water level H measured by the measuring 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. Furthermore, when 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 when 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.

[0062] 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 water to be treated W, the amount of solids (solid concentration) in the water to be treated 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 solid 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 for the system.

[0063] The operations of the supply unit 3, measurement unit 4, and control unit 5 may be performed automatically by a control program or may include manual operation by an operator. From the viewpoint of reducing the workload of the operator, it is preferable to automatically control the operations of the measurement unit 4 and control unit 5. This makes it possible to reduce the cost of maintaining and managing the dehydration system 100.

[0064] [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 it has a flocculant mixing tank 8 instead of the flocculant addition section 7 in the dehydration system 100 in the first embodiment, and adds and mixes flocculant G to the water to be treated W in the flocculant mixing tank 8. This allows the solids to be flocculated more efficiently with the flocculant G as a pretreatment for the dehydration treatment in the dehydrator 2.

[0065] A dehydration system 200 according to a 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.

[0066] As shown in FIG. 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.

[0067] [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.

[0068] The flocculant mixing tank 8 may have any structure or size as long as it can agitate and mix 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 by agitating 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.

[0069] Furthermore, in the dehydration system 200 of this embodiment, at least one flocculant mixing tank 8 may be provided, and multiple tanks may be provided depending on the type and properties of the flocculant G to be added to the water to be treated W. This makes it possible to add a combination of multiple flocculants G to the water to be treated W, thereby achieving more stable floc formation and improving the efficiency of the dehydration treatment.

[0070] The above-described embodiment shows an example of a dehydration system and a dehydration method. The dehydration system and the dehydration method according to the present invention are not limited to the above-described embodiment, and the dehydration system and the dehydration method according to the above-described embodiment may be modified within the scope of the gist of the claims.

[0071] For example, multiple dehydrators may be connected 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 allows for further improvement in the dehydration efficiency of the water to be treated and for the recovery of dehydrated cake with a reduced water content. [Industrial Applicability]

[0072] The dehydration system and dehydration method of the present invention can be used to dehydrate solid-containing water to be treated, for example, in the dehydration of various types of water to be treated generated in water treatment plants such as sewage treatment plants and wastewater treatment plants, food factories, plating factories, paper mills, dredging sites, construction sites, etc. [Explanation of symbols]

[0073] 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 supply unit, 24, 24A, 24B...dehydrated cake discharge unit, 25A, 25B...filtrate discharge unit, 3...supply unit, 4...measuring unit, 5...control unit, 6...flocculant storage tank, 7...flocculant addition unit, 8...flocculant mixing tank, L1...supply line, L2...addition line, D...dehydrated cake, H...water level, W...water to be treated

Claims

1. 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 in that the amount of the water to be treated supplied to the dehydrator is controlled so that the water level in the casing remains constant.

2. 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.

3. 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.

4. A dehydration system described in any one of claims 1 to 3, characterized in that the treated water is continuously supplied into the casing.

5. 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.

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