Water treatment device, water treatment system, and water treatment method

Abstract

A water treatment device (10) is characterized in that: the water treatment device comprises a first separation tank (1) in which wastewater (11) is received and separated into first effluent and first sediment (15), a reaction tank (2) in which the first effluent is received and brought into contact with microorganisms for reaction, and a second separation tank in which reacted water is received from the reaction tank and separated into second effluent and second sediment (12); the water treatment device further comprises a sediment modification unit (4) which retrieves at least a portion of the second sediment and generates modified sediment (14) obtained by transforming flocs, which are aggregates of microorganisms contained in the second sediment; and the modified sediment is transferred to the first separation tank, or transferred upstream to the first separation tank, and mixed with the wastewater.

Description

Water treatment device, water treatment system, and water treatment method

[0001] The present disclosure relates to a water treatment device, a water treatment system, and a water treatment method.

[0002] Wastewater, such as sewage, undergoes separation and removal of solids contained in the wastewater in a primary sedimentation tank. After that, organic matter, nitrogen, etc. are biologically treated by activated sludge, a collection of microorganisms called flocs, in a reaction tank where oxygen is supplied. This activated sludge is then separated and removed in a final sedimentation tank, after which the wastewater is discharged into a river or reused. Efforts have been made to recover the solids and activated sludge separated and removed in the primary and final sedimentation tanks during this water treatment process as sediments and use them as energy. Patent Document 1 discloses a method for increasing the amount of methane gas generated from the recovered sludge by providing a mixer that mixes excess sludge generated in biological treatment with organic wastewater as raw water, mixing the excess sludge with the organic wastewater, and performing solid-liquid separation in the primary sedimentation tank.

[0003] International Publication No. 2016 / 148086

[0004] However, although mixing oxygenated excess sludge with organic wastewater increases the amount of organic matter recovered in the primary sedimentation tank, there was a problem in that simply mixing oxygenated excess sludge with organic wastewater resulted in a low organic matter recovery rate.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a water treatment device that can improve the recovery rate of organic matter in the treatment of organic wastewater, as well as a water treatment system and a water treatment method using the same.

[0006] The water treatment device according to the present disclosure comprises a first separation tank that receives wastewater and separates it into a first effluent and a first precipitate; a reaction tank that receives the first effluent and brings the first effluent into contact with microorganisms to cause a reaction; and a second separation tank that receives the reacted water from the reaction tank and separates the reacted water into a second effluent and a second precipitate. The water treatment device further comprises a precipitate transformation unit that takes in at least a portion of the second precipitate and generates a modified precipitate by transforming flocs, which are aggregates of microorganisms contained in the second precipitate, and transports the modified precipitate to the first separation tank or upstream of the first separation tank and mixes it with wastewater.

[0007] The water treatment system according to the present disclosure also includes a water treatment device according to the present disclosure, a concentration device that concentrates precipitates including at least a first precipitate transferred from the water treatment device to form concentrated sludge, and a digestion device that heats the concentrated sludge to decompose organic matter in the concentrated sludge and generate digester gas.

[0008] The water treatment method according to the present disclosure also includes a first separation step of receiving wastewater and separating it into a first effluent and a first precipitate; a reaction step of receiving the first effluent and contacting the first effluent with microorganisms to cause a reaction; a second separation step of receiving the reaction water obtained in the reaction step and separating the reaction water into a second effluent and a second precipitate; a precipitate transformation step of taking in at least a portion of the second precipitate and transforming the state of flocs, which are aggregates of microorganisms contained in the second precipitate, to produce a modified precipitate; and a mixing step of mixing the generated modified precipitate with wastewater and incorporating and precipitating organic matter in the wastewater.

[0009] According to the present disclosure, by returning the modified precipitate obtained by modifying the second precipitate to the first separation tank or upstream of the first separation tank, more of the organic matter contained in the wastewater can be precipitated in the first precipitate, and the recovery amount of the first precipitate separated in the first separation tank can be increased, i.e., the recovery rate of the organic matter recovered as the first precipitate can be improved.

[0010] FIG. 1 is a schematic configuration diagram of a water treatment device according to embodiment 1. FIG. 2 is an image diagram of generating modified flocs according to embodiment 1. FIG. 3 is an image diagram of flocs adsorbing organic matter according to embodiment 1. FIG. 4 is an image diagram of modified flocs adsorbing organic matter according to embodiment 1. FIG. 5 is a schematic configuration diagram showing an example of a precipitate transformation unit according to embodiment 1. FIG. 6 is a schematic configuration diagram of an apparatus for determining a DOC removal rate according to embodiment 1. FIG. 7 is a relationship diagram between Q / V and DOC removal rate according to embodiment 1. FIG. 8 is a relationship diagram between mixing time of wastewater and modified precipitate and amount of precipitate according to embodiment 1. FIG. 9 is a schematic configuration diagram showing an example of a precipitate transformation unit according to embodiment 1. FIG. 10 is a schematic configuration diagram showing an example of a precipitate transformation unit according to embodiment 1. FIG. 11 is a schematic configuration diagram of a water treatment device according to embodiment 2. FIG. 12 is a schematic configuration diagram of a water treatment device according to embodiment 2. FIG. 13 is a schematic configuration diagram of a water treatment device according to embodiment 3. FIG. 14 is a schematic configuration diagram of a water treatment device according to embodiment 4. FIG. 15 is a schematic configuration diagram of a water treatment device according to embodiment 5. FIG. 16 is a schematic configuration diagram of a water treatment system according to embodiment 6. FIG. 17 is a flowchart showing a treatment flow executed by a water treatment device according to embodiment 7. 10 is a flowchart showing a processing flow executed by a water treatment device according to Embodiment 7. FIG. 11 is a schematic configuration diagram showing an example of a processing circuit that realizes each function of the water treatment device according to Embodiment 7. FIG.

[0011] The embodiments will be described with reference to the drawings, in which the same contents and corresponding parts are designated by the same reference numerals and detailed description thereof will be omitted.

[0012] Embodiment 1. Figure 1 is a schematic diagram of a water treatment device 10 according to Embodiment 1. The water treatment device 10 includes a first separation tank 1 that receives wastewater 11 and separates it into a first effluent 16 and a first precipitate 15; a reaction tank 2 that receives the first effluent 16 and contacts the first effluent 16 with a microbial aggregate (floc) to cause a reaction; a second separation tank 3 that receives reacted water 17 from the reaction tank 2 and separates the reacted water 17 into a second effluent and a second precipitate 12; and a first separation tank 1 that takes at least a portion of the second precipitate 12 into a precipitate transformation unit 4, transforms the second precipitate 12 to produce a transformed precipitate 14, and returns the transformed precipitate 14 to the first separation tank 1 or upstream of the first separation tank 1 to mix it with wastewater 11 to increase the amount of the first precipitate 15. A portion of the second precipitate 12 is returned to the reaction tank 2. The second separation tank 3 may include a membrane-based system, and the membrane may be integrated with the reaction tank 2.

[0013] As shown in Figure 2, the second precipitate 12 is formed by the aggregation of a large number of flocs 151, which are aggregates of microorganisms. Furthermore, the flocs 151 are aggregates of floc constituent units 152. The precipitate transformation unit 4 transforms the state of the flocs 151 in the second precipitate 12 to generate modified flocs 141. The modified flocs 141 are similarly aggregates of modified floc constituent units 142. A large number of modified flocs 141 aggregate to form the modified precipitate 14. For example, the modified flocs 141 are formed by breaking down the flocs 151 into small, dispersed clumps. The modified floc constituent units 142 may have the same properties as the floc constituent units 152, or may have different properties due to dissolution, decomposition, etc.

[0014] Fig. 3 is a diagram illustrating an image of flocs 151 coming into contact with wastewater 11 and solid organic matter 111 and dissolved organic matter 112 in the wastewater 11 being adsorbed onto the flocs 151. Because the flocs 151 are an aggregation of microorganisms, the microorganisms take in and adsorb the solid organic matter 111 and dissolved organic matter 112. Fig. 4 is a diagram illustrating an image of modified flocs 141 coming into contact with wastewater 11 and solid organic matter 111 and dissolved organic matter 112 in the wastewater 11 being adsorbed onto the modified flocs 141. Similarly, because the modified flocs 141 are an aggregation of microorganisms, the microorganisms take in and adsorb the solid organic matter 111 and dissolved organic matter 112. Furthermore, the surface area per unit volume of the modified flocs 141 is increased by, for example, being crushed, compared to unmodified flocs 151, and the modified flocs 141 can take in and adsorb more of the solid organic matter 111 and dissolved organic matter 112 in the wastewater 11.

[0015] The modified floc 141 may be floc 151 with a complex surface shape. Refining the floc or making the surface shape complex increases the surface area per unit volume of the floc, thereby increasing the amount of organic matter taken up by microorganisms and the amount of organic matter adsorbed by microorganisms. As a result, the modified floc 141 can contain more solid organic matter 111 and dissolved organic matter 112. The modified precipitate 14 thus modified can contain more solid organic matter 111 and dissolved organic matter 112 than the second precipitate 12 in the first separation tank 1, allowing more organic matter to be precipitated as the first precipitate 15. Furthermore, when a flocculant (described later) is added to the wastewater 11, the solid organic matter 111 and dissolved organic matter 112 that could not be taken up or adsorbed by the modified precipitate 14 can be flocculated and precipitated, allowing even more solid organic matter 111 and dissolved organic matter 112 to be contained in the first precipitate 15 in the first separation tank 1. Furthermore, the solid organic matter 111 and the dissolved organic matter 112 are taken up and adsorbed by the modified floc 141, thereby reducing the amounts of the solid organic matter 111 and the dissolved organic matter 112 in the first effluent 16 separated in the first separation tank 1. When the amounts of the solid organic matter 111 and the dissolved organic matter 112 in the first effluent 16 are reduced, the amount of aeration required to remove these organic matters by biological treatment in the reaction tank 2 can be reduced, thereby enabling energy conservation in the water treatment system.

[0016] Since the amount of organic matter contained in the flocs 151 can be increased by increasing the surface area per unit volume of the flocs 151, the generation of the modified flocs 141 can be achieved not only by a process of crushing the flocs 151 but also by a decomposition process or a dissolution process. That is, the precipitate modification unit 4 has the effect of increasing the surface area per unit volume by making the flocs 151 in the second precipitate 12 finer or more complex in shape, and performs at least one of a process of crushing, dissolving, and decomposing the flocs 151 in the second precipitate 12 in the precipitate modification unit 4. Here, the process may be one of crushing, decomposition, and dissolution, or a combination of two or more of these processes.

[0017] The precipitate transformation unit 4 for crushing the flocs 151 may be configured as shown in FIG. 5 . The precipitate transformation unit 4 includes a circulation circuit 47 that uses a pump 41 to take in the second precipitate 12 from a vessel 13 to which the second precipitate 12 has been sent and return it to the vessel 13. The pump 41 applies pressure to an absorber 43 in the circulation circuit 47, sending out the second precipitate 12, which then passes through the absorber 43, which has an inner diameter smaller than that of the circulation circuit. The absorber 43 is provided with an inlet 42 through which gas or liquid can be introduced. This generates negative pressure within the absorber 43, causing the gas or liquid to be sucked in through the inlet 42, crushing the flocs 151 in the second precipitate 12. The magnitude of the negative pressure in the absorber 43 in the circulation circuit can be adjusted by the inner diameter of the absorber 43. The smaller the inner diameter of the absorber 43 relative to the inner diameter of the circulation circuit 47, the greater the negative pressure, allowing more gas or liquid to be sucked in and resulting in a greater crushing effect. In the absorber 43, the sucked gas or liquid is mixed with the flocs 151 in the second precipitate 12. Since the inner diameter gradually increases toward the circulation circuit 47 connected to the downstream side of the absorber 43, the pressure returns from negative to positive, and at this time the flocs 151 and the sucked gas or liquid are agitated by the pressure change, and the flocs 151 are crushed to become metamorphosed flocs 141.

[0018] That is, the device may be configured to generate negative pressure in the circulating second precipitate 12 to introduce at least one of gas and liquid. In such a configuration, the flocs 151 in the vessel 13 are crushed to become finer or more complex-shaped metamorphic flocs 141. Because the negative pressure generated in the absorber 43 is utilized, the gas or liquid to be sucked into the absorber 43 can be sucked into the absorber 43 without pressure, but the gas or liquid may also be pressurized before being sent to the absorber 43. Examples of the gas to be introduced include air, ozone, a mixture of air and ozone, and the like. Examples of the liquid include an alkaline solution such as sodium hydroxide, an acid solution such as sulfuric acid, and the like. When mixing gas and liquid, a larger flow rate ratio G(Gas) / L(Liquid) of the gas and liquid is preferred because it increases the mixing force and enhances the floc crushing effect. The amount of the second precipitate 12 in the vessel 13 can also be monitored by installing a water level gauge or the like in the vessel 13.

[0019] To determine the optimal Q / V value when the circulation flow rate of the second precipitate 12 is Q and the input amount is V, the relationship between the Q / V value and the DOC (dissolved organic matter) removal rate when the modified precipitate 14 obtained by treating the second precipitate 12 is mixed with the wastewater 11 was investigated using the equipment shown in Figure 6. For example, Q / V = 10 means that 10 times the amount of the second precipitate 12 input was circulated. The DOC removal rate here refers to the ratio of the difference in DOC in the wastewater 11 before and after input of the modified precipitate 14 to the DOC before input of the modified precipitate 14. An ejector was used as the absorber 43 to suck in air, generating negative pressure in the circulation circuit 47 and crushing the flocs 151 of the second precipitate 12 to generate modified flocs 141. The modified precipitate 14 and air bubbles 18 are present in the container 13. The modified precipitate 14 removed from the container 13 was mixed with the wastewater 11, and the concentration of the dissolved organic matter 112 was measured with a concentration meter 133 to determine the DOC removal rate.

[0020] As shown in Fig. 7, the larger the Q / V value, i.e., the larger the circulation flow rate Q relative to the input amount V, the higher the DOC removal rate, and the DOC removal rate remained roughly constant at Q / V = 120. Therefore, a Q / V value of 10 or more is preferable. Furthermore, since the larger the Q / V value, the longer the time and power required to generate the modified flocs 141, a Q / V value of 120 or less is preferable. Furthermore, from the viewpoint of shortening the treatment time and saving energy, a Q / V value of 10 or more and 60 or less, more preferably 10 or more and 40 or less, is preferable, and a sufficient DOC removal rate of 7% to 15% can be obtained. When the modified precipitate 14 containing the modified flocs 141 thus generated is mixed with the wastewater 11, the amount of the modified precipitate 14 is preferably 10 or more and 60 or less, more preferably 10 or more and 40 or less, and a sufficient amount of the modified precipitate 14 containing the modified flocs 141 generated in this manner is preferably 10 or more and 60 or less, more preferably 10 or more and 40 or less, and a sufficient DOC removal rate of 7% to 15% can be obtained. 3 The amount of the modified precipitate 14 per 1000 ml is 0.01 kg-DS (Dried Sludge) / m 3 Above, 0.5kgDS / m 3 By setting the concentration to 0.01 kg-DS / m or less, the amount of the first precipitate 15 could be effectively increased. 3 If it is smaller than this, a sufficient DOC removal rate cannot be obtained, and the 3 If the concentration is greater than this, the recovery of the first precipitate 15 in the first separation tank 1 will be insufficient, and part of the modified precipitate 14 containing the solid organic matter 111 and the dissolved organic matter 112 in the wastewater 11 will be contained in the first effluent 16 and flow into the reaction tank 2. More preferably, the concentration is 0.05 kg-DS / m 3 Above, 0.15kg-DS / m 3 It is better to do the following:

[0021] The mixing time of the wastewater 11 and the modified precipitate 14 may be extended to allow the solid organic matter 111 and the soluble organic matter 112 to be incorporated into or adsorbed by the modified floc 141, thereby enhancing the effect of containing the solid organic matter 111 and the soluble organic matter 112 in the modified precipitate 14. Figure 8 shows the relationship between the mixing time of the wastewater 11 and the modified precipitate 14 and the amount of precipitate of the first precipitate 15 (the conditions are the same as those in Table 1, which will be described later). This shows that the amount of precipitate cannot be increased until about 3 minutes after the modified precipitate 14 is mixed with the wastewater 11. This is because the short mixing time does not provide sufficient opportunity for the modified precipitate 14 to come into contact with the solid organic matter 111 and the soluble organic matter 112, resulting in insufficient uptake and adsorption of the solid organic matter 111 and the soluble organic matter 112 into the modified precipitate 14. Furthermore, the amount of precipitate of the first precipitate 15 increases rapidly from about 6 minutes. This is because the solid organic matter 111 and soluble organic matter 112 in the wastewater 11 come into contact with the modified floc 141 more frequently, and the solid organic matter 111 and soluble organic matter 112 are taken up and adsorbed by the modified floc 141. Thereafter, the increase in the amount of precipitate gradually slows down. Therefore, the mixing time of the modified precipitate 14 and the wastewater 11 is preferably longer than 5 minutes. Furthermore, to avoid excessively long mixing times, the mixing time is preferably between 6 and 20 minutes. By appropriately setting the Q / V value and mixing time in this way, the amount of precipitate of the first precipitate 15 separated in the first separation tank 1 can be increased, and the recovery rate of organic matter can be improved.

[0022] As an apparatus for producing the modified precipitate 14 containing modified flocs 141 in which the flocs 151 in the second precipitate 12 have been refined or have complex shapes, there is, for example, a means for producing the modified precipitate 14 by heating or supplying an acid or alkaline solution, as shown in FIG. 9 . Heating or supplying an acid solution, or supplying an acid solution while heating, can be performed. By heating or supplying an alkaline solution, or supplying an alkaline solution while heating, the flocs 151 in the second precipitate 12 can be dissolved, decomposed, or dissolved and decomposed, thereby reducing the size of the flocs 151 or making the shape of the flocs 151 more complex. The heating temperature is, for example, 50°C to 100°C. Examples of the acid solution include sulfuric acid and hydrochloric acid, and examples of the alkaline solution include aqueous solutions of sodium hydroxide and potassium hydroxide. In this manner, the state of the flocs 151 in the second precipitate 12 can be modified to produce the modified precipitate 14. The amount of the first precipitate 15 can be increased by mixing the thus-produced modified precipitate 14 with the wastewater 11.

[0023] 10 , an ozone-containing gas 19 may be supplied to the second precipitate 12 to dissolve or decompose the flocs 151 in the second precipitate 12, thereby generating modified flocs 141 that are finer or have a more complex shape. This dissolves or decomposes the flocs 151 in the second precipitate 12, making it possible to reduce the size of the flocs 151 or to generate modified flocs 141 with a more complex shape. This increases the surface area per unit volume of the flocs, thereby promoting the uptake and adsorption of the solid organic matter 111 and the soluble organic matter 112. That is, by supplying ozone to the second precipitate 12 to generate a modified precipitate 14 containing modified flocs 141 obtained by modifying the state of the flocs 151 in the second precipitate 12, the amount of the first precipitate 15 can be increased by mixing the modified precipitate 14 with the wastewater 11.

[0024] Furthermore, an ultrasonic irradiator 44 can be used to break down the flocs 151 in the second precipitate 12, as shown in FIG. 11 . For example, by irradiating the second precipitate 12 with pulsed ultrasonic waves, the flocs 151 are broken down and modified flocs 141 with smaller or more complex shapes can be generated. This increases the surface area per unit volume of the flocs, thereby promoting the uptake and adsorption of the solid organic matter 111 and the dissolved organic matter 112. That is, the state of the flocs 151 in the second precipitate 12 is modified by the ultrasonic irradiator 44 to generate modified precipitates 14, which can be mixed with the wastewater 11 to increase the amount of the first precipitate 15.

[0025] The modified precipitate 14 may also be formed by combining two or more selected from the precipitate-modifying portions 4 shown in FIGS. 5 and 9 to 11.

[0026] Thus, the system includes a first separation tank 1 that receives wastewater 11 and separates it into first effluent 16 and a first precipitate 15; a reaction tank 2 that receives the first effluent 16 and brings the first effluent 16 into contact with microorganisms to cause a reaction; and a second separation tank 3 that receives reaction water 17 from the reaction tank 2 and separates the reaction water 17 into second effluent and a second precipitate 12. The system further includes a precipitate modification unit 4 that takes in at least a portion of the second precipitate 12 and produces modified precipitate 14 by modifying floc 151, which is an aggregate of microorganisms contained in the second precipitate 12. By transferring the modified precipitate 14 to the first separation tank 1 or upstream of the first separation tank 1 and mixing it with wastewater 11, the second precipitate 12 separated in the second separation tank 3 becomes modified precipitate 14 in the precipitate modification unit 4 and is mixed with wastewater 11, allowing a greater amount of solid organic matter 111 and dissolved organic matter 112 contained in the wastewater 11 to be contained in the first precipitate 15.

[0027] In the first separation tank 1, more organic matter can be precipitated as the first precipitate 15. The first precipitate 15 can be concentrated and digested to extract energy, such as methane gas, so increasing the amount of the first precipitate 15 increases the amount of energy recovered from the wastewater. Furthermore, if a portion of the excess sludge is converted into the modified precipitate 14 rather than removed from the water treatment device 10 as the second precipitate 12, the amount of the second precipitate 12, which is difficult to digest, can be reduced. Furthermore, if all of the excess sludge is converted into the modified precipitate 14, a water treatment system 100 can be constructed that does not discharge the second precipitate 12. Furthermore, the solid organic matter 111 and soluble organic matter 112 present in the first effluent 16 separated in the first separation tank 1 can be reduced, thereby reducing the amount of aeration required for biological treatment in the reaction tank 2 and saving energy.

[0028] Furthermore, the precipitate transformation unit 4 increases the surface area per unit volume by reducing the size or increasing the complexity of the flocs 151 in the second precipitate 12, allowing the generated modified precipitate 14 to contain a larger amount of the solid organic matter 111 and soluble organic matter 112 in the wastewater 11. Furthermore, by performing at least one of crushing, dissolving, and decomposing the flocs 151 in the second precipitate 12 in the precipitate transformation unit 4, it is possible to generate a modified precipitate 14 in which the state of the flocs 151, which are aggregations of microorganisms in the second precipitate 12, has been transformed. Furthermore, by generating a negative pressure in the circulated second precipitate 12 and introducing at least one of a gas and a liquid, it is possible to generate a modified precipitate 14 in which the state of the flocs 151, which are aggregations of microorganisms in the second precipitate 12, has been transformed. By supplying heat and at least one of an alkaline solution and an acid solution to the second precipitate 12 to dissolve the flocs 151 in the second precipitate 12, it is possible to produce a modified precipitate 14 in which the state of the flocs 151, which are aggregations of microorganisms in the second precipitate 12, has been modified. By supplying ozone to the second precipitate 12 to decompose the flocs 151 in the second precipitate 12, it is possible to produce a modified precipitate 14 in which the state of the flocs 151, which are aggregations of microorganisms in the second precipitate 12, has been modified. By irradiating the second precipitate 12 with ultrasound to break down the flocs 151 in the second precipitate 12, it is possible to produce a modified precipitate 14 in which the state of the flocs 151, which are aggregations of microorganisms in the second precipitate 12, has been modified.

[0029] By mixing the modified precipitate 14 produced in the precipitate transformation section 4 with the wastewater 11 in this manner, a larger amount of organic matter can be precipitated as the first precipitate 15 in the first separation tank 1, thereby increasing the amount of energy recovered and reducing the amount of energy required for biological treatment in the reaction tank 2.

[0030] 12 and 13 are schematic diagrams of a water treatment device 10 according to embodiment 2. The water treatment device 10 according to embodiment 2 differs from embodiment 1 in that it includes a flocculant addition section 5 that adds a flocculant to the modified precipitate 14 that is returned from the precipitate modification section 4 to the first separation tank 1 or to an area upstream of the first separation tank 1. The rest of the configuration is the same as that of embodiment 1.

[0031] The water treatment device 10 shown in FIG. 12 includes a flocculant adding section 5 that adds a flocculant to the mixture of wastewater 11 and modified precipitate 14 returned from the precipitate modifying section 4 upstream of the first separation tank 1. Examples of flocculants that can be used include polyaluminum chloride, aluminum sulfate, ferric chloride, and polymer flocculants. As described in the first embodiment with reference to FIG. 4 , when the modified floc 141 comes into contact with the wastewater 11, the solid organic matter 111 and soluble organic matter 112 in the wastewater 11 are adsorbed onto the modified floc 141. Adding a flocculant when mixing the wastewater 11 and the modified precipitate 14 facilitates the solid organic matter 111 and soluble organic matter 112 that are not adsorbed onto the modified precipitate 14 to coagulate and precipitate, thereby further increasing the amount of the first precipitate 15 in addition to the effects described in the first embodiment. Furthermore, the Al contained in the flocculant 3+ , Fe 3+ These cations form insoluble salts with phosphorus, so that the phosphorus contained in the wastewater 11 can be precipitated and removed.

[0032] When a metal-based flocculant is used as the flocculant, the flocculant addition rate is preferably 0.05 mg-ME / mg-SS or more and 0.25 mg-ME / mg-SS or less per unit weight of SS (suspended solids) of the altered precipitate 14 added to the wastewater 11. The metal used in the flocculant is expressed as ME. It may also be expressed as the SS of the second precipitate 12. This is because it has been confirmed that there is no significant difference between the SS of the second precipitate 12 and the altered precipitate 14. If the flocculant addition rate is less than 0.05 mg-ME / mg-SS, the amount of flocculant added is small, and the effect of further increasing the amount of the first precipitate 15 is not obtained. Furthermore, if the flocculant addition rate is greater than 0.25 mg-ME / mg-SS, the amount of the first precipitate 15 increases, but the cost of the flocculant becomes too high. Furthermore, iron, aluminum, etc. are used as metals. Furthermore, when a polymer organic flocculant is used as the flocculant, the flocculant addition rate is preferably 0.001 mg / mg-SS or more and 0.007 mg / mg-SS or less per unit weight of the modified precipitate 14 added to the wastewater 11. If the flocculant addition rate is less than 0.001 mg / mg-SS, the amount of flocculant added is small, and the effect of further increasing the amount of the first precipitate 15 is not obtained. If the flocculant addition rate is greater than 0.007 mg / mg-SS, the amount of the first precipitate 15 increases, but the cost of the flocculant becomes too high.

[0033] As described above, it is preferable that the flocculant be added based on the amount of modified precipitate 14 being transported to the first separation tank 1 or upstream thereof. For example, the flocculant addition unit 5 of the water treatment device 10 shown in Figure 13 is composed of a flocculant storage unit 51, an addition unit 52, and a flocculant addition amount control unit 53, and calculates the amount of flocculant to be supplied based on the measured values ​​of the solid concentration (hereinafter simply referred to as concentration) of the modified precipitate 14 and the flow rate, and adds flocculant based on the calculated supply amount. For example, measured values ​​are obtained from the concentration of the modified precipitate 14 transported from the sediment transformation unit 4 and the operating status of the modified precipitate water delivery device 45, such as a pump, and the flocculant addition amount control unit 53 calculates the amount of flocculant required based on the measured values. Then, flocculant is added in the addition unit 52 based on the amount of flocculant supplied calculated and controlled by the flocculant addition amount control unit 53. The concentration of the modified precipitate 14 may be measured using a concentration meter 63 shown in Figure 14 (described later), or a concentration meter (not shown) installed in the precipitate transformation unit 4, in the pipe connecting the precipitate transformation unit 4 and the wastewater 14, or the like. Since the amount of solids in the modified precipitate 14 is determined by multiplying the concentration by the flow rate, the amount of flocculant required can be calculated by the flocculant addition amount control unit 53, and the amount added can be adjusted by controlling the addition unit 52. Adding flocculant in this manner allows the flocculant to be used without excess or deficiency.

[0034] For example, when the amount of the altered precipitate 14 added to the wastewater 11 is 0.5 kg / m of sludge DS, 3 In this case, it is recommended to use FeCl3 as a coagulant and set the amount of modified precipitate 14 at 0.05 to 0.25 mg Fe / mg SS (SS is the amount of modified precipitate). A jar test was conducted using FeCl3 as a coagulant, with Q / V = 30, to test the mixture of coagulant, modified precipitate 14, and wastewater 11. The results showed that SS removal from the first effluent 16 was effective at 0.05 mg Fe / mg SS or higher, and that the organic matter removal effect in the wastewater 11 was greatest at 0.1 to 0.2 mg Fe / mg SS. Furthermore, when a polymer coagulant was used as the coagulant, the organic matter removal effect in the wastewater 11 was greatest at 0.002 to 0.005 mg / mg SS. Based on the above, the amount of first precipitate was increased by approximately 20% compared to when no coagulant was added.

[0035] The flocculant storage unit 51 and the addition unit 52 may be provided before mixing the altered precipitate 14 with the wastewater 11, or may be provided so that the flocculant is added during mixing. The set values, calculation formulas, etc. may be stored in advance in the flocculant addition amount control unit 53, or an input unit may be provided that allows the operator of the water treatment device 10 to input them.

[0036] In this way, the system is provided with a flocculant addition unit 5 that adds a flocculant to the modified precipitate 14 or a mixture of the modified precipitate 14 and wastewater 11 that is returned from the precipitate transformation unit 4 upstream of the first separation tank 1. By adding the flocculant, the solid organic matter 111 and soluble organic matter 112 in the wastewater 11 can be flocculated, thereby further increasing the amount of the first precipitate 15. Furthermore, by flocculating phosphorus with metal ions contained in the flocculant to form an insoluble salt, which is then precipitated in the first separation tank 1, the phosphorus concentration in the first effluent 16 can be reduced, improving the water quality. Furthermore, by acquiring measured values ​​of the concentration and flow rate of the modified precipitate 14 sent from the precipitate transformation unit 4, calculating the amount of flocculant to be supplied based on the measured values, and adding the flocculant based on the supplied amount, the appropriate amount of flocculant can be added.

[0037] In the first embodiment, the relationship between the mixing time of wastewater 11 and modified precipitate 14 and the amount of precipitate of first precipitate 15 was shown using Figure 8, but similar results were obtained when a flocculant was added. That is, the mixing time of modified precipitate 14 and wastewater 11 after adding a flocculant is preferably set to greater than 5 minutes. Furthermore, since the amount of precipitate does not increase significantly even if the mixing time is increased, the mixing time is preferably set to between 6 minutes and 20 minutes so as not to become too long.

[0038] Embodiment 3. Figure 14 is a schematic diagram of a water treatment device 10 according to embodiment 3. The water treatment device 10 according to embodiment 3 differs from embodiments 1 and 2 in that it includes a second sediment amount control unit 6 that controls the amount of second sediment transferred from the second separation tank 3 to the sediment transformation unit 4. The remaining configuration is the same as that of embodiment 1 or 2.

[0039] The water treatment device 10 shown in Figure 14 separates the reaction water 17 into second effluent and second precipitate 12 in the second separation tank 3. A portion of the second precipitate 12 is returned to the reaction tank 2, and the remaining second precipitate 12 is transferred to the precipitate transformation unit 4. The second precipitate amount control unit 6 calculates the amount of the second precipitate 12 from the concentration and flow rate measured using a concentration meter 63 that measures the solid concentration contained in the second precipitate 12 and a flow meter 62 that measures the flow rate of the second precipitate 12. The amount of second precipitate 12 transferred to the precipitate transformation unit 4 is controlled by controlling the opening and closing degree of the valve 61 so that the microbial concentration in the reaction tank 2 can be maintained at a predetermined value. In this case, the entire remaining amount excluding the amount of second precipitate 12 transferred to the reaction tank 2 may be transferred to the precipitate transformation unit 4, or a portion may be transferred to the precipitate transformation unit 4 and the remainder may be transferred to the concentration and digestion process. The second precipitate 12 is mainly composed of microorganisms in the reaction tank 2, i.e., activated sludge, and is less likely to generate digestion gas than the first precipitate 15 contained in the wastewater 11. Therefore, it is preferable to increase the amount of first precipitate 15 separated in the first separation tank 1 compared to the amount of second precipitate 12 separated in the second separation tank 3 as the precipitate to be recovered in the digestion step to generate digestion gas and use it as energy.

[0040] Therefore, the second precipitate amount control unit 6 controls the amount of the second precipitate 12 so that all or a portion of the remaining amount, excluding the amount of the second precipitate 12 required to maintain the microbial concentration in the reaction tank 2 at a predetermined value, is transferred to the precipitate modification unit 4. The predetermined microbial concentration maintained in the reaction tank 2 is a value that is preset for operating the water treatment device 10. By maintaining the microbial concentration in the reaction tank 2 at a predetermined value, the water treatment device 10 can be operated stably, and the modified precipitate 14 obtained by modifying the second precipitate 12 is returned to the first separation tank 1 or upstream of the first separation tank 1, so that the modified floc 141 in the modified precipitate 14 contains more of the solid organic matter 111 and dissolved organic matter 112 contained in the wastewater 11, thereby improving the recovery rate of organic matter by the first precipitate 15 separated in the first separation tank 1.

[0041] The transfer of the second precipitate 12 from the second separation tank 3 to the precipitate modification unit 4 may be carried out intermittently in accordance with the timing of the withdrawal of excess sludge from the water treatment device 10, or the transfer of the modified precipitate 14 from the precipitate modification unit 4 to the first separation tank 1 may be carried out continuously. In either case, it is preferable that the transfer of the modified precipitate 14 from the precipitate modification unit 4 to the first separation tank 1 or upstream of the first separation tank 1 be continuous. This allows the amount of the first precipitate 15 in the first separation tank 1 to be steadily increased in response to the continuously flowing in wastewater 11.

[0042] The formulas for calculating the predetermined microbial concentration to be maintained in the reaction tank 2, the set values ​​of the values ​​measured by the concentration meter 63 and the flow meter 62, the amount of the second precipitate 12 to be transferred to the precipitate transformation unit 4, etc. may be stored in advance in the second precipitate amount control unit 6, or an input unit may be provided that allows the operator of the water treatment device 10 to input the formulas.

[0043] Embodiment 4. Figure 15 is a schematic diagram of a water treatment device 10 according to embodiment 4. The water treatment device 10 according to embodiment 4 differs from embodiments 1 to 3 in that it includes a modified precipitate control unit 7 that monitors the state of the wastewater 11. Other configurations are similar to those of embodiments 1 to 3. In the water treatment device 10 shown in Figure 15, the organic component concentration of the wastewater 11 measured by the concentration meter 73, the flow rate of the first effluent 16 measured by the flow meter 72, and the solids concentration of the second precipitate 12 measured by the concentration meter 63 are sent to the modified precipitate control unit 7 to monitor their respective states. The modified precipitate control unit 7 then determines the conditions for modifying the modified precipitate 14 produced in the precipitate modification unit from the respective measured values ​​and transmits them to the precipitate modification unit 4. The precipitate modification unit 4 generates the modified precipitate 14 according to the conditions transmitted from the modified precipitate control unit 7 and transports it to the first separation tank 1 or its upstream. Here, the conditions for generating the modified precipitate 14 are numerical conditions according to the various configurations of the precipitate transformation unit 4 described in the first embodiment.

[0044] In this way, the state of the wastewater 11 and the second precipitate 12 is grasped based on the measured values ​​of the organic component concentration of the wastewater 11, the flow rate of the first effluent 16, and the solids concentration of the second precipitate 12, and by providing a modified precipitate control unit 7 that determines the conditions for generating the modified precipitate 14 to be transferred to the first separation tank 1 or upstream of the first separation tank 1 based on these values, it is possible to generate a modified precipitate 14 with appropriate properties in response to fluctuations in the temporal flow rate of the wastewater 11, the organic component concentration, the solids concentration of the second precipitate 12, etc.

[0045] The modified precipitate control unit 7 can determine conditions such as the equipment, Q / V, gas to be introduced, and solution for producing the modified precipitate 14. The modified precipitate control unit 7 can also grasp the amount of second precipitate 12 stored in the precipitate transformation unit 4 and use that amount to determine conditions for producing an appropriate modified precipitate 14. Data regarding the equipment previously installed to produce the modified precipitate 14 may be stored and called up from the modified precipitate control unit 7 as appropriate. The function of the modified precipitate control unit 7 may also be integrated into the precipitate transformation unit 4, and judgments and calculations may be performed by the precipitate transformation unit 4. Note that, although the flow rate of the first effluent 16 is measured in this embodiment, the flow rate of the wastewater 11 flowing into the first separation tank 1 may also be measured directly.

[0046] 16 is a schematic diagram of a water treatment device 10 according to a fifth embodiment. The water treatment device 10 according to the fifth embodiment is the same as that according to the fourth embodiment in that it includes a modified precipitate control unit 7 that monitors the state of the wastewater 11, but differs in that it can control the amount of modified precipitate 14 transferred to the wastewater 11. The remaining configuration is the same as that according to the first to fourth embodiments.

[0047] As described above, by mixing the modified precipitate 14 with the wastewater 11, a larger amount of the organic matter contained in the wastewater 11 can be incorporated into the modified precipitate 14, and the recovery rate of the organic matter by the first precipitate 15 separated in the first separation tank 1 can be improved. However, since the concentration and flow rate of the organic components in the wastewater 11 fluctuate from moment to moment, it is necessary to transfer an appropriate amount of modified precipitate 14 accordingly.

[0048] Therefore, the water treatment device 10 of this embodiment is equipped with a modified precipitate control unit 7 that monitors the state of the wastewater 11 and controls the supply amount of modified precipitate 14 transferred to the first separation tank 1 or its upstream. In the water treatment device 10 shown in FIG. 16 , the organic component concentration of the wastewater 11 measured by the concentration meter 73, the flow rate of the first effluent 16 measured by the flow meter 72, and the solids concentration of the second precipitate 12 measured by the concentration meter 63 are sent to the modified precipitate control unit 7 to monitor the state of each, and the amount of modified precipitate 14 to be mixed with the wastewater 11 is calculated from the measured values ​​acquired by the modified precipitate control unit 7. The calculated amount of modified precipitate 14 is then transmitted to the modified precipitate water supply device 45. The modified precipitate water supply device 45 transfers the transmitted amount of modified precipitate 14 to the first separation tank 1 or its upstream. Instead of the concentration meter 63, a concentration meter (not shown) installed in the sediment transformation unit 4 or in the piping connecting the sediment transformation unit 4 and the wastewater 14 may be used.

[0049] In this way, the modified precipitate control unit 7 is provided, which grasps the state of the wastewater 11 based on the organic component concentration and flow rate of the wastewater 11, and calculates the amount of modified precipitate 14 to be transferred to the first separation tank 1 or upstream of the first separation tank 1 based on the solids concentration of the second precipitate 12 or the modified precipitate 14. By transferring the modified precipitate 14 to the first separation tank 1 or upstream of the first separation tank 1 based on the calculation results, an appropriate amount of modified precipitate 14 can be transferred, just enough to accommodate the moment-to-moment fluctuations in the concentration and flow rate of the organic components in the wastewater 11. As a result, the amount of first precipitate 15 in the first separation tank 1 can be stably increased in response to the moment-to-moment fluctuations in the wastewater 11. Note that, although the flow rate of the first effluent 16 is measured in this embodiment, the flow rate of the wastewater 11 flowing into the first separation tank 1 may also be measured directly.

[0050] Sixth Embodiment. Figure 17 is a schematic diagram of a water treatment system 100 according to a sixth embodiment. The water treatment system 100 according to the sixth embodiment includes the water treatment device 10 described in any of the first to fifth embodiments. As shown in Figure 17, the water treatment system 100 includes, for example, the water treatment device 10 shown in Figure 1; a first concentrator 20 that concentrates a precipitate containing the first precipitate 15 transferred from the water treatment device 10 to form concentrated sludge; a second concentrator 21 that concentrates a precipitate containing the second precipitate 12 to form concentrated sludge; and a digester 30 that mixes and heats the concentrated sludge to decompose organic matter in the concentrated sludge and generate digester gas. The water treatment device 10 may have any of the configurations described in any of the first to fifth embodiments. Furthermore, if all of the second precipitate 12 is transferred to the precipitate transformation unit 4, the second concentrator 21 may not be used. That is, the concentrators may include at least the first concentrator 20, and may also include both the first concentrator 20 and the second concentrator 21.

[0051] Thus, the water treatment system 100 comprises the water treatment device 10 according to the present disclosure, a concentration device that concentrates the precipitate containing at least the first precipitate 15 transferred from the water treatment device 10 to form concentrated sludge, and a digester 30 that heats the concentrated sludge to decompose the organic matter contained in the concentrated sludge and generate digester gas. By returning the modified precipitate 14 obtained by transforming the second precipitate 12 to the first separation tank 1 or upstream of the first separation tank 1, the recovery rate of the organic matter from the first precipitate 15 separated in the first separation tank 1 can be improved, thereby generating more digester gas and utilizing it as carbon-neutral energy.

[0052] It is also possible to operate water treatment device 10 by combining any two or all of Embodiments 3 to 5, which allows a larger amount of organic matter to be recovered as first precipitate 15. Furthermore, by combining any two or all of Embodiments 1 to 5, an even larger amount of organic matter can be recovered as first precipitate 15.

[0053] Seventh Embodiment. Figure 18 shows a flowchart illustrating the treatment flow performed by the water treatment device 10. First, wastewater 11 is received and separated into first effluent 16 and first precipitate 15 (first separation step S101). Then, the first effluent 16 is received and reacted with microorganisms (reaction step S102). Then, reacted water 17 obtained in the reaction step is received and separated into second effluent and second precipitate 12 (second separation step S103). At least a portion of the second precipitate 12 is taken in, and the state of flocs 151, which are aggregates of microorganisms in the second precipitate 12, is altered to produce altered precipitate 14 (precipitate alteration step S104). The altered precipitate 14 is then mixed with wastewater 11, and organic matter in the wastewater 11 is taken in and precipitated (mixing step S105).

[0054] In this way, wastewater 11 is received and separated into first effluent 16 and first precipitate 15, first effluent 16 is received, the first effluent 16 is brought into contact with microorganisms to cause a reaction, the reacted water 17 is separated into second effluent and second precipitate 12, the state of floc 151, which is an aggregate of microorganisms contained in second precipitate 12, is altered to produce altered precipitate 14, the altered precipitate 14 is mixed with wastewater 11, and organic matter in wastewater 11 is taken up and precipitated, thereby allowing a larger amount of organic matter contained in wastewater 11 to be contained in altered precipitate 14, and the amount of first precipitate 15 separated in first separation tank 1 can be increased, thereby improving the recovery rate of organic matter.

[0055] Figure 19 is a flowchart showing a treatment flow executed by a water treatment device 10 including a flocculant addition unit 5 that adds a flocculant, as described in embodiment 2. The first separation step S101, reaction step S102, second separation step S103, precipitate transformation step S104, and mixing step S105 are the same as those described above, and include a flocculant addition step S106 in which a flocculant is added to a mixture of the transformed precipitate 14 and wastewater 11, thereby capturing and precipitating organic matter in the wastewater 11. A flocculant addition step in which a flocculant is added to the transformed precipitate 14 may be included before the mixing step S105. By adding a flocculant to the transformed precipitate 14 or a mixture of the transformed precipitate 14 and wastewater 11, and capturing and precipitating organic matter in the wastewater 11, the amount of the first precipitate 15 separated in the first separation tank 1 can be further increased, thereby further improving the recovery rate of organic matter.

[0056] Here, each function of the water treatment device 10 is realized by a processing circuit. FIG. 20 is a schematic diagram showing an example of a processing circuit that realizes each function of the water treatment device 10. The water treatment device 10 includes a processor 90, a storage device 91, a communication I / F (interface) 92, and the like. The processor 90 may be, for example, a CPU (Central Processing Unit). The storage device 91 transmits and receives data to and from the processor 90 and stores the data. Measurement data from the flow meters 62, 72, concentration meters 63, 73, and the like is acquired by the flocculant amount addition control unit 51, second precipitate amount control unit 6, altered precipitate control unit 7, and the like of the water treatment device 10 via the communication I / F 92. Calculations and judgments performed by the flocculant amount addition control unit 53, second precipitate amount control unit 6, altered precipitate control unit 7, and the like are executed by the processor 90. The acquired measurement data, calculation formulas, and the like are stored in the storage device 91.

[0057] The processor 90 and the storage device 91 may be one shared device or multiple devices may be provided. The processor 90 may include, for example, a logic circuit using an ASIC (Application Specific Integrated Circuit), an IC (Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or various signal processing circuits. Multiple processors 90, either of the same type or different types, may be provided, so that each process is shared and executed by multiple arithmetic processing devices.

[0058] The multiple storage devices 91 include, for example, a RAM (Random Access Memory) configured to allow data to be read from and written to the processor 90, a ROM (Read Only Memory) configured to allow data to be read from the processor 90, a hard disk, etc.

[0059] Each function of the water treatment device 10 is realized by the processor 90 executing software or programs stored in the storage device 91 and working in cooperation with the hardware. Setting data to be set in the water treatment device 10 may be stored in the storage device 91 as part of the software or program, or may be input by the operator of the water treatment device 10. A non-transitory recording medium 911 on which a water treatment program 912 is recorded may be distributed and installed in the storage device 91 of the water treatment device 10.

[0060] Specific examples of the present disclosure and effects of the present disclosure compared with comparative examples will be described. Example 1. Using the water treatment device 10 shown in FIG. 1 described in embodiment 1 and the precipitate conversion unit 4 shown in FIG. 5, a modified precipitate 14 was generated, and the modified precipitate 14 was returned upstream of the first separation tank 1 and mixed with wastewater 11. 150 L / d of wastewater containing organic matter was treated as raw water. The DOC of the wastewater 11 was 30 mg / L and the SS (suspended solids) was 130 mg / L. When the mixing ratio of the modified precipitate 14 to the wastewater 11 was 0.1 kg-sludge DS / m 3The modified precipitate 14 was added to the upstream of the first separation tank 1 by the precipitate transformation unit 4 and mixed therewith so that the first precipitate 15 and the second precipitate 12 were concentrated, and methane gas was extracted using an anaerobic digester. Furthermore, in the precipitate transformation unit 4, negative pressure was generated in the absorber 43 installed in the circulation circuit 47, causing air to be sucked in through the inlet 42. This crushed and transformed the flocs 151 in the second precipitate 12 to produce the modified precipitate 14. This modified precipitate 14 was returned to the first separation tank 1 and mixed with the wastewater 11 for 6 minutes, after which the DOC in the first effluent 16 was measured to determine the DOC removal rate. At this time, the Q / V was set to 30.

[0061] Example 2. Using the water treatment device 10 shown in FIG. 12 and described in the second embodiment, the altered precipitate 14 was returned upstream of the first separation tank 1 and mixed with the wastewater 11. A flocculant was also added and mixed. Ferric chloride FeCl3 was used as the flocculant, and the flocculant addition rate was 0.1 mg Fe / mg SS. The other conditions were the same as in Example 1.

[0062] Comparative Example 1: The water treatment device 10 shown in FIG. 1 and described in the first embodiment was used, but the precipitate conversion unit 4 was not used, and the second precipitate 12 was not returned upstream of the first separation tank 1 and mixed. The other conditions were the same as in Example 1.

[0063] Comparative Example 2: Using the water treatment device 10 shown in Figure 1 described in the first embodiment, the second precipitate 12 was returned directly to the upstream side of the first separation tank 1 without using the precipitate conversion unit 4 and mixed with the wastewater 11. The other conditions were the same as those in Example 1.

[0064] Table 1 shows the measurement results for each item in Examples 1 and 2 and Comparative Examples 1 and 2. From these results, the amount of sediment in Example 1 was 3.8 times (= 190 ÷ 50) that of Comparative Example 1 and 1.1 times (= 190 ÷ 170) that of Comparative Example 2, and the amount of sediment in Example 2 was 4.5 times (= 190 ÷ 50) that of Comparative Example 1 and 1.3 times (= 190 ÷ 50) that of Comparative Example 2. Furthermore, the DOC reduction rate of the first effluent 16 relative to Comparative Example 1 was 20% (= (30 - 24) ÷ 30 × 100) in Example 1, 33% (= (30 - 20) ÷ 30 × 100) in Example 2, 3% (= (30 - 29) ÷ 30 × 100) in Comparative Example 1, and 7% (= (30 - 28) ÷ 30 × 100) in Comparative Example 2. Furthermore, the SS reduction rate of the first effluent 16 was 48% (= (130 - 68) ÷ 130 × 100) in Example 1, 54% (= (130 - 60) ÷ 130 × 100) in Example 2, and 38% (= (130 - 80) ÷ 130 × 100) in Comparative Examples 1 and 2. From the above, it was confirmed that the Examples were more effective than the Comparative Examples. Accordingly, the aeration air volume required in the reaction tank 2 was reduced by 7% in Example 1 and 10% in Example 2 compared to Comparative Example 1. Furthermore, the amount of methane gas generated increased by 40% in Example 1 and 60% in Example 2 compared to Comparative Example 2. This is thought to be due to the fact that the amount of first precipitate 15 was increased by mixing the modified precipitate 14 with the wastewater 11, and the amount of SS and organic matter in the first effluent 16 was reduced.

[0065]

[0066] Furthermore, in the water treatment device 10 and water treatment system 100 according to the present disclosure, since there is a water flow of the wastewater 11, a mixing device for mixing the wastewater 11 and the metamorphic precipitate 14 is not required, but if there is sufficient space, a mixing device may be used for mixing.

[0067] Although various exemplary embodiments are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, and even cases where at least one component is extracted and combined with components of another embodiment.

[0068] 1 First separation tank, 2 Reaction tank, 3 Second separation tank, 4 Sediment modification section, 5 Flocculant addition section, 6 Second sediment amount control section, 7 Modified sediment control section, 10 Water treatment device, 11 Wastewater, 12 Second sediment, 13 Container, 14 Modified sediment, 15 First sediment, 16 First effluent, 17 Reaction water, 20 First concentrator, 21 Second concentrator, 30 Digestion device, 41 Pump, 42 Inlet, 43 Absorption device, 44 Ultrasonic irradiator, 45 Modified sediment water conveying device, 47 Circulation circuit, 52 Addition section, 53 Flocculant addition amount control section, 61 Valve, 62, 72 Flow meter, 63, 73 Concentration meter, 100 Water treatment system, 111 Solid organic matter, 112 Dissolved organic matter, 141 Modified floc, 142 Modified floc constituent unit, 151 Floc, 152 floc building blocks

Claims

1. A water treatment device comprising: a first separation tank that receives wastewater and separates it into a first effluent and a first precipitate; a reaction tank that receives the first effluent and brings the first effluent into contact with microorganisms to cause a reaction; and a second separation tank that receives the reacted water from the reaction tank and separates the reacted water into a second effluent and a second precipitate, and further comprising a precipitate modification unit that takes in at least a portion of the second precipitate and modifies flocs, which are aggregates of microorganisms contained in the second precipitate, to produce a modified precipitate, and transports the modified precipitate to the first separation tank or upstream of the first separation tank and mixes it with the wastewater.

2. A water treatment device as described in claim 1, characterized in that it is provided with a flocculant addition section that adds a flocculant to the mixture of the wastewater and the modified precipitate transported from the sediment transformation section to the first separation tank or upstream of the first separation tank.

3. A water treatment device according to claim 1 or 2, characterized in that the precipitate transformation section increases the surface area per unit volume by making the flocs contained in the second precipitate finer or more complex in shape.

4. A water treatment device as described in any one of claims 1 to 3, characterized in that the precipitate transformation unit performs at least one of the following processes to crush, dissolve, and decompose the flocs contained in the second precipitate.

5. A water treatment device as described in any one of claims 1 to 4, characterized in that the sediment transformation unit generates negative pressure in the circulated second sediment to introduce at least one of gas and liquid.

6. The water treatment device according to claim 5, wherein the gas is air.

7. A water treatment device as described in any one of claims 1 to 5, characterized in that the precipitate transformation unit supplies heat and at least one of an alkaline solution or an acid solution to the second precipitate to dissolve the flocs contained in the second precipitate.

8. A water treatment device according to any one of claims 1 to 5, characterized in that the precipitate transformation unit supplies ozone to the second precipitate to decompose the flocs contained in the second precipitate.

9. A water treatment device according to any one of claims 1 to 5, characterized in that the precipitate transformation unit irradiates the second precipitate with ultrasonic waves to break down the flocs contained in the second precipitate.

10. The water treatment device described in claim 2, characterized in that the coagulant addition unit calculates the amount of coagulant to be supplied based on the measured values ​​of the concentration and flow rate of the altered precipitate, and adds the coagulant based on the amount supplied.

11. A water treatment device as described in any one of claims 1 to 10, characterized in that it is provided with at least one of a second sediment amount control unit that controls the amount of second sediment transferred from the second separation tank to the sediment transformation unit, and a modified sediment control unit that controls the amount of modified sediment transferred from the sediment transformation unit to the first separation tank or upstream of the first separation tank.

12. The water treatment device described in claim 11, characterized in that the second sediment amount control unit controls the second sediment amount so that all or part of the remaining amount excluding the second sediment amount that maintains the microbial concentration in the reaction tank at a predetermined value is transferred to the sediment transformation unit.

13. A water treatment device as described in claim 11 or claim 12, characterized in that the second sediment amount control unit controls the second sediment amount so as to intermittently transfer the second sediment from the second separation tank to the sediment transformation unit, and continuously transfers the transformed sediment from the sediment transformation unit to the first separation tank or upstream of the first separation tank.

14. A water treatment device as described in any one of claims 1 to 13, characterized in that it is provided with a modified precipitate control unit that determines the conditions for generating the modified precipitate to be transported to the first separation tank or upstream of the first separation tank based on the state of the wastewater due to the organic component concentration of the wastewater, the flow rate of the wastewater, and the solid concentration of the second precipitate.

15. The water treatment device described in claim 14, characterized in that the modified sediment control unit calculates the amount of modified sediment to be transferred to the first separation tank or upstream of the first separation tank based on the organic component concentration of the wastewater, the flow rate of the wastewater, and the solid concentration of the second sediment, and controls the amount of modified sediment to be transferred to the first separation tank or upstream of the first separation tank in accordance with the calculated amount of modified sediment.

16. A water treatment system comprising: a water treatment device according to any one of claims 1 to 15; a concentrating device that concentrates precipitates including at least a first precipitate transferred from the water treatment device to produce concentrated sludge; and a digester that heats the concentrated sludge to decompose organic matter contained in the concentrated sludge and generate digester gas.

17. A water treatment method comprising: a first separation step of receiving wastewater and separating it into a first effluent and a first precipitate; a reaction step of receiving the first effluent and contacting the first effluent with microorganisms to cause a reaction; a second separation step of receiving reacted water obtained in the reaction step and separating the reacted water into a second effluent and a second precipitate; a precipitate modification step of taking in at least a portion of the second precipitate and modifying the state of flocs, which are aggregations of microorganisms contained in the second precipitate, to produce a modified precipitate; and a mixing step of mixing the generated modified precipitate with the wastewater and taking in and precipitating organic matter in the wastewater.

18. A water treatment method as described in claim 17, characterized in that it includes a coagulant addition step in which a coagulant is added to the altered precipitate altered in the precipitate alteration step or to a mixture of the altered precipitate and the wastewater, thereby capturing and precipitating organic matter in the wastewater.

Images