Wastewater treatment facility and wastewater treatment method

Abstract

To provide a wastewater treatment facility which enhances a recovery rate of reusable permeate water in wastewater treatment processes that separate wastewater generated at an incineration plant into concentrated wastewater and permeate water using separation membranes.SOLUTION: A wastewater treatment facility for treating wastewater generated by an incineration plant 1A including an incinerator for burning combustible materials and a heat recovery device for recovering heat from combustion exhaust gas discharged from the incinerator, comprises a forward osmosis membrane module 31 having a forward osmosis membrane 40, a reverse osmosis membrane module 32 having a reverse osmosis membrane 50, and a circulation circuit 33 circulating a drive liquid between a secondary side cell 42 of the forward osmosis membrane module 31 and a primary side cell 51 of the reverse osmosis membrane module 32. The wastewater treatment facility is configured to concentrate wastewater by permeating the wastewater from the primary side to the secondary side of the forward osmosis membrane 40, and to utilize the permeate water obtained in the secondary side cell 52 of the reverse osmosis membrane module 32 in the incineration plant 1A by permeating the drive liquid from the primary side to the secondary side of the reverse osmosis membrane 50.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wastewater treatment facility and a wastewater treatment method for treating wastewater generated in an incineration plant equipped with an incinerator that burns materials to be combusted and a heat recovery device that recovers heat from the combustion exhaust gas discharged from the incinerator. [Background technology]

[0002] Conventionally, wastewater generated in incineration plants has been discharged outside the incineration plant system after reducing suspended matter, BOD, dissolved salts, etc. in the wastewater to below discharge standard values ​​through coagulation treatment, biological treatment, membrane treatment, etc. However, in recent years, there has been a demand not to discharge wastewater even after purification treatment. Therefore, technology related to closed wastewater treatment, which treats wastewater within the incineration plant system, has been proposed (for example, see Patent Document 1).

[0003] Patent Document 1 discloses a technology related to wastewater treatment applied to an incineration plant in which heat from combustion exhaust gas discharged from an incinerator is recovered by a heat recovery device and the heat-recovered combustion exhaust gas is further cooled in a cooling tower. In the wastewater treatment disclosed in Patent Document 1, wastewater generated in the incineration plant is separated into concentrated wastewater and permeated water by a reverse osmosis membrane (RO membrane), and the concentrated wastewater is sprayed and vaporized in the cooling tower, while the permeated water is reused as equipment cooling water, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-89071 Summary of the Invention [Problem to be solved by the invention]

[0005] In the wastewater treatment system disclosed in Patent Document 1, the amount of heat recovered from combustion exhaust gas in the heat recovery device decreases in proportion to the amount of concentrated wastewater injected in the cooling tower. To prevent this decrease in heat recovery, it is effective to reduce the amount of concentrated wastewater injected in the cooling tower by increasing the recovery rate of reusable permeate. However, in order to increase the recovery rate of permeate, it is necessary to apply a pressure higher than the osmotic pressure to the wastewater to increase the concentration rate of the wastewater using the reverse osmosis membrane. This not only increases equipment and running costs, but also may cause clogging or damage to the reverse osmosis membrane. As a result, the recovery rate of permeate cannot be improved as desired, and the heat recovery rate from combustion exhaust gas cannot be improved.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide a wastewater treatment facility and a wastewater treatment method that can improve the recovery rate of reusable permeate in a wastewater treatment process in which wastewater generated in an incineration plant is separated into concentrated wastewater and permeate using a separation membrane. [Means for solving the problem]

[0007] The characteristic configuration of the wastewater treatment facility according to the present invention for solving the above problems is as follows: A wastewater treatment facility that treats wastewater generated in an incineration plant equipped with an incinerator that burns materials to be combusted and a heat recovery device that recovers heat from the combustion exhaust gas discharged from the incinerator, a forward osmosis membrane module having a forward osmosis membrane and a primary cell and a secondary cell formed on the primary side and the secondary side of the forward osmosis membrane, respectively; a wastewater treatment supply channel for supplying the wastewater to a primary cell of the forward osmosis membrane module; a reverse osmosis membrane module having a reverse osmosis membrane and a primary cell and a secondary cell formed on the primary side and the secondary side of the reverse osmosis membrane, respectively; a circulation circuit that circulates a drive liquid between a secondary cell of the forward osmosis membrane module and a primary cell of the reverse osmosis membrane module, The wastewater is concentrated by permeating the wastewater from the primary side to the secondary side of the forward osmosis membrane, and the driving liquid is permeated from the primary side to the secondary side of the reverse osmosis membrane to obtain permeate in the secondary cell of the reverse osmosis membrane module, which is then used in the incineration plant.

[0008] In this wastewater treatment system, wastewater is supplied to the primary cell of the forward osmosis membrane module via a wastewater supply line. A driving fluid (hyperosmotic solution) with a relatively higher osmotic pressure than the wastewater is circulated between the secondary cell of the forward osmosis membrane module and the primary cell of the reverse osmosis membrane module via a circulation circuit. The difference in osmotic pressure between the wastewater and the driving fluid across the forward osmosis membrane is utilized to move water from the wastewater side toward the driving fluid side. The driving fluid is diluted by the movement of water toward the driving fluid side. The water in the diluted driving fluid permeates the reverse osmosis membrane and is used in the incineration plant as permeate. This wastewater treatment system utilizes the difference in osmotic pressure between the wastewater and the driving fluid, allowing water from the wastewater side to smoothly move toward the driving fluid side. Furthermore, even if the driving fluid in the secondary cell of the forward osmosis membrane module is diluted by the water that permeated the forward osmosis membrane, it is introduced into the primary cell of the reverse osmosis membrane module, concentrated, and then returned to the secondary cell of the forward osmosis membrane module. In this case, the driving liquid only needs to be concentrated to a level that maintains a constant solute concentration. This eliminates the need to apply excessive pressure to the driving liquid to counteract the osmotic pressure difference across the reverse osmosis membrane, thereby preventing clogging or damage to the reverse osmosis membrane. Because the osmotic pressure difference between the wastewater and the driving liquid is maintained at a high and stable level, forward osmosis, which transfers water from the wastewater into the driving liquid through the forward osmosis membrane, is carried out efficiently and stably. This improves the recovery rate of reusable permeate and ultimately improves the heat recovery rate from combustion exhaust gas.

[0009] In the wastewater treatment facility according to the present invention, It is preferable that the wastewater be concentrated and the concentrated wastewater be utilized and / or treated in the incineration plant.

[0010] According to the wastewater treatment facility of this configuration, the concentrated wastewater is used and / or treated in an incineration plant. This allows the wastewater to be effectively used in applications that do not require a high degree of purification in an incineration plant, for example. Furthermore, by burning the concentrated wastewater in an incinerator, impurities in the concentrated wastewater can be reduced in volume and made harmless.

[0011] In the wastewater treatment facility according to the present invention, It is preferable that the system further comprises a pretreatment device that pretreats the wastewater before it is supplied to the primary cell of the forward osmosis membrane module.

[0012] According to the wastewater treatment equipment of this configuration, the wastewater is pretreated by the pretreatment device before being supplied to the primary cell of the forward osmosis membrane module. This allows solid fine particles and the like to be removed in advance, making the forward osmosis membrane less likely to become clogged and allowing the forward osmosis membrane to be used for a longer period of time.

[0013] Next, the characteristic configuration of the wastewater treatment method according to the present invention for solving the above problems is as follows: A wastewater treatment method for treating wastewater generated in an incineration plant equipped with an incinerator that burns materials to be combusted and a heat recovery device that recovers heat from combustion exhaust gas discharged from the incinerator, comprising: a wastewater treatment supply step of supplying the wastewater to the primary side of the forward osmosis membrane; a circulation step of circulating a drive liquid between the secondary side of the forward osmosis membrane and the primary side of the reverse osmosis membrane; It encompasses The wastewater is concentrated by permeating the wastewater from the primary side to the secondary side of the forward osmosis membrane, and the driving liquid is permeated from the primary side to the secondary side of the reverse osmosis membrane, and the permeate obtained on the secondary side of the reverse osmosis membrane is utilized in the incineration plant.

[0014] In this wastewater treatment method, wastewater is supplied to the primary side of a forward osmosis membrane (a process for supplying wastewater to be treated), and a driving fluid is circulated between the secondary side of the forward osmosis membrane and the primary side of the reverse osmosis membrane (a process for circulating). The osmotic pressure difference between the wastewater and the driving fluid across the forward osmosis membrane is utilized to move water from the wastewater side toward the driving fluid side. The driving fluid is diluted by the movement of water toward the driving fluid side, and the water in the diluted driving fluid permeates the reverse osmosis membrane and is used in the incineration plant as permeate. This wastewater treatment method utilizes the osmotic pressure difference between the wastewater and the driving fluid, allowing water from the wastewater side to smoothly move toward the driving fluid side. Furthermore, even if the driving fluid on the secondary side of the forward osmosis membrane is diluted by the water that permeated the forward osmosis membrane, it is concentrated on the primary side of the reverse osmosis membrane and then returned to the secondary side of the forward osmosis membrane. In this case, the driving liquid only needs to be concentrated to a level that maintains a constant solute concentration. This eliminates the need to apply excessive pressure to the driving liquid to counteract the osmotic pressure difference across the reverse osmosis membrane, thereby preventing clogging or damage to the reverse osmosis membrane. Because the osmotic pressure difference between the wastewater and the driving liquid is maintained at a high and stable level, forward osmosis, which transfers water from the wastewater into the driving liquid through the forward osmosis membrane, is carried out efficiently and stably. This improves the recovery rate of reusable permeate and ultimately improves the heat recovery rate from combustion exhaust gas.

[0015] In the wastewater treatment method according to the present invention, It is preferable that the method further comprises a concentrated wastewater supply step of supplying the concentrated wastewater obtained by concentrating the wastewater to the incineration plant for use and / or treatment in the incineration plant.

[0016] According to the wastewater treatment method of this configuration, a concentrated wastewater supply step is carried out in which the concentrated wastewater is supplied to an incineration plant, and the concentrated wastewater is used and / or treated in the incineration plant. This allows the concentrated wastewater to be effectively used, for example, in applications that do not require a high degree of purification in the incineration plant. Furthermore, by burning the concentrated wastewater in the incinerator, impurities in the concentrated wastewater can be reduced in volume and made harmless.

[0017] In the wastewater treatment method according to the present invention, It is preferable that the method further comprises a pretreatment step of pretreating the wastewater before it is supplied to the primary side of the forward osmosis membrane.

[0018] According to the wastewater treatment method of this configuration, pretreatment is performed on wastewater before it is supplied to the primary cell of the forward osmosis membrane (pretreatment step). This allows solid fine particles and the like to be removed in advance, making it less likely for the forward osmosis membrane to become clogged and allowing the forward osmosis membrane to be used for a longer period of time. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a block diagram showing the overall configuration of a wastewater treatment system in which wastewater treatment equipment according to one embodiment of the present invention is applied to an incineration plant that is not equipped with a cooling tower. [Figure 2] FIG. 2 is a schematic diagram showing the general configuration of the FO / RO treatment device. [Figure 3] FIG. 3 is a block diagram showing the overall configuration of a wastewater treatment system in which the wastewater treatment equipment according to one embodiment of the present invention is applied to an incineration plant equipped with a cooling tower. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described below with reference to the drawings. However, the present invention is not intended to be limited to the embodiments described below or the configurations shown in the drawings.

[0021] <Overall structure> Fig. 1 is a block diagram showing the overall configuration of a wastewater treatment system in which wastewater treatment equipment 10 according to one embodiment of the present invention is applied to an incineration plant 1A that does not have a temperature reducing tower. In Fig. 1, the incineration plant 1A is equipped with an incinerator 2 that combusts materials to be combusted, a heat recovery device 3 that recovers heat from the combustion exhaust gas discharged from the incinerator 2, and an exhaust gas treatment facility 5 that treats the combustion exhaust gas whose heat has been recovered by the heat recovery device 3. The temperature reducing tower is not an essential component but is an optional component that may be provided as needed (see Fig. 3).

[0022] <Combustion furnace> The incinerator 2 is used to burn materials to be combusted, such as waste materials such as municipal waste and biomass fuels, and the type of furnace is not limited as long as it can burn the materials to be combusted, and examples include stoker-type incinerators, fluidized bed incinerators, kiln-type incinerators, and gasification melting furnaces.

[0023] <Heat recovery equipment> The heat recovery device 3 may be, for example, a waste heat boiler or an economizer that uses heat recovered from combustion exhaust gas to heat water and generate steam or the like.

[0024] <Exhaust gas treatment equipment> The exhaust gas treatment facility 5 includes a dust collector 6, a denitration device 7, an induced draft fan 8, and a chimney 9, which are arranged in this order along the exhaust gas flow downstream of the heat recovery device 3 in the exhaust gas flow direction.

[0025] In the exhaust gas treatment facility 5, the exhaust gas from the heat recovery device 3 is sent to the dust collector 6 and the denitration device 7 by the induction action of the induced draft fan 8. In the dust collector 6, the combustion exhaust gas is subjected to dust removal treatment, and in the denitration device 7, the combustion exhaust gas is subjected to NOx removal treatment. The combustion exhaust gas that has been subjected to dust removal treatment and NOx removal treatment is then discharged to the outside via a chimney 9.

[0026] <Wastewater treatment equipment> The wastewater treatment facility 10 that treats wastewater generated in the incineration plant 1A is equipped with a pretreatment device 20 and an FO / RO treatment device 30. Here, the wastewater generated in the incineration plant 1A refers to wastewater generated within the premises of the incineration plant 1A, and includes at least equipment cooling wastewater after cooling the peripheral equipment of the incinerator 2. Examples of wastewater generated within the premises of the incineration plant 1A include blown wastewater blown out from a heat recovery device 3 such as a waste heat boiler, cleaning wastewater generated when washing platforms and building floors, car wash wastewater generated when washing waste collection vehicles, residue cooling wastewater used to cool the incineration residue and slag generated from the incinerator 2, domestic wastewater, and other wastewater generated within the incineration plant.

[0027] <Pretreatment device> The incineration plant 1A and the pretreatment device 20 are connected via the first drainage channel 11. The drainage discharged from the incineration plant 1A is introduced into the pretreatment device 20 via the first drainage channel 11. The pretreatment device 20 performs pretreatment on the introduced drainage to remove solid fine particles and the like contained in the drainage. As the pretreatment device 20, for example, a coagulation sedimentation device configured to separate and precipitate by aggregating fine particles into large lumps with a coagulant, a coagulation pressurized flotation device configured to remove suspended substances by capturing the suspended substances with fine bubbles and then floating them using the buoyancy of the bubbles, a filtration device using sand as a filter medium, a filtration device using an MF membrane (microfiltration membrane) or an UF membrane (ultrafiltration membrane), a biological treatment device configured to purify pollutants by utilizing microorganisms and bacteria, etc. can be mentioned, and one or a combination of any of these devices can be appropriately adopted.

[0028] A part of the drainage pretreated in the pretreatment device 20 is sent to the incineration plant 1A via the second drainage channel 12, and the remaining part of the drainage is introduced into the FO / RO treatment device 30 via the third drainage channel 13.

[0029] <FO / RO treatment device> The FO / RO treatment device 30 is configured to move water from the drainage side to the driving liquid side using the osmotic pressure difference between the drainage pretreated by the pretreatment device 20 and the driving liquid (high osmotic pressure solution) to concentrate the drainage, and at the same time, to concentrate the driving liquid diluted by the movement of water from the drainage side to the driving liquid side. The specific configuration of this FO / RO treatment device 30 will be described in detail below. Note that as the driving liquid, a liquid having a relatively higher osmotic pressure than the drainage can be used. Examples of the driving liquid include aqueous solutions of salts such as NaCl and MgCl2, and ionic liquids such as imidazolium salts and pyrrolidinium salts. In the following, the "driving liquid" is referred to as "DS".

[0030] 2 is a schematic diagram showing the general configuration of the FO / RO treatment device 30. As shown in FIG. 2, the FO / RO treatment device 30 includes a forward osmosis membrane module 31, a reverse osmosis membrane module 32, and a circulation circuit 33.

[0031] <Forward osmosis membrane module> The forward osmosis membrane module 31 has a forward osmosis membrane 40, as well as a primary cell 41 and a secondary cell 42 formed on the primary side and secondary side of the forward osmosis membrane 40, respectively.

[0032] <Forward osmosis membrane> The forward osmosis membrane 40 is not particularly limited, and various known semipermeable membranes that can be used in forward osmosis treatment can be used. A semipermeable membrane made of a cellulose-based material or a chlorine-resistant polyamide-based material is preferably used. Alternatively, a porous membrane made of an inorganic material such as ceramics may be used. Examples of cellulose-based materials include cellulose acetate, preferably cellulose triacetate (CTA). Examples of chlorine-resistant polyamide-based materials include highly chlorine-resistant polyamide polymers. The membrane may be in the form of a hollow fiber, tubular, spiral, flat, tubular, or monolithic. When a hollow fiber membrane is used, the liquid-storing compartment defined in the hollow fiber corresponds to the "primary cell" or "secondary cell" of the present invention, and the liquid-storing compartment defined outside the hollow fiber corresponds to the "secondary cell" or "primary cell" of the present invention.

[0033] In the forward osmosis membrane module 31, a primary cell 41 is provided with a wastewater inlet 43 on the upstream side in the flow direction and a wastewater outlet 44 on the downstream side in the flow direction. Furthermore, a secondary cell 42 is provided with a concentrated DS inlet 45 on the upstream side in the flow direction and a diluted DS outlet 46 on the downstream side in the flow direction. Note that, although the present embodiment shows an example of a parallel flow system in which the wastewater flowing in the primary cell 41 and the DS flowing in the secondary cell 42 flow in the same direction, the present invention is not limited to this and may also be a countercurrent system in which the wastewater and the DS flow opposite each other.

[0034] <Reverse osmosis membrane module> The reverse osmosis membrane module 32 has a reverse osmosis membrane 50, as well as a primary cell 51 and a secondary cell 52 formed on the primary side and secondary side of the reverse osmosis membrane 50, respectively.

[0035] <Reverse osmosis membrane> The reverse osmosis membrane 50 may be, for example, an organic polymer membrane or a ceramic membrane made of cellulose acetate, polyvinyl alcohol, polysulfone, aliphatic polyamide, aromatic polyamide, or a composite of these, and may be either an ultra-low pressure reverse osmosis membrane, a low pressure reverse osmosis membrane, or a medium pressure reverse osmosis membrane. As with the forward osmosis membrane 40, the membrane may be of any of a hollow fiber type, a tubular type, a spiral type, a flat membrane type, a tubular type, a monolith type, or the like.

[0036] In the reverse osmosis membrane module 32, a diluted DS inlet 53 is provided upstream of the flow direction in the primary cell 51, and a concentrated DS outlet 54 is provided downstream of the flow direction in the primary cell 51. In addition, a permeate outlet 55 is provided in the secondary cell 52.

[0037] <Circulation circuit> In the secondary cell 42 of the forward osmosis membrane module 31 and the primary cell 51 of the reverse osmosis membrane module 32, the diluted DS outlet 46 and the diluted DS inlet 53 are connected by a DS forward path 61, and the concentrated DS outlet 54 and the concentrated DS inlet 45 are connected by a DS return path 62. In this way, the secondary cell 42 of the forward osmosis membrane module 31, the DS forward path 61, the primary cell 51 of the reverse osmosis membrane module 32, and the DS return path 62 form a circulation circuit 33 for circulating DS between the secondary cell 42 of the forward osmosis membrane module 31 and the primary cell 51 of the reverse osmosis membrane module 32. By operating a pressure pump 63 interposed in the DS forward path 61, the DS in the primary cell 51 of the reverse osmosis membrane module 32 can be pressurized and circulated in the circulation circuit 33.

[0038] The wastewater inlet 43 and the pretreatment device 20 are connected by a third drainage channel 13. The wastewater outlet 44 and the incineration plant 1A are connected by a fourth drainage channel 14. The permeate outlet 55 and the permeate demand destination 70 in the incineration plant 1A are connected by a fifth drainage channel 15.

[0039] In the wastewater treatment facility 10 configured as described above, the pretreatment step, the wastewater to be treated supply step, the circulation step, and the concentrated wastewater supply step are carried out.

[0040] <Pretreatment process> As shown in Figure 1, wastewater generated in an incineration plant 1A is introduced into a pretreatment device 20 via a first drainage channel 11. In the pretreatment device 20, the introduced wastewater is first subjected to at least one of the following treatments: coagulation sedimentation, coagulation pressure flotation, sand filtration, screen filtration, magnetic separation, centrifugation, biological treatment, pH adjustment, adsorption treatment using activated carbon or the like, and ozone treatment, thereby removing SS components and suspended matter from the wastewater (first pretreatment step). Suspended matter includes organic fine particles, inorganic fine particles, and other solid fine particles.

[0041] Next, the wastewater from which suspended solids and the like have been removed in the first pretreatment step is subjected to a filtration process using an MF membrane or a UF membrane to remove fine particles, BOD, and the like from the wastewater (second pretreatment step). Note that the pretreatment steps (first pretreatment step and second pretreatment step) are not essential steps but are optional steps and may be omitted.

[0042] In this way, by carrying out a pretreatment process to reduce suspended solids and the like contained in the wastewater discharged from the incineration plant 1A, clogging of the forward osmosis membrane 40 in the FO / RO treatment device 30 becomes less likely, the continuous use period of the forward osmosis membrane 40 can be extended, and the frequency of replacement of the forward osmosis membrane 40 can be reduced.

[0043] A portion of the wastewater that has been pretreated in the first and second pretreatment processes in the pretreatment device 20 is sent to the incineration plant 1A via the second drainage channel 12 and can be reused as washing water for floors and other surfaces that require a certain degree of purity in the incineration plant 1A, washing water for waste collection vehicles, cooling water for incineration residues, etc.

[0044] <Treated wastewater supply process> As shown in Figure 2, the remainder of the wastewater (wastewater to be treated) that has been pretreated in the pretreatment device 20 is supplied to the inside of the primary cell 41 of the forward osmosis membrane module 31 in the FO / RO treatment device 30 via the third drainage channel 13 and the wastewater inlet 43.

[0045] <Circulation process> In the circulation circuit 33 , the pressure pump 63 is operated to circulate the DS between the secondary cell 42 of the forward osmosis membrane module 31 and the primary cell 51 of the reverse osmosis membrane module 32 .

[0046] In an FO / RO treatment device 30 that performs a wastewater supply process and a circulation process, water in the wastewater introduced into the primary cell 41 of a forward osmosis membrane module 31 permeates the forward osmosis membrane 40 due to the osmotic pressure difference between the wastewater and the DS, and moves into the DS inside the secondary cell 42. As a result, the wastewater in the primary cell 41 is concentrated, while the DS in the secondary cell 42 is diluted. The diluted DS is introduced into the primary cell 51 of the reverse osmosis membrane module 32 via the DS forward path 61 and the diluted DS inlet 53. The DS in the primary cell 51 is pressurized by the operation of a pressure pump 63, and the water in the diluted DS introduced into the primary cell 51 permeates the reverse osmosis membrane 50. As a result, the DS concentrated in the primary cell 51 is supplied into the secondary cell 42 of the forward osmosis membrane module 31 via the DS return path 62 and the concentrated DS inlet 45.

[0047] In the FO / RO treatment device 30, even if the DS in the secondary cell 42 of the forward osmosis membrane module 31 is diluted by water that has permeated the forward osmosis membrane 40, it is introduced into the primary cell 51 of the reverse osmosis membrane module 32, concentrated, and then returned to the secondary cell 42 of the forward osmosis membrane module 31. In this case, it is sufficient to concentrate the DS to a degree that maintains the solute concentration in the DS at a certain level or higher. This eliminates the need to apply excessive pressure to the DS to counter the osmotic pressure difference across the reverse osmosis membrane 50, thereby reducing energy consumption in the reverse osmosis treatment using the reverse osmosis membrane 50. Furthermore, substances that may cause clogging of the reverse osmosis membrane 50 are removed by the forward osmosis membrane 40, thereby preventing clogging of the membrane surface of the reverse osmosis membrane 50. In this way, the osmotic pressure difference between the wastewater side and the DS side is stably maintained at a high level, allowing for efficient and stable forward osmosis treatment, in which water in the wastewater moves into the DS through the forward osmosis membrane 40. Therefore, the recovery rate of reusable permeate can be improved, and further, the heat recovery rate from the combustion exhaust gas can be improved.

[0048] <Concentrated wastewater supply process> The concentrated wastewater concentrated in the primary cell 41 of the forward osmosis membrane module 31 is supplied to the incineration plant 1A via the wastewater outlet 44 and the fourth drainage channel 14. It is then utilized and / or treated in the incineration plant 1A. The concentrated wastewater in the incineration plant 1A can be utilized for purposes that do not require high purity, such as spraying water onto bottom ash and fly ash generated during the combustion of materials to be combusted in the incinerator 2 to cool and prevent scattering. The concentrated wastewater can be treated in the incineration plant 1A by supplying the concentrated wastewater to the incinerator 2, vaporizing the water in the concentrated wastewater, and combusting impurities such as organic matter present in high concentrations in the concentrated wastewater. This reduces the volume of the impurities in the concentrated wastewater and renders them harmless.

[0049] On the other hand, the water (permeate) that permeates the reverse osmosis membrane 50 and is recovered in the secondary cell 52 of the reverse osmosis membrane module 32 has a purity close to that of industrial water with a relatively high degree of purification, and is reused at the permeate demand destination 70 of the incineration plant 1A, which requires a relatively high degree of purification. In other words, the permeate is used in applications where it is difficult to use wastewater that does not reach a high degree of purification as is, such as raw boiler water for a waste heat boiler, equipment cooling water, plant water, and the like, which require a high degree of purification in the incineration plant 1A.

[0050] The wastewater treatment facility and the wastewater treatment method of the present invention have been described above based on one embodiment, but the present invention is not limited to the configuration described in the above embodiment, and the configuration can be changed as appropriate within the scope of the invention.

[0051] (Another embodiment 1) FIG. 3 is a block diagram showing the overall configuration of a wastewater treatment system in which a wastewater treatment equipment 10 according to one embodiment of the present invention is applied to an incineration plant 1B equipped with a temperature reducing tower 4. In the above embodiment, the wastewater treatment equipment 10 is applied to an incineration plant 1A not equipped with a temperature reducing tower. However, the present invention is not limited to this. As shown in FIG. 3, the wastewater treatment equipment 10 can also be applied to an incineration plant 1B equipped with a temperature reducing tower 4 interposed midway along the flue gas flow path between the heat recovery unit 3 and the dust collector 6. The temperature reducing tower 4 may, for example, include a tower body into which combustion exhaust gas whose heat has been recovered by the heat recovery unit 3 is introduced, and water is injected or sprayed onto the combustion exhaust gas introduced into the tower body to lower the temperature of the combustion exhaust gas by the heat of vaporization of the water. The water (permeated water) that permeates the reverse osmosis membrane 50 and is recovered in the secondary cell 52 of the reverse osmosis membrane module 32 may be used, for example, by supplying the permeated water to the temperature reducing tower 4 and injecting or spraying the permeated water onto the combustion exhaust gas introduced into the temperature reducing tower 4 to lower the temperature of the combustion exhaust gas by the heat of vaporization of the permeated water.

[0052] (Alternative embodiment 2) In the above embodiment and alternative embodiment 1, examples have been shown in which the wastewater treatment equipment 10 of the present invention is applied to incineration plants 1A, 1B equipped with a heat recovery device 3, but the wastewater treatment equipment 10 of the present invention can also be applied to incineration plants that do not have a heat recovery device 3, i.e., incineration plants that are configured not to recover heat from the combustion exhaust gas associated with combustion in the incinerator 2. [Industrial Applicability]

[0053] The wastewater treatment facility and wastewater treatment method of the present invention can be suitably used in applications where wastewater generated in an incineration plant is treated without being discharged outside the incineration plant system. [Explanation of symbols]

[0054] 1A, 1B Incineration Plant 2 Incinerator 3. Heat recovery equipment 10 Wastewater treatment facilities 13 Third drainage channel (treated wastewater supply channel) 14 Fourth drainage channel (concentrated wastewater supply channel) 20 Pretreatment device 30 FO / RO treatment equipment 31 Forward osmosis membrane module 32 Reverse osmosis membrane module 33 Circulation circuit 40 Forward osmosis membrane 41 Primary cell 42 Secondary cell 50 Reverse osmosis membrane 51 Primary cell 52 Secondary cell

Claims

1. A wastewater treatment facility that treats wastewater generated in an incineration plant equipped with an incinerator that burns materials to be combusted and a heat recovery device that recovers heat from the combustion exhaust gas discharged from the incinerator, a forward osmosis membrane module having a forward osmosis membrane and a primary cell and a secondary cell formed on the primary side and the secondary side of the forward osmosis membrane, respectively; a wastewater treatment supply channel for supplying the wastewater to a primary cell of the forward osmosis membrane module; a reverse osmosis membrane module having a reverse osmosis membrane and a primary cell and a secondary cell formed on the primary side and the secondary side of the reverse osmosis membrane, respectively; a circulation circuit that circulates a drive liquid between a secondary cell of the forward osmosis membrane module and a primary cell of the reverse osmosis membrane module, The wastewater treatment facility is configured to concentrate the wastewater by permeating the wastewater from the primary side toward the secondary side of the forward osmosis membrane, and to use the permeate obtained in the secondary cell of the reverse osmosis membrane module by permeating the driving liquid from the primary side toward the secondary side of the reverse osmosis membrane in the incineration plant.

2. The wastewater treatment facility according to claim 1, wherein the concentrated wastewater obtained by concentrating the wastewater is utilized and / or treated in the incineration plant.

3. The wastewater treatment facility according to claim 1 or 2, further comprising a pretreatment device that pretreats the wastewater before it is supplied to the primary cell of the forward osmosis membrane module.

4. A wastewater treatment method for treating wastewater generated in an incineration plant equipped with an incinerator that burns materials to be combusted and a heat recovery device that recovers heat from combustion exhaust gas discharged from the incinerator, comprising: a wastewater treatment supply step of supplying the wastewater to the primary side of the forward osmosis membrane; a circulation step of circulating a drive liquid between the secondary side of the forward osmosis membrane and the primary side of the reverse osmosis membrane; It encompasses The wastewater treatment method includes concentrating the wastewater by permeating the wastewater from the primary side toward the secondary side of the forward osmosis membrane, and permeating the driving liquid from the primary side toward the secondary side of the reverse osmosis membrane to obtain permeate at the secondary side of the reverse osmosis membrane, and utilizing the permeate at the incineration plant.

5. 5. The wastewater treatment method according to claim 4, further comprising a concentrated wastewater supply step of supplying the concentrated wastewater obtained by concentrating the wastewater to the incineration plant for use and / or treatment in the incineration plant.

6. 6. The wastewater treatment method according to claim 4, further comprising a pretreatment step of pretreating the wastewater before it is supplied to the upstream side of the forward osmosis membrane.

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