Water treatment system and water treatment method

Abstract

To provide a water treatment system and a water treatment method capable of securing electric power for water treatment and obtaining water adjusted to a proper temperature.SOLUTION: A water treatment system 1 includes: a methane fermentation facility 2 for generating a biogas by fermentation of methane; a biogas cogeneration facility 3 for generating an electric power and heat from the biogas; a desalination facility 4 for desalinating raw water by receiving an electric power from the biogas cogeneration facility 3; and an absorption type refrigerator 5 capable of adjusting a temperature of water that has been receiving heat from the biogas cogeneration facility 3 and desalinated by the desalination facility 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a water treatment system and a water treatment method. [Background technology]

[0002] Patent Document 1 describes a water treatment system for producing drinking water. The water treatment system for producing drinking water includes a prefilter, an MF membrane separation device, an MF membrane-treated water tank, a front-stage RO membrane device, a rear-stage RO membrane device, and an activated carbon adsorption device. The prefilter removes suspended matter from raw water sucked in by a lifting pump.

[0003] The treated water obtained after the suspended solids have been removed by the pre-filter is pressurized by a filtration pump and supplied to the MF membrane separation unit, where it is stored in the MF membrane treated water tank. The treated water in the MF membrane treated water tank is pressurized by a booster pump and a pressure pump and supplied to the first-stage RO membrane unit. The permeated water that passes through the first-stage RO membrane unit is supplied to the second-stage RO membrane unit, and the permeated water that passes through the second-stage RO membrane unit passes through an activated carbon adsorption unit before being discharged as drinking water (purified water). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-149285 Summary of the Invention [Problem to be solved by the invention]

[0005] Water treatment systems using RO (reverse osmosis) membranes, such as the drinking water production system mentioned above, are known to have a lower environmental impact than fossil fuel-based boiling evaporation systems. However, water treatment systems using RO membranes can require large amounts of electricity. Therefore, there is a need to ensure that electricity for water treatment can be secured. Furthermore, water treatment requires water that is adjusted to a more appropriate temperature.

[0006] An object of the present disclosure is to provide a water treatment system and a water treatment method that can reliably secure power for water treatment and obtain water adjusted to an appropriate temperature. [Means for solving the problem]

[0007] (1) The water treatment system according to the present disclosure includes a methane fermentation facility that produces biogas by fermenting methane, a biogas cogeneration facility that produces electricity and heat from the biogas, a desalination facility that receives electricity from the biogas cogeneration facility and desalinates raw water, and an absorption chiller that receives heat from the biogas cogeneration facility and can adjust the temperature of the water desalinated by the desalination facility.

[0008] In this water treatment system, the methane fermentation facility generates biogas, and the biogas cogeneration facility generates electricity and heat from the biogas. The desalination facility receives electricity generated from the biogas by the biogas cogeneration facility and desalinates raw water. Therefore, the electricity generated from the biogas can be used for water treatment, more reliably securing electricity for water treatment. The temperature of the water desalinated by the desalination facility is adjusted by an absorption chiller. This absorption chiller can obtain water adjusted to an appropriate temperature. Furthermore, the absorption chiller can adjust the temperature of the water by receiving heat generated from the biogas by the biogas cogeneration facility. Therefore, the heat generated from the biogas can be effectively used to adjust the temperature of the water, making this an environmentally friendly water treatment system.

[0009] (2) In the above (1), the methane fermentation facility may generate biogas by fermenting methane contained in livestock manure. In this case, biogas is generated from livestock manure obtained through livestock farming. Therefore, livestock manure can be effectively used for water treatment.

[0010] (3) In the above (1) or (2), the absorption chiller may adjust the temperature of the desalinated water to produce drinking water. In this case, drinking water adjusted to an appropriate temperature by the absorption chiller can be obtained.

[0011] (4) In any of the above (1) to (3), the absorption chiller may adjust the temperature of the desalinated water to generate a heat medium used in the heat exchange. In this case, the heat medium whose temperature has been adjusted by the absorption chiller can be obtained. Therefore, by repeatedly adjusting the temperature of the heat medium by passing it through a circulation path, the heat medium whose temperature has been adjusted using heat obtained from the biogas can be effectively utilized.

[0012] (5) The water treatment method according to the present disclosure includes a step of producing biogas by fermenting methane, a step of producing electricity and heat from the biogas, a step of desalination of raw water using electricity, and a step of adjusting the temperature of the desalinated water using heat in the desalination step.

[0013] In this water treatment method, electricity and heat can be obtained from the generated biogas, and raw water is desalinated using the electricity generated from the biogas. Therefore, as with the water treatment system described above, the electricity generated from the biogas can be used for water treatment, making it possible to more reliably secure electricity for water treatment. The temperature of the desalinated water is adjusted, so water adjusted to an appropriate temperature can be obtained. Furthermore, the temperature of the water is adjusted using the heat generated from the biogas. Therefore, the heat generated from the biogas can be effectively used to adjust the temperature of the water, making this an environmentally friendly water treatment method. [Effects of the Invention]

[0014] According to the present disclosure, it is possible to reliably secure electricity for water treatment and obtain water adjusted to an appropriate temperature. [Brief explanation of the drawings]

[0015] [Figure 1]FIG. 1 is a diagram showing the configuration of a water treatment system according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of an absorption chiller in the water treatment system of FIG. [Figure 3] FIG. 3 is a flowchart showing an example of steps of a water treatment method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of a water treatment system and a water treatment method according to the present disclosure will be described with reference to the drawings. In the description of the drawings, identical or corresponding elements are designated by the same reference numerals, and duplicate explanations will be omitted as appropriate. The drawings may be partially simplified or exaggerated for ease of understanding, and the dimensional proportions and the like are not limited to those shown in the drawings.

[0017] FIG. 1 is a diagram schematically illustrating the configuration of a water treatment system 1 according to this embodiment. The water treatment system 1 is installed, for example, in an island area. The water treatment system 1 produces fresh water. In general, water treatment systems often employ a method using a reverse osmosis membrane (RO membrane), which has a smaller environmental impact than a method of boiling and evaporating seawater using fossil fuels.

[0018] However, membrane-type freshwater facilities can require large amounts of electricity. In island areas, it can be difficult to supply large amounts of electricity to membrane-type freshwater facilities. On the other hand, livestock farming, such as beef cattle, pigs, and broilers, is often carried out in island areas. In this case, the burden of disposing of livestock waste can become a significant problem.

[0019] For example, the water treatment system 1 generates electricity and heat from livestock waste, desalinates seawater with the generated electricity, and uses the generated heat to adjust the temperature of the desalinated water. Therefore, by converting livestock waste in the island area into electricity and heat, and using the electricity for desalination and the heat to adjust the temperature of the freshwater, the livestock waste in the island area can be effectively used to produce freshwater. In other words, the livestock waste can be effectively treated and the electricity for producing freshwater can be secured.

[0020] The water treatment system 1 produces, for example, drinking water. However, the water treatment system 1 may also produce water to be used as a heat transfer medium, and there are no particular limitations on the use of the water produced by the water treatment system 1. The water treatment system 1 includes a methane fermentation facility 2, a biogas cogeneration facility 3, a desalination facility 4, and an absorption chiller 5.

[0021] The methane fermentation facility 2 ferments methane to produce biogas. The methane fermentation facility 2 decomposes organic matter using anaerobic bacteria under anaerobic conditions to produce biogas containing methane and carbon dioxide. In the methane fermentation facility 2, methane gas is produced as the microorganisms consume the organic matter in the anaerobic environment.

[0022] The methane fermentation facility 2 generates biogas by fermenting methane contained in, for example, livestock manure. In this case, livestock manure is the organic matter used in the methane fermentation facility 2. In this way, the methane fermentation facility 2 may generate biogas by fermenting methane contained in livestock manure.

[0023] However, the organic matter used in the methane fermentation facility 2 may also be brewery wastewater. In this case, high-temperature methane fermentation technology, which has a faster reaction rate, can be employed in the methane fermentation facility 2. Furthermore, the organic matter used in the methane fermentation facility 2 may be a wide variety of organic waste, including food waste, paper waste, plants, vegetable scraps, and other food residues, sewage sludge, and waste oil.

[0024] As an example, the methane fermentation facility 2 includes a slurry tank, a methane fermenter, and desulfurization equipment. The slurry tank stores organic matter that has been separated and hydrated to form a slurry, while blocking access to the outside air. The methane fermenter has a bioreactor containing methane fermentation bacteria, which use the methane fermentation bacteria to produce biogas containing methane gas and carbon dioxide from the organic matter contained in the slurry. The desulfurization equipment removes hydrogen sulfide produced during the production of biogas.

[0025] For example, the methane fermentation facility 2 generates biogas containing methane and carbon dioxide by mesophilic methane fermentation of accumulated livestock manure. The biogas is used as fuel for desalination and for adjusting the temperature of freshwater. For example, the biogas contains 60% to 70% methane and 30% to 40% carbon dioxide. The biogas generated in the methane fermentation facility 2 may be stored in a temporary storage tank. Alternatively, the biogas generated in the methane fermentation facility 2 may be sent to the biogas cogeneration facility 3.

[0026] The biogas cogeneration facility 3 generates electricity and heat from the biogas. For example, the biogas cogeneration facility 3 generates electricity for desalination and heat for adjusting the temperature of the fresh water. The biogas cogeneration facility 3 performs energy conversion through cogeneration using the biogas. For example, the biogas cogeneration facility 3 generates electricity using the biogas as fuel. The biogas cogeneration facility 3 may also generate electricity and hot water from the biogas.

[0027] The biogas cogeneration facility 3 may have, for example, a gas engine, a waste heat boiler, and a generator. In this case, the biogas cogeneration facility 3 can obtain electric power from the generator and steam from the waste heat boiler along with hot water. The biogas cogeneration facility 3 may have, for example, a gas turbine, a waste heat boiler, and a generator. In this case, the biogas cogeneration facility 3 can obtain electric power from the generator and steam from the waste heat boiler.

[0028] The steam and hot water mentioned above become waste heat. Therefore, the biogas cogeneration system 3 produces electricity generated by the generator and waste heat generated by the generator. For example, the power generation efficiency of the biogas cogeneration system 3 is between 20% and 30%, and the usable waste heat from the biogas cogeneration system 3 is 50%. The electricity produced in the biogas cogeneration system 3 is supplied to the desalination system 4, and the waste heat produced in the biogas cogeneration system 3 is supplied to the absorption chiller 5.

[0029] The desalination facility 4 receives power from the biogas cogeneration facility 3 and desalinates the raw water. For example, the raw water is seawater, and the desalination facility 4 is a seawater desalination device. In this case, the desalination facility 4 desalinates the seawater to produce fresh water (e.g., fresh water). For example, the desalination facility 4 is a reverse osmosis membrane device. As an example, in a water treatment system 1 installed on an island, the desalination facility 4 desalinates the seawater around the island.

[0030] The desalination facility 4 generates drinking water from seawater by, for example, desalinating the seawater. In this case, the desalination facility 4 has a reverse osmosis (RO) membrane that removes chloride ions from the seawater. As an example, the pore size of the RO membrane of the desalination facility 4 is 0.1 nm or more and 2 nm or less.

[0031] For example, the desalination facility 4 performs pretreatment on the seawater before passing it through an RO membrane. In the pretreatment, fine particles contained in the seawater are removed. For example, the desalination facility 4 has a sand filter device whose filter material is sand. The sand filter device removes suspended solids from the seawater. The desalination facility 4 may have a UF (Ultra Filtration membrane) membrane device and an MF (Micro Filtration membrane) membrane device.

[0032] The UF membrane device has a UF membrane (also called an ultrafiltration membrane) and removes bacteria and turbidity from seawater by passing the seawater through the UF membrane. The MF membrane device has an MF membrane (also called a microfiltration membrane) and removes fine particles and bacteria from seawater by passing the seawater through the MF membrane. As described above, the desalination facility 4 has at least one of a sand filtration device, a UF membrane device, and an MF membrane device as a device for pretreating seawater.

[0033] In the desalination facility 4, the pretreated seawater is passed through an RO membrane. For example, the desalination facility 4 has a pump that applies pressure to the seawater, and the pump applies pressure to the seawater, forcing the seawater through the RO membrane, causing the salt in the seawater to be removed in the RO membrane and fresh water to pass through the RO membrane. As described above, in the desalination facility 4, fresh water is obtained by passing the seawater through the RO membrane.

[0034] The desalination facility 4 has a plurality of pumps, such as the pumps described above, that transfer raw water. For example, electricity from the biogas cogeneration facility 3 is supplied to a plurality of pumps in the desalination facility 4. However, electricity from the biogas cogeneration facility 3 may also be supplied to devices other than the pumps in the desalination facility 4. In this way, the desalination facility 4 uses the electricity obtained from the biogas cogeneration facility 3.

[0035] The absorption chiller 5, for example, adjusts the temperature of water that receives heat from the biogas cogeneration facility 3 and is desalinated by the desalination facility 4. For example, the absorption chiller 5 adjusts the temperature of the desalinated water to produce drinking water. As an example, the absorption chiller 5 cools fresh water to produce drinking water cooled to a temperature of 5°C or higher and 7°C or lower. The absorption chiller 5 may also heat fresh water to produce drinking water heated to a temperature of 40°C or higher and 100°C or lower. In this way, the absorption chiller 5 can produce drinking water at various temperatures.

[0036] The absorption chiller 5 may adjust the temperature of the desalinated water to generate a heat medium used in heat exchange. For example, a heat medium pipe P leading to the building S may be connected to the absorption chiller 5, and the absorption chiller 5 may adjust the temperature of the heat medium supplied to the building S via the heat medium pipe P. Furthermore, the absorption chiller 5 and the heat medium pipe P may be provided inside the building S.

[0037] As an example, the heat medium passing through the heat medium piping P is used as a heat medium for an air conditioning system in the building S. For example, the absorption chiller 5 supplies a refrigerant to the air conditioning system via the heat medium piping P. The heat medium piping P may circulate while passing through the absorption chiller 5 and the building S. In this case, the heat medium whose temperature has been adjusted by the absorption chiller 5 can be constantly supplied to the building S via the heat medium piping P.

[0038] A detailed example of the absorption chiller 5 will be described below with reference to FIG. 2. The absorption chiller 5 converts heat from, for example, the biogas cogeneration facility 3 into cold energy. For example, the absorption chiller 5 produces chilled water and hot water. As shown in FIG. 2, the absorption chiller 5 includes a regenerator 6 to which heat H1 is supplied from the biogas cogeneration facility 3, a condenser 7 that converts waste heat H2, an evaporator 8 that absorbs heat H3, an absorber 9 that converts waste heat H4, an expansion device 10, and a pump 11. The absorption chiller 5 employs an absorption refrigeration cycle including evaporation, absorption, regeneration, and condensation. The absorption chiller 5 does not include, for example, an electrically powered compressor.

[0039] For example, low-temperature, low-pressure water and water vapor enter the evaporator 8. The inside of the evaporator 8 is in a vacuum state (almost a vacuum state). Inside the evaporator 8, the boiling point of water is lower than 100°C (for example, 7°C or higher and 10°C or lower). The evaporator 8 generates water vapor in an environment where the boiling point of water is lower than 100°C, and the generated water vapor is sent to the absorber 9.

[0040] An absorbing liquid flows between the absorber 9 and the regenerator 6 via a pump 11. The absorbing liquid is, for example, a lithium bromide solution. In the absorber 9, the water vapor sent from the evaporator 8 is absorbed by the absorbing liquid. The pump 11 sends the absorbing liquid, which has been diluted by absorbing the water vapor, to the regenerator 6.

[0041] The regenerator 6 heats the absorption liquid, which has been diluted by absorbing water vapor, with heat H1 from the biogas cogeneration facility 3. The regenerator 6 separates water vapor from the absorption liquid, which has been diluted by heating, to increase the concentration of the absorption liquid. As mentioned above, when the absorption liquid is a lithium bromide solution, the boiling point of lithium bromide is significantly higher than the boiling point of water, making it easy to separate water vapor from the absorption liquid. The concentrated absorption liquid is sent to the absorber 9 by a pump 11. The water vapor separated in the regenerator 6 is sent to the condenser 7.

[0042] The condenser 7 condenses (liquefies) the water vapor from the regenerator 6 and returns it to water. The expansion device 10 reduces the pressure (expands) of the water condensed in the condenser 7, and the water reduced in pressure in the expansion device 10 is sent to the evaporator 8. The water sent from the expansion device 10 to the evaporator 8 is converted back into water vapor inside the evaporator 8.

[0043] For example, fresh water from the desalination facility 4 is sent to the evaporator 8 and cooled in the evaporator 8, thereby producing at least one of drinking water and a heat medium in the absorption chiller 5. Alternatively, the fresh water from the desalination facility 4 may be heated in the evaporator 8 or a water heater (not shown) installed in the regenerator 6, thereby producing at least one of drinking water and a heat medium in the absorption chiller 5. In this way, the method for adjusting the temperature of the fresh water in the absorption chiller 5 can be changed as appropriate, and the temperature of the fresh water can be adjusted as desired by the absorption chiller 5.

[0044] The absorption chiller 5 uses water as a refrigerant, which has the advantages of low refrigerant costs and being environmentally friendly. In this embodiment, the absorption chiller 5 may produce both drinking water and a heat transfer medium from the fresh water sent from the desalination facility 4. In this case, livestock waste can be converted into energy in island areas to obtain drinking water and a heat transfer medium at appropriate temperatures, thereby realizing sustainable local circulation and local production and consumption.

[0045] Next, steps of the water treatment method according to this embodiment will be described with reference to FIG. 3. FIG. 3 is a flowchart showing an example of the steps of the water treatment method. An example of the water treatment method using the water treatment system 1 will be described below. First, biogas is generated (step of generating biogas, step S1). For example, livestock manure is input into the methane fermentation facility 2, which then decomposes the livestock manure using anaerobic bacteria under anaerobic conditions to generate biogas containing methane and carbon dioxide. As mentioned above, the methane fermentation facility 2 may also generate biogas from organic matter other than livestock manure.

[0046] Next, electricity and heat are generated from the biogas (step S2 of generating electricity and heat from biogas). For example, the biogas cogeneration facility 3 operates a generator using the biogas supplied from the methane fermentation facility 2, and generates electricity and heat through the operation of the generator. The biogas cogeneration facility 3 supplies the generated electricity to the desalination facility 4 and also supplies the generated heat to the absorption chiller 5.

[0047] Next, the raw water is desalinated using electricity from the biogas (a process of desalinating raw water, step S3). For example, the desalination facility 4 pretreats the raw seawater using at least one of a sand filtration device, a UF membrane device, and an MF membrane device, and generates fresh water by passing the pretreated seawater through an RO membrane. The desalination facility 4 sends the generated fresh water to an absorption chiller 5.

[0048] Next, the temperature of the desalinated water is adjusted using heat from the biogas (adjusting step, step S4). For example, the regenerator 6 of the absorption chiller 5 separates water vapor from the absorption liquid using heat from the biogas cogeneration facility 3, and the water vapor is condensed by the condenser 7 and sent to the evaporator 8, while the fresh water from the desalination facility 4 is cooled in the evaporator 8. Alternatively, the absorption chiller 5 may heat the fresh water from the desalination facility 4 in the evaporator 8 or a water heater (not shown) installed in the regenerator 6. The absorption chiller 5 produces at least one of drinking water and a heat medium from the fresh water by adjusting the temperature of the fresh water. Through the above steps, a series of steps in the water treatment method according to this embodiment is completed.

[0049] As described above, in the water treatment system 1 and water treatment method according to this embodiment, the methane fermentation facility 2 generates biogas, and the biogas cogeneration facility 3 generates electricity and heat from the biogas. The desalination facility 4 receives the electricity generated from the biogas by the biogas cogeneration facility 3 and desalinates the raw water. Therefore, the electricity generated from the biogas can be used for water treatment, making it possible to more reliably secure electricity for water treatment.

[0050] The temperature of the water desalinated by the desalination facility 4 is adjusted by the absorption chiller 5. Water adjusted to an appropriate temperature by the absorption chiller 5 can be obtained. Furthermore, the absorption chiller 5 can adjust the temperature of the water by receiving heat generated from the biogas by the biogas cogeneration facility 3. Therefore, the heat generated from the biogas can be effectively used to adjust the temperature of the water, making the water treatment system 1 environmentally friendly.

[0051] In this embodiment, the methane fermentation facility 2 may generate biogas by fermenting methane contained in livestock manure. In this case, biogas is generated from livestock manure obtained through livestock farming. Therefore, livestock manure can be effectively used for water treatment.

[0052] In this embodiment, the absorption chiller 5 may adjust the temperature of the desalinated water to produce drinking water. In this case, drinking water adjusted to an appropriate temperature by the absorption chiller 5 can be obtained.

[0053] In this embodiment, the absorption chiller 5 may adjust the temperature of the desalinated water to generate the heat medium used in the heat exchange. In this case, the heat medium whose temperature has been adjusted can be obtained by the absorption chiller 5. Therefore, by repeatedly adjusting the temperature of the heat medium by passing it through a circulation path such as the heat medium piping P, the heat medium whose temperature has been adjusted using heat obtained from the biogas can be effectively utilized.

[0054] The above describes embodiments of the water treatment system and water treatment method according to the present disclosure. However, the water treatment system and water treatment method according to the present disclosure are not limited to the contents of the above-described embodiments and may be modified within the scope of the gist described in the claims. In other words, the configuration and function of each part of the water treatment system, and the content and order of the steps of the water treatment method, may be modified as appropriate within the scope of the above-described gist.

[0055] For example, in the above-described embodiment, the water treatment system 1 is installed in an island area. However, the water treatment system may be installed in a location other than an island area, and the location where the water treatment system is installed and the location where the water treatment method is performed are not particularly limited. [Explanation of symbols]

[0056] 1...water treatment system, 2...methane fermentation equipment, 3...biogas cogeneration equipment, 4...desalination equipment, 5...absorption chiller, 6...regenerator, 7...condenser, 8...evaporator, 9...absorber, 10...expansion device, 11...pump, H1...heat, H2...waste heat, H3...heat absorption, H4...waste heat, P...heat medium piping, S...building.

Claims

1. A methane fermentation facility that ferments methane to produce biogas; a biogas cogeneration facility that generates electricity and heat from the biogas; a desalination facility that receives the electric power from the biogas cogeneration facility and desalinates raw water; an absorption chiller capable of adjusting the temperature of water that receives the heat from the biogas cogeneration facility and is desalinated by the desalination facility; Equipped with Water treatment system.

2. The methane fermentation facility ferments methane contained in livestock manure to produce the biogas. The water treatment system of claim 1 .

3. The absorption chiller adjusts the temperature of the desalinated water to produce drinking water. The water treatment system according to claim 1 or 2.

4. The absorption chiller adjusts the temperature of the desalinated water to generate a heat medium to be used for heat exchange. The water treatment system according to claim 1 or 2.

5. fermenting methane to produce biogas; generating electricity and heat from the biogas; desalination of raw water using the electric power; a step of adjusting the temperature of the desalinated water by the heat in the desalination step; Equipped with Water treatment methods.

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