Organic matter decomposition system

Abstract

Provided is an organic matter decomposition system for decomposing organic matter by anaerobic biological treatment without performing aerobic biological treatment. According to an embodiment, this organic matter decomposition system comprises: a hardness removal unit that removes a hardness component from raw water to be treated; a carbonic acid removal unit that removes a carbonic acid component from the raw water from which the hardness component has been removed; an alkali injection unit that injects an alkali into the raw water from which the carbonic acid component has been removed; an insoluble organic matter concentration unit that concentrates insoluble organic matter included in the raw water into which the alkali has been injected; and an anaerobic biological treatment unit that performs anaerobic biological treatment on the raw water in which the insoluble organic matter has been concentrated and decomposes the insoluble organic matter.

Description

Organic matter decomposition system

[0001] An embodiment of the present invention relates to an organic matter decomposition system that decomposes organic matter contained in raw water by anaerobic biological treatment.

[0002] BACKGROUND ART Conventionally, when raw water such as industrial wastewater or sewage contains organic matter, the organic matter is generally decomposed by biological treatment.

[0003] There are two types of biological treatment: aerobic biological treatment and anaerobic biological treatment. Aerobic biological treatment decomposes organic matter by supplying oxygen to aerobic microorganisms through aeration. However, the electricity consumption required for aeration is very large. On the other hand, anaerobic biological treatment does not use aeration, so electricity consumption is significantly reduced. In addition, the biogas generated can be used as energy. However, anaerobic biological treatment can only be applied to raw water that contains a high concentration of organic matter.

[0004] For this reason, many techniques have been devised to concentrate organic matter in raw water.

[0005] Organic matter in raw water can be divided into insoluble and soluble organic matter. Insoluble organic matter can be concentrated using a settling tank, a microfiltration membrane (hereinafter also referred to as "MF membrane"), or an ultrafiltration membrane (hereinafter also referred to as "UF membrane"). However, when using an MF membrane or UF membrane, the separation performance of the membrane is reduced due to biofouling. Furthermore, a settling tank can only recover solid organic matter with large particle sizes, and cannot recover organic matter with small particle sizes, even if it is in solid form.

[0006] On the other hand, soluble organic matter can be concentrated using a forward osmosis membrane (hereinafter also referred to as an "FO membrane") or a reverse osmosis membrane (hereinafter also referred to as an "RO membrane"). When using an FO membrane, a draw solution is required. This requires treatment and regeneration of the draw solution. Furthermore, when using an RO membrane to concentrate, not only organic matter but also inorganic ions are concentrated, which can cause hardness scaling and silica scaling. Furthermore, the RO membrane is prone to biofouling.

[0007] Japanese Patent Application Publication No. 61-234989 Japanese Patent Application Publication No. 2000-511109 Japanese Patent Application Publication No. 2014-8431

[0008] Thus, due to the problems of scaling and biofouling, there is no organic matter decomposition system that decomposes organic matter using only anaerobic biological treatment without also performing aerobic biological treatment.

[0009] If such an organic matter decomposition system were to be realized, it would not only be possible to decompose organic matter with little power consumption, but it would also be possible to recover bioenergy obtained from the decomposition of the organic matter.

[0010] The problem to be solved by the present invention is to provide an organic matter decomposition system that decomposes organic matter by anaerobic biological treatment without performing aerobic biological treatment.

[0011] The organic matter decomposition system of the embodiment includes a hardness removal unit that removes hardness components from the raw water to be treated, a carbon dioxide removal unit that removes carbon dioxide components from the raw water from which the hardness components have been removed, an alkali injection unit that injects alkali into the raw water from which the carbon dioxide components have been removed, an insoluble organic matter concentration unit that concentrates insoluble organic matter contained in the raw water from which the alkali has been injected, and an anaerobic biological treatment unit that performs anaerobic biological treatment on the raw water from which the insoluble organic matter has been concentrated, and decomposes the insoluble organic matter.

[0012] Fig. 1 is a block diagram showing an example of the configuration of an organic matter decomposition system according to a first embodiment of the present invention. Fig. 2 is a block diagram showing an example of the configuration of an organic matter decomposition system according to a second embodiment of the present invention. Fig. 3 is a block diagram showing an example of the configuration of an organic matter decomposition system according to a third embodiment of the present invention.

[0013] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc., are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and each drawing, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed and redundant explanations will be omitted as appropriate.

[0014] (First embodiment) An organic matter decomposition system according to a first embodiment of the present invention will be described.

[0015] FIG. 1 is a block diagram showing an example of the configuration of an organic matter decomposition system according to a first embodiment of the present invention.

[0016] That is, the organic matter decomposition system 10A of the first embodiment includes a raw water supply tank 12, a solid matter separation section 14, a hardness removal section 16, a carbon dioxide removal section 18, an alkali injection section 20, an insoluble organic matter concentration section 22, an anaerobic biological treatment section 24, and a post-treatment section 26.

[0017] The raw water supply tank 12 stores raw water a, such as industrial wastewater or sewage. Raw water a typically contains organic matter, hardness components (calcium, magnesium, and carbonate ions), scaling substances such as silica, and fouling substances. The raw water a may have a concentration range of, for example, a BOD (Biochemical Oxygen Demand) of 2000 mg / L or less, a COD (Chemical Oxygen Demand) of 2000 mg / L or less, or both. The raw water a stored in the raw water supply tank 12 is supplied from the raw water supply tank 12 to the solid separation section 14.

[0018] Furthermore, although the concentration range of raw water a can be set to either or both of a BOD of 2000 mg / L or less and a COD (Chemical Oxygen Demand) of 2000 mg / L or less, this condition may also be applied to raw water b from which solids have been separated in the solid separation section 14 described below.

[0019] The solid separation unit 14 separates solids from the raw water a supplied from the raw water supply tank 12, for example, by coagulation sedimentation or sand filtration. The raw water b from which the solids have been separated is supplied from the solid separation unit 14 to the hardness removal unit 16.

[0020] The hardness removal unit 16 removes hardness components from the raw water b supplied from the solid separation unit 14 using, for example, an ion exchange resin, thereby removing scaling substances. The raw water c from which the hardness components have been separated is supplied from the hardness removal unit 16 to the carbon dioxide removal unit 18.

[0021] The carbon dioxide removal unit 18 removes carbonate components from the raw water c supplied from the hardness removal unit 16, for example, by using a decarbonation tower. The raw water d from which the carbonate components have been removed is supplied from the carbon dioxide removal unit 18 to the insoluble organic matter concentration unit 22.

[0022] The alkali injection unit 20 is connected to the middle of the supply line from the carbon dioxide removal unit 18 to the insoluble organic matter concentrating unit 22, and injects an alkali e into the raw water d. The alkali e is not limited to, but may be, for example, caustic soda. By injecting the alkali e, the raw water d becomes raw water f with a high pH of 9 to 11, and is supplied to the insoluble organic matter concentrating unit 22. The raw water f with a high pH in this manner can avoid biofouling in membranes such as MF membranes and UF membranes used in the insoluble organic matter concentrating unit 22.

[0023] The insoluble organic matter concentrating section 22 concentrates the insoluble organic matter contained in the raw water f, and can be, for example, a filtration membrane with a pore size of approximately 0.01 μm to 10 μm. Suitable filtration membranes include, but are not limited to, MF membranes (pore size of 0.1 to 10 μm) and UF membranes (pore size of approximately 0.01 μm). Depending on the particle size of the insoluble organic matter contained in the raw water f, the insoluble organic matter concentrating section 22 can be implemented using only an MF membrane, only a UF membrane, or both an MF membrane and a UF membrane, such as by arranging an MF membrane and a UF membrane in series.

[0024] Concentrated water g, which is raw water in which insoluble organic matter has been concentrated by the insoluble organic matter concentrating section 22, is supplied to the anaerobic biological treatment section 24. In the insoluble organic matter concentrating section 22, raw water j, in which insoluble organic matter has been removed from raw water f, is also produced at the same time as concentrated water g is produced. The raw water j is discharged from the insoluble organic matter concentrating section 22 to the outside of the organic matter decomposition system 10A.

[0025] The anaerobic biological treatment unit 24 performs anaerobic biological treatment on the concentrated water g supplied from the insoluble organic matter concentrating unit 22, decomposing the insoluble organic matter contained in the concentrated water g. The biogas generated during the decomposition of the organic matter can also be recovered as energy. The treated water h containing the decomposed organic matter is supplied from the anaerobic biological treatment unit 24 to a post-treatment unit 26.

[0026] The post-treatment unit 26 is, for example, a settling tank or an evaporator, and performs post-treatment on the treated water (h) supplied from the anaerobic biological treatment unit 24. The post-treatment unit performs the treatment required for discharging the water outside the organic matter decomposition system 10A. For example, if the water is to be discharged into a river or a sewer, the post-treatment unit performs treatment that meets the respective discharge standards. If the goal is to reuse the treated water, the post-treatment unit performs treatment that meets the water quality standards required for reuse. In either case, if the water quality of the treated water (h) has already reached the required water quality standards, no post-treatment unit is particularly necessary.

[0027] As described above, according to the organic matter decomposition system 10A of this embodiment, a membrane such as an MF membrane or a UF membrane is used in the insoluble organic matter concentration section 22 to concentrate the organic matter, but before the raw water is introduced into the insoluble organic matter concentration section 22, hardness components are removed from the raw water by the hardness removal section 16, thereby removing scaling substances, and alkali is further added by the alkali injection section 20 to increase the pH, thereby preventing the occurrence of biofouling in the membrane.

[0028] The concentrated water g in which the organic matter has been concentrated in the insoluble organic matter concentrating section 22 is then supplied to the anaerobic biological treatment section 24, thereby enabling efficient decomposition of the organic matter through anaerobic biological treatment. Unlike aerobic biological treatment, anaerobic biological treatment does not involve aeration, which requires a large amount of electricity. This makes it possible to efficiently decompose organic matter while significantly reducing power consumption. Furthermore, biogas can also be recovered through anaerobic biological treatment.

[0029] Second Embodiment An organic matter decomposition system according to a second embodiment of the present invention will be described.

[0030] FIG. 2 is a block diagram showing an example of the configuration of an organic matter decomposition system according to the second embodiment of the present invention.

[0031] The organic matter decomposition system 10B of the second embodiment has a configuration in which a soluble organic matter concentrator 28 is added to the organic matter decomposition system 10A of the first embodiment. Therefore, the configuration already described for the organic matter decomposition system 10A of the first embodiment will not be described here, and only the differences from the organic matter decomposition system 10A will be described.

[0032] The soluble organic matter concentrating section 28 is a section that concentrates the soluble organic matter contained in the raw water j generated by the insoluble organic matter concentrating section 22, and an RO membrane can be used for this concentration.

[0033] When an RO membrane is used, the dissolved organic matter concentrating unit 28 uses the RO membrane to concentrate the organic matter contained in the raw water j by approximately 5 to 20 times. However, the concentration rate is not limited to this range, and depending on the conditions, it is possible to concentrate the organic matter up to 50 or 100 times. In addition, because the raw water j has a high pH, ​​silica scaling and biofouling in the RO membrane are prevented.

[0034] The soluble organic matter concentrating unit 28 concentrates the organic matter in the raw water j using an RO membrane to produce concentrated water k. The concentrated water k is supplied from the soluble organic matter concentrating unit 28 to the anaerobic biological treatment unit 24. Meanwhile, permeated water m, which is the raw water f that has permeated the RO membrane, is discharged from the soluble organic matter concentrating unit 28 to the outside of the organic matter decomposition system 10B.

[0035] As a result, in addition to the concentrated water g from the insoluble organic matter concentrating section 22, the concentrated water k from the soluble organic matter concentrating section 28 is also supplied to the anaerobic biological treatment section 24. Therefore, the anaerobic biological treatment section 24 performs anaerobic biological treatment on the concentrated water g and the concentrated water k, decomposing the soluble organic matter from the concentrated water g and the concentrated water k. The treated water h containing the organic matter decomposed in this manner is supplied from the anaerobic biological treatment section 24 to the post-treatment section 26.

[0036] As described above, according to the organic matter decomposition system 10B of this embodiment, the raw water j discharged from the insoluble organic matter concentrating unit 22 is not directly discharged, but is further concentrated by the soluble organic matter concentrating unit 28 to produce concentrated water k, and this concentrated water k can also be subjected to anaerobic biological treatment in the anaerobic biological treatment unit 24. This further improves the organic matter recovery efficiency. Although an RO membrane is preferably used for the soluble organic matter concentrating unit 28, even if an RO membrane is used for the soluble organic matter concentrating unit 28, the raw water j introduced into the RO membrane has had hardness components removed by the hardness removal unit 16 and has a high pH due to the supply of alkali e from the alkali injection unit 20, thereby preventing scaling and biofouling in the RO membrane.

[0037] In the above explanation, the concentrated water g from the insoluble organic matter concentrating section 22 and the concentrated water k from the soluble organic matter concentrating section 28 are supplied to the anaerobic biological treatment section 24, but if the organic matter concentration of the concentrated water g from the insoluble organic matter concentrating section 22 is low, the concentrated water g may be discharged outside the organic matter decomposition system 10B, and only the concentrated water k may be supplied to the anaerobic biological treatment section 24. In this case, the insoluble organic matter concentrating section 22 will no longer be able to contribute to the organic matter recovery efficiency, but supplying the raw water j from which solids have been removed to the soluble organic matter concentrating section 28 will contribute to protecting the soluble organic matter concentrating section 28.

[0038] (Third embodiment) An organic matter decomposition system according to a third embodiment of the present invention will be described.

[0039] FIG. 3 is a block diagram showing an example of the configuration of an organic matter decomposition system according to the third embodiment of the present invention.

[0040] The organic matter decomposition system 10C of the third embodiment is configured by excluding the insoluble organic matter concentrating section 22 from the organic matter decomposition system 10B of the second embodiment. This configuration is suitable when the raw water a or the raw water b treated in the solid separation section 14 has a low solid content. Below, the configuration already described for the organic matter decomposition system 10B of the second embodiment will be omitted, and only differences from the organic matter decomposition system 10B will be described.

[0041] That is, in the organic matter decomposition system 10C, raw water f is supplied to the dissolved organic matter concentrating section 28.

[0042] As described above, it is preferable to use an RO membrane in the dissolved organic matter concentrating section 28. When an RO membrane is used in the dissolved organic matter concentrating section 28, the RO membrane concentrates the organic matter contained in the raw water f by approximately 5 to 20 times, producing concentrated water k. In this embodiment, the concentration rate is not limited to this range, and depending on the conditions, the raw water f can be concentrated up to 50 times or 100 times. Furthermore, because hardness components have been removed from the raw water f and the pH has been increased, scaling and biofouling in the RO membrane are avoided.

[0043] The dissolved organic matter concentrating section 28 supplies the concentrated water (k) to the anaerobic biological treatment section 24. Meanwhile, the permeated water (m) that has permeated the RO membrane is discharged from the dissolved organic matter concentrating section 28 to the outside of the organic matter decomposition system 10C.

[0044] The anaerobic biological treatment unit 24 performs anaerobic biological treatment on the concentrated water k to decompose soluble organic matter contained in the concentrated water k. In this way, the treated water h from which the soluble organic matter has been decomposed is supplied from the anaerobic biological treatment unit 24 to the post-treatment unit 26.

[0045] As described above, when treating raw water a with a low content of insoluble organic matter, the organic matter decomposition system 10C of this embodiment can be configured without the insoluble organic matter concentrating section 22. This simplifies the configuration and also reduces costs.

[0046] As described above, the organic matter decomposition systems 10A to 10C according to the embodiments of the present invention do not perform aerobic biological treatment, but instead concentrate the organic matter in the raw water using a membrane, such as an MF membrane and / or UF membrane in the insoluble organic matter concentrating unit 22 or an RO membrane in the soluble organic matter concentrating unit 28, to sufficiently increase the concentration before performing anaerobic biological treatment. Anaerobic biological treatment not only consumes significantly less power than aerobic biological treatment, but also allows for the use of generated biogas as energy, thereby enabling energy savings.

[0047] On the other hand, the organic matter decomposition systems 10A-10C of the present invention do not perform biological treatment prior to the membrane-using sections (e.g., the insoluble organic matter concentrator 22 and the soluble organic matter concentrator 28), resulting in highly biodegradable wastewater passing through the membrane. Generally, not performing biological treatment prior to the membrane increases the risk of membrane biofouling. However, the organic matter decomposition systems 10A-10C of the present invention remove hardness components from the raw water prior to the membrane, thereby removing scaling substances. Furthermore, by adding alkali to the raw water to increase the pH of the raw water and increase the solubility of silica, scaling and biofouling in the membrane can be avoided. Note that if the pH is increased without removing the hardness components, the hardness components can easily cause scaling, so it is essential to remove the hardness components before increasing the pH.

[0048] The organic matter decomposition systems 10A to 10C according to the embodiments of the present invention can be applied to wastewater recycling and zero-discharge (ZLD) systems in addition to wastewater treatment intended for external discharge.

[0049] Furthermore, the organic matter decomposition systems 10A to 10C according to the embodiments of the present invention are applicable not only to the highly concentrated organic matter in wastewater but also to the highly concentrated beverages, seasonings, organic chemicals, and the like.

[0050] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

Claims

1. An organic matter decomposition system comprising: a hardness removal section which removes hardness components from raw water to be treated; a carbon dioxide removal section which removes carbon dioxide components from the raw water from which the hardness components have been removed; an alkali injection section which injects alkali into the raw water from which the carbon dioxide components have been removed; an insoluble organic matter concentration section which concentrates insoluble organic matter contained in the raw water into which the alkali has been injected; and an anaerobic biological treatment section which performs anaerobic biological treatment on the raw water in which the insoluble organic matter has been concentrated, and decomposes the insoluble organic matter.

2. The organic matter decomposition system of claim 1, further comprising a soluble organic matter concentration section that concentrates soluble organic matter contained in the raw water from which the insoluble organic matter has been removed by the insoluble organic matter concentration section, and the anaerobic biological treatment section also performs the anaerobic biological treatment on the raw water from which the soluble organic matter has been concentrated, thereby decomposing the soluble organic matter.

3. An organic matter decomposition system comprising: a hardness removal section which removes hardness components from raw water to be treated; a carbon dioxide removal section which removes carbon dioxide components from the raw water from which the hardness components have been removed; an alkali injection section which injects alkali into the raw water from which the carbon dioxide components have been removed; an insoluble organic matter concentration section which concentrates insoluble organic matter contained in the raw water into which the alkali has been injected; a soluble organic matter concentration section which concentrates soluble organic matter contained in the raw water from which the insoluble organic matter has been removed by the insoluble organic matter concentration section; and an anaerobic biological treatment section which performs anaerobic biological treatment on the raw water from which the soluble organic matter has been concentrated, and decomposes the soluble organic matter.

4. An organic matter decomposition system comprising: a hardness removal section which removes hardness components from raw water to be treated; a carbon dioxide removal section which removes carbon dioxide components from the raw water from which the hardness components have been removed; an alkali injection section which injects alkali into the raw water from which the carbon dioxide components have been removed; a soluble organic matter concentration section which concentrates soluble organic matter contained in the raw water into which the alkali has been injected; and an anaerobic biological treatment section which performs anaerobic biological treatment on the raw water in which the soluble organic matter has been concentrated, and decomposes the soluble organic matter.

5. An organic matter decomposition system according to any one of claims 1 to 3, wherein the insoluble organic matter concentrating section is equipped with an MF membrane or an UF membrane.

6. An organic matter decomposition system according to any one of claims 2 to 4, wherein the soluble organic matter concentrating section is equipped with a reverse osmosis membrane.

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