Wastewater treatment system, and wastewater treatment method

Abstract

To provide a wastewater treatment system and a wastewater treatment method of higher treatment efficiency.SOLUTION: A wastewater treatment system S according to one aspect of the present invention comprises a circulation type nitrification system 1 comprising a first storage tank 11 storing raw water, a nitrification tank 12 storing a nitrification agent 121, a first pipe 13 for supplying the nitrification tank with raw water from the first storage tank, a second pipe 16 for returning nitrification-treated water having been subjected to the nitrification treatment, and a first pump 14 attached to either of the first pipe and the second pipe. The wastewater treatment system according to another aspect of the present invention comprises a circulation type denitrification system 2 comprising a second storage tank 21 storing nitrification-treated water, a denitrification tank 22 storing a denitrification agent 221, a third pipe 23 for supplying the denitrification tank with nitrification-treated water from the second storage tank, a fourth pipe 25 for returning denitrification-treated water removed of nitrogen to the second storage tank, and a second pump 24 attached to either of the third pipe and the fourth pipe.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wastewater treatment system and a wastewater treatment method. [Background technology]

[0002] Wastewater from food manufacturing, chemical manufacturing, and other facilities after raising organisms contains a large amount of ammonia, and in order to release it outside the facility as wastewater, the ammonia concentration must be kept below a specified standard.

[0003] As a method for reducing the ammonia concentration to below a standard level, for example, Patent Document 1 listed below discloses a circulating breeding and cultivation device that includes a breeding layer for breeding aquatic organisms and a burnt soil filled layer that serves as a plant cultivation layer filled with burnt soil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-154383 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, although the technology described in Patent Document 1 is useful as a technology for simultaneously raising aquatic organisms and cultivating plants, there is a problem in that a system with higher treatment efficiency is required to treat wastewater containing a large amount of ammonia.

[0006] In view of the above problems, an object of the present invention is to provide a wastewater treatment system and a wastewater treatment method with higher treatment efficiency. [Means for solving the problem]

[0007] A wastewater treatment system according to one aspect of the present invention that solves the above-mentioned problems comprises a circulating nitrification system having a first storage tank for storing raw water, a nitrification tank for containing a nitrification agent having nitrifying bacteria supported on a carrier, a first pipe for supplying raw water from the first storage tank to the nitrification tank, a second pipe for returning nitrified water from the nitrification tank to the first storage tank, and a first pump provided in at least one of the first pipe and the second pipe.

[0008] In addition, in this respect, although not limited thereto, it is preferable to have an oxygen supplying means for supplying oxygen to the raw water.

[0009] In addition, in this respect, although not limited thereto, it is preferable that the circulating nitrification system has a pH adjusting means for adding a pH adjuster to the raw water.

[0010] In addition, from this viewpoint, it is preferable to have a circulating denitrification system having, although not limited to, a second storage tank for storing nitrification-treated water, a denitrification tank for storing a denitrification agent having denitrifying bacteria supported on a carrier, a third pipe for supplying the nitrification-treated water from the second storage tank to the denitrification tank, a fourth pipe for returning the denitrified denitrification-treated water from the denitrification tank to the second storage tank, and a second pump provided in at least one of the third pipe and the fourth pipe.

[0011] In addition, in this respect, although not limited thereto, it is preferable that the circulating denitrification system is in a low oxygen state in order to maintain an anaerobic state.

[0012] Furthermore, a wastewater treatment system according to another aspect of the present invention comprises a circulating denitrification system having a second storage tank for storing nitrification-treated water, a denitrification tank for containing a denitrification agent having denitrifying bacteria supported on a carrier, a third pipe for supplying the nitrification-treated water from the second storage tank to the denitrification tank, a fourth pipe for returning the denitrified denitrification-treated water from the denitrification tank to the second storage tank, and a second pump provided in at least one of the third pipe and the fourth pipe.

[0013] A wastewater treatment method according to another aspect of the present invention comprises a step of nitrifying raw water by circulating it through a nitrifying agent having nitrifying bacteria carried on a carrier, and a step of denitrifying the nitrified raw water by circulating it through a denitrifying agent having denitrifying bacteria carried on a carrier. Effect of the Invention

[0014] As described above, the present invention can provide a wastewater treatment system and a wastewater treatment method with higher treatment efficiency. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing an outline of a wastewater treatment system according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing an outline of another example of a wastewater treatment system according to an embodiment. [Diagram 3] FIG. 2 is a diagram showing an outline of another example of a wastewater treatment system according to an embodiment. BEST MODE FOR CARRYING OUT THEINVENTION

[0016] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be embodied in many different forms, and the specific examples described in the following embodiments and examples can be appropriately modified and adjusted, and the present invention is not limited thereto.

[0017] Fig. 1 is a diagram showing an outline of a wastewater treatment system S according to this embodiment (hereinafter simply referred to as "this system"). As shown in this figure, this system S comprises a circulating nitrification system (hereinafter simply referred to as "nitrification system") 1 and a circulating denitrification system (hereinafter simply referred to as "denitrification system") 2. This system S has its own nitrification system 1 and denitrification system 2, respectively, and each of them can perform treatment as a circulating system, which has the advantage of being very efficient.

[0018] In addition, the nitrification system 1 in this system S further includes a first storage tank 11 for storing raw water, a nitrification tank 12 for containing a nitrification agent 121 having nitrifying bacteria supported on a carrier 1211, a first piping 13 and a first pump 14 for supplying raw water from the first storage tank 11 to the nitrification tank 12, an oxygen supply means 15 for supplying oxygen to the raw water, and a second piping 16 for returning nitrified treated water from the nitrification tank 12 to the first storage tank 11.

[0019] The nitrification system 1 in the present system S is provided with a pH adjustment means 17 for adding a pH adjuster 171 to the raw water. The specific configuration of the pH adjustment means 17 will be described later.

[0020] The first storage tank 11 in the nitrification system 1 of this system S is used to store raw water, and as will be clear from the descriptions above and below, is also capable of storing water that has been nitrified by contact with the nitrification agent 121 in the nitrification tank 12 (nitrification-treated water).

[0021] In this embodiment, "raw water" refers to water to be purified by the nitrification system 1, and refers to water that contains a large amount of organic matter and ammonia and the like (hereinafter simply referred to as "ammonia, etc.") that is decomposed from organic matter, such as wastewater from food manufacturing, chemical manufacturing, and rearing organisms. The amount of ammonia, etc. contained in the raw water can be adjusted appropriately, but the effect can be felt for water that contains, for example, a BOD value of 160 mg / L or more, which is the environmental standard value, and treatment is possible without any particular upper limit on the amount of ammonia contained by adjusting the time for which the nitrification system 1 is circulated.

[0022] The size and material of the first storage tank 11 can be adjusted appropriately depending on the amount of wastewater to be treated and are not limited, but a range of 10 L or more and 500,000 L or less is preferable as this is a realistic range taking into account the amount of treatment and the treatment time required for that.

[0023] The material of the first storage tank 11 is not particularly limited, but from the viewpoint of storing water, it is preferable that the material is rust-resistant and can withstand basic conditions in order to contain a large amount of ammonia, and it is preferable that the material does not corrode, for example, metal or resin is preferable, and in the case of metal, it is preferable that the material is a corrosion-resistant material such as stainless steel, aluminum, titanium, etc., and in the case of resin, it is preferable that the material is polyvinyl chloride resin, polyethylene, polystyrene, acrylic resin, phenol resin, etc. In addition, in the case of resin, one preferable example is fiber reinforced plastic (FRP) obtained by blending glass fiber, carbon fiber, etc. with the above materials.

[0024] The nitrification tank 12 in the nitrification system 1 of the present system S contains a nitrification agent 121 in which nitrification bacteria are held on a carrier. The material of the nitrification tank 12 can be appropriately adjusted depending on the amount of wastewater to be treated, but is preferably a material that does not corrode, such as metal or resin. In the case of metal, it is preferably a material that is resistant to corrosion, such as stainless steel, aluminum, or titanium, and in the case of resin, it is preferably polyvinyl chloride resin, polyethylene, polystyrene, acrylic resin, phenolic resin, or the like. The nitrification tank 12 is filled with the nitrification agent 121, and when raw water is supplied into the nitrification tank 12, it is nitrified by contacting the nitrification agent 121. In the case of resin, a preferred example is fiber-reinforced plastic (FRP) in which glass fiber, carbon fiber, or the like is mixed with the above material.

[0025] In addition, the size of the nitrification tank 12 in the nitrification system 1 of this system S can be in the same capacity range as the first storage tank 11, but since it processes and circulates a portion of the first storage tank 11, it is preferable to make it smaller than the capacity of the first storage tank 11.

[0026] As described above, the system S is filled with the nitrifying agent 121. In this embodiment, the "nitrifying agent" is an agent that can oxidize ammonia contained in the raw water and convert it into nitrite or nitrate. The nitrifying agent 121 according to this embodiment is a carrier that holds nitrifying bacteria.

[0027] The carrier for the nitrifying agent 121 is preferably baked soil. The reason for using soil as the carrier is that nitrifying bacteria are generally found widely in soil and it is very preferable to create a state similar to their breeding environment, and the ion adsorption property due to the polarity of the soil is expected to provide a pH adjustment ability (hydrogen ion adsorption function). Baking the soil also makes it less likely to dissolve in water, and furthermore, it forms many pores on the surface and inside of the soil, increasing its specific surface area, making it easier to create an environment in which nitrifying bacteria can easily attach to the carrier surface.

[0028] The material of the carrier of the nitrification agent 121 is preferably soil as described above, but is not particularly limited, and is preferably black soil (black soil), red soil, clay, or a mixture of at least one of these. The soil may also be mixed with crushed stones or sand in powder form. The inclusion of powdered stones or the like has the effect of promoting the activation of bacteria by the effect of far infrared rays.

[0029] The shape of the carrier of the present nitrification agent 121 is preferably granular, although it is not particularly limited. By making it granular, a large surface area can be secured, and the efficiency of nitrification can be significantly improved. Furthermore, in the case of granular, although it is not limited, the size can be determined by measuring the particle size distribution, for example, with a laser analyzer, and the number average particle size can be obtained based on this. The average particle size of the carrier obtained by this is not limited as long as it can exhibit the above-mentioned functions, but is preferably 0.1 mm or more and 20 mm or less, more preferably 1 mm or more and 10 mm or less, and even more preferably 5 mm or less. By making it 0.1 mm or more, it is possible to prevent the carrier from dissolving in water and passing through a filter, etc., while by making it 20 mm or less, there is an advantage that a sufficiently large specific surface area relative to the volume can be secured, and the nitrification efficiency can be maintained high.

[0030] It is also important that the carrier of the nitrifying agent 121 has a sufficiently large specific surface area. Although not limited to this index, the specific surface area is the surface area per unit weight of the nitrifying agent, and this specific surface area is preferably 50 m 2 / g or more, more preferably 100m 2 / g or more. 50m 2 By setting the concentration at 100m / g or more, it is possible to form pores that are sufficient for the attachment of nitrifying bacteria. 2 This effect becomes more pronounced when the molecular weight is 300m / g or more. 2 It is preferable that the molecular weight is not more than 1 / g.

[0031] In addition, when the carrier of the nitrification agent 121 is soil, it is preferable to bake it, but if the temperature is too high, the water will be removed more than necessary and the carrier will become brittle, so it is preferable to bake it at a temperature that leaves a moderate amount of water. By baking at this temperature, there is an advantage that the soil of the carrier can be prevented from dissolving into water. Specifically, when the material is black soil, the temperature is preferably in the range of 200°C to 1000°C, more preferably 400°C or less, and even more preferably 280°C to 320°C.

[0032] The nitrifying bacteria of the nitrifying agent 121 are those capable of oxidizing ammonia to nitrite or nitrate, but are not limited thereto, and examples thereof include Nitrosomonas europaea and Nitrobacter winogradskyi. These nitrifying bacteria can stably convert organic matter to ammonia or oxidize ammonia in an environment in which oxygen is present. For this reason, it is preferable that the nitrifying system 1 is an open system, and more preferably, an oxygen supply means is provided.

[0033] In addition, there are various methods for attaching the nitrifying bacteria of the nitrifying agent 121 to the carrier, and the method is not limited thereto. For example, the nitrifying agent can be completed by filling the nitrifying tank 12 with carriers that have not been treated to attach bacteria, and circulating the raw water in contact with air for a long time, so that the nitrifying bacteria present in the water are attached and cultured on the surface of the carrier. The nitrifying bacteria are suspended in the air in small amounts, and when exposed to air, the nitrifying bacteria dissolve in the raw water, and are captured by contacting the carriers in the nitrifying tank 12, and naturally become a nitrifying agent. Of course, if you want to attach the desired nitrifying bacteria in a focused manner, you can also form it by immersing the carrier in water that contains a sufficient amount of the nitrifying bacteria, and the nitrifying bacteria can be attached to the carrier by adding the desired nitrifying bacteria to the raw water or normal water and circulating it in the nitrifying system 1.

[0034] The first pipe 13 in the nitrification system 1 of the present system S is for supplying raw water from the first storage tank 11 to the nitrification tank 12. The material of the first pipe 13 is not limited as long as it is tubular, and may be, for example, metal or resin. In the case of metal, stainless steel, titanium, aluminum, etc. can be used, and in the case of resin, polyvinyl chloride resin, polyethylene, polystyrene, acrylic resin, phenolic resin, etc. can be used, but are not limited thereto. In the case of resin, a fiber reinforced plastic (FRP) obtained by mixing glass fiber, carbon fiber, etc. with the above-mentioned material is also a preferable example. In addition, it is also preferable to provide the first pipe 13 with a valve 131 for controlling (opening and closing) the flow of water in the pipe.

[0035] The first pipe 13 may be arranged in any form as long as it has the above-mentioned function, and may be connected to the upper part of the nitrification tank 12 so that raw water can be supplied from above the nitrification agent 121, or may be arranged so that raw water can be supplied from the lower part of the nitrification tank 12. By allowing raw water to be supplied from the lower part of the nitrification tank 12, there is an advantage that water that has been in contact with the nitrification agent 121 sufficiently can be discharged from the nitrification tank 12, and by allowing raw water to be supplied from the upper part of the nitrification tank 12, there is an advantage that the water can be agitated by utilizing gravity and the contact efficiency can be increased, but this can be adjusted as appropriate.

[0036] Furthermore, the first pump 14 in the nitrification system 1 of this system S is a power source used to supply raw water from the first storage tank 11 to the nitrification tank 12, and is preferably provided near the inlet or midway of the pathway of the first piping 13, although this is not limited as long as it can exert the effect. However, since the first pump 14 forms the water circulation in the nitrification system 1 as described above, it is also possible to provide it in the second piping 16. The first pump 14 is connected to the first piping 13, but depending on the pump configuration, it may be disposed in the first storage tank 11, and this state is included in the state of being connected to the first piping 13. Similarly, when it is connected to the second piping 16, Depending on the pump configuration, even if the pump is provided inside the nitrification tank 12, it is included in the state of being connected to the second pipe 16.

[0037] In addition, the oxygen supplying means 15 in the nitrification system 1 of the present system S supplies oxygen to the raw water, and by supplying oxygen, ammonia can be effectively oxidized. Although not limited to, the oxygen supplying means 15 is preferably one having an air pump and a tube piping connected to the air pump. This makes it possible to easily supply air to the water. In addition, the oxygen supplying means 15 may be an agitation device that simply agitates the vicinity of the raw water surface to agitate and dissolve the air. In addition, if sufficient oxygen can be dissolved in the raw water by keeping the first storage tank 11 as an open system, the oxygen supplying means 15 can be omitted.

[0038] The second pipe 16 in the nitrification system 1 of the present system S is for returning the nitrified water from the nitrification tank 12 to the first storage tank 11, and may be made of the same material as the first pipe 13. It is also preferable to provide a valve 161 for adjusting (opening and closing) the water flow in the second pipe 16. In particular, as described later, when the nitrified water is to be stored in the second storage tank 21 for denitrification, the valve 161 plays an important role.

[0039] Here, as described above, "nitrification-treated water" refers to water that has been subjected to nitrification treatment of raw water, and more specifically, water that has been brought into contact with the nitrification agent 121 in the nitrification tank 12 and has had ammonia oxidized. However, it is difficult for almost all of the ammonia contained in the water to be completely nitrified by a single contact with the nitrification agent 121, and a sufficient proportion of the ammonia is nitrified by circulating between the first storage tank 11 and the nitrification tank 12 multiple times. Therefore, while keeping in mind that the distinction from raw water may not be clear, in this specification, water that has been treated by coming into contact with the nitrification agent 121 even once may be referred to as nitrification-treated water.

[0040] The connection relationship of the second pipe 16 is not particularly limited. When the first pipe 13 is connected to the lower side of the nitrification tank 12, it is preferable for the first pipe 13 to be connected to the upper side thereof in order to form an efficient circulation path, and when the first pipe 13 is connected to the upper side of the nitrification tank 12, it is preferable for the first pipe 13 to be connected to the lower side thereof. Furthermore, it is of course also possible to configure the nitrification tank 12 as a horizontal cylinder, with the first pipe 13 connected to one end and the second pipe 16 connected to the other end.

[0041] In addition, as described above, the nitrification system 1 in the present system S is preferably provided with a pH adjustment means 17 for adding a pH adjuster 171 to the raw water. The pH adjustment means 17 may be provided in any of the elements, such as the first storage tank 11, the first pipe 13, the nitrification tank 12, or the second pipe 16, as long as it is present in the circulating system. An example of the pH adjustment means is preferably one having a pH adjuster 171, a tank 172 for storing the pH adjuster 171, and an adding means 173 for adding the pH adjuster 171, and further preferably one having a pH sensor 174 for measuring the pH of the raw water (or the nitrification-treated water), and by adjusting the adding means according to the value of the pH sensor 174, it is possible to add an appropriate amount of the pH adjuster 171 according to the pH of the raw water, thereby adjusting the pH.

[0042] Here, it is important to bias the pH to a weak alkaline state. By biasing the pH from neutral to a weak alkaline state, it becomes possible for the nitrifying bacteria to efficiently convert ammonia in the water into nitrite or nitrate. The preferred pH can be adjusted as appropriate, but is preferably greater than 6 and equal to or less than 10. The pH adjuster 171 is not limited as long as it can make the water alkaline when added to the raw water, but is preferably one that contains ions that can generally be present in the environment, and examples of such ions include, but are not limited to, calcium hydroxide, potassium hydroxide, magnesium hydroxide, and sodium hydroxide.

[0043] In addition, in the nitrification system, it is preferable to provide a garbage trap to collect garbage such as leaves floating in the raw water. In particular, if garbage gets into the nitrification tank, it will cause clogging and interfere with circulation. Therefore, by providing garbage traps on the inlet side, outlet side, and intermediate positions of the first pipe, clogging can be prevented. This can also be done in the denitrification system, but since it is considered that the garbage is already removed in the nitrification system, it may be omitted.

[0044] As described above, the nitrification system 1 can efficiently convert ammonia in water into nitrite and nitrate. By converting ammonia into nitrite and nitrate, it can be returned to the air as nitrogen by the denitrification system 2 described below. In particular, the nitrification system 1 is characterized by being extremely efficient because it uses nitrifying bacteria and is a circulatory system.

[0045] Next, the denitrification system 2 in the present system S includes a second storage tank 21 for storing nitrification-treated water, a denitrification tank 22 for accommodating a denitrifying agent 221 having denitrifying bacteria held on a carrier, a third pipe 23 and a second pump 24 for supplying nitrified raw water from the second storage tank 21 to the denitrification tank 22, and a fourth pipe 25 for returning the denitrification-treated water from the denitrification tank 22 to the second storage tank 21. This denitrification system 2 makes it possible to reduce nitrites and nitrates converted from ammonia by the above-mentioned nitrification system 1 to nitrogen.

[0046] In the denitrification system 2 of the present system S, the second storage tank 21 can store the nitrification-treated water as described above. The nitrification-treated water can be obtained by connecting it to the water intake pipe 18 branched off from the second pipe 16 of the nitrification system 1. However, as described later, the nitrification-treated water may be provided as an independent system separate from the nitrification system 1 as long as it is available. In addition, the water intake pipe 18 may be provided by branching off from the second pipe 16 as described above, or may be provided directly in the first storage tank 11 separately from the second pipe 16, or may be provided directly in the nitrification tank 12 separately from the second pipe 16. It is preferable that the water intake pipe 18 is also provided with a valve 181 for controlling (opening and closing) the water flow path.

[0047] In addition, since the denitrification system 2 of the present system S circulates the nitrification treatment water in a sealed state with a low oxygen concentration (hypoxic state), the second storage tank 21 is preferably a sealable container so that the sealed state and low oxygen state can be maintained. Specifically, by providing a sealable lid member 211 on the second storage tank 21, it is possible to prevent air from entering from the outside. In this case, it is also preferable to close the lid member 211 equipped with a valve and then connect a degassing pump 212 for degassing so that as much remaining oxygen as possible is eliminated.

[0048] The size and material of the second storage tank 21 can be adjusted appropriately depending on the amount of wastewater to be treated, and are not limited thereto, but it is possible for the second storage tank 21 to have the same capacity as the first storage tank 11 described above.

[0049] The material of the second storage tank 21 is not particularly limited, but from the viewpoint of storing water, it is preferable that the material is rust-resistant and can withstand basic conditions because it contains a large amount of ammonia. It is also preferable that the material does not corrode, and a material similar to that of the first storage tank 11 described above can be used.

[0050] In the denitrification system 2 of this system S, the denitrification tank 22 contains a denitrifying agent 221 having denitrifying bacteria held on a carrier. The material of the denitrification tank 22 can be appropriately adjusted depending on the amount of wastewater to be treated, and the same materials as those of the first storage tank 11, the nitrification tank 12, and the second storage tank 21 can be used. The denitrification tank 22 is filled with the denitrifying agent 221, and when nitrification treatment water is supplied to the denitrification tank 22, the denitrification treatment is carried out by contacting the denitrifying agent 221.

[0051] Moreover, it is preferable that the denitrification tank 22 is also a sealable container since it is preferable to carry out the denitrification treatment in a sealed and low-oxygen state similarly to the second storage tank 21. In this case, if an opening is provided for performing operations such as replacing the denitrification agent 221, it is preferable to provide a lid member.

[0052] In addition, the size of the denitrification tank 22 in the denitrification system 2 of this system S is similar to that of the second storage tank 21, and can be adjusted appropriately and is not limited, but since it treats and circulates a portion of the second storage tank 21, it can be made smaller than the capacity of the second storage tank 21.

[0053] As described above, the system S is filled with the denitrifying agent 221. In this embodiment, the "denitrifying agent" is an agent that can reduce the nitrite and nitrate contained in the nitrification treatment water to nitrogen. As described above, the denitrifying agent 221 according to this embodiment is a carrier that holds denitrifying bacteria.

[0054] The carrier for the denitrifying agent 221 can be the same as the nitrifying agent 121. Specifically, it is preferable that the carrier is baked soil. The reason for using soil as the carrier is that denitrifying bacteria are generally present widely in soil and the like, and it is a very preferable environment for them. Furthermore, baking the soil forms many pores on its surface and inside, increasing its specific surface area, and making it easier to create an environment in which the denitrifying bacteria can easily attach to the carrier surface.

[0055] The material of the carrier of the denitrifying agent 221 is not limited, and the same carrier as that of the nitrifying agent 121 can be used. The shape and particle size of the carrier of the denitrifying agent 221 are not limited, and the same shape and particle size of the carrier as that of the nitrifying agent 121 can be used. Furthermore, the specific surface area of ​​the denitrifying agent 221 can be the same as that of the carrier of the nitrifying agent 121.

[0056] In addition, when the carrier of the present nitrification agent 121 is soil, it is preferable to sinter it, but if the temperature is too high, the water is removed more than necessary and it becomes brittle, so it is preferable to sinter it at a temperature that leaves a moderate amount of water. By setting the temperature at this level, it is possible to prevent the soil of the carrier from dissolving into water. Even in this temperature range, it is preferable to adopt the same sintering temperature range as the carrier in the above nitrification agent 121.

[0057] In addition, the denitrifying bacteria of the denitrifying agent 221 are bacteria that can release nitrogen compounds such as nitrites and nitrates into the atmosphere as nitrogen molecules, and examples of the denitrifying bacteria include, but are not limited to, Pseudomonas denitrificans, Paracoccus d., Thiobacillus d., etc.

[0058] Furthermore, there are various methods for the process of attaching the denitrifying bacteria of the denitrifying agent 221 to the carrier, and this is not limited to these. For example, the denitrifying tank 22 can be filled with carriers that have not been treated to attach bacteria, and specifically, the raw water or nitrified water can be circulated in a low-oxygen environment for a relatively long period of time, causing the denitrifying bacteria present in the water to attach and cultivate on the surface of the carrier, thereby completing the denitrifying agent 221.

[0059] In the denitrification system 2 of the present system S, the third pipe 23 is for supplying nitrification-treated water from the second storage tank 21 to the denitrification tank 22. The material of the third pipe 23 is not limited as long as it is tubular, and may be, for example, metal or resin. In the case of metal, examples include stainless steel, aluminum, titanium, etc., and in the case of resin, polyvinyl chloride resin, polyethylene, polystyrene, acrylic resin, phenolic resin, etc., but are not limited thereto. In the case of resin, a fiber-reinforced plastic (FRP) obtained by mixing glass fiber, carbon fiber, etc. with the above-mentioned material is also a preferred example. In addition, it is also preferred to provide the third pipe 23 with a valve 231 for controlling the flow of water in the pipe.

[0060] The third pipe 23 may be arranged in any form as long as it has the above-mentioned function, and may be connected to the upper part of the denitrification tank 22 so that the nitrification-treated water can be supplied from the upper side of the denitrification agent 221, or may be arranged so that the nitrification-treated water can be supplied from the lower part of the denitrification tank 22. By making it possible to supply the nitrification-treated water from the lower part of the denitrification tank 22, there is an advantage that the water that has been in contact with the denitrification agent 221 can be sufficiently discharged from the denitrification tank 22, and by making it possible to supply the nitrification-treated water from the upper part of the denitrification tank 22, there is an advantage that the water can be agitated by utilizing gravity and the contact efficiency can be increased, but this can be adjusted as appropriate. Furthermore, it is of course also possible to configure the denitrification tank 22 as a horizontal cylinder, with the third pipe 23 connected to one end and the fourth pipe 25 connected to the other end.

[0061] The second pump 24 in the denitrification system 2 of the present system S is a power source used to supply raw water from the second storage tank 21 to the denitrification tank 22, and is preferably provided near the inlet or midway of the path of the third pipe 23, although it is not limited as long as it can exert the effect. However, since the second pump 24 forms the water circulation in the denitrification system 2 as described above, it is also possible to configure it to be provided in the fourth pipe 25. The second pump 24 is connected to the third pipe 23, but may be disposed in the second storage tank 21 depending on the pump configuration, and this state is included in the state of being connected to the third pipe 23. In other words, when connected to the fourth pipe 25, the case where the pump is provided in the denitrification tank 22 depending on the pump configuration is also included in the state of being connected to the fourth pipe 25.

[0062] In the denitrification system 2 in the nitrification system 1 of the present system S, the fourth pipe 25 is for returning the denitrified nitrification treated water (hereinafter referred to as "denitrification treated water") from the denitrification tank 22 to the second storage tank 21, and may be made of the same material as the third pipe 23. It is also preferable that the fourth pipe 25 is provided with a valve 251 for adjusting the water flow.

[0063] Here, the term "denitrification treated water" refers to water that has been denitrified from nitrification treated water, as described above. More specifically, the denitrification treated water is water that has been denitrified by contacting the denitrification agent 221 in the denitrification tank 22, and the nitrogen atoms of nitrites and nitrates have become nitrogen molecules. However, it is difficult for the nitrites and nitrates contained in the water to be sufficiently denitrified by contacting the denitrification agent 221 once, and the water is sufficiently denitrified by circulating between the second storage tank 21 and the denitrification tank many times. Therefore, while keeping in mind that the distinction from nitrification treated water may not be clear, in this specification, water that has been treated by contacting the denitrification agent 221 even once may be called denitrification treated water. On the other hand, water that has been added to the denitrification tank once and then returned to the second storage tank 21 may be called nitrification treated water. Note that, when nitrogen is sufficiently removed from the denitrification treated water and the environmental release standard value is met, it is possible to release it outside the system.

[0064] There is also no particular limitation on the connection relationship of the fourth pipe 25. When the third pipe 23 is connected to the lower side of the denitrification tank 22, it is preferable for the fourth pipe 25 to be connected to the upper side thereof in order to form an efficient circulation path. When the third pipe 23 is connected to the upper part of the denitrification tank 22, it is preferable for the fourth pipe 25 to be connected to the lower side thereof.

[0065] In addition, the denitrification system 2 in the present system S is preferably in a low-oxygen state in order to maintain the anaerobic state. Specifically, the second storage tank 21, the denitrification tank 22, the third pipe 23, and the fourth pipe 25 are preferably sealed in a sealed container, or the second storage tank 21 and the denitrification tank 22, preferably the third pipe 23 and the fourth pipe 25, are preferably sealed by a sealed housing that covers the entirety of the second storage tank 21 and the denitrification tank 22. Note that the "sealed" state here is preferably a state in which no outside air enters, but it is not necessary to require such a level of sealing, and it may be a state in which the outside air and the space within the above-mentioned configuration are separated to some extent and oxygen is deficient. Generally, denitrifying bacteria are active in an anaerobic atmosphere, so that the activity of the denitrifying bacteria is activated by making the environment anaerobic by making it in a low-oxygen state, and nitrogen such as nitrite and nitrate can be converted into nitrogen gas and removed from the raw water.

[0066] As described above, the denitrification system 2 can efficiently convert nitrite, nitrate, and the like in the water into nitrogen gas. In particular, the denitrification system 2 is characterized by being extremely efficient because it uses denitrifying bacteria and is a circulation type.

[0067] (Wastewater treatment method) The effects are clear from the above configuration, but here, a wastewater treatment method realized by this system (hereinafter referred to as "this method") will be described.

[0068] This method comprises the steps of (S1) nitrifying raw water by circulating it through a nitrifying agent having nitrifying bacteria carried on a carrier, and (S2) denitrifying the nitrified raw water by circulating it through a denitrifying agent having denitrifying bacteria carried on a carrier.

[0069] In this method, the step (S1) of nitrifying raw water by circulating it through a nitrifying agent having nitrifying bacteria held on a carrier is a step using the above-mentioned nitrification system. That is, the raw water is supplied from the first storage tank through the first pipe to the nitrification tank, and the nitrified water that has been passed through the nitrifying agent in the nitrification tank is returned to the first storage tank through the second pipe, and the process is repeated. This converts the ammonia present in the raw water into nitrite or nitrate, making it possible to carry out the next step of the process. The number of times and the time of this circulation can be appropriately adjusted depending on the amount of ammonia in the raw water to be treated, but as a guideline for the time, it is preferable to circulate the raw water for about one hour or more and three days or less, and more preferably for half a day or more and two days or less. By setting it in this range, it is possible to meet the external discharge standard and stably purify the wastewater discharged every day.

[0070] In addition, in this method, the step (S2) of denitrifying the nitrified raw water by circulating it through a denitrifying agent having denitrifying bacteria held on a carrier is a step using the above-mentioned denitrification system. That is, the nitrification-treated water is supplied to the denitrification tank from the second storage tank through the third pipe, and the denitrification-treated water that has been passed through the denitrifying agent in the denitrification tank is returned to the second storage tank again through the fourth pipe, and the process is repeated. This converts the nitrite and nitrate present in the nitrification-treated water into nitrogen gas, and makes it possible to satisfy the wastewater treatment standard for external use. The number of times and the time of this circulation can be appropriately adjusted according to the amount of ammonia in the raw water to be treated, but as a guideline for the time, it is preferable to circulate the water for approximately one hour or more and three days or less, and more preferably for half a day or more and two days or less. By setting it in this range, it is possible to meet the external discharge standard and stably purify the wastewater discharged every day.

[0071] Here, the external discharge standards are preferably 160 mg / L or less for BOD and COD, 200 mg / L or less for SS (Suspended Solids), 120 mg / L or less for TN (Total Nitrogen), 100 mg / L or less for the amount of NH4 itself, 100 mg / L or less for the amount of NO2 itself, 100 mg / L or less for the amount of NO3 itself, and 16 mg / L or less for total phosphorus.

[0072] The timing for transitioning from step (S1) to step (S2) is when sufficient nitrification treatment has been performed. Specifically, the water to be treated can be transferred from the nitrification system to the denitrification system by opening a valve in an outlet pipe that is branched off to a second pipe or that is provided separately.

[0073] As described above, prior to step (S1), the method may include a step (S0-1) of forming a nitrifying agent in a nitrification tank. Specifically, it is preferable to include a step of filling a carrier in the nitrification tank and attaching nitrifying bacteria to the carrier to form a nitrifying agent. A further specific method is to repeat a circulation process in which raw water is supplied from a first storage tank to a nitrification tank through a first pipe, and then returned to the first storage tank through a second pipe. In this case, although it is very similar to step (S1), the carrier alone cannot perform nitrification treatment, while the nitrifying bacteria present in the raw water are repeatedly brought into contact with the carrier, so that the nitrifying bacteria attach to the periphery of the carrier and become a nitrifying agent.

[0074] As described above, prior to step (S1) or step (S2), the method may include a step (S0-2) of forming a denitrifying agent in a denitrification tank. Specifically, it is preferable to include a step of filling a carrier in the denitrification tank and attaching denitrifying bacteria to the carrier to form a denitrifying agent. A further specific method is to repeat a circulation process in which raw water or nitrification-treated water is supplied from the second storage tank to the nitrification tank through a third pipe, and then returned to the second storage tank through a fourth pipe. In this case, although it is very similar to step (S2), denitrification cannot be performed by the carrier alone, while the denitrifying bacteria present in the raw water or nitrification-treated water are repeatedly brought into contact with the carrier, so that the denitrifying bacteria attach to the periphery of the carrier and become a denitrifying agent.

[0075] As described above, this embodiment can provide a wastewater treatment system and a wastewater treatment method with higher treatment efficiency. In particular, according to this embodiment, each circulation type treatment is a batch treatment, but is circulated, and it is possible to perform nitrification treatment and denitrification treatment sequentially and simultaneously. For example, first, raw water is converted into nitrification-treated water using a circulation type nitrification system, and then this nitrification-treated water is transferred to a circulation type denitrification system. On the other hand, since this nitrification system can treat the raw water by that amount, nitrification treatment and denitrification treatment can be performed simultaneously. Furthermore, in this system, since the raw water can be purified to below the environmental standard simply by circulating it sequentially, water charges for dilution, disinfection tanks, and chemical charges can be significantly reduced. In particular, compared to the activated sludge method, equipment such as a blower pump is not required, and various running costs can be reduced. In addition, since biological nitrification and denitrification are performed in each circulation system, there is no need to use the discharged digestive liquid for cultivation, and no special maintenance treatment is required. Therefore, it is a very inexpensive system.

[0076] (Another example 1) Although the present system 1 is as described above, it is also possible to adopt other configurations. For example, as shown in Fig. 2, it is possible to make a system in which the nitrification system 1 and the denitrification system 2 are completely separated. This makes it possible to deal with cases in which only one system is sufficient, such as cases in which only nitrification treatment is required, or cases in which only denitrification is desired because nitrification-treated water is already present.

[0077] (Another example 2) In addition, in this system 1, depending on the type of bacteria, it becomes possible to perform nitrification and denitrification with one bacterium. An image of this case is shown in FIG. 3. For example, in the case of a bacterium that can perform nitrification in a high oxygen concentration state and denitrification in a low oxygen concentration state, the raw water can be nitrified in an open system or with an oxygen supply means 15 that is driven, and when the nitrification is sufficient, the lid 211 or the like can be closed, and degassed as necessary to create a low oxygen concentration state so that denitrification can be performed. In this way, it is possible to realize the system with one tank and one treatment tank. In this case, the nitrification tank 12 and the denitrification tank 22 are the same, the first storage tank 11 is also the second storage tank 21, the first pipe 13 is the same as the third pipe 23, and the second pipe 16 is the same as the fourth pipe 25. EXAMPLES

[0078] An experiment was carried out to actually treat raw water using the above-described system 1. The specific results are shown below.

[0079] First, a sufficient amount of raw water with a BOD value of 400 mg / L or more was prepared and stored in a first storage tank that could accommodate this amount.

[0080] (Nitrification tank preparation) A tank filled with 50 kg of burnt soil (a mixture of red and black soil) with an average particle size of approximately 1 mm was prepared, and the first storage tank and this tank were connected with the first and second pipes, respectively, to form a circulation path.

[0081] Next, the first pump was used to circulate the raw water between the first storage tank and the tank for three days while supplying oxygen to the raw water with an air pump, so that the nitrifying bacteria were sufficiently attached to the burnt soil and prepared as a nitrifying agent. As a result, this tank became a nitrification tank.

[0082] (Preparing the denitrification tank) Separately from the above, a tank filled with 50 kg of burnt soil (a mixture of red soil and black soil) with an average particle size of approximately 1 mm was prepared, and the first storage tank and this tank were connected with a third pipe and a fourth pipe, respectively, to form a circulation path.

[0083] Next, the raw water was circulated between the first storage tank and the tank using the second pump, which was then covered with a lid, deaerated, sealed, and circulated for three days to allow the denitrifying bacteria to attach sufficiently to the burnt soil, preparing it as a denitrifying agent. As a result, this tank became a denitrification tank.

[0084] Furthermore, 100L of raw water with a BOD value of 476mg / L was prepared as the raw water to be treated this time, and this was stored in the first storage tank and circulated for one day through the first pipe, the nitrification tank, and the second pipe. The results are as follows. Specifically, the BOD, which was initially 476mg / L, dropped to 13.3mg / L after one day, which was well below the environmental standard. On the other hand, it was confirmed that the COD value, which was initially 1290mg / L, dropped to 85.3mg / L after one day. Furthermore, the ammonia value was 400mg / L before treatment, but after one day of treatment it was 50mL, while the nitrite nitrogen, which was initially less than 0.1mg / L, dropped to 8.4mg / L, and the nitrate nitrogen, which was 35mg / L, dropped to 580mg / L, confirming that the water was sufficiently nitrified. [Table 1]

[0085] Next, the nitrification-treated water stored in the first storage tank was transferred to the second storage tank, and the third and fourth pipes were connected to the denitrification tank to form a circulation path, and the nitrification-treated water was treated for one day in the same manner as in the above circulation. The results are shown in Table 2 below. [Table 2]

[0086] Specifically, the results confirmed that the initial levels of nitrate nitrogen, which was 580 mg / L, and nitrite nitrogen, which was 8.4 mg / L, both had fallen to less than 0.1 mg / L.

[0087] As described above, it has been confirmed that this embodiment can provide a wastewater treatment system and a wastewater treatment method with higher treatment efficiency without using chemical agents. [Industrial Applicability]

[0088] INDUSTRIAL APPLICABILITY The present invention has industrial applicability as a wastewater treatment system and a wastewater treatment method. [Explanation of symbols]

[0089] S…Wastewater treatment system 1. Circulating nitrification system 11...First storage tank 12...Nitrification tank 13...First pipe 14…First pump 15...Oxygen supply means 16...Second piping 17...pH adjustment means 18…Water intake pipe 2. Circulating denitrification system 21...Second storage tank 22…Denitrification tank 23...Third Pipe 24…Second pump 25...Fourth Pipe

Claims

1. a first storage tank for storing raw water; a nitrification tank containing a nitrification agent having nitrifying bacteria supported on a carrier; a first pipe for supplying the raw water from the first storage tank to the nitrification tank; A second pipe for returning the nitrification-treated water from the nitrification tank to the first storage tank; a first pump provided in at least one of the first pipe and the second pipe.

2. 2. The wastewater treatment system according to claim 1, further comprising an oxygen supplying means for supplying oxygen to said raw water.

3. 2. The wastewater treatment system according to claim 1, wherein the circulating nitrification system further comprises a pH adjusting means for adding a pH adjuster to the raw water.

4. A second storage tank for storing the nitrification-treated water; a denitrification tank containing a denitrifying agent having denitrifying bacteria held in a carrier; a third pipe for supplying the nitrification treated water from the second storage tank to the denitrification tank; A fourth pipe for returning the denitrified denitrification treated water from the denitrification tank to the second storage tank; and a second pump provided in at least one of the third pipe and the fourth pipe.

5. 5. The wastewater treatment system according to claim 4, wherein the circulating denitrification system is kept in a low oxygen state in order to maintain an anaerobic state.

6. a second storage tank for storing the nitrification-treated water; a denitrification tank containing a denitrifying agent having denitrifying bacteria held in a carrier; a third pipe for supplying the nitrification treated water from the second storage tank to a denitrification tank; A fourth pipe for returning the denitrified denitrification treated water from the denitrification tank to the second storage tank; a second pump provided in at least one of the third piping and the fourth piping.

7. A step of nitrifying the raw water by circulating it through a nitrifying agent having nitrifying bacteria held on a carrier; The wastewater treatment method comprises a step of denitrifying the nitrified raw water by circulating the raw water through a denitrifying agent having denitrifying bacteria carried on a carrier.

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