Desiccation device

Abstract

To provide a low-cost and efficient aerobic denitrification apparatus which has no risk of hydrogen sulfide generation by preventing processing object water from being stored in a denitrification tank and preventing suspended particles from accumulating in a gap between filter materials.SOLUTION: An aerobic denitrification apparatus comprises: a denitrification tank to which processing object water is supplied, which has a cylindrical or spherical shape and has an opening for feeding / discharging water; a filter material which is filled in the denitrification tank, and holds denitrification bacteria that reduce nitrate nitrogen in the processing object water to nitrogen gas; and a drive unit for operating the denitrification tank. The aerobic denitrification apparatus prevents the processing object water from being stored in the denitrification tank and prevents suspended particles being the cause of the occlusion of the gap between filter materials from being accumulated by performing feeding and discharging of the processing object water while consecutively or intermittently driving the denitrification tank.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an apparatus for removing nitrate nitrogen in water, and more particularly to a denitrification apparatus for safely and efficiently removing nitrate nitrogen in breeding water in an aerobic environment for breeding fish and shellfish.

Background Art

[0002] When breeding fish and shellfish such as in aquaculture or stockpiling, ammonia is excreted from the fish and shellfish, and the water quality of the breeding water (hereinafter also referred to as "treated water") deteriorates. In a closed circulation system for breeding fish and shellfish without water exchange, ammonia rises to a concentration unsuitable for breeding, so a nitrification apparatus is installed that converts toxic ammonia into harmless nitric acid by the action of nitrifying bacteria that propagate on filter media such as coral, and reduces it to a concentration suitable for fish and shellfish breeding. On the other hand, since nitric acid was considered to have low toxicity and little effect on fish and shellfish, nitrate removal has not been conventionally performed. However, in recent years, it has been revealed that it is one of the causative substances causing growth retardation and death, and the number of cases where a denitrification apparatus is installed for the purpose of reducing production costs by promoting growth has increased. However, since conventional denitrification apparatuses perform treatment in an anaerobic environment, there is a high risk of generating toxic hydrogen sulfide, and the operation is also complicated, so they have not been widely spread. In recent years, an apparatus capable of denitrification even in an aerobic environment (aerobic denitrification apparatus) has been developed, eliminating the risk of hydrogen sulfide generation and becoming generally used.

[0003] Aerobic denitrification apparatuses include an intermittent filtration method, as shown in Patent Document 1, in which rearing water is continuously supplied while intermittently draining water using the siphon principle, causing the filter media containing denitrifying bacteria to alternately undergo air exposure and liquid immersion; a water-sprinkling filter bed method, as shown in Patent Document 2, in which rearing water is sprayed from the top of a denitrification tank with a drain outlet below the filter media, so that rearing water does not accumulate in the denitrification tank and the water flows through the gaps in the filter media, creating areas of air exposure and liquid immersion in the filter media containing denitrifying bacteria; and a rotating disc method, which has not been used in conventional anaerobic denitrification apparatuses because the filter media is always exposed to air, but has been used in nitrification apparatuses that oxidize ammonia, which reacts under aerobic conditions, to nitrate. The rotating disc system consists of a disc-shaped filter medium for holding nitrifying bacteria, a drive unit for rotating the disc-shaped filter medium, and a tank for storing the water to be treated. The disc-shaped filter medium is installed so that a portion of it is submerged in the water to be treated, and the rotation of the disc-shaped filter medium causes the filter medium to repeatedly be exposed to air and immersed in liquid. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6480015 [Patent Document 2] Japanese Patent Publication No. 20001-577 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The intermittent filtration method is a technique that utilizes the siphon principle to allow the denitrification reaction to proceed in an aerobic environment by repeatedly exposing the filter media containing denitrifying bacteria to air and immersing it in liquid. The water to be treated, supplied to the denitrification tank, is not drained from the tank until the water level at which the siphon acts is reached, and the filter media, where the denitrifying bacteria have proliferated, is immersed in the water to be treated. When the water level in the denitrification tank rises to the level at which the siphon acts, drainage begins, and the filter media is exposed to the air. When the water level drops to the drain outlet at the bottom of the denitrification tank, the siphon ends and drainage stops, and the water level in the denitrification tank rises again. By repeating this operation, nitrate nitrogen in the water to be treated is decomposed into nitrogen gas while maintaining an aerobic environment. Because the filter media is periodically exposed to air, anaerobic conditions do not occur, making it a safe treatment method that does not generate hydrogen sulfide.

[0006] However, because the intermittent filtration method uses the siphon principle to drain water, the denitrification tank must be installed higher than the tank to which the water is drained, requiring a sturdy and large support structure. Also, because drainage is performed intermittently, in a closed system such as closed-loop aquaculture, the volume of the tank at the bottom of the system increases by the amount of water drained from the denitrification tank in each pass, increasing the initial cost. Furthermore, because the water level in the denitrification tank fluctuates, there is a difference in the ratio of time the filter media is exposed to air and the time it is immersed in the liquid between the upper and lower layers, making it difficult to optimize the conditions for all the filter media in the denitrification tank.

[0007] Intermittent filtration has a low risk of hydrogen sulfide generation because the filter media is exposed to the air at regular intervals. However, if suspended solids in the treated water accumulate in the gaps between the filter media and cause blockage, the treated water trapped in these gaps will become anaerobic as denitrifying bacteria consume the dissolved oxygen. Therefore, if the filter media is not cleaned and blockage is left untreated for a long period, or if water supply is stopped for an extended period while the filter media is immersed, anaerobic conditions can occur, and this technology is not entirely free from the risk of hydrogen sulfide generation.

[0008] In the drip filter system, the water to be treated is sprayed from the top of the denitrification tank, and a drain outlet is located at the bottom of the tank. This prevents the water to be treated from accumulating in the tank, allowing it to flow through the gaps in the filter media and treat nitrate nitrogen. Therefore, it is important to spray the water to be treated uniformly onto the surface of the filter media, and in order to deliver the water to the entire denitrification tank, it is necessary to devise methods such as rotating the water outlet while spraying the water into the tank. However, even if water is uniformly sprayed onto the surface of the filter media, suspended particles accumulate in the gaps between the media over time, causing partial blockage. This results in uneven flow of the treated water in the denitrification tank, making it impossible to effectively utilize all of the installed filter media. Furthermore, similar to intermittent filtration systems, anaerobic conditions can develop where the treated water is held for extended periods, requiring periodic cleaning of the filter media.

[0009] In both of the aforementioned methods, the filter media used in the denitrification system serves as both a breeding ground for denitrifying bacteria and a source of organic carbon, requiring periodic replenishment due to media depletion. Furthermore, the depletion reduces the strength of the filter media, causing the lower layers to collapse and become clogged. Therefore, to reduce the burden of replenishment and replacement work and minimize the load on the lower layers of filter media, the denitrification tank is designed to be as shallow as possible, but there are limits to how shallow it can be made due to the constraints of the installation area.

[0010] Although the rotating disc method is not typically used in denitrification systems, recent studies have shown that denitrification can proceed even under aerobic conditions, making it possible to use it as an aerobic denitrification system. However, since denitrification always requires an organic carbon source, a separate device for adding the organic carbon source must be installed. While it is possible to simplify the system by mixing the organic carbon source into the disc filter media, it is consumed along with the denitrification reaction, requiring replenishment of the depleted organic carbon source. In the case of disc-shaped filter media, it is difficult to replenish only the depleted portion; still usable filter media must also be replaced, resulting in a lot of waste and high running costs.

[0011] The object of the present invention is to provide a safe and inexpensive denitrification apparatus that is easy to maintain, uses filter media efficiently, has high processing efficiency, and does not pose a risk of hydrogen sulfide generation, in view of the problems of the conventional technology described above, by making the denitrification tank, which is the drive unit, cylindrical or spherical and loading filter media inside, not accumulating water to be treated in the denitrification tank, efficiently bringing the filter media and the water to be treated into contact, moving the filter media to suppress clogging by suspended particles, and not allowing water between the filter media to remain stagnant for a long time. [Means for solving the problem]

[0012] The denitrification apparatus of the present invention, which solves the above problems, In a denitrification apparatus that removes nitrate nitrogen from water under aerobic conditions, It is cylindrical or rectangular in shape, divided by multiple partition plates, and has openings for water supply and drainage, into which the water to be treated is supplied. outer surface Preparation and equipped with drainage openings on the sides The denitrification tank, A filter material is installed in the denitrification tank and holds denitrifying bacteria that reduce nitrate nitrogen in the water to be treated into nitrogen gas, It consists of a rotating shaft disposed on the side to drive the denitrification tank, The driving force of the denitrification tank is water power, wind power, or electricity. While the denitrification tank is driven continuously or intermittently in air only, the water to be treated is supplied to the denitrification tank. save Supply and drainage without any issues. It is, The treated water is drained through the openings formed on the outer and side surfaces of the denitrification tank, so that it is not stored in the denitrification tank. A denitrification apparatus characterized by the following features.

[0013] In a denitrification apparatus that removes nitrate nitrogen from water under aerobic conditions, A cylindrical or rectangular tube into which the water to be treated is supplied, and is divided by multiple partition plates, and the water to be treated is supplied save A denitrification tank having an internal space and openings for water supply and drainage only on its outer surface, A filter material is installed in the denitrification tank and holds denitrifying bacteria that reduce nitrate nitrogen in the water to be treated into nitrogen gas, It consists of a rotating shaft disposed on the side to drive the denitrification tank, The driving force of the denitrification tank is water power, wind power, or electricity. While the denitrification tank is driven continuously or intermittently in air only, A denitrification apparatus characterized in that the water to be treated, supplied from the top, is drained from the same opening as it rotates, causing the filter material to repeatedly undergo exposure to air and immersion in liquid.

[0014] When the water to be treated is supplied by spraying from an external source, the water is drained from an opening located below the filter media in the denitrification tank. As a result, the water does not accumulate in the denitrification tank, and the filter media is not immersed in the water. Nitrate nitrogen in the water to be treated comes into contact with the filter media as it passes through the gaps in the filter media installed in the denitrification tank, and is taken up by denitrifying bacteria that have grown on the filter media. Since the entire surface of the filter media does not come into contact with the water to be treated, a portion of the filter media is constantly exposed to air, and the denitrification reaction proceeds in an aerobic environment.

[0015] The gaps between adjacent filter media in the denitrification tank are pathways for the treated water. If the water remains trapped in these gaps for an extended period, even partially, oxygen will be consumed by denitrifying bacteria, leading to anaerobic conditions. Treated water, such as water used for raising fish and shellfish, almost always contains suspended particles, which accumulate in the gaps between the filter media over time, causing blockages and resulting in the treated water remaining trapped in these areas for extended periods. To completely eliminate the risk of hydrogen sulfide generation, it is necessary to regularly clean the filter media to prevent blockage and remove suspended particles that accumulate in the gaps between the filter media. The denitrification apparatus of the present invention operates the denitrification tank to move the filter media loaded in the denitrification tank, changes the direction of the force acting on the pore water between the filter media, and moves the filter media with the water flow when the water to be treated flows into the denitrification tank. As a result, suspended particles do not accumulate in the gaps between the filter media, and the water to be treated is not retained in the gaps between the filter media for a long time, so anaerobic conditions do not occur and there is no risk of hydrogen sulfide generation.

[0016] If the rotating denitrification tank is not filled tightly with filter media, a part of the filter media will not move along with the rotation of the denitrification tank and will stay in place, so that the entire filled filter media will not contribute to the reaction. Therefore, a partition plate is arranged inside the denitrification tank to divide the internal space into multiple parts. Even when the filter media is depleted, the filter media will change its position in联动 with the denitrification tank, so that the treated water can contact the entire filter media. Also, since the filter media is both a dwelling place for denitrifying bacteria and an organic carbon source, it will be depleted along with the denitrification reaction and needs to be replenished regularly. The denitrification device of the present invention makes it easy to replace and replenish the filter media by dividing the denitrification tank into multiple spaces.

[0017] The denitrification tank is provided with an opening only outside the filter media. It may be characterized in that the denitrification tank is driven to drain water from the same opening through which the treated water is supplied, so that the filter media repeats air exposure and liquid immersion.

[0018] For example, as shown in Figure 3, the denitrification tank is divided by a partition plate, the rotating shaft arranged in the denitrification tank is moved to rotate the denitrification tank, and further, no opening is provided on the side of the denitrification tank and the opening is only provided on the outer periphery. In this way, near the top, the filter media is in a immersed state, and at positions below the horizontal, all the treated water is drained and it is in an air-exposed state. Since the denitrification tank is rotating, air exposure and liquid immersion are repeated alternately, and the denitrification reaction proceeds in an aerobic environment.

Advantages of the Invention

[0019] The denitrification device according to the present invention has the following effects. According to the present invention, by feeding the treated water while operating the denitrification tank divided into multiple spaces, the entire filter media can be effectively used, the treatment efficiency is increased, the device becomes compact, and the initial cost can be reduced.

[0020] According to the present invention, by operating the denitrification tank to move the filter media and change the direction of the force acting on the water in the gaps of the filter media, blockage due to the accumulation of suspended particles in the water to be treated is prevented, eliminating the need for periodic cleaning and reducing running costs. Furthermore, since uneven flow of the water to be treated within the denitrification tank caused by blockage is prevented, stable treatment can be performed without a decrease in treatment efficiency. In addition, since the water to be treated in the gaps of the filter media is not retained for long periods, there is no risk of hydrogen sulfide generation.

[0021] According to the present invention, since treated water does not accumulate in the denitrification tank, the weight of the equipment during operation is reduced, and the strength of the support structure required for installation can be decreased. Furthermore, in a closed circulation system, there is no need to increase the volume of the bottom water tank, so initial costs can be reduced.

[0022] According to the present invention, by dividing the inside of the denitrification tank into multiple spaces, the replenishment and replacement of filter media can be performed for each individual space, thereby reducing labor. Furthermore, since the filter layer can be made thinner, the load on the filter media in the lower layer is reduced, and the filter media can be used until the end without being crushed, resulting in less loss and lower running costs.

[0023] According to the present invention, by utilizing the flow of water to be treated (hydraulic power) instead of electricity as the power source for operating the denitrification tank, initial costs and running costs can be reduced. [Brief explanation of the drawing]

[0024] [Figure 1] A schematic diagram illustrating a denitrification apparatus according to the first embodiment of the present invention. [Figure 2] A schematic cross-sectional view illustrating the flow of water to be treated in a denitrification apparatus according to the first embodiment of the present invention. [Figure 3] A schematic diagram illustrating another configuration of the drive unit in the denitrification apparatus according to the first embodiment of the present invention. [Figure 4] A schematic cross-sectional view illustrating a denitrification apparatus according to a second embodiment of the present invention. [Figure 5] A schematic cross-sectional view illustrating a denitrification apparatus according to the third embodiment of the present invention. [Figure 6] A schematic cross-sectional view illustrating the flow of water to be treated and the immersion state of the filter material in a denitrification apparatus according to the fourth embodiment of the present invention. [Modes for carrying out the invention]

[0025] The embodiments of the present invention will be described in detail below with reference to the illustrated examples, but the present invention is not limited in any way to the embodiments described below and can be implemented with appropriate modifications.

[0026] Figures 1 and 2 (Figure 2 is a partial cross-sectional view of the denitrification apparatus in Figure 1) show a first embodiment of the present invention, which consists of a denitrification tank 1, a drive unit 2, and a filter material 3 for holding denitrifying bacteria. The denitrification tank 1 is cylindrical in shape, and a partition plate 14 is provided to divide the internal space 13 of the denitrification tank. While a cylindrical shape is preferable for the denitrification tank 1, it may also be rectangular or spherical, and is not limited in any way to its shape. The filter material 3 is loaded into each space divided by the partition plate 14 inside the denitrification tank.

[0027] The drive unit 2 consists of a rotating shaft 21 for rotating the denitrification tank 1 and a motor (not shown) that generates driving force. The rotating shaft 21 is positioned at the center of the side portion 12 of the denitrification tank. While it is common to use a motor to move the rotating shaft, as shown in Figure 3, a rotating blade 22 may be provided on the outer circumference 11 of the denitrification tank, and the denitrification tank 1 may be rotated by the downward force generated by blowing water or wind onto the rotating blade 22. The rotating blade 22 only needs to be able to generate driving force to rotate the denitrification tank 1, and its position and shape are not limited in any way. Furthermore, by making a part of the denitrification tank 1 a magnetic material, magnetic force can also be used as a power source.

[0028] As shown in Figure 2, the water to be treated is sprayed from above the denitrification tank and flows into the tank through opening 11a. The opening shown is slit-shaped, but any structure that allows the water to be treated to flow in but prevents the filter media from being released is acceptable, and it may have multiple holes or be made into a mesh. Alternatively, the filter media may be placed in a net and loaded to create a single large opening.

[0029] The water to be treated may be supplied from the rotating shaft 21 through the denitrification tank by providing an opening in the rotating shaft 21, rather than from the top. As long as water can be supplied to the denitrification tank, there are no limitations. The water to be treated supplied to the inside of the denitrification tank is drained from a drainage opening 11b provided near the rotating shaft on the side of the denitrification tank 12. Alternatively, the drainage opening 11b may not be provided on the side of the denitrification tank 12, and the rotating shaft 21 may be made hollow, with a hole drilled in the rotating shaft 21 through the denitrification tank, allowing drainage from the rotating shaft 21.

[0030] figure 4 This invention relates to the present invention. 2 This is an embodiment, and is a cross-sectional view illustrating the inflow and outflow of the water to be treated into the denitrification tank 1, the air exposure state of the filter media, and the liquid immersion state. 2 The embodiment is the same as the first embodiment, except that the opening 11b on the side portion 12 of the denitrification tank is not provided.

[0031] The water to be treated flows into the denitrification tank 1 through an opening 11a at the top of the internal space 13, which is divided by a partition plate 14 inside the denitrification tank. Since there is no drainage opening 11b on the side of the denitrification tank, the water to be treated accumulates in the denitrification tank 1 and the filter media 3 is submerged. As the rotation progresses and the internal space 13 where the water to be treated has accumulated tilts, the water to be treated begins to drain from the same opening 11c from which it entered, and when it reaches a horizontal position, all the water to be treated in the denitrification tank is drained. Alternatively, a cylindrical denitrification tank with an open top may be driven to accumulate water to be treated in a horizontal position, and then tilted to a vertical position to drain the water.

[0032] The filter media used in the denitrification apparatus of the present invention preferably has a porous structure so that many denitrifying bacteria that reduce nitrate nitrogen in the treated water to nitrogen gas can proliferate. Furthermore, while cellulose or a substance with a cellulose backbone is best as the organic carbon source for the filter media components, any substance that can be used by denitrifying bacteria that perform denitrification reactions in an aerobic environment is acceptable, and biodegradable plastics or chitosan may also be used. [Explanation of symbols]

[0033] 1 Denitrification tank 11 Denitrification tank outer periphery 11a Opening (supply port) 11b Opening (drain port) 11c Opening (water supply and drainage port) 12 Side of the denitrification tank 13 Interior space 14 partition plates 2 Drive unit 21 Rotation axis 22 Rotary blades 24 motors 3 filter media 4. Water storage tank

Claims

1. In a denitrification apparatus that removes nitrate nitrogen from water under aerobic conditions, A denitrification tank, which is cylindrical or rectangular in shape, divided by multiple partition plates, has openings on its outer surface for water supply and drainage, and has openings on its side for drainage, into which water to be treated is supplied. A filter material is installed in the denitrification tank and holds denitrifying bacteria that reduce nitrate nitrogen in the water to be treated into nitrogen gas, It consists of a rotating shaft disposed on the side to drive the denitrification tank, The driving force of the denitrification tank is water power, wind power, or electricity. The denitrification tank is operated continuously or intermittently in the air only, and the water to be treated is supplied and drained without being stored in the denitrification tank. The denitrification apparatus is characterized in that the water to be treated is drained from the openings formed on the outer circumferential surface and side surface of the denitrification tank, without accumulating in the denitrification tank.

2. In a denitrification apparatus that removes nitrate nitrogen from water under aerobic conditions, A denitrification tank is provided, which is cylindrical or rectangular in shape, divided by multiple partition plates, has an internal space for storing the water to be treated, and has openings for water supply and drainage only on its outer surface, and into which the water to be treated is supplied. A filter material is installed in the denitrification tank and holds denitrifying bacteria that reduce nitrate nitrogen in the water to be treated into nitrogen gas, It consists of a rotating shaft disposed on the side to drive the denitrification tank, The driving force of the denitrification tank is water power, wind power, or electricity. While the denitrification tank is driven continuously or intermittently in air only, A denitrification apparatus characterized in that the water to be treated, supplied from the top, is drained from the same opening as it rotates, causing the filter material to repeatedly undergo exposure to air and immersion in liquid.

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