Water purifier

Abstract

To provide an effective denitrification treatment of rearing water for aquatic organisms under aerobic conditions.SOLUTION: A water purification apparatus 100 includes a denitrification tank 11 into which water to be treated such as rearing water is supplied, a denitrification filter media 61 housed within the denitrification tank 11 for immobilizing aerobic denitrifying bacteria that reduce nitrate nitrogen in the water to be treated, and a denitrification air supply mechanism 13 that is disposed at the bottom of the denitrification tank 11 and promotes the denitrification reaction by denitrifying bacteria under aerobic conditions after continuously performing the oxygen uptake operation to expose the denitrification filter media 61 to air by supplying air to the water to be treated stored in the denitrification tank 11 at a volume rate of 50% to 5000% per minute relative to the storage volume of the water to be treated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water purification device. [Background technology]

[0002] Patent Document 1 discloses a technology for purifying wastewater containing nitrogen, in which an entrapment filter medium doubly entrapping nitrifying microorganisms and denitrifying microorganisms is placed in a reaction tank, and then wastewater (substrate aqueous solution) is supplied to the reaction tank, passed through the entrapment filter medium, and discharged out of the reaction tank, while oxygen necessary for nitrification is sent from a blower through an air diffuser into the reaction tank. In this way, when removing nitrogen contained in water, by fixing denitrifying microorganisms and nitrifying microorganisms to the same fixed filter medium, nitrification and denitrification can be performed in a single reaction tank, making it possible to improve the economic efficiency of wastewater (substrate aqueous solution) treatment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 7-14517 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology of Patent Document 1, oxygen contained in the air is sent from a blower to the wastewater using an aeration device, thereby supplying the oxygen to the nitrifying and denitrifying microorganisms. However, depending on the amount of oxygen supplied, the efficiency of the nitrifying and denitrifying reactions for the entire wastewater (substrate aqueous solution) in the reaction tank may become insufficient, and improvement is desired.

[0005] The present invention has been made in consideration of the above circumstances, and its object is to provide a water purification apparatus that can efficiently and stably perform denitrification treatment of wastewater or other water to be treated under aerobic conditions throughout the entire reaction tank. [Means for solving the problem]

[0006] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by, for example, supplying air from the bottom of a denitrification tank at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be treated, thereby carrying out the denitrification reaction, and have thus completed the present invention. Specifically, the present invention provides the following.

[0007] The present invention provides a denitrification tank to which the water to be treated is supplied; A denitrification filter material accommodated in the denitrification tank and adapted to establish aerobic denitrification bacteria that reduce nitrate nitrogen in the water to be treated; The water purification device is equipped with a denitrification air supply mechanism that is placed at the bottom of the denitrification tank and that continuously performs an oxygen intake operation by supplying air to the water to be treated stored in the denitrification tank at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be treated, thereby exposing the denitrification filter material to the air, thereby promoting the denitrification reaction by the denitrification bacteria under aerobic conditions.

[0008] According to the present invention, air is supplied from the bottom of the denitrification tank at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be treated, and the denitrification reaction is carried out while stirring the water to be treated and the denitrification filter material throughout the entire denitrification tank from the top to the bottom of the denitrification tank using the upward flow of air, thereby making it possible to efficiently and stably denitrify the water to be treated throughout the entire denitrification tank under aerobic conditions. [Effects of the Invention]

[0009] According to the present invention, denitrification of water to be treated can be efficiently and stably carried out in the entire denitrification tank under aerobic conditions. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram showing the cleaning treatment process by the water purification device. [Figure 2] FIG. 2 is an explanatory diagram showing the cleaning treatment process by the water purification device. [Figure 3]FIG. 3 is an explanatory diagram showing the purification process performed by the water purification device. [Figure 4] FIG. 4 is an explanatory diagram showing a modified example of the water purification device, illustrating the state of the denitrification filter medium (nitrification filter medium). [Figure 5] FIG. 5 is an explanatory diagram showing a modified example of the water purification device, illustrating the state of the denitrification filter medium (nitrification filter medium). [Figure 6] FIG. 6 is an explanatory diagram showing a modified example of the water purification device, illustrating the state of the denitrification filter medium (nitrification filter medium). [Figure 7] FIG. 7 is an explanatory diagram showing the purification process performed by the water purification device. DETAILED DESCRIPTION OF THE INVENTION

[0011] An example of a preferred embodiment for carrying out the present invention will be described below. Note that this is merely an example, and the technical scope of the present invention is not limited to this. That is, in the following description, water for raising aquatic organisms is used as an example of water to be treated, but the water is not limited to this and may be any water that requires purification, as will be described in detail later.

[0012] (Water Purification Device 100: Overview) As shown in FIG. 1, the water purification apparatus 100 is configured to supply air from the bottom of the denitrification tank 11 at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be treated, and to perform a denitrification reaction using the suspended air bubbles 7. This allows the water purification apparatus 100 to perform a denitrification reaction in the water to be treated using oxygen in the air rather than dissolved oxygen in the water. As a result, while the amount of dissolved oxygen in natural water is at most about 10 mg (10 ppm), the weight of oxygen in 1 liter of air is 258 mg. Therefore, the water purification apparatus 100, which performs a denitrification reaction using the abundant oxygen in the air rather than dissolved oxygen, can efficiently and stably perform denitrification of the water to be treated throughout the entire denitrification tank 11 under aerobic conditions.

[0013] Here, "denitrification" refers to the reaction in which nitrate nitrogen and nitrite nitrogen are reduced to nitrogen gas by the action of denitrifying bacteria. Denitrification under aerobic conditions is a reaction that uses oxygen as an electron donor, and is carried out under conditions of high oxygen concentration by aerobic bacteria. "Nitrate nitrogen (NO3 - ) and "nitrite nitrogen (NO2 - ) are nitrogen compounds with different oxidation states of nitrogen, and are intermediate products before being reduced to nitrogen gas by denitrifying bacteria in the denitrification reaction.

[0014] "Aerobic bacteria" is a general term for bacteria that grow in the presence of oxygen, and representative examples include denitrifying bacteria and nitrate-reducing bacteria. "Denitrifying bacteria" is a general term for bacteria that have the ability to reduce nitrate nitrogen and nitrite nitrogen to nitrogen gas, and representative examples include Paracoccus denitrificans, Pseudomonas stzerzeri, and Thiobacillus denitrificans. "Nitrate-reducing bacteria" is a general term for bacteria that have the ability to reduce nitrate nitrogen to nitrogen gas, and representative examples include Paracoccus pantotrophus, Pseudomonas aureofaciens, and Thiobacillus denitrificans.

[0015] Examples of "water to be treated" include sewage, livestock wastewater, agricultural wastewater, industrial wastewater, seawater, and water used to raise aquatic organisms. "Aquatic organisms" refer to organisms that live in water or near water, such as fish and shellfish, shrimp, and crabs. Note that "water" and "water used to raise aquatic organisms" here refer to either seawater or freshwater, and are not limited to one or the other.

[0016] The reason for supplying air at a volumetric rate of 50% to 5,000% per minute of the storage volume of the water to be treated is to enable the denitrification reaction to occur using oxygen in the air rather than dissolved oxygen in the water. The reason for the lower limit of the numerical range being 50% is that if the value is less than 50%, the denitrification process will be performed using dissolved oxygen in the water, resulting in a significant decrease in treatment capacity. On the other hand, the reason for the upper limit of the numerical range being 5,000% is that if the value exceeds 5,000%, the disadvantages of increased damage to the filter media and increased power consumption will outweigh the benefits of increased nitrification process capacity. Furthermore, when air is supplied from the bottom of the denitrification tank 11 at a volumetric rate of 50% to 5,000% per minute of the storage volume of the water to be treated, the water to be treated and the denitrification filter media 61 stored in the denitrification tank 11 are agitated throughout the tank by the upward air flow, and the denitrification reaction will occur evenly throughout the tank. Specifically, it was experimentally confirmed that the efficiency of the denitrification reaction improves when air is supplied from the bottom of the denitrification tank 11 at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be treated. Details will be explained in Examples and Comparative Examples below. The reason why the nitrification reaction occurs due to air bubbles 7 when air is supplied at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be treated is the same.

[0017] (Water Purification Device 100: Example) As a specific example of the water purification device 100, the water purification device 100 has a denitrification device 1 that denitrifies nitrate nitrogen and nitrite nitrogen in the breeding water stored in a breeding tank 8 used to breed aquatic organisms, using denitrifying bacteria under aerobic conditions, and a nitrification device 2 that nitrifies ammonia nitrogen in the breeding water using nitrifying bacteria under aerobic conditions. The nitrification device 2 will be described later.

[0018] (Denitrification equipment 1: Denitrification tank 11) The denitrification apparatus 1 has a denitrification tank 11 to which culture water stored in a breeding aquarium 8 used for breeding aquatic organisms is supplied. The denitrification tank 11 is cylindrical and has an open top. The opening of the denitrification tank 11 allows nitrogen gas generated in the denitrification reaction to escape to the outside, preventing the denitrification tank 11 from filling with nitrogen gas. Culture water from the breeding aquarium 8 is supplied to the denitrification tank 11 from above via a first culture water supply path 12. The first culture water supply path 12 has a culture water supply pump 124 connected to the bottom of the breeding aquarium 8, a culture water supply pipe 121 that guides the culture water to the denitrification tank 11 and the nitrification tank 21, a first supply valve 122 that can switch between supplying and stopping the supply of culture water to the denitrification tank 11, and a second supply valve 123 that can switch between supplying and stopping the supply of culture water to the nitrification tank 21 of the nitrification apparatus 2.

[0019] The denitrification tank 11 is also connected to a first breeding water recovery conduit 14 that delivers denitrified breeding water to the breeding tank 8. The first breeding water recovery conduit 14 has a breeding water supply pump 142 connected to the bottom of the denitrification tank 11 and a breeding water supply pipe 141 that guides the breeding water to the breeding tank 8. The amount of breeding water supplied from the breeding tank 8 and the amount of breeding water delivered to the breeding tank 8 are controlled so that the liquid level of the breeding water matches a predetermined first reference height. That is, the liquid level of the breeding water is controlled to match the first reference height by a combination of adjusting the delivery rates of the breeding water supply pump 124 and the breeding water supply pump 142 and switching the first supply valve 122 on and off. This allows the denitrification tank 11 to circulate the breeding water between the breeding tank 8 and the denitrification tank 11 intermittently at predetermined intervals or continuously, depending on the status of the denitrification treatment and the breeding status of the aquatic organisms in the breeding tank 8. The denitrification tank 11 is capable of carrying out denitrification treatment while storing a fixed amount of rearing water, whether in an intermittent circulation mode or a continuous circulation mode.

[0020] The liquid level of the rearing water is detected by a level gauge 15 provided in the denitrification tank 11. Examples of the liquid level gauge 15 include a float level gauge in which a float or a flotation device floats on the surface of the rearing water and detects the liquid level in conjunction with a pointer that indicates its position, a conductive level gauge that detects the liquid level by utilizing the conductivity of the rearing water, an ultrasonic level gauge that uses ultrasound to measure the distance to the surface of the rearing water to detect the liquid level, and a radar level gauge that detects the liquid level by using microwaves or radar signals.

[0021] (Denitrification device 1: Denitrification filter medium 61) The denitrification tank 11 contains a denitrification filter medium 61, which allows aerobic denitrification bacteria to settle and reduce nitrate nitrogen in the rearing water. The denitrification filter medium 61 has a porous structure that allows denitrification bacteria to settle easily. Examples of denitrification filter medium 61 include circular porous polyethylene filter medium, rectangular porous ceramic filter medium, bead-shaped porous activated carbon filter medium, sponge-shaped porous polyurethane filter medium, nonwoven porous polyester filter medium, and paper-shaped porous cellulose filter medium. The denitrification filter medium 61 preferably contains organic matter such as sugars, amino acids, lipids, and nucleic acids. This is because these organic matter provide the energy source necessary for the growth of denitrification bacteria. The denitrification filter medium 61 also preferably contains trace elements such as phosphorus, sulfur, magnesium, and potassium. These trace elements are essential for the metabolism of denitrification bacteria, and a deficiency of these elements reduces the activity of denitrification bacteria. The denitrification filter medium 61 may also use a carbon donor (carrier) with a CnHnOn structure, such as a chain of sugars, such as cellulose or starch. In this case, the denitrification filter medium 61 formed using a carbon donor (carrier) containing sugars such as cellulose or starch is consumed by bacteria that perform denitrification under aerobic conditions, providing the energy necessary for bacterial growth and activity and functioning as an electron donor in the denitrification process. As the denitrification filter medium 61 continues to be consumed by the bacteria, it will eventually decompose and disappear.

[0022] The denitrification filter media 61 are formed to have a mass and size sufficient to float in the rearing water. As a result, the denitrification filter media 61 are agitated as the air bubbles 7 rise, so that the surface of the denitrification filter media 61 is constantly washed with water and oxygen is distributed over the surface of the denitrification filter media 61, which activates the denitrification bacteria and makes it possible to increase the efficiency of nitrate nitrogen removal. Furthermore, agitating the denitrification filter media 61 in water disperses the stacked denitrification filter media 61, increasing the surface area of ​​the denitrification filter media 61 and increasing the amount of denitrification bacteria that can settle. Note that multiple denitrification filter media 61 may be stored in a mesh bag.

[0023] (Denitrification device 1: Denitrification air supply mechanism 13) The denitrification tank 11 is further provided with a denitrification air supply mechanism 13 that supplies oxygen-containing air into the denitrification tank 11. The denitrification air supply mechanism 13 is configured to generate air bubbles 7 in the culture water stored in the denitrification tank 11. The denitrification air supply mechanism 13 continuously performs an oxygen intake operation that exposes the denitrification filter medium 61 to the air of the air bubbles 7, thereby promoting the denitrification reaction by denitrifying bacteria under aerobic conditions. Specifically, when the air bubbles 7 come into contact with the denitrification filter medium 61 due to the oxygen intake operation, the oxygen in the air bubbles 7 diffuses to the surface of the denitrification filter medium 61. As a result, the surface of the denitrification filter medium 61 becomes saturated with oxygen, and the denitrification bacteria that have settled on the surface of the denitrification filter medium 61 use the oxygen to decompose nitrate nitrogen and nitrite nitrogen, promoting the aerobic denitrification reaction that produces nitrogen. Note that ozone gas may be added to the air supplied to the denitrification tank 11 in an amount that does not adversely affect aquatic organisms. The reason for this is that when aerobic denitrification is performed using aerobic denitrifying bacteria, the rearing water may turn brown, and ozone can remove this coloration. Furthermore, the strong oxidizing power of ozone can sterilize microorganisms such as bacteria and viruses, thereby maintaining good hygiene in the rearing water.

[0024] The denitrification air supply mechanism 13 includes a blower 131 disposed outside the denitrification tank 11 and an air supply pipe 132 connected to the exhaust port of the blower 131 and disposed at the bottom of the denitrification tank 11. The air supply pipe 132 has a plurality of through-holes 132a formed in its side. The denitrification air supply mechanism 13 supplies air bubbles from the bottom of the denitrification tank 11 to the culture water by having the blower 131 send air into the air supply pipe 132 and then expel the air through the through-holes 132a. The denitrification air supply mechanism 13 preferably includes a throttle mechanism, such as a diaphragm valve, that can change the diameter of the through-holes 132a, allowing the diameter of the through-holes 132a to be increased or decreased depending on the amount of air supplied. In this case, the average diameter of the floating air bubbles 7 can be adjusted by adjusting the amount of air supplied and the diameter of the through-holes 132a.

[0025] The air supply pipe 132 is arranged over the entire bottom surface of the denitrification tank 11 and is configured to supply air in the form of bubbles from the entire bottom surface of the denitrification tank 11. As a result, the denitrification air supply mechanism 13 supplies air from the entire bottom surface of the denitrification tank 11, thereby enabling air to be supplied evenly throughout the culture water in the denitrification tank 11 and circulating and agitating the culture water throughout the denitrification tank 11.

[0026] (Denitrification device 1: Other configurations) The denitrification tank 11 is preferably provided with a band heater and cooling piping (not shown) along with a temperature detector for detecting the temperature of the rearing water. In this case, even in seasons when the atmospheric temperature rises and falls significantly from room temperature, the temperature of the rearing water in the denitrification tank 11 can be detected by the temperature detector and the power supply to the band heater and the amount of water to the cooling piping can be adjusted to maintain a constant temperature while performing denitrification. The denitrification tank 11 is preferably provided with a foam separation device (protein skimmer). The foam separation device is a device for removing organic matter and proteins from the rearing water. It adsorbs highly hydrophobic organic matter and proteins onto the air bubbles 7 as they rise in the rearing water, and removes the organic matter and proteins that rise to the surface of the water.

[0027] (Nitrification equipment 2: Nitrification tank 21) The water purification system 100 equipped with the denitrification device 1 configured as described above further includes a nitrification device 2 that nitrifies ammonia nitrogen in the breeding water using nitrifying bacteria under aerobic conditions. The nitrification tank 21 has the same configuration as the denitrification tank 11 of the denitrification device 1, so a description thereof will be omitted. Here, "ammonia nitrogen" is a form of nitrogen that exists mainly in the form of ammonia and ammonium ions, and is produced by the decomposition of metabolic products of aquatic organisms and organic matter, and is efficiently converted into nitrite nitrogen and then nitrate nitrogen through nitrification by nitrifying bacteria.

[0028] The nitrification tank 21 is connected to the breeding aquarium 8 via a breeding water supply pipe 121 and a second supply valve 123. The breeding water supply pipe 121 supplies the breeding water drawn from the breeding aquarium 8 by a breeding water supply pump 124 from above the nitrification tank 21. A second breeding water recovery line 25, which delivers the nitrified breeding water to the breeding aquarium 8, is also connected to the nitrification tank 21. The second breeding water recovery line 25 includes a breeding water supply pump 252 connected to the bottom of the nitrification tank 21 and a breeding water supply pipe 251 that guides the breeding water to the breeding aquarium 8. The amount of breeding water supplied from the breeding aquarium 8 and the amount of breeding water supplied to the breeding aquarium 8 are controlled so that the level of the breeding water coincides with a predetermined second reference height. That is, the second supply valve 123 is opened and closed to control the level of the breeding water so that it coincides with the second reference height.

[0029] This allows the nitrification tank 21 to circulate the rearing water between the rearing tank 8 and the nitrification tank 21 either intermittently at predetermined intervals or continuously, depending on the status of the nitrification reaction and the rearing status of the aquatic organisms in the rearing tank 8. The nitrification tank 21 is capable of carrying out nitrification treatment with a fixed amount of rearing water stored in it, whether in the intermittent or continuous circulation mode. The level of the rearing water is detected by a level gauge 28 provided in the nitrification tank 21. Note that the level gauge 28 is the same as the level gauge 15 in the denitrification tank 11, and therefore a description thereof will be omitted.

[0030] (Nitrification tank 21: Nitrification air supply mechanism 24) The nitrification tank 21 is further provided with a nitrification air supply mechanism 24 that supplies air, which is an oxygen-containing gas, to the interior of the nitrification tank 21. The nitrification air supply mechanism 24 is configured to generate air bubbles 7 in the breeding water stored in the nitrification tank 21. The nitrification air supply mechanism 24 continuously performs an oxygen intake operation that exposes the nitrification filter medium 62 to the air in the air bubbles 7, thereby promoting the nitrification reaction by nitrifying bacteria under aerobic conditions. Specifically, when the air bubbles 7 come into contact with the nitrification filter medium 62 due to the oxygen intake operation, the oxygen in the air bubbles 7 diffuses to the surface of the nitrification filter medium 62. As a result, the surface of the nitrification filter medium 62 becomes saturated with oxygen, and the nitrifying bacteria that have settled on the surface of the nitrification filter medium 62 use the oxygen to decompose ammonia nitrogen, promoting the aerobic nitrification reaction that produces nitrogen.

[0031] Here, "nitrifying bacteria" is a general term for bacteria that oxidize ammonia nitrogen, such as ammonia and amines, to nitrite ions and then nitrate ions. "Nitrification reaction" is the reaction in which ammonia nitrogen is oxidized to nitrite nitrogen and then nitrate nitrogen.

[0032] The nitrification air supply mechanism 24 includes a blower 241 disposed outside the nitrification tank 21 and an air supply pipe 242 connected to the exhaust port of the blower 241 and disposed at the bottom of the nitrification tank 21. The air supply pipe 242 has a plurality of through-holes 242a formed on its side. The nitrification air supply mechanism 24 supplies air bubbles from the bottom of the nitrification tank 21 by having the blower 241 send air into the air supply pipe 242 and then expelling the air through the through-holes 242a. The nitrification air supply mechanism 24 preferably includes a throttle mechanism, such as a diaphragm valve, that can change the diameter of the through-holes 242a, similar to the denitrification air supply mechanism 13. The air supply pipe 242 is disposed over the entire bottom surface of the nitrification tank 21, allowing air bubbles to be supplied from the entire bottom surface of the nitrification tank 21. As a result, the nitrification air supply mechanism 24 supplies air from the entire bottom surface of the nitrification tank 21, thereby evenly supplying air to the entire breeding water in the nitrification tank 21 and enabling the breeding water to be circulated and stirred throughout the entire nitrification tank 21.

[0033] (Nitrification tank 21: Other components) The nitrification tank 21 is preferably provided with a band heater and cooling piping (not shown) along with a temperature detector for detecting the temperature of the rearing water. In this case, even in seasons when the atmospheric temperature rises and falls significantly from room temperature, the temperature of the rearing water in the nitrification tank 21 can be detected by the temperature detector and the power supply to the band heater and the amount of water in the cooling piping can be adjusted to maintain a constant temperature while performing nitrification treatment. The nitrification tank 21 is preferably provided with a foam separation device (protein skimmer).

[0034] (Breeding control device 3) The processing operations of the denitrification device 1 and nitrification device 2 configured as described above are controlled by a rearing control device 3. The rearing control device 3 includes a denitrification control unit 31 that controls the denitrification device 1, a nitrification control unit 32 that controls the nitrification device 2, and a rearing aquarium control unit 33 that controls the water level, temperature, etc. of the rearing tank 8. The rearing control device 3 may be a personal computer, a programmable controller, or a combination of a personal computer and a programmable controller. In the rearing control device 3, the denitrification control unit 31, the nitrification control unit 32, and the rearing aquarium control unit 33 may each be configured as a personal computer or a programmable controller. Furthermore, the rearing control device 3 may be connected to a monitoring device 4 operated by a manager 5 so as to be able to communicate data with the monitoring device 4. In this case, remote monitoring of the water purification device 100 is possible, and centralized monitoring of multiple water purification devices 100 installed in various locations is also possible.

[0035] (Variation 1) In the water purification device 100 described above, the denitrification tank 11 and the nitrification tank 21 are connected in parallel to the breeding aquarium 8 via the first breeding water supply path 12, and breeding water from the breeding aquarium 8 is supplied separately to the denitrification tank 11 and the nitrification tank 21, thereby independently carrying out denitrification and nitrification processes. However, this is not a limitation. As shown in FIG. 2 , the water purification device 100 may also have the nitrification device 2 and the denitrification device 1 connected in series to the breeding aquarium 8. Specifically, the breeding water from the breeding aquarium 8 may be supplied to the nitrification tank 21 via the breeding water supply pump 222 and the breeding water supply pipe 221 of the second breeding water supply path 22, and the breeding water from the nitrification tank 21 may be supplied to the denitrification tank 11 via the breeding water supply pump 232 and the breeding water supply pipe 231 of the third breeding water supply path 23. According to this configuration, the nitrification treatment of the breeding water in the nitrification device 2 and the denitrification treatment of the breeding water in the denitrification device 1 are carried out continuously, and the water quality of the breeding water in the breeding tank 8 is purified.

[0036] Furthermore, in the water purification apparatus 100 (FIG. 1), the air supply pipes 132, 242 of the denitrification air supply mechanism 13 and the nitrification air supply mechanism 24 are arranged over the entire bottom surface of the denitrification tank 11 and the nitrification tank 21, respectively, so that air bubbles are supplied from the entire bottom surface of each tank 11, 21. However, this is not a limitation. Specifically, the air supply pipes 242, 132 may be arranged at the center of the bottom surface of each tank 11, 21, so that air bubbles are supplied from the center of the bottom surface of each tank 11, 21. This arrangement generates a swirling flow that causes the culture water and air to rise from the center of the bottom surface of each tank 11, 21, swirl at the top, and then flow back down to the center of the bottom surface, thereby promoting agitation of the culture water and filter media 61, 62. In addition, either one of the denitrification air supply mechanism 13 or the nitrification air supply mechanism 24 may be configured to supply air bubbles 7 from the entire surface of FIG. 1, and the other may be configured to supply air bubbles 7 from the center of the bottom surface of FIG. 2.

[0037] The blowers 131 and 241 may also be designed to be able to control the amount of air they supply. If a constant amount of air is supplied, the flow rate and direction of the rearing water can be maintained constant. On the other hand, if the amount of air supplied is increased or decreased, the flow rate and direction of the rearing water can be changed. Thus, if the amount of air supplied by the blowers 131 and 241 is controllable, the swirling flow of the rearing water can be changed by changing the amount of air supplied, thereby promoting agitation of the rearing water in each tank 11 and 21.

[0038] Furthermore, in the above water purification apparatus 100, the denitrification filter medium 61 and the nitrification filter medium 62 are placed in separate tanks, the denitrification tank 11 and the nitrification tank 21, where the nitrification treatment and the nitrification treatment are carried out, respectively, but this is not limited to this, and the denitrification filter medium 61 and the nitrification filter medium 62 may be placed in a single treatment tank to carry out the nitrification treatment and the nitrification treatment of the breeding water. That is, the water purification apparatus 100 may carry out the nitrification treatment and the nitrification treatment of the breeding water in a state where the denitrification filter medium 61 and the nitrification filter medium 62 are mixed.

[0039] 3, the water purification apparatus 100 may include an air flow restricting member 101 disposed above the air supply pipe 132 (242) (air outlet) of the denitrification air supply mechanism 13 (nitrification air supply mechanism 24) and configured to restrict the flow direction of the upward flow of air supplied from the air supply pipe 132 (242) to the culture water (water to be treated) and concentrate it at one location, thereby circulating the culture water and the denitrification filter material 61 (nitrification filter material 62) throughout the denitrification tank 11 (nitrification tank 21). That is, the water purification apparatus 100 may include a cylindrical air flow restricting member 101 disposed underwater above the air supply pipe 132 (242) (air outlet) of the denitrification air supply mechanism 13 (nitrification air supply mechanism 24), with an opening area expanding from the top opening to the bottom opening, allowing the culture water and the denitrification filter material 61 (nitrification filter material 62) to pass through.

[0040] Specifically, the air flow regulating member 101 is provided above the air supply pipe 132 (242). The air flow regulating member 101 is provided at a height where it is immersed in the breeding water. The air flow regulating member 101 is formed in a cylindrical shape with openings on the top and bottom, and is provided so that the central axis passing through the centers of the top and bottom faces is in the vertical direction. The air flow regulating member 101 is opposed to the top face of the air supply pipe 132 (242) so that the opening on the bottom face covers the top face. This allows the air flow regulating member 101 to collect, within the air flow regulating member 101, air bubbles 7 that are discharged from the air supply pipe 132 (242) into the breeding water and rise.

[0041] The opening area of ​​the air flow restriction member 101 decreases from the bottom to the top. The air flow restriction member 101 may be a truncated cone with a circular top and a square bottom, a truncated hexagonal pyramid with a hexagonal top and an octagonal bottom, or a star-shaped cone with a star-shaped top and a circular bottom. This allows the air flow restriction member 101 to restrict the flow direction of the upward flow of air supplied from the air supply pipe 132 (242) to the rearing water (water to be treated) and concentrate it in one location. The opening on the top surface of the air flow restriction member 101 is sized to allow the denitrification filter material 61 (nitrification filter material 62) to pass through. The gap between the lower edge of the air flow restriction member 101 and the air supply pipe 132 (242) is sized to allow the denitrification filter material 61 (nitrification filter material 62) to pass through. As a result, the air flow regulating member 101 immersed in the breeding water discharges the air bubbles 7 rising from the air supply pipe 132 (242) together with the denitrification filter material 61 (nitrification filter material 62) from the opening on the top surface, thereby circulating the breeding water and the denitrification filter material 61 (nitrification filter material 62) throughout the denitrification tank 11 (nitrification tank 21).

[0042] According to the above configuration, the airflow restriction member 101 concentrates the airflow consisting of the bubbles 7, increasing the density of the bubbles 7. This efficiently supplies air to the denitrification filter media 61 (nitrification filter media 62), accelerating the denitrification reaction (nitrification reaction), just as the denitrification reaction (nitrification reaction) of the denitrification filter media 61 (nitrification filter media 62) occurs in the atmosphere. This same effect as the denitrification reaction (nitrification reaction) in the atmosphere can be continuously achieved in the rearing water circulating throughout the tank, thereby increasing the denitrification efficiency (nitrification reaction). Furthermore, the concentration of the bubbles 7 also concentrates the denitrification filter media 61 (nitrification filter media 62) floating in the rearing water, increasing the opportunities for the denitrification filter media 61 (nitrification filter media 62) to come into contact with each other, effectively cleaning the surfaces of the denitrification filter media 61 (nitrification filter media 62). This improves the efficiency of the denitrification reaction and prevents early deterioration of the treatment performance of the denitrification filter media 61 (nitrification filter media 62).

[0043] The air flow restriction member 101 may be partially connected to the air supply pipe 132 (242) of the denitrification air supply mechanism 13 (24) and incorporated into the denitrification air supply mechanism 13 (24) as a unit. In this case, the blower 131 (241) and the air supply pipe 132 (242) are connected by a flexible hose, and the denitrification air supply mechanism 13 (24) is made detachable from the denitrification tank 11 (21), so that the denitrification air supply mechanism 13 (24) can be easily attached to an existing denitrification tank 11 (21).

[0044] Furthermore, the water purification device 100 may be provided in water as a unit, as shown in FIG. 7 . Specifically, the water purification device 100 includes a filter media container 9 having an intermediate wall 94 between its upper and lower surfaces, with a plurality of through-holes 94a formed therein, and a communication portion 92a in the upper wall surface of the intermediate wall 94 that communicates with the outside, and an air supply mechanism 96 disposed below the intermediate wall 94 in the filter media container 9 and ejecting air as bubbles 7 into the breeding water (water to be treated). The filter media container 9 contains at least one of the filter media 61 and 62, which are supported by the intermediate wall 94 and include a denitrifying filter media 61 that colonizes aerobic denitrifying bacteria that reduce nitrate nitrogen in the breeding water and a nitrifying filter media 62 that colonizes aerobic nitrifying bacteria that oxidize ammonia nitrogen in the breeding water. The filter media container 9 may be configured such that the opening area is enlarged from the upper surface to the lower surface, so that the plurality of bubbles 7 are concentrated as they rise.

[0045] With the above configuration, the water purification device 100 is made into a unit, which allows it to be easily applied to existing purification facilities such as the breeding aquarium 8 and a septic tank. That is, it can be set up by the simple task of simply placing the water purification device 100 in the breeding aquarium 8. When air bubbles 7 are generated by the air supply mechanism 96, the air bubbles 7 rise and pass through the through-holes 94a to travel through the gaps between the filter media 61 and 62, and agitate the filter media 61 and 62, so that denitrification and nitrification treatments can be performed on the breeding water while raising fish, etc.

[0046] As shown in FIG. 4, the denitrification filter medium 61 (nitrification filter medium 62) may be porous and have multiple communication channels 611 (621) and may be fixed above the bubble 7 generation position, which is the installation position of the denitrification bubble generation mechanism 13 (nitrification air supply mechanism 24). For example, the filter medium 61 (62) may have communication channels 611 (621) in the vertical direction (the direction in which the bubbles 7 rise), and may be formed as a block body, such as a rectangular parallelepiped, of a predetermined size and shape. In this case, even if the horizontal size of each tank 11 (21) is large, by arranging multiple block bodies in parallel in the horizontal direction (the direction perpendicular to the direction in which the bubbles 7 rise), it is possible to cover the entire area above the air supply pipe 132 (242). Note that, when the vertical size of each tank 11 (21) is large, it is preferable to arrange multiple block bodies in multiple tiers in the vertical direction.

[0047] As shown in FIG. 5, the denitrification filter medium 61 (nitrification filter medium 62) may have a passage area of ​​the communicating passages 611 (621) that decreases from the bottom to the top. In this case, when air bubbles 7 rise through the communicating passages 611 (621) of the filter medium 61 (62), the passage area of ​​the communicating passages 611 (621) decreases from the bottom to the top, and the flow rate of the bubbles 7 increases as they rise. Then, due to the parachute effect of fluid dynamics, the bubbles 7 deform into a parachute shape, increasing their surface area and their contact area with the wall surfaces of the communicating passages 611 (621). This brings the bubbles 7 into closer contact with the wall surfaces of the communicating passages 611 (621), increasing the interaction between the bubbles 7 and the wall surfaces, locally increasing the pressure on the wall surfaces. This increases the amount of oxygen available for use by denitrification bacteria and nitrification bacteria.

[0048] According to the above configuration, the bubbles 7 are generated and pass through the communication passages 611 (621) of the filter medium 61 (62) as they rise in the breeding water. As the bubbles 7 flow along the communication passages 611 (621), they take on the average diameter of the communication passages 611 (621). This allows the denitrification reaction (nitrification reaction) to occur with the bubbles 7 in suspension whose average diameter is the average diameter of the communication passages 611 (621).

[0049] As shown in Figure 6, the filter medium 61 (62) may be formed as a block, such as a sphere, having a mesh of connecting passages 611 (621) and a specific gravity greater than that of the breeding water. In this case, by submerging the filter medium 61 (62) in the breeding water and allowing bubbles 7 to rise from below, some of the bubbles 7 move through the gaps between the filter medium 61 (62), while the rest pass through the connecting passages 611 (621) of the filter medium 61 (62) to form bubbles 7 with an average flow path diameter, thereby enabling denitrification and nitrification treatments.

[0050] (Water Purification Equipment 100: Summary) (1) As shown in Figures 1 and 2, the water purification device 100 includes a denitrification tank 11 to which breeding water stored in a breeding tank 8 used for breeding aquatic organisms is supplied, a denitrification filter material 61 housed in the denitrification tank 11 and adapted to settle aerobic denitrifying bacteria that reduce nitrate nitrogen in the breeding water, and a denitrification air supply mechanism 13 disposed at the bottom of the denitrification tank 11. The mechanism supplies air to the breeding water stored in the denitrification tank 11 at a volumetric rate of 50% to 5000% per minute of the breeding water storage volume, thereby continuously performing an oxygen intake operation to expose the denitrification filter material 61 to air, thereby promoting the denitrification reaction by the denitrifying bacteria under aerobic conditions.

[0051] According to the above configuration, air is supplied from the bottom of the denitrification tank 11 at a volumetric rate of 50% to 5000% per minute of the storage volume of the breeding water, thereby agitating the breeding water and the denitrification filter media 61 throughout the denitrification tank 11. The denitrification reaction is accelerated by continuously exposing the denitrification filter media 61 to air, thereby promoting the denitrification reaction. This enables efficient and stable denitrification of the breeding water for aquatic organisms throughout the denitrification tank 11 under aerobic conditions. Furthermore, the microbial activity that occurs during the denitrification process enables biological phosphorus removal (BPR), a phenomenon in which phosphorus is taken up into cells, to remove phosphorus.

[0052] (2) As shown in FIG. 3, the water purification device 100 has an air flow regulating member 101 that is disposed above the air discharge section (air supply pipe 132) of the denitrification air supply mechanism 13 and that regulates the flow direction of the upward flow of air supplied from the air discharge section (air supply pipe 132) to the rearing water (water to be treated) and concentrates it in one place, thereby circulating the rearing water (water to be treated) and the denitrification filter material 61 throughout the denitrification tank 11.

[0053] According to the above configuration, the air flow restricting member 101 concentrates the air flow consisting of the bubbles 7, thereby increasing the density of the bubbles 7. This efficiently supplies air to the denitrification filter media 61, accelerating the denitrification reaction, just as when the denitrification reaction of the denitrification filter media 61 is carried out in the atmosphere. The same effect as the denitrification reaction in the atmosphere can be continuously achieved in the rearing water (water to be treated) that is circulated throughout the denitrification tank 11, thereby improving the denitrification efficiency. Furthermore, the concentration of the bubbles 7 also concentrates the denitrification filter media 61 floating in the water to be treated, increasing the chances of the denitrification filter media 61 coming into contact with each other, effectively cleaning the surfaces of the denitrification filter media 61, improving the efficiency of the denitrification reaction, and preventing an early decline in treatment capacity.

[0054] (3) The water purification device 100 is housed in the denitrification tank 11 and has a nitrifying filter medium 62 for establishing aerobic nitrifying bacteria that oxidize ammonium nitrogen in the breeding water (water to be treated).

[0055] According to the above configuration, denitrification treatment and nitrification treatment can be carried out simultaneously in one denitrification tank 11.

[0056] (4) As shown in FIG. 3, the denitrification filter medium 61 is formed in a porous shape with a plurality of communication paths 611, and is fixed above the position where the bubbles 7 are generated. With the above configuration, the bubbles 7 are generated and pass through the communication paths 611 of the denitrification filter medium 61 as they rise in the rearing water. The bubbles 7 flow along the communication paths 611 and take on the average diameter of the communication paths 611. As a result, the denitrification reaction is carried out by the bubbles 7 whose average diameter in a floating state is the same as the average diameter of the communication paths 611, thereby accelerating the denitrification reaction.

[0057] (5) As shown in Figures 1 and 2, the water purification device 100 includes a nitrification tank 21 to which rearing water is supplied, a nitrification filter material 62 housed in the nitrification tank 21 and adapted to settle aerobic nitrifying bacteria that oxidize ammonia nitrogen in the rearing water, and a nitrification air supply mechanism 24 disposed at the bottom of the nitrification tank 21. The nitrification air supply mechanism 24 continuously supplies air to the rearing water stored in the nitrification tank 21 at a volumetric rate of 50% to 5000% per minute of the total volume of the rearing water, thereby exposing the nitrification filter material 62 to air and promoting the nitrification reaction by the nitrifying bacteria under aerobic conditions.

[0058] According to the above configuration, air is supplied at a volumetric rate of 50% to 5000% per minute of the storage volume of the breeding water, and the nitrification filter medium 62 is exposed to air to continuously perform an oxygen intake operation, thereby promoting the nitrification reaction. This makes it possible to efficiently perform nitrification treatment of the breeding water for aquatic organisms under aerobic conditions, in addition to denitrification treatment.

[0059] (6) As shown in FIG. 4, the nitrification filter medium 62 is formed in a porous shape with a plurality of communication paths 621 and is fixed above the position where the bubbles 7 are generated. With the above configuration, the bubbles 7 are generated and pass through the communication paths 621 of the nitrification filter medium 62 as they rise in the breeding water. The bubbles 7 flow along the communication paths 621 and take on the average diameter of the communication paths 621. As a result, the nitrification reaction is carried out by the bubbles 7, whose average diameter in a floating state is the same as the average diameter of the communication paths 621, thereby promoting the nitrification reaction.

[0060] In the water purification apparatus 100 configured as described above, it is preferable that the denitrification filter medium 61 and / or the nitrification filter medium 62 are made to be less likely to move even when affected by the air bubbles 7. For example, when the denitrification filter medium 61 is made to be less likely to move and the air bubbles 7 are used to perform the denitrification reaction, the fixed denitrification filter medium 61 allows the attachment of microorganisms to be maintained continuously, enabling a stable denitrification reaction over a long period of time. Since microorganisms are more likely to settle on the surface of the denitrification filter medium 61, the formation of a biofilm is promoted, creating an environment that is favorable for the habitation of denitrifying bacteria. Furthermore, the immobility of the denitrification filter medium 61 reduces the risk of wear and tear, thereby extending the life of the denitrification filter medium 61. The same applies to the nitrification filter medium 62.

[0061] Specific methods for preventing flow include, for example, using a mesh or net-like container or fixing structure to house the denitrification filter material 61 (nitrification filter material 62) and ensuring appropriate openings or gaps to control the buoyancy caused by the bubbles 7. Alternatively, a method can be adopted in which the specific gravity of the denitrification filter material 61 (nitrification filter material 62) itself is adjusted to resist buoyancy. Furthermore, a structure can be adopted in which a partition or divider is installed to prevent the bubbles 7 from directly hitting the denitrification filter material 61 (nitrification filter material 62) and causing turbulence, while promoting the denitrification reaction (nitrification reaction) through a gentle water flow. By combining these methods, sufficient contact with the bubbles 7 can be achieved even when the denitrification filter material 61 (nitrification filter material 62) is difficult to flow, thereby enabling efficient and stable denitrification (nitrification) treatment.

[0062] Next, an embodiment of the water purification device 100 will be described. [Example]

[0063] (Test Method) A pipette washer (manufactured by Ikeda Rika Co., Ltd., volume 10 liters) was used as the denitrification tank 11. Furthermore, porous cellulose particles (manufactured by Rengo Co., Ltd., Viscopal A (registered trademark), diameter 3 mm) were used as the denitrification filter medium 61 and were packed into the denitrification tank 11.

[0064] The breeding tank 8 used had a volume of 15 liters. This breeding tank 8 was filled with 10 liters of artificial seawater (manufactured by Aquarium Systems). Furthermore, the breeding water was sufficiently aerated throughout the experiment. This allowed the breeding water in the breeding tank 8, nitrification tank 21, and denitrification tank 11 to be maintained at a water temperature of 25±1°C, a salinity of 3.0-3.2%, a pH of 8.0-8.4, and a DO (dissolved oxygen) of 6-8 ppm. Because carbon was supplied by the decomposition of the cellulose used in the denitrification filter medium 61, no carbon source such as methanol was added as needed for the denitrification reaction.

[0065] Nitrification and denitrification were carried out by blowing air from the bottom of the denitrification tank 11. The amount of air supplied was measured during the nitrification and denitrification processes. The amount of air supplied was measured by installing a flow meter in the air supply line and accurately measuring the air flow.

[0066] The rearing water was periodically sampled and the nitrate nitrogen concentration in the rearing water was measured. That is, the rearing water was subjected to denitrification treatment, and the change in nitrate nitrogen concentration was measured after a specified time had passed from the start of the test. Here, the concentration was measured using a portable water quality measurement spectrophotometer DR900 (manufactured by HACH).

[0067] Examples 1 to 8 Next, in the same test method as above, the filling rate of the denitrification filter medium 61 was set to 100%, and only the amount of air supplied was changed, and the nitrification treatment was performed on the rearing water. After a predetermined time (24 hours) had elapsed since the start of the test, the change in the nitrate nitrogen concentration was measured. The measurement results are shown in Table 1.

[0068] [Table 1]

[0069] From the above measurement results, it was found that the nitriding treatment is carried out well when the air supply rate per minute is 1 L / min to 9 L / min, is carried out even better when it is 2 L / min to 5 L / min, and is carried out even better when it is particularly 5 L / min to 9 L / min. As with the nitriding treatment, it is estimated that the nitriding treatment is also carried out well when the air supply rate per minute is 1 L / min to 9 L / min, is carried out even better when it is 2 L / min to 5 L / min, and is carried out even better when it is particularly 5 L / min to 9 L / min.

[0070] This revealed that denitrification treatment was performed well when air was supplied at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be denitrified, exposing the denitrification filter material 61 to air and performing the oxygen intake operation continuously.

[0071] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Furthermore, the effects described in the above-described embodiments are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the above-described embodiments. Furthermore, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. [Explanation of symbols]

[0072] 1 Denitrification equipment 2 Nitrification equipment 3. Breeding control device 4 Monitoring device 5 Administrator 6. Denitrification filter media 7. Bubbles 8. Breeding tank 11 Denitrification tank 12 1st rearing water supply route 13 Denitrification air supply mechanism 14 Water recovery channel 15 Level gauge 21 Nitrification tank 22 Second feeding water supply road 23 The 3rd feeding water supply road 24 Air supply mechanism for nitrification

Claims

1. a denitrification tank to which the water to be treated is supplied; A denitrification filter material accommodated in the denitrification tank and adapted to establish aerobic denitrification bacteria that reduce nitrate nitrogen in the water to be treated; a denitrification air supply mechanism that is disposed at the bottom of the denitrification tank and that continuously performs an oxygen intake operation by supplying air to the water to be treated stored in the denitrification tank at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be treated, thereby exposing the denitrification filter medium to the air, thereby promoting the denitrification reaction by the denitrification bacteria under aerobic conditions; Water purification equipment.

2. An air flow regulating member is provided above the air discharge portion of the denitrification air supply mechanism, and regulates the flow direction of the upward flow of air supplied from the air discharge portion to the water to be treated and concentrates it at one location, thereby circulating the water to be treated and the denitrification filter material throughout the denitrification tank. The water purification device according to claim 1.

3. The denitrification tank has a nitrification filter medium for establishing aerobic nitrifying bacteria that oxidize ammonium nitrogen in the water to be treated. The water purification device according to claim 1.

4. a nitrification tank to which the water to be treated is supplied; A nitrification filter material accommodated in the nitrification tank and adapted to establish aerobic nitrification bacteria that oxidize ammonium nitrogen in the water to be treated; and a nitrification air supply mechanism that is disposed at the bottom of the nitrification tank and that continuously performs an oxygen intake operation by supplying air to the water to be treated stored in the nitrification tank at a volumetric rate of 50% to 5000% per minute of the storage volume of the water to be treated, thereby exposing the nitrification filter material to the air, thereby promoting the nitrification reaction by the nitrifying bacteria under aerobic conditions. Water purification equipment.

5. An air flow regulating member is provided above the nitrification air supply mechanism, and regulates the flow direction of the upward flow of air supplied from the nitrification air supply mechanism to the water to be treated and concentrates it at one location, thereby circulating the water to be treated and the nitrification filter material throughout the nitrification tank. The water purification device according to claim 4.

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