Denitrification treatment apparatus and denitrification treatment method

Abstract

To provide a denitrification treatment apparatus and a denitrification treatment method to demonstrate excellent, long-term and stable denitrification efficiency.SOLUTION: A denitrification treatment apparatus 15 has a denitrification carrier 2 containing a biodegradable resin, a reaction vessel 1 for housing the denitrification carrier, water flow means 4 for passing water to be treated into the reaction vessel, and pressurizing means 3 for pressurizing the water to be treated, passed into the reaction vessel, and a water flow inlet 5 for allowing the water to be treated to flow into the reaction vessel and a water outlet 6 for discharging the water to be treated outside the reaction vessel. A mechanism is provided to control the water flow rate so that the linear velocity (LV) of the water to be treated as it passes through the reaction vessel 1 is maintained between 0.4 and 14.0 m / h.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a denitrification treatment apparatus and a denitrification treatment method. This application claims priority based on Japanese Patent Application No. 2023-082409, filed with the Japan Patent Office on May 18, 2023, the contents of which are incorporated herein by reference. [Background technology]

[0002] A method using a two-stage reaction using microorganisms is known as a method for treating water containing ammonia nitrogen. This method consists of a nitrification reaction in which ammonia is converted to nitrate using microorganisms capable of nitrification (hereinafter referred to as "nitrifying bacteria"), and a denitrification reaction in which nitrate is decomposed into nitrogen using microorganisms capable of denitrification (hereinafter referred to as "denitrifying bacteria"). Since nitrogen generated from the water to be treated is released into the air, this is an environmentally friendly nitrogen removal method.

[0003] Since most of the denitrifying bacteria used in the denitrification reaction are heterotrophic bacteria, a hydrogen donor is required for the denitrification reaction. Liquid carbon sources such as methanol are known as typical hydrogen donors, but the toxicity of methanol is undesirable. In addition, in order to obtain stable denitrification ability, it is necessary to supply an amount of methanol corresponding to the concentration of nitrate nitrogen to the water to be treated, but it is not easy to control the supply amount of liquid carbon sources such as methanol. In addition, for example, in the case of denitrification treatment of water for breeding aquatic organisms, there is a concern that the remaining methanol without being consumed may affect the aquatic organisms.

[0004] Therefore, as an alternative to liquid carbon sources, biological denitrification methods are being investigated in which a microbial implantation device (hereinafter referred to as a "carrier") for immobilizing microorganisms, including biodegradable resins, is added to the water to be treated. In this technology, the biodegradable resin has the ability to slowly release hydrogen donors, so denitrification can be sustained without precise control of the amount added (for example, Patent Document 1). Patent Document 1 describes a bacterial implantation device formed by placing a biodegradable polymer in a hollow body of any shape with one or more holes, and using a continuous porous material between the hollow body and the biodegradable polymer to cover the biodegradable polymer and further fill it without any gaps. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-85782 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the investigations of the present inventors, the biological denitrification method using the bacterial settlement device of Patent Document 1 has room for improvement in terms of the long-term denitrification efficiency and stability of the denitrification rate. An object of the present invention is to provide a denitrification treatment apparatus and a denitrification method in which the denitrification efficiency and denitrification rate are stabilized and improved over the long term. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A denitrification method in which denitrification is carried out by passing water to be treated that contains nitrate nitrogen and / or nitrite through a reaction vessel containing a denitrification carrier containing a biodegradable resin, The water to be treated flows into the reaction vessel from a water inlet of the reaction vessel, comes into contact with the denitrification carrier, and is then discharged out of the reaction vessel from a water outlet of the reaction vessel; A denitrification method, comprising controlling the amount of water passing through the reaction vessel so that the linear velocity (LV) of the water to be treated is maintained at 0.4 to 14.0 (m / h). [2] The denitrification treatment method according to [1], wherein the water to be treated contains phosphorus components, and the concentration of the phosphorus components in the water to be treated is 0.01 mg-P / L or more. [3] The denitrification treatment method according to [1] or [2], wherein the water to be treated contains Cu ions and the concentration of Cu ions in the water to be treated is 0.7 mg-Cu / L or less. [4] The denitrification method according to any one of [1] to [3], wherein the reaction vessel has a columnar shape. [5] The denitrification method according to any one of [1] to [4], wherein the biodegradable resin is a biodegradable polyester. [6] The denitrification method according to [5], wherein the biodegradable polyester contains two or more types of constitutional units derived from dicarboxylic acid.

[0008] [7] A denitrification treatment device for denitrifying water containing nitrate nitrogen and / or nitrite nitrogen, A denitrification carrier containing a biodegradable resin; A reaction vessel in which the denitrification carrier is accommodated; A water passing means for passing the water to be treated through the reaction vessel; A pressurizing means for pressurizing the water to be treated passing through the reaction vessel; Equipped with The reaction vessel is formed with a water inlet for flowing the water to be treated into the reaction vessel and a water outlet for discharging the water to be treated out of the reaction vessel, The denitrification treatment device further comprises a mechanism for controlling the amount of water passing through so that the linear velocity (LV) of the water to be treated passing through the reaction vessel is maintained at 0.4 to 14.0 (m / h). [8] The denitrification treatment device according to [7], wherein the reaction vessel has a columnar shape. [9] The denitrification treatment device according to [7] or [8], wherein the biodegradable resin is a biodegradable polyester.

[10] The denitrification treatment device according to [9], wherein the biodegradable polyester contains two or more types of constitutional units derived from dicarboxylic acid. Effect of the Invention

[0009] According to the present invention, there are provided a denitrification treatment apparatus and a denitrification method in which the denitrification efficiency and denitrification rate are stabilized and improved over the long term. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 shows an example of a denitrification treatment device. [Diagram 2] FIG. 2 shows an example of a reaction vessel. [Diagram 3] FIG. 3 shows an example of a reaction vessel. [Figure 4] FIG. 4 shows an example of a reaction vessel. [Diagram 5] FIG. 5 shows an example of a reaction vessel. [Figure 6] FIG. 6 shows an example of a reaction vessel. [Figure 7] FIG. 7 shows an example of a circulating denitrification system equipped with a denitrification treatment device. [Figure 8] FIG. 8 shows an example of a single-pass denitrification system equipped with a denitrification treatment device. [Figure 9] FIG. 9 shows an example of an aquatic organism rearing system equipped with a denitrification treatment device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The meaning of the terms is as follows: The denitrifying bacteria refer to microorganisms having the ability to denitrify. The decomposing bacteria refers to microorganisms capable of decomposing biodegradable resins.

[0012] The carrier means a microbial implantation device which is a solid and / or gel-like substance on the surface of which the microorganisms are immobilized. The bulk volume of the carrier is the volume occupied by the assembly of carriers in the reaction vessel, and means the volume from the lower surface to the upper surface of the assembly of carriers when the carriers are placed in the reaction vessel. The denitrification carrier means a carrier in which the microorganisms to be immobilized are at least denitrifying bacteria. The biofilm means a biological film formed by immobilizing microorganisms on the surface of a carrier. A biofilm containing denitrifying bacteria and / or decomposing bacteria is formed on the surface of the carrier. The inter-carrier flow path means a flow path formed in the gap between the carriers.

[0013] The low molecular weight organic matter refers to organic matter that has been decomposed by microorganisms from a biodegradable resin and has a low molecular weight. Phosphorus refers to the soluble phosphorus contained in the water to be treated. The concentration of phosphorus in the water to be treated is measured using HACH DR2700 or HACHDR / 2010 and the corresponding reagent (Phos Ver3 Phosphate Reagent Powder Pillow Cat. No. 21060-69). The Cu ion means the Cu ion contained in the water to be treated, and the concentration of the Cu ion means the total concentration of monovalent and divalent copper ions. The concentration of the Cu ion in the water to be treated can be measured by ICP mass spectrometry as described in JIS K 0102 52.5.

[0014] Seawater is water that contains a salt concentration of 3.2% by mass or more. Brackish water is water that contains a salt concentration of 0.05% by mass or more and less than 3.2% by mass. On the other hand, fresh water is water that contains a salt concentration less than that of brackish water, and may be water that does not contain any salt at all.

[0015] Several embodiments of the present invention will be described in detail below. However, the description of the components described below is a representative example of an embodiment, and the present invention is not limited to the following content, and can be implemented in various modifications within the scope of the gist.

[0016] <Denitrification treatment device, denitrification treatment method> The denitrification treatment device of the present invention performs denitrification treatment on water to be treated that contains nitrate nitrogen and / or nitrite nitrogen. The denitrification treatment device includes a denitrification carrier containing a biodegradable resin, a reaction vessel in which the denitrification carrier is housed, a water passing means for passing the water to be treated through the reaction vessel, and a pressurizing means for pressurizing the water to be treated passing through the reaction vessel. The reaction vessel is provided with a water inlet for flowing the water to be treated into the reaction vessel and a water outlet for discharging the water to be treated out of the reaction vessel. The denitrification treatment device of the present invention further includes a mechanism for controlling the amount of water passing through the reaction vessel so that the linear velocity (LV) of the water to be treated passing through the reaction vessel is maintained at 0.4 to 14.0 (m / h).

[0017] In the denitrification method of the present invention, denitrification is performed by passing water to be treated that contains nitrate nitrogen and / or nitrite nitrogen through a reaction vessel containing a denitrification carrier that contains a biodegradable resin. In the denitrification method, the water to be treated flows into the reaction vessel from a water inlet of the reaction vessel, comes into contact with the denitrification carrier, and is then discharged from the reaction vessel through a water outlet of the reaction vessel. The method is characterized in that the amount of water passing through the reaction vessel is controlled so that the linear velocity (LV) of the water to be treated passing through the reaction vessel is maintained at 0.4 to 14.0 (m / h).

[0018] When denitrification treatment is performed for a long period of time, the thickness of the biofilm on the surface of the denitrification carrier gradually increases, and the flow paths formed by the gaps between the denitrification carriers (hereinafter referred to as "inter-carrier flow paths") decrease. This can result in a decrease in the penetration efficiency and diffusion efficiency of the water to be treated into and / or near the biofilm. In the denitrification treatment device and the denitrification treatment method of the present invention, the linear velocity (LV) of the water to be treated passing through the reaction vessel is within the range of 0.4 to 14.0 (m / h). Therefore, as the denitrification reaction progresses, the amount and thickness of the biofilm formed on the surface of the denitrification carrier increases, so that even after the inter-carrier flow path formed by the gaps between the denitrification carriers is narrowed, the water to be treated containing nitrate nitrogen and / or nitrite nitrogen efficiently passes through the flow path. The water to be treated efficiently permeates and diffuses into and / or near the biofilm on the surface of the denitrification carrier. Therefore, the denitrification performance is stably and satisfactorily exhibited for a long period of time.

[0019] <Denitrification treatment device, denitrification treatment method> Hereinafter, an embodiment of a denitrification treatment apparatus and a denitrification treatment method will be described with reference to the drawings. The denitrification treatment device 15 shown in FIG. 1 includes a reaction vessel 1, a denitrification carrier 2, a pressurizing means 3, a water passing means 4, a post-water passing transport means 7, a water passing opening and closing means 8, a post-water passing transport opening and closing means 9, and a flow meter 11.

[0020] The shape of the reaction vessel 1 is not particularly limited, but is preferably a shape that allows the water to be treated to pass uniformly through the denitrification carriers 2 housed therein. For example, a column-shaped reaction vessel is preferable. The column-shaped reaction vessel may be a cylinder as shown in Fig. 2, Fig. 4, Fig. 5, and Fig. 6, or a square tube having a rectangular cross section as shown in Fig. 3, or a square tube having a triangular or polygonal cross section.

[0021] The reaction vessel 1 may be a vessel through which the water to be treated can be passed in a vertical direction as shown in Figures 2, 3 and 5, respectively, or may be a vessel through which the water to be treated can be passed in a horizontal direction as shown in Figures 4 and 6, respectively. The capacity of the reaction vessel 1 is not particularly limited, and may be determined depending on the amount of water to be treated and the nitrogen load to be generated.

[0022] The reaction vessel 1 is provided with a water inlet 5 for allowing the water to be treated to flow into the reaction vessel, and a water outlet 6 for allowing the water to be treated to be discharged to the outside of the reaction vessel. The positions of the water inlet 5 and the water outlet 6 are not particularly limited. It is important that the water outlet 6 is installed so that the water to be treated that has flowed into the reaction vessel 1 is passed through the entire denitrification carrier 2 while being in uniform contact with the entire carrier, and is then discharged from the water outlet 6. For this reason, it is preferable that the water inlet 5 and the water outlet 6 are installed at positions separated from each other. For example, as shown in FIG. 1 and FIG. 6, it is preferable that the water inlet 5 is installed on the bottom surface or the lower side of the reaction vessel 1, and the water outlet 6 is installed on the upper surface or the upper side of the reaction vessel 1.

[0023] The denitrification treatment device 15 includes a water passage means 4 for passing the water to be treated through the reaction vessel 1. The water passage means 4 and the water inlet 5 are connected. Thus, the water to be treated is passed through the water passage means 4 and the water inlet 5 into the reaction vessel 1. The water passage means 4 includes a water passage opening / closing means 8 for opening and closing the water passage means 4 as necessary. The structure of the water passage opening / closing means 8 is not particularly limited, and may be a valve that is opened and closed manually, or may have a structure that opens and closes automatically. The denitrification treatment device 15 further includes a pressurizing means 3 for pressurizing the water to be treated passed through the reaction vessel 1. The structure of the pressurizing means 3 is not particularly limited, and for example, a pump may be used as shown in FIG. 1. In addition, a treatment water tank or other equipment in the front stage of the denitrification treatment device 15 may be installed at a higher position than the denitrification treatment device 15. The potential energy of the water to be treated may be utilized by ensuring a height difference between the denitrification treatment device 15 and the treatment water tank or the like.

[0024] The water to be treated after passing through the reaction vessel 1 is discharged outside the reaction vessel through a water outlet 6 provided in the reaction vessel 1. Thereafter, the water to be treated after passing through the denitrification carrier 2 in the reaction vessel 1 may be sent to a post-water-passing storage tank for storing the water to be treated through a post-water-passing transport means 7 connected to the water outlet 6. The post-water-passing transport means 7 is provided with a post-water-passing transport opening / closing means 9 for opening and closing the post-water-passing transport means 7 as necessary. The structure of the post-water-passing transport opening / closing means 9 is not particularly limited, and may be one that is opened and closed manually using a valve, or may have a structure that opens and closes automatically. When the denitrification treatment device 15 is used as a denitrification treatment device in an aquatic organism breeding system, the breeding aquarium may also be used as a post-water-passing storage tank.

[0025] The linear velocity (LV) of the water to be treated as it passes through the reactor is calculated using the following formula 1. Linear velocity (LV) [m / h] = Water flow rate V [L / h] ÷ Cross-sectional area of ​​reaction vessel A [m 2 ]÷1000[L / m 3 ] ...expression 1

[0026] The water flow rate V means the amount of water to be treated that passes through the reaction vessel per unit time. There is no particular limitation on the method for measuring the water flow rate, but it can be measured by installing a flow meter on the water flow means 4 or the post-water flow transport means 7.

[0027] The cross-sectional area A of the reaction vessel is the largest cross-sectional area of ​​the inside of the reaction vessel perpendicular to the flow direction of the water to be treated. For example, in the reaction vessel 1 shown in each of Figures 2, 3, and 4, the cross-sectional area A is the area of ​​the cross section S perpendicular to the water flow direction indicated by the arrow.

[0028] The water flow direction is determined after decomposing the distance L from the center of the water inlet 5 to the center of the water outlet 6 into a horizontal water flow distance X (m) and a vertical water flow distance Y (m) as shown in Figures 5 and 6. If X ≥ Y, the water flow direction is the horizontal direction, and if Y > X, the water flow direction is the vertical direction.

[0029] The denitrification treatment device 15 has a mechanism for controlling the amount of water passing through the reaction vessel 1 so that the linear velocity (LV) of the water passing through the reaction vessel 1 is maintained at 0.4 to 14.0 (m / h). As denitrification progresses, the thickness of the biofilm formed on the surface of the denitrification carrier increases, which may reduce the flow path of the water to be treated in the flow path between the carriers. If the linear velocity (LV) of the water to be treated passing through the reaction vessel is 0.4 to 14.0 (m / h), the water to be treated is efficiently passed through the flow path between the carriers even after the thickness of the biofilm increases. The water to be treated efficiently penetrates and diffuses into and / or near the biofilm on the surface of the denitrification carrier, thereby providing stable and excellent denitrification performance for a long period of time.

[0030] The linear velocity (LV) when the water to be treated passes through the reaction vessel is 0.4 m / h or more, preferably 0.8 m / h or more, more preferably 1.5 m / h or more, even more preferably 2.5 m / h or more, particularly preferably 3.4 m / h or more, and most preferably 3.7 m / h or more. The linear velocity (LV) when the water to be treated passes through the reaction vessel is 14.0 m / h or less, preferably 13.0 m / h or less, more preferably 12.0 m / h or less, and even more preferably 11.0 m / h or less. If the linear velocity (LV) when the water to be treated passes through the reaction vessel is within the above range, the water to be treated is efficiently passed through the flow path, and the water to be treated efficiently penetrates and diffuses into and / or near the biofilm on the surface of the denitrification carrier. As a result, the denitrification performance is stably and well exhibited for a long period of time.

[0031] The mechanism for controlling the amount of water passing so that the linear velocity (LV) is maintained within a predetermined range is not particularly limited, but the linear velocity (LV) can be maintained within a predetermined range by controlling the amount of water passing by a pressurizing means or by controlling the amount of water passing by changing the opening degree of the water passing opening / closing means and / or the post-water passing transport opening / closing means. The amount of water passing may be controlled automatically or manually.

[0032] In the reaction vessel 1, the space velocity (SV) ( / h) when the water to be treated passes through the denitrification carriers 2 is calculated by the following formula 2. Space velocity (SV) [ / h] = water flow rate (V) [L / h] ÷ bulk volume of denitrification carrier [L] Equation 2

[0033] The spatial velocity (SV) is preferably 0.4 / h or more, more preferably 1.0 / h or more, even more preferably 2.0 / h or more, and particularly preferably 3.0 / h or more. Also, it is preferably 14.0 / h or less, more preferably 12.5 / h or less, and even more preferably 11.5 / h or less. If the spatial velocity (SV) when the water to be treated passes between the denitrification carriers in the reaction vessel is within the above range, the water to be treated is efficiently passed through the flow path. The water to be treated efficiently penetrates and diffuses into and / or near the biofilm on the surface of the denitrification carrier. This allows the denitrification performance to be stably and satisfactorily exhibited for a long period of time.

[0034] The mechanism for controlling the water flow rate so that the space velocity (SV) is maintained within a predetermined range is not particularly limited, but the space velocity (SV) can be maintained within a predetermined range by controlling the discharge rate using a pressurizing means, or by controlling the water flow rate by changing the opening of the water flow opening / closing means and / or the post-water-flow transport opening / closing means. The water flow rate may be controlled automatically or manually.

[0035] The materials of the reaction vessel 1, the pressurizing means 3, the water passing means 4, the water inlet 5, the water outlet 6, the post-water passing transport means 7, the water passing opening and closing means 8, and the post-water passing transport opening and closing means 9 are not particularly limited, since they are determined according to the type of water to be treated. If the water to be treated is seawater or brackish water, SUS is preferable if it is made of metal, in order to prevent corrosion by salt. If there is no problem in terms of load resistance and strength, rigid polyvinyl chloride piping or the like can also be used.

[0036] In the denitrification carrier containing a biodegradable resin, the low molecular weight organic matter produced by hydrolysis of the biodegradable resin is used as a hydrogen donor required for the denitrification reaction. As the decomposition bacteria that decompose the biodegradable resin, known bacteria having the ability to decompose the biodegradable resin can be appropriately used.

[0037] The biodegradable resin is preferably a biodegradable polyester. Examples of the biodegradable polyester include PLA (polylactic acid), PBS (polybutylene succinate), PCL (poly caprolactone), PHB (poly hydroxybutyrate), PHA (polyhydroxy alkanoate), P3HA (poly-3-hydroxyrate), PBAT (polybutylene adipate / terephthalate), poly(terephthalate / succinate), PHBH (poly-3-hydroxybutyrate-co-3-hydroxyhexanoate), and PHBV (poly-3-hydroxybutyrate-co-3-hydroxyvalerate). Among the biodegradable polyesters, biodegradable polyesters having a dicarboxylic acid-derived structural unit are preferred, and biodegradable polyesters having a dicarboxylic acid-derived structural unit and a diol-derived structural unit are more preferred.

[0038] Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, adipic acid, glutaric acid, suberic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid, and phthalic acid. The biodegradable resin preferably has two or more types of dicarboxylic acid-derived structural units. This is because when a biodegradable resin having two or more types of dicarboxylic acid-derived structural units is used, the denitrification rate tends to be faster and the denitrification performance tends to be higher than when a biodegradable resin having one type of dicarboxylic acid-derived structural unit is used.

[0039] Of the above dicarboxylic acids, the biodegradable resin preferably has a constitutional unit derived from succinic acid. That is, a PBS-based biodegradable resin having a butylene succinate unit as the main repeating unit is preferred. Examples of PBS-based biodegradable resins include polybutylene succinate, poly(butylene succinate-co-adipate) (PBSA), poly(butylene succinate-co-carbonate), poly(butylene adipate-co-terephthalate) (PBAT), and poly(ethylene terephthalate-co-succinate). In particular, PBSA is preferred because of its high biodegradability and because it can supply a carbon source required for the denitrification reaction in a sustained release manner. Furthermore, PBSA is more easily decomposed than other biodegradable resins such as PHB, and therefore produces low molecular weight organic matter well.

[0040] The biodegradable resin may be PLA, PHA, PHBH (poly-3-hydroxybutyrate-co-3-hydroxyhexanoate), PHBV (poly-3-hydroxybutyrate-co-3-hydroxyvalerate), polyvinyl alcohol, cellulose, or other resins. These biodegradable resins may also be mixed with biodegradable resins having structural units derived from dicarboxylic acids. By mixing a biodegradable resin having structural units derived from dicarboxylic acids with these resins having different biodegradability, the biodegradable resin can be used as a carbon source for a long period of time.

[0041] The denitrification carrier may further contain a resin other than the biodegradable resin, for example, polyvinyl alcohol, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetic acid, polyvinyl chloride, and polystyrene.

[0042] The shape of the denitrification carrier is not particularly limited, and may be any shape such as a columnar shape, a spherical shape, a cylindrical shape, a chip shape, etc. As long as the denitrification performance is not impaired, inorganic components such as minerals and calcium, other low molecular weight organic substances, etc. can be used in combination as additives. The method of use is not particularly limited, but for example, a denitrification carrier in which an additive is previously mixed and dispersed in a biodegradable resin can be used.

[0043] In the denitrification carrier, denitrifying bacteria are immobilized on the surface of the denitrification carrier. The denitrifying bacteria are not particularly limited. They can be appropriately selected from known bacteria having denitrification ability, but heterotrophic denitrifying bacteria are preferred.

[0044] As denitrification progresses, a biofilm is formed on the surface of the denitrification carrier, and the biofilm is formed by decomposition bacteria and / or denitrifying bacteria. The decomposition bacteria adhere to the denitrification carrier and decompose the biodegradable resin contained in the denitrification carrier into low molecular weight organic matter. The water to be treated is efficiently passed through the inter-carrier flow path, and the water to be treated efficiently penetrates and diffuses into and / or near the biofilm on the surface of the denitrification carrier, thereby supplying oxygen and nutrient sources necessary for decomposing the biodegradable resin into low molecular weight organic matter to the vicinity of the decomposition bacteria. This activates the activity of the decomposition bacteria to decompose the biodegradable resin, producing low molecular weight organic matter, and the oxygen inside and / or near the biofilm is consumed by the activity of the decomposition bacteria. As a result, an oxygen-poor environment is formed inside and / or near the biofilm.

[0045] The denitrifying bacteria use the low molecular weight organic matter produced by the decomposition bacteria as a hydrogen donor to carry out the denitrification reaction. The water to be treated is efficiently passed through the flow path, and the water to be treated efficiently penetrates and diffuses into and / or near the biofilm on the surface of the denitrification carrier, thereby supplying nitrate nitrogen and / or nitrite nitrogen and a nutrient source required for the denitrification reaction to the vicinity of the denitrifying bacteria. In an oxygen-poor environment, the denitrifying bacteria can more efficiently reduce nitrate nitrogen and / or nitrite nitrogen to nitrogen gas by using low molecular weight organic matter. Low molecular weight organic matter derived from dicarboxylic acids is preferable as a hydrogen donor for the growth and proliferation of denitrifying bacteria. By immobilizing the decomposition bacteria on the denitrification carrier, more hydrogen donors can be supplied to the denitrifying bacteria than if the decomposition bacteria were not immobilized, and the growth or activity of the denitrifying bacteria is promoted, resulting in an improvement in the denitrification rate and amount of denitrification.

[0046] The water to be treated that is the subject of the purification treatment is not particularly limited as long as it contains nitrite nitrogen and / or nitrate nitrogen. The water to be treated may be water for raising aquatic organisms, or may be wastewater such as livestock wastewater, food wastewater, sewage, or septic tank wastewater. The water to be treated may be freshwater, brackish water, or seawater.

[0047] The nitrate nitrogen concentration of the water to be treated is not particularly limited, but is preferably 5 mg-N / L or more, more preferably 10 mg-N / L or more, even more preferably 20 mg-N / L or more, and particularly preferably 100 mg-N / L or more. Also, it is preferably 5000 mg-N / L or less, more preferably 2000 mg-N / L or less. If the nitrate nitrogen concentration is within the above range, denitrification is likely to proceed efficiently.

[0048] The water to be treated preferably contains phosphorus components. In one example, the phosphorus components in the water to be treated are important for maintaining good activity of decomposition bacteria and / or denitrification bacteria. When a certain amount of phosphorus components is contained in the water to be treated, the activity of decomposition bacteria to generate low molecular weight organic matter inside and / or in the vicinity of the biofilm is activated. At the same time, the activity of denitrification bacteria to carry out a denitrification reaction using low molecular weight organic matter is also activated.

[0049] In order to keep the activity of decomposition bacteria and / or denitrification bacteria good, the concentration of phosphorus components contained in the water to be treated is preferably 0.01 mg-P / L or more, more preferably 0.05 mg-P / L or more, even more preferably 0.5 mg-P / L or more, particularly preferably 1.0 mg-P / L or more, and most preferably 3.0 mg / L or more. The upper limit of the phosphorus compounds contained in the water to be treated is preferably 20 mg / L or less, more preferably 15 mg / L or less, and even more preferably 12 mg / L or less. If the concentration of phosphorus components is within the above range, the activity of decomposition bacteria and / or denitrification bacteria is easily kept good. Therefore, it is easy to maintain the denitrification performance stably and well.

[0050] The water to be treated preferably contains Cu ions in a predetermined concentration range. In one example, Cu ions in the water to be treated are important for maintaining good activity of decomposition bacteria and / or denitrification bacteria. When a certain amount of Cu ions is contained in the water to be treated, the activity of low molecular weight organic matter production by decomposition bacteria inside and / or near the biofilm is activated. The activity of denitrification bacteria to perform a denitrification reaction using low molecular weight organic matter is also activated. Furthermore, since the growth of various bacteria other than decomposition bacteria and / or denitrification bacteria is suppressed, excessive increase in biofilm is suppressed, and the state in which the water to be treated efficiently passes through the flow path is maintained in a good state. As a result, the state in which the activity of decomposition bacteria and / or denitrification bacteria is activated is maintained in a good state.

[0051] In order to keep the activity of decomposition bacteria and / or denitrification bacteria good, the concentration of Cu ions contained in the water to be treated is preferably 0.001 mg-Cu / L or more, more preferably 0.005 mg-Cu / L or more, even more preferably 0.01 mg-Cu / L or more, particularly preferably 0.1 mg-Cu / L or more, and most preferably 0.15 mg-Cu / L or more. The upper limit of the concentration of Cu ions contained in the water to be treated is preferably 0.70 mg-Cu / L or less, more preferably 0.60 mg-Cu / L or less, and even more preferably 0.50 mg-Cu / L or less. If the concentration of Cu ions is within the above range, the activity of decomposition bacteria and / or denitrification bacteria is easily kept good. Therefore, it is easy to maintain the denitrification performance stably and well.

[0052] The temperature of the water to be treated may be within the range of temperatures that the environment can take in nature, and is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher. Also, 40°C or lower is preferable, 35°C or lower is more preferable, and 30°C or lower is even more preferable. The water to be treated contains nitrate nitrogen, and may contain ammonia nitrogen and nitrite nitrogen. It may also contain organic matter derived from other than biodegradable resins. A suitable example of the water to be treated is breeding water used for culturing aquatic organisms. For example, it is suitable for purifying breeding water for aquatic organisms such as salmon, trout, sweetfish, char, eel, crab, and shrimp. According to the present invention, denitrification performance can be exhibited stably for a long period of time. Therefore, denitrification treatment of breeding water containing nitrate nitrogen after nitrification treatment is one of the suitable applications. When used for culturing aquatic organisms, it can be used as a denitrification treatment device for an aquatic organism breeding system described later.

[0053] The denitrification treatment device 15 may be provided with a plurality of each of the reaction vessel 1, denitrification carrier 2, pressurizing means 3, water passing means 4, water inlet 5, water outlet 6, post-water passing transport means 7, water passing opening / closing means 8, post-water passing transport opening / closing means 9, and flowmeter 11. For example, two or more reaction vessels 1 may be provided and connected for use.

[0054] <Application example> The denitrification treatment device and the denitrification method of the present invention can be suitably applied to a denitrification system. The denitrification system may be, for example, a circulating denitrification system 16 as shown in Fig. 7, or a one-pass denitrification system 17 as shown in Fig. 8.

[0055] 7 includes a water tank 10 for storing water to be treated, and the above-mentioned denitrification treatment device 15. In the circulating denitrification system 16, the water to be treated after passing through the denitrification carrier 2 in the reaction vessel 1 is resupplied to the water tank 10 for treatment, so that the denitrification treatment of the water to be treated can be carried out continuously.

[0056] The one-pass denitrification system 17 shown in Fig. 8 includes a water tank 10 to be treated, a denitrification treatment device 15, and a post-water-passage storage tank 12 for storing the water to be treated after it has been passed through the denitrification carrier 2 in the reaction vessel 1. In the one-pass denitrification system 17, the water to be treated after it has been passed through the denitrification carrier 2 in the reaction vessel 1 is stored in the post-water-passage storage tank 12 and then used for a desired purpose.

[0057] The aquatic organism breeding system 18 shown in Figure 9 comprises an aquarium 10 to be treated, a denitrification treatment device 15, a post-water flow storage tank 12, a breeding aquarium 13, and a nitrification treatment device 14 for performing a nitrification reaction on the water to be treated discharged from the breeding aquarium 13.

[0058] In the aquatic organism breeding system 18, aquatic organisms are breed in a breeding tank 13. Ammonia contained in the water to be treated discharged from the breeding tank 13 is converted to nitric acid in a nitrification treatment device 14. The nitric acid contained in the water to be treated is then converted to nitrogen in a denitrification treatment device. The water to be treated after passing through the denitrification carrier 2 in the reaction vessel 1 is stored in a storage tank 12 after passing the water, and is then supplied to the breeding tank 13.

[0059] Although several specific embodiments have been described above, each embodiment is presented as an example and does not limit the scope of the present invention. Each embodiment described in this specification can be modified in various ways within the scope of the effects of the invention, and can be combined with features described in other embodiments within the scope of feasibility. Furthermore, the objects and effects of the present invention are not limited to those specifically described above, but include those that will become apparent to a person skilled in the art from the entire specification. EXAMPLES

[0060] The present invention will be described in more detail below with reference to examples. However, it goes without saying that the scope of the present invention is not limited to the embodiments shown in the following examples.

[0061] <Example 1> (Simulated drainage) Sodium nitrate (NaNO) was added so that the concentrations of nitrate nitrogen, P, Mg ion, Na ion, Ca ion, and Cu ion were 105.0 mg-N / L, 5.5 mg-P / L, 8.8 mg-Mg / L, 1.03 mg-Na / L, 0.57 mg-Ca / L, and 0.15 mg-Cu / L, respectively. 3 ), dipotassium hydrogen phosphate (K 2 HPO 4 ), magnesium sulfate heptahydrate (MgSO 4 7H 2 O), disodium ethylenediaminetetraacetate (EDTA), calcium chloride dihydrate (CaCl 2 H 2 O), copper sulfate pentahydrate (CuSO 4 5H 2 A simulated wastewater was prepared by dissolving 1,2-dichlorophenyl ether (CO) in pure water.

[0062] (Test conditions) The conditions for the acclimation of the denitrification carrier and the denitrification test are as follows. Poly(butylene succinate / adipate) (manufactured by PTT MCC Biochem) (hereinafter referred to as "PBSA") molded into a cylindrical shape with a cross-sectional diameter of 6 mm and a length of 30 mm was placed in the reaction vessel 1 (inner diameter 2.5 cm, capacity 500 ml) of the denitrification treatment device 15 so that the bulk volume was 490 ml. The water to be treated in the treatment target water tank 10 was passed through the water inlet 5 to the reaction vessel 1 using the pressurizing means 3 and the water passing means 4, and after the denitrification carrier in the reaction vessel was brought into contact with the water to be treated, the water to be treated was discharged using the water outlet 6 and the post-water passing transport means 7. The water passing direction in this experiment was vertical, and the cross-sectional area A of the cross section perpendicular to the water passing direction was 4.9×10 -4 m 2 The water passage opening / closing means 8 and the post-water passage transport opening / closing means 9 were fully open, and the water passage speed (V) was adjusted by adjusting the discharge amount of the pressurizing means 3. The water passage speed was measured by a flow meter 11.

[0063] (Measurement of the concentrations of nitrate nitrogen, phosphorus components, and Cu ions) The nitrate nitrogen concentration was measured using a compact nitrate ion meter (HORIBA, Ltd.: "LAQUAtwin NO3-11"). The concentration of phosphorus was measured using HACH DR2700 or HACHDR / 2010 and the corresponding reagent (Phos Ver3 Phosphate Reagent Powder Pillow Cat. No. 21060-69). The concentration of Cu ions was measured by ICP mass spectrometry as described in JIS K 0102 52.5.

[0064] (Preparation of acclimated sludge and acclimation of denitrification carriers) The denitrification carrier was acclimated in the circulating denitrification system 16 shown in FIG. 7. Suspended water was collected from the purification equipment of the freshwater aquaculture tank of the A aquaculture farm, and concentrated by centrifuging at 3000 rpm for 5 minutes to prepare acclimated sludge with activated sludge suspended solids (MLSS) of 3600 mg / L. Then, 0.05 L of acclimated sludge was added to 5.0 L of the above-mentioned simulated wastewater to prepare 5.05 L of water to be treated (S) for acclimation. 5.05 L of water to be treated (S) was put into the water tank 10 (volume 5.2 L), and the water was passed through the reaction vessel 1 at a water passing speed (V) of 0.8 L / h using the pressurizing means 3 and the water passing means 4. The water to be treated (S) discharged from the water outlet 6 was returned to the water tank 10 by the transport means 7 after passing the water. Every 24 hours, the water to be treated (S) was sampled from the water outlet 6, and the nitrate nitrogen concentration was measured. When the measured value of the nitrate nitrogen concentration became less than 5.0 mg / L, the entire amount of the water to be treated (S) in the water tank 10 to be treated was replaced with new water to be treated S. These operations were repeated eight times to acclimate the denitrification carrier. The acclimatization period for the denitrification carrier was 60 days.

[0065] (Denitrification test) After the denitrification carrier was acclimated, a denitrification experiment was carried out in a one-pass denitrification system 17 shown in FIG. 8. The above-mentioned simulated wastewater was used as the water to be treated (A), and the water to be treated was appropriately supplied to the water tank 10 (capacity 20 L) so that the amount of water to be treated in the water tank 10 was always 10 L to 20 L. The water to be treated S discharged from the water outlet 6 was transported to the post-water-passing storage tank 12 by the post-water-passing transport means 7. The water passing velocity (V) was adjusted to 2.6 (L / h), the linear velocity (LV) was 5.25 (m / h), the spatial velocity (SV) was 5.25 ( / h), and the residence time (HRT) was 0.19 h. The residence time was calculated by the following formula 3. Residence time (HRT) [h] = bulk volume of denitrification carrier [L] ÷ water flow rate (L / h) Equation 3

[0066] The water to be treated (A) before denitrification treatment was collected from the water tank 10, and the concentrations of nitrate nitrogen (A), phosphorus compounds (A) and Cu ions (A) in the water to be treated (A) were measured. In addition, the water to be treated (B) after denitrification treatment by the denitrification treatment device 15 was collected from the post-water-passing storage tank 13, and the concentration of nitrate nitrogen (B) in the water to be treated (B) was measured. The measurement results of the concentrations of the phosphorus components (A) and Cu ions (A) are shown in Table 1.

[0067] The denitrification rate (Z) was used as an index of denitrification performance. The denitrification rate (Z) was calculated using the following formula 4 and is shown in Table 1. Denitrification rate (Z) [g-N / L-carrier / d] = (Nitrate nitrogen (A) [mg / L] - Nitrate nitrogen (B) [mg / L]) × Water flow rate (V) [L / h] × 24 [h / d] ÷ Bulk volume of denitrification carrier [L] ÷ 1000 [mg / g] ··· Equation 4

[0068] <Examples 2 to 9, Example 19, Comparative Examples 1 and 2> An experiment was carried out in the same manner as in Example 1, except that the water flow rate (V) was changed to each rate shown in Table 1. The results are shown in Table 1.

[0069] <Example 10, Example 12 to Example 14> An experiment was carried out in the same manner as in Example 1, except that the concentration of the phosphorus component (A) in the simulated wastewater, which was the water to be treated (A), was changed to each concentration shown in Table 1. The results are shown in Table 1.

[0070] <Example 11> An experiment was carried out in the same manner as in Example 1, except that the water flow rate (V) and the concentration of the phosphorus component (A) in the water to be treated (A) were changed to the rates and concentrations shown in Table 1. The results are shown in Table 1.

[0071] <Examples 15 to 18> An experiment was carried out in the same manner as in Example 1, except that the Cu ion (A) concentration in the treatment water (A) was changed to each concentration shown in Table 1. The results are shown in Table 1.

[0072] <Reference example 1> In the acclimation of the denitrification carrier, when the measured value of the nitrate nitrogen concentration of the water to be treated (S) became less than 5.0 mg / L, the water to be treated (S) was not replaced. Except for this, the experiment was carried out in the same manner as in Example 1. The results are shown in Table 1. The acclimation period of the denitrification carrier was 10 days.

[0073] [Table 1]

[0074] From Table 1, it was confirmed that in Examples 1 to 19, in which the linear velocity (LV) is within the specified range of the present invention, the denitrification rate (Z) is higher and shows excellent denitrification performance, compared to Comparative Examples 1 and 2, in which the linear velocity (LV) is outside the specified range of the present invention. Even when the Reference Example, in which the acclimatization period is 10 days, is compared with Example 1, in which the acclimatization period is 60 days, it was confirmed that the denitrification rate (Z) is stable and good over the long term. Even in a state in which the inter-carrier flow path is narrowed by the biofilm formed on the surface of the denitrification carrier due to long-term acclimatization of the denitrification carrier, that is, due to long-term denitrification treatment, the water to be treated is efficiently passed through the inter-carrier flow path, and the water to be treated penetrates and diffuses well into and / or near the biofilm, which is considered to have stabilized the denitrification treatment well.

[0075] In Comparative Examples 1 and 2, the linear velocity (LV) was outside the range of the present invention, the denitrification rate was low, and the denitrification performance was insufficient. It is considered that the denitrification carrier was acclimatized, that is, the biofilm formed on the surface of the denitrification carrier during long-term denitrification treatment narrowed the inter-carrier flow path, and the target water did not efficiently pass through the inter-carrier flow path, resulting in a decrease in denitrification efficiency and a decrease in denitrification rate.

[0076] From the results of the above examples, it was confirmed that by passing the water to be treated between the denitrification carriers at a linear velocity (m / h) within a specified range, the denitrification efficiency is stable and good over the long term, even after the flow path between the carriers is narrowed due to an increase in biofilm. It is believed that the water to be treated passes efficiently through the flow path between the carriers, and sufficiently penetrates and diffuses into and / or near the biofilm on the surface of the denitrification carriers. [Industrial Applicability]

[0077] According to the present invention, there are provided a denitrification treatment apparatus and a denitrification method in which the denitrification efficiency and denitrification rate are stabilized and improved over the long term. [Explanation of symbols]

[0078] 1 Reaction vessel 2. Denitrification carrier 3. Pressurizing means 4 Water flow means 5 Water inlet 6 Water outlet 7 Means of transportation after water passage 8 Water passage opening and closing means 9 Transportation opening / closing means after water flow 10. Treatment tank 11 Flowmeter 12 Post-water storage tank 13 Breeding tank 14 Nitrification treatment equipment 15 Denitrification treatment equipment 16 Circulating denitrification system 17 One-pass denitrification system 18 Aquatic Life Breeding System

Claims

1. A denitrification method for carrying out denitrification treatment by passing water to be treated that contains nitrate nitrogen and / or nitrite nitrogen through a reaction vessel that contains a denitrification carrier that contains a biodegradable resin, comprising: The water to be treated contains phosphorus components, and the concentration of the phosphorus components in the water to be treated is 1.0 mg-P / L or more; The water to be treated contains Cu ions, and the concentration of Cu ions in the water to be treated is 0.01 mg-Cu / L or more and 0.25 mg-Cu / L or less; The water to be treated flows into the reaction vessel from a water inlet of the reaction vessel, comes into contact with the denitrification carrier, and is then discharged out of the reaction vessel from a water outlet of the reaction vessel; A denitrification treatment method, characterized in that the amount of water passing through is controlled so that the linear velocity (LV) of the water to be treated passing through the reaction vessel is maintained at 1.5 to 13.0 (m / h).

2. 2. The denitrification method according to claim 1, wherein the reaction vessel has a columnar shape.

3. 2. The denitrification method according to claim 1, wherein the biodegradable resin is a biodegradable polyester.

4. The denitrification method according to claim 3 , wherein the biodegradable polyester contains two or more types of constitutional units derived from a dicarboxylic acid.

5. A denitrification treatment device for denitrifying water containing nitrate nitrogen and / or nitrite nitrogen, A denitrification carrier containing a biodegradable resin; A reaction vessel in which the denitrification carrier is accommodated; A water passing means for passing the water to be treated through the reaction vessel; A pressurizing means for pressurizing the water to be treated passing through the reaction vessel; Equipped with The water to be treated contains phosphorus components, and the concentration of the phosphorus components in the water to be treated is 1.0 mg-P / L or more; The water to be treated contains Cu ions, and the concentration of Cu ions in the water to be treated is 0.01 mg-Cu / L or more and 0.25 mg-Cu / L or less; The reaction vessel is formed with a water inlet for flowing the water to be treated into the reaction vessel and a water outlet for discharging the water to be treated out of the reaction vessel, The denitrification treatment device further comprises a mechanism for controlling the amount of water passing through the reaction vessel so that the linear velocity (LV) of the water to be treated is maintained at 1.5 to 13.0 (m / h).

6. The denitrification treatment apparatus according to claim 5 , wherein the reaction vessel has a columnar shape.

7. The denitrification treatment device according to claim 5 , wherein the biodegradable resin is a biodegradable polyester.

8. The denitrification treatment device according to claim 7 , wherein the biodegradable polyester contains two or more types of constitutional units derived from dicarboxylic acid.

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