JP2003260493A - Removal method for nitrate nitrogen in water and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a removal method for nitrate nitrogen in water due to a biological membrane method which enables the efficient removal of nitrate nitrogen in water to be treated at a relatively low cost by simple operation by adjusting the thickness of a liquid diffusion layer on the organism film of a rotary blade to keep the flow of water to be treated in a tank, and a removal apparatus using the same. <P>SOLUTION: This removal apparatus 2 for nitrate nitrogen in water is constituted so that a rotary shaft 7 is inserted in a tank having an introducing port 6 for water to be treated and a treated water discharge port 5 respectively provided to the lower and upper parts thereof and one or more blade members are provided to the rotary shaft so as to extend in a radial direction and the upper ends of the blade members are positioned under the opening part of the treated water discharge port. By this constitution of the removal apparatus, the moving speed of nitrate nitrogen on the surface of a biological membrane can be increased and the concentration of nitrate nitrogen of 10 mg/L or less regulated in Europe can be achieved in a relatively short time. Further, if the rotary blades are made small-sized, a small-sized denitrification treatment apparatus for nitrate nitrogen large in nitrate load capacity can be provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to nitrite ion (nitrite nitrogen) or nitrate ion (nitrate nitrogen) in water.
Or a nitrite ion and a nitrate ion (henceforth, nitrite nitrogen and / or nitrate nitrogen are collectively called nitrate nitrogen) regarding the removal method and removal apparatus, Especially this invention is groundwater,
The present invention relates to a method and a device for removing nitrate nitrogen in water such as lakes, rivers, tap water, and sewage by a biofilm. The present invention also relates to a method and an apparatus for removing nitrate nitrogen in waste water or waste water using a biofilm.

[0002]

2. Description of the Related Art Increasing population in cities, industrial and industrial development, and excessive fertilization on farmland cause water pollution in public waters, deteriorating natural environment and living environment. For example,
In the activated sludge method that is mainly adopted as a sewage treatment method,
The main purpose is to remove BOD (biochemical oxygen demand) and SS (suspended substances) in the water to be treated, and salts containing nitrogen and phosphorus, which are factors of eutrophication, are released to public water bodies without being removed. This causes problems such as eutrophication in the water area. In particular, most of the nitrate nitrogen components such as nitrite ion and / or nitrate ion present in the sewage-treated water and industrial wastewater are currently released without treatment. In addition, groundwater pollution due to excessive fertilizer fertilizer in agricultural land and groundwater pollution due to livestock excrement due to livestock promotion are progressing, and nitrate nitrogen such as nitrite ion and / or nitrate ion existing in groundwater is increasing. When the concentration of the above exceeds the standard value, pollution by nitrate nitrogen has become a problem. Therefore, with respect to these sewage and wastewater, removal of nitrate nitrogen by denitrifying bacteria is carried out by a rotating disk method, a fluidized bed method or the like. Examples of such denitrifying bacteria include, for example,
Pseudomonas, Micrococcus (Mic)
rococcus), Spirillum, Achromobacter, and Alcalig
denitrifying bacteria that use organic substances such as enes) as hydrogen donors, hydrogenomonas denitrificans that are denitrifying bacteria that use hydrogen gas as a hydrogen donor, and thiobacillus of denitrifying bacteria that use sulfides as hydrogen donors. There is denitrificans (Thiobacillus denitrificans) and the like, and hydrogen donors include methanol, acetic acid, ethanol, acetone, glucose, methyl ethyl ketone and isopropyl alcohol, but from the viewpoint of assimilability, manageability and economic efficiency, methanol Is the most used.

[0003]

However, the removal of nitrate nitrogen by denitrifying bacteria is carried out by growing the denitrifying bacteria while reducing nitrate nitrogen in the presence of a hydrogen donor, that is, an organic substance such as methanol. Denitrification is performed, and denitrification by this denitrifying bacterium is performed by a rotating disk method, an activated sludge method or a fluidized bed method. However, in any of the treatment methods, it is necessary to increase the transfer amount of the substrate, which complicates the operation operation and raises the maintenance cost, which is a problem.

When removing nitrate nitrogen by the rotating disk method, a plurality of disks having a diameter of 1 to 3 m are attached to the rotating shaft,
All of the plurality of disks are submerged in water and rotated to reduce nitrate nitrogen in water to nitrogen by denitrifying bacteria, thereby denitrifying the nitrogen. The denitrification of nitrate nitrogen by this rotating disc method, when the film thickness of the attached biofilm formed on the rotating disc becomes thick, the substrate reaction of the biofilm related to denitrification becomes slow, and denitrification becomes the substrate rate limiting. It's a problem. On the other hand, if the rotation speed of the rotating disk is increased, the film thickness of the adherent biofilm becomes smaller, so it is possible to avoid the substrate rate control of the biofilm for the time being, but the energy consumption increases and the power cost increases, which is a problem. is there. Further, it is difficult to rotate the rotating disc at a high speed because of the structure of the rotating disc and its mounting structure. Moreover,
It is said that the peripheral speed of the rotating disc is optimally 18 m / min in order to stabilize the attachment of the biofilm on the rotating disc. Therefore, the rotating disc usually operates at a rotation speed of 2 to 3 rpm. The thickness of the liquid diffusion layer on the attached biofilm of the rotating disk is 360 to 480 μm. In this case, the retention (contact) time of the water to be treated for denitrification treatment is 1 hour or more, which is a problem in terms of treatment capacity. Further, in the rotating disc method, the rotating discs are provided with an interval of about 20 to 30 mm, but when the biofilm grows, the spaces between the discs are almost occupied by the biofilm, and sometimes, This is a problem because it clogs and the surface of the biofilm cannot be effectively used.

On the other hand, in the fluidized bed method, particles of about 1.0 mm are suspended in the water to be treated by the flow of the water to be treated to grow the attached biofilm on the surface of the particles. This is a denitrification method. In this method, the thickness of the diffusion layer of the liquid on the adherent biofilm on the particle surface is calculated to be approximately 33 μm. Since the particles are small in this way, it is possible to increase the amount of attached organisms, but particles are attached to each other and the biofilm is easily broken. In order to avoid separation and destruction of the biofilm, it is necessary to suspend the particles by avoiding the mutual contact of the particles with the biofilm attached to the surface, but by controlling the water flow in that way. , It is very difficult to suspend particles with a biofilm attached on the surface by a water stream. As described above, removal of nitrate nitrogen by the rotating disk method, fluidized bed method, activated sludge method, etc. using denitrifying bacteria requires complicated operation, high maintenance costs, or denitrification. It is a problem because it is difficult to improve the rate.

[0006]

According to the present invention, the size of the rotary blade is reduced to a radius of rotation of, for example, less than 2 m, preferably less than 1 m to enable high-speed rotation, and the rotary blade is removed. It is based on the discovery that the removal rate of nitrate nitrogen can be improved by adjusting the thickness of the diffusion layer of the liquid on the biofilm on which the nitrifying bacteria adhere, by adjusting the rotation speed of the rotor. The present invention is
By adjusting the thickness of the diffusion layer of the liquid formed on the attached biofilm of the rotor blade, the flow of the treated water on the attached biofilm is maintained, and the nitrate nitrogen in the treated water is removed by denitrifying bacteria. It is an object of the present invention to provide a method and an apparatus for removing nitrate nitrogen in water by a biofilm method, which can remove nitrate nitrogen in water with a simple operation and at a relatively low cost. I am trying.

That is, according to the present invention, a hydrogen donor is mixed with water containing nitrate nitrogen, and the rotary blade to which the biofilm is attached is set to 10 rpm or more in the water mixed with the hydrogen donor. There is a method for removing nitrate nitrogen in water, characterized by decomposing and removing nitrate nitrogen in water by rotating at a rotation speed, and the present invention also provides a hydrogen donor in water containing nitrate nitrogen. By mixing and rotating the rotary blade having the biofilm in the water mixed with the hydrogen donor at a rotation speed of 10 rpm or more, the thickness of the diffusion layer of the liquid formed on the biofilm is set to 100.
A method for removing nitrate nitrogen in water, characterized by decomposing and removing nitrate nitrogen in water to less than or equal to μm. Further, the present invention has a treated water inlet at the bottom and a treatment at the top. A rotary shaft is provided by being inserted in a tank having a water discharge port, and one or more blade members are provided on the rotary shaft so as to extend in a radial direction, and an upper end of the blade member is provided with the treatment. In a device for removing nitrate nitrogen in water, which is characterized in that it is located below the opening of the water discharge port, and also has a treated water introduction port at the bottom and a treated water discharge port at the top. A rotary shaft is inserted in the tank having the blade, and a blade support member is radially provided on the rotary shaft, and the blade support member has one or more blade members concentric with the rotary shaft. All of the blade members are provided below the treated water outlet opening. Sometimes has a removal device of nitrate nitrogen in water, characterized in.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, denitrification treatment of water containing nitrate nitrogen is carried out by using a water treatment device in which a rotary shaft is radially or concentrically attached to a rotary blade. Rotation speed is 10 rpm or more, preferably 10 to 2
00 rpm, more preferably 10 to 120 rp
m, it is possible to introduce the water to be treated into the denitrification tank and perform it in a batch system or a continuous system. The rotation speed of the rotary blade is 20 rpm or more, and preferably 30 to 120 rp.
As m, the water to be treated can be introduced into the denitrification tank, and the method can be carried out batchwise or continuously. Hydrogen donors, that is, organic carbon sources (organic compounds) include methanol, acetic acid, ethanol, acetone, glucose, methyl ethyl ketone, isopropyl alcohol, etc., but alcohol-containing waste such as shochu lees and squeezing filtration wastewater in the fishing industry, etc. The organic-containing waste liquid of can be used as an organic carbon source. However, as the hydrogen donor, methanol is preferable from the viewpoint of its assimilation property, easiness of handling and economical efficiency.
The denitrifying bacteria used are only those capable of reducing nitrate nitrogen to nitrogen, and not only denitrifying bacteria whose hydrogen donor is an organic compound, but also denitrifying bacteria whose hydrogen donor is hydrogen or sulfide are used. can do.

When the hydrogen donor is, for example, methanol, the amount of methanol used is the amount usually used, for example, 1 mg of nitrate ion, that is, 1 mg of nitrate nitrogen.
1.9 mg or more, preferably 2.0 mg or more per 1 mg of nitrate nitrogen, and more preferably 2.5 mg per 1 mg of nitrate nitrogen. In this example, the treatment time required for denitrifying the nitrate nitrogen of the water to be treated, that is, the residence time in the denitrification tank, is the time at which the removal rate of nitrate nitrogen in the treated raw water is about 90% by weight or more. , For example, 4
It is 0 minutes or less. The residence time is preferably determined in advance for each treated raw water before treatment. For example, with respect to the treated water after a certain period of time, the residual nitrate nitrogen concentration, for example, the residual nitrate nitrogen concentration is analyzed, and the time when the residual nitrate nitrogen concentration becomes 3 mg / l or less is called the treatment time, that is, the residence time. can do.

In this example, for example, denitrification treatment of water containing 10 mg / l or more of nitrate nitrogen (hereinafter referred to as raw water) is carried out in a denitrification tank equipped with a rotary shaft to which a rotary blade having a biofilm is attached. In, the raw water mixed with the hydrogen donor, that is, the water to be treated is treated with a biofilm in a batch system or a continuous system. In the present invention, the rotary blade is mounted radially or concentrically with respect to the rotary shaft, and the rotation speed of the rotary blade during denitrification treatment is 10 rpm or more, preferably 20 rpm or more, more preferably 30 to 120 r.
pm. In the present invention, the length of the rotary blade from the rotation axis can be a radius of 2 m to 0.1 m. In this case, the length is preferably 2 m to 0.3 m. However, in order to downsize the device, the length of the rotary blade from the rotation axis can be set to 1 m or less, for example, 1 m to 0.1 m, and in this case, 1 m to 0.3 m. However, more preferably 0.5 m or less, for example 0.5 m to 0.1 m, and further preferably
It is 0.5 m to 0.3 m or less.

In the present invention, the liquid on the biofilm of the rotor is
The diffusion layer thickness (Ld) is calculated by the following formula: Ld = {1.15 [θ- (1/2) × sin2θ]^1/3/
sin θ} × (4Da^Two/ 3U)^1/3 Required by. Here, D is a diffusion layer coefficient (= 2 × 10⁹
m^Two/ Sec) and U is the velocity of water (velocity around the rod) (m
/ Sec), a is the radius of the rod (mm), and θ is the angle
(90 ° = π / 2). In the present invention,
The thickness of the liquid diffusion layer on the biofilm increases the rate of substrate migration.
100 μm or less, preferably 60 μm to influence
Hereafter, it is more preferably 40 μm.
In the present invention, the thickness of the attached water film on the biofilm of the rotor blade,
In other words, the thickness of the diffusion layer of the liquid on the biofilm is
As it moves away from the rotation axis
The thickness of 100 μm or less on the biofilm of the rotor blade.
To form the liquid diffusion layer of
It is necessary to set it to 0 rpm or more. In addition,
On the biofilm, for example, a liquid diffusion layer with a thickness of 60 μm or less
To form, the rotation speed of the rotor blade should be 30 rpm or more.
On the rotor blade biofilm
With a thickness of 40 μm or less, preferably 1 to 40 μm.
To form a liquid diffusion layer, the rotation speed of the rotor is 60
It is necessary to set it to rpm or more.

In the present invention, since the thickness of the liquid diffusion layer on the biofilm of the rotary blade can be reduced within the range of 100 μm or less in accordance with the rotation speed of the rotary blade, the moving speed of the substrate of the biofilm is reduced. It can be made large and the substrate rate limiting can be avoided. In the present invention, the biofilm formed on the rotor blade is several millimeters or less even if the biofilm becomes thick, and the liquid diffusion layer on the biofilm is 100 μm. A passage for the water to be treated can be always ensured between the biofilms formed. Therefore, according to the present invention, even if a thick biofilm is formed on the rotary blade, the passage of the water to be treated is not extremely narrowed, the flow of the water to be treated becomes smooth, and the operation is stopped due to the clogging of the passage or the like. Can be avoided, and the nitrate nitrogen removal rate can be improved.

In the present invention, it contains nitrate nitrogen,
In water mixed with an organic compound as a hydrogen donor, a rotary blade having a biofilm formed by denitrifying bacteria was rotated at a rotation speed of 10 rpm or more, preferably 30 to 12
It is rotated at 0 rpm to efficiently decompose and remove nitrite ion or nitrate ion in water by a biofilm. The denitrifying bacterium used in the present invention can be a denitrifying bacterium conventionally used for removing nitrate nitrogen in water.

In the present invention, the rotary blade can be formed of a perforated plate or a mesh plate. In this way, when the rotor blade is formed by a perforated plate or a mesh plate,
It is preferable because the resistance due to the water flow at the time of rotating the rotary blade can be reduced. Further, when the rotor blade is formed of a perforated plate or a mesh plate, the thickness of the liquid diffusion layer on the biofilm is 100 μm or less, preferably 60 μm, on the entire surface of the rotor blade.
Below, it is more preferable that the thickness is more preferably 40 μm or less, and the substrate reaction rate can be easily increased, which is preferable. In the present invention, since the length of the rotary blade from the rotary shaft, that is, the radius of rotation of the rotary blade is as small as 0.5 m or less,
The size of the denitrification tank can be reduced according to the length of the rotary blade. When the length of the rotary blade from the rotary shaft is reduced to 0.5 m or less, it is easy to increase the rotation speed of the rotary blade. When the rotary blade is made small and formed in a mesh shape as described above, for example, when the rotation speed is 10 rpm, the thickness of the liquid diffusion layer on the biofilm is, for example, 10 mm from the axis.
It is about 90 μm at that point, and about 50 μm at a point 500 mm from the axis farthest from the axis. Further, when the rotation speed is 30 rpm, the thickness of the diffusion layer of the liquid on the biofilm is, for example, about 60 μm at 10 mm from the axis and about 500 mm from the axis farthest from the axis. It is 30 μm. When the rotation speed is 50 rpm,
The thickness of the liquid diffusion layer on the biofilm is, for example, 10 m from the axis.
It is about 50 μm at m and about 30 μm at a position 500 mm from the axis farthest from the axis.

In the present invention, the nitrate nitrogen in the water to be treated is reductively decomposed in the presence of a hydrogen donor in the denitrification tank by the action of the denitrifying bacteria to become nitrogen gas, which is removed from the water to be treated. It The denitrification tank has an inlet for treated water at the bottom of the tank and an outlet for treated water at the top of the tank.In the denitrification tank, a rotary drive device such as a motor or gear box is connected to the rotating shaft. Are provided in the vertical direction (or the substantially vertical direction) or in the horizontal direction (or the substantially horizontal direction). The rotary shaft is provided with one or more, preferably two or more rotary blades. The number of rotary blades is such that the flow of the water to be treated is not extremely disturbed, and for example, the rotary blades can be provided on the rotary shaft at angular intervals of 15 ° or more. If multiple denitrification tanks are installed in series,
It is preferable because the denitrification rate can be improved.

In the present invention, since the denitrifying bacterium is anaerobic, the entire impeller having the biofilm of the denitrifying bacterium is immersed in the water to be treated to remove the nitrate nitrogen in the water to be treated as a hydrogen donor. Reductively decomposes to nitrogen in the presence. Therefore, the denitrification treatment apparatus for treated water of the present invention has a rotary shaft inserted vertically or horizontally in a tank having a treated water inlet in the lower portion and a treated water outlet in the upper portion. The entire rotary blade is located below the opening of the treated water outlet, that is, below the surface of the water to be treated, and one or more rotary blades are provided on the rotary shaft in a radial direction. Or concentrically with the rotary shaft.

In the present invention, the rotary blade is a plate-shaped body, a perforated plate such as a perforated plate or a mesh-shaped plate, and can be formed in a flat plate shape, a mountain shape or an arc shape. The rotary blades can be provided radially or concentrically around the rotation axis. When the rotor blades are provided radially about the rotation axis, the rotor blades are plate-shaped bodies, perforated plates, or perforated plates or mesh-shaped plates, and are formed into a flat plate shape, a mountain shape, or an arc shape. be able to. When the rotary blades are provided concentrically with respect to the rotary shaft, the rotary blades may be provided concentrically with respect to the rotary shaft, for example, on a support member radially provided on the rotary shaft. it can. When the rotary blade is provided concentrically with respect to the rotary shaft, the rotary blade is a plate, a perforated plate, or a perforated plate or a mesh plate, and is formed into a flat plate shape, a mountain shape, or an arc shape. be able to.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited to the following description and examples. FIG. 1 is an explanatory view showing the outline of a denitrification tank of one embodiment of the present invention. Figure 2
Regarding the denitrification tank in one embodiment of the present invention shown in FIG.
It is an outline side sectional view showing the outline of the example. Figure 3
FIG. 3 is a schematic plan sectional view showing an outline of the denitrification tank shown in FIG. 2. FIG. 4 is a denitrification tank having a structure different from that of the denitrification tank of FIG. 2 in the denitrification tank of the embodiment of the present invention shown in FIG.
It is an outline side sectional view showing the outline structure. Figure 5
FIG. 5 is a schematic plan sectional view showing an outline of the denitrification tank shown in FIG. 4. FIG. 6 is a diagram showing the relationship between the rotational speed of the rotary blade obtained in Example 2 and the thickness of the liquid diffusion layer on the biofilm of the rotary blade during the rotation. FIG. 7 is a diagram showing the relationship between the distance from the rotation axis obtained in Example 3 and the thickness of the diffusion layer of the liquid on the biofilm at the distance. Figure 8
It is a figure which shows the relationship between the denitrification rate measured in the denitrification process in Example 5 and Example 6, and the elapsed days. FIG. 9: is a figure which shows the relationship between the denitrification rate measured in the denitrification process in Example 7 and Example 8, and the elapsed days. FIG. 10 shows examples 9 and 10.
FIG. 3 is a diagram showing the relationship between the denitrification rate measured in the denitrification process in FIG. FIG. 11 is a diagram showing the relationship between the number of revolutions and the denitrification rate at a residence time of 40 minutes in Examples 8 to 10. 1 to 5, corresponding parts are designated by the same reference numerals.

Example 1 In this example, a raw water treatment apparatus 1 for removing nitrate nitrogen in raw water includes a denitrification tank 2 for performing denitrification of nitrate nitrogen in raw water, a raw water supply tank 3 and a hydrogen donor-containing unit. A solution supply tank 4 is provided. At the upper part of the denitrification tank 2, the treated water discharge port 5 for overflowing and discharging the treated water from which nitrate nitrogen has been removed
And a treated water introduction port 6 for introducing treated water containing raw water to be treated in the denitrification tank 2 at the lower part,
A rotation drive device 8 such as an electric motor is provided on the ceiling of the denitrification tank 2 to rotate the rotary shaft 7.

In this example, a raw water suction pipe 9 is inserted into the raw water supply tank 3 up to the bottom thereof, and the raw water suction pipe 9 is the suction portion 1 of a suction pump 10 for supplying raw water.
1, the raw water 12 contained in the raw water supply tank 3 can be pumped out by the suction pump 10 for supplying the raw water. Further, in this example, a hydrogen donor suction pipe 13 is inserted into the hydrogen donor supply tank 4 up to the bottom thereof, and the hydrogen donor suction pipe 13 is a suction pump 14 for supplying the hydrogen donor. The hydrogen donor contained in the hydrogen donor supply tank 4 can be pumped out by the suction pump 14 for supplying the hydrogen donor.

In this example, the raw water supply passage 18 connected to the discharge port 17 of the raw water suction pump 10 has a mixing valve 19
Of the hydrogen donor supply passage 22 connected to the introduction passage 20 of the first liquid of No. 1 and connected to the discharge port 21 of the hydrogen donor suction pump 14.
Is connected to the second liquid introduction path 23 of the mixing valve 19. The mixed liquid discharge port 24 of the mixing valve 19 is connected to an untreated water introducing passage 25 connected to the untreated water introducing port 6. In this example, a biofilm of denitrifying bacteria adhering to the impeller was formed by seeding water from the first settling basin of the sewage treatment plant.

Since this example is constructed as described above,
Raw water is put into the raw water supply tank 3, hydrogen donor is put into the hydrogen donor supply tank 4, and the raw water suction pump 10 and the hydrogen donor suction pump 14 are operated to suck the raw water 12 from the raw water supply tank 3. Extracted by pipe 9, raw water supply line 18
Through the introduction passage 20 to the mixing valve 19, and the hydrogen donor 16 is taken out from the hydrogen donor supply tank 4 by the hydrogen donor suction pipe 13 and supplied to the hydrogen donor supply passage 22.
Through the introduction passage 23 to the mixing valve 19. Raw water 12 and hydrogen donor 16 introduced into mixing valve 19
Are mixed in the mixing valve 19, and the mixed liquid of the mixing valve 19 flows out from the discharge port 24, and the treated water introducing passage 25
Further, it is sent to the denitrification tank 2 through the water to be treated 6 and is denitrified by the denitrifying bacteria attached to the rotor blades.

2 to 4 are detailed explanatory views of the denitrification tank 2 shown in FIG. In the denitrification tank 2 shown in FIGS. 2 and 3, the side wall portion 26 of the denitrification tank 2 has an upper flange portion 2 thereof.
In Fig. 7, the ceiling part 28 of the denitrification tank 2 is in close contact with the upper part of which is hermetically sealed, and the lower part of the side wall part 26 is hermetically sealed with the bottom wall part 29. The denitrification tank 2 is provided with a treated water discharge port 5 at its upper portion and a treated water introduction port 6 at its lower portion. In this example, the rotary shaft 7 to which the rotary blades 32 are attached has an upper bearing 30 provided on the ceiling portion 28.
And a lower bearing 31 provided on the bottom wall 29. In this example, the rotary blade 32 is formed of a plate-shaped net and is radially attached to the rotary shaft 7,
The whole is soaked in the water to be treated, that is, the rotor 3
The upper end portion 33 of the rotary blade 32 is provided below the treated water discharge port in the upper portion of the denitrification tank 2 so that the upper end portion 33 of 2 is provided below the water surface 34 of the water to be treated. ing. Also in this example, the biofilm of denitrifying bacteria adhering to the rotor was formed by planting water from the first settling basin of the sewage treatment plant.

In the denitrification tank 2 shown in FIGS. 4 and 5, the rotary blade 32 is formed of an arcuate plate, and is concentrically formed on the rotary shaft on a support member 35 radially mounted on the rotary shaft 7. It is provided. Also in this example, the entire rotary blade 32 is immersed in the water to be treated, that is, the rotary blade 32 is
The upper end portion 33 of the rotary blade 32 is disposed so that the upper end portion 33 of the rotary blade 32 is located below the water surface 34 of the water to be treated.
Is provided below the treated water discharge port. Also in this example, the biofilm of denitrifying bacteria adhering to the rotor was formed by planting water from the first settling basin of the sewage treatment plant.

Example 2 In this example, an acrylic resin rod having a diameter of 3 mm was used to fabricate a rotary blade having a mesh structure in which the distance between the rods was 10.0 mm × 10.0 mm. In this example, raw water treatment was performed on two series, series 1 and series 2. In series 1, the size of the mesh-shaped rotary blade 32 is set to 15.8 in the vertical direction.
cm, width 4.2 cm, 8 pieces are attached to the rotating shaft 7, the inner diameter is 10.9 cm, and the height is 22 cm. This is installed in the cylindrical container 2 of the denitrification tank made of acrylic resin and the series 1 raw water treatment device. And On the other hand, in the series 2, the size of the rotary blade 32 having the mesh structure is 15.2 cm in length and 4.0 cm in width.
Formed on the rotary shaft 7 and attached 12 pieces, the inner diameter 10.9
It was installed in the cylindrical container 2 of a denitrification tank made of acrylic resin and having a height of 22 cm and a height of 22 cm to obtain a second series of raw water treatment device.
In the series 1 and series 2 raw water treatment apparatuses, the biofilm of denitrifying bacteria adhering to the rotor was formed by planting the water of the first settling tank of the sewage treatment plant. Series 1 raw water treatment device 1
Was used to calculate the number of rotations of the rotary blade 32 and the thickness of the liquid diffusion layer on the biofilm of the rotary blade 32 during the rotation. The results are shown in Table 1 and FIG. This result is
The same was true for the series 2 raw water treatment device.

[0026]

[Table 1] As a comparative example, Table 1 shows the thickness of the diffusion layer of the liquid on the biofilm formed on the rotating disc in the conventional rotating disc method using a rotating disc having a diameter of 3 m, for example. . Also in the conventional rotating disc method, the biofilm of denitrifying bacteria adhering to the rotating disc was formed by planting water from the first settling basin of the sewage treatment plant. Compared to this conventional rotating disk method device,
The device of this example is small, and the thickness of the liquid diffusion layer formed on the biofilm is smaller than that of the rotating disk method. Thus, in the device of this example, since the thickness of the diffusion layer of the liquid on the biofilm is thin, the permeation resistance of the liquid in the diffusion layer of the liquid is smaller than in the conventional example, The permeation rate of the water to be treated in the liquid diffusion layer is increased, and the amount of the water to be treated by the biofilm can be increased.

Example 3 In this example, the change in the thickness of the diffusion layer of the liquid on the biofilm formed on the rotor blade surface was changed at different positions on the surface of the rotor blade 32 apart from the rotation axis. , Was calculated for each rotational speed of the rotor. In this example as well, the biofilm of denitrifying bacteria formed on the rotor blade was formed by planting the water in the first settling basin of the sewage treatment plant, as in the example of FIG. The measurement results in this example are shown in Table 2 and FIG. 7 below.

[Table 2] It was found that the thickness of the liquid diffusion layer formed on the biofilm of the rotary blade decreases as the distance from the peripheral surface of the rotary shaft 7 increases. Since the thickness of the liquid diffusion layer on the biofilm formed in the fluidized bed method is 40 μm, the rotation speed of the rotor in the following examples was set to 30 rpm or more.

Example 4 In order to make the thickness of the diffusion layer on the biofilm of the rotor blade 40 μm or less, the rotation speed of the rotor blade in this example is 30 rpm,
It was set to 60 rpm and 120 rpm. The residence time of the water to be treated in the denitrification treatment in this example was set to 40 minutes, which is an intermediate residence time between the fluidized bed method and the rotating disk method. The nitrate nitrogen concentration remaining in the treated water after the lapse of this residence time was measured, and the denitrification rate was obtained from the analyzed residual nitrate nitrogen concentration and the nitrate nitrogen concentration in the raw water. Also in this example, the biofilm of denitrifying bacteria adhering to the rotor was formed by planting water from the first settling basin of the sewage treatment plant. The raw water used in this example is an artificial substrate solution, the composition of which is shown in Table 3 below.

[Table 3] In this example, the concentration of nitrate nitrogen in the raw water was 24.94.
mg / l.

Example 5 In this example, the denitrification treatment for raw water was carried out by using a series 1 raw water treatment apparatus in which eight rotary blades were radially attached to the rotary shaft, and the rotational speed of the rotary blade was 30 rpm. It was carried out in a continuous manner. In this example as well, the biofilm of the denitrifying bacteria that adheres to the rotor blade was formed by planting the water in the first settling tank of the sewage treatment plant. Also in this example, methanol was used as a hydrogen donor, and the amount of methanol used was 2.5 mg per 1 mg of nitrate ion. In this example,
With respect to the treated water after a lapse of the residence time of 40 minutes, the residual nitrate nitrogen concentration was analyzed, the residual nitrate nitrogen concentration in the treated water was determined, and the denitrification rate was calculated. The results are shown in Table 4 and FIG.
Shown in. In FIG. 8, this example is indicated by a white circle graph.

[Table 4] In this example, the concentration of nitrate nitrogen in the water to be treated flowing into the raw water treatment device is 21.7 mg / l to 25.7 mg / l.
Although it fluctuated within the range of l, it was denitrified regardless of the concentration of nitrate nitrogen in the water to be treated. Denitrification rate is 7 until 9th
Although it is a relatively low value of 8% or less, the denitrification rate after 13 days when the growth of the biofilm is stable is around 90%, which is a relatively high value. Moreover, in this example, the nitrate nitrogen concentration of the treated water after the 13th day when the growth of the biofilm was stable was within the range of 2.7 to 2.3 mg / l, and all of the nitrate nitrogen concentrations in the tap water quality standard were 1 of the standard value of nitrogen concentration
It was less than 0 mg / l. Therefore, it is shown that the raw water treatment device in series 1 of this example can be used for denitrification of nitrate nitrogen in raw water. In this example, the denitrification rate is relatively low until 9 days after the start of the denitrification treatment, because the formation of the biofilm is not sufficient. Sufficient planting is required to accelerate biofilm formation.

Example 6 In this example, the denitrification treatment of nitrate nitrogen of raw water was carried out by using a raw water treatment apparatus of series 2 in which 12 rotary blades were radially attached to the rotary shaft, and the rotation speed of the rotary blades was changed. 30r
pm was performed continuously. In this example as well, the biofilm of denitrifying bacteria that adheres to the rotor blades was formed by planting water from the first settling basin of the sewage treatment plant. Also in this example,
Methanol was used as a hydrogen donor, and the amount of methanol used was 2.5 mg per 1 mg of nitrate nitrogen. In this example, the residual nitrate nitrogen concentration of the treated water after the residence time of 40 minutes was analyzed, the residual nitrate nitrogen concentration in the treated water was determined, and the denitrification rate was calculated. The results are shown in Table 5 and FIG. In FIG. 8, this example is shown by a black circle graph.

[Table 5] In this example, the concentration of nitrate nitrogen in the water to be treated which flows into the raw water treatment apparatus of series 2 is 17.7 mg / l to 25.
Although it varied within the range of 0 mg / l, it was denitrified regardless of the nitrate nitrogen concentration in the water to be treated. The denitrification rate was a relatively high value of 80% or more except for the fourth day after the start of denitrification treatment. Moreover, the nitrate nitrogen concentration of the treated water after 12 days is within the range of 2.2 to 1.5 mg / l, both of which are 1 of the standard value of the nitrate nitrogen concentration in the tap water quality standard.
It was less than 0 mg / l. Therefore, it is shown that the raw water treatment device of series 2 of this example can be used for denitrification of nitrate nitrogen in raw water. In this example, the denitrification rate is relatively high for up to 4 days after the start of denitrification.
It is considered that this is because the denitrifying bacterium was slightly attached because the device after the previous denitrification treatment was used.

Example 7 In this example, the denitrification treatment for raw water was carried out by using a series 1 raw water treatment apparatus in which eight rotary blades were radially attached to the rotary shaft, and the rotation speed of the rotary blade was 60 rpm. It was carried out in a continuous manner. Using methanol as a hydrogen donor,
The amount of methanol used is 2.5 per 1 mg of nitrate nitrogen.
It was mg. In this example, the residual nitrate nitrogen concentration of the treated water after the residence time of 40 minutes was analyzed, the residual nitrate nitrogen concentration in the treated water was determined, and the denitrification rate was calculated. The results are shown in Table 6 and FIG. In FIG. 9, this example is indicated by a white circle graph.

[Table 6] In this example, the concentration of nitrate nitrogen in the water to be treated flowing into the raw water treatment apparatus of series 1 is 16.8 mg / l to 28.
Although it varied within the range of 3 mg / l, it was denitrified regardless of the concentration of nitrate nitrogen in the water to be treated. The denitrification rate was within a range of 60 to 64% until 7 days after the start of denitrification, which was a relatively high value. The denitrification rate after 13 days when the biofilm became stable was within the range of 86 to 89%, and after 14 days, the nitrate nitrogen concentration in the treated water was 2.6 to 3.
It was within the range of 6 mg / l, and all were 10 mg / l or less of the standard value of the nitrate nitrogen concentration in the standard of tap water quality. Therefore, it is shown that the raw water treatment apparatus of series 1 of this example can be used for denitrification of nitrate nitrogen in raw water. In this example, the reason that the denitrification rate is relatively low until 7 days after the start of denitrification treatment is considered to be due to insufficient formation of the biofilm.

Example 8 In this example, the denitrification treatment of raw water was carried out by using a series 2 raw water treatment apparatus in which 12 rotary blades were radially attached to the rotary shaft, and the rotational speed of the rotary blade was 60 rpm. It was carried out in a continuous manner. In this example as well, the biofilm of the denitrifying bacteria that adheres to the rotor blade was formed by planting the water in the first settling tank of the sewage treatment plant. Also in this example, methanol was used as the hydrogen donor, and the amount of methanol used was 2.5 mg per 1 mg of nitrate nitrogen. In this example,
With respect to the treated water after a lapse of the residence time of 40 minutes, the residual nitrate nitrogen concentration was analyzed, the residual nitrate nitrogen concentration in the treated water was determined, and the denitrification rate was calculated. The results are shown in Table 7 and FIG.
Shown in. In FIG. 9, this example is shown by a black circle graph.

[Table 7] In this example, the concentration of nitrate nitrogen in the water to be treated flowing into the raw water treatment apparatus of Series 2 is 16.7 mg / l to 26.
Although it varied within the range of 9 mg / l, it was denitrified regardless of the nitrate nitrogen concentration in the water to be treated. The denitrification rate 2 days after the denitrification treatment was in the range of 86 to 90%, which was a high value. Moreover, the nitrate nitrogen concentration of the treated water after 2 days was
Within the range of 2.0 to 3.0 mg / l, both of which are 10 mg / l which is the standard value of the concentration of nitrate nitrogen in the standard of tap water quality.
It was 1 or less. Therefore, it is shown that the raw water treatment device of series 2 of this example can be used for denitrification of nitrate nitrogen in raw water.

Example 9 In this example, the denitrification treatment of raw water was carried out by using a series 1 raw water treatment apparatus in which eight rotary blades were radially attached to the rotary shaft, and the rotary speed of the rotary blade was 120 rpm. It was carried out in a continuous manner. In this example as well, the biofilm of the denitrifying bacteria that adheres to the rotor blade was formed by planting the water in the first settling tank of the sewage treatment plant. Also in this example, methanol is used as the hydrogen donor, and the amount of methanol used is
The amount was 2.5 mg per 1 mg of nitrate nitrogen. In this example, the residual nitrate nitrogen concentration of the treated water after the residence time of 40 minutes was analyzed, the residual nitrate nitrogen concentration in the treated water was determined, and the denitrification rate was calculated. The results are shown in Table 8 and FIG. In FIG. 10, this example is indicated by a white circle graph.

[Table 8] In this example, the concentration of nitrate nitrogen in the water to be treated flowing into the raw water treatment apparatus of series 1 is 2.3 mg / l to 28.6.
Although it varied within the range of mg / l, it was denitrified regardless of the concentration of nitrate nitrogen in the water to be treated. The denitrification rate is within a range of 15 to 78% up to 21 days after the denitrification treatment, which is a relatively low value, but the denitrification rate after 22 days is 8%.
It was within the range of 3 to 87%, which was a relatively high value. Moreover, the nitrate nitrogen concentration of the treated water after 19 days when the biofilm was stable was within the range of 2.7 to 3.4 mg / l, and both were 10 mg which is the standard value of the nitrate nitrogen concentration in the tap water quality standard. / L or less. Therefore, the series 1 of this example
It has been shown that the raw water treatment equipment of can be used for denitrification of nitrate nitrogen of raw water. In this example, 2 after starting denitrification
The low denitrification rate up to one day is considered to be due to insufficient planting after the start of denitrification treatment.

Example 10 In this example, the denitrification treatment for raw water was performed by using a series 2 raw water treatment apparatus in which 12 rotary blades were radially attached to the rotary shaft, and the rotary speed of the rotary blade was 120 rpm.
It was carried out in a continuous manner. Also in this example, the biofilm of denitrifying bacteria produced and attached to the rotary blade was formed by introducing the water of the first settling tank of the sewage treatment plant together with the sludge species, as in the example of FIG. Also in this example, methanol was used as the hydrogen donor, and the amount of methanol used was 2.5 mg per 1 mg of nitrate nitrogen. In this example, the residence time is 4
The residual nitrate nitrogen concentration of the treated water after the lapse of 0 minutes was analyzed, the residual nitrate nitrogen concentration in the treated water was determined, and the denitrification rate was calculated. The results are shown in Table 9 and FIG. In FIG. 10, this example is shown by a black circle graph.

[Table 9] In this example, the concentration of nitrate nitrogen in the water to be treated which flows into the raw water treatment apparatus of series 2 is 19.2 mg / l to 28.
Although it varied within the range of 5 mg / l, it was denitrified regardless of the concentration of nitrate nitrogen in the water to be treated. After the start of denitrification, the denitrification rate gradually increased, and the denitrification rate became 77% on the 23rd, and the denitrification rate after 24 days when the biofilm became stable was 81 to 86%.
It was within the range of, and was a relatively high value. Moreover, the nitrate nitrogen concentration of the treated water is 3.3 to 3.5 m after 24 days.
It was within the range of g / l and was 10 mg / l or less, which is the standard value of the concentration of nitrate nitrogen in the standard of tap water quality.
Therefore, it is shown that the denitrification treatment apparatus of series 2 of this example can be used for denitrification of nitrate nitrogen in raw water. In this example, the reason why the denitrification rate is relatively low until 23 days after the start of denitrification treatment is considered to be due to insufficient inoculation of denitrification bacteria after the start of denitrification treatment. .

The maximum denitrification rates of the series 1 and series 2 raw water treatment devices in the above example were compared with the rotation speed at a residence time of 40 minutes, and the results are shown in the following Table 10 and FIG.

[Table 10]

In this example, it was found that the denitrification rate had the highest result when the rotation speed was 30 rpm, although it was a slight difference. In each case, the pH value was at the lowest 7.5 at the inlet of the raw water treatment device and at the highest 8.7 at the outlet.

In addition to the above examples, using acrylic resin rods having a diameter of 3 mm, the distance between the rods is 5.0 mm × 5.0 m.
A rotary blade 32 having a mesh structure of m was produced. Also in this rotary blade having a mesh structure, raw water treatment was performed for two series 3 and 4 series. In the series 3 raw water treatment, the mesh-shaped rotary blade 32 is formed to have a size of 15.8 cm in length and 4.2 cm in width, and eight blades are attached to the rotary shaft 7 to have an inner diameter of 10.9 cm.
Then, the raw water treatment apparatus of Series 3 installed in the cylindrical container 2 of the denitrification tank made of acrylic resin having a height of 22 cm was used. On the other hand, in the series 4 raw water treatment, the mesh-shaped rotary blade 32 is formed to have a size of 15.2 cm in length and 4.0 cm in width, and 12 pieces are attached to the rotary shaft 7 to have an inner diameter of 10.9 cm.
Then, the raw water treatment apparatus of series 4 installed in the cylindrical container 2 of the denitrification tank made of acrylic resin having a height of 22 cm was used. Using the raw water treatment apparatuses 1 of Series 3 and Series 4, the relationship between the rotation speed of the rotary blade 32 and the thickness of the diffusion layer of the liquid on the biofilm formed on the rotary blade 32 was determined. The results were almost the same as in Table 1 above. Although the treated water was treated by the series 3 and series 4 raw water treatment apparatuses, the treatment result of the series 3 raw water treatment apparatus was the same as that of the series 1 raw water treatment apparatus. The treatment result of No. 1 was the same as that of the raw water treatment apparatus of Series 2.

[0038]

INDUSTRIAL APPLICABILITY The present invention relates to water containing nitrate nitrogen,
Mixing an organic compound as a hydrogen donor, in this water,
The diffusion layer of the liquid on the biofilm of the rotary blade adheres with a thickness of 100 μm or less. The rotary blade is rotated and brought into contact with the water to decompose and remove the nitrate nitrogen in the water. The resistance can be reduced, and a nitrate nitrogen concentration of 10 mg / l or less, which is the reference value of the nitrate nitrogen concentration in the tap water quality standard, can be achieved in a relatively short time. Moreover,
In the present invention, since the thickness of the liquid diffusion layer on the biofilm of the rotary blade is 100 μm or less and the residence time is short, the denitrification tank for nitrate nitrogen can be downsized and the nitric acid loading capacity can be improved. A large water treatment device can be provided. Moreover, in the present invention, since the rotary blade can be a porous member such as a mesh structure, the rotary blade has a low resistance to water flow, can rotate at high speed, and can form a diffusion layer of a liquid adhered and formed on the biofilm of the rotary blade. The thickness can be reduced, and the denitrification treatment of low-concentration nitrate nitrogen can be performed in a short time, which enables downsizing and high efficiency of the denitrification apparatus. Further, the present invention is capable of removing nitrate nitrogen in a relatively small space, and in an individual treatment facility for nitrate nitrogen-containing wastewater contained in agricultural fertilizer, livestock excrement and other industrial wastewater, etc. It can be used and is useful for solving the problem of nitrate nitrogen in groundwater, lakes and rivers, which has already been found in Europe.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of an embodiment of the present invention.

FIG. 2 is a schematic side sectional view showing an outline of an example of the denitrification tank in the embodiment of the present invention shown in FIG.

FIG. 3 is a schematic plan sectional view showing the outline of the denitrification tank shown in FIG.

4 is a schematic side sectional view showing a schematic structure of the denitrification tank of the embodiment of the present invention shown in FIG. 1 having a different structure from the denitrification tank of FIG.

5 is a schematic plan sectional view showing the outline of the denitrification tank shown in FIG. 4;

FIG. 6 is a diagram showing the relationship between the rotational speed of the rotor and the thickness of the diffusion layer of the liquid adhering and formed on the biofilm of the rotor determined in Example 2;

FIG. 7 is a diagram showing the relationship between the distance from the rotation axis and the thickness of the liquid diffusion layer on the biofilm obtained in Example 3.

FIG. 8 is a diagram showing the relationship between the denitrification rate measured in the denitrification treatment in Examples 5 and 6 and the elapsed days.

FIG. 9 is a diagram showing the relationship between the denitrification rate measured in the denitrification treatment in Examples 7 and 8 and the number of days elapsed.

FIG. 10 is a diagram showing the relationship between the denitrification rate measured in the denitrification treatment in Examples 9 and 10 and the number of days elapsed.

FIG. 11 is a graph showing the relationship between the number of rotations and the denitrification rate at a residence time of 40 minutes in Examples 8 to 10.

[Explanation of symbols]

1 Raw water treatment equipment 2 denitrification tank 3 Raw water supply tank 4 Hydrogen donor-containing solution supply tank 5 Treated water outlet 6 Treated water inlet 7 rotation axis 8 rotary drive 9 Raw water suction pipe 10 Suction pump for raw water supply 11 Suction part of suction pump 10 for supplying raw water 12 Raw water 13 Hydrogen donor suction tube 14 Suction pump for supplying hydrogen donor 15 Suction part of suction pump 14 for supplying hydrogen donor 16 Hydrogen donor-containing solution 17 Discharge port of suction pump 10 for supplying raw water 18 Raw water supply channel 19 mixing valve 20 First liquid introduction path of mixing valve 19 21 Discharge port of suction pump 14 for supplying hydrogen donor 22 Hydrogen donor supply path 23 Inlet passage for second liquid of mixing valve 19 24 Mixed valve discharge port of mixing valve 19 25 Introductory route for treated water 26 Side wall of denitrification tank 2 27 Upper Flange of Side Wall 26 28 Ceiling of denitrification tank 2 29 Bottom wall of denitrification tank 2 30 upper bearing 31 Lower bearing 32 rotors 33 Upper end of rotor 32 34 Water surface of treated water 35 Support member

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Fujimoto             Kiyo, 163-133 Todoro-cho, Nobeoka-shi, Miyazaki             Inside Hon Tetsuko Co., Ltd. (72) Inventor Tatsuo Minamino             Kiyo, 163-133 Todoro-cho, Nobeoka-shi, Miyazaki             Inside Hon Tetsuko Co., Ltd. F-term (reference) 4D003 AA09 AA10 DB01 DB05 DB08                       EA07 EA19 FA02 FA04 FA06                       FA10                 4D040 AA04 AA34 AA55 AA61 BB91                       BB93

Claims (11)

[Claims] 1. A hydrogen donor is mixed with water containing nitrate nitrogen, and a rotary blade having a biofilm attached thereto is rotated at a rotation speed of 10 rpm or more in water mixed with the hydrogen donor. A method for removing nitrate nitrogen in water, which comprises decomposing and removing nitrate nitrogen in water. 2. A hydrogen donor is mixed with water containing nitrate nitrogen, and the rotary blade having a biofilm is rotated at a rotation speed of 10 rpm or more in water mixed with the hydrogen donor,
A method for removing nitrate nitrogen in water, which comprises decomposing and removing nitrate nitrogen in water by setting a thickness of a liquid diffusion layer formed on a biofilm to 100 μm or less. 3. The method for removing nitrate nitrogen in water according to claim 1 or 2, wherein the number of revolutions in water of the rotor to which the biofilm is attached is 10 to 200 rpm. 4. The method for removing nitrate nitrogen in water according to claim 1, 2 or 3, wherein the thickness of the liquid diffusion layer on the biofilm of the rotor is 60 μm or less. 5. A rotary shaft is inserted and provided in a tank having a treated water inlet at a lower portion and a treated water outlet at an upper portion, and the rotary shaft has one or more blade members. Is provided so as to extend in the radial direction, and the upper end of the blade member is located below the opening of the treated water discharge port. 6. A rotary shaft is inserted into a tank having a treated water inlet in the lower portion and a treated water outlet in the upper portion,
A blade support member is radially provided on the rotating shaft, and one or more blade members are provided concentrically with respect to the rotating shaft on the blade support member. An apparatus for removing nitrate nitrogen in water, which is provided below the opening of the treated water outlet. 7. The apparatus for removing nitrate nitrogen in water according to claim 5, wherein the rotary shaft is inserted vertically or substantially vertically in the tank. 8. The apparatus for removing nitrate nitrogen in water according to claim 5, wherein the rotary shaft is inserted horizontally or substantially horizontally in the tank. 9. The apparatus for removing nitrate nitrogen in water according to claim 5 or 6, wherein the blade member is formed of a perforated plate member or a net member. 10. The apparatus for removing nitrate nitrogen in water according to claim 5, wherein the length of the blade member from the rotation axis is 0.1 to 2 m. 11. The blade support member has a length of 0.
7. The apparatus for removing nitrate nitrogen in water according to claim 6, which has a length of 1 to 2 m.