JP2022191066A - Water treatment method and water treatment apparatus - Google Patents

Abstract

To provide a water treatment method and a water treatment apparatus in which clogging by SS during water treatment can easily be suppressed and NH4-N can satisfactorily be removed from water to be treated.SOLUTION: The water treatment method is a water treatment method for removing one or more of organic matter and ammonia-nitrogen in water to be treated under an aerobic condition, and includes passing water to be treated through one or more reaction tanks packed with a carrier having micropore in a direction selected from downward flow and upward flow, and in which, during water flowing, the reaction tank has a high-density region and a low-density region in the distribution of the carrier, and the high-density region is located at the bottom of the reaction tank.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a water treatment method and a water treatment apparatus for biologically treating organic substances and ammonia nitrogen (hereinafter also referred to as "NH ₄ -N") in water to be treated.

As a water treatment method using river water, lake water, groundwater, etc. as a water source, biological treatment, RO membrane, activated carbon, sand filtration, coagulation sedimentation, etc. are combined to reduce turbidity, organic matter, NH ₄ -N in the water to be treated. and finally removing residual NH ₄ —N in the water to be treated by adding hypochlorous acid.

If the amount of NH ₄ —N remaining in the final stage is large, the amount of hypochlorous acid used will increase, resulting in increased running costs and a chlorine-derived odor remaining in the treated water. Therefore, removing NH ₄ —N as much as possible in the pretreatment leads to a reduction in running costs and an improvement in treated water quality.

Biofiltration is one of the biological treatment methods used for pretreatment. Carriers used in biofiltration include activated carbon, anthracite, sponges, gels, plastics, and the like. The water treatment method using a carrier has stable treatment properties and is easy to operate.

However, in biological filtration, when the water to be treated continues to flow downward or upward, suspended solids contained in the water to be treated (hereinafter also referred to as "SS" (SS: Suspended Solids)) Clogging occurs. In order to eliminate such SS clogging, it is generally necessary to periodically interrupt the water treatment and backwash the reactor.

As a water treatment method that can eliminate the clogging of SS, for example, Patent Document 1 discloses a three-dimensional structure made of a material that has a specific gravity similar to that of water and has the property of floating by upward water flow and/or adhesion of air bubbles. A biofiltration method with an upflow biofiltration device using reticulated particulate matter as a carrier is described. Specifically, in the biological filtration method described in Patent Document 1, a fixed bed of carriers is formed in the upper part of the biological filtration device, and a fluidized bed of carriers is formed in the lower part. The raw water is biologically treated by passing the contained gas in an upflow.

Various other methods are also known as methods of biological filtration.

For example, Patent Literature 2 describes a biological contact filter material made of chemical fibers as a raw material, which can increase the porosity of the filter material structure after molding and increase the filtration speed. Specifically, the biological contact filter material described in Patent Document 2 is a nonwoven fabric in which raw material chemical fibers containing chemical fibers that develop crimps by heat treatment and heat-fusible chemical fibers are fused together. The nonwoven fabric is twisted and wound so that it overlaps a plurality of times, and the overlapped nonwoven fabrics are fused to each other to form a substantially cylindrical shape.

Furthermore, for example, Patent Document 3 describes a water treatment method using a carrier capable of obtaining treated water with stable treatability and excellent quality. Specifically, in Patent Document 3, the water content of the carrier, the pore size of the communicating pores of the carrier, the concentration of organic matter and ammonia nitrogen in the water to be treated, and the retention time of the water to be treated in the reaction tank A water treatment method is described in which the range is defined and the water to be treated is passed through a reaction tank to take the form of complete mixing and treatment under aerobic conditions.

Japanese Patent No. 2584386 Japanese Patent No. 6090991 WO2020/004662

In the biological filtration method described in Patent Document 1, the carrier in the fluidized bed portion configured in the lower portion of the treatment tank is in a state of being freely fluidized by the gas-liquid mixed phase flow of raw water and oxygen-containing gas. Therefore, organic matter in the raw water is efficiently removed by the microorganisms immobilized on the carrier in the fluidized bed portion, and then the raw water is sent to the fixed bed portion. Therefore, in the fixed bed portion, the growth of microorganisms retained on the carrier is moderately suppressed, and the progress of clogging (SS clogging) in the fixed bed can be suppressed. In addition, in the biological filtration method described in Patent Document 1, it is essential to pass the raw water in an upward flow.

However, it would be preferable if clogging of the SS could be eliminated by a simpler method. Specifically, even when water is passed in either direction of downward flow or upward flow, or when water is passed in a combination of both directions of downward flow and upward flow, It would be preferable if there was a novel and simple biological filtration method capable of suppressing the progress of clogging of the SS and capable of stable continuous operation.

Furthermore, according to conventional water treatment methods related to biological filtration, there is a problem that NH ₄ -N cannot be removed to a sufficiently low concentration when the NH ₄ -N concentration in the water to be treated is as high as 10 mg / L. do.

For example, the biological contact filter material described in Patent Document 2 is in a state in which chemical fibers are twisted and wound, and nonwoven fabrics are fused together. Therefore, it is difficult to appropriately form minute voids inside the filter medium, and there is a problem that large protozoa and the like other than bacteria easily enter the voids. As a result, even with the method using the biologically contacting filter material described in Patent Document ₂ , it is difficult to say that the nitrification reaction is favorably promoted. cannot remove NH4 _- N to sufficiently low concentrations.

Furthermore, when using a treatment tank as shown in FIG. 1 of Patent Document 3, that is, the water flow direction is set to the horizontal direction, the water to be treated is stirred inside the reaction tank to disperse the carriers substantially uniformly and flow. It is possible to reduce the NH ₄ —N concentration in the water to be treated to a certain level when the nitrification reaction is caused by reducing the concentration of NH 4 —N. However, even with this method, the inside of the tank is completely mixed. Therefore, when the NH ₄ —N concentration in the water to be treated is as high as about 10 mg/L, NH ₄ — is efficiently removed until the concentration becomes sufficiently low. It is hard to say that N is removable.

Accordingly, the present invention provides a water treatment method and a water treatment apparatus capable of easily suppressing SS clogging during water treatment and satisfactorily removing NH ₄ —N from water to be treated. intended to

The present inventors arrived at the present invention as a result of intensive studies to solve the above problems. That is, the present invention includes the following preferred embodiments.

A water treatment method according to a first aspect of the present invention is a water treatment method for removing one or more of organic matter and ammonia nitrogen in water to be treated under aerobic conditions,
Flowing water to be treated in one or more reaction tanks filled with carriers having micropores in a direction selected from downward flow and upward flow,
During water passage, the reaction vessel has a high-density region and a low-density region in the carrier distribution, and the high-density region is located at the bottom of the reaction vessel.

In the water treatment method described above, it is preferred that the carrier in the low density region is in motion.

In the water treatment method described above, the pore size of the fine pores is more preferably 0.1 μm or more and less than 1000 μm.

In the water treatment method described above, it is more preferable that 20% or more of the carriers in the reaction tank are moving.

In the water treatment method described above, it is preferable that the carriers are in a fluidized state in which the inside of the reaction vessel is not completely mixed. Preferably, among the moving carriers, carriers moving at a speed of 2.5 cm/sec or more represent less than 50% of the total amount of the moving carriers.

In the water treatment method described above, it is more preferable that the filling rate of the carrier in 10% or more of the total amount of carrier in the reaction tank is 80% or more in apparent volume. Specifically, it is more preferable that the filling rate of the carrier in 40% of the total amount of carrier in the reaction vessel is 90% or more in terms of apparent volume.

In the water treatment method described above, it is particularly preferable that the carrier has a specific gravity of 1.00 to 1.20 when the carrier supports the bacteria.

In the water treatment method described above, the carrier is more preferably made of polyvinyl alcohol.

In the water treatment method described above, it is more preferable that the carrier has a specific surface area of 50000 m ² /m ³ or more.

In the water treatment method described above, the reaction tank has a high-density region and a low-density region in the distribution of the carriers when the water is passed through, and at least a portion of the moving carriers is in the reaction tank. It is particularly preferable to move while moving the positions of the low density region and the high density region within.

In the water treatment method described above, it is preferable that the entire amount of the carrier in the reaction tank is moving when the water is passed.

In the water treatment method described above, the entire amount of the carriers in the reaction tank is moving when water is passed through, the reaction tank has a high-density region and a low-density region in the distribution of the carriers, and More preferably, at least a portion of the moving carriers moves while moving between the positions of the low density region and the high density region within the reaction vessel.

A water treatment apparatus according to a second aspect of the present invention is a water treatment apparatus that removes one or more of organic matter and ammonia nitrogen in water to be treated under aerobic conditions,
one or more reaction vessels filled with a carrier having micropores;
a to-be-treated water supply unit and a treated water discharge unit for causing the water to be treated to flow in the one or more reaction tanks in a direction selected from a downward flow and an upward flow,
During water passage, the reaction vessel has a high-density region and a low-density region in the distribution of the carrier, and the high-density region is located at the bottom of the reaction vessel.

In the aforementioned water treatment device, it is preferred that the carrier in the low density region is in motion.

In the water treatment device described above, it is more preferable that the fine pores have a pore size of 0.1 μm or more and less than 1000 μm.

In the water treatment apparatus described above, it is more preferable that 20% or more of the carriers in the reaction tank are moving.

In the water treatment apparatus described above, it is preferable that the carriers are in a fluidized state in which the inside of the reaction vessel is not completely mixed. Preferably, among the moving carriers, carriers moving at a speed of 2.5 cm/sec or more represent less than 50% of the total amount of the moving carriers.

In the water treatment apparatus described above, it is more preferable that the filling rate of the carrier in 10% or more of the total amount of carrier in the reaction tank is 80% or more in apparent volume. Specifically, it is more preferable that the filling rate of the carrier in 40% of the total amount of carrier in the reaction vessel is 90% or more in terms of apparent volume.

In the water treatment apparatus described above, it is particularly preferable that the carrier has a specific gravity of 1.00 to 1.20 in a state in which the bacteria are supported.

In the water treatment device described above, the carrier is more preferably made of polyvinyl alcohol.

In the water treatment device described above, it is more preferable that the carrier has a specific surface area of 50000 m ² /m ³ or more.

The water treatment apparatus as described above, wherein the reaction vessel has a high density region and a low density region in the carrier distribution, and at least a portion of the moving carrier is in the low density region within the reaction vessel. It is particularly preferred to move while moving the position of the area and said high density area.

In the water treatment apparatus described above, it is preferable that the entire amount of the carrier in the reaction tank is moving when the water is passed.

In the water treatment apparatus described above, the entire amount of the carriers in the reaction tank is moving during water flow, the reaction tank has a high-density region and a low-density region in the distribution of the carriers, and More preferably, at least a portion of the moving carriers moves while moving between the positions of the low density region and the high density region within the reaction vessel.

According to the present invention, there is provided a water treatment method and a water treatment apparatus capable of easily suppressing SS clogging during water treatment and satisfactorily removing NH ₄ —N from water to be treated. can do.

FIG. 1 is a diagram showing an example of the configuration of a water treatment apparatus used in the water treatment method according to this embodiment. FIG. 2 is a diagram showing Modification 1 of the configuration of the water treatment apparatus shown in FIG. FIG. 3 is a diagram showing Modification 2 of the configuration of the water treatment apparatus shown in FIG. FIG. 4 is a diagram showing Modification 3 of the configuration of the water treatment apparatus shown in FIG. FIG. 5 is a diagram showing Modification 4 of the configuration of the water treatment apparatus shown in FIG. 6 is a graph showing the NH ₄ —N concentration in the water to be treated and the NH ₄ —N concentration in the discharged treated water in Example 1 along with the number of days of use of the water treatment apparatus. FIG. 7 is a graph showing the NH ₄ —N concentration in the water to be treated and the NH ₄ —N concentration in the discharged treated water in Comparative Example 3 along with the number of days of use of the water treatment apparatus.

The present inventors have conducted various studies on a water treatment method and a water treatment apparatus capable of suppressing SS clogging during water treatment and satisfactorily removing NH ₄ —N from the water to be treated. repeated. Then, the present invention was completed by paying attention to the behavior of the carrier in the reaction tank during water treatment and the flow direction of the water to be treated. Specifically, the water to be treated is allowed to pass through the reaction tank in a downward flow or an upward flow, or a combination of downward and upward flows using two or more reaction tanks. And, when water is passed, it has a high-density region and a low-density region in the distribution of the carrier, and the high-density region is located in the lower part of the reaction tank, so clogging of the SS during water treatment is easy. NH ₄ —N in the water to be treated can be satisfactorily removed.

Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the gist of the present invention.

(To-be-treated water containing organic matter and NH4 _- N)
As used herein, "water to be treated" is not particularly limited as long as it is a liquid containing one or more of organic substances and NH4 _- N. Preferably, the water to be treated is one or more of river water, lake water and groundwater, which have relatively low concentrations of organic matter and NH4 _- N. By using any of these raw waters as the water to be treated, SS clogging during water treatment can be more suitably suppressed, and NH ₄ —N in the water to be treated can be removed more satisfactorily. can do. As a result, the treated water can be used as tap water.

(Configuration of water treatment equipment)
First, an example of the configuration of a water treatment apparatus used in a water treatment method in an embodiment described later will be described with reference to FIG. As shown in FIG. 1 , the water treatment apparatus 1 mainly includes a reaction tank 2 , a carrier 3 , a water supply pipe 4 to be treated, a treated water discharge pipe 5 and an air supply pipe 6 . Generally, in the water treatment apparatus 1, first, water to be treated (raw water) containing bacteria is allowed to flow for a certain period of time, so that a certain amount of bacteria is supported on the carrier 3 (after the apparatus is started up). , water treatment is carried out. Alternatively, a carrier 3 on which bacteria are previously carried may be provided. The water treatment device 1 is a device that decomposes organic matter in the water to be treated and/or nitrifies and removes NH ₄ —N in the water to be treated.

Although the reaction tank 2 is not particularly limited, for example, a tank having a shape such as a cylinder or a rectangular parallelepiped is filled with the carrier 3 . The size of the reaction vessel 2 is not particularly limited. can use a cylindrical column of 1000 mm or more and 7000 mm or less, more preferably 2000 mm or more and 5900 mm or less. Carrier 3 will be described later in detail. An inlet for the water to be treated is provided in the upper part of the reaction tank 2 and is connected to a water supply pipe 4 for supplying the water to be treated into the reaction tank 2 . A treated water discharge port is provided at the bottom of the reaction tank 2 and connected to a treated water discharge pipe 5 through which the treated water discharged from the reaction tank 2 flows.

The water treatment apparatus 1 is provided with an air inlet at the bottom of the reaction tank 2 and is connected to an air supply pipe 6 for supplying air into the reaction tank 2 . That is, the treated water in the reaction tank 2 in FIG. 1 is aerated. By aerating the treated water, decomposition of organic matter and nitrification of NH ₄ —N in the water to be treated can be efficiently advanced. The specific method of aeration is not particularly limited, and not only the method of providing an air inlet at the bottom of the reaction tank 2, but also the use of an air diffuser connected to the air supply pipe 6 in the lower region of the reaction tank 2, for example. may be provided. Alternatively, the water to be treated may be aerated in advance and then supplied into the reaction tank 2 .

Thus, in the water treatment apparatus 1 shown in FIG. 1, the water to be treated is supplied to the reaction tank 2 through the water to be treated supply pipe 4 (the water to be treated supply portion), and the treated water is discharged through the treated water discharge pipe. 5 (treated water discharge part) to allow the water to be treated to flow downward (hereinafter also referred to as "downward flow type") into the reaction tank 2 filled with the carrier 3. be able to.

In the example shown in FIG. 1, the structure of the water treatment apparatus 1 in which the treated water is aerated is adopted, but the treated water in the reaction tank 2 may not be aerated. FIG. 2 shows Modified Example 1 of the structure of the water treatment device 1 shown in FIG. 1 as a structure of a non-aerated device. In this embodiment, it is necessary to have a high-density region and a low-density region in the carrier distribution when water is passed through. Therefore, in the case of no aeration, the water treatment apparatus must have a structure in which water flows upward from the bottom to the top of the reaction tank (hereinafter also referred to as "upward flow type").

When the treated water is aerated, in the example shown in FIG. It may be an upward flow type structure in which water flows upward from. FIG. 3 shows Modification 2 of the configuration of the water treatment device 1 shown in FIG. As shown in FIG. 3, in the case of the upward flow type, a water supply pipe 4 to be treated is connected to the lower part of the reaction tank 2 and a treated water discharge pipe 5 is connected to the upper part of the reaction tank 3 . By causing the water to be treated to flow downward or upward in this manner, a gradient of the NH ₄ —N concentration of the water to be treated along the direction of water flow can be formed in the reaction tank. Therefore, according to the water treatment apparatus of the present embodiment, compared to the case where the water flow direction is set to the horizontal direction, for example, the water to be treated is stirred inside the reaction tank, and the carriers are dispersed and flowed substantially uniformly (for example, patent Reference 3), NH4 _- N can be removed well to low concentrations.

Alternatively, in a modification of the water treatment apparatus in the present embodiment, the water treatment apparatus includes two or more reaction tanks, and the water to be treated in each reaction tank is in a direction selected from downward flow and upward flow. You can let water pass through. In other words, water treatment may be performed in any number of reactors with downward flow and any number of reactors with upward flow.

(Carrier)
Next, the carrier provided in the water treatment apparatus described above will be described in detail.

The carrier can carry bacteria capable of decomposing organic matter in the water to be treated and/or bacteria capable of removing NH ₄ —N in the water to be treated by nitrification (nitrifying bacteria), And it is not particularly limited as long as it has micropores.

The micropores of the carrier preferably have a continuous pore structure. As used herein, the term "interconnected pore structure" refers to a structure that constitutes a part of a porous body, in which a plurality of fine pores are formed from the surface of the carrier toward the inside, and the plurality of pores are It means a structure in which the pores do not exist independently, but communicate (connect) with each other. According to this open-pore structure, water can permeate the interior of the carrier by allowing water to pass through all the fine pores formed in the carrier.

The pore size of the micropores of the carrier, preferably the pore size of the continuous pores, is preferably less than 1000 µm. The pore size of the micropores or continuous pores of the carrier is preferably 500 μm or less, more preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. By using a carrier in which fine pores or continuous pores with a pore size of less than 1000 μm are formed, the specific surface area of the carrier can be increased, and large organisms other than bacteria can enter and occupy the inner surface of the carrier. can be prevented. On the other hand, a biological contact filter material (see, for example, Patent Document 2) formed in a wound state using a granular carrier such as anthracite or a chemical fiber conventionally used in biological filtration as a raw material has such a size. Since it is difficult to form such micropores, the inner surface of the carrier is occupied by large protists other than bacteria. Moreover, the pore size of the micropores or continuous pores of the carrier is preferably 0.1 μm or more. By setting the pore diameter to 0.1 μm or more, bacteria can stably live in the pores.

In the present specification, the pore size of the micropores or continuous pores of the carrier of 0.1 μm or more or less than 1000 μm means that 50% or more of the micropores formed in the carrier have a pore diameter of 0.1 μm or more or less than 1000 μm. means At this time, the pore diameter is the diameter of the pores observed when the cross section of the carrier is observed with an electron microscope. In this specification, the pore size can be specifically measured by the following method. A cross section of the carrier is observed with an electron microscope to obtain an electron microscope image. Ten straight lines are drawn vertically at equal intervals on the obtained image, and ten straight lines are drawn horizontally at equal intervals. Then, 100 holes existing at the intersection of the straight lines are selected, and the diameter of each hole is measured. At this time, if no hole exists at the intersection, the hole closest to the intersection is selected. This measurement is made on a scaled image where the hole does not straddle the two intersections. As a result, a range of 100 hole diameters can be determined. When the hole is not a perfect circle, the equivalent circle diameter, that is, the diameter of a perfect circle having the same area as the cross-sectional area of the hole, corresponds to the hole diameter.

The specific surface area of the carrier is preferably 50000 m ² /m ³ or more. By setting the specific surface area of the carrier to 50000 m ² /m ³ or more, SS clogging during water treatment can be more easily suppressed, and NH ₄ —N in the water to be treated can be removed more satisfactorily. be able to. Specifically, when the carrier has a specific surface area of 50000 m ² /m ³ or more, a large amount of bacteria can be efficiently supported inside the carrier. As a result, it is possible to suppress the deposition of a thick biofilm on the surface of the carrier, to easily and reliably suppress clogging of the SS, and to improve the organic matter and/or NH ₄ —N. can be removed. On the other hand, since a granular carrier such as anthracite, which has been generally used in conventional biological filtration, cannot possess such a large specific surface area, bacteria can stably live in the pores of the carrier. I can't let you.

In this specification, the specific surface area of the carrier is a numerical value measured by the krypton gas adsorption method, as in the examples described later.

The specific surface area of the carrier is more preferably 60,000 m ² /m ³ or more, still more preferably 70,000 m ² /m ³ or more, and particularly preferably 80,000 m ² /m ³ or more. Also, the specific surface area of the carrier is preferably 2,000,000 m ² /m ³ or less. By setting the specific surface area of the carrier to 2,000,000 m ² /m ³ or less, the internal structure of the carrier becomes dense, limiting the habitat area for microorganisms and preventing the effective use of the interior.

As the carrier, for example, a carrier made of known constituent materials such as organic polymers and inorganic compounds can be used. Examples of organic polymers include polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyethylene, polypropylene, polystyrene, polyurethane, foams obtained by mixing these resins with a foaming agent, and cellulose. Examples of inorganic compounds include commercially available filter media, adsorbents, granular diatomaceous earth, granular zeolite, granular activated carbon, and powdered activated carbon.

Among these, the carrier is preferably a polymer gel carrier from the viewpoint of high affinity with bacteria and excellent bacterial habitability, and a gel carrier made of polyvinyl alcohol (hereinafter referred to as " It is more preferable to be a "PVA gel carrier"). The PVA gel carrier may be an acetalized PVA gel carrier. By using a PVA gel carrier as the carrier, it is easy to control the specific surface area of the carrier so that it becomes large, so clogging of the SS can be suppressed easily and more satisfactorily.

The water content of the carrier is preferably 50% or more, more preferably 70% or more, and still more preferably 85% or more in terms of mass. By setting the water content of the carrier to 50% or more, the growth environment of bacteria can be improved, and the bacteria can be easily propagated and supported. Also, the water content of the carrier is preferably 98% or less, more preferably 96% or less. By setting the moisture content of the carrier to 98% or less, damage to the carrier can be prevented, and there is almost no need to add additional carrier, making it possible to operate the apparatus for a long period of time.

As used herein, the moisture content of the carrier is the ratio of the weight of water to the weight of the carrier in the hydrated state. The weight of water can be calculated from the difference between the weight of the carrier in the hydrated state and the weight of the carrier when the carrier in the hydrated state is completely dried.

The shape of the carrier is not particularly limited as long as it can be filled in the reaction tank and does not affect the effects of the water treatment method and water treatment apparatus of the present embodiment. Examples of the shape of the carrier include spherical, elliptical, cubic, rectangular parallelepiped, and columnar shapes. Among these, the shape of the carrier is preferably spherical from the viewpoint of improving contact efficiency with bacteria.

The equivalent sphere diameter of the carrier is preferably 0.5 mm or more and 20 mm or less. By setting the equivalent sphere diameter to 0.5 mm or more, the carrier can be prevented from flowing out of the reaction vessel. Further, even when a screen is installed to prevent the outflow of the carrier as in the modified example described later, by setting the equivalent sphere diameter to 0.5 mm or more, the mesh size of the screen is made too small, causing clogging. can be prevented. By setting the equivalent sphere diameter to 20 mm or less, it is possible to easily fill the reaction tank with the carrier, and to prevent a decrease in the fluidity of the carrier when the carrier is made to flow.

The equivalent sphere diameter of the carrier is more preferably 1 mm or more, and still more preferably 2 mm or more. Further, the equivalent sphere diameter of the carrier is more preferably 15 mm or less, still more preferably 10 mm or less. As used herein, the equivalent sphere diameter of the carrier means the diameter of a sphere having a volume equal to the volume of the carrier.

The specific gravity of the carrier in the state of carrying bacteria is the same as or slightly larger than that of water, and when the water to be treated is supplied to the reaction tank in an upward or downward flow, the carrier is stable without flowing out or clogging. It is not particularly limited as long as water treatment is possible. In addition, the specific gravity of the carrier in the state of supporting the bacteria is preferably a specific gravity that facilitates formation of desired carrier distribution and carrier behavior as described later. Specifically, the carrier preferably has a specific gravity of 1.00 to 1.20 when the carrier supports bacteria. By setting the specific gravity to such a range that is the same as or slightly larger than that of water, it is possible to not only pass water in the direction of upward flow (see, for example, Patent Document 1), but also to flow in either direction of downward flow or upward flow. Continuous operation can be stably performed even when water is passed through at At the same time, according to this range of specific gravity, the flow of the carrier can be easily controlled by passing water and/or aeration, and the distribution of the carrier and the behavior of the carrier, which will be described later, can be easily adjusted. Conventionally, a carrier with a specific gravity close to that of water is used to improve fluidity and is used in a complete mixing tank. By using such a carrier, it is possible to treat the water to be treated in a fluid state of an extrusion flow while each carrier is in a state of being able to flow, and the NH ₄ —N in the water to be treated can be increased. It is possible to efficiently remove to a low concentration and suppress SS clogging. In addition, backwashing is facilitated because the flow of the carrier can be easily controlled.

As used herein, the term "the specific gravity of the carrier in a state of supporting bacteria" means that water treatment is continuously performed after the start of use of the water treatment apparatus of the present embodiment or the start of the water treatment method of the present embodiment. , means the specific gravity of the carrier when it already stably carries a substantially constant amount of bacteria. Hereinafter, it is simply referred to as "the specific gravity of the carrier".

The ratio (filling ratio) of the apparent volume of the carrier filled in the reaction vessel to the total volume of the reaction vessel can be appropriately determined according to the type of water to be treated, the type of carrier, the size of the carrier, and the like. The filling rate is, for example, preferably 10% or more and 98% or less in terms of apparent volume. By setting the filling rate to 10% or more, the decomposition reaction and nitrification reaction of organic matter in the reaction tank can be efficiently advanced. By setting the filling rate to 98% or less, when fluidity is required for the carrier, the fluidity can be ensured, and a decrease in the efficiency of decomposition reaction and/or nitrification reaction of organic matter can be prevented. In this specification, the apparent volume refers to the total volume including the volume of the carrier itself and the gap between the carriers. In addition, in the present specification, the filling rate refers to the ratio of the apparent volume of the carrier filled in the reaction vessel to the total volume of the reaction vessel.

The filling rate is more preferably 50% or more, still more preferably 60% or more.

(Distribution of Carrier in Reaction Tank and Behavior of Carrier)
In the water treatment method or the water treatment apparatus of the present embodiment, the reaction tank has a high-density region and a low-density region in the carrier distribution during water flow, and the high-density region is located at the bottom of the reaction tank. ing. In addition, it is preferable that the carrier in the low-density region is moving during water passage. In the present specification, the term "when water is passed" means when water treatment is possible after the start of use of the water treatment apparatus in this embodiment or after the start of the water treatment method in this embodiment, preferably stable It means the time when water treatment is possible (that is, the time of water treatment after completion of start-up).

As used herein, the term "high-density region in the carrier distribution" refers to the carrier density when all the carriers are evenly dispersed in the region in the reaction vessel in which all the packed carriers are dispersed. It means a region in which carriers are dispersed at a higher density. On the other hand, as used herein, the term “low-density region in the carrier distribution” refers to the carrier density when all the carriers are evenly dispersed in the region in the reaction vessel in which all the packed carriers are dispersed. , means a region in which the carriers are dispersed at a lower density. Clogging due to SS can be more reliably prevented by having such a carrier distribution in the reaction tank when water is passed through, and preferably by moving (preferably flowing) the carrier in the low-density region. . In addition, organic matter and/or NH ₄ —N in the water to be treated can be removed more satisfactorily by controlling the flow state of the carrier in the reaction tank to create a state of extrusion flow. Furthermore, since the low-density region is located at the bottom of the reaction tank, if the direction of water flow is upward flow and a screen for carrier separation is installed at the top, the screen will be clogged with the carrier. can be prevented. Further, when the water flow direction is downward flow, clogging of the SS can be suppressed even when a biofilm is formed on the surface of the carrier by positioning the low-density region in the upper part of the reaction vessel.

For example, using the water treatment apparatus 1 shown in FIG. The carrier 3 is dispersed at a higher density than the density, and is the region indicated by V2 located at the bottom of the reaction vessel. On the other hand, in the low-density region, the carriers 3 are dispersed at a lower density than the density of the carriers 3 when all the carriers 3 are evenly dispersed in the region obtained by adding the region indicated by V1 and the region indicated by V2. This is the region indicated by V1. Additionally, the carrier 3 in the region indicated by V1 is preferably in motion.

Whether or not the reaction tank has a high-density region and a low-density region in the carrier distribution during water flow can be determined by inserting a water sampling bottle into the reaction tank when the operation stabilizes after the start of operation, and examining the carrier. can be determined by collecting the water and the carrier in the region in the reaction vessel where is dispersed and confirming the ratio of the amount of the carrier to the obtained water. Furthermore, whether or not the carrier is flowing in the low-density region can be determined by visually observing from the outside, observing the internal state by inserting an underwater camera into the reaction tank, and/or measuring the average moving distance of the carrier. It can be determined by a method of measuring and converting the measured moving distance of the carrier into velocity.

Furthermore, in the water treatment method or water treatment apparatus of the present embodiment, it is preferable that 20% or more of the total amount of carriers in the reaction tank is moving. In the present specification, "the carrier is moving" means "the carrier is flowing", "the carrier is rocking", and "the carrier changes its vertical and horizontal positions and the carrier is moving." are moving", "the stacked carriers are moving (as the stacked carriers expand, gaps are created between the carriers, and the range of motion of each carrier increases)", and "the carriers are It includes all concepts of "moving at a speed of 1 mm/s or more". In other words, "the carrier is in motion" generally includes behavior of the carrier other than the state in which the carrier is stationary. When 20% or more of the total amount of carriers in the reaction tank exhibits such behavior when water is passed through, SS clogging during water treatment can be easily and reliably suppressed.

Further, "20% or more of the total amount of carriers are moving" means that a specific 20% or more of the total amount of carriers is always moving (in other words, less than 80% of the specific This includes both the case where the carriers are always stationary) and the case where an arbitrarily selected 20% or more of the carriers out of the total amount of carriers are always in motion. Specifically, in the latter case, for example, the moving carrier stops due to a change in position in the reaction vessel (e.g., the height in the reaction vessel), while the stationary carrier moves inside the reaction vessel. This includes the case of movement due to a change in the position in (for example, the height in the reaction vessel). In other words, at least a portion of the moving carriers may move while changing the height position in the reaction vessel. The carriers are optionally stationary or moving while changing their position in the reaction vessel to form a lawn that can suitably nitrify a wide range of NH4 _- N concentrations in one carrier. In other words, if the positions of the carriers in the reaction vessel are not changed, the entire carrier will form a bacterial lawn. In that case, there is a possibility that the processability may become unstable when the distribution state of the carrier in the reaction tank changes. However, when a suitable bacterial lawn is formed on one carrier, stable treatment is possible even when the carrier distribution state in the reaction vessel changes.

For example, in the water treatment device 1 shown in FIG. 1, the carrier 3 in the region indicated by V1 is moving, specifically flowing. In addition, the carrier 3 in the region indicated by V2 is "the carrier is swinging", "the carrier is moving by changing the vertical and horizontal positions of the filled carrier", and "(the stacked carrier is Either of "the stacked carriers are moving" and "the carriers are moving at a speed of 1 mm/sec or more" (due to expansion, creating a gap between the carriers and expanding the range of motion of each carrier). It may be in that state, or it may be in a state where the carrier 3 is stationary. Furthermore, in the water treatment apparatus 1 shown in FIG. 1, the carrier 3 present in the region indicated by V1 and the carrier 3 present in the region indicated by V2 are exchanged with each other in the reaction tank 2 during water passage. good too.

The water treatment apparatus 1 shown in FIG. 2 is also substantially the same as the water treatment apparatus 1 shown in FIG. In the water treatment device 1 shown in FIG. 2, the carrier 3 in the region indicated by V1 is moving, specifically flowing. In addition, the carrier 3 in the region indicated by V2 is "the carrier is swinging", "the carrier is moving by changing the vertical and horizontal positions of the filled carrier", and "(the stacked carrier is Either of "the stacked carriers are moving" and "the carriers are moving at a speed of 1 mm/sec or more" (due to expansion, creating a gap between the carriers and expanding the range of motion of each carrier). It may be in that state, or it may be in a state where the carrier 3 is stationary. Further, the positions of the carriers 3 present in the region indicated by V1 and the carriers 3 present in the region indicated by V2 may be exchanged in the reaction vessel 2 during the passage of water.

A portion of the carrier may be stationary, but preferably at least 20% of the total carrier is in motion.

In addition, it is preferable that the carrier is in a fluid state in which the inside of the reaction vessel is not completely mixed when water is passed through. Of the moving carriers, the carriers moving at a speed of 2.5 cm/sec or more preferably account for less than 50%, more preferably less than 40%, of the total amount of the moving carriers. .

In addition, it is more preferable that 25% or more of the total amount of carriers in the reaction tank is moving during water passage, and 30% or more of the total amount of carriers in the reaction tank is moving. More preferred. Furthermore, it is particularly preferable that the entire amount of the carrier in the reaction vessel is in motion during the passage of water.

It should be noted that whether or not the conditions for the behavior of the carrier in the reaction vessel are satisfied during water flow can be determined by setting the same conditions using a transparent column and starting the operation, and when the operation stabilizes. A method of visually observing from the outside, a method of observing the internal state by placing an underwater camera in the reaction tank, and/or measuring the average moving distance of the carrier and converting the measured moving distance of the carrier into the velocity. can be determined by the method. The ratio of the carrier in motion was determined by setting the same conditions using a transparent column. It can be obtained by calculating the ratio to the total amount of the carrier in the tank.

In addition, it is preferable that the conditions for the distribution of the carrier and/or the conditions for the behavior of the carrier as described below are satisfied in the reaction tank when the water is passed.

It is preferable that the apparent volume of the carrier in 10% or more of the total amount of the carrier in the reaction tank when water is passed is 80% or more. Further, it is more preferable that the filling rate of the carrier in 20% or more of the total amount of carrier in the reaction vessel is 80% or more in terms of apparent volume. By having such a carrier distribution in the reaction tank when water is passed through, organic substances and/or NH ₄ —N in the water to be treated can be removed more satisfactorily.

For example, when explaining using the water treatment apparatus 1 shown in FIG. % or more.

In addition, when water is passed through the reactor, the filling rate of the carrier in 15% or more of the total carrier amount in the reaction tank is more preferably 80% or more in apparent volume, and the carrier in 20% or more of the total carrier amount in the reaction tank. is more preferably 80% or more in terms of apparent volume.

Whether or not the carrier distribution conditions are satisfied in the reaction tank when water is passed through is checked by inserting a water sampling bottle into the reaction tank when the operation is stabilized after the start of operation, and mixing the water and the carrier. It can be determined by sampling and confirming the ratio of the carrier amount to the obtained water.

In addition, when water is passed through, the reaction tank has a high-density region and a low-density region in the carrier distribution, and at least a part of the moving carriers is a low-density region and a high-density region in the reaction tank. It is particularly preferable to move while moving the position of In this case, it is more preferable that the entire carrier in the reaction vessel is in motion.

For example, using the water treatment device 1 shown in FIG. 1, at least one or more of the carriers 3 move between a position included in the low density region V1 and a position included in the high density region V2. It is particularly preferable to move while moving. The reaction vessel is partitioned into a fixed bed portion and a fluidized bed portion by moving the carrier while moving in a height and a predetermined carrier density region in the reaction vessel, and the carrier moves only in the fluidized bed portion. In comparison (see, for example, Patent Document 1), it is believed that NH ₄ —N in the water to be treated can be removed better and more efficiently. This is assumed to be due to the formation of bacterial lawns in the carrier that can suitably nitrify a wide range of NH ₄ —N concentrations due to such behavior of the carrier, and that the flow state in the reaction vessel is extruded flow. NH4-N can be removed to a lower concentration.

The distribution of the carrier and the state of the behavior of the carrier in the reaction vessel are, for example, the size of the reaction vessel, the type of carrier, the size of the carrier, the specific gravity of the carrier, the filling rate of the carrier, the direction of water flow, and the aeration. Elements such as the presence and position of the water to be treated, the supply speed of the water to be treated, the discharge speed of the treated water, the air supply speed, the hydraulic retention time of the water to be treated (HRT: Hydraulic Retention Time) are appropriately selected and / or It can be formed by adjusting.

For example, the water treatment apparatus 1 shown in FIG. 3 differs from the water treatment apparatus 1 shown in FIG. there is The distribution of the carriers 3 in the reaction tank 2 and the state of the behavior of the carriers 3 are determined by the supply speed of the water to be treated, the discharge speed of the treated water, the air supply speed, the air diffusion structure, the position of the aeration, and the water to be treated. can be changed by appropriately adjusting factors such as the HRT of .

Further, for example, the water treatment apparatus 1 shown in FIG. 1 may further include a controller (not shown) capable of adjusting the flow of the water to be treated in the reaction tank 2 . The control unit is connected to, for example, one or more of the treated water supply pipe 4, the treated water discharge pipe 5, and the air supply pipe 6, and the supply speed of the water to be treated, the discharge speed of the treated water, the air It is preferable that the supply rate, the HRT of the water to be treated, etc. can be adjusted. By further providing the control section, it is possible to more easily form the state of carrier distribution and carrier behavior in the reaction tank during water flow as described above. Note that the control unit can be configured by including, for example, a CPU and its peripheral circuits.

(Water treatment method)
The water treatment method in this embodiment can be carried out similarly using the water treatment apparatus in the above-described embodiments.

Specifically, the water treatment method in this embodiment will be described using the example shown in FIG. By discharging the treated water through the treated water discharge pipe 5, the water to be treated flows downward into the reaction tank 2 filled with the carrier 3 (or upward flow or a combination of downward and upward flows). ).

According to the water treatment method of the present embodiment, as in the water treatment apparatus described above, the bacteria carried on the carrier decompose organic matter in the water to be treated in the reaction tank, and/or NH4 _- N in the water to be treated is nitrified and removed.

The aeration, water flow direction, details of the carrier, carrier distribution and carrier behavior in the reaction tank are as described above. Therefore, according to the water treatment method of the present embodiment, SS clogging during water treatment can be easily suppressed, and NH ₄ —N in the water to be treated can be satisfactorily removed.

Regarding the supply rate of the water to be treated into the reaction tank, the linear velocity (hereinafter also referred to as "LV") is preferably 10000 m/d or less, more preferably 8000 m/d or less, and 5000 m/d or less. It is more preferably 1000 m/d or less, particularly preferably 500 m/d or less. If the LV exceeds this range, the outflow or clogging of the carrier may make stable water treatment difficult.

The concentration of organic substances in the water to be treated supplied to the reaction tank is preferably BOD ₅ of 100 mg/L or less. By reducing the concentration of organic matter in the water to be treated to 100 mg/L or less in terms of BOD ₅ , the organic matter in the water to be treated can be decomposed to a suitable concentration. The concentration of organic matter in the water to be treated supplied to the reaction tank is more preferably 80 mg/L or less, and still more preferably 50 mg/L or less. BOD ₅ refers to biochemical oxygen demand. Specifically, it refers to the amount of dissolved oxygen consumed in 5 days when microorganisms decompose organic matter contained in water. In this specification, BOD ₅ is a value measured by the method described in JIS K 0102, as in the examples below.

The NH ₄ —N concentration in the water to be treated supplied to the reaction tank is preferably 50 mg/L or less. By setting the NH ₄ —N concentration in the water to be treated to 50 mg/L or less, the NH ₄ —N concentration after treatment can be reduced to an extremely low concentration. The NH ₄ —N concentration in the water to be treated supplied to the reaction tank is more preferably 30 mg/L or less, still more preferably 10 mg/L or less. The NH ₄ —N concentration in the water to be treated supplied to the reaction tank is 0 mg/L or more. In this specification, the NH ₄ —N concentration in the water to be treated is a value measured by the indophenol blue absorptiometric method or the like, as in the examples below.

The concentration of SS in the water to be treated supplied to the reaction tank is preferably 500 mg/L or less. By setting the concentration of SS in the water to be treated to 500 mg/L or less, it is possible to avoid affecting the effects of the present embodiment due to an excessive amount of SS. The concentration of SS in the water to be treated supplied to the reaction tank is more preferably 400 mg/L or less, still more preferably 300 mg/L or less, particularly preferably 200 mg/L, and most preferably 100 mg/L. is L. In this specification, the concentration of SS in the water to be treated is calculated by measuring the dry weight of the insoluble substances remaining on the filter paper with a pore size of 1 μm after filtering the water to be treated, as in the examples below. value.

The HRT of the water to be treated in the reaction tank is preferably 0.2 minutes or more and 60 minutes or less. By setting the HRT to 0.2 minutes or more, the water treatment can be sufficiently advanced, and the decomposition of organic matter and the removal of NH ₄ —N in the water to be treated can be sufficiently performed. Also, water treatment can be efficiently performed by setting the HRT to 60 minutes or less. HRT is more preferably 1 minute or longer, more preferably 5 minutes or longer. Also, the HRT is more preferably 30 minutes or less, still more preferably 15 minutes or less.

The pH of the water to be treated in the reaction tank is preferably 5 to 9, more preferably 6 to 8, from the viewpoint of the growth environment of bacteria. By setting the pH of the water to be treated in the reaction tank to an environment where bacteria can easily grow, the decomposition rate of organic substances and the rate of nitrification can be increased.

The temperature of the water to be treated in the reaction tank is not particularly limited, but is preferably 10° C. to 40° C., more preferably 15° C. to 35° C., from the viewpoint of the growth environment of bacteria. By setting the temperature of the water to be treated in the reaction tank to an environment where bacteria can easily grow, the decomposition rate of organic substances and the rate of nitrification can be increased.

The dissolved oxygen concentration (DO: Dissolved Oxygen) in the reaction tank is preferably 2 mg/L or more. By setting the DO in the reactor to 2 mg/L or more, the decomposition rate of organic matter and the nitrification rate can be maintained at a sufficient rate.

(Other modifications)
FIGS. 4 and 5 show modified examples 3 and 4 of the configuration of the water treatment apparatus 1 shown in FIG. The water treatment apparatus 1 shown in FIGS. 4 and 5 is provided inside the reaction tank 2 with a screen 7 for preventing the carrier 3 from flowing out. In the water treatment apparatus 1 shown in FIGS. 4 and 5, as described above, for example, the size of the reaction tank, the type of carrier, the size of the carrier, the specific gravity of the carrier, the filling rate of the carrier, and the supply rate of the water to be treated , discharge rate of treated water, air supply rate, HRT of the water to be treated, etc. can be appropriately selected and/or adjusted to form the desired carrier 3 distribution and carrier 3 behavior. .

Since the water treatment apparatus 1 of FIGS. 4 and 5 is provided with the screen 7, the carrier 3 in the high-density region located at the bottom of the reaction tank 2 is laminated even when water is passed in either an upward flow or a downward flow. , while the carriers 3 in the lower density region located at the top of the reaction vessel 2 are dispersed and preferably in motion. The carrier 3 in the high-density region located in the lower part of the reaction tank 2 may be completely stationary, but for example, "the carrier is rocking" or "the positions of the filled carriers are changed vertically and horizontally." "The carriers are moving with each other", "The stacked carriers are moving (due to the expansion of the stacked carriers, the formation of gaps between the carriers, and the expansion of the range of motion of each carrier)" and It may be in any state of "the carrier is moving at a speed of 1 mm/sec or more".

In the water treatment apparatus and water treatment method according to the present embodiment described above, for example, the water treatment apparatus 1 shown in FIG. , one water treatment device may be configured. Moreover, the water treatment apparatus as a whole may include not only the reaction tank but also various incidental equipment such as an activated sludge tank, a coagulating sedimentation tank, membrane filtration, RO, sand filtration, activated carbon, and the like.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited by the examples.

(Example 1)
In Example 1, water to be treated containing organic matter and NH ₄ —N was continuously treated over a period of half a year or more using the water treatment apparatus 1 shown in FIG. 1 and having a downward flow direction. went.

<Water to be treated (raw water) containing organic matter and NH ₄ —N>
The components of the water to be treated were measured before supply to the reaction tank and found to be as follows. For the treated water, the values of each component fluctuated depending on the measurement date. SS (mg/L) was obtained by measuring the dry weight of insoluble substances remaining on a filter paper with a pore size of 1 μm after filtering the water to be treated. NH4 _- N concentration (mg/L) was measured by indophenol blue spectrophotometry.
SS: 3 mg/L to 10 mg/L
NH4 _- N concentration: 10 mg/L to 12 mg/L

<Reaction tank filled with carrier>
A column (diameter: 40 mm, height: 1500 mm) was used as the reactor, and 0.94 L of the carrier described below was charged into the column (apparent filling rate: 50%).

<Carrier>
A spherical PVA gel carrier was used as the carrier. The equivalent sphere diameter of the PVA gel carrier is 4 mm, and the specific gravity of the PVA gel carrier in the state of supporting bacteria is 1.04. Observation of the surface and interior of the PVA gel carrier using an electron microscope confirmed pores communicating with each other. The specific surface area of the PVA gel carrier was 800000 m ² /m ³ . The specific surface area was measured by the krypton gas adsorption method. When the pore sizes of the surface and the inside of the PVA gel carrier were measured using an image observed by an electron microscope, the pore sizes were 0.5 μm to 20 μm. The water content of the PVA gel carrier was 94% by mass.

<Water treatment equipment>
In the water treatment apparatus 1 having the configuration shown in FIG. The supplied water to be treated undergoes decomposition of organic substances and nitrification of NH ₄ —N by bacteria carried on carrier 3 made of PVA gel carrier in reaction tank 2 . After that, the treated water was discharged out of the reaction tank 2 through the treated water discharge pipe 5 . In addition, at the time of passing water, air was sent into the reaction tank 2 through the air supply pipe 6 to aerate the treated water.

<Start-up of water treatment equipment and subsequent management>
The water to be treated (raw water) was directly supplied to the reaction tank into which the PVA gel carrier (PVA gel carrier not carrying bacteria) was charged, and the treatment was continued for 130 days. After that, the pH was set to 6 to 8 and DO was set to 4 mg/L to 9 mg/L as the control conditions of the reaction tank. The temperature in the reactor was set at 22°C. The supply rate of the water to be treated was 126 ml/min so that the HRT was 15 minutes. The amount of air supplied during aeration was 2 L/min.

<Distribution of Carrier in Reaction Tank and Behavior of Carrier>
After starting up the water treatment apparatus, the distribution of the carrier and the behavior of the carrier in the reaction tank in which the operation was stably performed were confirmed by visually observing from the outside. As a result, the distribution of the carrier and the behavior of the carrier in the reaction vessel were such that the low-density region of the carrier in the upper part of the reaction vessel was flowing violently, and the carrier was stacked in the lower part of the reaction vessel to form a high-density region. It was confirmed that Furthermore, by observing the inside of the carrier layered in the lower part of the reaction vessel from the outside using a transparent column, the average moving speed of the carrier was converted from the moving distance of the carrier in the lower part of the reaction vessel. As a result, it was confirmed that the carrier in the lower part of the reaction vessel moved at an average moving speed of 1 mm/sec or more. That is, it was observed that the entire amount of carrier in the reaction tank was moving. In addition, by observing the state inside the reaction vessel from the outside using a transparent column, it was confirmed that one or more carriers flowing in the low-density region moved to the position of the high-density region. We were able to. In addition, it was observed that 60% of the moving carriers in the reactor flowed at a speed of 2 cm/sec or less. In addition, it was observed that 50% of the total amount of carriers had a filling rate of 90% or more in the high-density region laminated at the bottom. It was also observed that the fill factor of the upper low-density region was 40% or less.

<Results>
After the start of use of the water treatment apparatus, the treatment was continued for 130 days, and the water quality of the treated water discharged from the reaction tank was continuously examined. FIG. 6 shows the NH ₄ -N concentration in the water to be treated and the NH ₄ -N concentration in the discharged treated water along with the number of days of use of the water treatment apparatus. As shown in FIG. 6, even after 87 days from the use of the water treatment equipment, the NH ₄ —N concentration of the water to be treated could be reduced from about 10 mg/L to about 0.01 mg/L. rice field. Furthermore, according to the water treatment apparatus of this embodiment, the NH ₄ —N concentration can be satisfactorily reduced without clogging the SS even after half a year or more, which exceeds the number of days shown in FIG. It was possible to operate the device stably.

In particular, in the existing water treatment method or water treatment apparatus for removing organic substances and/or NH ₄ —N, when the NH ₄ —N concentration of the water to be treated (raw water) is about 10 mg/L, the HRT is reduced to 15. It is very difficult to lower the NH ₄ —N concentration after treatment to less than 0.5 mg/L per minute (see, for example, Comparative Example 2 below). Therefore, according to the water treatment apparatus of the present embodiment, it is possible to treat the NH ₄ —N concentration in the object to be treated to a very low concentration, so that the NH ₄ —N removal effect is extremely excellent. I know there is.

(Example 2)
In Example 2, the water treatment test of the water to be treated was carried out under the same conditions as in Example 1, except that the direction of water flow was changed from the downward flow type to the upward flow type. As a result, the NH ₄ —N concentration of the water to be treated can be reduced to about 0.01 mg/L, and the apparatus can be stably operated without clogging the SS for 30 days or longer. there were.

The distribution of the carrier and the behavior of the carrier in the reaction tank are the same as in Example 1, the carrier in the low-density region in the upper part of the reaction tank is flowing, and the high-density region in the lower part of the reaction tank is stacked. It was confirmed that the carrier moved at an average moving speed of 1 mm/sec or more. Furthermore, it was also confirmed that one or more carriers flowing in the low density region moved to the position of the high density region. In addition, it was observed that 60% of the moving carriers in the reactor flowed at a speed of 2 cm/sec or less. In addition, it was observed that 50% of the total amount of carriers had a filling rate of 90% or more in the high-density region laminated at the bottom. It was also observed that the fill factor of the upper low-density region was 40% or less.

(Example 3)
In Example 3, a water treatment test of the water to be treated was carried out under the same conditions as in Example 1, except that a column with a height of 800 mm was used as the reaction tank and the apparent packing ratio was set to 94%. Since the volume of the reactor was smaller than in Example 1, the HRT was 8 minutes. As a result, the NH ₄ —N concentration of the water to be treated can be reduced to about 0.01 mg/L, and the apparatus can be stably operated without clogging the SS for 30 days or more. there were.

Regarding the distribution of the carrier and the behavior of the carrier in the reaction vessel, the carrier is stacked in 95% of the volume of the reaction vessel in the lower part of the reaction vessel (high density region), and the upper part of the reaction vessel is full of the volume of the reaction vessel. At 5% the carrier was flowing (low density area). In addition, the filling rate of the stacked carriers in 95% of the volume of the reaction vessel was 95% in terms of apparent volume. The ratio (%) of the layered carrier region and the ratio (%) of the flowing carrier region to the total volume of the reactor were obtained by visual observation and measurement from the outside of the column. In addition, when the operation is stable, the filling rate in the apparent volume of the laminated support is obtained by inserting a water sampling bottle into the reaction tank and mixing the water in the lower part of the reaction tank with the laminated support. It was collected and determined from the amount of water collected and the amount of carrier collected. As in Example 1, it was confirmed that the stacked carriers were moving at an average moving speed of 1 mm/sec or more even in the lower part of the reaction vessel. It was observed that 60% of all carriers in the reactor were moving. Furthermore, it was also confirmed that one or more carriers flowing in the low density region moved to the position of the high density region. In addition, it was observed that 60% of the moving carriers in the reactor flowed at a speed of 2 cm/sec or less. In addition, it was observed that 80% or more of the total amount of carriers had a filling rate of 90% or more in the high-density region laminated at the bottom. It was also observed that there is a high density region with a filling rate of 95% or more in the lower portion and a low density region with a filling rate of 75% or less in the upper portion.

(Example 4)
In Example 4, a column with a height of 800 mm was used as the reaction tank, the apparent packing rate was 94%, and the direction of water flow was not a downward flow type but an upward flow type, except that A water treatment test of the water to be treated was carried out under the same conditions as in Example 1. Since the volume of the reactor was smaller than in Example 1, the HRT was 8 minutes. As a result, the NH ₄ —N concentration of the water to be treated can be reduced to about 0.01 mg/L, and the apparatus can be stably operated without clogging the SS for 30 days or longer. there were.

The carrier distribution and carrier behavior in the reaction tank were the same as in Example 3. That is, in the lower part of the reaction tank, the carriers are stacked while moving at an average moving speed of 1 mm / sec or more in 95% of the reaction tank volume (high density area), and in the upper part of the reaction tank, in 5% of the reaction tank volume. It was observed that the carrier was flowing (low density area) and 60% of the total carrier in the reactor was in motion. Furthermore, it was also confirmed that one or more carriers flowing in the low density region moved to the position of the high density region. In addition, it was observed that 60% of the moving carriers in the reactor flowed at a speed of 2 cm/sec or less. In addition, it was observed that 80% or more of the total amount of carriers had a filling rate of 90% or more in the high-density region laminated at the bottom. It was also observed that there is a high density region with a filling rate of 95% or more in the lower portion and a low density region with a filling rate of 75% or less in the upper portion.

(Example 5)
In Example 5, BOD ₅ (mg/L) was 1 mg/L to 6 mg/L, and the NH ₄ -N concentration was 10 mg/L to 12 mg/L, except that the water to be treated was used. A water treatment test of the water to be treated was carried out under the same conditions as in 1. BOD ₅ (mg/L) was measured by the method described in JIS K 0102. As a result, the BOD ₅ concentration of the water to be treated can be reduced to about 1 mg/L, and the NH ₄ -N concentration can be reduced to about 0.01 mg/L, and the SS is not clogged for more than 7 days and is stable. It was possible to operate the device effectively.

The distribution of the carrier and the behavior of the carrier in the reaction tank are the same as in Example 1, the carrier in the low-density region in the upper part of the reaction tank is flowing, and the high-density region in the lower part of the reaction tank is stacked. It was confirmed that the carrier moved at an average moving speed of 1 mm/sec or more. Furthermore, it was also confirmed that one or more carriers flowing in the low density region moved to the position of the high density region. In addition, it was observed that 60% of the moving carriers in the reactor flowed at a speed of 2 cm/sec or less. In addition, it was observed that 50% of the total amount of carriers had a filling rate of 90% or more in the high-density region laminated at the bottom. It was also observed that the fill factor of the upper low-density region was 40% or less.

(Comparative example 1)
In Comparative Example 1, a water treatment test of the water to be treated was conducted under the same conditions as in Example 1, except that the entire amount of the carriers was maintained stationary by fixing the carriers with a net. As a result, clogging of the SS occurred in about one week, the water permeability of the water treatment apparatus decreased, and the apparatus could not be operated stably.

As described above, regarding the distribution of the carrier and the behavior of the carrier in the reaction vessel before the water permeability decreased, it was confirmed that the entire amount of the carrier fixed in the lower part of the reaction vessel was stationary.

(Comparative example 2)
In Comparative Example 2, a water treatment test of water to be treated was conducted under the same conditions as in Example 3, except that anthracite having a particle size of 1.2 mm and a specific gravity of 1.5 was used as the carrier. As a result, clogging of the SS occurred in about one week, the water permeability of the water treatment apparatus decreased, and the apparatus could not be operated stably.

Regarding the distribution of the carrier and the behavior of the carrier in the reaction tank before the water permeability decreased, it was confirmed that 85% or more of the total amount of the carrier in the reaction tank was stationary.

(Comparative Example 3)
Comparative Example 3 was the same as Example 1, except that a water treatment apparatus equipped with a reaction tank having a volume of 1 L and having a horizontal water flow direction was used, and the apparent filling rate of the carrier in the reaction tank was set to 60%. A water treatment test was conducted on the water to be treated under the same conditions. As a result, although the apparatus could be operated stably for 112 days, the NH ₄ —N concentration after the treatment could only be lowered to about 0.5 mg/L. FIG. 7 shows the NH ₄ —N concentration in the water to be treated and the NH ₄ —N concentration in the discharged treated water in Comparative Example 3 along with the number of days of use of the water treatment apparatus.

Regarding the distribution of the carriers and the behavior of the carriers in the reaction tank, it was observed that the carriers dispersed substantially uniformly and flowed and moved. Moreover, it was observed that the entire amount of the carrier was vigorously flowing at a speed of 2.5 cm/sec or more, indicating that the carrier was in a completely mixed state.

It should be understood that the embodiments and examples disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

1 water treatment equipment 2 reaction tank 3 carrier 4 water supply pipe to be treated (water supply part to be treated)
5 Treated water discharge pipe (treated water discharge part)
6 Air supply pipe (air supply part)
7 screen

Claims (14)

A water treatment method for removing one or more of organic matter and ammonia nitrogen in water to be treated under aerobic conditions,
Passing the water to be treated through one or more reaction tanks filled with carriers having micropores in a direction selected from downward flow and upward flow,
A water treatment method, wherein the reaction tank has a high-density region and a low-density region in the distribution of the carrier, and the high-density region is located in the lower part of the reaction tank when water is passed through the reaction tank. 2. The water treatment method according to claim 1, wherein the carrier in the low density region is moving when water is passed through. The water treatment method according to claim 1 or 2, wherein the fine pores of the carrier have a pore size of 0.1 µm or more and less than 1000 µm. The water treatment method according to any one of claims 1 to 3, wherein 20% or more of the total amount of carriers in the reaction tank is moving. 5. The water treatment method according to any one of claims 1 to 4, wherein the filling rate of the carrier in 10% or more of the total amount of carrier in the reaction tank is 80% or more in apparent volume when water is passed. The water treatment method according to any one of claims 1 to 5, wherein the carrier has a specific gravity of 1.00 to 1.20 in a state of carrying bacteria. The water treatment method according to any one of claims 1 to 6, wherein the carrier is made of polyvinyl alcohol. A water treatment apparatus for removing one or more of organic matter and ammonia nitrogen in water to be treated under aerobic conditions,
one or more reaction vessels filled with a carrier having micropores;
a to-be-treated water supply unit and a treated water discharge unit for causing the water to be treated to flow in the one or more reaction tanks in a direction selected from a downward flow and an upward flow,
A water treatment apparatus according to claim 1, wherein the reaction tank has a high-density region and a low-density region in the distribution of the carrier, and the high-density region is located at the lower portion of the reaction tank when water is passed through the reaction tank. 9. The water treatment device according to claim 8, wherein the carriers in the low density region are moving when water is passed through. The water treatment device according to claim 8 or 9, wherein the fine pores of the carrier have a pore size of 0.1 µm or more and less than 1000 µm. 11. The water treatment apparatus according to any one of claims 8 to 10, wherein 20% or more of the carriers in the reaction tank are moving. 12. The water treatment apparatus according to any one of claims 8 to 11, wherein when water is passed through the reaction tank, the filling rate of the carrier in 10% or more of the total amount of the carrier in the reaction tank is 80% or more in apparent volume. The water treatment device according to any one of claims 8 to 12, wherein the carrier has a specific gravity of 1.00 to 1.20 in a state of carrying bacteria. The water treatment device according to any one of claims 8 to 13, wherein the carrier is made of polyvinyl alcohol.

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