Denitrification treatment system and method

Abstract

To provide a denitrification treatment system that suppresses a generation of deposits such as gypsum that is formed on a surface of a denitrification pellet.SOLUTION: There is provided a denitrification treatment system 11 that performs denitrification treatment to remove nitrogen from wastewater containing nitrate nitrogen, etc., the system including: a treatment tank 13 including a pellet layer 25 in which pellets of a carrier for supporting sulfur-oxidizing bacteria that perform denitrification treatment are layered, and wastewater introduced from outside is passed through the pellet layer 25 to produce treated water from which nitrogen has been removed; an inlet pipe 18 connected to the treatment tank 13 for introducing wastewater from the outside to an upstream side of the denitrification treatment of the pellet layer 25; a circulation pipe 15 for passing treated water from a downstream side of the denitrification treatment of the pellet layer 25 to an upstream side of the denitrification treatment of the pellet layer; and an electromagnetic field generator 17 provided in at least one of the inlet pipe 18 and the circulation pipe 15, to generate a magnetic field and an electric field inside the pipe.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a denitrification treatment system and a denitrification treatment method for removing nitrogen from wastewater by sulfur-oxidizing bacteria.

Background Art

[0002] Conventionally, there is known a denitrification treatment apparatus that removes nitrogen from wastewater flowing through a reactor by sulfur-oxidizing bacteria supported on the surface of a denitrification material (denitrification pellet) containing sulfur and carbonate (see Patent Document 1).

[0003] The above denitrification treatment apparatus utilizes the function of sulfur-oxidizing bacteria to reduce nitrate nitrogen or nitrite nitrogen containing nitrate nitrogen to nitrogen while oxidizing sulfur under anoxic conditions. The above denitrification is carried out by a sulfur denitrification reaction by the action of sulfur-oxidizing bacteria growing on the surface of sulfur contained in the denitrification material layer in the reactor containing the denitrification material when the wastewater passes through the denitrification material layer, changing nitrate nitrogen or the like to nitrogen and discharging it outside the reactor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the above denitrification treatment apparatus, it is expected that the denitrification activity is high and the denitrification materials do not mix into the water tank to be treated, for example, enabling long-term breeding of aquatic organisms. However, when the concentration of sulfate ions produced in proportion to nitrogen removal increases, there is a problem that the activity of sulfur-oxidizing bacteria decreases. Furthermore, sulfate ions combine with calcium carbonate contained in the denitrification pellets or calcium ions contained in the wastewater to precipitate gypsum (calcium sulfate), and when this crystallizes on the surface of the denitrification pellets, it leads to a decrease in the denitrification reaction and even the cessation of the denitrification reaction.

[0006] The denitrification pellets used in the denitrification treatment apparatus of Patent Document 1 are formed by melting and stirring sulfur and calcium carbonate. In order to solve the problem of gypsum precipitation, it has been proposed to change to magnesium carbonate instead of the above calcium carbonate. However, magnesium carbonate is very expensive, and there is a problem that the initial cost of the denitrification system increases, and the material change of the denitrification pellets is not appropriate. As another solution, it is conceivable to make the pellets themselves very fine and consume the pellets before gypsum crystal adhesion occurs. However, the pellets may be consumed earlier than the theoretical value, and there is a risk that the expected denitrification effect cannot be achieved.

[0007] An object of the present invention is to provide a denitrification treatment system and a denitrification treatment method that suppress the generation of deposits such as gypsum produced on the surface of denitrification pellets.

Means for Solving the Problems

[0008] In order to solve the above problems, a denitrification treatment system according to the present invention is a denitrification treatment system that performs denitrification treatment to remove nitrogen from wastewater containing nitrate nitrogen and the like, and includes a pellet layer in which pellets of a carrier carrying sulfur-oxidizing bacteria for performing denitrification treatment are stacked. A treatment tank that uses the wastewater introduced from the outside as treated water from which nitrogen has been removed through the pellet layer, an introduction pipe connected to the treatment tank for introducing the wastewater from the outside to the upstream side of the denitrification treatment of the pellet layer, and a downstream side of the denitrification treatment of the pellet layer A circulation pipe for flowing the treated water to the upstream side of the denitrification treatment of the pellet layer, and an electromagnetic field generator provided in at least one of the introduction pipe and the circulation pipe for generating a magnetic field and an electric field inside the pipe.

[0009] According to such a configuration, in the denitrification treatment for removing nitrogen from wastewater by sulfur-oxidizing bacteria, since an electromagnetic field generator is provided in at least one of the introduction pipe and the circulation pipe, the Lorentz force acts on the water molecules and charged particles in the water contained in the wastewater and the treated water due to the influence of the magnetic field, and a large flow is generated in the solution (MHD effect). From such a phenomenon, it is considered that there is a difference in the crystals deposited by the generated electric and magnetic fields. That is, when the electric and magnetic fields are not generated, it is a single crystal system crystal, but when the electric and magnetic fields are generated, it is a triclinic crystal system crystal, so the surface is smooth and slippery and difficult to adhere, suppressing scale adhesion such as gypsum on the pellet surface, and the denitrification treatment can be continued. The electromagnetic field generator may be provided in either one of the introduction pipe and the circulation pipe, or may be provided in both pipes. However, it is considered that the effect of the electric and magnetic fields is greater when the electromagnetic field generator is provided in the circulation pipe. In addition, the circulation pipe connects the downstream side and the upstream side of the denitrification treatment to circulate the treated water. In addition, by providing a treated water storage tank for temporarily storing the treated water in the middle of the circulation pipe, the amount of water for the denitrification treatment can be adjusted, and the quality of the treated water can be measured. In addition, nitrate nitrogen and the like mean nitrate nitrogen and nitrite nitrogen. Furthermore, a circulation pipe for circulating the treated water can be provided between the treatment tank and another treatment tank, and an electromagnetic field generator and a pump for circulating the treated water can be provided in the middle of the path of the circulation pipe.

[0010] In the denitrification treatment system according to the present invention, the treatment tank is provided with the pellet layer in the middle part inside the treatment tank, and further provided with a filter medium for filtering the treated water above the pellet layer on the downstream side of the denitrification treatment of the pellet layer. The introduction pipe is connected to the lower part of the treatment tank on the upstream side of the denitrification treatment of the pellet layer, and the circulation pipe is provided outside the treatment tank, with one end connected to the upper part of the treatment tank on the downstream side of the denitrification treatment of the pellet layer and the other end connected to the lower part of the treatment tank on the upstream side of the denitrification treatment of the pellet layer respectively.

[0011] According to such a configuration, since the pellet layer is arranged in the middle part inside the tank and the filter medium is arranged above it, in the wastewater treatment introduced into the treatment tank, the crystals precipitated by the generation of the electric field and magnetic field become triclinic crystals, which are smooth and difficult to adhere. Therefore, the generation of scale adhesion such as gypsum on the pellet surface can be suppressed, and further, the scale such as crystals contained in the treated water can be filtered by the filter medium. Note that the filter medium is not limited to being provided above the pellet layer inside the treatment tank. The filter medium can be provided separately in a filtration tank equipped with the filter medium, and the treated water discharged from the treatment tank can be introduced into the filtration tank for filtration. By providing a separate filtration tank, the regular replenishment of the pellets to the pellet layer can be easily performed. In addition, when it is not necessary to remove residues, scale containing gypsum, etc. contained in the treated water, it is not necessary to provide a filter medium inside the treatment tank or a separate filtration tank.

[0012] In the denitrification treatment system according to the present invention, the introduction pipe is provided with a first pump for introducing the wastewater from the outside into the treatment tank, and the circulation pipe is provided with a second pump for circulating the treated water from the downstream side to the upstream side of the pellet layer from one end to the other end.

[0013] According to such a configuration, by providing the first pump in the introduction pipe, the drainage can be passed through to the treatment tank for denitrification treatment. By providing the second pump in the circulation pipe, the treated water after denitrification treatment can be circulated from the downstream side to the upstream side of the pellet layer, so that the denitrification treatment can be repeatedly performed, and it is possible to provide treated water with a high denitrification effect. At this time, by providing an electromagnetic field generator in the circulation pipe, it is possible to suppress the adhesion of scale such as gypsum to the pellet surface.

[0014] In the denitrification treatment system according to the present invention, the electromagnetic field generator may have a configuration including a coil portion that winds around the pipe, a power supply portion that passes an alternating current through the coil portion, and a control portion that modulates the frequency of the alternating current from the power supply portion over time within a predetermined frequency band.

[0015] According to such a configuration, by passing the alternating current from the power supply portion through the coil portion that winds around the pipe, an electric field and a magnetic field can be generated in the pipe. The power supply portion supplies, for example, a current in a frequency band of 20 Hz to 1 MHz, preferably 100 to 5000 Hz, and the control portion can modulate the frequency over time and supply it to the coil portion. As described above, by generating an electric field and a magnetic field in the pipe, the generated crystals become triclinic crystals that are difficult to adhere, so that the adhesion of scale such as gypsum to the pellet surface can be suppressed, and the denitrification treatment can be continued.

[0016] Further, the denitrification treatment method according to the present invention is a denitrification treatment method for removing nitrogen from drainage containing nitrate nitrogen and the like, and includes a drainage introduction step of introducing the drainage into a treatment tank for performing denitrification treatment, a drainage treatment step of removing nitrogen from the drainage introduced into the treatment tank through a pellet layer in which pellets carrying sulfur-oxidizing bacteria for performing denitrification treatment are stacked to obtain treated water, a circulation step of circulating the treated water to the introduction side of the treatment tank, and an electromagnetic field generation step of generating a magnetic field and an electric field inside the pipe by an electromagnetic field generator provided in at least one of the introduction pipe for introducing the drainage and the circulation pipe for circulating the treated water.

Effect of the Invention

[0017] According to the present invention, in a denitrification treatment for removing nitrogen from wastewater by sulfur-oxidizing bacteria supported on pellets which are denitrification materials containing sulfur and carbonate, since an electromagnetic field generator for generating an electromagnetic field is provided in at least one of an introduction pipe for introducing wastewater and a circulation pipe for circulating treated water, adhesion of scale such as gypsum (calcium sulfate) crystallized on the surface of the pellets is suppressed, and the denitrification treatment can be continued.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0020] (First Embodiment) FIG. 1 is a diagram showing a schematic configuration of a denitrification treatment system according to a first embodiment of the present invention. Here, the denitrification treatment means discharging by changing nitrate nitrogen etc. (nitrate nitrogen, nitrite nitrogen) into nitrogen by a sulfur denitrification reaction by the action of sulfur-oxidizing bacteria. As shown in FIG. 1, the denitrification treatment system 11 includes a storage tank 12 for storing wastewater containing nitrate nitrogen etc., a treatment tank (reactor) 13 that performs a denitrification treatment for extracting nitrogen from the wastewater sent from the storage tank 12, a pellet layer 25 laminated and arranged in the middle part in the vertical direction of the treatment tank 13, a filter medium 27 provided above the pellet layer 25, a circulation pipe 15 connected to the lower side and the upper side of the side surface of the treatment tank 13 so that both ends communicate with the lower part and the upper part of the treatment tank 13, an electromagnetic field generator 17 provided near the approximate middle of the circulation pipe 15, a second pump 19 provided in the middle of the circulation pipe 15 in series with the electromagnetic field generator 17 for circulating the treated water denitrified in the pellet layer 25 to the side where the wastewater at the lower part of the treatment tank 13 is introduced, an introduction pipe 18 for introducing wastewater from the storage tank 12 into the treatment tank 13, a first pump 16 provided in the middle of the introduction pipe 18 for sending out the wastewater from the storage tank 12 to the treatment tank 13, a gas vent pipe 22 connected to the ceiling surface of the treatment tank 13 for discharging the nitrogen removed from the wastewater inside the treatment tank 13 to the outside, and a discharge pipe 23 connected to the upper part of the treatment tank 13 for discharging the treated water after the denitrification treatment and having a residual nitrate nitrogen etc. below a predetermined standard. Note that, on the peripheral wall of the treatment tank 13, there are provided an introduction nozzle 24a to which the end of the introduction pipe 18 is attached, a circulation upper nozzle 24b to which one end of the circulation pipe 15 is attached, a circulation lower nozzle 24c to which the other end of the circulation pipe 15 is attached, and a discharge nozzle 24d to which the end of the discharge pipe 23 is attached. Further, on the ceiling wall of the treatment tank 13, there is provided a gas vent nozzle 24e to which the end of the gas vent pipe 22 is attached.

[0021] The storage tank 12 is a water tank that stores the wastewater to be denitrified, and examples include a water tank that stores domestic wastewater, a water tank in a fish farm, a wastewater tank at livestock farms such as a pig farm, etc. The treatment tank 13 has a pellet layer 25 formed by stacking pellets for denitrification treatment in the middle part in the vertical direction inside the treatment tank 13. A filter material 27 for filtering pellet residues and the like contained in the treated water after denitrification treatment is provided above the pellet layer 25. At the lower part of the treatment tank 13, an introduction pipe 18 for introducing the wastewater from the storage tank 12 is connected via an introduction nozzle 24a. At the upper and lower parts of the treatment tank 13, both ends of a circulation pipe 15 for circulating the treated water filtered by the filter material 27 to the lower drainage side are respectively connected via a circulation upper nozzle 24b and a circulation lower nozzle 24c. In the treatment tank 13, the wastewater introduced from the lower side of the side surface of the treatment tank 13 is subjected to denitrification treatment by the pellet layer 25, and the treated water sent out as an upward flow with the bottom side as the upstream and the top side as the downstream is filtered by the filter material 27 and circulated to the bottom drainage side by the circulation pipe 15 from the upper side of the side surface of the treatment tank 13. Also, in order to discharge the nitrogen (N2) generated by the denitrification treatment in the pellet layer 25 to the outside, a gas vent pipe 22 is connected to the top surface of the treatment tank 13 via a gas vent nozzle 24e. Also, a control box equipped with a flow meter and an adjustment valve for controlling the flow rate can be provided. Note that the second pump 19, which has the role of circulating the treated water to the lower drainage side in the treatment tank 13, causes the lower drainage to rise, so that it can come into contact evenly with the pellet layer 25 to improve the denitrification effect, and the generated nitrogen can be lifted without staying in the pellet layer 25. The lifted nitrogen is discharged to the outside by the gas vent pipe 22. In the denitrification treatment in the treatment tank 13, the lower side of the pellet layer 25 is the upstream side of the denitrification treatment, and the upper side of the pellet layer 25 is the downstream side of the denitrification treatment.

[0022] The pellet layer 25, which is stacked and arranged in the vertical middle part of the treatment tank 13, is made by stacking and arranging pellets (1 mm to 100 mm in particle size) which are a medium for supporting sulfur oxidizing bacteria, which are microorganisms that perform denitrification treatment. The arrangement in the middle part is a general mechanical structure using, for example, a fine wire mesh. The denitrification treatment is a treatment to change nitrate nitrogen and the like into nitrogen by a sulfur denitrification reaction caused by the action of sulfur oxidizing bacteria growing on the surface of sulfur. Since sulfur particles are water repellent, the sulfur is hydrophilized with a surfactant, and when the sulfur is oxidized by the denitrification treatment and the amount of sulfur salt ions increases, the pH decreases and the sulfur denitrification reaction decreases, so the pellets are formed as a mixture carrier of sulfur and carbonate (calcium carbonate), which is an alkaline substance. The wastewater introduced from the inlet pipe 18 to the bottom of the treatment tank 13, which is the upstream side, is denitrified while passing through the pellet layer 25 as an upward flow by the action of the first pump 16, and is sent to the downstream filter material 27 as treated water.

[0023] The filter material 27 filters pellet residues, scales including gypsum, etc., contained in the treated water. The filter material 27 is a porous material made of resin having a bubble structure, and has an apparent specific gravity of less than 1.0 because it floats on the treated water. In this specification, the apparent specific gravity is the mass of the filter material in a water-containing state divided by the volume, and indicates the actual specific gravity as a filter material. The filter material 27 may be in the form of a sheet, but using multiple spherical or lumpy pieces is more suitable for repeated use after cleaning, etc. As the material for the filter material 27, for example, ceramics in addition to the above resins can be used, but it is preferable that the filter material is made of a porous resin having a bubble structure because it floats on the treated water. Examples of porous resins include polyvinyl alcohol, polyurethane, polypropylene, and polyethylene.

[0024] As shown in FIG. 2, the electromagnetic field generator 17 includes a coil portion 31 that winds an electric wire around a predetermined range, which is a substantially middle portion of a circulation pipe 15 communicating the upper and lower portions of the treatment tank 13, a power supply portion 32 that supplies an alternating current of a predetermined frequency, and a control portion 33 that supplies the coil portion 31 with an alternating current whose frequency is modulated over time from the alternating current from the power supply portion 32. The control portion 33 has a function of generating an electric field and a magnetic field inside the first pipe 15 by supplying the coil portion 31 with an alternating current in the range of a frequency of 20 Hz to 1 MHz and modulating the frequency over time. The coil portion 31 includes a first coil portion 31a and a second coil portion 31b provided with a predetermined gap from the first coil portion 31a. The first coil portion 31a and the second coil portion 31b are electrically connected. Further, the coil portion 31, the power supply portion 32, and the control portion 33 may be manufactured as an integrated device.

[0025] As shown in FIG. 2, the alternating current supplied to the coil portion 31 (31a, 31b) changes the flowing directions (35a, 35b) alternately, and a magnetic field is generated inside the first pipe 15 with the directions 36a, 36b changing alternately. There are differences in the crystals deposited due to the influence of the electric and magnetic fields generated by the alternating current. That is, when the electric and magnetic fields are not generated, the generated crystals are single crystal system crystals, but when the electric and magnetic fields are generated, they are triclinic crystal system crystals. Therefore, the surface is smooth, slippery, and difficult to adhere, suppressing the adhesion of scale such as gypsum to the pellet surface and enabling the denitrification treatment to be continued.

[0026] Next, with reference to FIGS. 1 and 2, the operation of the denitrification treatment system according to this embodiment will be described. From the storage tank 12 in which wastewater containing nitrate nitrogen and the like generated in livestock farming, aquaculture, etc. is stored, the wastewater is sent from the lower side to the bottom of the treatment tank 13 through the introduction pipe 18 by the first pump 16 provided in the middle of the pipe. At the position of the middle part in the vertical direction of the treatment tank 13, a pellet layer 25 in which pellets (granular shape: 1 mm to 100 mm), which are a medium carrying sulfur-oxidizing bacteria, which are microorganisms that perform denitrification treatment as described above, are stacked is provided. In the pellet layer 25, nitrate nitrogen and the like in the wastewater are changed to nitrogen by the sulfur denitrification reaction due to the action of sulfur-oxidizing bacteria growing on the surface of sulfur contained in the pellet layer.

[0027] This sulfur denitrification reaction utilizes the function of sulfur-oxidizing bacteria, which are a type of autotrophic bacteria, to reduce nitrate nitrogen and the like (nitrate nitrogen, nitrite nitrogen) to nitrogen while oxidizing sulfur under anoxic conditions. After the wastewater from which nitrate nitrogen and the like have been reduced and removed to nitrogen is filtered by the filter medium 27 to remove residues of pellets and the like as treated water. Nitrogen, which is slightly lighter than air, passes through the filter medium and is then discharged to the outside through the gas vent pipe 22 connected to the top surface of the treatment tank 13.

[0028] Both ends of the circulation pipe 15, which connects the upper circulation nozzle 24b at the upper part of the side surface and the lower circulation nozzle 24c at the lower part of the side surface of the treatment tank 13, are respectively connected. Due to the operation of the second pump 19, the treated water is sent from the upper circulation nozzle 24b through the circulation pipe 15 to the lower part of the treatment tank 13 from the lower circulation nozzle 24c, and the denitrification treatment is performed again in the pellet layer 25. At this time, the Lorentz force acts on the water molecules and various ions (charged particles) in the treated water due to the influence of the magnetic field, and a large flow is generated in the solution (MHD effect). From such a phenomenon, it is considered that there is a difference in the crystals deposited by the generated electric and magnetic fields. That is, when the electric and magnetic fields are not generated, it is a single crystal system crystal, but when the electric and magnetic fields are generated, it is a triclinic crystal system crystal. Therefore, since the surface is smooth and slippery and difficult to adhere, the adhesion of scale such as gypsum to the pellet surface can be suppressed. Thereby, the decrease in the denitrification reaction can be prevented. The effect of the above electric and magnetic fields by the electromagnetic field generator 17 is considered to continue for several days.

[0029] The treated water that has been repeatedly denitrified as described above is discharged to the outside through the discharge pipe 23 connected to the discharge nozzle 24d. For example, the treated water that has undergone denitrification treatment for a predetermined time or more can be discharged to the outside. In addition, when the denitrification treatment is repeatedly performed by circulation, the introduction of the drainage from the storage tank 12 can be stopped by an electromagnetic valve (not shown) or the like. In the conventional denitrification treatment, due to the generation of sulfate ions by the sulfur denitrification reaction by the action of sulfur-oxidizing bacteria, gypsum (calcium sulfate: CaSO4) crystallizes on the surface of the pellet, leading to a decrease in the denitrification reaction. However, in this embodiment, since the electromagnetic field generator 17 is provided in the circulation pipe 15 connected to the upper and lower side surfaces of the treatment tank 13, as described above, the adhesion of scale such as gypsum to the pellet surface can be suppressed, and the decrease in the denitrification reaction can be prevented.

[0030] In this embodiment, the filter medium 27 is provided above the pellet layer 25 in the treatment tank 13, but the present invention is not limited to this. A separate filtration tank equipped with a filter medium can be provided, and the treated water discharged from the treatment tank 13 can be introduced into the filtration tank for filtration. For example, a filtration tank can be connected in the middle of the discharge pipe 23 to discharge the filtered treated water. By providing a separate filtration tank in this way, since there is no filter medium above the pellet layer, the regular replenishment of the pellets can be easily performed. When it is not necessary to remove scale such as residues and gypsum contained in the treated water, it is not necessary to provide a filter medium in the treatment tank or a separate filtration tank. Further, a treated water storage tank for temporarily storing the treated water can be provided in the middle of the circulation pipe 15. By providing a treated water storage tank, the amount of water for denitrification treatment can be adjusted, and the quality of the treated water can be further measured. Further, in actual denitrification treatment, a plurality of treatment water tanks may be installed in parallel. Even in such a case, a treated water storage tank for temporarily storing the treated water is provided, and the treated water stored in the treated water storage tank can be returned from the circulation lower nozzle 24c to the lower part (upstream of the denitrification treatment) of the treatment tank 13 using the second pump 19. Further, a circulation pipe (not shown) for circulating the treated water between the treatment tank 13 and another treatment tank (not shown) can be provided, and an electromagnetic field generator (not shown) and a pump (not shown) for circulating the treated water can be provided in the middle of the path of the circulation pipe. This includes a first case where only the electromagnetic field generator 17a is provided in the circulation pipe 15, a second case where only an electromagnetic field generator (not shown) is provided in a circulation pipe (not shown), and a third case where the electromagnetic field generator 17a is provided in the circulation pipe 15 and an electromagnetic field generator (not shown) is provided in a circulation pipe (not shown).

[0031] (Second Embodiment) Next, a denitrification treatment system according to the second embodiment of the present invention will be described with reference to FIG. 3. Regarding the denitrification treatment system 41 of the second embodiment, the description will focus on the differences from the denitrification treatment system 11 of the first embodiment, and the common points will be omitted as appropriate. Components having the same shape and function as those of the denitrification treatment system 11 according to the first embodiment will be described using the same reference numerals.

[0032] As shown in FIG. 3, the denitrification treatment system 41 according to this embodiment is characterized in that electromagnetic field generators 17 are provided at two locations. The electromagnetic field generator 17a is provided in the circulation pipe 15, and the electromagnetic field generator 17b is provided in the introduction pipe 18, respectively.

[0033] As shown in FIG. 3, in addition to the electromagnetic field generator 17a in the circulation pipe 15, an electromagnetic field generator 17b is also provided in the introduction pipe 18. Therefore, the wastewater newly introduced into the treatment tank 13 is also under the influence of the electromagnetic field, and it is considered that the crystallization of gypsum on the pellet surface can be suppressed more than in the first embodiment. Although the treated water is affected by the electromagnetic field generated by the electromagnetic field generator 17, similar to the first embodiment, electric field energy is imparted to the water molecules contained in the treated water and various ions in the water, and the crystallization of gypsum on the pellet surface can be suppressed. Similar to the first embodiment, a circulation pipe (not shown) for circulating the treated water between the treatment tank 13 and other treatment tanks (not shown) can be provided, and an electromagnetic field generator (not shown) and a pump (not shown) for circulating the treated water can be provided in the middle of the path of the circulation pipe.

[0034] (Third Embodiment) Next, the denitrification treatment system according to the third embodiment of the present invention will be described with reference to FIG. 4. The denitrification treatment system 51 of the third embodiment will be described mainly focusing on the differences from the denitrification treatment system 11 of the first embodiment, and the common points will be omitted as appropriate. For the components having the same shape and function as those of the denitrification treatment system 11 according to the first embodiment, the same reference numerals will be used for description.

[0035] As shown in FIG. 4, the denitrification treatment system 51 according to this embodiment is characterized in that, different from the first embodiment, an electromagnetic field generator is not provided in the circulation pipe 15, and an electromagnetic field generator 17c is provided in the introduction pipe 18.

[0036] As shown in FIG. 4, by the electromagnetic field generator 17c provided in the introduction pipe 18, water molecules and various ions (charged particles) contained in the wastewater flowing through the introduction pipe 18 are affected by the electromagnetic field, and as described above, it is possible to suppress the adhesion of scale such as gypsum to the surface of the pellets, and the denitrification treatment can be continued. In the present embodiment, the electromagnetic field generator 17c is provided only in the introduction pipe 18 instead of the circulation pipe 15. However, since the introduced wastewater is affected by the electromagnetic field, the effect of suppressing the adhesion of gypsum on the pellet surface can be confirmed. It is considered that the effect is greater when the electromagnetic field generator 17 is provided in the circulation pipe 15 for preventing the adhesion of gypsum. However, a predetermined effect can also be confirmed in the present embodiment. Similar to the first embodiment, a circulation pipe (not shown) for circulating the treated water between the treatment tank 13 and another treatment tank (not shown) is provided, and an electromagnetic field generator (not shown) and a pump (not shown) for circulating the treated water are provided in the middle of the path of the circulation pipe.

[0037] In the first embodiment, the electromagnetic field generator 17 is provided in the introduction pipe 15, in the second embodiment, the electromagnetic field generators 17a and 17b are provided in the circulation pipe 15 and the introduction pipe 18, respectively, and in the third embodiment, the electromagnetic field generator 17c is provided in the introduction pipe 18. However, the present invention is not limited to this. For example, a plurality of circulation pipes may be provided, and electromagnetic field generators may be provided in each of them. The number and arrangement location of the electromagnetic field generators 17 can be set according to the treatment amount of the wastewater, the content of nitrate nitrogen in the wastewater, etc. Also, depending on the efficiency of the denitrification treatment, etc., it is possible to add a predetermined amount of the wastewater in the storage tank 12 from the outside.

[0038] As described above, some embodiments of the present invention and modification examples of each part have been described. However, these embodiments and modification examples of each part are presented as examples and are not intended to limit the scope of the invention. These novel embodiments described above can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims.

Industrial Applicability

[0039] As described above, according to the denitrification treatment system of the present invention, by providing the electromagnetic field generator in the pipe, it is possible to suppress the adhesion of scale such as gypsum (calcium sulfate) that crystallizes on the surface of the pellets for denitrification. Therefore, it is useful as a denitrification treatment system for removing nitrogen from wastewater containing nitrate nitrogen and the like.

Explanation of symbols

[0040] 11 Denitrification treatment system 12 Storage tank 13 Treatment tank 15 Circulation pipe 16 First pump 17, 17a, 17b, 17c Electromagnetic field generator 18 Introduction pipe 19 Second pump 22 Gas vent pipe 23 Discharge pipe 24a Introduction nozzle 24b Circulation upper nozzle 24c Circulation lower nozzle 24d Discharge nozzle 24e Gas vent nozzle 25 Pellet layer 27 Filter material 31(31a, 31b) Coil part 32 Power supply part 33 Control part 41, 51 Denitrification treatment system

Claims

1. A denitrification treatment system that performs a denitrification treatment to remove nitrogen from wastewater containing nitrate nitrogen, etc. a treatment tank including a pellet layer in which pellets of a carrier for supporting sulfur-oxidizing bacteria that perform denitrification treatment are stacked, and the wastewater introduced from the outside is passed through the pellet layer to produce treated water from which nitrogen has been removed; an inlet pipe connected to the treatment tank and configured to introduce the wastewater from the outside to an upstream side of the denitrification treatment of the pellet bed; a circulation pipe for passing the treated water from a downstream side of the denitrification treatment of the pellet layer to an upstream side of the denitrification treatment of the pellet layer; an electromagnetic field generator provided in at least one of the inlet pipe and the circulation pipe, for generating a magnetic field and an electric field inside the pipe; A denitrification treatment system having the above structure.

2. The treatment tank is provided with the pellet layer in an intermediate portion of the treatment tank, and a filter material for filtering the treated water is provided on an upper portion of the pellet layer downstream of the denitrification treatment of the pellet layer. The introduction pipe is connected to a lower portion of the treatment tank which is an upstream side of the denitrification treatment of the pellet layer, 2. The denitrification treatment system according to claim 1, wherein the circulation piping is provided outside the treatment tank, one end of the circulation piping is connected to an upper portion of the treatment tank that is downstream of the denitrification treatment of the pellet layer, and the other end of the circulation piping is connected to a lower portion of the treatment tank that is upstream of the denitrification treatment of the pellet layer.

3. 3. The denitrification treatment system according to claim 1 or 2, wherein the inlet pipe is provided with a first pump for introducing the wastewater from the outside into the treatment tank, and the circulation pipe is provided with a second pump for circulating the treated water from the downstream side to the upstream side of the pellet layer from the one end to the other end.

4. 2. The denitrification treatment system according to claim 1, wherein the electromagnetic field generator comprises: a coil section that winds around the piping; a power supply section that supplies alternating current to the coil section; and a control section that modulates the frequency of the alternating current from the power supply section over time within a predetermined frequency band.

5. A denitrification method for removing nitrogen from wastewater containing nitrate nitrogen, etc., comprising: A wastewater introduction step of introducing the wastewater into a treatment tank for performing a denitrification treatment; a wastewater treatment step of removing nitrogen from the wastewater introduced into the treatment tank through a pellet layer made of pellets of a carrier supporting sulfur-oxidizing bacteria that perform denitrification treatment, thereby obtaining treated water; a circulation step of circulating the treated water to a drainage side of the treatment tank; an electromagnetic field generating step of generating a magnetic field and an electric field inside the piping by an electromagnetic field generating device provided in at least one of an inlet piping for introducing the wastewater and a circulation piping for circulating the treated water; The denitrification method comprises the steps of:

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