JP3339376B2 - Method and apparatus for immobilizing biocatalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for immobilizing a biocatalyst on an electrode surface. The present invention relates to a method and an apparatus for immobilizing a catalyst. The present invention also relates to a method and an apparatus for treating nitrate-nitrogen-containing water using the above-described method and apparatus for immobilization.

[0002]

2. Description of the Related Art Conventionally, as a method for removing nitrate nitrogen such as nitric acid or nitrous acid contained in wastewater or groundwater, for example, a physicochemical denitrification method (ion exchange method, reverse osmosis method, catalyst reduction method, etc.) ) And biological denitrification methods (rotating disk method, activated sludge method, etc.) are known. The biological denitrification method has attracted attention because it has the advantages that the final form is N ₂ gas, there is no risk of secondary pollution, and the cost is relatively low.

[0003] This biological denitrification method utilizes microorganisms (biocatalysts) that catalyze the reaction of producing nitrogen gas and water from nitrate nitrogen and hydrogen, and brings such microorganisms into contact with the water to be treated. In addition, by supplying hydrogen from the outside, nitrate nitrogen in the water to be treated is converted into nitrogen gas and removed. Among them, a cathode having the microorganisms immobilized on the surface and a suitable anode are used. Biocatalyst immobilization by immersion in the water to be treated, applying a voltage between both electrodes to electrolyze the water to generate hydrogen at the cathode, and denitrify the nitrate-nitrogen-containing water through the microorganism using the hydrogen. It is said that the denitrification method using an activated electrode is particularly practical because it does not generate excess sludge after treatment and does not use explosive hydrogen gas.

In the above-mentioned denitrification method, it is necessary to immobilize hydrogen-assimilating denitrifying bacteria on the electrode surface before water treatment, and this immobilization is conventionally carried out in the form of a slurry containing bacterial cells. This has been done by immersing the electrode in the sludge and holding it for about one month while adding the substrate.

[0005]

However, in the above-mentioned conventional immobilization method, it is difficult to uniformly immobilize the biofilm on the electrode surface, and it takes a long time to immobilize the biofilm. Furthermore, since the electrode is simply immersed, the adhesion is weak,
There was also a problem that the bacteria tended to peel off from the electrode surface. The present invention has been made in view of the above circumstances,
In the water treatment for denitrification of nitrate-nitrogen-containing water by a method using a biocatalyst-immobilized electrode, the biocatalyst can be uniformly and strongly immobilized on the cathode surface, and the time required for the immobilization process is greatly increased. An object of the present invention is to provide a method and an apparatus for immobilizing a biocatalyst on an electrode surface, which can be shortened to a short time. It is another object of the present invention to provide a method and an apparatus for treating nitrate-nitrogen-containing water using such an immobilization method and apparatus.

[0006]

In order to solve the above-mentioned problems, a method for immobilizing a biocatalyst according to the present invention is to provide a sludge slurry containing hydrogen-utilizing denitrifying bacteria in a treatment tank provided with a cathode. The method is characterized in that it is guided from the bottom and flows upward, discharged from the upper part of the processing tank, again guided to the bottom of the processing tank and circulated, and hydrogen-assimilating denitrifying bacteria are attached to the cathode. Also,
The biocatalyst immobilization device of the present invention has an inlet for introducing slurry-like sludge containing hydrogen-assimilating denitrifying bacteria into a treatment tank provided with a cathode at the bottom, and an outlet for discharging the sludge. And a sludge circulating means for guiding sludge into the treatment tank from the inlet, discharging the sludge from the outlet, guiding the sludge again to the inlet, and circulating the sludge. As described above, in the fixing method and apparatus of the present invention, the sludge is transferred upward from the bottom of the processing tank containing the cathode and circulated, so that the sludge is transferred to the cathode surface in a uniform flow, The biocatalyst can be uniformly and strongly immobilized on the cathode surface, and the time required for immobilization can be reduced.

Here, the biocatalyst immobilized on the cathode in the present invention is a microorganism or a microorganism capable of catalyzing a reaction for producing nitrogen and water from nitrate nitrogen contained in the liquid to be treated and hydrogen generated on the cathode. Any bacteria can be used, but generally Paracoccus denitr contained in sludge
ificans, Micrococcus denitrificans, Alcaligenes, Ps
eudomonas, C. aceticum, A. woodii, Methanobacteriu
m denitrificans, Enterobacter cloacal and the like. Therefore, the slurry sludge used in the present invention may be any sludge containing the biocatalyst, and sludge such as human waste sludge can be used as it is. An organic substrate is added to the treatment tank together with the sludge and circulated.

The treatment tank used in the present invention may have any shape such as a rectangular parallelepiped or a cylindrical shape as long as it can accommodate the cathode therein. Are provided with outlets. Further, preferably, the sludge is transferred to the processing tank at the bottom of the processing tank, and the sludge is transferred to the inlet, the inside of the processing tank, and the outlet. Means are attached. This circulation means is usually constituted by a pump installed outside the processing tank.

A cathode for immobilizing a biocatalyst on the surface is accommodated in the treatment tank. The material of the cathode is not particularly limited, and carbon, platinum, nickel, gold, silver,
Or various things, such as platinum-coated nickel, are mentioned.
However, a plate-like carbon electrode is preferable because it is particularly suitable for immobilizing a biocatalyst and is inexpensive. Further, the plate-like carbon electrode may be further subjected to a treatment such as forming irregularities on the surface so that the biocatalyst is more easily fixed.

In the immobilizing apparatus and method according to the present invention, preferably, the bottom of the processing tank is a conical part whose cross-sectional area gradually decreases downward, and the lower end of the conical part is formed. Is provided with the inflow port. By doing so, the flow of the slurry-like sludge can be smoothly flowed radially upward, and the immobilization of the biocatalyst is uniformly performed on the plurality of electrode members.

[0011] More preferably, the bottom of the processing tank,
In particular, a dispersing plate having a large number of through holes is provided in the weight-shaped portion. When such a dispersion plate is interposed, sludge does not flow in a short-circuit manner, but flows evenly between the electrodes. In addition, the contact time of the sludge with the electrode is prolonged, and the biofilm can be more efficiently and uniformly immobilized on the electrode.

In this case, the dispersing plate may be provided only in a single sheet or in a state in which a plurality of sheets are positioned on the same plane. In this case, the dispersing effect can be more reliably achieved. In addition, in the case of providing in multiple stages, it is preferable that the position of the through hole of the upper dispersion plate and the position of the through hole of the lower dispersion plate are shifted from each other because the dispersion effect is further enhanced.

It is preferable to provide a temperature control means for maintaining the temperature of the treatment tank at a constant temperature so that the activity of the biocatalyst is not lost during the circulation operation. For example, the temperature inside the processing tank may be controlled by arranging a constant temperature tank for circulating constant temperature water around the outer periphery of the side surface and / or the bottom surface of the processing tank. The temperature of the treatment tank is about 10 to 35 ° C, preferably 20 to 30 ° C.
Adjust to ° C.

Thus, in the immobilizing method and apparatus according to the present invention, the slurry sludge is guided from the inlet into the treatment tank, transported to the surface of the cathode, and recirculated through the outlet through the outlet. And circulated. Here, the period of the circulation operation varies depending on the sludge to be used, the fixed amount to be fixed, and the like. For example, if it is performed for about 2 to 8 weeks, the fixing is generally completed. The flow rate of the circulating sludge is not particularly limited, but is preferably 0.1
To 1.0 m / min, more preferably 0.3 to 0.6 m / min.

After immobilizing the biocatalyst on the cathode by the above operation, it is possible to take out the cathode from the treatment tank, store it in a separate electrolysis tank, and perform water treatment.
Preferably, the treatment tank itself is used as an electrolysis tank, and the sludge is removed and the water to be treated is flown as it is instead of sludge to perform water treatment. That is, the present invention also provides a method and an apparatus for treating nitrate-nitrogen-containing water using the immobilization method and apparatus, wherein the treatment method comprises a slurry containing hydrogen-utilizing denitrifying bacteria. Sludge is guided upward from the bottom into a processing tank equipped with a cathode and an anode,
Discharged from the top of the treatment tank, guided again to the bottom of the treatment tank and circulated, attached hydrogen assimilating denitrifying bacteria to the cathode, then introduced nitrate nitrogen-containing water into the treatment tank, electrolyzed and cathode To generate nitrogen and denitrify the nitrate nitrogen-containing water via hydrogen-assimilating denitrifying bacteria. Further, the nitrate-nitrogen-containing water treatment apparatus of the present invention is a method in which a slurry sludge containing hydrogen-assimilating denitrifying bacteria or a nitrate-nitrogen-containing water is supplied to an electrolysis tank provided with a cathode and an anode. An inlet for guiding is provided at the bottom, and an outlet for discharging the sludge or the treated water is provided on the upper side. The sludge is guided from the inlet to the electrolysis tank, discharged from the outlet, and then guided to the inlet again. And a means for circulating the sludge is provided.

The difference between the water treatment device and the immobilization device is that an anode is not necessarily required in the immobilization device,
The anode is indispensable in the water treatment equipment, and the cathode and anode are electrically connected to a predetermined power supply, and the treatment tank is an electrolysis tank. It is. Here, the anode is not particularly limited in its material and shape, but may be carbon, platinum, nickel, gold,
Silver or platinum-coated nickel may be used, and a carbon material is practically preferable.

Further, in the present invention, when treating wastewater containing organic nitrogen such as wastewater from a food factory, it is desirable to perform pretreatment for removing organic substances. Therefore, in the treatment method according to another aspect of the present invention, the slurry sludge containing the hydrogen-assimilating denitrifying bacteria is guided upward from the bottom into a treatment tank provided with a cathode and an anode, and is treated upward. After discharging from the upper part of the treatment tank and circulating again to the bottom of the treatment tank, hydrogen-assimilating denitrifying bacteria are attached to the cathode, and then organic nitrogen-containing water is introduced to the contact oxidation tank to remove organic substances, and then the treatment is performed. It is introduced into a tank, electrolyzed to generate hydrogen at the cathode, and subjected to denitrification treatment through hydrogen-utilizing denitrifying bacteria. In this case, a part of the treatment water discharged from the treatment tank is circulated to the contact oxidation tank,
More preferably, the pH of the nitrogen-containing water flowing into the treatment tank is adjusted. Further, as an apparatus for carrying out the treatment method, it is preferable that a contact oxidation tank for removing organic substances in the water to be treated is connected continuously below the above-mentioned electrolysis tank. A treatment water circulation channel for guiding a part of the water to the contact oxidation tank is provided, and the circulation of the treatment water circulation channel is adjusted by adjusting the circulation amount of the treatment water to adjust the pH of the nitrogen-containing water flowing into the electrolysis tank. Amount adjustment means is provided. With such a single device, space saving can be achieved.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a biocatalyst fixing device of the present invention which also serves as a water treatment device will be described in detail with reference to the drawings, but this does not limit the scope of the present invention. Needless to say. As shown in FIG. 1 as a whole, a biocatalyst fixing apparatus 1 of the present invention includes a rectangular parallelepiped treatment tank 2 also serving as an electrolysis tank. In the vicinity of the upper end of the side wall of the treatment tank 2, an overflow portion for receiving sludge or treated water overflowing from the side wall is formed, and an outflow pipe 3 serving as an outlet for the sludge or treated water is connected to the overflow portion. The bottom of the treatment tank 2 is formed as a conical portion 4 having a rectangular cross-sectional area gradually decreasing downward, and an inflow pipe at the top of the conical portion 4 serving as an inlet for sludge or water to be treated. 5 is attached. And the weight 4
A plurality (three in the illustrated example) of which a plurality of through-holes 6a, 7a, 8a are formed substantially uniformly over the entire surface.
Are horizontally and vertically spaced from each other. These dispersion plates 6,
Although the through holes provided in 7 and 8 are rectangular as shown in an enlarged view in FIG. 2, a circular through hole as shown in FIG. 3 may of course be used.

Further, inside the processing tank 2, a dispersion plate 6,
A plurality of plate-shaped cathode members 9 and anode members 10 smaller than the processing tank 2 are fixed on the upper parts of the tanks 7 and 8, and the lower ends thereof are fixed to the tank wall so that the interval between adjacent electrode members is constant. And supported alternately in a substantially vertical state. These electrode members are connected to a power source (not shown) so that the processing tank can be used as an electrolysis tank.

The outflow pipe 3 of the processing tank 2 has a circulation pump 1
The circulation pump 12 has a discharge side connected to the inflow pipe 5 through a discharge pipe 13. Then, by the operation of the circulation pump 12, the sludge in the processing tank 2 is circulated, transferred from the lower part to the upper part in the processing tank 2, and fixed to the cathode member 9 during that time. In FIG. 1, 14 is an opening / closing valve, 15 is an exhaust valve for discharging gas in the processing tank 2, 16 is a supply pipe for adding an organic substrate or the like into the processing tank 2, and 17 is a processing pipe. A jacket for keeping the temperature constant, 18 is a sampling cock, and 19 is a lid of the processing tank 2.

In the processing apparatus, the sludge is put into the processing tank 2 and the circulation pump 12 is started. The sludge in the treatment tank 2 is rectified by the dispersing plates 6, 7, 8 and pushed by the sludge supplied from below, and is brought into contact with the cathode surface while flowing, whereby the biocatalyst contained in the sludge adheres to the cathode surface. Immobilized. Then, it overflows and is again guided from the outflow pipe 3 into the processing tank 2 by the circulation pump 12 and circulated.

After the immobilization of the biocatalyst on the cathode is completed, the sludge is removed, and the water to be treated containing nitrate nitrogen is supplied from the inflow pipe 5. When a voltage is applied to the cathode and the anode in this state, hydrogen is generated on the cathode, and this hydrogen and nitrate nitrogen in the water to be treated are converted into nitrogen and water through the catalytic action of the biocatalyst, and the hydrogen is generated. The nitrate nitrogen in the treated water is removed. The treated water from which the nitrate nitrogen has been removed is discharged from the outflow pipe 3. The switching between the sludge and the water to be treated is performed by switching the suction side of the circulating pump to the supply source of the water to be treated and by switching the transfer destination of the outflow pipe 3 to a tank or a drain port for storing the treated water. Then, the circulation pump can be used as it is for the transfer of the water to be treated.

FIGS. 4 and 5 show another embodiment of the water treatment apparatus according to the present invention, which shows a widely applicable apparatus for treating wastewater containing organic nitrogen. In this figure, the same parts as those of the apparatus of FIG. In the figure, reference numeral 20 denotes a well-known contact oxidation tank which has a substantially same cross-sectional shape as the processing tank 2 and is installed concentrically and integrally below the processing tank 2. The lower part of the contact oxidation tank 20 is formed as a conical part 21 having a rectangular cross-sectional area gradually decreasing downward, and an inlet for water to be treated is provided at the top of the conical part 21. . Further, inside the contact oxidation tank 20, an annular contact portion 22 including a large number of contact materials is vertically arranged with the axis thereof oriented vertically and the axis substantially aligned with the center of the tank.

Further, an inflow pipe 24 connected to a discharge port of a raw water supply pump 23 is connected to the inflow port, and a circulation for circulating a part of the processing water in the processing tank 2 through the inflow pipe 24. A pipe 25 is connected, and an adjustment valve 26 for adjusting the circulation amount and a check valve 27 are attached to the circulation pipe 25. A discharge pipe of a blower 28 is connected to the circulation pipe 25 so that air can be sent into the pipe by the operation of the blower 28. In addition, processing tank 2
Is connected to a pH sensor 29 for measuring the pH of the treated water, and the signal from the pH sensor 29 adjusts the opening of the adjusting valve 26.

In the water treatment apparatus, waste water containing organic nitrogen such as food factory waste water is supplied to the raw water supply pump 2.
3 to the contact oxidation tank 20. The drainage is assisted by the air supplied from the blower 28,
Under the aeration, the contact material of the contact portion 22 undergoes contact oxidation. As a result, the organic matter is decomposed here, and the wastewater after the treatment rises as it is and enters the treatment tank 2, and undergoes the denitrification treatment already described in the treatment tank 2. in this way,
When the contact oxidation tank 20 is provided, it is possible to widely treat the wastewater containing organic nitrogen, and since the treatment equipment is vertically integrated with the treatment tank 2 and the contact oxidation tank 20, extra treatment is possible. No installation space is required.

Here, in the catalytic oxidation treatment, the pH of the wastewater is lowered to, for example, 6 to 6.5, but when the wastewater flows into the treatment tank 2 and is treated, the pH is increased to, for example, 8 to 9.5. Become. On the other hand, it is preferable to maintain the pH of the wastewater entering the processing tank 2 at about 7 in order to secure the processing performance in the processing tank 2. Therefore, the opening degree of the adjusting valve 26 is adjusted to circulate a part of the high-pH treatment water to the contact oxidation tank 20, and the pH in the contact oxidation tank 20, that is, the pH flowing into the treatment tank 2 is increased and adjusted. . This pH adjustment operation can be performed by a manual operation.
It is automatically controlled based on the pH value measured by the sensor 29. In the contact oxidation tank 20, the type and number of the contact material used, the shape and size of the contact portion, the contact residence time, the amount of air supply, and the like are appropriately selected by those skilled in the art according to the properties of the target wastewater. Is what is done.

[0027]

According to the method and apparatus for immobilizing a biocatalyst of the present invention, sludge is transported upward from the bottom of the treatment tank containing the cathode and circulated, so that the sludge flows uniformly on the cathode surface. And the biocatalyst can be uniformly and strongly immobilized on the surface of the cathode, and the time required for immobilization can be reduced. Further, in the water treatment method and apparatus of the present invention, water treatment can be continuously performed after the completion of the biocatalyst immobilization operation, and in the water treatment,
Since the contact time between the water to be treated and the electrode is prolonged, the treatment efficiency is improved. Further, by adding a contact oxidation treatment tank, wastewater treatment containing organic nitrogen can be easily performed.

[0028]

【Example】

(Example 1) The biocatalyst immobilization method of the present invention was carried out using the processing apparatus 1 shown in FIG. However, the volume of the treatment tank was 8.5 liters, and the temperature was controlled at 35 ° C. As the biocatalyst-containing medium, human waste sludge from O City, S Prefecture was used as it was. After repeating the circulation operation for two weeks with the flow rate of circulating the sludge set at 20 to 30 liters / minute,
Sludge in the treatment tank was discharged. On the cathode surface, a uniform biofilm was formed over the front surface, and the weight of the immobilized biocatalyst was 3.55 g / cm ² .

(Comparative Example 1) As shown in FIG.
02, a cathode 103 and an anode 104 are erected alternately horizontally in a horizontal direction, a biocatalyst-containing medium is supplied from the side of the processing tank 102 in parallel with the longitudinal direction of the electrode, and the circulation operation is performed from the opposite side. The biocatalyst was immobilized using a processing device of a type in which the above was repeated. The processing bath 102 is housed in a constant temperature bath 106 whose temperature is controlled at 35 ° C. Even after the circulation operation was repeated for one month, the biocatalyst was only loosely immobilized on the cathode surface, and the weight of the immobilized biocatalyst was 0.2429 g / cm ² .

(Example 2) In Example 1 and Comparative Example 1, a treatment experiment in which nitrate-nitrogen-containing water was treated was carried out using the treatment apparatus in which the biocatalyst was fixed on the cathode surface. As the water to be treated, nitrate nitrogen 400 mg / liter, total organic carbon 400 m
Using a simulated wastewater containing g / liter, the mixture was treated at a flow rate of 5.9 ml / min while controlling the temperature at 35 ° C. Example 1
7 shows the results of the processing apparatus of Comparative Example 1, and the results of the processing apparatus of Comparative Example 1 are shown in FIG.

When the treatment apparatus is provided with a cathode immobilized according to the biocatalyst immobilization method of the present invention and supplies the liquid to be treated from below, the nitrate nitrogen content in the treated water is remarkable. However, in the apparatus of Comparative Example 1 in which water was supplied from the side, it was found that the amount of nitrate nitrogen in the water to be treated did not decrease so much.

(Example 3) The water to be treated was continuously treated for about three months using the treatment apparatus of Example 1. FIG. 9 shows the nitrate nitrogen concentration in the water to be treated supplied to the treatment apparatus and the concentration of nitrate nitrogen in the treatment water discharged from the treatment apparatus, and plotted against the number of days elapsed from the start of treatment. is there. The nitrate nitrogen concentration (inflow) in the water to be treated before the treatment varied between about 200 and about 500 mg / liter, but the concentration (outflow) in the treated water denitrified by the treatment apparatus of the present invention was about 3%. Even after a lapse of months, it is maintained at about 10 mg / liter or less. That is, in the treatment apparatus provided with the cathode immobilized by the biocatalyst immobilization method of the present invention, the immobilized biocatalyst can work well without being detached even when used continuously for about three months. all right.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a biocatalyst fixing device of the present invention.

FIG. 2 is a top view of a dispersion plate preferably used in the apparatus of FIG.

FIG. 3 is a top view showing a modification of the dispersion plate of FIG. 2;

FIG. 4 is a schematic vertical sectional view showing an example of the nitrogen-containing water treatment apparatus of the present invention.

FIG. 5 is a schematic view of the device of FIG. 4 taken along line VV.

FIG. 6 is a diagram showing a processing apparatus used in Comparative Example 1.

FIG. 7 is a graph showing a change in the concentration of nitrate nitrogen in the water to be treated when the treatment is performed by the treatment apparatus of Example 1.

FIG. 8 is a graph showing a change in the concentration of nitrate nitrogen in the water to be treated when treated by the treatment apparatus of Comparative Example 1.

FIG. 9 is a graph showing changes in the concentrations of nitrate nitrogen in the water to be treated and the treated water when the treatment apparatus of Example 1 performs continuous treatment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Immobilization processing apparatus 2 ... Processing tank (Electrolysis tank) 3 ... Outflow pipe 5 ... Inflow pipe 6, 7, 8 ... Dispersion plate 9 ... Cathode 10 ... Anode 12 ... Circulation pump 20 ... Contact oxidation tank 26 ... Adjustment valve 29… pH sensor

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masayuki Watanabe 1-14-16 Kudankita, Chiyoda-ku, Tokyo Techno-Oteuchi Co., Ltd. (56) References JP-A-9-155388 (JP, A) JP-A Heihei 9-224598 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 3/28-3/34 C02F 1/46

Claims (14)

(57) [Claims] 1. A slurry sludge containing a hydrogen-assimilating denitrifying bacterium is guided upward from a bottom into a treatment tank provided with a cathode, discharged from the upper part of the treatment tank, and discharged again from the treatment tank. A method for immobilizing a biocatalyst, wherein the method is carried out by circulating the solution to the bottom and attaching hydrogen-assimilating denitrifying bacteria to the cathode. 2. A perforated plate is disposed below a cathode in a treatment tank, and sludge guided from the bottom of the treatment tank is dispersed through the perforated plate and transferred to the cathode. Item 4. The method for immobilizing a biocatalyst according to Item 1. 3. A cathode is constituted by a plurality of plate-like electrode members, said plurality of plate-like electrode members are disposed substantially vertically, and said sludge is circulated through a gap between said plate-like electrode members. The method for immobilizing a biocatalyst according to claim 1 or 2. 4. An inlet for introducing slurry sludge containing hydrogen-assimilating denitrifying bacteria into the treatment tank, and an outlet for discharging the sludge at an upper side of the treatment tank provided with a cathode. And a sludge circulating means for introducing the sludge into the treatment tank through the inlet, discharging the sludge from the outlet, guiding the sludge again to the inlet, and circulating the sludge. 5. A perforated plate is provided below a cathode in a processing tank, and sludge guided from the bottom of the processing tank is passed through the perforated plate, dispersed and transferred to the cathode. The biocatalyst immobilization device according to claim 4, characterized in that: 6. A structure in which a cathode is constituted by a plurality of plate-like electrode members, said plurality of plate-like electrode members are disposed substantially vertically, and said sludge is circulated through a gap between said plate-like electrode members. 6. The method according to claim 4, wherein
The biocatalyst immobilizing device according to the above. 7. A slurry sludge containing a hydrogen-assimilating denitrifying bacterium is guided from the bottom into a treatment tank provided with a cathode and an anode, flows upward, discharged from the top of the treatment tank, and treated again. It is led to the bottom of the tank and circulated.Hydrotrophic denitrifying bacteria are attached to the cathode, and then the water containing nitrate nitrogen is introduced into the treatment tank, and is electrolyzed to generate hydrogen at the cathode. A method for treating nitrate-nitrogen-containing water, comprising denitrifying nitrate-nitrogen-containing water via a denitrifying bacterium. 8. A perforated plate is disposed below an anode and a cathode in a processing tank, and sludge introduced from the bottom of the processing tank is dispersed through the perforated plate and transferred between the anode and the cathode. The method for treating nitrate-nitrogen-containing water according to claim 7. 9. A sludge in the form of slurry containing hydrogen-assimilating denitrifying bacteria is guided upward from the bottom into a treatment tank provided with a cathode and an anode, discharged from the top of the treatment tank, and treated again. After being led to the bottom of the tank and circulated, hydrogen-assimilating denitrifying bacteria are attached to the cathode, and then wastewater containing organic nitrogen is led to the contact oxidation tank to remove organic matter, and then led into the treatment tank,
A method for treating nitrate-nitrogen-containing water, comprising subjecting the cathode to hydrogen generation by electrolysis and subjecting the wastewater to denitrification treatment through hydrogen-assimilating denitrifying bacteria. 10. The nitrate nitrogen-containing water according to claim 9, wherein a part of the treatment water discharged from the treatment tank is circulated to the contact oxidation tank to adjust the pH of the wastewater flowing into the treatment tank. Processing method. 11. An electrolysis tank provided with a cathode and an anode is provided with an inlet for introducing sludge sludge containing hydrogen-assimilating denitrifying bacteria or nitrogen-containing water into the electrolysis tank at the bottom thereof. Outlets for discharging water are respectively provided on the upper side, and sludge circulating means for guiding the sludge into the electrolysis tank from the inlet, discharging from the outlet, guiding the sludge to the inlet again, and circulating the sludge is provided. A nitrogen-containing water treatment apparatus characterized by the above-mentioned. 12. A perforated plate is provided below an anode and a cathode in a processing tank, and sludge led from the bottom of the processing tank is dispersed by passing through the perforated plate to be interposed between the anode and the cathode. The nitrogen-containing water treatment apparatus according to claim 11, wherein the apparatus is configured to be transferred. 13. The nitrogen-containing water treatment apparatus according to claim 11, wherein a contact oxidation tank for removing organic substances in the water to be treated is connected below the electrolysis tank. 14. The electrolysis tank is provided with a treated water circulation channel for guiding a part of the treated water to the contact oxidation tank, and the treated water circulation channel is controlled by adjusting a circulation amount of the treated water. The nitrogen-containing water treatment apparatus according to any one of claims 11 to 13, further comprising a circulation amount adjusting means for adjusting the pH of the nitrogen-containing water flowing into the decomposition tank.