JP2009061390A - Direct oxidation method of ammonia nitrogen in water and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treating method and a water treatment apparatus efficiently oxidizing and removing ammonia nitrogen at cost lower than that in a conventional method, and recovering electric energy by this treatment, in treatment of water containing ammonia nitrogen. <P>SOLUTION: The water treatment apparatus comprises a negative electrode tank having a biological membrane electrode using a microorganic membrane formed on a conductive carrier as a negative electrode, and a positive electrode tank having a positive electrode therein across a diaphragm. In the water treating method, water to be treated containing ammonia nitrogen is introduced into the negative electrode tank, the ammonia nitrogen is directly oxidized to nitrogen gas by a microorganism reaction in an anaerobic condition, electrons generated at the negative electrode in the oxidization are transferred to the positive electrode, to reduce dissolved oxygen at the positive electrode. Slight DC voltage, about 0.5V, is preferably applied between the positive and negative electrodes. Movement of electrons from the negative electrode to the positive electrode allows recovery of electric energy. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water treatment method and a water treatment apparatus, and in particular, for removing nitrogen compounds in water, ammonia nitrogen is directly oxidized to nitrogen gas under anaerobic conditions, and at the same time, electric energy can be recovered. The present invention relates to a water treatment method and a water treatment apparatus.

  Ammonia nitrogen is originally a substance that is a nutrient source for microorganisms, but is contained in high concentrations in various wastewaters such as livestock wastewater, domestic wastewater, and factory wastewater. When these effluents are discharged into the environment, some of the ammonia nitrogen contained in the effluent becomes nitrogen compounds such as nitrate nitrogen and nitrite nitrogen by the action of microorganisms, and these nitrogen containing ammonia nitrogen The problem arises that the compound results in eutrophication of closed waters. This ammoniacal nitrogen can be rendered harmless to nitrogen gas by biological techniques. Among various methods for detoxifying nitrogen compounds, a method using a nitrification / denitrification reaction caused by bacteria called nitrifying bacteria and denitrifying bacteria has become mainstream. Ammonia nitrogen is oxidized in the nitrification process to nitrate nitrogen or nitrous acid nitrogen under aerobic conditions. Nitrate nitrogen and nitrous nitrate produced in the nitrification process are reduced to nitrogen gas and detoxified in the denitrification process under anaerobic conditions (see, for example, Non-Patent Document 1).

In such a conventional biological treatment method, dissolved oxygen is required as an electron acceptor in the nitrification process. Therefore, it is necessary to aerate the reaction tank, which is a factor of high cost. In addition, in the denitrification process, it is necessary to supply an organic substance or the like as an electron donor. As an electron donor supply method, an AO process using an organic substance contained in the water to be treated, an organic substance that supplies an organic substance such as acetic acid or methanol Addition methods and the like have been proposed. Here, the AO process is also referred to as an anaerobic aerobic activated sludge method, and has an anaerobic tank and an aerobic tank that are independent in the order of the flow path of the treated water. In this method, the nitrogen compound is oxidized to nitrogen, and the nitrogenous compound of nitrate nitrogen or nitrous acid nitrous acid is reduced to nitrogen gas by using an organic substance in waste water as an electron donor in an anaerobic tank.
However, in these conventional water treatment methods, it is difficult to grasp the optimum amount of organic matter added, and it is necessary to treat excessively added organic matter, and in addition to excess sludge generated by adding organic matter. Processing is essential, and the processing process is complicated.

  In addition to such a nitrification / denitrification process, a biological treatment method for ammonia nitrogen treatment has been proposed, and one of them is the ANAMOX process. The ANAMOX process uses planctomycetes as a microorganism capable of oxidizing ammonia by making a balanced presence of ammonia nitrogen and nitrite nitrogen produced by nitrite-type nitrification of ammonia nitrogen under anaerobic conditions. Is a water treatment method in which ammonia nitrogen is directly oxidized to nitrogen gas by requiring nitrite nitrogen as an electron acceptor. Thus, the ANAMOX process can complete the entire process under anaerobic conditions. However, since raw nitrous acid nitrogen is required, in order to supply this, it is necessary to nitrify a part of the ammonia nitrogen in the water, and this requires a relatively large cost for aeration. In addition, a technology for efficiently nitrite-type nitrification of ammonia nitrogen in water has not been established, and the ANAMMOX process has a problem that it is relatively difficult to stabilize the treatment compared to nitrification / denitrification treatment (Non-Patent Document). 1).

  The nitrification / denitrification process as described above is an ammoniacal nitrogen treatment method that has been established, but requires a nitrification process that uses oxygen as an electron acceptor, which requires aeration costs, and an anaerobic treatment method. There is a problem that the processing cost is higher than that.

  In addition, since it is necessary to supply organic matter as an electron acceptor in the denitrification process, an AO process or an organic matter addition method has been proposed. However, in the AO process, the amount of organic matter contained in the wastewater may be relatively small. In many cases, the nitrogen removal rate is as low as 50 to 60%. The organic substance addition method, which is also a countermeasure for the AO process, has a problem in that the treatment process becomes complicated because it is necessary to treat excess sludge and remove excess organic substances.

  In addition, in the ANAMOX process, which is an anaerobic treatment method of ammonia nitrogen, the reaction by the planctomycetes bacterium used here is greatly inhibited by oxygen etc., and the growth rate of the planctomycetes bacterium is very slow, and the nitrification / denitrification process As compared with, the processing is unstable and the processing speed is relatively slow.

  Furthermore, in recent years, various environmental problems that are thought to be caused by global warming have become apparent, and in order to minimize the dependence on fossil fuels, biotechnology obtained by biologically treating plants and livestock waste Attempts have been made to disperse energy sources such as the use of ethanol or biomethane gas.

Japanese Examined Patent Publication No. 6-10423 JP 2002-346666 A T.Khin, A.P. Annachhatre “Biotechnology Advances”, 22 (2004), 519-532

  The present invention has been proposed in view of the problems of the conventional wastewater treatment methods as described above, and solves the problems of these conventional methods, and ammonia nitrogen in the water to be treated under anaerobic conditions. An object of the present invention is to provide a water treatment method and a water treatment apparatus that can oxidize water directly into nitrogen gas at a low cost and that can recover electrical energy using this oxidation treatment. To do.

  The present inventors use a conductive carrier having a microbial membrane formed on its surface as a negative electrode, connect it to a positive electrode separated by a diaphragm, and treat the treated water containing ammonia nitrogen in the negative electrode tank. The present invention has been completed by finding that a kind of battery structure can be obtained by introducing NO, and that ammonia nitrogen can be directly oxidized to nitrogen gas by causing a microbial reaction under an anaerobic condition in the negative electrode chamber.

That is, the present invention has the following contents.
(1) A water treatment method for removing ammonia nitrogen in water, a negative electrode tank having a biofilm electrode using a microbial film formed on a conductive carrier as a negative electrode, and a positive electrode inside with a diaphragm A positive electrode tank having ammonia gas is introduced into the negative electrode tank, and ammonia nitrogen is directly oxidized into nitrogen gas by performing a microbial reaction under anaerobic conditions. A water treatment method characterized by transmitting generated electrons to a positive electrode to reduce dissolved oxygen in the water in the positive electrode tank or oxygen in the air.
(2) The water treatment method according to (1), wherein a minute direct current voltage is applied between the positive electrode and the negative electrode.
(3) After introducing water to be treated containing ammoniacal nitrogen into the negative electrode tank and introducing the electrolyte solution into the positive electrode tank, a microbial reaction is performed under anaerobic conditions with a minute DC voltage applied between both electrodes. The water treatment method according to (1) or (2), wherein the water treatment method is performed.
(4) The biofilm electrode according to any one of the above (1) to (3), wherein a microbial membrane is formed on the surface of a conductive carrier, and the conductive carrier is connected to a negative electrode material. Water treatment method.
(5) A microbial membrane comprising a positive electrode tank having a positive electrode inside separated by a diaphragm, a negative electrode tank having a negative electrode inside, and a wire connecting the two electrodes, wherein the negative electrode is formed on the surface of the conductive carrier. A water treatment apparatus, which is a biofilm electrode used.
(6) The water treatment apparatus according to (5), wherein a direct-current power source is provided between the positive electrode and the negative electrode, and a minute voltage is applied between both electrodes.

  By using the water treatment method of the present invention, ammonia nitrogen contained in agricultural wastewater, industrial wastewater and other various water containing ammonia nitrogen is passed through nitrate nitrogen and nitrous acid nitrous acid. Therefore, it is possible to directly oxidize nitrogen gas without removing nitrogen in water containing ammoniacal nitrogen. Furthermore, according to this method, the oxidation treatment of ammonia nitrogen can be performed under anaerobic conditions, so that it is not necessary to aerate the water to be treated which is required in the nitrification process by the conventional method. The problem of high processing costs can be solved. Further, in the conventional method, it is necessary to add an organic substance or the like as an electron acceptor in the denitrification process. However, according to the method of the present invention, it is not necessary to add such an extra organic substance. Simplification and cost reduction became possible.

  Furthermore, the apparatus of the present invention has a structure similar to that of a battery, and electrons are released during the oxidation treatment in the negative electrode tank, and this is used for the reduction reaction at the positive electrode. Therefore, a current flows between the two electrodes as the water is treated, and the water treatment method and the water treatment apparatus are capable of recovering electrical energy.

  The present invention has a two-cell structure of a positive electrode tank and a negative electrode tank separated by a diaphragm such as an ion exchange membrane, and an energy-generating ammoniacal nitrogen oxidation apparatus equipped with electrodes serving as a positive electrode and a negative electrode in each tank, and This is a water treatment method that enables recovery of electrical energy by oxidizing electrons generated during oxidation treatment while oxidizing ammonia nitrogen directly to nitrogen gas under anaerobic conditions.

The present invention will be described below with reference to the drawings.
FIG. 1 is an overall schematic configuration diagram of a water treatment apparatus of the present invention.

  In FIG. 1, in the negative electrode tank 16, the inside is filled with a conductive carrier 18 in contact with the negative electrode material 8, and a biofilm electrode is formed by forming a microbial film on the surface thereof. It is desirable to use the activated sludge 19 in order to ensure the formation of a microbial membrane for ammonia oxidation and to promote its formation rate. A negative electrode solution inlet 17 and a negative electrode solution outlet 15 are provided in the negative electrode tank. A negative electrode solution which is water to be treated containing ammoniacal nitrogen is introduced from the negative electrode solution inlet 17. The positive electrode tank 10 and the negative electrode tank 16 are completely separated by a diaphragm 6 such as a cation exchange membrane.

  In order to accelerate the collection of electric energy and the processing speed in the negative electrode tank, it is preferable that a minute voltage is applied between the electrodes by a DC power source 1 or the like. The purpose of voltage application is not to generate a large potential difference between both electrodes, which causes electrolysis of water, but to induce a minute potential difference in advance, thereby inducing the desired microbial reaction. It is for promoting. Therefore, the voltage applied between both electrodes needs to be a very small potential difference as long as it is suitable for this purpose. Specifically, it can be used at 2.0 volts or less, preferably 0.1. It may be about -1.0 volts, more preferably about 0.3-0.8 volts. When a voltage exceeding 2.0 volts is applied between both electrodes, water electrolysis begins to proceed, which is not preferable for the purpose of the present invention.

  In the negative electrode tank 16, the ammonia energy is directly oxidized into nitrogen gas by the biofilm electrode, and electric energy is recovered by utilizing the flow of electrons generated at this time. The treated negative electrode solution flows out of the apparatus from the negative electrode solution outlet 15 as treated water. Electrons generated when the ammonia nitrogen is directly oxidized into nitrogen gas move to the positive electrode 7, and in the positive electrode tank 10, dissolved oxygen in the positive electrode solution or oxygen in the air is reduced to water. The positive electrode solution is introduced from the positive electrode solution inlet 11 and flows out of the apparatus from the positive electrode solution outlet 9.

In the negative electrode tank 16, ammonia nitrogen in the water to be treated is directly oxidized into nitrogen gas under anaerobic conditions according to the following reaction formula (1).
2NH ₄ ⁺ → N ₂ + 8H ⁺ + 6e ⁻ (1)
Moreover, in the positive electrode tank 10, the dissolved oxygen in the positive electrode solution is reduced to water according to the following reaction formula (2).
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)
From the above reaction formulas (1) and (2), the overall reaction formula is the following reaction formula (3).
4NH ₄ ⁺ + 3O ₂ → 2N ₂ + 4H ⁺ + 6H ₂ O (3)
The Gibbs free energy change in the reaction formula (3) becomes a reaction of ΔG _r ⁰ = −1106 (kJ / mol), and the reaction proceeds from left to right.

  As the conductive carrier 18 for forming the microbial membrane, activated carbon, conductive plastic, carbon material pellets, porous metal material and the like can be used, and among these, activated carbon is most preferable.

  In addition, microorganisms that can be used in the biofilm electrode of the present invention are abundant in activated sludge and have the ability to oxidize ammoniacal nitrogen in water under anaerobic conditions while growing at room temperature. Can be used. Specifically, those obtained from sludge present in an anaerobic tank or an aerobic tank such as an AO process of a domestic wastewater treatment system are suitable.

  The water treatment apparatus of the present invention is a two tank type divided into a positive electrode tank and a negative electrode tank by a diaphragm. The role of this diaphragm is to prevent substances that are present and generated at both poles from mixing with each other by diffusion and convection while maintaining electrical conductivity. It is desirable to have biological corrosion resistance, a small potential difference, a large mechanical strength, excellent workability, and easy mounting and management. Actually, as the diaphragm of the present invention, it is possible to use a thin filter cloth having a very fine pore, an unglazed plate, a ceramic, a nonwoven fabric, a hydrophilic polymer membrane, an ion exchange membrane, etc. For good reaction, a cation exchange membrane is optimal as a diaphragm.

  The water treatment apparatus of the present invention can be used in either a batch type or a continuous type. In the case of the batch type, for example, in FIG. 1, first, a negative electrode tank is filled with a conductive carrier 18 such as activated carbon in contact with the negative electrode material 8, and activated sludge 19 is introduced to form a biofilm electrode. . Next, water to be treated containing ammoniacal nitrogen is introduced through the negative electrode liquid inlet 17. On the other hand, an electrolyte solution such as a phosphate buffer is introduced into the positive electrode tank as a positive electrode solution. Next, a voltage of about 0.5 volts is applied between the positive electrode 7 and the negative electrode 8 from the DC power source 1 by adjusting the variable resistor 2. By leaving it in this state, a microbial reaction proceeds in the negative electrode tank, and ammonia nitrogen in the negative electrode solution is oxidized and discharged from the discharge port 14 to the outside as nitrogen gas. Electrons are generated along with the oxidation of ammoniacal nitrogen at the negative electrode, and the electrons move to the positive electrode through the connection. At the positive electrode, the moved electrons reduce dissolved oxygen in the positive electrode solution or oxygen in the air to become water. Since ammonia nitrogen in the negative electrode solution decreases with the progress of the microbial reaction, the reaction is terminated when the amount reaches the target value, and the liquid to be treated is extracted.

  In the case of the continuous type, as in the case of the batch type, a biofilm electrode is formed, water to be treated is introduced into the negative electrode, a positive electrode solution is introduced into the positive electrode, and a voltage is applied between the two electrodes. Allow the reaction to proceed. The water to be treated is continuously injected into the negative electrode tank and the treated water is continuously discharged. At this time, the concentration of ammoniacal nitrogen in the treated water is the target value according to the progress of the microbial reaction. The injection volume is controlled to be as follows.

In addition, in order to remove nitrate nitrogen or nitrite nitrogen in water, water is electrolyzed using a biocatalyst electrode or a biofilm electrode as a negative electrode, and hydrogen generated by this electrolysis is used by a biofilm electrode. A method of removing biochemically or biologically nitrate nitrogen or nitrite nitrogen in water has been proposed (see, for example, Patent Document 1 and Patent Document 2). However, these methods utilize hydrogen generated by electrolysis of water as a supply source of hydrogen which is an electron acceptor necessary for the denitrification reaction.
On the other hand, the method of the present invention does not perform such electrolysis of water but oxidizes ammoniacal nitrogen in water to nitrogen gas by the microbial reaction itself of the biofilm electrode. In order to further accelerate the reaction, a very small potential difference that does not cause electrolysis is applied between the two electrodes, which is based on a completely different reaction mechanism. In other words, the applied voltage is very small, such as about 0.5 volts, and this is for inducing and promoting the microbial reaction of the biofilm electrode. It does not consume.

  EXAMPLES Next, although an Example demonstrates this invention in more detail, this invention is not limited at all by these Examples.

  By removing dissolved oxygen, artificially creating ammonia-containing simulated wastewater containing 90 ppm of ammonia nitrogen, and oxidizing the ammonia nitrogen contained in the simulated wastewater directly into nitrogen gas using the water treatment device shown in FIG. Processed. The positive electrode tank 10 of this water treatment apparatus is 0.6 liters, the negative electrode tank 16 is 0.6 liters, and a cation exchange resin membrane (trade name: Nafion) manufactured by DuPont is provided as the diaphragm 7. The simulated waste water was oxidized by batch operation.

  First, argon gas was introduced into the apparatus from the argon gas inlet 13, and the gas inside the apparatus was discharged from the gas discharge port 14, whereby the gas inside the apparatus was replaced with argon gas. A mixture of sludge 19 of 100 ml of nitrified sludge and 100 ml of activated sludge mixed with 180 g of activated carbon was charged into the negative electrode tank 16 of this water treatment apparatus. A small amount of simulated waste water was put here and allowed to stand at room temperature to grow microorganisms in the sludge, and a microbial film was formed on the surface of activated carbon 18 which is a conductive carrier. Activated carbon having a microbial film formed on the surface was placed in contact with the negative electrode 8 to obtain a biofilm electrode.

In this way, in a water treatment apparatus equipped with a biofilm electrode in the negative electrode tank, an ammonia-containing simulated waste water containing 90 ppm of ammonia nitrogen by removing dissolved oxygen by batch operation once a week is treated as negative electrode. The solution was supplied from the solution inlet 17 to the negative electrode tank 16, and the negative electrode tank 16 was kept under anaerobic conditions. Similarly, the positive electrode tank was supplied from the positive electrode solution inlet 11 to the positive electrode tank 10 by a batch operation once a week as a positive electrode solution containing a phosphate buffer containing about 5 to 8 ppm of dissolved oxygen.
In order to promote the oxidation reaction by the biofilm and the recovery of electrons generated during the treatment, a very small voltage of 0.5 V was continuously applied between the positive electrode 7 and the negative electrode 8 using the DC power source 1. The gas generated during the batch processing experiment was collected in a Tedlar bag connected to the nitrogen collection port 12 with the gas discharge port 14 closed.

The reaction with the biofilm electrode was allowed to stand for 1 week in this state, and water treatment was performed with the water treatment apparatus of the present invention.
At each batch treatment, the negative electrode solution is recovered from the negative electrode solution outlet 15, and the ammonia nitrogen concentration, nitrate nitrogen concentration and nitrite nitrogen concentration in the negative electrode solution are measured, and the amount of nitrogen gas in the Tedlar bag Was measured. During the treatment, the current value generated between the electrodes was measured once a day.

  In the treatment of the simulated waste water by the water treatment device, the positive electrode tank 10 and the negative electrode tank 16 are separated by the cation exchange membrane 6 which is a diaphragm, so that ammonia nitrogen may flow out from the negative electrode tank 16 to the positive electrode tank 10. Although only a very small amount of ammonia nitrogen in the positive electrode solution could be detected, it is considered that there was almost no outflow amount of ammonia nitrogen through the cation exchange membrane 6 to the positive electrode chamber 10.

  As a comparative control, in the water treatment apparatus of FIG. 1, the same waste water treatment operation was performed using a water treatment apparatus in which only the activated carbon was used in the DC power source 1, the variable resistance 2, and the negative electrode tank 16 without using the mixed sludge 19. For each batch treatment experiment, the amount of ammonia nitrogen adsorbed on the activated carbon and the amount of nitrogen gas remaining in the Tedlar bag from the beginning of the batch treatment experiment were measured. This was performed in order to grasp and correct the amount of ammonia nitrogen adsorbed on the activated carbon and the amount of nitrogen gas remaining in the Tedlar bag before the start of the experiment in each operation. This corrects the effluent ammonia nitrogen treatment amount, the effluent nitrate nitrogen treatment amount, the effluent nitrite nitrogen treatment amount, and the nitrogen gas amount generated during the batch treatment experiment in the wastewater treatment operation of the present invention. Calculated.

  The results of these simulated wastewater treatment experiments are shown in FIGS. In FIG. 2, a is the amount of ammoniacal nitrogen in the simulated wastewater before treatment (about 10.5 mg), b is the amount of ammoniacal nitrogen in the treated wastewater after treatment (about 9.5 mg), and c is the simulated amount after treatment. The amount of nitrate nitrogen and nitrite nitrogen (0.0 mg) in the wastewater, d is the amount of nitrogen gas generated during one batch treatment experiment (about 1.0 mg), and e is the ammonia in the treated water after treatment The total value (about 10.5 mg) of the amount of nitrogen, the amount of nitrate nitrogen, the amount of nitrous acid back nitrogen, and the amount of nitrogen gas generated during the batch treatment experiment is shown. Further, f in FIG. 3 is a current value generated between the electrodes (about 50.0 μA), and g is a current value flowing between the electrodes by a voltage of 0.5 V applied between the electrodes using the DC power supply 1 (22. About 0 μA).

As can be seen from FIG. 2, the amount of ammonia nitrogen (b) after the treatment is smaller than the amount of ammonia nitrogen (a) before the treatment, and the amount of nitrate nitrogen and the amount of nitrogen in the negative electrode solution after the treatment are reduced. Since the amount of nitrogen nitrate (c) is hardly measured, it can be seen that ammonia nitrogen is treated and reduced, and the amount of nitrate nitrogen and nitrogen nitrite are not generated. In addition, it can be seen that the total amount of nitrogen (e) after treatment is larger than the amount of ammoniacal nitrogen (a) before partial treatment, but this is due to fluctuations due to measurement errors in the nitrogen gas amount (d) This is due to the fact that, on average, this is a value approximately equal to the ammoniacal nitrogen amount (a) before treatment. The amount of ammonia nitrogen reduced by this treatment is approximately the same as the amount of nitrogen gas (d) generated during the treatment, and these values and current values substantially satisfy the relationship of equation (1). Thus, it was found that ammonia nitrogen was directly oxidized into nitrogen gas under anaerobic conditions, and electrons were recovered.
Further, as shown in FIG. 3, it can be seen that a current value (f) larger than the flowing current value (g) is generated by applying a voltage of 0.5 V between the electrodes during the processing period. . From the above, it is possible to recover electrical energy by applying a voltage between the electrodes while oxidizing ammonia nitrogen directly to nitrogen under anaerobic conditions, and reaction treatment with a biofilm electrode in the negative electrode tank It has been found that speed can be promoted.

  According to the method and apparatus of the present invention, it is possible to recover electric energy while processing ammonia nitrogen directly into nitrogen gas under anaerobic conditions, so that the cost and environmental load are low compared to conventional methods. It is possible to process ammonia nitrogen in water with energy saving, purification treatment of environmental water such as groundwater, treatment of industrial water, agricultural water, etc., and wastewater treatment of sewage, industrial wastewater, agricultural wastewater, etc. Useful in the field of

It is a whole schematic block diagram of the water treatment apparatus of this invention. It is a graph which shows the process result of ammonia nitrogen in an Example. It is a graph which shows the electron collection | recovery in an Example.

Explanation of symbols

1: DC power supply, 2: variable resistance, 3: variable resistance, 4: voltmeter, 5: ammeter, 6: diaphragm (Nafion film), 7: positive electrode, 8: negative electrode, 9: positive electrode solution outlet, 10: Positive electrode tank, 11: Positive electrode solution inlet, 12: Nitrogen sampling port, 13: Argon gas inlet, 14: Gas outlet, 15: Negative electrode solution outlet, 16: Negative electrode tank, 17: Negative electrode solution inlet, 18: Activated carbon, 19: Mixed sludge (digested sludge and activated sludge)
a: Ammonia nitrogen amount before treatment,
b: amount of ammoniacal nitrogen after treatment,
c: amount of nitrate nitrogen and nitrite nitrogen after treatment,
d: the amount of nitrogen gas generated during the batch processing experiment,
e: Total amount of ammonia nitrogen after treatment, nitrate nitrogen, nitrous acid back nitrogen and nitrogen gas generated during batch treatment experiment,
f: current value generated between the electrodes,
g: Value of current flowing between the electrodes due to a voltage of 0.5 V applied between the electrodes,

Claims (6)

  A water treatment method for removing ammonia nitrogen in water, a negative electrode tank having a biofilm electrode using a microbial membrane formed on a conductive carrier as a negative electrode, and a positive electrode having a positive electrode inside with a diaphragm Electrons generated in the negative electrode during oxidation treatment by introducing water to be treated containing ammonia nitrogen into the negative electrode tank and oxidizing the ammonia nitrogen directly to nitrogen gas by conducting a microbial reaction under anaerobic conditions. Is transmitted to the positive electrode, and dissolved oxygen in the water in the positive electrode tank or oxygen in the air is reduced.   The water treatment method according to claim 1, wherein a minute DC voltage is applied between the positive electrode and the negative electrode.   After introducing water to be treated containing ammonia nitrogen into the negative electrode tank and introducing the electrolyte solution into the positive electrode tank, a microbial reaction is performed under anaerobic conditions with a minute voltage applied between both electrodes. The water treatment method according to claim 1, wherein the water treatment method is characterized.   The water treatment method according to any one of claims 1 to 3, wherein the biofilm electrode is formed by forming a microbial membrane on the surface of the conductive carrier and connecting the conductive carrier to a negative electrode material.   A living body using a microbial membrane, which is composed of a positive electrode tank having a positive electrode inside separated by a diaphragm, a negative electrode tank having a negative electrode inside, and a connection connecting both electrodes, the negative electrode formed on the surface of the conductive carrier A water treatment apparatus, which is a membrane electrode.   The water treatment apparatus according to claim 5, wherein a direct current power source is provided between the positive electrode and the negative electrode, and a minute voltage is applied between the two electrodes.

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