JP2000334478A - Physicochemical method for removal of nitrate nitrogen in water and denitrifying apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove nitrate nitrogen contained in underground water, or the like, by blowing gaseous hydrogen into the water containing nitrate ions and electrochemically converting the nitrate ions to gaseous nitrogen on a catalyst under reducing conditions. SOLUTION: Water containing nitrate ions is pre-heated in a warming apparatus 1, a small amount of gaseous hydrogen is blown into the water in a gaseous hydrogen mixing and saturating apparatus 2 and the water is saturated with hydrogen by high-speed stirring to adjust the redox potential of the hydrogen- saturated water below that of water. In a denitrifying apparatus 3, the water is irradiated with short wavelength light such as UV on a catalyst under reducing conditions, electric current is supplied between electrodes and electromagnetic field conversion is carried out to excite and react the nitrate ions and hydrogen atoms and the nitrate ions are reduced and discharged as gaseous nitrogen into the air. The water freed of nitrate nitrogen is sent to a treated water oxidation acclimation apparatus 4, where oxygen is blown into the water in the reduced state to convert and acclimate to an oxidized state. In this way, the nitrate nitrogen included in underground water, or the like, is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications] In recent years, with the development of industry worldwide and the rapid increase in population, water pollution by nitric acid has progressed, and groundwater pollution by nitric acid in Europe and Japan is also intensifying.
This is because nitrogen discharged from human wastewater, such as human wastewater, domestic wastewater, which is a water-based environmental pollutant, livestock wastewater treatment liquid, industrial wastewater treatment water, etc., and nitrogen derived from fertilizers are finally converted by nitrification. It is mainly converted to nitric acid. This is regulated as drinking water with a NO ₃ concentration of 10 ppm or less. The present invention is a technique for removing nitrate nitrogen dissolved in lakes, marshes, river water, groundwater, and the like, and can be applied to purification of water immediately before drinking tap water and the like. It is particularly effective in preventing groundwater pollution, and is also applied to the field of removing nitrate nitrogen efficiently and efficiently at low cost before drainage. In addition, with the aim of purifying the water quality of inland water systems such as lakes and marshes and closed water systems, which are widely discussed as environmental problems, the efficiency of nitrogen removal in water systems is improved to a level never before by combining a circulating water flow system and a filter system for lakes and marshes. It is possible. As described above, basic technology for removing nitrate nitrogen from rivers, lakes, marshes, sea areas, and groundwater is provided, and it is thought that an enormous amount of water can be treated in the future by improving the technology. In other words, there is a prospect as an effective means for expanding the use range of depleted water resources.

[0002]

2. Description of the Related Art Many patents and utility models have been proposed in the past for nitric acid removal of solutions in industry (14 cases) and water purification technology for environmental water systems. The contents of these technologies are as follows: As technology for removing nitrogen contained in night soil and livestock excreta, the pH is increased at the stage of ammonia nitrogen before being subjected to nitrification, alkalinized and volatilized as ammonia gas, and absolute nitric acid is removed. Technology to reduce volume. For nitrated nitrogen, a method using an ion exchange resin,
The mainstream is a technique of decomposing and removing by microorganisms, a technique of removing from the hydrosphere together with sludge from a biofilm tank, a technique of absorbing and removing by aquatic plants, and a technique using a natural treatment tank such as an infiltration type sewage treatment. The technologies using these natural treatment tanks, etc., increase rapidly increasing urban wastewater, factory wastewater, livestock wastewater,
Insufficient for groundwater contamination by fertilizers. In particular, the method of volatilization as ammonia gas may cause odor pollution due to ammonia odor, and also has a disadvantage that some nitrogen undergoes nitrification to generate nitrous acid and nitric acid.
Thus, the reality is that concrete methods for removing nitric acid from rivers, lakes, and seas are at a standstill. Even more recently, groundwater contamination by nitric acid, which has been increasing rapidly, has no technology to remove it, and must rely on regulations such as control of livestock excreta, control of domestic waste urine and urine treatment, and control of industrial wastewater. It is also a situation where regulatory restrictions are conceivable. In particular, nitrate nitrogen discharged from the past and mixed into groundwater is expected to continue to increase in concentration for some 100 years in some regions. It is not expected to be recovered. So we have to deal with this problem from the basics.

[0003]

Means for Solving the Problems In order to achieve the above object, a technique for reducing and denitrifying nitric acid in water by an electrochemical method has been developed. In the denitrification process, a small amount of hydrogen gas is passed through the denitrification tank, and high-speed stirring is performed to saturate the water with hydrogen.
Adjust the oxidation-reduction potential of water, place the water under reducing conditions, irradiate short-wavelength light such as ultraviolet light on the catalyst, energize it, excite nitric acid ions and hydrogen atoms by magnetic field conversion, and react with nitric acid. Is a system for reducing and evaporating as nitrogen gas in the air. The chemical reaction depends on Chemical formula 1.

[0004]

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[0005] As shown in Fig. 1, the structure of the nitrogen nitrate removing device includes a heating device, a hydrogen gas mixing / saturation device, a denitrification device, and a treated hydroxylation acclimation device.

[0006] The heating device is a water tank which is pre-heated before being introduced into the nitrogen nitrate removing device, since the nitric acid reducing action in water by the above-mentioned electrochemical method is greatly affected by the temperature. The method of heating may be any of solar heating, steam heating, geothermal heating, and electric heating.

The hydrogen gas mixing and saturating device comprises a hydrogen gas injection nozzle and a hydrogen gas mixing and stirring device. Hydrogen gas injection for setting the water reduction conditions is performed by adding about 100 ml of hydrogen gas to 10 l of water and stirring at high speed.
It is possible to adjust the oxidation-reduction potential (Eh) of water to 100 mV or less. That is, there is no danger of explosion or the like since the amount of gas to be added is extremely small to achieve the purpose, but there is no danger of explosion or the like.

The denitrification device comprises a catalyst device, a device for irradiating short-wavelength light such as ultraviolet light, a device for energizing current, a device for disturbing magnetic fields, and the like. Nitric acid contained in the device is continuously supplied when water requiring treatment passes through the device. Is reduced and volatilized as nitrogen gas.

The catalyst device is a device for promoting a nitrate reduction reaction. The catalyst is made of a material mainly composed of a transition metal element such as iron, copper, nickel, tin, antimony, iridium, zirconium, and palladium. Select elements that will help prevent environmental pollution.

A short-wavelength light irradiation device such as ultraviolet light is a device that excites hydrogen atoms and nitrate ions under reducing conditions, and is 4,000Å.
The following short wavelength light is irradiated. Usually, an ultraviolet irradiation lamp is used.

The current applying device is a device that promotes the transfer of electrons to the elements simultaneously with the excitation of hydrogen atoms and nitrate ions under reducing conditions, and is composed of a rectifying device and an electrode plate exposed in the water in the tank. The current is a low-voltage current of 100 V or less.
The type of current may be DC or AC. However, electricity is not applied to salt water such as seawater.

The magnetic field disturbance device utilizes a large electromagnet. It always gives the positional change of the magnetic field, the yin-yang change. In order to treat a large amount of water, it is necessary to increase the reaction efficiency.Because the electromagnetic field conversion of the whole water in the tank preliminarily excites hydrogen atoms and nitrate ions of the whole water, not a part, it converts it to a catalyst. Improve the reaction efficiency.

The nitrate-nitrogen that has reacted with hydrogen is vaporized as nitrogen gas, and is forcibly discharged out of the tank with a fan together with the remaining trace amount of hydrogen gas.

Since the water from which nitrate nitrogen has been removed has a strong reducing property, if it is discharged as it is, it will affect the inhabitation of living organisms. It is sent and converted into oxidizing conditions for use.

[0015]

EXAMPLE 1 A demonstration test was conducted on the basic principle of decomposing and removing nitrate nitrogen in water by a model experiment. The experiment was performed with 500 m of an aqueous solution containing 20 ppm of NO _3.
1 into a beaker 11 and adding hydrogen gas at a jetting rate of 5 ml per minute, and saturating the water with hydrogen gas while stirring with a magnetic rotating stirrer. After the lapse of 10 minutes, when the nitric acid solution reaches the reducing condition, at a temperature condition of 10 ° C., while stirring with a magnetic rotating stirrer, insert a catalyst / electrode of iron, copper, and platinum and electrolyze with a 2.5 V battery for 20 minutes. Was done. As a result, in the case of a transition metal element using iron and copper, NO ₃ 18 pp
m. However, in the case of platinum, NO ₃ 19
The determination of the decrease in concentration at the ppm concentration was unknown. The experiment was a three-part system, but all were the same. (See Table 1)

[0016]

[Table 1]

Example 2 The experiment was conducted by applying an electric current of 2.5 V to an aqueous solution containing 20 ppm of NO ₃ at a temperature of 30 ° C. as in Example 1. As a result, in the case of a transition metal element using iron and copper, NO
₃ was reduced to a concentration of 16ppm. However, when iron and copper electrodes were used for both the positive and negative electrodes, elution of the metal element into the solution was observed. From these facts, it is considered that the conditions for regulating the reaction are influenced by the temperature, the type of the catalytic element, the strength of the magnetic field, the voltage and the current to be applied.
In addition, as a catalyst element, iron, copper, manganese, nickel, tin, antimony, iridium, zirconium,
Although heavy metal elements mainly including transition metal elements such as palladium are involved, elution of the metal elements is also considered, and it is necessary to select one that does not cause environmental pollution.

[0018]

[Table 2]

Example 3 An experiment was conducted by applying an electric current of 2.5 V to an aqueous solution containing 20 ppm of NO ₃ at 30 ° C. at a temperature of 30 ° C. in the same manner as in Example 1. However, when one of the electrodes was made of platinum, metal was used. Was not eluted. Also in this case, the nitrate nitrogen is approximately NO ₃ 16p
pm. (See Table 3)

[0020]

[Table 3]

[0021]

As described above, the present invention provides a technique for removing nitrate nitrogen contained in groundwater, river water, lake water, and seawater by physicochemical treatment. In the past, nitrate nitrogen contamination of groundwater, rivers, lakes, marshes, or sea areas has been artificially progressing, and even in water systems that are unsuitable for drinking, this technology can regenerate potable water, and the range of use is It is thought to be very diverse. Basically, it was proved that this technology reduces the concentration of nitric acid contained in water.However, by further improving the technology and introducing a large-scale system, the efficiency is improved, and Processing is possible. Therefore, it is a technology that can be used for domestic and overseas groundwater pollution control.

[Brief description of the drawings]

FIG. 1 is a connection diagram of a nitric acid removing device and respective devices in a nitric acid removing step of water according to the present invention.

[Explanation of symbols]

1-warming device, 2-hydrogen gas mixing / saturation device, 3-denitrification device, 4-treatment hydroxylation-accumulation device, 5-water supply port to nitric acid removal device, 6-preheating, 7-stirrer, 8- Stirrer motor, 9-Hydrogen cylinder, 10-Forced discharge of residual hydrogen in the hydrogen gas mixing / saturation device, 11-Catalyst device, 1
2-short wavelength light irradiation device such as ultraviolet light, 13-magnetic field conversion device,
14-Electrification device (rectifier), 15-Emission of nitrogen gas, 16-Air pump, 17-Explosion, 18-Excess air outlet, 19-Outlet of nitric acid removing device, 20-Gas exhaust The mark → except for the exit indicates the direction of treatment water induction.

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Claims (4)

[Claims] 1. A method for reducing the concentration of nitrate ions in water by passing hydrogen gas through water containing nitrate ions, electrochemically converting nitrate ions to nitrogen gas on a catalyst under reducing conditions, and vaporizing and evaporating the nitrate ions. Nitrogen device. 2. A denitrification technique for water by passing hydrogen gas through water containing nitrate ions and supplying electricity to an electrode on a catalyst under reducing conditions. 3. A denitrification technique for water by passing hydrogen gas through water containing nitrate ions and performing electromagnetic conversion on a catalyst under reducing conditions. 4. A technique for denitrifying water by passing hydrogen gas through water containing nitrate ions and irradiating the catalyst with ultraviolet light and light under reducing conditions.