KR100598596B1 - Electrochemical wastewater treatment method for nitrogen removal and device thereof - Google Patents

Abstract

The present invention relates to an electrochemical water treatment method and apparatus for removing nitrogen in water, and more particularly, various types of nitrogen in water (NH ₃ -N, NO ₂ -N, NO ₃ -N, using a highly efficient electrochemical method). The present invention relates to an economical and environmentally friendly water treatment method and apparatus for simultaneously discharging Org-N) in the form of nitrogen gas and recycling the treated water to heavy water.

Unlike the conventional electrolysis method, the water treatment method and apparatus of the present invention can increase current efficiency by concentrating and treating nitrogen in water at a high concentration, thereby significantly reducing operating costs such as power costs.

Nitrogen removal, water treatment, electrochemistry, anode, cathode, ion exchange resin

Description

Electrochemical wastewater treatment method for nitrogen removal and device

1 is an overall treatment process diagram including an electrochemical reactor suitable for water treatment according to the present invention,

Figure 2 is a graph showing the treatment efficiency of nitrate nitrogen when applying a cathode reduction electrode according to the present invention.

<Description of the symbols for the main parts of the drawings>

1-1: cation exchange resin 1-2: anion exchange resin

2-1: electrochemical reactor 2-2: conductivity sensor

2-3: electrolyte supply tank

3-1: residual chlorine reduction tank 3-2: ORP sensor

3-3: Reductant Supply Tank

[Industrial use]

The present invention relates to an electrochemical water treatment method and apparatus for removing nitrogen from water, which can reduce power cost by increasing current efficiency by performing high-efficiency electrochemical treatment by concentrating nitrogen in water at a high concentration unlike conventional electrolysis methods. .

[Prior art]

Nitrogen in water is largely composed of organic nitrogen (Organic nitrogen), ammonia nitrogen (NH ₃ -N), nitrite nitrogen (NO ₂ -N) and nitrate nitrogen (NO ₃ -N). When these nitrogens are introduced into the water system and contaminated, the eutrophication of the water system is promoted and algae are generated, which causes the ecosystem to be destroyed, such as the death of fish due to lack of oxygen and the release of toxic substances. It is important. In addition, if the river water containing a large amount of nitrate nitrogen is used as a constant source water, it may cause health problems such as infant skin paleness and goiter, so appropriate measures are required.

Due to industrial development, the amount of wastewater generated is steadily increasing year by year. Among these, water quality is deteriorating as high concentration of nitrogen-containing wastewater generated in industries such as fertilizers, plating, gunpowder, dyes and electronics flows into lakes, reservoirs and rivers. In particular, the semiconductor and electronics industry, which is leaping to the global stage, emits large amounts of difficult-decomposable nitrogen-containing wastewater, which is considered as a major factor worsening the water quality.

Currently, most technologies for treating nitrogen in water are based on biological treatment, and there is no effective and economical treatment method for hardly degradable wastewater containing biotoxic substances, low nutrients or low biodegradation. This is desperate. In the biological treatment method, a carbon source such as methanol must be added separately, and the reaction time is long, so that a lot of space is required. Also, the treatment efficiency is greatly changed by factors such as water temperature, dissolved oxygen amount, and microbial concentration, which makes it difficult to operate. There are many.

In order to make up for the shortcomings of such biological treatment methods, various methods have been studied, one of which is an electrochemical method. The electrochemical method is known to be an effective method for the treatment of hardly degradable industrial wastewater because of its high removal rate and short operating time regardless of the biodegradability of pollutants. Electrochemical treatment is a method of treating ammonia nitrogen and organic nitrogen through anodization and nitrate nitrogen through cathodic reduction. The electrochemical redox removal mechanisms for ammonia nitrogen (NH ₃ ) and nitrate nitrogen (NO ₃ ) are divided into anodic oxidation and cathodic reduction.

Oxidation on Anode

2NH ₃ + 6OH ^-- > N ₂ ↑ + 6H ₂ O + 6e ^-

Reduction on Cathode

^{_{NO 3 - + 2H 2 O +}} 3e - -> NO + 4OH -

_{^{NO 3 - + 4H + + 3e}} - -> NO + 2H 2 O

2N + 2NO-> 2N ₂ ↑ + O ₂ ↑

Many of these electrochemical treatments have been developed since the 1990s because of the tightening of nitrogen regulation. However, due to the low current efficiency, high power costs and stability of the equipment have not been widely commercialized. Do. In particular, in the case of nitrate nitrogen, the reduction efficiency is more than five times lower than that of the same power as the oxidation efficiency of ammonia nitrogen, which is considered as a major driving cost increase factor. Therefore, in order for the electrochemical treatment method to be commercialized as a general hardly degradable wastewater treatment technology, a method capable of increasing the current efficiency based on nitrate nitrogen is needed.

The present invention has been invented to solve the above problems, an object of the present invention is to increase the current efficiency of the electrochemical treatment method of electrochemical water treatment method for the removal of nitrogen in water, which can significantly reduce the power cost for nitrogen treatment. To provide.

It is also an object of the present invention to provide a water treatment apparatus for implementing the electrochemical water treatment method for removing the nitrogen in water.

In order to achieve the above object, the present invention

In the electrochemical water treatment method for removing nitrogen in water,

(a) a pretreatment step of treating the nitric acid (NO ₃ ⁻ ) or ammonium (NH ₄ ⁺ ) ions with an ion exchange resin to concentrate nitrogen concentration 10 to 100 times compared to raw water;

(b) removing the concentrated high concentration nitrogen by electrochemical oxidation or reduction; And

(c) recycling the nitrogen-treated treated water to the regenerated water of the ion exchange resin by an electrochemical method

It provides an electrochemical water treatment method for removing nitrogen in water comprising a.

The present invention also provides

In the electrochemical water treatment apparatus for removing nitrogen in water,

(a) an ion exchange resin treatment unit for treating nitric acid (NO ₃ ⁻ ) or ammonium (NH ₄ ⁺ ) ions with an ion exchange resin to concentrate nitrogen concentration from 10 to 100 times;

(b) an electrochemical treatment unit for removing the concentrated high concentration nitrogen by electrochemical oxidation or reduction; And

(c) Residual chlorine reduction unit for removing residual chlorine by injecting a reducing agent into the ion-exchange resin regeneration water from which the nitrogen is removed in the electrochemical treatment unit

It provides an electrochemical water treatment apparatus for removing nitrogen in water, comprising a.

The inventors of the present invention, whether to find an electrochemical method for improving the efficiency of nitrogen removal in water, using a ion exchange resin to treat nitrogen in the ammonium form and nitric acid in the water to make a high concentration of nitrogen and then electrochemical oxidation reaction Alternatively, by removing nitrogen by the reduction reaction and recycling the nitrogen-removed treated water to regenerated water of the ion exchange resin, the efficiency of the current consumed when using the electrochemical method for removing nitrogen from the water was increased. Through treatment and discharged through the treatment water found that can be recycled to heavy water to complete the present invention.

First, the water treatment method of the present invention comprises: (a) a pretreatment step of concentrating nitrogen concentration 10 to 100 times compared to raw water by treating an ion exchange resin with nitric acid (NO ₃ ⁻ ) or ammonium (NH ₄ ⁺ ) ions; Secondly, (b) removing the concentrated high concentration nitrogen by electrochemical oxidation or reduction; And (c) recycling the treated water from which nitrogen has been removed by the electrochemical method into regenerated water of the ion exchange resin. In this case, the nitrogen concentration of the treated water can be adjusted to 10 mg / L or less of TN, and the ion exchange resin to be applied has an ion exchange efficiency of 99% or more with respect to ammonium ions and nitrate ions. Since the treated water discharged through the above method can be recycled to heavy water, the present invention is another feature of the present invention that it is an environmentally friendly water treatment method.

In water nitrate (NO ₃ ^-) and ammonium (NH ₄ ⁺⁾ is passed through an ion exchange resin packed column ion concentration of nitrogen than the raw water is concentrated to more than 10 to 100 times the concentration, so that the electric conductivity is increased at least 50mS / cm or more The key point of the present invention is that the power consumption can be reduced when passing through the electrochemical reactor to remove the nitrogen. In addition to passing through the ion exchange resin packed column, secondary nitrate reduction in the electrochemical reactor is generally 5 times lower than the ammonia nitrogen treatment efficiency under the same current supply conditions. In order to improve the improvement of power consumption efficiency of more than 2 to 3 times by replacing the negative electrode material with a high current efficiency electrode for nitric acid reduction can also be said to be the core of the present invention. After passing through an electrochemical reactor to the treated water thus added, a separate reducing agent is added to remove residual chlorine, and recycled as an ion exchange resin regeneration water to block nitrogen discharge at the source, thereby further enhancing the technical completion of the present invention. Could.

Ion-exchanged nitrogen is concentrated at high concentrations through regeneration. In general, the nitrogen of the TN 100mg / L containing a level of 100m ³ / day-scale waste water is concentrated to a TN 10,000mg / L in 1m ³ / day capacity is possible through the regeneration process. The composition of the recycled water used varies slightly depending on the type of ion exchange resin, but NaCl is generally used, and Na ⁺ and Cl ⁻ are used as cation exchange materials. Nitrogen concentrated in the regenerated water is treated through an electrochemical reactor, and the electrical conductivity of the regenerated water increases by 10 to 100 times compared with the concentration before the concentration, so the increase in voltage can be minimized under the same current density conditions. As a result, power consumption can be reduced. On average, the electrical conductivity of general wastewater is in the range of 1 ~ 10mS / cm, but the regeneration water is very high in 50 ~ 200mS / cm, which can reduce the power cost by lowering the resistance of aqueous solution to 5 ~ 200. Regenerated water from which nitrogen has been removed through the electrochemical treatment is converted into chlorine ions using residual reducing chlorine (Na ₂ SO ₃ or NaHSO ₃ ) and then recycled into regenerated water. It is not discharged and can reduce NaCl to 10 ~ 20%.

If residual chlorine passes through the ion exchange resin, the performance and lifespan of the resin can be degraded. Therefore, the residual chlorine must be converted into chlorine ions to be used as regeneration water. At this time, in order to quantitatively control the input amount of the reducing agent, the system was configured to enable automatic adjustment to the level of 100 ~ 300mV using ORP electrode. At the ORP 100-300mV level, residual chlorine can be converted to chlorine ions.

Secondly, in order to directly improve the current efficiency of the electrochemical treatment reactor, a new negative electrode material was applied, particularly with respect to the negative electrode reduction. Nitrogen in concentrated water is divided into ammonium and nitric acid. Ammonium nitrogen is removed by anodizing and nitric acid is removed by cathodic reduction. In the present invention, using the DSA electrode coated with Ir, Pt, Sn-based metal oxide as the anode, it was possible to control the dissolution and corrosion of the electrode and to oxidize and remove ammonia nitrogen in the form of nitrogen gas. In addition, nitrate nitrogen can be treated through cathodic reduction, but materials such as Ni, Ti, Stainless, Graphite, etc., which are generally used as a cathode, have very low nitrate reduction efficiency. Is low. In the present invention, by using the Zn, Sn, Pb or Fe as a negative electrode material from the existing negative electrode material to achieve a conventional nitrogen reduction treatment efficiency of at least 2 to 4 times. This is because when Zn, Sn, Pb, or Fe is used as a negative electrode material, the hydrogen overvoltage is higher than that of other materials, so that the amount of hydrogen gas generated in the electrochemical treatment reactor is less and the reduction treatment of nitric acid is increased.

The electrochemical water treatment apparatus for removing nitrogen in water according to the present invention for implementing the water treatment method of the present invention is (a) treating the nitric acid (NO ₃ ⁻ ) or ammonium (NH ₄ ⁺ ) ion with an ion exchange resin to compare the nitrogen concentration to that of raw water 10 to 100 times concentrated ion exchange resin treatment unit; (b) an electrochemical treatment unit for removing the concentrated high concentration nitrogen by electrochemical oxidation and reduction; And (c) a residual chlorine reduction unit for removing residual chlorine by introducing a reducing agent into the ion-exchange resin regenerated water from which the nitrogen has been removed in the electrochemical treatment unit.

An electrochemical water treatment apparatus for removing nitrogen in water according to the present invention will be described in detail with reference to FIG. 1. (A) the ion exchange resin treatment part of the present invention is a structure comprising a cation exchange resin (1-1), an anion exchange resin (1-2), (b) the electrochemical treatment part is an electrochemical reactor (2-1), (C) the residual chlorine reducing unit includes the residual chlorine reducing tank 3-1 and the ORP sensor 3-2. It is a structure.

As shown in FIG. 1, nitrogen in the ammonium form and the nitric acid form is substituted in the ion exchange resin through the ion exchange resin treatment unit (cationic exchange resin: 1-1, anion exchange resin: 1-2) and the treated water is discharged. When the ion exchange resin reaches a certain capacity, it can be regenerated by regeneration water such as NaCl at a concentration level of 10 to 20%, and nitrogen is contained in the regeneration water at a high concentration. Nitrogen concentration is contained is determined by the concentration ratio, typically a nitrogen 100m of the TN 100mg / L level of the waste water containing the ³ / day scale is concentrated to a 1m ³ / day dose for TN 10,000mg / L through the reproduction process It is possible.

Nitrogen concentrated in regenerated water is treated through an electrochemical reactor (2-1), which constitutes an electrochemical treatment unit, and the electrical conductivity of regenerated water increases by 10 to 100 times compared to before concentration by the concentration process. The conductivity is in the range of 1 ~ 10mS / cm, but the regeneration water is very high in 50 ~ 200mS / cm, which can reduce the power cost by lowering the resistance of the aqueous solution to 5 ~ 200. Electrical conductivity is observed through the electrical conductivity sensor 2-2 in the electrochemical reactor 2-1, and a separate electrolyte supply tank 2-3 for preventing the electrical conductivity from being rapidly reduced during the electrochemical reaction process. It is configured to maintain constant electrical conductivity at all times in electrochemical reaction in conjunction with. In addition, the cathode material is composed of Zn, Sn, Pb, Fe to directly increase the current efficiency in the electrochemical reactor. The configuration may be single or hybrid. 2 is an example of using Ti as the cathode electrode material and Zn, Sn, Pb, Fe as in the present invention, the experiment using the water treatment method and apparatus according to the present invention, the ion exchange resin packed column It is a graph showing the residual amount of nitrate nitrogen after passing through. As shown in FIG. 2, when Zn, Sn, Pb, and Fe were used as the cathode electrode material, the amount of nitrate nitrogen was found to be very small compared to Ti, which is represented by Zn, Sn, Pb, Fe as the cathode electrode material. If used, the efficiency of substituting nitrogen for nitrate nitrogen is high.

When the concentrated nitrogen in the regeneration water is treated by the above method, the solution can be recycled back to the regeneration water of ion exchange. At this time, the residual chlorine contained in the treatment solution may reduce the performance and life of the ion exchange resin, so it is converted into chlorine ions by adding a reducing agent (Na ₂ SO ₃ or NaHSO ₃ ). Therefore, the treatment solution is transferred to the residual chlorine reduction tank 3-1 forming the residual chlorine reduction unit, and the reducing agent introduced is transferred from the reducing agent supply tank 3-3 and mounted in the reduction tank ORP sensor 3-2. By quantitative control. The control range is 100-300mV, in which residual chlorine is reduced to chlorine ion.

The electrochemical water treatment method and apparatus for removing nitrogen in water of the present invention have been described above. Those skilled in the art may make various modifications and changes to the present invention without departing from the spirit and scope of the invention as set forth in the claims below, but such modifications and changes may also be made. It is all included.

As described above, the present invention can reduce the power ratio by 40-80% or more compared to the conventional method by applying a new nitrogen concentration process and a cathode material to the conventionally known electrochemical method for removing nitrogen in water. It is an economical and environmentally friendly water treatment method that enables recycling by converting chlorine into chlorine ion by adding reducing agent to the discharged water treated through exchange resin. Therefore, the method according to the present invention can be used as a very economical technology very useful for all water treatment fields where nitrogen is a problem.

Claims (9)

In the electrochemical water treatment method for removing nitrogen in water, (a) a pretreatment step of treating the nitric acid (NO ₃ ⁻ ) or ammonium (NH ₄ ⁺ ) ions with an ion exchange resin to concentrate nitrogen concentration 10 to 100 times compared to raw water; (b) removing the concentrated high concentration nitrogen by electrochemical oxidation or reduction; And (c) recycling the treated water from which nitrogen has been removed by electrochemical method into regenerated water of the ion exchange resin; Electrochemical water treatment method for removing nitrogen in water comprising a. The method of claim 1, The negative electrode material used in the electrochemical reduction reaction is selected from at least one or more of the group consisting of Zn, Sn, Pb and Fe electrochemical water treatment method for removing nitrogen in water. The method of claim 1, Electrochemical water treatment method for removing nitrogen in water, characterized in that the addition of a reducing agent to the treated water undergoing the electrochemical oxidation or reduction reaction to convert the residual chlorine into chlorine ions to recycle to the regeneration water of the ion exchange resin. In the electrochemical water treatment apparatus for removing nitrogen in water, (a) an ion exchange resin treatment unit for treating nitric acid (NO ₃ ⁻ ) or ammonium (NH ₄ ⁺ ) ions to concentrate nitrogen concentration 10 to 100 times compared to raw water; (b) an electrochemical treatment unit for removing the concentrated high concentration nitrogen by electrochemical oxidation or reduction; And (c) a residual chlorine reduction unit for removing residual chlorine by introducing a reducing agent into the ion-exchange resin regenerated water from which nitrogen has been removed from the electrochemical treatment unit; Electrochemical water treatment apparatus for removing nitrogen in water, comprising a. The method of claim 4, wherein The cathode of the electrochemical treatment unit (b) is Zn, Sn, Pb or Fe is composed of at least one of the group consisting of electrochemical water treatment apparatus for removing nitrogen in water, characterized in that the configuration is a single system or a hybrid system. The method of claim 4, wherein The electrochemical water treatment device for removing nitrogen in water, characterized in that the (b) the electrochemical reactor of the electrochemical treatment unit interlocks the conductivity sensor and the electrolyte supply tank to maintain a constant electrical conductivity. The method of claim 4, wherein An electrochemical water treatment apparatus for removing nitrogen from water, wherein the treated water from which high concentration of nitrogen is removed through the electrochemical reactor is recycled to regenerated water of ion exchange resin, so that the discharge of trace amount of nitrogen components is blocked at the source. The method of claim 4, wherein Residual chlorine is removed by adding a reducing agent to the previous step of recycling the treated water from which nitrogen is removed in high concentration through the electrochemical reactor to the regenerated water of the ion exchange resin. Electrochemical water treatment device for removing nitrogen in water, characterized in that the reducing agent is added to adjust the range of 100-300mV in conjunction with the installed ORP sensor. The method of claim 8, The reducing agent is Na ₂ SO ₃ or NaHNO ₃ electrochemical water treatment apparatus for nitrogen removal in water, characterized in that.

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