DE19856840A1 - Wastewater treatment process and treatment apparatus therefor - Google Patents

Abstract

In a wastewater treatment process, electrolysis is carried out in such a way that the wastewater (7) containing nitrogen compounds is fed into the anode space (4) of an electrolyte bath (6) in which a diaphragm (3 ), which has a selective ion permeability, is arranged between electrodes (1, 2), as a result of which reduced nitrogen compounds such as hydrazine or ammonium ions in the waste water (7) by oxygen which is generated at the anode (1) , are oxidized to nitrogen gas and removed from the waste water (7). In addition, after an oxidation reaction has been carried out, the second electrolysis is carried out in such a way that only the oxidized liquid is fed to the cathode compartment (5), as a result of which nitrogen oxides such as nitrate ions or nitrite ions in the liquid are reduced to nitrogen gas and can be removed from the waste water (7). Thus, without generating secondary wastes, even under normal temperature and pressure conditions, the nitrogen compounds can be effectively removed from the wastewater (7) generated in a thermal power plant or the like.

Description

The present invention relates to a method for wastewater treatment and a Treatment device therefor. The invention further relates in detail to a method for Removal of nitrogen compounds such as nitrogen gas from the waste water containing the nitrogen compounds, e.g. B. reduced nitrogen compounds (Nitrogen-hydrogen compounds) such as hydrazine and the ammonium Ion and nitrogen oxides such as the nitrate ion and the nitrite ion electrochemically oxidizing or reducing the nitrogen compounds. By the way said in the sense of the present description the terms "nitrogen Ver bonds "," reduced nitrogen compounds "and" nitrogen oxides "also ionic Levels of these connections.

Deoxidation treatment (to prevent oxidation) and corrosion protection for feed water systems or condensation systems from Thermal power plants by adding a reducing volatile chemical as in for example hydrazine or ammonia. Therefore remains in the wastewater contained in such Power plants, the added hydrazine or ammonia (ammonium ions) in the water. Removal of these substances remaining in the water by application any treatment is therefore desirable.

So far there are the following procedures for removing the nitrogen compounds such as. B. hydrazine or ammonium ions:

• (1) A method of oxidizing using an oxidizing agent such as for example hypochlorous acid, hydrogen peroxide, oxygen or the same;  
• (2) a method of oxidizing under high temperature and high conditions Pressure in the presence of catalysts such as copper, lead or the like;
• (3) a method of filtering under pressure using a reverse o mose membrane;
• (4) a method of electrodialysis by arranging many ion exchange memes branches between electrodes separating the ions by electrophoresis;
• (5) a method of decomposition by oxidation using Mi microorganisms that consume a nitrogen component.

In all of these methods, however, there were problems such as that that it was difficult in the control of the reaction or that of secondary waste or By-products formed by adding an oxidizing agent or a catalyst as shown below.

• (1) Oxidation treatment with an oxidizing agent is not all Difficulty in handling the oxidant, but there are also a problem related to the occurrence of a by-product due to excessive reaction;
• (2) In the oxidation process using a catalyst, there is in addition to the fact that the catalyst itself is a dangerous second där drop is the problem that the control of the reaction is difficult;
• (3) in the process of filtering under pressure using a reverse Rosmose membrane is in addition to the fact that only a small one Lots of water can be processed, the problem being that the concentrated Wastewater must be treated;
• (4) In the electrodialysis process, compounds other than charged ones can be used Ions cannot be processed; there is also a problem that the concentrated ion component is a further aftertreatment required.

Therefore, under the current circumstances, the method designated with (5) above, that is, a process of decomposition by oxidation using a microorganism most effective. However, there are problems with this method in that the space requirements for the system are enormous, extraordinary high and training-intensive experience in the cultivation of microorganisms required Lich, a large amount of organic feed is required, the conditions conditions in the water tank are difficult to control and moreover once the decomposition reaction has been disturbed, the appropriate reaction is reset conditions takes a long time.

The present invention has set itself the task of solving the problems mentioned sen. In other words, it is an object of the present invention to solve the problems to create a wastewater treatment process with the under Bedin conditions of normal temperature and pressure without generating secondary waste len nitrogen compounds such as hydrazine, ammonium ions, nitrate ions, Nitrite ions or the like can be removed from the waste water as nitrogen gas nen, and also to provide a treatment device for such a method.

The wastewater treatment method according to the first embodiment of the invention is characterized in that electrolysis is carried out in such a way that the waste water, which contains nitrogen compounds, at least one of the anode spaces Space and cathode space of an electrolyte bath in which a selective ion Diaphragm having permeability arranged between the anode and the cathode and thereby oxidizes the nitrogen compounds in the waste water to nitrogen gas or reduced.

A wastewater treatment process according to the second embodiment of the invention is characterized in that it comprises:

• - a first electrolysis step in which the first electrolysis in the way is carried out that the waste water containing nitrogen compounds an anode room of an electrolyte bath in which a selective Diaphragm with ion permeability between the anode and the Is arranged cathode and thereby the nitrogen compounds in the Waste water oxidized to nitrogen gas; and
• - a second electrolysis step in which the second electrolysis in the manner is carried out by oxidizing the Ab in the first electrolysis step water to the cathode compartment of the electrolyte bath and thereby stick Oxides of matter in the wastewater reduced to nitrogen gas.

A waste water treatment device according to the present invention comprises:

• - An electrolyte bath in which a selective ion permeability Diaphragm is arranged between an anode and a cathode and that through the diaphragm into an anode space and a cathode space is divided;
• - A DC power source that provides a DC voltage between the Anode and cathode;
• a first liquid supply device for feeding an electrolyte Solution in the anode space of the electrolyte bath;
• - A first liquid drain device for draining the electrolyte solution from the anode room of the electrolyte bath;
• a second liquid supply device for feeding an electrolyte Solution in the cathode space of the electrolyte bath;
• - A second liquid drain device for draining the electrolyte solution from the cathode compartment of the electrolyte bath; and
• - A gas discharge device for discharging the generated by the electrolysis Gas from the gas phase of the anode space and / or cathode space Electrolyte bath.

In the context of the present invention, an anion exchange membrane, a cation exchange membrane and a composite ion exchange membrane in which an anion exchange membrane is used can be used as the diaphragm which divides the electrolyte bath into an anode compartment and a cathode compartment. Membrane and a cation exchange membrane are put together. These ion exchange membranes consist of the solid electrolyte, have a selective permeability for an ion species and interrupt the movement of a special ion between the anode space and the cathode space. Furthermore, membranes made of common solid electrolytes such as silver iodide (α-AgI), aluminum oxide (β-Al ₂ O ₃ ) or stabilized zirconium oxide can be used.

In addition, in the context of the present invention, the anode and the cathode Shapes that differ from a rod or plate, the inside of which is filled are shaped, namely, for example, to form a networked structure or porous structure. In addition, such an anode and cathode can the state in which they are separated from one another at suitable locations in the anode Space and cathode space, which are separated by the diaphragm, can be arranged can be arranged such that they have the diaphragm arranged between them and be in close contact with each other. Especially in the case where an elec trolysis is carried out using an electrolyte bath containing an anode and a cathode with cross-linked structure or porous structure in such close proximity are arranged that a diaphragm is arranged between them, finds the elek trochemical reaction takes place on the surface of the electrode because of the contact interface between the electrodes and the electrolyte conductor is large and the distance between the electrodes is small. Therefore, the effectiveness of the oxidation or reduction treatment of nitrogen compounds in the wastewater high.

The nitrogen treated by electrolysis according to the present invention Compounds are reduced nitrogen compounds (nitrogen-hydrogen compounds gen) such as hydrazine or ammonium ions and nitrogen oxides such as wise nitrate ions or nitrite ions. The reduced nitrogen compounds  oxidized in the anode compartment of the electrolyte bath, while the nitrogen oxides in the Cathode space of the electrolyte bath can be reduced.

Further, nitrogen compounds contained in the waste water may be the following Compounds are mentioned: hydroxylamine, amines, diamines, amides, nitroamides, Tetrazine, nitric acid, nitric oxide, nitrous oxide, nitrogen dioxide, distick tetraoxide, nitrous oxide, nitrides, azides, diazo compounds, cyanides, nitro syl salts and nitroxyl salts. These nitrogen compounds are used in electrolysis the anode space or cathode space also oxidized or reduced to nitrogen gases and can be removed as nitrogen gas.

In the first embodiment of the invention, water in the waste water which is supplied to the anode space or the cathode space of the electrolyte bath is oxidized or reduced at the anode or at the cathode, as is shown in the following equations :

At the anode: 2 H ₂ O - 4 e⁻ → O ₂ + 4 H⁺
At the cathode: 2 H ₂ O + 2 e⁻ → H ₂ + 2 OH⁻.

Then the nitrogen compounds such as hydrazine, ammonium Ions, nitrate ions and nitrite ions contained in the wastewater with oxygen or Hydrogen generated by the oxidation at the anode or the reduction at the cathode in the Anode space or in the cathode space of the electrolyte bath are formed, whereby Nitrogen gas and water are formed.

In other words, the reduced nitrogen compounds (e.g., hydrazine or ammonium ions) in the wastewater react in the anode space with oxygen generated at the anode, as shown in the following equations, whereby nitrogen Gas and water are formed:

N ₂ H ₄ + O ₂ → N ₂ ↑ + 2 H ₂ O
4 NH ₄ ⁺ + 3 O ₂ → 2 N ₂ ↑ + 4 H⁺ + 6 H ₂ O.

Furthermore, nitrogen oxides (e.g. nitrate ions or nitrite ions) react in the cathode space with the hydrogen formed on the cathode, as shown in the following equations, whereby nitrogen gas and water are formed:

2 NO ₃ ⁻ + 5 H ₂ → N ₂ ↑ + 2 OH⁻ + 4 H ₂ O
2 NO ₂ ⁻ + 3 H ₂ → N ₂ ↑ + 2 OH⁻ + 2 H ₂ O.

The nitrogen gas formed moves from the liquid phase into the gas phase of the Electrolyte bath and is further withdrawn from the gas phase and removed.

In the second embodiment of the invention, the nitrogen Ver waste water containing bonds (in the first electrolysis step) first in the anode Electrolyte bath space electrolyzed, reducing the nitrogen compounds are oxidized in the wastewater to form nitrogen gas and water. On finally, the waste water oxidized in the first electrolysis step is fed into the cathode Room of the electrolysis bath fed and there (in the second electrolysis step) elec trolyzes, which releases the nitrogen oxides in the wastewater to form nitrogen gas and water can be reduced. So the reduced nitrogen compounds and Nitrogen oxides in the wastewater each electrolyzed to form nitrogen gas and removed from the liquid phase. Can continue with electrolysis in the cathode space because together with the reduction of nitrogen oxides in the wastewater Oxygen or the like, which is dissolved in the liquid, is also reduced to water the amount of dissolved oxygen will be reduced.

The invention is further described below with reference to the figures. In the figures show in detail:  

Fig. 1 is a diagram schematically showing the configuration of the first guide die From shows the present invention;

Fig. 2 is a graph showing the change in the concentrations of hydrazine and ammonium ions in the waste water in the anode space when carried out according to the first embodiment of the invention;

Fig. 3 is a diagram schematically guide form the configuration of the second one of the present invention;

FIGS. 4A and 4B are a perspective view and an exploded drawing voltage reproduced perspective view showing a wastewater treatment device as used before lying invention according to the second embodiment;

Fig. 5 is a graph showing the change in the concentrations of hydrazine and ammonium ions in the waste water in the anode space according to the second embodiment;

Fig. 6 is a graph showing the change in the pH of the liquid in the cathode chamber is according to the second embodiment;

Fig. 7 is a graph showing the change in current in the case of electrolysing pure water in an electrolytic bath having an anode and a cathode with a cross-linked structure;

Fig. 8 is a diagram showing schematically the configuration of the third guide die from the present invention;

9A and 9B are a perspective view and a drawing reproduced in exploded perspective view showing a Abwasserbehand lungs apparatus which is used before lying invention according to the third embodiment.

Fig. 10 is a graph showing the change in the concentrations of nitrate ions and nitrite ions in the waste water in the cathode space according to the third embodiment;

FIG. 11 is a diagram showing the configuration of the fourth embodiment of the present invention;

FIG. 12 is a graph showing the change in the total nitrogen concentration in the waste water is generated guide die in a heat power plant according to the fourth off;

FIG. 13 is a graph showing the fifth embodiment of the present invention approximately shows the change of concentrations of nitrate ions and nitrite ions in the waste water in the cathode space in accordance with;

FIG. 14 is a graph of the total nitrogen concentration shows the change in the waste water according to the sixth embodiment of the present invention;

FIG. 15 is a diagram schematically guide die, the configuration of the seventh from the present invention;

16A and 16B are a perspective view and a drawing in Exploring sion reproduced perspective view showing a wastewater treatment device, which is used according to the seventh embodiment of the present invention.

Fig. 17 is a graph showing the change in the total nitrogen concentration in the waste water is according to the seventh embodiment;

FIG. 18 is a graph showing the change in the total nitrogen concentration in the effluent shows that the invention is generated in a thermal power plant in accordance with the approximate shape seventh exporting;

Fig. 19 is a graph showing the change in pH of the liquids in the anode and cathode spaces in the case of electrolysis of an aqueous solution of sodium sulfate which is carried out in an electrolyte bath having a composite ion exchange membrane ;

FIG. 20 is a graph showing the change of the amount of to be generated hydrogen gas according to the electrochemical calculation in the eighth embodiment of the present invention; and

Fig. 21 is a graph showing the change in the metal ion concentration in the liquid of the cathode space in the ninth embodiment of the present invention.

The invention is described in more detail below on the basis of the preferred embodiments described.

Embodiment 1

Fig. 1 is a diagram schematically showing the waste water treatment process shows the configuration for explaining the first embodiment according to the present invention. In the first embodiment, as shown in Fig. 1, between a plate of an anode 1 and a cathode 2, a diaphragm 3 is arranged, which is made of alumina, which is a commonly used solid electrolyte. Next, in an electrolytic bath 6 , which is divided into an anode space 4 and a cathode space 5 by this diaphragm 3 , an electrolysis is carried out in such a way that from water (an aqueous waste water solution) 7 , the / the at least one reduced nitrogen compound such. B. contains hydrazine or ammonium ions, feeds into the anode space 4 and 5 pure water 8 supplies the cathode space. It can be used as waste water 7 , the at least one reduced nitrogen compound such. B. contains hydrazine or ammonium ions, the wastewater used, which is generated for example in a thermal power plant.

The water contained in the waste water 7 , which is supplied to the anode space 4 , is oxidized at the anode 1 , as shown by the following reaction equation, whereby oxygen is generated:

2 H ₂ O - 4 e⁻ → O ₂ + 4 H⁺.

The reduced nitrogen compounds (e.g. hydrazine and / or ammonium ions) are then each oxidized, as shown by the following equations. The oxidation takes place with the oxygen generated at the anode 1 according to the aforementioned reaction equation with the formation of nitrogen gas. The nitrogen gas generated moves from the liquid phase into the gas phase and is removed from the waste water 7 :

N ₂ H ₄ + O ₂ → N ₂ ↑ + 2 H ₂ O
4 NH ₄ ⁺ + 3 O ₂ → 2 N ₂ ↑ + 4 H⁺ + 6 H ₂ O.

Incidentally, reference numeral 9 in the figure denotes the oxidized liquid that is discharged from the anode space 4 .

Fig. 2 is a graph showing the measured results of a change of concen NEN of hydrazine and ammonium ions in the waste water 7 shows the anode chamber 4, when in the context of the first embodiment, an electrolysis under the conditions of an electrolysis area of 0 75 dm ² , an electrical current density of 5 to 7 A / dm ² , a liquid volume of 500 ml and liquid temperatures of 25 to 35 ° C.

From this figure it can be seen that, according to the first embodiment, hydrazine and Ammonium ions in the wastewater can be effectively removed and the concentrations of these two connections can be pushed below the respective detection limits nen.

Embodiment 2

Fig. 3 is a diagram schematically explaining the second embodiment of the present invention showing the configuration.

In the second embodiment of the invention - as shown in FIG. 3 - an anion exchange membrane 3 a is arranged between the anode 1 and the cathode 2 in the electrolyte bath 6 , which through this anion exchange membrane 3 a in an anode Room 4 and a cathode room 5 is divided. An electrolysis is carried out, water from 7 , the reduced nitrogen compounds such. B. contains hydrazine and ammonium ions, is fed into the anode space 4 , while pure water 8 is filled in the cathode space 5 . In this case, the anode 1 has a cross-linked structure in which platinum is plated onto the surface of a titanium base material. The cathode 2 consists of SUS and has a cross-linking structure in the same way as the anode 1 . Further, a anion exchange membrane is disposed (strongly basic anion exchange membrane) 3 a between these electrodes, and the electrodes are arranged in close proximity to the anion exchange membrane.

In the context of this second embodiment, the reduced nitrogen compounds in the wastewater 7 , which is fed to the anode space 4 , are oxidized by the oxygen generated at the anode 1 and thus become nitrogen gas. The nitrogen gas formed moves from the liquid phase into the gas phase and is thus removed from the waste water 7 .

FIGS. 4A and 4B are a perspective view and an exploded drawing voltage reproduced perspective view showing structures of a Abwasserbe action-device such as is used in the second embodiment of the present invention. This treatment device comprises - as shown in the figures - an electrolyte bath 6 is disposed in close proximity and between the anode 1 and the cathode 2 in which an anion exchange membrane 3 a, which both have a crosslinked structure. The electrolyte bath is divided into the anode space and the cathode space by this anion exchange membrane 3 a. The device also includes an external DC power source 10 , which applies a DC voltage between the anode 1 and the cathode 2 , a first liquid supply line 11 a, which contains the waste water 7 containing the reduced nitrogen compounds in the anode space of the Electrolyte bath 6 feeds, a first liquid drain line 12 a, with which the oxidized liquid 9 is discharged from the anode space, a second liquid supply line 11 b, which feeds the liquid, such as pure water 8, into the cathode space , And a second liquid drain line 12 b, with which the liquid is discharged from the cathode chamber 5 . The first liquid supply line 11 a and the first liquid discharge line 12 a each penetrate a plate 13 forming the anode space and are fastened in the interior of the anode space with openings, and the second liquid supply line 11 b and the second liquid discharge line Line 12 b each penetrate a plate 14 forming the cathode space and are fastened within the cathode space with openings. In addition, the first liquid supply line 11 a and the first liquid discharge line 12 a via the first liquid reserve tank 15 a and the first liquid circulation pump 16 a are connected, and the second liquid supply line 11 b and the second liquid discharge line 12 b are connected via the second liquid reserve tank 15 b and the second liquid circulation pump 16 b. In addition, on the side of the anode space of the electrolytic bath 6, a gas discharge device (not shown in the figure) for discharging the nitrogen gas formed by the electrolysis is attached. Incidentally, reference numeral 17 in the figure denotes an anode support body which forms an underside portion of the anode space 4 , and reference numeral 18 denotes a cathode support body which forms an underside portion of the cathode space 5 .

In the second embodiment according to the invention, which corresponds to the embodiment described above, electrolysis was carried out under the conditions of an electrolysis area of 0.75 dm ² , a current density of 5 to 7 A / dm ² , a liquid volume of 500 ml and Liquid temperatures of 25 to 35 ° C carried out. The measured results of the change in the concentrations of hydrazine and ammonium ions in the waste water 7 in the anode space 4 are shown in FIG. 5.

It can be derived from this figure that, according to the second embodiment of the invention, the concentrations of hydrazine and ammonium ions in the waste water 7 can be suppressed below the respective detection limits.

In addition, since in the second embodiment the anion exchange membrane 3 a, which is used as the diaphragm, only allows anions in the liquid to pass through, but does not allow cations to pass through, the movement of the reduced nitrogen compounds to the cathode space 5 is prevented by the anode. Room 4 interrupted. Therefore, an oxidation reaction of the reduced nitrogen compounds in the anode space 4 can be carried out effectively.

In addition, due to the action of the fixed ions in the anion exchange membrane OH⁻ migrates from the cathode space 5 into the anode space 4 . Accordingly, the increase in pH (increase in the concentration of OH⁻) accompanying the electrolysis can be suppressed in the cathode space 5 , and a decrease in the current efficiency can be suppressed. In addition, since the OH⁻ ions passing through the membrane carry an electrical charge, the loss due to the electrical resistance of the liquid becomes very small.

In the second embodiment, the electrolysis was carried out under conditions of an electrolysis area of 0.75 dm ² , a current density of 2 to 3 A / dm ² , a liquid volume of 500 ml and liquid temperatures of 25 to 35 ° C.

The measured results of the change in the pH of the liquid in the cathode space 5 are shown in FIG. 6.

From this figure, it can be understood that in the case where an anion exchange membrane 3 a is used as the diaphragm, the increase in pH in the liquid in the cathode space 5 accompanying the electrolysis is small. Incidentally, also in Fig. 6, for comparison purposes, the change in pH in the case that the electrolysis is carried out in an identical manner to that in the second embodiment, but a diaphragm is used which consists of a generally used solid electrolyte, namely alumina, shown.

In addition, in the second embodiment, the contact interface between the electrode and the electrolyte solution increases remarkably since both an anode 1 and a cathode 2 , both of which have a cross-linked structure, are used compared to the case that an electrode from a filled rod or from a plate is used as the electrode. Furthermore, because the anode 1 and the cathode 2 with a cross-linked structure are arranged in close proximity to one another as in the present embodiment and an anion exchange membrane 3 a is arranged between them, the distance between the electrodes is short. Therefore, the electrode reaction proceeds well, whereby an oxidation of the reduced nitrogen compounds such. B. hydrazine and ammonium ions in wastewater 7 is carried out effectively in a short time.

The electrolysis was carried out in the electrolyte bath 6 , in which an anode 1 and ei ne cathode 2 , both of which have a cross-linked structure, are arranged in close proximity to one another and an anion exchange membrane 3 a is arranged between them, the Anode space 4 and the cathode space 5 pure water is supplied. The measured results of the change in current are shown in FIG. 7. Incidentally, the electrolysis was carried out under conditions of an electrolysis area of 0.75 dm ² , an input voltage of 10 V (constant) and water temperatures of 25 to 35 ° C.

From this figure it is understandable that due to the use of an anode 1 and a cathode 2 , both of which have a cross-linked structure, a sufficiently strong electrolysis can be carried out even in pure water.

Embodiment 3

Fig. 8 is a diagram schematically showing the configuration for explaining the third embodiment of the present invention.

In the third embodiment - as shown in Fig. 8 - a cation exchange membrane 3 b is arranged between the anode 1 and the cathode 2 . In an electrolyte bath 6 , which is divided into an anode space 4 and a cathode space 5 by this cation exchange membrane 3 b, the electrolysis is carried out in such a way that waste water 7 , the nitrogen oxides such as nitrate ions or contains nitrite ions, is introduced into the cathode space 5 and that pure water 8 is introduced into the anode space 4 . In this embodiment, the anode 1 has a cross-linked structure in which platinum plating is applied to the surface of a titanium base material, and the cathode 2 is made of SUS and has a cross-linked structure that is identical to that of the anode 1 . In addition, a cation exchange membrane (strongly acidic cation exchange membrane) 3 b is arranged between these electrodes, and the electrodes are arranged in close proximity to this cation exchange membrane 3 b.

Water in the wastewater 7 , which is fed into the cathode space 5 , is reduced at the cathode 2 , as shown in the following reaction equation, and forms hydrogen:

2 H ₂ O + 2 e⁻ → H ₂ + 2 OH⁻.

The nitrogen oxides (nitrate ions and / or nitrite ions) in the waste water 7 are then each reduced in the manner shown in the following equations. This is done by the hydrogen formed on the cathode 2 by the above-described reaction, whereby nitrogen gas is formed. The nitrogen gas generated moves from the liquid phase to the gaseous phase and is removed from the waste water 7 :

2 NO ₃ ⁻ + 5 H ₂ → N ₂ ↑ + 2 OH⁻ + 4 H ₂ O
2 NO ₂ ⁻ + 3 H ₂ → N ₂ ↑ + 2 OH⁻ + 2 H ₂ O.

In this way, the nitrogen oxides in the waste water 7 are reduced in the cathode space 5 with the formation of nitrogen gas which is removed. Incidentally, the reference numeral 19 in the figure denotes the reduced liquid which is withdrawn from the cathode space 5 .

Is FIGS. 9A and 9B are a perspective view and a reproduced voltage perspective view in an exploded drawing, each showing the structure of a waste water treatment apparatus as incorporated in the third embodiment employs. This treatment device, as shown in the figures, comprises an electrolyte bath 6 , in which a cation exchange membrane 3 b is arranged in close proximity between the anode 1 and the cathode 2 , both of which have a cross-linked structure, and this through this cation exchange membrane 3 b is divided into an anode space and a cathode space, an external direct current energy source 10 which applies a direct current voltage between the anode 1 and the cathode 2 , a first liquid supply line 11 a, with which the liquid such. B. pure water 8 is fed into the anode space of the electrolyte bath 6 , a first liquid drain line 12 a, with which liquid is withdrawn from the anode space, a second liquid supply line 11 b with which the waste water 7th , which contains nitrogen oxides, is fed into the cathode space, and a second liquid discharge line 12 b, with which the reduced liquid 19 is discharged from the cathode space 5 . In addition, the first liquid supply line 11 a and the first liquid discharge line 12 a each pass through the plate 13 forming the anode space and are fastened in the interior of the anode space with openings, and the second liquid supply line 11 b and the second liquid drain line 12 b penetrate the plate 14 forming the cathode space and are fastened in the interior of the cathode space with openings. In addition, the first liquid supply line 11 a and the first liquid discharge line 12 a via the first liquid reserve tank 15 a and the first liquid circulation pump 16 a are connected, and the second liquid supply line 11 b and the second liquid discharge line 12 b are connected via the second liquid reserve tank 15 b and the second liquid circulation pump 16 b. In addition, on the side of the cathode space of the electrolyte bath 6, a gas discharge device (omitted in the figures) for discharging the nitrogen gas generated during the electrolysis is attached.

Incidentally, reference numeral 17 in the figure denotes an anode support body which forms an underside portion of the anode space, and reference numeral 18 denotes a cathode support body which forms an underside portion of the cathode space 5 .

In the present third embodiment, the electrolysis was carried out under conditions of an electrolysis area of 0.75 dm ² , current densities of 5 to 7 A / dm ² , a liquid amount of 500 ml and liquid temperatures of 25 to 35 ° C.

The measured results of the change in the concentration of nitrate ions and nitrite ions in the waste water 7 in the cathode chamber 5 are shown in FIG. 10.

From this figure it can be understood that according to the third embodiment, the nitrate ions and the nitrite ions in the wastewater 7 are each effectively removed and that the concentrations of these ions can be suppressed below their detection limits.

Embodiment 4

Fig. 11 is a diagram schematically showing a configuration for explaining the fourth embodiment of the present invention.

In the fourth embodiment, as shown in FIG. 11, a diaphragm 3 made of aluminum oxide is arranged between an anode 1 and a cathode 2 , each consisting of a plate. The arrangement is located in an electrolyte bath 6 , which is divided into an anode space 4 and a cathode space 5 by this diaphragm 3 . Waste water 7 , which contains at least one of the substances hydrazine and ammonium ions, is fed to the anode space 4 , and pure water is filled into the cathode space 5 . This is how the first electrolysis is carried out. As a result, the reduced nitrogen compounds (hydrazine and / or ammonium ions) in the wastewater 7 are oxidized to nitrogen gas by the oxygen which is formed at the anode 1 . Subsequently, the second electrolysis is carried out by pouring the oxidized liquid 9 into the cathode space 5 and by pouring pure water into the anode space or by adding wastewater 7 again . The oxidized substances in the wastewater 7 are reduced. In this embodiment, for example as wastewater 7 , which contains at least one of the substances hydrazine and ammonium ions, for example wastewater that was generated in a thermal power plant can be used. Furthermore, the electrolysis of the waste water 7 is carried out in batches: after completion of the first electrolysis, the total amount of the oxidized liquid 9 in the anode chamber 4 can be fed to the cathode chamber 5 in order to carry out the second electrolysis. However, a continuous treatment process can also be carried out. In other words, while the oxidized liquid 9 is continuously fed from the anode chamber 4 into the cathode chamber 5 and the reduced liquid 19 is continuously withdrawn from the cathode chamber 5 , the second electrolysis can be carried out.

In this embodiment, after the time at which the reduced nitrogen compounds (hydrazine and / or ammonium ions) in the waste water 7 have been electrochemically oxidized in the anode space 4 and have been removed from the waste water 7 as nitrogen gas, the oxidized substances in the wastewater 7 electrochemically reduced in the cathode chamber 5 . In addition, in the case where nitrogen oxides such as nitrate ions and nitrite ions are contained in the waste water 7 , the nitrogen oxides are reduced to nitrogen gas and removed from the waste water 7 . In addition, due to the reduction in the cathode space 5, the dissolved oxygen or the like in the waste water 7 is removed.

In the fourth embodiment described above, the electrolysis of the waste water 7 , each containing hydrazine and ammonium ions generated in a thermal power plant, was continuous under conditions of an electrolysis area of 0.75 dm ² , current densities of 5 to 7 A / dm ² , a liquid amount of 500 ml and liquid temperatures from 25 to 35 ° C. The measured results of the change in the total nitrogen concentration in the waste water 7 are shown in FIG. 12. In addition to said, the measurement of the total nitrogen concentration in the liquid was carried out, which was continuously drained from the cathode space 5 . From this figure, it can be seen that, according to the fourth embodiment, the nitrogen component in the waste water 7 generated in a thermal power plant can be effectively removed.

Embodiment 5

In the fifth embodiment, using an identical electrolyte bath 6 as in the fourth embodiment while feeding the waste water 7 , which contains at least one of the compounds hydrazine and ammonium ions and at least one of the compounds nitrate ions and nitrite ions, in the anode space 4 is carried out in the same way as in the fourth embodiment, the first electrolysis. After hydrazine and / or ammonium ions in the wastewater 7 have been oxidized by the oxygen which has been formed at the anode 1 , the second electrolysis is carried out by feeding the oxidized liquid 9 into the cathode space 5 , as a result of which the nitrate content -Ions and / or nitrite ions in the wastewater 7 is reduced.

In this embodiment, after the time at which hydrazine and / or ammonium ions (the reduced nitrogen compounds) in the waste water 7 have been electrochemically oxidized in the anode space 4 and removed as nitrogen gas from the waste water 7 , the The content of nitrate ions and / or nitrite ions (nitrogen oxide) is reduced electrochemically in the cathode space 5 , and these compounds are removed from the waste water 7 as nitrogen gas.

In the fifth embodiment as described above, the electrolysis was carried out under conditions of an electrolysis area of 0.75 dm ² , current densities of 5 to 7 A / dm ² , a liquid amount of 500 ml and liquid temperatures of 25 to 35 ° C. The measured results of the change in the concentrations of nitrate ions and nitrite ions in the waste water 7 of the cathode chamber 5 are shown in FIG. 13.

It can be seen from this figure that according to the fifth embodiment of the invention, the nitrate ions and nitrite ions in the waste water 7 can be effectively removed.

Embodiment 6

In the sixth embodiment, using the identical electrolyte bath 6 as in the fourth embodiment, feeding the waste water which contains at least one of the compounds hydrazine and ammonium ions and at least one of the compounds nitrate ions and nitrite ions and the like also contains nitrogen compounds other than these, in the anode space 4 in an identical manner as in the fourth embodiment, the first electrolysis is carried out. The second electrolysis is then carried out while feeding the oxidized liquid 9 into the cathode space 5 , as a result of which the nitrogen compounds in the waste water 7 are oxidized and reduced in this order.

In this embodiment, after the time at which hydrazine and / or ammonium ions and other reduced nitrogen compounds in the waste water 7 have been oxidized in the anode space 4 , the nitrate ions and / or nitrite ions and other nitrogen oxides in the cathode are oxidized -Room 5 reduced, and all reaction products can be removed from the waste water 7 as nitrogen gas and water.

In the sixth embodiment described above, the continuous electrolysis of the waste water 7 containing the nitrogen compounds was carried out under the conditions of an electrolysis area of 0.75 dm ² , current densities of 5 to 7 A / dm ² , a liquid amount of 500 ml and Liquid temperatures of 25 to 35 ° C carried out. The measured results of the change in the total nitrogen concentration in the waste water 6 are shown in FIG. 14.

From this figure, it can be seen that according to the sixth embodiment, the various types of nitrogen compounds in the waste water 7 can be effectively removed.

Embodiment 7

In the seventh embodiment - as shown in FIG. 15 - between an anode 1 and a cathode 2, a composite ion exchange membrane 3 c is arranged, which consists of an anion exchange membrane and a cation exchange membrane. In an electrolyte bath 6 , which is divided by this composite ion exchange membrane 3 c into an anode space 4 and a cathode space 5 , the first electrolysis is carried out in such a way that waste water 7 , the nitrogen Contains compounds, feeds into the anode space 4 and first fills pure water into the cathode space. Reduced nitrogen compounds in the wastewater 7 are oxidized to nitrogen gas by the oxygen which is generated at the anode 1 . The second electrolysis is then carried out in such a way that the oxidized liquid 9 is introduced into the cathode chamber 5 . As a result, the oxidized substances in the waste water 7 are reduced. In this embodiment, the anode 1 has a cross-linked structure in which platinum plating has been applied to the surface of a titanium base material, and the cathode 2 is made of SUS and has an identical cross-linked structure as the anode 1 . In addition, the composite ion exchange membrane 3 c is arranged between these electrodes, and the electrodes are arranged in close proximity to this ion exchange membrane.

According to this embodiment, after the time when the reduced nitrogen compounds such. B. hydrazine and ammonium ions in the wastewater 7 were electrochemically oxidized in the anode space 4 and were removed from the wastewater 7 as nitrogen gas, the oxidized substances in the wastewater 7 electrochemically reduced in the cathode space 5 . In the event that nitrogen oxides such as nitrate ions and nitrite ions are contained in the waste water 7 , the nitrogen oxides are reduced to nitrogen gas and removed from the waste water 7 .

Figs. 16A and 16B are a perspective view and an exploded drawing represented in perspective view, showing a structure of a sewage treatment apparatus which was used in the seventh embodiment.

This treatment device comprises - as shown in these figures - an electrolyte bath 6 , in which a composite ion exchange membrane 3 c is arranged in close proximity between an anode 1 and a cathode 2, each with a cross-linked structure, and this through this composite ion exchange -Membrane 3 c is divided into the anode space 1 and the cathode space 2 , an external direct current energy source 10 , which applies a direct current voltage between the anode 1 and the cathode 2 , a first liquid supply line 11 a Waste water 7 , which contains the nitrogen compounds, feeds into the anode space of the electrolyte bath 6 , a first liquid drain line 12 a, with which the oxidized liquid 9 is discharged from the anode space, a second liquid supply line 11 b, the waste water 7 , which contains nitrogen compounds, feeds into the cathode chamber 5 , and a second liquid drain line 12 b, with which the reduced liquid speed 19 from the Ka method room 5 is drained. The first liquid supply line 11 a and the first liquid discharge line 12 a penetrate the plate forming the anode space 13 and are placed on the inside of the anode space with openings, and the second liquid supply line 11 b and the second liquid drain - Line 12 b penetrate the plate 14 forming the cathode space and are attached to the inside of the cathode space with openings. In addition, the second liquid discharge line 12 b and the first liquid supply line 11 a via the third liquid reserve tank 15 c and the third liquid circulation pump 16 c are connected and the first liquid discharge line 12 a and the second liquid supply Line 11 b connected via the fourth liquid circulation pump 16 d. The first electrolysis treatment in the anode compartment and the second electrolysis treatment in the cathode compartment are carried out continuously. In addition, on the sides of the anode space and the cathode space of the electrolyte bath 6, a gas discharge device (omitted in the figures) for discharging the nitrogen gas formed during the electrolysis is attached. Incidentally, reference numeral 17 in the figure denotes an anode support body which forms an underside portion of the anode space, and reference numeral 18 denotes a cathode support body which forms an underside portion of the cathode space.

In the seventh embodiment described above, the electrolysis of the waste water 7 containing hydrazine and / or ammonium ions was continuous under conditions of an electrolysis area of 0.75 dm ² , current densities of 5 to 7 A / dm ² , an amount of liquid of 500 ml and liquid temperatures of 25 to 35 ° C. The measured results of the change in the total nitrogen concentration in the waste water 7 are shown in FIG. 17. Incidentally, the measurement of the total nitrogen concentration was carried out on the liquid which was continuously discharged from the cathode space 5 .

From this figure, it can be understood that according to the seventh embodiment, the nitrogen compounds such as hydrazine and ammonium ions in the waste water 7 can be effectively removed.

Fig. 18 is a graph showing, in the seventh embodiment, the measured results of the change in the total nitrogen concentration in the waste water 7 in the case that the waste water 7 containing the nitrogen compounds and which was generated in a thermal power plant , are treated in the same way as described above.

From this figure, it can be seen that the various types of nitrogen compounds in the waste water 7 generated in a thermal power plant can also be effectively removed according to the seventh embodiment of the present invention. As a result, the concentration of nitrogen components can be markedly reduced.

In addition, in the seventh embodiment, a composite ion exchange membrane 3 c is arranged as a diaphragm, which is composed of an anion exchange membrane and a cation exchange membrane. The cation exchange membrane, from which this composite ion exchange membrane 3 c consists, only allows the passage of cations and prevents anions from passing through and the anion exchange membrane allows only anions to pass through and prevents that Cations pass through or migrate through. Accordingly, the oxidation reaction in the anode space 4 and the reduction reaction in the cathode space 5 can each be carried out effectively. In addition, in both the anode space 4 and the cathode space 5, an increase in the concentration of H⁺ and OH⁻ is suppressed, which deteriorates the current efficiency, and a change in the pH of the liquid is suppressed.

To ensure such an effect, electrolysis of an aqueous solution of sodium sulfate was carried out using an electrolyte bath which has a composite ion-exchange membrane consisting of a cation-exchange membrane and an anion-exchange membrane (electrolysis area: 0, 75 dm ² , current density: 2 to 3 A / dm ² , amount of liquid: 500 ml, liquid temperature: 25 to 35 ° C).

Fig. 19 is a graph showing the measured results of the change in the pH of the anode space and the cathode space, respectively, in such an electrolysis of an aqueous sodium sulfate solution.

It can be understood from this figure that because the composite ion exchange Membrane keeps both cations and anions from passing through the membrane to enter or to walk through in both rooms, namely in the anode room and in Cathode space, the change in pH is small.

Embodiment 8

In the eighth embodiment, using the identical electrolyte bath 6 as in the first embodiment, the electrolysis is carried out in such a way that the wastewater 7 , which contains hydrazine and ammonium ions in each case, is fed into the anode space 4 and in that pure water 8 is filled into the cathode space 5 . As a result, hydrazine and ammonium ions in the waste water 7 in the anode space 4 are oxidized and removed from the waste water 7 as a nitrogen gas. At the same time, the hydrogen gas generated at the cathode 2 is recovered.

Water is electrolyzed at the cathode 2 (reduction decay), as shown in the following reaction equation, and hydrogen is generated:

2 H ₂ O + 2 e⁻ → H ₂ + 2 OH⁻.

The hydrogen gas thus generated is recovered, and the recovered hydrogen becomes used again.

Fig. 20 is a graph showing an example of change of the amount of hydrogen gas for the eighth embodiment to be obtained in accordance with the electrochemical calculation. From this figure, it can be seen that because the hydrogen gas is continuously generated, the reusable hydrogen gas can be continuously obtained by recovering it.

Embodiment 9

In the ninth embodiment, the first electrolysis is carried out using the same electrolyte bath 6 as in the fourth embodiment while feeding a first waste water 7 , which contains metal ions as well as hydrazine and ammonium ions, into the anode space 4 . After the oxidation of hydrazine and ammonium ions to nitrogen gas takes place in this way, the oxidized liquid 9 is conducted into the cathode chamber 5 and the second electrolysis is carried out there. The metal ions (metal ions with a lower standard electrode potential than hydrogen) in the waste water 7 are reduced to metal at the cathode 2 , as shown in the following reaction equation, and are deposited on the surfaces of the cathode 2 . By recovering the precipitated metal, the metal ions in the wastewater 7 can be removed:

M⁺ + e⁻ → M (metal).

Fig. 21 is a graph showing the measured results of the change in the concentration of metal ions in the liquid in the cathode chamber 5 according to the ninth exporting approximately form. From this figure it can be understood that, according to the ninth embodiment, the metal ions in the waste water 7 can be deposited on the cathode 2 and obtained.

As described above, according to the present invention, when performing a Electrolysis under normal temperature and pressure conditions by arrangement NEN of a diaphragm that has a selective ion permeability, e.g. B. an ion exchange membrane, between an anode and a cathode the content of nitrogen Compounds in the wastewater formed in a thermal power plant or the like, can be reduced or oxidized to nitrogen gas without generating secondary waste and can be removed effectively.

Claims (18)

1. Wastewater treatment process, in which an electrolysis is carried out in such a way that the wastewater ( 7 ) containing nitrogen compounds, at least one of the rooms anode room ( 4 ) and cathode room ( 5 ) of an electrolyte Bades ( 6 ) leads in which a diaphragm ( 3 ), which has a selective ion permeability, is arranged between an anode ( 1 ) and a cathode ( 2 ), whereby the nitrogen compounds in the waste water ( 7 ) to nitrogen -Gas oxidized or reduced. 2. Waste water treatment method according to claim 1, wherein the first electrolysis is carried out in such a way that the waste water ( 7 ) containing reduced nitrogen compounds, the anode space ( 4 ) of an electrolyte bath ( 6 ) is fed , in which the diaphragm ( 3 ), which has a selective ion permeability, is arranged between an anode ( 1 ) and a cathode ( 2 ), whereby the reduced nitrogen compounds in the waste water ( 7 ) are oxidized to nitrogen gas . 3. Waste water treatment method according to claim 1, wherein the second electrolysis is carried out by introducing the waste water ( 7 ) containing nitrogen oxides into the cathode space ( 5 ) of an electrolyte bath ( 6 ) in which the diaphragm ( 3 ), which has a selective ion permeability, is arranged between the anode ( 1 ) and the cathode ( 2 ), whereby the nitrogen oxides in the waste water ( 7 ) are reduced to nitrogen gas. 4. Wastewater treatment process comprising:

• - A first electrolysis step by performing a first electrolysis while introducing the nitrogen-containing waste water ( 7 ) into an anode space ( 4 ) of the electrolyte bath ( 6 ), in which a diaphragm ( 3 ) containing a selective ion -Permeability, is arranged between an anode ( 1 ) and a cathode ( 2 ), whereby the nitrogen compounds in the waste water ( 7 ) are oxidized to nitrogen gas; and
• - A second electrolysis step by carrying out a second electrolysis while introducing the waste water ( 7 ) oxidized in the first electrolysis step into the cathode space ( 5 ) of the electrolyte bath ( 6 ), whereby the nitrogen oxides in the waste water ( 7 ) to be reduced to nitrogen gas.

5. Wastewater treatment method according to one of claims 1 to 4, wherein the wastewater ( 7 ) contains at least one of the compounds hydrazine and ammonium ions as reduced nitrogen compounds. 6. Waste water treatment method according to one of claims 1 to 5, wherein the waste water ( 7 ) contains at least one of the compounds nitrate ions and nitrite ions as nitrogen oxides. 7. Waste water treatment method according to one of claims 1 to 6, wherein the waste water ( 7 ) is generated in a thermal power plant. 8. Wastewater treatment method according to one of claims 1 to 7, wherein at least one of the two electrodes anode ( 1 ) and cathode ( 2 ) has a cross-linked or porous structure and the anode ( 1 ) and the cathode ( 2 ) in close proximity to Di aphragma ( 3 ) are arranged, which is arranged between them. 9. Wastewater treatment method according to one of claims 1 to 8, wherein the diaphragm ( 3 ) is an ion exchange membrane. 10. Wastewater treatment method according to claim 9, wherein the diaphragm ( 3 ) is an anion exchange membrane. 11. Wastewater treatment method according to one of claims 1 to 9, wherein the diaphragm ( 3 ) is a composite ion exchange membrane in which a cation exchange membrane and an anion exchange membrane are combined. 12. A wastewater treatment device comprising:

• - An electrolyte bath ( 6 ) in which a diaphragm ( 3 ), which has a selective ion permeability, is arranged between an anode ( 1 ) and a cathode ( 2 ) and through the diaphragm ( 3 ) in one Anode space ( 4 ) and a cathode space ( 5 ) is divided;
• - A DC power source that applies a DC voltage between the anode ( 1 ) and the cathode ( 2 );
• - A first liquid supply device ( 11 a) for supplying an electrolyte solution in the anode space ( 4 ) of the electrolyte bath ( 6 );
• - A first liquid drain device ( 12 a) for draining the electrolyte solution from the anode space ( 4 ) of the electrolyte bath ( 6 );
• - A second liquid supply device ( 11 b) for supplying an electrolyte solution in the cathode space ( 5 ) of the electrolyte bath ( 6 );
• - A second liquid drain device ( 12 b) for draining the electrolyte solution from the cathode space ( 5 ) of the electrolyte bath ( 6 ); and
• - A gas discharge device for discharging the gas formed during the electrolysis from the gas phase of the anode compartment ( 4 ) and / or the cathode compartment ( 5 ) of the electrolyte bath ( 6 ).

13. The waste water treatment apparatus according to claim 12, comprising:

• - An electrolyte bath ( 6 ), in which a diaphragm ( 3 ), which has selective ion permeability, is arranged between an anode ( 1 ) and a cathode ( 2 ) and through the diaphragm ( 3 ) in one Anode space ( 4 ) and a cathode space ( 5 ) is divided;
• - A DC power source that applies a DC voltage between the anode ( 1 ) and the cathode ( 2 );
• - A first liquid supply device ( 11 a) for introducing waste water, which contains nitrogen compounds, into the anode space ( 4 ) of the electrolyte bath ( 6 );
• - A first liquid drain device ( 12 a) for draining the oxidized waste water ( 7 ) from the anode space ( 4 ) of the electrolyte bath ( 6 );
• - A second liquid supply device ( 11 b) for introducing the nitrogen-containing waste water ( 7 ) into the cathode space ( 5 ) of the electrolyte bath ( 6 );
• - A second liquid drain device ( 12 b) for draining the reduced waste water from the cathode space ( 5 ) of the electrolyte bath ( 6 ); and
• - A nitrogen gas discharge device for discharging the nitrogen gas formed by the electrolysis from the gas phase of the anode compartment ( 4 ) and / or the cathode compartment ( 5 ) of the electrolyte bath ( 6 ).

14. Wastewater treatment device according to claim 12 or claim 13, wherein the first liquid discharge device ( 12 a) and the second liquid supply device ( 11 b) are connected to one another. 15. Wastewater treatment device according to one of claims 12 to 14, wherein at least one of the electrodes anode ( 1 ) and cathode ( 2 ) has a cross-linked or porous structure and the anode ( 1 ) and the cathode ( 2 ) in close proximity to that Diaphragm ma ( 3 ) are arranged and this is arranged between them. 16. Wastewater treatment device according to one of claims 12 to 15, wherein the diaphragm ( 3 ) is an ion exchange membrane. 17. Wastewater treatment device according to claim 16, wherein the diaphragm ( 3 ) is an anion exchange membrane. 18. Wastewater treatment device according to one of claims 12 to 16, wherein the diaphragm ( 3 ) is a composite ion exchange membrane in which a cation exchange membrane and an anion exchange membrane are combined.