JP2005185946A - Water treatment method and water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment method capable of efficiently performing the removal treatment of a nitrogen compound or a phosphorus compound. <P>SOLUTION: A pair of ferrite electrodes 5 and 6 are at least partially immersed in the water to be treated in the treatment chamber 4 of an electrolytic treatment cell 2 and one electrode 5 is used as an anode and the other electrode 6 as a cathode to treat the nitrogen compound and the phosphorus compound in the water to be treated by an electrochemical technique. Further, a heat exchanger 12 is provided as a cooling means for cooling the water to be treated in the treatment chamber 4 to adjust the temperature of the water to be treated to a temperature suitable for electrochemical treatment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a water treatment method and a water treatment apparatus for treating nitrogen compounds and phosphorus compounds contained in water to be treated by an electrochemical technique.

  Conventionally, for example, thermal power plants have taken seawater and used it as cooling water during power generation. However, when the jellyfish occurs every year, there was an inconvenience that the jellyfish were clogged in the water intake and the seawater could not be taken in. Therefore, in the past, the jellyfish clogged in the water intake was treated by incineration. However, such incineration treatment has a problem that the treatment time is remarkably increased and the cost is increased. Attempts have been made to disassemble and remove.

  Here, a method for decomposing the jellyfish will be described. First, jellyfish floating in seawater are decomposed using biochemical treatment methods such as heat treatment, ultrasonic treatment, ultraviolet treatment and active oxygen treatment, or physicochemical methods such as microbial treatment and enzyme treatment. As a result, the jellyfish are melted in the seawater in a muddy state. Next, seawater containing the decomposed jellyfish (hereinafter referred to as treated water) is treated.

  This treated water contains nitrogen compounds and phosphorus compounds, and the treated water was conventionally treated by biological treatment, like the treatment of nitrogen compounds such as rivers and lakes. In the treatment method, since two steps of a nitrification step of converting ammonia nitrogen into nitrate nitrogen and a denitrification step of converting nitrate nitrogen into nitrogen gas are performed, two reaction tanks are necessary and the treatment is performed. Since the time is slow, there is a problem that the processing efficiency is lowered.

  In addition, in the biological treatment, a large-capacity anaerobic tank is required to hold denitrifying bacteria, and there has been a problem that the equipment construction cost increases and the installation area of the apparatus increases. Furthermore, since the denitrifying bacteria are significantly affected by the ambient temperature environment and other components contained in the water to be treated, the activity is reduced and the denitrifying action is lowered particularly in winter when the temperature is low. There is also a problem that the processing efficiency becomes unstable.

  Therefore, in order to solve the above technical problem, there is a method in which current is supplied to the water to be treated to oxidize ammonia, nitrite nitrogen, or nitrate nitrogen or to reduce and decompose them into nitrogen gas. In this case, in the conventional electrolysis method of water to be treated, for example, a noble metal material such as platinum, iridium, or palladium is used for the anode.

Then, by passing an electric current through the water to be treated, ammonia nitrogen is oxidized at the anode by active oxygen or hypochlorous acid, and the nitrogen compound is converted into nitrogen gas, whereby the nitrogen compound is treated. (For example, see Patent Document 1).
Japanese Patent Laid-Open No. 10-174976

  However, in the conventional treatment method of nitrogen compounds by electrolysis, the nitrogen compound removal treatment ability is low, and thus it was difficult to actually treat nitrogen compounds in the treatment of water to be treated. In addition, nitrate nitrogen is difficult to turn into nitrogen gas, and it is difficult to remove low-concentration nitrate ions. Therefore, there is a problem that it remains as a nitrogen component in water and cannot be removed.

  Therefore, the applicant previously proposed a method for electrolyzing water to be treated using an alloy such as copper and zinc or copper and nickel for the cathode and a noble metal material such as platinum, iridium or palladium for the anode. . According to this treatment method, the reduction reaction of nitrate nitrogen in the water to be treated at the cathode to nitrite nitrogen and ammonia is promoted, and the ammonia produced at the cathode is denitrified with hypochlorous acid produced at the anode. As a result, the synergistic effect reduces the time required for the reduction reaction and can treat nitrate ions at a low concentration.

  However, when an alloy containing copper is used for the cathode, toxic copper ions eluted in the water to be treated inevitably become a problem. Therefore, it has been desired to develop a method for treating a nitrogen compound that does not cause such toxicity.

  In order to solve the conventional technical problem, an object of the present invention is to provide a water treatment method and apparatus capable of efficiently removing nitrogen compounds and phosphorus compounds without causing toxicity.

  That is, in the water treatment method of the invention of claim 1, at least part of a pair of electrodes is immersed in the water to be treated, and the material of one of the electrodes constituting the anode is hypohalous acid or A conductive material capable of generating ozone or active oxygen is used, and the nitrogen compound in the water to be treated is treated by an electrochemical method using the other electrode material constituting the cathode as ferrite.

  The water treatment method of the invention of claim 2 is characterized in that after completion of the treatment, the polarity of the electrode is switched and the phosphorus compound in the water to be treated is treated by an electrochemical method.

  According to the water treatment method of the invention of claim 3, at least a part of a pair of ferrite electrodes is immersed in the water to be treated, one electrode serves as an anode, and the other electrode serves as a cathode. A compound and a phosphorus compound are treated.

  The water treatment method according to a fourth aspect of the invention is characterized in that the polarity of the electrode is switched in the third aspect of the invention.

  The water treatment method of the invention of claim 5 is characterized in that the water to be treated in each of the above inventions contains 20,000 ppm or more of chloride ions.

  The water treatment method of the invention of claim 6 is characterized in that after the water to be treated containing organic matter is subjected to biochemical treatment or physicochemical treatment, the treatment of the method of each of the above inventions is performed.

  The water treatment device of the invention of claim 7 comprises a pair of ferrite electrodes at least partially immersed in the water to be treated, and a cooling means for cooling the water to be treated, with one electrode serving as an anode and the other electrode The water to be treated is treated by an electrochemical method using as a cathode.

  According to the invention of claim 1, a pair of electrodes are at least partially immersed in the water to be treated, and the material of one of the electrodes constituting the anode is hypohalous acid, ozone, or Since the conductive water capable of generating active oxygen is used and the water to be treated is treated by an electrochemical technique using the other electrode material constituting the cathode as a ferrite, when the nitrogen compound in the water to be treated is treated, The reduction reaction of nitrate nitrogen in the water to be treated to nitrite nitrogen and ammonia is promoted at the ferrite electrode constituting the cathode, reducing the time required for the reduction reaction and treating nitrate ions at low concentrations. it can. Particularly in this case, since the other electrode constituting the cathode is a ferrite electrode and does not use copper, the problem of toxicity due to the elution of copper in the water to be treated can be solved.

  In addition, ammonia generated in the ferrite electrode constituting the cathode will undergo a denitrification reaction with a substance such as hypochlorous acid as hypohalous acid produced in one of the electrodes constituting the anode. Nitrogen components such as nitrogen, ammonia nitrogen and nitrogen compounds can be effectively removed. As a result, nitrogen compounds can be efficiently removed from the water to be treated containing nitrogen compounds discharged from factories, plants, thermal power plants, etc., and the nitrogen compound treatment capacity is improved. .

  According to the second aspect of the present invention, after the treatment is completed, the polarity of the electrode is switched and the phosphorus compound in the treated water is treated by an electrochemical method. Therefore, iron is treated in the treated water from the ferrite electrode serving as the anode. (II) ions are eluted, and the iron (III) ions oxidized to iron (III) ions in the water to be treated are chemically reacted with phosphate ions as phosphorus compounds in the water to be treated. As will be able to be precipitated.

  Thereby, the phosphorus compound in to-be-processed water can also be processed now. In particular, since the ferrite electrode as an anode has less elution of iron (II) ions than when an iron electrode is used, the inconvenience of excessive elution and extremely short electrode life can be solved.

  According to the invention of claim 3, at least a part of the pair of ferrite electrodes is immersed in the water to be treated, and the water to be treated is treated by an electrochemical method using one electrode as an anode and the other electrode as a cathode. Therefore, the reduction reaction of nitrate nitrogen in the treated water to nitrite nitrogen and ammonia is promoted at the ferrite electrode constituting the cathode, the time required for the reduction reaction is shortened, and low-concentration nitrate ions are also treated. be able to. Particularly in this case, since the other electrode constituting the cathode is a ferrite electrode and does not use copper, the problem of toxicity due to the elution of copper in the water to be treated can be solved.

  In addition, ammonia generated in the ferrite electrode constituting the cathode has a denitrification reaction with hypochlorous acid as a hypohalous acid produced in the ferrite electrode constituting the anode. Nitrogen components such as nitrogen, ammonia nitrogen and nitrogen compounds can be effectively removed. In particular, in this case, since the electrode constituting the anode is ferrite, a substance such as hypochlorous acid as hypohalous acid is not generated excessively even when the chloride ion concentration in the water to be treated is high. This makes it possible to prevent or suppress the disadvantage that hypochlorous acid or the like is excessively generated and nitrite ions generated on the cathode side are oxidized.

  In addition, iron (II) ions are eluted from the ferrite electrode serving as the anode into the water to be treated, and the iron (III) ions oxidized to iron (III) ions in the water to be treated and phosphorus compounds in the water to be treated Phosphate ions can be chemically reacted and precipitated as iron phosphate. Thereby, the phosphorus compound in to-be-processed water can also be processed now. In particular, since the ferrite electrode as an anode has less elution of iron (II) ions than when an iron electrode is used, the inconvenience of excessive elution and extremely short electrode life is also eliminated.

  With these, nitrogen compounds and phosphorus compounds can be efficiently removed from the water to be treated discharged from factories, plants, thermal power plants, and the like.

  According to the invention of claim 4, since the polarity of the electrode is switched in the above, it is possible to maintain a high processing capability by reducing the scale growing on the cathode side and anode side electrodes.

  In particular, the above method is suitable for treating water to be treated containing 20000 ppm or more of chloride ions, for example, nitrogen compounds and phosphorus compounds in seawater as in the invention of claim 5.

  In addition, if the water to be treated containing organic matter is subjected to biochemical treatment or physicochemical treatment before the treatment as in the invention of claim 6, the electrochemical treatment can proceed efficiently.

  Further, the water treatment apparatus according to claim 7 includes a pair of ferrite electrodes at least partially immersed in the water to be treated, and a cooling means for cooling the water to be treated, with one electrode serving as an anode and the other electrode Since the water to be treated is treated by an electrochemical method with the cathode as a cathode, the reduction reaction of nitrate nitrogen in the water to be treated to nitrite nitrogen and ammonia is promoted at the ferrite electrode constituting the cathode, and the time required for the reduction reaction And nitrate ions at a low concentration can be treated. Particularly in this case, since the other electrode constituting the cathode is a ferrite electrode and does not use copper, the problem of toxicity due to the elution of copper in the water to be treated can be solved.

  In addition, ammonia generated in the ferrite electrode constituting the cathode has a denitrification reaction with hypochlorous acid as a hypohalous acid produced in the ferrite electrode constituting the anode. Nitrogen components such as nitrogen, ammonia nitrogen and nitrogen compounds can be effectively removed. In particular, in this case, since the electrode constituting the anode is ferrite, a substance such as hypochlorous acid as hypohalous acid is not generated excessively even when the chloride ion concentration in the water to be treated is high. This makes it possible to prevent or suppress the disadvantage that hypochlorous acid or the like is excessively generated and nitrite ions generated on the cathode side are oxidized.

  In addition, iron (II) ions are eluted from the ferrite electrode serving as the anode into the water to be treated, and the iron (III) ions oxidized to iron (III) ions in the water to be treated and phosphorus compounds in the water to be treated Phosphate ions can be chemically reacted and precipitated as iron phosphate. Thereby, the phosphorus compound in to-be-processed water can also be processed now. In particular, since the ferrite electrode as an anode has less elution of iron (II) ions than when an iron electrode is used, the inconvenience of excessive elution and extremely short electrode life is also eliminated.

  Thus, nitrogen compounds and phosphorus compounds can be efficiently removed from the water to be treated discharged from factories, plants, thermal power plants, and the like. In particular, in this case, since the cooling means for cooling the water to be treated is provided, it is possible to prevent the disadvantage that the temperature of the water to be treated is abnormally high due to the heat generated in the ferrite electrode having a large resistance, which is suitable for electrochemical treatment By adjusting the temperature, it is possible to perform more efficient removal treatment of the nitrogen compound and phosphorus compound.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing an outline of a water treatment apparatus 1 for realizing a water treatment method according to an embodiment of the present invention. The water treatment apparatus 1 in this embodiment is at least partially immersed in the electrolytic treatment tank 2 that constitutes a treatment chamber 4 having an inflow and an outflow of drainage (not shown) inside, and the water to be treated in the treatment chamber 4. A pair of electrodes 5 and 6 arranged so as to face each other, a power source (not shown) for energizing the electrodes 5 and 6, a control device for controlling the power source, and the like. In the electrolytic treatment tank 2, a stirring means for stirring the inside may be provided.

  The electrode 5 is composed of a noble metal electrode such as a mixture of platinum (Pt) or iridium (Ir), or an insoluble conductor covering them, and the electrode 6 is one of ceramic based conductors. It consists of a certain ferrite electrode. In addition, although the electrode 5 is comprised by the noble metal electrode or the insoluble conductor which coat | covered these, it shall be a ceramic type conductor, a carbon type conductor, or stainless steel besides this. In this embodiment, a mixture of platinum and iridium (platinum / iridium) is used.

  With the above configuration, water to be treated containing nitrogen compound and phosphorus compound is stored in the treatment chamber 4 in the electrolytic treatment tank 2, the power is turned on by the control device, and a positive potential is applied to the electrode 5 and a negative potential is applied to the electrode 6. Apply (left side of FIG. 1). Thereby, the electrode 5 becomes an anode and the electrode 6 becomes a cathode.

By applying such a potential, electrons generated on the electrode 5 side constituting the anode are supplied to the ferrite electrode 6 side constituting the cathode, and nitrate ions as nitrate nitrogen contained in the water to be treated are converted into nitrite ions. Reduction (reaction A). Further, nitrate nitrogen reduced to nitrite ions is supplied with electrons on the electrode 6 side constituting the cathode, and is reduced to ammonia (ammonium ions) (reaction B). Reaction A and reaction B are shown below.
Reaction A NO ₃ ⁻ + H ₂ O + 2e ⁻ → NO ₂ ⁻ + 2OH ⁻
Reaction B NO ₂ ⁻ + 5H ₂ O + 6e ⁻ → NH ₃ (aq) + 7OH ⁻

  On the other hand, on the platinum / iridium electrode 5 side constituting the anode, chloride ions as halide ions contained in the water to be treated emit electrons to generate chlorine. And this chlorine melt | dissolves in water and produces | generates hypochlorous acid. At the same time, ozone or active oxygen is also generated. In this example, since chloride ions are contained in the water to be treated, hypochlorous acid is generated, but other halide ions are contained in the water to be treated in addition to this. Even if hypohalous acid such as hypofluorous acid or hypobromous acid is generated, the same effect is obtained.

  Here, when the concentration of chloride ions contained in the water to be treated is low, for example, in the water to be treated, halogen ions such as chloride ions, iodide ions, and bromide ions, compounds containing these halogen ions, For example, sodium chloride or potassium chloride may be added.

The chloride ions originally contained in the water to be treated and the sodium chloride added as described above are oxidized at the platinum / iridium electrode 5 constituting the anode to produce chlorine (reaction C. Sodium chloride). The produced chlorine reacts with water in the treated water to produce hypochlorous acid (reaction D). The produced hypochlorous acid reacts with ammonia (ammonium ions) produced in the water to be treated in the above-mentioned reaction B, undergoes a plurality of chemical changes, and is converted to nitrogen gas (reaction E). . Hereinafter, Reaction C to Reaction E are shown.
Reaction C NaCl → Na ⁺ + Cl ⁻
2Cl ⁻ → Cl ₂ + 2e ⁻
Reaction D Cl ₂ + H ₂ O → HClO + HCl
Reaction E NH ₃ + HClO → NH ₂ Cl + H ₂ O
NH ₂ Cl + HClO → NHCl ₂ + H ₂ O
NH ₂ Cl + NHCl ₂ → N ₂ ↑ + 3HCl

In addition, ammonia (ammonium ions) in the water to be treated reacts with ozone generated on the electrode 5 side constituting the anode or active oxygen as shown in the reaction F, and this is also denitrified into nitrogen gas.
Reaction F 2NH ₃ (aq) +3 (O) → N ₂ ↑ + 3H ₂ O

  In this way, nitrogen compounds such as nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the water to be treated can be treated in the same electrolytic treatment tank 2.

  Further, by using ferrite as a cathode as in this example, the reduction reaction of nitrate nitrogen in the water to be treated to nitrite nitrogen and ammonia is promoted, the time required for the reduction reaction is shortened, and low concentration Nitrate ions can be processed.

  In particular, in this case, it becomes possible to solve the problem of toxicity due to the elution of copper into the water to be treated as in the case of using copper for the electrode while maintaining the nitrogen compound treatment ability.

  In addition, the ammonia generated in the ferrite electrode 6 constituting the cathode has a denitrification reaction with a substance such as hypochlorous acid as hypohalous acid produced in the platinum / iridium electrode 5 constituting the anode. The effect makes it possible to effectively remove nitrogen components such as nitrate nitrogen, ammonia nitrogen and nitrogen compounds. As a result, nitrogen compounds can be efficiently removed from the water to be treated containing nitrogen compounds discharged from factories, plants, thermal power plants, etc., and the nitrogen compound treatment capacity is improved. .

  After such nitrogen compound treatment (nitrogen treatment step), the control device switches the polarity of the potential applied to the electrodes 5 and 6 (right side in FIG. 1; phosphorus treatment step. The above nitrogen treatment reaction continues in water). Thus, the electrode 5 constitutes a cathode and the electrode 6 constitutes an anode. As a result, the water to be treated is subjected to an electrolytic treatment as an electrochemical method, and the electrode 6 constituting the anode is composed of the conductor as described above, so that iron (II) ions are contained in the water to be treated. And is oxidized to iron (III) ions in the water to be treated.

The generated iron (III) ions coagulate and precipitate with phosphate ions in the water to be treated by a dephosphorylation reaction as shown in reaction G to produce iron phosphate that is sparingly soluble in water.
Reaction G Fe ³⁺ + PO ₄ ^3- → FePO ₄ ↓
Thereby, the phosphate ion as a phosphorus compound contained in to-be-treated water can be subjected to precipitation treatment as iron phosphate.

  In addition, in this case, a part of the iron (III) ions eluted in the state of iron (II) ions in the treated water for supply of electrons and oxidized on the electrode or in the treated water constitutes the cathode. Electrons are supplied again on the electrode 5 side, reduced to iron (II) ions, and again oxidized on the electrode 6 side constituting the anode.

Further, the scale (CaCO ₃ , Mg (OH) _2, etc.) grown on the surface of the electrode 6 constituting the cathode in the nitrogen treatment step is dropped from the surface when the electrode 6 becomes an anode in the phosphorus treatment step. Thereby, the electrolytic performance of the electrode 6 can be maintained high. In particular, the ferrite electrode 6 serving as an anode in the phosphoric acid treatment step has less elution of iron (II) ions than the case where an iron electrode is used as the electrode. The inconvenience is also eliminated.

  Thus, the nitrogen compound and phosphorus compound in the water to be treated can be effectively treated by performing the electrochemical treatment as described above. Therefore, it becomes possible to treat the nitrogen compound and the phosphorus compound in the water to be treated in the same electrolytic treatment tank 2, eliminating the need for installing a large biological treatment tank as in the prior art, increasing the equipment construction cost and the equipment installation area. An increase can be avoided.

  Furthermore, the complicated maintenance work of denitrifying bacteria required in biological treatment can be eliminated, and stable high nitrogen and phosphorus treatment efficiency can be provided.

  Next, another embodiment of the present invention will be described with reference to FIG. FIG. 2 is an explanatory view showing an outline of the water treatment apparatus 10 for realizing the water treatment method of Example 2 of the present invention. In FIG. 2, the same reference numerals as those in FIG. 1 have the same or similar effects.

  The water treatment apparatus 10 in this embodiment is also at least partially immersed in the electrolytic treatment tank 2 constituting the treatment chamber 4 having an inflow and an outflow of drainage (not shown) inside, and the water to be treated in the treatment chamber 4. A pair of electrodes 5 and 6 arranged so as to face each other, a power source (not shown) for energizing the electrodes 5 and 6, a control device for controlling the power source, and the like. In the figure, reference numeral 12 denotes a heat exchanger for cooling the water to be treated in the treatment chamber 4, and the water to be treated is deprived of heat by the water cooling system and cooled by the heat exchanger 12. In the figure, 14 is a membrane separation tank, and a permeable membrane 16 is disposed in the membrane separation tank 14. The permeation membrane 16 is a membrane for separating precipitates such as iron compounds containing iron phosphate floating in the water to be treated from the water to be treated that has been electrolytically treated in the electrolytic treatment tank 2. The inside of the permeable membrane 16 is a hollow portion, and a discharge port 18 for discharging treated water is formed above. In addition, you may provide the stirring means for stirring the inside in the electrolytic treatment tank 2 similarly.

  In addition, the electrodes 5 and 6 of this embodiment are made of a ceramic conductor ferrite.

  With the above configuration, water to be treated is stored in the treatment chamber 4 in the electrolytic treatment tank 2, the power is turned on by the control device, and a positive potential is applied to the electrode 5 and a negative potential is applied to the electrode 6 (left side in FIG. 2). ). Thereby, the electrode 5 becomes an anode and the electrode 6 becomes a cathode.

By applying such a potential, electrons generated on the ferrite electrode 5 side constituting the anode are supplied to the ferrite electrode 6 side constituting the cathode, and nitrate ions as nitrate nitrogen contained in the water to be treated are converted to nitrite ions. (Reaction A). Further, nitrate nitrogen reduced to nitrite ions is supplied with electrons on the electrode 6 side constituting the cathode, and is reduced to ammonia (ammonium ions) (reaction B). Reaction A and reaction B are shown below.
Reaction A NO ₃ ⁻ + H ₂ O + 2e ⁻ → NO ₂ ⁻ + 2OH ⁻
Reaction B NO ₂ ⁻ + 5H ₂ O + 6e ⁻ → NH ₃ (aq) + 7OH ⁻

  On the other hand, on the ferrite electrode 5 side constituting the anode, chloride ions as halide ions contained in the water to be treated release electrons to generate chlorine. And this chlorine melt | dissolves in water and produces | generates hypochlorous acid. At the same time, ozone or active oxygen is also generated. In this example, since chloride ions are contained in the water to be treated, hypochlorous acid is generated, but other halide ions are contained in the water to be treated in addition to this. Even if hypohalous acid such as hypofluorous acid or hypobromous acid is generated, the same effect is obtained.

  Here, the chloride ion concentration contained in the water to be treated includes 20,000 ppm or more of chloride ions. When the chloride ion concentration in the water to be treated is low, for example, chloride ions or iodine Halogen ions such as chloride ions and bromide ions, and compounds containing these halogen ions, such as sodium chloride and potassium chloride, are added.

The chloride ions originally contained in the water to be treated and the sodium chloride added as described above are oxidized at the ferrite electrode 5 constituting the anode to generate chlorine (reaction C. shown in the case of sodium chloride). The produced chlorine produces water, Hanno city, and hypochlorous acid in the treated water (reaction D). The produced hypochlorous acid reacts with ammonia (ammonium ions) produced in the water to be treated in the above-mentioned reaction B, undergoes a plurality of chemical changes, and is converted to nitrogen gas (reaction E). . Hereinafter, Reaction C to Reaction E are shown.
Reaction C NaCl → Na ⁺ + Cl ⁻
2Cl ⁻ → Cl ₂ + 2e ⁻
Reaction D Cl ₂ + H ₂ O → HClO + HCl
Reaction E NH ₃ + HClO → NH ₂ Cl + H ₂ O
NH ₂ Cl + HClO → NHCl ₂ + H ₂ O
NH ₂ Cl + NHCl ₂ → N ₂ ↑ + 3HCl

In addition, ammonia (ammonium ions) in the water to be treated reacts with ozone generated on the electrode 5 side constituting the anode or active oxygen as shown in the reaction F, and this is also denitrified into nitrogen gas.
Reaction F 2NH ₃ (aq) +3 (O) → N ₂ ↑ + 3H ₂ O

  In this way, nitrogen compounds such as nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the water to be treated can be treated in the same electrolytic treatment tank 2.

  Further, by using ferrite as a cathode as in this example, the reduction reaction of nitrate nitrogen in the water to be treated to nitrite nitrogen and ammonia is promoted, the time required for the reduction reaction is shortened, and low concentration Nitrate ions can also be treated. Furthermore, while maintaining the nitrogen compound treatment capability, it becomes possible to solve the problem of toxicity due to the elution of copper into the water to be treated as in the case of using copper for the electrode.

  In addition, the ammonia generated in the ferrite electrode 6 constituting the cathode has a denitrification reaction with a substance such as hypochlorous acid as hypohalous acid produced in the ferrite electrode 5 constituting the anode. Nitrogen components such as nitrate nitrogen, ammonia nitrogen and nitrogen compounds can be effectively removed.

  Furthermore, generation of hypochlorous acid can be suppressed by configuring the anode with ferrite. That is, when hypochlorous acid is excessively generated, the reaction in which nitric acid reduced to nitrite ions generated on the cathode side in the reaction A is oxidized and returned is promoted. However, since the anode is made of ferrite, the amount of hypochlorous acid generated is reduced, so that the disadvantage that nitrite ions are oxidized and returned to nitric acid can be prevented or suppressed. Thereby, removal of nitrogen compounds can be promoted.

  On the other hand, from the ferrite electrode 5 side constituting the anode, iron (II) ions are eluted into the treated water and are oxidized to iron (III) ions in the treated water.

The generated iron (III) ions coagulate and precipitate with phosphate ions in the water to be treated by a dephosphorylation reaction as shown in reaction G to produce iron phosphate that is sparingly soluble in water.
Reaction G Fe ³⁺ + PO ₄ ^3- → FePO ₄ ↓
Thereby, the phosphate ion as a phosphorus compound contained in to-be-processed water can be made into iron phosphate.

  In addition, in this case, a part of the iron (III) ions eluted in the state of iron (II) ions in the treated water for supply of electrons and oxidized on the electrode or in the treated water constitutes the cathode. Electrons are supplied again on the electrode 5 side, reduced to iron (II) ions, and again oxidized on the electrode 6 side constituting the anode.

  On the other hand, when ferrite electrodes are used as the electrodes 5 and 6, since the ferrite has a very high resistance and generates heat, the temperature of the water to be treated rises to about 80 ° C to 90 ° C. Here, the water to be treated in the treatment chamber 4 is subjected to heat exchange with the cooling water flowing through the heat exchanger 12 in the heat exchanger 12, so that the water to be treated is heated in the heat exchanger 12. Deprived and cooled. Thereby, even when a ferrite electrode having a high resistance is used, it is possible to prevent the disadvantage that the temperature of the water to be treated is abnormally high due to the heat generated in the ferrite electrode. In addition, since the temperature of the water to be treated can be lowered to a temperature suitable for electrochemical treatment by the heat exchanger 12, more efficient treatment of nitrogen compounds and phosphorus compounds can be performed. . In addition, if the cooling water heated by exchanging heat with the water to be treated in the heat exchanger 12 is used, for example, if the microorganisms of the microorganism treatment described later are heated, there is a disadvantage that the activity of the microorganisms in the winter season or the like decreases. Can be prevented.

  Thus, even if it is a case where a ferrite electrode is used by cooling to-be-processed water with the heat exchanger 12, the problem that the temperature of to-be-processed water in the process chamber 4 rises can be avoided. It becomes like this.

  On the other hand, the water to be treated treated in the electrolytic treatment tank 2 as described above is sent to the membrane separation tank 14 from an outlet not shown. In the membrane separation tank 14, the water to be treated passes through the permeable membrane 16 and is discharged from the discharge port 18. Further, since deposits such as iron compounds containing iron phosphate cannot pass through the permeable membrane 16, they are separated from the water to be treated and settle in the membrane separation tank 14.

  Thus, when a ferrite electrode is used for both electrodes 5 and 6, the nitrogen compound and the phosphorus compound can be removed simultaneously. That is, when the electrode 5 is made of platinum / iridium and the electrode 6 is made of ferrite as in the above embodiment, the nitrogen compound is removed as shown in the left side of FIG. A step of applying a negative potential to the electrode 6 to treat the nitrogen compound, and after removing the nitrogen compound, switching the polarity of the electrodes 5 and 6 to apply a negative potential to the electrode 5 and a positive potential to the electrode 6 to The compound could not be removed without going through two steps of treating the compound. However, by using ferrite electrodes for both electrodes 5 and 6, it becomes possible to treat the nitrogen compound at the cathode and the phosphorous compound at the anode, and the treatment time of the water to be treated can be significantly shortened.

  Further, since the elution of iron (II) ions is less when a ferrite electrode is used than when an iron electrode is used, the disadvantage that the electrode life is extremely shortened due to excessive dissolution is also eliminated.

On the other hand, when the treatment water is treated for a long time, scales (CaCO ₃ , Mg (OH) _2, etc.) grow on the surface of the ferrite electrode 6 constituting the cathode as described above. In this case, the polarity of the applied potential is switched. Thus, the electrode 5 constitutes a cathode and the electrode 6 constitutes an anode.

In this way, the polarity of the potential is switched and the electrode 6 becomes an anode, so that the scale is dropped from the surface. Thereby, the electrolytic performance of the electrode 6 can be maintained high. Further, by switching the potential, scales such as silica (SiO ₂ ) are removed on the ferrite electrode 5 side serving as the cathode, and the nitrogen compound is removed, and iron (II) ions are removed on the ferrite electrode 6 side serving as the anode. Elution is performed to remove the phosphorus compound.

  Therefore, even when the potential is switched, the nitrogen compound and the phosphorus compound can be removed at the same time, so that the water treatment efficiency can be remarkably improved.

  Here, the water treatment apparatus 1, 10 for treating the waste water discharged from the factory or plant for realizing the water treatment method of the present embodiment described above, for example, seawater used as cooling water in a thermal power plant An example in the case of adopting the processing for removing jellyfish clogged in the water intake, which is a problem, will be described with reference to FIG. Moreover, in a present Example, the seawater containing the jellyfish which is an organic substance corresponds to the to-be-processed water of each said Example, and shall treat the said to-be-processed water. In addition, FIG. 3 is explanatory drawing which showed the process process of the said jellyfish.

  The jellyfish removal treatment method is a jellyfish decomposition process (organic substance treatment process) for decomposing jellyfish in seawater, and seawater containing jellyfish decomposed by the jellyfish decomposition process is treated using an electrochemical method as in the above embodiments. It is comprised by two processes with the water treatment process.

  As shown in FIG. 3, the jellyfish decomposition step is one that decomposes jellyfish by physicochemical treatment such as microbial treatment or enzyme treatment as described above, and biochemical treatment such as heat treatment, ultrasonic treatment, ultraviolet treatment, or active oxygen treatment. Some jellyfish are decomposed by treatment.

  The seawater containing jellyfish decomposed by these methods is then treated by an electrical technique as in the above embodiments in the water treatment step. Further, in this embodiment, seawater is treated in the electrolytic treatment tank 2, but since 20000 ppm abnormal chloride ions are present in the seawater, the seawater described in each of the above embodiments is used. As described above, each of the above implementations can be carried out without adding halogen ions such as chloride ions, iodide ions and bromide ions, and compounds containing these halogen ions, such as sodium chloride and potassium chloride. Example reactions C through E occur. This makes it possible to treat nitrogen compounds and phosphorus compounds as in the above embodiments.

  As described above, after the water to be treated containing an organic substance such as jellyfish is decomposed by biochemical treatment or physicochemical treatment, the electrical treatment can be performed efficiently by performing the electrical treatment. become.

It is explanatory drawing which shows the outline | summary of the Example of the water treatment apparatus for implement | achieving the water treatment method of this invention. It is explanatory drawing which shows the outline | summary of the other Example of the water treatment apparatus for implement | achieving the water treatment method of this invention. It is a figure shown about the jellyfish processing method in the seawater to which the water processing method of this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10 Water treatment apparatus 2 Electrolytic processing tank 4 Processing chamber 5, 6 Electrode 12 Heat exchanger 14 Membrane separation tank 16 Permeation membrane 18 Outlet

Claims (7)

Immerse at least part of the pair of electrodes in the water to be treated,
The material of one of the electrodes constituting the anode is a conductor capable of generating hypohalous acid, ozone, or active oxygen by an electrochemical method,
A water treatment method characterized in that a nitrogen compound in the water to be treated is treated by an electrochemical technique using ferrite as a material for the other electrode constituting the cathode.   2. The water treatment method according to claim 1, wherein the phosphorus compound in the water to be treated is treated by an electrochemical method after switching the polarity of the electrode.   Treating at least part of a pair of ferrite electrodes in the water to be treated, treating the nitrogen compound and phosphorus compound in the water to be treated by an electrochemical method using one of the electrodes as an anode and the other electrode as a cathode; A water treatment method characterized.   The water treatment method according to claim 3, wherein the polarity of the electrode is switched.   The water treatment method according to claim 1, 2, 3, or 4, wherein the water to be treated contains chloride ions of 20000 ppm or more.   The method of claim 1, claim 2, claim 3, claim 4 or claim 5 is performed after the water to be treated containing organic matter is subjected to biochemical treatment or physicochemical treatment. Water treatment method. A pair of ferrite electrodes at least partially immersed in the water to be treated; and a cooling means for cooling the water to be treated.
A water treatment apparatus, wherein the water to be treated is treated by an electrochemical method using one of the electrodes as an anode and the other electrode as a cathode.

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