JP2003053365A - Water cleaning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water cleaning system capable of preventing an increase of sludge and also capable of suppressing a nitrate ion and ammonia from mixing and increasing in waste water to the outside. SOLUTION: The water treating system S is composed of an activated sludge treating tank 11 performing biological treatment of the water to be treated, a settling tank 12 for settling sludge in the water to be treated, treated at the activated sludge treating tank 11, a nitrogen treating device 1 for treating a nitrogen compound in the settled sludge at the settling tank 12 by an electrochemical technique and a pump 14 for returning the sludge treated at the nitrogen treating device 1 to the activated sludge treating tank 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water purification system for treating water to be treated such as domestic wastewater and factory wastewater containing nitrogen compounds.

[0002]

2. Description of the Related Art Conventionally, one of the causes of eutrophication of rivers and lakes
It is well known that there is the presence of nitrogen compounds. A large amount of this nitrogen compound is present in water to be treated such as domestic household wastewater and factory wastewater, but it is the current situation that purification treatment is difficult and effective measures cannot be taken. In a commonly used water purification system, the treated water is treated by biological treatment, which causes BOD in the treated water due to the growth of microorganisms.
(Biochemical oxygen demand) and COD (chemical oxygen demand) are being reduced.

Other types of biological treatment are BOD and C described above.
In addition to those that reduce OD, in biological treatment,
By using a denitrifying bacterium, a denitrification step of converting nitrate nitrogen into nitrogen gas and a nitrification step of converting ammonia nitrogen into nitrate nitrogen are carried out, thereby removing nitrate nitrogen and nitrogen contained in the water to be treated. Some treat ammonia nitrogen.

After the biological treatment is performed, the water to be treated is allowed to stand still, so that sludge containing nitrate nitrogen or ammonia nitrogen, which could not be biologically treated, is precipitated in the water to be treated. . By performing biological treatment from time to time,
A large amount of settled sludge is deposited in the water to be treated, and when a certain amount or more is deposited, there is a problem that it must be removed by removal maintenance or the like.

Therefore, in order to reduce the amount of sludge produced in a large amount, the sludge is returned to the biological treatment again, and further biological treatment is performed to reduce BOD and COD, and at the same time, nitric acid contained in the sludge is reduced. There is a water purification system that denitrifies nitrogen and ammonia nitrogen. However, only by repeating the biological treatment, there is a problem that organic substances and microorganisms, which are difficult to decompose by the biological treatment, remain and the sludge cannot be efficiently reduced.

In order to solve such a problem, sludge obtained by performing a biological treatment and allowing it to stand is transported to an electrolytic means by a transport means, and the sludge is subjected to an electrochemical method such as ozone or ozone. There is a method in which active oxygen and further hypochlorous acid are generated to destroy the cell walls of organic substances and microorganisms contained in sludge, and the sludge subjected to electrolytic treatment is again subjected to biological treatment.

In this case, organic substances and microorganisms contained in the sludge by the electrolytic treatment can be easily denitrified, and the amount of sludge produced can be reduced.

[0008]

However, in the above-mentioned water purification system, by performing electrolytic treatment, nitrate ions and ammonia are generated when organic substances and microorganisms are decomposed, and nitrate ions and ammonia in the wastewater of the treated water increase. However, there is a problem that the drainage is discarded to the outside.
Therefore, there is a problem that bacteria are propagated and algae are generated from the waste water of the water purification system.

Therefore, the present invention has been made in order to solve the conventional technical problems, and it is possible to prevent the increase of sludge and to increase nitrate ion and ammonia mixed in the waste water discharged to the outside. It is an object of the present invention to provide a water purification system capable of suppressing water pollution.

[0010]

The water purification system of the present invention comprises a biological treatment / purification means for biologically treating the water to be treated and a sludge in the treated water treated by the biological treatment / purification means. From a settling means for settling, a nitrogen treatment means for treating the nitrogen compounds of sludge settled in the sedimentation means by an electrochemical method, and a returning means for returning the sludge treated by this nitrogen treatment means to the biological treatment purification means. It is characterized by being configured.

According to the water purification system of the present invention, a biological treatment / purification means for biologically treating the water to be treated, and a sedimentation means for precipitating sludge in the water to be treated treated by the biological treatment / purification means. And a nitrogen treatment means for treating nitrogen compounds of sludge precipitated in the precipitation means by an electrochemical method, and a return means for returning the sludge treated by this nitrogen treatment means to the biological treatment purification means. The sludge after destroying the cell wall of the microorganisms contained in the nitrogen treatment and sludge by the nitrogen treatment means can be returned to the biological treatment purification means, and the sludge is treated by the biological treatment purification means. It can be easily biodegraded and the amount of sludge waste can be reduced. As a result, it becomes possible to reduce the cost running required for the conventional sludge treatment.

Further, the nitrogen treatment means can treat even those substances which are difficult to decompose by biological treatment and purification means such as nitrate nitrogen and ammonia nitrogen contained in sludge in the water to be treated.

A water purification system according to a second aspect of the present invention is, in addition to the first aspect of the present invention, a conductor containing a group Ib group or a group IIb group of the periodic table as a metal material constituting the cathode of the nitrogen treatment means, Alternatively, it is characterized in that a conductor of the same family is used.

According to the water purifying system of the invention of claim 2, in addition to the invention of claim 1, as the metal material constituting the cathode of the nitrogen treatment means, a group Ib group or I group of the periodic table.
Since a conductor containing a group Ib or a conductor coated with the same group is used, the reduction reaction of nitrate nitrogen in sludge to nitrite nitrogen and ammonia can be promoted,
It becomes possible to shorten the time required for the reduction reaction and remove low-concentration nitrogen compounds. This improves the throughput of nitrogen compounds.

The water purification system of the invention of claim 3 is, in addition to the invention of claim 1 or claim 2, as a metal material constituting the cathode, copper and zinc, copper and iron, copper and nickel, or copper and aluminum. It is characterized by using an alloy or a sintered body containing.

According to the water purification system of the invention of claim 3, in addition to the invention of claim 1 or 2, as the metal material constituting the cathode, copper and zinc, copper and iron, copper and nickel or copper. Since an alloy or a sintered body containing aluminum and aluminum is used, the reduction reaction of nitrate nitrogen in sludge to nitrite nitrogen and ammonia can be further accelerated, and the time required for the reduction reaction can be shortened. Will be able to. As a result, the nitrogen compound treatment capacity is further improved.

In addition to the invention of claim 1, claim 2 or claim 3, the water purification system of the invention of claim 4 uses an insoluble material or carbon as a conductive material constituting the anode of the nitrogen treatment means. At the same time, the area of the cathode of the nitrogen treatment means is made larger than the area of the anode.

According to the water purification system of the invention of claim 4, in addition to the invention of claim 1, claim 2 or claim 3,
As a conductive material that constitutes the anode of the nitrogen treatment means,
Since the area of the cathode of the nitrogen treatment means is made larger than the area of the anode while using an insoluble material or carbon, the nitrogen compound generated at the anode, particularly, the oxidation reaction from nitrite nitrogen to nitrate nitrogen is reduced, Along with this, the reduction reaction of nitrate nitrogen generated at the cathode can be promoted.

In addition to the invention of claim 1, claim 2, claim 3 or claim 4, the water purifying system of the invention of claim 5 allows passage of ions and blocks passage of oxygen bubbles. The member is arranged between the cathode and the anode of the nitrogen treatment means so that the flowing water does not affect the anode side.

According to the water purification system of the invention of claim 5, in addition to the invention of claim 1, claim 2, claim 3 or claim 4, passage of ions is allowed and passage of oxygen bubbles is blocked. Since the shielding member to be arranged is disposed between the cathode and the anode of the nitrogen treatment means, the denitrification reaction of the nitrogen compound is performed by the active oxygen generated on the anode side, and at the same time, only the ions pass through the shielding member, so that the nitrogen compound, especially It becomes possible to promote the reduction reaction of nitrate nitrogen.

Further, since the anode side has a structure that is not affected by running water, and a shielding member that allows the passage of ions is arranged, stirring of the sludge by running water promotes the reduction reaction of nitrate nitrogen on the cathode side. At this time, the sludge on the anode side is prevented from being agitated, and the supply of dilute chlorine ions to the anode by electrophoresis is promoted. As a result, the treatment capacity of nitrogen compounds is improved by hypochlorous acid.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of the water purification system S of the present invention. The water purification system S in this embodiment has an activated sludge treatment tank 11 as a biological treatment purification means, a settling tank 12 as a precipitation means, and a nitrogen treatment device 1 as a nitrogen treatment means. The processing tank 11, the precipitation tank 12, and the nitrogen processing apparatus 1 are connected in an annular shape by pipe connection. 13 and 1 in FIG.
4 is a pump as a forced circulation means and a return means.

The activated sludge treatment tank 11 in this embodiment is
It is composed of an anaerobic tank 11A and an aerobic tank 11B, and is partitioned by a partition plate 15 equipped with a valve device (not shown) that can be opened and closed. The anaerobic tank 11A has an inlet (not shown) for taking in treated water such as domestic household wastewater or factory drainage, and the aerobic tank 11B has an outlet (not shown) for drainage. Has been done. The anaerobic tank 11A and the aerobic tank 11B contain different types of denitrifying bacteria, and the reproduction of the bacteria is activated by maintaining the ambient temperature environment and the like.

In the anaerobic tank 11A, a denitrification step of converting nitrate nitrogen contained in the water to be treated into nitrogen gas by denitrifying bacteria is performed, and the water to be treated in the anaerobic tank 11A is treated by the valve By opening the device, the gas is introduced into the aerobic tank 11B. In the aerobic tank 11B, a nitrification step of converting ammonia nitrogen contained in the water to be treated into nitrate nitrogen by denitrifying bacteria is performed. The anaerobic tank 11A and the aerobic tank 11B may be provided with a stirring means (not shown) to promote the activation of the denitrifying bacteria.

In this embodiment, a settling tank 12 is provided adjacent to the activated sludge treatment tank 11 as shown in FIG. 1, and a valve device (not shown) is opened / closed to treat the water to be treated in the activated sludge treatment tank 11. Allows transportation (outflow). Other than this, it is also possible to pipe the activated sludge treatment tank 11 and the sedimentation tank 12 to carry the water to be treated in the activated sludge treatment tank 11.

In the settling tank 12, the water to be treated conveyed from the inside of the activated sludge treatment tank 11 is allowed to stand, and the solid content (hereinafter referred to as "sludge") contained in the water to be treated is separated into other waste water. To do. The wastewater separated from the sludge can be discharged to the outside through a drain port (not shown) formed in the upper part of the settling tank 12, for example.

On the other hand, a sludge discharge port (not shown) is formed at the bottom or bottom of the settling tank 12 and is controlled to be openable / closable by a valve device (not shown). This sludge discharge port is connected to the inlet of the pump 13 as the forced circulation means through the inflow pipe 13A.
Of the nitrogen treatment device 1 through the outflow pipe 13B.
It is connected to the.

Here, the nitrogen treatment apparatus 1 will be described with reference to FIGS. 2 to 5. The nitrogen treatment apparatus 1 in the present embodiment is configured so that at least a part thereof is immersed in the sludge in the treatment chamber 2 and a treatment tank 2 which constitutes a treatment chamber 4 having an inlet and an outlet for sludge (not shown). A pair of electrodes arranged to face each other, that is, an anode 5, a cathode 6, and
A power source 7 for energizing the electrodes 5 and 6 and a controller (not shown) for controlling the electrodes 7 are provided. In the figure, 10 is an agitator as an agitating means for agitating the inside of the processing tank 2.

The cathode 6 is composed of an alloy or a sintered body of copper and zinc, copper and iron, copper and nickel, or copper and aluminum, and the anode 5 is an insoluble metal.
For example, it is an insoluble electrode or carbon made of platinum, iridium, palladium or an oxide thereof.

A shielding member 9 formed in a cylindrical shape as shown in FIG. 3 is provided between the anode 5 and the cathode 6 so as to surround the anode 5.
The shielding member 9 is made of, for example, a non-conductive member such as a glass fiber or a plastic mesh, so that oxygen bubbles generated from the anode 5 can be prevented from flowing into the cathode 6.
It can be prevented from passing to the side. At this time,
The ions present on the anode 5 side can pass through the shielding member 9 and move to the cathode 6 side. Further, the shielding member 9 does not affect the running water on the anode by stirring generated by running water of sludge or stirring by the stirring bar 10.

With the above construction, when treating the sludge stored in the treatment tank 2 of the nitrogen treatment apparatus 1, the controller 7 turns on the power source 7 to turn the cathode 6 and the anode 5 on.
Energize. On the cathode 6 side, nitrate ions contained in the sludge are converted into nitrite ions by a reduction reaction (reaction A). Further, the nitrite ion generated by the reduction reaction of nitrate ion is further converted into ammonia by the reduction reaction (reaction B). Below, reaction A and reaction B
Indicates. 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 side of the anode 5, ozone, active oxygen and hypochlorous acid are generated from the surface of the anode 5, thereby destroying the organic matter contained in the sludge and the cell walls of microorganisms and decomposing them. Further, nitrogen gas is generated by the denitrification action of ammonia in the sludge (reaction C).
The reactions C to F are shown below. Reaction _{C NH 3 (aq) +3 (} O) → N 2 ↑ + 3H 2 O The reaction ^{D NaCl → Na + + Cl -} 2Cl - → Cl 2 + 2e - reaction _{E Cl 2 + H 2 O →} HClO + HCl Reaction F 2NH ₄ + 4HClO → N ₂ ↑ + 4HCl + 4H ₂ O

Now, the constituent electrodes of the cathode 6 will be described with reference to FIGS. 4 and 5. In the actual electrolysis of nitrogen treatment, the nitrogen treatment ability remarkably differs depending on the kind of metal forming the cathode 6. FIG. 4 is a diagram showing the reduction characteristics of a cathode composed of various simple metals.
The experimental results shown in FIG. 5 show the concentration of NO ₃ ⁻ over time when 300 ml of a solution containing 0.001 M KNO ₃ was electrolyzed under conditions without chloride ions. The anode 5 used at this time is platinum, and the area ratio between the cathode 6 and the anode 5 is 10: 1.

As shown in FIG. 4, if the cathode 6 is made of a conductor containing Group Ib or Group IIb of the periodic table, for example, zinc, copper, silver, or brass which is an alloy of zinc and copper,
It can be seen that the reducing characteristics are remarkable in nitrate nitrogen, that is, in a low concentration of NO ₃ ⁻ . Further, under the same conditions, platinum, nickel, and titanium showed almost no reducing property. From this, it can be seen that when the cathode 6 is made of a conductor containing a group Ib group or a group IIb group of the periodic table, it is effective for the treatment of NO ₃ ⁻ and NO ₂ ⁻ .

FIG. 5 is a diagram showing the reducing characteristics of the cathode made of various copper alloys. The experiment result shown in FIG. 5 is performed under the same conditions as the experiment of FIG. According to FIG. 5, when Advance, which is an alloy of copper, nickel, and manganese, phosphor bronze, which is an alloy of copper and tin, and cupro-nickel, which is an alloy of copper and nickel, are used for the cathode 6, respectively, Compared to the case of using a single metal of zinc for the cathode 6, NO
₃ ^- it was those percentage of decrease is small.

From the above, copper and zinc, copper and nickel, and copper and aluminum are effective for the treatment of NO ₃ ⁻ and NO ₂ ⁻ as the copper alloy under the condition of no chlorine ion or diluted chlorine ion. Further, when manganese or tin is used as the copper alloy, it is possible to obtain a low concentration of NO regardless of the amount thereof.
₃ ^- and NO ₂ ^- it is understood that the reduction performance of remarkably lowered. In addition to copper alloys, copper-iron sintered bodies also have high reduction characteristics.

As a result, when the alloy of copper and zinc is used for the cathode 6, compared with the case where a simple metal of zinc or copper is used, in particular, nitrite nitrogen and nitric acid nitrogen in sludge are Can accelerate the reduction reaction to ammonia,
The time required for the reduction reaction can be shortened. When the solution becomes alkaline with the progress of electrolysis, copper
The reduction rate of NO ₃ ⁻ and NO ₂ ⁻ decreases, but in the case of brass, which is an alloy of copper and zinc, zinc, which has a greater ionization tendency than copper, acts as a sacrificial electrode, so the reduction rate of nitrogen compounds is reduced. The pH dependence of the
This is because the reducing property is improved as compared with zinc alone.

[0038] Particularly, in the case of using a brass cathode 6 is significantly NO ₃ ^- it is possible to reduce the concentration,
The reduction reaction of nitrate nitrogen in the water to be treated to nitrite nitrogen and ammonia can be further promoted, the time required for the reduction reaction can be shortened, and nitrate ion of low concentration can also be reduced.

On the other hand, on the anode 5 side, in addition to the denitrification reaction as described above, on the cathode 6 side, nitrate ion is reduced to nitrite ion, and is also oxidized to nitrite ion to nitrate ion. A reaction is taking place. Thereby, with respect to the reduction reaction of nitrate ions at the cathode 6,
Since the oxidation reaction (reaction K) of the nitrite ion occurs at the anode 5, there is a problem that the nitrogen treatment efficiency deteriorates.
The reaction K is shown below. Reaction K NO ₂ ⁻ + H ₂ O → NO ₃ ⁻ + H ⁺ + 2e ⁻

Therefore, in the nitrogen treatment apparatus 1 of the present embodiment, the surface area of the cathode 6 is increased in order to delay the oxidation reaction of the nitrite ion generated at the anode 5 and accelerate the reduction reaction of the nitrate ion generated at the cathode 6. Is larger than the surface area of the anode 5.

As a result, the nitrogen compound generated at the anode 5, particularly, the oxidation reaction from nitrite nitrogen, that is, nitrite ion to nitrate nitrogen, that is, nitrate ion is reduced, and the nitric acid generated at the cathode is also reduced. It becomes possible to accelerate the reduction reaction of ions.

Furthermore, since the nitrogen treatment apparatus 1 in this embodiment is provided with the shielding member 9 located between the anode 5 and the cathode 6 so as to surround the anode 5, as described above. Thus, it becomes possible to prevent the active oxygen generated from the surface of the anode 5 from moving to the cathode 6 and inhibiting the reduction reaction at the cathode 6.

Further, since only the ions in the water to be treated permeate the shielding member 9, nitrate nitrogen, that is, nitrate ions permeate the shielding member 9, and the anode 5 to the cathode 6
It is possible to accelerate the reduction reaction of nitrate ions, since the reduction reaction can be carried out at the cathode and the reduction reaction can be performed at the cathode.

Further, since the anode 5 side has a structure that is not affected by running water, and a shielding member that allows the passage of ions is arranged, stirring of sludge with running water or stirring by the stirring bar 10 is performed by the cathode 6 When accelerating the reduction reaction of the nitrate nitrogen on the side of the anode 5, the water to be treated on the side of the anode 5 is prevented from being agitated, and the supply of dilute chlorine ions to the anode 5 by electrophoresis is promoted. Improved treatment of nitrogen compounds with acids.

Furthermore, since the shielding member 9 is formed in a cylindrical shape and opened downward as described above, NO ₃ ⁻ is positively applied to the anode 5 by completely surrounding the anode 5 with the shielding member 9. Are attracted to the cathode electrode 6
It becomes possible to prevent the efficiency of the reduction reaction of NO ₃ ⁻ from decreasing without the movement of O ₃ ⁻ . Thereby, the reduction reaction of nitrate nitrogen can be further promoted, and the treatment efficiency of the nitrogen compound can be improved.

Further, in order to accelerate the denitrification reaction to ammonia in the anode 5, halogen ions such as chlorine ions, iodine ions and bromine ions, and compounds containing these halogen ions, such as chlorine ions, are contained in the water to be treated. It is also possible to add sodium chloride or potassium chloride.

When sodium chloride is used as the additive, the removal efficiency of nitrogen compounds is remarkably improved.
The areas of the anode 5 and the cathode 6 can be the same. As a result, the structure of the nitrogen treatment apparatus that realizes the present invention can be simplified, and the apparatus can be downsized.

On the other hand, a sludge discharge port (not shown) is formed in the treatment tank 2 of the nitrogen treatment device 1 and is controlled to be openable / closable by a valve device (not shown). The sludge discharge port is connected to an inflow port of a pump 14 serving as the return means via an inflow pipe 14A, and an activated sludge treatment tank 11 is connected to an outflow port of the pump 14 via an outflow pipe 14B.
It is connected to the.

The processing operation of the water purification system 1 of the present invention having the above configuration will be described. First, activated sludge treatment tank 11
The treated water such as domestic household wastewater and factory wastewater, which has been taken into the anaerobic tank 11A, is carried into the aerobic tank 11B after a denitrification step of converting nitrate nitrogen into nitrogen gas. The water to be treated carried into the aerobic tank 11B is subjected to a nitrification step of converting ammonia nitrogen into nitrate nitrogen, a part of the water is returned to the anaerobic tank 11A, and the rest is transferred into the precipitation tank 12. To be done.

Then, in the settling tank 12, the untreated water to be treated, which does not contain sludge, is discharged to the outside as waste water. At this time, since the water to be treated has been denitrified and nitrified in the activated sludge treatment tank 11 as described above, the BOD and COD of the water to be treated are highly treated, and the wastewater should be treated in a state suitable for the environment. You can

On the other hand, the sludge settled in the settling tank 12 is carried out from the sludge discharge port into the processing tank 2 of the nitrogen processing apparatus 1 by the pump 13. Nitrate ions contained in the sludge carried into the treatment tank 2 are electrochemically treated by the anode 5 and the cathode 6 to be converted into nitrite ions, and the nitrite ions are further converted into ammonia. Further, the organic matter contained in the sludge and the cell walls of microorganisms are destroyed by ozone, active oxygen or hypochlorous acid generated from the surface of the anode 5, and are converted into a state where they are easily biodegraded. Furthermore, the ammonia in sludge is
It is converted to nitrogen gas by denitrification.

In the treatment tank 2, the sludge in which nitrate nitrogen and ammonia nitrogen are efficiently treated and the cell walls of organic substances and microorganisms which are difficult to biodegrade are decomposed is formed in the treatment tank 2. It is again carried into the activated sludge treatment tank 11 by the pump 14 via the sludge discharge port.

The sludge that has been subjected to nitrogen treatment and decomposition of microorganisms in the nitrogen treatment apparatus 1 is taken into the activated sludge treatment tank 11 again, and is again subjected to denitrification in the anaerobic tank 11A and nitrified in the aerobic tank 11B. It is processed.

At this time, since the nitrate nitrogen and the ammonia nitrogen contained in the sludge have been effectively treated in the previous stage, the sludge volume is remarkably reduced, and the biological treatment can be performed more efficiently. it can. Further, in the nitrogen treatment device 1, since the cell walls of organic substances and microorganisms have been decomposed, biological treatment can be easily performed. As a result, it is possible to further reduce the volume of sludge.

Further, the volume of sludge can be further reduced by repeating the above-mentioned steps, ie, the biological treatment in the activated sludge tank, the sedimentation in the sedimentation tank, and the electrochemical treatment by the nitrogen treatment apparatus 1. Therefore, the sludge disposal amount, which has been a problem in the past, can be reduced. Along with this, it becomes possible to reduce the running cost required for the maintenance work of sludge treatment and the related treatment.

Then, the sludge treated in the activated sludge treatment tank 11 is conveyed again into the settling tank 12 and only the solid content is precipitated. At this time, as described above, the nitrogen treatment device 1
Water produced from sludge by treatment of sludge is in a state where BOD and COD are reduced, and nitrate ions, nitrite ions, or ammonia are effectively treated, which is suitable for the environment. The drainage can be performed in the closed state. Therefore, it is possible to eliminate the inconvenience that is caused by the increase of nitrate nitrogen in the sludge, which has been a problem in the past, which causes the growth of bacteria and the generation of algae from the drainage.

Furthermore, since the sludge can be sterilized by ozone, active oxygen or hypochlorous acid in the nitrogen treatment apparatus 1, the water produced from the sludge is also sterilized and the environment is further improved. Drainage can be performed in a suitable state.

[0058]

As described in detail above, according to the water purification system of the present invention, the biological treatment / purification means for biologically treating the water to be treated and the treatment target treated by the biological treatment / purification means. Precipitating means for precipitating sludge in water, nitrogen treatment means for treating nitrogen compounds in sludge precipitated in the precipitating means by an electrochemical method, and sludge treated by this nitrogen treatment means is returned to biological treatment and purification means Since it is composed of the returning means, it becomes possible to return the sludge after the nitrogen treatment by the nitrogen treatment means and the cell walls of the microorganisms contained in the sludge, to the biological treatment and purification means. The biological treatment / purification means can easily biodegrade and reduce the amount of sludge waste. As a result, it becomes possible to reduce the cost running required for the conventional sludge treatment.

Further, the nitrogen treatment means can treat even those substances which are difficult to decompose by biological treatment and purification means such as nitrate nitrogen and ammonia nitrogen contained in sludge in the water to be treated.

According to the water purifying system of the invention of claim 2, in addition to the invention of claim 1, as the metal material constituting the cathode of the nitrogen treatment means, a group Ib group or I group of the periodic table is used.
Since a conductor containing a group Ib or a conductor coated with the same group is used, the reduction reaction of nitrate nitrogen in sludge to nitrite nitrogen and ammonia can be promoted,
It becomes possible to shorten the time required for the reduction reaction and remove low-concentration nitrogen compounds. This improves the throughput of nitrogen compounds.

According to the water purification system of the third aspect of the present invention, in addition to the first or second aspect of the present invention, copper and zinc or copper and iron or copper and nickel or copper are used as the metal material constituting the cathode. Since an alloy or a sintered body containing aluminum and aluminum is used, the reduction reaction of nitrate nitrogen in sludge to nitrite nitrogen and ammonia can be further accelerated, and the time required for the reduction reaction can be shortened. Will be able to. As a result, the nitrogen compound treatment capacity is further improved.

According to the water purification system of the invention of claim 4, in addition to the invention of claim 1, claim 2 or claim 3,
As a conductive material that constitutes the anode of the nitrogen treatment means,
Since the area of the cathode of the nitrogen treatment means is made larger than the area of the anode while using an insoluble material or carbon, the nitrogen compound generated at the anode, particularly, the oxidation reaction from nitrite nitrogen to nitrate nitrogen is reduced, Along with this, the reduction reaction of nitrate nitrogen generated at the cathode can be promoted.

According to the water purification system of the invention of claim 5, in addition to the invention of claim 1, claim 2, claim 3 or claim 4, the passage of ions is allowed and the passage of oxygen bubbles is blocked. Since the shielding member to be arranged is disposed between the cathode and the anode of the nitrogen treatment means, the denitrification reaction of the nitrogen compound is performed by the active oxygen generated on the anode side, and at the same time, only the ions pass through the shielding member, so that the nitrogen compound, especially It becomes possible to promote the reduction reaction of nitrate nitrogen.

Further, since the structure is such that the anode side is not affected by the flowing water and the shielding member which allows the passage of ions is arranged, the stirring of the sludge by the flowing water promotes the reduction reaction of the nitrate nitrogen on the cathode side. At this time, the sludge on the anode side is prevented from being agitated, and the supply of dilute chlorine ions to the anode by electrophoresis is promoted. As a result, the treatment capacity of nitrogen compounds is improved by hypochlorous acid.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a water treatment system of the present invention.

FIG. 2 is an explanatory diagram showing an outline of a nitrogen treatment device.

FIG. 3 is a structural explanatory view of an anode.

FIG. 4 is a diagram showing reduction characteristics of a cathode formed of various simple metals.

FIG. 5 is a diagram showing reduction characteristics of a cathode formed of various copper alloys.

[Explanation of symbols]

S water purification system 1 Nitrogen treatment equipment 2 processing tanks 4 Wastewater treatment room 5 anode 6 cathode 11 Activated sludge treatment tank 11A Anaerobic tank 11B aerobic tank 12 settling tank 13, 14 pump

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koizumi Friend             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F-term (reference) 4D028 AA08 BC18 BD08 BD11 BD16                 4D040 BB02 BB52                 4D059 AA03 BK21 CA28                 4D061 DA10 DB19 DC14 DC15 EA03                       EA04 EB01 EB04 EB11 EB19                       EB27 EB28 EB29 EB30 EB31                       EB33 ED13 FA15

Claims (5)

[Claims] 1. A biological treatment / purification means for biologically treating treated water, a sedimentation means for precipitating sludge in the treated water treated by the biological treatment / purification means, and an electrochemical method as described above. A water purification system comprising a nitrogen treatment means for treating nitrogen compounds of sludge precipitated in the precipitation means, and a return means for returning the sludge treated by the nitrogen treatment means to the biological treatment purification means. 2. The metal material constituting the cathode of the nitrogen treatment means is a conductor containing a group Ib group or a group IIb of the periodic table, or a conductor coated with the same group. The water purification system according to claim 1. 3. The alloy or sintered body containing copper and zinc, copper and iron, copper and nickel, or copper and aluminum, or a sintered body is used as the metal material forming the cathode. Water purification system. 4. An insoluble material or carbon is used as a conductive material forming the anode of the nitrogen treatment means, and the area of the cathode of the nitrogen treatment means is made larger than the area of the anode. Item 1,
The water purification system according to claim 2 or 3. 5. A shielding member, which allows passage of ions and blocks passage of oxygen bubbles, is arranged between the cathode and the anode of the nitrogen treatment means so that the flowing water does not affect the anode side. Claims 1, 2, characterized in that
The water purification system according to claim 3 or 4.