JP4865651B2 - Wastewater treatment method and apparatus - Google Patents

Description

  The present invention relates to a water treatment method and apparatus for generating OH radicals by electrolysis in the presence of ozone, and for decomposing and removing organic substances in waste water, particularly difficult-to-decompose organic compounds, using the OH radicals. The present invention relates to a wastewater treatment method and apparatus that can promote the decomposition of a hardly decomposable organic compound more efficiently.

Conventionally, as a method for removing organic compounds in water, a method utilizing a microbial action as typified by an activated sludge method has been used. However, in the above method, it is difficult to decompose biologically indegradable organic substances.
As a water treatment method that compensates for the above disadvantages, such as ozone alone treatment, ozone hydrogen peroxide combined treatment that generates OH radicals having stronger oxidizing power than ozone (Patent Document 1), ozone ultraviolet light combined treatment (Patent Document 2), etc. Application of chemical treatment is being studied and is being used in practice.
However, ozone alone treatment can decompose organic compounds and reduce the molecular weight, but it does not lead to mineralization and complete removal.

  In addition, in the combined treatment with ozone and hydrogen peroxide, it is necessary to continuously add hydrogen peroxide as a medicine. Furthermore, sewage effluent, manure effluent, livestock effluent, and marine food processing effluent contain a large amount of colored substances, SS components, and BOD components, and landfill leachate must contain colored substances. In addition, since smoke-washed wastewater that has been cleaned inside the chimney of a garbage incinerator has a pH that is not near neutral, these components significantly reduce the efficiency of ultraviolet irradiation and the generation of OH radicals from hydrogen peroxide. There is a problem that processing becomes difficult.

Therefore, in Patent Document 3 (Japanese Patent Application Laid-Open No. 2005-103391), a DC voltage is applied to an electrode immersed in a refractory organic compound-containing effluent to electrolyze the effluent to generate hydroxyl ions at the cathode electrode. At the same time, a method has been proposed in which ozone is supplied to the waste water, the hydroxyl ions and ozone are reacted to generate OH radicals, and the refractory organic compound is decomposed by the OH radicals. There is a method of supplying ozone by aeration.
Reference 4 reports that when electrolysis is performed in the presence of ozone, ozone is one-electron reduced at the cathode electrode to generate ozonide ions (O ₃ ⁻ ), and the generation of OH radicals is promoted. Yes.
This technology does not directly generate OH radicals by a single power source such as a high-voltage pulse power source, but applies a DC voltage with a current density controlled by a DC-stabilized power source to the waste water and electrolyzes hydroxyl ions. (OH ⁻ ) is generated, and ozone is allowed to act on the alkaline water mass region generated by the hydroxyl ions to generate OH radicals, and OH is generated via ozonide ions generated by reducing ozone with the cathode electrode. Through the process of generating radicals, the OH radicals are used to oxidatively decompose difficult-to-decompose organic compounds.

OH radicals are generated through the following reaction by ozone and hydroxyl ions.
H ₂ O → H ⁺ + OH ⁻ (electrolysis step) (1)
OH ⁻ + O ₃ → • O ₃ ⁻ + • OH (ozone contact process) (2)
OH ⁻ + O ₃ → O ₂ ⁻ + OOH (3)
・ OOH⇔H ⁺ + ・ O ₂ ⁻ (4)
O ₃ + · O ₂ ⁻ → · O ₃ ⁻ + O ₂ (5)
・ O ₃ ⁻ + H + → ・ O ₃ H (6)
・ O ₃ H → OH + O ₂ (7)

Also, adsorbed ozone on the electrode, · O ₃ in such a reaction the following (8) ^- to produce a. It was produced here · _{O 3} ^- by reaction of the above (6) to (7), to produce OH radicals.
O ₃ + e ⁻ → · O ₃ ⁻ (8)
By using the strong oxidizing power of the OH radicals generated in this way, the hardly decomposable organic compound in the waste water was decomposed and removed.

Japanese Patent Publication No. 60-006718 Japanese Patent No. 2874126 JP 2005-103391 A Water Research Vol.39, pp.4661-4672, 2005

As described in Patent Document 3 and Document 4 described above, it is an effective technique to generate OH radicals that electrolyze wastewater in the presence of ozone to decompose difficult-to-decompose organic compounds. It is difficult to generate a water mass locally because there is a drainage flow, and it has not been possible to stably maintain high treatment efficiency. Further, in such ozone electrolysis treatment, when the concentration of carbonic acid or ammonia in the waste water is high, there is a problem that this becomes an inhibitor and the reaction efficiency is lowered.
Therefore, in view of the above-mentioned problems of the prior art, an object of the present invention is to provide a wastewater treatment method and apparatus that can decompose a hardly decomposable organic compound more efficiently.

Therefore, in order to solve this problem, the present invention provides:
DC voltage is applied to the treatment area of organic compound containing wastewater with high carbonic acid concentration such as human waste or livestock manure wastewater, and OH radicals are generated in the presence of ozone, and the OH radicals cause indegradability in the wastewater. In a wastewater treatment method for decomposing and removing organic compounds,
The electrodes to which the DC voltage is applied are separated by a partition wall, separated into a cathode region and an anode region, and a drainage flow is set from the anode region to the cathode region, and ozone is contained on the cathode region side. The water is introduced or ozone is aerated in the cathode region, and air is aerated in the anode region .

Further, after the process water are respectively processed in the cathode region and the anode region is merged at the downstream side of the processing zone, and characterized in that to reversals at least a portion of the treated water flowed該合the anode region side To do.

In addition, a DC voltage is applied to an electrolytic cell into which organic compound-containing wastewater having a high carbonic acid concentration flows , such as human waste or livestock manure wastewater, and OH radicals are generated in the presence of ozone to generate OH radicals in the wastewater. In wastewater treatment equipment that decomposes and removes difficult-to-decompose organic compounds,
The inter-electrode to which a DC voltage is applied is separated by the partition wall, wherein the electrolytic cell is separated into a cathode compartment and an anode compartment, along with waste water flow is set to the cathode chamber from the anode chamber, the cathode chamber side An introduction port for introducing water containing ozone into the cathode chamber is provided , or aeration means for aeration of ozone is provided in the cathode chamber, and air aeration means is provided in the anode chamber. And

Further, the wastewater treatment apparatus that processes the waste water containing ammonia nitrogen content,
The partition is made of a combination of an anion exchange membrane and a diaphragm other than the anion exchange membrane.
Further, the diaphragm other than the anion exchange membrane is characterized by comprising a cation exchange membrane or a glass filter.

In the wastewater treatment equipment for treating wastewater containing persistent organic compounds,
An ozone-resistant cation exchange membrane is used for the partition wall, such as a fluororesin cation exchange membrane, and an electrode having a large number of small gaps such as a mesh type, punching metal, or slit type so as to sandwich the partition wall. It is installed and configured to advance the ozone electrolysis reaction while supplying ozone to the cathode chamber .

Furthermore, after respectively treated treatment water in the cathode compartment and the anode compartment was merged at the outlet side flow path of the ozone electrolytic cell, it is reversed at least part of the treated water flowed該合in the anode chamber side A return path is provided.
Furthermore, the organic compound-containing wastewater is an organic wastewater containing a lot of COD components after the SS component is removed.

  As described above, according to the present invention, the partition wall is arranged in the electrolytic cell, separated into the anode region and the cathode region, and by supplying ozone to the cathode region, the cathode region is separated from the alkaline region by electrolysis of water. Therefore, in addition to the normal generation of OH radicals by ozone / electrolysis, OH radicals are generated by the self-decomposition of ozone, and the decomposition of the hardly decomposable organic compound is promoted. At this time, the separation of the anode region and the cathode region by the partition wall makes it possible to reliably form an alkali state in the cathode region, and to stably maintain high processing efficiency.

  In addition, by separating the inside of the electrolytic cell by partition walls, it is possible to promote the generation of OH radicals and obtain high treatment efficiency, and even when the concentration of carbonic acid, which is a reaction inhibitor, is high, first the anode After removing carbonic acid by aeration under acidic conditions in the region, oxidative decomposition treatment is performed with OH radicals in the cathode region, so that high treatment efficiency can be maintained without being affected by inhibitors. Is possible.

In addition, by using a partition made of a combination of an anion exchange membrane and other membranes as a partition that separates the anode chamber and the cathode chamber, ammonia in the raw water can be removed in the anode chamber and is hardly decomposed mainly in the cathode chamber. It is possible to remove organic compounds efficiently.
Furthermore, in the present invention, a part of the treated water is branched and allowed to flow into the anode chamber, so that an acidic solution can be formed. However, since the outflow water from the other cathode chamber is alkaline, these are discharged from the electrolytic cell outlet. It becomes possible to maintain pH neutral by mixing with (3). Therefore, the pH can be adjusted without adding a pH adjuster, and the running cost can be reduced.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
1 is a schematic configuration diagram of an apparatus according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view illustrating a configuration example of an electrolytic cell according to the present embodiment, and FIG. 3 is a schematic diagram of an apparatus according to the second embodiment of the present invention. FIG. 4 is a schematic configuration diagram of an apparatus according to Example 3 of the present invention, FIG. 9 is a schematic diagram of ion migration through a bipolar membrane, and FIG. 10 is a schematic diagram of ion migration in the case of only a cation exchange membrane, FIG. 13 is a schematic configuration diagram of an apparatus according to Embodiment 4 of the present invention, and FIGS. 5 to 8 and FIGS. 11 and 12 are graphs and the like showing the results of the respective verification tests.

The present embodiment is applied to an ozone electrolysis process in which a DC voltage is applied to a treatment area of organic compound-containing wastewater (hereinafter referred to as raw water) to generate OH radicals and supply ozone to the treatment area. Is done.
In order to realize this treatment, the wastewater treatment apparatus of the present embodiment includes an anode and a cathode in an electrolytic cell, and a DC power source that applies a predetermined DC voltage between these electrodes. In the ozone electrolysis treatment using this apparatus, the anode side becomes acidic due to electrolysis of water, and the cathode side becomes alkaline due to generation of hydroxyl ions (OH ⁻ ). Furthermore, ozone is self-decomposed by allowing ozone to act on the alkaline water mass region generated by the hydroxyl ions, generating OH radicals, and oxidative decomposition treatment of the hardly decomposable organic compounds in the raw water with the OH radicals. is there.

  However, the efficiency of the anode chamber (anode region) and the cathode chamber (cathode region) described above is obtained when the inside of the electrolytic cell is formed in one region as in the conventional ozone electrolysis treatment (see JP-A-2005-103391). A good response was not available. That is, it is difficult to reliably maintain the alkaline water mass region formed in the vicinity of the cathode, and if the self-decomposition reaction of ozone does not proceed smoothly, the OH radical production reaction efficiency may decrease.

Therefore, as a characteristic configuration of the present embodiment, a partition is used in order to perform the reaction more efficiently in each region. The partition wall is installed between the anode and the cathode, and the partition wall forms an anode chamber having an anode and a cathode chamber having a cathode.
As the partition, a partition having a function as a simple diaphragm such as a glass filter, or a partition made of a combination of an anion exchange membrane and another diaphragm is used. Examples of the ion exchange membrane include a piper membrane composed of an anion exchange membrane and a cation exchange membrane, and a partition wall composed of a combination of an anion exchange membrane and a glass filter. Specific examples of the configuration of these partition walls will be described in Examples 1 to 4 below.

Furthermore, the cathode chamber is provided with an ozone supply unit for supplying ozone. The ozone supply unit may be an inlet for introducing organic waste water containing ozone into the cathode chamber, or an aeration means for aspirating ozone gas into the cathode chamber.
According to the present embodiment, the partition walls are arranged in the electrolytic cell, separated into the anode chamber and the cathode chamber, and by supplying ozone to the cathode chamber, the cathode chamber becomes an alkaline region by electrolysis of water, In addition to the normal generation of OH radicals by ozone / electrolysis, OH radicals are generated by the self-decomposition of ozone, and the decomposition of the hardly decomposable organic compound is promoted. At this time, the separation of the anode chamber and the cathode chamber by the partition wall makes it possible to reliably form an alkali state in the cathode chamber, and it is possible to stably maintain high processing efficiency.

Here, the result of having performed the test which verifies the effect by a partition is shown.
FIG. 5 is a graph (a) showing a change in _CODCr concentration when ozone electrolysis treatment is performed in the case of having a partition wall as a present example and in the case of having no partition wall as a comparative example, and a table (b) ).
As shown in the graph, Examples, COD _Cr concentration in the raw water before treatment in both comparative examples are substantially the same, the process water after the ozone electrolytic treatment, the case with the partition wall in comparison with the case without the partition wall the _{COD Cr} concentration who is low. This indicates that the decomposition efficiency of the hardly decomposable organic compound in the raw water is high. Therefore, it was proved that the hard-to-decompose organic compound can be efficiently decomposed and removed by separating the anode chamber and the cathode chamber by the partition walls as in this example.

With reference to FIG. 1, the basic configuration of the first embodiment will be described.
Example 1 is an ozone electrolysis treatment that efficiently treats a hardly decomposable organic compound, and is particularly suitable for the treatment of raw water having a high carbonic acid concentration. When the carbon dioxide concentration in the raw water is high, the presence of carbonic acid becomes carbonate ions (CO ₃ ²⁻ ) due to alkaline conditions in the vicinity of the cathode accompanying electrolysis, which acts as a strong radical scavenger and inhibits the reaction. ing. Therefore, the present embodiment proposes a configuration that can suppress the inhibition by the carbonate ions.

The wastewater treatment apparatus 1 of the present embodiment has an electrolytic cell 2 into which raw water 12 flows, and one or more electrode pairs composed of an anode 3 and a cathode 4 are disposed in the electrolytic cell 2. The anode 3 and the cathode 4 are each connected to a DC power source 5. The DC power source 5 is a device that applies a DC voltage to the electrode pair, and may include a multimeter (not shown) that monitors the voltage, current, resistance value, and the like between the electrode pair.
A partition wall 20 is provided between the anode 3 and the cathode 4 to separate these electrodes, an anode chamber 21 is formed on the anode 3 side, and a cathode chamber 22 is formed on the cathode 4 side. In the anode chamber 21 and the cathode chamber 22, a part of the raw water 12 flows. For example, a glass filter or the like is preferably used as the partition wall 20.

  The anode chamber 21 is provided with a raw water supply unit that supplies the raw water 12 and an air supply unit that supplies air 13 from the tank bottom to the raw water for aeration. The cathode chamber 22 is provided with an ozone supply unit. The ozone supply unit may be a means for supplying a gas by supplying ozone gas from the bottom, or a means for supplying water containing ozone. As an example, in the figure, the ozone supply unit includes an ozone generator 6 that generates ozone from oxygen 14 and an ozone monitor 7 that monitors the supply state of the ozone, and an appropriate amount of ozone gas 15 is stored in the tank of the cathode chamber 22. It is configured to be supplied from the bottom.

In the upper part of the electrolytic cell 2, a treated water outlet for extracting treated water from each of the anode chamber 21 and the cathode chamber 22 is provided, and the treated water outlet is connected to gas-liquid separators 8 and 11, respectively.
The gas-liquid separator 11 connected to the treated water outlet of the anode chamber 21 is a device for separating the gas 19 mainly composed of oxygen and the treated water 18. At least a part of the treated water 18 is preferably returned to the anode chamber 21 together with the raw water 12 and circulated.
The gas-liquid separator 8 connected to the treated water outlet of the cathode chamber 22 is a device that separates the gas 17 mainly composed of hydrogen and ozone from the treated water 16. On the gas 17 discharge line, a gas dryer 9 and an ozone monitor 10 for monitoring the ozone concentration in the gas are provided.

Here, an example of a specific internal structure of the electrolytic cell will be described with reference to FIG.
In the rectangular electrolytic cell 2 (see FIG. 1), the plate-like anode 3 and the cathode 4 are arranged apart from each other by a predetermined distance, and the partition wall 20 is arranged in the middle so as to isolate the anode 3 and the cathode 4 from each other. Has been. A spacer 33 is disposed between the anode 3 and the partition wall 20. The spacer 33 is provided with a diffuser 33a for supplying air in a distributed manner at a lower portion thereof, and a gasket 32 is attached to one surface thereof. Similarly, a spacer 43 is disposed between the cathode 4 and the partition wall 20, and a diffuser 43 a for supplying ozone gas in a dispersed manner is provided at the lower portion of the spacer 43, and a gasket 42 is attached to one side thereof. It has been. Further, covers 31 and 41 are provided on the anode 3 and the cathode 4, respectively.

In the wastewater treatment apparatus 1 having such a configuration, the raw water 12 supplied from the bottom of the anode chamber 21 is electrolyzed by the DC voltage applied between the anode 3 and the cathode 4 by the DC power source 5, thereby the anode The chamber 21 moves to the acidic side, and the cathode chamber 22 moves to the alkali side. The raw water 12 supplied from the bottom of the anode chamber 21 becomes carbon dioxide (CO ₂ ) in the acidic anode chamber 21, and the anode chamber 21 is aerated by the air 13 from the bottom thereof. Removed from. In the anode chamber 21, carbonate ions that are radical scavengers are removed.
The raw water 12 from which the carbonate ions have been removed permeates the partition wall 20 and flows into the cathode chamber 22. In the cathode chamber 22, dissolved ozone is present due to aeration of the ozone gas 15. Decomposition produces OH radicals. The decomposition of the hardly decomposable organic compound in the raw water 12 is promoted by the OH radical having a strong oxidizing power. In addition, there is a reaction for generating OH radicals by a normal electrolytic treatment. Moreover, since ozone itself has an oxidizing power, it is a matter of course that organic substances are decomposed by ozone.

  The treated water from which organic substances such as hardly decomposable organic substances have been decomposed and removed is discharged together with the gas from the upper part of the tank and separated into the treated water 16 and the gas 17 by the gas-liquid separator 8. It is discharged outside the process or system. On the other hand, after the gas 17 is dried by the gas dryer 9, the ozone consumption can be monitored by detecting the ozone concentration in the exhaust gas by the ozone monitor 10.

  According to this example, separation of the inside of the electrolytic cell by the partition promotes the generation of OH radicals, and it is possible to obtain high treatment efficiency, and the case where the concentration of carbonic acid that is a reaction inhibitor is high. However, since carbon dioxide is first removed by aeration in an acidic condition in the anode chamber, and oxidative decomposition treatment is performed with OH radicals in the cathode chamber, high processing efficiency without being affected by inhibitors. Can be maintained.

Here, a test was conducted to verify the effect of the first embodiment.
The apparatus used for the test is the apparatus shown in FIG. 1 and FIG. 2, a flow reactor with a distance between electrodes of 2 cm and an electrode effective area of 31 cm ² is used as the electrolytic cell, and air is aerated from the diffuser at the lower part of the anode chamber. The ozone gas was aerated from the diffuser at the bottom of the cathode chamber. The partition employed a structure in which a glass filter having a pore size of 2.7 μm was sandwiched between glass cloths. The raw water flows into the anode chamber, then passes through the partition wall and flows into the cathode chamber, and is discharged together with the gas from the upper part. Ti / Pt was used for the anode and the cathode. In each electrode chamber, it was assumed that they were completely mixed, and the effluent water after the lapse of 6 times residence time was sampled and used for analysis.

In this test, the COD _Cr (1,4dioxane) concentration change when the ozone electrolysis treatment of Example 1 is performed in two raw waters having different carbonic acid concentrations is compared. The COD _Cr concentration in the raw water is almost the same in any raw water. Further, 49.4 mM (about 50 mM) NaHCO ₃ was added to the raw water having a high carbonic acid concentration, and 24.7 mM (about 25 mM) NaHCO ₃ was added to the raw water having a low carbonic acid concentration. As other test conditions, the liquid flow rate was 10.2 ml / min, the energization amount was 0.62 A, the voltage was 15 to 16 V, the O ₃ gas flow rate was 100 ml / min, and the air aeration flow rate was 300 mL / min.

As a result, the graph and table shown in FIG. 6 were obtained. Figure 6 is a table (b) representing a numerical value and graph (a) showing the change in COD _Cr concentration in the process at the time of addition carbonate.
From the figure, it can be seen that the reduction rate of COD _Cr contained in the raw water having a low carbonic acid concentration is larger than that of the raw water having a high carbonic acid concentration, and the raw water having a low carbonic acid concentration has a higher decomposition efficiency of the hardly decomposable organic compound. That is, by forming an acidic state in the anode chamber, that is, by setting an appropriate current condition and performing air aeration, carbon dioxide that is an inhibitor of the reaction can be removed, and consequently, a hardly decomposable organic compound. It is possible to improve the decomposition efficiency.

  Moreover, the graph of the change of the carbonic acid concentration (M alkalinity-P alkalinity (mM)) in each process in FIG. 7 is shown. In this test, air aeration is performed in any raw water, and it can be seen that the carbonic acid concentration rapidly decreases in the anode chamber. Thereby, it turns out that it is possible to reduce a carbonic acid density | concentration by performing air aeration to an anode chamber in the electrolytic cell provided with the partition. Further, in the same figure, from the result of changing the amount of current, when the electrolytic current is increased, the processing speed is increased. This can be attributed to the contribution of the alkaline ozone reaction accompanying the increase in the pH of the cathode chamber, and the decarboxylation due to the decrease in pH of the anode chamber and air aeration. Therefore, in consideration of current efficiency, it is possible to appropriately eliminate the influence of carbonic acid by setting electrolysis conditions corresponding to the alkalinity of the raw water.

Further, as another embodiment (not shown) of FIG. 1, an ozone-resistant cation exchange membrane is used for the partition wall, such as a fluororesin cation exchange membrane, and a mesh type or punching is provided so as to sandwich the partition wall. An electrode having a large number of small gaps such as a metal or slit type may be provided, and the ozone electrolysis reaction may be advanced while supplying ozone to the cathode chamber. In this case, as the partition wall, a solid electrolyte having an impregnation property is preferably used. This solid electrolyte has electrical conductivity and is stable against an oxidizing agent such as ozone.
The raw water supplied from the bottom of the anode chamber is electrolyzed by a DC voltage applied between the anode and the cathode by a DC power source, and the generated hydrogen ions have a small gap in the anode, a partition wall having impregnation properties, and a small gap in the cathode. It passes through these in order and moves to the cathode chamber. Further, the ozone gas supplied to the cathode chamber becomes ozonide ions, and the ozonide ions and hydrogen ions are combined to generate OH radicals. The OH radicals having a strong oxidizing power promote the decomposition of the hardly decomposable organic compound in the raw water mainly in the cathode chamber. According to this embodiment, since the distance between the electrodes can be shortened, the power consumption for electrolysis can be reduced. In addition, ozone electrolysis can be applied smoothly to waste water that does not contain electrolyte.

With reference to FIG. 3, the basic configuration of the second embodiment will be described. Hereinafter, in the second to fourth embodiments, detailed description of the same configurations as those of the first embodiment is omitted.
The present Example 2 is an ozone electrolysis treatment that efficiently treats a hardly decomposable organic compound, and is particularly suitable for the treatment of raw water having a low carbonic acid concentration.

The wastewater treatment apparatus 1 of the second embodiment includes an electrolytic cell 2, an anode 3 and a cathode 4 that are disposed opposite to each other in the electrolytic cell, and a DC power source 5, as in the first example. A partition wall 20 is installed between the cathodes 4 to form an anode chamber 21 and a cathode chamber 22.
Furthermore, in the second embodiment, the cathode chamber 22 is provided with a raw water supply unit that supplies the raw water 12 and an ozone supply unit that supplies the ozone 16. The main flow path of the raw water 12 is supplied from the cathode chamber 22, passes through the partition wall 20, and is discharged from the anode chamber 21.

  In the wastewater treatment apparatus 1 having such a configuration, the raw water 12 supplied from the bottom of the cathode chamber 22 is electrolyzed by the DC voltage applied between the anode 3 and the cathode 4 by the DC power source 5, thereby the anode The chamber 21 moves to the acidic side, and the cathode chamber 22 moves to the alkali side. The raw water 12 supplied from the bottom of the cathode chamber 22 is separated from the partition wall after the decomposition of the hardly-decomposable organic compound in the raw water 12 is promoted by OH radicals generated by the self-decomposition of the ozone gas 15 in the alkaline cathode chamber 22. 20 passes through the anode chamber 21 and is discharged. The discharged treated water is gas separated by the gas-liquid separator 11, and then at least a part thereof is supplied into the tank together with the raw water 12 and circulated as necessary.

  According to the present embodiment, it is possible to promote the generation of OH radicals by separating the inside of the electrolytic cell by the partition walls, and to obtain high processing efficiency. Further, since the raw water is configured to flow from the cathode chamber 22 to the anode chamber 21, the processing efficiency can be improved compared to the configuration in which the raw water is flowed from the anode chamber 21 to the cathode chamber 22. This is because when the raw water 12 is first introduced into the cathode chamber 22, the alkaline ozone reaction proceeds because the cathode chamber 22 becomes a strong alkali due to electrolysis of water. However, in the case of raw water having a high carbonic acid concentration, since the carbonic acid becomes an inhibitory substance, the configuration of Example 1 in which the carbon dioxide is allowed to flow from the anode chamber 21 to the cathode chamber 22 is effective.

Here, a test was conducted to verify the effect of the second embodiment.
The apparatus used for the test is the apparatus shown in FIG. 2 and FIG. 3, a flow reactor having a distance between electrodes of 2 cm and an electrode effective area of 31 cm ² is used as the electrolytic cell, and air is aerated from the diffuser at the lower part of the anode chamber. The ozone gas was aerated from the diffuser at the bottom of the cathode chamber. The partition employed a structure in which a glass filter having a pore size of 2.7 μm was sandwiched between glass cloths. The raw water flows into the anode chamber, then passes through the partition wall and flows into the cathode chamber, and is discharged together with the gas from the upper part. Ti / Pt was used for the anode and the cathode. In each electrode chamber, it was assumed that they were completely mixed, and the effluent water after the lapse of 6 times residence time was sampled and used for analysis.

In this test, a comparative example without a partition, a comparative example in which the liquid flow shown in Example 1 was changed from the anode chamber to the cathode chamber, and a liquid flow shown in Example 2 from the anode chamber to the cathode were used. A test was conducted for the case of a room.
FIG. 8 is a graph (a) showing a change in _CODCr concentration when ozone electrolysis is performed in each example, and a table (b) showing the numerical values thereof. As test conditions, the liquid flow rate was 10.2 ml / min, the energization amount was 0.62 A, the voltage was about 10 to 12, and the O ₃ gas flow rate was 100 ml / min.

As shown in the figure, the decrease rate of _CODCr concentration was larger in Examples 1 and 2 with the partition than in the case without the partition, and the liquid flow was changed from the cathode chamber to the anode chamber. However, it is larger than that in Example 1 in which the liquid flow is changed from the anode chamber to the cathode chamber. Therefore, in the raw water having a high carbonic acid concentration, the raw water is circulated from the cathode chamber to the anode chamber.

With reference to FIG. 4, the basic configuration of the third embodiment will be described.
Example 3 is an ozone electrolysis process for efficiently treating a hardly decomposable organic compound, and is particularly suitable for the treatment of raw water having a high ammonia concentration and containing chloride ions.
The waste water treatment apparatus 1 according to the third embodiment includes an electrolytic cell 2, an anode 3 and a cathode 4 that are disposed to face each other in the electrolytic cell, and a DC power source 5, as in the first example. A partition wall 20 is installed between the cathodes 4 to form an anode chamber 21 and a cathode chamber 22. The anode chamber 21 is provided with a raw water supply unit that supplies the raw water 12, and the cathode chamber 22 is provided with an ozone supply unit that supplies ozone 16. The main flow path of the raw water 12 is supplied from the anode chamber 21, passes through the partition wall 20 ′, and is discharged from the cathode chamber 22.

  In the third embodiment, the partition wall 20 ′ is configured using a combination of an anion exchange membrane and a diaphragm other than the anion exchange membrane. Preferably, a bipolar membrane comprising an anion exchange membrane and a cation exchange membrane, or a membrane comprising a combination of an anion exchange membrane and a glass filter is used. When a bipolar membrane composed of an anion exchange membrane and a cation exchange membrane is used as the partition wall 20 ', the treatment efficiency is improved because both cations and anions in the raw water can move through the partition wall. On the other hand, when a membrane made of a combination of an anion exchange membrane and a glass filter is used as the partition wall 20 ', it is possible to maintain a processing efficiency and to make a membrane having high strength at a low cost.

In the wastewater treatment apparatus 1 having the above configuration, in the raw water 12, chlorine generated from chloride ions contained in the raw water in the anode chamber 21 reacts with ammonia, and the removal of ammonia is promoted. On the other hand, in the cathode chamber 22, the hardly decomposable organic substances are decomposed and removed by the OH radicals generated by supplying ozone.
FIG. 9 shows a schematic diagram of ion movement through the bipolar membrane. As a comparative example, FIG. 10 shows a schematic diagram of ion migration in the case of only a cation exchange membrane.
As shown in FIG. 9, ammonium ions (NH ₄ ⁺ ) in the raw water flowing into the anode chamber remain in the anode chamber without passing through the anion exchange membrane, and can be reliably removed in the anode chamber. On the other hand, as shown in FIG. 10, in the case of a cation exchange membrane alone, NH ₄ ⁺ flows into the cathode chamber and remains in the treated water.
As described above, according to the third embodiment, the partition wall 20 ′ that partitions the anode chamber 21 and the cathode chamber 22 is a partition wall made of a combination of an anion exchange membrane and other diaphragms. In addition, it is possible to efficiently remove the hardly decomposable organic compound mainly in the cathode chamber.
In addition, trihalomethane or the like produced as a by-product by the reaction between ammonia and chlorine can be decomposed in the cathode chamber at the subsequent stage.

Here, a test was conducted to verify the effect of the third embodiment.
The apparatus used for the test is the apparatus shown in FIG. 2 and FIG. 4, a flow reactor with a distance between electrodes of 2 cm and an electrode effective area of 31 cm ² is used for the electrolytic cell, and air is aerated from the diffuser at the lower part of the anode chamber. The ozone gas was aerated from the diffuser at the bottom of the cathode chamber. The raw water flows into the anode chamber, then passes through the partition wall and flows into the cathode chamber, and is discharged together with the gas from the upper part. Ti / Pt was used for the anode and the cathode. In each electrode chamber, it was assumed that they were completely mixed, and the effluent water after the lapse of 6 times residence time was sampled and used for analysis.
Moreover, as a partition, the cation exchange membrane single-piece | unit was used for the comparative example, and the bipolar membrane which consists of an anion exchange membrane and a cation exchange membrane was used for Example 3. FIG.
As other test conditions, the liquid flow rate was 2.5 ml / min, the energization amount was 0.62 A, the voltage was about 11 to 14, and the O ₃ gas flow rate was 100 ml / min.

FIG. 11 is a graph showing changes in the TN concentration in ozone electrolysis treatment. In both the comparative example and the example, the TN concentration in the raw water before treatment is almost the same, but the TN concentration in the treated water is lower when the bipolar membrane of the example is used.
The change in the COD _Cr concentration in the cathode chamber is almost the same in the reduction rate of the COD _Cr concentration in both the comparative example and the example.
From these results, it can be seen that by using the bipolar film, ammonia can be efficiently removed and the processing efficiency of the hardly decomposable organic compound similar to that of the partition wall shown in Example 1 can be obtained.

  FIG. 12 shows the TN removal rate when a partition wall made of a combination of an anion exchange membrane and a glass filter is used. As a comparative example, a case where a partition wall made of a single cation exchange membrane is used is shown. As is clear from this figure, it is clear that ammonia can be removed with high efficiency by using a partition made of a combination of an anion exchange membrane and a glass filter, whereas ammonia is hardly removed by a cation exchange membrane alone. is there.

A basic configuration of the fourth embodiment will be described with reference to FIG.
The fourth embodiment has a configuration that suppresses the increase in pH of the cathode chamber in the processing of the first to third embodiments.
The waste water treatment apparatus 1 according to the fourth embodiment includes an electrolytic cell 2, an anode 3 and a cathode 4 that are disposed to face each other in the electrolytic cell, a DC power source 5, and the anode 3. A partition wall 20 is installed between the cathodes 4 to form an anode chamber 21 and a cathode chamber 22. The anode chamber 21 is provided with a raw water supply unit that supplies the raw water 12, and the cathode chamber 22 is provided with an ozone supply unit that supplies ozone 16. The main flow path of the raw water 12 is supplied from the anode chamber 21, passes through the partition wall 21, and is discharged from the cathode chamber 22.

  As ozone electrolysis progresses, the pH of the cathode chamber increases and the alkalinity becomes stronger, and it is necessary to adjust the pH of the discharged treated water. Therefore, in Example 4, a part of the treated water is branched and allowed to flow into the anode chamber, so that a pH acidic liquid is formed. However, since the outflow water from the other cathode chamber is alkaline, these are electrolyzed. By mixing at the tank outlet, the pH can be kept neutral. Therefore, the pH can be adjusted without adding a pH adjuster, and the running cost can be reduced.

It is a schematic block diagram of the apparatus which concerns on Example 1 of this invention. It is a disassembled perspective view which shows the structural example of the electrolytic cell which concerns on a present Example. It is a schematic block diagram of the apparatus which concerns on Example 2 of this invention. It is a schematic block diagram of the apparatus which concerns on Example 3 of this invention. It is the table | surface (b) showing the graph (a) and the numerical value which compared _CODCr density | concentration change with the case without a partition, and the case with a partition. It is the table | surface (b) showing the graph (a) which compared the _CODCr density | concentration change in case a carbonic acid concentration is high, and a carbonic acid concentration is low, and the numerical value. It is a graph which shows the change of the carbonic acid concentration in ozone electrolysis processing. It is the table | surface (b) showing the graph (a) and the numerical value which compared the _ODCr density _| concentration change in the case where there is no partition, and when a liquid flow is made different with a partition. It is a schematic diagram of the ion movement through a bipolar membrane. It is a schematic diagram of the ion movement in the case of only a thione exchange membrane. It is a graph which shows the TN density | concentration change of a cation exchange membrane single-piece | unit and a bipolar membrane. It is a graph which shows the TN removal rate of a cation exchange membrane single-piece | unit and an anion exchange membrane. It is a schematic block diagram of the apparatus which concerns on Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waste water treatment apparatus 2 Electrolysis tank 3 Anode 4 Cathode 5 DC power supply 20, 21 Partition 21 Anode chamber (anode region)
22 Cathode chamber (cathode region)

Claims (8)

DC voltage is applied to the treatment area of organic compound containing wastewater with high carbonic acid concentration such as human waste or livestock manure wastewater, and OH radicals are generated in the presence of ozone, and the OH radicals cause indegradability in the wastewater. In a wastewater treatment method for decomposing and removing organic compounds,
The electrodes to which the DC voltage is applied are separated by a partition wall, separated into a cathode region and an anode region, and a drainage flow is set from the anode region to the cathode region, and ozone is contained on the cathode region side. A wastewater treatment method comprising introducing introduced water or aeration of ozone into the cathode region and aeration of air into the anode region . After respectively treated treated water are merged at the downstream side of the processing area in the cathode region and the anode region, wherein, characterized in that for the reversal of at least a portion of the treated water that flowed該合the anode region side Item 1. A wastewater treatment method according to Item 1 . A DC voltage is applied to an electrolytic cell into which organic compound-containing wastewater having a high carbonic acid concentration flows , such as human waste or livestock excreta wastewater, and OH radicals are generated in the presence of ozone to cause difficulty in the wastewater. In wastewater treatment equipment that decomposes and removes degradable organic compounds,
The inter-electrode to which a DC voltage is applied is separated by the partition wall, wherein the electrolytic cell is separated into a cathode compartment and an anode compartment, along with waste water flow is set to the cathode chamber from the anode chamber, the cathode chamber side An introduction port for introducing water containing ozone into the cathode chamber is provided , or aeration means for aeration of ozone is provided in the cathode chamber, and air aeration means is provided in the anode chamber. Wastewater treatment equipment. The waste water treatment apparatus according to claim 3 , wherein waste water containing ammonia nitrogen is treated.
The waste water treatment apparatus, wherein the partition wall comprises a combination of an anion exchange membrane and a diaphragm other than the anion exchange membrane.   The wastewater treatment apparatus according to claim 4, wherein the diaphragm other than the anion exchange membrane is composed of a cation exchange membrane or a glass filter. The wastewater treatment apparatus according to claim 3 , wherein wastewater containing a hardly decomposable organic compound is treated.
An ozone-resistant cation exchange membrane is used for the partition wall, such as a fluororesin cation exchange membrane, and an electrode having a large number of small gaps such as a mesh type, punching metal, or slit type so as to sandwich the partition wall. A wastewater treatment apparatus that is installed and configured to advance an ozone electrolysis reaction while supplying ozone to a cathode chamber. After respectively treated treatment water in the cathode compartment and the anode compartment was merged at the outlet side flow path of the ozone electrolytic cell, reversal path for reversals at least part of the treated water flowed該合in the anode chamber side the wastewater treatment device according to claim 3 Symbol mounting, characterized in that provided. The wastewater treatment apparatus according to any one of claims 3 to 7 , wherein the organic compound-containing wastewater is an organic wastewater containing a lot of COD components after the SS component is removed.

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