JP2010069457A - Waste water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment method by which the control in the water quality of waste water after treatment is easier compared with the conventional method. <P>SOLUTION: The waste water treatment method comprises: a hypohalous acid treatment stage where hypohalous acid 2 is acted on waste water 1 so as to purify the same; an anode side treatment stage where the waste water is fed to an anode side region 4 in a diaphragm-containing electrolytic mechanism 3; and a cathode side treatment stage where the waste water is fed to a cathode side region 5, and in which at least a part passed through the cathode side region 5 is circulated through the anode side region 4. Since hypohalous acid is acted on the waste water, and the waste water is purified and is fed to the diaphragm-containing electrolytic mechanism, the waste water is roughly purified with hypohalous acid, and thereafter, the remaining stain components can be more finely treated by the diaphragm membrane-containing electrolytic mechanism. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for treating industrial water and other various waste water.

Conventionally, various proposals have been made regarding wastewater treatment technology (for example, Patent Document 1), but a certain liquid crystal manufacturing factory performs the following treatment.
That is, groundwater is sent from the local pumping station to the liquid crystal manufacturing factory as industrial water. A little less than half of this is supplied to cooling towers for air conditioning, dissipating the heat generated by the cooling water production equipment by evaporation to the atmosphere, and then filtering the activated carbon and diluting it with pure water as necessary. To be released. On the other hand, more than half of the water supplied to the factory is supplied to the industrial water treatment facility in the factory, where components such as silica, calcium, and magnesium are removed and sent to the pure water production and supply facility. Pure water is produced.
This ultrapure water is used in glass substrate cleaning, scrubber exhaust cleaning, cooling water manufacturing equipment, etc. in the liquid crystal manufacturing process. And the organic waste water which comes out after use adds sodium hypochlorite, decomposes | disassembles and purifies an oxidizable substance, and reduces COD and TOC to less than predetermined value. By the way, after the wastewater purification treatment, surplus effective chlorine remains, so it will be crushed with a reducing agent such as sodium bisulfite, but once the decomposed oxidants are restored during the reduction, COD and TOC There is a problem that it is difficult to control the final water quality with a reducing agent.
Such a problem of reducing agent treatment is not limited to wastewater from liquid crystal manufacturing factories, but is also widely observed in water quality management of swimming pools, wastewater from food processing plants, washing wastewater from contaminated soil, and various other types of water.
JP 2006-281194 A

  Accordingly, the present invention is intended to provide a wastewater treatment method in which control of the quality of wastewater after treatment is easier than before.

In order to solve the above problems, the present invention takes the following technical means.
(1) The wastewater treatment method of the present invention comprises a hypohalous acid treatment step for purifying the wastewater by applying hypohalous acid, an anode side treatment step for supplying to the anode side region of the diaphragm electrolysis mechanism, and a cathode side region And a cathode-side treatment step for supplying at least a part of the cathode-side region to the anode-side region.
Here, examples of the waste water include factory waste water, restaurant waste water, general household waste water, contaminated soil waste water, painting factory and other VOC gas substituted with water by a scrubber. All the water that needs to be done is included. Examples of the soil component in the waste water include normal organic components (acetaldehyde, etc.), persistent organic compounds such as benzene, toluene, dioxins, PCB, ammonia nitrogen and other inorganic components. Examples of the hypohalous acid include hypochlorous acid and hypobromous acid. Examples of the purification index include reduction of COD, BOD, and TOC. The electrodes of the diaphragm electrolysis mechanism can be made of platinum-plated electrodes or conductive ceramics that are difficult to elute due to the material. In addition, a titanium electrode or the like can also be used as an electrode on the cathode side. For example, a reverse osmosis membrane can be used as the diaphragm.

In this wastewater treatment method, hypohalous acid is applied to the wastewater for purification and supplied to the diaphragm electrolysis mechanism. Therefore, hypohalous acid (electrolytically generated radicals are generated to improve resolution. After the waste water is roughly purified, the remaining dirt components can be processed more finely by the diaphragm electrolysis mechanism.
Moreover, since it has an anode side treatment step for supplying to the anode side region of the diaphragm electrolysis mechanism together with the hypohalous acid treatment step, it receives anodization in the anode side region, and the remaining dirt component of the waste water, that is, in the waste water The organic components and the like can be decomposed to reduce COD and TOC, and the remaining soil components of the waste water are also decomposed by hypohalous acid generated by electrolysis on the anode side. In addition, the remaining hypohalous acid supplied from the hypohalous acid treatment process is electrolyzed in the anode side region to generate very active radical species (such as active oxygen and OH radicals). The remaining soil components in the wastewater are also decomposed in real time by the active radical species.

In addition, since there is a cathode side treatment step for supplying to the cathode side region, residual chlorine remaining in the waste water after decomposition of dirt components in the anode side treatment step is deactivated and reduced in an alkaline atmosphere. be able to. As a result, the residual chlorine concentration can be adjusted to a concentration suitable for release into sewage, rivers, etc., or can be adjusted to a concentration suitable for reuse as service water (factory water, tap water, etc.).
Here, in the cathode side region, a part of the dirt component decomposed in the anode side region may be restored (COD and TOC increase), but at least a part of the dirt side region is circulated to the anode side region. Since it did in this way, decomposition | disassembly of the restored stain | pollution | contamination component can be advanced again in an anode side area | region. That is, since the dirt component revived in the cathode side region is a part of the amount reduced in the anode side region, the dirt component is reduced as a whole as the circulation is repeated. In this way, waste water purification treatment (reduction of COD and TOC) in the anode side region and residual chlorine reduction treatment in the cathode side region can be performed simultaneously in parallel.

By adding a route for circulating the anode side region as it is, the organic components in the waste water can be decomposed more sufficiently, and hypochlorous acid can be generated and concentrated by circulation. Note that this concentrated hypochlorous acid water has an oxidizing action, and should be used as a purification process to reduce COD and TOC in various wastewater by taking it out of the circulation path, and as sterilizing water in factories and other places. You can also. On the other hand, if a path for circulating the cathode side region as it is is added, it is possible to decompose the residual chlorine that has not been previously decomposed by reducing it again.
When supplying from the cathode side region to the cathode side region, cations tend to stick to the electrode in the cathode side region, but the cation stuck to the cathode electrode by the acidic water supplied through the anode side region is The environment is easy to dissolve and leave.

The anode-side treatment step and the cathode-side treatment step can be performed by sequentially supplying drainage to the anode-side region and the cathode-side region, respectively, and by converting the polarity of the anode and the cathode every predetermined time. If it does in this way, it can melt | dissolve and wash | clean automatically by changing the polarity of the anode side with a strong tendency to adhere to a cation to the cathode side every predetermined time. Moreover, if it does in this way, even if it is a batch type process instead of a continuous type, this waste water treatment method can be applied.
If a porous material is added to the diaphragm in the anode side region to function as a structural material, the diaphragm can be prevented from being bent and deformed to the anode side due to a differential pressure. When several layers of the cathode side region and the anode side region are stacked and accumulated, a large volume of wastewater to be treated can be treated more compactly.
By the way, the activated sludge method using biological treatment generates a large amount of sludge, and this treatment requires a lot of labor and cost. However, this wastewater treatment method does not feed microorganisms with the soil components but decomposes them electrochemically. This method has the advantage that sludge is hardly generated.

(2) The cathode side region may be set to have a higher water pressure than the anode side region.
With this configuration, the cathode side region has a higher water pressure and a differential pressure than the anode side region, so residual chlorine (such as hypochlorous acid) in the anode side region enters the cathode side region through the diaphragm. It is possible to prevent the region from being contaminated. On the other hand, the chlorine ions in the cathode side region pass through the diaphragm due to the differential pressure and the electrical attraction from the anode side and are easily pushed out and reduced to the anode side region, and also migrate to the anode side region. Chlorine ions are a source for regenerating residual chlorine by electrolysis.
In addition, the cathode side electrolysis is an alkaline atmosphere, but the hydroxide ions are also subjected to stress that is pressed against the diaphragm by the differential pressure, and the interaction with the residual chlorine in the vicinity of the diaphragm is accelerated by the pressurization to inactivate the residual chlorine. Is promoted, and the ionic species after the reaction easily pass through the diaphragm and are pushed out to the anode side region to be easily removed and purified.

(3) The cathode side region and the anode side region may have a flow in opposite directions through the diaphragm.
As a mode having a flow in the opposite direction through the diaphragm, in the flow direction along the diaphragm, the opposite direction (for example, one side of the diaphragm arranged in the vertical direction flows from left to right and the other side flows from right to left. Or a crossing direction (for example, one side of the diaphragm arranged in the vertical direction flows from the lower left to the upper right, and the other side flows from the lower right to the upper left).
If comprised in this way, the relative gap | deviation speed of the flow of both area | regions will become large, and the interaction through a diaphragm will increase. In addition, due to this, regarding the transfer of ion species from the cathode side to the anode side where the water pressure is high, chlorine ions in the cathode side region are electrically attracted to the anode side region via the diaphragm and are transferred and eliminated. The tendency to be reduced will be increased. Furthermore, it can suppress that a diaphragm bends and deform | transforms in one direction (flow direction) like the case where it flows in the same direction.

(4) In the cathode side region and the anode side region, a plurality of columnar electrodes may be arranged as a cathode electrode and an anode electrode, respectively. The columnar electrodes constituting each electrode row of the anode side region and the cathode side region can be arranged so as to contact each other.
If comprised in this way, electrolysis efficiency can be increased by being able to expand a surface area three-dimensionally by the row | line | column which consists of a columnar electrode instead of a flat surface like a plate-shaped electrode.
In addition, the treated wastewater does not flow as a mere laminar flow along the electrode surface like a plate electrode, but acts as a turbulent flow around the columnar electrode array to change the flow direction in a complex manner. The mixing is promoted by the stirring action of the wastewater to be treated. In addition to this, the reduction reaction of residual chlorine can be accelerated by amplifying the turbulent flow by the differential pressure of water pressure.

In the row composed of the plurality of columnar electrodes, the anode side and the cathode side may be arranged such that the center positions of the columnar cross sections are shifted by the length of the radius distance. In this way, the pulsation of the water flow can be made difficult to occur by setting the distance between the anode side electrode row and the cathode side electrode row to a substantially constant distance. That is, when the center positions of the columnar electrodes on the anode side and the cathode side are matched, the distance between them is reduced, and the distance between them is enlarged and the portion where they do not match is enlarged, so that pulsation is likely to occur. .
Here, the columnar electrode may be formed by connecting a plurality of short electrodes in the longitudinal direction. With such a short articulated structure, the yield at the time of firing in the case of being made of ceramics is improved as compared with the long body. Examples of the shape of the columnar electrode include a columnar shape, a cylindrical shape, a polygonal cross-sectional shape with smoothed corners to prevent local discharge, an elliptical cross-sectional shape, and those in which spherical electrodes are continuously arranged in a columnar shape.

(5) Conventionally, residual chlorine was generally treated with a reducing agent such as sodium bisulfite, but it was hardly possible to control the residual chlorine concentration by controlling the amount of reducing agent. In other words, the amount of the reducing agent was excessively adjusted, and there was a tendency that the amount of the reducing agent was too much or too little to go too quickly. On the other hand, according to this wastewater treatment method, the concentration after reduction of residual chlorine can be controlled more precisely by adjusting the applied voltage, current value during electrolysis, the residence time of the wastewater to be treated in the electrolysis region, etc. For example, if the wastewater after treatment is reused without being discharged, adjust it to an appropriate residual chlorine concentration (for drinking water or sterilizing water in the factory) according to its use. Can do.

  This wastewater treatment method can be applied when chlorine disinfection is performed so that groundwater such as well water is pumped and filtered to make drinking water. That is, the chloric acid concentration can be suitably reduced and controlled. Also applied when wastewater COD and TOC are reduced by addition of oxidant or electrolysis, and the remaining hypohalous acids are reduced or removed to regenerate drinking water, sterilizing water, or industrial water. be able to. Furthermore, it can be suitably applied to residual chlorine concentration management in swimming pools, baths (baths), hot springs, and the like.

The present invention is configured as described above and has the following effects.
First, after roughly purifying the wastewater with hypohalous acid, the remaining dirt components can be processed more finely with the following diaphragm membrane electrolysis mechanism, so the water quality of the treated wastewater is easier to control than before. A wastewater treatment method can be provided.

Embodiments of the present invention will be described below.
(Embodiment 1)
As shown in FIG. 1, the wastewater treatment method of this embodiment is a hypohalous acid treatment process in which hypohalous acid 2 is applied to the wastewater 1 for purification, and subsequently supplied to the anode side region 4 of the diaphragm electrolysis mechanism 3. An anode side treatment step and a cathode side treatment step for supplying the cathode side region 5 to the anode side region 4 through the cathode side region 5 and part of the waste water treatment system. It is made to transfer to the flow path which discharges to the side.
As the waste water 1, factory waste water, restaurant waste water, general household waste water, contaminated soil waste water, paint factory and other waste water obtained by substituting VOC gas into water with a scrubber can be purified. Reduction of COD, BOD, and TOC can be selected as the purification index. As soil components in the wastewater, ordinary organic components (acetaldehyde and the like), refractory organic compounds such as benzene, toluene, dioxins and PCBs, ammonia nitrogen and other inorganic components can be decomposed.
The two treatment steps (the anode side treatment step and the cathode side treatment step) in the hypohalous acid treatment step and the diaphragm electrolysis mechanism 3 are not divided, and are performed in a continuous and integral series of flows. As a result, it is ensured that different water quality elements in the wastewater are smoothly controlled, that is, COD and TOC are reduced and residual chlorine concentration is reduced.

Specifically, in the hypohalous acid treatment step, the soil components are oxidatively decomposed and purified with hypohalous acid 2 while being sufficiently stirred in the wastewater treatment tank 6. Is supplied by a pump P from a drainage tank 7 in which is stored. The anode electrode 8 of the diaphragm electrolysis mechanism 3 is made of a conductive ceramic that is difficult to elute due to the material, and a titanium electrode is used as the cathode electrode 9. A reverse osmosis membrane is used as the diaphragm 10.
Here, hypochlorous acid (sodium hypochlorite aqueous solution) is used as the hypohalous acid 2 in this embodiment, but hypobromous acid may be used. The wastewater treatment tank 6 is supplied with a sodium hypochlorite aqueous solution electrolyzed by an electrolysis mechanism 11 in a state where very active radical species (active oxygen, OH, radicals, etc.) are generated. In this way, sodium hypochlorite aqueous solution was used as hypohalous acid 2. However, an aqueous solution in which hypochlorous acid or hypobromite was produced by electrolyzing water in the presence of sodium chloride or sodium bromide was used. You may make it exert in a hypohalous acid treatment process.

The cathode side region 5 is set to have a higher water pressure than the anode side region 4, and a porous material 12 is added to the diaphragm 10 in the anode side region 4 to function as a structural material. The diaphragm 10 is prevented from being bent and deformed by the differential pressure toward the anode side.
The cathode side region 5 and the anode side region 4 have a flow in opposite directions through the diaphragm 10. As a mode having a flow in the opposite direction through the diaphragm 10, the flow direction along the diaphragm 10 as shown in FIG. 2 is the opposite direction (for example, one side of the diaphragm 10 arranged in the vertical direction flows from left to right. , The other side flows from right to left), and as shown in FIG. 3, the crossing direction (for example, one side of the diaphragm 10 arranged in the vertical direction flows from the lower left to the upper right, and the other side from the lower right to the upper left. Flow).

Next, the use state of this waste water treatment method will be described.
In this wastewater treatment method, first, hypohalous acid 2 (hypochlorous acid) is applied to the wastewater 1 in the hypohalous acid treatment step to purify it and supply it to the diaphragm electrolysis mechanism 3. After roughly purifying the waste water 1 by 2, the remaining dirt components can be processed more finely by the diaphragm electrolysis mechanism 3, reducing COD and TOC and residual chlorine concentration in the waste water after the hypohalous acid treatment process It is easier to control different water quality factors, such as reducing the amount of water.
In addition, since the anode side treatment step for supplying to the anode side region 4 of the diaphragm electrolysis mechanism 3 is provided together with the hypohalous acid treatment step, the remaining dirt component of the waste water is subjected to anodization in the anode side region 4. That is, the organic components in the wastewater can be decomposed to reduce COD and TOC, and the remaining soil components of the wastewater are also decomposed by hypohalous acid generated by electrolysis on the anode side. .

Further, the remaining hypohalous acid supplied from the hypohalous acid treatment step is electrolyzed in the anode side region 4 to generate active radical species (active oxygen, OH radicals, etc.), and this activity The remaining soil components of the wastewater are also decomposed in real time by radical species.
In addition, since there is a cathode side treatment step for supplying to the cathode side region 5, residual chlorine remaining in the waste water after decomposition of the soil components in the anode side treatment step is deactivated and reduced in an alkaline atmosphere. It can be shown. As a result, the residual chlorine concentration can be adjusted to a concentration suitable for release into sewage, rivers, etc., or can be adjusted to a concentration suitable for reuse as service water (factory water, tap water, etc.).

Here, in the cathode side region 5, a part of the dirt component decomposed in the anode side region 4 may be restored (COD and TOC increase), but at least part of the dirt side region 5 passes through the cathode side region 5. Therefore, the decomposition of the restored dirt component can be promoted again in the anode side region 4. That is, since the dirt component revived in the cathode side region 5 is a part of the amount reduced in the anode side region 4, the dirt component is reduced as a whole as the circulation is repeated. In this way, the waste water purification process (reduction of COD and TOC) in the anode side region 4 and the residual chlorine reduction process in the waste water in the cathode side region 5 can be simultaneously performed in parallel.
When supplying from the anode side region 4 to the cathode side region 5, cations tend to adhere to the electrode in the cathode side region 5, but the acidic water supplied through the anode side region 4 causes the cathode electrode 9 to adhere to the cathode electrode 9. The fixed cation dissolves and easily leaves.

The anode-side treatment step and the cathode-side treatment step are performed by sequentially supplying drainage to the anode-side region 4 and the cathode-side region 5, respectively, and by converting the polarity of the anode and the cathode every predetermined time. be able to. If it does in this way, it can melt | dissolve and wash | clean automatically by changing the polarity of the anode side with a strong tendency to adhere to a cation to the cathode side every predetermined time. Moreover, if it does in this way, even if it is a batch type process instead of a continuous type, this waste water treatment method can be applied.
The cathode side region 5 is set to have a higher water pressure than the anode side region 4, and the cathode side region 5 has a higher water pressure and a differential pressure than the anode side region 4. Hypochlorous acid or the like) can pass through the diaphragm 10 and enter the cathode side region 5 to prevent the region from being contaminated. On the other hand, the chlorine ions in the cathode side region 5 are easily removed and reduced by passing through the diaphragm 10 and being pushed out to the anode side region 4 by the differential pressure and the electrical attraction from the anode side. The chlorine ions transferred to 4 serve as a source for regenerating residual chlorine by electrolysis.

In addition, although the cathode side electrolysis results in an alkaline atmosphere, the hydroxide ions are also subjected to stress that is pressed against the diaphragm 10 by the differential pressure, and the interaction with residual chlorine in the vicinity of the diaphragm is accelerated by pressurization, and the residual chlorine is inactivated. The reaction is facilitated, and the ionic species after the reaction pass through the diaphragm 10 and are pushed out to the anode side region 4 to be easily removed and purified.
The cathode side region 5 and the anode side region 4 have a flow in the opposite direction through the diaphragm 10, and the relative deviation speed of the flow in both regions is increased so that the interaction through the diaphragm 10 is performed. Increase. Further, due to this, regarding the transfer of ion species from the cathode side to the anode side where the water pressure is high, the chlorine ions in the cathode side region 5 are electrically attracted to the anode side region 4 through the diaphragm 10 and transferred. Therefore, the tendency to be eliminated / reduced is increased. Furthermore, it is possible to suppress the diaphragm 10 from being bent and deformed in one direction (flow direction) as in the case of flowing in the same direction.

Here, if a flow path that circulates as it is through the anode side region 4 is added, the organic components in the wastewater can be more fully decomposed, and hypochlorous acid can be generated and concentrated by circulation. Yes (not shown). Note that this concentrated hypochlorous acid water has an oxidizing action, and should be used as a purification process to reduce COD and TOC in various wastewater by taking it out of the circulation path, and as sterilizing water in factories and other places. You can also. On the other hand, if a flow path that circulates as it is on the cathode side region 5 side is added, the residual chlorine that has not been previously decomposed can be reduced again and decomposed (not shown).
By the way, the activated sludge method using biological treatment generates a large amount of sludge, and this treatment requires a lot of labor and cost. However, this wastewater treatment method does not feed microorganisms with the soil components but decomposes them electrochemically. This method has the advantage that sludge is hardly generated.

(Embodiment 2)
As shown in FIG. 4, in this embodiment, the cathode side region 5 and the anode side region 4 are arranged such that a plurality of columnar electrodes are arranged as the cathode electrode 9 and the anode electrode 8, respectively. In addition, since the surface area can be expanded three-dimensionally by a row of a plurality of columnar electrodes rather than a flat surface like a plate-like electrode, the electrolysis efficiency can be increased.
In addition, the treated wastewater does not flow as a mere laminar flow along the electrode surface like a plate electrode, but acts as a turbulent flow around the columnar electrode array to change the flow direction in a complex manner. The mixing is promoted by the stirring action of the wastewater to be treated. In addition to this, the reduction reaction of residual chlorine can be accelerated by amplifying the turbulent flow by the differential pressure of water pressure.

  Here, the columnar electrodes are formed by connecting a plurality of short electrodes in the longitudinal direction (not shown). With such a short articulated structure, the yield at the time of firing in the case of being made of ceramics is improved as compared with the long body. Examples of the shape of the columnar electrode include a columnar shape, a cylindrical shape, a polygonal cross-sectional shape with smoothed corners to prevent local discharge, an elliptical cross-sectional shape, and those in which spherical electrodes are continuously arranged in a columnar shape.

(Embodiment 3)
As shown in FIG. 5, the row of the plurality of columnar electrodes is arranged such that the center position of each columnar section is shifted by the length of the radius (r) on the anode side and the cathode side. Thus, the pulsation of the water flow can be made difficult to occur by setting the distance between the anode-side electrode row and the cathode-side electrode row to a substantially constant distance. The columnar electrodes constituting each electrode row of the anode side region 4 and the cathode side region 5 are disposed so as to contact each other.
That is, when the center positions of the columnar electrodes on the anode side and the cathode side are matched, the mutual distance is reduced at the matching position and is enlarged at the non-matching position, and pulsation is likely to occur. Although there is a tendency, in this embodiment, such pulsation hardly occurs.

  After roughly purifying the wastewater with hypohalous acid, the remaining soil components can be processed more finely with the diaphragm electrolysis mechanism, and the water quality of the treated wastewater can be controlled more easily than before. It can be applied to the use of wastewater treatment.

The flowchart explaining Embodiment 1 of the waste water treatment method of this invention. Explanatory drawing of the one aspect | mode of embodiment of the waste water treatment method of FIG. Explanatory drawing of the one aspect | mode of embodiment of the waste water treatment method of FIG. The flowchart explaining Embodiment 2 of the waste water treatment method of this invention. The flowchart explaining Embodiment 3 of the waste water treatment method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drainage 2 Hypohalous acid 3 Separation membrane electrolysis mechanism 4 Anode side area | region 5 Cathode side area | region 8 Anode electrode 9 Cathode electrode
10 Diaphragm

Claims (4)

Hypohalous acid treatment step for purifying the wastewater 1 by applying hypohalous acid 2, an anode side treatment step for supplying to the anode side region 4 of the diaphragm electrolysis mechanism 3, and a cathode side treatment for supplying to the cathode side region 5 A wastewater treatment method comprising a step of circulating at least part of the cathode side region 5 to the anode side region 4. The waste water treatment method according to claim 1, wherein the cathode side region is set to have a higher water pressure than the anode side region. The waste water treatment method according to claim 1 or 2, wherein the cathode side region (5) and the anode side region (4) have flow in opposite directions through the diaphragm (10). The waste water treatment method according to any one of claims 1 to 3, wherein the cathode side region (5) and the anode side region (4) are each provided with a plurality of columnar electrodes as cathode electrodes (9) and anode electrodes (8).