JP2005334822A - Apparatus and method for treating wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment apparatus capable of removing a treatment target substance contained in the wastewater efficiently and at a low cost, and a wastewater treatment method. <P>SOLUTION: First, in a concentration part 10, raw water 2 is concentrated and separated by a RO (reverse osmosis) membrane, and filtering-treated water 4a and concentrated wastewater 3 are obtained. The concentrated wastewater 3 is sent to an electrolytic treatment part 30 through a measuring part 20. Nextly, in the measuring part 20, a physicochemical amount of the concentrated wastewater 3 is measured and the measured result 5 is sent to the concentration part 10. Then, the degree of concentration in the concentration part 10 is adjusted so that the physicochemical amount of the concentrated wastewater 3 becomes constant based on the measured result 5. Next, in the electrolytic treatment part 30, the concentrated wastewater 3 is subjected to electrolytic treatment, thereby decomposing and removing the treatment target substance in the concentrated wastewater 3 to obtain electrolytically treated water 4b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wastewater treatment apparatus and a wastewater treatment method for treating wastewater by electrolysis without performing biological treatment, and particularly relates to a wastewater treatment apparatus and a wastewater treatment method using conductive diamond.

  Conventionally, methods for treating wastewater by electrolysis have been proposed (see Patent Documents 1 and 2). In the wastewater treatment method described in Patent Document 1, first, raw water is biologically treated with activated sludge or the like, and a suspension contained in the biologically treated water is subjected to a microfiltration membrane (MF membrane) or ultrafiltration. Separation is performed by a separation membrane such as a membrane (UF membrane). Next, the membrane permeate containing salt and permeabilized COD (Chemical Oxygen Demand) components that passed through the separation membrane was passed through the reverse osmosis membrane (RO membrane), and the membrane permeated through the RO membrane. Water is taken out as treated water, and concentrated wastewater that does not permeate the RO membrane and is enriched with salt and persistent COD components is electrolyzed to decompose and remove COD components and the like. This electrolysis method can also remove BOD (Biochemical Oxygen Demand) components, nitrogen, phosphorus, pigments, and the like that could not be removed by biological treatment.

  Further, in the concentrated electrolysis method described in Patent Document 2, wastewater is concentrated by electrodialysis, freeze concentration, reverse osmosis membrane method, evaporation method, etc. without performing biological treatment, and then electrolysis is performed. By doing so, the electrolysis efficiency is improved and the processing cost is reduced.

  In general, when wastewater treatment is performed by electrolysis, an electrolyte such as sodium chloride is required, and the concentration of the electrolyte in the concentrated wastewater affects the treatment capacity of the electrolysis treatment. Methods for measuring the concentration of components contained in wastewater include a method using an infrared, visible or ultraviolet absorbance meter, a method using liquid chromatography, a method using a total chlorine analyzer, etc. (Patent Literature) 3).

JP-A-7-155759 JP 2003-326263 A JP 2003-279542 A

  However, the conventional techniques described above have the following problems. That is, the wastewater treatment method described in Patent Document 1 has a problem that it cannot be applied to wastewater that cannot be biologically treated because the treatment is performed by combining the biological treatment method and the electrolysis treatment method. In addition, since the concentration electrolysis method described in Patent Document 2 does not control the concentration, the concentration of the wastewater varies, and the efficiency of the electrolysis process decreases, or the substance to be processed is discharged without being processed. There is a problem of being.

  Furthermore, as described in Patent Document 3, when measuring the concentration of components in wastewater using liquid chromatography, the measurement time is long, so the measurement results are fed back to adjust the concentration of wastewater. Is difficult. On the other hand, photoabsorbance meters and total chlorine analyzers have a short measurement time and can be used online, but there may be no correlation between the measurement results and the concentration of the substance to be treated. There is a problem that the concentration of the target substance cannot be measured.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a wastewater treatment apparatus and a wastewater treatment method capable of efficiently and inexpensively removing a target substance contained in wastewater. To do.

  A wastewater treatment apparatus according to the first invention of the present application is provided between a concentration unit for concentrating wastewater, an electrolytic treatment unit for electrolyzing the concentrated wastewater, and between the concentration unit and the electrolytic treatment unit. And a concentration unit that adjusts the concentration of the wastewater based on the measurement result of the measurement unit so that the physical chemical amount of the concentrated wastewater is constant. It is characterized by that.

  In the present invention, the wastewater is concentrated, and the physical chemical amount of the concentrated wastewater is measured. Based on the measurement result, the concentration of the electrolyte and the target substance contained in the concentrated wastewater is optimized for the electrolysis treatment. In addition, since the degree of concentration in the concentration part is adjusted, the substance to be treated can be decomposed and removed with extremely high efficiency without adding an electrolyte. Thereby, processing cost can be reduced.

  In the wastewater treatment apparatus, the measurement unit can measure at least one physical chemical amount selected from the group consisting of conductivity, ion concentration, and light reflectance. Thereby, the density | concentration of electrolyte and a process target substance can be measured easily. Moreover, a conductive diamond electrode can be provided in the electrolytic treatment section. This makes it difficult for the electrolytic product to adhere to the electrode surface, and also facilitates the removal of the attached electrolytic product, thereby reducing the maintenance cost.

  The waste water treatment method according to the second invention of the present application includes a step of concentrating waste water, a step of measuring a physical chemical amount of the concentrated waste water, and a step of electrolyzing the concentrated waste water, and the physical stoichiometry. Based on the measurement result, the concentration of the waste water is adjusted to make the physical chemical amount of the concentrated waste water to be electrolyzed constant.

  The step of measuring the physical stoichiometry measures, for example, at least one physical stoichiometry selected from the group consisting of conductivity, ion concentration and light reflectance of the concentrated waste water. Furthermore, in the electrolytic treatment section, electrolysis treatment may be performed using a conductive diamond electrode.

  According to the present invention, the wastewater is concentrated, and the physical chemical amount of the concentrated wastewater is measured. Based on the measurement result, the concentration of the electrolyte and the substance to be treated contained in the concentrated wastewater is optimal for the electrolysis treatment. Thus, since the degree of concentration in the concentration unit is adjusted, the substance to be processed can be decomposed and removed with extremely high efficiency without adding an electrolyte, and the processing cost can be reduced.

  Hereinafter, a wastewater treatment apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. First, the waste water treatment apparatus according to the first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view schematically showing a wastewater treatment apparatus of this embodiment. As shown in FIG. 1, the wastewater treatment apparatus 1 of this embodiment includes a concentration unit 10 that concentrates untreated wastewater 2 (hereinafter referred to as raw water 2), and wastewater that is concentrated in the concentration unit 10. The electrolysis water 4b is obtained by decomposing and removing the target substance contained in the concentrated waste water by electrolyzing the concentrated waste water 3 with the measuring unit 20 that measures the physical chemical amount (hereinafter referred to as the concentrated waste water 3). An electrolytic treatment unit 30 is provided.

  In the concentration unit 10 in the wastewater treatment apparatus 1, a reverse osmosis membrane (RO membrane) 12 that does not transmit ions and fine particles but transmits only water is disposed in the concentration tank 11. The concentration tank 11 is separated into an input part 11a and a storage part 11b by an RO membrane 12, and the raw water 2 is input to the input part 11a. And the raw | natural water 2 thrown into the injection | throwing-in part 11a is isolate | separated by RO membrane 12, The membrane permeated water which does not contain ion and microparticles | fine-particles is stored in the storage part 11b, and is taken out as filtering process water 4a. On the other hand, the wastewater remaining in the charging unit 11a is reduced in moisture to become concentrated wastewater 3.

  The measuring unit 20 is provided between the concentrating unit 10 and the electrolytic processing unit 30 and includes a physical stoichiometric measuring tank 21 and a physical stoichiometric measuring device 22. In the measurement unit 20, the physical stoichiometry derived from the concentration of the electrolyte in the concentrated waste water 3 stored in the physical stoichiometry tank 21 and the substance to be processed is measured by the physical stoichiometry meter 22. As the physical stoichiometry meter 22, for example, a conductivity meter, an ion detector, a light reflectance meter, and the like can be used, and these can be used in combination.

  Further, the electrolytic treatment unit 30 is provided with an electrolytic treatment tank 31 in which the concentrated waste water 3 is stored, and a pair of electrode plates 32 for electrolyzing the concentrated waste water 3. As the electrode plate 32 in the electrolytic treatment unit 30, for example, a conductive diamond electrode plate in which a conductive diamond film is formed on a base material made of molybdenum or the like can be used. In general, when the concentration of the substance to be processed increases, electrolytic products and the like adhere to the electrode surface, but substances other than diamond are essentially difficult to deposit on the diamond surface. In addition, conductive diamond is extremely excellent in mechanical durability and has a high oxidation potential. Therefore, when conductive diamond is used for the electrode plate, surface deposits can be easily removed by an electrical method such as mechanical polishing and reverse bias pulse. As a result, the maintenance cost of the treatment apparatus can be reduced as compared with a wastewater treatment apparatus using a conventional electrode.

Next, an operation of the waste water treatment apparatus 1 according to the first embodiment of the present invention, that is, a waste water treatment method using the waste water treatment apparatus 1 will be described. FIG. 2 is a block diagram showing the operation of the wastewater treatment apparatus of this embodiment. As shown in FIG. 2, first, the raw water 2 is separated and concentrated by the RO membrane 12 in the concentration unit 10. Specifically, the raw water 2 is charged into the charging part 11 a of the concentration tank 11, and a pressure equal to or higher than the osmotic pressure is applied to the raw water 2. Thereby, only the water | moisture content which does not contain ion and microparticles | fine-particles moves to the storage part 11b, and the waste_water | drain which remains in the injection | throwing-in part 11a is concentrated. In general, when a solution is separated by an RO membrane, the solution is supplied to the RO membrane surface while applying a pressure higher than the chemical potential (osmotic pressure) of the solution itself determined by the solute concentration of the solution. For example, when seawater is separated by an RO membrane, a pressure of at least about 3 × 10 ⁶ Pa or more and about 5 × 10 ⁶ Pa or more are necessary in consideration of practicality.

  Thereafter, the membrane permeated water that has permeated through the RO membrane 12 and stored in the storage portion 11b is taken out as filtered water 4a, and the concentrated wastewater 3 that does not pass through the RO membrane 12 and is stored in the input portion 11a Is sent to the electrolytic treatment unit 30. At this time, the measurement unit 20 measures the physical chemical amount derived from the concentration of the electrolyte in the concentrated waste water 3 and the substance to be treated, and sends the measurement result 5 to the concentration unit 10. Examples of the physicochemical quantity measured by the measurement unit 20 include conductivity, light reflectance, and the concentration of specific ions. The conductivity of the concentrated waste water is a parameter that is directly related to the electrolysis treatment, although it is affected by the concentration of the electrolyte added intentionally and components other than the target substance contained in the raw water. Then, by incorporating the conductivity meter into the processing device, the measurement result can be easily fed back to the concentration step.

  Further, the measurement of the light reflectance is a method suitable for the case where the substance to be treated is in the form of particles and is present in the raw water, or is colored or emits light. Since this light reflectance correlates with an essential physical quantity that is directly related to the concentration of the substance to be processed, it is suitable as a parameter for concentration control. Furthermore, as a method for detecting the concentration of specific ions, there is a method using an ion selective electrode or an ion selective device. For example, in an ion selective sensor whose surface is made of diamond, the thickness of the depletion layer on the diamond surface changes and the resistivity changes depending on the electronegativity of the ion species adsorbed on the sensing part. For this reason, when ionic species having a correlation with the concentration of the substance to be treated is known, it can be applied to various wastewaters and substances to be treated by changing the monitored potential. Note that the physical stoichiometry of the concentrated waste water 3 in the measurement unit 20 may be performed by either a batch method or a flow method.

  Then, the concentration unit 10 adjusts the concentration of the raw water 2 based on the measurement result 5 sent from the measurement unit 20. As a method for adjusting the degree of concentration in the concentration unit 10, there is a method for adjusting the pressure applied to the raw water 2. For example, the concentration rate of water is used as an index indicating the degree of concentration in the concentration unit 10, and the concentration rate of water in the default state is set to 50%. And while the signal which shows that it is an appropriate enrichment is sent from the measurement part 20, the pressure applied to the raw | natural water 2 maintains a default state, and the signal which shows that it is concentrating too much from the measurement part 20 Is sent, the pressure applied to the raw water 2 is reduced. On the other hand, when a signal indicating that the concentration is insufficient is sent from the measurement unit 20, the pressure applied to the raw water 2 is increased.

  Next, in the electrolytic treatment unit 30, the concentrated drainage 3 is electrolyzed. Specifically, first, the concentrated drainage 3 is stored in the electrolytic treatment tank 31. Next, a pair of electrode plates 32 is inserted into the stored concentrated waste water 3 to perform electrolysis, and the target substance in the concentrated waste water 3 is decomposed and removed. In that case, it is preferable to use a conductive diamond electrode plate as an electrode plate for electrolysis. The surface of the conductive diamond electrode is less likely to deposit electrolytic products than the surface of commonly used metal electrodes, and it is easier to remove the deposited electrolytic products, which can reduce maintenance costs. it can. Thereafter, the electrolytically treated water 4b that has been electrolyzed in the electrolytic treatment tank 31 is taken out to complete the treatment.

  In the wastewater treatment apparatus 1 of the present invention, the physical chemical amount in the concentrated wastewater is measured, and based on the result, the concentration of the electrolyte and the substance to be treated contained in the concentrated wastewater falls within the optimum range for the electrolysis treatment. Thus, since the degree of concentration is adjusted, the target substance can be decomposed and removed with extremely high efficiency. In addition, since the concentrated drainage water is concentrated by using an RO membrane or the like and the concentration of the electrolyte component is increased, it is not necessary to supply an electrolyte. As a result, the processing cost can be reduced as compared with the conventional waste water treatment apparatus.

  In the wastewater treatment apparatus 1 of this embodiment, the raw water is concentrated by the RO membrane 12, but the present invention is not limited to this, and a concentration method other than the reverse osmosis membrane method such as an evaporation method is used. It can also be applied.

  Further, in the wastewater treatment apparatus 1 of the present embodiment, for example, a valve is provided in a pipe between the measurement unit 20 and the electrolytic treatment unit 30, and only the concentrated wastewater whose physical chemical amount is a predetermined value or more is electrolytically treated. 30, the waste water that is less than the predetermined value in physical and chemical quantity is returned to the concentration unit 10 and is re-concentrated, so that the concentration of the electrolyte and the substance to be treated in the concentrated waste water 3 is optimal for the electrolysis treatment. It can also be adjusted to be in range.

  Furthermore, the wastewater treatment apparatus 1 of the present embodiment includes sewage separation wastewater, development waste liquid discharged from a semiconductor device manufacturing process, organic substance-containing wastewater discharged from a brewery factory, etc., phenol-containing wastewater that cannot be biologically treated, It can be applied to organic phosphorus and nitrogen-containing wastewater from laundry factories, colored wastewater from textile factories, difficult-to-separate organic matter-containing wastewater from food industry, and chlorine-containing wastewater from pulp factories. it can.

Hereinafter, the effect of the Example of this invention is demonstrated compared with the comparative example which remove | deviates from the scope of the present invention. As Example 1 of the present invention, the wastewater treatment apparatus 1 shown in FIG. 1 was used, and 40 liters of sewage separation wastewater having an NH ₄ —N concentration of 2 g / liter was treated. First, the RO membrane (NTR759, manufactured by Nitto Denko Corporation) was used in the concentration unit 10 to concentrate the sewage separation wastewater five times. At this time, the conductivity of the concentrated wastewater was measured with a conductivity meter in the measuring unit 20, and the concentration was adjusted so that the concentration of the electrolyte and the material to be treated was five times that of the raw water. Next, in the electrolytic treatment unit 30, a pair of diamond electrode plates, in which a conductive diamond film is vapor-phase synthesized on the surface of a disk-shaped molybdenum substrate having a diameter of about 50 mm, is formed in the concentrated waste water. The film-formed surfaces were arranged so as to face each other, and this pair of diamond electrode plates was subjected to electrolysis treatment using a cathode and an anode, respectively. At this time, the distance between the electrodes was maintained at 5 mm, and the amount of energization during the electrolysis treatment was adjusted to 2.0A. Further, during the electrolysis treatment, the concentrated waste water was constantly stirred and circulated between the electrodes at a water flow rate of about 0.03 liter / min. And the treated water was extract | collected at the exit of the electrolytic treatment tank 31 every hour, and the water quality was analyzed.

Further, as Comparative Example 1, sewage separation wastewater having an NH ₄ —N concentration of 2 g / liter is subjected to an electrolysis treatment in the same manner and under the same conditions as in Example 1 while keeping the raw water without concentrating. The treated water was collected at the outlet of the electrolytic treatment tank and the water quality was analyzed. Figure 3 takes the electrolysis treatment time on the horizontal axis and the vertical axis represents the NH 4 _-N concentration, a graph showing the residual NH 4 _-N concentration of the electrolysis treated effluent in Example 1 and Comparative Example 1 is there.

As shown in FIG. 3, the treated water of Example 1, which was electrolyzed after concentrating the raw water 5 times, the NH ₄ —N concentration decreased to 200 mg / liter or less after 5 hours of treatment. On the other hand, the treated water of Comparative Example 1, which was electrolyzed without concentrating the raw water, had to be treated for 4 hours in order to make the NH ₄ —N concentration 200 mg / liter or less. Comparing this result with raw water, the method of Example 1 can treat 40 L of waste water in 5 hours, whereas the method of Comparative Example 1 requires 20 hours. Therefore, in the method of Example 1, the treatment time could be shortened to about ¼ compared to the case of performing the electrolysis treatment without concentrating the raw water.

  Next, as Example 2, the wastewater treatment apparatus shown in FIG. 1 was used to treat the development waste solution containing photoresist and TMAH (Tetramethylammonium hydroxide) discharged from the semiconductor device manufacturing process. Analysis of the development waste before processing revealed that the TMAH concentration was 1.3% by mass, the reflectance of light having a wavelength of 550 nm derived from the photoresist was 70%, the Na concentration was 23 ppm, the Fe concentration was 6 ppm, and the Al concentration was 5 ppm. Met. First, while measuring the reflectance of light having a wavelength of 550 nm in the measurement unit 20, the developer waste solution in the concentration unit 10 has a reflectance of light having a wavelength of 550 nm of 81% or more by the same RO film as in Example 1. Until concentrated. Thereafter, in the electrolytic treatment unit 30, 200 liters of concentrated waste water was electrolyzed for 5 hours with an energization amount of 5A and an interelectrode potential of 30V. And when the TMAH density | concentration of collect | recovered treated water was analyzed by the ion chromatography, it was reducing below the detection limit.

  Next, as Example 3, the wastewater treatment apparatus shown in FIG. 1 was used to treat the organic matter-containing wastewater discharged from the brewery factory. The organic matter contained in the wastewater is various, but its concentration was an average of 800 mg / liter in terms of TOC (Total Organic Carbon). First, hydrochloric acid that promotes electrolysis was added to the wastewater, and then concentrated three times in the concentration unit 10 where the same RO membrane as in Example 1 was installed. At this time, a chlorine ion sensitive sensor was installed in the measurement unit 20 and the hydrochloric acid concentration in the concentrated waste water sent to the electrolytic treatment unit 30 was adjusted to 0.001 mol / liter. Thereafter, in the electrolytic treatment unit 30, electrolysis treatment was performed under the same conditions as in Example 1 described above with an average residence time of 50 minutes. As a result, the TOC equivalent concentration of the treated water at the outlet of the electrolytic treatment tank 31 was 4 mg / liter, and organic substances in the waste water were almost removed.

It is sectional drawing which shows typically the waste water treatment apparatus of the 1st Embodiment of this invention. It is a block diagram which shows operation | movement of the waste water treatment equipment of the 1st Embodiment of this invention. Take the electrolysis treatment time on the horizontal axis and the vertical axis represents the NH 4 _-N concentration is a graph showing the residual NH 4 _-N concentration of the electrolysis treated effluent in Example 1 and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,; Waste water treatment apparatus 2; Raw water 3; Concentrated waste water 4a, 4b; Treated water 5; Measurement result 10; Concentration part 11; Concentration tank 11a; Input part 11b; Storage part 12; RO membrane 20; Stoichiometric measuring tank 22; Physical stoichiometric measuring instrument 30; Electrolytic processing part 31; Electrolytic processing tank 32; Electrode plate

Claims (6)

A concentration unit for concentrating waste water, an electrolytic treatment unit for electrolyzing the concentrated waste water, and a measurement unit for measuring a physical stoichiometry of the concentrated waste water provided between the concentration unit and the electrolytic treatment unit. And the concentration unit adjusts the concentration of the wastewater based on the measurement result of the measurement unit so that the physical chemical amount of the concentrated wastewater is constant. The wastewater treatment apparatus according to claim 1, wherein the measurement unit measures at least one physical chemical amount selected from the group consisting of conductivity, ion concentration, and light reflectance. The wastewater treatment apparatus according to claim 1, wherein the electrolytic treatment part is provided with a conductive diamond electrode. A step of concentrating the wastewater, a step of measuring the physical chemical amount of the concentrated wastewater, and a step of electrolyzing the concentrated wastewater, and based on the measurement result of the physical chemical amount, the concentration of the wastewater The waste water treatment method characterized by adjusting the physical chemical amount of the concentrated waste water to be electrolyzed by adjusting the amount of water. 5. The step of measuring the physical stoichiometry measures at least one kind of physical stoichiometry selected from the group consisting of conductivity, ion concentration and light reflectance of the concentrated waste water. Wastewater treatment method. The wastewater treatment method according to claim 4 or 5, wherein the electrolysis treatment is performed using a conductive diamond electrode.

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