JP2008200654A - Wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment apparatus capable of enhancing treatment efficiency and also reducing the cost for the wastewater treatment. <P>SOLUTION: A porous material TiC/Ir obtained via a combustion/synthesis reaction is adopted as a material for electrodes 2, 3 for decomposing the wastewater 11. Because the porous material includes continuous pores which open outside at the surface, the wastewater can be supplied into an electrolysis chamber 1 through the continuous pores of one of the porous material electrodes and the decomposed wastewater 12 can be discharged outside through those of the other of the porous material electrodes. The electrodes made of the porous material can secure a large area of contact between the supplied wastewater and the electrode due to the large surface area thereof and can have the high efficiency for treating the wastewater because of the capability to adsorb and concentrate an organic chemical substance in the wastewater. Therefore, the apparatus requires neither increasing the number of the electrodes to promote the decomposition, nor adding any additives to enhance the electric conductivity of the wastewater, thus reducing the cost for the wastewater treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wastewater treatment apparatus for treating wastewater containing organic chemical substances and the like.

  Organic chemical substances contained in wastewater include dioxins, endocrine disrupting substances, and pharmaceuticals discharged from homes, etc., and conventionally, ozone has been sent to wastewater containing these to decompose it. The method of adsorbing and removing these on activated carbon has been adopted. However, since many of these organic chemicals are chemically stable and hardly decomposable, they are not sufficiently decomposed by the above-described decomposition treatment, and those having high water solubility such as pharmaceuticals are difficult to be adsorbed by activated carbon or the like. There was a problem of being. For this reason, the organic chemical substances may be discharged into rivers or the like without being sufficiently decomposed and removed.

  In order to efficiently decompose and remove such organic chemical substances, an electrolysis method having the configuration shown in FIG. 3 has been studied. In this electrolysis method, anode 2 and cathode 3 are immersed in waste water 11 containing an organic chemical substance, both electrodes of anode 2 and cathode 3 are dc-energized, and the organic chemical substance in waste water 11 is chemistryd by the energization. To be disassembled and removed.

Since the electrolysis is more likely to occur in the vicinity of both electrodes 2 and 3, it is necessary to induce the organic chemical substance as close to both electrodes 2 and 3 as possible in order to promote the decomposition.
This organic chemical is essentially uncharged itself and in most cases is electrically neutral. Therefore, this organic chemical substance is not electrically attracted to the vicinity of both electrodes 2 and 3. Therefore, as shown in FIG. 3, the electrolysis tank 1 is installed in a stirrer 13, for example, and the waste water 11 is stirred with a stirrer 14, or a large number of electrodes are arranged in the treatment tank as shown in Patent Document 1. Thus, studies have been made to increase the opportunity for undecomposed organic chemicals to approach the vicinity of the electrode.

In addition, the electrolysis tends to proceed as the current density between the electrodes 2 and 3 increases, but the waste water 11 contains almost no electrical conductor, so its electrical conductivity is low and it is difficult to increase the current density. . Therefore, as shown in Patent Document 2, studies have been made to increase the electrical conductivity of the wastewater 11 by adding an additive such as a metal salt to the wastewater 11.
JP 2006-281013 A JP 2006-289285 A

As described above, the method of stirring waste water and the method of increasing the number of electrodes are disadvantageous in terms of processing cost because it leads to an increase in the size of the device and an increase in the number of device parts.
In addition, a method of adding an additive such as a metal salt to waste water is not preferable because the additive itself may become a source of environmental pollution, and the cost of the additive leads to an increase in processing cost.

  Then, this invention makes it a subject to raise the processing efficiency, suppressing a wastewater treatment cost.

In order to solve the above problems, the present invention provides an electrode used for decomposing an organic chemical substance in wastewater by a conductive porous material obtained by subjecting two or more kinds of inorganic powders to combustion synthesis reaction. It was decided to compose.
Since the surface area of the electrode made of this porous material is overwhelmingly larger than the surface area of the non-porous material having the same outer shape, the waste water and the porous material are easily in contact with each other, and the waste water is quickly decomposed. The

  Since the porous material obtained by this combustion synthesis reaction easily adsorbs organic chemical substances, the organic chemical substances are concentrated in the pores of the porous material by this adsorption effect. By concentrating in this way, more organic chemical substances stay in the pores for a long time, so that the decomposition of the organic chemical substances is performed more efficiently.

  In this configuration, at least one of the electrodes (anode and cathode) made of a porous material is formed with connected pores opened on the surface, and the waste water is supplied to the electrolysis tank through the connected pores, or If the water is drained, the opportunity for the waste water to be supplied or drained to come into contact with the surface of the electrode increases, so that the above decomposition is performed more quickly.

  In the combustion synthesis reaction for synthesizing this porous material, the inorganic material powder as a raw material is solidified to form a molded body, and the molded body is ignited to cause a combustion reaction in a part of the molded body. As a driving force, combustion and synthesis reaction are continuously generated over the entire compact. Therefore, if it is a single inorganic powder that can generate sufficient heat of reaction and the inorganic powder can serve as a binder for bonding the powders, two or more inorganic powders can be mixed. Even if not, the inorganic powder can be used as a raw material for the combustion synthesis reaction.

  Accordingly, the present invention provides a wastewater treatment apparatus for supplying wastewater containing an organic chemical substance into an electrolysis tank and decomposing the organic chemical substance by energizing between an anode and a cathode provided in the electrolysis tank. At least one of the anode and the cathode is composed of a conductive porous material having connected pores opened on the surface, obtained by subjecting an inorganic powder to combustion synthesis reaction, and supplying the waste water to the electrolysis tank In addition, when discharging the treated water obtained by decomposing the organic chemical substance, at least one of the water supply and drainage is performed through at least one of the water supply and drainage through the connected pores of the anode and the cathode made of the porous material. can do.

Since this decomposition action is superior to an electrode that does not pass at all if waste water passes through at least one electrode, it is sufficient that the waste water passes through at least one of the anode or the cathode. It is preferable from the viewpoint of decomposition efficiency. For this reason, only one electrode can be a conductive porous material, and the other electrode can be a non-porous material through which conventional wastewater does not pass. As a means for passing the wastewater through the electrode, it is conceivable that the wastewater is flowed by a pump or the like and the electrode is interposed in the flow.
In addition, it is preferable that all of the waste water entering the electrolysis tank and the treated water coming out of the electrolysis tank pass through the electrode (porous material), but compared to the electrode of the non-porous material (electrode through which the waste water cannot pass). If the electrode passes through even a little, the decomposition action is excellent. For this reason, the amount of waste water passing through the electrode (the amount of waste water flowing) is set appropriately in consideration of the flowability, processing capacity, and the like. The flow rate is adjusted by appropriately setting the size (width) of the entrance or exit to the electrolysis tank with the electrode.
Furthermore, if the decomposition of the organic chemical substance is promptly performed, it is not necessary to add an additive to the wastewater to increase the electric conductivity.

  In addition, if a chloride salt is added to the wastewater containing the organic chemical substance, the production of free chlorine that contributes to the decomposition of the organic chemical substance is promoted, so that the decomposition of the organic chemical substance near the electrode surface is further improved. It can be done promptly.

The porous material may be a conductive material composed of at least one of intermetallic compounds, boride ceramics, nitride ceramics, carbide ceramics, and silicide ceramics.
Furthermore, if at least one kind of metal powder selected from platinum, iridium, and osmium is added to the electrode, each metal powder exerts a reaction catalytic action upon decomposition, so that an organic substance in the vicinity of the electrode surface can be obtained. Chemical substances can be decomposed more rapidly.

In the present invention, an electrode is composed of a conductive porous material obtained by a combustion synthesis reaction, and waste water containing organic matter is electrolyzed using the electrode. The obtained porous material has an action of adsorbing organic chemical substances in the wastewater and concentrating them in the pores of the porous material. Therefore, this organic chemical substance can be efficiently decomposed compared with conventional activated carbon or the like.
Further, since the surface area of the porous material used for the electrodes is very wide, the organic chemical substance can be decomposed sufficiently quickly without increasing the number of electrodes. In addition, since the efficiency of the decomposition treatment is high in the first place, it is not necessary to add an additive to the wastewater in order to increase the current density. Therefore, the cost required for the electrodes and additives can be greatly reduced.

The wastewater treatment apparatus according to the present invention supplies wastewater containing an organic chemical substance into an electrolysis tank, energizes between an anode and a cathode provided in the electrolysis tank, and decomposes the organic chemical substance by this energization. Are to be processed.
This embodiment will be described with reference to FIG. This waste water treatment apparatus is composed of an anode 2 made of a porous material produced by a combustion synthesis reaction on the waste water supply side of a cylindrical electrolysis tank 1 and a porous material also made by a combustion synthesis reaction on the discharge side. The electrolysis tank 1 is sealed with both electrodes 2 and 3 without a gap. The electrodes 2 and 3 are respectively provided with rings 4 and 4 made of platinum in which holes through which waste water flows are formed in close contact with each other, and both the rings 4 and 4 are connected to a DC power source 6 by a conducting wire 5. Yes.

The waste water supply side of the electrolysis tank 1 is connected to a waste water tank 8 by a tube 7, and the discharge side is connected to a treated water tank 10 by a tube 7 via a pump 9. When the pump 9 is operated, the waste water 11 in the waste water tank 8 is sucked (white arrow in the figure) and supplied into the electrolysis tank 1 through the anode 2. When passing through the anode 2, the organic chemical substances in the waste water 11 are decomposed.
At this time, the organic chemical substance is adsorbed and concentrated in the connected pores of the porous material. In this concentrated state, it is decomposed on the electrode surface or decomposed by free chlorine described later.
Further, when the waste water 11 flows through the cathode 3, the organic chemical substances remaining in the waste water 11 are decomposed. The treated water 12 after most of the organic chemical substance is decomposed is stored in the treated water tank 10.

  Here, the porous material used for both electrodes 2 and 3 will be described. This porous material is obtained by dispersing iridium in titanium carbide, and is produced by the following procedure.

First, titanium powder and carbon powder are mixed at a molar ratio of 1: 0.9, and iridium powder is further mixed at a ratio of about 3% by weight. The iridium powder is preferably in the range of 1 to 5% by weight. The mixed powder is filled into a mold and pressed to form a square plate-like molded body having a side of 100 mm and a thickness of 10 mm.
Next, the molded body is placed in the shape of a graphite plate, and discharge ignition is performed on one end of the molded body. By this discharge ignition, a combustion synthesis reaction of the molded body starts, and the combustion synthesis reaction propagates to the entire molded body. By the combustion synthesis reaction during the combustion, a porous body of titanium carbide (TiC / Ir) in which iridium is dispersed is obtained. In the case of a molded body of this size, the time required for the combustion synthesis reaction is about 10 seconds.

In the production of the electrode used in the above embodiment, two types of powders, titanium and carbon, were used as the main raw materials, but the characteristics of the electrode (porosity of connected pores, electrical conductivity, corrosion resistance, etc.) were desired. In order to make it a specification, a raw material other than this can be used, and the kind can also be made into three or more kinds.
Further, instead of the iridium powder, platinum or osmium powder may be used, and these may be used in appropriate mixture.
In the above-described combustion synthesis reaction, instead of the discharge ignition, an ignition method by laser irradiation or heating using a carbon heater may be employed.

  Using the wastewater treatment apparatus shown in the above embodiment, a solution (simulated wastewater 11) in which various pharmaceutical ingredients, which are a kind of the organic chemical substance, were dissolved was treated. The pharmaceutical components used here are as follows.

CA: Clofibric acid (antilipidemic drug and its metabolite)
CAM: clarithromycin (antibiotics)
IDM: Indomethacin (Indomethacin)
KEP: Ketoprofen (Ketoprofen)
DCF: Diclofenac sodium (Diclofenac Sodium: analgesic / anti-inflammatory / antipyretic)
NPX: Naproxen (Naproxen: analgesic / anti-inflammatory / antipyretic)
IPA: Isopropylantipyrine (An antipyretic analgesic)
GFZ: Gemfibrozil (An anti-inflammatory agent for antipyretic analgesia)
IBP: Ibuprofen (Ibuprofen: anti-inflammatory, analgesic, antipyretic)
CBZ: Carbamazepine (Carbamapine)

  The concentration of each dissolved drug component is 10 mg / l, which is higher than the concentration of the drug detected in the actual waste water 11. That is, if the pharmaceutical component can be decomposed by a predetermined amount or more from the high concentration simulated waste water 11 (if the concentration can be adjusted so as not to affect the environment), the decomposition processing capacity of the porous material is saturated in the actual waste water treatment. It can be avoided that the wastewater treatment is disturbed.

  In this wastewater treatment, the suction flow rate of the simulated wastewater 11 was set to 40 ml / min. In addition, 1 ml is sampled from the treated water 12 after passing through the cathode 3 every 5 to 10 minutes until 60 minutes have elapsed from the start of the treatment, and the concentration of the pharmaceutical components remaining in the treated water 12 is determined by high performance liquid chromatography. Measured with a graph mass spectrometer. The limit of quantification of this device is 1 μg / l. During this measurement, the amount of free chlorine was also measured.

FIG. 2 shows the change over time in the concentration of the residual pharmaceutical ingredient after the treatment with the wastewater treatment apparatus. From this result, it was revealed that the removal rate of any pharmaceutical ingredient increased rapidly in about 10 minutes after the start of the treatment. Further, even after 60 minutes of treatment, a removal rate of approximately 50% or more was achieved.
This removal rate can be further increased by increasing the frequency of cleaning / replacement of the porous material, or by treating the treated water 12 treated by this treatment apparatus again with a multi-stage treatment apparatus of the same type.

  In this treatment, almost no free chlorine was detected until 5 minutes after the start of treatment, but free chlorine was detected after 10 minutes when the removal rate rapidly increased. This suggests that free chlorine is involved in improving the removal rate (decomposition of organic chemicals), and a chloride salt that promotes the production of this free chlorine is added to the wastewater in advance. Thus, an improvement in the removal rate immediately after the start of processing can be expected. If sodium chloride or the like is employed as the chloride salt, there is little risk of adverse effects on the environment even if the chloride salt is discharged into a river or the like after the treatment.

Regarding the configuration of the wastewater treatment apparatus, it is not always necessary to use the anode 2 on the wastewater supply side and the cathode 3 on the discharge side, and the polarity can be reversed.
Moreover, in the said embodiment, it was set as the structure which sealed the electrolysis tank 1 with both the electrodes 2 and 3 without gap, For example, a hole is provided in a part of both electrodes 2 and 3, and waste water 11 or the treated water 12 of A part may be directly supplied to or discharged from the electrolysis tank 1 without going through the connecting pores.

  The concentration of the pharmaceutical ingredient contained in the actual wastewater is considerably lower than the concentration of the pharmaceutical ingredient contained in the simulated wastewater used in this embodiment. When treating the organic chemical substance in the diluted wastewater, if the porous material obtained by the combustion synthesis reaction is used as an electrode, the electrode adsorbs the organic chemical substance, and the adsorption causes the diluted wastewater. The decomposition is very efficient because the organic chemicals in it are concentrated.

  As a comparative example, FIG. 4 shows a result obtained by processing a part of the simulated waste water 11 in contact with the electrode by the configuration of the batch system shown in FIG. The waste liquid treatment by this batch method has a large variation in the removal rate of each pharmaceutical component, and only a low removal rate of 20% or less was obtained for several types of pharmaceutical components.

  In the above embodiment, the waste water (treated water) supplied to and discharged from the electrolysis tank 1 is forcibly distributed to the electrodes 2 and 3, but any aspect can be used as long as the waste water flows through the electrodes 2 and 3. But you can. Further, even when the electrodes 2 and 3 are simply immersed in the electrolysis tank 1 shown in FIG. 3, if the electrode made of the porous material according to this embodiment is used, the effects of the present invention are exhibited to some extent. be able to.

Device configuration diagram showing one embodiment The figure which shows the removal rate after the wastewater treatment with the same equipment System configuration diagram by batch method The figure which shows the removal rate after the wastewater treatment with the same equipment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolysis tank 2 Anode 3 Cathode 4 Ring 5 Conductor 6 DC power supply 7 Tube 8 Waste water tank 9 Pump 10 Treated water tank 11 Waste water 12 Treated water 13 Stirrer 14 Stirrer

Claims (5)

  Using a conductive porous material obtained by molding a mixed powder composed of two or more types of inorganic powders and subjecting the resulting molded body to a combustion synthesis reaction as an electrode (2, 3), including an organic chemical substance A wastewater treatment apparatus characterized by electrolyzing wastewater (11). Waste water (11) containing an organic chemical substance is supplied into the electrolysis tank (1), and the organic chemical substance is supplied by energizing between the anode (2) and the cathode (3) provided in the electrolysis tank (1). In the wastewater treatment equipment that decomposes,
At least one of the anode (2) and the cathode (3) is composed of a conductive porous material having connected pores opened on the surface, obtained by subjecting an inorganic powder to combustion synthesis reaction, and the waste water ( 11) is supplied to the electrolysis tank (1), and when the treated water (12) obtained by decomposing the organic chemical substance is discharged, at least one of the water supply and drainage, the anode (2) made of the porous material. And at least one of the water supply and drainage through the connected pores of the cathode (3).   The electrode (2, 3) made of the porous material is made of at least one of intermetallic compounds, boride ceramics, nitride ceramics, carbide ceramics and silicide ceramics. The wastewater treatment apparatus as described.   The electrode (2, 3) made of the porous material is obtained by adding at least one metal powder selected from platinum, iridium, and osmium. Wastewater treatment equipment.   The wastewater treatment apparatus according to any one of claims 1 to 4, wherein a chloride salt is added to the wastewater (11) containing the organic chemical substance.

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