KR100754119B1 - Water Treatment Apparatus - Google Patents

Abstract

The present invention can treat the treated water containing the fluorine component to a possible state suitable for the environment, and does not affect the concentration of the treated water containing the nitrogen compound, and can treat the nitrogen compound. To provide.

Therefore, the present invention provides a fluorine powder removal device 2 for separating a removal target object from the target water in which the target object containing fluorine powder is mixed, and at least one pair of electrodes ( 29, 30), and an electrochemical treatment apparatus 3 for immersing at least a part of the treatment by an electrochemical technique, and a biological treatment apparatus 4 for biotreating the treated water treated by the electrochemical technique.

Water treatment device, electrolytic treatment, biotreatment

Description

Water Treatment Apparatus

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing of the water treatment apparatus of the Example of this invention.

2 is a schematic explanatory diagram of an electrolytic treatment apparatus and a biological treatment tank.

3 is a schematic explanatory diagram of an electrolytic treatment apparatus.

4 is a view showing the change in ORP and pH with respect to the electrolysis time.

5 is a graph showing changes in nitrogen nitrate concentration, ammonia nitrogen concentration and free chlorine concentration with respect to the electrolysis time.

6 is a flowchart showing control contents based on the change of the ORP.

<Brief description of symbols for the main parts of the drawings>

1 water treatment unit

2 fluorine removal device

3 electrolytic treatment device

4 biological processing unit

5 reservoir

6 electrolyzer

7 Pretreatment Tank

8 thermostat

9 biological treatment tank

10 discharge tank

11 storage tank

12 Chinese tank

17 neutralizer addition device

18 nitrate sensor

20 calcium chloride addition unit

22 Nitrogen Gas Supply Path

29, 30 electrodes

34 pH sensor

35 ORP sensor

36 pH adjuster

37, 38 reducing agent addition device

41 diffuser

42 Nitrogen Gas Supply Path

43 circulation piping

45 organics feeder

46 Diluent Feeder

53 Denitrification Reaction Chamber

54 Granule Sludge

56 filtration membrane

61 outlet piping

[Patent Document 1] Japanese Patent Application Laid-Open No. 54-16844

[Patent Document 2] Japanese Patent Application Laid-Open No. 2004-330182

[Patent Document 3] Japanese Unexamined Patent Publication No. 2004-122032

TECHNICAL FIELD This invention relates to the processing apparatus of the to-be-processed water containing the fluorine powder discharged | emitted from a semiconductor factory, etc., or a nitrogen compound, etc., for example.

Background Art It has already been known that nitrogen compounds exist as one of the causes of eutrophication of rivers and lakes. Moreover, although many of these nitrogen compounds exist in wastewater, such as the domestic wastewater of a general household or wastewater of a factory, it is difficult to carry out a purification process and the effective measures are not obtained.

In general, aerobic anaerobic and biological treatments are carried out for the treatment of nitrogen compounds, but the nitriding step of converting ammonia nitrogen to nitrous nitrite and converting nitrous nitrogen to nitrate nitrogen again and nitrogen nitrate to nitrogen It is performed by two processes of the denitrification process converting into gas. For this reason, not only two reaction tanks are required, but also the processing time becomes slow, and there existed a problem of processing efficiency becoming low. In particular, since the reaction efficiency of the nitriding process of oxidizing ammonia to nitrogen nitrate is poor, a large reaction tank is required.

Therefore, in the treatment of the nitrogen compound, a noble metal material such as platinum, iridium, palladium, etc. is used for the anode, and ammonia nitrogen, nitrite, nitrite and nitrogen nitrate in the waste water are supplied with an electric current to the waste water to be treated. The electrolytic treatment which processes even gas is performed (for example, refer patent document 1).

However, when treating the water to be treated containing a high concentration of nitrogen compounds, there is a problem that the power cost is enormous. For this reason, reducing the treated water containing the nitrogen compound of high concentration to nitrogen gas only by electrolytic treatment has a problem that it costs remarkably.

Therefore, as an apparatus which treats the to-be-processed water containing the conventional nitrogen compound, there exists a water treatment apparatus as shown by patent document 2 and patent document 3, for example. These water treatment apparatuses are each equipped with an electrolytic treatment means and a biological treatment means, and by treating the treated water after the treatment with the electrolytic treatment means again by the biological treatment means, the nitrogen compound remaining in the water to be treated effectively To deal with. Thereby, not only the increase of the cost which arises by processing only by electrolytic treatment can be suppressed, but the fall of the processing efficiency which arises by processing only with biological processing means was able to be improved.

On the other hand, as the to-be-processed water containing a nitrogen compound as mentioned above, hydrofluoric acid wastewater discharged from a semiconductor manufacturing plant etc. are mentioned, for example. The hydrofluoric acid drainage is a wastewater containing hydrofluoric acid used in an etching process of a semiconductor manufacturing process, and the hydrofluoric acid is called a buffered hydrofluoric acid, and in addition to hydrofluoric acid, ammonium fluoride, nitric acid, or hydrogen peroxide water may be used at a predetermined concentration. Prepared high concentration hydrofluoric acid solution is used.

For this reason, the hydrofluoric acid solution containing such a high concentration of nitrogen compounds cannot be treated with hydrofluoric acid-containing wastewater only by a water treatment apparatus that combines the electrolytic treatment or biological treatment for treating the nitrogen compounds as described above. There is. Therefore, since the wastewater containing hydrofluoric acid cannot be discharged to the environment as it is, it has to be treated as industrial waste, which is an important problem in terms of environmental suitability and processing cost.

Further, in each of the above water treatment apparatuses, biological treatment is performed after the electrolytic treatment, and the biological treatment has dependent bacteria which reduce nitrogen nitrate or nitrite nitrogen to nitrogen gas in a large single tank. By supplying the water to be treated after the electrolytic treatment into the tank, reduction treatment of the nitrogen nitrate or the nitrogen nitrite remaining in the water to be treated is performed. In this case, even in the water to be treated after the electrolytic treatment, the concentration of the nitrogen compound in the water to be treated varies greatly depending on the concentration of raw water, that is, the nitrogen compound in the waste water. For this reason, the fluctuation | variation of the load with respect to the bacterium in a tank used for biological treatment increases with the density | concentration of to-be-processed water. In particular, with respect to the nitrogen compound concentration of the water to be treated at the end of the previous treatment, when the concentration of the nitrogen compound in the subsequent treatment is significantly high, the state of the load on the bacterium greatly changes, and this causes the bacteria to become overloaded so that the treatment This leads to a decrease in efficiency.

Therefore, this invention is made | formed in order to solve the conventional technical subject, and can process the to-be-processed water containing a fluorine component to the state suitable for an environment, and affects the density | concentration or quantity of the to-be-processed water containing a nitrogen compound. Provided is a water treatment apparatus capable of treating a nitrogen compound without impairment.

The water treatment apparatus of claim 1 further comprises: a fluorine powder removal device for separating a substance to be removed from the target water into which the target object containing the fluorine powder is mixed; And an electrochemical treatment apparatus for treating by an electrochemical method, and a biological treatment apparatus for biotreating the water to be treated.

The water treatment apparatus of claim 2 has an electrochemical treatment apparatus for at least partially immersing at least a pair of electrodes in the water to be treated and treated by an electrochemical technique, and a plurality of biological treatment tanks. And a biological treatment apparatus for biotreating the treated water, wherein the number of the biological treatment tanks is changed based on the concentration of nitric acid and / or the amount of the water to be treated.

In each of the above inventions, in the water treatment apparatus of claim 3, the electrochemical treatment apparatus detects the pH of the water to be treated during the treatment by the electrochemical method, and the pH of the water to be treated. pH detection means, ORP detection means for detecting the redox potential of the water to be treated, termination determination means for determining the end of the treatment by the electrochemical method, and control means for controlling the energization to the electrode. During the treatment by the electrochemical method, the pH of the water to be treated is adjusted within the predetermined range by the pH adjusting means, and the termination determining means ends based on the detection output of the pH detecting means and / or the detection output of the ORP detecting means. The control means terminates the energization to the electrode by this determination output.

In the water treatment apparatus of claim 4, in the above invention, the electrochemical treatment apparatus includes: hypohalogenic acid reduction treatment means for reducing hypohalogenic acid in the water to be treated and reduction for terminating the reduction treatment of hypohalogenic acid; After the completion of the energization to the electrode by the control means, the hypohalogenic acid reduction treatment means performs the reduction treatment of the hypohalogenic acid, and the reduction treatment end determination means has an ORP detection means output of a predetermined value or less. When it is determined, the end of the reduction treatment is determined, and the operation of the hypohalogenous acid reduction treatment means is completed.

In the water treatment apparatus of claim 5, in the invention of claim 3, the pH adjusting means adjusts the pH of the water to be treated to 5 to 8.

The water treatment apparatus of the sixth invention is characterized in that in each of the above inventions, means is provided for removing oxygen in the water to be treated in the previous step of the biological treatment.

In the water treatment apparatus of the seventh aspect of the present invention, the biological treatment apparatus treats the water to be treated by using granule sludge.

The water treatment apparatus of claim 8 is to biotreat the water to be treated, and has a biotreatment tank for storing granule sludge, and supplies the treated water from the biotreatment tank to be biotreated. And installing a filtration membrane in the biological treatment tank, and allowing the water to be treated in the biological treatment tank to flow out of the biological treatment tank through the filtration membrane.

Best Mode for Carrying Out the Invention

Next, embodiment of this invention is described in detail based on drawing. FIG. 1: is explanatory drawing which shows the outline | summary of the water treatment apparatus 1 which processes the to-be-processed water containing the fluorine component and nitrogen compound of this invention. The water treatment apparatus 1 in the present embodiment treats wastewater containing fluorine components used in an etching process in a semiconductor factory, for example, as water to be treated. More specifically, a large amount of wastewater containing fluorine is discharged in the step of etching semiconductors, glass, metals and the like. In these etching processes, hydrofluoric acid is used in order to improve the corrosion property at the time of etching. Here, hydrofluoric acid is a so-called buffered hydrofluoric acid, for example, rich hydrofluoric acid containing about 49% of hydrogen fluoride (HF), or containing a fluorine component as ammonium fluoride (NH ₄ HF ₂ , NH ₄ F). Hydrofluoric acid and concentrated hydrofluoric acid containing a predetermined ratio of hydrofluoric acid and nitric acid (HNO ₃ ). These include nitrogen compounds such as ammonia and nitric acid in high concentrations in addition to hydrofluoric acid having a high risk, and since the wastewater discharged from the plant contains high concentrations of fluorine and nitrogen compounds, Processing must be done.

The water treatment apparatus 1 in the embodiment is characterized by electrochemically treating the fluorine powder removal device 2 which performs the removal process of the to-be-removed substance containing the fluorine component in to-be-processed water, and the to-be-processed water after a fluorine powder removal process is performed. And an electrolytic treatment apparatus 3 for treating with water and a biological treatment apparatus 4 for biologically treating the water to be treated after the electrochemical treatment is performed.

The fluorine powder removal device 2 includes a storage tank 11, a neutralization tank 12, a reaction tank 13, a membrane separation device 14, and a pressure filter 15. The storage tank 11 is a tank for storing the wastewater containing the fluorine component or the nitrogen compound discharged from a factory or the like, i.e., the water to be treated once, by a pipe 16 in which a pump (not shown) is opened for the subsequent step. It is connected to the neutralization tank 12. Moreover, since the to-be-processed water conveyed from the storage tank 11 to the neutralization tank 12 turns into strong acid whose pH is about 2 by hydrofluoric acid, mixed acid, etc., the neutralization tank 12 is made of glass, etc. which was excellent in acid resistance. It is supposed to be formed of a material.

The neutralization tank 12 is equipped with the neutralizer addition apparatus 17 as a means which manufactures pH. In this embodiment, since the pH of the to-be-processed water returned from the storage tank 11 is about 2, the neutralizing agent added to the neutralizing agent addition apparatus 17 uses the aqueous solution containing 25 weight% of sodium hydroxide (NaOH). . Moreover, in this neutralization tank 12, the nitric acid sensor 18 for detecting nitric acid concentration in to-be-processed water is provided, and the said nitric acid sensor 18 is connected to the control apparatus which is not shown in figure.

And the neutralization tank 12 is connected to the reaction tank 13 of a subsequent step by the piping 19 by which the pump which is not shown in figure was opened. The reactor 13 is equipped with the calcium chloride addition apparatus 20 as a means of adding calcium powder. Calcium chloride addition device 20, for example, a device for the addition of calcium chloride (CaCl _2), aqueous solution of about 30% by weight of the water to be treated in the reaction tank (13).

And the reaction tank 13 is connected to the membrane separation apparatus 14 in order to carry out membrane separation process of the to-be-processed water in the said reaction tank 13 by piping 21. The membrane separation device 14 is a device in which the filtration membrane 14A is immersed in a storage tank for storing the water to be treated. The filtration membrane 14A is immersed in the water to be stored stored in the storage tank and has a function of filtration of the water to be treated. As the filtration membrane 14A, a filtration mechanism capable of exerting a filtration effect in a fluid can be generally employed.

In addition, the membrane separation device 14 includes an air diffuser 14B that supplies bubbles to the filtration membrane 14A under the reservoir in which the water to be treated is stored. Although the acidifier may be air, in the present embodiment, the nitrogen gas supply path 22 connected to the nitrogen supply means is connected to the acidizer device 14B, whereby the filtration membrane 14A of the membrane separation device 14 is connected. The bubble of nitrogen gas is supplied to it. For this reason, by using an inert gas such as nitrogen, anaerobic biotreatment in a later step can be performed more efficiently.

The membrane separation device 14 is connected by a pipe 23 to the pressure filter 15 in a subsequent step of processing the separated solids and solidified substances to be removed. The pressure filter 15 is a device for lowering the moisture content of the substance to be removed. In this embodiment, the pressure filter 15 is provided with a water supply path 24, for example, to supply water to the pressure filter 15, and to be contained in the substance to be contained in the pressure filter 15, for example, Neutral salts such as sodium chloride are washed and removed.

In addition, the membrane separation device 14 is provided with a pipe (not shown) for conveying the water to be treated filtered by the filtration membrane 14A to a storage tank 5 constituted separately from the fluorine powder removal device 2. (25) is connected.

And the storage tank 5 is connected to the electrolytic cell 6 which comprises the electrolytic treatment apparatus 3 by the piping 27 in which the pump 26 as a conveyance means was opened. Here, the electrolytic treatment apparatus 3 includes at least a part of an electrolytic cell 6 constituting an electrolytic chamber 28 in an interior having an inlet and an outlet of untreated water, which is not shown in the figure, and the treated water in the electrolytic chamber 28. A pair of electrodes 29 and 30 disposed to be immersed so as to be immersed, the power supply 31 for energizing the electrodes 29 and 30, the control device for controlling the power supply 31, and the like. . Moreover, the electrolytic cell 6 can also be provided with stirring means for stirring the inside.

The electrodes 29 and 30 are made of, for example, a precious metal electrode such as platinum (Pt) or a mixture of platinum and iridium (Ir), or an insoluble conductor covering them. In this embodiment, a platinum electrode is used. In addition, in this embodiment, although each electrode 29 and 30 is comprised by the precious metal or the conductor which coat | covered these precious metals, respectively, when the polarity switching of the electrodes 29 and 30 is not performed, at least an anode is carried out. It is assumed that only the electrode 29 constituting the electrode is made of a noble metal or a conductor coated with the noble metal, and the electrode 30 constituting the cathode may be made of another conductor.

In addition, the above-described conductor coated with a noble metal or a noble metal may be plated with a noble metal on the conductor or sintered.

In this embodiment, a circulation pipe 33 communicating with the electrolytic chamber 28 and circulated by the pump 32 is provided, and the circulation pipe 33 is provided in the electrolytic chamber 28. A pH sensor 34 for detecting the pH of the water to be introduced from the water and an ORP sensor 35 for detecting the redox potential (ORP) are provided. The pH sensor 34 and the ORP sensor 35 are end determination means for determining the end of the treatment by an electrochemical method and / or end of the reduction treatment for determining the end of the reduction treatment of the hypohalogenic acid in the water to be treated. It is connected to the control apparatus which comprises a determination means. In addition, the electrolytic cell 6 is equipped with a pH adjusting device 36 as a pH adjusting means. As the regulator to be charged in the pH adjusting device 36 in this embodiment, an aqueous solution containing sodium hydroxide (NaOH) is used.

In the present embodiment, the electrolytic cell 6 is provided with reducing agent addition devices 37 and 38 as a means for reducing the hypohalogenic acid such as hypochlorous acid generated in the water to be treated. In the present embodiment, sodium nitrite solution is used as the reducing agent of hypochlorous acid in the reducing agent adding device 37. In addition, oxalic acid is used for the reducing agent addition apparatus 38 as a reducing agent of hypochlorite dissipation, or as a function of pH adjustment of the to-be-processed water. In addition to addition of a reducing agent, hypohalogenic acid can also be reduced by exposure to a catalyst or air.

And the electrolytic cell 6 is connected to the pretreatment tank 7 via the piping 40. The pretreatment tank 7 adjusts the water to be treated after being electrochemically treated in the electrolytic cell 6 in order to efficiently carry out the treatment in the bioprocessing apparatus 4 that performs the biological treatment in the subsequent steps. to be. In the pretreatment tank 7, an diffuser device 41 is provided, and a nitrogen gas supply path 42 connected to the nitrogen supply means is connected to the diffuser device 41 similarly to the diffuser device 14B. .

In addition, the pretreatment tank 7 is connected with a circulation pipe 43 connected to the constant temperature tank 8. This thermostat 8 is heated so that the temperature of the to-be-processed water in the thermostat 8 does not become +15 degrees C or less, for example. In addition, waste heat may be used for heating the thermostat 8, such as performing heat exchange with another apparatus that generates heat in the apparatus 1, for example, an electrolytic bath 6.

The pretreatment tank 7 is also connected with an organic matter supply device 45 for supplying organic matter necessary for the activity of living organisms in biological treatment. Methanol is used for the organic material in this embodiment, for example, but besides this, for example, alcohols containing any one or plural kinds of ethanol, propanol, isopropyl alcohol, etc. may be used.

In addition, the pretreatment tank 7 is connected with a diluent supply device 46 for diluting the water to be treated at a predetermined nitric acid concentration or less. In this embodiment, the nitric acid concentration of the to-be-processed water is controlled using what was previously detected by the nitric acid sensor 18 in the neutralization tank 12 in the fluorine powder removal apparatus 2. In FIG. In addition, the dilution water supply device 46 pretreats not only tap water, such as city water, but also water to be treated after being treated by the water treatment device 1 according to the present embodiment by the circulation pipe 47. It may be replaced by supplying to tank (7) and reusing it.

And this pretreatment apparatus 7 is connected by the piping 48 to the biological processing apparatus 4 of a later step. The biological treatment apparatus 4 of the present embodiment includes a plurality of biological treatment tanks 9. In the embodiment shown in FIG. 1, three biological treatment units 51 equipped with two biological treatment tanks 9 and a pump 50 as one conveying means with respect to two are treated by branch piping 52. A total of six biological treatment tanks 9 are connected in parallel.

In each of the biological treatment tanks 9, a denitrification reaction chamber 53 having an inlet for the water to be treated is formed in the lower part or the bottom, respectively, and the denitrification reaction chamber 53 has an anaerobic state in which dissolved oxygen does not exist. It is. In addition, dissolved oxygen is replaced with nitrogen gas in the pretreatment apparatus 7 in the to-be-processed water supplied to the biological treatment tank 9. In addition, the denitrification reaction chamber 53 is filled with granule sludge 54 at the bottom and gas solid-liquid separation means 55 at the top.

Granule sludge 54 is a dependent bacterium (microorganism) that reduces nitrogen nitrate or nitrite nitrogen in treated water to nitrogen gas under at least anaerobic conditions, such as Micrococcus denitrificans or Pseudomonas denitrificans or Pseudomonas aerufinosa and the like are self-assembled in the form of particles of about 0.5 to 2 mm.

In addition, although the granule sludge 54 is filled in the denitration reaction chamber 53 in this Example, the denitrification process can also be performed by filling the denitration reaction chamber 53 with the microorganism supported by the support | carrier. In this case, the concentration of microorganisms in the denitrification reaction chamber 53 can be increased, and the water to be treated can be treated more effectively.

In the denitrification reaction chamber 53, the filtration membrane 56 is provided in a state where at least a part of the denitrification reaction chamber 53 is in contact with the layer made of granule sludge, and a part is embedded. The filtration membrane 56 in this embodiment is constituted by a so-called flat membrane. The flat membrane is provided with filters on the front and rear surfaces of the spherical frame, and is configured to discharge the filtered liquid from the filter to the outside from an upper outlet formed in communication with a space formed between these filters. In this embodiment, the outlet of the filtration membrane 56 is connected to a pipe 58 in which a pump 57 is formed. And all the piping 58 connected to each biological treatment tank 9 is connected to the discharge tank 10 of a subsequent step.

The discharge tank 10 is a tank for storing the water to be treated once processed in the biological treatment device 4 of the previous step, and the discharge tank 10 is used for decomposing and treating the organic matter contained in the water to be treated. An air diffuser 59 is provided. An air supply path 62 is connected to the diffuser 59. Moreover, not only the discharge pipe 61 in which the pump 60 was opened is connected to the discharge tank 10, but the circulation pipe 61 is connected to the discharge pipe 61 on the downstream side of the pump 60. The pipe 47 is connected. Thereby, the to-be-processed water after the said process can be supplied to the pretreatment tank 7 as a diluent.

With the above configuration, the processing operation by the water treatment apparatus 1 in the present embodiment will be described. In addition, as mentioned above, the to-be-processed water shall be wastewater in the semiconductor factory containing a high concentration of a fluorine component and a nitrogen compound.

(1) Fluorine removal treatment

First, to-be-processed water is removed by the fluorine powder removal apparatus 2 by the removal process of the to-be-removed material containing a fluorine component. The to-be-treated water whose pH is about 2 by hydrofluoric acid, mixed acid, etc. is stored in the storage tank 11 once, and is conveyed suitably to the neutralization tank 12 of a subsequent step through the piping 16 by a pump. do.

And in the neutralization tank 12, pH adjustment of the to-be-processed water is performed by the neutralizer addition apparatus 17. As shown in FIG. In this case, the pH of the water to be supplied to the neutralization tank 12 is about 2, and the water to be treated is, for example, pH 7 to 25% by weight of a sodium hydroxide (NaOH) aqueous solution used as a neutralizing agent. Is adjusted between 8. Further, in the vicinity of neutral, 99.9% or more of hydrogen fluoride in the water to be treated dissociates into hydrogen ions and fluoride ions.

And the to-be-processed water adjusted to pH in the neutralization tank 12 is conveyed to the reaction tank 13 of a subsequent step suitably by the pump not shown through the piping 19. FIG. In the reactor 13, calcium powder, i.e., about 30% by weight aqueous calcium chloride (CaCl ₂ ) solution is added to the fluorine powder contained in the water to be treated after pH adjustment by the calcium chloride adding device 20. In the treated water, calcium fluoride (CaF) is produced. Thus, the fluorine component in the water to be treated is fixed as calcium fluoride. Moreover, the to-be-processed water containing this calcium fluoride turns into a slurry-like cloudy liquid.

And the white to-be-processed water in the reaction tank 13 is conveyed to the membrane separation apparatus 14 of a later step via the piping 21. FIG. In this membrane separation device 14, the filtration treatment of the water to be treated is performed by the filtration membrane 14A immersed in the reservoir. In this embodiment, the solid-liquid separation between calcium fluoride and the water to be treated is performed by filtration using a self-forming film formed on the surface of the filtration membrane 14A. As a result, the slurry-like turbid water to be treated containing calcium fluoride is subjected to solid-liquid separation between calcium fluoride and the water to be treated by the filtration action of the filter membrane 14A.

In addition, the above-mentioned self-forming film may be a self-forming film containing a substance to be removed containing calcium fluoride generated in the water to be treated. That is, the to-be-processed water is filtered by the to-be-adsorbed substance adsorbed by the filtration surface of 14 A of filtration membranes. In addition, when recovering calcium fluoride, this self-forming film is also removed from the filtration film 14A and recovered.

In addition, the calcium fluoride separated by the membrane separation device 14 is aged by the treated water for a predetermined time after the reaction in the reaction vessel 13 to improve the filtration efficiency, so that the particles of calcium fluoride are, for example, 0.25 μm or more. It is effective to grow. In this case, the membrane separation of calcium fluoride becomes easy.

In addition, the membrane separation device 14 according to the present embodiment is provided with an air diffuser device 14B for supplying air bubbles to the filtration membrane 14A below the reservoir in which the water to be treated is stored, thereby filtration membrane 14A. Is supplied with bubbles of nitrogen gas.

Thus, bubbles generated in the diffuser 14B move upward along the filtration surface of the filtration membrane 14A. Thus, by generating air bubbles in the diffuser 14B, the thickness of the self-forming film formed on the surface of the filtration membrane 14A can be made constant. Thereby, it becomes possible to hold | maintain the filtration efficiency of the to-be-processed water, suppressing the blockage of the self-forming film | membrane and ensuring a certain flux.

In addition, in this embodiment, nitrogen gas which is an inert gas is employ | adopted as the gas generate | occur | produced in the diffuser 14B. When air is supplied to the to-be-processed water by the acidic apparatus 14B, there exists a possibility that the carbon dioxide gas contained in air and the calcium content contained in the to-be-processed water may react and the density | concentration of calcium fluoride may fall. However, since the gas supplied from the diffuser device 14B is nitrogen gas which is an inert gas, the above hazard can be avoided.

The solid content separated by the membrane separation device 14, that is, the solidified substance to be removed is conveyed to the pressure filter 15 through the pipe 23. Since the water filter passage 24 for washing | cleaning is connected to this pressure filter 15 as mentioned above, neutralizing salts, such as sodium chloride, contained in the to-be-removed object accommodated in the pressure filter 15, It is washed and removed.

Accordingly, most of the neutralized salt is released to the outside from the pressure filter 15, and calcium fluoride having a lower solubility than that of the neutralized salt remains in the pressure filter 15, and dehydrated in the pressure filter 15, thereby providing high purity calcium fluoride. As a result, the fluorine component can be recovered from the water to be treated. Specifically, after dewatering the object to be removed by the pressure filter 15, the object to be removed in the semi-solidified state is taken out. In this state, the water content of the substance to be removed is about 50% by weight. Subsequently, by drying the object to be removed, a block of the object to be solidified is formed. In this Example, the to-be-removed substance containing 85 weight% of calcium fluoride is obtained.

In the present embodiment, since solid-liquid separation treatment is performed without using a flocculant such as a polymer flocculant, it is possible to obtain a fixed calcium fluoride (generally fluorite) from treated water containing fluorine. It becomes possible. The obtained calcium fluoride can be reused in a semiconductor manufacturing process or the like as hydrofluoric acid by reacting with a strong acid (for example sulfuric acid). Moreover, it is also possible to use the high purity calcium fluoride obtained by this Example as a flux mixed with steel. Calcium chloride can also be obtained by adding hydrochloric acid to the obtained calcium fluoride. In addition, since sulfuric acid, hydrochloric acid, etc. which are added in order to recycle | reuse calcium fluoride are chemicals which are prepared in a semiconductor factory, calcium fluoride can be reused without adding a new facility in a factory.

On the other hand, the liquid fraction separated by the membrane separation device 14, that is, the water to be treated after the calcium fluoride is removed is returned to the storage tank 5 through the pipe 25 by a pump. Since the fluorine content is removed, the to-be-processed water stored in this storage tank 5 contains nitrogen compounds, such as nitric acid and ammonia, and chlorine, sodium, and calcium. The to-be-processed water conveyed to the storage tank 5 is conveyed to the electrolytic cell 6 via the piping 27 by the pump 26 suitably.

(2) electrochemical treatment

In the state where the water to be treated is stored in the electrolytic cell 6, the power supply 31 is turned on by the control device, and a positive potential is applied to the electrode 29 and a negative potential is applied to the electrode 30. As a result, the electrode 29 becomes an anode, and the electrode 30 becomes a cathode.

By applying such a potential, each of the electrodes 29, 30 is composed of hypohalogenic acid or an insoluble conductor capable of generating ozone or active oxygen. Therefore, on the electrode 29 side of the anode, Chloride ions (halide ions) contained in the treated water release electrons to generate chlorine (halogen) (Scheme 1). This chlorine (halogen) is dissolved in water to produce hypochlorous acid (hypohalogenic acid) (Scheme 2). At this time, ozone or active oxygen is also generated. Hereinafter, reaction scheme 1 and scheme 2 are shown.

2Cl ^- → C1 ₂ + 2e ^-

Cl ₂ + H ₂ O → HClO + HCl

In addition, since each of the electrodes 29 and 30 is an insoluble conductor, it is possible to avoid the problem that the electrodes 29 and 30 are eluted in the water to be treated by electrolysis, so that maintenance such as replacement of the electrodes 29 and 30 can be avoided. This will simplify your work. In addition, since the noble metal electrode or the electrode is coated with the noble metal electrode as in the present embodiment, it is possible to more effectively produce hypohalogen acid and the like in the water to be treated. In addition, since electrolytic solution containing calcium is produced, scale adhesion such as calcium hydroxide occurs on the cathode side. To prevent this, change the polarity.

The produced hypochlorous acid (hypohalogenic acid) is reacted with ammonia or ammonium ions (ammonia nitrogen) contained in the water to be treated, and after being subjected to a plurality of chemical changes, is converted into nitrogen gas (Scheme 3). Hereinafter, Scheme 3 is shown.

NH ₃ + HClO → NH ₂ Cl + H ₂ O

NH ₂ Cl + HClO → NHCl ₂ + H ₂ O

NH ₂ Cl + NHCl ₂ → N ₂ ↑ + 3HCl

In addition, ammonia or ammonium ions (ammonia nitrogen) in the water to be treated react with ozone or active oxygen generated at the electrode 29 side constituting the anode as shown in Scheme 4, thereby denitrifying with nitrogen gas. do. Hereinafter, reaction scheme 4 is shown.

2NH ₃ (aq) +3 (O) → N ₂ ↑ + 3H ₂ O

Accordingly, ammonia nitrogen of ammonia or ammonium ions in the water to be treated is subjected to electrolytic treatment of the water to be denitrated with nitrogen gas.

As described above, in this electrolytic treatment, as shown in Scheme 3 above, ammonia reacts with hypochlorous acid, whereby intermediate products such as monochloroamine and dichloroamine are formed, and nitrogen is reacted by the reaction of these intermediate products. The denitrification treatment in which gas is generated is performed. Here, intermediate products such as monochloroamine and dichloroamine have high pH dependence, trichloroamine is present when the pH is higher than 4.4, dichloroamine is present when the pH is 4.4 to 5, and pH is higher than 8. In the lower case monochloroamine is present. For this reason, in order for both monochloroamine and dichloroamine to exist in to-be-processed water, pH needs to be 5-8.

On the other hand, as shown in Scheme 3, as the denitrification of ammonia nitrogen is carried out, hydrochloric acid is generated in the water to be treated. For this reason, pH of the to-be-processed water becomes near acidic in proportion to the throughput of the ammonia nitrogen in the to-be-processed water. However, as described above, when the pH is lowered to a predetermined value or less, generation of intermediate products such as monochloroamine and dichloroamine produced by the reaction of ammonia nitrogen and hypochlorous acid is inhibited, and finally, ammonia It becomes difficult to perform denitrification with nitrogen gas.

In addition, when the pH of the water to be treated is acidic at 4 or less, the hypochlorous acid in the water to be treated slowly exhibits a form as chlorine gas, and chlorine gas diffuses into the gas, which is not preferable for treatment.

For this reason, in the present Example, the sodium hydroxide aqueous solution is added as a regulator by the pH adjusting device 36 based on the output of the pH sensor 34 during the said electrolytic treatment. Thereby, pH of the to-be-processed water is adjusted and generation | occurrence | production of chlorine gas is suppressed. In addition, in the present embodiment, in order to promote the production of intermediate products such as monochloroamine and dichloroamine, which are generated during the denitrification treatment of ammonia, the control device is based on the output of the pH sensor 34 to control the water to be treated. Is adjusted to a range of 5-8.

The control device then determines the end point of the electrolytic treatment based on the output of the ORP sensor 35 and ends the electrolytic treatment.

Here, with reference to FIGS. 3 to 5, the determination of the end of treatment of ammonia in the water to be treated will be described. FIG. 3 is a schematic explanatory diagram of the electrolytic treatment apparatus 3, and FIGS. 4 and 5 show experimental results. In the electrolytic cell 6, ammonia in the water to be treated is reduced with nitrogen gas in accordance with the chemical reactions of the reaction schemes 1 to 3. In this case, when the treatment of ammonia in the water to be treated proceeds, the redox potential (ORP) due to the amount of hypochlorous acid accumulated in the water to be treated changes. Further, as described above, the pH is changed by the reduction of the amount of ammonia in the water to be treated and by sodium hydroxide as the adjusting agent added by the pH adjusting device 36. Accordingly, in this embodiment, the degree of progress of the ammonia removal reaction is estimated based on the ORP and pH of the water to be treated in the electrolytic cell 6, and the power supply to the electrodes 29 and 30 is controlled based on the estimation. do.

4 shows an example of the relationship between the electrolysis time in the electrolytic cell 6 and the ORP and pH of the water to be treated when the ammonia nitrogen is removed by the electrolytic reaction of the electrolytic treatment device 3. FIG. 5 shows the relationship between the nitrogen nitrate concentration, the ammonia nitrogen concentration and the free chlorine concentration when the ammonia nitrogen is removed by the electrolytic reaction of the electrolytic treatment apparatus 3 corresponding to FIG. 4. In the experiments in Figs. 4 and 5, 1,000 mL of simulated treated water having a chloride ion concentration of 10,000 mg / L, a nitrogen nitrate concentration of 2,000 mg / L, and an ammonia nitrogen concentration of 1,000 mg / L was used. At the value 3A, the electrolytic treatment was performed while adjusting the pH to 8 by using a pH adjuster composed of sodium hydroxide.

In FIG. 5, ammonia nitrogen is reduced slowly, and removal of ammonia nitrogen is complete | finished in the part whose electrolysis time is about 120 minutes. As the removal of the ammonia nitrogen is completed, free chlorine, that is, hypochlorous acid, in the water to be treated is rapidly increasing. On the other hand, in FIG. 4, ORP of the to-be-processed water of the electrolytic cell 6 decreases finely up and down with processing time, and shows a rapid rise in the part whose electrolysis time is about 120 minutes. It is thought that this ORP of the water to be treated is changed by the influence of hypochlorous acid (hypohalogenic acid), monochloroamine or dichloroamine contained in the water to be treated in the electrolytic cell 6.

In other words, when ammonia is sufficiently present in the water to be treated, the monochloroamine and dichloro are removed by proceeding with the ammonia removal process while the balance between the production and consumption of monochloroamine and dichloroamine as intermediate products is almost constant. As the balance between the production and consumption of amines is disrupted, and monochloroamine and dichloroamine decrease, the ORP of the water to be treated gradually decreases. From the point where ammonia (ammonia nitrogen) in the water to be treated is removed, hypochlorous acid (hypohalogenic acid) produced by electrolysis is not consumed and remains in the water to be treated. ORP value of treated water rises rapidly.

In this embodiment, the progress of the removal reaction of ammonia nitrogen is estimated on the basis of the degree of change of ORP of the water to be treated in the electrolytic cell 6 and the value of pH, and based on the progress of the electrode 29, While controlling the current value flowing between 30), the change in the ORP change of the water to be treated in the electrolytic cell 6, or the pH of the water to be treated in the electrolytic cell 6 becomes a predetermined value, or both. It is assumed that the removal of the ammonia nitrogen is completed at the above, and the electric power supplied to the electrodes 29 and 30 is controlled.

The control contents based on the change in the ORP according to the present embodiment will be described below with reference to the flowchart of FIG. 6. First, the controller starts the electrolytic treatment while controlling the pH to a predetermined pH 8 in S1, and then, in S2, the ORP of the water to be treated in the electrolytic cell 6 is measured by the ORP sensor 35, and the measured ORP The value is stored as ORPmax. Next, ORP is measured in S3, and the measured ORP value is stored as ORPa.

Then, at S4, the controller calculates the difference between ORPmax and ORPa. If ORPmax is smaller than ORPa, the control apparatus substitutes and stores ORPa at ORPmax at S5, and then returns to S3. On the other hand, if ORPmax is greater than ORPa, the process proceeds to S6. If ORPmax minus ORPa is 100 mV or less, the process returns to S3, and if greater than 100 mV, the process proceeds to S7.

Next, ORP is measured in S7, and the measured ORP value is stored as ORPb. At S8, the controller calculates the difference between ORPmax and ORPb, returns to S7 if the value obtained by subtracting ORPb from ORPmax is 10 mV or more, and proceeds to S9 if it is smaller than 10 mV, and the electrodes 29, 30 ) Is terminated, and then the process is terminated. As a result, it is possible to determine the change in the ORP at the end of the treatment treatment, and that the treatment reaction of the treatment water in the electrolytic cell 6 is finished.

Therefore, by judging the progress of the electrolytic reaction of the ammonia nitrogen in the water to be treated in the electrolytic cell 6 by the change in ORP, not only can the ammonia nitrogen in the water to be treated correctly, but also more than necessary. The problem of consuming power can be avoided.

On the other hand, as described above, the pH of the water to be treated changes in pH due to the reduction of the amount of ammonia in the water to be treated and sodium hydroxide as a regulator added by the pH adjusting device 36. When the reaction between ammonia and hypochlorous acid in the water to be treated is finished, hydrochloric acid is not generated in the water to be treated, so that the pH of the water to be treated does not become acidic. For this reason, the control apparatus periodically adds sodium hydroxide as a pH adjuster to the water to be treated quantitatively at regular intervals, and the pH of the water to be treated does not become close to acid with respect to the added amount, that is, shifted toward alkaline with respect to the pH adjustment degree. At this point in time, the progress of the ammonia removal reaction is estimated, and the power supply to the electrodes 29 and 30 is controlled based on the estimation.

As a result, the energization of the treated water detected by the ORP sensor 35 to the electrodes 29 and 30 is controlled based on the degree of change of the ORP, so that a liquid solution such as an ammonia nitrogen concentration meter is not used. Instead, it is possible to accurately determine the end time of the treatment of ammonia nitrogen in accordance with the concentration of ammonia nitrogen in the water to be treated.

As a result, the treatment of ammonia nitrogen in the water to be treated is terminated in the middle, thereby avoiding the problem of remaining ammonia nitrogen in the treated water after the treatment and the problem of waste of power by performing electrolysis more than necessary. . For this reason, a running cost can be reduced. In particular, since electrolysis is not performed more than necessary, it becomes possible to suppress the problem of excessive generation of hypohalogenous acid in the water to be treated.

In particular, in this embodiment, since the end time of ammonia nitrogen treatment is judged based on the change in ORP and pH of the water to be treated, electrolytic control can be performed more precisely, and power saving can be performed accurately. do.

In addition, since the pH of the to-be-processed water in the electrolytic cell 6 is adjusted to the range of 5-8 by the pH adjuster 36 as mentioned above, the hypohalogen produced | generated in to-be-processed water by an electrochemical method is mentioned. In the denitrification reaction of acid and ammonia, the production of intermediate products such as monochloroamine and dichloroamine is not greatly influenced. For this reason, the fluctuation of pH of the to-be-processed water does not have a big influence on the fluctuation of ORP, and it becomes possible to judge the completion | finish timing of ammonia nitrogen nitrogen more accurately.

In addition, since the pH of the water to be treated does not become 4 or less, it becomes possible to suppress the problem that hypohalogen acids such as hypochlorous acid generated in the water to be treated are released into the gas as halogen gas such as chlorine gas.

After the completion of the electrolytic treatment, the control device adds a sodium nitrite solution and oxalic acid as reducing agents of hypochlorous acid (hypohalogenic acid) to the water to be treated by the reducing agent addition devices 37 and 38 provided in the electrolytic cell 6.

Here, the control apparatus determines the end time of reduction of hypochlorous acid (hypohalogenic acid) based on the detection of the ORP sensor 35 and the pH sensor 34. That is, the control device adjusts the pH of the water to be treated in a predetermined range, for example, in the range of 5 to 8 by the pH adjusting device 36, based on the detection of the pH sensor 34, and performs electrolytic treatment. After that, the ORP of the water to be treated is continuously detected.

Since ORP fluctuates based on the amount of hypochlorous acid (hypohalogenic acid) in the water to be treated, ORP is detected at a time when the water to be treated has reached a predetermined range of pH so that the ORP becomes less than or equal to a predetermined value. It can be judged that the reduction process of hypochlorous acid (hypohalogenic acid) is complete | finished.

In particular, in the present embodiment, when judging the end of reduction of hypochlorous acid (hypohalogenic acid) based on ORP, by adjusting the pH of the water to be treated to a certain range, the influence of ORP depending on pH can be reduced, It is possible to more accurately determine the end time of the reduction treatment of hypochlorous acid (hypohalogenic acid).

As a result, it is possible to reduce the treatment of hypochlorous acid (hypohalogenic acid) in the water to be treated without excessive deficiency. It is not only possible to avoid this adverse effect such as generation, but also eliminate the problem that the running cost skyrockets because the reducing agent of hypochlorous acid (hypohalogenic acid) is not used in vain.

In particular, in the present embodiment, since the oxidizing agent is continuously reduced in the electrolytic cell 6 after the end of the electrolytic treatment, an expensive treatment such as an ORP sensor 35 or the like is not provided only for the reduction treatment. It becomes possible to use the ORP sensor 36 used in. As a result, the device can be simplified, and the number of parts can be reduced.

Thus, hypochlorous acid (hypohalogenic acid) generated in the water to be treated is returned to the biological treatment apparatus 4 in a subsequent step in a reduced treatment state. For this reason, it is possible to avoid the problem that an oxidizing agent such as hypochlorous acid generated in the water to be treated in the electrochemical treatment adversely affects the denitrifying bacteria, in this embodiment, granule sludge 54, which generates a denitrification reaction used in a later step. have. For this reason, it becomes possible to suppress the problem that the processing efficiency in the biological treatment in a later step is degraded by the oxidant produced by electrolysis.

In addition, in this embodiment, since oxalic acid is used as the reducing agent, the pH of the water to be treated can be maintained at about 5 to 6 even with the oxalic acid. Thereby, it becomes possible to adjust the to-be-processed water to the pH suitable for biological treatment in a later step, and can improve the treatment efficiency of a nitrogen compound.

In addition, although sodium nitrite and oxalic acid are used as a reducing agent in a present Example, it is not limited to this combination, A thiosulfate, or a combination thereof, or any one of these may be used. However, in the case of thiosulfate, it is preferable to use the said sulfate trace in the range which does not affect the biological process of a next step. This is because the thiosulfate is advantageous in terms of cost.

In addition, although the reducing agent is used as a means for reducing hypochlorous acid (hypohalogenic acid) in the present Example, it is not limited to this, It is not limited to this, Even if it exposes to the catalyst comprised of metal peroxide, etc., or air, It is assumed that halogen acid can also be reduced. Also in this case, as in the case of using a reducing agent, it is possible to easily reduce the hypohalogen acid in the water to be treated, and to easily improve the treatment efficiency in each biological treatment tank 9. In this case, the end timing of the reduction treatment of hypochlorous acid (hypohalogenic acid) is determined based on the ORP detected by the ORP sensor 35 as in the case described above.

Thereafter, in the electrolytic cell 6, after the reduction treatment of the oxidizing agent such as hypohalogenous acid in the water to be treated is completed, the control apparatus passes the treated water in the electrolytic cell 6 through the pipe 40 in a subsequent pretreatment tank. It returns to (7).

(3) pretreatment of biological treatment

Nitrogen gas is supplied to the to-be-processed water conveyed to the pre-treatment tank 7 by the acidic device 41, and dissolved oxygen in a to-be-processed water is replaced by nitrogen gas. Accordingly, the water to be treated is anaerobic suitable for treatment by the granule sludge 54 used for biological treatment. In addition, the to-be-processed water in the pretreatment tank 7 is connected to the thermostat tank 8 through the circulation pipe 43. For this reason, when the temperature of the to-be-processed water is lower than +15 degreeC, for example, it heats by the said thermostat 8 so that the temperature of the to-be-processed water may be +15 degreeC or more, for example. Accordingly, the water to be treated in the pretreatment tank 7 is adjusted to a temperature of + 15 ° C. or more suitable for the subsequent biological treatment. As described above, the heating in the thermostatic chamber 8 may use waste heat, such as heat exchange with another apparatus that generates heat in the apparatus 1, for example, the electrolytic cell 6. As a result, the temperature of the water to be treated can be increased without installing a heat generator.

In addition, the organic matter supply apparatus 45 supplies the to-be-processed water in this pretreatment tank 7 with the organic substance required for the biological activity of the biological process in a later step. In addition, in the present embodiment, since alcohols containing methanol and isopropyl alcohol are used as organic substances, it is possible to supply organic substances necessary for biological treatment without adversely affecting biological treatment. The treatment efficiency of the treatment can be improved, and the environmental suitability of the water to be treated after treatment can be improved.

In addition, the control device is based on the detection of the nitric acid sensor 18 provided in the neutralization tank 12 of the fluorine powder removing device 2, when the nitric acid concentration of the water to be treated is higher than a predetermined concentration, the pretreatment tank In (7), it is assumed that the diluent is supplied by the diluent supply device 46, and the nitric acid concentration of the water to be treated is adjusted to a predetermined concentration or less. As the diluent, not only tap water, such as water, but also water to be treated after being treated in the water treatment apparatus 1 according to the present embodiment is supplied to the pretreatment tank 7 by the circulation pipe 47, and reused. It may be possible.

Thus, after adjusting the to-be-processed water after electrolytic treatment to the state suitable for biological treatment, the control apparatus passes the to-be-processed water in the pre-treatment tank 7 through the piping 48 to the biological treatment apparatus 4 of a subsequent step. Return.

(4) biological treatment

The treated water returned to the biological treatment device 4 is treated with nitrogen compounds such as fluorine powder and ammonia contained in the treated water by the treatment up to the previous stage. Nitric acid is contained as a treatment target. As mentioned above, the to-be-processed water discharged from the etching process in a semiconductor factory contains not only a high concentration of fluorine component but a high concentration of ammonia and nitric acid. Although nitric acid is partially denitrified by the previous electrolytic treatment, in order to denitrify all nitric acid in the water to be treated by electrolytic treatment, the time required for the electrolytic treatment is required for a longer time. There is a problem that results, and it is not preferable in terms of treatment cost or in terms of treatment efficiency.

In addition, the concentration of nitric acid in the treated water discharged from the factory is not constant, and fluctuations in the case of high concentrations or almost no treatment targets are large, so that the variation in the processing load in the biological treatment device 4 also increases. .

Therefore, in the biological processing apparatus 4 of this embodiment, the biological processing tank used based on the nitric acid concentration previously detected by the nitric acid sensor 18 in the neutralization tank 12 of the fluorine powder removal apparatus 2 is used. The number of (9) is changed.

Specifically, although the dilution of the concentration is carried out to some extent by the diluent supply device 46 in the pretreatment tank 7 of the previous step, when the concentration of nitric acid detected by the nitric acid sensor 18 is significantly high, In this embodiment, all three pumps 50 are operated, and all six biological treatments of the water to be treated in the biological treatment tank 9 are performed.

The water to be treated is distributed and supplied to the denitrification reaction chamber 53 at the lower portion of each biotreatment tank 9 through the branch pipe 52. The water to be fed to the denitrification reaction chamber 53 contains almost no ammonia nitrogen since the treatment of ammonia nitrogen is almost completed as described above by the electrolytic treatment.

The treated water fed into the denitrification reaction chamber 53 at the bottom of the biotreatment tank 9 flows upward to ascend in the granule sludge 54 filled therein. In the meantime, the nitrogen nitrate and nitrogen nitrite in the water to be treated come into contact with the denitrifying bacteria as described above and decompose to nitrogen gas. That is, denitrification bacteria oxidize organic matter with oxygen to obtain energy, but in this embodiment, since the denitrification reaction chamber 53 is in an anaerobic state, denitrification bacteria are pretreated in the previous step using oxygen in nitric acid or nitrous acid. Oxidative decomposition of organic substances, such as methanol, previously supplied in the tank (7) is performed. Accordingly, nitrogen nitrate and nitrous nitrite in the water to be treated are denitrified by denitrification bacteria and reduced to nitrogen gas (Scheme 5). Hereinafter, reaction scheme 5 is shown. In addition, hydrogen in Reaction 5 is supplied from the organic substance added to the to-be-processed water.

^{_{2NO 2 - +3 (H 2)}} → N 2 ↑ + 2H 2 O + 2OH -

^{_{2NO 3 - +5 (H 2)}} → N 2 ↑ + 4H 2 O + 2OH -

As described above, when the concentration of nitric acid in the water to be treated is high, biological treatment is performed by distributing and supplying the water to each biological treatment tank 9 so that each biological treatment is independent of the concentration of nitric acid contained in the water. The load on the tank 9 can be reduced.

Thereby, the treatment efficiency in each biological treatment tank 9 can be improved, and the treatment efficiency of the to-be-processed water as a whole can be improved. In particular, by distributing and supplying to the plurality of biological treatment tanks 9, it becomes possible to reduce the load on the living organisms in each tank 9 due to introduction and discharge of the water to be treated into the biological treatment tank 9. .

In addition, in the present embodiment, the granulated sludge 54 is used to treat the water to be treated in the biological treatment, so that the nitrogen nitrate and the nitrite nitrogen in the water can be treated more effectively.

In addition, since the to-be-processed water supplied to each biological treatment tank 9 is diluted below the predetermined | prescribed nitric acid concentration by the dilution water supply apparatus 46 in the pretreatment tank 7 as mentioned above, a living organism also by this By the nitric acid concentration suitable for the treatment, the treatment can be performed, and the treatment efficiency can be improved.

In addition, since the to-be-processed water supplied to the biological treatment tank 9 is previously adjusted by the thermostat 8 to predetermined temperature, ie, +15 degreeC or more, biological treatment is performed by the temperature suitable for a biological treatment. It becomes possible. As a result, for example, when the water treatment apparatus 1 is installed outdoors, the external air temperature is remarkably lowered depending on the season, and thus the activity of the organism is lowered, thereby avoiding the problem of lowering the treatment efficiency. Will be. For this reason, the treatment efficiency of the biological treatment can be maintained without being affected by the outside air temperature.

The nitrogen gas and the carbon dioxide gas generated in the denitrification reaction chamber 53 are discharged to the outside through the gas solid-liquid separation means 55 provided at the upper portion of the bioprocessing tank 9. In addition, the water to be treated after denitrification by the denitrification bacteria is returned to the discharge tank 10 in the subsequent step by the pipe 58 through the filtration membrane 56 by operating the pump 57.

Here, since the water to be treated after denitrification in the denitrification reaction chamber 53 is returned to the next step through the filtration membrane 56, the granule sludge 54 which rises with nitrogen gas or carbon dioxide gas, etc., is transferred to the filtration membrane 56. Since the filtration process is carried out by the filtration process, it is possible to suppress the problem of spilling into the discharge tank 10 in a subsequent step.

In particular, the filtration membrane 56 is at least in contact with the layer formed by the granule sludge 54 of the denitrification reaction chamber 53, and is disposed in the buried state in the present embodiment, so that each particle of the granule sludge 54 is disposed. Nitrogen gas, carbon dioxide gas, etc. adhering to the surface can be actively peeled off by the filtration membrane 56 and discharged. For this reason, since nitrogen gas and carbonic acid gas are effectively removed from the surface of each granule sludge 54 particle | grains, the area effective for the denitrification process of the said granule sludge 54 becomes large, thereby improving the denitrification treatment efficiency. do.

In addition, in this embodiment, although the to-be-processed water is conveyed to the discharge layer 10 through the filtration membrane 56 by operating the pump 57, it is not limited to this, For example, the supply path of to-be-processed water And by closing the denitrification reaction chamber 53 other than the outflow path, the treated water treated in the denitrification reaction chamber 53 is supplied from the supply path of the treated water without using a conveying means such as a pump. It becomes possible to discharge from an outflow path. As a result, not only the device can be simplified, but also the cost of parts can be reduced.

In addition, although the filtration membrane 56 is embedded in the granule sludge 54 in this Example, it is not limited to this, It is inside the denitration reaction chamber 53 or outside the denitration reaction chamber 53, and is to be processed. By installing in the outflow path of the water, the granule sludge 54 is discharged out of the treatment tank, and the problem that the environmental load increases by the granule sludge can be suppressed.

On the other hand, the concentration of nitric acid detected by the nitric acid sensor 18 is lower than a predetermined value, so that the denitrification treatment of nitrogen nitrate and nitrogen nitrite in the water to be treated can be performed without using all the biological treatment tanks 9. If possible, one or two pumps 50 are operated, and the number of biological treatment tanks 9 to be used is reduced to two or four, and biological treatment of the water to be treated is performed.

As such, as the concentration of nitric acid in the treated water is lowered, the number of biological treatment tanks 9 to supply the treated water is reduced, and the control to increase the number of biological treatment tanks to supply the treated water as the nitric acid concentration is increased. By performing the above, the water to be treated can be treated by the number of the biological treatment tanks 9 corresponding to the nitric acid concentration. As a result, the biological treatment can be efficiently performed, and the treatment efficiency can be improved.

In this case, the selection of the biological processing unit 51 to be used does not always use the same unit 51, but it is assumed that the control for switching the biological processing unit 51 to be used regularly is executed. Thereby, the problem by the load difference between each biological treatment tank 9 by using only some biological treatment tank 9 can be avoided.

Then, air is supplied from the air supply path 62 to the to-be-processed water processed by the bioprocessing device 4 and returned to the discharge tank 10 by the air diffuser device 59. Thereby, the decomposition of the organic substance remaining by adding too much in the to-be-processed water is performed. After the organic matter is decomposed, the water to be treated is discharged to the environment such as a river through the discharge pipe 61 by the pump 60. In this state, the treated water is not only removed from the fluorine component but also effectively removed from nitric acid, ammonia, and the like at a high concentration, so that even if released into the environment, the load is not provided to the environment. For this reason, it is not necessary to treat the to-be-processed water discharged | emitted from a factory as industrial waste, and it is preferable also from an environment point of view and a processing cost point.

In addition, even after being processed by the bioprocessing device 4 and conveyed to the discharge tank 10, for example, when the nitric acid concentration detected by the nitric acid sensor 18 is remarkably high and requires more advanced processing than usual, It is also assumed that the treated water conveyed to the discharge tank 10 can be conveyed to the pretreatment tank 7 through the circulation pipe 47 to perform the treatment in the biological treatment device 4 again.

As described above, according to the water treatment apparatus 1 of the present invention, the treated water containing fluorine powder or nitrogen compound, such as hydrofluoric acid wastewater discharged from a semiconductor factory or the like, for example, the fluorine powder removing device 2 In addition to being able to remove fluorine, the treated water containing fluorine and at least the nitrogen compound can be treated by the electrochemical treatment device 3 and the biological treatment device 4.

As a result, it is possible to treat wastewater discharged from a plant or the like and at least a nitrogen compound to a state suitable for the environment, to reduce the cost of wastewater treatment, and to improve the suitability for the environment. It can be improved.

Furthermore, since the water to be treated biotreats the water to be treated by the electrochemical method, the running cost can be remarkably lowered compared to the case of only the treatment by the electrochemical method, and the water to be treated. Can improve the processing efficiency.

In this embodiment, since the treatment of the water to be treated containing fluorine is taken as an example, the fluorine powder removal device 2 is provided, but the treatment of the water to be treated that does not require the treatment of fluorine is performed. By treating with the water treatment apparatus 1 except the said fluorine powder removal apparatus 2, the to-be-processed water containing a high concentration of nitrogen compound can be processed efficiently.

In the present embodiment, the fluorine powder removal device 2, the electrolytic treatment device 3, and the biological treatment device 4 are installed in a related procedure, and the treated water is treated accordingly. The order of the processing of is not limited to this, and even if all of the orders are changed, the processing of the water to be treated is possible.

According to the water treatment device of claim 1, the fluorine powder removal device for separating the removal object from the treated water in which the removal object containing the fluorine powder is mixed, and at least a partial immersion of at least one pair of electrodes in the treatment water And an electrochemical treatment apparatus for treatment by an electrochemical technique and a biological treatment apparatus for biotreating the water to be treated, for example, fluorine powder or nitrogen compounds such as fluoric acid wastewater discharged from a semiconductor factory or the like. Not only can the fluorine component of the water to be treated containing be removed from the fluorine component removal apparatus, but also the treated water containing at least the nitrogen compound can be treated by the electrochemical treatment apparatus and the biological treatment apparatus.

As a result, the wastewater containing fluorine and at least nitrogen compounds discharged from the factory can be treated in a state suitable for the environment, and the cost of wastewater treatment can be reduced, and the suitability for the environment can be improved. It can be improved.

According to the water treatment apparatus of Claim 2, it has an electrochemical treatment apparatus which immerses at least one pair of electrodes in the to-be-processed water and processes it by an electrochemical technique, and has a some biological treatment tank, and by an electrochemical technique A biological treatment apparatus for biotreating the treated water is included in the treated water because the number of the biological treatment tanks is changed based on the concentration of nitric acid and / or the amount of the water to be treated. Regardless of the concentration to be treated, that is, the concentration of nitric acid or the amount of water to be treated, the load on each biological treatment tank can be reduced.

Thereby, the treatment efficiency in each biological treatment tank can be improved, and the treatment efficiency of the to-be-processed water as a whole can be improved.

According to the water treatment apparatus of Claim 3, in each said invention, an electrochemical treatment apparatus detects the pH of the to-be-processed water during the process by an electrochemical method, and the pH of the to-be-processed water. A pH detecting means for detecting, an ORP detecting means for detecting the redox potential of the water to be treated, an end determining means for determining the end of the treatment by the electrochemical method, and a control means for controlling the energization to the electrode, During the treatment by the electrochemical method, the pH of the water to be treated is adjusted within the predetermined range by the pH adjusting means, and the termination determining means stops the termination based on the detection output of the pH detecting means and / or the detection output of the ORP detecting means. The control means terminates the energization to the electrode by this determination output, thereby avoiding the use of expensive sensors such as ammonia nitrogen concentration meter and the like. Therefore, the concentration of nitrogen you AP, it is possible to accurately determine the end time of processing of the ammonium nitrogen.

As a result, the problem of ammonia nitrogen in the water to be treated is terminated in the middle and the problem of ammonia nitrogen remaining in the treated water after treatment or electrolysis more than necessary can be avoided. For this reason, a running cost can be reduced. In particular, since electrolysis is not performed more than necessary, it becomes possible to suppress the problem of excessive generation of hypohalogenous acid in the water to be treated.

In particular, since the pH of the water to be treated is adjusted to a predetermined range by the pH adjusting means during the treatment by the electrochemical method, mono in the denitrification reaction between the hypohalogen acid and the ammonia generated in the water to be treated by the electrochemical method. It does not affect the production | generation of intermediate products, such as chloroamine and dichloroamine, much. For this reason, the fluctuation of the pH of the water to be treated does not significantly affect the fluctuation of the redox potential, and it becomes possible to determine the end time of the ammonia nitrogen treatment more precisely.

According to the water treatment apparatus of claim 4, in the invention, the electrochemical treatment apparatus includes: hypohalogenic acid reduction treatment means for reducing hypohalogenic acid in the water to be treated and reduction for terminating the reduction treatment of hypohalogenic acid; After the completion of the energization to the electrode by the control means, the hypohalogenic acid reduction treatment means performs the reduction treatment of the hypohalogenic acid, and the reduction treatment end determination means has an ORP detection means output of a predetermined value or less. When the reduction treatment ends, the end of the reduction treatment is determined, and the operation of the hypohalogenous acid reduction treatment means is terminated, so that it is possible to accurately determine the reduction treatment termination time of the hypohalogenic acid remaining in the water to be treated.

As a result, it is possible to reduce the hypohalogenic acid in the water to be treated without excess and deficiency, so that in the biological treatment of the water to be treated at a later stage, it becomes possible to avoid the adverse effects caused by the hypohalogenic acid, as well as the hypohalogen. By not using the acid reduction means in vain, the problem that a running cost spikes can be solved.

In particular, since the end of the reduction treatment of the hypohalogenic acid is performed based on the detection of the ORP detecting means provided in the electrochemical treatment apparatus, the end of the denitrification reaction of the ammonia is performed based on the detection of the ORP detecting means as described above. In this case, it is possible to determine the end time of the reduction treatment of hypohalogenic acid without providing a means for detecting hypohalogenic acid.

For this reason, the hypohalogenous acid contained in the to-be-processed water adversely affects the living thing in a biological treatment tank, and can suppress the problem that a treatment efficiency falls.

According to the water treatment apparatus of claim 5, in the invention of claim 3, since the pH adjusting means adjusts the pH of the water to be treated to 5 to 8, the hypohalogen acid generated in the water to be treated by the electrochemical method; In the denitrification reaction of ammonia, the production of intermediate products such as monochloroamine and dichloroamine is not greatly influenced.

In addition, since the pH of the water to be treated is not 4 or less, it is possible to suppress the problem that the hypohalogenic acid such as hypochlorous acid generated in the water to be treated by the electrochemical method is released into the gas as halogen gas such as chlorine gas. It becomes possible.

According to the water treatment apparatus of the sixth aspect of the present invention, in each of the above inventions, there is provided a means for removing oxygen in the water to be treated in the previous step of the biological treatment.

According to the water treatment apparatus of the invention of claim 7, in each of the above inventions, the biological treatment apparatus uses granule sludge to treat the water to be treated, thereby improving the treatment efficiency by the anaerobic microorganisms used in the biological treatment. You can do it.

According to the water treatment apparatus of claim 8, the biological treatment of the water to be treated is provided with a biological treatment tank for storing granule sludge, and the biological treatment is performed by supplying the treatment water from the biological treatment tank. By installing a filtration membrane in the treatment tank and flowing out the water to be treated in the biological treatment tank through the filtration membrane to the outside of the biological treatment tank, granule sludge in the biological treatment tank is mixed in the treated water flowing out of the biological treatment tank, and the granule Sludge can suppress the problem that an environmental load increases.

Claims (8)

A fluorine powder removing device for separating the substance to be removed from the water to be treated containing the fluorine powder in the semiconductor drainage; An electrochemical treatment apparatus for immersing at least a portion of at least a pair of electrodes in the water to be treated and treating the same by an electrochemical method; Biological treatment apparatus for biological treatment of the water to be treated And The electrochemical treatment apparatus includes pH adjusting means for adjusting the pH of the water to be treated in the range of 5 to 8 during treatment by the electrochemical method, pH detecting means for detecting the pH of the water to be treated, and ORP detection means for detecting a redox potential due to the amount of hypochlorous acid in the treated water, end determination means for determining the end of the treatment by the electrochemical method, and control means for controlling the energization to the electrode. With During the treatment by the electrochemical method, the pH adjustment means adjusts the pH of the water to be treated within a predetermined range, and the termination determining means detects the output of the pH detection means, detects the output of the ORP detection means, or both. And the control means terminates the energization to the electrode by the determination output. delete delete The electrochemical treatment apparatus according to claim 1, wherein the electrochemical treatment apparatus has a hypohalogen acid reduction treatment means for reducing hypohalogen acid in the water to be treated and a reduction treatment end determination means for determining the termination of the reduction treatment of hypohalogenic acid, After the completion of the energization of the electrode by the control means, the hypohalogenic acid reduction treatment is performed by the hypohalogenic acid reduction treatment means, and the reduction treatment end determination means determines that the output of the ORP detection means becomes equal to or less than a predetermined value. It is determined that the reduction treatment ends, and the operation of the hypohalogenous acid reduction treatment means is terminated. delete The water treatment apparatus according to claim 1, further comprising means for removing oxygen in the water to be treated in a previous step of the biotreatment. The water treatment apparatus according to claim 1, wherein the biological treatment apparatus treats the treated water using granule sludge. delete

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