JP2007050312A - Method and apparatus for biologically treating waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently treat waste water which contains alkylene carbonate such as ethylene carbonate and propylene carbonate and is discharged from a plant for manufacturing an electronic device. <P>SOLUTION: The apparatus 10 for treating waste water biologically is provided with an aerobic treatment tank 12, a denitrification tank 14 and a re-aeration tank 16. Kjeldahl nitrogen-containing water containing ammonia nitrogen or the like is supplied to the aerobic treatment tank 12 from a nitrogen-containing water line 31 to oxidize Kjeldahl nitrogen aerobically. The nitrified liquid withdrawn from the aerobic treatment tank 12 is sent to the denitrification tank 14 to denitrify ethylene carbonate or the like contained in alkylene carbonate-containing water to be supplied to the denitrification tank from an alkylene carbonate-containing water line 32 into a hydrogen donor. Namely, Kjeldahl nitrogen-containing water and alkylene carbonate-containing water are separately collected and the former is introduced into the aerobic treatment tank 12 and the latter is introduced in the denitrification tank 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a biological treatment method for wastewater containing ethylene carbonate, and more particularly to a biological treatment method and biological treatment apparatus for wastewater discharged from a manufacturing process of an electronic device using a stripping solution containing ethylene carbonate.

  In the manufacturing process of an electronic device such as a semiconductor element or a liquid crystal element, various chemicals are used in a lithography process, a processing process such as etching, a peeling process, a cleaning process, and the like, and wastewater having various properties is generated from each process. For example, in a substrate pretreatment process for polishing a substrate, wastewater containing chemical-mechanical polishing (CMP) or the like is discharged, and in an etching process for etching a substrate or the like, wastewater containing acetic acid or the like is discharged. Is discharged.

  Such waste water is appropriately mixed with waste water discharged from other processes as needed, and is treated physicochemically or biologically depending on the properties of the waste water. For example, conventionally, inorganic wastewater such as CMP-containing wastewater is treated by physicochemical methods such as coagulation sedimentation, filtration, activated carbon adsorption, ion exchange, or membrane separation. On the other hand, organic wastewater containing acetic acid, ethanol, acetone, or the like is often treated biologically.

  By the way, in the peeling process which is one of the manufacturing processes of an electronic device, various types of stripping solutions are used in order to remove the photoresist applied to the board or the like from the substrate or the like. Conventionally, as a stripping solution, a mixed solution of sulfuric acid and hydrogen peroxide, a hydrofluoric acid-based liquid containing a fluorine compound such as hydrofluoric acid, or an organic amine-based liquid including monoethanolamine is used. Yes. In recent years, liquids containing ethylene carbonate or propylene carbonate (hereinafter referred to as “alkylene carbonate”) have also been used.

For this reason, recently, water containing alkylene carbonate including alkylene carbonate is also discharged from the manufacturing process of electronic devices. Although alkylene carbonate is an organic substance, it is considered to be difficult to be assimilated by microorganisms involved in biological treatment of wastewater because it is stable. That is, conventionally, it is considered that alkylene carbonate-containing water is difficult to treat with a normal activated sludge process, and in order to promote the biodegradation of alkylene carbonate, an alkylene carbonate-degrading bacterium acclimatized under predetermined conditions is used. There has been proposed a method for performing biological treatment using the method (for example, Patent Document 1).
Japanese Patent Laid-Open No. 2005-13929

  However, in the method described in Patent Document 1, it is necessary to separately provide a treatment tank for maintaining a high concentration of alkylene carbonate-decomposing bacteria acclimatized to treat alkylene carbonate-containing water in the wastewater treatment facility of the electronic device manufacturing factory. There is. For this reason, the waste water treatment facility of the electronic device manufacturing factory is enlarged.

  In addition, as described above, since various types of wastewater are generated in addition to the alkylene carbonate-containing water in the electronic device manufacturing factory, the method of Patent Document 1 in which the alkylene carbonate-containing water is treated alone is the entire electronic device manufacturing factory. The wastewater treatment efficiency cannot be improved. On the other hand, when water containing alkylene carbonate is mixed with wastewater discharged from other processes, the quality of the treated water is affected by fluctuations in the flow rate of wastewater discharged from other processes or the concentration of contaminants. Becomes unstable.

  The present invention has been made in view of the above problems, prevents an increase in wastewater treatment facility of an electronic device manufacturing factory that discharges alkyl carbonate-containing water, contributes to improvement of wastewater treatment efficiency of the whole factory, and has stable water quality. An object of the present invention is to provide a biological treatment method for waste water from which treated water can be obtained, and a biological treatment apparatus for waste water.

  The inventor of the present invention has found that water containing alkylene carbonate, which has been conventionally considered to be difficult to be decomposed biologically, is effective as an electron donor in the biological denitrification process, and has completed the present invention. . That is, the present invention pays attention to the fact that alkylene carbonate-containing water is an energy source for dependent denitrifying bacteria, and by incorporating the treatment of alkylene carbonate-containing water into the treatment process of Kjeldahl nitrogen-containing water, The biological treatment is organically combined with the biological treatment of alkyl carbonate-containing water to perform a rational treatment. Specifically, the present invention provides the following.

  (1) an aerobic step of introducing Kjeldahl nitrogen-containing water containing Kjeldahl nitrogen into an aerobic tank equipped with an oxygen supply means, and nitrifying the Kjeldahl nitrogen in the presence of nitrifying bacteria to obtain a nitrification solution; A denitrification step of introducing a treatment liquid and an alkylene carbonate-containing water containing alkylene carbonate and substantially free of Kjeldahl nitrogen into a denitrification tank and denitrifying in the presence of denitrifying bacteria; Processing method.

  In the present invention, the Kjeldahl nitrogen-containing water and the alkyl carbonate-containing water are not mixed and are separately introduced into the biological treatment apparatus. The Kjeldahl nitrogen-containing water contains Kjeldahl nitrogen as an ammonia source, that is, ammonia nitrogen and / or organic nitrogen compounds measured by the Kjeldahl method. In the aerobic process, organic nitrogen compounds are decomposed into ammonia nitrogen by the action of aerobic microorganisms. Therefore, Kjeldahl nitrogen-containing water not only contains only ammonia nitrogen, but also contains only organic nitrogen compounds, or even contains ammonia nitrogen and organic nitrogen compounds, it can be used for the treatment according to the method of the present invention as it is. Can be provided.

  Kjeldahl nitrogen-containing water is a biodegradable contaminant other than Kjeldahl nitrogen, such as nitrite nitrogen and / or nitrate nitrogen (hereinafter referred to as “non-Kjeldahl nitrogen”), and BOD (as biological oxygen demand) Organic component to be measured) and the like may be included.

  Specific examples of Kjeldahl nitrogen-containing water discharged during the electronic device manufacturing process include the following. Wastewater containing tetramethylammonium hydroxide (TMAH) discharged from a lithography process in which a photoresist or the like is applied to a substrate such as a silicon wafer for a semiconductor or a glass substrate for liquid crystal to transfer the pattern, the substrate according to the transferred pattern, etc. Wastewater containing ammonia discharged from a processing step such as etching, and wastewater discharged from a stripping step, including wastewater containing alkanolamine such as monoethanolamine.

  On the other hand, the alkylene carbonate-containing water contains alkylene carbonate and does not substantially contain Kjeldahl nitrogen. In this specification, “alkylene carbonate” specifically means ethylene carbonate and / or propylene carbonate. Further, “substantially free of Kjeldahl nitrogen” means that the Kjeldahl nitrogen concentration is less than 20% by mass of the BOD concentration.

  The alkylene carbonate concentration contained in the alkylene carbonate-containing water is arbitrary and is not particularly limited, and can be treated with the concentration discharged as waste water. The water containing alkylene carbonate may contain organic substances other than alkylene carbonate, such as isopropyl alcohol (IPA), ethanol, acetone, acetic acid, propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), and the like. Further, the alkylene carbonate-containing water may contain contaminants other than Kjeldahl nitrogen, for example, non-Kjeldahl nitrogen at an arbitrary concentration.

  The alkylene carbonate-containing water is used as an electron donor when reducing non-Kjeldahl nitrogen contained in a nitrification treatment liquid obtained by treating Kjeldahl nitrogen-containing water in an aerobic tank to nitrogen gas. For this reason, it is not necessary to provide a special process and equipment for biologically treating the alkylene carbonate-containing water. In addition, it is not necessary to add methanol or IPA that has been added in the conventional denitrification reaction by heterotrophic denitrifying microorganisms, or the amount of methanol or the like can be reduced.

  Specifically, in the denitrification reaction by heterotrophic denitrifying microorganisms, organic matter such as methanol, which is 2.5 times the amount of non-Kjeldahl nitrogen flowing into the denitrification tank, is theoretically required. However, since the utilization factor of the organic matter used for the denitrification reaction is not 100%, 110 to 130% by mass of the theoretically necessary amount of organic matter is usually added to the denitrification tank.

Here, Kjeldahl nitrogen-containing water discharged during the electronic device manufacturing process uses alkylene carbonate, while Kjeldahl nitrogen concentration is 30 to 500 mg / L, and the discharged water amount is 500 to 5,000 m ³ / day. The concentration of alkylene carbonate contained in the wastewater discharged from the peeling step is 100 to 3,000 mg-as BOD / L, and the amount of discharged water is 500 to 5,000 m ³ / day. For this reason, according to this invention, about 30-300 mass% of the amount of organic substances required for a denitrification reaction can be covered by adding the waste_water | drain discharged | emitted from the peeling process using an alkylene carbonate to a denitrification tank. In the following, waste water discharged from a peeling process using alkylene carbonate and having a main contaminant (for example, 70% by mass or more) of alkylene carbonate is distinguished from water containing alkylene carbonate containing organic substances other than alkylene carbonate. Therefore, the former may be referred to as “alkylene drainage” and the latter as “mixed alkylene drainage”.

  When the nitrogen concentration of Kjeldahl nitrogen-containing water is high or the discharge amount is large, if the amount of organic matter necessary for the denitrification reaction is insufficient only by adding the alkylene drain solution, the alkylene drain solution is discharged from other processes. A mixed alkylene drainage obtained by mixing the organic substance-containing water may be allowed to flow into the denitrification tank. Waste water from other processes mixed with the alkylene waste liquid includes IPA-containing water, ethanol-containing water, acetone-containing water discharged from the cleaning process and rubbing process of the electronic device, and acetic acid-containing water discharged from the etching process. Is mentioned.

  (2) A re-aeration step of introducing the effluent from the denitrification step into a re-aeration tank equipped with an oxygen supply means, and decomposing organic substances contained in the effluent from the de-nitrification step in the presence of aerobic microorganisms. The biological treatment method of waste water according to (1), further comprising:

  In the denitrification reaction by subordinate microorganisms, a method for controlling the amount of organic matter added by measuring redox potential (ORP) or NOx-N is proposed in order to supply the necessary amount of organic matter to the denitrification tank without excess or deficiency. Has been. However, such a control method may not always have sufficient followability or measurement accuracy. For this reason, a certain amount of organic substance of about 110 to 130% of the theoretical required amount is often supplied to the denitrification tank. In such a case, if the Kjeldahl nitrogen load in the aerobic tank is reduced due to a decrease in the Kjeldahl nitrogen concentration of the Kjeldahl nitrogen-containing water, organic substances may remain in the effluent from the denitrification tank.

  In the invention described in (2), the water quality of the effluent from the denitrification tank deteriorates even when the Kjeldahl nitrogen load in the aerobic tank is reduced by providing a re-aeration process after the denitrification process. Can be prevented.

  (3) Collecting the Kjeldahl nitrogen-containing water and the alkylene carbonate-containing water separately from the electronic device manufacturing process for discharging the Kjeldahl nitrogen-containing water and the alkylene carbonate-containing water, The biological treatment method of waste water according to (1) or (2), wherein the method is introduced into the aerobic tank, and the alkylene carbonate-containing water is introduced into the denitrification tank.

  In the present invention, wastewater treatment from an electronic device manufacturing process including at least a process of discharging Kjeldahl nitrogen-containing water and a process of discharging an alkylene drainage is rationalized in the manufacturing process of the electronic device. That is, in the present invention, of the waste water discharged from the electronic device manufacturing factory, waste water mainly containing Kjeldahl nitrogen (nitrogen-based waste water) is introduced into the aerobic tank through the nitrogen-containing water channel. On the other hand, wastewater containing alkylene waste liquid and other organic matter (organic matter wastewater) is collected separately from nitrogen wastewater and introduced into the denitrification tank through the alkylene carbonate-containing water channel without being introduced into the aerobic tank. By collecting nitrogen wastewater and organic matter wastewater separately, supplying them to different biological treatment tanks and treating them in separate treatment steps, the load on organic matter in the aerobic tank can be lowered. The enlargement of the tank can be prevented.

  In addition, the properties of the wastewater discharged from the electronic device manufacturing process, that is, the concentration of pollutants or the amount of generated wastewater vary for each electronic device manufacturing process. For this reason, if wastewater from a plurality of manufacturing processes is mixed indiscriminately and introduced into the aerobic tank, the aerobic tank is enlarged. Further, when the Kjeldahl nitrogen load on the aerobic tank is lowered, the denitrification reaction in the denitrification tank does not proceed, so the organic matter removal in the denitrification tank does not proceed and the water quality of the effluent from the denitrification tank deteriorates.

  On the other hand, if nitrogen-based wastewater and organic-based wastewater are collected separately according to the present invention, it is possible to treat multiple types of wastewater that are discharged from multiple electronic device manufacturing processes and whose properties change at different timings. It becomes easy to rationalize. Specifically, the deterioration of the water quality of the effluent from the denitrification tank can be easily prevented by adjusting the timing of the inflow of the nitrogenous wastewater into the biological treatment apparatus and the inflow of the organic wastewater. More specifically, for example, an alkylene carbonate-containing water storage tank may be provided in the middle of the alkylene carbonate-containing water channel to adjust the flow rate of the alkylene carbonate-containing water flowing into the denitrification tank.

  (4) an aerobic tank comprising a nitrogen-containing water channel to which Kjeldahl nitrogen-containing water containing Kjeldahl nitrogen is supplied, and an oxygen supply means, and nitrifying the Kjeldahl nitrogen in the presence of nitrifying bacteria to obtain a nitrification treatment solution; Is connected to the aerobic tank and is supplied with the nitrification solution, and an alkylene carbonate-containing water channel is supplied with alkylene carbonate-containing water containing alkylene carbonate and substantially free of Kjeldahl nitrogen. A biological treatment apparatus for wastewater, including a denitrification tank for denitrification in the presence of nitrifying bacteria.

  (5) A denitrification treatment liquid path, one end of which is connected to the denitrification tank and supplied with the effluent from the denitrification tank, and an oxygen supply means, and the effluent from the denitrification tank in the presence of aerobic microorganisms The biological treatment apparatus for wastewater according to (4), further comprising a re-aeration tank for decomposing the organic matter contained therein.

  (6) The re-aeration tank is designed so that 90% by mass or more of all BOD components contained in the alkylene carbonate-containing water can be decomposed, and the biological wastewater according to (4) or (5) Processing equipment.

  In this invention, the alkylene carbonate containing water discharged | emitted from an electronic device manufacturing process is made into the main organic substance source of the denitrification reaction in a denitrification tank. For this reason, the denitrification tank is designed in consideration of the processing conditions of the aerobic tank, fluctuations in the properties of Kjeldahl nitrogen-containing water introduced into the aerobic tank, fluctuations in the properties of alkylene carbonate-containing water, etc. Is preferred. Specifically, the denitrification tank has a tank volume so that almost all of the non-Kjeldahl nitrogen contained in the nitrification solution and brought into the denitrification tank can be denitrified when the Kjeldahl nitrogen load on the aerobic tank is maximized. Etc. are preferably determined.

  The re-aeration tank is designed to reduce the BOD component contained in the alkylene carbonate-containing water to a certain value (for example, less than 5 mg / L) even when the non-Kjeldahl nitrogen load of the denitrification tank decreases. It is preferable. In particular, the re-aeration tank decomposes 90% by mass or more of the BOD component contained in the alkylene carbonate-containing water even when the non-Kjeldahl nitrogen load of the denitrification tank becomes the minimum value, and the treated water having a BOD concentration of less than 5 mg / L. It is preferable that it is designed so that it can be obtained.

  The types of the aerobic tank, the denitrification tank, and the re-aeration tank (hereinafter may be collectively referred to as “biological treatment tank”) are not particularly limited. Specifically, floating type that keeps activated sludge in the tank in a floating state, biofilm type that keeps activated sludge attached to the carrier, and upward flow sludge that holds activated sludge as granulated sludge There is a floor (USB) type, and in the biofilm type, the activated sludge bed held by the carrier is fixed, the activated sludge bed held by the carrier is contacted with the water to be treated. Various biological treatment tanks such as a fluidized bed type that is fluidized and brought into contact with the water to be treated, and a developed bed type that is in contact with the treated water by expanding the activated sludge bed held on the carrier can be used.

  When a floating biological treatment tank is used, solid-liquid separation means is provided at the subsequent stage of the biological treatment tank in order to separate the treated water and activated sludge. The solid-liquid separation means may be provided at least after the last biological treatment tank. However, in order to keep the sludge concentration in each biological treatment tank in a predetermined range, it may be provided in the subsequent stage of each biological treatment tank, and the separated sludge may be returned to each biological treatment tank. The solid-liquid separation means is not particularly limited, and for example, a sedimentation basin or a membrane separation device can be used.

  When using a carrier that holds activated sludge, the type of the carrier is not particularly limited. Specifically, a support made of activated carbon, plastic, gel, sponge, or the like can be used. In particular, a sponge carrier such as ester polyurethane is preferable because it maintains microorganisms at a high concentration. The size and shape of the carrier are not particularly limited, but are preferably 10 mm square or less, and particularly about 3 to 7 mm square for the carrier filled in the aerobic tank and the re-aeration tank. The filling amount of the carrier is preferably about 20 to 50% of the tank capacity for the aerobic tank, and about the same for the denitrification tank and the re-aeration tank.

  ADVANTAGE OF THE INVENTION According to this invention, the processing efficiency of the whole waste water treatment of an electronic device manufacturing factory can be aimed at, the enlargement of waste water treatment equipment can be prevented, and the stable treated water quality can be obtained. Moreover, the addition cost of the organic substance added for the denitrification reaction can be reduced, and the wastewater treatment cost can be reduced. In addition, since various wastewater discharged from multiple processes in the electronic device manufacturing factory is divided into nitrogen-based wastewater and organic wastewater and processed by biological treatment equipment, the design of multiple biological treatment tanks constituting the biological treatment equipment Can be easily done.

  The present invention will be described below with reference to the drawings. In the following, the same members are denoted by the same reference numerals, and description thereof is omitted or simplified.

  FIG. 1 is a schematic view of a wastewater biological treatment apparatus (hereinafter simply referred to as “treatment apparatus”) 10 according to an embodiment of the present invention. The processing apparatus 10 is configured by arranging an aerobic tank 12, a denitrification tank 14, and a re-aeration tank 16 in this order. A water recovery device 20 is provided downstream of the processing device 10 in order to recover the treated water of the processing device 10 and use it as raw water for an ultrapure water production device (not shown) or the like. The water recovery device 20 includes a coagulation treatment device 22, a filtration device 24, a microfiltration membrane (MF membrane) device 26, and a reverse osmosis membrane (RO membrane) device 28.

  The aerobic tank 12 and the denitrification tank 14 are connected by a nitrification treatment liquid path 33, and the denitrification tank 14 and the re-aeration tank 16 are connected by a denitrification treatment liquid path 35, and the re-aeration tank 16 and the water recovery device 20 are connected. Are connected by a treatment water channel 37. One end of a nitrogen-containing water channel 31 to which Kjeldahl nitrogen-containing water is supplied is connected to the aerobic tank 12, and the other end of the nitrogen-containing water channel 31 is a drainage water collection channel (such as a lithography process) for discharging Kjeldahl nitrogen-containing water (see FIG. (Not shown). Moreover, one end of an alkylene carbonate-containing water channel (hereinafter abbreviated as “alkylene-containing water channel”) 32 is connected to the denitrification tank 14 separately from the nitrification treatment liquid channel 33, and the other end of the alkylene-containing water channel 32 is an alkylene carbonate Is connected to a drainage water collecting channel (not shown) in a peeling process using a peeling solution containing.

An aerobic tank 12 is filled with a sponge carrier 11 made of ester polyurethane, and an aeration tube 13 for supplying an oxygen-containing gas such as air is provided as an oxygen supply means. This aerobic tank 12 has an MLSS concentration of 3,000 to 20, with activated sludge mainly composed of ammonia oxidizing bacteria and / or nitrite oxidizing bacteria (hereinafter referred to as “nitrifying bacteria”) held in the sponge carrier 11. About 000 mg / L is retained. The aerobic tank 12 in the present embodiment is a fluid biological treatment tank in which the sponge carrier 11 is fluidized by the gas blown from the air diffuser 13. The processing conditions for nitrification processes, the dissolved oxygen concentration (DO) 0.5~4mg / L, in particular 1-3 mg / L, Kjeldahl nitrogen volume loading 0.2~1.0kg-N / ^{m 3} / day, Kjeldahl nitrogen When the contained water contains an organic substance, the BOD volume load is preferably 1 to 2 kg-N / m ³ / day.

The denitrification tank 14 is filled with a gel carrier 15 made of polyethylene glycol. In the denitrification tank 14, an MLSS concentration of about 3,000 to 20,000 mg / L is retained in a state where activated sludge mainly composed of denitrifying bacteria is retained on the gel carrier 15. The denitrification tank 14 in this embodiment is a fluid biological treatment tank in which the gel carrier 15 is fluidized by a stirrer, and the denitrification reaction is performed under anaerobic conditions. As processing conditions of a denitrification process, it is preferable to set it as the nitrate nitrogen load 0.5-2 kg-N / m < ³ > / day on the anaerobic condition which DO does not exist substantially.

  The re-aeration tank 16 is filled with a sponge carrier 11 made of ester polyurethane, and an aeration tube 13 is provided as an oxygen supply means. The air diffuser 13 has the same configuration as the air diffuser 13 in the aerobic tank 12, but the gas supply capacity of the air diffuser 13 is appropriately set according to the capacity of the tank. In this embodiment, the gas supply capacity of the air diffuser 13 of the re-aeration tank 16 is greater than that of the air diffuser 13 of the aerobic tank 12. In this re-aeration tank 16, MLSS concentration of about 3000 to 20,000 mg / L is held in a state where activated sludge is held on the sponge carrier 11. The re-aeration tank 16 in the present embodiment is a fluid biological treatment tank in which the sponge carrier 11 is fluidized by the gas blown from the diffusion tube 13.

The re-aeration tank 16 can obtain treated water having a BOD concentration of less than 5 mg / L by biologically decomposing a large portion (for example, about 90% or more) of the total BOD contained in the alkylene carbonate-containing water. It is preferable that it is designed. Specifically, the processing conditions of the re-aeration process are dissolved oxygen concentration (DO) of 0.5 to 4 mg / L, particularly 1 to 3 mg / L, and BOD nitrogen volume load of 1 to 2 kg-N / m ³ / day. It is preferable that it is designed as follows.

  The re-aeration tank 16 and the coagulation treatment apparatus 22 are connected by a treatment water channel 37. In this embodiment, since the sponge carrier 11 is held in the re-aeration tank 16, a solid-liquid separation device that separates sludge contained in the treated water flowing out from the re-aeration tank 16 is not necessary. However, when the re-aeration tank 16 is a floating type, a sedimentation basin is provided instead of the agglomeration treatment device 22, and the sedimentation basin and the re-aeration tank 16 are connected by a sludge return path and separated by the agglomeration treatment device 22. It is preferable to return the sludge to the re-aeration tank 16. A sedimentation basin may be provided in the middle of the nitrification treatment liquid passage 33 and the denitrification treatment liquid passage 35, and sludge separated in each precipitation basin may be returned to the aerobic tank 12 and the denitrification tank 14, respectively.

  The coagulation treatment apparatus 22 constituting the water recovery apparatus 20 uses the treated water of the biological treatment apparatus 10 as treated water, and adds an aggregating agent such as iron salt, aluminum salt, or polymer polymer to the treated water. The pH is adjusted accordingly, and the insoluble suspension (SS) contained in the water to be treated is aggregated and removed. As the agglomeration processing device 22, an arbitrary type such as a pressure floating type or a coagulation precipitation type can be used.

  The filtration device 24 is connected to the aggregation treatment device 22 via the aggregation treatment liquid passage 41, and further removes SS of the aggregation treatment liquid obtained by removing the SS of treated water by the aggregation treatment device 22. The filtration device 24 includes a granular filter medium. Gravity or pressure is applied as a filtration pressure, a single layer, two layers, or three layers are used as the number of filtration layers, and a downward flow or an upward flow is used as a filtration direction. It can be configured in a form combining these methods.

  The MF membrane device 26 is connected to the filtration device 24 via the filtrate passage 43, and membrane filtrates the filtrate obtained by clarifying the aggregating treatment solution with the filtration device 24 with the MF membrane. As the MF membrane, those having a pore diameter of 30 μm or less are preferable, and as the membrane module type of the MF membrane, a flat membrane type or a hollow fiber type can be used.

  The RO membrane device 28 is connected to the MF membrane device 26 via the MF treatment liquid channel 45, and desalinates the MF treatment solution obtained by membrane filtration of the filtrate in the MF membrane device 26 with the RO membrane. As the RO membrane, a polyamide membrane or the like is preferable, and a membrane module of any type such as a spiral type can be used. A desalted water channel 47 is connected to the RO membrane device 28, and desalted water obtained by desalting the MF treatment liquid with the RO membrane is taken out.

  In the present embodiment, the treated water obtained by removing SS in the agglomeration treatment device 22 is further treated by the filtration device 24 and the MF membrane device 26, and the clear water in which the SS concentration is extremely reduced is supplied to the RO membrane device 28. Supply. For this reason, the load of the RO membrane device 28 is small, the contamination of the RO membrane is reduced, and the performance of the RO membrane device 28 can be stabilized. In particular, according to the biological treatment apparatus 10 according to the present invention, treated water with reduced nitrogen and organic matter concentrations can be stably obtained, so that the water recovery apparatus 20 is prevented from being contaminated and demineralized water obtained from the RO membrane apparatus 28. Can be used as cleaning water for electronic devices.

  Hereinafter, the present invention will be described in more detail based on examples using waste water discharged from a liquid crystal factory that manufactures liquid crystals as electronic devices.

[Example 1]
As Example 1, using the processing apparatus 10 shown in FIG. 1, Kjeldahl nitrogen-containing water mixed with drainage discharged from a lithography process, a cleaning process, and an etching process using buffered hydrofluoric acid, a peeling process, a rubbing process, And the alkylene carbonate containing water (mixed alkylene drainage liquid) which mixed the drainage discharged | emitted from an etching process was processed.

Kjeldahl nitrogen-containing water is drained from a lithography process containing TMAH at a concentration of 50 mg-as N / L and from a washing process using a cleaning agent containing N-methyl-2-pyrrolidone (NMP). 50 mg-as N / L) and waste liquid discharged from the etching process using buffered hydrofluoric acid (containing 200 mg-as N / L of ammonia nitrogen). BOD concentration of Kjeldahl nitrogen-containing water 600 mg / L, Kjeldahl nitrogen concentration 300 mg / L, nitrate nitrogen _(NO 3 -N) as a non-Kjeldahl nitrogen concentration was 111 mg / L.

Kjeldahl Nitrogen-containing water, BOD inflow 600 kg / day through a nitrogen-containing water channel 31, _NO 3 -N inflow 200 kg / day, were introduced into the aerobic tank 12 so that the Kj-T inflow 300 kg / day. The conditions of the aerobic tank 12 were as follows.
[Aerobic tank conditions]
Capacity: 1,800m ³
Kjeldahl nitrogen inflow load; 300 kg / m ³ / day Kjeldahl nitrogen volume load; 0.25 kg / m ³ / day BOD inflow load; 600 kg / m ³ / day BOD volume load; 1 kg / m ³ / day MLSS; 3,000 mg / day L
Sponge carrier filling amount; 30% of tank capacity
pH: 5.8 to 8.6
DO: 2 mg / L

  Alkylene carbonate-containing water is an alkylene drainage discharged from the stripping process (containing 1,000 mg / L of ethylene carbonate as alkylene carbonate), a rubbing process drainage containing IPA at a concentration of 600 mg / L, and 80 mg of PGME. This is a mixture of a cleaning process drainage liquid containing a concentration of / L and a cleaning process drainage liquid containing PGMEA at a concentration of 20 mg / L. The BOD concentration of alkylene carbonate-containing water is 2,000 mg / L.

  The denitrification tank 14 was designed to satisfy the following processing conditions in consideration of the processing conditions of the aerobic tank 12. Further, a denitrification tank is introduced at an BOD inflow rate of 2,000 kg / day from the alkylene-containing water channel 32 so that 120% by mass of an organic substance of a theoretical amount necessary for denitrification of the entire amount of non-Kjeldahl nitrogen flowing into the denitrification tank 14 is added. 14 was supplied with water containing alkylene carbonate.

[Denitrification tank conditions]
Capacity: 1,000m ³
Nitrate nitrogen inflow load; 500 kg / m ³ / day Nitrate nitrogen volume load; 0.5 kg / m ³ / day MLSS; 3,000 mg / L
Gel carrier filling amount: 30% of tank capacity
pH: 5.8 to 8.6
DO: 0 mg / L

  The re-aeration tank 16 is designed so that the total amount of organic matter (BOD) contained in the alkylene carbonate-containing water brought into the processing apparatus 10 can be decomposed. Specifically, the processing conditions are as follows.

[Re-aeration tank conditions]
Capacity: 2,000m ³
BOD inflow load; 2,000 kg / m ³ / day BOD volume load; 1 kg / m ³ / day MLSS; 3,000 mg / L
Sponge carrier filling amount: 30% of tank capacity
pH: 5.8 to 8.6
DO: 2 mg / L

  In Example 1, Kjeldahl nitrogen-containing water is introduced into the aerobic tank 12 from the nitrogen-containing water channel 31, and air is blown from the air diffuser 13 so that the DO in the tank is 2 mg / L, thereby oxidizing the Kjeldahl nitrogen and organic matter. An aerobic process was performed.

  The nitrification liquid flowing out from the aerobic tank 12 was introduced into the denitrification tank 14 via the nitrification liquid path 33. In the denitrification tank 14, a denitrification step of denitrifying non-Kjeldahl nitrogen contained in the nitrification solution while adding a fixed amount of alkylene carbonate-containing water from the alkylene-containing water channel 32 to a BOD inflow load of 2,000 kg / day. Went.

  The denitrification treatment liquid flowing out from the denitrification tank 12 was introduced into the re-aeration tank 16 through the denitrification treatment liquid path 35. In the re-aeration tank 16, air was blown from the air diffuser 13 so that the DO in the tank was 2 mg / L, and the denitrification solution was treated aerobically to obtain treated water.

The treated water is introduced into the pressure-floating type agglomeration apparatus 22 via the treatment water channel 37, ferric chloride is added at 500 mg / L as a flocculant, SS is removed by pressure flotation, and the agglomeration treatment liquid. Got. The flocculation treatment liquid was introduced from the flocculation treatment liquid passage 41 into a downward flow type two-layer filtration device 24 using anthracite and sand as a filter medium, and SS was removed by the filtration device 24 to obtain a filtrate. The filtrate was introduced into the cartridge type MF membrane device 26 from the filtrate path 43 and the MF treatment liquid was taken out from the MF treatment liquid path 45. The MF treatment solution was treated with an RO membrane device 28 having a spiral RO membrane to obtain demineralized water. Table 1 processing liquid in each processing stage, shown BOD, S-TOC, TOC, Kj-N, NO 3 -N, SS concentration, the unit as mg / L. In the table below, * is the value including sludge.

[Example 2]
In order to examine the influence when the inflow amount of Kjeldahl nitrogen brought into the processing apparatus 10 is lowered, an experiment was conducted as Example 2 in which Example 1 was changed in the following points. First, about the Kjeldahl nitrogen containing water supplied to the aerobic tank 12, the etching process waste_water | drain using the buffer hydrofluoric acid was removed so that it might become Kj-N density | concentration of 100 mg / L. Thereby, the Kj-N inflow rate to the aerobic tank 12 was reduced to 100 kg / day. The processing conditions of the aerobic tank 12 and the denitrification tank 14 changed by this change are as follows.

[Aerobic tank conditions]
Kjeldahl nitrogen inflow load: 100 kg / m ³ · day [denitrification tank conditions]
Nitrate nitrogen inflow load; 300kg / ^{m 3} · day

  The experimental conditions of Example 2 were the same as those of Example 1 except for the points described above. The results are shown in Table 2.

[Comparative Example 1]
As Comparative Example 1, a test was performed using the processing apparatus 100 shown in FIG. The processing apparatus 100 is connected to the nitrogen-containing water channel 31 instead of the alkylene-containing water channel 32 to the denitrification tank 14, and is connected to the IPA channel 36 for injecting IPA into the denitrification tank 14. The configuration is different from the processing apparatus 10.

  In Comparative Example 1, Kjeldahl nitrogen-containing water and alkylene carbonate-containing water having the same properties as in Example 1 were treated water, but both Kjeldahl nitrogen-containing water and alkylene carbonate-containing water were introduced into the aerobic tank 12. Along with this, in the denitrification tank 14, IPA was added from the IPA path 36 at 1,500 kg / day as an organic substance source necessary for the denitrification reaction.

  The configurations of the aerobic tank 12, the denitrification tank 14, and the re-aeration tank 16 are the same as those of the aerobic tank 12 of the processing apparatus 10. However, in Comparative Example 1, since both Kjeldahl nitrogen-containing water and alkylene carbonate-containing water are introduced into the aerobic tank 12, an aerobic tank supplied with a mixed liquid to be treated with Kjeldahl nitrogen-containing water and alkylene carbonate-containing water is supplied. The BOD inflow to 12 was 2,600 kg / day. With this change, the processing conditions of the aerobic tank 12 and the re-aeration tank 16 were changed as follows.

[Aerobic tank conditions]
Capacity: 3,800m ³
BOD inflow load: 2,600 kg / m ³ · day [re-aeration tank conditions]
Capacity: 250m ³
BOD inflow load: 250 kg / m ³ · day

  The experimental conditions of Comparative Example 1 were the same as those of Example 1 except for the points described above. The results are shown in Table 3.

[Comparative Example 2]
In order to examine the influence when the inflow amount of Kjeldahl nitrogen brought into the processing apparatus 100 decreases, Comparative Example 2 was performed as an experiment in which Comparative Example 1 was changed in the following points in accordance with Example 2. First, about the Kjeldahl nitrogen containing water supplied to the aerobic tank 12, the etching process waste_water | drain using the buffer hydrofluoric acid was removed so that it might become Kj-N density | concentration of 100 mg / L. Thereby, Kj-N inflow derived from Kjeldahl nitrogen-containing water into the aerobic tank was reduced by 100 kg / day. With this change, the processing conditions for the aerobic tank 12 and the denitrification tank 14 were changed as compared to Comparative Example 1 as follows.

[Aerobic tank conditions]
Kjeldahl nitrogen inflow load: 100 kg / m ³ · day [denitrification tank conditions]
Nitrate nitrogen inflow load; 300kg / ^{m 3} · day

  The experimental conditions of Comparative Example 2 were the same as those of Comparative Example 1 except for the points described above. The results are shown in Table 4.

  As shown in Tables 1 and 3, in Comparative Example 1, the BOD value of treated water was 10 mg / L and the S-COD value was 9 mg / L, whereas in Example 1, the BOD value of treated water was 6 mg. / L, S-TOD value is 4 mg / L, indicating that there is a sufficiently significant difference for those skilled in the art. This value greatly affects the degree of membrane contamination, particularly when the water recovery device 20 having the RO membrane device 28 is provided at the subsequent stage of the treatment device 10 and the treated water is reused.

  Further, as shown in Tables 1 to 4, in Examples 1 and 2, the quality of the treated water was constant even when the properties of Kjeldahl nitrogen-containing water with respect to the treatment apparatus 10 were changed, whereas the comparative example In 1 and Comparative Example 2, when the properties of Kjeldahl nitrogen-containing water with respect to the treatment apparatus 100 were changed, the IPA added in the denitrification tank 14 could not be decomposed in the re-aeration tank 16, and the quality of the treated water was greatly deteriorated.

Furthermore, in Example 1 and Example 2, the capacity of the biological treatment tank in the entire treatment apparatus 10 was 4,800 m ³ , whereas in Comparative Example 1 and Comparative Example 2, the capacity of the biological treatment layer in the treatment apparatus 100 as a whole. Became as large as 5,050 m ³ . As described above, according to the present invention, it is possible to obtain treated water having a small size and stable with respect to fluctuations in properties of the liquid to be treated.

  The present invention can be used for the treatment of waste water discharged from an electronic device manufacturing factory or the like.

It is a schematic diagram of the biological treatment apparatus of the waste_water | drain which concerns on one Embodiment of this invention. It is a schematic diagram of the biological treatment apparatus of the waste_water | drain based on the prior art example used for the comparative example.

Explanation of symbols

10 Wastewater biological treatment equipment 12 Aerobic tank 13 Air diffuser (oxygen supply means)
14 Denitrification tank 16 Re-aeration tank 31 Nitrogen-containing water channel 32 Alkylene carbonate-containing water channel 35 Denitrification treatment liquid channel

Claims (6)

An aerobic step of introducing Kjeldahl nitrogen-containing water containing Kjeldahl nitrogen into an aerobic tank equipped with an oxygen supply means, and nitrifying the Kjeldahl nitrogen in the presence of nitrifying bacteria to obtain a nitrification treatment solution;
A denitrification step of introducing the nitrification treatment liquid and alkylene carbonate-containing water containing alkylene carbonate and substantially free of Kjeldahl nitrogen into a denitrification tank, and denitrifying in the presence of denitrifying bacteria. Biological treatment method.   The method further includes a re-aeration step of introducing the effluent from the denitrification step into a re-aeration tank having an oxygen supply means, and decomposing organic substances contained in the effluent from the de-nitrification step in the presence of aerobic microorganisms. The biological treatment method of waste water according to claim 1.   From the electronic device manufacturing process for discharging the Kjeldahl nitrogen-containing water and the alkylene carbonate-containing water, the Kjeldahl nitrogen-containing water and the alkylene carbonate-containing water are collected separately, and the Kjeldahl nitrogen-containing water is aerobic. The biological treatment method of wastewater according to claim 1 or 2, wherein the wastewater is introduced into a tank and the water containing alkylene carbonate is introduced into the denitrification tank. A nitrogen-containing water channel to which Kjeldahl nitrogen-containing water containing Kjeldahl nitrogen is supplied, and an oxygen supply means, and an aerobic tank for nitrifying the Kjeldahl nitrogen in the presence of nitrifying bacteria to obtain a nitrification treatment solution;
A nitrification liquid channel having one end connected to the aerobic tank and supplied with the nitrification liquid, and an alkylene carbonate-containing water channel supplied with alkylene carbonate-containing water containing alkylene carbonate and substantially free of Kjeldahl nitrogen, A biological treatment apparatus for wastewater, comprising a denitrification tank that denitrifies in the presence of denitrifying bacteria.   An organic substance contained in the effluent from the denitrification tank in the presence of an aerobic microorganism, comprising a denitrification treatment liquid path having one end connected to the denitrification tank and supplied with the effluent from the denitrification tank, and oxygen supply means The biological treatment apparatus for waste water according to claim 4, further comprising a re-aeration tank for decomposing the waste water.   The biological treatment apparatus for wastewater according to claim 4 or 5, wherein the re-aeration tank is designed so that 90% by mass or more of all BOD components contained in the alkylene carbonate-containing water can be decomposed.

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