JP2010221112A - Wastewater treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment method for anaerobically treating tetraalkylammonium hydroxide-containing wastewater which can inhibit a decrease in an activity of decomposing tetraalkylammonium hydroxide. <P>SOLUTION: In the wastewater treatment method for the tetraalkylammonium hydroxide-containing wastewater, the wastewater is anaerobically treated in the presence of a monohydric alcohol. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method.

  In recent years, tetraalkylammonium hydroxide such as tetramethylammonium hydroxide (hereinafter sometimes referred to as TMAH) has been used as a positive resist developer for photolithography in the manufacture of semiconductors and liquid crystal panels. With the increase in production of liquid crystals and liquid crystals, the amount of wastewater containing tetraalkylammonium hydroxide is increasing.

  Conventionally, as a treatment method of wastewater containing tetraalkylammonium hydroxide, a treatment method in which tetraalkylammonium hydroxide is thermally decomposed by heating, a treatment method in which tetraalkylammonium hydroxide is removed by a reverse osmosis membrane, an ion exchange resin is used. A processing method to be removed by use is known. However, in the treatment method in which the tetraalkylammonium hydroxide is pyrolyzed, fuel or the like is required for heating, and in the method using a reverse osmosis membrane or an ion exchange resin, the removed tetraalkylammonium hydroxide must be disposed of. is there. Therefore, this type of processing method has a problem that the processing cost is relatively high.

  Further, as a method for treating wastewater containing tetraalkylammonium hydroxide such as TMAH, a wastewater treatment method by aerobic treatment using aerobic microorganisms is known (Patent Document 1). However, the wastewater treatment method by aerobic treatment has a problem that the amount of waste generated with the growth of microorganisms is relatively large, power for supplying oxygen is necessary, and the wastewater treatment cost is relatively high. is there.

  On the other hand, as a wastewater treatment method capable of treating wastewater containing tetraalkylammonium hydroxide such as TMAH at a relatively low cost, a wastewater treatment method by anaerobic treatment (such as methane fermentation) using anaerobic microorganisms is known. Such a wastewater treatment method does not require a fuel for thermal decomposition unlike a treatment method by pyrolysis or the like, and unlike a treatment method using a reverse osmosis membrane or an ion exchange resin, the recovered tetraalkylammonium hydroxide is removed. Further disposal may be unnecessary. However, in the anaerobic treatment performed to decompose most of organic substances such as tetraalkylammonium hydroxide, the decomposition activity of organic substances such as tetraalkylammonium hydroxide tends to decrease over time, and the decomposition activity is reduced. There is a problem that it is difficult to keep it high.

  Therefore, there is a demand for a wastewater treatment method for wastewater containing tetraalkylammonium hydroxide, which can suppress a decrease in the decomposition activity of tetraalkylammonium hydroxide and which can suppress the degradation activity of the tetraalkylammonium hydroxide.

JP 2006-326435 A

  This invention makes it a subject to provide the wastewater treatment method by the anaerobic treatment of the tetraalkylammonium hydroxide containing waste water which can suppress the fall of the decomposition activity of the tetraalkylammonium hydroxide in view of the said problem, a request point, etc. .

  In order to solve the above problems, a wastewater treatment method according to the present invention is a wastewater treatment method for wastewater containing tetraalkylammonium hydroxide, characterized in that the wastewater is subjected to anaerobic treatment in the presence of a monohydric alcohol. To do.

  According to the wastewater treatment method having the above-described configuration, since the wastewater is subjected to anaerobic treatment in the presence of a monohydric alcohol, the monohydric alcohol enhances metabolic activity by which anaerobic microorganisms can decompose tetraalkylammonium hydroxide. Can do. The principle that tetraalkylammonium hydroxide is easily decomposed by the monohydric alcohol is not completely elucidated, but the metabolic activity at which anaerobic microorganisms can decompose tetraalkylammonium hydroxide has been described. It is thought that the monohydric alcohol increases. That is, it is considered that the metabolic activity of anaerobic microorganisms becomes active in order to metabolize the monohydric alcohol, and accordingly, the metabolic activity to decompose tetraalkylammonium hydroxide also becomes active.

  In the wastewater treatment method according to the present invention, the monohydric alcohol is preferably isopropyl alcohol. When the monohydric alcohol is isopropyl alcohol, there is an advantage that metabolic activity capable of degrading tetraalkylammonium hydroxide by anaerobic microorganisms can be further enhanced.

  Moreover, in the waste water treatment method according to the present invention, the monovalent amount of the organic carbon amount of 0.5 to 2 parts by weight with respect to 1 part by weight of the organic carbon amount of the tetraalkylammonium hydroxide contained in the waste water. It is preferable to anaerobically treat the waste water in the presence of alcohol.

  The wastewater treatment method according to the present invention can enhance metabolic activity capable of degrading tetraalkylammonium hydroxide of anaerobic microorganisms. Therefore, the wastewater treatment method of the present invention has an effect that it is possible to suppress a decrease in the decomposition activity of the tetraalkylammonium hydroxide in the anaerobic treatment.

The schematic diagram showing the waste water treatment facility used with the waste water treatment method of this embodiment. The graph which shows the S-TOC removal rate in the waste water treatment of Test Example 1. The graph which shows the removal rate of TMAH by the TMAH density | concentration measurement in the waste water treatment of Test Example 1. The graph which shows the S-TOC removal rate in the waste water treatment of Test Example 2. The graph which shows the removal rate of TMAH by the TMAH density | concentration measurement in the waste water treatment of Test Example 2.

  The wastewater treatment method according to the present invention is a wastewater treatment method for anaerobically treating wastewater containing tetraalkylammonium hydroxide in the presence of a monohydric alcohol.

  Hereinafter, an embodiment of a wastewater treatment method according to the present invention will be described.

The waste water treatment method of this embodiment implements each process described below.
That is, in the wastewater treatment method of the present embodiment, a mixing step of mixing wastewater containing tetraalkylammonium hydroxide and a monohydric alcohol, and the wastewater containing tetraalkylammonium hydroxide are used in the presence of the monohydric alcohol. An anaerobic treatment step for performing anaerobic treatment using anaerobic microorganisms and a separation step for separating the anaerobically treated waste water into treated water and sludge are performed.

  The waste water treatment method of the present embodiment will be described more specifically with reference to the drawings.

The waste water treatment method of this embodiment can be implemented using the waste water treatment facility shown in FIG.
That is, in the mixing step, for example, a raw water tank 1 in which the waste water is stored and a collecting tank 2 in which the waste water supplied from the raw water tank 1 and the monohydric alcohol are mixed are used. Specifically, for example, wastewater containing tetraalkylammonium hydroxide stored in the raw water tank 1 is supplied to the collecting tank 2, and the monohydric alcohol is added to the wastewater supplied to the collecting tank 2. In this way, the waste water containing tetraalkylammonium hydroxide and the monohydric alcohol are mixed.

  In the anaerobic treatment step, the waste water to which the monohydric alcohol has been added is supplied from the collecting tank 2 to a reactor 3 filled with granular sludge (granular sludge) containing anaerobic microorganisms. The waste water containing tetraalkylammonium hydroxide is subjected to anaerobic treatment in the presence of the monohydric alcohol by utilizing anaerobic metabolism of the anaerobic microorganisms contained in the sludge.

  In the separation step, a separation tank 4 that separates the treated water and sludge treated in the anaerobic treatment step and a treated water tank 5 that stores the treated water treated in the anaerobic treatment step are used. Specifically, the liquid mixture containing sludge discharged from the upper portion of the reactor 3 in accordance with the anaerobic treatment of the waste water is separated into treated water and sludge treated with the waste water in the separation tank 4, and the separation tank The treated water separated in 4 is supplied to the treated water tank 5 to store the treated water, and the sludge separated in the separating tank 4 is sent to the collecting tank 2.

  Of the above steps, the details of the anaerobic treatment step will be described first.

  In the anaerobic treatment step, the wastewater containing tetraalkylammonium hydroxide is anaerobically anaerobically treated using the anaerobic microorganisms contained in the sludge in the reactor 3 in the presence of the monohydric alcohol. That is, the anaerobic treatment step is carried out anaerobically using metabolic activity of anaerobic microorganisms in a state where the monohydric alcohol and the waste water containing the tetraalkylammonium hydroxide are mixed.

  The waste water to be treated in the anaerobic treatment step is not particularly limited as long as it contains tetraalkylammonium hydroxide. The tetraalkylammonium hydroxide is used as a positive photoresist developer for photolithography, for example, in the manufacture of semiconductors and liquid crystal panels, and can be included in the wastewater of a semiconductor or liquid crystal panel manufacturing factory. . It is also included in wastewater from chemical manufacturing plants that produce tetraalkylammonium hydroxide.

  The waste water treated in the anaerobic treatment step may contain various components in addition to tetraalkylammonium hydroxide. For example, the waste water may contain a resist component, a surfactant, and the like dissolved and dissolved.

  Examples of the tetraalkylammonium hydroxide include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), and benzyltrimethylammonium hydroxide. Is exemplified. Among them, tetramethylammonium hydroxide (TMAH) is most commonly used as the developer for the positive photoresist described above, and is usually contained in the wastewater of a semiconductor or liquid crystal panel manufacturing factory. Examples of tetraalkylammonium hydroxide include tetramethylammonium hydroxide (TMAH).

  The concentration of the tetraalkylammonium hydroxide contained in the waste water is preferably 12,000 mg / L or less. By being 12,000 mg / L or less, it becomes a suitable load with respect to the anaerobic microorganisms currently hold | maintained in a reactor, Furthermore, the ammonia concentration which is a decomposition product of the tetraalkylammonium hydroxide is an allowable range of anaerobic treatment. Since the growth of anaerobic microorganisms can be suppressed easily, tetraalkylammonium hydroxide can be efficiently decomposed. Moreover, as a density | concentration in which the said tetraalkylammonium hydroxide is contained in the said waste_water | drain, 100 mg / L or more is preferable and 500 mg / L or more is more preferable. When it is 100 mg / L or more, there is an advantage that the tetraalkylammonium hydroxide can be easily used as an organic substance used for metabolism of anaerobic microorganisms. There is an advantage that it can be easily done. In the case of treatment using granular sludge that can easily retain anaerobic microorganisms in the reactor and maintain a higher removal rate of the tetraalkylammonium hydroxide, the concentration is 1500 mg / L or more. Is preferred.

The monohydric alcohol is a water-soluble compound that has one hydroxy group in the molecule and dissolves in water at an arbitrary ratio. Examples of the monohydric alcohol include methyl alcohol, ethyl alcohol, isopropyl alcohol and the like.
The monohydric alcohol can be used alone or in combination of two or more.

  As the monohydric alcohol, isopropyl alcohol is preferable in that the tetraalkylammonium hydroxide is more easily decomposed by the anaerobic treatment.

  In the anaerobic treatment step, a monohydric alcohol composition containing the monohydric alcohol can be used to add the monohydric alcohol to the waste water. Specifically, as the monohydric alcohol composition, for example, waste liquid containing monohydric alcohol, waste water containing monohydric alcohol discharged from a factory, or the like can be used. Examples of the waste liquid containing monohydric alcohol include waste liquid containing a relatively high concentration of monohydric alcohol used when manufacturing industrial materials such as liquid crystal panels. Examples include waste water in which monohydric alcohol is discharged from a factory or the like together with washing water in washing the material. By using waste liquid and waste water containing such monohydric alcohol as a monohydric alcohol supply source, it is possible to suppress degradation of the decomposition activity of tetraalkylammonium hydroxide without purchasing monohydric alcohol, and at the same time contain monohydric alcohol. There is an advantage that waste liquid and waste water can be purified.

The addition amount of the monohydric alcohol is not particularly limited, but is an amount that provides 0.5 to 2 parts by weight of organic carbon with respect to 1 part by weight of organic carbon of tetraalkylammonium hydroxide. Preferably there is. When the amount of the monohydric alcohol is such that the amount of the organic carbon is 0.5 parts by weight or more with respect to 1 part by weight of the organic carbon of the tetraalkylammonium hydroxide, the decomposition of the tetraalkylammonium hydroxide Is promoted, and there is an advantage that the decomposition activity of the tetraalkylammonium hydroxide can be maintained for a longer time.
Moreover, when the addition amount of the monohydric alcohol is an amount that is 2 parts by weight or less of the organic carbon amount of 1 part by weight of the tetraalkylammonium hydroxide, it is metabolized by anaerobic microorganisms. There is an advantage that the load on the metabolic activity of anaerobic microorganisms can be reduced because organic substances that are decomposed into lower molecular weight compounds are reduced. That is, there is an advantage that the metabolic activity for decomposing the monohydric alcohol, which is one kind of organic substance, can be suppressed to a lower level, and the metabolism for decomposing the tetraalkylammonium hydroxide can be increased accordingly. . In addition, since the load on the metabolic activity of anaerobic microorganisms can be kept lower, the metabolic activity of anaerobic microorganisms is less likely to reach its limit, and even when the concentration of tetraalkylammonium hydroxide, an organic substance, increases. There is an advantage that stable waste water treatment can be possible.

The anaerobic treatment step can be performed, for example, by measuring the concentration of tetraalkylammonium hydroxide and controlling the amount of the monohydric alcohol to be added to a predetermined amount according to the change in the concentration. By carrying out in this way, there is an advantage that the monohydric alcohol to be added can be minimized, and the load on the metabolic activity of the anaerobic microorganisms can be reduced.
Specifically, in the anaerobic treatment step, while measuring the amount of tetraalkylammonium hydroxide contained in the wastewater, 0.1 part by weight of the organic carbon content of the tetraalkylammonium hydroxide determined by the measurement. The waste water is preferably subjected to anaerobic treatment in the presence of an amount of monohydric alcohol that is an amount of 5 to 2 parts by weight of organic carbon.

  Further, in the anaerobic treatment step, after the decomposition rate of the tetraalkylammonium hydroxide becomes relatively high, the decomposition rate of the tetraalkylammonium hydroxide is maintained relatively high without adding a monohydric alcohol to the waste water. obtain. By not adding monohydric alcohol to the waste water, the monohydric alcohol used can be reduced, and the load on the metabolic activity of anaerobic microorganisms can be further reduced.

  Here, the amount of organic carbon is a value used to indicate the mass of carbon atoms contained in the organic substance. That is, in the case of a compound having a clear molecular structure, the value is obtained by multiplying the proportion of the atomic weight of carbon atoms in the molecular weight of the compound by the weight of the predetermined amount of the compound. In addition, when using a monohydric alcohol mixture or the like in which the content of each monohydric alcohol is unknown, a predetermined amount of the mixture is dissolved in a predetermined amount of water, and the total organic carbon content of the solution is determined as the total organic carbon concentration. It is a value determined as the amount of organic carbon in the monohydric alcohol mixture by measuring with a meter and calculating from the measured value and the amount of the dissolved mixture.

Since the anaerobic treatment does not need to continue supplying molecular oxygen, the power cost consumed for this can be suppressed. Therefore, it can be carried out at a lower cost as compared with the aerobic treatment using the aerobic metabolic activity of the aerobic microorganism that needs to continue to supply molecular oxygen. In addition, although the growth rate of microorganisms is slower than that of the aerobic treatment, it is suitable for the treatment of wastewater containing a relatively high concentration of organic substances, and the amount of sludge generated can be suppressed, so surplus sludge treatment etc. is also low cost. This is a process that can be performed.
In the anaerobic treatment, various organic substances can be decomposed into lower molecular weight compounds by metabolic activities of anaerobic microorganisms, and various inorganic substances can be metabolized into other substances. As what can be produced | generated in the said anaerobic process, ammonia, hydrogen, hydrogen sulfide, etc. other than methane, a carbon dioxide gas, etc. are mentioned. Specifically, a part of the organic substance to be treated can be decomposed by the anaerobic treatment, and biogas containing methane or the like can be generated. This biogas can be recovered from the reactor 3 and used, for example, as fuel.

  In the anaerobic treatment step, the waste water containing the monohydric alcohol is treated by the anaerobic treatment. That is, in the anaerobic treatment, the tetraalkylammonium hydroxide contained in the waste water can be decomposed into lower molecular weight compounds by the anaerobic microorganisms contained in the sludge. In the anaerobic treatment, the monohydric alcohol can enhance the ability of anaerobic microorganisms to decompose tetraalkylammonium hydroxide, and can maintain the activity of the anaerobic microorganisms to decompose tetraalkylammonium hydroxide for a longer time.

  The principle that tetraalkylammonium hydroxide is easily decomposed by the monohydric alcohol is not completely elucidated, but the metabolic activity at which anaerobic microorganisms can decompose tetraalkylammonium hydroxide has been described. It is thought that the monohydric alcohol increases. That is, it is considered that the metabolic activity of anaerobic microorganisms becomes active in order to metabolize the monohydric alcohol, and accordingly, the metabolic activity to decompose tetraalkylammonium hydroxide also becomes active.

The sludge used in the anaerobic treatment step is not particularly limited as long as it contains anaerobic microorganisms and can perform the anaerobic treatment, but the anaerobic microorganisms can be kept at a high concentration in the reactor. The granular sludge is preferred in that it can be easily separated from the treated water by solid-liquid separation. It is also possible to use carrier-attached sludge in which anaerobic microorganisms are attached to a carrier such as plastic.
Moreover, as said sludge, the sludge which carried out the anaerobic process of the organic waste water can be used. Specifically, anaerobic sludge that has been anaerobically treated for organic wastewater such as chemical factory wastewater, papermaking wastewater, sewage sludge, food wastewater, and hair washing wastewater can be used. It is preferable to use anaerobic sludge in which organic wastewater containing monohydric alcohol is anaerobically treated.

  The concentration of the sludge in the reaction tank is preferably 10,000 to 100,000 mg / L, and more preferably 20,000 to 50,000 mg / L. Moreover, as the residence time of the waste_water | drain in a reaction tank, about 2-48 hours are preferable and 4-48 hours are more preferable.

  Although the method of the anaerobic treatment process is not particularly limited, an upward flow using granulated sludge is used as in the method performed in the reactor 3 in that a high load operation is possible and the apparatus can be made compact. It is preferable to employ a type anaerobic sludge bed (UASB) system.

  The anaerobic treatment step is preferably performed in the presence of nutrient salts for anaerobic microorganisms such as phosphorus and iron. By carrying out in the presence of the nutrient salt, an environment in which anaerobic microorganisms can easily grow can be obtained, and therefore, there is an advantage that metabolic activity of the anaerobic microorganisms can be activated.

  Next, details of each of the mixing step and the separation step will be described with reference to the drawings.

  In the mixing step, waste water containing tetraalkylammonium hydroxide and the monohydric alcohol are mixed.

  That is, in the mixing step, for example, first, wastewater containing tetraalkylammonium hydroxide stored in the raw water tank 1 is supplied to the collecting tank 2. As a means for supplying, a general pump P can be used.

  In order to optimize the efficiency of the anaerobic treatment step, the pH of the waste water in the collecting tank 2 can be adjusted with an alkaline aqueous solution or the like. An alkaline aqueous solution or the like can be supplied to the collecting tank 2 from a tank (not shown). The pH in the anaerobic treatment is preferably 6-8.

  Next, in the mixing step, the monohydric alcohol is added to the wastewater supplied to the collecting tank 2. A desired amount of the monohydric alcohol can be added to the collecting tank 2 in order to optimize the efficiency of the anaerobic treatment in the reactor 3.

  In the mixing step, as described above, the monohydric alcohol and waste water containing tetraalkylammonium hydroxide can be mixed using waste liquid or waste water containing monohydric alcohol.

  In the mixing step of the present embodiment, the monohydric alcohol is added to the collecting tank 2, but the method is not necessarily limited to such a method. For example, the monohydric alcohol can be directly added to the raw water tank 1 and the monohydric alcohol and the waste water can be mixed in the raw water tank 1. Further, the monohydric alcohol is added in the middle of the pipe connecting the raw water tank 1 and the collecting tank 2, or in the middle of the pipe connecting the collecting tank 2 and the reactor 3, or the monohydric alcohol is added to the reactor 3. For example, a method of mixing the monohydric alcohol and the waste water may be employed.

  Subsequently, the separation step will be described. In the separation step, the waste water that has been anaerobically treated is separated into treated water and sludge.

That is, in the separation step, first, the mixed liquid containing the sludge discharged from the upper part of the reactor 3 in accordance with the anaerobic treatment of the wastewater is separated into treated water and sludge treated with the wastewater. . The separation can be performed by using a separation tank 4 used in general anaerobic treatment.
The separation step is not carried out using the separation tank 4 as described above, but a solid-liquid separation means such as a GSS device (gas-solid-liquid separation device) composed of a plurality of inclined plates is provided on the reactor 3. By providing, it can be implemented.

  In the separation step, the treated water is supplied to the treated water tank 5 for storing the treated water separated in the separation tank 4 to store the treated water. The tetraalkylammonium hydroxide concentration of the treated water can be lower than the concentration of the waste water before the anaerobic treatment by performing the anaerobic treatment step. Moreover, the density | concentration of the organic substance contained in the said treated water shown by total organic carbon amount (TOC) etc. can become smaller than the said waste_water | drain before anaerobic treatment.

Further, in the separation step, the separated sludge is sent to the collecting tank 2. There is an advantage that the anaerobic sludge concentration in the reaction tank can be maintained at a high concentration by sending the separated sludge back to the collecting tank 2.
When the anaerobic treatment method is a fixed bed type, the sludge separated in the separation tank 4 is not normally sent to the reactor, but when the anaerobic sludge concentration in the reactor decreases, the separation tank 4 The separated sludge can be sent to the reactor 3. Thereby, there exists an advantage that the anaerobic sludge density | concentration can be recovered | restored.

  In addition, the aspect which performs another process to the said waste_water | drain further before or after the said anaerobic treatment process may be contained in this invention. That is, for example, after the anaerobic treatment step, an aerobic treatment using metabolic activity of aerobic microorganisms can be performed, and for example, an anaerobic treatment of a different method from the anaerobic treatment step is performed before the anaerobic treatment step. It can also be implemented. In addition, the step of separating the photoresist in the waste water from the waste water can be performed before the anaerobic treatment step.

The present invention is not limited to the above-exemplified waste water treatment method.
Moreover, the various aspects used in a general waste water treatment method can be employed within a range that does not impair the effects of the present invention.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Test Example 1)
According to the wastewater treatment flow shown in FIG. 1, wastewater treatment for anaerobic treatment was performed as follows.
A 5 L reactor having an inner diameter of 100 mmφ and a liquid surface height of 635 mm was filled with granular sludge from a food factory wastewater treatment facility (UASB facility) so that the sludge concentration would be 25,000 mg / L. In the raw water tank, wastewater to which a predetermined amount of tetramethylammonium hydroxide (TMAH) as tetraalkylammonium hydroxide or isopropyl alcohol (hereinafter also referred to as “IPA”) as a monohydric alcohol is appropriately added, that is, artificial water is added. Simulated wastewater that can be prepared in an automated manner was stored. Such simulated waste water was sent to the collecting tank, and the pH adjustment value of the waste water in the collecting tank was 7.0. Waste water in the collecting tank was supplied from the bottom of the reactor. The water temperature in the reactor was controlled to 35 ° C. Under such conditions, wastewater treatment by anaerobic treatment was performed while appropriately adding a predetermined amount of TMAH or IPA to the raw water tank.
Specifically, wastewater treatment was performed under the conditions shown in Table 1. That is, until the start of the 52nd day, the TMAH concentration in the wastewater was set to 5000 mg / L so that the total organic carbon content (TOC) was about 2640 (mg / L). In addition, wastewater treatment was carried out with a daily wastewater supply amount of 1.7 L.
The TOC removal rate started to increase from the 10th day after the start of the test, and reached a TOC removal rate of nearly 100% on the 20th day. However, since the removal rate began to decrease after the 20th day, the TOC removal rate started on the 52nd day. Replace the granular sludge with the same one at the start, and set the TMAH concentration in the waste water to 2500 mg / L so that the total organic carbon content (TOC) is about 1320 (mg / L). The wastewater treatment was continued with 3.7 L of wastewater supplied per day.
After exchanging the granule sludge, the TOC removal rate started to rise, but suddenly decreased again, and the waste water containing no monohydric alcohol could not be decomposed by TMAH.
The degradability of TMAH is the same as that of the treated water that was discharged from the upper part of the reactor and then separated in the separation tank. Treated water TOC concentration (S-TOC) of filtered water filtered by 5C filter paper (corresponding to 5 types C specified in JIS P 3801 [filter paper (for chemical analysis)]) and waste water supplied to the collecting tank The drainage TOC concentration (S-TOC) was evaluated based on the measured value. More specifically, these two TOC concentrations are measured over time, and the value obtained by dividing the difference between the wastewater TOC concentration and the treated water TOC concentration at that time by the wastewater TOC concentration is the soluble TOC removal rate (S-TOC removal). Rate). The TOC concentration was measured using a commercially available total organic carbon densitometer. A graph showing the S-TOC removal rate is shown in FIG.
Furthermore, the concentration of TMAH was analyzed by ion chromatography, and the removal rate was calculated by the same method as the TOC concentration. A graph showing the removal rate of TMAH by TMAH concentration measurement is shown in FIG.

(Test Example 2)
Except for the points shown in Table 2, wastewater treatment was started in the same manner as in Test Example 1.
That is, at the start of the test, the IPA concentration in the waste water was set to 1500 mg / L so that the total amount of organic carbon (TOC) was 900 (mg / L). In addition, the supply amount of the wastewater per day was 3L.
Since the TOC removal rate became stable about 2 weeks after the start of the test, the total organic carbon content (TOC) of TMAH was 880 (mg / L) and the total organic carbon content (TOC) of IPA was 1760 (mg / L) on the 29th day. The waste water adjusted to L) was supplied 1.5 L per day, and the waste water treatment was continued.
From the 56th day onward, the total organic carbon content (TOC) of TMAH was adjusted to 1060 (mg / L), and the total organic carbon (TOC) of IPA was adjusted to 1580 (mg / L).
From the 85th day onward, the total organic carbon content (TOC) of TMAH was adjusted to 1320 (mg / L), and the total organic carbon (TOC) of IPA was adjusted to 1320 (mg / L).
From the 104th day onward, the total organic carbon content (TOC) of TMAH was adjusted to 1760 (mg / L), and the total organic carbon (TOC) of IPA was adjusted to 880 (mg / L).
After the 133rd day from the start, the addition of IPA was stopped, the total organic carbon content (TOC) of TMAH was adjusted to 1760 (mg / L), and the amount of wastewater supplied per day was set to 3L.
The test was completed on the first 179 days.
FIG. 4 shows a graph showing the S-TOC removal rate, and FIG. 5 shows a graph showing the TMAH removal rate by TMAH concentration measurement.

  As can be recognized from FIGS. 4 and 5, by adding IPA in an amount corresponding to 0.5 parts by weight or more of the total organic carbon weight with respect to 1 part by weight of the organic carbon weight of TMAH, the decomposition activity of TMAH. Can be kept high. In addition, the activity of decomposing TMAH can be maintained for a relatively long time even after the addition of IPA is stopped.

DESCRIPTION OF SYMBOLS 1 ... Raw water tank 2 ... Collecting tank 3 ... Reactor 4 ... Separation tank 5 ... Treated water tank

Claims (3)

  A wastewater treatment method for wastewater containing tetraalkylammonium hydroxide, wherein the wastewater is anaerobically treated in the presence of a monohydric alcohol.   The wastewater treatment method according to claim 1, wherein the monohydric alcohol is isopropyl alcohol.   The waste water is anaerobically treated in the presence of the monohydric alcohol in an amount of 0.5 to 2 parts by weight with respect to 1 part by weight of the organic carbon content of the tetraalkylammonium hydroxide contained in the waste water. The wastewater treatment method according to claim 1 or 2.

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