Method for treating wastewater containing TMAH

Abstract

To provide a treatment method of TMAH-containing wastewater that can suppress organic acid accumulation in an anaerobic treatment tank and can maintain a TMAH decomposition rate to be high.SOLUTION: In a treatment method of TMAH-containing wastewater by introducing and treating TMAH-containing wastewater in an anaerobic treatment tank having a volume load of CODCr of 4 kg-CODCr / m3 / d or over, an organic acid concentration of the treatment water is (volume load of CODCr)×(50+100)mg / L or under as a sum total of CODCr conversion concentration of the organic acid. Preferably, the TMAH-containing wastewater includes TMAH at a concentration of 80wt% or over of TOC and operation is run at a MAH concentration of 5000 mg / L or over.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for treating wastewater containing TMAH (tetramethylammonium hydroxide), and more particularly to a method for anaerobic treatment of wastewater containing TMAH. [Background technology]

[0002] As a method for treating TMAH-containing wastewater discharged from the electronic component manufacturing process or the like, there is a method for subjecting TMAH-containing wastewater to anaerobic treatment (Patent Documents 1 to 3).

[0003] Patent Document 1 describes a method for anaerobic treatment of TMAH-containing wastewater by reducing the TMAH concentration to 20,000 mg / L or less.

[0004] Patent Document 2 describes the addition of molasses to TMAH-containing wastewater to perform anaerobic treatment.

[0005] Patent Document 3 describes the addition of an alkalinity regulator such as a phosphate or carbonate to TMAH-containing wastewater to perform anaerobic treatment. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-184178 A [Patent Document 2] JP 2010-274207 A [Patent Document 3] JP 2011-11171 A Summary of the Invention [Problem to be solved by the invention]

[0007] During anaerobic treatment of wastewater containing TMAH, the TMAH decomposition rate may suddenly decrease, resulting in an increase in the residual TMAH concentration in the treated water.

[0008] As a result of extensive research, the present inventors have found that this decrease in the TMAH decomposition rate is caused by the accumulation of organic acids in the anaerobic treatment tank.

[0009] An object of the present invention is to provide a method for treating wastewater containing TMAH, which can suppress the accumulation of organic acids in the anaerobic treatment tank and maintain a high TMAH decomposition rate. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides the following method.

[0011] [1] COD of TMAH-containing wastewater Cr Volume load 4kg-COD Cr / m 3 / d or more into an anaerobic treatment tank for treatment. The organic acid concentration in the treated water is the COD of organic acids. Cr As the sum of the converted concentrations (COD Cr The volumetric load of TMAH-containing wastewater is less than (volume load of TMAH x 50 + 100) mg / L.

[0012] [2] The method for treating TMAH-containing wastewater according to [1], wherein the TMAH-containing wastewater contains TMAH at 80 wt% or more of TOC and is anaerobically treated when the TMAH concentration is 5,000 mg / L or more.

[0013] [3] COD of organic acids in the treated water Cr The total converted concentration (COD Cr If the COD concentration of the treated water is greater than the volumetric load of (COD x 50 + 100) mg / L, the organic acid concentration of the treated water can be reduced by adding sludge containing organic acid-utilizing methanogenic bacteria to the anaerobic treatment tank. Cr As the sum of the converted concentrations (COD Cr The method for treating TMAH-containing wastewater according to [1] or [2], characterized in that the TMAH-containing wastewater is treated so that its volumetric load is not more than (volume load of TMAH x 50 + 100) mg / L.

[0014] [4] The method for treating TMAH-containing wastewater according to [3], wherein sludge containing the organic acid-utilizing methanogenic bacteria is added at 0.5 to 30 wt%-VSS relative to the amount of sludge held in the anaerobic treatment tank.

[0015] [5] The organic acid activity of the sludge containing the organic acid-utilizing methanogenic bacteria is 0.01 kg-COD Cr The method for treating TMAH-containing wastewater according to any one of [1] to [4], wherein the TMAH concentration is 1 / kg-VSS / d or more.

[0016] [6] The method for treating TMAH-containing wastewater according to any one of [1] to [5], characterized in that after the addition of sludge containing the organic acid-utilizing methanogens, the proportion of the organic acid-utilizing methanogens in the total amount of methanogens in the anaerobic treatment tank is 10 to 30 wt%.

[0017] [7] The method for treating TMAH-containing wastewater according to any one of [3] to [6], wherein the organic acid-utilizing methanogenic bacterium belongs to the genus Methanosarcina.

[0018] [8] The method for treating TMAH-containing wastewater according to [6] or [7], wherein the proportion of the genus Methanomethylovorans among all methanogenic bacteria in the anaerobic treatment tank is 30 to 80 wt%.

[0019] [9] The method for treating TMAH-containing wastewater according to any one of [1] to [8], wherein the pH in the anaerobic treatment tank is 7.0 to 8.3.

[0020]

[10] The method for treating TMAH-containing wastewater according to any one of [1] to [9], wherein the hydrogen concentration in the gas phase is 5% or less. Effect of the Invention

[0021] In the present invention, the organic acid concentration in the anaerobic treatment tank is Cr As the sum of the converted concentrations (COD CrBy anaerobically treating the TMAH-containing wastewater so that the TMAH decomposition rate is less than (volume load of TMAH x 50 + 100) mg / L, a high TMAH decomposition rate can be maintained. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a flow chart showing an example of the method of the present invention. [Diagram 2] FIG. 1 is a flow chart showing an example of the method of the present invention. [Diagram 3] FIG. 1 is a flow chart showing an example of the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will now be described in further detail.

[0024] In the present invention, the organic acid concentration in the anaerobic treatment tank is Cr As the sum of the converted concentrations (COD Cr The wastewater containing TMAH is anaerobically treated so that the TMAH concentration is not more than (volume load of the anaerobic treatment tank) × 50 + 100 mg / L. The treated water is preferably effluent from the anaerobic treatment tank, but if the anaerobic treatment is of the complete mixing type, the water in the tank may be used.

[0025] The decomposition of TMAH is inhibited by organic acids. A certain amount of organic acids is always produced during the decomposition process of TMAH. When the TMAH volume load is low, TMAH decomposition is inhibited even at low organic acid concentrations. However, when the TMAH volume load is high, the TMAH decomposition activity increases, allowing the plant to tolerate higher organic acid concentrations. Therefore, the COD Cr The inhibitory concentration of organic acids was determined by the proportional equation of volume loading.

[0026] The inhibition concentration of this organic acid is Cr Batch tests were carried out using test sludge with different volume loads, and the organic acid concentration at which the TMAH decomposition activity decreased by 10% was calculated for each COD Cr The volumetric load of COD CrThe relationship between the volume load of COD and the inhibition concentration of organic acids is shown in Table 1. Cr As the sum of the converted concentrations (COD Cr It was experimentally found that the volume load of the septic tank should be less than (volume load of the septic tank x 50 + 100) mg / L.

[0027] [Table 1]

[0028] In addition, measures to deal with high TMAH volumetric loads include diluting the raw water, adjusting the raw water inflow rate, and promoting the decomposition of organic acids.

[0029] In addition, TMAH is COD Cr Since TMAH cannot be detected by COD, the theoretical oxygen demand (ThOD) of TMAH is calculated by Cr Specifically, the value of TMAH measured by liquid chromatography or ion chromatography, etc., converted into ThOD is calculated as COD Cr In addition, if the majority of the organic matter in the raw water is TMAH or if other organic components are known substances, a correlation between TOC and ThOD may be obtained and continuous measurements may be performed using a TOC meter.

[0030] The TMAH concentration in the TMAH-containing wastewater to be treated by the method of the present invention is preferably 5,000 mg / L or more, more preferably 7,500 mg / L or more, and particularly preferably 10,000 mg / L or more. The TMAH concentration in the TMAH-containing wastewater is preferably 250,000 mg / L or less, and particularly preferably 50,000 mg / L or less.

[0031] In this TMAH-containing wastewater, 80 wt % or more, preferably 90 wt % or more, and more preferably 95 wt % or more of the TOC in the wastewater is TMAH.

[0032] An example of such TMAH-containing wastewater is wastewater from an electronic device manufacturing process, but is not limited to this.

[0033] The above TMAH-containing wastewater was treated as COD Cr Volume load 4kg-COD Cr / m 3 / d or more, it is introduced into the anaerobic treatment tank and treated anaerobically. Cr The volume load is 4~20kg-COD Cr / m 3 d, especially 8~15kg-COD Cr / m 3 ·d level is preferable.

[0034] The preferred form of anaerobic treatment is the MBR method (especially the outer membrane type), the UASB method, or the carrier method.

[0035] Figure 1 shows an anaerobic treatment apparatus using an external membrane MBR system. Raw water (wastewater containing TMAH) is supplied to anaerobic treatment tank 1 and undergoes anaerobically treatment. Anaerobic treatment tank 1 is equipped with an agitator blade 2, which agitates the inside of the tank. A portion of the liquid in the tank is sent via piping 3 and pump 4 to a raw liquid chamber 5a of a membrane separator 5 outside the tank. The anaerobic treatment tank 1 may be filled with a carrier.

[0036] Inside the membrane separator 5, a raw liquid chamber 5a and a permeate chamber 5b are formed by a separation membrane 5m. A UF ​​membrane is preferably used as the membrane 5m. The permeate that permeates the membrane 5m is taken out from the permeate chamber 5b as treated water. The liquid that does not permeate the membrane 5m is returned to the anaerobic treatment tank 2 through a pipe 6.

[0037] Figure 2 shows an anaerobic treatment device using the UASB method. Raw water is passed upward through a UASB reactor 7, which serves as an anaerobic treatment tank, and anaerobically treated as it passes through a sludge blanket 7a. Biogas and treated water are taken out from the top of the tower.

[0038] Figure 3 shows an anaerobic treatment tank using the carrier method. A carrier, for example a gel-like carrier, is placed in the anaerobic treatment tank 8. A draft tube 10 is provided surrounding a propeller-type agitator 9. By rotating the agitator 9, a downward flow is formed in the draft tube 10, and an upward flow is formed between the draft tube 10 and the inner wall of the tank.

[0039] The gel carrier is not particularly limited, but polymer gel carriers such as polyvinyl alcohol, polyethylene glycol, polyurethane, etc., can be used.

[0040] As mentioned above, when TMAH is anaerobically treated at a high load, hydrogen accumulates in the gas phase and organic acids produced by hydrogen-utilizing acetogenic bacteria, as well as organic acids produced via other pathways, can accumulate, inhibiting the methanogenic bacteria that break down TMAH.

[0041] In order to prevent the accumulation of organic acids in the anaerobic treatment tank, the concentration of organic acids in the treated water is monitored and the COD of the organic acids is checked. Cr The total of the converted concentration is calculated as a specified value (COD Cr When the concentration of organic acid assimilation in the anaerobic treatment tank exceeds "volume load of the anaerobic treatment tank" × 50 + 100) mg / L, organic acid assimilating methanogens, preferably organic acid and hydrogen assimilating methanogens, are added. The organic acid assimilating methanogens may be added directly to the anaerobic treatment tank or may be added to the raw water introduced into the anaerobic treatment tank.

[0042] By adding organic acid-utilizing methanogens in this way, the ratio of methanogens in the anaerobic treatment tank is increased, and the TMAH decomposition rate can be maintained high. According to the present invention, the TMAH concentration in the treated water can be reduced to 300 mg / L or less, particularly 100 mg / L or less.

[0043] As described above, the treated water in which the organic acid concentration is measured may be the effluent water from the anaerobic treatment tank, or in the case of a complete mixing type anaerobic treatment tank, it may be the water in the tank.

[0044] In the present invention, it is preferable to measure the organic acid concentration in the treated water at least once a week, and particularly preferably once every 2 to 3 days.

[0045] In the present invention, the COD of organic acids in the treated water is Cr The total converted concentration is below a specified value (COD CrThe volume load of the organic acid is adjusted to less than (volume load x 50 + 100) mg / L. Cr The method for measuring the converted concentration is to use values ​​obtained by converting organic acid measurements by liquid chromatography into values ​​calculated using ThOD. Alternatively, gas chromatography can be used, and EC and COD of organic acids can be used. Cr It is also possible to take a correlation with the temperature and measure continuously using an EC meter.

[0046] Organic Acid COD Cr When the total converted concentration is higher than the above-mentioned predetermined value, sludge containing organic acid-utilizing, preferably organic acid- and hydrogen-utilizing methanogenic bacteria is added in an amount of 0.5 to 30%-VSS, preferably 1 to 25%-VSS, more preferably 2 to 20%-VSS by weight of sludge relative to the amount of sludge held in the anaerobic treatment tank.

[0047] As organic acid-utilizing methanogens, Methanosarcina and Methanosaeta are preferred. Methanosarcina and Methanosaeta are organic acid and hydrogen-utilizing methanogens. As sludge containing organic acid-utilizing methanogens, sludge collected from an anaerobic treatment tank for food factory wastewater containing organic acids in the treatment process, or a sludge digestion tank for sewage, is preferred. The sludge to be added may be in the form of granules or suspended sludge.

[0048] The sludge containing organic acid-utilizing methanogenic bacteria added to the anaerobic treatment tank has an organic acid activity of 0.01 kg-COD Cr It is desirable to have a capacity of 0.05kg-COD / kg-VSS / d or more. Cr / kg-VSS / d or more, more preferably 0.1kg-COD Cr / kg-VSS / d or more. The organic acid activity is calculated by taking a sample of the sludge in the tank, conducting a batch test using organic acid, preferably acetic acid, as the substrate, and calculating the maximum decomposition rate from the methane production rate. By adding this sludge, the organic acid activity of the entire anaerobic treatment tank is 0.002 kg-COD Cr It is desirable that it is / kg-VSS / d or higher.

[0049] After the addition of sludge containing organic acid-utilizing methanogens, it is preferable that 30 to 80 wt% of the total number of methanogens in the anaerobic treatment tank be of the genus Methanomethylovorans and 10 to 30 wt% be of the genus Methanosarcina, which is an organic acid and hydrogen-utilizing methanogen.

[0050] In the present invention, in order to improve the accuracy of the treatment status in the anaerobic treatment tank, the concentration of hydrogen (hydrogen molecules) in the biogas generated in the anaerobic treatment tank may also be measured. + However, during high-load treatment, it tends to remain in the tank, and if it does remain, it becomes hydrogen, and if there are bacteria that produce organic acids from hydrogen and CO2, and if there are few methanogenic bacteria in the system that can assimilate organic acids and hydrogen, this leads to an accumulation of organic acids.When treating wastewater containing high concentrations of TMAH, the TMAH itself and ammonia produced as a metabolic product tend to reduce the number of methanogenic bacteria in the system that can assimilate organic acids and hydrogen.

[0051] In general, the pH in the anaerobic treatment tank is preferably 7.0 to 8.0, and particularly preferably 7.2 to 7.8. The pH in the anaerobic treatment tank rises as the anaerobic treatment of TMAH-containing wastewater continues. When the anaerobic treatment of TMAH-containing wastewater is operated at a high pH, ​​the inhibitory effect of ammonia becomes stronger, so it is necessary to lower the pH in the anaerobic treatment tank, and in order to operate the tank well, it is preferable to keep the pH at 7.2 or less. However, in the present invention, even when the anaerobic treatment tank is operated at a pH of 7.2 or more, particularly 7.5 or more, and especially 7.8 or more, TMAH can be efficiently decomposed as long as the pH is 8.3 or less.

[0052] In addition, even if the organic acid is being consumed, if the hydrogen concentration in the gas phase is high, there is a possibility that the organic acid will be generated and the methanogenic bacteria that decompose TMAH will be inhibited. Therefore, even when the organic acid concentration decreases due to the above measures, if hydrogen remains in the gas phase, it is desirable to add sludge containing Methanosarcina, which also has the ability to assimilate hydrogen, and operate the system so that the hydrogen concentration in the gas phase is 5% or less, preferably 2% or less, and more preferably 1% or less.

Example

[0053] [Example 1] The following simulated raw water (TMAH-containing wastewater) was passed through the anaerobic treatment tank of the outer membrane type MBR system shown in Fig. 1 under the following conditions to perform the decomposition treatment of TMAH.

[0054] For the measurement of the TMAH concentration, liquid chromatography was used. The measurement of the organic acid concentration was also performed by liquid chromatography.

[0055] <Raw water> A solution prepared by dissolving 7500 mg / L of TMAH (TOC 4000 mg / L) in pure water. Temperature 36°C, pH 7.8 Water flow rate: 0.6 L / d <MBR reaction tank> Volume: 1.5 L Volume loading: 8 kg-COD Cr / m 3 / d Initial sludge input: Sludge collected from an anaerobic reaction tank treating TMAH-containing wastewater (the proportion of Methanomethylovorans in methanogenic bacteria is 80%, and the proportion of Methanosarcina is 2%) Sludge concentration: MLSS 22000 mg / L, MLVSS 20000 mg / L Sludge loading: 0.4 kg-COD Cr / kg-VSS / d

[0056] The initial sludge input has a volume loading of 3.8 kg-COD Cr / m 3 / d, and the volume load was 4kg-COD for the first to fifth days. Cr / m 3 / d, and the volume load was 5kg-COD from the 6th to the 20th day. Cr / m 3 / d, and the volumetric load was 6kg-COD from the 21st to 40th day. Cr / m 3 / d, and the volumetric load was 7kg-COD from the 41st to 60th day. Cr / m 3 / d, and after the 61st stop, the volume load is 8kg-COD Cr / m 3 / d, the organic acid concentration in the treated water was 65 days lower than the COD Cr The TMAH concentration in the treated water was 50 mg / L, resulting in a TMAH removal rate of 99%.

[0057] After that, the water was continued to flow under the above conditions, and after one week (72 days after the start of water flow), the organic acid concentration in the treated water was Cr The hydrogen concentration in the gas phase at this time was 5.2%.

[0058] In addition, the proportion of the genus Methanomethylovorans among methanogens gradually decreased from 80 wt% to 60 wt%, while the genus Methanosarcina remained at 2%.

[0059] On the 73rd day after the start of water supply, sludge containing Methanosarcina genus taken from an anaerobic reactor treating wastewater (containing organic acids) from a food factory was added as additional sludge to the sludge held in the anaerobic treatment tank at 5% VSS, and operation was continued. The organic acid activity of this additional sludge was 0.03 kg-COD Cr / kg-VSS / d.

[0060] <Results and Discussion> Five days after the addition of additional sludge (78 days after the start of water flow), the TOC of the treated water had dropped to 100 mg / L (TMAH concentration 150 mg / L). The proportion of Methanomethylovorans was 70-80 wt%, and the proportion of Methanosarcina was 15%. The hydrogen concentration in the gas phase at this time had dropped to below 0.5%.

[0061] [Comparative Example 1] Water was passed through the system in the same manner as in Example 1, except that no additional sludge was added.

[0062] <Results and Discussion> In this Comparative Example 1, since no additional sludge was added, on the 83rd day after the start of water flow, the TOC of the treated water was 800 mg / L (TMAH concentration 1000 mg / L). In addition, the genus Methanomethylovorans accounted for 80% of the methanogens, and the genus Methanosarcina remained at 2%. The hydrogen concentration in the gas phase at this time remained at 5.2%. [Explanation of symbols]

[0063] 1 Anaerobic treatment tank 2 Stirring blade 5 Membrane separator 5m separation membrane 7. UASB Reactor 7a Sludge Blanket 8 Anaerobic treatment tank 9 Mixer 10 Draft Tube

Claims

1. COD of TMAH-containing wastewater Ｃｒ Volume load 4kg-COD Ｃｒ / m ３ / d or more into an anaerobic treatment tank to obtain treated water, The organic acid concentration of the treated water is Ｃｒ As the sum of converted concentrations (COD Ｃｒ The present invention relates to a method for treating TMAH-containing wastewater, and a TMAH concentration in the wastewater is 100 mg / L or less.

2. A method for treating TMAH-containing wastewater, comprising introducing TMAH-containing wastewater into an anaerobic treatment tank at a volumetric load of COD Cr of 4 kg-COD Cr / m 3 / d or more and treating the wastewater to obtain treated water, A method for treating TMAH-containing wastewater, comprising controlling the organic acid concentration in the treated water to be equal to or less than ("volume load of COD Cr" x 50 + 100) mg / L as a total of the organic acid COD Cr converted concentrations.

3. 2. The method for treating TMAH-containing wastewater according to claim 1, wherein the TMAH-containing wastewater contains TMAH in an amount of 80 wt % or more of TOC and is anaerobically treated at a TMAH concentration of 5,000 mg / L or more.

4. A method for treating TMAH-containing wastewater, comprising introducing TMAH-containing wastewater into an anaerobic treatment tank at a volumetric load of COD Cr of 4 kg-COD Cr / m 3 / d or more and treating the wastewater to obtain treated water, A method for treating TMAH-containing wastewater, wherein the organic acid concentration of the treated water is equal to or less than (“volume load of COD Cr”×50+100) mg / L as a total of the organic acid COD Cr converted concentrations, COD of organic acids in the treated water Ｃｒ The total converted concentration (COD Ｃｒ When the COD concentration of the treated water is greater than the volume load of the anaerobic digester (×50 + 100) mg / L, the organic acid concentration of the treated water is reduced by adding sludge containing organic acid-utilizing methanogenic bacteria to the anaerobic digester. Ｃｒ As the sum of converted concentrations (COD Ｃｒ The present invention relates to a method for treating wastewater containing TMAH, the method comprising the steps of:

5. 5. The method for treating TMAH-containing wastewater according to claim 4, wherein the sludge containing the organic acid-utilizing methanogenic bacteria is added in an amount of 0.5 to 30%-VSS based on the amount of sludge held in the anaerobic treatment tank.

6. The organic acid activity of the sludge containing the organic acid-utilizing methanogenic bacteria is 0.01 kg-COD Ｃｒ 5. The method for treating TMAH-containing wastewater according to claim 4, wherein the TMAH concentration is 1 / kg-VSS / d or more.

7. 5. The method for treating TMAH-containing wastewater according to claim 4, wherein the ratio of organic acid-utilizing methanogens to the total amount of methanogens in the anaerobic treatment tank after the addition of the sludge containing the organic acid-utilizing methanogens is 10 to 30 wt %.

8. 5. The method for treating TMAH-containing wastewater according to claim 4, wherein said organic acid-utilizing methanogenic bacteria belong to the genus Methanosarcina.

9. 8. The method for treating TMAH-containing wastewater according to claim 7, wherein the proportion of the genus Methanomethylovorans in the total methanogenic bacteria in the anaerobic treatment tank is 30 to 80 wt %.

10. 2. The method for treating TMAH-containing wastewater according to claim 1, wherein the pH in the anaerobic treatment tank is 7.0 to 8.

3.

11. A method for treating TMAH-containing wastewater according to any one of claims 1 to 10, characterized in that the hydrogen concentration in the gas phase in the anaerobic treatment tank is 5% or less.

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