Wastewater Treatment System Using Microorganisms

Abstract

The present invention relates to a water treatment system using microorganisms, wherein the microorganisms inside a reaction tank having a certain volume are used to remove contaminants from water to be treated, and the contaminants include TMAH (Tetramethylammonium hydroxide).

Description

Technology Field

[0001] The present invention relates to a water treatment system using microorganisms, and more specifically, to a water treatment system using microorganisms for purifying wastewater or sewage containing tetramethylammonium hydroxide. Background Technology

[0003] Tetramethylammonium hydroxide (TMAH) is a strong alkaline compound used as a photoresist developer in semiconductor etching processes. It is widely used in the manufacture of highly integrated circuits due to its role in enabling precise anisotropic etching of silicon wafers, and as semiconductor production expands, the usage of TMAH and its discharge into wastewater are also increasing.

[0004] Due to its chemically stable properties, TMAH persists in water systems and has an adverse effect on ecosystems. Furthermore, TMAH is highly alkaline, toxic, and difficult to decompose, making stable and sustainable removal difficult using only existing physical and chemical treatment technologies.

[0005] For the effective treatment of TMAH, not only simple decomposition but also complete mineralization into harmless end products such as carbon dioxide and ammonium, and removal through the nitrification and denitrification processes of ammonium are required.

[0006] Conventional physicochemical treatment technologies, such as coagulation-sedimentation, activated carbon adsorption, and Advanced Oxidation Processes (AOPs), have limitations in achieving such mineralization, and operational risks, including exothermic reactions, the generation of hazardous byproducts, and explosion hazards, exist, particularly under high-concentration industrial wastewater conditions. These limitations imply the need for more stable and effective biological alternatives. Prior art literature

[0008] Korean Published Patent No. 2006-0030823 (April 11, 2006) Korean Published Patent No. 2020-0068814 (June 16, 2020) Korean Published Patent No. 2009-0044973 (May 7, 2009) Korean Published Patent No. 2025-0095361 (June 26, 2025) The problem to be solved

[0009] In order to solve the above-mentioned problems, the present invention aims to provide a water treatment system using microorganisms capable of stably treating pollutants, including tetramethylammonium hydroxide, contained in wastewater or sewage. means of solving the problem

[0011] A water treatment system using microorganisms according to the present invention for achieving the above objective is characterized by removing contaminants from water to be treated using microorganisms inside a reaction tank having a certain volume, wherein the contaminants include TMAH (Tetramethylammonium hydroxide).

[0012] In addition, in the water treatment system using microorganisms according to the present invention, the reaction tank is characterized as being a Membrane Bio-Reactor (MBR) containing a separation membrane.

[0013] In addition, in the water treatment system using microorganisms according to the present invention, the water to be treated is characterized as being wastewater or sewage.

[0014] In addition, in the water treatment system using microorganisms according to the present invention, the wastewater is characterized as being wastewater generated during semiconductor manufacturing.

[0015] In addition, the water treatment system using microorganisms according to the present invention is characterized by introducing a carrier into the reaction tank.

[0016] In addition, in a water treatment system using microorganisms according to the present invention, the carrier comprises sulfur and a binder and is characterized by being porous.

[0017] In addition, in a water treatment system using microorganisms according to the present invention, the binder is characterized by including a silica component. Effects of the invention

[0019] According to the water treatment device and water treatment system using microorganisms according to the present invention, by introducing a sulfur-based carrier into a Membrane Bio-Reactor (MBR) that is operated with the membrane immersed, there is an advantage that contaminants including tetramethylammonium hydroxide (TMAH) can be effectively removed. Brief explanation of the drawing

[0021] FIG. 1 is a schematic diagram of a water treatment device according to a preferred embodiment of the present invention. Figure 2 shows the results of the change in TMAH concentration and removal rate according to the number of days of continuous operation. Figure 3 shows the results of TN concentration change and removal rate according to the elapsed days of continuous operation. Figure 4 shows the results of the change in NH3-N concentration and removal rate according to the elapsed days of continuous operation. Figure 5 shows the results of the change in NO3-N concentration and removal rate according to the number of days of continuous operation. Figure 6 shows the reaction tanks and sulfate (SO₄) of the treated water according to the TMAH concentration of the raw water. 2- ) is the result. Figure 7 shows the results of TOC concentration change and removal rate according to the number of days of continuous operation. Figure 8 shows the filtration performance results of the membrane according to the number of days of continuous operation. Specific details for implementing the invention

[0022] Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, and based on the principle that the inventor can appropriately define the concepts of the terms to best describe his invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0024] The water treatment system using microorganisms according to the present invention removes pollutants from the water to be treated by using microorganisms inside a reaction tank having a certain volume.

[0025] At this time, the contaminant may be wastewater or sewage containing TMAH (Tetramethylammonium hydroxide), and the wastewater may be wastewater generated during semiconductor manufacturing, but there are no specific restrictions if it is wastewater or sewage containing TMAH (Tetramethylammonium hydroxide).

[0026] In addition, the reaction vessel may be a Membrane Bio-Reactor (MBR) in which a membrane is housed to remove contaminants through the membrane and microorganisms.

[0027] Here, the membrane is not specifically limited to hollow fiber or flat plate types, and it is preferable that it be an ultrafiltration membrane or a microfiltration membrane.

[0028] When operating a reactor containing a membrane, it is recommended to operate by intermittently introducing a carrier into the reactor in a range of 10 to 20 volume % of the effective volume of the reactor.

[0029] Since TMAH (Tetramethylammonium hydroxide) is not only highly toxic but also a difficult-to-decompose substance, a carrier that allows microorganisms to attach and grow and function as an electron donor is introduced into the reaction vessel to provide conditions that increase the survival rate of microorganisms and maximize their activity.

[0030] Here, the carrier may be composed of sulfur, calcium carbonate (CaCO₃), and a binder.

[0031] The sulfur may be in the form of a powder of approximately 200 μm or less, and such sulfur may function to induce the dominance of sulfur-oxidizing denitrifying bacteria.

[0032] Sulfur-oxidizing denitrifying bacteria, which are autotrophic microorganisms, utilize various sulfur compounds such as sulfides, elemental sulfur, and thiosulfates as substrates to obtain energy and oxidize them into sulfates. They carry out denitrification by reducing nitrate nitrogen to nitrogen gas in oxygen-deficient environments, and the genus Thiobacillus is known as a representative sulfur-oxidizing denitrifying bacterium.

[0033] Calcium carbonate (CaCO₃) is a representative alkalinity-inducing substance that can be used not only as a source of alkalinity but also provide inorganic carbon for cell synthesis of sulfur-oxidizing denitrifying bacteria.

[0034] The binder is a component for binding the sulfur-based carriers together so that they can form pores along with mechanical strength, and may be a material containing silica components, for example, liquid sodium silicate (Na₂SiO₃).

[0035] It is preferable that these sulfur, calcium carbonate (CaCO₃), and binder be mixed in a weight ratio in the range of 4 to 6 : 3 to 5 : 8 to 10, and more preferable that they be mixed in the range of 4.5 to 5.5 : 3.5 to 4.5 : 8.5 to 9.5.

[0036] Meanwhile, the carrier of the present invention may have a density in the range of 0.57 to 1.20 g / cm³ and a porosity in the range of 37 to 64%.

[0038] The present invention will be explained in more detail below through examples. These examples are intended solely to explain the present invention more specifically and do not limit the present invention.

[0040] Examples

[0041] Carrier manufacturing

[0042] In order to prepare a carrier to be introduced into the reaction vessel of the present invention, powdered sulfur (S0), calcium carbonate (CaCO3), and sodium silicate (Na2SiO3) were prepared, and then S : CaCO₃ : Na2SiO3 were introduced and mixed in a weight ratio of 5 : 4 : 9.

[0043] The uniformly stirred mixture was poured into a silicone mold with a width, length, and height of 1 cm and then dried.

[0044] At this time, the drying conditions involved heating the mold filled with the mixture in an oven at 100–110°C for 24 hours to evaporate the moisture from the sodium silicate and induce physical hardening.

[0045] Afterward, the dried carrier was washed with running water to remove residual components from the surface and simultaneously adjust the carrier's pH to near neutral, and then air-dried.

[0046] The carrier was stored in a sealed container to protect it from external contamination and moisture, and was washed once with running water before use.

[0048] Driving conditions

[0049] As shown in Figure 1, a Membrane Bio-Reactor (MBR) was used in which a membrane is immersed inside the reactor and operated.

[0050] The effective volume of the reactor is 10 L, and the membrane flux is 10 LMH (L / m²). 2 / hr), it was set to rest for 1 minute after 9 minutes of filtration, and to suppress fouling, physical cleaning, specifically backwashing, was automatically performed at intervals of every 2 to 3 cycles (about 10 to 20 minutes) during operation.

[0051] The carrier was filled in an amount corresponding to 20% of the effective volume of the reactor, and the MLSS in the reactor was adjusted to 6,000–8,000 mg / L, while air was supplied through an aerator at the bottom of the reactor to maintain the dissolved oxygen (DO) at 2–3 mg / L (see Table 1).

[0053] Effective volume of the reactor (V) 10 L Supply flow rate (Q) 1.25 L / h HRT 8 hours SRT 30 days or more MLSS 6,000~8,000 mg / L Carrier filling rate 20% Flux 10 LMH(L / m 2 / hr) pH 7.0~8.0 DO 2-3 mg / L temperature 20~25℃

[0054] In addition, the separator used is a 'U'-shaped hollow fiber separator made of PVDF (Polyvinylidene Fluoride) material with an outer diameter of 2.0 mm, an inner diameter of 0.8 mm, and a pore size of 0.1 μm.

[0055] Meanwhile, the seeding sludge was collected in a certain amount from the activated sludge of Incheon A Wastewater Treatment Plant, and after undergoing a stabilization process in a Sequencing Batch Reactor (SBR) for about 3 weeks without supplying a carrier and TMAH (Tetramethylammonium hydroxide), it was confirmed that the ability to remove organic matter and nitrogen had been restored, and then introduced into the reactor.

[0056] The characteristics of the raw water used for continuous operation are shown in Table 2. In particular, to verify the removal rate according to the concentration of TMAH (Tetramethylammonium hydroxide), the concentration of TMAH (Tetramethylammonium hydroxide) was increased stepwise at one-week intervals. That is, starting from 100 mg / L, it was increased in the order of 200 mg / L, 500 mg / L, 700 mg / L, 1000 mg / L, and 1200 mg / L at one-week intervals.

[0057] density NH4Cl 382.14 mg / L NaHCO3 1440 mg / L KH2PO4 5 mg / L MgSO4·7H2O 50 mg / L FeSO4·7H2O 10 mg / L Glucose 375 mg / L TMAH 100~1200 mg / L EDTA 500 mg / L CaCl2·2H2O 60 mg / L CuSO4·5H2O 20 mg / L CoCl2·6H2O 20 mg / L FeSO4·7H2O 50 mg / L MnCl2·4H2O 50 mg / L ZnSO4·7H2O 220 mg / L

[0058] TMAH results

[0059] The TMAH results were analyzed for the influent raw water supplied to the MBR reactor and the treated water, which is the effluent from which pollutants have been removed through microbial action and a membrane in the MBR reactor.

[0060] Figure 2 shows the results of the change in TMAH concentration and removal rate according to the number of days of continuous operation.

[0061] TMAH was measured using an Ion Chromatograph (Shimadzu HIC-20). Referring to Figure 2, the removal rate of TMAH was approximately 42% at the beginning of operation when the TMAH concentration in the raw water was 100 mg / L, but it was confirmed that TMAH in the treated water was stably removed to the point where it was not detected even when the TMAH concentration was gradually increased to 1200 mg / L.

[0063] TN results

[0064] Figure 3 shows the results of TN concentration change and removal rate according to the number of days of continuous operation. TN was measured according to the Chromotropic Acid Method (HACH, DR-2800).

[0065] Total nitrogen (TN) is ammonia nitrogen (NH₄ + -N), nitrite nitrogen (NO₂ - -N), nitrate nitrogen (NO₃ - It is one of the items used to evaluate the treatment performance of biological nitrogen removal processes, serving as an indicator that integrates all forms of nitrogen, including organic nitrogen (-N).

[0066] As can be seen in Figure 3, the TN concentration in the raw water tended to increase as the TMAH concentration increased. In the results for the treated water, the denitrification reaction was limited to a certain level due to the operating conditions of the MBR, which maintains an aerobic state at all times, and consequently, the TN removal rate was found to be less than 50%.

[0068] NH₃-N results

[0069] Figure 4 shows the results of the change in NH3-N concentration and removal rate according to the elapsed days of continuous operation. TN was measured according to the Nessler Method (HACH, DR-2800).

[0070] Ammonia nitrogen (NH₃-N) is the first form of organic nitrogen converted through biological decomposition and is a key indicator representing the performance of the initial stage of nitrogen removal reactions within the reaction system.

[0071] As shown in Figure 4, the NH₃-N concentration in the raw water remained stable at 48–54 mg / L in most sections, but the NH₃-N concentration increased slightly from the section where the TMAH concentration increased to 700 mg / L or higher. This is expected to be due to the partial decomposition of TMAH, which was artificially added during the raw water production process, during storage or neutralization.

[0072] In the results of the treated water, TMAH was detected at a negative removal rate, meaning it was detected at a higher concentration than the raw water, with a value of 500 mg / L or more, which indicates that the TMAH in the raw water was decomposed.

[0074] NO₃-N results

[0075] Figure 5 shows the results of changes in NO3-N concentration and removal rate according to the number of days of continuous operation. NO3-N was measured according to the Chromotropic Acid Method (HACH, DR-2800).

[0076] Nitrate Nitrogen (NO₃) - -N) is the form of ammonia nitrogen (NH3-N) oxidized through the nitrification process, and is an indicator used to evaluate whether the denitrification reaction, a later reaction pathway in the biological nitrogen removal process, is functioning normally.

[0077] As shown in Figure 5, the concentration of nitrate nitrogen (NO3-N) in the raw water was maintained at a constant level of 1 to 2 mg / L, but the concentration of nitrate nitrogen (NO3-N) in the treated water was found to have increased to a maximum of 20 mg / L, which means that the decomposed NH₃-N was oxidized.

[0078] Meanwhile, it was confirmed that the nitrate nitrogen (NO3-N) concentration decreased again in the region where the TMAH concentration was 500 mg / L or higher. Although the MBR is maintained under operating conditions that always keep the aerobic state, the dissolved oxygen concentration is relatively low in the range of 2-3 mg / L, and since the carrier introduced is porous, it is predicted that the nitrate nitrogen (NO3-N) was reduced to nitrogen (N2) by the proliferation of sulfur carrier-based denitrifying bacteria in the micro-anaerobic region inside the carrier.

[0080] SO₄ 2- result

[0081] Figure 6 shows the reaction tanks and sulfate (SO₄) of the treated water according to the TMAH concentration of the raw water. 2- ) is the result. Sulfate (SO₄ 2- ) was measured according to the SulfaVer4 Method (HACH, DR-2800).

[0082] Sulfate (SO₄) 2- ) is an indicator for tracking the oxidation reaction of the sulfur-based carrier used in the biological degradation process of TMAH.

[0083] As can be seen in Fig. 6, sulfates (SO₄) inside the reactor and in the treated water are proportional to the TMAH concentration in the raw water. 2- The concentration increased. Since sulfur components are not present in the raw water, the measured SO₄ 2- It is entirely the result of sulfur constituting the carrier being oxidized by microorganisms.

[0085] TOC results

[0086] Figure 7 shows the changes in TOC concentration and removal rate over the course of continuous operation. The supplied raw water contains 375 mg / L of glucose and TMAH, which form the organic carbon load, and the total organic carbon (TOC) of the raw water varied in the range of approximately 160 to 780 mg / L depending on the amount of TMAH injected.

[0087] However, in the range where the TMAH injection amount is 200 mg / L or higher, the total organic carbon (TOC) removal rate is measured to be 95% or higher, confirming that the total organic carbon (TOC) removal rate is very high.

[0088] Considering that TMAH mixed in the raw water is not substantially removed by the membrane provided in the reactor, and that the total organic carbon (TOC) removal rate in the early stages of operation was only about 55% when the TMAH concentration, which can be considered the adaptation period of microorganisms, was in the 100 mg / L range, it can be inferred that microorganisms contribute significantly to the removal of total organic carbon (TOC).

[0090] Microbial community results

[0091] Table 3 shows the results of 16S rRNA-based microbial community analysis of the raw water and the reactor. Here, the raw water refers to the activated sludge from Incheon A Wastewater Treatment Plant, which is the seeding sludge, and the reactor refers to the reactor when operated under the condition of TMAH 1,200 mg / L.

[0092] As summarized in Table 3, Ferruginibacter and Methyloversatilis, microorganisms reported to have sulfation and TMAH degradation and resistance functions, were not detected in the raw water, whereas they were detected in the MBR reactor.

[0094] Genus Raw material (%) MBR Reactor (%) Key Features Ferruginibacter - 13.8 Sulfur oxidation, organic matter decomposition Methyloversatilis - 4.2 TMAH-degrading / resistant microorganisms GU454927_g 14.7 5.0 - Terrimonas 4.2 2.4 Organic matter oxidation, aerobic Hyphomicrobium 3.6 - Methylation Flavobacterium - 2.3 Carbon source oxidation etc 77.5 72.3

[0096] Membrane operation results

[0097] Figure 8 shows the filtration performance results of the membrane according to the number of days of continuous operation. As can be seen in Figure 8, the trans-membrane pressure (TMP) gradually increased over about 30 days to reach about 38 kPa, and recovered to the initial pressure range of 10–12 kPa through Cleaning In Place (CIP). Afterwards, it rose again in the same trend, and the TMP reached 42 kPa at about 60 days.

[0098] As the TMAH of the raw water increased, the rate of increase of the transmembrane pressure (TMP) increased, but the difference was minimal and filtration proceeded relatively stably.

[0100] As described above, although the present invention has been explained by limited embodiments and drawings, the present invention is not limited thereto and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

Claims

Claim 1 A water treatment system using microorganisms, characterized in that the contaminants in the water to be treated are removed using microorganisms inside a reaction tank having a certain volume, wherein the contaminants include TMAH (Tetramethylammonium hydroxide), the reaction tank is a Membrane Bio-Reactor (MBR) containing a separation membrane, and a carrier containing sulfur, potassium carbonate, and sodium silicate as a binder, but not activated carbon, is introduced into the reaction tank, and the sulfur, potassium carbonate, and sodium silicate constituting the carrier are mixed in a weight ratio of 4.5~5.5 : 3.5~4.5 : 8.5~9.

5. Claim 2 delete Claim 3 A water treatment system using microorganisms according to claim 1, characterized in that the water to be treated is wastewater or sewage. Claim 4 A water treatment system using microorganisms, characterized in that, in paragraph 3, the wastewater is wastewater generated during semiconductor manufacturing. Claim 5 delete Claim 6 A water treatment system using microorganisms according to claim 1, wherein the carrier is porous. Claim 7 delete

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