Method and device for removing color from organic wastewater

Abstract

To provide a method and an apparatus for removing chromaticity from organic wastewater capable of efficiently removing chromaticity from organic wastewater in a shorter time with a smaller amount of chemicals.SOLUTION: The method for removing chromaticity from organic wastewater performs pre-treatment of organic wastewater with biological treatment S1, coagulation sedimentation treatment S2 in which a coagulant is added and coagulation sedimentation treatment is carried out under acidic conditions, and filtration treatment S3, in this order, followed by decolorization treatment S4 in which a decoloring agent is added to the organic wastewater after pre-treatment.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for removing color from organic wastewater. [Background technology]

[0002] In recent years, there has been an increasing demand for the chromaticity of effluent water from the viewpoint of water environment conservation and safety in rivers and other areas. For example, food wastewater, drinking wastewater, human waste, septic tank sludge, and the like often contain chromatic components, and therefore it is required to remove these components when they are discharged. In advanced treatment for chromatic components, coagulation and sedimentation treatment using inorganic coagulants is often used. However, in coagulation and sedimentation treatment, a large amount of coagulant may be added to remove the chromatic components. This leads to an increase in chemical costs and the amount of sludge generated, which is a factor in high treatment costs. Furthermore, when the chromatic components are not sufficiently removed in the coagulation and sedimentation treatment, activated carbon adsorption or ozone treatment may be performed, which leads to a further increase in treatment costs.

[0003] 2. Description of the Related Art There are known decolorization methods for treating colored beverage wastewater using a chlorine-based oxidizing agent (for example, JP-A-2004-358421, JP-A-2008-43919, and JP-A-2011-136296).

[0004] In addition, a decolorization method is known in which treated water obtained by activating the separated liquid from the thermal sludge treatment is coagulated and precipitated, and then treated with ozone oxidation or hypochlorite in the presence of nickel peroxide (JP Patent Publication 152600 / 1980). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-358421 A [Patent Document 2] JP 2008-43919 A [Patent Document 3] JP 2011-136296 A [Patent Document 4] Japanese Patent Application Publication No. 55-152600 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the inventions described in Patent Documents 1 to 3, when the water to be treated contains a large amount of persistent organic matter and suspended solids (SS), the persistent organic matter and SS in the water to be treated react with the chlorine-based oxidizing agent, and the decolorization effect may not be sufficient. If a large amount of chlorine-based oxidizing agent is added to obtain a sufficient decolorization effect, the amount of chemical solution increases and harmful chlorine-based organic compounds are generated in large amounts in the treated water.

[0007] In the invention described in Patent Document 4, ferric chloride is added to the activated sludge treatment water of the sewage sludge heat treatment separation liquid, the pH is adjusted to 7.0 with sodium hydroxide, and coagulation precipitation treatment is performed, and further, 1000 to 10000 ppm of sodium hypochlorite aqueous solution with 12% available chlorine is added, and nickel peroxide powder is added as a catalyst to perform decolorization treatment. However, in the method described in Patent Document 4, depending on the coagulation state and sedimentation separation conditions of the coagulation precipitation treatment, fine sludge flocs containing iron hydroxide remain in the treated water. When this reacts with hypochlorous acid, iron-derived color remains, and the color removal effect may not be sufficiently obtained. In addition, in Patent Document 4, the amount of hypochlorite consumed is very large, which leads to an increase in chemical costs. Furthermore, in the treatment described in Patent Document 4, the color is not stable in a short reaction time, so a long reaction time is required, making the treatment complicated.

[0008] In view of the above problems, the present invention provides a method and apparatus for removing color from organic wastewater, which are capable of efficiently removing the color from the organic wastewater in a shorter period of time with a smaller amount of chemical solution. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors to solve the above problems, it was discovered that it is effective to carry out three pretreatment processes, namely, biological treatment, coagulation and sedimentation treatment in an acidic range, and filtration treatment, before carrying out decolorization treatment to remove the color of organic wastewater.

[0010] One aspect of an embodiment of the present invention, which has been completed based on the above findings, is a method for removing color from organic wastewater, which comprises pretreatment of organic wastewater, in which a biological treatment, a coagulation-sedimentation treatment in which a coagulant is added to perform coagulation-sedimentation treatment in an acidic range, and a filtration treatment, in that order, and then adding a decolorizing agent to the organic wastewater after the pretreatment to perform a decolorizing treatment.

[0011] In one embodiment of the method for removing color from organic wastewater according to the embodiment of the present invention, the coagulation and sedimentation treatment includes treatment in an acidic range where the pH is 5.0 to 6.5.

[0012] In another embodiment of the method for removing color from organic wastewater according to the embodiment of the present invention, the decolorization treatment includes contacting the pretreated organic wastewater with a decolorizing agent for 3 to 10 minutes.

[0013] In still another embodiment of the method for removing color from organic wastewater according to the embodiment of the present invention, the decolorizing agent is a chlorine-based oxidizing agent.

[0014] In yet another embodiment of the method for removing color from organic wastewater according to the present invention, a reducing agent is added to the treated water after the decolorization treatment, and a chlorine-based oxidizing agent remaining in the treated water after the decolorization treatment is removed.

[0015] In yet another embodiment of the method for removing color from organic wastewater according to the embodiment of the present invention, the method includes measuring the color of the organic wastewater after pretreatment and adjusting the amount of decolorizing agent to be added based on the results of the color measurement.

[0016] In yet another embodiment of the method for removing color from organic wastewater according to the embodiment of the present invention, the organic wastewater has a color of 100 to 1000 degrees, a COD MnThis includes BOD being 100 mg / L or more and BOD being 200 mg / L or more.

[0017] Another aspect of an embodiment of the present invention is an organic wastewater treatment device including a biological treatment tank for biologically treating organic wastewater and removing organic matter in the organic wastewater, a coagulation and sedimentation tank for subjecting the biologically treated water obtained in the biological treatment tank to coagulation and sedimentation treatment in an acidic range and removing suspended solids generated by the biological treatment, a filtration device for filtering the coagulation and sedimentation treated water obtained in the coagulation and sedimentation tank, and a decolorization treatment tank for removing color from the filtered water obtained in the filtration device by adding a decolorizing agent to the filtered water obtained in the filtration device and performing a decolorization treatment.

[0018] In one embodiment, the organic wastewater treatment device according to the present invention further includes a color measuring device that measures the color of the filtered water flowing into the decolorization treatment tank, and a control device that controls the amount of decolorizing agent added based on the results of the color measurement of the filtered water. Effect of the Invention

[0019] According to the present invention, there can be provided a method and an apparatus for removing color from organic wastewater, which are capable of efficiently removing the color in the organic wastewater in a shorter time with a smaller amount of chemical solution. [Brief description of the drawings]

[0020] [Figure 1] 1 is a flowchart showing an example of a method for removing chromaticity from organic wastewater according to an embodiment of the present invention. [Diagram 2] 1 is a schematic diagram showing an example of a color removal device for organic wastewater according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are given the same or similar reference numerals. Note that the embodiments shown below are examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the structure, arrangement, etc. of the components to those described below.

[0022] As shown in FIG. 1, the method for removing color from organic wastewater according to an embodiment of the present invention includes carrying out pretreatment on the organic wastewater in the order of biological treatment S1, coagulation-sedimentation treatment S2 in which a coagulant is added to perform coagulation-sedimentation treatment in an acidic range, and filtration treatment S3, and then carrying out decolorization treatment S4 by adding a decolorizing agent to the organic wastewater after the pretreatment.

[0023] The organic wastewater to be treated is not limited as long as it contains colored organic matter. For example, wastewater obtained from a food factory or beverage factory, dyeing wastewater, or wastewater containing organic waste, sludge, human waste, septic tank sludge, food waste, etc. can be used as the organic wastewater according to the present embodiment. In particular, when drinking wastewater generated in the beverage manufacturing process or organic wastewater containing human waste is used as the organic wastewater according to the present embodiment, a high color removal effect can be obtained, and further, it is preferable to treat drinking wastewater.

[0024] Although not limited thereto, the color of the organic wastewater to be treated is typically about 100 to 1000 degrees, more typically 200 to 1000 degrees, and even more typically 200 to 500 degrees. The SS of the organic wastewater is typically 50 to 1000 mg / L, more typically 50 to 500 mg / L, and even more typically 50 to 300 mg / L. The COD of the organic wastewater is Mn is typically 100 to 1000 mg / L, more typically 200 to 1000 mg / L, and even more typically 200 to 550 mg / L. Mnis typically 100 to 1000 mg / L, more typically 200 to 1000 mg / L, and further typically 200 to 500 mg / L. The BOD of the organic wastewater is typically 200 to 1500 mg / L, and more typically 200 to 1000 mg / L. The S-BOD of the organic wastewater is typically 200 to 1500 mg / L, and more typically 200 to 600 mg / L. In this embodiment, the color, SS, COD of the organic wastewater are Mn , S-COD Mn , BOD, and S-BOD can be measured in accordance with known sewage test methods.

[0025] (Biological treatment S1) Organic wastewater is first introduced into biological treatment, where biological treatment S1 using microorganisms is performed. In biological treatment S1, substances that microorganisms can prey on in the organic wastewater, basically BOD, are removed, but COD and color components are also removed as part of the BOD. SS is classified into organic SS that becomes a BOD component and inorganic SS other than that, and biological treatment S1 mainly removes organic SS. By subjecting organic wastewater to biological treatment S1, it is possible to reliably remove biologically decomposable BOD contained in the organic wastewater, and thus COD and color components can also be removed. By performing this treatment as a pretreatment for the decolorization treatment, it is possible to reduce the amount of decolorizing agent in the decolorization treatment described below, and it is possible to remove color more efficiently in a shorter time. Furthermore, in this biological treatment S1, if the concentration of microorganisms in the biological reaction tank is increased and the activity of the microorganisms is increased, it is possible for the microorganisms to further prey on COD and color removal components that have not been preyed on by the microorganisms, and therefore the removal rate of COD and color components is also improved.

[0026] As the biological treatment S1, for example, the activated sludge process, the biofilm process, the anaerobic treatment process, the biological nitrification and denitrification process, the membrane separation activated sludge process, the fluidized carrier process, etc. can be used, but among them, the activated sludge process is preferred from the viewpoint of maintenance cost and efficient treatment. By using the activated sludge process, BOD, as well as COD and color components contained as part of BOD, can be separated as sedimentation sludge by solid-liquid separation. Therefore, the burden of color removal in the decolorization process is reduced, and the color removal effect is also improved.

[0027] When the activated sludge process is used as the biological treatment S1, the membrane bioreactor (MBR) method, which can maintain a high MLSS concentration in the aeration tank, and the multi-stage activated sludge process, which can obtain stable sedimentation separation, are preferred. If the MLSS concentration can be maintained high and the BOD-SS load can be reduced, the COD and color components in the raw water that are difficult to decompose are gradually decomposed by the activation of the acclimatized microorganisms, and the COD and color of the treated water are greatly reduced. For example, if the BOD-SS load is set to 0.05 to 0.20 kg / kg / d, preferably 0.05 to 0.10 kg / kg / d, it becomes possible to partially decompose the COD and color components in the raw water that are difficult to decompose.

[0028] As the biological treatment S1, stable COD and color removal can be performed by using a fluidized carrier system or a hybrid system of fluidized carrier + activated sludge, which uses both fluidized carrier and activated sludge. In the case of using only fluidized carrier, the carrier loading rate in the aeration tank is 20V% or more, preferably 30V%. Since a high carrier loading rate can maintain a high microbial concentration in the aeration tank, some of the COD and color components in the raw water that are difficult to decompose can be gradually decomposed by the activation of the acclimatized microorganisms. In the case of a hybrid system of fluidized carrier + activated sludge, if the MLSS of the activated sludge is 1500 to 3000 mg / L, it is possible to sufficiently maintain the microbial concentration in the aeration tank. In this case, the SS of the treated water is lowered by solid-liquid separation in the settling tank, so the subsequent coagulation and sedimentation treatment is stable. In addition, in either of the above systems, the BOD volume load of the aeration tank is set to 1.5 kg / m 3 / d or less, preferably 1.0 kg / m 3 / d or less, some of the difficult-to-decompose COD and color components in the raw water can be decomposed by the acclimatized microorganisms.

[0029] (Coagulation and sedimentation treatment S2) The biologically treated water obtained by the biological treatment typically has a color of 50 to 800 degrees, more typically 50 to 500 degrees, a SS of 10 to 500 mg / L, more typically 10 to 300 mg / L, and even more typically 10 to 100 mg / L, a COD Mn is 50-500 mg / L, more typically 50-250 mg / L, S-COD Mn The BOD, particularly the S-BOD, in the biological treatment water is reduced to about 10 to 250 mg / L, more typically 20 to 100 mg / L, the BOD, to about 5 to 50 mg / L, more typically 5 to 10 mg / L, and the S-BOD, to about 1 to 10 mg / L, more typically 1 to 5 mg / L. By reliably reducing the BOD, particularly the S-BOD, in the biological treatment water, it becomes possible to reduce the amount of chemicals injected in the subsequent coagulation and sedimentation treatment and decolorization treatment, and to remove color to a low concentration.

[0030] In the coagulation and sedimentation treatment S2, it is preferable to carry out the coagulation and sedimentation treatment in an acidic region with a pH of 5.0 to 6.5, more preferably 5.5 to 6.4, and even more preferably 6.0 to 6.3. It is preferable to carry out the coagulation and sedimentation treatment at a pH lower than that of the biological treatment water, and it is even more preferable to carry out the coagulation and sedimentation treatment at a pH lower than that of the organic wastewater. As the coagulant, for example, one or a combination of a plurality of acidic inorganic coagulants composed of aluminum compounds such as aluminum sulfate, polyaluminum chloride (PAC), and iron compounds such as polyferric sulfate can be used.

[0031] When an acidic inorganic coagulant is used in the coagulation and settling treatment S2, the pH is lowered by adding the coagulant to the biological treatment water. In general, an alkaline agent is added to adjust the pH to a neutral range of about pH 6.5 to 7. In contrast, in this embodiment, the coagulation and settling treatment is performed in an acidic range of about pH 5.0 to 6.5, or even in a weakly acidic range of 5.0 or more and less than 6.5, by adding a coagulant without adding an alkaline agent or with a small amount of an alkaline agent. This makes it possible to more efficiently reduce the persistent organic matter, SS, and color remaining in the biological treatment water. As a result, a high degree of color removal can be achieved while reducing the amount of decolorant added in the decolorization treatment described below.

[0032] By carrying out the coagulation and sedimentation treatment S2 in an acidic range of pH 5.0 to 6.5, the amount of chlorine compounds remaining in the decolorized water can be reduced while reducing the amount of decolorizing agent added in the decolorization treatment S4 described below, and the amount of chlorine compounds discharged into the environment can also be reduced. In addition, even when removing the decolorizing agent remaining in the decolorized water by adding a reducing agent, the amount of reducing agent added can be reduced. Therefore, by carrying out the coagulation and sedimentation treatment S2 in an acidic range, the amount of chemicals used in each treatment step is reduced synergistically and in a chain reaction manner, so that a high level of color removal can be achieved while significantly reducing the amount of chemicals used in the decolorization treatment S4 and the subsequent reduction treatment S5.

[0033] The amount of inorganic flocculant added can be typically 100 to 1000 mg / L, more typically 100 to 500 mg / L. In particular, in order to efficiently remove suspended SS and color in the biologically treated water obtained in the biological treatment S1, it is preferable to add 50 to 300 mg / L, more preferably 50 to 150 mg / L of the flocculant.

[0034] Examples of inorganic flocculants that can be used include PAC, aluminum chloride, iron chloride, ferric sulfate, and polyferric sulfate. However, when the flocculation pH is in the weak acid range of 5.0 to 6.5, it is preferable to use an iron-based inorganic flocculant as the inorganic flocculant, and good flocculation treatment can be performed. In addition, polyferric sulfate reduces the pH less than ferric chloride after addition, and the addition of alkali required for pH adjustment is unnecessary or reduced. Polymer flocculants such as cationic polymer flocculants, anionic polymer flocculants, and nonionic polymer flocculants may be used in the flocculation settling tank in which the flocculation flocs are formed. In addition, by using a flocculation aid, an alkali agent such as slaked lime, sodium hydroxide, or soda ash, and a flocculation aid in combination, suspended SS derived from biological treatment, including microorganisms, can be more reliably removed.

[0035] A part of the coagulated sludge discharged from the coagulation sedimentation tank may be returned to the coagulation sedimentation tank. This allows the sludge flocs in the coagulation sedimentation tank to be stably and large, enabling good solid-liquid separation. In addition, the amount of polymer flocculant added can be reduced.

[0036] (Filtration process S3) The coagulation sedimentation treated water obtained in the coagulation sedimentation treatment S2 has, but is not limited to, a pH of typically 5.0 to 6.5, a color of 50 to 300 degrees, more typically 50 to 200 degrees, a SS of 2 to 15 mg / L, more typically 2 to 10 mg / L, a COD Mn The sewage treatment water is reduced to 10 to 100 mg / L, more typically 10 to 50 mg / L, and the BOD to 2 to 10 mg / L, more typically 2 to 5 mg / L. In this embodiment, by subjecting the coagulation-sedimentation treated water to the filtration treatment S3, it is possible to separate and remove metal hydroxides derived from fine sludge flocs and inorganic coagulants in the coagulation-sedimentation treated water to an even higher degree.

[0037] In the above-mentioned coagulation and sedimentation treatment S2, the treatment with weak acidity may reduce the settling speed of the flocs and cause some fine flocs to float to the surface, which may increase the amount of suspended matter in the coagulation and sedimentation treated water. According to this embodiment, the coagulation and sedimentation treated water obtained by the coagulation and sedimentation is filtered in the filtration treatment S3, which makes it possible to more reliably remove suspended matter, thereby enabling more stable treatment in the decolorization treatment described below.

[0038] As the filtration process S3, sand filtration, membrane filtration, filtration equipment using a filter medium made of fiber or polymer material, etc. can be used, among which sand filtration is preferred from the viewpoint of maintenance and the like. As the filter medium used in the sand filtration process, for example, an aerobic filter using silica sand having an effective diameter of 0.2 to 0.7 mm, more preferably an effective diameter of 0.4 to 0.7 mm, anthracite having an effective diameter of 2.0 to 5.0 mm, more preferably an effective diameter of 2.0 to 3.0 mm, etc. can also be used. By setting the filter layer thickness to, for example, 2,000 to 5,000 mm, more preferably 2,000 to 4,000 mm, fine sludge flocs in the coagulation sedimentation treatment water and metal hydroxides derived from inorganic coagulants can be effectively removed. The filtration speed can be, for example, 5 to 50 m / d.

[0039] (Bleaching treatment S4) The filtered water obtained in the filtration process S3 has, but is not limited to, a pH of typically 5.0 to 6.5, a color of 50 to 300 degrees, more typically 50 to 150 degrees, a SS of 10 mg / L or less, more typically 5 mg / L or less, a COD Mn The BOD, COD, and COD are reduced to 5 to 100 mg / L, more typically 5 to 50 mg / L, and in one embodiment to 15 mg / L or less. By reliably reducing the COD in the preceding coagulation and sedimentation treatment S2 and filtration treatment S3, it becomes possible to reduce the amount of chemicals injected in the subsequent decolorization treatment and to remove color to a low concentration. Therefore, in this embodiment, by passing through the biological treatment S1, the coagulation and sedimentation treatment S2, and the filtration treatment S3, the BOD, COD, and COD are reduced. Mn The filtered water with sufficiently reduced SS is subjected to a decolorization treatment S4 using a decolorizing agent.

[0040] Examples of the decolorizing agent include chlorine-based oxidizing agents. Examples of the chlorine-based oxidizing agent that can be used include sodium hypochlorite, calcium hypochlorite, potassium hypochlorite, and solid chlorine agents. In general, it is preferable to use sodium hypochlorite, which is inexpensive and easy to handle. It is preferable to determine the decolorizing reaction time based on the properties of the filtered treated water, such as the chromaticity and organic matter concentration. In this embodiment, since an effective decolorizing effect can be obtained in a short time of about 3 to 10 minutes, or even about 3 to 5 minutes, by mixing the pretreated organic wastewater and the decolorizing agent, the treatment is easy.

[0041] The reaction pH in the decolorization treatment S4 is not particularly limited. When hypochlorite is used as the decolorization agent, the filtered water to be used as the decolorization raw water is weakly acidic, so that the oxidation reaction with hypochlorite is efficiently carried out, and therefore pH adjustment is not required. Even if pH adjustment is performed, it is preferable to adjust to a pH range equivalent to that of the coagulation and precipitation treatment S2. This allows the amount of hypochlorite added to be reduced while reducing the amount of chemicals such as pH adjusters used.

[0042] The amount of the decolorizing agent added can be typically 5 to 50 mg / L, more typically 5 to 30 mg / L, and even more typically 5 to 20 mg / L, in terms of chlorine. According to this embodiment, the BOD, COD, and other chemicals are removed from the wastewater that has been subjected to the biological treatment S1, the coagulation and sedimentation treatment S2 in an acidic range, and the filtration treatment S3. Mn Since the organic wastewater with sufficiently reduced SS is supplied to the decolorization treatment S4, the inhibition of the color removal reaction caused by these components and the consumption of the decolorizing agent can be reduced, and the amount of the decolorizing agent added can be reduced. Even if the organic wastewater contains components that are difficult to remove with a decolorizing agent, if these are color components that can be removed by the biological treatment S1, the coagulation and sedimentation treatment S2 in an acidic range, and the filtration treatment S3, they will not remain after the decolorization treatment, and color removal to low concentrations is possible.

[0043] In addition, since the filtered water that has been subjected to the coagulation and precipitation treatment S2 and the filtration treatment S3 in an acidic range exhibits weak acidity, in the decolorization treatment S4, advanced treatment is possible without adding a catalyst for the decolorization reaction. There is no limit to the pH of the decolorization treatment, but it is preferable to perform the decolorization treatment at a lower pH than the biological treatment water. It is also more preferable to perform the decolorization treatment at a higher pH than the coagulation and precipitation treatment water. Although a catalyst may be used, not using a catalyst not only eliminates the need for catalyst costs, but also eliminates the need for a separation process for the catalyst components, thereby simplifying the treatment. In addition, since there is no need for a space to accommodate the catalyst components, especially the solid catalyst, the reaction tank can be made more compact. Furthermore, there is no concern about the leakage of harmful components due to the leakage of the catalyst, especially fine solid catalysts, eluted components from the solid catalyst, or liquid catalyst, so the treatment can be performed more safely.

[0044] The amount of decolorizing agent added is preferably adjusted based on the chromaticity of the filtered water flowing into the decolorizing process S4. In this embodiment, it is preferable to determine in advance by testing or the like the relationship between the amount of decolorizing agent added necessary to achieve a target chromaticity of treated water by the decolorizing process S4 for filtered water having a predetermined chromaticity, and to increase or decrease the amount of decolorizing agent added based on that relationship. For example, by measuring the chromaticity of the filtered water flowing into the decolorizing process S4 with a colorimeter or the like, and controlling the amount of decolorizing agent added based on the measurement results, the amount of decolorizing agent used can be reduced, and efficient processing can be performed.

[0045] For example, when sodium hypochlorite is used as the decolorizing agent, it is preferable to adjust the supply amount of the decolorizing agent so that sodium hypochlorite is supplied to the inflow raw water at a concentration (mg / L) that is 1 / 5 to 1 / 10 times the required removal color, assuming that the difference between the color of the inflow raw water flowing into the decolorizing treatment S4 and the target color of the treated water after the decolorizing treatment S4 is the "required removal color." For example, if the color of the filtered treated water flowing into the decolorizing treatment S4 is 200 degrees and the target color of the treated water is 30 degrees, the required removal color is 170 degrees. In this case, if the supply amount of sodium hypochlorite is 1 / 5 to 1 / 10 times the required removal color, that is, 17 to 34 mg / L, the target color of the treated water can be sufficiently achieved.

[0046] (Reduction process S5) A reducing agent may be added to the treated water after the decolorization treatment S4, and a reduction treatment S5 may be performed to remove chlorine-based oxidizing agents remaining in the treated water after the decolorization treatment. The reducing agent is not particularly limited as long as it can be used for the purpose of removing chlorine-based oxidizing agents, but it is preferable to use sulfites such as sodium thiosulfate, sodium sulfite, and sodium hydrogen sulfite. According to this embodiment, by providing the reduction treatment S5 after the decolorization treatment S4, even if sodium hypochlorite temporarily remains in the treated water after the decolorization treatment due to changes in the water quality of the filtered treated water, which is the raw water for the decolorization treatment S4, it can be completely removed by the reduction treatment S5, so that the impact of chlorine on the discharge water quality can be minimized.

[0047] The amount of reducing agent added is preferably adjusted based on the chromaticity of the filtered water flowing into the decolorization treatment S4 and the amount of decolorization agent supplied. For example, when sodium hydrogen sulfite is used as the reducing agent, its supply amount (mg / L) is sufficient at about 0.2 to 0.5 times that of sodium hypochlorite. On the other hand, when the chromaticity of the filtered water flowing into the decolorization treatment S4 is high at 300 degrees or more, a large amount of sodium hypochlorite may remain in the decolorization treatment water. Therefore, the amount of sodium hydrogen sulfite added is preferably 0.5 to 1.5 times, preferably 0.5 to 1.0 times, the amount of sodium hypochlorite added.

[0048] According to the method for removing color from organic wastewater according to the embodiment of the present invention, the color of the organic wastewater can be more reliably reduced to a target value by carrying out four stages of treatment: biological treatment S1, coagulation and sedimentation treatment S2 under an acidic condition, filtration treatment S3, and decolorization treatment S4. Organic wastewater is not only wastewater with low levels of persistent organic matter and SS, but also wastewater with a color of 100 to 1000 degrees and COD Mn Since color removal can be performed even on wastewater with a relatively high organic content of 100 mg / L or more, BOD of 200 to 1000 mg / L, and SS of 50 mg / L or more, color removal can be effectively performed even on organic wastewater whose color cannot be removed by conventional decolorization treatment using oxidizing agents and reducing agents alone.

[0049] As shown in FIG. 2, the organic wastewater color removal device according to the embodiment of the present invention comprises a biological treatment tank 1 for biologically treating organic wastewater and removing organic matter in the organic wastewater, a coagulation and sedimentation tank 2 for subjecting the biologically treated water obtained in the biological treatment tank 1 to coagulation and sedimentation treatment in an acidic range and removing suspended solids produced in the biological treatment, a filtration device 3 for filtering the coagulation and sedimentation treated water obtained in the coagulation and sedimentation tank 2, and a decolorization treatment tank 4 for removing color from the filtered water obtained in the filtration device 3 by adding a decolorizing agent to the filtered water.

[0050] The biological treatment tank 1 is a reaction tank for carrying out the activated sludge process, biofilm process, anaerobic treatment process, biological nitrification / denitrification process, membrane separation activated sludge process, multi-stage activated sludge process, fluidized bed carrier process, etc., and may be equipped with an aeration device, etc., as necessary. Biological treatment using microorganisms is carried out in the biological treatment tank 1. Typically, an activated sludge tank that contains activated sludge is used as the biological treatment tank 1.

[0051] The coagulation and sedimentation tank 2 is a reaction tank for coagulation and sedimentation treatment by adding a coagulant to the biological treatment water supplied from the biological treatment tank 1, and various coagulation and sedimentation devices can be used. A coagulant addition means 12 is connected to the coagulation and sedimentation tank 2, and an acidic inorganic coagulant such as aluminum sulfate, polyaluminum chloride (PAC), ferric chloride, or polyferric sulfate is added to the coagulation and sedimentation tank 2 via the coagulant addition means 12.

[0052] The filtration device 3 is a reaction tank for filtering the coagulation-sedimentation treated water obtained in the coagulation-sedimentation tank 2 to remove suspended solids remaining in the coagulation-sedimentation treated water, and various types of filtering devices such as a sand filter and a membrane filter can be used. Typically, a sand filter is suitable. The filtered water obtained in the filtration device 3 is sent to the decolorization treatment tank 4.

[0053] A decolorizing agent adding means 14 for adding a decolorizing agent is connected to the decolorizing tank 4. The decolorizing agent is added to the decolorizing tank 4 by the decolorizing agent adding means 14, and the decolorizing treatment is performed. A colorimeter 13 for measuring the chromaticity of the filtered water is provided in the piping between the filtration device 3 and the decolorizing tank 4 or in the inlet of the decolorizing tank 4. For example, a colorimeter capable of measuring absorbance in the visible light range of wavelengths 380 to 780 nm is used as the colorimeter 13, so that the chromaticity can be measured with high accuracy even if the chromaticity is low. In the example of FIG. 2, the colorimeter 13 is provided in the piping between the filtration device 3 and the decolorizing tank 4, but a colorimeter 13 may be further provided in the outlet of the decolorizing tank 4 and the reduction tank 5 described later so that the chromaticity of the treated water can be measured.

[0054] A reducing agent adding means 15 for adding a reducing agent is connected to the reduction tank 5. A reducing agent is added to the reduction tank 5 by the reducing agent adding means 15, and the chlorine-based oxidizing agent remaining in the decolorized water after the decolorization treatment is removed.

[0055] The control device 6 is connected to the flocculant adding means 12, the colorimeter 13, the decolorizing agent adding means 14, and the reducing agent adding means 15, and is configured to control the addition rates of the flocculant, the decolorizing agent, and the reducing agent based on the color measurement result by the colorimeter 13. For example, the control device 6 can calculate a required removal color represented by the difference between the color of the filtered water measured by the colorimeter 13 and the target color of the treated water flowing out from the decolorizing treatment tank 4, and control the decolorizing agent adding means 14 so as to add sodium hypochlorite as a decolorizing agent at a concentration (mg / L) that is 1 / 5 to 1 / 10 times the value of the required removal color into the decolorizing treatment tank 4. The control device 6 controls the supply of the decolorizing agent from the decolorizing agent adding means 14, so that the amount of decolorizing agent supplied to the decolorizing treatment tank 4 can be supplied only in the required amount, and thus a stable color removal treatment can be performed while reducing the amount of chemicals used.

[0056] When the reducing agent adding means 15 is controlled by the control device 6, for example, based on the chromaticity measurement result of the colorimeter 13, when the chromaticity is 300 degrees or more, the control device 6 can control the supply of the reducing agent by the reducing agent adding means 15 so that the amount of sodium hydrogen sulfite added as a reducing agent is 0.5 to 1.5 times, preferably 0.5 to 1.0 times, the amount of sodium hypochlorite added as a decolorizing agent. When the chromaticity measurement result of the colorimeter 13 is less than 300 degrees, the control device 6 can control the supply of the reducing agent by the reducing agent adding means 15 so that the amount of sodium hydrogen sulfite added as a reducing agent is 0.2 to 0.5 times the amount of sodium hypochlorite added as a decolorizing agent. Furthermore, if the chromaticity of the filtered water exceeds a predetermined value as a result of chromaticity measurement by the chromaticity meter 13, the control device 6 can control the flocculant addition means 12 to add more flocculant, and if the chromaticity of the filtered water is less than a predetermined value, the control device 6 can control the flocculant addition means 12 to gradually reduce the amount of flocculant added.

[0057] According to an organic wastewater treatment device according to an embodiment of the present invention, a biological treatment tank 1, a coagulation and sedimentation tank 2, and a filtration device 3 are provided upstream of a decolorization treatment tank 4. The biological treatment tank 1, the coagulation and sedimentation tank 2, and the filtration device 3 can remove persistent organic matter and SS contained in the organic wastewater in advance and adjust the color to an optimum value for color removal in the decolorization treatment tank 4, so that in the decolorization treatment tank 4, the color in the organic wastewater can be efficiently removed in a shorter time with a smaller amount of chemical solution.

[0058] In addition, since the color meter 13 can monitor the color of the filtered water before it is introduced into the decolorization treatment tank 4, the amount of decolorizing agent and reducing agent added can be controlled to an optimum amount early on even if the properties of the organic wastewater change. The control of the amount of chemicals added by the flocculant adding means 12, the decolorizing agent adding means 14, and the reducing agent adding means 15 is not limited to the above-mentioned embodiment. For example, it is also possible to control the amount of decolorizing agent added gradually to increase when the measurement result of the color meter 13 is higher than a preset reference value, and gradually decrease when the measurement result is equal to or lower than the preset reference value. By controlling in this manner, the color of the treated water can be always maintained below the target value, and treated water suitable for discharge from which harmful substances such as organic chlorine compounds have been removed can be stably obtained while avoiding excessive injection of chemicals.

[0059] Although the present invention has been described with reference to the above embodiment, the description and drawings forming a part of this disclosure should not be understood as limiting the present invention. In other words, the present disclosure is not limited to the above embodiment, and it is of course possible to combine and modify the components to embody the present disclosure without departing from the spirit of the present disclosure. EXAMPLES

[0060] Examples of the present invention will be described below together with comparative examples. These examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

[0061] Example 1 In Example 1, a color removal treatment of organic wastewater was carried out according to the flow shown in Figure 1. Raw water (organic drinking wastewater) having the properties shown in Table 1 was used, and biological treatment was carried out on this raw water using a fluidized carrier system to obtain biologically treated water, which was then subjected to coagulation and precipitation treatment in an acidic range, and the resulting coagulation and precipitation treated water was sand filtered to obtain filtered water. This sand filtered water was introduced into a decolorization treatment tank, and sodium hypochlorite was added as a decolorizing agent to carry out a decolorization treatment, thereby carrying out a color removal treatment.

[0062] As shown in Table 1, the raw water S-BOD and color were 550mg / L and 750 degrees, respectively, while the biologically treated water S-BOD and color were 10mg / L and 400 degrees, respectively, and color decreased with BOD removal. When this biologically treated water was subjected to coagulation sedimentation treatment (acidic coagulation sedimentation treatment) under conditions of coagulation pH 6.0 and polyiron injection rate of 100mg / L, the treated water SS: 5mg / L, COD: 10mg / L, and COD: 10mg / L. Mn The color level decreased to 17.0 mg / L. However, the color level remained high at 120 degrees. Even after sand filtration of this acidic sedimentation treated water, the color level remained high at 100 degrees.

[0063] When 15 mg / L of sodium hypochlorite was added to the filtered water obtained by sand filtration in the decolorization tank and the water was stirred for 5 minutes to react, the color of the treated water dropped to 20 degrees. At this time, the residual chlorine in the treated water was 5 mg / L, and by adding 5 mg / L of sodium hydrogen sulfite in the reduction tank, the residual chlorine in the discharged water became less than 0.5 mg / L.

[0064] [Table 1]

[0065] Comparative Example 1 Table 2 shows the results of removing color by performing coagulation sedimentation treatment in the neutral pH range of pH 7.0 without performing the decolorization and reduction treatments shown in Fig. 1. In Comparative Example 1, even when the polyferric sulfate injection rate was increased to 500 mg / L in the coagulation sedimentation treatment using the same biologically treated water as in Example 1, the color of the coagulation sedimentation treated water remained at 40 degrees, and even the filtered water after sand filtration had a color of 30 degrees. Compared to Comparative Example 1, in Example 1, the polyferric sulfate injection rate in the coagulation sedimentation treatment could be reduced to approximately 1 / 5 of that in Comparative Example 1, and the amount of sludge generated could also be reduced to approximately 1 / 5. This shows that Example 1 can achieve a reduction in treatment costs.

[0066] [Table 2]

[0067] Comparative Example 2 A color removal process was carried out under the conditions shown in Table 3 using the same treatment device as in Example 1. In Comparative Example 2, the color of the treated water was 200 degrees when the same polyferric sulfate injection rate as in Example 1 was 100 mg / L, which was higher than that of Example 1. In the decolorization process, in order to make the color of the filtered water 20 degrees, the same as in the Example, the amount of sodium hypochlorite added was 50 mg / L, which was about three times that of the Example. Therefore, in the reduction tank, the amount of sodium hydrogen sulfite added for reducing residual chlorine was 30 mg / L, which was six times that of the Example.

[0068] [Table 3] [Explanation of symbols]

[0069] 1...Biological treatment tank 2...Flocculation and settling tank 3. Filtration device 4. Decolorization tank 5…Reduction tank 6...Control device 12...Flocculant adding means 13...Chromaticity meter 14... Means for adding decolorizing agent 15...Means for adding reducing agent

Claims

1. The organic wastewater is pretreated by carrying out a biological treatment, a coagulation and sedimentation treatment in which a coagulant is added to perform coagulation and sedimentation treatment in an acidic range, and a filtration treatment in that order. The color of the filtered water obtained by the filtration is measured, Based on the measurement result of the color, an amount of decolorizing agent to be added to the filtered treated water is determined; A method for removing color from organic wastewater, comprising the step of adding a chlorine-based oxidizing agent as a decolorizing agent to the filtered treated water in the determined amount to perform decolorization treatment.

2. 2. The method for removing color from organic wastewater according to claim 1, wherein the coagulation and sedimentation treatment includes treatment in an acidic range having a pH of 5.0 to 6.

5.

3. 3. The method for removing color from organic wastewater according to claim 1, wherein the decolorization treatment comprises contacting the filtered water with the decolorizing agent for 3 to 10 minutes.

4. The method for removing color from organic wastewater according to any one of claims 1 to 3, further comprising adding a reducing agent to the treated water after the decolorization treatment, and removing the chlorine-based oxidizing agent remaining in the treated water after the decolorization treatment.

5. The organic wastewater has a chromaticity of 100 to 1000 degrees and a COD Mn The method for removing color from organic wastewater according to any one of claims 1 to 4, wherein the organic matter concentration is 100 mg / L or more, and the BOD is 200 mg / L or more.

6. A method for removing color from organic wastewater as described in any one of claims 1 to 5, comprising carrying out said biological treatment on said organic wastewater at a BOD volume loading of 1.5 kg / m3 / d or less using a fluidized bed carrier system or a hybrid system that combines fluidized bed carriers and activated sludge.

7. A method for removing color from organic wastewater as described in claim 4, comprising adding the reducing agent to the treated water after the decolorization treatment so that the amount of the reducing agent added is 0.2 to 1.5 times the amount of the decolorizing agent added.

8. a biological treatment tank for biologically treating the organic wastewater and removing organic matter from the organic wastewater; a coagulation and sedimentation tank for subjecting the biologically treated water obtained in the biological treatment tank to coagulation and sedimentation treatment in an acidic range and removing suspended solids generated by the biological treatment; A filtration device that filters the coagulation-sedimentation treated water obtained in the coagulation-sedimentation tank; a decolorization treatment tank for removing color from the filtered water by adding a chlorine-based oxidizing agent as a decolorizing agent to the filtered water obtained by the filtration device; a color measuring device for measuring the color of the filtered water flowing into the decolorization treatment tank; a control device for controlling the amount of the decolorizing agent added based on the result of the chromaticity measurement of the filtered water; An organic wastewater color removal device comprising:

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