Decolorization method for food and beverage wastewater

Abstract

To provide a discoloration method capable of obtaining a high-level chromaticity reduction effect while controlling the amount of coagulated sludge generated when discoloring highly colored food and beverage wastewater.SOLUTION: A method for discoloring food and beverage wastewater includes step 1 in which a tannin derivative having a cationic substituent is added to food and beverage wastewater with a chromaticity of 450 or more after undergoing biological treatment and the wastewater is agitated, step 2 in which an anionic polymer coagulant is added to the wastewater after performing the step 1 and the wastewater is agitated, and step 3 in which colored components are separated from the wastewater after performing the step 2 by solid-liquid separation and the treated water with reduced coloration is obtained.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for decolorizing food and beverage wastewater. [Background technology]

[0002] Wastewater generated during the production of soy sauce, coffee drinks, barley tea drinks, etc. is very deeply colored, and decolorization is generally performed in the purification process of this wastewater (hereinafter referred to as "colored wastewater"). Conventional decolorization treatment technologies include coagulation and sedimentation treatment, biological treatment (biological treatment), and oxidation treatment using oxidizing agents such as ozone (O3). However, biological treatment is insufficient in reducing the color of colored wastewater, and oxidation treatment has the problem of increasing initial and running costs in order to achieve a sufficient color reduction effect.

[0003] On the other hand, coagulation and sedimentation treatment is more effective in reducing color than biological treatment and does not have the cost issues associated with oxidation treatment, making it suitable for decolorizing colored wastewater. A known method of coagulation and sedimentation treatment involves adding an inorganic coagulant to wastewater to separate it into coagulated sludge and treated water. However, in order to further improve the color reduction effect, methods have been proposed in which a coagulant or an organic polymer coagulant is used instead of the inorganic coagulant, or a combination of these methods is used (see JP-A-6-226265 and JP-A-2001-162285).

[0004] JP 2001-79309 describes quaternary ammonium tannates as plant-based coagulation / flocculants for removing colloidal material from water.

[0005] JP 2001-79563 describes pyrocatechin tannin, an aqueous extract of Acacia mearnsii bark, an organic coagulation / flocculation agent of plant origin with cationic properties.

[0006] Japanese Patent Application Laid-Open No. 61-97362 describes a method for producing red cabbage pigments, which comprises soaking red cabbage in acidic water or alcoholic water to obtain a pigment extract, adding tannin and / or tannic acid to the extract, coprecipitating coexisting proteins and other impurities, and collecting the supernatant. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-226265 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-162285 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-79309 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-79563 [Patent Document 5] Japanese Patent Application Publication No. 61-97362 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the above-mentioned conventional decolorization methods using coagulation and sedimentation treatment, for example, it is necessary to add a very large amount of inorganic coagulant or organic coagulant to sufficiently reduce the color of the colored wastewater, resulting in the generation of a large amount of sludge. Also, as described in the above-mentioned patent document, tannin derivatives such as quaternary ammonium tannates are known as coagulants, but there is still room for improvement in the decolorization effect on colored wastewater.

[0009] The present invention has been made in view of the above circumstances, and one object of the present invention is to provide a decolorization method that can achieve a high level of color reduction effect while suppressing the amount of coagulated sludge produced when decolorizing highly chromatic food and beverage wastewater. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems and have found that it is advantageous to separate colored components from food and beverage wastewater using a tannin derivative having a cationic substituent and an anionic polymer flocculant according to a predetermined procedure. The present invention was completed based on this finding and is exemplified below.

[0011] [Aspect 1] Step 1: adding a tannin derivative having a cationic substituent to food and beverage wastewater having a color of 450 or more after biological treatment and stirring the wastewater; Step 2: adding an anionic polymer flocculant to the wastewater after step 1 is performed and stirring the wastewater; Step 3: separating colored components from the wastewater after step 2 into solid and liquid to obtain treated water with reduced color; A method for decolorizing food and beverage wastewater, comprising: [Aspect 2] Aspect 1: The decolorization method according to aspect 1, wherein in step 1, the tannin derivative having a cationic substituent is added to the wastewater so as to give a concentration of 50 to 300 mg / L in terms of solid matter. [Aspect 3] 3. The bleaching method according to claim 1, wherein the tannin derivative having a cationic substituent includes a tannin derivative having a trimethylammonium chloride group. [Aspect 4] A decolorization method according to any one of Aspects 1 to 3, wherein in step 2, the anionic polymer flocculant is added to the wastewater so as to give a concentration of 0.01 to 10 mg / L in terms of solid matter. [Aspect 5] 5. The decolorization method according to any one of Aspects 1 to 4, wherein in Step 1, the wastewater has a pH of 5 to 9 before the tannin derivative having a cationic substituent is added. [Aspect 6] A bleaching method according to any one of Aspects 1 to 5, wherein steps 1, 2, and 3 are carried out in separate tanks. [Aspect 7] A decolorization method according to any one of aspects 1 to 6, comprising carrying out step 1', before carrying out step 2, of adding an organic coagulant and / or an inorganic coagulant other than an anionic polymer coagulant to the wastewater after carrying out step 1, and stirring the mixture. [Aspect 8] Aspect 8. The decolorization method according to aspect 7, wherein in step 1′, the organic coagulant is added to the wastewater so as to give a concentration of 5 to 200 mg / L in terms of solid matter. [Aspect 9] A decolorization method according to aspect 7 or 8, wherein in step 1′, the inorganic flocculant is added to the wastewater so as to give a concentration of 50 to 500 mg / L in terms of solid matter. [Aspect 10] 10. The decolorizing method according to any one of Aspects 7 to 9, wherein Step 1, Step 2, Step 3, and Step 1′ are carried out in separate tanks. [Effects of the Invention]

[0012] According to a method for decolorizing food and beverage wastewater according to one embodiment of the present invention, when decolorizing highly chromatic food and beverage wastewater, it is possible to achieve a high level of color reduction while suppressing the amount of flocculated sludge produced. Furthermore, decolorization also enables the removal of COD components. Furthermore, the amount of inorganic flocculant used, which is a cause of sludge generation, can be significantly reduced, thereby reducing not only chemical costs but also industrial waste disposal costs. Therefore, this decolorization method has extremely high industrial value as a low-cost method for treating highly chromatic food and beverage wastewater. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram of a wastewater treatment device suitable for carrying out a food and beverage wastewater decolorization method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] <1. Method for decolorizing food and beverage wastewater> A method for decolorizing food and beverage wastewater according to one embodiment of the present invention includes: Step 1: adding a tannin derivative having a cationic substituent to food and beverage wastewater having a color of 450 or more after biological treatment and stirring the wastewater; Step 2: adding an anionic polymer flocculant to the wastewater after step 1 is performed and stirring the wastewater; Step 3: separating colored components from the wastewater after step 2 into solid and liquid to obtain treated water with reduced color; This includes carrying out the following.

[0015] (1-1.Process 1) The wastewater to be treated by the decolorization method of the present invention is food and beverage wastewater having a color value of 450 or more, typically 450 to 1000, and more typically 450 to 600, after biological treatment. This is because food and beverage wastewater with a color value of less than 450 can have its color removed by a known coagulation and sedimentation method. Food and beverage wastewater refers to wastewater containing at least one of food and beverage, and typical examples include wastewater discharged from the production process of food such as soy sauce, and wastewater discharged from the production process of beverages such as coffee, barley tea, soft drinks, and fruit juice.

[0016] In the present invention, chromaticity refers to the chromaticity of platinum-cobalt as defined in JIS K0101:1998, and is measured by a transmitted light measurement method that measures absorbance at around 390 nm. If the chromaticity is too high, the sample may be diluted appropriately with pure water and then measured, and the measured value may be multiplied by the dilution factor.

[0017] The wastewater to be treated by the decolorization method of the present invention has previously undergone biological treatment. By subjecting food and beverage wastewater to biological treatment in advance, the color reduction effect of the decolorization method of the present invention can be improved. There are no particular limitations on the type of biological treatment method, and examples include aerobic treatment, anaerobic treatment, and a combination of both. In addition, a step of removing solids may be carried out during the biological treatment process.

[0018] Furthermore, the wastewater to be treated by the decolorization method of the present invention has been previously subjected to biological treatment, and therefore usually has a pH close to neutral. Specifically, the pH of the wastewater after biological treatment is generally 5 to 9, and typically 6 to 8. However, if necessary, when carrying out step 1, the pH may be adjusted to the range of 6 to 8 by adding a pH adjuster.

[0019] In step 1, a tannin derivative having a cationic substituent is added to food and beverage wastewater with a color of 450 or more after biological treatment and then stirred. Step 1 alone is not very effective in flocculating colored components, but by carrying out step 1, the colored components and COD components are adsorbed to the tannin derivative, promoting the formation and / or growth of flocs, which make it easier for the colored components and COD components in the wastewater to form flocs that are easy to settle when an anionic polymer flocculant is added in a later step.

[0020] In this specification, tannin refers to polyphenols including tannic acids, catechins, leucoanthocyanins, and chlorogenic acids, and is widely found in plants in nature. Tannins can be broadly divided into two types: hydrolyzable tannins (pyrogallol-type tannins) and condensed tannins (catechol-type tannins). Examples of hydrolyzable tannins include chestnut tannin and myrobalan tannin, while examples of condensed tannins include mimosa tannin and quebracho tannin. Examples of tannic acids include gallnut tannin and gall tannin. Among these, plant tannins extracted from mimosa, quebracho, chestnut, etc., which are industrially mass-produced, are preferred. These tannins may be used alone or in combination to produce tannin derivatives.

[0021] The cationic substituent is not particularly limited as long as it is a primary to quaternary amino group, and examples thereof include a trialkylammonium chloride group. Of these, a trimethylammonium chloride group is preferred. The position of the cationic substituent is not particularly limited.

[0022] There are no particular limitations on the method for producing such tannin derivatives having a cationic substituent, and examples of methods that can be used include those described in JP-A Nos. 2001-79309 and 2001-79563. Specific examples include a method in which tannin is aminomethylated by the Mannich reaction using a dialkylamine having 1 to 2 carbon atoms and formalin, and then converted into a tertiary ammonium salt with a mineral acid and an organic acid, and a method in which tannin similarly aminomethylated by the Mannich reaction is converted into a quaternary ammonium salt with an alkyl halide having 1 to 2 carbon atoms, benzyl halide, and a diester of sulfuric acid with an alcohol having 1 to 2 carbon atoms.

[0023] Furthermore, commercially available tannin derivatives having a cationic substituent can also be used. Examples of such commercially available products include "TANFLOC SA" (trade name) and "TANFLOC SS" (trade name) from Tanac SA (Brazil). When using commercially available tannin derivatives having a cationic substituent, it is preferable to dissolve them in water and add them in a fixed amount using a pump or the like. When adding a tannin derivative having a cationic substituent in the form of an aqueous solution, the appropriate dissolution concentration is 1 to 10 w / v% (grams of tannin derivative in 100 mL of water).

[0024] The tannin derivative having a cationic substituent is preferably added to the wastewater at a concentration of 10 to 500 mg / L in terms of solids. An excellent decolorizing effect can be obtained by adding a concentration of 10 mg / L or more. Furthermore, since the decolorizing effect tends to saturate when the concentration exceeds 500 mg / L, adding a concentration of 500 mg / L or less can achieve both decolorizing effect and economic efficiency. The tannin derivative having a cationic substituent is more preferably added to the wastewater at a concentration of 50 to 300 mg / L in terms of solids, and even more preferably added to the wastewater at a concentration of 100 to 300 mg / L. Tannin derivatives having a cationic substituent may be used alone or in combination of two or more. When two or more types are used in combination, it is preferable to add them so that the total concentration falls within the above-mentioned concentration range.

[0025] After the addition of the tannin derivative having a cationic substituent in step 1 is completed, it is preferable to stir the wastewater before carrying out the next step. This is to ensure that the added tannin derivative having a cationic substituent is uniformly dispersed throughout the wastewater. The stirring method is not particularly limited, and the concept of stirring includes mechanical stirring using a stirring device as well as mixing using only a water current. The timing for starting stirring the wastewater may be before the addition of the tannin derivative having a cationic substituent, during the addition of the tannin derivative having a cationic substituent, or after the addition of the tannin derivative having a cationic substituent is completed. In particular, from the viewpoint of quickly dispersing the tannin derivative having a cationic substituent in the wastewater and bringing it into contact with coloring components and COD components, it is desirable to add the tannin derivative having a cationic substituent after stirring has already begun.

[0026] There are no particular restrictions on the time for stirring the wastewater after the addition of the tannin derivative having a cationic substituent has been completed, and from the viewpoint of increasing the opportunity for contact with colored components and COD components in the treated water, it is preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more.

[0027] (1-2.Process 1') After step 1, step 2 may be performed consecutively, in which an anionic polymer flocculant is added. However, prior to performing step 2, an organic coagulant and / or inorganic coagulant other than the anionic polymer flocculant may be added. Specifically, prior to performing step 2, step 1' is performed, in which an organic coagulant and / or inorganic coagulant other than the anionic polymer flocculant is added to the wastewater after performing step 1 and stirred. This can have the effect of promoting the formation and / or growth of flocs. However, even if an organic coagulant and / or inorganic coagulant is added without performing step 1, the formation and / or growth of flocs is limited. Therefore, performing step 1 and then adding an organic coagulant and / or inorganic coagulant is advantageous for effectively flocculating colored components in the subsequent step.

[0028] Examples of inorganic coagulants include aluminum sulfate, aluminum chloride, polyaluminum chloride (PAC), ferric chloride, polyferric sulfate (polyiron), etc. Most organic coagulants are cationic, but examples include polyamines, dicyandiamides, polydicyandiamides, polydiallyldimethylammonium chlorides (also called "polyDADMAC"), amino condensation systems, and melamine acid colloids. More specifically, examples of the organic coagulant and / or inorganic coagulant include polyalkylpolyamine, polyethyleneimine, diallyldimethylammonium chloride, ethylenediamine-epichlorohydrin polycondensate, methylolmelamic acid colloid, dicyandiamide-ammonium chloride-formaldehyde polycondensate, polyethylene-polyamine-dimethylamine-epichlorohydrin polycondensate, dialkylamine-epichlorohydrin polycondensate (particularly dimethylamine-epichlorohydrin polycondensate), polyallylamine hydrochloride, polydiallylmethylamine hydrochloride, a copolymer of diallyldimethylammonium chloride and sulfur dioxide, a copolymer of diallyldimethylammonium chloride and acrylamide, and a copolymer of diallylamine hydrochloride and sulfur dioxide. These organic coagulants and / or inorganic coagulants may be used alone or in combination of two or more.

[0029] In step 1', the inorganic flocculant is preferably added to the wastewater so that the solids concentration is 50 to 500 mg / L, more preferably 100 to 300 mg / L. In step 1', the organic coagulant is preferably added to the wastewater so that the solids concentration is 5 to 200 mg / L, more preferably 10 to 100 mg / L. If the inorganic flocculant and organic coagulant are solid, they may be dissolved before addition. The above-mentioned addition ratios of the inorganic flocculant and organic coagulant are typical values, but by using a tannin derivative in combination, it is possible to reduce the addition ratio required to achieve the same color reduction effect and COD reduction effect.

[0030] After the addition of the organic coagulant and / or inorganic flocculant in step 1' is completed, it is preferable to stir the wastewater before carrying out the next step. This is to ensure that the added organic coagulant and / or inorganic flocculant is uniformly dispersed throughout the wastewater. The stirring method is not particularly limited, and the concept of stirring includes mechanical stirring using a stirring device as well as mixing using only a water current. The timing for starting stirring the wastewater may be before the addition of the organic coagulant and / or inorganic flocculant, during the addition of the organic coagulant and / or inorganic flocculant, or after the addition of the organic coagulant and / or inorganic flocculant is completed. Furthermore, if the pH of the wastewater fluctuates from near neutrality due to the addition of the organic coagulant and / or inorganic flocculant, a pH adjuster may be added to adjust the pH to near neutral, for example, in the range of 6 to 8.

[0031] There are no particular restrictions on the time for stirring the wastewater after the addition of the organic coagulant and / or inorganic flocculant is completed, but from the viewpoint of efficiently bringing the organic coagulant and / or inorganic flocculant into contact with the colored components and COD components in the treated water, it is preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more.

[0032] (1-3.Process 2) In step 2, an anionic polymer flocculant is added to the wastewater after step 1, preferably after step 1'. This causes the flocs generated in the previous step to grow through a flocculation reaction, making them more likely to settle in the next step. Even if the order of steps 2 and 1' is reversed after step 1 is performed, or if only step 1' is performed without step 2, it is difficult to obtain a satisfactory settling rate.

[0033] Examples of anionic polymer flocculants include partial hydrolyzates of polyacrylamide, polymers of anionic monomers, and copolymers of anionic monomers and nonionic monomers such as acrylamide. The anionic polymer flocculant preferably has a weight-average molecular weight of 3,000,000 to 20,000,000, and more preferably 5,000,000 to 15,000,000, although this is not limitative. Anionic polymer flocculants can be used alone or in combination with two or more. Anionic polymer flocculants are generally provided as aqueous solutions, with a dissolution concentration of about 0.01 to 0.5% by mass.

[0034] Examples of anionic monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 2-allylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methallylamidoethanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid, 4-acryloyloxybutanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfonic acid, and metal salts or ammonium salts thereof, such as alkali metals and alkaline earth metals. These anionic monomers may be used alone or in combination of two or more.

[0035] Examples of the nonionic monomer include acrylamide, methacrylamide, methacrylonitrile, vinyl acetate, etc. These nonionic monomers may be used alone or in combination of two or more. The anionic polymer flocculant of the present invention also includes homopolymers of the above nonionic monomers.

[0036] Preferred examples of the copolymer of anionic monomer and nonionic monomer include acrylamide-acrylate copolymer and acrylamide-2-acrylamido-2-methylpropanesulfonic acid copolymer.

[0037] In step 2, the amount of anionic polymer flocculant added may be about the same as that used in a typical coagulation and sedimentation treatment. Specifically, the amount added to the wastewater is preferably 0.01 to 10 mg / L, more preferably 0.1 to 5 mg / L, in terms of solids.

[0038] After the addition of the anionic polymer flocculant in step 2 is completed, it is preferable to stir the wastewater before carrying out the next step. This is to ensure that the added anionic polymer flocculant is uniformly dispersed throughout the wastewater. There are no particular limitations on the stirring method, but the concept of stirring includes mechanical stirring using a stirring device as well as mixing using only water flow. The wastewater may be stirred before the addition of the anionic polymer flocculant, during the addition of the anionic polymer flocculant, or after the addition of the anionic polymer flocculant is completed. In particular, from the perspective of diffusing the anionic polymer flocculant throughout the water to be treated, it is desirable to start stirring the wastewater before the addition of the anionic polymer flocculant.

[0039] There are no particular restrictions on the time for stirring the wastewater after the addition of the anionic polymer flocculant is completed, but from the viewpoint of diffusing the anionic polymer flocculant into the water to be treated, it is preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more. Furthermore, from the viewpoint of not breaking down the flocs formed by the anionic polymer flocculant, the time for stirring the wastewater after the addition of the anionic polymer flocculant is preferably 30 minutes or less, but is not particularly limited.

[0040] (1-4.Process 3) By carrying out step 2, the colored components in the wastewater grow into coarse flocs through a coagulation reaction. Therefore, in step 3, the colored components are separated from the wastewater after step 2 to obtain treated water with reduced color. The method for solid-liquid separation is not limited, but a coagulation sedimentation method is preferred. When using the coagulation sedimentation method, the wastewater after step 2 is allowed to stand, allowing the flocs of the coagulated colored components to settle. The standing time can be set appropriately depending on the amount of wastewater. Next, the obtained supernatant water is separated from the precipitate to obtain treated water with reduced color.

[0041] The above series of steps may be carried out in a batch-type wastewater treatment device in which all steps are carried out in one tank, or in a continuous-type wastewater treatment device in which each step is carried out in a separate tank. A preferred method can be selected depending on the amount of food and beverage wastewater to be treated.

[0042] <2. Example of wastewater treatment equipment configuration> A continuous wastewater treatment device suitable for carrying out a method for decolorizing food and beverage wastewater according to one embodiment of the present invention will now be described with reference to the drawings. Fig. 1 shows a schematic diagram of an example of the configuration of a wastewater treatment device 100 according to the present invention. The wastewater treatment device 100 includes a relay tank 110, a primary reaction tank 120, a secondary reaction tank 130, a coagulation tank 140, a settling tank 150, and a treated water tank 160.

[0043] (2-1. Relay tank) Food and beverage wastewater 10 having a color value of 450 or more after biological treatment flows into relay tank 110 through drainage line 101. Food and beverage wastewater 10 is temporarily stored in relay tank 110. Food and beverage wastewater 10 stored in relay tank 110 is appropriately sent to primary reaction tank 120 through liquid transfer line 102 installed between relay tank 110 and primary reaction tank 120. The food and beverage wastewater 10 can be sent from relay tank 110 to primary reaction tank 120 by pump 112 installed midway along liquid transfer line 102, for example.

[0044] (2-2. Primary Reactor) The food and beverage wastewater 10 that flows into the primary reaction tank 120 is acted upon by a tannin derivative 122 having a cationic substituent that is added to the primary reaction tank 120. This promotes the formation and / or growth of flocs of colored components contained in the food and beverage wastewater 10. Furthermore, it is preferable to install an agitator 121 in the primary reaction tank 120. This allows the tannin derivative 122 having a cationic substituent to be added while the food and beverage wastewater 10 is being stirred. The food and beverage wastewater 10 can continue to be stirred even after the addition of the tannin derivative 122 having a cationic substituent has been completed. There are no particular restrictions on the type of agitator 121, and any agitation device commonly used in the relevant field can be used, including, for example, a mechanical agitator that uses a propeller or blade to rotate and agitate the liquid in the tank.

[0045] In the case of a mechanical stirrer, the rotation speed may be set appropriately. From the viewpoint of uniformly dispersing the tannin derivative 122 having a cationic substituent in the primary reaction tank 120 while generating and / or growing flocs, the rotation speed is preferably 30 rpm to 500 rpm, and more preferably 100 rpm to 500 rpm.

[0046] The tannin derivative 122 having a cationic substituent may be added by dissolving it in water or by adding it in powder form. From the viewpoint of easy control of the injection amount, the tannin derivative 122 having a cationic substituent is preferably dissolved in water and added at a fixed amount by a pump or the like.

[0047] The retention time of food and beverage wastewater 10 in primary reaction tank 120 is not limited, but from the viewpoint of efficiently bringing tannin derivatives 122 into contact with colored components and COD components in the water to be treated, it is preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more. When food and beverage wastewater 10 is treated while being continuously supplied to primary reaction tank 120, the retention time can be determined by dividing the volume V of food and beverage wastewater 10 in primary reaction tank 120 by the flow rate F of food and beverage wastewater 10 supplied to primary reaction tank 120, V / F.

[0048] (2-3. Secondary Reactor) After being treated in the primary reaction tank 120, the food and beverage wastewater 10 is then sent to the secondary reaction tank 130. There are no particular limitations on the method for sending the food and beverage wastewater 10 from the primary reaction tank 120 to the secondary reaction tank 130, and examples include a liquid sending method in which overflow from an overflow section such as an overflow weir installed at the top of the primary reaction tank 120 is poured into the secondary reaction tank 130, and a liquid sending method using a pump.

[0049] The food and beverage wastewater 10 that flows into the secondary reaction tank 130 is subjected to the action of an organic coagulant and / or inorganic flocculant 132 added to the secondary reaction tank 130. This promotes the formation and / or growth of flocs of colored components contained in the food and beverage wastewater 10. It is also preferable to install an agitator 131 in the secondary reaction tank 130. This makes it possible to add the organic coagulant and / or inorganic flocculant 132 while the food and beverage wastewater 10 is being stirred. The food and beverage wastewater 10 can continue to be stirred even after the addition of the organic coagulant and / or inorganic flocculant 132 is complete. There are no particular restrictions on the type of agitator 131, and agitation devices commonly used in the relevant field can be used, such as mechanical agitators that use a propeller, blades, etc. to rotate and agitate the liquid in the tank.

[0050] In the case of a mechanical agitator, the rotation speed may be set appropriately, but from the viewpoint of generating and / or growing flocs while uniformly dispersing the organic coagulant and / or inorganic flocculant 132 in the secondary reaction tank 130, the rotation speed is preferably 30 rpm to 1000 rpm, and more preferably 100 rpm to 500 rpm.

[0051] Since the organic coagulant and / or inorganic flocculant 132 is often a liquid product, it is preferable to add a fixed amount directly using a pump, etc. If the organic coagulant and / or inorganic flocculant 132 is provided as a solid such as a powder, it may be added after being dissolved in water, or may be added in powder form, but from the viewpoint of ease of controlling the injection amount, it is preferable to dissolve the organic coagulant and / or inorganic flocculant 132 in water and add a fixed amount using a pump, etc.

[0052] The residence time of food and beverage wastewater 10 in secondary reaction tank 130 is not limited, but from the viewpoint of efficiently bringing the organic coagulant and / or inorganic flocculant 132 into contact with the colored components and COD components in the water to be treated, it is preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more. When food and beverage wastewater 10 is treated while being continuously supplied to secondary reaction tank 130, the residence time can be determined by dividing the volume V of food and beverage wastewater 10 in secondary reaction tank 130 by the flow rate F of food and beverage wastewater 10 supplied to secondary reaction tank 130, V / F.

[0053] It is also possible to omit the secondary reaction tank 130 and send the food and beverage wastewater 10 directly to the coagulation tank 140 after treatment in the primary reaction tank 120, but providing the secondary reaction tank 130 is preferable because it is more effective in promoting the production and / or growth of flocs.

[0054] (2-4.Flocculation tank) After being treated in the secondary reaction tank 130, the food and beverage wastewater 10 is then sent to the coagulation tank 140. There are no particular limitations on the method for sending the food and beverage wastewater 10 from the secondary reaction tank 130 to the coagulation tank 140, and examples include a liquid sending method in which overflow from an overflow section such as an overflow weir installed at the top of the secondary reaction tank 130 is poured into the coagulation tank 140, and a liquid sending method using a pump.

[0055] The food and beverage wastewater 10 that flows into the coagulation tank 140 is subjected to the action of the anionic polymer flocculant 142 added to the coagulation tank 140. This causes flocs of colored components contained in the food and beverage wastewater 10 to grow and become coarse. It is also preferable to install an agitator 141 in the coagulation tank 140. This makes it possible to add the anionic polymer flocculant 142 while the food and beverage wastewater 10 is being stirred. The food and beverage wastewater 10 can continue to be stirred even after the addition of the anionic polymer flocculant 142 has been completed. There are no particular restrictions on the type of agitator 141, and commonly used agitation devices can be used, including mechanical agitation devices that rotate and agitate the liquid in the tank using a propeller, blades, etc.

[0056] In the case of a mechanical agitator, the rotation speed may be set appropriately, but from the viewpoint of growing flocs while uniformly dispersing the anionic polymer flocculant 142 in the flocculation tank 140, the rotation speed is preferably 10 rpm to 300 rpm, more preferably 30 rpm to 200 rpm, and even more preferably 50 rpm to 100 rpm.

[0057] The anionic polymer flocculant 142 may be added by dissolving it in water or in powder form. From the viewpoint of ease of controlling the injection amount, it is preferable that the anionic polymer flocculant 142 be dissolved in water and added at a fixed amount using a pump or the like.

[0058] The residence time of food and beverage wastewater 10 in coagulation tank 140 is not limited, but is preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more, from the viewpoint of diffusing anionic polymer flocculant 142 into the water to be treated. Furthermore, from the viewpoint of not breaking down the flocs formed by anionic polymer flocculant 142, the time for stirring the wastewater after addition of anionic polymer flocculant 142 is preferably 30 minutes or less, but is not particularly limited. When food and beverage wastewater 10 is treated while being continuously supplied to coagulation tank 140, the residence time can be calculated as V / F, which is the volume V of food and beverage wastewater 10 in coagulation tank 140 divided by the flow rate F of food and beverage wastewater 10 supplied to coagulation tank 140.

[0059] (2-5. Sedimentation tank) After being treated in the coagulation tank 140, the food and beverage wastewater 10 is then sent to the settling tank 150. There are no particular limitations on the method for sending the food and beverage wastewater 10 from the coagulation tank 140 to the settling tank 150, and examples include a liquid sending method in which overflow from an overflow section such as an overflow weir installed at the top of the coagulation tank 140 is poured into the settling tank 150, and a liquid sending method using a pump.

[0060] The colored components in the food and beverage wastewater 10 grow into coarse flocs in the coagulation tank 140. Therefore, when the food and beverage wastewater 10 flows into the settling tank 150, the flocs of the colored components further coarsen, causing the flocs to coagulate and settle, forming coagulated sludge, while supernatant water with reduced color is obtained.

[0061] When food and beverage wastewater 10 is treated while being continuously supplied to sedimentation tank 150, the volume V of food and beverage wastewater 10 in sedimentation tank 150 divided by the flow rate F of food and beverage wastewater 10 supplied to sedimentation tank 150, V / F, can be used as the residence time.

[0062] (2-6. Treatment tank) The supernatant water in the settling tank 150 may be discharged directly from the settling tank 150 as treated water, or may be sent to the treated water tank 160 in order to adjust the amount of treated water to be discharged. There are no particular limitations on the method for sending the supernatant water from the settling tank 150 to the treated water tank 160, and examples include a method of sending the supernatant water by pouring overflow from an overflow section such as an overflow weir provided at the top of the settling tank 150 into the treated water tank 160, or a method of sending the supernatant water using a pump. The treated water tank 160 can store supernatant water with reduced color, and it is appropriately discharged as treated water 20. For example, the treated water can be discharged by overflowing from an overflow section such as an overflow weir provided at the top of the treated water tank 160. [Example]

[0063] 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.

[0064] Example 1 Wastewater discharged from a barley tea manufacturing process was biologically treated using a fluidized-bed biofilm treatment method. The color of the resulting biologically treated wastewater (hereinafter referred to as "treated water") was measured using a colorimeter WA7700 manufactured by JEOL Ltd., which employs a transmitted light measurement method that measures absorbance at around 390 nm, and was found to be 454. The pH was also within the range of 5 to 9.

[0065] A 10 w / v% aqueous solution (hereinafter referred to as "10% tannin") was prepared using "TANFLOC SA" (trade name) from Tanac SA (Brazil). 100 mL of the water to be treated prepared above was placed in a 100 mL beaker, and 100 mg / L of 10% tannin was added in solid form, followed by stirring with a magnetic stirrer for 3 minutes.

[0066] Next, 100 mg / L of liquid inorganic coagulant (PAC) was added in terms of solid matter, and 10% caustic soda was added dropwise to adjust the pH to 7.5, after which stirring (rotation speed: 800 rpm) was continued for 3 minutes.

[0067] Next, a powdered anionic polymer flocculant "Evagrose (registered trademark) A-151" (trade name) manufactured by Suing Corporation, which contains a copolymer of sodium acrylate and acrylamide, was dissolved in water to prepare a 0.1% by mass aqueous solution, and 2 mg / L in terms of solid matter was added. The solution was stirred for 3 minutes (rotation speed: 200 rpm), after which the stirring was stopped and the solution was allowed to stand for 3 minutes. This allowed flocs of colored components to settle, and supernatant water was obtained.

[0068] The color of the supernatant water was measured and found to be 218. The COD was measured and found to be 165 mg / L.

[0069] <Comparative Example 1> The same test as in the example was conducted except that wastewater that had not been subjected to biological treatment was treated. In this case, no floc formation was observed, and the effects of color reduction and COD removal were not confirmed. From these results, it is clear that biological treatment is necessary beforehand.

[0070] <Comparative Example 2> The same test as in the example was conducted, except that neither inorganic coagulant (PAC) nor anionic polymer coagulant was used. In this case, no floc formation was observed, and the effects of color reduction and COD removal were not confirmed. From these results, it can be seen that the effects of color reduction and COD removal cannot be obtained by using tannin derivatives alone.

[0071] <Comparative Example 3> To the same treated water as in the example, 300 mg / L of liquid inorganic coagulant (PAC) was added, and 10% caustic soda was added dropwise to adjust the pH to 7.5, after which stirring (rotation speed 800 rpm) was continued for 3 minutes. Next, a powdered anionic polymer flocculant "Evagrose (registered trademark) A-151" (trade name) manufactured by Suing Corporation, which contains a copolymer of sodium acrylate and acrylamide, was dissolved in water to prepare a 0.1% by mass aqueous solution, and 2 mg / L in terms of solid matter was added. The solution was stirred for 3 minutes (rotation speed: 200 rpm), after which the stirring was stopped and the solution was allowed to stand for 3 minutes. This allowed flocs of colored components to precipitate, and supernatant water was obtained.

[0072] The color of the supernatant water was measured and found to be 316. The COD was measured and found to be 165 mg / L.

[0073] <Comparative Example 4> The same test as in Comparative Example 3 was carried out, except that the inorganic coagulant (PAC) addition rate was 100 mg / L. The supernatant water was sampled and the color was measured, which was 377. The COD was measured, which was 195 mg / L.

[0074] From the results of Comparative Examples 3 and 4, it can be seen that when treatment with only an inorganic flocculant and an anionic polymer flocculant is performed without treatment with a tannin derivative, it is necessary to use more than three times as much inorganic flocculant as in the Examples to achieve the same level of color reduction effect as in the Examples. [Explanation of symbols]

[0075] 10:Food and beverage wastewater 20: Treated water 100: Wastewater treatment equipment 101: Drain line 102: Liquid transfer line 110: Relay tank 112: Pump 120: Primary reaction tank 121: Mixer 122: Tannin derivatives 130: Secondary reaction tank 131: Mixer 132: Inorganic flocculant 140:Flocculation tank 141: Mixer 142: Anionic polymer flocculant 150: Sedimentation tank 160: Treatment tank

Claims

1. Step 1: adding a tannin derivative having a cationic substituent to food and beverage wastewater having a high color after biological treatment and stirring the wastewater; Step 1' of adding an organic coagulant and / or an inorganic coagulant other than an anionic polymer coagulant to the wastewater after step 1 is carried out and stirring; Step 2: adding an anionic polymer flocculant to the wastewater after step 1' is performed and stirring the wastewater; a step 3 of separating flocs of colored components from the wastewater after the step 2 has been carried out, thereby obtaining treated water with reduced color; A method for decolorizing food and beverage wastewater, comprising:

2. 2. The decolorization method according to claim 1, wherein in step 1, the tannin derivative having a cationic substituent is added to the wastewater so as to give a concentration of 50 to 300 mg / L in terms of solid matter.

3. 3. The decolorizing method according to claim 1, wherein in step 1, the tannin derivative having a cationic substituent includes a tannin derivative having a trimethylammonium chloride group.

4. 2. The decolorization method according to claim 1, wherein in step 2, the anionic polymer flocculant is added to the wastewater so as to be 0.01 to 10 mg / L in terms of solid matter.

5. 2. The method for decolorizing according to claim 1, wherein in step 1, the pH of the wastewater is 5 to 9 before the tannin derivative having a cationic substituent is added.

6. 2. The decolorization method according to claim 1, wherein steps 1, 2, and 3 are carried out in separate tanks.

7. 2. The decolorization method according to claim 1, wherein in step 1', the organic coagulant is added to the wastewater so as to have a concentration of 5 to 200 mg / L in terms of solid matter.

8. 2. The decolorization method according to claim 1, wherein in step 1′, the inorganic flocculant is added to the wastewater so as to be 50 to 500 mg / L in terms of solid matter.

9. 2. The decolorization method according to claim 1, wherein steps 1, 2, 3, and 1' are carried out in separate tanks.

10. 2. The method for decolorizing food and beverage wastewater according to claim 1, wherein the food and beverage wastewater with high color has a color of 450 or more.

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