Method for decolorizing organic waste water

Abstract

To provide a decoloring method of organic waste water capable of decoloring the waste water to a desired chromaticity with a smaller input electric quantity, i.e., low power consumption while using an electrochemical flocculation method, and a decoloring apparatus of organic waste water capable of efficiently decoloring the waste water to the desired chromaticity.SOLUTION: A method for decoloring organic wastewater, comprising a step of calculating an input amount of electricity required for reducing raw water absorbance of the organic wastewater before treatment to predetermined absorbance, and a step of filling a treatment tank, in which an anode containing iron or aluminum and a cathode are disposed, with the organic wastewater, applying a current to the anode and the cathode to exert an electrochemical coagulation action on the organic wastewater, and stopping the application of the current after the input amount of electricity is reached.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for decolorizing organic wastewater discharged from livestock farms, food factories, dye factories, and the like. [Background technology]

[0002] Livestock wastewater from livestock farms and organic wastewater from food factories and dye factories are treated to remove certain impurities, and then the treated liquid is discharged into the environment, such as rivers. There are no specific standards regarding the coloration (chromaticity) of such organic wastewater, so even colored organic wastewater that has undergone certain treatment is allowed to be discharged into rivers, etc. However, there has been a problem in that when local residents see colored wastewater, they have the preconceived notion that purification is insufficient, and this can lead to complaints.

[0003] Therefore, several technologies for decolorizing colored organic wastewater have been proposed. For example, a continuous decolorization method for livestock industry wastewater is known in which a decolorizing agent is added to remove color caused by organic matter in the livestock industry wastewater, light of a wavelength effective for detecting yellowish-brown pigments is applied to the livestock industry wastewater, the amount of light absorbed is detected, and the amount of the decolorizing agent is controlled based on the detected value of absorbance (Patent Document 1). However, treatment methods that use decolorizing agents such as hypochlorous acid have high running costs, and since chlorine is contaminated in the treated wastewater, there is a possibility that it may have an adverse effect on fish in rivers and the like.

[0004] Also, a wastewater purification method is known in which water-soluble chlorides are added to wastewater, and at least one pair of electrodes, each having iron electrodes as the anode and cathode, and another pair of electrodes, each having platinum electrodes as the anode and cathode, are inserted into the same purification tank, and electricity is passed through them, and the colored flocs that are produced are removed (Patent Document 2). This wastewater purification method is a so-called electrochemical coagulation method, in which Cl is coagulated by a platinum electrode. - ions into hypochlorite ions (ClO - ) and this oxidizing power causes the oxidation of Fe from the iron electrode. 2+ Fe 3+The method produces iron(III) hydroxide as a catalyst, which allows inorganic and organic substances to be adsorbed and precipitated, and the remaining hypochlorous acid decomposes the organic substances, resulting in decolorization and deodorization. This method involves electrochemical coagulation, in which the decolorization effect increases with increasing reaction time (amount of electricity input) (Tables 1 and 3). Patent Document 2 does not mention reaction time, but with electrochemical coagulation, excessive reaction time leads to wasted electrical energy and an increase in secondary products. In particular, the wasted electrical energy, coupled with the recent rise in electricity prices, directly leads to increased treatment costs, posing a major challenge to practical application. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-1278 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-82864 Summary of the Invention [Problem to be solved by the invention]

[0006] When the present inventors treated organic wastewater using electrochemical coagulation, they found that the efficiency decreased exponentially as the color decreased during the treatment, and that because aggregates formed in the effluent, it was necessary to not only visually check the actual color but also to remove the aggregates even if the liquid was sampled, making it difficult to grasp the color in real time. Therefore, in conventional decolorization treatments of organic wastewater using electrochemical coagulation, there was no way to set the optimal conditions for decolorization to the target color, so the only option was to extend the current application time and input an excessive amount of electricity, which resulted in a major problem of increased power consumption.

[0007] Therefore, the present invention aims to solve the above-mentioned problems and to provide a method for decolorizing organic wastewater that can decolorize to a desired color level using an electrochemical coagulation method with a smaller input of electricity, i.e., with low power consumption. Another object of the present invention is to provide an apparatus for decolorizing organic wastewater that can efficiently decolorize the wastewater to a desired color level. [Means for solving the problem]

[0008] The inventors have conducted extensive research to solve the above problems and have found that when organic wastewater is decolorized under certain charge conditions by electrochemical coagulation using a specific anode, the degree of decolorization from the raw water can be predicted quite accurately using a specific reaction rate equation using the raw water absorbance.They have then succeeded for the first time in the field of industrial wastewater treatment in measuring the amount of electricity required to reach the desired decolorization state from the raw water absorbance before dewatering, thereby completing the present invention.

[0009] The gist of the present invention is [1] A step of calculating the amount of electricity required to reduce the absorbance of the raw organic wastewater before treatment to a predetermined absorbance; A process of filling the organic wastewater into a treatment tank in which an anode containing iron or aluminum and a cathode are placed, passing a current between the anode and the cathode to cause electrochemical coagulation of the organic wastewater, and then stopping the current flow after the input amount of electricity is reached. A method for decolorizing organic wastewater, comprising: [2] The method for decolorizing organic wastewater according to [1], wherein the input amount of electricity is calculated by the following step (a), step (b), or step (c): (a) calculating using the following formulas (1) and (2):

[0010]

number

[0011] (In the formula, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, k is the reaction rate constant, and L is the volume of the organic wastewater.)

[0012] (b) calculating using the above formula (2) and the following formulas (3) and (4):

[0013]

number

[0014] (Where, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, A eq represents the absorbance after the reaction has reached equilibrium, k1 represents reaction rate constant 1, and k2 represents reaction rate constant 2.)

[0015] (c) calculating using the above formula (2) and the following formulas (5) and (6):

[0016]

number

[0017] (Where, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, A eq represents the absorbance after the reaction has reached equilibrium, k1 represents reaction rate constant 1, and k2 represents reaction rate constant 2.)

[0018] [3] Current density is 1mA / cm 2 ~500mA / cm 2 The bleaching method according to the above [1] or [2], wherein the amount of the bleaching agent is adjusted to fall within the range of [4] A calibration curve between the absorbance and electrical conductivity of the organic wastewater is obtained in advance, The decolorization method according to any one of [1] to [3] above, wherein the raw water absorbance and a desired absorbance are determined from the electrical conductivity measured in the raw organic wastewater using the calibration curve, and the amount of electricity required to reduce the absorbance to the predetermined absorbance is calculated. [5] A treatment tank for subjecting the organic wastewater to electrochemical coagulation, the treatment tank having an inlet and an outlet for the organic wastewater and having an anode containing iron or aluminum for electrochemical coagulation and a cathode disposed therein; an electrochemical coagulation control means for automatically stopping the current supply after a predetermined input amount of electricity is reached; A decolorization apparatus for organic wastewater, comprising: [6] The predetermined amount of electricity is A value calculated based on the following formula (1) and formula (2):

[0019]

number

[0020] (In the formula, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, k is the reaction rate constant, and L is the volume of the organic wastewater.)

[0021] A value calculated based on the above formula (2), the following formulas (3) and (4), or

[0022]

number

[0023] (Where, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, A eq represents the absorbance after the reaction has reached equilibrium, k1 represents reaction rate constant 1, and k2 represents reaction rate constant 2.)

[0024] A value calculated based on the above formula (2) and the following formulas (5) and (6):

[0025]

number

[0026] (Where, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, A eq represents the absorbance after the reaction has reached equilibrium, k1 represents reaction rate constant 1, and k2 represents reaction rate constant 2.)

[0027] The decolorization apparatus for organic wastewater according to [5] above, [7] The decolorization apparatus for organic wastewater according to [5] or [6], wherein a storage tank for storing raw water of the organic wastewater is provided and connected to the treatment tank by piping, and an electric conductivity measuring unit for the organic wastewater is arranged in the storage tank. [8] The decolorization device for organic wastewater according to any one of [5] to [7], further comprising a calculation unit electrically connected to the electrical conductivity measurement unit, which calculates the absorbance of raw water from the electrical conductivity of the raw organic wastewater measured by the electrical conductivity measurement unit based on a calibration curve previously obtained by the calculation unit between the absorbance and electrical conductivity of the organic wastewater. Regarding. [Effects of the Invention]

[0028] By using the method for decolorizing organic wastewater of the present invention, colored organic wastewater discharged from livestock farms, food factories, dye factories, etc. can be decolorized to a desired color level using electrochemical coagulation with a smaller input of electricity, i.e., low power consumption. Furthermore, the decolorization device for organic wastewater of the present invention can efficiently carry out the decolorization method, and by using this device, the colored organic wastewater can be decolorized to the desired color level with a smaller input of electricity (low power consumption). [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic diagram showing an example of an embodiment of the organic wastewater decolorization device of the present invention. [Figure 2] 1 is a graph showing the actual measured values ​​(points) of chromaticity (Abs) measured by the decolorization method for organic wastewater carried out in Example 1, and the results (solid line) of a relational equation for measuring the input electrical quantity (Q / L) from the predetermined absorbance A, obtained from the equation for time t and the desired absorbance A obtained by substituting the reaction rate coefficient k into equation (1). [Figure 3]1 is a graph showing the actual measured values ​​(points) of chromaticity (Abs) measured by the decolorization method for organic wastewater carried out in Example 2, and the results (solid line) of a relational equation for measuring the input quantity of electricity (Q / L) from a predetermined absorbance A, which is obtained by substituting reaction rate coefficients k1 and k2 into equations (3) and (4) to create an equation for calculating time t using absorbance A, and then substituting the current value and the time t into equation (2). [Figure 4] 1 is a graph showing the actual measured values ​​(points) of chromaticity (Abs) in the decolorization method carried out in Example 3, and the results (solid line) of a relational equation for measuring the input electricity quantity (Q / L) from a predetermined absorbance A, which is obtained by substituting reaction rate coefficients k1 and k2 into equations (5) and (6) to create an equation for calculating time t using absorbance A, and then substituting the current value and the time t into equation (2). DETAILED DESCRIPTION OF THE INVENTION

[0030] (Method for decolorizing organic wastewater) The method for decolorizing organic wastewater according to the present invention (hereinafter also referred to as the method of the present invention) comprises: A step (hereinafter referred to as the first step) of calculating the amount of electricity required to reduce the absorbance of the raw organic wastewater before treatment to a predetermined absorbance; A process of filling the organic wastewater into a treatment tank in which an anode containing iron or aluminum and a cathode are placed, applying a current to the anode and the cathode to cause electrochemical coagulation of the organic wastewater, and then stopping the current application after the input amount of electricity is reached (hereinafter referred to as the second process). The present invention is characterized by having the following.

[0031] In the present invention, "electrochemical coagulation" refers to the process of passing an electric current through organic wastewater to elute metal ions from an anode and adsorb organic substances to the resulting coagulates. When the coagulates adsorbing the colored components are separated, the absorbance of the organic wastewater decreases. The coagulated colored components can be removed from the organic wastewater by known methods such as precipitation and centrifugation.

[0032] In the present invention, organic wastewater refers to colored wastewater containing organic matter discharged from industrial sites such as livestock farms, food factories, and dye factories. Livestock wastewater refers to wastewater containing excrement and the wastewater from washing it, discharged from livestock farms that breed, raise, or fatten livestock such as cattle, pigs, horses, sheep, and goats, and poultry such as chickens, ducks, and quails. Food factory wastewater refers to wastewater discharged during the food manufacturing process at various food factories, including beverages, dairy products, confectionery, grain products, sweeteners, spices, brewed foods, fresh foods, meat products, fish and marine products, and food colorings. Dye factory wastewater refers to wastewater discharged from dye factories.

[0033] In the present invention, the absorbance refers to the value measured when light having a wavelength of 390 mm is irradiated onto organic wastewater. The predetermined absorbance refers to the absorbance of the organic wastewater that has been decolorized to a target color that is lower than that of the raw water. The absorbance may be measured using a spectrophotometer. The type of spectrophotometer is not particularly limited as long as it can measure water as a sample.

[0034] In the present invention, the input electricity quantity refers to the electricity quantity per volume of organic wastewater to be subjected to electrochemical coagulation (hereinafter also referred to as the electricity quantity per volume of target water). In the present invention, the amount of electricity input is calculated by the following formula (2) which is made up of the current [A] applied to the organic wastewater, the time [S] for which a predetermined current is applied, and the volume of the organic wastewater (L). Amount of electricity input (Q / L) = Amount of current x Time (t) / Volume (L) Formula (2) In the present invention, the amount of current is set to a constant current value, which makes it easier to predict the degree of decolorization of the organic wastewater to which electricity is passed. Specifically, the volume (L) may be the volume of organic wastewater filled in a treatment tank in which electricity is passed through the organic wastewater. Also, when electricity is applied while organic wastewater is being fed into and discharged from the treatment tank, the volume of the organic wastewater filled in the treatment tank is used.

[0035] In the present invention, the raw organic wastewater refers to the organic wastewater to be subjected to decolorization treatment. There are no particular limitations on the coloring level (also referred to as chromaticity) of the raw water. The chromaticity of organic wastewater can be measured by a measuring instrument that uses light, such as a colorimeter, color difference meter, or turbidity meter, but since organic wastewater generally contains a large amount of organic matter, it is difficult to measure it by such a measuring instrument. In this case, as described in the examples below, a calibration curve between the absorbance and electrical conductivity of the organic wastewater may be obtained in advance, and the raw water absorbance and the desired absorbance may be obtained from the electrical conductivity measured in the raw water of the organic wastewater using the calibration curve, and the amount of electricity required to reduce the absorbance to the predetermined absorbance may be calculated. By preparing the calibration curve, the absorbance of the organic wastewater can be confirmed by measuring the electrical conductivity of the organic wastewater. The electrical conductivity may be measured using an electrical conductivity meter.

[0036] In the method of the present invention, by carrying out the first step before starting full-scale decolorization treatment, the amount of electricity required to bring the organic wastewater to the desired decolorized state can be measured before the dewatering treatment, and the amount of electricity required for the decolorization treatment, i.e., the power consumption, can be appropriately adjusted.

[0037] The amount of electricity input can be calculated by the following step (a), step (b), or step (c).

[0038] In the step (a), the input amount of electricity is calculated using the following formulas (1) and (2).

[0039]

number

[0040] (In the formula, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, k is the reaction rate constant, and L is the volume of the organic wastewater.)

[0041] For example, after measuring the absorbance (A0) of the raw organic wastewater, the raw organic wastewater is filled into a treatment tank in which an anode containing iron or aluminum and a cathode are placed, and a constant current (current value) is passed through the anode and cathode to cause electrochemical coagulation of the organic wastewater, and the absorbance is measured continuously. Next, the reaction rate constant k is calculated from the measured values ​​using the formula (1). Next, the reaction rate coefficient k is substituted into equation (1) to create an equation that can calculate the time t using the absorbance A. Next, by substituting the current value, the time t, and the volume (L) of the organic wastewater filled in the treatment tank into equation (2), a relational equation for measuring the input electrical quantity (Q / L) from a predetermined absorbance A can be calculated.

[0042] In the step (b), the amount of electricity input can be calculated using the above formula (2) and the following formulas (3) and (4).

[0043]

number

[0044] (Where, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, A eq represents the absorbance after the reaction has reached equilibrium, k1 represents reaction rate constant 1, and k2 represents reaction rate constant 2.)

[0045] For example, after measuring the absorbance (A0) of the raw organic wastewater, the raw organic wastewater is filled into a treatment tank in which an anode containing iron or aluminum and a cathode are placed, and a constant current is passed through the anode and cathode to cause electrochemical coagulation of the organic wastewater. The absorbance is measured continuously, and the absorbance A0 after the electrochemical coagulation reaction reaches equilibrium is eq Measure. The fact that the electrochemical agglutination reaction has reached equilibrium can be confirmed by the fact that the amount of change in the absorbance measurement described above becomes small. Next, the reaction rate constants k1 and k2 are calculated using the measured values ​​from equations (3) and (4). Next, the reaction rate coefficients k1 and k2 are substituted into equations (3) and (4) to create an equation that can calculate the time t using the absorbance A. Next, by substituting the current value, the time t, and the volume (L) of the organic wastewater filled in the treatment tank into equation (2), a relational equation for measuring the input electrical quantity (Q / L) from a predetermined absorbance A can be calculated.

[0046] In the step (c), the amount of electricity input can be calculated using the above formula (2) and the following formulas (5) and (6).

[0047]

number

[0048] (Where, t is time, A is the absorbance at time t, A0 is the absorbance of the raw organic wastewater, A eq represents the absorbance after the reaction has reached equilibrium, k1 represents reaction rate constant 1, and k2 represents reaction rate constant 2.)

[0049] For example, after measuring the absorbance (A0) of the raw organic wastewater, the raw organic wastewater is filled into a treatment tank in which an anode containing iron or aluminum and a cathode are placed, and a constant current is passed through the anode and cathode to cause electrochemical coagulation of the organic wastewater. The absorbance is measured continuously, and the absorbance A0 after the electrochemical coagulation reaction reaches equilibrium is eq Measure. The fact that the electrochemical agglutination reaction has reached equilibrium can be confirmed by the fact that the amount of change in the absorbance measurement described above becomes small. Next, the reaction rate constants k1 and k2 are calculated using the measured values ​​according to the formulas (5) and (6). Next, the reaction rate coefficients k1 and k2 are substituted into equations (5) and (6) to create an equation that can calculate the time t using the absorbance A. Next, by substituting the current value, the time t, and the volume (L) of the organic wastewater filled in the treatment tank into equation (2), a relational equation for measuring the input electrical quantity (Q / L) from a predetermined absorbance A can be calculated.

[0050] By preparing the relational expressions calculated in the steps (a), (b) and (c) in advance, when organic wastewaters of different types or different raw water chromaticities are used, it becomes possible to grasp the amount of electricity required to reduce the absorbance to a desired level by measuring the absorbance at two or three points successively while subjecting the organic wastewater to electrochemical coagulation.

[0051] The treatment tank used in the step (a), (b), or (c) may have the same anode and cathode materials as those in the treatment tank used in the second step described below. The shapes, sizes, numbers, etc. of the anodes, cathodes, and treatment tank used in the step (a), (b), or (c) may be the same as or different from those of the treatment tank used in the second step. For example, the treatment tank used in step (a), (b) or (c) may be a small container such as a beaker, which may have a simple structure equipped with one anode and one cathode.

[0052] Alternatively, a calibration curve between the absorbance and electrical conductivity of diluted organic wastewater may be prepared in advance, and the absorbance may be calculated from the electrical conductivity of the organic wastewater using the calibration curve. The electrical conductivity can be easily determined by measuring the absorbance of the organic wastewater. The electrical conductivity may be measured using an electrical conductivity meter. The calibration curve may be prepared by inputting the results obtained in the steps (a), (b) or (c) into commercially available spreadsheet software and using the attached functions.

[0053] The amount of current used in the steps (a), (b), or (c) is not particularly limited. For example, the current density may be 1 mA / cm 2 ~500mA / cm2 By adjusting the temperature to this range, the amount of electricity required for the bleaching treatment can be reduced, which is preferable. . The current density in the present invention can be measured from the size of the electrodes used and the current passed therethrough. The current density may be adjusted by adjusting the current value.

[0054] In the second step carried out following the first step, the organic wastewater is filled into a treatment tank in which an anode containing iron or aluminum and a cathode are placed, and an electric current is passed through the anode and the cathode to cause electrochemical coagulation of the organic wastewater.

[0055] The anode containing iron or aluminum may be any anode that can cause electrochemical coagulation by passing an electric current through organic wastewater, and there are no particular limitations on the material, size, shape, etc. that constitutes the anode.

[0056] The cathode may be any one that can cause electrochemical coagulation by passing an electric current through the organic wastewater, and there are no particular limitations on the material, size, shape, etc. that constitute the cathode.

[0057] The treatment tank may be any tank that is equipped with the anode and the cathode and that can apply an electric current to the organic wastewater filled therein to cause an electrochemical coagulation action, and there are no particular limitations on the material, size, shape, etc. that constitutes the treatment tank.

[0058] In the second step, the current flow is stopped after the input amount of electricity is reached, so that the organic wastewater can be decolorized to the desired color level using a smaller input amount of electricity, i.e., low power consumption, while still using the electrochemical coagulation method.

[0059] The temperature at which the first and second steps of the present invention are carried out may be room temperature, but is not particularly limited.

[0060] (Decolorization equipment for organic wastewater) The organic wastewater decolorization apparatus of the present invention (hereinafter referred to as the apparatus of the present invention) comprises: a treatment tank for subjecting the organic wastewater to electrochemical coagulation, the treatment tank having an inlet and an outlet for the organic wastewater, and having an anode containing iron or aluminum for electrochemical coagulation and a cathode disposed therein; an electrochemical coagulation control means for automatically stopping the current supply after a predetermined input amount of electricity is reached; The present invention is characterized by comprising:

[0061] By using the device of the present invention, colored organic wastewater can be decolorized to a desired color level with a smaller input of electricity (low power consumption). The apparatus of the present invention is used in the second step of the method of the present invention, but may also be used in the first step.

[0062] The anode containing iron or aluminum may be any anode that can cause electrochemical coagulation by passing an electric current through organic wastewater, and there are no particular limitations on the material, size, shape, etc. that constitutes the anode.

[0063] The cathode may be any one that can cause electrochemical coagulation by passing an electric current through the organic wastewater, and there are no particular limitations on the material, size, shape, etc. that constitute the cathode. The material of the cathode is not particularly limited, and may be iron, aluminum, stainless steel, or the like.

[0064] The treatment tank is provided with an inlet and an outlet for organic wastewater, and is configured so that the organic wastewater can be stored within the tank. There is no particular limitation on the positions of the inlet and the outlet.

[0065] Furthermore, when piping is connected to the inlet and the outlet, the flow rate of the organic wastewater entering and leaving the treatment tank can be easily controlled by installing a pump in the piping.

[0066] The anode and the cathode are disposed in the treatment tank. The positions at which the anode and the cathode are disposed are not particularly limited as long as they are capable of contacting the organic wastewater stored in the treatment tank.

[0067] The electrodes such as the anode and cathode may be fixed to an electrode holder at a predetermined interval that allows for appropriate current flow. The number of electrode holders arranged in the treatment tank may be one or more.

[0068] The anode and the cathode are connected to an electrochemical coagulation control means. The electrochemical coagulation control means can automatically stop the current supply after a predetermined input amount of electricity is reached. The electrochemical coagulation control means may be composed of only a power source, or may be further connected to a device that controls the voltage and current supplied from the power source to a predetermined value.

[0069] The power supply may have a switch function for passing a predetermined current, but may also have functions such as a voltage and current adjustment function, a current and voltage value display function, a communication function with a control unit such as a programmable logic controller (PLC), and a timer function.

[0070] The predetermined input amount of electricity is a value calculated based on the formula (1) and the formula (2), A value calculated based on the above formula (2), the following formulas (3) and (4), or A value calculated based on the above formula (2) and the following formulas (5) and (6): That's fine.

[0071] A storage tank for storing raw water of the organic wastewater may be provided and connected to the treatment tank by piping, and a unit for measuring the electrical conductivity of the organic wastewater may be disposed in the storage tank. The electrical conductivity of the organic wastewater can be converted into color. Therefore, the color of the raw organic wastewater can be confirmed by measuring the electrical conductivity of the organic wastewater undergoing electrochemical coagulation in the storage tank using the electrical conductivity measuring unit. Examples of the storage tank include a raw water tank for temporarily storing the recovered organic wastewater, and an adjustment tank for stabilizing the state of the organic wastewater before treatment.

[0072] The treatment tank may be equipped with measuring instruments such as a pH meter and a thermometer. By using these measuring instruments to measure the pH and temperature conditions of the organic wastewater while it is energized, the treatment can be appropriately controlled.

[0073] The device of the present invention may be a device capable of automatically controlling the electrochemical coagulation action. In order to automatically control the electrochemical coagulation action, for example, a calculation unit electrically connected to the electrical conductivity measurement unit may be provided. The calculation unit may have a function of storing a calibration curve previously determined between the absorbance and electrical conductivity of the organic wastewater, and a function of calculating the absorbance of the raw water from the electrical conductivity of the raw water of the organic wastewater measured by the electrical conductivity measurement unit based on the calibration curve.

[0074] In order to efficiently carry out electrochemical coagulation, the treatment tank may be provided with a stirring means, a defoaming means, etc.

[0075] An example embodiment of the device of the present invention is shown in FIG. The apparatus shown in FIG. 1 includes a raw water tank 2 for temporarily storing the recovered organic wastewater, an adjustment tank 5 for stabilizing the state of the organic wastewater before treatment; a measuring tank 7 for measuring the amount of organic wastewater to be sent; a treatment tank 10 for subjecting organic wastewater to electrochemical coagulation; a coagulation tank 14 for coagulating the colored components that have been subjected to electrochemical coagulation to a larger extent; a settling tank 17 for settling the flocculated colored components and separating them from the supernatant; a pH adjustment tank 20 for adjusting the pH of the supernatant; A discharge tank 22 for stabilizing the state of the supernatant liquid so that it can be discharged into the environment. The tanks are connected by piping so that they are in series.

[0076] In the apparatus shown in FIG. 1, first, organic wastewater is introduced from an inlet pipe 1 into the raw wastewater tank 2 and stored therein until a predetermined amount is reached.

[0077] The organic wastewater stored in the raw water tank 2 until it reaches a predetermined amount is sent to the adjustment tank 5 through the raw water tank pressure feed pipe 4 by a pressure pump 3a provided at the bottom of the raw water tank 2.

[0078] After the stored organic wastewater in the adjustment tank 5 reaches a stable state suitable for electrochemical coagulation treatment, the liquid is sent to the metering tank 7 through the adjustment tank pressure feed pipe 6 by the pressure pump 3b.

[0079] In the metering tank 7, a predetermined amount of organic wastewater is fed into the treatment tank 10 through a metering tank water feed pipe 8 and an inlet provided at the top of the treatment tank 10. On the other hand, the organic wastewater exceeding the predetermined amount is returned from the metering tank 7 to the adjusting tank 5 via the metering tank return pipe 9 . The predetermined amount is adjusted by adjusting the water level in the measuring tank 7 or the opening / closing degree of the valve.

[0080] The treatment tank 10 contains an electrode unit 27 equipped with an anode and a cathode containing iron or aluminum, and a pressure pump 3c is disposed at the bottom of the treatment tank 10. The pressure pump 3c is connected to a shower unit 12 disposed at the top of the treatment tank 10 through a shower pressure pipe 11, and is configured so that organic wastewater can be sprayed from the shower unit 12 onto the surface of the water stored in the treatment tank 10. When an electrochemical coagulation reaction is performed in the treatment tank 10, a large amount of bubbles are generated on the surface of the stored organic wastewater. These bubbles tend to inhibit the flow of electricity through the organic wastewater, preventing the desired reaction from occurring. In the apparatus of the present invention, bubbles are significantly eliminated by spraying organic wastewater from the shower unit 12 in the treatment tank 10, allowing the electrochemical coagulation reaction to be performed efficiently.

[0081] An electrical conductivity measuring unit 24 is provided in the raw water tank 2, and the measured value of the electrical conductivity of the organic wastewater measured by this electrical conductivity measuring unit 24 is sent as an electrical signal to a control unit 25. The electrical conductivity measuring unit 24 may be provided in the adjustment tank 5 instead of the raw water tank 2.

[0082] The control unit 25 is a control means (electrochemical coagulation control means) for adjusting the electrochemical coagulation in the treatment tank 10, and has a function of adjusting the voltage and current supplied from a power source (not shown). The control unit 25 is electrically connected to the electrode unit 27 arranged in the treatment tank 10 via a rectifier 26, and is configured to adjust the electrochemical coagulation in the treatment tank 10 by adjusting the voltage and current supplied from the rectifier 26.

[0083] The control unit 25 is electrically connected to an electric conductivity measuring unit 24 for detecting the electric conductivity of the organic wastewater in the raw water tank 2 and a calculation unit (not shown). The calculation unit has a function of calculating the absorbance of the raw water from the electrical conductivity of the raw organic wastewater measured by the electrical conductivity measuring unit 24, based on a calibration curve previously obtained between the absorbance and electrical conductivity of the organic wastewater.

[0084] Using the raw water absorbance calculated by the calculation unit, a predetermined input amount of electricity for electrochemical coagulation is calculated by a calculation means built into the control unit 25 that uses the formula (1) and the formula (2), or a calculation means that calculates based on the formula (2) and the following formulas (3) and (4), or a calculation means that uses the formula (2) and the following formulas (5) and (6).

[0085] In the control unit 25, the electrochemical coagulation action in the treatment tank 10 can be adjusted by stopping the current supply when a predetermined amount of electricity has been supplied. However, from the viewpoint of efficiently controlling the electrochemical coagulation action, it is preferable that the control unit 25 has a function to automatically stop the current supply after supplying a predetermined amount of electricity.

[0086] Although not shown, measuring instruments such as a pH meter and a thermometer may be installed in the treatment tank 10.

[0087] The organic wastewater that has been subjected to electrochemical coagulation by passing a predetermined amount of electricity through it is sent to a coagulation tank 14 through an outlet provided near the top of the treatment tank 10 and a treatment tank water supply pipe 13.

[0088] A stirring means 15a is provided in the coagulation tank 14, and by stirring the organic wastewater that has been subjected to electrochemical coagulation, the size of the coagulated particles of the colored components can be made larger to form coagulated masses.

[0089] The organic wastewater containing the aggregates of colored components is sent from the coagulation tank 14 through the coagulation tank water supply pipe 16 to the settling tank 17 .

[0090] Agglomerates of colored components are precipitated in the settling tank 17. The precipitate of colored components is discharged from a pressure pump 3d disposed at the bottom of the settling tank 17 through a settling tank sludge pressure pipe 18 to the outside of the apparatus. The discharged colored components can be dehydrated into solid matter and then disposed of as industrial waste.

[0091] The supernatant liquid separated from the precipitate of colored components in the settling tank 17 becomes a decolorized liquid whose color is significantly reduced compared to the organic wastewater. The supernatant liquid is sent from an outlet provided at the top of the settling tank 17 through a settling tank water supply pipe 19 to the pH adjustment tank 20 .

[0092] In the pH adjustment tank 20, the supernatant liquid filled therein is stirred by the stirring means 15b while a pH adjuster is added and mixed, thereby adjusting the pH of the supernatant liquid to near neutral and stabilizing it so that it can be discharged to the external environment.

[0093] The supernatant liquid stabilized as described above is sent from the top of the pH adjustment tank 20 through the pH adjustment tank water supply pipe 21 to the discharge tank 22, and is discharged to the external environment through the discharge tank pressure supply pipe 23 from the pressure pump 3e installed at the bottom of the discharge tank 22.

[0094] Furthermore, the positions of the pipes 13, 16, 19, and 21 may be at the same height, or may have steps, or may be provided with pumps in order to efficiently transfer the liquid.

[0095] Although an embodiment of the present invention has been described above with reference to FIG. 1, the present invention is not limited to FIG. 1 at all, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention. [Example]

[0096] In the following examples, experiments were carried out using the following equipment. (Electrochemical coagulation device A) Treatment vessel a (volume: 300 mL, glass beaker) was equipped with a plate-shaped anode (Fe electrode, width: 4 cm x immersion depth: 5 cm), a plate-shaped cathode (Fe electrode, width: 4 cm x immersion depth: 5 cm), a pH meter, and a thermometer. The anode and cathode were each connected to a stabilized power supply via a voltage-current meter (STRAWBERRY LINUX "INA226 I2C Digital Current / Voltage / Wattmeter Module"; the same applies hereinafter). (Electrochemical coagulation device B) Six electrode holders are arranged in series against the water flow in a treatment vessel b (volume 40 L, made of vinyl chloride) equipped with an inlet for introducing livestock wastewater and an outlet for discharging the wastewater. The livestock wastewater is continuously in contact with the six electrode holders before being discharged. The electrode holder was fixed with a resin material so that two plate-shaped anodes (Fe electrodes, width 15 cm, immersion depth: 20 cm, thickness 0.3 mm) and two plate-shaped cathodes (Fe electrodes, width 15 cm, immersion depth: 20 cm, thickness 0.3 mm) were alternately arranged in parallel at uniform intervals. The anode and the cathode are each connected to a stabilized power supply via a voltage / current measuring device.

[0097] (Example 1: Embodiment using step (a)) Colored livestock wastewater obtained from a pig farm in Shimane Prefecture was prepared, and the absorbance of the raw water, A0, was determined using the transmitted light measurement method according to the Sewage Test Method, Part 2, Chapter 2, Section 4, 2, and C = C S ×D Formula (1) (C: chromaticity, C S From the above, it was found that the initial chromaticity could be used instead, and the initial chromaticity was measured to be 890 using a Shimadzu UV-1800 spectrophotometer.

[0098] The electrical conductivity of the raw water was measured using an electrical conductivity meter, and was found to be proportional to the color measured above and could be used as a substitute. Specifically, the measured electrical conductivity and absorbance results were input into a spreadsheet software, and a calibration curve was created using the spreadsheet function. Using the obtained calibration curve, it was possible to convert the measured electrical conductivity into absorbance. Therefore, in the subsequent experiments, the electrical conductivity was measured, and the absorbance (chromaticity) was calculated from the measured value.

[0099] Next, 300 mL of livestock wastewater was filled into the treatment vessel a of the electrochemical coagulation device A, and electricity was applied to the anode and cathode (current: 1 A, current density: 50 mA / cm 2The livestock wastewater was sampled over time and the electrical conductivity was measured to calculate the color. The measurement results for the amount of electricity input per volume are shown in Table 1. The amount of electricity input per volume (C / L) was calculated as follows: Electrical quantity Q [C] (unit: coulomb) = current [A] x processing time t [sec] When the current is 1A, the input electricity quantity Q [C] can be considered to be equal to the processing time t [sec]. Amount of electricity input per volume (Q / L) = Amount of electricity input Q / 0.3 (Volume: L)

[0100] [Table 1]

[0101] Next, using the measured values, the reaction rate constant k was calculated as 1.64 × 10 ‐6 It was calculated that: Next, a relational equation for measuring the input quantity of electricity (Q / L) from the predetermined absorbance A was calculated from the equation between time t and desired absorbance A obtained by substituting the reaction rate coefficient k into the equation (1) and the equation (2). Specifically, the calculation was performed using a spreadsheet software (Excel) function on a personal computer. The obtained measured values ​​(points) and the results of the above relational expression (solid line) are shown in FIG.

[0102] Next, 40 L of raw livestock wastewater (raw water collected from the same facility on a different day) was filled into the treatment vessel b of the large coagulation treatment device B, and a current (156 A, current density 10.6 mA / cm 2 ]) was energized to cause electrochemical coagulation of the organic wastewater. Livestock wastewater was flowed into treatment vessel b from the inlet at a rate of 1.4 L / min so as to be continuously brought into contact with the six electrode holders. After the electricity was applied up to the specified input amount of 5200 [C / L], the electricity was stopped and the chromaticity of the organic wastewater was measured. The chromaticity was 110 degrees, which was almost the same as the predicted value (103 degrees) calculated from the above relational equation. Therefore, it was found that the time and the amount of electricity required to reduce the color of organic wastewater to a desired level can be predicted before treatment.

[0103] (Example 2: Embodiment using step (b)) Colored raw livestock wastewater obtained on a different day from the same piggery in Shimane Prefecture as in Example 1 was prepared. 300 mL of this raw water was filled into the treatment vessel a of the electrochemical coagulation device A, and electricity was applied to the same anode and cathode as in Example 1 (current: 1 A, current density 50 [mA / cm 2 The livestock wastewater was sampled over time, the electrical conductivity was measured, and the color was calculated. Table 2 shows the amount of electricity input per volume and the measurement results for color.

[0104] [Table 2]

[0105] In addition, the absorbance Aeq after the electrochemical aggregation reaction reached equilibrium was calculated to be 108°C. It was. Next, using the measured values, the reaction rate constant k1 was calculated as 1.66 × 10 -3 , k2 is 2.41 × 10 -4 It was confirmed that this is the case. Next, the reaction rate coefficients k1 and k2 were substituted into formulas (3) and (4) to create a formula that can calculate the time t using the absorbance A, and the current value and the time t were substituted into formula (2) to calculate the relational equation for measuring the input quantity of electricity (Q / L) from a given absorbance A. Specifically, the calculation was performed using the functions of a spreadsheet software (Excel) on a personal computer. The obtained measured values ​​(points) and the results of the above relational expression (solid line) are shown in FIG.

[0106] Next, 40 L of raw livestock wastewater (raw water collected from the same facility on another day) was filled into the treatment vessel b of the large coagulation treatment device B, and a current (156 A, current density 10.6 mA / cm 2]) was energized to cause electrochemical coagulation of the organic wastewater. Livestock wastewater was flowed into treatment vessel b from the inlet at a rate of 1.4 L / min so as to be continuously brought into contact with the six electrode holders. After applying a specified amount of electricity per volume (Q / L) of 5,200 [C / L], the current was stopped and the color of the organic wastewater was measured. The color A was 110 degrees, which was almost the same as the value (108 degrees) calculated from the relationship formula. Therefore, it was found that the time and the amount of electricity required to reduce the color of organic wastewater to a desired level can be predicted before treatment.

[0107] (Example 3: Embodiment using step (c)) Colored livestock wastewater obtained on a different day from the same piggery in Shimane Prefecture as in Example 1 was prepared, and 300 mL of this raw water was filled into the treatment vessel a of the electrochemical coagulation device A. The same cathode and cathode as in Example 1 were inserted, and electricity was applied (current: 1 A, current density 50 [mA / cm 2 The livestock wastewater was sampled over time, the electrical conductivity was measured, and the color was calculated. Table 3 shows the amount of electricity input per volume and the measurement results of color.

[0108] [Table 3]

[0109] In addition, the absorbance Aeq after the electrochemical aggregation reaction reached equilibrium was calculated to be 106°C. It was. Next, using the measured values, the reaction rate constant k1 was calculated as 1.17 × 10 -3 , k2 is 1.70 × 10 -4 It was calculated that: Next, the reaction rate coefficients k1 and k2 were substituted into formulas (5) and (6) to create a formula that can calculate the time t using the absorbance A. The current value and the time t were then substituted into formula (2) to calculate a relational equation for measuring the input electrical quantity (Q / L) from a given absorbance A. When the desired chromaticity A was set to 200 degrees, the amount of electricity input per volume (Q / L) was 1422 [C / L]. The obtained measured values ​​(points) and the results of the above relational expression (solid line) are shown in FIG.

[0110] Next, 40 L of raw livestock wastewater (raw water collected from the same facility on another day) was filled into the treatment vessel b of the large coagulation treatment device B, and a current (156 A, current density 10.6 mA / cm 2 ]) was energized to cause electrochemical coagulation of the organic wastewater. Livestock wastewater was flowed into treatment vessel b from the inlet at a rate of 1.4 L / min so as to be continuously brought into contact with the six electrode holders. After applying a specified amount of electricity per volume (Q / L) of 5,200 [C / L], the current was stopped and the color of the organic wastewater was measured. The color A was 110 degrees, which was almost the same as the value calculated from the relationship formula. Therefore, it was found that the time and the amount of electricity required to reduce the color of organic wastewater to a desired level can be predicted before treatment.

[0111] The results of Examples 1 to 3 show that by using the method of the present invention, it is possible to predict in advance the amount of electricity required to reduce the color of organic wastewater to a desired level, and therefore, while using electrochemical coagulation, organic wastewater can be decolorized to a desired level with a smaller amount of electricity input, i.e., with lower power consumption. [Explanation of symbols]

[0112] 1 Inflow pipe 2 Raw Water Tank 3a, 3b, 3c, 3d, 3e pressure pump 4 Raw water tank pressure transfer piping 5 Adjustment tank 6. Pressure feed piping for adjusting tank 7 Measuring tank 8 Measuring tank water supply piping 9 Measuring tank return piping 10 Treatment tank 11 Shower pressure pipe 12 Shower section 13 Treatment tank water supply piping 14 Coagulation tank 15a, 15b Stirring means 16 Coagulation tank water supply piping 17 Sedimentation tank 18 Sedimentation tank sludge pressure transfer piping 19 Sedimentation tank water supply piping 20 pH adjustment tank 21 pH adjustment tank water supply piping 22 Outlet tank 23 Discharge tank pressure transfer piping 24 Electrical conductivity measurement section 25 Control Unit 26 Rectifier 27 Electrode section

Claims

1. A step of calculating the amount of electricity required to reduce the absorbance of the raw organic wastewater before treatment to a predetermined absorbance; A process of filling the organic wastewater into a treatment tank in which an anode containing iron or aluminum and a cathode are placed, passing a current between the anode and the cathode to cause electrochemical coagulation of the organic wastewater, and then stopping the current flow after the input amount of electricity is reached. A method for decolorizing organic wastewater, comprising:

2. 2. The method for decolorizing organic wastewater according to claim 1, wherein the input amount of electricity is calculated by the following step (a), step (b), or step (c): (a) calculating using the following formulas (1) and (2): [Equation 1] (where t is time, A is the absorbance at time t, A ０ is the absorbance of the raw organic wastewater, k is the reaction rate constant, and L is the volume of the organic wastewater. (b) calculating using the above formula (2) and the following formulas (3) and (4): [Equation 2] (where t is time, A is the absorbance at time t, A ０ is the absorbance of the raw organic wastewater, A ｅｑ is the absorbance after the reaction reaches equilibrium, k １ is the reaction rate constant 1, k ２ indicates the reaction rate constant 2.) (c) calculating using the above formula (2) and the following formulas (5) and (6): [Equation 3] (where t is time, A is the absorbance at time t, A ０ is the absorbance of the raw organic wastewater, A ｅｑ is the absorbance after the reaction reaches equilibrium, k １ is the reaction rate constant 1, k ２ indicates the reaction rate constant 2.)

3. The current density was 1 mA / cm ２ ~500mA / cm ２ The bleaching method according to claim 1 or 2, wherein the concentration is adjusted to a range of

4. A calibration curve between the absorbance and electrical conductivity of the organic wastewater is obtained in advance.

3. The decolorization method according to claim 1, further comprising the steps of: determining a raw water absorbance and a desired absorbance from the electrical conductivity measured in the raw organic wastewater using the calibration curve; and calculating an amount of electricity required to reduce the absorbance to the predetermined absorbance.

5. a treatment tank for subjecting the organic wastewater to electrochemical coagulation, the treatment tank having an inlet and an outlet for the organic wastewater, and having an anode containing iron or aluminum for electrochemical coagulation and a cathode disposed therein; an electrochemical coagulation control means for automatically stopping the current supply after a predetermined input amount of electricity is reached; A decolorization device for organic wastewater, comprising:

6. The predetermined amount of electricity is A value calculated based on the following formula (1) and formula (2): [Equation 4] Amount of electricity input (Q / L) = Amount of current x Time (t) / Volume (L) Formula (2) (where t is time, A is the absorbance at time t, A ０ is the absorbance of the raw organic wastewater, k is the reaction rate constant, and L is the volume of the organic wastewater. A value calculated based on the above formula (2), the following formulas (3) and (4), or [Equation 5] (where t is time, A is the absorbance at time t, A ０ is the absorbance of the raw organic wastewater, A ｅｑ is the absorbance after the reaction reaches equilibrium, k １ is the reaction rate constant 1, k ２ indicates the reaction rate constant 2.) A value calculated based on the above formula (2) and the following formulas (5) and (6): [Equation 6] (where t is time, A is the absorbance at time t, A ０ is the absorbance of the raw organic wastewater, A ｅｑ is the absorbance after the reaction reaches equilibrium, k １ is the reaction rate constant 1, k ２ indicates the reaction rate constant 2.) 6. The decolorizing apparatus for organic wastewater according to claim 5, wherein

7. 7. The organic wastewater decolorization apparatus according to claim 5, further comprising a storage tank for raw organic wastewater connected to the treatment tank by piping, and a unit for measuring the electrical conductivity of the organic wastewater disposed in the storage tank.

8. 7. The organic wastewater decolorization apparatus according to claim 5, further comprising a calculation unit electrically connected to the electrical conductivity measurement unit, wherein the calculation unit calculates the absorbance of the raw organic wastewater from the electrical conductivity of the raw organic wastewater measured by the electrical conductivity measurement unit, based on a calibration curve previously obtained between the absorbance and electrical conductivity of the organic wastewater.

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