JP4650764B2 - Decolorization control method, decolorization control device and wastewater treatment system for dyeing wastewater - Google Patents

Description

  The present invention relates to a dyeing drainage decoloring control method, a decoloring control device, and a wastewater treatment system, and in particular, a dyeing drainage that can reliably control decoloring treatment of dyeing wastewater, and can keep equipment costs and maintenance costs low. The present invention relates to a decoloring control method, a decoloring control device, and a wastewater treatment system.

  In dyeing factories, various woven fabrics and leather products such as fabrics are dyed using various dyes such as direct dyes, acid dyes, disperse dyes and reactive dyes, pigments and dyeing assistants. Yes. When dyeing an object to be dyed or washing with water, a large amount of dye wastewater containing dyes, pigments, etc. is generated. Dyeing wastewater is mainly composed of substances such as dyes, pigments, and glue. When discharging dyed wastewater into rivers, it is necessary to (1) remove organic matter, (2) remove solid suspended solids (SS), (3) neutralize acid and alkali, etc. from the viewpoint of release standards. . In addition, although the discharge | release standard is not set about a chromaticity component, when a river colors, it may become a problem from the point of environmental conservation or environmental beautification.

  Conventionally, organic treatments such as paste components and solid suspended solids such as pigments and cloths have been removed by a method that combines biological treatment and coagulation sedimentation, but it is difficult to remove dyes dissolved in water. In some cases, the dyed wastewater is discharged into the river while being colored.

  In order to remove the chromaticity component of the dyed wastewater, the following various methods are performed. First, the Fenton method, which is a decolorization method by adding hydrogen peroxide and iron salt, can decolor most of the colored substances, but the equipment is complicated and the equipment costs are high, and the maintenance and management such as the control of the chemical injection amount are also complicated. And sludge treatment costs are high. In the ozone treatment method, the hydrazine group of the azo group of the dye component is oxidized and becomes carboxylic acid, and thus the color fades. However, since the oxidizing power is weak and cannot be completely decomposed, the total organic carbon (TOC) hardly changes, and BOD Tend to increase. In addition, the cost of equipment such as an ozone generator is very high, and pigments may remain.

  In the activated carbon adsorption method, the equipment cost of the activated carbon adsorption tower is relatively low, but when colored wastewater with organic matter remaining is removed by adsorption, only the chromaticity component cannot be selectively removed by adsorption, and the running cost is very high. There is a drawback of becoming.

  Further, Patent Document 1 discloses that a dye component is decomposed by adding a sodium hypochlorite solution to dyeing waste water, and then the treated water is treated with a filter cloth and activated carbon. In Patent Document 1, the dyeing wastewater is oxidatively decolorized by adding sodium hypochlorite liquid to the dyeing wastewater, the chromaticity component is adsorbed by activated carbon, and sodium hypochlorite liquid and activated carbon are used in combination. Decolorization is performed.

  Patent Document 2 discloses a method for purifying dyeing process wastewater in which the dyeing process wastewater is brought into contact with a tablet containing chlorinated isocyanuric acid. In Patent Document 2, by contacting a tablet containing chlorinated isocyanuric acid with the dyeing process wastewater, the chlorinated isocyanuric acid eluted from the tablet decomposes the dissolved dye in the wastewater and decolorizes it. (Chemical oxygen demand) and BOD (biochemical oxygen demand) are reduced.

Japanese Patent Laid-Open No. 7-100469 Japanese Examined Patent Publication No. 63-1114

  However, Patent Document 1 describes that the addition amount of sodium hypochlorite is adjusted according to the color concentration of dyeing wastewater, but the addition amount of sodium hypochlorite according to the end point of discoloration. It is not intended to control. Moreover, when organic matter remains, activated carbon is used for adsorption of organic matter. However, when the adsorption of organic matter reaches saturation, the activated carbon must be replaced, and there is a disadvantage that running cost becomes high. Furthermore, in Patent Document 2, in order to efficiently achieve decolorization and purification of wastewater, the wastewater flow rate and the contact surface area of the tablet containing chlorinated isocyanuric acid are appropriately selected. It is not disclosed how to control the flow rate and the contact surface area of the tablets.

  If the amount of sodium hypochlorite added is not properly adjusted, excessive sodium hypochlorite may be added. Discharging such treated water directly into the river is environmental conservation. Not desirable. In addition, it is necessary to add a reducing agent to neutralize excessive sodium hypochlorite and the like, but for excessive sodium hypochlorite and the like and a reducing agent that neutralizes this. There was a problem that unnecessary costs were incurred.

  The present inventor added sodium hypochlorite and measured the absorbance, residual chlorine, and redox potential before and after decolorization for dyeing wastewater with different coloring conditions. As a result, when the absorbance was measured, it was confirmed that the absorbance was maximized at around 580 nm, and the absorbance was surely decreased by the addition of sodium hypochlorite. However, since the absorbance at the end point of decolorization varies depending on the coloring degree of the dye waste water, it is difficult to control the end point of decolorization using the absorbance as an index.

  In addition, when sodium hypochlorite was added to the dyeing wastewater and the residual chlorine before and after decoloring was measured, the residual chlorine was measured from the beginning when sodium hypochlorite was added to the dyeing wastewater. There was no significant change in the amount of residual chlorine, and it was difficult to control the decolorization end point using the amount of residual chlorine as an index.

  In contrast, when sodium hypochlorite was added to dyeing wastewater and the redox potential before and after decoloring was measured, the redox potential in the vicinity of the decoloring end point was the same for any dyeing wastewater with different degrees of coloring. Value. In other words, with the addition of chlorinated oxidants such as sodium hypochlorite, it was found that the amount of added chlorinated oxidant can be added without excess or deficiency by measuring the oxidation-reduction potential at the decolorization end point of dyeing wastewater in advance. did.

  The present invention was made in order to solve the conventional problems based on such knowledge, and can control the decoloring treatment of dyeing wastewater reliably, and can suppress equipment costs and maintenance costs at low cost. It is an object of the present invention to provide a method and apparatus for controlling the decolorization of dyed wastewater, and a wastewater treatment system.

  In order to solve the above-described problems and achieve the object, the dyeing wastewater decoloring control method according to claim 1 of the present invention is a method for controlling the decoloring treatment of the dyeing wastewater, wherein the dyeing drainage The oxidation-reduction potential of the dyeing waste water is measured while adding a chlorine-based oxidant to the oxidant, and control is performed to stop the addition of the chlorine-based oxidant at a corresponding oxidation-reduction potential immediately before the decoloration end point.

  Moreover, in the decoloring control method of the dyeing waste_water | drain of Claim 2 of this invention, it is a method of controlling the decoloring process of dyeing waste_water | drain, Comprising: While adding a chlorine-type oxidizing agent to the said dyeing waste_water | drain, the said dyeing drainage The redox potential corresponding to the decoloration end point is measured, the obtained redox potential is set as a control value, and the addition of the chlorine-based oxidant and the stop of the addition are performed with this control value as a target. It is characterized by controlling.

  Moreover, in the decoloring control method of the dyeing waste_water | drain of Claim 3 of this invention, after decoloring the said dyeing waste_water | drain with the said chlorine type oxidizing agent, residual chlorine is further reduced with a reducing agent, It is characterized by the above-mentioned. .

  Moreover, in the decoloring control apparatus of the dyeing waste_water | drain of Claim 4 of this invention, it is an apparatus which controls the decoloring process of dyeing drainage, Comprising: Chlorine is contained in the decoloring tank which accommodates the said dyeing drainage, and the said decoloring tank A chlorinated oxidant addition unit for adding a oxidant, a redox potentiometer for measuring a redox potential of the dyeing waste water in the decolorization tank, and the chlorinated oxidation at a corresponding redox potential immediately before the decolorization end point And a control unit that performs control to stop the addition of the agent.

  The dyeing drainage decoloring control apparatus according to claim 5 of the present invention is an apparatus for controlling the dyeing drainage decoloring treatment, and includes a decoloring tank for storing the dyeing drainage, and a chlorine in the decoloring tank. A chlorine-based oxidant addition unit for adding a system oxidant, an oxidation-reduction potentiometer for measuring the oxidation-reduction potential of the dyeing wastewater in the decolorization tank, and a redox potential corresponding to the decoloration end point are set as control values, And a control unit for controlling the addition and stop of the addition of the chlorinated oxidant with the control value as a target.

  Moreover, in the waste water treatment system according to claim 6 of the present invention, an adjustment tank that stores the waste water in order to make the water amount and water quality uniform, and a neutralization tank that neutralizes the waste water from the adjustment tank, The aeration tank for decomposing organic substances contained in the waste water from the neutralization tank, the waste water from the aeration tank is introduced, the aggregation precipitation tank for removing the aggregate sediment, and the waste water from the aggregation precipitation tank is decolorized A decolorization control device for controlling, a reduction tank for reducing the waste water from the decolorization control device, and a monitoring tank for comparing and monitoring the waste water from the reduction tank with predetermined setting conditions, A decoloring tank that contains the waste water, a chlorine-based oxidant addition unit that adds a chlorine-based oxidizing agent to the decoloring tank, a redox potential meter that measures the redox potential of the waste water in the decoloring tank, and a decolorization end point As a control value, the redox potential corresponding to Constant, and is characterized in that a control unit for controlling the addition and stopping the addition of the chlorine-based oxidizing agent the control value to the target.

  According to the decolorization control method and the decolorization control apparatus for dyeing wastewater according to the present invention, the oxidation-reduction potential of the dyeing wastewater is measured while adding a chlorine-based oxidizing agent to the dyeing wastewater, and the redox potential corresponding to immediately before the decoloration end point is obtained. Since the control to stop the addition of the chlorinated oxidant is performed, or the obtained redox potential is set as a control value, and the addition of the chlorinated oxidant and the stop of the addition are controlled with this control value as a target. Since the addition of the chlorine-based oxidant can be reliably terminated at the decolorization end point and the addition of the chlorine-based oxidant can be avoided, the effect of reducing the amount of the reducing agent added to reduce residual chlorine can be achieved.

  Further, according to the wastewater treatment system according to the present invention, since the decolorization treatment and reduction treatment are performed in addition to the neutralization treatment of the wastewater, the aeration treatment, and the removal of the aggregated sediment, the decolorization end point is removed together with the removal of the organic matter and the suspended solids in the wastewater. The addition of the chlorinated oxidant is controlled by setting the redox potential corresponding to the control value as a control value, so that the addition of the chlorinated oxidant can be surely terminated, and the excessive addition of the chlorinated oxidant can be avoided. In addition, the amount of addition of a reducing agent that reduces residual chlorine can be suppressed.

  DESCRIPTION OF EMBODIMENTS Embodiments of a decoloring drainage decoloring control method, a decoloring control apparatus, and a wastewater treatment system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

In the dyeing wastewater decoloring control method, the decoloring control device, and the wastewater treatment system according to the present invention, the decoloring control can be applied to both batch processing and continuous processing. In batch processing, the later-described decolorization, reduction, and monitoring can be performed in one water tank, and the oxidation-reduction potential of the dye wastewater is measured while adding a chlorine-based oxidizing agent to the dye wastewater to be decolorized. Next, an operation for obtaining a redox potential corresponding to the decolorization end point is performed. In the batch processing, it is possible to control to stop the addition of the chlorine-based oxidant by the oxidation-reduction potential corresponding immediately before the obtained decolorization end point. When the amount of dye wastewater to be decolorized is relatively small, for example, about 10 to 20 m ³ / day, batch processing is advantageously employed.

On the other hand, when the amount of dye wastewater to be decolorized is large, for example, at 1000 m ³ / day, the tank capacity is large in batch processing (for example, 1000 m ³ water tank is required when the amount of dye wastewater is 1000 m ³ / day). Therefore, continuous processing is adopted because it is not realistic. In the continuous processing, an oxidation-reduction potential corresponding to the decoloration end point is obtained, the obtained oxidation-reduction potential is set as a control value, and addition of the chlorine-based oxidant and stop of the addition are controlled with this control value as a target. This control value can be obtained from basic data obtained in advance by batch processing that can be carried out relatively easily. That is, the redox potential corresponding to the decoloring end point is obtained by batch processing, and this can be used as a control value to perform decoloring control by continuous processing.

  In the dyeing waste water decoloring control method, the decoloring control device, and the waste water treatment system according to the present invention, the following first to third embodiments describe decoloring control by continuous processing, and the fourth embodiment describes decoloring control by batch processing. To do.

(Embodiment 1)
Hereinafter, Embodiment 1 of a decoloring drainage control method and a decolorization control apparatus according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a decolorization control apparatus according to Embodiment 1 of the present invention. In FIG. 1, a decoloring control device 1 </ b> A includes a first decoloring tank 2 and a second decoloring tank 3 as decoloring tanks that perform decolorization by adding a chlorine-based oxidizing agent to a dyed wastewater that has been subjected to a predetermined treatment as will be described later. It has. In addition, chlorine-based oxidant storage tanks 4 and 5 for supplying a chlorine-based oxidant are provided for the first decolorization tank 2 and the second decolorization tank 3, and chlorine-based oxidation is performed by electromagnetic valves 6 and 7, respectively. The supply amount of the agent is controlled. Note that the chlorine-based oxidant may be supplied by turning on or off the power of the pumps provided on the downstream side of the solenoid valves 6 and 7, respectively.

  Further, the first decolorization tank 2 and the second decolorization tank 3 are respectively provided with oxidation-reduction potentiometers 8 and 9 for measuring the oxidation-reduction potential (ORP). In FIG. 1 and the like, P represents a pump, and M represents a stirring motor.

  Next, a reducing tank 10 is provided adjacent to the second decoloring tank 3 to reduce the dyeing waste water by adding a reducing agent. A reducing agent storage tank 11 for supplying a reducing agent is provided for the reducing tank 10, and the supply amount of the reducing agent is controlled by an electromagnetic valve 12. The reduction tank 10 may be provided with a residual chlorine concentration meter 13, and the amount of reducing agent added may be controlled with respect to the set value of the residual chlorine concentration meter 13. Further, a monitoring tank 14 for monitoring the treated water is provided adjacent to the reduction tank 10. The monitoring tank 14 is provided with a pH meter 15 and a residual chlorine concentration meter 16 for monitoring the pH of the treated water and the residual chlorine concentration, respectively. The first decolorization tank 2, the second decolorization tank 3, the reduction tank 10 and the monitoring tank 14 are communicated with each other through freely openable and closable flow ports 17, 18 and 19.

  Here, measurement signals from the oxidation-reduction potentiometers 8 and 9 are input to the control unit 20, and the control unit 20 performs control to open and close the electromagnetic valves 6, 7 and 12 according to the measurement signals. Or you may control the addition amount of a chlorine-type oxidizing agent or a reducing agent by turning ON / OFF the power supply of the pump provided in the downstream of these solenoid valves 6, 7, and 12, respectively. As will be described later, the control unit 20 also controls the discharge of the treated water and the return to the raw water adjustment tank based on the measurement signals from the pH meter 15 and the residual chlorine concentration meter 16. Further, it is possible to perform control for turning on or off the power of each pump.

  As the chlorine-based oxidizing agent used in the first decolorization tank 2 and the second decolorization tank 3, sodium hypochlorite, bleached powder, calcium hypochlorite, etc. can be suitably used, and these are used in an aqueous solution. It is preferable to do this. Moreover, as a reducing agent used with the reduction tank 10, sodium thiosulfate, sodium bisulfite, etc. can be used conveniently. In the following description, a case where sodium hypochlorite is used as the chlorine-based oxidant and sodium thiosulfate is used as the reducing agent will be described.

  In order to perform the decolorization treatment of the dye wastewater with the decolorization control apparatus 1A configured as described above, the dye wastewater that has passed through the adjustment tank, the neutralization tank, the fluidized bed aeration tank, the coagulation reaction tank, and the coagulation sedimentation tank, which will be described later, 1 Introduce into decoloring tank 2. In the first decolorization tank 2, for example, sodium hypochlorite is added as a chlorine-based oxidant to decolorize wastewater containing colored components that could not be removed in the fluidized bed aeration tank and the coagulation sedimentation tank.

  At this time, for example, the relationship between the amount of sodium hypochlorite added and the oxidation-reduction potential of the wastewater containing the coloring component is obtained in advance by batch processing in Embodiment 4 described later. The present inventor has found a phenomenon in which the oxidation-reduction potential increases rapidly in the vicinity of the decolorization end point when the amount of sodium hypochlorite added is increased. In other words, with the addition of sodium hypochlorite, the oxidation-reduction potential increases almost linearly, but the oxidation-reduction potential increases slowly while sodium hypochlorite is consumed for decolorization of the coloring component. When decolorization is completed, sodium hypochlorite is no longer consumed for decolorization of the colored components, so the redox potential is thought to increase rapidly from the decolorization end point.

  In the vicinity of the end point of decolorization, a phenomenon occurs in which the redox potential suddenly increases due to the addition of sodium hypochlorite.By setting the end point redox potential as a control value, a small amount of sodium hypochlorite Addition raises the oxidation-reduction potential, and excessive addition of sodium hypochlorite hardly occurs and control becomes easy.

  However, since various kinds of substances are mixed in the treated water and the decolorization reaction system is complicated, it is considered that the decolorization end point shifts to a potential higher than the potential at which the oxidation-reduction potential increases rapidly. In other words, when the oxidation-reduction potential increases rapidly, a predetermined high potential from the oxidation-reduction potential that starts to increase rapidly becomes the decolorization end point. Specifically, when the oxidation-reduction potential suddenly increased at about 550 mV, it was confirmed that decolorization was completed at a potential higher by about 100 mV to 200 mV than this value or a potential higher by 100 mV to 300 mV. The final decoloration end point is determined by visual observation.

  The oxidation-reduction potential corresponding to such a decolorization end point is obtained by batch processing in a fourth embodiment described later. That is, the oxidation-reduction potential of the dyeing wastewater is measured while adding a chlorine-based oxidizing agent to the dyeing wastewater, and the oxidation-reduction potential corresponding to the decoloration end point is obtained. The obtained oxidation-reduction potential can be set as a control value, and the addition and stop of addition of the chlorine-based oxidant can be controlled with this control value as a target.

  In the first decoloring tank 2 of FIG. 1, a control value corresponding to the decoloring end point is input to the control unit 20. Next, the oxidation-reduction potential in the first decolorization tank 2 is measured by the oxidation-reduction potentiometer 8 and input to the control unit 20. When the oxidation-reduction potential starts to increase rapidly, the control unit 20 controls the amount of sodium hypochlorite added by turning on or off the solenoid valve 6 or the pump.

  For example, a two-stage decoloring tank can be installed, and the first stage can be subjected to rough decolorization, and the next stage can be subjected to finish decolorization. When the final target control value is 750 mV, in the first stage, sodium hypochlorite is added from the chlorine-based oxidant storage tank 4 to the first decolorization tank 2 by operating the solenoid valve 6 or the pump, and the oxidation-reduction potential is roughly decolorized. The control unit 20 performs control to stop the addition of sodium hypochlorite at the target value of 700 mV. Thereby, most of the coloring of waste water can be eliminated. If the coloration of the waste water is not completely decolorized, the second decoloring tank 3 may be further subjected to finishing decolorization.

  Next, the waste water treated in the first decolorization tank 2 is guided into the second decolorization tank 3 through the circulation port 17. In the second decolorization tank 3, the oxidation-reduction potential of the dyed waste water is measured by the oxidation-reduction potentiometer 9 and input to the control unit 20. For example, when the control value is 750 mV, sodium hypochlorite is added from the chlorinated oxidant storage tank 5 to the second decolorization tank 3 by operating the solenoid valve 7 or the pump, and when the redox potential is 750 mV, hypochlorite Control part 20 performs control which stops addition of sodium acid. In this way, the decolorization of the waste water can be accurately finished.

  In this way, there is no need to add excess sodium hypochlorite for decolorization, and the amount of sodium thiosulfate used to reduce residual chlorine can be reduced, reducing the cost of the chemicals used. can do. In addition, it is desirable from the viewpoint of environmental conservation when the treated water is finally discharged into the river. In addition, when the waste water is almost decolorized in the first decolorization tank 2 and coloring is not recognized, the injection of sodium hypochlorite may be stopped. By using the 2nd decoloring tank 3 together with the 1st decoloring tank 2, the decoloring process according to the coloring condition of treated water is attained.

  Next, the wastewater treated in the second decolorization tank 3 is introduced into the reduction tank 10 through the circulation port 18. In the reducing tank 10, sodium thiosulfate is added as a reducing agent in order to reduce and remove the excessively injected sodium hypochlorite. Sodium thiosulfate is added from the reducing agent storage tank 11 to the reduction tank 10 by opening and closing the electromagnetic valve 12 by the control unit 20. Or you may control the addition amount of sodium thiosulfate by turning on or off the power supply of the pump provided in the downstream of the solenoid valve 12. FIG. When the residual chlorine concentration at the reduction end point is stable at, for example, 3 to 5 mg / l, the amount of sodium thiosulfate corresponding to this is quantitatively injected.

  Furthermore, using the residual chlorine concentration meter 13, for example, when the residual chlorine concentration is 0.5 mg / l or more, sodium thiosulfate is injected, and when the residual chlorine concentration is 0.2 mg / l or less, sodium thiosulfate Control for stopping the addition of may be performed by the control unit 20.

  Subsequently, the wastewater treated in the reduction tank 10 is guided into the monitoring tank 14 via the circulation port 19. In the monitoring tank 14, the hydrogen ion concentration and residual chlorine concentration of the treated water are monitored by the pH meter 15 and the residual chlorine concentration meter 16, respectively, and the measurement result is input to the control unit 20. As the hydrogen ion concentration and the residual chlorine concentration of the treated water, preset concentrations are stored in the control unit 20 and collated with the measurement results obtained by the pH meter 15 and the residual chlorine concentration meter 16, respectively.

  When the hydrogen ion concentration and the residual chlorine concentration in the treated water are within the preset concentration range, the treated water is discharged into a river or the like. On the other hand, when the hydrogen ion concentration and residual chlorine concentration of the treated water deviate from the preset concentration range, as will be described later, the discharge valve that discharges the treated water is closed and the treated water is returned to the raw water adjustment tank. Control part 20 performs control which opens a valve. Thereby, it can prevent that the waste_water | drain exceeding a predetermined reference value is discharged into a river as it is.

(Embodiment 2)
FIG. 2 is a schematic configuration diagram showing a decolorization control apparatus according to Embodiment 2 of the present invention. In FIG. 2, the decoloring control device 1B has the same configuration as the decoloring control device 1A of FIG. 1 in the first embodiment, but as a decoloring tank that performs decolorization by adding a chlorine-based oxidant to the dyeing waste water. The difference is that only the decoloring tank 2 is provided. Therefore, the description of the same configuration as that in Embodiment 1 is omitted.

  In order to perform the decolorization processing of the dyeing wastewater by the decoloring control device 1B, the dyeing wastewater that has passed through the adjustment tank, the neutralization tank, the fluidized bed aeration tank, the coagulation reaction tank, and the coagulation sedimentation tank described later is introduced into the first decolorization tank 2. . In the first decolorization tank 2, for example, sodium hypochlorite is added as a chlorine-based oxidant to decolorize wastewater containing colored components that could not be removed in the fluidized bed aeration tank and the coagulation sedimentation tank.

  In order to perform the decoloring process of the dye waste water by the decoloring control apparatus 1B of FIG. 2, the amount of sodium hypochlorite added and the coloring component are changed by the batch process in the fourth embodiment to be described later, as in the first embodiment. A relationship with the oxidation-reduction potential of the contained wastewater is obtained in advance, and the decoloring end point is input to the control unit 20. Next, the oxidation-reduction potential in the first decolorization tank 2 is measured by the oxidation-reduction potentiometer 8, and the solenoid valve 6 or the pump is turned on or off to the control value set in the control unit 20, thereby hypochlorous acid. Control the amount of sodium added.

  Specifically, when the control value corresponding to the decoloring end point is 700 mV, the addition of sodium hypochlorite is controlled around 700 mV. That is, when the oxidation-reduction potential is less than 680 mV, the solenoid valve 6 or the pump is turned on and sodium hypochlorite is added from the chlorine-based oxidant storage tank 4 to the first decolorization tank 2. When the redox potential exceeds 720 mV, the solenoid valve 6 or the pump is turned off and the addition of sodium hypochlorite is stopped.

  When the redox potential of the dyeing wastewater drops due to the discontinuation of the supply of sodium hypochlorite, the pump is turned on again when the redox potential is less than 680 mV, or the solenoid valve 6 is opened and sodium hypochlorite is Supply. Thus, the oxidation-reduction potential of the dyed wastewater in the first decolorization tank 2 falls within a certain range (680 to 720 mV) with the control value 700 mV as the center. Furthermore, by repeating the supply and stop of supply of sodium hypochlorite, the redox potential can be converged to the control value of 700 mV, and the dyeing waste water can be completely decolorized.

  If decolorization is not completed, the control value can be increased. For example, when the control value is raised from 700 mV to 750 mV, when the redox potential is less than 730 mV, the pump is turned on, or the solenoid valve 6 is opened to supply sodium hypochlorite. When the redox potential exceeds 770 mV, the supply of sodium hypochlorite can be stopped.

  Next, the wastewater treated in the first decolorization tank 2 is guided into the reduction tank 10 through the distribution port 17, and further treated in the reduction tank 10 through the distribution port 19, and then the dyeing wastewater is monitored in the monitoring tank 14. Then, the same processing as in the first embodiment is performed.

  The present inventor has confirmed that when the components in the dyeing waste water are similar, the same result can be obtained even in the waste water that is heavily dyed, intermediate, and light. In addition, when decoloring different dyeing waste water, the control value corresponding to the decoloring end point is obtained again by batch processing, and decoloring can be performed in continuous processing with this control value as a target.

(Embodiment 3)
FIG. 3 is a schematic configuration diagram showing a wastewater treatment system according to Embodiment 3 of the present invention, and the wastewater treatment system 100 includes the decolorization control device 1A described in Embodiment 1. In FIG. 3, a large amount of dye wastewater containing dyes, pigments, and the like is generated at the time of dyeing or washing with water in a dyeing factory or the like. Examples of the dye include various chemical dyes. Examples of the chemical dye include reactive dyes such as Cibacron Blue, sulfur dyes such as Asaciosol, Sulfur Blue 7, and acid dyes such as Kayakaran Black. Examples of the pigment include Ryudai W, Neulactimin, Sundai Super, Neo, Ultraviolet. The dyes and pigments are not limited to these dyes and pigments, and various dyes and pigments may be contained alone or in combination.

  Dyeing wastewater containing such dyes and pigments is first stored in the raw water adjustment tank 21 in order to make the amount and quality of water as uniform as possible and to reduce the load fluctuation applied to the next wastewater treatment facility. Next, the dyed waste water that has passed through the raw water adjustment tank 21 is introduced into the neutralization tank 22.

  In the neutralization tank 22, for example, sulfuric acid and sodium hydroxide respectively stored in the acid solution storage tank 23 and the alkaline solution storage tank 24 are injected by opening and closing the electromagnetic valves 25 and 26. The hydrogen ion concentration in the neutralization tank 22 is measured by the pH meter 27, and the measurement result is input to the control unit 20. The control unit 20 controls the amount of sulfuric acid and sodium hydroxide to be injected by turning on and off the electromagnetic valves 25 and 26 so that the dyeing waste water in the neutralization tank 22 becomes neutral. Alternatively, the amounts of sulfuric acid and sodium hydroxide to be injected may be controlled by turning on or off the power sources of the pumps provided on the downstream side of the electromagnetic valves 25 and 26, respectively.

  The dyed waste water neutralized in the neutralization tank 22 is introduced into the fluidized bed aeration tank 28 as an aeration tank. Here, the aeration tank in the present invention is a so-called biological treatment tank, which is not a floating activated sludge system, but a system in which an organic substance is decomposed by microorganisms attached to the surface by introducing a filler. Such an aeration tank is also called a fixed bed or a fluidized bed. As a result, the treated water can be directly coagulated and precipitated at the subsequent stage. In the fluidized bed aeration tank 28, the carrier to which the microorganisms are attached is fluidized by aeration from the aeration blower 29 to biologically decompose organic matter. In particular, the paste component can be effectively decomposed and removed in the dye waste water.

  The dyed wastewater treated in the fluidized bed aeration tank 28 is introduced into the aggregation reaction tanks 30a and 30b. In the agglomeration reaction tank 30a, the inorganic flocculant is injected into the dye waste water by controlling the electromagnetic valve 32a by the control unit 20 from the inorganic flocculant storage tank 31a in which the inorganic flocculant is stored. Alternatively, the inorganic flocculant may be injected into the dyeing waste water by turning on or off the power supply of the pump provided on the downstream side of the electromagnetic valve 32. Next, in the agglomeration reaction tank 30b, the polymer flocculant is injected from the polymer flocculant storage tank 31b in which the polymer flocculant is stored into the dyeing waste water by controlling the electromagnetic valve 32b by the control unit 20. Alternatively, the polymer flocculant may be injected into the dyeing waste water by turning on or off the power supply of the pump provided on the downstream side of the electromagnetic valve 32b.

  As a result of the treatment in these agglomeration reaction tanks 30a and 30b, solids that have passed through a screen (not shown) arranged on the inlet side of the neutralization tank 22, surplus sludge microorganisms generated in the fluidized bed aeration tank 28, pigments, etc. Aggregate suspended matter. Next, the aggregates aggregated in the aggregation reaction tanks 30a and 30b are introduced into the aggregation precipitation tank 33, and the precipitates are removed. The sediment removed from the dye wastewater is conveyed to a sludge storage tank, and after removing moisture with a sludge dewatering machine (not shown), it is processed into a cake and discarded or reused.

  The dyed waste water from which the sediment has been removed in the coagulation sedimentation tank 33 is the same as the decolorization control apparatus 1A described in the first embodiment, in the decolorization treatment and reduction tank 10 in the first decolorization tank 2 and the second decolorization tank 3. Perform reduction treatment. In FIG. 3, the decoloring process is performed using the first decoloring tank 2 and the second decoloring tank 3, but as described in the second embodiment, the decoloring process is performed only by the first decoloring tank 2. May be. Subsequently, as described in Embodiment 1, in the monitoring tank 14, the hydrogen ion concentration and the residual chlorine concentration of the treated water are monitored by the pH meter 15 and the residual chlorine concentration meter 16, respectively.

  When the hydrogen ion concentration and the residual chlorine concentration of the treated water are within the concentration range preset in the control unit 20, the control unit 20 opens the discharge valve 34 to discharge the treated water to a river or the like. On the other hand, when the hydrogen ion concentration and residual chlorine concentration of the treated water deviate from the preset concentration range, the control valve 20 closes the discharge valve 34 for discharging the treated water and returns the treated water to the raw water adjustment tank 21. The return valve 35 is opened. In this way, waste water exceeding a predetermined reference value can be prevented from being discharged into the river as it is, and waste water exceeding the predetermined reference value can be reprocessed.

(Embodiment 4)
FIG. 4 is a schematic configuration diagram showing a decolorization control apparatus according to Embodiment 4 of the present invention. In the fourth embodiment, control of decoloring processing by batch processing will be described. In FIG. 4, the decolorization control device 1 </ b> C includes a reaction tank 40 that can perform both the decolorization, reduction, and monitoring processes of the dye wastewater. Further, an acid solution storage tank 23 and an alkali solution storage tank 24 may be provided in order to adjust the dyeing wastewater to neutrality by injecting acid and alkali into the reaction tank 40. For example, sulfuric acid and sodium hydroxide stored in the acid solution storage tank 23 and the alkaline solution storage tank 24 are injected by opening and closing the electromagnetic valves 25 and 26. Or you may control the supply_amount | feed_rate of a sulfuric acid and sodium hydroxide by turning on or off the power supply of the pump provided in the downstream of the solenoid valves 25 and 26, respectively.

  The hydrogen ion concentration in the reaction tank 40 is measured by the pH meter 15, and the measurement result is input to the control unit 20. The control unit 20 controls the liquidity of the dye waste water to be neutral by turning on or off the electromagnetic valves 25 and 26 or the power of the pump based on the input pH measurement result.

  Next, in order to perform the decoloring process, the chlorine-based oxidant stored in the chlorine-based oxidant storage tank 4, for example, sodium hypochlorite, is opened or closed by opening or closing the electromagnetic valve 6 or turning the pump power on or off. The reaction vessel 40 is supplied. At this time, the oxidation-reduction potential of the dyed waste water is obtained by the oxidation-reduction potentiometer 8, and the relationship between the amount of sodium hypochlorite added and the oxidation-reduction potential is obtained. That is, the oxidation-reduction potential of the dyeing wastewater is measured while adding a chlorine-based oxidizing agent to the dyeing wastewater, and the oxidation-reduction potential corresponding to the decoloration end point is obtained.

  As described above, when the amount of sodium hypochlorite added is increased, the redox potential increases rapidly in the vicinity of the decolorization end point. For example, when the oxidation-reduction potential that starts to increase rapidly is 500 mV, the oxidation-reduction potential is measured while gradually adding sodium hypochlorite, and the decoloring end point is confirmed visually. At this time, the oxidation-reduction potential when decolorization is completed is about 700 mV.

  Next, sodium thiosulfate is added as a reducing agent in order to reduce and remove the excessively injected sodium hypochlorite. Sodium thiosulfate adds sodium thiosulfate from the reducing agent storage tank 11 to the reaction tank 40 by opening and closing the electromagnetic valve 12 by the control unit 20. Or you may control the addition amount of sodium thiosulfate by turning on or off the power supply of the pump provided in the downstream of the solenoid valve 12. FIG. When the residual chlorine concentration at the reduction end point is stable at, for example, 3 to 5 mg / l, the amount of sodium thiosulfate corresponding to this is quantitatively injected.

  Furthermore, using the residual chlorine concentration meter 13, for example, when the residual chlorine concentration is 0.5 mg / l or more, sodium thiosulfate is injected, and when the residual chlorine concentration is 0.2 mg / l or less, sodium thiosulfate Control for stopping the addition of may be performed by the control unit 20.

  Next, the hydrogen ion concentration and the residual chlorine concentration of the treated water are monitored by the pH meter 15 and the residual chlorine concentration meter 13, respectively. These measurement results are input to the control unit 20. As the hydrogen ion concentration and the residual chlorine concentration of the treated water, preset concentrations are stored in the control unit 20 and collated with the measurement results by the pH meter 15 and the residual chlorine concentration meter 13.

  When the hydrogen ion concentration and residual chlorine concentration of the treated water are within the preset concentration ranges, the control unit 20 controls the opening of the discharge valve 34 to discharge the treated water to a river or the like. On the other hand, when the hydrogen ion concentration and residual chlorine concentration of the treated water deviate from the preset concentration range, a reducing agent, acid, or alkali is added to the treated water so as to be within a predetermined standard.

  As described above, the batch process can be advantageously applied to a decoloring process when the amount of dye waste water to be decolored is relatively small. The present invention can also be applied to obtain a redox potential corresponding to the decoloring end point in the continuous processing described in the first to third embodiments, that is, a control value. In this case, although the decoloring control apparatus 1C shown in FIG. 4 may be used, it is also possible to use a beaker as a reaction vessel on a laboratory scale, and the control value can be obtained more easily.

  Hereinafter, based on an Example, this invention is demonstrated further more concretely. As dyeing wastewater, three kinds of dyeing wastewater containing mainly reactive dye Cibacron Blue and having different concentrations were prepared. Each of these dyeing wastewaters flowed into the reaction tank 40 shown in FIG. 4, and the dyeing wastewaters were adjusted to be neutral by adding sulfuric acid and sodium hydroxide. Next, the oxidation-reduction potential of the dyed waste water was measured with the oxidation-reduction potentiometer 8 while adding sodium hypochlorite.

  The measurement result of the obtained oxidation-reduction potential is shown in FIG. In FIG. 5, a curve A is a measurement result for a dyed wastewater having a light coloration, a curve B is a measurement result for a dyed wastewater having a normal coloration, and a curve C is a measurement result for a dyed wastewater having a high coloration. . In each dye wastewater, the oxidation-reduction potential increased with the addition of sodium hypochlorite, and the oxidation-reduction potential increased rapidly at about 550 mV. Further, it was confirmed that decolorization was completed at about 750 mV. That is, in the curves A to C, the measurement points D, E, and F indicate the decolorization end points.

  As described above, the decolorization control method and the decolorization control apparatus for dyeing wastewater according to the present invention can reliably end the addition of the chlorine-based oxidant at the decolorization end point, or the chlorine reduction with the redox potential corresponding to the decoloration end point as the control value. Since the addition of oxidizer can be controlled, it is possible to avoid excessive addition of chlorinated oxidizer, so it is useful for decoloring treatment of dyeing wastewater. It is suitable for a wastewater treatment system that can end the addition of chlorine-based oxidant with certainty.

It is a schematic block diagram which shows the decoloring control apparatus by Embodiment 1 of this invention. It is a schematic block diagram which shows the decoloring control apparatus by Embodiment 2 of this invention. It is a schematic block diagram which shows the waste water treatment system by Embodiment 3 of this invention. It is a schematic block diagram which shows the decoloring control apparatus by Embodiment 4 of this invention. It is a diagram which shows the relationship between the addition amount of sodium hypochlorite measured in the Example of this invention, and the oxidation-reduction potential of dyeing | draining waste_water | drain.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B Decoloring control apparatus 2 1st decoloring tank 3 2nd decoloring tank 4,5 Chlorine oxidant storage tank 6,7,12,25,26,32 Solenoid valve 8,9 Oxidation-reduction potentiometer 10 Reduction tank 11 Reducing agent Reservoir 13,16 Residual chlorine concentration meter 14 Monitoring tank 15, 27 pH meter 17, 18, 19 Flow port 20 Control unit 21 Raw water adjustment tank 22 Neutralization tank 23 Acid solution storage tank 24 Alkaline solution storage tank 28 Fluidized bed aeration tank 29 Aeration blower 30a, 30b Coagulation reaction tank 31a Inorganic coagulant storage tank 31b Polymer coagulant storage tank 33 Coagulation sedimentation tank 34 Release valve 35 Return valve 40 Reaction tank

Claims (6)

  A method for controlling decolorization treatment of dyeing wastewater, wherein the oxidation-reduction potential of the dyeing wastewater is measured while adding a chlorine-based oxidizing agent to the dyeing wastewater, and the chlorine-based treatment is performed at a corresponding redox potential immediately before the decoloration end point. A method for controlling the decolorization of dyeing wastewater, characterized in that control for stopping the addition of an oxidizing agent is performed.   A method for controlling the decolorization treatment of dyeing wastewater, measuring a redox potential of the dyeing wastewater while adding a chlorine-based oxidizing agent to the dyeing wastewater, obtaining a redox potential corresponding to the decoloration end point, and obtaining the obtained oxidation A method for controlling the decolorization of dyeing waste water, wherein a reduction potential is set as a control value, and the addition and stop of the addition of the chlorinated oxidant are controlled with the control value as a target.   3. The method for controlling the decolorization of dyed wastewater according to claim 1 or 2, further comprising reducing residual chlorine with a reducing agent after decolorizing the dyed wastewater with the chlorine-based oxidizing agent.   An apparatus for controlling the decoloring treatment of dyeing wastewater, a decoloring tank for storing the dyeing wastewater, a chlorine-based oxidizing agent adding unit for adding a chlorine-based oxidizing agent to the decoloring tank, and the dyeing wastewater in the decoloring tank Dyeing drainage characterized by comprising: a redox potentiometer that measures the redox potential of the liquid; and a control unit that controls to stop the addition of the chlorinated oxidant at a redox potential corresponding to immediately before the decolorization end point Decolorization control device.   An apparatus for controlling the decoloring treatment of dyeing wastewater, a decoloring tank for storing the dyeing wastewater, a chlorine-based oxidizing agent adding unit for adding a chlorine-based oxidizing agent to the decoloring tank, and the dyeing wastewater in the decoloring tank An oxidation-reduction potentiometer for measuring the oxidation-reduction potential, and a control unit for setting the oxidation-reduction potential corresponding to the decolorization end point as a control value, and controlling the addition and stop of the addition of the chlorine-based oxidant with this control value as a target A decolorization control device for dyeing drainage. An adjustment tank that stores drainage to make the amount of water and water quality uniform, a neutralization tank that neutralizes drainage from the adjustment tank, and an aeration tank that decomposes organic matter contained in the drainage from the neutralization tank The waste water from the aeration tank is introduced, the coagulation sedimentation tank for removing the aggregate sediment, the decolorization control device for controlling the decoloration of the waste water from the coagulation sedimentation tank, and the reduction for reducing the waste water from the decolorization control device A tank and a monitoring tank for comparing and monitoring the drainage from the reduction tank with a predetermined setting condition,
The decolorization control device includes a decolorization tank that houses the wastewater, a chlorine-based oxidant addition unit that adds a chlorine-based oxidant to the decolorization tank, and a redox that measures a redox potential of the wastewater in the decolorization tank. An electrometer and a control unit that sets an oxidation-reduction potential corresponding to the decoloration end point as a control value and controls the addition and stop of the addition of the chlorine-based oxidant with the control value as a target are provided. Wastewater treatment system.

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