JP2010064016A - Method for treating drainage and drainage treatment facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating drainage drained from an incineration plant which hardly deteriorate an RO membrane, and can efficiently recover the heat of combustion exhaust gas in an incineration plant, and to provide drainage treatment facilities. <P>SOLUTION: In the method for treating drainage drained from an incineration plant equipped with: an incineration apparatus firing organic matter; a heat recovery apparatus recovering the heat of combustion exhaust gas exhausted from the incineration apparatus; and a temperature reduction apparatus further reducing the temperature of the combustion exhaust gas heat-recovered by the heat recovery apparatus, the method includes: a chlorine amount measurement stage where the amount of free residual chlorine comprised in the drainage is measured; a dechlorination agent adding stage where a dechlorination agent is added to the drainage; a dechlorination agent increasing stage where the dechlorination agent to be added to the drainage is increased correspondingly to the increase of the amount of the free residual chlorine; an RO membrane separation stage where concentrated water is separated away from the drainage to which the dechlorination agent has been added with a reverse osmosis membrane (RO membrane); and a temperature reducing stage where the temperature of the heat-recovered combustion exhaust gas is reduced with the heat of vaporization of the concentrated water by the temperature reduction apparatus. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method for wastewater discharged from an incineration plant and a wastewater treatment facility for the wastewater.

  Conventionally, an incinerator that combusts organic matter, a heat recovery device that recovers the heat of combustion exhaust gas discharged from the incinerator, and a temperature reduction device that further reduces the temperature of the combustion exhaust gas recovered by the heat recovery device. As a wastewater treatment method for wastewater discharged from an incineration plant provided, a wastewater treatment method in which the wastewater is agglomerated with a coagulant and then filtered is known.

  As a conventional wastewater treatment method, for example, a wastewater treatment method is known in which wastewater discharged from an incineration plant is agglomerated by a flocculant or the like, then biologically treated, and further filtered by sand filtration (Patent Literature). 1). This type of wastewater treatment method describes that most of the purified water can be discharged.

  By the way, as a wastewater treatment method for wastewater discharged from an incineration plant, there is a strong demand for a method using a method in which purified water purified by wastewater treatment is not discharged as much as possible in order to cope with so-called environmental problems.

  However, in such a wastewater treatment method, in order to prevent the purified water from being discharged as much as possible, it is possible to reduce the volume of the purified water by injecting most of the purified water into a temperature reducing device such as a temperature reducing tower to vaporize it. Has been done. Specifically, the combustion exhaust gas after heat recovery by a heat recovery device such as a waste heat boiler is injected with purified water in the temperature reducing device to vaporize the purified water and reduce its capacity. The temperature of the combustion exhaust gas recovered by heat is reduced by the heat of vaporization of purified water. That is, in such a wastewater treatment method, a relatively large amount of purified water is used for temperature reduction in the temperature reduction device.

  In this way, in the wastewater treatment method that employs a method in which the purified water purified by the wastewater treatment is not discharged as much as possible, the amount of purified water that is injected into the temperature reducing device is relatively large. The temperature range to be heated is set to be relatively large. Accordingly, in the heat recovery device such as a waste heat boiler on the upstream side of the temperature reduction device, the amount of heat recovered from the combustion exhaust gas has to be set small. That is, as the temperature range for reducing the temperature in the temperature reducing device is relatively large, the amount of heat recovered from the combustion exhaust gas in the heat recovery device is further reduced, and the heat recovery efficiency from the combustion exhaust gas in the incineration plant is low. There is a problem that it is easy to become.

Japanese Patent Laid-Open No. 10-99898

  Therefore, there is a demand for a wastewater treatment method for wastewater discharged from an incineration plant, which can efficiently recover the heat of combustion exhaust gas in the incineration plant.

  In addition, in wastewater treatment methods for wastewater discharged from incineration plants, wastewater may contain oxidizing substances such as hypochlorite ions, and its concentration may increase suddenly. There is a problem that the reverse osmosis membrane used as the waste water treatment equipment is particularly susceptible to deterioration due to the oxidizing substance contained in the water. Thus, there is a demand for a wastewater treatment method that can rapidly reduce the oxidizing substance even when the concentration of the oxidizing substance suddenly increases, and that does not deteriorate the reverse osmosis membrane.

  The present invention is a wastewater treatment method for wastewater discharged from an incineration plant in view of the above-mentioned problems, demands, etc., and is a wastewater that can hardly recover the reverse osmosis membrane and can efficiently recover the heat of combustion exhaust gas in the incineration plant. It is an object to provide a processing method. It is another object of the present invention to provide a wastewater treatment facility for wastewater discharged from an incineration plant, which is unlikely to deteriorate a reverse osmosis membrane and can efficiently recover the heat of combustion exhaust gas in the incineration plant.

  In order to solve the above problems, a wastewater treatment method according to the present invention includes an incinerator for burning organic matter, a heat recovery device for recovering the heat of combustion exhaust gas discharged from the incinerator, and heat recovery by the heat recovery device. A wastewater treatment method for wastewater discharged from an incineration plant provided with a temperature reducing device for further reducing the temperature of the exhausted flue gas, the chlorine amount measuring step for measuring the amount of free residual chlorine contained in the wastewater, A dechlorinating agent adding step for adding a dechlorinating agent to the waste water, a dechlorinating agent increasing step for increasing the dechlorinating agent added to the waste water in response to an increase in the amount of free residual chlorine, and the dechlorination RO membrane separation step of separating and removing concentrated water from the waste water to which the agent has been added by a reverse osmosis membrane (RO membrane), and reducing the temperature of the combustion exhaust gas that has been recovered by the temperature reducing device by the heat of vaporization of the concentrated water Implementing a temperature reduction process And wherein the Rukoto.

  According to the wastewater treatment method having the above-described configuration, by carrying out a dechlorinating agent addition step of adding a dechlorinating agent to the wastewater, free residual chlorine contained in the wastewater is removed by the dechlorinating agent added to the wastewater. The concentration of free residual chlorine that is reduced and contained in the wastewater can be kept relatively low. Furthermore, a chlorine amount measuring step for measuring the amount of free residual chlorine contained in the wastewater, and a dechlorinating agent increasing step for increasing the amount of dechlorinating agent added to the wastewater in response to an increase in the amount of free residual chlorine, As a result, even if the amount of free residual chlorine contained in the wastewater suddenly increases, an increase in the free residual chlorine concentration can be detected quickly, and the drainage added to the wastewater is correspondingly detected. The chlorine agent can be increased rapidly. Therefore, even if the concentration of free residual chlorine contained in the waste water suddenly increases, the free residual chlorine contained in the waste water can be rapidly reduced.

  In addition, according to the wastewater treatment method having the above-described configuration, the wastewater discharged from the incineration plant and containing impurities and the like can be concentrated by a reverse osmosis membrane, and separated and removed as the concentrated water having a reduced volume. When the temperature of the combustion exhaust gas recovered by heat is reduced by the temperature reduction device by the heat of vaporization of the concentrated water, such as by injecting the concentrated water into the temperature reduction device, the volume is reduced by concentration. Since the amount of water to be generated is small, the temperature range for reducing the temperature of the combustion exhaust gas can be reduced. Further, the heat-recovered combustion exhaust gas reduced in temperature by the temperature-reducing device is heat recovered by the heat-recovery device on the upstream side, and the heat-recovered combustion exhaust gas is reduced in temperature by the temperature-reducing device. The amount of heat recovered from the combustion exhaust gas in the heat recovery device on the upstream side can be increased by reducing the temperature range.

  Moreover, it is preferable that the waste water treatment method which concerns on this invention implements the pre-processing process which reduces the suspended | floating matter contained in the said waste_water | drain before implementing the said dechlorinating agent addition process. By carrying out the pretreatment step before carrying out the dechlorinating agent addition step, suspended matters that can be contained in the waste water can be reduced, and clogging of the reverse osmosis membrane can be suppressed. Therefore, there is an advantage that the frequency of replacement of the reverse osmosis membrane is reduced, the separated water can be obtained more efficiently, and the heat of the combustion exhaust gas in the incineration plant can be recovered more efficiently.

  In the wastewater treatment method according to the present invention, in the pretreatment step, the wastewater is separated by a microfiltration membrane (MF membrane) and the MF membrane is permeated through the MF membrane so as to reduce suspended matter contained in the wastewater. It is preferable to separate and remove the permeated waste water from the waste water. In the pretreatment step, the wastewater is separated by the MF membrane, and the MF membrane permeated wastewater that has permeated the MF membrane is separated and removed from the wastewater, so that the suspended matter contained in the wastewater can be further reduced. Clogging of the reverse osmosis membrane in the RO membrane separation step is less likely to occur, and the continuous use period of the reverse osmosis membrane can be longer. Therefore, there is an advantage that the frequency of replacement of the reverse osmosis membrane is reduced, the separated water can be obtained more efficiently, and the heat of the combustion exhaust gas in the incineration plant can be recovered more efficiently.

  The wastewater treatment facility according to the present invention further reduces an incinerator that burns organic matter, a heat recovery device that recovers the heat of combustion exhaust gas discharged from the incinerator, and the combustion exhaust gas that has been heat recovered by the heat recovery device. A wastewater treatment facility for wastewater discharged from an incineration plant equipped with a temperature reducing device for heating, a chlorine amount measuring means for measuring the amount of free residual chlorine contained in the wastewater, and a dechlorinating agent for the wastewater A dechlorinating agent adding means for adding, a dechlorinating agent increasing means for increasing the dechlorinating agent added to the wastewater in response to an increase in the amount of free residual chlorine, and the wastewater to which the dechlorinating agent is added RO membrane separation means for separating and removing the concentrated water from the reverse osmosis membrane (RO membrane), and a temperature reducing means for reducing the temperature of the heat-recovered combustion exhaust gas by the temperature reducing device by the heat of vaporization of the concentrated water. It is characterized by That.

In the wastewater treatment method according to the present invention, the free residual chlorine is reduced by the dechlorinating agent added to the wastewater, and the concentration of free residual chlorine contained in the wastewater can be kept at a relatively low concentration. Moreover, even if the free residual chlorine concentration contained in the wastewater suddenly increases, the increase in the free residual chlorine concentration can be detected quickly, and a corresponding dechlorinating agent added to the wastewater can be quickly detected. Since it can increase, the free residual chlorine contained in the said waste_water | drain can be reduced rapidly. Accordingly, the reverse osmosis membrane is unlikely to deteriorate due to free residual chlorine that may be contained in the waste water.
In addition, as described above, the wastewater treatment method according to the present invention concentrates the wastewater with a reverse osmosis membrane, and can separate and remove the concentrated water whose volume has been reduced from the wastewater. Since the amount of water used to reduce the temperature of the heat-recovered combustion exhaust gas by the heat of vaporization is small, the temperature range for reducing the temperature of the heat-recovered combustion exhaust gas by the temperature reducing device can be reduced. Further, the amount of heat recovered from the combustion exhaust gas in the heat recovery device can be increased by reducing the temperature range in which the temperature of the heat recovery combustion exhaust gas is decreased in the temperature reducing device.
Therefore, the wastewater treatment method of the present invention has an effect that the reverse osmosis membrane is hardly deteriorated and the heat of the combustion exhaust gas in the incineration plant can be efficiently recovered.

  Hereinafter, an embodiment of a wastewater treatment method according to the present invention will be described.

  The wastewater treatment method of the present embodiment includes an incinerator 1 that burns organic matter, a heat recovery device 2 that recovers the heat of combustion exhaust gas discharged from the incinerator 1, and combustion that is heat recovered by the heat recovery device 2 A wastewater treatment method for wastewater discharged from an incineration plant provided with a temperature reducing device 3 for further reducing the temperature of exhaust gas (hereinafter also referred to as heat recovery combustion exhaust gas), wherein the amount of free residual chlorine contained in the wastewater A chlorine amount measuring step for measuring the amount of chlorine, a dechlorinating agent adding step for adding a dechlorinating agent to the wastewater, and a dechlorination for increasing the amount of dechlorinating agent added to the wastewater in response to an increase in the amount of free residual chlorine An agent increasing step, an RO membrane separation step of separating and removing concentrated water from the waste water to which the dechlorinating agent has been added by a reverse osmosis membrane (hereinafter also referred to as RO membrane), and the heat recovery combustion exhaust gas from the concentrated water Reduced temperature by heat of vaporization A waste water treatment method for implementing a temperature reducing step to decrease the temperature of at location 3.

Specifically, the wastewater treatment method of the present embodiment includes an incinerator 1 that burns organic matter, a heat recovery device 2 that recovers the heat of combustion exhaust gas discharged from the incinerator 1, and heat recovery by the heat recovery device 2. A wastewater treatment method for wastewater discharged from an incineration plant equipped with a temperature reducing device 3 for further reducing the temperature of the exhaust gas emitted from the combustion exhaust,
A chlorine amount measurement step for continuously measuring the amount of free residual chlorine contained in the waste water, a dechlorination agent addition step for adding a predetermined amount of dechlorination agent to the waste water, and an increase in the amount of free residual chlorine Correspondingly, a dechlorinating agent increasing step for increasing the dechlorinating agent added to the wastewater, and a RO membrane separation step for separating and removing concentrated water from the wastewater to which the dechlorinating agent has been added by a reverse osmosis membrane (RO membrane) And a temperature reduction step of reducing the temperature of the heat recovery combustion exhaust gas by the temperature reduction device 3 by the heat of vaporization of the concentrated water, and further before the step of adding the dechlorinating agent, This is a wastewater treatment method for carrying out a pretreatment process for reducing suspended matters.

More specifically, the wastewater treatment method of the present embodiment includes an incinerator 1 that burns organic matter, a heat recovery device 2 that recovers the heat of combustion exhaust gas discharged from the incinerator 1, and heat generated by the heat recovery device 2. A wastewater treatment method for wastewater discharged from an incineration plant equipped with a temperature reducing device 3 for further reducing the temperature of recovered combustion exhaust gas,
In order to reduce suspended matter contained in the wastewater, the wastewater is separated by a microfiltration membrane (hereinafter also referred to as MF membrane), and the MF membrane permeated wastewater that has permeated the microfiltration membrane (MF membrane) is separated and removed from the wastewater. A pretreatment step, a chlorine amount measurement step for continuously measuring the amount of free residual chlorine contained in the MF membrane permeated wastewater, and an amount of dechlorinating agent that can reduce the free residual chlorine to a predetermined amount or less are added to the wastewater. A dechlorinating agent adding step, a dechlorinating agent increasing step for increasing the dechlorinating agent to be added to the wastewater in response to an increase in the amount of free residual chlorine, and a reverse operation from the wastewater to which the dechlorinating agent is added. Waste water treatment for performing a RO membrane separation step of separating and removing concentrated water by an osmosis membrane (RO membrane), and a temperature reduction step of reducing the temperature of the heat recovery combustion exhaust gas by the temperature reduction device 3 by heat of vaporization of the concentrated water Is the method.

Here, the said incinerator 1, the said heat recovery apparatus 2, and the said temperature reduction apparatus 3 with which the said incineration plant is equipped are demonstrated. In addition, the said incineration plant may be equipped with another apparatus etc. suitably as needed.
FIG. 1 shows a schematic diagram of an incineration plant including the incinerator 1, the heat recovery device 2, and the temperature reducing device 3.

  The said incinerator 1 burns organic substance, and specifically, an incinerator is mentioned, for example. Although it does not specifically limit as an organic substance to burn, For example, municipal waste, industrial waste, waste wood, sewage sludge, sludge etc. are mentioned. In addition, as said incinerator 1, the conventionally well-known general thing can be used in the technical field of incineration plants, such as a stoker furnace, a fluidized-bed incinerator, a gasification melting furnace, an ash melting furnace.

  The heat recovery device 2 recovers the heat of the combustion exhaust gas discharged from the incinerator 1. Examples of the heat recovery device 2 include a waste heat boiler that recovers the heat of combustion exhaust gas and transmits it to water, and replaces it with water vapor or hot water. The combustion exhaust gas introduced into the heat recovery apparatus 2 is usually at a temperature of about 800 to 1300 ° C. In addition, as the said heat recovery apparatus 2, the conventionally well-known general thing can be used in the technical field of an incineration plant.

  The temperature reducing device 3 further reduces the temperature of the combustion exhaust gas recovered by the heat recovery device 2. The temperature reducing device 3 is not particularly limited, but water is sprayed or sprayed on the heat recovery combustion exhaust gas introduced from the heat recovery device 2, and the heat recovery is performed using heat of vaporization of water. A temperature reducing tower that lowers the temperature of the combustion exhaust gas may be used. The combustion exhaust gas heat recovered by the heat recovery device 2 is usually at a temperature of about 250 to 400 ° C. In addition, as the said temperature reduction apparatus 3, a conventionally well-known general thing can be used in the technical field of an incineration plant.

  The temperature of the gas after the heat recovery combustion exhaust gas has been reduced by the temperature reducing device 3 is usually about 150 to 200 ° C. This gas contains water vapor obtained by evaporating the water of the concentrated water, and dust and the like are further removed by a dust collector or the like and released into the atmosphere.

  The waste water discharged from the incineration plant includes at least equipment cooling waste water after cooling the peripheral equipment of the incinerator 1. Other examples of the waste water include blow waste water blown from the heat recovery device 2 such as a waste heat boiler, residue cooling waste water for cooling incineration residues and slag generated from an incineration plant, and waste collection vehicles Wastewater generated in the incineration plant, such as car wash wastewater, domestic wastewater, etc.

  Next, each process implemented with the waste water treatment method of this embodiment is demonstrated in detail. In addition, the schematic of the apparatus used with the waste water treatment method of this embodiment is shown in FIG.

  In the wastewater treatment method of this embodiment, first, a pretreatment process for reducing suspended matters contained in wastewater discharged from an incineration plant is performed before the dechlorinating agent addition process.

  By carrying out the pretreatment step before the dechlorination agent addition step, the suspended matter that can be contained in the waste water can be reduced, and the RO membrane separation step performed after the dechlorination agent addition step is used. RO membrane clogging can be suppressed. Therefore, the replacement frequency of the RO membrane is reduced, the separated water can be obtained more efficiently, and the heat of the combustion exhaust gas in the incineration plant can be recovered more efficiently. Therefore, the replacement frequency of the RO membrane is reduced, the separated water can be obtained more efficiently, and the heat of the combustion exhaust gas in the incineration plant can be recovered more efficiently.

  Examples of the suspended matter include organic fine particles and inorganic fine particles, and other solid fine particles. These floating substances can be included in the waste water discharged from the incineration plant.

  In the pretreatment step, as shown in FIG. 2, in order to reduce suspended matter contained in the wastewater, the wastewater is separated by an MF membrane, and the MF membrane permeated wastewater that has permeated the MF membrane is separated and removed from the wastewater. .

  In the pretreatment step, the wastewater is separated by the MF membrane, and the MF membrane permeated wastewater that has permeated the MF membrane is separated and removed from the wastewater, so that the relatively small suspended matter that can be contained in the wastewater is removed by the MF membrane. It is possible to remove the clogging of the reverse osmosis membrane (RO membrane) used in the RO membrane separation step. Therefore, the exchange frequency of the reverse osmosis membrane (RO membrane) is reduced, and the concentrated water can be obtained more efficiently. That is, as described above, the heat of the combustion exhaust gas in the incineration plant can be recovered more efficiently, and the separated water can be obtained more efficiently.

  In the pretreatment step, wastewater that has not yet been subjected to the dechlorinating agent addition step is separated by an MF membrane, and thus the wastewater may contain free residual chlorine. By separating the wastewater that may contain free residual chlorine by the microfiltration membrane (MF membrane), the growth of microorganisms in the microfiltration membrane (MF membrane) can be suppressed. That is, the growth of microorganisms in the microfiltration membrane (MF membrane) can be suppressed by free residual chlorine contained in the waste water. As described above, the wastewater treatment method of the present embodiment is capable of suppressing the growth of microorganisms in the microfiltration membrane (MF membrane) and suppressing the deterioration of the RO membrane as described later. After the processing step and before the RO membrane separation step, the dechlorinating agent addition step is performed.

  As the microfiltration membrane (MF membrane), a conventionally known general microfiltration membrane can be used in the technical field of water treatment. Specifically, as the microfiltration membrane (MF membrane), a porous membrane can be used, and a filtration membrane unit can be used. Examples of the filtration membrane unit include those in which a hollow fiber membrane, a spiral membrane, and a tubular membrane are held in a vessel. Examples of the microfiltration membrane (MF membrane) include those in which a hollow fiber membrane or a flat membrane is used as it is by immersing it in the water to be treated. The microfiltration membrane (MF membrane) usually has pores with a pore diameter of about 50 nm to 10 μm.

  In the pretreatment step, in addition to the microfiltration membrane (MF membrane), the pore size is usually larger than the pore size of the RO membrane and usually has a pore size of about 2 nm to 200 nm, for example, an ultrafiltration membrane ( UF membrane) or the like can be used, and a combination of these or a combination of these can be used.

  Further, in the pretreatment step, for the purpose of reducing the suspended matter contained in the wastewater, a flocculant is added to the wastewater, and agglomerate mainly formed by aggregation of the suspended matter is generated and precipitated. A process can be performed. By carrying out the coagulation sedimentation step, aggregates can be removed from the waste water, and the suspended matter that can be contained in the waste water can be reduced.

  By adding a flocculant to the waste water, there is an advantage that the suspended matter becomes agglomerated and easily settles. The supernatant water after the aggregates have settled is separated by an MF membrane, and the MF membrane permeated wastewater that has permeated the MF membrane is separated and removed from the wastewater. Thereby, clogging of the RO membrane can be further suppressed.

  A conventionally known general flocculant can be used as the flocculant. Examples of the flocculant include iron-based flocculants such as ferrous sulfate, ferric sulfate, and ferric chloride, aluminum-based flocculants such as aluminum sulfate (sulfuric acid band), polyaluminum chloride (PAC), and the like. Examples of such a mixture are illustrated. The amount of the flocculant added can be adjusted as appropriate.

  The coagulation sedimentation step can be carried out using a coagulation apparatus provided so that a predetermined amount of the waste water is stored and the coagulant is added. The aggregating apparatus is provided so that the aggregating agent is appropriately added in an appropriate amount to the drainage at an appropriate time. The supernatant water after the suspended matter contained in the waste water is precipitated as an aggregate by the coagulant can be used in the next step as shown in FIG.

  In addition, in the pretreatment step, a sand filtration step can be performed after the coagulation sedimentation step is performed for the purpose of reducing the suspended matter contained in the waste water. Since the sand filtration step is performed using the supernatant water after the aggregate is precipitated after the aggregation and precipitation step, the suspended matter that has not precipitated as the aggregate can be further reduced. There is an advantage that the suspended matter contained in the waste water can be more reliably reduced.

  The sand filtration step can be performed, for example, using a sand filtration device in which a layer of filtration media such as sand or anthracite is laid on a gravel layer. The sand filter mainly reduces suspended matters contained in the waste water, and examples of the sand filter include those commonly used. The water that has passed through the sand filtration device can be used in the next step as shown in FIG. Moreover, a part of the water which permeate | transmitted the said sand filtration apparatus can be mixed with the said concentrated water, and can be used at the said temperature reduction process mentioned later for details.

  Next, the chlorine amount measuring step, the dechlorinating agent adding step, and the dechlorinating agent increasing step will be described. FIG. 3 is a schematic view of devices used in each of these steps, and shows the dechlorination water tank 4 in FIG. 2 in more detail. Moreover, the dechlorinating agent storage tank 5 is represented.

  In the wastewater treatment method of the present embodiment, a chlorine amount measurement step for continuously measuring the amount of free residual chlorine contained in the wastewater is performed after the pretreatment step. Specifically, the chlorine amount measurement step is performed after the pretreatment step and before the RO membrane separation step.

  Moreover, the waste water treatment method of this embodiment implements the dechlorination agent addition process which adds the quantity of dechlorination agent which can keep the said free residual chlorine below to predetermined amount to the said waste water after the said pre-treatment process. Specifically, the dechlorinating agent addition step is performed after the pretreatment step and before the RO membrane separation step.

  Moreover, the wastewater treatment method of this embodiment implements the dechlorinating agent increase process which increases the dechlorinating agent added to the said wastewater corresponding to the raise of the quantity of the said free residual chlorine after the said pretreatment process. Specifically, the dechlorinating agent increasing step is performed after the pretreatment step and before the RO membrane separation step.

  In addition, the said chlorine amount measurement process and the said dechlorinating agent addition process are normally implemented simultaneously, and are implemented continuously. That is, a predetermined amount of dechlorinating agent is continuously added to the waste water while continuously detecting the free residual chlorine concentration of the waste water. The dechlorinating agent increasing step is a step of increasing the amount of the dechlorinating agent added to the waste water in response to an increase in free residual chlorine concentration, and is performed as necessary. That is, when the concentration of free residual chlorine rises above a predetermined value in the chlorine content measurement step, the amount of dechlorinating agent added to the wastewater is increased to release free hypochlorite ions and the like contained in the wastewater. Residual chlorine is reduced and reduced.

More specifically, the chlorine amount measuring step is a step of measuring the amount of free residual chlorine such as hypochlorite ions contained in the wastewater by measuring the oxidation-reduction potential or free residual chlorine concentration of the wastewater. Specifically, the chlorine amount measurement step is provided in the dechlorination water tank 4 for temporarily storing the MF membrane permeated wastewater that has permeated the MF membrane, as shown in FIG. It can be implemented by using a free residual chlorine amount detection device. As the free residual chlorine amount detection device, an oxidation-reduction potentiometer (ORP) or a chlorine meter can be used.
In addition, as a redox potential meter (ORP) or a chlorine meter, the conventionally well-known general and commercially available thing can be used in the technical field of water treatment.

More specifically, the free residual chlorine includes hypochlorite ions (ClO ⁻ ), hypochlorous acid (HClO), and chlorine molecules (Cl ₂ ).
In addition, the wastewater discharged | emitted from an incineration plant may raise the density | concentration of the free residual chlorine which is an oxidizing substance suddenly by the operation state of the said incineration plant, and the operation | work in a plant. When the concentration of free residual chlorine contained in the wastewater rises, the oxidation-reduction potential of the wastewater rises. Therefore, the value of the oxidation-reduction potential serves as an index indicating the concentration of free residual chlorine contained in the wastewater.

  Specifically, the dechlorinating agent adding step is a step of adding a predetermined amount of dechlorinating agent to the waste water for the purpose of suppressing the deterioration of the RO membrane due to the free residual chlorine which is an oxidizing substance. Specifically, the dechlorinating agent adding step is, for example, in the stage shown in FIG. 3 while the dechlorinating agent storage tank 5 for storing the dechlorinating agent and the MF membrane permeating wastewater being led to the RO membrane. The dechlorinating agent storage tank 5 can be used by supplying the dechlorinating agent with a pump and adding it. By performing the dechlorinating agent addition step, it is possible to suppress the deterioration of the RO membrane, particularly the RO membrane formed of aromatic polyamide, due to free residual chlorine which is an oxidizing substance.

  Here, the predetermined amount of dechlorinating agent is a normal amount of dechlorinating agent capable of keeping the amount of free residual chlorine in the waste water before performing the RO membrane separation step below a predetermined amount, for example, It is a normal amount of dechlorinating agent capable of keeping the oxidation-reduction potential of the waste water at 100 mV or less, or the free residual chlorine concentration of the waste water at 10 ppm or less. In addition, since the quantity of the free residual chlorine contained in the said waste_water | drain can be fluctuate | varied with the operation state in the said incineration plant, and the operation | work in a plant, the predetermined amount of the dechlorinating agent added may fluctuate. In addition, as described above, the concentration of free residual chlorine in the waste water may increase suddenly, and with only a predetermined amount of dechlorinating agent, the increase in the concentration of free residual chlorine in the waste water separated by the RO membrane can be suppressed. It can disappear.

  As the dechlorinating agent, an inorganic reducing agent is preferable in that it is difficult to raise the COD of the waste water after being added. As the inorganic reducing agent, for example, bisulfites such as sodium bisulfite (sodium hydrogen sulfite), thiosulfates such as sodium thiosulfate, etc., those conventionally known in the field of water treatment are used. Can do. In addition, these dechlorinating agents can be dissolved in water to form an aqueous solution and then added to the waste water.

  Specifically, the dechlorinating agent increasing step is provided so that the dechlorinating agent can be supplied from the dechlorinating agent storage tank 5 to the dechlorinating water tank 4 as required, for example, as shown in FIG. When the redox potential or free residual chlorine concentration is greater than a predetermined value by using the pump and the redox potential meter or chlorine meter, the pump is linked with the redox potential meter or chlorine meter. It can be implemented by adding a dechlorinating agent from the dechlorinating agent storage tank 5 to the dechlorinating water tank 4 by operating a pump. Even if free residual chlorine such as hypochlorite ions contained in the wastewater is suddenly increased by performing the dechlorinating agent increasing step, hypochlorite ions contained in the wastewater, etc. The increase in the concentration of free residual chlorine can be suppressed, and deterioration of the RO membrane due to free residual chlorine which is an oxidizing substance can be suppressed.

  Here, in the dechlorinating agent increasing step, the method corresponding to the increase in the oxidation-reduction potential or the free residual chlorine concentration is not particularly limited. For example, when the oxidation-reduction potential or the free residual chlorine concentration is larger than a predetermined value. This method corresponds to the case where a continuous increase in redox potential and free residual chlorine concentration is recognized. The method etc. are mentioned. Thus, in the dechlorinating agent increasing step, the amount of dechlorinating agent added to the waste water can be increased in response to an increase in redox potential or free residual chlorine concentration.

  In addition, although the said dechlorinating agent addition process and the said dechlorinating agent increase process can also be implemented by a separate means as shown in FIG. 3 as mentioned above, they can also be implemented using the same means. Specifically, for example, the dechlorinating agent storage tank 5 is connected to the dechlorinating water tank 4 by a pump provided so that the dechlorinating agent can be supplied from the dechlorinating agent storage tank 5 to the dechlorination water tank 4. The dechlorinating agent addition step was carried out by adding a certain amount of dechlorinating agent, and the redox potential and free residual chlorine concentration were larger than the predetermined values by linking the pump with the redox potential meter or chlorine meter. In this case, the dechlorinating agent increasing step can be performed by increasing the supply capacity of the pump and increasing the amount of the dechlorinating agent supplied from the dechlorinating agent storage tank 5 to the dechlorinating water tank 4.

  In the wastewater treatment method of this embodiment, the RO membrane separation step is performed after the pretreatment step and before the temperature reduction step. In the RO membrane separation step, concentrated water is separated and removed from the wastewater by the RO membrane. That is, the waste water discharged from the incineration plant is separated by the RO membrane, and the concentrated water whose impurities are concentrated and the volume is substantially reduced is separated and removed. Therefore, it can also be recognized that a part of the waste water can be converted into water having a higher degree of contamination by performing the RO membrane separation step to separate and remove the concentrated water from the waste water. Water with a relatively high degree of contamination usually cannot be discharged, but is mixed with the waste water and drained again, as in the temperature reduction step (described later) in the waste water treatment method of this embodiment. In order to increase the efficiency of wastewater treatment, it is preferable to vaporize the concentrated water having a relatively high degree of contamination to reduce its capacity.

  On the other hand, in the RO membrane separation step, wastewater discharged from the incineration plant can be separated by the RO membrane, impurities contained in the wastewater can be reduced, and the permeate having a substantially reduced volume can be separated and removed. The permeated water has a relatively high purification level comparable to that of industrial water by reducing impurities contained in the wastewater, and can be used in applications that require a relatively high level of purification. That is, for example, the permeated water can be discharged, or it is contaminated for uses such as boiler raw water, equipment cooling water, plant water used in the plant, etc. that require a high degree of purification in the incineration plant. It can be used in applications where the waste water cannot be applied as it is. Accordingly, the RO membrane separation step is performed to separate and remove the permeate from the wastewater, so that a part of the wastewater is made into water having a relatively high purification degree, and is applied to applications where a higher degree of purification is required. be able to.

  Here, examples of the impurities include ionic components and organic substances. Examples of the ionic component of the impurity include a cationic substance, an anionic substance, and the like. Specifically, calcium ions that are ionic-bonded to anions and easily generate scales that are not easily dissolved in water, A magnesium ion etc. are illustrated. Examples of the organic substance include a water-soluble organic substance dissolved in the raw water.

  As the reverse osmosis membrane (RO membrane), a conventionally known general reverse osmosis membrane can be used in the technical field of water treatment. Specifically, for example, a reverse osmosis membrane unit may be used as the reverse osmosis membrane. Examples of the reverse osmosis membrane unit include those in which a filtration membrane installed in a state of a hollow fiber membrane, a spiral membrane, a tubular membrane or the like is held in a vessel and can withstand high pressure. Moreover, as said reverse osmosis membrane, the composite membrane comprised by the dense layer and microporous layer of an asymmetric membrane is mentioned, for example. In addition, 2 nm or less is normally illustrated as a hole diameter of the hole in the said reverse osmosis membrane.

  In the RO membrane separation step, a scale inhibitor is added to the MF membrane permeated wastewater that has permeated the MF membrane for the purpose of preventing precipitates (so-called scales) from being generated in the concentrated water concentrated by the RO membrane. Can be added. By adding a scale inhibitor to the MF membrane permeated wastewater, components that can become scales contained in the MF membrane permeated wastewater (hardness components such as ionic silica, calcium ions, magnesium ions, soluble evaporation residues, It is possible to suppress the precipitation of carbonic acid and the like as a scale.

  As the scale inhibitor, specifically, a compound having a chelating agent action, more specifically, polyphosphoric acid, phosphonic acid, a carboxylic acid polymer electrolyte (generally called a low molecular weight polymer) or the like is used. it can.

  In the RO membrane separation step, a biofouling inhibitor can be added to the MF membrane permeated wastewater for the purpose of preventing biofouling that may occur in the RO membrane. By adding a biofouling inhibitor to the MF membrane permeated wastewater, biofouling that causes clogging of the RO membrane can be suppressed.

  As the biofouling inhibitor, a conventionally known general agent in the technical field of water treatment can be used.

  In the RO membrane separation step, two units of the reverse osmosis membrane (RO membrane) can be connected in series (not shown). By connecting two units of the reverse osmosis membrane (RO membrane) in series, the degree of purification of the permeated water that has permeated the reverse osmosis membrane can be further increased, and the permeated water is supplied to, for example, a waste heat boiler. It can be applied as highly purified water such as water.

  In the wastewater treatment method of this embodiment, the temperature reduction step is performed after the RO membrane separation step. In the temperature reduction step, the temperature of the heat recovery gas is reduced by the heat of vaporization of the concentrated water.

  Specifically, in the temperature reduction step, the heat recovery is performed by injecting the concentrated water in the temperature reduction device 3 to the heat recovery combustion exhaust gas from which heat has been recovered through the heat recovery device 2. Reduce the temperature of combustion exhaust gas further. The temperature reduction, that is, the temperature reduction, is performed using heat of vaporization when the concentrated water evaporates.

  In the temperature reduction step, when the heat recovery combustion exhaust gas is reduced in temperature by the heat of vaporization of the concentrated water, such as by injecting the concentrated water into the temperature reducing device 3, the volume of the waste water is reduced and the volume is reduced. Since the amount of water to be vaporized is small due to the concentrated water, the temperature range for reducing the temperature of the heat recovery combustion exhaust gas can be set small. Further, the heat recovery combustion exhaust gas reduced in temperature by the temperature reduction device 3 is heat recovered from the combustion exhaust gas by the heat recovery device 2 on the upstream side, and the heat recovery combustion exhaust gas is converted into the temperature reduction device. The amount of heat recovered from the combustion exhaust gas in the heat recovery device 2 on the upstream side can be set larger by the amount of the temperature range to be decreased in 3. In addition, the water | moisture content of the said concentrated water is normally discharge | released in air | atmosphere as water vapor | steam by implementing the said temperature reduction process.

Specifically, for example, when the combustion exhaust gas is 1000 ° C. and the heat recovery combustion exhaust gas is set to be reduced to 150 ° C. by the temperature reduction step, in the wastewater treatment method of the present embodiment, Since the concentrated water is relatively small, the heat recovery flue gas can be set to be reduced in temperature range from 300 ° C. to 150 ° C., that is, 150 ° C. by the temperature reduction step. Therefore, the heat recovery apparatus 2 can recover heat from 1000 ° C. to 300 ° C., that is, 700 ° C.
On the other hand, in the conventional wastewater treatment method, since a relatively large amount of water is used in the temperature reduction step, for example, the heat recovery combustion exhaust gas is reduced from 400 ° C. to 150 ° C. by the temperature reduction step, ie, 150 ° C. in the above example. The temperature may be set to decrease at a temperature range of 250 ° C. (greater than the temperature range). Therefore, the heat recovery apparatus 2 can recover only heat from 1000 ° C. to 400 ° C., that is, 600 ° C. (less than 700 ° C. in the above example).

  In addition, when there are many suspended | floating matter (SS) contained in the said MF membrane concentrated water, when the said concentrated water is injected in the said temperature reduction apparatus 3, etc., it may cause clogging of piping or a nozzle. . In order to prevent such a phenomenon, all or part of the MF membrane concentrated water is returned to the upstream side, and the pretreatment step is performed on all or part of the MF membrane concentrated water, and the MF membrane You may perform the process which removes the suspended | floating matter contained in concentrated water.

  As described above, the wastewater treatment method of the present embodiment can increase the amount of heat recovered from the combustion exhaust gas in the heat recovery device 2 by performing the RO membrane separation step and the temperature reduction step. Preferably, it is carried out in a system that does not discharge the drained water as much as possible, and more preferably in a system that does not discharge the waste water substantially.

  Specifically, in the conventional wastewater treatment method, a part of the water after the wastewater treatment can be used for cooling the peripheral equipment of the incinerator 1 or other plant water for the purpose of preventing the drained water from being discharged as much as possible. However, most of the water after the waste water treatment is vaporized by being injected into the heat recovery combustion exhaust gas passing through the temperature reducing device 3 to reduce the capacity of the water after the waste water treatment. That is, a relatively large amount of water is used for temperature reduction in the temperature reduction device 3. Since a relatively large amount of water is jetted to the temperature reducing device 3, the temperature range for reducing the temperature by the heat of vaporization is set to be relatively large. Accordingly, in the heat recovery device 2 on the upstream side of the temperature reducing device 3, the amount of heat recovered from the combustion exhaust gas must be set small. That is, as the temperature range for reducing the temperature in the temperature reducing device 3 is increased, the heat recovery amount from the combustion exhaust gas in the heat recovery device 2 is reduced, and the heat recovery efficiency from the combustion exhaust gas in the incineration plant is reduced. Cheap.

  Therefore, as in the wastewater treatment method of the present embodiment, the wastewater discharged from the incineration plant by the RO membrane separation step is separated by the RO membrane, the impurities contained in the wastewater are concentrated, and the pollution degree is further increased. The concentrated water is separated and removed. Water with a relatively high degree of contamination usually cannot be discharged, etc., and is mixed with the waste water to be drained again, so that the concentrated water with a relatively high degree of contamination is vaporized to increase its capacity. The reduction is preferable in terms of achieving the purpose of preventing the drained water from being discharged as much as possible.

  On the other hand, in the RO membrane separation step, wastewater discharged from the incineration plant can be separated by the RO membrane, impurities contained in the wastewater can be reduced, and the permeate having a substantially reduced volume can be separated and removed. The permeated water has a relatively high degree of purification, such as industrial water, with reduced impurities and the like contained in the wastewater, and can be used in applications that require a relatively high degree of purification. . That is, for example, it can be used for purposes such as boiler raw water, equipment cooling water, and plant water used in the plant, which require a relatively high degree of purification in the incineration plant. Therefore, by carrying out the RO membrane separation step and generating the permeate having a relatively high degree of purification from a part of the waste water, the permeate can be applied to various uses in an incineration plant. It is preferable in that the purpose of preventing the treated water from being discharged as much as possible is achieved.

  In addition, the concentrated water used in the temperature reduction step is a concentrated water whose impurities contained in the waste water discharged from the incineration plant are concentrated, and thus, for example, boiler raw water, equipment cooling water, It cannot be used as it is in applications that require a relatively high degree of purification, such as plant water used in Therefore, in order to prevent the concentrated water from being discharged as much as possible, the wastewater treatment is performed again, and the amount of wastewater treatment increases by the amount of wastewater treatment again. Therefore, instead of mixing the concentrated water with the wastewater, the temperature reducing step is performed as in the wastewater treatment method of the present embodiment, the concentrated water is evaporated by the temperature reducing device 3, and the concentrated water is vaporized. By reducing the temperature of the heat recovery combustion exhaust gas by heat, it is possible to increase the amount of heat recovered from the combustion exhaust gas in the heat recovery device 2 as described above, and to suppress an increase in the amount of wastewater treatment.

  The concentrated water used in the temperature reducing step can be mixed with the MF membrane concentrated water in which the waste water is concentrated by the MF membrane in the pretreatment step. Further, the concentrated water can be mixed with waste water when the MF membrane is backwashed (backwashed) or chemically washed. That is, other waste water or the like can be mixed with the concentrated water as necessary.

  In the wastewater treatment method of the present embodiment, a post-treatment process that further handles the permeated water that has permeated the RO membrane in the RO membrane separation step can be performed after the RO membrane separation step.

  Specifically, in the post-treatment step, the permeated water has a water quality equivalent to that of pure water, and thus the permeated water can be directly supplied to the waste heat boiler. In addition, in the said post-processing process, when the complete closed system is not necessarily employ | adopted in an incineration plant, the said permeated water can be discharged | emitted to the sea, a river, or sewage.

  In addition, before the said pretreatment process, the aspect which employ | adopts a conventionally well-known water treatment method can also be included in this invention, for example. For example, the aspect which employ | adopts a conventionally well-known water treatment method after the said post-processing process can also be contained in this invention.

  Subsequently, an embodiment of the wastewater treatment facility according to the present invention will be described.

The wastewater treatment facility of the present embodiment includes an incinerator 1 that burns organic matter, a heat recovery device 2 that recovers the heat of combustion exhaust gas discharged from the incinerator 1, and a combustion that is heat recovered by the heat recovery device 2 A wastewater treatment facility for wastewater discharged from an incineration plant equipped with a temperature reducing device 3 for further reducing the temperature of exhaust gas (heat recovery combustion exhaust gas),
Chlorine amount measuring means for measuring the amount of free residual chlorine contained in the wastewater, dechlorinating agent adding means for adding a dechlorinating agent to the wastewater, and the drainage in response to an increase in the amount of free residual chlorine. A dechlorinating agent increasing means for increasing a dechlorinating agent to be added; a RO membrane separating means for separating and removing concentrated water from the waste water to which the dechlorinating agent is added by a reverse osmosis membrane (RO membrane); and the heat recovery combustion And a temperature reducing means for reducing the temperature of the exhaust gas by the temperature reducing device 3 by heat of vaporization of the concentrated water.

  Examples of the chlorine amount measuring means include conventionally known general devices in the technical field of water treatment. For example, a dechlorination water tank provided with an oxidation-reduction potentiometer or a chlorine meter and temporarily storing the MF membrane permeated waste water 4 etc. are mentioned.

  Examples of the dechlorinating agent adding means include a conventionally known general apparatus in the technical field of water treatment. For example, the dechlorinating agent storage tank 5 for storing the dechlorinating agent, and the MF membrane permeate drainage lead to the RO membrane. An example of the pipe is a pipe provided to add the dechlorinating agent from the dechlorinating agent storage tank 5 in the middle of the process.

  Examples of the dechlorinating agent increasing means include conventionally known general devices in the technical field of water treatment. For example, a dechlorinating agent is supplied from the dechlorinating agent storage tank 5 to the dechlorinating water tank 4 as necessary. A pump provided so that it can be added, and the pump operates when the redox potential or free residual chlorine concentration is greater than a predetermined value in conjunction with the redox potential meter or chlorine meter, and the dechlorinating agent For example, a device provided so that a dechlorinating agent is added from the storage tank 5 to the dechlorinated water tank 4 may be used.

  Examples of the RO membrane separation means include general devices conventionally known in the technical field of water treatment, and examples thereof include the above-described RO membrane or RO membrane unit.

  Examples of the temperature reducing means include conventionally known general devices in the technical field of water treatment. For example, water is injected or sprayed on the heat recovery combustion exhaust gas introduced from the heat recovery device 2, and the temperature recovery device 3 such as a temperature reduction tower that lowers the temperature of the heat recovery combustion exhaust gas by the heat of vaporization of water is used. An apparatus (not shown) for drawing concentrated water may be used.

  In addition, the wastewater treatment facility of the present embodiment separates the wastewater by a microfiltration membrane (hereinafter also referred to as MF membrane) to reduce suspended matters contained in the wastewater, and permeates the microfiltration membrane (MF membrane). Pretreatment means for separating and removing the MF membrane permeated wastewater from the wastewater may be provided.

  In addition, the wastewater treatment facility according to the present embodiment includes a flocculation apparatus in which a predetermined amount of the wastewater is stored and the flocculant is added to the wastewater at an appropriate amount at an appropriate time, or sand or ansula on a gravel layer. Commonly used sand filtration devices such as those with a layer of filtration media such as a site may be provided.

  The waste water treatment facility of the present embodiment can be manufactured by a general method. That is, as the MF membrane, the RO membrane, the aggregating device, the sand filtering device, etc., those generally used in the technical field of water treatment can be adopted, and the piping and wiring necessary for these can be adopted. The waste water treatment facility of the present embodiment can be manufactured by a normal method by combining them by installing them.

The present invention is not limited to the waste water treatment method and waste water treatment equipment for waste water discharged from the incineration plant illustrated above.
Moreover, the various aspects used in a general water treatment method and water treatment equipment can be employed within a range that does not impair the effects of the present invention.

A simplified diagram showing the incineration plant. Schematic of the apparatus used with the waste water treatment method of this embodiment. Schematic of the apparatus used in a chlorine amount measurement process, a dechlorinating agent addition process, and a dechlorinating agent increase process.

Explanation of symbols

1 ... Incinerator (incinerator)
2. Heat recovery device (waste heat boiler)
3 ... Temperature reduction device (temperature reduction tower)
4 ... Dechlorination water tank 5 ... Dechlorination agent storage tank 6 ... Free residual chlorine amount detection device (redox potential meter or chlorine meter)
P ... Pump

Claims (4)

An incinerator that combusts organic matter, a heat recovery device that recovers the heat of the combustion exhaust gas discharged from the incineration device, and a temperature reduction device that further reduces the temperature of the combustion exhaust gas recovered by the heat recovery device. A wastewater treatment method for wastewater discharged from an incineration plant,
A chlorine amount measuring step for measuring the amount of free residual chlorine contained in the waste water, a dechlorinating agent adding step for adding a dechlorinating agent to the waste water, and the waste water corresponding to an increase in the amount of free residual chlorine. A dechlorinating agent increasing step for increasing the dechlorinating agent to be added, a RO membrane separating step for separating and removing concentrated water from the waste water to which the dechlorinating agent was added by a reverse osmosis membrane (RO membrane), and heat recovery A wastewater treatment method, comprising: performing a temperature reduction step of reducing the temperature of combustion exhaust gas by the temperature reduction device using the heat of vaporization of the concentrated water.   The wastewater treatment method according to claim 1, wherein a pretreatment step for reducing suspended matters contained in the wastewater is performed before the dechlorinating agent addition step.   In the pretreatment step, in order to reduce suspended matter contained in the wastewater, the wastewater is separated by a microfiltration membrane (MF membrane), and the MF membrane permeated wastewater that has permeated the MF membrane is separated and removed from the wastewater. The waste water treatment method according to 2. An incinerator that combusts organic matter, a heat recovery device that recovers the heat of the combustion exhaust gas discharged from the incineration device, and a temperature reduction device that further reduces the temperature of the combustion exhaust gas recovered by the heat recovery device. Wastewater treatment facility for wastewater discharged from an incineration plant,
Chlorine amount measuring means for measuring the amount of free residual chlorine contained in the wastewater, dechlorinating agent adding means for adding a dechlorinating agent to the wastewater, and the drainage in response to an increase in the amount of free residual chlorine. A dechlorinating agent increasing means for increasing the dechlorinating agent to be added; an RO membrane separating means for separating and removing concentrated water from the waste water to which the dechlorinating agent has been added by a reverse osmosis membrane (RO membrane); and heat recovery A waste water treatment facility comprising: a temperature reducing means for reducing the temperature of the combustion exhaust gas by the heat of vaporization of the concentrated water by the temperature reducing device.

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