TW201636304A - Wastewater treatment method of incineration plant - Google Patents

Abstract

A wastewater treatment method for an incineration plant is provided which can efficiently recover the heat of combustion exhaust gas in the incineration plant and can stably and efficiently concentrate wastewater. This wastewater treatment method is for treating wastewater discharged from an incineration plant which is provided with an incineration device 1, a combustion exhaust gas heat recovery device 2, and a temperature reduction device 3 for further reducing the temperature of the combustion exhaust gas from which heat has been recovered by said heat recovery device. This method involves performing a membrane separation step 6 for separating the wastewater discharged from the incineration plant into permeated water and concentrated water by means of a separation membrane, and involves lowering the temperature of the combustion exhaust gas by spraying at least part of said concentrated water into the temperature reduction device 3. A wastewater mixture of at least two types of incineration plant wastewater, namely boiler stored water, boiler blowdown water, cooling tower blowdown water and gray water, is subjected to the membrane separation treatment step 6.

Description

Wastewater treatment method for incineration plant

The present invention relates to a method of treating wastewater discharged from a self-incineration plant.

As a method of treating waste water discharged from an incineration plant including a heat treatment device that burns an organic matter, a heat recovery device that collects combustion exhaust gas discharged from the incineration device, and a temperature reduction device that further cools the heat recovery combustion exhaust gas A wastewater treatment method in which the wastewater is subjected to agglomeration treatment by a coagulant or the like and then subjected to filtration treatment is known.

In addition, a wastewater treatment method in which the wastewater discharged from the self-incineration plant is subjected to agglomeration treatment, followed by biological treatment, and further subjected to filtration treatment by sand filtration is also known (Patent Document 1). Patent Document 1 describes that most of the purified water purified by the wastewater treatment method can be discharged.

In recent years, it has been required to release as much as possible the purified water produced by the treatment of the wastewater discharged from the self-incineration plant.

In order to prevent the purified water generated by the treatment of the waste water discharged from the self-incineration plant from being discharged as much as possible, a part of the purified water is sprayed into a cooling device such as a cooling tower to vaporize it, thereby reducing the capacity of the purified water. In the method, in detail, in the cooling device, the purified water is injected into the combustion exhaust gas after heat recovery from the combustion exhaust gas by a heat recovery device such as a waste heat boiler, thereby purifying the purified water and reducing the capacity thereof. On the other hand, the combustion exhaust gas is cooled by its heat of vaporization.

In this way, when as much purified water as possible is supplied to the cooling device so as not to release the purified water purified by the wastewater treatment, the heat recovery device such as a waste heat boiler located on the upstream side of the cooling device The amount of heat recovered from the combustion exhaust gas must be set to be small. That is, in order to evaporate a large amount of purified water in the cooling device, it is necessary to reduce the amount of heat recovery from the combustion exhaust gas in the heat recovery device, and the heat recovery efficiency of the combustion exhaust gas from the incineration plant is lowered.

In order to reduce the amount of water sprayed into the cooling device, Patent Document 2 discloses that a microfiltration (MF) membrane is used to treat incineration plant wastewater, and reverse Osmosis (RO) membrane treatment is performed on the permeated water. Then, the concentrated water of the MF membrane and the concentrated water of the RO membrane are supplied to the cooling device.

According to this method, by concentrating the wastewater with the MF membrane and the RO membrane, the amount of water sprayed toward the cooling device can be reduced, and the reduction in the amount of heat recovery can be suppressed.

However, there are various types of waste water discharged from the self-incineration plant, and there are problems such as clogging of the membrane due to water quality, inability to sufficiently reduce the amount, or unstable operation, or frequent maintenance and cleaning treatment. Further, the backwash water of the membrane filtration device is water in a state in which the solid suspended matter (Suspend Solid, SS) in the wastewater is concentrated, and therefore there is a drawback that the nozzle is clogged at the time of spraying, and maintenance is required.

Patent Document 1: Japanese Patent Laid-Open No. Hei 10-99898, Patent Document 2: Japanese Patent No. 5636163

An object of the present invention is to provide a waste water treatment method for an incineration plant which can efficiently recover the heat of combustion exhaust gas in an incineration plant and can concentrate and treat the wastewater stably and efficiently.

The waste water treatment method of the incineration plant of the present invention is further provided from a heat recovery device including an incinerator for burning organic matter, combustion exhaust gas discharged from the incineration device, and combustion exhaust gas recovered by the heat recovery device. a wastewater treatment method for wastewater discharged from an incineration plant of a temperature-lowering cooling device, which performs a membrane separation step of separating waste water discharged from a self-incineration plant into a permeated water and concentrated water by a separation membrane, and supplying at least a part of the concentrated water to the The cooling device is blown into the combustion exhaust gas to evaporate, thereby cooling the combustion exhaust gas, and the waste water treatment method of the incineration plant is characterized in that the boiler water in the incineration plant is mixed with the boiler water and the boiler row The mixed wastewater of at least two of sewage, cooling tower sewage, and miscellaneous wastewater is supplied to the membrane separation treatment step.

In one aspect of the present invention, the waste water is treated as a mixed wastewater by a first pretreatment step having at least one of neutralization, coagulation, precipitation, filtration, and biological treatment.

In one aspect of the present invention, after the mixed wastewater is treated by using a pretreatment device of a filter, an MF membrane, or an ultrafiltration (UF) membrane, in the membrane separation step, the RO membrane is used. The membrane separation treatment is carried out.

In one aspect of the present invention, after the mixed wastewater is treated by using a pretreatment device of a filter, an MF membrane, or a UF membrane, the membrane separation treatment is performed by the RO membrane in the membrane separation step. The concentrated water or the backwashing wastewater of the pretreatment apparatus is sent to the first pretreatment step.

In one aspect of the present invention, at least one of the floor washing wastewater and the car wash wastewater of the incineration plant is not subjected to reverse osmosis treatment, and is supplied to the cooling device.

In one aspect of the present invention, at least one of the floor washing wastewater and the car wash wastewater of the incineration plant is treated by a second pretreatment step having at least one of neutralization, coagulation, sedimentation, filtration, and biological treatment. Thereafter, it is supplied to the cooling device. [Effects of the Invention]

In the wastewater treatment method of the present invention, as in Patent Document 2, in the membrane separation step, the wastewater discharged from the incineration plant is concentrated by a separation membrane to prepare a concentrated water having a reduced volume, and the concentration is concentrated. Since the water is supplied to the cooling device, the amount of concentrated water supplied to the cooling device is small, and the temperature of the combustion exhaust gas introduced into the cooling device can be lowered. As a result, in the heat recovery device provided on the upstream side of the temperature lowering device, the amount of heat recovered from the combustion exhaust gas can be increased.

In the wastewater treatment method of the present invention, it is preferred to subject the mixed wastewater to membrane separation treatment using an RO membrane.

For the stabilization and efficiency of the treatment, water treatment chemicals such as a dispersant or a slime control agent are contained in the boiler water, the boiler sewage, and the cooling water. By selecting a stabilizer that does not adversely affect the membrane treatment and contributes to the membrane treatment to be used as the chemicals, the RO treatment can be stably or completely re-added to the RO membrane treatment. Membrane separation treatment.

The dispersant contained in the boiler sewage and the cooling water discharge sewage becomes a hindrance factor of the coagulation treatment. The slime control agent has an adverse effect on biological treatment, and there is an example in which biological activity is lowered. In one aspect of the present invention, the water is subjected to a simple pretreatment including a sand filtration, an MF membrane or a UF membrane, and then subjected to a membrane separation treatment, so that the size of the wastewater treatment facility can be reduced.

In one aspect of the wastewater treatment method of the present invention, the waste water is treated by a pretreatment step having at least one of neutralization, coagulation, sedimentation, filtration, and biological treatment, and the SS component in the wastewater is organic. After the components are removed, the concentration operation is carried out by membrane treatment. As described above, by pretreating the waste water, the SS component and the organic component contained in the wastewater can be reduced, and clogging of the separation membrane is less likely to occur, and the subsequent use period of the separation membrane can be prolonged. Thereby, the frequency of replacement of the separation membrane becomes low, the concentrated water can be efficiently obtained, and the heat of the combustion exhaust gas in the incineration plant can be recovered more efficiently.

It is preferable that the concentrated water or the backwash water of the pretreatment apparatus is also treated by the first pretreatment step to remove the SS component and the organic component. However, the processing can also be performed by the second pre-processing step.

Regarding the car wash waste water and the floor washing waste water, it is preferred to spray in a cooling device without performing a membrane treatment. In the car wash waste water or the floor washing waste water, a substance which blocks the MF film or the RO film, such as an oil component or a surfactant, may be contained, and the concentration may not be fixed, and it may be difficult to perform stable treatment. Therefore, it is preferred to treat the car wash wastewater and the floor washing wastewater by a second pretreatment step having at least one of neutralization, coagulation, sedimentation, filtration, and biological treatment, thereby performing solid-liquid separation and removal of organic components. After that, spraying is performed in the cooling device.

In the present invention, the mixed wastewater may also be a mixture of waste water other than the boiler water.

Hereinafter, an embodiment of the wastewater treatment method of the present invention will be described with reference to the drawings.

As shown in Fig. 1, an incineration plant to which the wastewater treatment method of the present embodiment is applied includes an incinerator 1 for burning organic matter, a heat recovery device 2 for recovering combustion exhaust gas discharged from the incineration device 1, and a heat recovery device 2 The cooling device 3 for further cooling of the combustion exhaust gas (hereinafter, also referred to as heat recovery combustion exhaust gas) recovered by the recovery device. Further, other devices and the like can be provided.

As the incineration device 1, an incineration plant such as a coal charging furnace, a fluidized bed furnace, a gasification melting furnace, or an ash melting furnace can be used.

The organic substance to be burned is not particularly limited, and examples thereof include municipal waste, industrial waste, sewage sludge, and waste wood. The combustion exhaust gas discharged from the self-incineration device 1 usually becomes a temperature of about 800 ° C to 1300 ° C.

The heat recovery device 2 recovers the heat of the combustion exhaust gas discharged from the incineration device 1. Examples of the heat recovery device 2 include a waste heat boiler and the like.

The cooling device 3 further cools the combustion exhaust gas (heat recovery combustion exhaust gas) recovered by the heat recovery device 2. The temperature lowering device 3 is configured such that water is sprayed or sprayed into the heat recovery combustion exhaust gas introduced into the self-heat recovery device 2, and the temperature of the heat recovery combustion exhaust gas is lowered by the heat of vaporization of water. The heat recovery combustion exhaust gas introduced into the temperature lowering device 3 usually has a temperature of about 250 ° C to 400 ° C. The water sprayed or sprayed in the cooling device 3 is a mixture of at least two mixed wastewaters of boiler water, boiler sewage, cooling tower sewage, and miscellaneous wastewater mixed in the incineration plant wastewater by using a separation membrane. Concentrated water.

In the present invention, the amount of water to be blown into the temperature lowering device 3 is smaller than that in the case of Patent Document 2, so that the temperature of the introduced exhaust gas in the temperature lowering device 3 can be made lower than that of Patent Document 2. Thereby, the amount of heat recovery in the heat recovery device 2 can be increased.

The temperature of the exhaust gas cooled by the temperature lowering device 3 usually becomes about 150 ° C to 200 ° C. The gas contains water vapor obtained by vaporizing the concentrated water. The exhaust gas is purified by the dust collector 4 or the like and then released to the atmosphere.

The wastewater discharged from the self-incineration plant refers to the wastewater generated in the land of the incineration plant. The wastewater generated in the land of the incineration plant, for example, the boiler sewage discharged from the heat recovery device 2 such as a waste heat boiler, is filled in the tank of the heat recovery device at the time of stopping, and the boiler water is discharged before the restart. The floor washing waste water generated when the cooling tower discharges the sewage and the floor in the incineration plant, and the washing waste water generated when the waste collecting vehicle is cleaned may include domestic wastewater or miscellaneous wastewater. Examples of the waste water include waste cooling waste water which is cooled by incineration residue or slag generated in an incineration plant 1 such as a self-incineration furnace, or waste water other than the above-mentioned surfactant or oil component which is generated in an incineration plant. .

As shown in Fig. 2, it is preferred to carry out the pretreatment of the mixed wastewater mixed with the boiler water, the boiler sewage and the cooling tower sewage (excluding the boiler water), by the membrane separation step. 6 to carry out membrane separation treatment. At least a part of the concentrated water is supplied to the temperature reducing device 3 to evaporate the concentrated water to cool the combustion exhaust gas.

Regarding the mixed waste water, it is preferable to carry out the first pretreatment 7, and mix with the boiler water, the boiler sewage, and the cooling tower sewage, and then supply it to the pretreatment 5. By pretreating the waste water as described above, the clogging of the membrane of the membrane separation step 6 is suppressed.

As the pretreatment 5, a sand filter, an MF membrane, a UF membrane, or the like can be used.

By pretreating the mixed wastewater as described above, clogging of the membrane of the membrane separation step 6 is suppressed. As the membrane of the membrane separation step 6, an RO membrane is suitable.

The first pretreatment 7 for treating the waste water is preferably at least one of neutralization, coagulation, precipitation, filtration, and biological treatment.

The car wash waste water and the floor washing waste water are preferably mixed with the membrane concentrated water from the membrane separation step 6 after the second pretreatment 8 for removing the SS component and the organic component, and then supplied to the temperature lowering device 3. As the second pretreatment, at least one of neutralization, coagulation, precipitation, filtration, and biological treatment is preferred.

When the MF membrane or the UF membrane is used in the pretreatment 5, it is preferred to treat the MF membrane concentrated water or the UF membrane concentrated water by the first pretreatment 7, and to remove the SS component and the organic component. However, the processing can also be performed by the second pre-processing 8. Since the MF membrane concentrated water or the UF membrane concentrated water of the pretreatment 5 is not sprayed in the cooling device 3, clogging of the spray nozzle can be prevented, and stable cooling treatment can be performed.

As described above, in order to stabilize and improve the treatment, water is treated in the boiler water, the boiler sewage, and the cooling tower sewage, including an anti-corrosion agent, a dispersing agent or a slime controlling agent, a condensing amine agent, and an oxygen scavenger. Chemicals. Selecting a stabilizer that does not adversely affect the membrane treatment and contributes to the membrane treatment as the chemicals, and only pre-treating the boiler water, the boiler sewage, and the cooling tower sewage, and then performing the RO membrane. By this, it is possible to re-add a water treatment chemical for the RO membrane treatment, and an efficient membrane separation treatment can be performed. When the chemical concentration is insufficient, the required chemicals can also be added.

The dispersant contained in the boiler sewage and the cooling water discharge sewage becomes a hindrance factor of the coagulation treatment. Therefore, when the boiler discharge water and the cooling water discharge sewage are flown into the first pretreatment 7, the required amount of the coagulant is remarkably increased. The slime control agent has an adverse effect on biological treatment, and there is an example in which biological activity is lowered, and it is necessary to additionally perform detoxification when performing wastewater treatment. Therefore, the water is not pretreated and supplied to the pretreatment 5, whereby the pretreatment apparatus can be reduced.

The car wash waste water and the floor washing waste water are sprayed in the temperature lowering device 3 after the second pretreatment 8 . In the car wash waste water or the floor washing waste water, a substance which blocks the MF film or the RO film, such as an oil component or a surfactant, may be contained, and the concentration thereof is not fixed, and it is difficult to stably perform the membrane separation treatment. Therefore, the car wash wastewater and the floor washing wastewater are treated by the second pretreatment 8 having at least one of neutralization, coagulation, sedimentation, filtration, and biological treatment, and after solid-liquid separation and removal of organic components, The cooling device 3 performs spraying.

In the first pretreatment 7 and the second pretreatment 8, in order to reduce the SS component and the organic component contained in the water to be treated, a coagulant may be added to the wastewater, and the floating matter may be mainly aggregated and then sanded. Instead of filtration, a filtration treatment such as filtration or a precipitation step is performed. When the load is high, a step of pressurizing and floating may be added. In order to appropriately carry out the coagulation treatment, a pH adjustment step may be added. By performing a series of pretreatment steps, the agglomerates can be removed from the wastewater and the SS components and organic components that can be included in the car wash wastewater and floor washing wastewater can be reduced.

In the first pretreatment 7 and the second pretreatment 8, an MF membrane (immersion membrane) may be used instead of the sand filtration device, and the membrane separation activated sludge method may be used. After the agglomerates captured by the MF membrane (impregnated membrane) are taken out, they are put into a garbage pit, and incinerated by the incinerator 1.

Examples of the aggregating agent include iron-based aggregating agents such as ferrous sulfate, iron sulfate, and ferric chloride; and aluminum-based aggregating agents such as aluminum sulfate and polyaluminium chloride (PAC). Mixtures, etc. The amount of the coagulant added can be appropriately adjusted.

Examples of the polymer flocculating agent to be added to the water to be treated as a coagulant include poly(meth)acrylic acid, a copolymer of (meth)acrylic acid and (meth)acrylamide, and alkali metal salts thereof. An anionic organic polymer flocculating agent, a nonionic organic polymer coagulant such as poly(meth)acrylamide, or a dimethylaminoethyl (meth)acrylate or a quaternary ammonium salt thereof, a homopolymer of a cationic monomer such as dimethylaminopropyl (meth) acrylamide or a quaternary ammonium salt thereof, and a copolymer of the cationic monomer and a nonionic monomer copolymerizable An cation-based organic polymer flocculant, and an amphoteric organic polymer agglomerate as a copolymer of the anionic monomer, a cationic monomer or a nonionic monomer copolymerizable with the monomer Agent. The amount of the polymer flocculating agent to be added is not particularly limited, and may be adjusted in accordance with the properties of the water to be treated, but is preferably from 0.01 mg/L to 10 mg/L in terms of solid content with respect to the water to be treated. A phenol type coagulant or the like described in WO2011/018978 can also be used.

When the RO film is used in the membrane separation step 6, examples of the impurities removed by the RO membrane include an ionic component, an organic substance, and the like. Specific examples of the ionic component include a cationic substance and an anionic substance. Specific examples thereof include calcium ions and magnesium ions which are easily ionically bonded to an anion to cause scale which is hardly dissolved in water. Examples of the organic substance include water-soluble organic substances dissolved in waste water.

When the MF membrane is used in the pretreatment 5, since the scale, the suspended matter, the organic matter, and the like adhere to the surface of the MF membrane, the MF membrane differential pressure rises. In this case, back pressure cleaning or chemical cleaning of the MF membrane is performed. In the back pressure cleaning of the MF membrane, from the viewpoint of further suppressing the increase in the differential pressure of the MF membrane, it is preferred to perform the cleaning periodically/irregularly using water containing hypochlorite such as sodium hypochlorite.

The MF film usually has pores having a pore diameter of about 50 nm to 10 μm. As the MF membrane, for example, a membrane unit in which a hollow fiber membrane, a spiral membrane, or a tubular membrane is held in a container can be used. A hollow fiber membrane or a flat sheet membrane may also be directly immersed in the water to be treated for use. Instead of the MF membrane, an ultrafiltration membrane (UF membrane) having a pore diameter of about 2 nm to 200 nm can also be used.

As the MF film, polyvinylidene difluoride (PVDF) can be suitably used. As the UF film, polyfluorene can be suitably used. The RO film can be suitably used as a material, but it is not limited thereto. this.

The RO film may, for example, be a composite film of a fine layer and a fine porous layer containing an asymmetric membrane.

As the RO membrane, a unit in which a filtration membrane provided in a state of a hollow fiber membrane, a spiral membrane, a tubular membrane, or the like is held in a container can be used.

As the dispersing agent used in the cooling water treatment or the like, an inorganic polyphosphoric acid such as sodium hexametaphosphate or sodium tripolyphosphate, or a phosphonic acid such as hydroxyethylidene diphosphonic acid or phosphinium butane tricarboxylic acid can be used. a raw material containing a carboxyl group such as butenedioic acid, acrylic acid or itaconic acid, if necessary, with a sulfonic acid, allylsulfonic acid, 2-methylpropenylamine-2-methylpropanesulfonic acid, etc. A copolymer other than the raw materials listed herein may be applied to a copolymer of an acid group-based vinyl monomer or a nonionic vinyl monomer such as acrylamide. A terpolymer may also be used as the third component of the dispersant. For example, as the third component, N-t-butyl acrylamide or the like is used. As the dispersing agent, a polymer containing HAPS, AMPS and acrylic acid and/or methacrylic acid is preferred. HAPS is 3-allyloxy-2-hydroxy-1-propanesulfonic acid and AMPS is 2-propenylamine-2-methylpropanesulfonic acid.

The molecular weight of the dispersant is preferably 1,000 or more and 30,000 or less. When the molecular weight is 1,000 or less, a sufficient dispersion effect cannot be obtained, and if it is 30,000 or more, the pretreatment film is removed.

As the slime control agent, hypochlorite such as sodium hypochlorite (NaClO), chlorinating agent such as chlorine gas, chloramine or chlorinated isocyanurate, chlorine such as monochloramine sulfonic acid and guanamine sulfuric acid, A chlorinating agent formed by reacting a guanamine sulfate-based compound, a brominating agent such as dibromomethine, a hypobromite such as sodium hypobromite, and a Dibromonitrilo propionamide (DBNPA). An organic agent such as methyl isothiazolinone (Methylisothiazolone, MIT). As the chlorine-based oxidizing agent which can be used in the present invention, in addition to the chlorine gas, hypochlorous acid or a salt thereof, chlorous acid or a salt thereof, chloric acid or a salt thereof, perchloric acid or a salt thereof, and chlorinated heterotrimerization can be used. Cyanic acid or a salt thereof. Examples of the salt include an alkali metal salt such as sodium or potassium, an alkaline earth metal salt such as hydrazine, another metal salt such as nickel, and an ammonium salt. These may be used in more than one type. Among these, sodium hypochlorite is preferred because of its excellent handleability.

Examples of the nitrogen compound to which the free chlorine is bonded include ammonia or a compound thereof, melamine, urea, acetamide, thioguanamine, cyclamate, amine sulfonic acid, toluene sulfonamide, and butyl succinimide. , o-xylylenediamine, iso-cyanuric acid, N-chlorotoluenesulfonamide, uric acid, saccharin or a salt thereof. The bonding chlorinating agent used in the present invention is one in which the free chlorine is bonded to the nitrogen compounds. The bonding chlorinating agent used in the present invention is preferably obtained by mixing the nitrogen compound and a free chlorinating agent, and in particular, mixing the two in an aqueous solution to carry out a reaction. .

As such a bonding chlorinating agent, in addition to a chlorinating agent containing a chloramine or a chlorine-based oxidizing agent and an aminesulfonic acid compound, chloramine-T (N-chloro-4-methylbenzenesulfonamide) may be mentioned. Sodium salt), chloramine-B (sodium salt of N-chloro-benzenesulfonamide), sodium salt of N-chloro-p-nitrobenzenesulfonamide, trichloromelamine, mono- or di-chloromelamine a sodium or potassium salt, a trichloro-isocyanurate, a sodium or potassium salt of mono- or di-chloroisocyanuric acid, a sodium or potassium salt of mono- or di-chloroamine sulfonic acid, Monochloro-Hintone or 1,3-dichloro-haitone, 5,5-alkyl-like derivative such as 5,5-dimethylhine.

In the boiler water treatment, a clearing agent, an oxygen scavenger, and an amine are used singly or in combination. As the clearing agent, phosphoric acid and/or a salt thereof, a polymerized phosphoric acid and/or a salt thereof, a phosphonic acid and/or a salt thereof, a chelating agent such as Ethylene Diamine Tetraacetic Acid (EDTA), or a poly(A) can be used. Acrylic acid and/or a salt thereof, a polymer comprising AMPS and acrylic acid and/or methacrylic acid, and the like. As the oxygen scavenger, 1-amino-4-methylpiperazine, anthracene, carbonium, erythorbic acid and/or a salt thereof, gluconic acid and/or a salt thereof, N,N-diethylhydroxyl group can be used. Amine, sulfurous acid and/or a salt thereof, heavy sulfurous acid and/or a salt thereof, tannic acid and/or a salt thereof, gallic acid and/or a salt thereof, isopropylhydroxylamine or the like. As the amine, it can be used: monoisopropanolamine, 3-methoxy-propylamine, cyclohexylamine, 2-aminoethanol, 2-amino-2-methyl-1-propanol, morpholine A neutralizing amine such as 2-diethylaminoethanol or a film amine such as octadecylamine.

A part of the MF membrane permeating water of the pretreatment 5 can be used as a car wash water or the like. The RO membrane permeating the membrane separation step 6 can be used as boiler raw water, machine cooling water, factory water, etc. of the waste heat boiler. The MF membrane may be allowed to permeate water through the sea, the river, the sewer, or the like, and the RO membrane may permeate the water through water or the like.

In the incineration plant, in order to remove the NOx gas which may be contained in the combustion exhaust gas, the mixed gas in which the combustion exhaust gas and the ammonia are mixed is brought into contact with the denitration catalyst, and the NOx gas is decomposed by contact reduction reaction. Since ammonia remains in the combustion exhaust gas, ammonia (ammonium ions) may be contained in the wastewater discharged from the self-incineration plant. Therefore, it is also possible to provide a biological treatment device on the upstream side of the pretreatment step to reduce ammonium ions and the like.

For the biological treatment step, for example, a biological treatment device including a nitrification tank that performs a nitrification step by an aerobic microorganism and a denitrification tank that performs a denitrification step using a facultative anaerobic microorganism can be used.

Although the detailed description is omitted, if the garbage is incinerated in an incineration plant, harmful gases such as HCl and SO _X are generated, and dioxin, fly ash containing heavy metals, and the like are required. Therefore, the steps of treating these are required. For example, when acid gas treatment is performed in front of the dust collector, slaked lime or sodium hydrogencarbonate, oxidized dolomite is added, or when acid gas treatment is performed in a cooling device or a scrubber, neutralization using an alkali such as NaOH is applied. A known processing method such as processing. Well-known methods are also applied in the treatment of dioxin treatment or fly ash treatment. Example

[Example 1] According to the flow of Fig. 3, boiler sewage, cooling tower sewage, miscellaneous wastewater, domestic wastewater, car wash wastewater and floor washing wastewater discharged from an incineration plant of self-incineration combustible waste were treated.

The boiler discharge water 10 m ³ /h and the cooling tower sewage 10 m ³ /h were directly supplied to the pretreatment (MF membrane 11).

About 2 m ³ /h of waste water, after the first pretreatment (by adding PAC 10 mg/L and high molecular weight 2 mg/L coagulation treatment 13 and gravity double-layer sand filtration treatment 14) It is supplied to the MF film 11. The permeated water (recovery rate: 95%) of the MF membrane 11 was supplied to the RO membrane 12, and the permeated water (recovery rate: 75%) of 17 m ³ /h was supplied as supplemental water to the cooling tower.

The RO concentrated water was sprayed in the cooling device 18 at 6 m ³ /h. The concentrated water of the MF membrane 11 is supplied to the coagulation treatment 13 .

The domestic wastewater 2 m ³ /h is supplied to the coagulation treatment 13 after the biological treatment 15 .

2nd pretreatment of car wash wastewater 1 m ³ /h and floor cleaning wastewater 1 m ³ /h (using PAC 10 mg/L and high molecular weight 2 mg/L coagulation treatment 16 and gravity double-layer sand filtration treatment 17 Then, spraying is performed in the cooling device 18.

The boiler sewage contains a dispersing agent, and the dispersing agent and the slime controlling agent are contained in the cooling water discharged sewage, and the mixed wastewater containing the MF membrane 11 is treated, and then the RO membrane 12 is treated, thereby in the RO membrane treatment, Even if no slime control agent or dispersant is added, it can be processed stably. Further, the floor washing wastewater and the car wash wastewater are treated by using these different systems, whereby the recovery rate of the RO membrane 12 can be improved. As shown in Fig. 1, the amount of water sent to the cooling device 3 is as small as 8 m ³ /h, and the heat recovery amount of the heat recovery device 2 (Fig. 2) is increased. The recovered water of the RO membrane 12 of 17 m ³ /h can be reused as the supplementary water for the cooling water, and the corresponding amount of replenished water can be reduced.

[Comparative Example 1] Each wastewater of the incineration plant of Example 1 was treated according to the flow of Fig. 4 . In other words, the respective wastewaters (the respective flow rates of the same as in the first embodiment) other than the domestic wastewater were directly subjected to a coagulation treatment 21 of adding 200 mg/L of PAC and 2 mg/L of a polymer. About 2 m ³ /h of domestic wastewater, after carrying out biological treatment 25, it supplies to the coagulation process 21. The treated water of the coagulation treatment 21 is subjected to gravity double-layer sand filtration treatment filtration 22, and then supplied to the MF membrane 23, and permeated water (recovery rate 95%) is supplied to the RO membrane 24, and RO is permeated with water 15 m ^{3 .} /h (recovery rate 60%) is used as cooling tower make-up water. The concentrated water of the MF membrane 23 was sprayed with 1 m ³ /h of the MF membrane 23 and the concentrated water of the RO membrane 24 was 9 m ³ /h.

In Comparative Example 1, since the amount of concentrated water supplied to the temperature lowering device 3 was as large as 10 m ³ /h, it was necessary to reduce the amount of heat recovery in the heat recovery device 2 and to increase the temperature of the introduced exhaust gas toward the temperature lowering device 3.

The amount of PAC added is 200 mg/L due to the dispersant contained in the boiler sewage and cooling water. For the stabilization of the membrane treatment, a slime controlling agent and a dispersing agent are required. As a membrane treatment slime control agent, 5 mg/L of Kuriverter EC-503 was used. As a membrane treatment dispersant, 5 mg/L of Kuriverter N-500 was used.

In Comparative Example 1, since the oil component was mixed from the floor washing wastewater and the car wash wastewater, the RO recovery rate was lowered to 60%. In Comparative Example 1, the amount of water to be agglomerated increased, and a large amount of pretreatment equipment was required.

The present invention has been described in detail with reference to the specific embodiments thereof. It is obvious to those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention. The present application is based on Japanese Patent Application No. 2015-072958, filed on-

1‧‧‧Incineration unit
2‧‧‧heat recovery unit
3‧‧‧ cooling device
4‧‧‧dust collector
5‧‧‧Pre-processing steps
6‧‧‧ membrane separation step
7‧‧‧1st pretreatment
8‧‧‧2nd pretreatment
11, 23‧‧‧ MF membrane
12, 24‧‧‧ RO film
13, 16, ‧ ‧ condensate treatment
14, 17, 22‧‧‧ Gravity double-layer sand filtration treatment
15, 25‧‧ Biological treatment

Figure 1 is a block diagram of an incineration plant. Fig. 2 is a flow chart of the embodiment. Figure 3 is a flow chart of an embodiment. 4 is a flow chart of a comparative example.

3‧‧‧ cooling device

5‧‧‧Pre-processing steps

6‧‧‧ membrane separation step

7‧‧‧1st pretreatment

8‧‧‧2nd pretreatment

Claims (6)

A waste water treatment method for an incineration plant, which is a heat recovery device including an incinerator that burns organic matter, combustion exhaust gas discharged from the incineration device, and combustion that is recovered by heat recovery by the heat recovery device A wastewater treatment method for wastewater discharged from an incineration plant of a cooling device that further cools the exhaust gas, which performs a membrane separation step of separating the wastewater discharged from the incineration plant into a permeated water and concentrated water by using a separation membrane, and supplying at least a part of the concentrated water To the cooling device and blown into the combustion exhaust gas to evaporate it, thereby cooling the combustion exhaust gas, the waste water treatment method of the incineration plant is characterized by: mixing the boiler water in the waste water of the incineration plant At least two mixed wastewaters of boiler blowdown water, cooling tower sewage, and miscellaneous waste water are supplied to the membrane separation treatment step. The wastewater treatment method of an incineration plant according to claim 1, wherein the waste water is subjected to a first pretreatment step of at least one of neutralization, coagulation, precipitation, filtration, and biological treatment. After the treatment, it is mixed as the mixed wastewater. The wastewater treatment method of an incineration plant according to claim 1 or 2, wherein the mixed wastewater is treated by a pretreatment device using a filter, a microfiltration membrane, or an ultrafiltration membrane, In the membrane separation step, the membrane separation treatment is carried out by a reverse osmosis membrane. The wastewater treatment method of an incineration plant according to claim 2, wherein the mixed wastewater is treated by a pretreatment device using a filter, a microfiltration membrane, or an ultrafiltration membrane, In the separating step, the membrane separation treatment is carried out by a reverse osmosis membrane, and the concentrated water or the backwashing wastewater of the pretreatment apparatus is sent to the first pretreatment step. The wastewater treatment method of the incineration plant according to any one of the above-mentioned claims, wherein the at least one of the floor washing wastewater and the car wash wastewater of the incineration plant is not subjected to reverse osmosis treatment, and is supplied to the In the cooling device. The wastewater treatment method of an incineration plant according to any one of claims 1 to 4, wherein the second pretreatment is performed by at least one of neutralization, coagulation, precipitation, filtration, and biological treatment. The step of treating at least one of the floor washing wastewater and the car wash wastewater of the incineration plant is supplied to the cooling device.