JP6123833B2 - Wastewater treatment method for incineration plant - Google Patents

Description

  The present invention relates to a method for treating wastewater discharged from an incineration plant.

  Emission from an incineration plant equipped with an incinerator for burning organic matter, a heat recovery device for recovering the heat of combustion exhaust gas discharged from the incinerator, and a temperature reducing device for further reducing the temperature of the exhaust gas recovered by heat recovery As a wastewater treatment method, a wastewater treatment method is known in which the wastewater is subjected to a coagulation treatment with a coagulant or the like and then filtered.

  There is also known a wastewater treatment method in which wastewater discharged from an incineration plant is agglomerated by a flocculant or the like and then biologically treated, and further filtered by sand filtration (Patent Document 1). Patent Document 1 describes that most of the purified water purified by this wastewater treatment method can be discharged.

  In recent years, it has been demanded that purified water generated by treatment of waste water discharged from an incineration plant should not be discharged as much as possible.

  In order to prevent the purified water generated by the treatment of the waste water discharged from the incineration plant as much as possible, a part of the purified water is vaporized by jetting it to a temperature reducing device such as a temperature reducing tower to reduce the capacity of the purified water. A reduction has been made. Specifically, in this method, purified water is vaporized by injecting purified water or the like in the temperature reduction device to the combustion exhaust gas after heat recovery from the combustion exhaust gas by a heat recovery device such as a waste heat boiler. The capacity is reduced while the combustion exhaust gas is reduced in temperature by the heat of vaporization.

  Thus, when supplying as much purified water as possible to the temperature reducing device so as not to discharge the purified water purified by the waste water treatment as much as possible, in the heat recovery device such as a waste heat boiler on the upstream side of the temperature reducing device Therefore, the amount of heat recovered from the combustion exhaust gas must be set small. That is, in order to evaporate a large amount of purified water in the temperature reducing device, it is necessary to reduce the amount of heat recovered from the combustion exhaust gas in the heat recovery device, and the heat recovery efficiency from the combustion exhaust gas in the incineration plant is lowered.

  In order to reduce the amount of water sprayed to the temperature reducing device, Patent Document 2 discloses that incineration plant wastewater is treated with an MF membrane, the permeate is treated with an RO membrane, and MF membrane concentrated water and RO membrane concentrated water. Is supplied to a temperature reducing device.

  With this method, the amount of water sprayed on the temperature reducing device can be reduced by concentrating the wastewater with the MF membrane and the RO membrane, and the reduction in the amount of heat recovery can be suppressed.

  However, there is a wide variety of wastewater discharged from incineration plants, and depending on the water quality, there is a problem that the membrane may be clogged and the amount cannot be reduced sufficiently, the operation is not stable, or frequent maintenance and cleaning processes are required. there were. In addition, since the backwash water of the membrane filtration device is water in which SS in the drainage is concentrated, there is a drawback that the nozzle during spraying is blocked and maintenance is required.

Japanese Patent Laid-Open No. 10-99898 Japanese Patent No. 5636163

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

The wastewater treatment method for an incineration plant according to claim 1 includes an incinerator for burning organic matter, a heat recovery device for recovering heat of the combustion exhaust gas discharged from the incinerator, and a combustion exhaust gas recovered by the heat recovery device. A wastewater treatment method for wastewater discharged from an incineration plant equipped with a temperature reducing device for further reducing the temperature of the wastewater, wherein the wastewater discharged from the incineration plant is separated into permeated water and concentrated water by a separation membrane In the wastewater treatment method for an incineration plant, in which at least a part of the concentrated water is supplied to the temperature reducing device and is blown into the combustion exhaust gas to evaporate, thereby reducing the temperature of the combustion exhaust gas. Wastewater treatment of an incineration plant that supplies mixed wastewater mixed with at least two kinds of canned water, boiler blowwater, cooling tower blowwater, and miscellaneous wastewater to the membrane separation treatment step A law, is characterized in by performing the following processing (A) and (B), or the following processes (A) and (C).
(A) After treating the mixed waste water of boiler blow water and cooling tower blow water with a pretreatment device using a filter, MF membrane, or UF membrane without performing a coagulation sedimentation treatment , in the membrane separation step, RO Membrane separation treatment is performed using a membrane.
(I) Neutralizing miscellaneous wastewater, which is wastewater other than surfactant and oil, except for boiler blow water, boiler can water, cooling tower blow water, floor washing wastewater, car wash wastewater, and domestic wastewater . After being treated in the first preliminary treatment step having at least one of agglomeration, precipitation, filtration, and biological treatment, mixed wastewater together with the boiler blow water and cooling tower blow water of (a) above, before (a) After processing by the processing apparatus, membrane separation processing is performed by the RO membrane .
(C) After treating at least one of floor washing wastewater and car washing wastewater in a second preliminary treatment step having at least one of neutralization, aggregation, precipitation, filtration, and biological treatment, the RO membrane of (a) above It is supplied to the temperature reducing device together with the separated concentrated water.
The wastewater treatment method for an incineration plant according to claim 2 includes an incinerator for combusting organic matter, a heat recovery device for recovering heat of the combustion exhaust gas discharged from the incinerator, and a combustion exhaust gas heat recovered by the heat recovery device. A wastewater treatment method for wastewater discharged from an incineration plant equipped with a temperature reducing device for further reducing the temperature of the wastewater, wherein the wastewater discharged from the incineration plant is separated into permeated water and concentrated water by a separation membrane In the wastewater treatment method for an incineration plant, in which at least a part of the concentrated water is supplied to the temperature reducing device and is blown into the combustion exhaust gas to evaporate, thereby reducing the temperature of the combustion exhaust gas. Wastewater treatment of an incineration plant that supplies mixed wastewater mixed with at least two kinds of canned water, boiler blowwater, cooling tower blowwater, and miscellaneous wastewater to the membrane separation treatment step A law, 該雑drainage, Boiraburo water, boiler Hokan water, cooling tower blow water, floor cleaning waste water, car washing wastewater, a wastewater other than domestic wastewater, be a waste water without surfactant and oil The following processes (d) and (e) are performed.
(D) After treating the mixed wastewater containing no surfactant with a pretreatment device using a filter, MF membrane, or UF membrane without performing a coagulation sedimentation treatment , in the membrane separation step, RO Membrane separation treatment is performed using a membrane.
(E) Wastewater containing a surfactant is treated in a second pretreatment step having at least one of neutralization, flocculation, precipitation, filtration, and biological treatment, and then the RO membrane separation and concentration of (d) above. The water is supplied to the temperature reducing device together with water.

In one aspect of the present invention, neutralizing the gray water, flocculation, sedimentation, filtration, and after treatment with the first pretreatment step with at least one of the biological treatment, a surfactant of the (d) The wastewater is mixed with wastewater containing no wastewater, and then treated with the pretreatment device (D) and RO membrane .

In one aspect of the present invention, sending the concentrated water or backwash effluent of the pretreatment device to the first pretreatment step.

  In the wastewater treatment method of the present invention, similarly to Patent Document 2, in the membrane separation step, the wastewater discharged from the incineration plant is concentrated by the separation membrane to obtain concentrated water having a reduced volume, and this concentrated water is reduced. Since the temperature is supplied to the temperature device, the amount of concentrated water supplied to the temperature reduction device is small, and the temperature of the combustion exhaust gas introduced into the temperature reduction device can be lowered. As a result, it is possible to increase the amount of heat recovered from the combustion exhaust gas in the heat recovery device installed on the upstream side of the temperature reducing device.

  In the wastewater treatment method according to the present invention, the mixed wastewater is preferably subjected to membrane separation treatment with an RO membrane.

  Boiler water, boiler blow water, and cooling water blow water contain water treatment chemicals such as a dispersant and a slime control agent in order to stabilize and increase the efficiency of the treatment. By selecting and using these chemicals that do not adversely affect the membrane treatment and contribute to stabilization of the membrane treatment, at the time of RO membrane treatment, without newly adding or almost no water treatment chemicals, A membrane separation process can be stably performed.

  In particular, the dispersant contained in the boiler blow water and the cooling water blow water becomes an impeding factor for the aggregation treatment. In addition, the slime control agent has an adverse effect on the biological treatment, and the biological activity may decrease. In one embodiment of the present invention, these waters are subjected to a simple pretreatment consisting of sand filtration, an MF membrane, or a UF membrane, and then subjected to membrane separation treatment, so that the size of the wastewater treatment facility can be reduced.

  In one aspect of the wastewater treatment method according to the present invention, miscellaneous wastewater is treated in a preliminary treatment step having at least one of neutralization, aggregation, precipitation, filtration, and biological treatment, and SS components in the wastewater and organic components are removed. After removal, concentration is performed by membrane treatment. Thus, by pre-processing miscellaneous wastewater, it is possible to reduce the SS component and organic components contained in the wastewater, and the clogging of the separation membrane is unlikely to occur, and the continuous use period of the separation membrane can be extended. . In addition, this reduces the frequency of replacement of the separation membrane, makes it possible to efficiently obtain the concentrated water, and more efficiently recover the heat of the combustion exhaust gas in the incineration plant.

  Concentrated water or backwash water in the pretreatment device is also preferably treated in the first preliminary treatment step to remove organic components from SS. However, it may be processed in the second preliminary processing step.

  Car wash wastewater and floor washing wastewater are preferably sprayed by a temperature reducing device without membrane treatment. Car wash wastewater and floor wash wastewater may contain substances that block the MF membrane or RO membrane, such as oil and surfactant, and the concentration is not constant, which may make stable treatment difficult. . Therefore, car wash wastewater and floor wash wastewater are treated in a second preliminary treatment step having at least one of neutralization, aggregation, precipitation, filtration, and biological treatment, and solid-liquid separation and organic component removal are performed. In addition, spraying with a temperature reducing device is preferred.

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

It is a block diagram of an incineration plant. It is a flowchart of an embodiment. It is a flowchart of an Example. It is a flowchart of a comparative example.

  Hereinafter, an embodiment of a wastewater treatment method according to 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 that combusts organic matter, a heat recovery device 2 that recovers heat of combustion exhaust gas discharged from the incinerator 1, and And a temperature reducing device 3 for further reducing the temperature of the combustion exhaust gas (hereinafter also referred to as heat recovery combustion exhaust gas) recovered by the heat recovery device. In addition, you may provide another apparatus etc.

  As the incinerator 1, an incinerator plant or the like such as a stoker furnace, a fluidized bed furnace, a gasification melting furnace, an ash melting furnace, or the like can be used.

  Although it does not specifically limit as an organic substance to burn, For example, municipal waste, industrial waste, sewage sludge, waste wood, etc. are mentioned. The combustion exhaust gas discharged from the incinerator 1 is usually at a temperature of about 800 to 1300 ° C.

  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.

  The temperature reducing device 3 further reduces the temperature of the combustion exhaust gas (heat recovery combustion exhaust gas) recovered by the heat recovery device 2. The temperature reducing device 3 is configured to inject or spray water on the heat recovery combustion exhaust gas introduced from the heat recovery device 2, and to reduce the temperature of the heat recovery combustion exhaust gas by the heat of vaporization of water. The heat recovery combustion exhaust gas introduced into the temperature reducing device 3 is usually at a temperature of about 250 to 400 ° C.

  In the present invention, since the amount of water blown into the temperature reducing device 3 is smaller than that in Patent Literature 2, the exhaust gas temperature introduced into the temperature reducing device 3 can be made lower than that in Patent Literature 2. As a result, the amount of heat recovered by the heat recovery apparatus 2 can be increased.

  The temperature of the exhaust gas after being reduced in temperature by the temperature reducing device 3 is usually about 150 to 200 ° C. This 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 into the atmosphere.

  In the present invention, the waste water discharged from the incineration plant means waste water generated within the site of the incineration plant. Examples of the waste water generated in the premises of the incineration plant include boiler blow water blown from the heat recovery device 2 such as a waste heat boiler, boiler maintenance filled in the can of the heat recovery device when stopped, and discharged before restarting In addition to canned water, cooling tower blow water, floor washing wastewater generated when washing floors in incineration plants, car wash wastewater generated when washing waste collection vehicles, domestic wastewater and miscellaneous wastewater are listed. Examples of miscellaneous wastewater include incineration residue generated from an incinerator 1 such as an incinerator, residue cooling wastewater that cools slag, and wastewater other than the above that does not contain a surfactant and oil generated in an incineration plant.

  In the present invention, as shown in FIG. 2, mixed wastewater mixed with boiler canned water, boiler blow water, and cooling tower blow water (however, boiler canned water may be excluded) is preferably pretreated 5. Thereafter, a membrane separation process is performed in the membrane separation step 6. At least a part of the concentrated water is supplied to the temperature reducing device 3 to evaporate the concentrated water to reduce the temperature of the combustion exhaust gas.

  The miscellaneous wastewater is preferably mixed with boiler canned water, boiler blow water, and cooling tower blow water after the first preliminary treatment 7 and supplied to the pretreatment 5. By preliminarily treating the miscellaneous wastewater in this manner, the blockage of the membrane in the membrane separation step 6 is suppressed.

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

  By pretreating the mixed waste water in this way, the membrane clogging in the membrane separation step 6 is suppressed. As the membrane in the membrane separation step 6, an RO membrane is suitable.

  As the first preliminary treatment 7 for treating miscellaneous wastewater, at least one of neutralization, aggregation, precipitation, filtration, and biological treatment is preferable.

  Car wash wastewater and floor wash wastewater may be mixed with the membrane concentrated water from the membrane separation step 6 after being subjected to the second preliminary treatment 8 for removing organic components for SS, and supplied to the temperature reducing device 3. preferable. As the second pretreatment, at least one of neutralization, aggregation, precipitation, filtration, and biological treatment is preferable.

  When the MF membrane or the UF membrane is used in the pretreatment 5, the MF or UF membrane concentrated water is preferably treated in the first preliminary treatment 7 to remove the organic component for SS. However, the second preliminary process 8 may be used. By not spraying the MF or UF membrane concentrated water of the pretreatment 5 with the temperature reducing device 3, the spray nozzle is prevented from being blocked and a stable temperature reduction treatment is possible.

  As described above, in boiler canned water, boiler blow water, and cooling tower blow water, anti-corrosion agents, dispersants and slime control agents, condensate amine agents, oxygen scavengers, etc., for stabilization and efficiency of treatment. Contains water treatment chemicals. As these chemicals, those that do not adversely affect the membrane treatment and contribute to the stabilization of the membrane treatment are selected, and the boiler can water, the boiler blow water, and the cooling tower blow water are subjected only to the pretreatment 5 to perform RO. By performing the membrane treatment, an efficient membrane separation treatment can be performed without newly adding a water treatment chemical for the RO membrane treatment. In addition, when the chemical concentration is insufficient, a necessary chemical may be added.

  The dispersant contained in the boiler blow water and the cooling water blow water becomes an impediment to the agglomeration treatment. Therefore, when the boiler blow water and the cooling water blow water are flowed into the first pretreatment 7, the necessary amount of the flocculant is remarkably increased. In addition, the slime control agent has an adverse effect on the biological treatment, and there are cases where the biological activity is reduced. Therefore, by supplying these waters to the pretreatment 5 without pretreatment, the pretreatment facility can be reduced.

  Car wash wastewater and floor washing wastewater are sprayed by the temperature reducing device 3 after the second preliminary treatment 8. Car wash wastewater and floor wash wastewater may contain substances that block the MF membrane or RO membrane, such as oil and surfactant, and the concentration is not constant, making it difficult to perform membrane separation treatment stably. is there. Therefore, the car wash wastewater and the floor wash wastewater are treated by the second pretreatment 8 having at least one of neutralization, aggregation, precipitation, filtration, and biological treatment to perform solid-liquid separation and organic component removal. In addition, spraying is performed by the temperature reducing device 3.

  In the first and second pretreatments 7 and 8, for the purpose of reducing the organic component in the SS component contained in the water to be treated, after adding a flocculant to the waste water, mainly aggregating the suspended matter, A filtration process such as sand filtration may be performed, or a precipitation step may be performed instead of filtration. Further, when the load is high, a pressure levitation process can be added. In order to appropriately perform the aggregation treatment, a pH adjustment step can be added. By performing a series of preliminary treatment steps, aggregates can be removed from the waste water, and organic components can be reduced by the amount of SS that can be contained in the car wash waste water and floor washing waste water.

  In the first and second preliminary treatments 7 and 8, a membrane separation activated sludge method using an MF membrane (immersion membrane) instead of the sand filtration device can be used. Aggregates captured by the MF film (immersion film) are extracted and then put into a garbage pit and incinerated by the incinerator 1.

  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. A mixture etc. are illustrated. The amount of the flocculant added can be adjusted as appropriate.

  Examples of the polymer flocculant added to the water to be treated as a flocculant include poly (meth) acrylic acid, a copolymer of (meth) acrylic acid and (meth) acrylamide, and alkali metal salts thereof. Anionic organic polymer flocculants, nonionic organic polymer flocculants such as poly (meth) acrylamide, dimethylaminoethyl (meth) acrylate or quaternary ammonium salts thereof, dimethylaminopropyl (meth) acrylamide or Cationic organic polymer flocculants such as homopolymers composed of cationic monomers such as quaternary ammonium salts, and copolymers of nonionic monomers copolymerizable with these cationic monomers, and the above anionic properties Monomers, cationic monomers and nonionic monomers copolymerizable with these monomers Organic polymer flocculant of amphoteric copolymers thereof. Moreover, there is no limitation in particular also in the addition amount of a polymer flocculant, and what is necessary is just to adjust according to the property of to-be-processed water, but it is 0.01-10 mg / L in solid content with respect to to-be-processed water. In addition, a phenol type flocculant described in WO2011 / 018978 can also be used.

  When an RO membrane is used in the membrane separation step 6, examples of impurities removed by the RO membrane include ionic components and organic substances. Examples of ionic components include cationic substances, anionic substances, and the like. Specifically, calcium ions, magnesium ions, etc. that easily form scales that are ion-bonded to anions and are not easily dissolved in water. Illustrated. Moreover, as an organic substance, the water-soluble organic substance etc. which are melt | dissolving in the waste_water | drain are mentioned.

  In the pretreatment 5, when an MF membrane is used, the MF membrane differential pressure increases due to adhesion of scale, turbidity, organic matter, etc. to the MF membrane surface. In this case, back pressure cleaning and chemical cleaning of the MF membrane are performed. In the back pressure cleaning of the MF membrane, it is preferable to periodically / irregularly wash with water containing hypochlorite such as sodium hypochlorite in that the increase in the MF membrane differential pressure can be further suppressed. .

  The MF membrane usually has pores with 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, and a tubular membrane are held in a vessel can be used. A hollow fiber membrane or a flat membrane can be used as it is by immersing it in the water to be treated. 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.

  PVDF is used as the MF membrane, polysulfone is used as the UF membrane, and polyamide is used as the RO membrane, but it is not limited to this.

  Examples of the RO membrane include a composite membrane composed of a dense layer of an asymmetric membrane and a microporous layer.

  As the RO membrane, a unit 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 can be used.

  Examples of the dispersant used for cooling water treatment include inorganic polyphosphoric acids such as sodium hexametaphosphate and sodium tripolyphosphate, phosphonic acids such as hydroxyethylidenediphosphonic acid and phosphonobutanetricarboxylic acid, maleic acid, acrylic acid, and itacone. Carboxyl group-containing materials such as acids, and if necessary, vinyl monomers having sulfonic acid groups such as vinyl sulfonic acid, allyl sulfonic acid, 2-methacrylamide-2-methylpropane sulfonic acid, and nonionic vinyl monomers such as acrylamide Can be used, but materials other than those listed here can also be applied. Further, as the third component of the dispersant, a terpolymer can be used by using other components. For example, N-tert-butylacrylamide is used as the third component. Among them, the dispersant is most preferably a polymer containing HAPS, AMPS and acrylic acid and / or methacrylic acid. (HAPS is 3-allyloxy-2-hydroxy-1-propanesulfonic acid, and AMPS is 2-acrylamido-2-methylpropanesulfonic acid.)

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

  Slime control agents include hypochlorites such as sodium hypochlorite (NaClO), chlorine agents such as chlorine gas, chloramine, and chlorinated isocyanurates, chlorine such as monochlorosulfamic acid, amide sulfate, and amide sulfate. Bonded chlorine agent reacted with a compound having hydrogen, bromine agent such as dibromohydantoin, hypobromite such as sodium hypobromite, organic agent such as DBNPA (dibromonitrilopropionate), MIT (methylisothiazolone) . Examples of the chlorine-based oxidizing agent that can be used in the present invention include the above 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, chlorinated isocyanur. An acid or a salt thereof can be used. Examples of the salt include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as barium, other metal salts such as nickel, ammonium salts, and the like. One or more of these can be used. Among these, sodium hypochlorite is preferable because of its excellent handleability.

  The nitrogen compounds to which the free chlorine is bonded include ammonia or its compounds, melamine, urea, acetamide, sulfamide, cyclolamic acid, sulfamic acid, toluenesulfonamide, succinimide, phthalimide, isocyanuric acid, N-chloro. Examples thereof include toluenesulfonamide, uric acid, saccharin, and salts thereof. The bonded chlorine agent used in the present invention is a compound in which the above-mentioned free chlorine is bonded to these nitrogen compounds. As the combined chlorine agent used in the present invention, those obtained by mixing and reacting the above nitrogen compound and free chlorine agent, particularly those obtained by mixing and reacting each in the state of an aqueous solution are preferable.

  Examples of such a chlorinated agent include chloramine, a chlorinated oxidant and a sulfamic acid compound, chloramine-T (a sodium salt of N-chloro-4-methylbenzenesulfonamide), chloramine-B. (Sodium salt of N-chloro-benzenesulfonamide), sodium salt of N-chloro-paranitrobenzenesulfonamide, trichloromelamine, sodium salt or potassium salt of mono- or di-chloromelamine, trichloro-isocyanurate, mono- or 5, sodium salt or potassium salt of di-chloroisocyanuric acid, sodium salt or potassium salt of mono- or di-chlorosulfamic acid, monochlorohydantoin or 1,3-dichlorohydantoin, 5,5-dimethylhydantoin - alkyl derivatives.

  Further, in boiler water treatment, a canning agent, an oxygen scavenger, and amines are used alone or in combination. Examples of the canning agent include phosphoric acid and / or salt thereof, polymerized phosphoric acid and / or salt thereof, phosphonic acid and / or salt thereof, chelating agent such as EDTA, poly (meth) acrylic acid and / or salt thereof, and AMPS. And a polymer containing acrylic acid and / or methacrylic acid can be applied. Examples of the oxygen scavenger include 1-amino-4-methylpiperazine, hydrazine, carbohydrazide, erythorbic acid and / or its salt, gluconic acid and / or its salt, N, N-diethylhydroxylamine, sulfurous acid and / or its salt Bisulfite and / or a salt thereof, tannic acid and / or a salt thereof, gallic acid and / or a salt thereof, isopropylhydroxylamine and the like can be applied. Examples of amines include neutralizing amines such as monoisopropanolamine, 3-methoxy-propylamine, cyclohexylamine, 2-aminoethanol, 2-amino-2-methyl-1-propanol, morpholine, 2-diethylaminoethanol, and the like. A film-forming amine such as octadecylamine can be applied.

  A part of the MF membrane permeated water of the pretreatment 5 can be used as car wash water. Further, the RO membrane permeated water in the membrane separation step 6 can be used as boiler raw water for waste heat boilers, equipment cooling water, plant water, and the like. Permeated water such as the MF membrane permeated water and the RO membrane permeated water may be discharged to the sea, rivers, sewage, or the like.

  In an incineration plant, in order to remove NOx gas that may be contained in combustion exhaust gas, a mixed gas obtained by mixing combustion exhaust gas and ammonia is brought into contact with a denitration catalyst, and NOx gas is decomposed by a catalytic reduction reaction. ing. Since ammonia remains in this combustion exhaust gas, the waste water discharged from the incineration plant may contain ammonia (ammonium ions). Therefore, a biological treatment apparatus may be provided upstream of the pretreatment process to reduce ammonium ions and the like.

  The biological treatment process includes, for example, a biological treatment apparatus including a nitrification tank that performs a nitrification process using aerobic microorganisms and a denitrification tank that performs a denitrification process using facultative anaerobic microorganisms. Can be used.

Incidentally, detailed description will be omitted, when incinerated garbage incineration plants, HCl, since toxic gases such as SO _X, dioxin, fly ash, etc. containing heavy metals occurs, treating them is necessary. For example, when acid gas treatment is performed in front of the dust collector, slaked lime, baking soda, or hydrohydrite hydroxide is added, or when acid gas treatment is performed in a temperature reducing device or a scrubber, an alkali such as NaOH is used. Known processing means such as sum processing is applied. Moreover, a well-known method is applied also in a dioxin process and a fly ash process.

[Example 1]
Boiler blow water, cooling tower blow water, miscellaneous waste water, domestic waste water, car wash waste water and floor washing waste water discharged from an incineration plant for incinerating combustible waste were treated according to the flow of FIG.

Boiler blow water 10 m ³ / h and cooling tower blow water 10 m ³ / h were supplied as they were to the pretreatment (MF membrane 11).

The miscellaneous wastewater 2 m ³ / h was treated by the first preliminary treatment (flocculation treatment 13 by adding PAC 10 mg / L and polymer polymer 2 mg / L and gravity two-layer sand filtration treatment 14), and then supplied to the MF membrane 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%) 17 m ³ / h was supplied to the cooling tower as makeup water.

The RO concentrated water 6 m ³ / h was sprayed by the temperature reducing device 18. The concentrated water of the MF membrane 11 was supplied to the aggregation treatment 13.

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

Car wash drainage 1m ³ / h and floor washing drainage 1m ³ / h are subjected to a second pretreatment (flocculation treatment 16 with PAC 10 mg / L and high polymer 2 mg / L and gravity two-layer sand filtration treatment 17). Spraying was performed with a temperature reducing device 18.

The boiler blow water contains a dispersant, and the cooling water blow water contains a dispersant and a slime control agent. By treating the mixed waste water containing these with the MF membrane 11 and then performing the RO membrane 12 treatment, The treatment could be performed stably without adding a slime control agent or a dispersant. Moreover, the recovery rate of RO membrane 12 was able to be made high by processing floor washing waste_water | drain and car wash waste_water | drain by these different systems. As shown in FIG. 1, the amount of water sent to the temperature reducing device 3 was as small as 8 m ³ / h, and the heat recovery amount of the heat recovery device 2 (FIG. 2) increased. The recovered water 17m ³ / h of the RO membrane 12 could be reused as the replenishing water for the cooling water, and the amount of the replenishing water could be reduced accordingly.

[Comparative Example 1]
Each waste water of the incineration plant of Example 1 was processed according to the flow of FIG. That is, the above effluent other than domestic effluent (each flow rate is the same as in Example 1) was directly subjected to agglomeration treatment 21 by adding PAC 200 mg / L and polymer polymer 2 mg / L. About domestic wastewater 2m < ³ > / h, after performing the biological treatment 25, it supplied to the aggregation process 21. FIG. The treated water of the agglomeration treatment 21 is subjected to gravity two-layer sand filtration treatment filtration 22, supplied to the MF membrane 23, permeated water (recovery rate 95%) is supplied to the RO membrane 24, and RO permeated water 15 m ³ / h (recovered) 60%) was used as cooling tower make-up water. Was sprayed with the concentrated water ^{1 m} 3 / concentrated water of h and RO membranes 24 ^9m 3 / h the temperature reducing apparatus 18 of the MF membrane 23.

In Comparative Example 1, since the amount of concentrated water supplied to the temperature reducing device 3 is as large as 10 m ³ / h, the amount of heat recovered in the heat recovery device 2 is reduced, and the exhaust gas temperature introduced into the temperature reducing device 3 is increased. There was a need to do.

  The amount of PAC added was 200 mg / L because of the dispersant contained in the boiler blow water and the cooling water blow water. In addition, a slime control agent and a dispersant are necessary for stabilizing the membrane treatment. As a membrane treatment slime control agent, Cryverter EC-503 5 mg / L was used. As a membrane treatment dispersant, Krivator N-500 5 mg / L was used.

  In Koo Comparative Example 1, since oil was mixed from floor washing wastewater and car wash wastewater, the RO recovery rate was reduced to 60%. In addition, the amount of water for the agglomeration treatment increased, and a huge pretreatment facility was required.

3 Temperature Reduction Device 5 Pretreatment Step 6 Membrane Separation Step 7 First Pretreatment 8 Second Pretreatment

Claims (4)

An incinerator for burning organic matter, a heat recovery device for recovering the heat of the combustion exhaust gas discharged from the incineration device, and a temperature reducing device for further reducing 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 membrane separation step is performed to separate the waste water discharged from the incineration plant into permeate and concentrated water using a separation membrane, and at least a part of the concentrated water is supplied to the temperature reducing device and blown into the combustion exhaust gas to evaporate. In the wastewater treatment method of the incineration plant that reduces the temperature of the combustion exhaust gas,
Among the incineration plant wastewater, a wastewater treatment method for an incineration plant that supplies mixed wastewater mixed with at least two types of boiler canned water, boiler blow water, cooling tower blow water, and miscellaneous wastewater to the membrane separation treatment step,
A wastewater treatment method for an incineration plant, characterized by performing the following treatments (a) and (b) or the following treatments (a) and (c).
(A) After treating the mixed waste water of boiler blow water and cooling tower blow water with a pretreatment device using a filter, MF membrane, or UF membrane without performing a coagulation sedimentation treatment , in the membrane separation step, RO Membrane separation treatment is performed using a membrane.
(I) Neutralizing miscellaneous wastewater, which is wastewater other than surfactant and oil, except for boiler blow water, boiler can water, cooling tower blow water, floor washing wastewater, car wash wastewater, and domestic wastewater . After being treated in the first preliminary treatment step having at least one of agglomeration, precipitation, filtration, and biological treatment, mixed wastewater together with the boiler blow water and cooling tower blow water of (a) above, before (a) After processing by the processing apparatus, membrane separation processing is performed by the RO membrane .
(C) After treating at least one of floor washing wastewater and car washing wastewater in a second preliminary treatment step having at least one of neutralization, aggregation, precipitation, filtration, and biological treatment, the RO membrane of (a) above It is supplied to the temperature reducing device together with the separated concentrated water. An incinerator for burning organic matter, a heat recovery device for recovering the heat of the combustion exhaust gas discharged from the incineration device, and a temperature reducing device for further reducing 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 membrane separation step is performed to separate the waste water discharged from the incineration plant into permeate and concentrated water using a separation membrane, and at least a part of the concentrated water is supplied to the temperature reducing device and blown into the combustion exhaust gas to evaporate. In the wastewater treatment method of the incineration plant that reduces the temperature of the combustion exhaust gas,
Among the incineration plant wastewater, a wastewater treatment method for an incineration plant that supplies mixed wastewater mixed with at least two types of boiler canned water, boiler blow water, cooling tower blow water, and miscellaneous wastewater to the membrane separation treatment step,
The miscellaneous waste water is waste water other than boiler blow water, boiler can water, cooling tower blow water, floor washing waste water, car wash waste water, domestic waste water, and does not contain surfactant and oil.
A wastewater treatment method for an incineration plant, characterized by performing the following treatments (d) and (e):
(D) After treating the mixed wastewater containing no surfactant with a pretreatment device using a filter, MF membrane, or UF membrane without performing a coagulation sedimentation treatment , in the membrane separation step, RO Membrane separation treatment is performed using a membrane.
(E) Wastewater containing a surfactant is treated in a second pretreatment step having at least one of neutralization, flocculation, precipitation, filtration, and biological treatment, and then the RO membrane separation and concentration of (d) above. The water is supplied to the temperature reducing device together with water. According to claim 2, neutralize the wastewater, flocculation, sedimentation, include filtration, and after treatment with the first pretreatment step with at least one of the biological treatment, the surface active agent of (d) A wastewater treatment method for an incineration plant, characterized in that the wastewater is mixed with wastewater and then treated with a pretreatment device (RO) and an RO membrane .   The wastewater treatment method for an incineration plant according to claim 1 or 3, wherein concentrated water or backwash wastewater from the pretreatment device is sent to the first preliminary treatment step.

Images