JP5020490B2 - Organic sludge treatment method and organic sludge treatment equipment - Google Patents

Description

  The present invention relates to a technique for treating organic sludge generated from wastewater treatment facilities such as sewage treatment.

  In general, this type of organic sludge treatment method includes wastewater (raw water) such as sewage containing organic substances, consisting of a first sedimentation tank (first sedimentation tank), a biological treatment tank, and a final sedimentation tank (final sedimentation tank). The excess sludge generated in the final settling basin and the raw sludge generated in the first settling basin are anaerobically digested, and the sludge digested liquid is dehydrated and separated (hereinafter referred to as `` dewatered ''). A treatment method that further biologically treats (sometimes referred to as liquid separation) and returns it to the entry side of the wastewater treatment facility is employed.

  As a biological treatment method of the desorption liquid, a COD component is obtained by separately providing a treatment tank for the sludge concentrated separation liquid in the first sedimentation basin and a treatment tank for the desorption liquid, and performing aerobic biological treatment respectively. A treatment method has been proposed in which the treated water is first returned to the settling basin after removing the water (see Patent Document 1).

However, in this method, since the biologically degradable substance is contained in the detachment liquid, the biologically degradable substance remains even when the detachment liquid is biologically treated. Therefore, if the separated water obtained by subjecting the effluent to biological treatment is returned to the wastewater treatment facility, the quality of the treated water discharged from the final sedimentation basin of the wastewater treatment facility may not be maintained well. In particular, when a solubilization treatment such as a heat treatment is performed before the anaerobic digestion treatment, the amount of the hardly biodegradable substance increases, and it becomes difficult to secure good treated water.
Japanese Patent Laid-Open No. 2004-97903

  The present invention eliminates such conventional problems and efficiently reduces pollutants such as biodegradable substances remaining in the dehydrated separation liquid after digesting organic sludge from wastewater treatment facilities. It is an object of the present invention to provide an organic sludge treatment method and treatment equipment capable of stably maintaining a good quality of treated water discharged from a wastewater treatment system.

  And the structure made into the summary of this invention completed in order to achieve the said subject is as follows.

(1) Solubilization treatment of organic sludge, anaerobic digestion of the solubilized sludge obtained by the solubilization treatment , dehydration treatment of the sludge digestion liquid obtained by the anaerobic digestion treatment, and further the dehydration dehydration separation liquid obtained by the process are treated catalytic wet oxidation, a the solubilization treatment is a heat treatment method for treating organic sludge temperature of the heat treatment, characterized in 120 to 200 [° C. der Rukoto ( Claim 1).

(2) the method of treating organic sludge according to the above (1), wherein the temperature of the catalytic wet oxidation treatment is 200 to 300 [° C. (Claim 2).

( 3 ) The method for treating organic sludge according to ( 1 ) or ( 2 ) above, wherein waste heat generated in the catalytic wet oxidation treatment is used as a heat source in the solubilization treatment (Claim 3 ). .

( 4 ) The organic sludge treatment method according to any one of (1) to ( 3 ), wherein at least one of a phosphorus component, a metal component, and a suspended substance is removed before the catalyst wet oxidation treatment. (Claim 4 ).

( 5 ) The method for treating organic sludge according to any one of (1) to ( 3 ) above, wherein a phosphorus component, a metal component, and a suspended substance are removed before the catalyst wet oxidation treatment (Claim 5 ).

( 6 ) A solubilization treatment tank for solubilizing organic sludge, a digestion tank for anaerobic digestion treatment of the solubilized sludge obtained by the solubilization treatment, and a sludge digestion liquid obtained by the anaerobic digestion treatment. a dewatering device for dewatering process, the dehydration process by resulting dehydrated separated liquid look containing a catalytic wet oxidation apparatus for treating catalytic wet oxidation, the solubilization treatment tank be by heat treatment, the temperature of the heat treatment An organic sludge treatment facility having a temperature of 120 to 200 ° C. (Claim 6 ).

(7) Organic sludge treatment installation according to the above (6) the process temperature in the catalytic wet oxidation apparatus is characterized in that it is a 200 to 300 [° C. (Claim 7).

( 8 ) The above ( 6 ) or ( 6 ), wherein at least one of a phosphorus component removing device, a metal component removing device, and a suspended substance removing device is provided between the dehydrating device and the catalytic wet oxidation device. 7 ) The organic sludge treatment facility described in (Claim 8 ).

( 9 ) The organic as described in ( 6 ) or ( 7 ) above, wherein a phosphorus component removing device, a metal component removing device and a suspended substance removing device are sequentially provided between the dehydrating device and the catalytic wet oxidation device. Sludge treatment equipment (Claim 9 ).

  According to the present invention, the biodegradability remaining in the dehydrated separation liquid after digesting the organic sludge from the wastewater treatment facility by effectively incorporating the catalytic wet oxidation treatment into the organic sludge treatment process. Pollutants such as substances can be efficiently reduced, and the quality of the treated water released from the wastewater treatment system can be stably maintained by returning the purified treatment liquid to the wastewater treatment facility. In addition, it is possible to obtain an excellent effect such that the installation area can be reduced in terms of equipment.

  In addition, when the solubilization treatment is performed with heat, the amount of biologically degradable substances contained in the dehydrated separation liquid increases, but the decomposition treatment is not particularly problematic, and the heat generated by the catalytic wet oxidation is recovered. Thus, a part of the recovered heat can be used for a part of the solubilization process, and the energy efficiency of the entire process can be improved.

  Furthermore, by removing the phosphorus component, metal component and / or suspended substance contained in the dehydrated separation liquid before the catalytic wet oxidation treatment, the efficiency of catalytic oxidation and the life of the catalyst can be improved, and it is stable and economical. In addition, biodegradable substances can be reduced.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings focusing on its embodiments.

  FIG. 1 is a process flow diagram showing an embodiment of the present invention. In FIG. 1, wastewater such as sewage containing various organic substances is used as raw water A from the first sedimentation tank 1, the biological treatment tank 2, and the final sedimentation tank 3. The waste water treatment facility is introduced, treated, and discharged as purified treated water B.

  On the other hand, the sludge that has been solid-liquid separated from the treated water B in the final sedimentation tank 3 is returned to the biological treatment tank 2 as a return sludge C in order to maintain the microorganism concentration in the biological treatment tank 2 within a predetermined range. And another part is sent to the concentration apparatus 4 as the excess sludge D, and is concentrated to a predetermined concentration (2 to 5% by weight in solid concentration). The first settling sludge (raw sludge) E discharged from the first settling tank 1 is sent to the concentrating device 5, where it is also concentrated to a predetermined concentration (2 to 5% by weight in solid concentration). As the concentrating devices 4 and 5, a gravity sedimentation concentrating device, a flotation concentrating device, a membrane separation device or the like is used.

  The sludge concentrated and reduced in volume by the concentrators 4 and 5, respectively, is sent to the digester 6 as the mixed concentrated sludge F, digested under anaerobic conditions, further reduced in volume, and methane gas is removed. Converted to digestion gas as the main component. The generated digestion gas G is recovered from the top of the digestion tank 6 and used as boiler fuel or the like.

  Next, the sludge digestion liquid H treated in the digestion tank 6 is sent to a dehydration device 7 such as a belt press or a screw press, where the dewatered sludge (cake) I and the desorption liquid (dehydration separation liquid) J are solid-liquid. To be separated. As the dehydrator 7, a belt press, a filter press, a screw press, a centrifugal dehydrator, a rotary pressure dehydrator, or the like is used.

  The desorbed liquid J discharged from the dehydrator 7 is usually returned to the initial settling tank 1 of the wastewater treatment facility as it is and treated together with the raw water A. However, in the present invention, the catalyst is not directly returned to the catalyst. It is supplied to the wet oxidizer 8 for further processing.

    A specific treatment of the desorbed liquid J by the catalytic wet oxidation apparatus 8 will be described with reference to FIG. 3 showing an example of the apparatus.

    The desorbed liquid J is pressurized by the booster pump 11, heated through the heat exchanger 17 by the desorbed liquid pipe 12, and then supplied to the lower part of the catalytic reactor 14 by the pipe 13. At the same time, the air pressurized by the compressor 15 is introduced into the desorbed liquid pipe 12 through the air pipe 16 and supplied to the catalyst reactor 14 together with the desorbed liquid J, thereby maintaining the inside of the reactor in an oxidizing atmosphere.

  The catalytic reactor 14 is filled with a solid oxidation catalyst and is operated under high temperature and high pressure conditions. The desorbed liquid J flows upward through the reactor 14 and passes through the packed catalyst layer. In the process, the desorbed liquid J is difficult to be decomposed by normal biological treatment contained in the liquid, such as COD and nitrogen compounds. Degradable substances are oxidatively decomposed and purified.

  The purified gas-liquid mixture is discharged from the upper part of the catalyst reactor 14, returned to the heat exchanger 17 through the gas-liquid pipe 18, cooled to room temperature, and then sent to the gas-liquid separator 20 through the pipe 19. The gas-liquid separator 20 performs liquid level control and gas pressure control while storing a certain amount of the gas-liquid mixture, and sequentially separates and discharges the gas and the processing liquid.

  The oxidation catalyst is preferably iron, manganese, nickel, cobalt, copper, platinum, rhodium, ruthenium, or an oxide of these metals, and other well-known oxidation catalysts can be used as a matter of course.

  It is important to operate at a high reaction temperature in the catalytic reactor in order to efficiently decompose and reduce the biodegradable substance of the desorbed liquid. Specifically, the reaction is preferably performed at 200 to 300 ° C. . If the temperature is lower than 200 ° C., the oxidative decomposition of the hardly decomposable substance is insufficient and the cleanliness of the treatment liquid is lowered. On the other hand, if the temperature is higher than 300 ° C., the energy efficiency is lowered and the heat load on the oxidation treatment apparatus is increased. With the above disadvantages. The reaction pressure is preferably 1.5 to 10 MPa. If the pressure is less than 1.5 MPa, it is difficult to maintain the liquid phase in the reactor. Conversely, if the pressure exceeds 10 MPa, the operating cost increases and a reactor with extremely high pressure strength is required, resulting in high equipment costs.

  The treatment liquid K obtained by oxidizing the desorption liquid J with the catalytic wet oxidation device 8 in this way is returned to the inlet side of the first settling tank 1 of the wastewater treatment facility, and the first settling is performed similarly to the raw water A. The tank 1, the biological treatment tank 2 and the final sedimentation tank 3 are processed in this order and separated into the settled organic sludge and the supernatant water, and finally discharged as treated water B purified from the final sedimentation tank 3.

  According to this embodiment, organic sludge such as excess sludge D and primary sedimentation sludge E generated in the wastewater treatment facility comprising the first sedimentation tank 1, the biological treatment tank 2 and the final sedimentation tank 3 is concentrated by the concentration devices 4 and 5. After that, the anaerobic digestion treatment is performed in the digestion tank 6, and then the sludge digestion liquid H obtained by the anaerobic digestion treatment is dehydrated by the dehydrator 7, and the desorbed liquid J obtained by the dehydration treatment is the catalyst. The treatment liquid K which has been oxidized by the wet oxidation apparatus 8 and oxidized is first returned to the settling tank 1.

  Therefore, the desorption liquid J after the dewatering treatment of the sludge digestive liquid H obtained by the digestion process efficiently decomposes pollutants such as biologically indegradable substances remaining in the liquid by catalytic wet oxidation. The treated liquid K that has been removed and purified is returned to the wastewater treatment facility. For this reason, the treated water B discharged from the wastewater treatment facility can stably maintain a good water quality.

  Next, FIG. 2 is a process flow diagram showing another embodiment of the present invention. In this figure, the same reference numerals and names as those in FIG. 1 are the same, and in the following description of the present embodiment, the overlapping parts centering on the parts different from those in FIG. 1 are omitted.

  In this embodiment, the concentrated sludge F concentrated and mixed by the concentration apparatuses 4 and 5 is not directly sent to the digestion tank 6 as in the above embodiment, but is further concentrated and solubilized. Sent later. That is, first, the concentrated sludge F is sent to the high-concentration concentrator 9, concentrated to a higher concentration (8 to 15 wt% in solid content) and reduced in volume, and becomes highly concentrated sludge L. As the high concentration concentrator 9, a centrifuge, a screw press concentrator, a belt press concentrator, a rotary pressure concentrator, or the like is used.

  Then, the highly concentrated sludge L obtained by further concentration processing by the concentration device 9 is then sent to the solubilization tank 10 where the solubilization processing is performed.

  On the other hand, the separation liquid M generated by the solid-liquid separation by the high concentration concentrator 9 is also combined with the processing liquid K and returned to the precipitation tank 1 first.

  By the way, although there are various methods as the solubilization treatment, a method by heat treatment is recommended in the present invention. As the heat treatment type solubilization tank 10, for example, a cylindrical reaction vessel for high temperature and high pressure is used.

  As conditions for solubilization by this heat treatment, the concentration, temperature, pressure, treatment time and the like of the highly concentrated sludge L to be supplied are important.

    The concentration of sludge is preferably in the range of 8 to 15%. If the concentration is less than 8%, the solubilization tank 10 is enlarged and the cost of the apparatus is increased, and if it exceeds 15%, the ammonia concentration in the digestion tank 6 in the next process is increased. May inhibit digestive function.

  The sludge heat treatment temperature, that is, the heating temperature in the solubilization tank 10 is preferably in the range of 120 to 200 ° C. If the heating temperature is less than 120 ° C, the organic matter in the sludge is insufficiently solubilized, and a sufficient organic matter decomposition rate cannot be obtained, or the amount of methane generated in the digestion process in the next step is reduced. The amount of dewatered sludge increases, and it may be difficult to effectively reduce the moisture content. On the other hand, at a high temperature exceeding 200 ° C., the overall energy efficiency becomes lower than the rate of increase in the solubilization rate, and the heat load of the solubilizer increases.

  The pressure in the solubilization tank 10 is preferably in the range of 0.2 to 1.5 MPa. If this pressure is less than 0.2 MPa, the organic matter in the sludge is not sufficiently decomposed, and a sufficient solubilization rate cannot be obtained. Therefore, the amount of methane generated is reduced, and the water content of the dewatered sludge can be effectively reduced. become unable. Conversely, at high pressures exceeding 1.5 MPa, the overall energy efficiency becomes worse compared to the rate of increase in solubilization rate, the solubilizing device body must be made robust, and a precise sealing structure is required, resulting in device costs. However, it is disadvantageous in that it requires more frequent equipment inspection and maintenance.

  The solubilization time in the solubilization tank 10 is preferably in the range of 30 to 90 minutes. If it is less than 30 minutes, sufficient solubilization is not promoted, the amount of methane generated in the digestion process is insufficient, and the water content of the dewatered sludge becomes insufficient. On the other hand, in a long time exceeding 90 minutes, an increase in the solubilization rate can hardly be expected although the productivity is lowered.

  The highly concentrated sludge L solubilized by the solubilization tank 10 under the preferable conditions as described above becomes the solubilized sludge N and is discharged from the solubilization tank 10.

  This solubilized sludge N is sent to the digestion tank 6 and subjected to digestion treatment under anaerobic conditions. Further, the solubilized sludge N is reduced in volume and converted into digestion gas G containing methane gas as a main component. The generation of digestion gas G here is intended for digestion of sludge N that has been solubilized as described above, so that the reaction proceeds actively, and as a result, a large amount of methane gas can be recovered. Become.

  And the methane gas collect | recovered with the digestion tank 6 is converted into high temperature water vapor | steam through a boiler, and is supplied to the solubilization tank 10 as heat source Q1 required for a solubilization process.

  In addition, the dehydration process of the sludge digestive liquid H after the digestion process by the dehydrator 7, the oxidation process of the desorbed liquid J by the catalyst wet oxidation apparatus 8, the return of the process liquid K after the oxidation process to the first sedimentation tank 1, etc. The processing is the same as in the above embodiment.

  According to this embodiment, organic sludges such as excess sludge D and initial settling sludge E generated in the wastewater treatment facility comprising the first settling tank 1, the biological treatment tank 2 and the final settling tank 3 are concentrated by the concentration devices 4 and 5. After that, the anaerobic digestion treatment is performed in the digestion tank 6, and then the sludge digestion liquid H obtained by the anaerobic digestion treatment is dehydrated by the dehydrator 7, and the desorbed liquid J obtained by the dehydration treatment is the catalyst. The treatment liquid K which has been oxidized by the wet oxidation apparatus 8 and oxidized is first returned to the settling tank 1. Further, a part of the separation liquid M concentrated by the high concentration concentrator 9 is joined with the oxidized treatment liquid K that is first returned to the settling tank 1. When the catalyst wet oxidation treatment is performed at a temperature higher than the temperature of the solubilization treatment, heat is generated by the oxidation reaction. Therefore, heat is recovered by the heat exchanger 17, and a part of the recovered heat Q2 is used as a heating source for the solubilization treatment. It is preferable because it can be used for a part of the above.

  Therefore, according to the embodiment of the present invention, in addition to the operational effects of the above-described embodiment, that is, the point that the treated water B discharged from the wastewater treatment facility can stably maintain good water quality, the digestion efficiency of organic sludge, Since the volume reduction rate and dehydration can be further increased, and a large amount of methane gas can be efficiently recovered, it can be effectively used as a necessary heat source in the system such as the catalytic wet oxidation apparatus 8, Overall energy efficiency can be improved. Further, a part of the separation liquid M concentrated by the high concentration concentrator 9 is joined with the oxidized treatment liquid K that is first returned to the settling tank 1. In the embodiment, more biologically degradable substances are transferred to the desorbed liquid J by solubilization of sludge in the solubilization tank 10, but this is effectively decomposed by the catalytic wet oxidation treatment 8. Therefore, it is possible to sufficiently secure a good quality of the treated water B.

  As another embodiment, although not shown, a phosphorus component removing device, a metal component removing device, and a suspended material removing device are sequentially provided between the dehydrating device 7 and the catalyst wet oxidation treatment 8, and a desorbed solution (dehydrated separating solution) is provided. ) It is preferable to remove the phosphorus component, metal component and suspended substance contained in J prior to catalytic wet oxidation. Here, as a phosphorus component removing device, a device that removes a phosphorus component by a MAP method or a coagulation precipitation method using aluminum or iron, etc., and as a metal component removing device, a chelating agent or an ion exchange membrane is used. Examples of the apparatus for removing various metal components, and examples of the suspended substance removing apparatus include an apparatus for removing suspended substances using a membrane such as UF and MF. Of course, in this case, it is not always necessary to provide all of these devices depending on the components contained in the desorbing liquid J, and a necessary removing device may be selectively installed according to the component to be removed.

  By adopting such an embodiment, the phosphorus component, metal component and / or suspended substance contained in the desorbing liquid J are removed before the catalytic wet oxidation treatment, thereby improving the efficiency of catalytic oxidation and the life of the catalyst. It is possible to reduce biodegradable substances and the like stably and economically.

  In the biological treatment tank 2, the normal activated sludge method, the AO method (anaerobic-aerobic method) and the A2O method (anaerobic-anoxic-aerobic method) are employed, but the desorbed solution contains ammonia. In addition, since nitric acid and nitrous acid may be oxidized by catalytic wet oxidation, it is preferable to employ a method combining anaerobic (anoxic) and aerobic such as AO method and A2O method that can be denitrified.

It is a flowchart explaining embodiment of this invention. It is a flowchart explaining other embodiment of this invention. It is explanatory drawing which showed an example of the catalyst wet oxidation apparatus applied to this invention.

Explanation of symbols

1: First sedimentation tank 2: Biological treatment tank 3: Final sedimentation tank 4, 5: Concentrator
6: Digestion tank 7: Dehydration device 8: Catalyst wet oxidation device 9: High concentration concentration device 10: Solubilization tank
11: Booster pump 12, 13: Desorbed liquid piping 14: Catalytic reactor
15: Compressor 16: Air piping 17: Heat exchanger
18, 19: Gas-liquid piping 20: Gas-liquid separator A: Raw water (organic wastewater) B: Treated water C: Return sludge D: Surplus sludge E: Initial sludge F: Concentrated sludge G: Digestion gas H: Sludge digestion Liquid I: Dehydrated sludge J: Dehydrated separation liquid (desorption liquid) K: Treatment liquid L: Highly concentrated sludge M; Separation liquid Q1, Q2: Heat source

Claims (9)

Organic sludge is solubilized, solubilized sludge obtained by the solubilization treatment is subjected to anaerobic digestion treatment, and then the sludge digestion liquid obtained by the anaerobic digestion treatment is dehydrated, and further obtained by the dehydration treatment. The resulting dehydrated separation liquid is subjected to catalytic wet oxidation treatment ,
A the solubilization treatment is a heat treatment method for treating organic sludge temperature of the heat treatment, characterized in 120 to 200 [° C. der Rukoto. The method for treating organic sludge according to claim 1, wherein the temperature of the catalyst wet oxidation treatment is 200 to 300 ° C. The method for treating organic sludge according to claim 1 or 2 , wherein waste heat generated in the catalytic wet oxidation treatment is used as a heat source in the solubilization treatment. The organic sludge treatment method according to any one of claims 1 to 3, wherein at least one of a phosphorus component, a metal component, and a suspended substance is removed before the catalyst wet oxidation treatment. The organic sludge treatment method according to any one of claims 1 to 3, wherein a phosphorus component, a metal component, and a suspended substance are removed before the catalyst wet oxidation treatment. A solubilization treatment tank for solubilizing organic sludge, a digestion tank for anaerobic digestion of the solubilized sludge obtained by the solubilization treatment, and a sludge digestion liquid obtained by the anaerobic digestion treatment are dehydrated. and dehydrating apparatus, a dehydration separated liquid obtained by the dehydration treatment and a catalytic wet oxidation apparatus for catalytic wet oxidation treatment seen including,
An organic sludge treatment facility, wherein the solubilization treatment tank is by heat treatment, and the temperature of the heat treatment is 120 to 200 ° C. The organic sludge treatment facility according to claim 6 , wherein a treatment temperature in the catalytic wet oxidation apparatus is 200 to 300 ° C. The organic material according to claim 6 or 7 , wherein at least one of a phosphorus component removing device, a metal component removing device, and a suspended substance removing device is provided between the dehydrating device and the catalytic wet oxidation device. Sludge treatment equipment. The organic sludge treatment facility according to claim 6 or 7 , wherein a phosphorus component removal device, a metal component removal device, and a suspended substance removal device are sequentially provided between the dehydration device and the catalytic wet oxidation device.

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