JP2004243204A - Digestion treatment method for organic waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially advantageous digestion treatment method for organic waste which decomposes or digests organic matter in organic waste rapidly in a high decomposition ratio and produces methane or fertilizer efficiently, and an apparatus therefor. <P>SOLUTION: Mordenite type zeolite is added to perform anaerobic digestion treatment. This treatment method has a process (I) for supplying organic waste and mordenite type zeolite to an anaerobic digestion tank and a process (II) for subjecting the supplied mixture of the mordenite type zeolite and the organic waste to be digested to anaerobic digestion treatment in the presence of anaerobic digesting sludge. Preferably, the obtained gaseous phase part is recovered as fuel and the obtained solid phase part is recovered and used as organic fertilizer or the like. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to organic waste, for example, food waste discharged from households, supermarkets, convenience stores, food factories, etc., and organic sludge discharged from wastewater treatment facilities, sewage treatment plants, etc., such as domestic septic tanks and factories. The present invention relates to a method for treating organic waste such as human waste, animal excrement, and organic wastewater, and an apparatus for implementing the method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in digesting organic wastes, solid auxiliary materials such as wood chips, twigs, dried chicken dung pellets, etc. are mixed with particulate or sludge-like organic wastes, and anaerobic at a water content of about 80%. Although a method of promoting digestion is known (Patent Document 1), the digestion reaction is inhibited by ammonia generated in an anaerobic digestion process due to an increase in the concentration of organic substances, and methane cannot be efficiently produced. There were drawbacks.
[0003]
In addition, as a technology for highly purifying ammonia-containing wastewater such as sewage, the use of an ammonia-adsorbed zeolite-based mineral has been proposed (Patent Document 2). However, this proposal relates to nitrogen removal of wastewater, and is anaerobic digestion. Not about.
[0004]
In addition, as a method of producing solid fertilizer from manure of livestock and the like, a solid fertilizer is prepared by mixing zeolite as a water absorbent with a digestive juice of anaerobic digested manure and drying and granulating the paste-like mixture. (Patent Document 3), but this proposal does not teach the effect of improving the efficiency of anaerobic digestion.
[0005]
[Patent Document 1] Japanese Patent Application Laid-Open No. 11-306463 [Patent Document 2] Japanese Patent Application Laid-Open No. 9-314183 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-29871
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned prior art, and in a method for treating organic waste, it is possible to quickly decompose and digest organic substances in organic waste at a high decomposition rate and to remove methane. It is an object of the present invention to provide an industrially advantageous organic waste treatment method and apparatus capable of efficiently producing fertilizer and fertilizer.
[0007]
[Means for Solving the Invention]
The present inventors have conducted intensive studies to solve the above problems, and as a result, completed the present invention.
That is, according to the present invention, the following inventions are provided.
(1) A method for anaerobic digestion of organic waste, wherein the anaerobic digestion treatment is performed in the presence of a mordenite zeolite.
(2) An anaerobic digestion treatment method of an organic waste, comprising: (I) a step of supplying an organic waste and a mordenite zeolite to an anaerobic digestion tank; (II) a step of supplying the supplied organic waste and a mordenite The method for treating organic waste according to the above (1), wherein the mixture with the zeolite is subjected to anaerobic digestion treatment in the presence of anaerobic digestion sludge.
(3) The method for treating organic waste according to (2), wherein the methane-containing gas phase obtained in the step (II) is used as a fuel.
(4) The organic waste according to (2) or (3), wherein the digestion treatment residue obtained in the step (II) is directly or solid-liquid separated and used as a fertilizer and / or a raw material for the fertilizer. How to handle things.
(5) The method for treating organic waste as described in (4) above, wherein the treatment residue contains a mordenite zeolite in which ammonia is adsorbed.
(6) An anaerobic digestion treatment apparatus for organic waste, comprising an apparatus for supplying organic waste and mordenite zeolite to an anaerobic digestion tank. Processing equipment.
(7) An apparatus for anaerobic digestion of organic waste, which supplies organic waste and mordenite zeolite to the anaerobic digestion tank, and digests the supplied mixture in the anaerobic digestion tank. The method for treating organic waste according to the above (6), further comprising an apparatus.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The most important feature of the present invention is that mordenite is added to organic waste in order to overcome the inhibition of microbial digestion by ammonia, to reduce the efficiency of methane production, and to promote the effective use of further processing residues in fertilizers. The point is that anaerobic digestion treatment is made more efficient by adding and mixing a zeolite.
[0009]
That is, in the conventional anaerobic digestion treatment, if the nitrogen content in the organic waste is high, the ammonia concentration becomes high, and the instability of operation such as inhibition of methane production, cessation of methane production reaction and reduction of methane production rate According to the method of the present invention, in the process of digesting the organic waste in advance, the mordenite zeolite was mixed with the anaerobic digestive sludge, so that excess ammonia was adsorbed by the mordenite zeolite. Therefore, the conversion reaction from organic waste to methane and carbon dioxide in the anaerobic digestion process is performed efficiently.
[0010]
In the method of the present invention, as described above, the reason why the conversion reaction from organic waste to methane and carbon dioxide efficiently proceeds in the anaerobic digestion treatment step is not clear at present, but the organic waste Is mixed with anaerobic digestion sludge and anaerobic digestion treatment, the mordenite zeolite adsorbs ammonia generated from raw organic waste in the process of anaerobic digestion, and the methane formation reaction by ammonia is inhibited. The conversion of organic waste to methane and carbon dioxide in the anaerobic digestion process is controlled because the characteristics of the mordenite surface are reduced and the mordenite surface becomes easy to proliferate for methanogenic microorganisms, creating optimal conditions for methanogenic microorganisms. Is estimated to proceed efficiently.
[0011]
The organic waste to be treated in the present invention is food waste from households, restaurants, hotels, food factories, supermarkets, convenience stores, and the like. Mixtures of organic matter and water such as proteins, carbohydrates, lipids, and fibers called primary sediment sludge generated during wastewater treatment in food factories, septic tanks, sewage treatment plants, etc., and microorganisms that have grown during wastewater purification called surplus sludge, Wastewater treatment sludge, which is a mixture of primary sludge and excess sludge discharged after wastewater treatment in food factories, septic tanks, sewage treatment plants, etc. It includes plant waste and agricultural waste such as night soil, livestock excrement, waste paper, pruned branches, and general organic waste such as digested sludge discharged after anaerobic digestion.
[0012]
As used herein, a mordenite zeolite is a type of zeolite, which is generally a porous substance having a large number of cavities in a crystal (crystal structure MOR). In the form of a condensed acid salt substituted by aluminum, a typical composition is represented by the following general formula (1).
Embedded image
_{(Ca, K 2, Na 2} ) [AlSi 5 O 12] 2 · 7H 2 O (1)
Unlike other sodalite, hollandite, filipsite, and chabazite zeolite, this mordenite zeolite exhibits ammonia-adsorbing properties, significantly promotes the growth of methanogenic microorganisms, and has excellent methane productivity. It is a thing.
Examples of such a mordenite zeolite include gismondin, mordenite, yugawarite, and erionite, and mordenite is preferable in terms of methane productivity.
As the mordenite, natural mordenite and synthetic mordenite are known, and both can be used in the present invention. Further, those obtained by ion-exchanging ions in mordenite with other metal ions can also be used.
[0013]
An example of the anaerobic digestion method preferably employed in the method of the present invention is shown below.
First, the organic waste to be treated is crushed and mixed with the anaerobic digestive seed sludge and the mordenite zeolite. The water content of this mixture is adjusted to 60-99.9%, preferably 75-90% dry, or 90-95% wet, and medium-temperature fermentation at 10-100 ° C, preferably 30-35 ° C, or 50-90 ° C. Anaerobic digestion is performed by high-temperature fermentation at 70 ° C to generate methane. The addition amount of the mordenite zeolite is 0.1 to 50% by weight, preferably 2 to 20% by weight.
[0014]
In the present invention, the method of mixing the organic waste to be treated, the mordenite zeolite and the anaerobic digestive seed sludge is not particularly limited, and the garbage is mixed with the mordenite zeolite and the anaerobic digestive seed sludge after crushing the organic waste to be treated. However, after the organic matter to be treated and the anaerobic digestive seed sludge are mixed in the anaerobic digestion tank, the mordenite zeolite may be added and mixed. In any method, if the mordenite zeolite is uniformly mixed with the organic waste to be treated and the anaerobic digestive seed sludge, ammonia is adsorbed by the mordenite zeolite in the anaerobic digestion tank and efficiently anaerobic. The sexual digestion reaction proceeds.
[0015]
As anaerobic digestive seed sludge, for example, the usual anaerobic digestion sludge used for anaerobic digestion of sewage sludge containing acid-fermenting microorganisms and methane-fermenting microorganisms, and aerobic digestion of existing anaerobic digestion sludge Cultured products can be used.
The acid-fermenting microorganism refers to a microorganism that produces an organic acid or the like in anaerobic digestion, and Bacteroides sp. Clostridium sp. Bacillus sp. Lactobacillus sp. And the like. Further, the methane fermentation microorganisms, means a microorganism that produce methane in anaerobic digestion, Methanosarcina sp. , Methanosaeta sp. , Metanogeum sp. And the like. Both are well known in the past.
[0016]
As described above, when the organic waste is subjected to the biodegradation treatment under anaerobic conditions together with the mordenite zeolite, excess ammonia generated in the anaerobic digestion process is adsorbed and removed by the mordenite zeolite, and methane production is inhibited by conventional ammonia. Is prevented. Therefore, in the method of the present invention, the anaerobic digestion process proceeds efficiently.
[0017]
Methane generated during anaerobic digestion can be used as fuel for boiler fuel, digestion gas power generation, micro gas turbines and fuel cells after reforming to hydrogen.
[0018]
In the method of the present invention, the digestion residue after anaerobic digestion contains mordenite zeolite, and since this mordenite zeolite adsorbs ammonia, when used as a raw material for fertilizers such as compost or soil improvement material, ammonia is immediately It has the advantage that it does not flow out and has a low water content. Therefore, this residue can be used as it is and / or after solid-liquid separation as it is as a liquid fertilizer or a solid fertilizer and / or as a raw material of a fertilizer / soil improving material.
[0019]
Next, a processing apparatus for preferably executing the method of the present invention will be described in detail with reference to the drawings.
[0020]
In FIG. 1, 1 is an organic waste storage tank, 2 is an organic waste pipe, 3 is an anaerobic digestion tank, 4 is a mordenite zeolite storage tank, 5 is a mordenite zeolite pipe, 6 is a digestion gas pipe, 7 Is a digestion gas storage tank, 8 is an anaerobic treated pipe, 9 is a solid-liquid separator, 10 is a treated liquid phase pipe, 11 is a treated liquid phase storage tank, 12 is a treated solid phase pipe, and 13 is a treated solid pipe. Each phase storage tank is shown.
[0021]
In the apparatus of FIG. 1, raw materials are supplied from an organic waste storage tank 1 through an organic waste pipe 2 to an anaerobic digestion tank 3 that generates methane. The mordenite zeolite is supplied from the mordenite zeolite storage tank 4 to the anaerobic digestion tank 3 through the mordenite zeolite pipe 5. In the anaerobic digestion tank 3, the organic waste, the mordenite zeolite, and the anaerobic digestion sludge are mixed and stirred to promote anaerobic digestion. In the anaerobic digester 3, organic waste is decomposed into methane, carbon dioxide, ammonia, and the like by the action of acid-producing microorganisms and methane-producing microorganisms. At this time, since the mordenite zeolite is added to the anaerobic digestion tank 3, the concentration of free ammonia is kept low, and the methane production reaction is not hindered.
[0022]
The digestion gas containing methane generated in the anaerobic digestion tank 3 is stored in the digestion gas storage tank 7 through the digestion gas pipe 6. The digestion gas in this case usually contains CH4: 50 to 100 mol%, CO2: 0 to 50 mol%, and H2: 0 to 10 mol%.
[0023]
The processed material that has undergone anaerobic digestion is transferred to the solid-liquid separation device 9 through the anaerobic processed product pipe 8. In the solid-liquid separation device 9, the anaerobic digestion product is separated into solid and liquid, and the liquid phase is stored in the processing liquid phase storage tank 11 through the processing liquid phase piping 10. The solid phase portion is stored in the processing solid phase storage tank 13 through the processing solid phase piping 12. The solid-liquid separator 9 includes a filter, a centrifuge, a settling tank, and the like.
[0024]
The treated solid phase has a high quality as a soil conditioner or a raw material of an organic fertilizer because ammonia as a fertilizer component is adsorbed on the mordenite zeolite. In the treatment liquid phase, ammonia is adsorbed by the mordenite zeolite and is largely transferred to the solid phase, so that the ammonia concentration is low and the ammonia removal treatment of the waste liquid becomes easy.
[0025]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples.
[0026]
Example 1
To a glass bottle having a capacity of 50 ml, 40 ml of digested sludge, 4500 mg N / l of ammonia, and 5% by weight of mordenite zeolite (natural mordenite (0.5-1.5 mm standard), manufactured by Izka Corporation) were added. . After sealing with a rubber stopper, the inside gas was replaced with nitrogen to make the inside of the glass bottle anaerobic. The cells were cultured at 35 ° C. for 2 weeks while measuring the amount of digested gas generated with a syringe. The methane concentration in the digested gas was measured by gas chromatography. The ammonia concentration in the anaerobic digestive fluid was measured by ion chromatography.
[0027]
Comparative Example 1
The same treatment as in Example 1 was performed except that the mordenite zeolite was not added, and the methane concentration in the digested gas was measured by gas chromatography.
[0028]
[Experimental results of Example 1 and Comparative example 1 and consideration thereof]
The amount of digestion gas generated was 226 ml in Comparative Example 1 in which the mordenite zeolite was not added, but 600 ml was generated from the glass bottle of Example 1 to which 5% by weight of the mordenite zeolite was added.
The methane concentration in the digestion gas was 46% in Comparative Example 1 in which the mordenite zeolite was not added, but was 62% in the glass bottle of Example 1 in which 5% by weight of the mordenite zeolite was added. .
[0029]
The ammonia concentration in the digestive juice was 3154 mg N / l in Comparative Example 1 to which no mordenite zeolite was added, but 2405 mg N from the glass bottle of Example 1 to which 5% by weight of mordenite zeolite was added. / L.
[0030]
These experimental results show that the mordenite zeolite used in the present invention has a function of adsorbing ammonia and suppressing the inhibition of ammonia on methane fermentation.
[0031]
【The invention's effect】
Since the present invention has the above configuration, when organic waste is anaerobically digested, ammonia which is a methane production inhibitor is adsorbed and removed by the mordenite zeolite, whereby anaerobic digestion proceeds smoothly, In addition, the characteristics of the mordenite surface provide an environment in which methane-producing microorganisms can easily proliferate, creating optimal conditions for methane-producing microorganisms. move on. According to the present method, the finally generated residue (the treated solid phase) contains ammonia adsorbed on the mordenite zeolite, and has high quality as a raw material for soil conditioners and organic fertilizers. It has a number of advantages, such as a low ammonia concentration in the treatment liquid phase portion, which facilitates the ammonia removal treatment of the waste liquid.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an apparatus for anaerobic digestion of organic waste according to the present invention.
[Explanation of symbols]
1. Organic waste storage tank 2. 2. Organic waste piping Anaerobic digester 4. 4. Mordenite zeolite storage tank 5. Mordenite zeolite piping 6. Digestion gas piping 7. Digestion gas storage tank Anaerobic treatment piping 9. Solid-liquid separator 10. Processing liquid phase piping 11. Processing liquid phase storage tank 12. Processing solid phase piping 13. Processing solid phase storage tank

Claims (7)

A method for anaerobic digestion of organic waste, comprising anaerobic digestion treatment in the presence of a mordenite zeolite. An anaerobic digestion treatment method for organic waste, comprising: (I) a step of supplying an organic waste and a mordenite zeolite to an anaerobic digestion tank; (II) a step of supplying the supplied organic waste and a mordenite zeolite The method for treating organic waste according to claim 1, wherein the mixture is subjected to anaerobic digestion treatment in the presence of anaerobic digestion sludge. The method for treating organic waste according to claim 2, wherein the gaseous phase containing methane obtained in the step (II) is used as fuel. The method for treating organic waste according to claim 2, wherein the digestion treatment residue obtained in the step (II) is directly or solid-liquid separated and used as a fertilizer and / or a raw material of the fertilizer. The method for treating organic waste according to claim 4, wherein the treatment residue contains mordenite zeolite having ammonia adsorbed thereon. An anaerobic digestion treatment apparatus for organic waste, comprising: an apparatus for supplying organic waste and mordenite zeolite to an anaerobic digestion tank. An anaerobic digestion treatment apparatus for organic waste, comprising: an apparatus for supplying organic waste and mordenite zeolite to an anaerobic digestion tank; and an apparatus for digesting the supplied mixture in an anaerobic digestion tank. The apparatus for anaerobic digestion of organic waste according to claim 6, wherein:

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