JP6666346B2 - Organic substance processing method and processing apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for treating organic matter, and more particularly, to a method and apparatus for anaerobic treatment of organic matter.

  Methane fermentation is also called anaerobic treatment or anaerobic digestion. In the present specification and claims, “anaerobic treatment” includes methane fermentation and anaerobic digestion, and sludge obtained by anaerobic treatment of organic matter is referred to as “anaerobic treated sludge”.

  Methane fermentation for organic substances such as food residues, food production residues, garbage, and various types of sludge enables anaerobic treatment of organic substances, reduces waste, generates methane gas from waste, and recovers energy. It is a technology that has attracted attention as a technology that can reduce environmental load. However, the generated anaerobic sludge is often a hardly dewaterable sludge, and in the sludge dewatering treatment after the anaerobic treatment, a large amount of a flocculant is required, and the water content of the dewatered cake is high. In addition, the generated anaerobic sludge can be coagulated only with an expensive amidine-based polymer coagulant, and there is a problem that the operation cost is high.

  For this reason, there is a need for a technique for efficiently recovering methane gas by methane fermentation at a low operating cost and efficiently dewatering the generated anaerobic sludge.

  The following prior art is known as a technique related to a method for improving the dewaterability of anaerobic treated sludge.

  Patent Document 1 discloses that a fermentation residue obtained by subjecting organic waste to methane fermentation and a solution containing other anaerobic organic compounds to a pH of 5.5 or less and a liquid treatment step of contacting with an oxidizing agent. A method for treating a fermentation residue and a liquid containing other anaerobic organic compounds, which is a feature, is described.

  Patent Document 2 discloses an anaerobic digestion treatment of methane fermentable organic waste such as sewage sludge and kitchen waste, a digestion residue is aerated with an oxygen-containing gas, and then mechanically dewatered. Treatment of organic waste, characterized in that it is brought into direct contact with the air discharged from an aeration blower that supplies air to the aeration tank in the biological treatment process of organic wastewater, which is the source of organic waste, and is dried by the retained heat A method is described.

  Patent Document 3 discloses that after performing aeration on anaerobic digested sludge, excess sludge is mixed, a metal salt is added to the obtained mixed sludge, and then an amphoteric organic polymer flocculant is added to perform coagulation treatment, A method for dewatering anaerobic digested sludge, which comprises dewatering coagulated sludge with a dehydrator, is described.

JP 2005-334713 A JP-A-60-38099 JP-A-8-206699

  An object of the present invention is to provide a method and an apparatus for treating organic matter, which can efficiently anaerobic treat organic matter and efficiently coagulate anaerobic treated sludge.

  The present invention relates to an anaerobic treatment of an organic substance, in which an iron compound is injected before or in an anaerobic treatment step to form an anaerobic treated sludge containing an iron compound, and then an anaerobic treatment containing an iron compound. The oxygen-containing gas is brought into contact with the oxidized sludge to form an aerated sludge containing iron (III) in which iron (II) is oxidized, and then a coagulant is injected into the aerated sludge containing iron (III). And then dehydrated after coagulation.

Specifically, the following aspects are provided by the present invention.
[1] an anaerobic treatment step of anaerobically treating organic matter to form anaerobic treated sludge;
An aeration treatment step of contacting the oxygen-containing gas with the anaerobic treatment sludge to form an aeration treatment sludge;
Injecting a flocculant into the aeration-treated sludge, having a flocculation step to form a flocculated sludge,
Before the anaerobic treatment step, or in the anaerobic treatment step, inject an iron compound into the organic matter,
In the aeration treatment step, the oxidation-reduction potential (oxidation-reduction potential based on a silver / silver chloride electrode) of the aeration-treated sludge is controlled to -100 mV or less, and the anaerobic treatment sludge containing an iron compound and the oxygen-containing gas are mixed. Oxidizes iron (II) contained in the anaerobic treated sludge by contacting
A method for treating an organic substance, wherein iron (III) oxidized in the aggregation step is used as an aggregation agent.
[2] The method for treating organic matter according to [1], wherein the concentration of iron contained in the sludge after iron is injected in the anaerobic treatment step is 100 mg / L or more in terms of iron.
[3] The method for treating organic matter according to [1] or [2], wherein in the aeration treatment step, the dissolved oxygen concentration of the aeration treatment sludge is controlled to 1.0 mg / L or less.
[4] The method further comprises a nitrification step of nitrifying ammonia contained in the dehydration separation liquid from the dehydration step,
The method for treating organic matter according to any one of [1] to [3], wherein the exhaust gas from the nitrification step is reused as an oxygen-containing gas in the aeration treatment step.
[5] The anaerobic treated sludge has a TS concentration of 25 g / L or more, and an SS concentration of 5 g / L or more lower than the TS concentration, [1] to [4]. 2. The method for treating an organic substance according to 1.
[6] iron compound injection means for injecting an iron compound into an organic substance,
An anaerobic treatment tank for anaerobic treatment of organic matter in the presence of iron (II) to form anaerobic treatment sludge;
An aeration tank having an oxidation-reduction potential measuring device, and bringing an oxygen-containing gas into contact with the anaerobic treated sludge to oxidize iron (II) to iron (III) to form an aerated treated sludge containing iron (III) When,
Injecting a coagulant into the aerated sludge, a coagulation tank to form coagulated sludge,
A dehydration device for dehydrating the coagulated sludge,
A nitrification tank for nitrifying ammonia contained in the dehydration separation liquid from the dehydration device,
A process for carrying out the method for treating an organic substance according to any one of [1] to [5], comprising an oxygen-containing gas supply pipe for supplying exhaust gas from the nitrification tank to the aeration tank. apparatus.
[7] The iron compound injection means is the anaerobic treatment tank, or at least one tank selected from an organic matter storage tank, a solubilization tank, and a solubilized matter storage tank provided in a preceding stage of the anaerobic treatment tank, or A pipe connecting the at least one tank and the anaerobic treatment tank, or a pipe connecting the at least two tanks of the organic matter storage tank, the solubilization tank, and the solubilized matter storage tank is provided in any one or more of the pipes. The processing device according to [6], wherein:

ADVANTAGE OF THE INVENTION According to this invention, while anaerobic treatment of organic matter is efficiently performed, anaerobic treatment sludge can be efficiently aggregated. As a secondary effect, the load on the wastewater treatment, desulfurization treatment, and deodorization treatment can be reduced. More specifically, the following effects are obtained.
(1) By performing an anaerobic treatment on an organic substance into which an iron compound has been injected, a stable anaerobic treatment of the organic substance can be performed, and the volume reduction rate and the amount of methane gas generated can be increased.
(2) By performing anaerobic treatment on an organic substance into which an iron compound is injected, sulfur contained in the organic substance is combined with iron to suppress generation of hydrogen sulfide, and the load in the subsequent desulfurization processing and deodorization processing is reduced. Can be reduced.
(3) The amount of coagulant injected in the subsequent coagulation step by contacting oxygen with the anaerobic treatment sludge in the aeration treatment step to oxidize iron contained in the anaerobic treatment sludge and using it as a coagulant Can be reduced.
(4) Aggregation inhibitors (eg, high molecular substances such as polysaccharides, proteins, glycoproteins, nucleic acids, phospholipids, and humic acids) contained in the anaerobic treated sludge are decomposed in the aeration treatment step, which is expensive. For anaerobic treated sludge that can only be agglomerated with amidine-based polymer flocculants, inexpensive non-amidine-based polymer flocculants or inexpensive non-amidine-based polymer flocculants mixed with amidine-based polymer flocculants The blended product can be used in the aggregation step, and the aggregation cost can be reduced.
(5) In the aeration treatment step, the anaerobic treatment sludge is brought into contact with oxygen, whereby the aggregation inhibitory substances (eg, polysaccharides, proteins, glycoproteins, nucleic acids, phospholipids, humic acids, etc.) contained in the anaerobic treatment sludge are contacted. (Polymeric substance) can be decomposed, the amount of coagulant injected in the subsequent aggregation step can be reduced, and the water content of the dewatered cake obtained in the subsequent dehydration step can be reduced.
(6) The carbon dioxide gas dissolved in the anaerobic treated sludge is removed by bringing oxygen into contact with the anaerobic treated sludge in the aeration treatment step, and the foaming phenomenon when the coagulant is injected in the subsequent coagulation step is suppressed. It is possible to do.
(7) When the dewatered separated liquid separated in the subsequent dewatering step is subjected to drainage treatment, since a part of the organic components (BOD component, COD component, and the like) is decomposed in the aeration treatment step, The organic substance load can be reduced.
(8) When the exhaust gas from the nitrification step for nitrifying ammonia contained in the dehydration separation liquid from the dehydration step is reused as the oxygen-containing gas in the aeration step, the amount of exhaust gas from the nitrification step should be reduced. And energy loss in the entire treatment facility can be reduced.

FIG. 2 is a schematic explanatory view showing a flow of a processing step in the method for processing an organic substance of the present invention together with an apparatus configuration. FIG. 2 is a schematic explanatory diagram showing a processing flow further including a dehydration processing step after the aggregation step in the processing step shown in FIG. 1 together with the apparatus configuration. FIG. 2 is a schematic explanatory view showing a flow of a processing step together with an apparatus configuration when two or more coagulation tanks are provided in the processing step shown in FIG. 1. FIG. 2 is a schematic explanatory diagram showing, together with the apparatus configuration, a processing flow in a case where the processing step shown in FIG. 1 further includes a dehydration processing step after an aggregation step, and the aggregation step is performed by a dehydration apparatus. FIG. 3 is a schematic explanatory view showing a processing flow further including a nitrification step after a dehydration processing together with the apparatus configuration in the processing step shown in FIG. 2. FIG. 4 is a schematic explanatory view showing an embodiment in which an iron compound is injected into an organic substance through a pipe before the organic substance is introduced into an anaerobic treatment tank. FIG. 4 is a schematic explanatory view showing an embodiment in which an iron compound is injected into organic matter in a solubilization tank provided in a stage preceding the anaerobic treatment tank. FIG. 4 is a schematic explanatory view showing an embodiment in which an iron compound is injected into organic matter in a solubilization storage tank provided in a stage preceding the anaerobic treatment tank. FIG. 4 is a schematic explanatory view showing a mode in which a plurality of solubilization tanks are provided and an iron compound is injected when a solubilized material solubilized in the solubilization tank is stored in one storage tank. It is a graph which shows the processing result in Examples 2 and 3 by the relationship between aeration time and cake moisture content.

Preferred embodiment

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  In the treatment method of the present invention, an iron compound is injected into the organic matter to be treated in the anaerobic treatment step, and the organic matter is anaerobically treated in the presence of iron (II). In the subsequent aeration treatment step containing (II), the oxidation-reduction potential (oxidation-reduction potential based on a silver / silver chloride electrode) of the aeration-treated sludge is controlled to -100 mV or less, and an anaerobic treatment containing an iron compound is performed. By contacting sludge with an oxygen-containing gas, iron (II) contained in anaerobic treated sludge is oxidized, and iron (III) oxidized in a subsequent coagulation step is used as a coagulant. .

  FIGS. 1 to 5 show an embodiment in which an iron compound is injected into an organic substance in an anaerobic treatment step, and FIGS. 6 to 9 show organic substances in a pipe, a solubilization tank, or a solubilization storage tank which is a former stage of the anaerobic treatment step. Shows an embodiment in which an iron compound is injected.

First, a method for treating an organic substance according to the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 3,
(1) an anaerobic treatment step of anaerobically treating organic matter to form anaerobic treated sludge;
(2) an aeration treatment step of forming an aeration treatment sludge by bringing an oxygen-containing gas into contact with the anaerobic treatment sludge;
(3) a flocculating step of injecting a flocculant into the aerated sludge to form a flocculated sludge;
Injecting an iron compound into organic matter in the anaerobic treatment step,
In the aeration treatment step, the oxidation-reduction potential (oxidation-reduction potential based on a silver / silver chloride electrode) of the aeration-treated sludge is controlled to -100 mV or less, and the anaerobic treatment sludge containing an iron compound and the oxygen-containing gas are mixed. The iron (II) contained in the anaerobic treated sludge is oxidized by contacting with iron and the iron (III) oxidized in the coagulation step is used as a coagulant.

  As shown in FIGS. 2, 4 and 5, a dehydration step may be included after the aggregation step, and a nitrification step after the dehydration step may be included.

  Next, the injection point of the iron compound into the organic matter will be described with reference to FIGS. FIG. 6 shows an embodiment in which an iron compound is injected into an organic substance through a pipe in a stage before an anaerobic treatment step, and FIG. 7 shows an embodiment in which an iron compound is injected into an organic substance in a solubilization step in a stage before the anaerobic treatment step. 8 and 9 show an embodiment in which the iron compound is injected into the organic matter in the step of storing the solubilized substance after the solubilizing step and before the anaerobic treatment step. Except at the point of injection of the iron compound, the embodiment of FIGS. 6 to 9 can be arbitrarily combined with the aggregation step and the dehydration step shown in FIGS.

  Hereinafter, each step will be described.

(1) Iron compound injection step Before the anaerobic treatment step or the anaerobic treatment step, an iron compound is injected into an organic substance, and the organic substance is subjected to anaerobic treatment in the presence of iron (II) in the anaerobic treatment step. Prepare to be able to. The injection of the iron compound into the organic matter is not particularly limited as long as it is performed before the anaerobic treatment step or the anaerobic treatment step, and the organic matter before being supplied to the anaerobic treatment tank or the organic matter stored in the organic matter storage tank The iron compound may be directly injected into the anaerobic treatment tank, the iron compound may be injected into the organic matter in the anaerobic treatment tank (FIG. 1), or the iron compound may be injected into a pipe for supplying the organic substance to the anaerobic treatment tank. (FIG. 6), an iron compound may be injected into a solubilization tank (FIG. 7) or a solubilization storage tank (FIGS. 8 and 9) which is a stage preceding the anaerobic treatment tank.

  The solubilization step in which the solubilization treatment is performed is performed in an anaerobic environment at a reaction temperature of 25 to 70 ° C., pH of 3 to 6, and a hydraulic retention time (HRT) of 0.5 to 5 days using a complete mixing fermenter. Is preferred. In particular, depending on the type of organic substance, the solubilization step of the solid substance tends to be rate-limiting, and therefore, it is preferable to perform HRT in a high temperature reaction of 35 to 70 ° C. for 3 to 5 days. Heat treatment by a high-temperature reaction and solubilization by a thermophilic organism are achieved simultaneously. Furthermore, by performing HRT control, anaerobic microorganisms that usually have high growth rate ability can be dominant, and anaerobic solubilization treatment becomes possible. In addition, by performing the solubilization treatment in a high-temperature reaction at a reaction temperature of 35 to 70 ° C., mixing and stirring can be easily performed under a relatively low viscosity condition even for a high concentration organic waste having a TS concentration of 10 to 15%. It becomes possible. In the solubilization treatment step, usually, the solubilized organic matter is rapidly hydrolyzed or acid-fermented, so that anaerobic fermentation mainly comprising lactic acid fermentation and acid fermentation proceeds almost simultaneously. Therefore, the fermentation environment in which the solubilized bacteria and the acid-fermenting bacteria coexist predominantly in the solubilization treatment step.

  The solubilized material after solubilization is often stored before anaerobic treatment. By injecting the iron compound into the solubilized substance stored in the solubilized substance storage tank, the iron compound can be uniformly dispersed in the organic substance as the solubilized substance.

  The iron compound may be injected directly into the anaerobic treatment tank or a pipe for supplying the organic substance directly or from the solubilization tank or the solubilized substance storage tank to the anaerobic treatment tank. When an iron compound is injected into these pipes or anaerobic treatment tanks, the iron concentration contained in the anaerobic treatment sludge can be directly controlled.

  The injection amount of the iron compound with respect to the organic matter is such that the concentration of iron contained in the sludge treated in the anaerobic treatment step is 100 mg / L or more in terms of iron, preferably 100 to 600 mg / L, more preferably 150 to 500 mg / L, It is particularly preferably adjusted to be 150 to 450 mg / L. By injecting the iron compound into the organic matter before the anaerobic treatment step, the anaerobic treatment of the organic matter is promoted, the volume reduction rate increases, and the methane gas recovery rate improves.

  In the present invention, as the iron compound to be injected into the organic matter before the anaerobic treatment step or the anaerobic treatment step, ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric polysulfate, And ferrous polysulfate.

(2) Anaerobic treatment step In the anaerobic treatment step, organic substances are anaerobically treated, the organic substances are converted into anaerobic sludge by the action of anaerobic microorganisms, the volume is reduced, and methane gas is generated. In the present invention, an organic compound to be treated in the anaerobic treatment step is injected with an iron compound. The organic matter is anaerobically treated in the presence of iron (II), and the anaerobic treated sludge formed is iron (II). Will be contained.

  The operating conditions of the anaerobic treatment process are generally a treatment temperature of 30 to 60 ° C. and a residence time (HRT) of 12 to 40 days. The anaerobic treatment includes a completely mixed type (anaerobic treatment while stirring a liquid substance) and dry methane fermentation (anaerobic treatment while stirring a semi-solid substance), but the treatment form is not particularly limited.

  Organic substances to be treated in the anaerobic treatment include food residues, food production residues, garbage, various sludges, and the like. Examples of various sludges include sewage sludge (primary sludge, surplus sludge, mixed raw sludge), agricultural settlement drainage sludge, human waste sludge (raw human waste, septic tank sludge), and sludge generated from various wastewater treatments. In addition, the solubilized product obtained by solubilizing the above organic substance by an acid treatment, an alkali treatment, a heat treatment, an acid fermentation treatment, or the like can also be subjected to the anaerobic treatment.

  The anaerobic treatment sludge formed in the anaerobic treatment step preferably has a TS concentration of 25 g / L or more and an SS concentration of 5 g / L or less than the TS concentration. More preferably, it is an anaerobic treated sludge having a TS concentration of 25 to 60 g / L, and even more preferably a TS concentration of 30 to 45 g / L. Further, more preferably, the anaerobic treated sludge having an SS concentration 10 g / L or more lower than the TS concentration. Even more preferably, it is an anaerobic treated sludge having an SS concentration 15 g / L or more lower than the TS concentration. Further, the viscosity of the anaerobic treated sludge formed in the anaerobic treatment step is preferably 200 to 1500 mPa · s, and more preferably 300 to 1000 mPa · s. Note that TS and SS mean the total evaporation residue and suspended matter, respectively, and the analysis of TS and SS was based on JIS K-0102. The viscosity is a value measured at 35 ° C. and 60 rpm using a B-type rotational viscometer.

(3) Aeration Treatment Step According to the present invention, an anaerobic treatment sludge containing an iron compound is formed in the anaerobic treatment step. In the aeration process, the anaerobic sludge containing an iron compound is aerated with an oxygen-containing gas to oxidize iron (II) present in the sludge into iron (III) and to remove carbonic acid dissolved in the sludge. Remove the gas. The aeration treatment step in the present invention does not achieve the dissolved oxygen amount or the oxidation-reduction potential to the extent required for general aerobic treatment, but does not achieve the oxidation-reduction potential (oxidation reduction based on the silver / silver chloride electrode). The potential is controlled to -100 mV or less, which is different from the aerobic treatment. In the aeration process, the coagulation inhibiting component present in the sludge is biologically or chemically decomposed. Aggregation inhibiting components include polysaccharides, proteins, glycoproteins, nucleic acids, phospholipids, humic acids and the like.

  The iron (III) oxidized by the aeration treatment can be used as a flocculant in a subsequent flocculation treatment step. Iron in the anaerobic sludge is present as iron (II) because it is under a reducing atmosphere. Iron (II) is oxidized to iron (III) by the aeration treatment. Generally, the ability of iron (III) as an aggregating agent is significantly higher than that of iron (II). The amount of coagulant required for the process can be reduced.

  Moreover, the carbon dioxide gas in the sludge can be removed by aeration treatment, and foaming in the subsequent aggregation step can be suppressed. Generally, in anaerobic treatment, carbon dioxide gas is generated together with methane gas, and a large amount of carbon dioxide gas is dissolved in sludge. When the coagulant is injected into the anaerobic treated sludge, the dissolved carbon dioxide gas is degassed and the coagulated sludge foams, causing troubles such as coagulation inhibition and coagulation sludge overflow from the coagulation tank. The foaming trouble is particularly remarkable when an inorganic coagulant is injected, and sometimes the inorganic coagulant cannot be used. Since the dissolved carbon dioxide gas is degassed by the aeration treatment, foaming trouble can be avoided in the subsequent aggregation step.

  In addition, the agglomeration treatment can be used to biologically or chemically decompose the coagulation-inhibiting components present in the sludge, thereby reducing the amount of coagulant required in the subsequent coagulation step, and further reducing the water content of the cake in the subsequent dehydration step. Rate can be reduced. Generally, anaerobic treated sludge contains high molecular substances such as polysaccharides, proteins, glycoproteins, nucleic acids, phospholipids, and humic acids as coagulation inhibiting components. These aggregation-inhibiting components include components produced by microorganisms during anaerobic treatment and components derived from organic materials as raw materials. In addition, since the viscosity of sludge is reduced by decomposing a high molecular weight polymer substance among the coagulation inhibiting components, the mixing of the sludge and the coagulant in the subsequent coagulation step is facilitated, and the coagulant is efficiently removed. It can be used, and the injection amount of the flocculant can be reduced.

  It is desirable that the aeration process is performed in a temperature range of 10 to 50 ° C, preferably 20 to 45 ° C, more preferably 25 to 40 ° C.

  In the aeration treatment step, it is desirable to adjust the pH of the anaerobic treated sludge to a range of 6.5 to 8.5, preferably 7.0 to 8.5, and more preferably 7.0 to 8.0. . Adjustment of the pH range improves the coagulation action in the subsequent coagulation step and lowers the water content of the dehydrated cake.

It is desirable that the amount of aeration air in the aeration process is in the range of 0.1 to 0.5 m ³ -Air / (m ³ -sludge · min), and the aeration time in the aeration process is in the range of 3 to 48 hours. Is desirable. If the amount of aeration air, which is the amount of air (m ³ ) per unit time (min) with respect to the amount of sludge (m ³ ) in the aeration tank, is less than 0.1 m ³ -Air / (m ³ -sludge · min), the sludge viscosity is lower. When it is high, it is difficult to aerate the entire sludge, and a long time is required for performing aeration treatment on the entire sludge. On the other hand, aeration amount 0.5 m ³ -Air / - if ^{(m 3} sludge · min) is greater than the large blower is required to aeration, also increases the risk of foaming. When the aeration air volume and the aeration time are excessive, not only the coagulation inhibiting component in the sludge but also the sludge itself is decomposed, which adversely affects the subsequent coagulation step and dehydration step. On the other hand, when the aeration air volume and the aeration time are not sufficient, the time required for the aeration treatment becomes long and a huge aeration tank is required, which is not economical.

  It is desirable that the dissolved oxygen concentration (DO) of the sludge in the aeration treatment step is 1.0 mg / L or less, preferably 0.5 mg / L or less, more preferably 0.2 mg / L or less. The oxidation reaction from iron (II) to iron (III) proceeds sufficiently when the dissolved oxygen concentration is 1.0 mg / L or less. Aggregation inhibiting components such as polysaccharides, proteins, glycoproteins, nucleic acids, phospholipids, and humic acids are biologically or chemically degraded even when the dissolved oxygen concentration is 1.0 mg / L or less. In other words, the oxidation reaction of iron and the decomposition of the coagulation-inhibiting component proceed even without strong aerobic conditions.

  The oxidation-reduction potential of the anaerobic treated sludge in the aeration treatment step (oxidation-reduction potential based on a silver / silver chloride electrode) is -100 mV or less, desirably -400 to -100 mV, preferably -350 to -100 mV, and more preferably. Is -350 to -150 mV. The oxidation reaction from iron (II) to iron (III) proceeds sufficiently when the oxidation-reduction potential based on the silver / silver chloride electrode is -100 mV or less. Aggregation inhibiting components such as polysaccharides, proteins, glycoproteins, nucleic acids, phospholipids, and humic acids are biologically or chemically degraded if the oxidation-reduction potential with respect to the silver / silver chloride electrode is -100 mV or less. Is done. In other words, the oxidation reaction of iron and the decomposition of the coagulation-inhibiting component proceed even without strong oxidation conditions.

  As the oxygen-containing gas used in the aeration process, there is no problem as long as it contains oxygen gas, from the air inside and outside the facility that performs anaerobic treatment, from the waste receiving pit and the waste sorting facility inside the facility that performs anaerobic treatment, etc. Low-concentration and high-concentration odor gases containing malodorous components generated, and aerated exhaust gas generated from activated sludge treatment equipment for wastewater can be used. In the case where the dehydration treatment step includes a nitrification step of the dehydrated separated liquid after the dehydration treatment step, the exhaust gas from the nitrification step can be reused as an oxygen-containing gas. The exhaust gas from the nitrification process has a lower oxygen content than ordinary air, but contains sufficient oxygen as a gas for aerating the anaerobic treated sludge.

The aerated sludge formed in the aeration process has a reduced viscosity because the polymer substance is decomposed, and using a B-type rotational viscometer, the sludge pH is 7.5 to 9.5, the temperature is 35 ° C, and the rotor The viscosity measured under the condition of a rotation speed of 60 min ⁻¹ is 200 mPa · s or less, preferably 150 mPa · s or less, more preferably 120 mPa · s or less.

  The aeration process may be a continuous type or a batch type.

(4) Coagulation Step Next, the coagulant is injected into the aeration-treated sludge containing iron (III) in the coagulation step to form coagulated sludge. Coagulated sludge is also called floc.

  The flocculant is not particularly limited, but an inorganic flocculant and a polymer flocculant are used. Examples of the inorganic coagulant include polyaluminum chloride, a sulfate band, aluminum chloride, ferrous chloride, ferric chloride, ferrous polysulfate, and ferric polysulfate. Examples of the polymer flocculant include a cationic polymer flocculant, an amphoteric polymer flocculant, an anionic polymer flocculant, and a nonionic polymer flocculant.

  Examples of the cationic polymer flocculant include a polymer of a cationic monomer, a copolymer of a cationic monomer and a nonionic monomer, an amidine-based polymer flocculant having an amidine unit, an amidine-based polymer flocculant and A polymer coagulant mixed with an amidine-based polymer coagulant is exemplified. Examples of the cationic monomer include dialkylaminoalkyl (meth) acrylates, tertiary salts of dialkylaminoalkyl (meth) acrylates, and quaternary salts of dialkylaminoalkyl (meth) acrylates. For example, dimethylaminoethyl (meth) Acrylates, tertiary salts of dimethylaminoethyl (meth) acrylate, quaternary salts of dimethylaminoethyl (meth) acrylate and the like can be mentioned. Note that acrylate or methacrylate is referred to as (meth) acrylate. Also, acrylic acid or methacrylic acid is referred to as (meth) acrylic acid. Acrylamide or methacrylamide is referred to as (meth) acrylamide.

  Examples of the anionic polymer coagulant include a polymer of an anionic monomer and a copolymer of an anionic monomer and a nonionic monomer. Examples of the anionic monomer include (meth) acrylic acid and sodium (meth) acrylate. Examples of the nonionic monomer include (meth) acrylamide and N, N-dimethyl (meth) acrylamide.

  Examples of the amphoteric polymer flocculant include a copolymer of the above-described cationic monomer and anionic monomer, and a copolymer of a cationic monomer, an anionic monomer, and a nonionic monomer.

  The injection rate of the polymer flocculant is preferably 1 to 7% by mass, and more preferably 2 to 5% by mass with respect to the TS concentration of the sludge, but compared with the injection amount in the conventional anaerobic treatment sludge coagulation method. 10 to 30% reduction can be achieved. Here, TS is the total evaporation residue. The analysis method of TS was based on the sewer test method. The floc preferably has a diameter, that is, a floc diameter of about several millimeters, and has high sedimentation and separability.

  Before the coagulation, the aerated sludge may be diluted, and the coagulant injection rate can be further reduced. The diluent may have any properties that do not affect the agglutination reaction. For example, water having a low soluble component concentration is preferable. For example, tap water, drinking water, industrial water, biologically treated water, filtered water of biologically treated water, biologically treated water of biological deodorizer waste liquid, and the like can be mentioned. By diluting, the viscosity of the aerated sludge decreases, and the concentration of dissolved salts decreases, and the dispersibility of the flocculant further improves. The M-alkalinity of the diluted aerated sludge is preferably 4000 mg / L or less, more preferably 2500 mg / L or less. The electric conductivity of the diluted digested sludge is preferably adjusted to 1200 mS / m or less, more preferably 750 mS / m or less.

(5) Dehydration Step In the dehydration step, the coagulated sludge is solid-liquid separated into a dewatered cake and a dewatered separation liquid. The concentrated sludge obtained by the concentration treatment before the dehydration may be subjected to solid-liquid separation into a dehydrated cake and a dehydrated separation liquid. Since the water content of the dehydrated cake obtained by the treatment method of the present invention is as low as 85% or less, it is possible to recycle compost, charcoal, fuel and the like.

(6) Concentration Step The coagulated sludge formed by coagulation may be concentrated by solid-liquid separation and then dewatered. By the concentration, solid-liquid separation into a concentrated sludge and a concentrated separated liquid is performed. Sludge having a TS concentration of 5 to 15% by mass can be dewatered more efficiently in the dewatering step.

  Next, an apparatus for carrying out the method for treating organic matter according to the present invention will be described.

The organic material treatment apparatus of the present invention, an iron compound injection means for injecting an iron compound into the organic material,
An anaerobic treatment tank having a pipe for injecting an iron compound, anaerobically treating organic matter in the presence of iron (II) to form anaerobic treated sludge,
An aeration tank having an oxidation-reduction potential measuring device, and bringing an oxygen-containing gas into contact with the anaerobic treated sludge to oxidize iron (II) to iron (III) to form an aerated treated sludge containing iron (III) When,
Injecting a coagulant into the aerated sludge, a coagulation tank to form coagulated sludge,
A dehydration device for dehydrating the coagulated sludge,
A nitrification tank for nitrifying ammonia contained in the dehydration separation liquid from the dehydration device,
An oxygen-containing gas supply pipe for adding exhaust gas from the nitrification tank to the aeration tank,
Is provided.

  An iron compound injection means for injecting an iron compound into an organic substance is an organic substance storage tank, a solubilization tank, a solubilized substance storage tank, a pipe for transporting the organic substance or the solubilized substance treated in the solubilization tank to each tank, or an anaerobic treatment tank. At least one of the following.

  The aeration tank and the coagulation tank may be electrically connected to a controller for adjusting the amount of aeration air of the oxygen-containing gas according to the viscosity of the sludge in the aeration tank, and the viscosity for measuring the viscosity of the sludge in the aeration tank. It is preferable to install a meter.

  Hereinafter, each tank will be described.

(A) Solubilization tank A solubilization tank generally used for solubilizing organic substances can be used without limitation, except that a means for injecting an iron compound is provided.

(B) Solubilized matter storage tank Except for having a means for injecting an iron compound, a solubilized matter tank generally used for storing a solubilized substance after solubilizing an organic substance until anaerobic processing. Can be used without limitation.

(C) Piping A pipe generally used for transporting an organic substance or a solubilized substance to each tank can be used without limitation, except that a means for injecting an iron compound is provided.

(D) Anaerobic treatment tank Known anaerobic treatment tanks such as a completely mixed anaerobic treatment tank and a dry methane fermentation tank generally used in waste biomass treatment facilities and sewage treatment facilities can be used without limitation.

(E) Aeration tank An aeration tank generally used in a water treatment facility or the like can be used without limitation. The aeration tank is provided with means for supplying anaerobic treated sludge, aeration means for supplying oxygen-containing gas to the aeration tank, and means for extracting aerated sludge. Examples of the aeration means include an aeration type, a mechanical stirring type, and a combination type of an aeration type and a mechanical stirring type. A diffuser-type aerator is composed of a diffuser and a blower. Examples of the diffuser include a diffuser plate, a diffuser tube, a perforated tube, and a sparger. The aeration means is preferably provided so that air bubbles can be supplied from the bottom of the aeration tank to the sludge in the aeration tank. The aeration tank preferably includes a pH meter, a DO meter, an ORP meter, and a viscometer as measuring devices for operation management. Further, in order to control the pH of the sludge in the aeration tank, it is preferable to provide an acid injection unit or an alkali injection unit.

(F) Coagulation tank A coagulation tank generally used in water treatment facilities and the like can be used without limitation, and a means for supplying aerated aerated sludge, a means for injecting a coagulant, and mixing the aerated sludge and a coagulant. And a means for extracting coagulated sludge.

  Further, two or more coagulation tanks may be provided, and the coagulant may be dividedly injected. For example, when two or more coagulation tanks are provided, an inorganic coagulant may be injected in the first coagulation tank, and a polymer coagulant may be injected in the second and subsequent coagulation tanks to form coagulated sludge. The polymer flocculant may be injected into the first flocculation tank, and the polymer flocculant may be injected into the second and subsequent flocculation tanks. When three or more coagulation tanks are provided, the inorganic coagulant may be dividedly injected into the first coagulation tank, and the polymer coagulant may be dividedly injected into the second coagulation tank and the third and subsequent coagulation tanks. The injection amount and the number of injections of the coagulant can be appropriately set according to the properties of the sludge to be treated and the number of coagulation tanks.

  Further, the coagulation tank may be provided in a dehydrator. Examples of such a dehydrator include some centrifugal dehydrators, and such a centrifugal dehydrator has an area corresponding to a flocculation tank therein, and mixes sludge and a flocculant by centrifugal force, Form coagulated sludge.

(G) Dewatering device A dewatering device is provided to dewater coagulated sludge adjusted in the coagulation tank or concentrated sludge concentrated in the concentrator. The dewatering apparatus is not particularly limited, and preferably includes a means for applying pressure to the coagulated sludge or the concentrated sludge, and a means for separating the solid matter and the dewatered separation liquid. Examples of the dehydrating apparatus include a belt press, a screw press, a centrifugal dehydrator, a filter press, a multiple disk type dehydrator, a multiple disk type screw press, a rotary press, and the like.

(H) Nitrification tank The nitrification tank for nitrifying ammonia contained in the dewatered separation liquid from the dehydration apparatus is a water treatment facility except that it has an oxygen-containing gas supply pipe for sending exhaust gas from the nitrification tank to the aeration apparatus. For example, a nitrification tank generally used can be used without limitation.

(I) Viscometer The aeration tank and the coagulation tank may be electrically connected to a control device that adjusts the amount of oxygen-containing gas to be aerated according to the viscosity of the sludge in the aeration tank. Normally, the viscosity of sludge in an aeration tank is measured by a viscometer after a sample is taken, so that automatic continuous measurement cannot be performed. In the present invention, based on the stirring speed of the stirrer of the flocculation tank, the viscosity of the anaerobic treated sludge in the flocculation tank is estimated, the viscosity of the anaerobic treated sludge during the aeration treatment is estimated, and the amount of aeration air is adjusted. You may. Specifically, for example, a current detection unit is provided in the agitation device of the flocculation tank, a stirring speed, that is, a stirring resistance is determined from the detected current, and a viscosity change of the anaerobic sludge in the aeration tank is estimated. Adjust the aeration air volume.

(J) Concentrating Device A solid-liquid separating device that forms a concentrated sludge by subjecting the coagulated sludge formed in the coagulation tank to solid-liquid separation may be provided. The solid-liquid separation device is not particularly limited, and a simple tank to which gravity concentration is applied, a centrifuge to which centrifugal concentration is applied, a separator to which flotation concentration is applied, a separator using a screen, and the like. Is mentioned. Among them, a screen having a large number of slits through which the concentrated separated liquid passes, and a large number of elliptical plates arranged in the slit to remove clogging of the slit and transport the concentrated sludge from the inflow side to the discharge side of the thickener. An elliptic plate type concentrator provided with is preferred. In the elliptic plate type concentrator, for example, the flocculated sludge received by the screen is conveyed on the screen by a number of elliptical plates rotating in the exit direction, and in this process, the concentrated separated liquid falls from the gap between the slit and the elliptical plate. The solid component in the coagulated sludge is separated and collected. Further, a mechanical structure in which a pressurizing plate for squeezing coagulated sludge on the screen is arranged at the upper part of the screen can be preferably used.

  Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

[Example 1]
In order to confirm that the injection of the iron compound improves the efficiency of the anaerobic treatment, the iron compound was injected at different concentrations, and the anaerobic treatment of the organic matter was performed. A mixture of various food production wastes was used as the organic material of the processing raw material. Ferric polysulfate was used as the iron compound. The test method is as follows.

In a methane fermentation treatment facility (facility F1) which is actually operating, raw materials are charged into an anaerobic treatment tank of 800 m ³ for ³⁰ days in HRT, and the iron concentration in the anaerobic treated sludge after the injection of the iron compound is shown in Table 1 below. An iron compound was injected so as to have a concentration as shown in Table 2, and subjected to anaerobic treatment at a temperature of 35 ° C, and the amount of generated gas and the concentration of organic acid were measured. The gas generation amount was measured using a membrane gas meter. The measurement of the organic acid concentration was performed using high performance liquid chromatography (detector: RI, separation column: Shodex RSpak KC-811, column temperature: 60 ° C., mobile phase: 0.1% phosphoric acid aqueous solution).

  Table 1 shows the test results. From these test results, when the iron concentration in the anaerobic treated sludge after the injection of the iron compound is 100 mg / L or more in terms of iron, the amount of generated gas is large, the accumulation of organic acids is small, and the anaerobic treatment is more efficient. It was confirmed that it could be stabilized.

[Example 2]
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following test was conducted to confirm that the anaerobic treatment was made more efficient, the coagulation was made more efficient, and the dehydration was made more efficient by forming the coagulated sludge and finally dewatering the coagulated sludge. went.

In the same methane fermentation treatment facility (facility F1) as in Example 1, a mixture of various food production wastes was used as a raw material, and the iron concentration in the anaerobic treated sludge after the injection of the iron compound was 63 mg / L (iron equivalent) or An anaerobic treatment was performed by injecting an iron compound so as to be 297 mg / L (in terms of iron). Next, 10 L of the anaerobic treated sludge was charged into a 20 L aeration tank, and aerated at a temperature of 35 ° C. and an aeration air flow of 0.3 m ³ -Air / (m ³ -sludge · min) for 24 hours. Next, the sampled aerated sludge was agglomerated with an amidine-based polymer flocculant and dehydrated with a belt press dehydrator. Table 2 shows the test results.

  From these test results, the anaerobic treatment can be made more efficient by injecting the iron compound so that the iron concentration in the anaerobic treated sludge after the injection of the iron compound becomes 100 mg / L (iron conversion) or more. It was confirmed that the water content could be reduced. The DO of the sludge in the aeration treatment tank was 0.0 to 0.2 mg / L, and the ORP (ORP based on the silver / silver chloride electrode) was -240 to -350 mV.

[Example 3]
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following test was conducted to confirm that the anaerobic treatment was made more efficient, the coagulation was made more efficient, and the dehydration was made more efficient by forming the coagulated sludge and finally dewatering the coagulated sludge. went.

In a methane fermentation treatment facility (facility F2) different from those in Examples 1 and 2, the raw material was charged into an anaerobic treatment tank of 1000 m ³ for 30 days at HRT, and subjected to anaerobic treatment at a temperature of 35 ° C. Using a solubilized material obtained by solubilizing a mixture of various food manufacturing wastes as a raw material, the iron concentration in the anaerobic treated sludge after injecting the iron compound into the solubilized material storage tank is 50 mg / L (iron equivalent) or 200 mg / L. An anaerobic treatment was performed by injecting an iron compound so as to obtain (in terms of iron). Ferric polysulfate was used as the iron compound.

Next, 10 L of the anaerobic treated sludge was charged into a 20 L aeration tank, and aerated at a temperature of 35 ° C. and an aeration air flow of 0.3 m ³ -Air / (m ³ -sludge · min) for 24 hours. Next, the sampled aerated sludge was agglomerated with an amidine-based polymer flocculant and dehydrated with a belt press dehydrator. Table 3 shows the test results.

  From these test results, the anaerobic treatment can be made more efficient by injecting the iron compound so that the iron concentration in the anaerobic treated sludge after the injection of the iron compound becomes 100 mg / L (iron conversion) or more. It was confirmed that the water content could be reduced. The DO of the sludge in the aeration treatment tank was 0.0 to 0.2 mg / L, and the ORP (ORP based on the silver / silver chloride electrode) was −210 to −330 mV.

[Example 4]
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following tests were performed to confirm that the coagulation sludge was formed, and finally, the coagulation sludge was dehydrated to improve coagulation efficiency and dehydration efficiency. The test method is as follows.

  In the same methane fermentation treatment facility (facility F2) as in Example 3, the iron concentration in the anaerobic treated sludge after injection of the iron compound was determined using the solubilized material obtained by solubilizing a mixture of various food manufacturing wastes as a raw material. An iron compound was injected into the solubilization storage tank so that the concentration became 200 mg / L (in terms of iron), and anaerobic treatment was performed. Ferric polysulfate was used as the iron compound.

Next, 10 L of the anaerobic treated sludge was charged into a 20 L aeration tank, and aerated at a temperature of 35 ° C. and an aeration air flow of 0.3 m ³ -Air / (m ³ -sludge · min). The aerated sludge was sampled after a predetermined aeration time. Next, the sampled aerated sludge was injected with an amidine-based polymer flocculant to cause flocculation, and then dewatered by a belt press. Table 4 shows the test results.

  From these test results, it can be seen that the aerated sludge can reduce the water content of the cake, the coagulant injection rate can be reduced, and the agglomeration of the aerated sludge with respect to the anaerobic treated sludge without aeration (aeration time 0 h). It can be confirmed that the foaming phenomenon did not occur. The aeration time was 3 to 48 hours, and the water content of the cake could be reduced, and finally the water content of the cake could be reduced to 82% or less. The anaerobic sludge without aeration was black, but the anaerobic sludge turned brown after 3 hours of aeration, and iron (II) was oxidized to iron (III) by the aeration. It was confirmed. The DO of the sludge in the aeration treatment tank was 0.0 to 0.2 mg / L, and the oxidation-reduction potential (ORP) based on the silver / silver chloride electrode was -170 to -320 mV.

[Example 5]
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following tests were performed to confirm that the coagulation sludge was formed, and finally, the coagulation sludge was dehydrated to improve coagulation efficiency and dehydration efficiency. Example 4 was different from Example 4 in the amount of aeration air. The test method is as follows.

In the same methane fermentation treatment facility (facility F2) as in Examples 3 and 4, a solubilized material obtained by solubilizing a mixture of various food production wastes was used as a raw material, and iron in the anaerobic treated sludge after injection of an iron compound was used. An anaerobic treatment was performed by injecting an iron compound into the solubilized substance storage tank so that the concentration was 200 mg / L (in terms of iron). Next, 10 L of anaerobic treated sludge was charged into a 20 L aeration tank and aerated at a temperature of 35 ° C. and an aeration air flow of 0.1 m ³ -Air / (m ³ -sludge · min). The aerated sludge was sampled after a predetermined aeration time. Next, an amidine-based polymer flocculant was injected into the sampled aerated sludge to cause coagulation, and dewatered by a belt press dehydrator. Table 5 shows the test results.

  From these test results, it can be seen that the aeration-treated sludge can reduce the water content of the cake, the coagulant injection rate can be reduced, and the foaming of the aeration-treated sludge at the time of coagulation with respect to the anaerobic treatment sludge (0h) without the aeration treatment. It can be confirmed that no phenomenon occurred. The aeration time was 3 to 48 hours, and the water content of the cake was reduced, and finally the water content of the cake was reduced to 82% or less. The anaerobic sludge without aeration was black, but the anaerobic sludge turned brown after 3 hours of aeration, and iron (II) was oxidized to iron (III) by the aeration. It was confirmed. The DO of the sludge in the aeration tank was 0.0 to 0.1 mg / L, and the ORP (ORP based on the silver / silver chloride electrode) was -240 to -310 mV.

  The results of Examples 4 and 5 are shown in FIG. From FIG. 10, it can be seen that, even with the same coagulant injection rate, the water content of the dehydrated cake decreases as the amount of aerated air increases.

[Example 6]
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following tests were performed to confirm that the coagulation sludge was formed, and finally, the coagulation sludge was dehydrated to improve coagulation efficiency and dehydration efficiency. In Examples 3 to 5, the aeration process was performed in a batch system, but in Example 6, the aeration process was performed in a continuous system. The test method is as follows.

  In the same methane fermentation treatment facility (facility F2) as in Examples 3 to 5, a solubilized material obtained by solubilizing a mixture of various food manufacturing wastes was used as a raw material, and iron in the anaerobic treated sludge after injection of an iron compound was used. An iron compound was injected into the solubilization storage tank so that the concentration became 200 mg / L (in terms of iron), and anaerobic treatment was performed. Ferric polysulfate was used as the iron compound.

Next, the anaerobic treated sludge was supplied to the 60 m ³ aeration treatment tank at 4 m ³ / h, and the aeration treatment sludge was pulled out from the aeration treatment tank at 4 m ³ / h and supplied to the coagulation tank. Aeration air volume 0.3m ³ -Air / - was ^{(m 3} sludge · min). Sulfuric acid was injected into the sludge in the aeration tank, and the pH of the sludge was controlled to 8.0 to 8.2. In the flocculation tank, the aerated sludge and the amidine-based polymer flocculant were mixed to form flocculated sludge. The coagulated sludge was dehydrated with a screw press dehydrator.

  As a comparative example, anaerobic treated sludge without aeration treatment was coagulated and dehydrated in the same manner. Table 6 shows the test results.

  From these test results, it can be seen that the aerated sludge can reduce the water content of the cake, the coagulant injection rate can be reduced, and the bubbling phenomenon during the agglomeration of the aerated sludge with respect to the anaerobic sludge without aeration. You can confirm that there was no. The anaerobic treated sludge without aeration treatment was black. The aerated sludge was brown, and it was confirmed that iron (II) was oxidized to iron (III) by the aeration. The temperature of the sludge in the aeration treatment tank was 24-38 ° C., the DO was 0.0-0.1 mg / L, and the ORP (ORP based on the silver / silver chloride electrode) was −170 to −380 mV.

[Example 7]
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following tests were performed to confirm that the coagulation sludge was formed, and finally, the coagulation sludge was dehydrated to improve coagulation efficiency and dehydration efficiency. In the present example, it was confirmed that the pH of the aerated sludge was changed to improve the efficiency of dehydration.

In the same methane fermentation treatment facility (facility F2) as in Examples 3 to 6, a solubilized material obtained by solubilizing a mixture of various food manufacturing wastes was used as a raw material, and iron in anaerobic treated sludge after injection of an iron compound was used. An anaerobic treatment was performed by injecting an iron compound into the solubilized substance storage tank so that the concentration was 200 mg / L (in terms of iron). Next, 10 L of anaerobic treated sludge was charged into a 20 L aeration tank, and aerated at a temperature of 35 ° C. and an aeration air flow of 0.1 m ³ -Air / (m ³ -sludge · min) for 9 hours. Next, sulfuric acid was injected into the aerated sludge to adjust the pH. The aerated sludge sampled with an amidine-based polymer flocculant was flocculated and dewatered with a belt press dehydrator.

  As a comparative example, the same test was performed on sludge whose pH was not adjusted. The pH of the sludge without pH adjustment was 8.6. Table 7 shows the test results.

  From these test results, it was confirmed that the moisture content of the cake can be reduced by adjusting the pH of the aerated sludge. The DO of the sludge in the aeration tank was 0.0 to 0.1 mg / L, and the ORP (ORP based on the silver / silver chloride electrode) was -240 to -310 mV.

Example 8
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following tests were performed to confirm that the coagulation sludge was formed, and finally, the coagulation sludge was dehydrated to improve coagulation efficiency and dehydration efficiency. In this example, a non-amidine polymer flocculant, a quaternary salt of dimethylaminoethyl acrylate and acrylamide (acrylate polymer flocculant) was used.

In the same methane fermentation treatment facility (facility F2) as in Examples 3 to 7, a solubilized material obtained by solubilizing a mixture of various food manufacturing wastes was used as a raw material, and iron in anaerobic treated sludge after injection of an iron compound was used. An anaerobic treatment was performed by injecting an iron compound into the solubilized substance storage tank so that the concentration was 200 mg / L (in terms of iron). Next, 10 L of the anaerobic treated sludge was charged into a 20 L aeration tank, and aerated at a temperature of 35 ° C. and an aeration air flow of 0.3 m ³ -Air / (m ³ -sludge · min) for 24 hours. Next, the aerated sludge sampled with the acrylate polymer flocculant was flocculated and dewatered with a belt press dehydrator.

  As a comparative example, a similar test was performed on sludge not subjected to aeration treatment. Table 8 shows the test results.

  From these test results, it was confirmed that the water content of the cake can be reduced by coagulating the aerated sludge with the acrylate polymer coagulant. Anaerobic sludge without aeration was black, but after 24 hours of aeration, the anaerobic sludge turned brown, and iron (II) was oxidized to iron (III) by aeration. It was confirmed. The DO of the sludge in the aeration treatment tank was 0.0 to 0.1 mg / L, and the ORP (ORP based on the silver / silver chloride electrode) was -250 to -330 mV.

[Example 9]
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following tests were performed to confirm that the coagulation sludge was formed, and finally, the coagulation sludge was dehydrated to improve coagulation efficiency and dehydration efficiency. In this example, a polymer of a quaternary salt of dimethylaminoethyl methacrylate (methacrylate polymer flocculant), which is a non-amidine polymer flocculant, was used.

In the same methane fermentation treatment facility (facility F2) as in Examples 3 to 8, a solubilized material obtained by solubilizing a mixture of various food manufacturing wastes was used as a raw material, and iron in the anaerobic treated sludge after injection of an iron compound was used. An anaerobic treatment was performed by injecting an iron compound into the solubilized substance storage tank so that the concentration was 200 mg / L (in terms of iron). Next, 10 L of the anaerobic treated sludge was charged into a 20 L aeration tank, and aerated at a temperature of 35 ° C. and an aeration air flow of 0.3 m ³ -Air / (m ³ -sludge · min) for 24 hours. Next, the aerated sludge sampled with a methacrylate polymer flocculant was flocculated and dewatered with a belt press dewatering machine.

  As a comparative example, a similar test was performed on sludge not subjected to aeration treatment. Table 9 shows the test results.

  From these test results, it was confirmed that the water content of the cake can be reduced by coagulating the aerated sludge with a methacrylate polymer coagulant. The anaerobic sludge without aeration was black, but the anaerobic sludge turned brown in 24 hours of aeration, indicating that iron (II) was oxidized to iron (III) by the aeration. confirmed. The DO of the sludge in the aeration treatment tank was 0.0 to 0.1 mg / L, and the ORP (ORP based on the silver / silver chloride electrode) was -250 to -330 mV.

[Example 10]
Perform anaerobic treatment by injecting an iron compound to form anaerobic treated sludge, then aerobically treat the anaerobic treated sludge, form an aerated treated sludge, and then coagulate the aerated treated sludge with a flocculant, The following tests were performed to confirm that the coagulation sludge was formed, and finally, the coagulation sludge was dehydrated to improve coagulation efficiency and dehydration efficiency. The test method is as follows.

  In the same methane fermentation treatment facility (facility F1) as in Example 1 and Example 2, anaerobic treatment after injecting an iron compound with a solubilized material obtained by solubilizing a mixture of various food manufacturing wastes as a raw material An anaerobic treatment was performed by injecting an iron compound into the solubilization storage tank so that the iron concentration in the sludge was 200 mg / L (in terms of iron). Ferric polysulfate was used as the iron compound. Anaerobic treatment was performed in the same methane fermentation treatment facility (facility F2) as in Example 3.

  For the aeration treatment, anaerobic treated sludge (sludge A) collected at the methane fermentation treatment facility F1 and a plurality of anaerobic treatment sludges (sludge B, sludge C, and sludge D) collected at different dates and times at the methane fermentation treatment facility F2 are used. used. As comparative examples, anaerobic treated sludge (sludge E) collected from sewage treatment plant S1 and anaerobic treated sludge (sludge F) collected from sewage treatment plant S2 were used.

  In the aeration treatment, 10 L of anaerobic treated sludge was charged into a 20 L aeration tank and aerated at a temperature of 35 ° C. The aerated sludge was sampled, polymer coagulant was injected and coagulated, and then dewatered with a belt press dewatering machine.

  Table 10 shows the properties of each sludge, aeration conditions, dehydration conditions, and cake moisture content. The analysis of TS and SS was based on JIS K-0102, and the viscosity was measured at 35 ° C. and 60 rpm using a B-type rotational viscometer.

From these results, it was confirmed that the water content of the cake can be reduced by aerating the anaerobic treated sludge having a TS concentration of 25 g / L or more and an SS concentration of 5 g / L or less than the TS concentration. did.

Claims (4)

An anaerobic treatment step of anaerobically treating organic matter to form anaerobic treated sludge;
An aeration treatment step of contacting the oxygen-containing gas with the anaerobic treatment sludge to form an aeration treatment sludge;
A flocculating step of injecting a flocculant into the aerated sludge to form a flocculated sludge;
A dewatering step of dewatering the coagulated sludge;
A nitrification step of nitrifying ammonia contained in the dehydration separation liquid from the dehydration step,
Before the anaerobic treatment step or in the anaerobic treatment step, inject an iron compound into the organic matter,
In the aeration treatment step, the oxidation-reduction potential (oxidation-reduction potential based on a silver / silver chloride electrode) of the aeration-treated sludge is controlled to -100 mV or less, and the anaerobic treatment sludge containing an iron compound and the oxygen-containing gas are mixed. By contacting, the iron (II) contained in the anaerobic treated sludge is oxidized, and the iron (III) oxidized in the coagulation step is used as a coagulant,
An organic matter processing method, wherein exhaust gas from the nitrification step is reused as an oxygen-containing gas in the aeration step. The method for treating organic matter according to claim 1, wherein the anaerobic treated sludge has a TS concentration of 25 g / L or more and an SS concentration of 5 g / L or less lower than the TS concentration. Iron compound injection means for injecting an iron compound into the organic matter,
An anaerobic treatment tank for anaerobic treatment of organic matter in the presence of iron (II) to form anaerobic treatment sludge;
An aeration tank having an oxidation-reduction potential measuring device, and bringing an oxygen-containing gas into contact with the anaerobic treated sludge to oxidize iron (II) to iron (III) to form an aerated treated sludge containing iron (III) When,
Injecting a coagulant into the aerated sludge, a coagulation tank to form coagulated sludge,
A dehydration device for dehydrating the coagulated sludge,
A nitrification tank for nitrifying ammonia contained in the dehydration separation liquid from the dehydration device,
3. The processing apparatus according to claim 1, further comprising an oxygen-containing gas supply pipe that supplies exhaust gas from the nitrification tank to the aeration tank. 4. The iron compound injecting means is the anaerobic treatment tank, or at least one tank selected from an organic matter storage tank, a solubilization tank, and a solubilized matter storage tank provided in a preceding stage of the anaerobic treatment tank, or at least one of the at least one tank. That is provided in any one or two or more of pipes connecting between the tank and the anaerobic treatment tank, or pipes connecting between at least two tanks of the organic matter storage tank, the solubilization tank, and the solubilized matter storage tank. The processing apparatus according to claim 3, wherein:

Images