JP4289454B2 - Methane fermentation process and methane fermentation system - Google Patents

Description

  The present invention relates to a methane fermentation process and a methane fermentation system, and more particularly, to a methane fermentation process and a methane fermentation system for efficiently removing heavy metals and the like from a fermentation liquid obtained by subjecting organic waste to methane fermentation. .

  Organic waste such as food waste, livestock manure, and sewage sludge is subjected to methane fermentation treatment, composted, and returned to farmland. However, the methane fermentation broth may contain salts such as heavy metals and salt, which may hinder recycling of organic waste. In particular, for heavy metals with low solubility, the possibility of accumulating in the soil cannot be discarded, and there is concern that it may cause soil contamination.

  For salt contained in food waste in a relatively large amount, when it is composted after methane fermentation treatment and reduced to farmland, the concentration in the soil gradually decreases due to elution by rainwater and penetration into the underground, causing salt damage. Although it is thought that it is difficult to produce, depending on the regional characteristics and weather conditions, it may contain salts with concentrations that are clearly unsuitable for agricultural land reduction.

  In view of the above situation, a method for treating organic waste in which methane fermentation treatment is performed after desalting the organic waste containing salts has been proposed (for example, Patent Document 1).

JP 2002-273488 A

  The method described in Patent Document 1 is a method of desalinating organic waste having low fluidity before methane fermentation, but organic waste before fermentation has a large viscosity, and salts (ions) and heavy metals Is present in a state where it is difficult to move, the removal efficiency is low, and in particular, the removal effect of heavy metals can hardly be expected. In addition, a high-pressure pump is required to process organic waste with a high viscosity, and power consumption is increased, which is not economical. If the organic waste is refined and water is added and diluted, the viscosity can be reduced, but if the water during the methane fermentation process becomes too much, the equipment size must be increased. Absent.

  An object of the present invention is to provide a method for efficiently removing salts and heavy metals from a methane fermentation liquid when organic waste is subjected to methane fermentation treatment and reused as compost or the like.

  In order to solve the above-mentioned problems, a first aspect of the present invention is a methane fermentation process characterized in that organic waste is subjected to methane fermentation treatment, and the fermentation solution is subjected to electrodialysis treatment and / or electrodeposition treatment. . By electrodialysis, a part of the organic waste-derived salts and heavy metals contained in the methane fermentation liquid can be efficiently removed. Similarly, heavy metals can be efficiently removed by electrodeposition. Therefore, the methane fermentation broth after electrodialysis or electrodeposition has a low content of salt and heavy metals, and even when composted and applied to soil, there is no problem of accumulation of salt damage and heavy metals. Furthermore, since electrodialysis and electrodeposition are performed on the liquid after methane fermentation, it is an economical process with good treatment efficiency and low energy consumption.

  According to a second aspect of the present invention, in the first aspect, a methane fermentation process characterized by performing an electrodialysis treatment or an electrodeposition treatment after adjusting the oxidation-reduction state and / or hydrogen ion concentration of the fermentation broth. It is. By adjusting the oxidation-reduction state and hydrogen ion concentration of the methane fermentation broth, heavy metals contained in the methane fermentation broth can be ionized to be in a dissolved state. Therefore, the removal efficiency by electrodialysis or electrodeposition can be greatly improved.

  According to a third aspect of the present invention, in the first or second aspect, the heavy metals removed from the fermentation liquor by the electrodeposition treatment are eluted by reversing the polarity of the voltage applied to the electrodeposition tank and recovered. This is a methane fermentation process. Thereby, heavy metals precipitated and separated from the methane fermentation liquid can be easily recovered.

  According to a fourth aspect of the present invention, in a water treatment facility, sludge generated from the facility is subjected to methane fermentation treatment, the fermentation solution is electrodialyzed, and water from the water treatment facility is placed on the concentrate side in the electrodialysis treatment. It is a methane fermentation process characterized by supplying. In electrodialysis treatment, a large amount of water is required as a concentrate, and the treatment is also necessary. In the fourth aspect of the present invention, the water of the water treatment facility is used as the concentrate by cooperating with the water treatment facility. Since the water supply means and the treatment means are secured, the process is efficient.

  The fifth aspect of the present invention includes a methane fermentation tank for subjecting organic waste to methane fermentation, an electrodialysis apparatus for electrodialyzing the fermentation liquid, and / or an electrodeposition apparatus for electrodepositioning the fermentation liquid. This is a methane fermentation system. This methane fermentation system is suitable for carrying out the process of the first aspect.

  According to a sixth aspect of the present invention, in the fifth aspect, an oxidation-reduction potentiometer, a sulfide ion detector, or a pH electrode is provided as a detector before the electrodialysis apparatus or the electrodeposition apparatus. It is a methane fermentation system. This methane fermentation system is suitable for carrying out the process of the second aspect.

  By electrodialysis, a part of the organic waste-derived salts and heavy metals contained in the methane fermentation liquid can be efficiently removed. Similarly, heavy metals can be efficiently removed by the electrodeposition process. Therefore, the methane fermentation broth after electrodialysis or electrodeposition has a low content of salt and heavy metals, and even when composted and applied to soil, there is no problem of accumulation of salt damage and heavy metals. Furthermore, since electrodialysis and electrodeposition are performed on the liquid after methane fermentation, it is an economical process with good treatment efficiency and low energy consumption.

<Organic waste>
In the present invention, organic waste includes, for example, livestock waste, green farm waste, wastewater treatment sludge, and the like. Examples of livestock waste include livestock manure, carcass and / or processed products thereof. More specifically, livestock carcasses such as cattle, sheep, goats and chickens, and bones separated therefrom. In addition to meat, fat, internal organs, blood, brain, eyeballs, skin, hoofs, horns, etc., crushed material of bones, meat, etc. of livestock carcasses represented by meat and bone meal, meat meal, bone meal, blood meal In addition, a dried product obtained by drying blood or the like is also included. In addition to household garbage, green agricultural waste includes agricultural and industrial waste, food processing waste, etc. as industrial waste.

<Heavy metals and salts>
Examples of heavy metals to be removed in the present invention include zinc contained in livestock manure, cadmium, lead, copper, chromium, etc. contained in sewage sludge. Examples of the salts include sodium chloride contained in food waste.

<Fermentation process>
In the process of the present invention, prior to methane fermentation, depending on the state of organic waste as a raw material, a crushing / sorting step can be performed as a pretreatment as necessary. The crushing / sorting step can be performed by, for example, fractionating crushing as shown below, or crushing the entire amount.
In the case of fractional crushing, a crushing / separating machine is used to collect a portion that can be easily crushed in organic waste as a slurry together with a liquid. On the other hand, parts that are difficult to crush are collected separately as a lump. The water content of the slurry is 70 to 90% by weight, and the water content of the lump is about 40 to 60% by weight. The crushing / separating machine crushes organic solids by a shearing force and a pulling force, and a two-axis type or a three-axis type cutter can be used. When animal carcasses such as cattle are used as raw materials, it is preferable to crush the triaxial type from the viewpoint of the fineness and uniformity of the crushed material.

  The mixed plastics and sheets to be sorted and removed can be removed by mesh sorting, wind sorting (wind sorting), or the like.

  In the case of pulverizing the entire amount, for example, the entire object is crushed using a crusher such as a disposer. The water content is 60 to 70% by weight as an example, but takes a wide range depending on the type of organic waste.

  Methane fermentation can be applied to any of a so-called medium temperature type, a high temperature type, a slurry (wet) type, and a dry (dry) type.

  The fermenter is composed of a tank in which air is completely shut off in the latter stage even in the case of a fermentation process using a two-tank system in order to maintain the activity due to the anaerobic methane fermentation bacteria. The shape and operating conditions of the fermenter vary depending on the solid concentration (usually in the range of 3 to 40% by weight) and the fermentation temperature (usually 37 ° C for medium temperature fermentation and 55 ° C for high temperature fermentation). For example, in the case of a raw material having a high water content (up to a solid concentration of 10% by weight) mixed with washing waste water, a wet type complete mixing method fermenter, a raw material having a low water content (solids concentration of 30 to 30%) 40 wt%), it is preferable to use a so-called dry type plug flow type (extrusion type) fermenter.

  In addition to the recovery means for recovering the biogas to be produced, it is preferable that the fermenter is provided with a heating means for keeping warm if necessary. In addition, the biogas recovery means may be provided with a desulfurization apparatus as required. Those having a known configuration can be used.

  In the case of a raw material with a high water content (solids concentration up to about 10% by weight), a complete mixing type fermenter is used, and in a high-temperature methane-fermenting bacterium (optimum temperature 55 ° C.), the retention time (Retention Time) is 10 About 15 to 15 days, with medium temperature methane fermentation bacteria (optimum temperature 37 ° C.), the residence time can be about 20 to 30 days.

  In the case of a raw material having a low water content (solids concentration of 30 to 40% by weight), the solid content concentration of the object to be treated is adjusted to 30 to 40% by weight to adjust the hardness to such an extent that an extrusion type fermenter can be used. About residence time, it can set similarly to the case of high moisture content. Further, for the adjustment of the C / N ratio, some organic components can be introduced as necessary.

  The fermentation residue after methane fermentation of high water content type is, for example, a liquid containing a moisture content of 95% by weight and a solid content of about 5% by weight, and various amino acids derived from anaerobic microorganisms and their metabolites Contains a large amount of organic acids.

  A solid-liquid separation step of the fermentation residue can be provided as necessary after methane fermentation. For the solid-liquid separation, an apparatus capable of increasing the slurry concentration, such as a decanter, a coagulation sedimentation tank, a centrifugal dehydrator, a screw press, and a membrane separator, can be used, and is selected according to the properties of the fermentation residue.

  In the above methane fermentation, the biogas produced by fermentation varies depending on the type of organic waste, but typically contains about 60% by weight of methane and about 40% by weight of carbon dioxide. It can be used as fuel for steam boilers, gas turbines, fuel cells and the like. Among these, in particular, by employing a cogeneration system such as a gas engine, a gas turbine, or a fuel cell, heat and electric power can be recovered using biogas as fuel.

  The heat recovered using biogas as fuel is supplied in the form of steam, for example, and can be used as a heat source for heating the methane fermentation tank or concentrating the fermentation broth.

  In addition, in fermenters and concentrators, power is consumed as power for decompression devices such as vacuum pumps, stirring devices, etc., but it is possible to cover all of the power at this time with power generated by cogeneration. Electricity can be diverted to other uses.

<Electrodialysis treatment and electrodeposition treatment>
Electrodialysis treatment and electrodeposition treatment (also referred to as electrodeposition treatment or electrolytic treatment) can be carried out according to conventional methods. There is no restriction | limiting in particular as an electrodialysis apparatus or an electrodeposition apparatus, The thing of a known structure can be used conveniently.

  In the present invention, prior to electrodialysis or electrodeposition, it is preferable to adjust the oxidation-reduction state and / or hydrogen ion concentration of the fermentation broth. In order to efficiently remove heavy metals in the electrodialysis method and electrodeposition tank (electrodeposition / elution tank), it is important that the heavy metals are dissolved (ionized). For example, arsenic and iron are easily eluted in a reducing atmosphere, chromium and mercury are easily eluted in an oxidizing atmosphere, and lead and cadmium are significantly improved in solubility at a low pH value (for example, about pH 6 or less). Zinc is highly soluble at low pH (eg, about pH 6 or lower) or high pH (eg, about pH 8 or higher).

  Therefore, by adjusting the oxidation-reduction state and pH of the fermentation broth, dissolution of heavy metals in the fermentation broth can be promoted. The optimum value that expresses high solubility varies greatly depending on the heavy metal of interest, the coexisting components of the fermentation broth, the acceptable cost, and the like. Moreover, it is preferable to make especially the fermentation liquid distribution | circulation time from the adjustment tank mentioned later to a detector into the time until it reaches | attains practically sufficient equilibrium, and can take several tens of seconds normally.

  In the adjustment of the redox state, the anaerobic / aerobic degree is first adjusted in the adjustment tank, and then the redox state of the fermentation broth is detected using a detector. Thereafter, the fermentation broth is fed to an electrodialysis tank and / or an electrodeposition tank (electrodeposition / elution tank). That is, as an example of the processing procedure, the order is the adjustment tank → detector → electrodialysis tank / electrodeposition tank. Here, as a detector, a redox electrode (a detector comprising a noble metal electrode such as platinum or gold, a carbon electrode, a reference electrode such as a silver-silver chloride electrode, or a temperature detection electrode as a detection electrode) or sulfide ion An ion electrode (a detector comprising a solid electrolyte electrode such as silver halide, a reference electrode, and a temperature detection electrode) can be used. These detectors may be provided in the adjustment tank, but are preferably provided on a path (pipe) from the adjustment tank to the electrodialysis tank or the electrodeposition tank.

  In the adjustment tank, the anaerobic / aerobic level can be adjusted by performing the following operations. In the case of aerobic, it can be adjusted, for example, by injecting air into the upstream side of the fermentation liquor pipe incorporating a static mixer or the like. In the case of anaerobic, for example, a part of the fermentation liquor pipe is used as a jacket type heat exchanger, and the temperature of the fermentation liquor is temporarily raised to about 50 ° C. through warm water or steam through the jacket part. This accelerates the decomposition of organic matter in the fermentation broth and consumes oxygen.

  Similarly to the above, the pH can be controlled by combining, for example, a pH electrode, an acid / alkali injection device, a mixer, and the like. Examples of the acid and alkali to be injected for pH adjustment include acids such as hydrochloric acid and sulfuric acid, and alkalis such as sodium hydroxide and calcium hydroxide. In addition, as needed, operation which readjusts pH (for example, returns to original pH) after an electrodialysis and electrodeposition (electrodeposition) process can be performed.

  The heavy metal removed from the fermentation broth by the electrodeposition treatment can be eluted in the recovered liquid by reversing the polarity of the voltage applied to the electrodeposition tank. The eluted heavy metals can be recovered by a method such as insolubilization by adding a chelating agent or the like and adsorption to an adsorbent.

Hereinafter, preferred embodiments of the methane fermentation process of the present invention will be described with reference to the drawings.
First embodiment:
According to FIG. 1, organic waste such as livestock manure is subjected to methane fermentation, and heavy metals such as zinc are removed by electrodialysis and / or electrodeposition.
First, livestock manure such as pigs is once stored in a receiving tank and then introduced into a pretreatment tank where crushing / pasting, pre-fermentation, and the like are performed. The pre-treated swine manure is introduced into the digestion tank.

  When a predetermined fermentation period elapses in the digestion tank and the anaerobic digestion is completed, the methane fermentation solution is extracted and guided to the concentration tank. In the concentration tank, the supernatant is collected by gravity sedimentation, and the precipitate is transferred to the adjustment tank.

  In the adjustment tank, the redox state and pH of the fermentation broth are adjusted by aeration or the like. By this operation, heavy metals contained in the methane fermentation liquid can be ionized, and the efficiency of electrodialysis and electrodeposition can be increased. For example, in aeration, air is introduced into a methane fermentation broth to achieve aerobic conditions, and sulfides and / or sulfide ions are oxidized. The aeration is preferably performed while monitoring the amount of sulfide ions using a detector.

  The methane fermentation broth treated in the adjustment tank is measured by its detector for its oxidation-reduction potential, sulfide concentration, pH, etc. Introduce sequentially. Thereby, desalination of methane fermentation liquid and removal of heavy metals are performed. Metals such as zinc in manure are in a dissolved state mainly by forming complex ions with ammonia, and are removed by electrodialysis or electrodeposition. In the methane fermentation treatment of livestock manure such as pigs and protein-centered food waste, a relatively large amount of ammonia is produced in the fermentation broth, so that zinc is easily dissolved as an ammonia complex. Heavy metals deposited in the electrodeposition tank by electrodeposition are eluted by reversing the polarity of the voltage applied to the electrodeposition tank and recovered in the heavy metal recovery tank.

  The methane fermentation liquid that has passed through the electrodialysis tank and / or the electrodeposition tank is introduced into a composting facility and composted. Since the compost obtained in this way has a low salt content and heavy metals have been removed, there is no fear of causing salt damage or contamination with heavy metals even when reduced to farmland.

Second embodiment:
As shown in Fig. 2, organic waste such as garbage and sewage sludge is composted by methane fermentation. Heavy metals such as arsenic are removed by electrodialysis, and mercury and lead are removed by electrodeposition. Process.

  First, organic waste such as garbage is introduced into the pretreatment tank from the receiving tank, where crushing, pasting, pre-fermentation, and the like are performed. The pre-treated garbage paste is introduced into the digestion tank. On the other hand, water treatment sludge is directly introduced into the digestion tank, mixed with garbage paste, and methane fermentation is performed.

  When the predetermined fermentation period has elapsed and the anaerobic digestion has been completed, the methane fermentation solution is extracted and guided to the concentration tank. In the concentration tank, the supernatant is collected by gravity sedimentation, and the precipitate is transferred to the adjustment tank.

  Next, in the adjustment tank, the redox state and pH of the fermentation broth are adjusted. By this operation, heavy metals contained in the methane fermentation liquid can be ionized, and the efficiency of electrodialysis and electrodeposition can be increased. For example, when arsenic or the like is assumed as a heavy metal contained in the fermentation broth, it is adjusted to an oxidation-reduction state (for example, pH 6 or less, oxidation-reduction potential −50 mV or less) in which arsenic is easily eluted. In the case of arsenic, it is easier to elute the fermentation broth in a slightly anaerobic state and it is easier to remove by electrodialysis. However, in a complete anaerobic state, it is often a suspension as a sulfide and is difficult to remove by electrodialysis. The charged arsenic colloid can be removed by electrodeposition.

  Moreover, when pH adjustment is required before electrodialysis or electrodeposition, it is preferable to inject | pour an acid or an alkali using a metering pump similarly to the case where aeration is performed in an adjustment tank.

  The methane fermentation broth after the treatment in the adjustment tank is measured by a detector to measure the oxidation-reduction potential, sulfide concentration, pH, etc. Introduce. Thereby, desalination of methane fermentation liquid and removal of heavy metals are performed. Heavy metals deposited in the electrodeposition tank by electrodeposition are eluted by reversing the polarity of the voltage applied to the electrodeposition tank and recovered in the heavy metal recovery tank. In this embodiment, water from the water treatment facility can be supplied to the concentrate side of electrodialysis. Thereby, the process can be operated efficiently.

  The methane fermentation liquid that has passed through the electrodialysis tank and the electrodeposition tank is introduced into a composting facility and composted. Since the compost obtained in this way has a low salt content and heavy metals have been removed, there is no fear of causing salt damage or contamination with heavy metals even when reduced to farmland.

  As shown in FIG. 2, since the methane fermentation system of the present invention and the water treatment facility are linked, the concentrated water obtained by electrodialysis can be diluted with the water of the water treatment facility, so that the treatment is very easy. Become. In addition, since the anode chamber solution and cathode chamber solution used for electrodialysis and the counter electrode water used for electrodeposition can be introduced from the water treatment facility, an efficient system is obtained.

  EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited by these. In Examples and Comparative Examples, electrodialysis tanks and electrodeposition tanks having the following configurations were used.

<Electrodialysis tank>
A small flow cell having a sample flow portion of 10 mm in width, 100 mm in length, and a thickness of 1 mm in each chamber was used as an electrodialysis tank. This electrodialysis tank is composed of presser plate / electrode plate / spacer (concentration chamber) / diaphragm / spacer (dilution chamber) / diaphragm / spacer (concentration chamber) / electrode plate / presser plate.

<Electrodeposition tank>
An electrodeposition tank in which a permeation chamber having a thickness of 2 mm was made of an electrode plate and a diaphragm was used. This electrodeposition tank is composed of press plate / electrode plate (working electrode, zinc electrodeposition electrode) / spacer (2 mm thickness) / spacer (2 mm thickness) / electrode plate (counter electrode) / press plate.

Comparative Example 1
A micro sample of garbage (garbage paste) was directly electrodialyzed and then subjected to methane fermentation.
Garbage paste was passed through the dilution chamber of the electrodialysis tank and the fermentation broth was passed through the concentration chamber, respectively, and a current of 20 mA was passed. By circulating the garbage paste through this electrodialysis tank, the salt (NaCl) contained in the garbage on a dry matter basis was reduced to 1.5% by weight. Ratio (current efficiency) was 79%]. Although the salt removal efficiency was good, the required outlet pressure of the pump in this experiment reached 0.3 kPa because of high-pressure transport to the electrodialysis tank. Moreover, due to the pressure feeding to the electrodialysis tank, leakage of the fermentation broth occurred from the electrodialysis tank during the experiment (in contrast to this, in the examples of the present invention described later, the required pump pressure is usually 0.1 kPa or less). .

Example 1
Garbage treatment was carried out according to FIG. After separating and refining raw garbage before desalting, methane fermentation treatment in the digestion tank, separating the supernatant in the concentration tank, and adjusting the redox state and pH of the fermentation liquid in the adjustment tank A desalting experiment using an electrodialysis tank was performed. As a result, the salt content of the dry matter base decreased from 3.0% by weight to 1.2% by weight with a current of 20 mA. The current efficiency at this time was calculated to be 62%. Even when this dialysis treatment was performed, the amount of change (decrease) in the amount of total nitrogen and potassium as fertilizer components was 10% by weight or less.

  That is, salt components (sodium ions and chloride ions) coexisting excessively were preferentially removed by electrodialysis, and potassium ions having a lower concentration were hardly removed. From this result, it was found that the effectiveness can be maintained even when aging as a fertilizer.

Example 2 and Comparative Example 2
According to FIG. 4, pig manure was processed. First, swine manure was once stored in a receiving tank and then introduced into a pretreatment tank, where crushing / pasting, pre-fermentation, and the like were performed. The swine manure that had been pretreated was introduced into the digestion tank and fermented with methane. After this fermentation broth was introduced into a concentration tank and the supernatant was separated, it was subjected to aeration treatment for 5 minutes in an adjustment tank, and further introduced into an electrodialysis tank to examine the removal of zinc. When energization of 20 mA was performed in the electrodialysis tank, the zinc content in the fermentation broth decreased from 0.02 wt% to 0.01 wt% on a dry matter basis (Example 2-1).

  On the other hand, the case where an oxidation reduction electrode was inserted into the methane fermentation broth and aeration treatment was performed for about 8 minutes until the indicated value showed a positive value was also examined in parallel (Example 2-2). When this solution was similarly energized with 20 mA and treated in an electrodialysis tank, the zinc content was reduced to 0.005% by weight on a dry matter basis.

  Further, as Comparative Example 2, when the electrodialysis treatment was performed without performing the aeration treatment at all, zinc could not be removed. This was thought to be because sulfide ions were generated in anaerobic conditions and bound to zinc, preventing its ionization.

Example 3
According to FIG. 5, the sewage treatment sludge was treated. Sludge from the sewage treatment plant was introduced into the digestion tank and subjected to methane fermentation. The digested sludge was separated into the supernatant in a concentration tank and introduced into an electrodialysis tank in an anaerobic state for demetalization treatment. In the electrodialysis tank, when 20 mA was energized, the total arsenic concentration in the digested sludge could be reduced from 108 ppm to 5 ppm.

  When the digested sludge was left in the air for about 1 hour before electrodialysis, the total arsenic concentration could only be reduced to 70 ppm. Digested sludge left in the air for about 1 hour had a redox electrode potential shifted to the positive side from −50 mV or more to about −5 mV. For this reason, it was considered that the solubility of arsenic was lowered.

Example 4
According to FIG. 6, methane fermentation treatment and electrodeposition treatment of garbage were performed. The fermented liquor pretreated and fermented in methane in the same manner as in Example 1 was separated in the supernatant in the concentration tank, adjusted in the redox state and / or pH in the adjustment tank, and then passed through the electrodeposition tank.

  A methane fermentation broth (slurry) was circulated on both the working electrode side and the counter electrode side of the electrodeposition tank, and a current of 20 mA was applied. As a result of electrodeposition, the zinc concentration at the outlet of the electrodeposition tank was 0.002% by weight or less on a dry matter basis. Next, when the DC voltage applied to the electrodeposition tank was reversed, it was observed that zinc exceeding 0.05% was eluted temporarily. As a result, it has been clarified that heavy metals after methane fermentation can be treated and recovered by electrodeposition / elution treatment, which is a problem in reducing agricultural land.

  The present invention has been described above with reference to various embodiments. However, the present invention is not limited to the above embodiments, and can be applied to other embodiments within the scope of the invention described in the claims. It is.

  The methane fermentation process and the methane fermentation system of the present invention can be used for methane fermentation treatment of organic waste to make fertilizer and the like.

It is a block diagram explaining the outline | summary of the process which concerns on 1st embodiment of this invention. It is a block diagram explaining the outline | summary of the process which concerns on 2nd embodiment of this invention. FIG. 3 is a block diagram illustrating an overview of a process according to the first embodiment. FIG. 10 is a block diagram illustrating an outline of a process according to a second embodiment. FIG. 10 is a block diagram illustrating an outline of a process according to a third embodiment. FIG. 10 is a block diagram illustrating an outline of a process according to a fourth embodiment.

Claims (1)

  In a water treatment facility, methane is subjected to methane fermentation treatment of sludge generated from the facility, and the fermentation solution is electrodialyzed, and water from the water treatment facility is supplied to the concentrate side in the electrodialysis treatment Fermentation process.

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