JP2005125320A - Treatment method and apparatus for organic waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating organic waste which remarkably reduce a residue discharged from a process for producing valuable material by using microorganisms and have extremely low environmental load. <P>SOLUTION: The method and apparatus for treating the organic waste are characterized in that, in the organic waste treatment method comprising the process for producing the valuable material by using the microorganisms and a waste liquid treatment process for treating waste liquid containing the residue discharged from the process for producing the valuable material, the whole or a part of the waste liquid containing the residue, discharged from the valuable material production process, is fed to a hydrothermal electrolysis process for supplying a direct current, at a temperature not less than 100°C and below the critical temperature of the waste liquid, under the pressure making the waste liquid maintain its liquid phase. It is preferable that hydrogen gas is recovered in the hydrothermal electrolysis process and the waste liquid treatment process comprises a phosphorus and/or nitrogen removal process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for treating a waste liquid containing a residue discharged from a process of recovering valuable materials using microorganisms.

  Technology to produce valuable materials such as alcohol using microorganisms has been used in the industry as a fermentation industry, but in recent years, it is a resource recovery type for organic waste such as garbage, food processing residues, and sewage sludge. As a treatment technology, and as an effective utilization technology of woody biomass such as thinned wood and agricultural residue, it has been attracting attention.

  In the production of valuable materials (fermentation) using microorganisms, it is necessary to supply raw materials (substrates) suitable for the microorganisms that produce the target product. When using woody biomass, pre-treatment steps such as solid grinding, polymer solubilization, and saccharification are essential before the fermentation process, but organic waste containing solids is treated with methane fermentation. Also, various pretreatment techniques for promoting methane fermentation are being studied. However, when an organic waste having a complicated composition is used as a raw material, it is not always possible to convert all the organic matter into a target substance. Further, in the pretreatment process, in order to thoroughly convert the raw material to a low molecular weight compound that can be used by microorganisms, a large amount of energy is consumed, which is not practical.

On the other hand, in fermentation, since a part of the substrate is used for the growth of microorganisms, surplus cells are generated. When microorganisms are immobilized and used, the amount of growth is expected to be extremely small. However, in such a case as well, the cells need to be renewed, so that it is still the same that excessive cells are generated periodically.
That is, in the technology for producing valuables using microorganisms, especially when organic wastes with complex compositions are used as raw materials, surplus cells and raw material undegraded are included from the production process of valuable materials. The residue is always discharged. Conventionally, waste liquid (sludge) containing these residues is disposed of as industrial waste, or after post-treatment such as aerobic biological treatment, solid-liquid separated treated water is discharged, solids are surplus It was disposed of as industrial waste as sludge.

  In recent years, the area of industrial waste disposal sites has become tight, and it has become necessary to significantly reduce the amount of excess sludge disposal. In organic wastewater treatment, some of the excess sludge is treated with ozone treatment or ultrasonic treatment. A process has been developed to reduce the amount of excess sludge generated by returning to a biological treatment tank after a solubilization step by physicochemical treatment or microbial treatment such as thermophilic bacteria.

  However, in the production of valuable materials (fermentation) using microorganisms, a substrate suitable for fermentation microorganisms is necessary as described above, and even if a fermentation residue containing surplus cells and undegraded products is solubilized, Not all are used by microorganisms. In particular, when the substrate is limited or when the fermenting microorganisms are vulnerable to contamination with bacteria, it is not realistic to return the waste solution solubilized liquid containing the residue to the biological reaction process.

  In addition, when aerobic biological treatment is performed as a post-treatment of waste liquid (sludge) containing these residues, a high-capacity device and aeration energy are required because the organic matter concentration is high. In addition, if the valuables to be collected have a composition that does not contain nitrogen, such as alcohol or methane, the balance between the organic matter in the waste liquid (sludge) containing the residue and the concentration of nitrogen and phosphorus is poor, and biologically It is difficult to carry out the simultaneous treatment with phosphorus and nitrogen, and in particular, removal of nitrogen requires organic substances in the denitrification step, so that it is often necessary to add methanol or the like, and there has been an economic problem.

  As described above, conventionally, waste liquid (sludge) containing these residues has been mainly disposed of as industrial waste, but it has become necessary to significantly reduce the amount of disposal. In addition, the waste liquid (sludge) containing these residues is a waste liquid (sludge) that is extremely difficult to treat, such as high organic matter concentration and poor balance between organic matter and nitrogen or phosphorus concentration, so an economical treatment method has been established. There wasn't.

  The present invention has been made in view of such a conventional problem, and organic waste that significantly reduces the residue discharged from the process of producing valuable materials using microorganisms and has an extremely low environmental load. It is an object of the present invention to provide a processing method and apparatus.

  In order to solve the above-mentioned problems, the present inventors reduced the total amount or a part of the waste liquid including the residue at a temperature at which the waste liquid maintains a liquid phase at a temperature of 100 ° C. or higher and lower than the critical temperature of the waste liquid. It has been found that the organic matter concentration and nitrogen concentration of the waste liquid can be greatly reduced by hydrothermal electrolysis that supplies a direct current, and that hydrogen gas can be recovered at the same time, and the present invention has been completed.

That is, this invention solved the said subject by the following means.
(1) Producing valuables in an organic waste processing method comprising a process of producing valuables using microorganisms and a waste liquid treatment process for treating waste liquid containing residues discharged from the process of producing valuables Hydrothermal electricity that supplies direct current under a pressure at which the waste liquid maintains a liquid phase at a temperature that is 100 ° C. or higher and lower than the critical temperature of the waste liquid. A method for treating organic waste, wherein the organic waste is treated in a decomposition step.
(2) The organic as described in (1) above, wherein the waste liquid treatment step for treating a waste liquid containing a residue discharged from the step of producing the valuable material includes a step of removing phosphorus and / or nitrogen Waste disposal method.

(3) An apparatus for producing valuable materials using microorganisms, an apparatus for treating waste liquid containing residues discharged from the process of producing valuable materials, and a waste liquid containing residues discharged from apparatuses producing valuable materials Supplying at least a pair of electrodes for electrolysis inside a reactor capable of withstanding the pressure at which the waste liquid maintains a liquid phase at a temperature of 100 ° C. or more and less than the critical temperature of the waste liquid, supplying all or part of the waste liquid An organic waste treatment apparatus comprising a hydrothermal electrolysis apparatus provided.
(4) In the said hydrothermal electrolysis apparatus, a solar cell equipment and / or a heat exchange equipment are utilized, The organic waste processing apparatus as described in said (3) characterized by the above-mentioned.
(5) The apparatus according to (3) or (4), wherein the apparatus for treating the waste liquid containing the residue discharged from the process of producing the valuable material includes equipment for removing phosphorus and / or nitrogen. Organic waste treatment equipment.

In the present invention, the residue discharged from the process of producing valuable materials such as amino acids, organic acids, alcohols, hydrogen or methane using microorganisms is greatly reduced, and organic wastes with extremely low environmental impacts are produced. A processing method can be provided. In particular, liquid fuels such as alcohol produced from unused resources including organic waste, gaseous fuels such as hydrogen and methane, and industrial raw material production processes such as lactic acid are used to discharge waste liquid containing a large amount of residues. Alternatively, the effect of reducing the environmental load is more exhibited, and can greatly contribute to the reduction of CO ₂ emissions.

  Any valuable material produced using a microorganism, such as amino acids, organic acids, alcohols, hydrogen, or methane, may be used as the valuable material produced in the process of producing the valuable material using the microorganism of the present invention. In particular, liquids such as alcohol produced from unused resources including organic waste, gaseous fuels such as hydrogen and methane, and industrial raw materials such as lactic acid discharge waste liquids that contain a large amount of residue. Therefore, it is more preferable.

  In the present invention, as a preferred embodiment of producing a gaseous fuel such as hydrogen or methane from organic waste as a valuable material production process using a biological method, an acid fermentation method, a hydrogen fermentation method, a methane fermentation method, etc. Can be mentioned. All of these are fermentation methods called anaerobic treatment methods, and hydrogen is a valuable material in an anaerobic atmosphere at a temperature of 30 to 70 ° C., a pH of 5 to 8.5, and a redox potential of −100 to −600 mV. And gaseous fuels such as methane. In these anaerobic fermentation systems, microbial cells (excess sludge) and ammonia nitrogen are also produced, and solids that are hardly decomposable remain as undegraded residues.

  Here, the hydrogen fermentation method is a biological reaction process in which hydrogen is generated in an anaerobic fermentation process such as acid fermentation, ethanol fermentation, and lactic acid fermentation after the solid matter of organic waste is hydrolyzed. In the hydrogen fermentation step, the reaction temperature is preferably 30 to 70 ° C., pH 4.5 to 7, more preferably pH 5 to 6, and hydraulic residence time (HRT) 1 to 5 days. In particular, depending on the type of organic waste, the solubilization step tends to be rate-determining, and therefore it is preferable to carry out the reaction at a temperature of 45 to 70 ° C. for 2 to 5 days. In processes such as acid fermentation, lactic acid fermentation, ethanol fermentation, hydrogen fermentation, in addition to hydrogen, carbon dioxide, hydrogen sulfide, organic acids such as formic acid, acetic acid, propionic acid, lactic acid, butyric acid, valeric acid, caproic acid, ethanol, Alcohols such as propanol, 2,3-butanediol, acetone and butanol are mainly produced.

In methane fermentation, biogas such as methane, carbon dioxide, hydrogen sulfide and ammonia is mainly produced. In methane fermentation, 0.35 m ³ (standard state) of methane is produced per 1 kg of decomposed organic matter. The methane fermentation method is performed in a fermentation temperature of 30 to 70 ° C, preferably in a mesophilic methane fermentation region of 35 to 40 ° C or in a high temperature methane fermentation region of 50 to 65 ° C. This is because the optimum growth temperature of many mesophilic or thermophilic methanogenic bacteria and other anaerobic bacteria is within these ranges. It is preferable to operate under pH 6-9, more preferably pH 7-8, HRT 5-30 days, more preferably 10-25 days operating conditions.

  In the methane fermentation process of organic waste treatment according to the present invention, any of the floating treatment type, fixed bed type, fluidized bed type, and UASB (upward flow type anaerobic sludge blanket) type can be applied as a reaction treatment type. It is. In this selection, it is necessary to pay particular attention to the SS (Suspended Solids) concentration and the fat and oil concentration. Specifically, when the SS concentration is 2,000 mg / L or more, it is preferable to apply floating bed type methane fermentation. Moreover, as oil and fat concentration, when it is 1,000 mg / L or more, it is preferable to apply floating bed type methane fermentation. In the methane fermenter, neutral fats and higher fatty acids have higher dispersibility at higher temperatures. Therefore, when applying waste materials that contain a large amount of fats and oils, select a high-temperature methane fermentation method of 50 to 65 ° C. It is preferable to do.

  In the present invention, in the hydrothermal electrolysis method for supplying all or part of the waste liquid containing residues discharged from the process of producing valuable materials using microorganisms, the hydrothermal reaction and electrolysis are performed simultaneously. It is possible to effectively oxidize and decompose reducing substances such as organic substances and ammonia. However, in order to promote the oxidation reaction of reducing substances such as organic substances and ammonia, oxygen gas, ozone gas, hydrogen peroxide, An oxidizing agent such as a halogen acid may be added. However, in the hydrothermal electrolysis method, when the waste liquid contains salts such as halide ions, the halide ions are involved in the oxidative decomposition of the reducing substance to promote the decomposition (hydrothermal electrolysis method and apparatus) Therefore, in the waste liquid containing the residue discharged from the process of producing valuables using microorganisms as in the present invention, the oxidizing agent is satisfactorily oxidized even if little or almost no oxidant is added. The decomposition reaction proceeds.

In the hydrothermal electrolysis reaction in the present invention, an acid or alkali can be added to carry out the hydrothermal electrolysis reaction.
In the present invention, when the hydrothermal electrolysis reaction is carried out with very little or no oxidizer added, when organic sludge is an object, for example, the reaction is expressed as shown in formula (1) Can do.
C ₅ H ₇ NO ₂ + 8H ₂ O → 11.5H ₂ + 5CO ₂ + 0.5N ₂ (1)
If ammonia is the target, as shown in equation (2),
2NH ₃ → N ₂ + 3H ₂ (2)
Thus, hydrogen gas is generated.

  That is, when the hydrothermal reaction and electrolysis are simultaneously performed in a reducing atmosphere, unlike the normal temperature and normal pressure, the reaction in which oxygen and hydrogen are generated simultaneously does not occur, and hydrogen can be generated safely from ammonia. Hydrogen gas can be recovered and supplied to a fuel cell, for example, to produce electrical energy. In the case where the valuable material produced in the present invention is a gaseous fuel such as hydrogen and / or methane, it is more preferable to recover hydrogen in the hydrothermal electrolysis reaction step.

  In the hydrothermal electrolysis reaction, the removal rate varies depending on the concentration of organic matter or ammonia, the reaction temperature, pressure, pH of the reaction solution, the presence or absence of the addition of an oxidant, and the like in the present invention, a process for producing valuable materials using microorganisms. The removal rate in the hydrothermal electrolysis reaction process of organic matter or ammonia contained in the waste liquid including residues discharged from the wastewater is determined by the ratio of the waste liquid transferred to the hydrothermal electrolysis reaction process and the conditions of the hydrothermal electrolysis reaction. Can be adjusted by.

The basic reaction of hydrothermal electrolysis will be described. When the aqueous solution is electrolyzed at room temperature and normal pressure, hypohalous acid is generated when halogen such as oxygen or chlorine ions is contained in the anode. Even if ammonia or an organic substance is contained, in this case, the efficiency of the oxidation reaction is poor and the reaction hardly proceeds or becomes very slow, so that basically a large amount of oxygen is generated at the anode. In this case, a large amount of hydrogen is generated at the cathode.
When the same electrolysis reaction is carried out under hydrothermal conditions, oxygen and hypohalous acid are not generated (or consumed immediately even if they are generated), and organic matter and ammonia are oxidized and decomposed into CO ₂ , N ₂ and water. Again, hydrogen is generated at the cathode.

  When an oxidant such as oxygen is positively inserted from the outside into a reaction field in which an aqueous solution containing ammonia and organic substances is hydrothermally electrolyzed, hydrogen is not generated at the cathode, and oxygen is converted into active oxygen. This active oxygen causes ammonia and organic substances to oxidize. Similarly, at the anode, a reaction for oxidizing these ammonia and organic substances proceeds, so that all contaminants in the aqueous solution are mineralized to carbon dioxide and nitrogen gas. However, since hydrogen gas is not generated in this case, the hydrothermal electrolysis reaction in which oxygen is positively added is merely a purification reaction and not a valuable material recovery reaction.

  Furthermore, when a NaCl aqueous solution that does not contain oxidizable substances such as ammonia and organic substances is hydrothermally electrolyzed, hydrogen, oxygen, and hypochlorous acid are not generated. Under this condition, the phenomenon of “electrolysis of water without hydrogen and oxygen” occurs. More precisely, there is a possibility that oxygen and hydrogen are generated at the anode and the cathode, but some neutralization such that the oxidant generated at the anode is reduced at the cathode or the hydrogen generated at the cathode is reduced at the anode. The reaction takes place (the mechanism is still unknown), and as a result, no explosive hydrogen and oxygen gas mixture accumulates in the reactor. Hydrothermal electrolysis is a safe process because such a neutralization reaction proceeds or hydrogen and oxygen are not generated simultaneously.

In hydrothermal electrolysis, the diaphragm is basically not used. One of the reasons is that there is no film that can withstand this hydrothermal condition (in terms of heat resistance, corrosion resistance, and pressure resistance). For a fluororesin-based diaphragm such as Nafion (Dupont, registered trademark), the usable limit is 150 to 160 ° C. Ceramic solid electrolytes used in solid electrolyte fuel cells, for example, ceramic solid electrolytes such as yttrium-stabilized zirconia, have problems such as cracking when the temperature shock or pressure balance is broken or corrosion in a hydrothermal atmosphere. In fact, the diaphragm cannot be used. Another reason is that no diaphragm is required because explosive gas is not generated without a diaphragm as described above. When ammonia and organic substances are hydrothermally electrolyzed without adding an oxidizing agent, hydrogen is generated at the cathode, but only CO ₂ and N ₂ are generated at the anode, and oxygen is not generated, which is safe. It is also an advantage of hydrothermal electrolysis that the reaction proceeds without using a diaphragm.
Note that the liquid that has undergone reduction at the cathode and the liquid that has undergone oxidation at the anode are mixed and the reverse reaction does not occur at the counter electrode. In hydrothermal electrolysis, the hydrothermal reaction atmosphere is basically oxidative, so when organic matter and ammonia are treated, the overall reaction is an oxidative decomposition reaction.

The temperature conditions for hydrothermal electrolysis are preferably high-temperature and high-pressure liquid water of 100 ° C. or higher, preferably 150 ° C. or higher, more preferably 200 ° C. or higher, and a critical temperature of less than 374 ° C. As the pressure condition, the saturated vapor pressure of the reaction temperature or higher, preferably saturated vapor pressure to saturated vapor pressure + 10 MPa, more preferably saturated vapor pressure to saturated vapor pressure + 3 MPa. The voltage under the electrolysis conditions is 1.0 V to 500 V, preferably 1.5 V to 100 V, more preferably 2 V to 50 V. The current density conditions of the electrolysis 0.1 mA / cm ² or more 2000 mA / cm ² or less, preferably 1 mA / cm ² or more 1000 mA / cm ² or less, still more preferably is 10 mA / cm ² or more 1000 mA / cm ² or less.

The hydrothermal electrolysis reaction is greatly influenced by the amount of electricity applied to the aqueous solution to be treated. The quantity of electricity is the product of current and energization time, and its unit is C (1 coulomb = 1 As) or Ah. When 10 A is passed through a 1 L aqueous solution for 1 hour, the amount of electricity applied to the solution is 10 Ah / L. The decomposition rate of organic matter or ammonia contained in the solution varies depending on the initial COD concentration (chemical oxygen consumption) of the solution. In the present invention, basically, no oxidizing agent is added or only a small amount of oxidizing agent is added. In this case, it can be calculated from the Faraday rule that 3.3 Ah needs to be given to completely decompose 1 gram of COD. For example, when an amount of electricity of 3.3 Ah is applied to 1 L of residual waste liquid having a COD of 1 g / L, organic matter and ammonia contained in the solution can be completely mineralized to CO ₂ and nitrogen. When the residual waste liquid has a COD concentration of 10 g / L, if 33 Ah / L is given, it can be completely mineralized. Thus, in hydrothermal electrolysis, the organic matter decomposition rate can be controlled by the amount of electricity.

  The present invention does not limit how many times the theoretical amount of electricity is given to the waste liquid. In the case where only a part of the residual waste liquid in the valuable material production process is hydrothermally electrolyzed, it may be completely decomposed by giving 10 times or less of this theoretical electricity amount. In addition, since it will be a waste of electric power if it gives extra, Preferably it is 4 times or less of theoretical amount. More preferably, it is 2 times or less. In the case where the entire amount of the residue from the biological value production process is sent to the hydrothermal electrolysis process, a theoretical electric quantity or less may be given. In addition, as will be described later, when surplus sludge from the activated sludge process that is in the subsequent process of hydrothermal electrolysis is returned to hydrothermal electrolysis, the amount of COD that is the sum of the residue flowing from the valuable production process and the returned sludge The theoretical amount of electricity can be calculated from In the present invention, there is no need to completely decompose the residual COD discharged from the process of producing valuable materials. What is necessary is just to be able to reduce the organic matter and ammonia load in the post-process biological water treatment or phosphorus recovery process and to improve efficiency.

The treatment apparatus used to carry out the organic waste treatment method of the present invention includes a hydrothermal electrolysis tank, a reaction tank for performing biological treatment for introducing the remainder of the waste liquid containing residues, an aeration tank, and a solid liquid It consists of a separation tank. In addition, the whole waste liquid processing apparatus including a hydrothermal electrolysis apparatus can be drive | operated by a conventional method.
As a single device necessary for the hydrothermal electrolysis treatment of the present invention, a raw material sludge storage tank, a feed pump (for example, a Mono pump), a high pressure pump (for example, a triple head diaphragm pump), a heat exchanger (for example, a shell) And tube), preheater (eg, electric heater equipped with a stirrer), hydrothermal electrolysis reactor (eg, reactor equipped with internal electrode), solid-liquid separator (eg, high-pressure strainer), gas-liquid separator (eg, , Liquid level control type gas-liquid separator), treated water storage tank, and the like.

  In the present invention, solar cell equipment and / or heat exchange equipment can be used in the hydrothermal electrolysis apparatus. As an outline of the operation of the solar battery DC power supply system, during power generation by the solar battery, it is converted to AC200V by the inverter for system linkage, supplied to the DC power supply device, DC-converted, and transmitted to the hydrothermal electrolysis tank. When solar cell power generation is impossible at night or in rainy weather, power is supplied to the DC power supply device with a commercial power supply (AC 200 V). As a solar cell array, for example, a single crystal solar cell array of 6,450 mm × 3,560 mm [maximum output operating voltage (Vpm) 330 V, maximum output operating current (Ipm) 10.11 A, maximum output (PmW) 3.3 kW] Can be used with the following module specifications: That is, a solar cell array having an outer shape of 1,185 × 645 mm, a maximum output operating voltage (Vpm) of 33 V, a maximum output operating current (Ipm) of 3.75 A, and a maximum output (PmW) of 111.2 W is connected in 10 series × 3 parallel connections. use. In this case, a system linking inverter 3.5 kW and a current collecting panel are attached. As a DC power supply device, for example, power may be transmitted to the hydrothermal electrolysis tank using a power supply device on the input side (voltage: 1φ AC 200 V, current 12 A AC) and output side (voltage 0 to 10 V DC, current 0 to 100 A DC). it can.

  In the present invention, when organic substances remain in the hydrothermal electrolysis reaction treatment liquid, the treatment liquid can be introduced into a waste liquid process by an aerobic biological treatment such as an activated sludge method. In the present invention, since all or part of the waste liquid including residues discharged from the process of producing valuable materials has undergone hydrothermal electrolysis, the load on organic matter in the waste liquid treatment process is reduced, and waste water The processing apparatus can also be extremely miniaturized. In addition, you may return the whole quantity or one part of the excess sludge in the said waste liquid processing process to a hydrothermal electrolysis reaction process.

  In the present invention, when organic matter, nitrogen and phosphorus remain in the hydrothermal electrolysis reaction treatment solution, the treatment solution is subjected to simultaneous removal of organic matter, nitrogen and phosphorus as in the anaerobic aerobic activated sludge modification method. It can be introduced into the waste liquid process by possible biological treatment. In the present invention, all or part of the waste liquid including residues discharged from the process of producing valuable materials has undergone hydrothermal electrolysis, so the organic matter and nitrogen loads in the waste liquid treatment process are reduced. Also, the waste water treatment device can be extremely miniaturized.

  In the present invention, when organic matter and nitrogen remain in the hydrothermal electrolysis reaction treatment liquid, the treatment liquid is subjected to biological treatment capable of simultaneous removal of organic matter and nitrogen, such as a circulating nitrification denitrification method. It can be introduced into the waste liquid process. In the present invention, all or part of the waste liquid including residues discharged from the process of producing valuable materials has undergone hydrothermal electrolysis, so the organic matter and nitrogen loads in the waste liquid treatment process are reduced. Not only can the apparatus be miniaturized, but even when an organic substance for denitrification is added, an extremely small addition amount is sufficient. In addition, you may return the whole quantity or one part of the excess sludge in the said waste liquid processing process to a hydrothermal electrolysis reaction process.

  In the present invention, when organic matter and nitrogen remain in the hydrothermal electrolysis reaction treatment liquid below the discharge standard and phosphorus remains at a high concentration, the treatment liquid is treated with chemicals such as coagulation precipitation and crystallization. It can be introduced into the process of removing phosphorus. In the method of crystallizing hydroxyapatite (HAP method) among chemical phosphorus removal, it is known that the presence of chrominance components such as humic substances and high concentration of carbonic acid in raw water inhibits the crystallization reaction. In particular, the decarboxylation process is expensive and hinders the spread of the HAP method. In the hydrothermal electrolysis reaction, the chromaticity component can be decomposed (see JP 2003-290740 A), and since carbonic acid is vaporized, there is no need to provide a separate decarboxylation step, and the HAP method is particularly preferable among chemical phosphorus removal. . That is, the treated water from the hydrothermal electrolysis reactor is subjected to heat recovery with a heat exchanger or the like and then depressurized, so that the carbon dioxide is moved to the gas phase by flushing and separated as a treated gas.

  In the present invention, not only when the total amount of waste liquid including residues discharged from the process of producing valuable materials undergoes hydrothermal electrolysis, but also when a portion of the waste liquid undergoes hydrothermal electrolysis. When the phosphorus concentration of the waste liquid is relatively low, the chemical after the hydrothermal electrolysis treatment even when the waste liquid treatment process that is processed without hydrothermal electrolysis is not included in the waste liquid. If the concentration is below the COD and phosphorus release standards when mixed with the waste liquid that has undergone the general phosphorus removal process, a part of the waste liquid is hydrothermally electrolyzed, and then phosphorus removal such as coagulation precipitation and crystallization is performed. Can be directly introduced into the chemical waste liquid process.

  In the hydrothermal electrolysis reaction, in addition to the progress of the ammonia oxidation reaction, which is difficult to process in the conventional hydrothermal reaction or wet oxidation reaction, the chromaticity components produced from organic substances are decomposed by the usual hydrothermal reaction or wet oxidation reaction. You can also This chromaticity component is a substance that is extremely difficult to biologically treat, and coagulation precipitation treatment and activated carbon treatment were necessary to remove it. However, when hydrothermal electrolysis is used, A removal step is not necessary.

  Hereinafter, the present invention will be specifically described with reference to the drawings. FIG. 1 is a block diagram showing a process of combination with waste liquid treatment by a standard activated sludge method. A waste liquid (hereinafter also referred to as “raw material”) 5 containing the residue enters a reaction tank 1 that produces valuables using microorganisms, for example, a reaction tank that produces alcohol by fermentation, where alcohol is produced by fermentation. A part of the residual waste liquid 6 after separating the alcohol from the liquid coming out of the reaction tank 1 is supplied to the hydrothermal electrolysis reaction tank 3 for hydrothermal electrolysis. The hydrogen gas 11 generated by the hydrothermal electrolysis is put into the hydrogen storage tank 12 and supplied from the hydrogen storage tank 12 to the user at the time of use. The remainder of the residue waste liquid 6 is combined with the hydrothermal electrolysis reaction treatment liquid 7 coming out of the hydrothermal electrolysis reaction tank 3 and put into the aeration tank 2 for aerobic treatment. The treatment liquid is sludge in the solid-liquid separation tank 4. Is separated and settled as discharged water 8 into the water area. Most of the settled sludge in the solid-liquid separation tank 4 is returned to the aeration tank 2 as return sludge 9, and excess sludge is taken out as excess sludge and processed in a conventional manner.

FIG. 2 is a block diagram showing a process of combination with waste liquid treatment by a crystallization dephosphorization tank (HAP method). Here, the hydrothermal electrolysis reaction treatment liquid 7 coming out of the hydrothermal electrolysis reaction tank 3 is supplied to the crystallization dephosphorization tank 13, and by adding slaked lime 14, phosphorus is recovered as HAP by the HAP method and the supernatant. The liquid is discharged water 8. In this step, valuable phosphorus can be recovered.
FIG. 3 is a block diagram showing a process of combination with the biological nitrogen / phosphorus removal method (A2O method). In this method, an anaerobic tank 15 and an anaerobic tank 16 are arranged in front of the aeration tank 2, and sludge from the aeration tank 2 is sent to the anoxic tank 16 as a circulating sludge 17 for biological nitrogen / phosphorus removal (A 2 O). Law).

FIG. 4 is a block diagram showing the steps of the combination [(1) When the phosphorus concentration is low] with the waste liquid treatment by the circulation type nitrification denitrification method. In this method, the aeration tank 2 is configured in the order of a first denitrification tank 18, an aeration tank (nitrification tank) 2A, a second denitrification tank 19, and a re-aeration tank 20, and the nitrification liquid from the nitrification tank 2A is used as the first. While circulating to the 1 denitrification tank 18, the methanol 21 of an organic substance source is supplied to the 2nd denitrification tank 19, and a denitrification reaction is fully performed.
FIG. 5 is a block diagram showing the steps of the combination [(2) when the phosphorus concentration is high] with the waste liquid treatment by the circulating nitrification denitrification method. In this method, the hydrothermal electrolysis reaction treatment liquid 7 exiting from the hydrothermal electrolysis reaction tank 3 shown in FIG. 2 is supplied to the crystallization dephosphorization tank 13 and slaked lime 14 is added to the process of FIG. And a process for recovering phosphorus as HAP by the HAP method. Both denitrification and phosphorus recovery can be performed.
FIG. 6 shows a block diagram when a solar battery DC power supply system is used in the hydrothermal electrolysis process according to the present invention, depending on the electric power obtained by using the methane or hydrogen. This is effective when a solar cell DC power supply system is applied as a supplement means when the power required for the hydrothermal electrolysis reactor is insufficient. The current generated in the solar cell array 23 is collected in the current collector panel 24, sent to the DC power supply 22 through the diode 25 and the system linkage inverter 26, and used in the electrolytic cell 3 which is a hydrothermal electrolysis reaction tank. .

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

Example 1
Production of valuable materials by high-temperature methane fermentation using human waste, garbage, and excess sludge as raw materials. From this valuable material production process using anaerobic microorganism treatment, raw fuel gas (biogas) with a component composition of CH ₄ 62% and CO ₂ 38% is obtained, organic matter decomposition rate is 78% (VS standard), gas The conversion rate of COD _Cr into the components was 75% or more. The properties of the residual sludge discharged from this valuable material production process are MLSS concentration 30,600 mg / L, total COD _Cr concentration 44,700 mg / L, soluble COD _Cr concentration 3,300 mg / L, acetic acid concentration 6 mg / L, ammonia The nitrogen concentration was 2,410 mg / L, the phosphate ion concentration was 15 mg / L, and the pH was 7.7. This residue waste liquid was all treated in a hydrothermal electrolysis process. In the hydrothermal electrolysis, an electric quantity (theoretical electric quantity) of 147 Ah / L was given to the residual waste liquid. The gas generated by hydrothermal electrolysis was 66.1 L of hydrogen (73 vol%) and 24 L of CO ₂ (27 vol%) with respect to 1 L of residual sludge. The properties of the hydrothermal electrolysis solution are MLSS concentration 11,300 mg / L, total COD _Cr concentration 3,200 mg / L, soluble COD _Cr concentration 600 mg / L, acetic acid concentration 240 mg / L, ammoniacal nitrogen concentration 30 mg / L, phosphorus The acid ion concentration was 210 mg / L, pH 6.8.

  In the hydrothermal electrolysis reaction, the phosphate ion concentration increased by about 14 times, the acetic acid concentration increased by 40 times, and conversely, the MLSS concentration and ammonia concentration decreased significantly. In terms of sludge treatment, the amount of solid matter was reduced to 1/3 or less, and the amount of organic matter was reduced to 1/10 or less. Further, most of the SS component of the hydrothermal electrolysis treatment liquid was inorganic. In the hydrothermal electrolysis solution, no significant coloring was observed, and the chromaticity was 2,800 before the hydrothermal electrolysis treatment and 700 after the treatment. Furthermore, in the hydrothermal electrolysis reaction, the viscosity of the fermentation residue can be significantly reduced, and the filterability of the SS component is significantly improved compared to the methane fermentation sludge before the hydrothermal electrolysis reaction.

This hydrothermal electrolysis reaction treatment liquid was treated with activated sludge. The activated sludge seed sludge used was an aerobic sludge acclimatized with a hydrothermal electrolysis solution for about 1.5 months, and the treatment conditions were a temperature of 23 to 25 ° C., an SRT of 4 to 10 days, and an MLSS concentration of about 3,500 mg / day. L performed. As a result, the treated water quality by activated sludge is COD _Mn concentration 120 mg / L, BOD concentration 20 mg / L or less, acetic acid concentration 0 mg / L, TOC concentration 30 mg / L, ammoniacal nitrogen concentration 10 mg / L, phosphate ion concentration 180 mg / L. PH 7.2. As a result of the cost calculation of this method, it was found that the fermentation residue can be treated at about half price compared to the disposal cost when methane fermentation sludge is consigned to industrial waste treatment.

(note)
¹⁾ VS (Volatile Solids)
²⁾ MLSS (Mixed Liquor Suspended Solids)
³⁾ COD _Cr (Chemical Oxygen Demand, chemical oxygen consumption; potassium dichromate method)
⁴⁾ COD _Mn (Chemical Oxygen Demand, chemical oxygen consumption; potassium permanganate method)
⁵⁾ BOD (Biochemical Oxygen Demand, biochemical oxygen consumption)
⁶⁾ TOC (Total Organic Carbon, Total Organic Carbon)

Example 2
Production of valuable materials by high-temperature methane fermentation using human waste, garbage, and excess sludge as raw materials. From the valuable material production process using the anaerobic microorganism treatment, raw fuel gas (biogas) having a component composition of CH ₄ 62% and CO ₂ 38% is obtained, the organic matter decomposition rate is 78% (VS standard), gas The conversion rate of COD _Cr into the components was 75% or more. The properties of the residual sludge discharged from this valuable material production process are MLSS concentration 30,600 mg / L, total COD _Cr concentration 44,700 mg / L, soluble COD _Cr concentration 3,300 mg / L, acetic acid concentration 6 mg / L, ammonia The nitrogen concentration was 1,310 mg / L, the phosphate ion concentration was 15 mg / L, and the pH was 7.4. This residue waste liquid was all treated in a hydrothermal electrolysis process. In hydrothermal electrolysis, an electric quantity of 20 Ah / L (0.14 times the theoretical quantity of electricity) was given to the residual waste liquid. The gas generated by hydrothermal electrolysis was 8.5 L of hydrogen (74 vol%) and 3 L of CO ₂ (26 vol%) with respect to 1 L of residual sludge. The properties of the hydrothermal electrolysis solution are MLSS concentration 18,200 mg / L, total COD _Cr concentration 39,200 mg / L, soluble COD _Cr concentration 11,100 mg / L, acetic acid concentration 1,430 mg / L, ammoniacal nitrogen concentration 910 mg. / L, phosphate ion concentration was 170 mg / L.

In the hydrothermal electrolysis treatment, the phosphate ion concentration increased, the acetic acid concentration increased significantly, and the soluble COD component increased. Conversely, the MLSS concentration was greatly reduced. The ammonia concentration decreased slightly. Moreover, the filterability of the SS component was significantly improved compared to the methane fermentation sludge before the reaction.
The hydrothermal electrolysis solution was centrifuged (2,500 / min, 5 min), and the supernatant from which the solids had been removed was subjected to biological nitrification and denitrification. As a result, the treated water quality by activated sludge is COD _Mn concentration 120 mg / L, BOD concentration 10 mg / L or less, acetic acid concentration 0 mg / L, TOC concentration 40 mg / L, ammoniacal nitrogen concentration 15 mg / L, phosphate ion concentration 80 mg / L. PH 7.1.

  Compared to the case of direct nitrification and denitrification treatment of methane fermentation sludge, it is possible to reduce the amount of methanol added by 35% and reduce the amount of sludge generated by about 50%, and the aeration tank capacity in the aerobic treatment process is also 1 / It can be reduced to 3 or less, and at the same time, foaming troubles in the aerobic treatment process can be solved.

  The present invention greatly reduces the amount of residue discharged from the process of producing valuable materials using microorganisms, has a large environmental impact reduction effect, and is a liquid fuel such as alcohol from organic waste or the like, or hydrogen or methane. It is useful for industries that produce gaseous fuels such as lactic acid or industrial raw materials such as lactic acid.

It is a block diagram which shows the process of the combination with the waste liquid process by a standard activated sludge method. It is a block diagram which shows the process of a combination with the waste liquid process by a crystallization dephosphorization tank (HAP method). It is a block diagram which shows the process of a combination with biological nitrogen and phosphorus removal method (A2O method). It is a block diagram which shows the process of the combination with a waste liquid process by a circulation type nitrification denitrification method (when (1) phosphorus concentration is low). It is a block diagram which shows the process of the combination with a waste liquid process by a circulation type nitrification denitrification method (when (2) phosphorus concentration is high). It is a block diagram which shows the hydrothermal electrolysis process in this invention using a solar cell DC power supply system.

Explanation of symbols

1 Reaction tank for producing valuable materials using microorganisms 2 Aeration tank 2A Aeration tank (nitrification tank)
DESCRIPTION OF SYMBOLS 3 Hydrothermal electrolysis reaction tank 4 Solid-liquid separation tank 5 Raw material 6 Residue waste liquid 7 Hydrothermal electrolysis reaction processing liquid 8 Discharged water 9 Return sludge 10 Surplus sludge 11 Hydrogen gas 12 Hydrogen storage tank 13 Crystallization dephosphorization tank (HAP method) )
DESCRIPTION OF SYMBOLS 14 Slaked lime 15 Anaerobic tank 16 Anoxic tank 17 Circulating sludge 18 1st denitrification tank 19 2nd denitrification tank 20 Re-aeration tank 21 Methanol 22 DC power supply device 23 Solar cell array 24 Current collection panel 25 Diode 26 System linkage inverter

Claims (5)

  From the process of producing valuable materials in the organic waste processing method comprising the steps of producing valuable materials using microorganisms and the waste liquid treatment step of treating waste liquid containing residues discharged from the steps of producing valuable materials In a hydrothermal electrolysis process for supplying a direct current under a pressure at which the waste liquid maintains a liquid phase at a temperature not lower than the critical temperature of the waste liquid at 100 ° C. A method for treating organic waste, characterized by comprising treating.   2. The organic waste according to claim 1, wherein the waste liquid treatment step of treating a waste liquid containing a residue discharged from the step of producing the valuable material includes a step of removing phosphorus and / or nitrogen. Processing method.   A total amount or one of the waste liquid containing the residue discharged from the apparatus for producing valuable materials using microorganisms, the apparatus for treating the waste liquid containing residues discharged from the process of producing valuable materials, and the apparatus for producing valuable materials Water provided with at least a pair of electrodes for electrolysis inside the reactor capable of withstanding the pressure at which the waste liquid maintains a liquid phase at a temperature of 100 ° C. or higher and lower than the critical temperature of the waste liquid. An organic waste processing apparatus comprising: a thermoelectrolysis apparatus.   The organic waste treatment apparatus according to claim 3, wherein the hydrothermal electrolysis apparatus uses a solar cell facility and / or a heat exchange facility.   The organic waste according to claim 3 or 4, wherein the apparatus for treating the waste liquid containing the residue discharged from the process of producing the valuable material includes a facility for removing phosphorus and / or nitrogen. Material processing equipment.

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