JP4488794B2 - Method and system for treating fermentation residual liquid and other anaerobic organic compound-containing liquid - Google Patents

Description

  The present invention relates to a processing method and a processing system for a fermentation residual liquid obtained by subjecting organic waste to methane fermentation and other anaerobic organic compound-containing liquid.

  Methane fermentation is adopted as one of the methods for treating organic waste such as livestock waste and garbage. Methane fermentation is an organic waste treatment method that can accept organic loads with high density, and has features that other treatment methods do not have in that it can recover flammable gas that can be used as a fuel called methane gas. ing. The fermentation residual liquid (digestion liquid) obtained by subjecting organic waste to methane fermentation is a liquid substance that usually contains about 95% by weight of water and about 5% by weight of solids depending on the fermentation conditions. Since this fermentation residual liquid contains a large amount of plant nutrients, it can be used as liquid fertilizer or as solid fertilizer by composting (composting).

  However, in so-called farmland reduction in which fermentation residual liquid is treated as liquid fertilizer, there is a problem that groundwater is contaminated by nitric acid, nitrous acid, etc. because there are too many nitrogen components. On the other hand, when composting the fermentation residual liquid, for example, an inorganic or polymer flocculant is added to the fermentation residual liquid to improve the solid-liquid separation, and then the solid content is separated. It is necessary to perform post-treatment such as coagulation sedimentation treatment, biological treatment (aeration, biofilm method, etc.), decolorization treatment, etc. so that the nitrogen component and phosphorus component reach the discharge standard. Further, there is a problem that the flocculant is mixed in the compost.

  In addition, when composting the fermentation residue without solid-liquid separation, it is necessary to concentrate and dry the fermentation residue having a moisture content of about 95% by weight, which requires a large amount of heat energy and is practical. is not. Thus, the large processing load of the fermentation residual liquid is a factor that hinders the spread of methane fermentation treatment of organic waste.

  The processing of the fermentation residual liquid is difficult because the solid content concentration in the fermentation residual liquid is generally as high as about 5% by weight, the hydrophilicity of the solid content is remarkably large and solid-liquid separation is difficult, In general, COD is larger than BOD and it is difficult to apply biological treatment, and decolorization treatment is necessary for discharge. The hydrophilicity of the solid content is manifested by having many hydrophilic groups such as hydroxyl groups and carbonyl groups, and these properties are also found in corrosive substances such as fumaric acid and humic acid. is there.

By the way, as a technique for adding an acid to a fermentation residual liquid, JP-A-7-96297 (Patent Document 1) discloses a method of adding an inorganic acid to biological sludge so as to have a pH of 5 or less and treating this with ozone. ing. This technique aims to reduce the amount of ozone used when biological sludge is ozone-treated, and is a technique limited to ozone treatment. Japanese Patent Application Laid-Open No. 2003-275788 (Patent Document 2) discloses a method in which sludge extracted from an anaerobic digester is adjusted to pH 5 or lower and then subjected to solid-liquid separation, and the resulting separated sludge is treated with ozone. Yes. This technique adjusts the pH to 5 or less for the purpose of avoiding consumption of ozone by reducing substances such as Fe ²⁺ and Mn ²⁺ , and is limited to ozone treatment of digested sludge. The above matters can be similarly applied to some leachate containing humic organic substances and anaerobic, and can be satisfactorily treated in the treatment method of the present invention.

JP-A-7-96297 JP 2003-275788 A

  This invention is made | formed in view of such a situation, The subject is processing easily the fermentation residual liquid (digestion liquid) obtained by methane fermentation of organic waste, and other anaerobic organic compound containing liquid. It is providing the processing method and processing system of the fermentation residual liquid which can be performed.

  In order to solve the above-mentioned problems, a method for treating a fermentation residual liquid and other anaerobic organic compound-containing liquid according to the first aspect of the present invention includes a fermentation residual liquid obtained by subjecting an organic waste to methane fermentation and other methods. It includes a liquid treatment step of adjusting the anaerobic organic compound-containing liquid to pH 5.5 or lower and contacting with an oxidizing agent.

  According to this feature, since the liquid (digested liquid) obtained by methane fermentation of organic waste is adjusted to pH 5.5 or lower, the solid-liquid separation can be improved, and the subsequent treatment (for example, solid-liquid separation) Processing efficiency in processing, concentration processing, drying processing, etc.) can be significantly improved. Moreover, since the liquid property which is a strong reducing atmosphere can be adjusted to an oxidizing atmosphere by making the said liquids, such as a fermentation residual liquid, contact with an oxidizing agent, solid-liquid separability can be improved further. . Further, since dissolved carbon dioxide can be diffused, an efficient treatment that avoids foaming of carbon dioxide is possible when the treatment liquid is subjected to, for example, vacuum treatment (vacuum concentration treatment, vacuum drying treatment, etc.).

  Moreover, the processing method of the fermentation residual liquid and other anaerobic organic compound containing liquid which concerns on the 2nd aspect of this invention is the fermentation residual liquid obtained by carrying out methane fermentation of organic waste, and other anaerobic organic compound containing It includes a liquid treatment step of adjusting the liquid to pH 5.5 or lower and contacting with an oxidizing agent, and a solid-liquid separation step of solid-liquid separation of the treatment liquid in the liquid treatment step.

  According to this feature, since the liquid (digested liquid) obtained by methane fermentation of organic waste is adjusted to pH 5.5 or less, the solid-liquid separation property can be improved, and the processing efficiency in the solid-liquid separation process can be improved. It can be significantly improved. Moreover, since the liquid property which is a strong reducing atmosphere can be adjusted to an oxidizing atmosphere by making the said liquids, such as a fermentation residual liquid, contact with an oxidizing agent, solid-liquid separability can be improved further. . In addition, since dissolved carbon dioxide can be diffused, an efficient treatment that avoids foaming of carbon dioxide is possible when the treatment liquid is subjected to, for example, vacuum treatment (vacuum concentration treatment, decompression drying treatment, etc.).

  Moreover, the processing method of the fermentation residual liquid and the other anaerobic organic compound containing liquid which concerns on the 3rd aspect of this invention is the fermentation residual liquid obtained by methane fermentation of organic waste, and other anaerobic organic compound containing A liquid treatment step for adjusting the liquid to pH 5.5 or lower and contacting with an oxidizing agent, a solid-liquid separation step for solid-liquid separation of the treatment liquid in the liquid treatment step, and a liquid component in the solid-liquid separation step are concentrated under reduced pressure. And a concentration step.

  According to this feature, the fermentation liquid (digested liquid) obtained by methane fermentation of organic waste and other anaerobic organic compound-containing liquids are adjusted to pH 5.5 or lower, thereby improving solid-liquid separation. And the processing efficiency in the solid-liquid separation step can be remarkably improved. Moreover, since the liquid property which is a strong reducing atmosphere can be adjusted to an oxidizing atmosphere by making the said liquids, such as a fermentation residual liquid, contact with an oxidizing agent, solid-liquid separability can be improved further. . Moreover, since dissolved carbon dioxide can be diffused, it can be processed while avoiding foaming of carbon dioxide in the concentration step of concentrating the liquid under reduced pressure, and an efficient concentration process is possible.

  Moreover, the processing method of the fermentation residual liquid and the other anaerobic organic compound-containing liquid according to the fourth aspect of the present invention is the liquid processing step according to any one of the first aspect to the third aspect. The contact with the oxidizing agent is controlled to be noble from -15 mV at the oxidation-reduction potential with respect to the silver-silver chloride electrode.

  According to this feature, the contact between the liquid such as the fermentation residual liquid in the liquid treatment step and the oxidizing agent is more noble (positive) than −15 mV at the redox potential based on the silver-silver chloride electrode (Ag / AgCl). Therefore, dissociation of hydrophilic groups (hydroxyl group, carbonyl group, etc.) present in the liquid can be effectively suppressed, and hydrophilicity can be reduced by oxidizing the reducing hydrophilic group to some extent. Thus, the solid-liquid separability of the liquid such as the fermentation residual liquid can be reliably improved.

  Moreover, the processing system of the fermentation residual liquid and other anaerobic organic compound-containing liquid according to the fifth aspect of the present invention includes a fermentation residual liquid obtained by methane fermentation of organic waste and other anaerobic organic compounds. The liquid tank is adjusted to pH 5.5 or lower, and an adjustment tank for contacting with the oxidizing agent is provided. According to this feature, the same effect as in the first aspect can be obtained.

  According to the present invention, the solid-liquid separability of the fermentation residual liquid and the other anaerobic organic compound-containing liquid can be improved, so that the processing efficiency in the subsequent processing can be significantly improved. Moreover, since the dissolved carbon dioxide can be diffused, foaming when concentrating the treatment liquid can be suppressed and the concentration treatment can be performed easily and reliably. That is, according to the present invention, the solid-liquid separability of the fermentation residual liquid and other anaerobic organic compound-containing liquids is improved, and the processing efficiency in various treatments in the subsequent stage is remarkably improved by releasing dissolved carbon dioxide. It can be made to.

  The method for treating a liquid such as a fermentation residue according to the present invention includes at least a liquid treatment step of adjusting a liquid obtained by methane fermentation of organic waste to pH 5.5 or lower and contacting with an oxidizing agent. It is a feature.

  The present invention will be described below with reference to the drawings. Here, FIG. 1 is a block diagram showing an outline of the entire system including the processing system according to the present invention, and FIG. 2 is a drawing showing the processing system.

  Examples of the organic waste used in the present invention include livestock waste, green farm waste, and wastewater treatment sludge. Here, livestock waste includes livestock excrement and carcass, and processed products thereof. More specifically, livestock carcasses such as cattle, sheep, goats and chickens, bones, meat separated from them, In addition to fat, internal organs, blood, brain, eyeballs, skin, hoofs, horns, etc., bones, meat, etc. of animal carcasses represented by meat and bone meal, meat meal, bone meal, blood meal, etc. The dried product is also included. In addition to household garbage, examples of green agricultural waste include agricultural and marine industrial waste, food processing waste, and the like as industrial waste.

  Depending on the state of the organic waste, a crushing / sorting step can be performed as a pretreatment as necessary. The crushing / sorting step can be performed, for example, by the following fractional crushing or whole quantity crushing. In the case of fractional crushing, a crushing / separating machine is used to collect a portion of the organic waste that can be crushed relatively easily as a slurry together with the liquid. On the other hand, parts that are difficult to crush are collected separately as a lump. The water content of the slurry is about 70 to 98% by weight, and the water content of the lump is about 40 to 60% by weight. The crushing / separating machine crushes organic solids by shearing and pulling force, and the cutter part can be a biaxial or triaxial type. When animal carcasses such as cows are used as raw materials, it is preferable to crush them with a triaxial crushing and sorting machine from the viewpoint of crushing fineness and uniformity. It is preferable to remove mixed plastics, sheets and the like to be sorted and removed by sorting with a mesh, wind sorting or the like.

  The fermenter 10 as a methane fermenter for methane fermentation of organic waste does not interfere with the activity of methane fermenting bacteria that are absolutely anaerobic, even in the case of a fermentation process using a two-tank system, Consists of a completely shut off tank. The methane fermentation can be applied to a so-called medium temperature type, a high temperature type, a slurry (wet) type, or a dry (dry) type. The fermenter 10 sets a shape, an operating condition, etc. with solid content concentration (usually the range of 4-40 weight%) and fermentation temperature (about 37 degreeC in normal temperature fermentation, about 55 degreeC in high temperature fermentation). In the case of high moisture content (up to 10 wt% solid content), a wet type fully mixed fermenter, and in the case of low moisture content (solid content of 30-40 wt%), a dry type plug A flow type (extrusion type) fermenter can be used. In addition, the fermenter 10 can be provided with a heating means for keeping warm if necessary. In general, methane fermentation takes a residence time of about 20 to 30 days for medium temperature fermentation and about 15 days for high temperature fermentation.

  The fermentation residue obtained by methane fermentation of organic waste is a liquid substance having a water content of about 95% by weight and a solid content concentration (TS) of about 5% by weight, although it varies depending on the organic waste and fermentation conditions. It contains a large amount of various amino acids, organic acids and the like derived from bacterial cells of the sex microorganisms and their metabolites, and has a highly reducing atmosphere. Similarly, leachate from disposal sites filled with organic waste has the same properties.

  The fermentation residual liquid and other anaerobic organic compound-containing liquid discharged from the fermenter 10 are transferred to the adjustment tank 20. As shown in FIG. 2, the adjustment tank 20 according to the present embodiment that performs the fermentation residual liquid treatment step includes an acid supply device 21, a pH measuring device 22, a stirrer 25, and a redox potential measuring device 26. .

  The fermentation residual liquid introduced into the adjustment tank 20 is adjusted to pH 5.5 or less, preferably about pH 5.5 to 3.0, and more preferably about pH 4.5 to 3.5. The pH can be adjusted by adding an acid from the acid supply device 21 to the fermentation residue. Examples of the acid to be added include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid.

By adjusting the pH value of the liquid such as fermentation residual liquid to the above range, dissociation of hydrophilic groups such as hydroxyl groups and carbonyl groups can be suppressed, and the hydrophilicity of many organic acids can be lowered. Therefore, the solid-liquid separation property can be remarkably improved, and the processing efficiency in the subsequent solid-liquid separation apparatus 30 can be remarkably improved. Moreover, the carbon dioxide component dissolved in the liquid such as the fermentation residual liquid can be diffused, and the concentration efficiency in the subsequent concentration apparatus 40 can be remarkably improved. Moreover, precipitation of calcium salt and magnesium salt can be suppressed, and an acid (organic acid) cleaning treatment that has been conventionally required about once a day is unnecessary. Moreover, since it is possible to avoid the generation of MAP (MgNH ₄ PO ₄ .6H ₂ O), which is called a digestion tank / pipe scale, mechanical cleaning work in the pipe, which has been frequently required in the past, becomes unnecessary. The solubility of this scale is 2000 mg / L at pH 5.0, 100 mg / L at pH 7.5, and ˜0 mg / L at pH 8.0. Further, since the heavy metal is ionized and dissolved, the heavy metal ion can be transferred from the solid content side to the liquid content side, and this can be easily and efficiently recovered by an electrodialysis method or the like.

  Moreover, in the adjustment tank 20, liquids, such as a fermentation residual liquid, are made to contact with an oxidizing agent. The contact between the liquid such as the fermentation residual liquid and the oxidizing agent is, for example, a noble (positive) side from −15 mV, preferably about −15 to +50 mV at a redox potential based on a silver-silver chloride electrode (Ag / AgCl). It is desirable to control so that it becomes about −10 to +20 mV. In addition, the oxidation-reduction potential value at the time of using a silver-silver chloride electrode as a reference electrode is about 220-230 mV and a noble (positive) side than the case where a hydrogen electrode potential is used.

  An oxidizing agent is not specifically limited, For example, air, oxygen, hypochlorous acid, hypochlorite etc. can be illustrated. When a gaseous oxidant such as air or oxygen is used, it is preferably introduced into the fermentation residual liquid by a mechanical method such as a stirrer or aeration, and hypochlorous acid, hypochlorite, etc. When the liquid or solid oxidizing agent is used, it is preferably added as it is or as an aqueous solution to a fermentation residue.

  In this embodiment, as shown in FIG. 2, by disposing a part of the stirring blade 25a of the stirrer 25 so as to come out into the air from the water surface, air as an oxidant is left as a fermentation residue as the stirring blade 25a rotates. It is configured to be introduced into a liquid such as a liquid. Thus, by allowing a part of the stirring blade 25a to protrude above the water surface, air (oxidant) can be easily and efficiently involved in the liquid, and the air can be uniformly dispersed, Efficient processing is possible in a short time.

  A commercially available glass electrode type measuring instrument can be used for the pH measuring instrument 22, and a measuring instrument comprising an indicator electrode made of a platinum wire and a reference electrode made of a silver-silver chloride electrode can be used for the oxidation-reduction potential measuring instrument 26. Can do.

  By bringing the liquid such as the fermentation residual liquid into contact with the oxidizing agent, the liquid property of the liquid which is a strong reducing atmosphere can be adjusted to the oxidizing atmosphere. Therefore, the dissociation of hydrophilic groups (hydroxyl group, carbonyl group, etc.) present in the liquid can be effectively suppressed, and reducing hydrophilic groups (amino group, thiol group, etc.) having nitrogen element, sulfur element, etc. Hydrophilicity can be reduced by oxidizing to some extent. Thereby, the solid-liquid separation property can be further improved, and the processing efficiency in the subsequent solid-liquid separation device 30 can be remarkably increased.

  That is, in this embodiment, the single adjustment tank 20 performs simultaneously the combined treatment of the pH adjustment treatment of the liquid such as the fermentation residual liquid and the oxidizing agent contact treatment.

  In addition, the order of pH adjustment processing of liquids, such as a fermentation residual liquid, and oxidizing agent contact processing is not specifically limited, For example, the form (form shown in FIG. 2) processed simultaneously in a single adjustment tank, pH adjustment processing It can be set as the form which performs an oxidizing agent contact process later, and the form (form shown in FIG. 4 mentioned later) which adjusts pH after an oxidizing agent contact process. Since the effect of the oxidizing agent can be enhanced more in an acidic atmosphere, from that viewpoint, the form in which the oxidizing agent is contacted after simultaneous treatment or pH adjustment treatment is preferable, and the liquid such as the fermentation residual liquid has a high concentration. In the case of containing an ammonia component, a form in which pH adjustment treatment is performed after the oxidizing agent contact treatment is preferable from the viewpoint of reducing the amount of acid used.

  In the solid-liquid separation device 30 that performs the solid-liquid separation step, the treatment liquid is separated into a solid component and a liquid component. Solid-liquid separation can be performed by, for example, a mechanical device such as a gravity separation type, a decanter type, or a centrifugal type, and is selected according to the properties of a liquid such as a fermentation residual liquid. By treating the treatment liquid whose solid-liquid separation property has been improved in the liquid treatment step described above in the solid-liquid separation step, for example, a solid content with a solid content concentration of about 7 to 20% by weight and a solid content concentration of 1 to 4% by weight It can be efficiently separated into liquids of a certain degree. The liquid component can be provided with a film treatment step or an antifoaming agent treatment step depending on the state.

  In the concentration apparatus 40 which implements a concentration process, the concentrate of solid content concentration about 20-30 weight% is produced | generated by concentrating the liquid part in a solid-liquid separation process. Concentration can be carried out using a known concentrator, for example, preferably using a multi-effect type concentrator under reduced pressure. As a multi-effect type concentrator, a device having a known configuration such as a double-effect can, a triple-effect can, or a quadruple-effect can can be used. By using a multi-effect type concentrator, concentration at a relatively low temperature is possible, and the energy efficiency in the concentration step can be significantly increased. Multiple effect cans require approximately 1/3 (for triple or quadruple effect cans) to 1/4 (for quadruple or quintuple effect cans) compared to concentrators with a single evaporator. Can be reduced to

  In the multi-effect system, a concentrator provided with a steam compressor (efficiency is difficult to improve even if attached to a small system) on the steam introduction path connecting each can is also preferable. By forcibly recompressing the steam with a steam compressor, it becomes possible to increase the temperature again, improve the thermal efficiency, and improve the concentration efficiency. The condensate produced during the concentration step may contain nitrogen components and the like, but these components can be processed in a simple denitrification apparatus 50 as necessary.

  Here, the concentration apparatus 40 which can be used suitably for the processing system of this invention is demonstrated along FIG. The concentrator 40 is a multi-effect type concentrator, and is composed of a first can 41, a second can 42, and a third can 43, and is a forced-circulation type triple effect can that forcibly circulates fluid in each can. . The forced circulation method is a method for avoiding evaporation in a heating unit (not shown) and forcibly circulating the inside of the concentration can as a liquid having a saturation temperature. Since the viscosity of liquid components increases as the degree of concentration increases, the fluidity of the concentrated concentrate is secured by adopting the forced circulation method, and the occurrence of scaling in the device is minimized. be able to.

  The heat generated by the external heat source is introduced into the first can 41 as steam through the path 45a, and the liquid from the solid-liquid separator 30 is introduced through the path 31a. The liquid component is preheated with steam in a heating unit (not shown) and then introduced into the first can 41.

  The inside of the first can 41 is maintained in a negative pressure state by a decompression device (not shown), and the liquid component is efficiently concentrated. The concentrate concentrated to the predetermined concentration in the first can 41 is transferred to the second can 42 via the path 31b, where it is concentrated in the same manner as the first can 41, and then the third can 43 via the path 31c. To be concentrated in the same way. Moreover, the vapor | steam discharged | emitted from the 1st can 41 is sent to the 2nd can 42 through the path | route 45b, and the vapor | steam discharged | emitted from the 2nd can 42 is sent to the 3rd can 43 through the path | route 45c. Steam compressors 48, 48 are disposed in the paths 45b, 45c through which the steam passes. In this way, heat can be repeatedly used as the evaporation heat source in the first can 41, the second can 42, and the third can 43, so that it is possible to concentrate with a heat quantity that is a fraction of that of the single effect method. , Energy efficiency can be significantly increased. The temperature and pressure in each can are, for example, about 130 ° C. and about 0.27 MPa for the first can 41, about 115 ° C. and about 0.17 MPa for the second can 42, about 100 ° C. for the third can 43, About 10 MPa.

  A drying step can be provided as necessary after the concentration step. In the drying apparatus 60 that performs the drying process, the solid content in the solid-liquid separation process and the concentrate in the concentration process are mixed to a solid content concentration of 70% by weight or more, preferably about 80 to 95% by weight. dry. Controlling the solid content concentration within the above range facilitates long-term storage of the dried product. In addition, mixing with a solid content and a concentrate can be performed using a line mixer etc.

  Drying can be performed using a known drying apparatus, and for example, it is preferably performed under vacuum using a multi-effect drying apparatus. As a multi-effect drying apparatus, a known apparatus such as a double-effect can, triple-effect can, or quadruple-effect can or a drum dryer type can be used. These enable drying at a relatively low temperature and can significantly increase energy efficiency in the drying process. In the multi-effect can, the required amount of heat can be reduced to about 1/3 to 1/4 as compared with a drying apparatus using a single drying can.

  The dried product is introduced into the pelletizing apparatus 70 and pelletized to form pellets. The shape, size, etc. of the pellet are appropriately changed according to the situation in which it is used. Moreover, long-term preservability and handleability can be improved by introducing pellets into a drying apparatus (not shown) and further drying as necessary. The pellet can be used as a solid fertilizer such as a general fertilizer when special fertilizer, fertilizer raw material, or component adjustment is performed.

  FIG. 4 is a drawing for explaining a processing system according to another embodiment. In the present embodiment, the oxidizing agent contact treatment and the pH adjustment treatment are configured to be performed by separate apparatuses. Specifically, the packed tower 80 for bringing the fermentation residual liquid into contact with air as the oxidizing agent, and the pH adjustment. PH adjustment tank 90 which performs.

  The fermentation residual liquid discharged from the fermenter 10 is introduced into the upper portion of the packed tower 80 via the nozzle 11, the temporary storage tank 13 and the pump 15, and sprayed into the packed tower 80 from the nozzle. On the other hand, air is introduced from the bottom of the packed tower 80 from the blower 81, whereby the fermentation residual liquid and the air are brought into contact with each other. The packed tower 80 is filled with a filler, and is configured so that the fermentation residual liquid and the air are in efficient gas-liquid contact. In addition, the ratio of the fermentation residual liquid introduction amount to the packed tower 80 and the air introduction amount is appropriately adjusted according to the oxidation-reduction potential value of the fermentation residual liquid. A redox potential measuring device 26 is provided at the bottom of the packed tower 80. This treatment can be similarly applied to the leachable water containing reducing organic substances.

  The contact between the liquid such as the fermentation residue in the packed tower 80 and the air is, for example, a noble (positive) side from −15 mV, preferably −15 to +50 mV at a redox potential based on a silver-silver chloride electrode (Ag / AgCl). It is desirable to control so as to be about -10, more preferably about -10 to +20 mV.

  The treatment liquid discharged from the packed tower 80 is transferred to the pH adjustment tank 90. The pH adjusting tank 90 includes an acid supply device 21, a pH measuring device 22, and a stirrer 93. By adding an acid to the introduced processing liquid, the pH is 5.5 or less, preferably pH 5.5-3. Adjust to about 0.0, more preferably about pH 4.5 to 3.5. The treatment liquid after pH adjustment is introduced into the solid-liquid separator 30 and separated into a solid part and a liquid part. A plate tower may be used instead of the packed tower.

  The treatment system according to the present embodiment performs a pH adjustment treatment after an oxidizing agent contact treatment of a liquid such as a fermentation residue. In the present embodiment, for example, when the ammonia component is contained at a high concentration in a liquid such as a fermentation residue, the ammonia component can be diffused in the oxidizing agent contact treatment, and the amount of acid used in the subsequent pH adjustment treatment can be reduced. This is effective from the viewpoint of reduction.

  Next, the effect | action which can improve solid-liquid separability by adjusting an fermentation residual liquid to pH 5.5 or less and making an oxidizing agent contact is demonstrated based on the test which evaluated solid-liquid separability.

<Test 1>
Fermentation residue obtained by methane fermentation of milking cow manure [redox potential (vs Ag / AgCl): -190 mV, pH: 8.3] 100 ml is taken into a centrifuge tube with a capacity of about 700 ml, and acid (hydrochloric acid) is added. A plurality of samples having different pH values were prepared. A test was conducted to evaluate the solid-liquid separability of the sample that was allowed to stand after being sufficiently stirred while entraining air. In the evaluation of solid-liquid separability, the sample adjusted to pH 5.5 or less causes severe foaming due to carbon dioxide, so after degassing through a centrifugal separator, the supernatant water layer (liquid component) and the precipitate layer (solid Min) and comparing the amount. When the amount of the supernatant water was 25 ml or more, it was evaluated that the solid-liquid separation property was high. The rotation speed of the centrifugal separator was 2000 ppm and the temperature was 15 ° C. The results are shown in Table 1.

  In addition, the oxidation-reduction potential (vs Ag / AgCl) after centrifugation operation was in the range of −80 mV to +10 mV. The pH value was measured using a commercially available glass electrode type pH meter, and the redox potential was measured using a platinum wire as an indicator electrode and a commercially available silver-silver chloride electrode (Ag / AgCl) as a reference electrode.

＜試験２＞
搾乳牛糞尿をメタン発酵して得られる発酵残液〔酸化還元電位（vs Ag/AgCl）：−１９０ｍＶ〕をエアレーション（曝気）処理して酸化還元電位（vs Ag/AgCl）を＋１５ｍＶに調整した（この際、ｐＨが８．３から７．５に変化した。これはエアレーションの効果だけでなくアンモニア成分の飛散も影響しているものと考えられる。）。

<Test 2>
Fermentation residue obtained by methane fermentation of milked cow manure [redox potential (vs Ag / AgCl): -190 mV] was aerated (aerated) to adjust the redox potential (vs Ag / AgCl) to +15 mV ( At this time, the pH changed from 8.3 to 7.5, which is considered to be influenced not only by the aeration effect but also by the scattering of the ammonia component.

  Take 100 ml of this liquid in a centrifuge tube with a capacity of about 700 ml, add acid (hydrochloric acid) to prepare a plurality of samples with different pH values, stir well while entraining air, and then leave the liquid solid for separation. The test to evaluate was done. In the evaluation of solid-liquid separation, since foaming derived from carbon dioxide occurs in the sample adjusted to pH 5.5 or lower, after degassing through a centrifugal separator, the supernatant water layer (liquid component) and the precipitate layer (solid component) ) And comparing the amount. When the amount of the supernatant water was 25 ml or more, it was evaluated that the solid-liquid separation property was high. The rotation speed of the centrifugal separator was 2000 ppm and the temperature was 15 ° C. The results are shown in Table 2. The pH value was measured using a commercially available glass electrode type pH meter, and the redox potential was measured using a platinum wire as an indicator electrode and a commercially available silver-silver chloride electrode (Ag / AgCl) as a reference electrode.

＜試験３＞
さらに、酸化還元電位の効果を確認するために、以下の試験を行った。
搾乳牛糞尿をメタン発酵して得られる発酵残液〔酸化還元電位（vs Ag/AgCl）：−１９０ｍＶ〕をエアレーション（曝気）処理して酸化還元電位（vs Ag/AgCl）を−２０ｍＶ、０ｍＶに調整した。

<Test 3>
Furthermore, in order to confirm the effect of the redox potential, the following test was performed.
Fermentation residue obtained by methane fermentation of milking cow manure [oxidation-reduction potential (vs Ag / AgCl): -190 mV] is aerated (aerated) to reduce the oxidation-reduction potential (vs Ag / AgCl) to -20 mV and 0 mV. It was adjusted.

  Take 100 ml of this liquid in a centrifuge tube with a capacity of about 700 ml, add acid (hydrochloric acid) to prepare a plurality of samples with different pH values, stir well while entraining air, and then leave the liquid solid for separation. The test to evaluate was done. In the evaluation of the solid-liquid separation property, the sample adjusted to pH 5.8 or less causes intense foaming derived from carbon dioxide. Therefore, after degassing through a centrifugal separator, the supernatant water layer (liquid component) and the precipitate layer (solid phase) Min) and comparing the amount. The rotation speed of the centrifugal separator was 2000 ppm, the centrifugal time was 3 minutes, and the temperature was 15 ° C. The results are shown in Table 3. The pH value was measured using a commercially available glass electrode type pH meter, and the redox potential was measured using a platinum wire as an indicator electrode and a commercially available silver-silver chloride electrode (Ag / AgCl) as a reference electrode.

これらの試験結果より、発酵残液をｐＨ５．５以下に調整するとともに酸化剤を接触させることで、固液分離性を著しく向上させることが可能であることが判る。

From these test results, it can be seen that the solid-liquid separability can be remarkably improved by adjusting the fermentation residual liquid to pH 5.5 or lower and contacting the oxidizing agent.

  Note that the pH of the test conducted in the same manner as in Test 2 except that the redox potential (vs Ag / AgCl) was adjusted to +20 mV using hypochlorous acid as the oxidizing agent should be adjusted to 5.5 or lower. The high solid-liquid separation property was confirmed.

  In addition, the above test was also conducted on the methane fermentation residual liquid (solid content concentration 6.5% by weight, pH 7.8) of food waste slurry and the methane fermentation residual liquid (solid content concentration 4.8% by weight, pH 8.8) of pig manure. The test similar to 1-3 was done. As a result, it was confirmed that a high solid-liquid separation property was exhibited by controlling the redox potential (vs Ag / AgCl) to a noble side from −15 mV at pH 5.5 or lower. However, in the case of pig manure raw material, the amount of acid used was significantly increased because the ammonia concentration in the fermentation residue was extremely high. The amount used may have reached more than five times that of milked cow manure, for example. Therefore, when applying to the fermentation residue of swine manure from the viewpoint of reducing the amount of acid used, first add oxygen and remove ammonia component by sufficient aeration treatment, then add acid to adjust pH It is preferable.

  EXAMPLES Hereinafter, although an Example etc. are given and this invention is demonstrated in detail, this invention is not restrict | limited at all by these.

Example 1
Sulfuric acid was added to the fermentation residual liquid having a moisture content of 95% by weight, a solid content concentration (TS) of 5% by weight, pH 8.0, and a temperature of 50 ° C., and aeration treatment was performed. AgCl) was adjusted to -10 mV and a temperature of 40 ° C. When this was subjected to solid-liquid separation using a gravity separation type solid-liquid separation apparatus with an average residence time (separator capacity / flow rate) of 10 minutes, an upper layer (liquid content) with a solid content concentration of 1% by weight and a solid content concentration of 10 It was possible to separate into a lower layer (solid content) of wt%. In addition, BOD after carrying out the film processing of the upper layer was 205 mg / L, and SS was 30 mg / L.

Comparative Example 1
The same procedure as in Example 1 was performed except that sulfuric acid was not added (pH adjustment). As a result, even if it processed with the solid-liquid separator, it could not be separated into two phases clearly. Furthermore, even if the average residence time in the solid-liquid separator is 20 minutes, the upper layer (liquid component) having a solid content concentration of 4.5% by weight and the lower layer (solid component) having a solid content concentration of 5.5% by weight are obtained. It was only separated and solid-liquid separation was difficult.

Comparative Example 2
The procedure was the same as in Example 1 except that the aeration treatment was not performed, and the pH was adjusted to 5.0, the oxidation-reduction potential (vs Ag / AgCl) was adjusted to -85 mV, and the temperature was 40 ° C. This was subjected to solid-liquid separation using a gravity separation type solid-liquid separation apparatus with an average residence time of 10 minutes. As a result, an upper layer (liquid component) having a solid content concentration of 3% by weight and a lower layer (solid component concentration of 7% by weight). ) And separated. However, since the solid-liquid separation property is not sufficient, it is necessary to keep the backwash frequency in the upper layer membrane treatment 10 times or more that in Example 1, and stable operation is difficult.

Example 2
Hydrochloric acid is added to the fermentation residue with a moisture content of 95% by weight, a solid content concentration of 5% by weight, pH 8.0, and a temperature of 50 ° C., and aeration treatment is performed to adjust the pH to 4.8 and the redox potential (vs Ag / AgCl). It adjusted to -5mV and the temperature of 40 degreeC. When this is subjected to solid-liquid separation using a centrifugal solid-liquid separator, it can be separated into an upper layer (liquid component) having a solid content concentration of 1% by weight and a lower layer (solid component) having a solid content concentration of 18% by weight. did it.
When the liquid component is concentrated with a triple effect concentration device, a concentrate with a solid content of 30% by weight can be obtained, and the solid content is dried with a drum dryer dryer together with the solid content to obtain a solid content of 90% by weight. Of dry fertilizer could be adjusted.

Comparative Example 3
The procedure was the same as in Example 2 except that the aeration treatment was not performed, and the pH was adjusted to 4.8, the oxidation-reduction potential (vs Ag / AgCl) was adjusted to -92 mV, and the temperature was 40 ° C. When this was subjected to solid-liquid separation using a centrifugal solid-liquid separation device, it was separated into an upper layer (liquid component) having a solid content concentration of 3.5% by weight and a lower layer (solid component) having a solid content concentration of 15% by weight. .
When the liquid is dried with a concentrating device, it becomes a concentrate having a solid content of 25% by weight, and this concentrate is dried with a drying device together with the solid to prepare a dry fertilizer with a solid content of 90% by weight. It was too big and not practical.

Example 3
Hydrochloric acid is added to the fermentation residue with a moisture content of 95% by weight, a solid content concentration of 5% by weight, pH 8.0, and a temperature of 50 ° C., and aeration treatment is performed to adjust the pH to 5.5 and the redox potential (vs Ag / AgCl). The temperature was adjusted to -11 mV and the temperature was 40 ° C. This was separated into solid and liquid by solid-liquid separation using a centrifugal solid-liquid separator. The liquid is treated with an antifoaming agent and then concentrated with a triple effect concentration device to obtain a concentrate, and this concentrate is dried together with the solids with a drum dryer drying device to obtain a dry fertilizer with a solid content of 90% by weight. Could be adjusted.

Comparative Example 4
The same procedure as in Example 3 was performed except that the pH was adjusted to 5.7. This was separated into solid and liquid by solid-liquid separation using a centrifugal solid-liquid separator. Although the liquid was treated with an antifoaming agent, foaming was severe and concentration was difficult.

Example 4
The final disposal site leachate containing 0.8% organic solids such as humic substances and having an oxidation-reduction potential of -110 mV vs Ag / AgCl, pH 8.5 was treated by the method of Example 1. The supernatant solid concentration after the gravity separation type solid-liquid separator was 0.05%, and the lower layer was 2.5%. The BOD of the upper layer after membrane treatment was 160 mg / l, and SS was 20 mg / l.

  INDUSTRIAL APPLICABILITY The present invention can be used as a processing method and processing system for a fermentation residue obtained by subjecting organic waste to methane fermentation and other anaerobic organic compound-containing liquids.

It is a block diagram which shows the outline of the whole system.

It is drawing used for description of the processing system which concerns on this invention.

It is drawing used for description of the triple effect type concentration apparatus.

It is drawing used for description of the processing system which concerns on other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fermenter 20 Adjustment tank 21 Acid supply device 22 pH measuring device 26 Oxidation reduction potential measuring device 30 Solid-liquid separation device 40 Concentration device 50 Denitrification device 60 Drying device 70 Pelletization device 80 Packing tower 90 pH adjustment tank

Claims (4)

The liquid processing step of contacting an oxidizing agent with adjusting the resulting organic waste to methane fermentation fermented residual liquid and other anaerobic organic compound-containing solution to pH5.5 or less including calling酵残liquid and other A method of treating an anaerobic organic compound-containing liquid ,
The fermentation residue and other anaerobic organic compounds are characterized in that the contact with the oxidizing agent in the liquid treatment step is controlled to be -15 mV to 50 mV at a redox potential based on a silver-silver chloride electrode . Processing method of contained liquid. A liquid treatment step of adjusting the fermentation residue obtained by methane fermentation of organic waste and other anaerobic organic compound-containing liquid to pH 5.5 or lower and contacting with an oxidizing agent;
A processing method of the liquid treatment and solid-liquid separation step of processing liquid to solid-liquid separation in the step, the including origination酵残liquid and other anaerobic organic compound containing liquid,
The fermentation residue and other anaerobic organic compounds are characterized in that the contact with the oxidizing agent in the liquid treatment step is controlled to be -15 mV to 50 mV at a redox potential based on a silver-silver chloride electrode . Processing method of contained liquid. A liquid treatment step of adjusting the fermentation residue obtained by methane fermentation of organic waste and other anaerobic organic compound-containing liquid to pH 5.5 or lower and contacting with an oxidizing agent;
A solid-liquid separation step for solid-liquid separation of the treatment liquid in the liquid treatment step;
Wherein a solid-liquid processing method of separation and concentration step was concentrated under reduced pressure a liquid fraction in step a including origination酵残liquid and other anaerobic organic compound containing liquid,
The fermentation residue and other anaerobic organic compounds are characterized in that the contact with the oxidizing agent in the liquid treatment step is controlled to be -15 mV to 50 mV at a redox potential based on a silver-silver chloride electrode . Processing method of contained liquid. The fermentation residue obtained by methane fermentation of organic waste and other anaerobic organic compound-containing liquids are adjusted to pH 5.5 or lower, and at a redox potential of -15 mV to 50 mV based on a silver-silver chloride electrode. A processing system for a fermentation residual liquid and other anaerobic organic compound-containing liquid, comprising an adjustment tank that is controlled to come into contact with an oxidizing agent.

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