JP7546623B2 - Anaerobic treatment apparatus and anaerobic treatment method - Google Patents
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- Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
Description
本発明は排水の嫌気性処理装置及び嫌気性処理方法に関する。 The present invention relates to an anaerobic wastewater treatment device and an anaerobic treatment method.
有機性廃棄物を、メタン発酵を用いて嫌気性処理する方法は、活性汚泥法等の好気性処理に比べると曝気のためのエネルギーが不要であり運転コストが低いこと、嫌気性処理後の消化液が生物学的に安定していること、嫌気性処理で得られる消化ガス（メタンガス）をエネルギーとして利用できることなど、多くのメリットがある。そのため、近年では厨芥、残飯、食品及び飲料品の製造残渣、下水汚泥、有機性の排水処理汚泥、家畜糞尿などの有機性廃棄物を対象とした嫌気性処理装置の需要が増加している。 The method of anaerobic treatment of organic waste using methane fermentation has many advantages compared to aerobic treatment methods such as the activated sludge method. For example, it does not require energy for aeration and therefore has low operating costs, the digestive liquid after anaerobic treatment is biologically stable, and the digestive gas (methane gas) obtained during anaerobic treatment can be used as energy. For these reasons, there has been an increase in demand in recent years for anaerobic treatment equipment for organic waste such as kitchen waste, leftover food, food and beverage manufacturing residues, sewage sludge, organic wastewater treatment sludge, and livestock manure.
しかしながら、有機性廃棄物と一口に言ってもその中に含まれる有機物は排出源に応じて大きく変動する。このため、有機性廃棄物中に含まれる有機物の種類に応じて適切な嫌気性処理装置の設計及び運転が必要になる。このような背景から、これまで有機性廃棄物の種類に応じた各種の嫌気性処理装置が提案されており、その改良が続けられてきた。 However, even though it is generally referred to as organic waste, the amount of organic matter contained therein varies greatly depending on the source of discharge. For this reason, it is necessary to design and operate an anaerobic treatment device appropriate for the type of organic matter contained in the organic waste. Against this background, various anaerobic treatment devices have been proposed to date according to the type of organic waste, and improvements to these devices have continued.
特許文献１（特開２０１８－０１５６９１号公報）には、化学工場などから排出されるメタノールやホルムアルデヒドなどの低分子有機物を主成分とする有機性廃水では、グラニュール汚泥を形成しにくく、維持しにくいという問題を背景として、嫌気性反応槽の立ち上げ運転期間を短縮した有機性廃水の嫌気性処理方法を提供することを課題とする発明が記載されている。具体的には、嫌気性微生物を担持することができる担体を保持する嫌気性反応槽と、当該嫌気性反応槽に投入するための嫌気性微生物が付着している馴致担体を調製する馴致担体調製用嫌気性反応槽と、を具備することを特徴とする有機性廃水の嫌気性処理装置が記載されている。特許文献１に記載の有機性廃水の嫌気性処理装置によれば、嫌気性微生物が付着している馴致担体を投入するため、担体表面に高いメタン生成活性度を有する生物膜が形成されやすく立ち上げ期間の短縮を行うことができるとされる。 Patent Document 1 (JP Patent Publication 2018-015691A) describes an invention that aims to provide an anaerobic treatment method for organic wastewater that shortens the start-up operation period of an anaerobic reaction tank, against the background of the problem that granular sludge is difficult to form and maintain in organic wastewater mainly composed of low-molecular-weight organic matter such as methanol and formaldehyde discharged from chemical plants and the like. Specifically, an anaerobic treatment device for organic wastewater is described that is characterized by having an anaerobic reaction tank that holds a carrier capable of supporting anaerobic microorganisms, and an anaerobic reaction tank for preparing an acclimatized carrier to which anaerobic microorganisms are attached for preparation, which prepares an acclimatized carrier to be introduced into the anaerobic reaction tank. According to the anaerobic treatment device for organic wastewater described in Patent Document 1, since an acclimatized carrier to which anaerobic microorganisms are attached is introduced, a biofilm with high methane generation activity is easily formed on the carrier surface, and the start-up period can be shortened.
特許文献２（特開２０１７－１５４０８２号公報）には、油脂は、嫌気性処理条件下で生分解されにくいといった問題があることに鑑み、嫌気性処理における高級脂肪酸の分解効率を高めた嫌気性排水処理装置を提供することを課題とする発明が記載されている。具体的には、油脂を含む排水を導入し、処理菌により油脂を分解して酸を含む一次処理水を生成する酸生成槽と、一次処理水を導入し、処理菌によりメタン発酵して二次処理水を生成する反応槽と、を備え、反応槽から排出される処理菌を酸生成槽に返送する返送手段及び／又は酸生成槽を有する、嫌気性排水処理装置が記載されている。 Patent Document 2 (JP Patent Publication 2017-154082A) describes an invention that aims to provide an anaerobic wastewater treatment device that improves the decomposition efficiency of higher fatty acids in anaerobic treatment, in consideration of the problem that fats and oils are difficult to biodegrade under anaerobic treatment conditions. Specifically, the invention describes an anaerobic wastewater treatment device that includes an acid production tank into which wastewater containing fats and oils is introduced and the fats and oils are decomposed by treatment bacteria to produce primary treated water containing acid, and a reaction tank into which the primary treated water is introduced and the treatment bacteria ferment it into methane to produce secondary treated water, and that has a return means for returning the treatment bacteria discharged from the reaction tank to the acid production tank and/or the acid production tank.
特許文献３（特開２００５－１６１１７３号公報）には、廃水中にたんぱく質が存在すると、嫌気的条件下で次第に低分子化し、その際に、たんぱく質中の有機性窒素が無機化してアンモニアが発生することで、メタン菌の活性が低下するという問題を解決するための発明が記載されている。具体的には、たんぱく質含有排水をメタン発酵処理する方法において、該たんぱく質含有排水を乳酸発酵してｐＨを低下せしめ、該排水中のたんぱく質を凝固して分離したのちに、該分離水をメタン発酵処理することを特徴とするたんぱく質含有排水のメタン発酵処理方法が記載されている。 Patent Document 3 (JP Patent Publication 2005-161173 A) describes an invention for solving the problem that when proteins are present in wastewater, they gradually break down into smaller molecules under anaerobic conditions, during which time the organic nitrogen in the proteins becomes inorganic and ammonia is generated, resulting in a decrease in the activity of methanogens. Specifically, the invention describes a method for treating protein-containing wastewater by methane fermentation, which is characterized in that the protein-containing wastewater is subjected to lactic acid fermentation to lower the pH, the proteins in the wastewater are coagulated and separated, and the separated water is then subjected to methane fermentation.
特許文献４（特開２０１０－０４２３５２号公報）には、酢酸が高濃度に含まれる廃水や酸発酵処理水がメタン発酵槽に流入した場合、高濃度の酢酸に接触する流入部で阻害が起こる可能性があることを背景に、改良された嫌気性処理装置が記載されている。具体的には、グラニュール汚泥及び／又は担体を充填した、ガス・液・固分離装置を多段に有する上向流嫌気性処理装置を用いて有機性廃水を生物学的に処理する嫌気性処理装置において、前記グラニュール汚泥及び／又は担体の界面より上方に配置し、かつ、最上段に設置されたガス・液・固分離部よりも下方に配置した循環水の取水口から上向流嫌気性処理装置内の水を循環水として引き抜き、前記循環水を上向流嫌気性処理装置の底部及び／又は原水流入箇所及び／又は当該上向流嫌気性処理装置の前段処理装置に循環させることを特徴とする嫌気性処理装置が記載されている。当該嫌気性処理装置によれば、上向流嫌気性処理装置内の最上段に設置されたガス・液・固分離部でのガス・液・固分離性能を維持したまま循環水の水量を増加させることができ、これにより、原水中の高濃度では阻害のある酢酸等の物質の希釈、処理水のアルカリ度を供給、さらに循環水量の増加によるグラニュール汚泥及び／又は担体の流動化を促進することができるとされている。 Patent Document 4 (JP Patent Publication 2010-042352 A) describes an improved anaerobic treatment device, which is based on the fact that when wastewater or acid fermentation treatment water containing a high concentration of acetic acid flows into a methane fermentation tank, inhibition may occur at the inlet where the high concentration of acetic acid comes into contact. Specifically, the anaerobic treatment device biologically treats organic wastewater using an upflow anaerobic treatment device filled with granular sludge and/or carriers and having multiple stages of gas-liquid-solid separation devices, and is characterized in that water in the upflow anaerobic treatment device is drawn as circulating water from a circulating water intake located above the interface of the granular sludge and/or carriers and below the gas-liquid-solid separation unit installed in the uppermost stage, and the circulating water is circulated to the bottom of the upflow anaerobic treatment device and/or the raw water inlet and/or the treatment device in the previous stage of the upflow anaerobic treatment device. This anaerobic treatment device can increase the amount of circulating water while maintaining the gas-liquid-solid separation performance in the gas-liquid-solid separation section installed at the top stage of the upflow anaerobic treatment device, which is said to dilute substances such as acetic acid that are inhibiting at high concentrations in the raw water, provide alkalinity to the treated water, and promote fluidization of the granular sludge and/or carriers by increasing the amount of circulating water.
特許文献５（特開２０１８－００８２０３号公報）には、食品廃棄物を処理対象とした湿式メタン発酵設備に関する発明が記載されている。具体的には、食品廃棄物を処理してメタンガスを得るための、酸発酵槽及びメタン発酵槽を有する、２槽発酵の湿式メタン発酵設備であって、酸発酵槽の発酵液のｐＨが３から４であり、酸発酵槽に存在する酸発酵菌の８０％以上が乳酸菌である、湿式メタン発酵設備が記載されている。この湿式メタン発酵設備により、酸発酵槽に存在する酸発酵菌の大部分が乳酸菌となり、酸発酵槽で生成する有機酸が乳酸となる。そして、酸発酵槽で乳酸が多量に生成し、メタン発酵槽において、それを栄養源としたＷＷＥ１門の真正細菌を優先菌としたメタン発酵液の発酵効果により、メタンガスの生成量が増加することで、安定的に多量のメタンガスが回収可能となると推論されている。 Patent Document 5 (JP Patent Publication 2018-008203A) describes an invention relating to a wet methane fermentation facility for treating food waste. Specifically, the wet methane fermentation facility for two-tank fermentation, having an acid fermentation tank and a methane fermentation tank, for treating food waste to obtain methane gas is described, in which the pH of the fermentation liquid in the acid fermentation tank is 3 to 4, and 80% or more of the acid fermentation bacteria present in the acid fermentation tank are lactic acid bacteria. With this wet methane fermentation facility, most of the acid fermentation bacteria present in the acid fermentation tank become lactic acid bacteria, and the organic acid produced in the acid fermentation tank becomes lactic acid. It is inferred that a large amount of lactic acid is produced in the acid fermentation tank, and that the fermentation effect of the methane fermentation liquid in the methane fermentation tank, in which the eubacteria of the WWE1 phylum are used as a nutrient source, increases the amount of methane gas produced, making it possible to stably recover a large amount of methane gas.
特許文献６（特開２０１４－０２４０３２号公報）には、低水温の条件においては、電子産業工場やパルプ製造工場、化学工場等から排出される有機物を主成分とする排水を嫌気処理することが困難であったという問題を解決することを課題とする発明が記載されている。当該発明は、有機物を含有する排水をゲル状の担体の存在下で嫌気性生物処理を行うことを特徴とする。これにより、水温３５℃未満の低水温の条件においても高負荷で安定してメタン発酵する嫌気性生物処理を行うことができるとされている。また、当該発明は特に、半導体製造工場等から排出されるテトラメチルアンモニウムヒドロキシド（ＴＭＡＨ）やメタノール等の有機物を含有する排水の処理に好適であるとされている。 Patent document 6 (JP 2014-024032 A) describes an invention aimed at solving the problem that it is difficult to anaerobicly treat wastewater containing organic matter as a main component, discharged from electronics factories, pulp manufacturing factories, chemical factories, etc., under low water temperature conditions. This invention is characterized in that wastewater containing organic matter is subjected to anaerobic biological treatment in the presence of a gel-like carrier. It is said that this makes it possible to perform anaerobic biological treatment with stable methane fermentation under high load even under low water temperature conditions of less than 35°C. Furthermore, this invention is said to be particularly suitable for treating wastewater containing organic matter such as tetramethylammonium hydroxide (TMAH) and methanol, which is discharged from semiconductor manufacturing factories, etc.
特許文献７（特開２００８－２７９３８４号公報）には、グラニュール汚泥の維持、増殖が困難であった蒸発凝縮水を被処理液とする高負荷高速処理を長期に渡り、安定的に継続するための発明が記載されており、グラニュール汚泥が保持されメタン発酵が行われる反応槽と、パルプ製造工程から排出される蒸発凝縮水を反応槽に導入する被処理液路と、製紙工程から排出され澱粉を含む澱粉含有廃液を反応槽または被処理液路の途中に供給する澱粉廃液路と、を含む製紙排水の嫌気性処理装置が記載されている。 Patent document 7 (JP Patent Publication 2008-279384A) describes an invention for stably continuing high-load, high-speed treatment over a long period of time using evaporated condensed water as the liquid to be treated, which has been difficult to maintain and grow as granular sludge. The invention describes an anaerobic treatment device for papermaking wastewater that includes a reaction tank where granular sludge is held and methane fermentation is carried out, a treated liquid passage that introduces evaporated condensed water discharged from a pulp manufacturing process into the reaction tank, and a starch waste liquid passage that supplies starch-containing waste liquid discharged from a papermaking process to the reaction tank or the treated liquid passage.
排水の中には、食品製造系排水等のように乳酸の濃度が高い排水がある。また、上記の特許文献にも記載されているように有機性廃棄物を処理する過程で乳酸を含有する排水が生成する場合もある。乳酸は上記の特許文献にも記載されているようにメタン発酵処理する方法が知られている。 Some wastewater, such as wastewater from food manufacturing, contains high concentrations of lactic acid. As described in the above patent document, wastewater containing lactic acid may also be produced during the process of treating organic waste. As described in the above patent document, a method of treating lactic acid through methane fermentation is known.
しかしながら、乳酸を高濃度に含有する排水に対して上記の特許文献に記載されているような嫌気性処理装置を用いて処理しても十分な処理性能が達成困難な場合がある。 However, when wastewater containing a high concentration of lactic acid is treated using an anaerobic treatment device such as those described in the above patent documents, it may be difficult to achieve sufficient treatment performance.
上記事情に鑑み、本発明は、乳酸を高濃度に含有する排水の処理性能の向上が可能な嫌気性処理装置及び嫌気性処理方法を提供する。 In view of the above circumstances, the present invention provides an anaerobic treatment device and an anaerobic treatment method that can improve the treatment performance of wastewater containing a high concentration of lactic acid.
本発明者は上記課題を解決すべく鋭意検討したところ、乳酸を含む排水に対し、単糖類、二糖類以上の多糖類、タンパク質のいずれかを含む副基質を含有させることが有効であるとの知見を得た。 The inventors conducted extensive research to solve the above problems and discovered that it is effective to add a sub-substrate containing either monosaccharides, disaccharides or higher polysaccharides, or proteins to wastewater containing lactic acid.
以上の知見に基づき、本発明は一側面において、有機酸を含有し、該有機酸のうち５０質量％以上が乳酸を占める排水を導入し、排水中の乳酸を嫌気的に分解して酢酸及びプロピオン酸を含む一次処理液を生成する乳酸分解槽と、一次処理液を導入し、一次処理液をメタン発酵処理して二次処理液を生成するメタン発酵槽と、メタン発酵槽内の二次処理液を乳酸分解槽内へ返送する返送手段と、排水又は一次処理液に単糖類、二糖類以上の多糖類、タンパク質のいずれかを含む副基質を添加する副基質添加手段と、を備える嫌気性処理装置である。 Based on the above findings, in one aspect, the present invention provides an anaerobic treatment device that includes a lactic acid decomposition tank that receives wastewater containing organic acids, with lactic acid accounting for 50% by mass or more of the organic acids, and anaerobically decomposes the lactic acid in the wastewater to produce a primary treatment liquid containing acetic acid and propionic acid, a methane fermentation tank that receives the primary treatment liquid and subjects the primary treatment liquid to methane fermentation to produce a secondary treatment liquid, a return means that returns the secondary treatment liquid in the methane fermentation tank to the lactic acid decomposition tank, and a secondary substrate adding means that adds a secondary substrate containing either monosaccharides, polysaccharides of disaccharides or more, or proteins to the wastewater or the primary treatment liquid.
本発明に係る嫌気性処理装置は一実施態様において、メタン発酵槽内に、バイオフィルム形成菌、メタン発酵菌、及び共生微生物を担持する担体を備える。 In one embodiment, the anaerobic treatment device according to the present invention is provided with a carrier carrying biofilm-forming bacteria, methane fermentation bacteria, and symbiotic microorganisms in a methane fermentation tank.
本発明に係る嫌気性処理装置は別の一実施態様において、副基質添加手段は、排水に副基質を添加可能な副基質添加ラインと、メタン発酵槽内に導入される一次処理液に副基質を添加可能なバイパスラインとを備える。 In another embodiment of the anaerobic treatment device according to the present invention, the sub-substrate adding means includes a sub-substrate adding line capable of adding a sub-substrate to the wastewater and a bypass line capable of adding a sub-substrate to the primary treatment liquid introduced into the methane fermentation tank.
本発明に係る嫌気性処理装置は更に別の一実施態様において、排水は、排水中のＣＯＤｃｒに対して炭素数３以下の有機酸が２０～８０％を占める排水であり、副基質は、排水中のＣＯＤｃｒに対して１～２０％を占めるように添加される。 In yet another embodiment of the anaerobic treatment device according to the present invention, the wastewater is one in which organic acids having 3 or less carbon atoms account for 20 to 80% of the CODcr in the wastewater, and the co-substrate is added so that it accounts for 1 to 20% of the CODcr in the wastewater.
本発明に係る嫌気性処理装置は更に別の一実施態様において、乳酸分解槽の液中ｐＨが５．０～７．５の範囲であり、メタン発酵槽の液中ｐＨが６．５～８．２の範囲であり、乳酸分解槽の液中ｐＨがメタン発酵槽の液中ｐＨよりも低い。 In yet another embodiment of the anaerobic treatment device of the present invention, the liquid pH in the lactic acid decomposition tank is in the range of 5.0 to 7.5, the liquid pH in the methane fermentation tank is in the range of 6.5 to 8.2, and the liquid pH in the lactic acid decomposition tank is lower than the liquid pH in the methane fermentation tank.
本発明に係る嫌気性処理装置は更に別の一実施態様において、単糖類が、グルコース又はフルクトースを含み、二糖類以上の多糖類が、スクロース、オリゴ糖、でんぷんのいずれかを含み、タンパク質が、アミノ酸を含む。 In yet another embodiment of the anaerobic treatment device of the present invention, the monosaccharides include glucose or fructose, the disaccharide or higher polysaccharides include sucrose, oligosaccharides, or starch, and the proteins include amino acids.
本発明は別の一側面において、有機酸を含有し、有機酸のうち５０質量％以上が乳酸を占めており、単糖類、二糖類以上の多糖類、タンパク質のいずれかを含む副基質を含有する排水中の乳酸を乳酸分解槽で嫌気的に分解して酢酸及びプロピオン酸を含む一次処理液を生成する乳酸分解処理と、一次処理液をメタン発酵処理して二次処理液を生成するメタン発酵処理と、メタン発酵菌及び共生微生物を含む二次処理液を乳酸分解処理へ返送する返送処理と、を有する嫌気性処理方法である。 In another aspect, the present invention is an anaerobic treatment method comprising a lactic acid decomposition process in which lactic acid in wastewater containing organic acids, 50% by mass or more of which is lactic acid, and containing a secondary substrate including any one of monosaccharides, disaccharides or higher polysaccharides, and proteins is anaerobically decomposed in a lactic acid decomposition tank to produce a primary treatment liquid containing acetic acid and propionic acid, a methane fermentation process in which the primary treatment liquid is subjected to a methane fermentation process to produce a secondary treatment liquid, and a return process in which the secondary treatment liquid containing methane fermenting bacteria and symbiotic microorganisms is returned to the lactic acid decomposition process.
本発明に係る嫌気性処理方法は一実施態様において、副基質が、排水中のＣＯＤｃｒに対して１～２０％を占めるように排水に含有されている。 In one embodiment of the anaerobic treatment method according to the present invention, the secondary substrate is contained in the wastewater so that it accounts for 1 to 20% of the CODcr in the wastewater.
本発明によれば、乳酸を高濃度に含有する排水の処理性能の向上が可能な嫌気性処理装置及び嫌気性処理方法が提供できる。 The present invention provides an anaerobic treatment device and an anaerobic treatment method that can improve the treatment performance of wastewater containing a high concentration of lactic acid.
（１．排水）
従来技術では、乳酸を高濃度で含有する排水を嫌気性処理すると、酢酸及びプロピオン酸が残留しやすく、ＣＯＤｃｒ除去率が低下しやすいという問題がある。本発明に係る嫌気性処理装置の一実施形態によれば、乳酸を高濃度で含有する排水に対しても優れたＣＯＤｃｒ除去率を達成することができる。従って、本発明が処理対象とする排水は一実施形態において、有機酸を含有し、有機酸のうち５０質量％以上が乳酸を占める排水に対して優れた処理性能を発揮することができる。排水は、有機酸のうち７０質量％以上が乳酸を占めていてもよいし、８０質量％以上が乳酸を占めていてもよい。排水中の各種有機酸の濃度はＨＰＬＣ（高速液体クロマトグラフ法）（ＪＩＳ Ｋ０１２４：２０１１、ＪＩＳ Ｋ０２１４：２０１３）により測定可能である。
(1. Drainage)
In the conventional technology, when wastewater containing a high concentration of lactic acid is anaerobically treated, there is a problem that acetic acid and propionic acid are likely to remain, and the CODcr removal rate is likely to decrease. According to one embodiment of the anaerobic treatment device of the present invention, an excellent CODcr removal rate can be achieved even for wastewater containing a high concentration of lactic acid. Therefore, in one embodiment, the wastewater to be treated by the present invention can exhibit excellent treatment performance for wastewater containing organic acids and in which 50 mass% or more of the organic acids are lactic acid. The wastewater may contain 70 mass% or more of lactic acid, or 80 mass% or more of the organic acids. The concentration of various organic acids in the wastewater can be measured by HPLC (high performance liquid chromatography) (JIS K0124: 2011, JIS K0214: 2013).
また、本発明が処理対象（基質）とする排水は一実施形態において、排水中のＣＯＤｃｒ（二クロム酸カリウムによる酸素要求量）に対して炭素数３以下の有機酸が２０～８０％を占める。排水は、排水中のＣＯＤｃｒに対して炭素数３以下の有機酸が４０～８０％を占めてもよく、典型的には５０～８０％を占める。 In one embodiment, the wastewater to be treated (substrate) in the present invention is one in which organic acids with 3 or less carbon atoms account for 20-80% of the CODcr (oxygen demand by potassium dichromate) in the wastewater. Organic acids with 3 or less carbon atoms may account for 40-80% of the CODcr in the wastewater, and typically account for 50-80%.
本発明において、炭素数３以下の有機酸は、乳酸（Ｃ3Ｈ6Ｏ3）、ギ酸（ＨＣＯＯＨ）、酢酸（ＣＨ3ＣＯＯＨ）、及びプロピオン酸（Ｃ3Ｈ6Ｏ2）を指す。排水中のＣＯＤｃｒに対する炭素数３以下の有機酸の濃度は、以下の手順により求める。まず、排水中のＣＯＤｃｒ（単位：ｍｇ／Ｌ）をＪＩＳ Ｋ０１０２：２０１６に規定される蓋付き試験管を用いた吸光光度法に準拠して求める。また、乳酸、ギ酸、酢酸、及びプロピオン酸の排水中の濃度をＨＰＬＣによりそれぞれ求め、これらの有機酸の濃度（単位：ｍｇ／Ｌ）に対して酸素換算係数を乗ずることでＣＯＤｃｒに換算する。酸素換算係数は乳酸：０．９３６、ギ酸：０．３４３、酢酸：１．０１、プロピオン酸：１．４６とする。例えば、排水中の乳酸濃度が１０００ｍｇ／Ｌの場合、ＣＯＤｃｒに換算した乳酸の値は９３６ｍｇ／Ｌとなる。乳酸、ギ酸、酢酸、及びプロピオン酸のＣＯＤｃｒ換算値の合計を、排水のＣＯＤｃｒで除することで、排水中のＣＯＤｃｒに対する炭素数３以下の有機酸の割合が求められる。 In the present invention, organic acids having 3 or less carbon atoms refer to lactic acid ( C3H6O3 ), formic acid ( HCOOH ), acetic acid ( CH3COOH ), and propionic acid ( C3H6O2 ). The concentration of organic acids having 3 or less carbon atoms relative to the CODcr in wastewater is determined by the following procedure. First, the CODcr (unit: mg /L) in the wastewater is determined in accordance with the absorptiometry using a capped test tube as specified in JIS K0102:2016. In addition, the concentrations of lactic acid, formic acid, acetic acid, and propionic acid in the wastewater are determined by HPLC, and the concentrations of these organic acids (unit: mg/L) are multiplied by the oxygen conversion coefficient to convert them into CODcr. The oxygen conversion coefficients are 0.936 for lactic acid, 0.343 for formic acid, 1.01 for acetic acid, and 1.46 for propionic acid. For example, when the concentration of lactic acid in the wastewater is 1000 mg/L, the value of lactic acid converted into CODcr is 936 mg/L. The ratio of organic acids having a carbon number of 3 or less to the CODcr in the wastewater can be obtained by dividing the sum of the CODcr converted values of lactic acid, formic acid, acetic acid, and propionic acid by the CODcr of the wastewater.
本発明が処理対象とする排水のＣＯＤｃｒの下限は、特に制限はないが、例えば、メタン発酵槽が担体を有する場合は、５００ｍｇ／Ｌ以上とすることができ、１，０００ｍｇ／Ｌ以上とすることもでき、２，０００ｍｇ／Ｌ以上とすることもできる。また、メタン発酵槽が担体を有しない場合は、ＣＯＤｃｒが低すぎるとグラニュールが崩壊してしまう可能性があるため、３，０００ｍｇ／Ｌ以上とすることが好ましい。本発明が処理対象とする排水のＣＯＤｃｒの上限は、特に制限はないが、例えば、２０，０００ｍｇ／Ｌ以下とすることができ、１５，０００ｍｇ／Ｌ以下とすることもでき、１０，０００ｍｇ／Ｌ以下とすることもできる。 The lower limit of the CODcr of the wastewater to be treated by the present invention is not particularly limited, but for example, when the methane fermentation tank has a carrier, it can be 500 mg/L or more, 1,000 mg/L or more, or 2,000 mg/L or more. When the methane fermentation tank does not have a carrier, if the CODcr is too low, the granules may collapse, so it is preferable to set it to 3,000 mg/L or more. The upper limit of the CODcr of the wastewater to be treated by the present invention is not particularly limited, but for example, it can be 20,000 mg/L or less, 15,000 mg/L or less, or 10,000 mg/L or less.
本発明が処理対象とする排水の具体例としては、乳酸系飲料排水、乳酸菌製造設備等からの乳酸系排水、し尿、浄化槽汚泥等からの乳酸系汚泥、生ごみメタン発酵の可溶化液が挙げられる。 Specific examples of wastewater that can be treated by the present invention include wastewater from lactic acid beverages, lactic acid wastewater from lactic acid bacteria production facilities, lactic acid sludge from human waste and septic tank sludge, and solubilized liquid from methane fermentation of food waste.
（２．副基質）
有機酸のうち５０質量％以上が乳酸を占める排水に対して副基質を添加することにより、酸発酵槽でバイオフィルムを形成するAnaerolinea属、Rectinema属等のバイオフィルム形成菌の増殖が促進され、バイオフィルム形成菌の増殖によりメタン発酵槽内での担体へ付着するバイオフィルム形成菌の付着量が増える。その結果、メタン発酵槽内においてメタン菌と共生関係を構築する微生物が担体に付着し、これによりバイオフィルム形成菌とメタン菌共生微生物とが安定して形成されることで、Methanosaeta属等のメタン生成古細菌を多数維持しながら排水をメタン発酵処理することが可能となるため、排水の処理性能が向上する。
(2. Substrates)
By adding a sub-substrate to wastewater in which lactic acid accounts for 50% by mass or more of the organic acids, the growth of biofilm-forming bacteria such as Anaerolinea and Rectinema that form biofilms in the acid fermentation tank is promoted, and the growth of the biofilm-forming bacteria increases the amount of biofilm-forming bacteria that adhere to the carrier in the methane fermentation tank. As a result, microorganisms that form a symbiotic relationship with methanogens in the methane fermentation tank adhere to the carrier, and the biofilm-forming bacteria and methanogen-symbiotic microorganisms are stably formed, making it possible to perform methane fermentation treatment of the wastewater while maintaining a large number of methanogenic archaea such as Methanosaeta, thereby improving the treatment performance of the wastewater.
副基質としては、単糖類、二糖類以上の多糖類、タンパク質のいずれかを含む物質が用いられる。単糖類には、グルコース又はフルクトース等が含まれる。二糖類以上の多糖類には、スクロース、オリゴ糖、でんぷん等が含まれる。タンパク質には、アミノ酸等が含まれる。副基質は、乳酸菌製造工場で得られる乳酸系排水や、炭水化物又は糖又はタンパク質を含有する食品系廃棄物等を利用することができる。 Substrates that can be used are substances that contain either monosaccharides, disaccharides or higher polysaccharides, or proteins. Monosaccharides include glucose or fructose. Disaccharides or higher polysaccharides include sucrose, oligosaccharides, starch, and the like. Proteins include amino acids. Substrates that can be used include lactic acid wastewater obtained from lactic acid bacteria manufacturing plants, food waste containing carbohydrates, sugar, or proteins, and the like.
副基質の排水への添加量が少なすぎると所定の効果が得られず、多すぎると酸発酵に必要な滞留時間が増加する場合がある。一実施態様においては、副基質は、排水中のＣＯＤｃｒに対して１～２０％を占めるように添加されることが好ましい。これにより、バイオフィルムを形成させるバイオフィルム形成菌の増殖を促進させることができ、メタン発酵槽内で浮遊する担体への汚泥付着量を増加させることができる。担体への汚泥付着量が増加することにより、メタン発酵槽処理における共生微生物の存在量が増大するため、排水を安定的に処理できる。副基質は、排水中のＣＯＤｃｒに対して５～２０％を占めるように排水に添加されることがより好ましく、排水中のＣＯＤｃｒに対して１０～２０％を占めるように排水に添加されることが更に好ましい。 If the amount of the co-substrate added to the wastewater is too small, the desired effect will not be obtained, and if the amount is too large, the retention time required for acid fermentation may increase. In one embodiment, the co-substrate is preferably added to account for 1 to 20% of the CODcr in the wastewater. This can promote the growth of biofilm-forming bacteria that form biofilms, and can increase the amount of sludge attached to the carrier floating in the methane fermentation tank. By increasing the amount of sludge attached to the carrier, the amount of symbiotic microorganisms present in the methane fermentation tank treatment increases, allowing the wastewater to be stably treated. It is more preferable that the co-substrate is added to the wastewater to account for 5 to 20% of the CODcr in the wastewater, and even more preferable that it is added to the wastewater to account for 10 to 20% of the CODcr in the wastewater.
基質である乳酸を含む排水に対し、副基質を添加する場合には、排水に対し、栄養塩又は微量元素を更に添加することが好ましい。栄養塩は、例えばアンモニア、リン、マグネシウムなど、微量元素は例えばカリウム、カルシウム、鉄、コバルト、ニッケル、モリブデン、硫黄などが該当する。単糖類、二糖類以上の多糖類、タンパク質を含む副基質の添加に加えて栄養塩又は微量元素を排水に更に添加することで、排水中の乳酸を酢酸およびプロピオン酸に分解する例えばAneromusa属が、酸発酵処理において優先的に働くため、排水の安定的な処理が可能となる。栄養塩又は微量元素は、排水のＣＯＤｃｒに対して０．００１％～２％、より好ましくは０．００１％～１％添加できる。 When adding a secondary substrate to wastewater containing lactic acid as a substrate, it is preferable to further add nutrients or trace elements to the wastewater. Examples of nutrients include ammonia, phosphorus, and magnesium, and examples of trace elements include potassium, calcium, iron, cobalt, nickel, molybdenum, and sulfur. By further adding nutrients or trace elements to the wastewater in addition to the addition of secondary substrates including monosaccharides, disaccharides or higher polysaccharides, and proteins, organisms such as Aneromusa, which break down lactic acid in the wastewater into acetic acid and propionic acid, will act preferentially in the acid fermentation process, enabling stable treatment of the wastewater. Nutrients or trace elements can be added at 0.001% to 2%, more preferably 0.001% to 1%, based on the CODcr of the wastewater.
（３．乳酸分解槽）
乳酸分解槽では、排水中の乳酸を嫌気的に分解して酢酸及びプロピオン酸を含む一次処理液を生成する乳酸分解処理を行う。乳酸を高濃度に含有する排水をメタン発酵槽単独で処理すると、酢酸及びプロピオン酸が残留しやすく、十分なＣＯＤｃｒ除去率が得られない場合がある。本実施形態によれば、メタン発酵槽の前段に、乳酸発酵槽が設けられるため、排水をメタン発酵槽単独で処理する場合に比べて、二次処理液に含まれる酢酸及びプロピオン酸の残留量を低減でき、十分なＣＯＤｃｒを得ることができる。また、乳酸分解時の中間生成物である酢酸及びプロピオン酸をスムーズにメタンに分解することが可能になるため、乳酸を高濃度で含有する排水に対するＣＯＤｃｒ除去率を有意に向上させることができる。
(3. Lactic acid decomposition tank)
In the lactic acid decomposition tank, a lactic acid decomposition process is performed in which lactic acid in the wastewater is anaerobically decomposed to generate a primary treatment liquid containing acetic acid and propionic acid. When wastewater containing a high concentration of lactic acid is treated only in a methane fermentation tank, acetic acid and propionic acid tend to remain, and a sufficient CODcr removal rate may not be obtained. According to this embodiment, since a lactic acid fermentation tank is provided in the upstream of the methane fermentation tank, the amount of residual acetic acid and propionic acid contained in the secondary treatment liquid can be reduced compared to when wastewater is treated only in a methane fermentation tank, and a sufficient CODcr can be obtained. In addition, since acetic acid and propionic acid, which are intermediate products during lactic acid decomposition, can be smoothly decomposed into methane, the CODcr removal rate for wastewater containing a high concentration of lactic acid can be significantly improved.
乳酸分解槽内は、限定的ではないが、Pelobacter属、Veillonella属、Pseudo-flavonifractor属、Anaeromusa Desulfovibrio属、Clostridium属（乳酸分解菌）、Desulfovibrio属（硫酸還元細菌）等の酸発酵菌及びその他の嫌気性菌を含むことができる。後述するメタン発酵槽からの抽出液を返送することで更に、Syntrophobacter属、Syntrophaceticus属等の微生物も処理に寄与する。Syntrophobacter属、Syntrophaceticus属等は、メタン発酵槽内の二次処理液を返送することで、メタン生成古細菌等のメタン発酵菌及びSyntrophaceae属、Geobacter属、Syntrophorahabdus属、Pelotomaculum属、Syntrophomonas属、Syntrophobacter属などの共生微生物との共生関係が構築されるため、乳酸発酵槽内において、プロピオン酸の酢酸への分解処理を安定して行うことができる。また、メタン生成古細菌が直接利用できないプロピオン酸を酢酸に変換することで、後段でのメタン発酵処理をより安定・高速で行うことが可能となる。 The lactic acid decomposition tank may contain, but is not limited to, acid fermentation bacteria such as Pelobacter, Veillonella, Pseudo-flavonifractor, Anaeromusa Desulfovibrio, Clostridium (lactic acid decomposition bacteria), Desulfovibrio (sulfate reducing bacteria), and other anaerobic bacteria. By returning the extract from the methane fermentation tank described below, microorganisms such as Syntrophobacter and Syntrophaceticus also contribute to the treatment. By returning the secondary treatment liquid from the methane fermentation tank, the Syntrophobacter and Syntrophaceticus species form a symbiotic relationship with methane fermentation bacteria such as methanogenic archaea and symbiotic microorganisms such as Syntrophaceae, Geobacter, Syntrophorahabdus, Pelotomaculum, Syntrophomonas, and Syntrophobacter, so that the decomposition treatment of propionic acid to acetic acid can be stably performed in the lactic acid fermentation tank. In addition, by converting propionic acid, which methanogenic archaea cannot directly use, into acetic acid, the subsequent methane fermentation process can be carried out more stably and quickly.
乳酸分解槽では乳酸を酢酸まで分解することを主たる目的としているため、乳酸分解槽の液中ｐＨはメタン発酵槽の液中ｐＨよりも低くすることが好ましい。具体的には、乳酸分解槽の液中ｐＨの上限値は７．５以下とすることが好ましい。一方で、乳酸分解槽の液中ｐＨが低すぎると、水素発酵が進みやすい状況になる。例えば、排水中には、乳酸の前段物質である糖質基質が流入することがある。糖質基質から乳酸が生成される乳酸発酵では乳酸生成に伴いｐＨが４～５程度まで低下する。そこで、乳酸発酵槽の液中ｐＨの下限値は５．０以上とすることが好ましく、６．０以上とすることがより好ましい。よって、乳酸分解槽の液中ｐＨは５．０～７．５であることが好ましく、６．０～７．５であることがより好ましい。排水への副基質添加により増大し処理を安定化させる働きを持つバイオフィルム形成菌及び共生微生物の至適ｐＨは５．０～６．０であるところ、乳酸分解槽における液中ｐＨは、メタン発酵槽よりもこの至適ｐＨに近い。このため、乳酸分解槽においてメタン発酵菌及び共生微生物がその能力をより発揮できる。 Since the main purpose of the lactic acid decomposition tank is to decompose lactic acid to acetic acid, it is preferable that the liquid pH of the lactic acid decomposition tank is lower than that of the methane fermentation tank. Specifically, it is preferable that the upper limit of the liquid pH of the lactic acid decomposition tank is 7.5 or less. On the other hand, if the liquid pH of the lactic acid decomposition tank is too low, it becomes a situation where hydrogen fermentation is likely to proceed. For example, carbohydrate substrates, which are precursors to lactic acid, may flow into the wastewater. In lactic acid fermentation, in which lactic acid is produced from carbohydrate substrates, the pH drops to about 4 to 5 as lactic acid is produced. Therefore, it is preferable that the lower limit of the liquid pH of the lactic acid fermentation tank is 5.0 or more, and more preferably 6.0 or more. Therefore, it is preferable that the liquid pH of the lactic acid decomposition tank is 5.0 to 7.5, and more preferably 6.0 to 7.5. The optimum pH for biofilm-forming bacteria and symbiotic microorganisms, which increase with the addition of secondary substrates to wastewater and act to stabilize the treatment, is 5.0 to 6.0, and the liquid pH in the lactic acid decomposition tank is closer to this optimum pH than in the methane fermentation tank. This allows the methane fermentation bacteria and symbiotic microorganisms to better demonstrate their capabilities in the lactic acid decomposition tank.
乳酸分解槽のｐＨを上げるために乳酸分解槽にアルカリ剤を添加してもよいが、乳酸分解槽にアルカリを添加するとメタン発酵槽のｐＨも高くなり、別途一次処理液のｐＨ中和が必要になるため非効率的であることがある。メタン発酵槽では、メタンガス発生量が増えて、二酸化炭素の比率が下がることや有機酸が分解される過程でアルカリ度が増えてｐＨが高くなる。そのため、アルカリ剤を添加せずに、メタン発酵槽からｐＨの高い液を乳酸分解槽に返送することでｐＨが調整するようにすることで、二次処理液ｐＨの上昇を招くこともなく効率的にｐＨを好適な範囲に維持することができる。 Although an alkaline agent may be added to the lactic acid decomposition tank to raise the pH of the lactic acid decomposition tank, adding an alkaline agent to the lactic acid decomposition tank also raises the pH of the methane fermentation tank, which can be inefficient because it requires separate pH neutralization of the primary treatment liquid. In the methane fermentation tank, the amount of methane gas generated increases, the ratio of carbon dioxide decreases, and the alkalinity increases during the process of decomposing organic acids, raising the pH. Therefore, by adjusting the pH by returning the high-pH liquid from the methane fermentation tank to the lactic acid decomposition tank without adding an alkaline agent, the pH can be efficiently maintained within an appropriate range without causing an increase in the pH of the secondary treatment liquid.
乳酸分解槽から流出する一次処理液中の酢酸に対するプロピオン酸のモル比は、低いほうが好ましい。当該モル比が低いということは酢酸に分解されるプロピオン酸の比率が高いことを意味するからである。乳酸から生成されるプロピオン酸と酢酸の比率は酸化還元電位（ＯＲＰ）と相互関係にあるため、乳酸分解槽内の液又は一次処理液のＯＲＰの監視制御を行うことで処理状況を推測することができる。酢酸に対するプロピオン酸のモル比が低くなるほど、当該ＯＲＰは低くなる傾向にある。そこで、乳酸分解槽内の液、望ましくは乳酸分解槽から流出する一次処理液のＯＲＰは－１００ｍＶ以下を示すことが好ましく、－２００ｍＶ以下を示すことがより好ましい。当該ＯＲＰに下限は特に設定されないが、低すぎるとメタン発酵を介して後処理で好気性処理を行う場合に曝気風量が多くなるといった懸念もあるため、－５００ｍＶ以上であることが好ましい。 The molar ratio of propionic acid to acetic acid in the primary treatment liquid discharged from the lactic acid decomposition tank is preferably low. This is because a low molar ratio means that a high proportion of propionic acid is decomposed into acetic acid. The ratio of propionic acid and acetic acid generated from lactic acid is correlated with the oxidation-reduction potential (ORP), so the treatment status can be estimated by monitoring and controlling the ORP of the liquid in the lactic acid decomposition tank or the primary treatment liquid. The lower the molar ratio of propionic acid to acetic acid, the lower the ORP tends to be. Therefore, the ORP of the liquid in the lactic acid decomposition tank, preferably the primary treatment liquid discharged from the lactic acid decomposition tank, is preferably -100 mV or less, and more preferably -200 mV or less. There is no particular lower limit set for the ORP, but since there is a concern that if it is too low, the aeration air volume will be large when aerobic treatment is performed in post-treatment via methane fermentation, it is preferable that it is -500 mV or more.
乳酸分解槽のその他の運転条件は、例えば、以下のように設定することができる。
・滞留時間：３～１５時間、好ましくは４～８時間
・水温：３０～３５℃、好ましくは３２～３５℃
・攪拌：機械攪拌
Other operating conditions for the lactic acid decomposition tank can be set, for example, as follows.
Residence time: 3 to 15 hours, preferably 4 to 8 hours Water temperature: 30 to 35°C, preferably 32 to 35°C
・Mixing: Mechanical mixing
乳酸分解槽においては、メタン発酵槽からの返送液に含まれるメタン発酵菌によりメタンが生成されることがある。また、メタン発酵槽からの返送液が乳酸分解槽に返送されることによりｐＨが上昇してメタン発酵が行われることも想定される。このため、乳酸分解槽にはバイオガスを回収するためのガス回収系統が接続されていることが好ましい。 In the lactic acid decomposition tank, methane may be produced by methane fermentation bacteria contained in the return liquid from the methane fermentation tank. It is also expected that the pH will increase and methane fermentation will occur when the return liquid from the methane fermentation tank is returned to the lactic acid decomposition tank. For this reason, it is preferable that a gas recovery system for recovering biogas is connected to the lactic acid decomposition tank.
乳酸系排水の乳酸分解時には、上述した栄養塩や微量元素の必要添加量に留意する必要がある。その他、乳酸分解槽にｐＨ計器及び／又はガス発生量計器を設置することで、乳酸分解槽で安定処理が行われていることを確認することも可能である。 When decomposing lactic acid wastewater into lactic acid, it is necessary to pay attention to the necessary amounts of nutrients and trace elements mentioned above. In addition, by installing a pH meter and/or a gas generation meter in the lactic acid decomposition tank, it is possible to confirm that stable treatment is being carried out in the lactic acid decomposition tank.
（４．メタン発酵槽）
乳酸分解槽の後段に設置されるメタン発酵槽では、乳酸分解処理で得られる一次処理液を、メタン発酵処理して二次処理液を生成するメタン発酵処理を行うことができる。
(4. Methane fermentation tank)
In the methane fermentation tank installed downstream of the lactic acid decomposition tank, a primary treatment liquid obtained in the lactic acid decomposition process can be subjected to methane fermentation treatment to produce a secondary treatment liquid.
一次処理液には酢酸が含まれている。また、乳酸分解槽で分解できなかったプロピオン酸も含まれている。このため、メタン発酵槽では酢酸からメタンへの分解反応が行われる。メタン発酵槽には、ＵＡＳＢ（上向流嫌気性汚泥床法）及びＥＧＳＢ（膨脹汚泥床法）のような上向流型の他、固定床型、流動床型及び完全混合型等の方式がある。本発明においては、何れの方式のメタン発酵槽を用いてもよいが、担体の流動を促進させる理由から、完全混合型が好ましい。 The primary treatment liquid contains acetic acid. It also contains propionic acid that could not be decomposed in the lactic acid decomposition tank. For this reason, the decomposition reaction from acetic acid to methane takes place in the methane fermentation tank. There are various types of methane fermentation tanks, including upflow types such as UASB (upflow anaerobic sludge bed process) and EGSB (expanded sludge bed process), as well as fixed bed types, fluidized bed types, and complete mixing types. In the present invention, any type of methane fermentation tank may be used, but a complete mixing type is preferred because it promotes the flow of the carrier.
メタン発酵槽内には、バイオフィルム形成菌、メタン発酵菌、及び共生微生物を担持する担体を備える。担体の性状としては、微生物を担持し、担体表面で微生物を繁殖させることができるものであれば特に制限無く用いることができる。乳酸等の低分子有機物を主成分とする排水においてはグラニュール汚泥の形成及び維持が難しいという問題がある。そこで、投入した担体にバイオフィルム形成菌、メタン発酵菌、及び共生微生物を付着させることで、槽内にこれらの微生物を安定的に留めておくことが可能となる。また、ＵＡＳＢやＥＧＳＢのような上向流型であれば投入したグラニュール汚泥を保持できるが、完全混合型ではグラニュール汚泥は短期間で流出してしまう。そこで担体を槽内に保持するためにスクリーンにより流出した担体を収集し、槽内に戻すことも可能である。 The methane fermentation tank is equipped with a carrier that supports biofilm-forming bacteria, methane fermenting bacteria, and symbiotic microorganisms. There are no particular limitations on the properties of the carrier, as long as it can support microorganisms and allow them to grow on the surface of the carrier. There is a problem in that it is difficult to form and maintain granular sludge in wastewater that mainly contains low-molecular-weight organic matter such as lactic acid. Therefore, by attaching biofilm-forming bacteria, methane fermenting bacteria, and symbiotic microorganisms to the added carrier, it is possible to stably retain these microorganisms in the tank. In addition, while an upflow type such as UASB or EGSB can retain the added granular sludge, in a complete mixing type, the granular sludge will flow out in a short period of time. Therefore, in order to retain the carrier in the tank, it is possible to collect the carrier that flows out using a screen and return it to the tank.
担体の形状は、球状、円柱状、直方体、中空状などいずれの形状でもよいが、微生物の担持量、繁殖した微生物と排水との接触効率、メタン発酵槽内での担体の保持量などを考慮して、特に球状が好ましい。 The shape of the carrier may be any shape, such as spherical, cylindrical, rectangular, or hollow, but a spherical shape is particularly preferred, taking into consideration the amount of microorganisms supported, the contact efficiency between the propagated microorganisms and the wastewater, and the amount of carrier held in the methane fermentation tank.
担体の素材は、嫌気性微生物が付着すればどのような素材でも良いが、上述の諸要件を充足することから、特に活性炭、ポリビニルアルコール、ポリエチレングリコールなどが好ましい。メタン発酵槽内で担体が流動することで担体に付着した微生物が担体から剥離する。このため、メタン発酵槽内の液（典型的には二次処理液）を乳酸分解槽に返送することで、バイオフィルム形成菌、メタン発酵菌、及び共生微生物をメタン発酵槽内に添加することが可能である。 The carrier may be made of any material to which anaerobic microorganisms can adhere, but activated carbon, polyvinyl alcohol, polyethylene glycol, etc. are particularly preferred because they satisfy the above-mentioned requirements. The microorganisms attached to the carrier are detached from the carrier as the carrier flows in the methane fermentation tank. Therefore, by returning the liquid in the methane fermentation tank (typically the secondary treatment liquid) to the lactic acid decomposition tank, it is possible to add biofilm-forming bacteria, methane fermentation bacteria, and symbiotic microorganisms to the methane fermentation tank.
メタン発酵槽内は、限定的ではないが、Anaerolinea等のバイオフィルム形成菌、MethanosaetaやMethanobacterium等のメタン生成古細菌、及びSyntrophaceae属、Geobacter属、Syntrophorahabdus属、Pelotomaculum属、Syntrophomonas属、Syntrophobacter属などの共生微生物（共生菌）、Geobacter属（酢酸資化性細菌）、Pelotomaculum属（プロピオン酸酸化細菌）及びその他の嫌気性菌を含む。本実施形態では、排水に対して副基質が添加されることによって、一次処理液中にはバイオフィルムを形成するAnaerolinea等が多く存在する。このAnaerolineaをメタン発酵槽内へ導入してメタン発酵処理することにより、Syntrophobacter属、Syntrophaceticus、メタン生成古細菌等のメタン発酵菌及び共生菌との共生関係が構築されるため、乳酸発酵槽内において、プロピオン酸の酢酸への分解処理を安定して行うことができる。また、メタン生成古細菌が直接利用できないプロピオン酸を酢酸に変換することで、後段でのメタン発酵処理をより安定・高速で行うことが可能となる。 The methane fermentation tank contains, but is not limited to, biofilm-forming bacteria such as Anaerolinea, methanogenic archaea such as Methanosaeta and Methanobacterium, symbiotic microorganisms (symbiotic bacteria) such as the genera Syntrophaceae, Geobacter, Syntrophorahabdus, Pelotomaculum, Syntrophomonas, and Syntrophobacter, Geobacter (acetate-utilizing bacteria), Pelotomaculum (propionate-oxidizing bacteria), and other anaerobic bacteria. In this embodiment, a secondary substrate is added to the wastewater, so that a large amount of Anaerolinea and the like that form biofilms is present in the primary treatment liquid. By introducing this Anaerolinea into the methane fermentation tank and performing methane fermentation, a symbiotic relationship is established between the methane fermentation bacteria and symbiotic bacteria such as the genera Syntrophobacter, Syntrophaceticus, and methanogenic archaea, and thus the decomposition process of propionic acid into acetic acid can be stably performed in the lactic acid fermentation tank. In addition, by converting propionic acid, which methanogenic archaea cannot directly use, into acetic acid, the subsequent methane fermentation process can be carried out more stably and quickly.
メタン発酵槽の液中ｐＨはメタン発酵に適した６．５～８．２とすることが好ましく、７．０～８．０とすることがより好ましい。つまり、メタン発酵に適したｐＨは乳酸分解槽における至適ｐＨよりも高い。このことも、メタン発酵槽とは別に乳酸分解槽を設置する利点である。 The pH of the liquid in the methane fermentation tank is preferably 6.5 to 8.2, which is suitable for methane fermentation, and more preferably 7.0 to 8.0. In other words, the pH suitable for methane fermentation is higher than the optimal pH in the lactic acid decomposition tank. This is another advantage of installing a lactic acid decomposition tank separately from the methane fermentation tank.
メタン発酵槽内の液、望ましくはメタン発酵槽から流出する二次処理液のＯＲＰは、メタン発酵を安定して進める理由から、－２００ｍＶ以下を示すことが好ましく、－３００ｍＶ以下を示すことがより好ましい。当該ＯＲＰに下限は特に設定されないが、低すぎると後処理で好気性処理を行う場合に曝気風量が多くなるといった懸念もあるため－５００ｍＶ以上であることが好ましい。 The ORP of the liquid in the methane fermentation tank, preferably the secondary treatment liquid flowing out from the methane fermentation tank, is preferably -200 mV or less, and more preferably -300 mV or less, in order to ensure stable methane fermentation. There is no particular lower limit for the ORP, but if it is too low, there is a concern that the aeration air volume will increase when aerobic treatment is performed in post-treatment, so it is preferably -500 mV or more.
メタン発酵槽のその他の運転条件は、例えば、以下のように設定することができる。
・滞留時間：２～８時間、好ましくは５～８時間
・水温：３０～３５℃、好ましくは３２～３５℃
・攪拌：メタンガスが発生することによるガス攪拌
Other operating conditions of the methane fermenter can be set, for example, as follows.
Residence time: 2 to 8 hours, preferably 5 to 8 hours Water temperature: 30 to 35°C, preferably 32 to 35°C
・Mixing: Gas mixing due to the generation of methane gas
メタン発酵槽においては大量のメタンが生成することから、メタン発酵槽にはバイオガスを回収するためのガス回収系統が接続されていることが好ましい。 Since a large amount of methane is produced in the methane fermentation tank, it is preferable that the methane fermentation tank is connected to a gas recovery system for recovering biogas.
乳酸系排水のメタン発酵時には栄養塩又は微量元素の必要添加量に留意する必要がある。栄養塩はアンモニア、リン、マグネシウムなど、微量元素はカリウム、カルシウム、鉄、コバルト、ニッケル、モリブデン、硫黄などが該当する。 When performing methane fermentation on lactic acid wastewater, attention must be paid to the necessary amount of nutrients or trace elements to be added. Nutrients include ammonia, phosphorus, magnesium, etc., and trace elements include potassium, calcium, iron, cobalt, nickel, molybdenum, sulfur, etc.
特に、排水に炭水化物又は糖質を含む副基質を添加して乳酸発酵処理を行った場合には、鉄を利用して酢酸及びプロピオン酸に分解するAneromusa属が酸発酵において優先したことから、メタン発酵槽には栄養塩又は微量元素として典型的には鉄の添加が重要となる。鉄の添加が少なすぎるとヘムや非ヘムタンパク質などの微生物構成成分が不足し、活性が低下し、鉄の添加が多すぎると余剰汚泥が増加する場合がある。そのため、メタン発酵槽への添加量は、一実施形態では、排水のＣＯＤｃｒに対して０．００１～０．０２％とすることが好ましく、０．００１～０．０１％とすることがより好ましい。 In particular, when a secondary substrate containing carbohydrates or sugars is added to wastewater and lactic acid fermentation is performed, the Aneromusa genus, which uses iron to decompose the wastewater into acetic acid and propionic acid, takes precedence in acid fermentation, so it is important to add iron to the methane fermentation tank as a nutrient salt or trace element. If too little iron is added, microbial components such as heme and non-heme proteins will be insufficient and activity will decrease, while if too much iron is added, excess sludge may increase. Therefore, in one embodiment, the amount of iron added to the methane fermentation tank is preferably 0.001 to 0.02% of the CODcr of the wastewater, and more preferably 0.001 to 0.01%.
その他、メタン発酵槽には、ｐＨ計器及び／又はガス発生量計器を設置することで、メタン発酵槽で安定処理が行われていることを確認することも可能である。 In addition, by installing a pH meter and/or a gas generation meter in the methane fermentation tank, it is possible to confirm that stable treatment is being carried out in the methane fermentation tank.
（５．返送系統）
本発明に係る嫌気性処理装置は、メタン発酵槽中のメタン発酵菌及び共生微生物等を含む二次処理液を乳酸分解槽に返送するための返送系統を備える。返送系統の構成は、メタン発酵槽中のメタン発酵菌、バイオフィルム形成菌、及び共生微生物等を一定量以上乳酸分解槽に返送することができれば、特に制限はない。以下に返送系統の構成を例示する。
(5. Return System)
The anaerobic treatment device according to the present invention includes a return system for returning the secondary treatment liquid containing methane fermentation bacteria, symbiotic microorganisms, etc. in the methane fermentation tank to the lactic acid decomposition tank. There are no particular limitations on the configuration of the return system as long as it can return a certain amount or more of the methane fermentation bacteria, biofilm-forming bacteria, symbiotic microorganisms, etc. in the methane fermentation tank to the lactic acid decomposition tank. An example of the configuration of the return system is shown below.
一実施形態において、返送系統は、メタン発酵槽からの抽出液、典型的には二次処理液と共にメタン発酵菌、バイオフィルム形成菌及び共生微生物を乳酸分解槽に返送するための返送ラインを有する。すなわち、一実施形態において、メタン発酵槽からの二次処理液は乳酸発酵槽に直接供給される。二次処理液中には、メタン発酵菌、バイオフィルム形成菌及び共生微生物等が浮遊しているため、担体の有無に関わらず、抽出液を乳酸分解槽に返送することでメタン発酵菌、バイオフィルム形成菌及び共生微生物等を乳酸分解槽に返送可能となる。メタン発酵槽内の液は、完全混合型の場合に担体の流出を抑制しやすいという理由により、水位の中心よりも上方から抽出することが好ましく、水位頂部から抽出することがより好ましい。 In one embodiment, the return system has a return line for returning the extract from the methane fermentation tank, typically the secondary treatment liquid, together with the methane fermentation bacteria, biofilm-forming bacteria, and symbiotic microorganisms to the lactic acid decomposition tank. That is, in one embodiment, the secondary treatment liquid from the methane fermentation tank is directly supplied to the lactic acid fermentation tank. Since the methane fermentation bacteria, biofilm-forming bacteria, symbiotic microorganisms, etc. are suspended in the secondary treatment liquid, it is possible to return the methane fermentation bacteria, biofilm-forming bacteria, symbiotic microorganisms, etc. to the lactic acid decomposition tank by returning the extract to the lactic acid decomposition tank, regardless of the presence or absence of a carrier. The liquid in the methane fermentation tank is preferably extracted from above the center of the water level, and more preferably extracted from the top of the water level, because it is easier to suppress the outflow of the carrier in the case of a complete mixing type.
抽出液を乳酸分解槽に返送する際、返送ラインに担体が混入することがある。担体を抽出液と一緒に乳酸分解槽に返送するという方法も考えられるが、担体の管理が煩雑になる場合がある。一実施形態においては、返送ラインの途中で担体を抽出液から分離し、メタン発酵槽に戻すように構成することができる。例えば、メタン発酵槽からの抽出液から担体を分離するための手段（例えばスクリーンや遠心分離機）を返送ラインの途中に設ける方法がある。担体分離後の抽出液は乳酸分解槽に送ることができる。 When returning the extract to the lactic acid decomposition tank, the carrier may get mixed in the return line. One possible method is to return the carrier to the lactic acid decomposition tank together with the extract, but this may make the management of the carrier complicated. In one embodiment, the carrier can be separated from the extract midway through the return line and returned to the methane fermentation tank. For example, one method is to provide a means (e.g., a screen or centrifuge) for separating the carrier from the extract from the methane fermentation tank midway through the return line. The extract after separation of the carrier can be sent to the lactic acid decomposition tank.
分離後の担体は、メタン発酵槽に戻すことができる。担体の全量をメタン発酵槽に戻してもよいが、一部を乳酸分解槽に返送できるように、担体返送ラインを設置することも可能である。排水に添加して副基質の分解に好適な共生微生物等の微生物が付着した担体を乳酸分解槽に返送することで、乳酸分解槽内の汚泥量を効果的に増加させることができ、酸発酵槽においてもメタン発酵を促進できる。従って、排水の乳酸負荷が高いときに特に有効である。 After separation, the carriers can be returned to the methane fermentation tank. The entire amount of the carriers may be returned to the methane fermentation tank, but it is also possible to install a carrier return line so that a portion of the carriers can be returned to the lactic acid decomposition tank. By adding the carriers to the wastewater and returning to the lactic acid decomposition tank the amount of sludge in the lactic acid decomposition tank to which microorganisms such as symbiotic microorganisms suitable for decomposing the secondary substrate are attached, the amount of sludge in the lactic acid decomposition tank can be effectively increased, and methane fermentation can be promoted in the acid fermentation tank as well. Therefore, this is particularly effective when the wastewater has a high lactic acid load.
返送ラインの途中には懸濁物質の濃縮装置を備えてもよい。例えば上記の分離手段によって担体を分離した抽出液に対し、濃縮装置を使用して共生微生物等の濃度を高めることが可能である。抽出液中の共生微生物等の濃度が高まることで、返送量の可変域を広げたり、同じ返送量で菌体量を大きく増やしたりすることができる。濃縮装置における濃縮度は、２～１０倍が良く５～１０倍程度がより好ましい。懸濁物質の濃縮装置としては、公知の任意の装置を使用可能であり、例えば遠心濃縮、浮上濃縮、ベルト濃縮、ろ過濃縮、重力濃縮等の方式の濃縮装置が挙げられる。濃度が２～５倍の場合は重力濃縮でも良いが、より濃縮度を高める場合は、遠心濃縮、浮上濃縮、ベルト濃縮、ろ過濃縮が好ましい。 A device for concentrating suspended matter may be provided in the middle of the return line. For example, a concentrator can be used to increase the concentration of symbiotic microorganisms, etc., in the extract from which the carrier has been separated by the above-mentioned separation means. Increasing the concentration of symbiotic microorganisms, etc. in the extract can widen the range of return volume, and the amount of bacteria can be significantly increased with the same return volume. The degree of concentration in the concentrator is preferably 2 to 10 times, and more preferably about 5 to 10 times. Any known device can be used as the device for concentrating suspended matter, and examples include concentrators using methods such as centrifugal concentration, floating concentration, belt concentration, filtration concentration, and gravity concentration. Gravity concentration may be used when the concentration is 2 to 5 times, but centrifugal concentration, floating concentration, belt concentration, and filtration concentration are preferred when the concentration is to be increased even further.
メタン発酵槽中の水素資化性メタン発酵菌を乳酸分解槽に返送する際の、共生微生物の返送量については、乳酸分解槽に流入する排水中のＣＯＤｃｒ、乳酸分解槽の大きさ等により変動するが、乳酸分解槽内の液又は乳酸分解槽から流出する一次処理液中の酢酸に対するプロピオン酸の質量濃度比が２．５以下となるように、好ましくは２．０以下となるように、より好ましくは１．５以下となるように、メタン発酵槽から乳酸分解槽への返送量を制御することが好ましい。一般に、返送量を多くすればするほど酢酸に対するプロピオン酸の質量濃度比を下げることができる。 When returning the hydrogen-utilizing methane fermentation bacteria in the methane fermentation tank to the lactic acid degradation tank, the amount of symbiotic microorganisms returned varies depending on the CODcr in the wastewater flowing into the lactic acid degradation tank, the size of the lactic acid degradation tank, etc., but it is preferable to control the amount returned from the methane fermentation tank to the lactic acid degradation tank so that the mass concentration ratio of propionic acid to acetic acid in the liquid in the lactic acid degradation tank or the primary treatment liquid flowing out of the lactic acid degradation tank is 2.5 or less, preferably 2.0 or less, and more preferably 1.5 or less. In general, the greater the return amount, the lower the mass concentration ratio of propionic acid to acetic acid.
共生微生物はメタン発酵槽からの抽出液と共に乳酸分解槽に返送する方法が利便性の観点で有利である。この場合、乳酸分解槽に流入する排水の質量流量に対して、乳酸分解槽に返送する抽出液の質量流量（“循環比”と呼ぶ）は、抽出液中の共生微生物の濃度にもよるが、経験的には、５００≦ＣＯＤｃｒ（ｍｇ／Ｌ）／循環比≦４０００、典型的には６００≦ＣＯＤｃｒ（ｍｇ／Ｌ）／循環比≦３０００とすることで、上述した酢酸に対するプロピオン酸のモル比を達成することができる。上記の式中、ＣＯＤｃｒは乳酸分解槽に流入する排水（原水）のＣＯＤｃｒを指す。 From the viewpoint of convenience, it is advantageous to return the symbiotic microorganisms to the lactic acid degradation tank together with the extract from the methane fermentation tank. In this case, the mass flow rate of the extract returned to the lactic acid degradation tank relative to the mass flow rate of the wastewater flowing into the lactic acid degradation tank (called the "circulation ratio") depends on the concentration of the symbiotic microorganisms in the extract, but empirically, the molar ratio of propionic acid to acetic acid described above can be achieved by setting the ratio to 500≦CODcr (mg/L)/circulation ratio≦4000, typically 600≦CODcr (mg/L)/circulation ratio≦3000. In the above formula, CODcr refers to the CODcr of the wastewater (raw water) flowing into the lactic acid degradation tank.
（６．装置構成例）
以下、図面を用いて本発明に係る嫌気性処理装置の構成例について例示的に説明する。
(6. Device Configuration Example)
Hereinafter, an example of the configuration of an anaerobic treatment apparatus according to the present invention will be described with reference to the drawings.
図１には、本発明に係る嫌気性処理装置１００の第一構成例が模式的に示されている。嫌気性処理装置１００は、乳酸分解槽１１０、メタン発酵槽１２０及び担体分離装置１４０を備える。乳酸を含有する排水は、排水ライン１０１を通って乳酸分解槽１１０に流入する。排水ライン１０１には、排水に副基質を添加する副基質添加手段としての副基質添加ライン１８０が接続されている。図１に示すように、副基質添加手段として、乳酸発酵槽をバイパスして、メタン発酵槽内に導入される一次処理液に副基質を添加可能なバイパスライン１９０を更に備え、メタン発酵槽内に必要に応じて副基質を添加することで、処理性能をより向上できる。 Figure 1 shows a schematic diagram of a first configuration example of an anaerobic treatment device 100 according to the present invention. The anaerobic treatment device 100 includes a lactic acid decomposition tank 110, a methane fermentation tank 120, and a carrier separation device 140. Wastewater containing lactic acid flows into the lactic acid decomposition tank 110 through a drainage line 101. A sub-substrate addition line 180 is connected to the drainage line 101 as a sub-substrate addition means for adding a sub-substrate to the wastewater. As shown in Figure 1, the device further includes a bypass line 190 as a sub-substrate addition means, which bypasses the lactic acid fermentation tank and can add a sub-substrate to the primary treatment liquid introduced into the methane fermentation tank. By adding a sub-substrate to the methane fermentation tank as needed, the treatment performance can be further improved.
乳酸分解槽１１０では、乳酸分解槽１１０内に保持されている嫌気性生物の働きにより、乳酸の嫌気性分解が行われ、酢酸及びプロピオン酸を含む一次処理液が生成される。一次処理液は、乳酸分解槽１１０から流出し、一次処理液ライン１０２を通ってメタン発酵槽１２０に流入する。メタン発酵槽１２０では、メタン発酵槽１２０内に保持されている嫌気性生物の働きにより、メタン発酵処理が行われ、二次処理液が生成する。メタン発酵槽１２０内には担体１２２が保持されている。嫌気性生物による乳酸の分解を促進する観点で、攪拌機１１２によって乳酸分解槽１１０内を機械的に攪拌することが好ましい。 In the lactic acid decomposition tank 110, anaerobic decomposition of lactic acid is carried out by the action of anaerobic organisms held in the lactic acid decomposition tank 110, and a primary treatment liquid containing acetic acid and propionic acid is produced. The primary treatment liquid flows out of the lactic acid decomposition tank 110 and flows into the methane fermentation tank 120 through the primary treatment liquid line 102. In the methane fermentation tank 120, methane fermentation processing is carried out by the action of anaerobic organisms held in the methane fermentation tank 120, and a secondary treatment liquid is produced. A carrier 122 is held in the methane fermentation tank 120. From the viewpoint of promoting the decomposition of lactic acid by anaerobic organisms, it is preferable to mechanically stir the inside of the lactic acid decomposition tank 110 with an agitator 112.
乳酸分解槽１１０からの流出位置は、後段のメタン発酵槽１２０の流入高さに近づけて底部に設置することにより、配管材料費を抑えることができる。その場合配管形状も単純化できるので汚泥等による閉塞を抑止することもできる。一方、メタン発酵槽１２０についてみると、流入位置と流出位置を異なる高さに設置することで、メタン発酵槽１２０内の短絡を防止することができ、また、担体の流動が促進されるという利点が得られる。短絡防止を優先する場合は、必要に応じてメタン発酵槽１２０の流出位置を水位の中心よりも上部にしても良い。 The outflow position from the lactic acid decomposition tank 110 can be set at the bottom close to the inflow height of the downstream methane fermentation tank 120, thereby reducing the cost of piping materials. In this case, the shape of the piping can be simplified, which can prevent clogging due to sludge, etc. On the other hand, in the case of the methane fermentation tank 120, setting the inflow and outflow positions at different heights has the advantage of preventing short circuits within the methane fermentation tank 120 and promoting the flow of carriers. If preventing short circuits is a priority, the outflow position of the methane fermentation tank 120 can be set above the center of the water level as necessary.
メタン発酵槽１２０内の流動性を上げるために、メタン発酵槽内の液を循環させるための循環ライン１０７を設置してもよい。一実施形態において、循環ライン１０７は、メタン発酵槽１２０の水位の中心よりも上方、典型的には頂部に流出口を有し、メタン発酵槽１２０の水位の中心よりも下方、典型的には底部に流入口を有する。循環ライン１０７の途中にはポンプ１０９を設置することで、循環量を制御することができる。図１において、メタン発酵槽１２０から抽出された液は下方に向かって循環ライン１０７内を流れるが、これとは逆に上方に向かって流すことも可能である。 In order to increase the fluidity in the methane fermentation tank 120, a circulation line 107 for circulating the liquid in the methane fermentation tank may be installed. In one embodiment, the circulation line 107 has an outlet above the center of the water level in the methane fermentation tank 120, typically at the top, and an inlet below the center of the water level in the methane fermentation tank 120, typically at the bottom. The circulation amount can be controlled by installing a pump 109 midway along the circulation line 107. In FIG. 1, the liquid extracted from the methane fermentation tank 120 flows downward through the circulation line 107, but it is also possible to flow it upward instead.
二次処理液は、メタン発酵槽１２０から流出し、二次処理液ライン１０３を通って担体分離装置１４０に流入する。二次処理液中に含まれる担体１２２は、担体分離装置１４０で分離される。例えば、担体分離装置１４０は、外槽１４１、外槽１４１の中に収容されている内槽１４２、及びスクリーン１４３を有する。内槽１４２の内面は曲面形状を有しており、内槽１４２に流入した二次処理液は旋回しながら、内槽１４２内を流れ、内槽１４２の側面に設けられたスクリーン１４３から流出する。二次処理液が旋回しながら内槽１４２内を流れることでスクリーン１４３の目詰まりを防止することができる。スクリーン１４３を介して内槽１４２から流出した二次処理液は外槽１４１に流入する。その後、二次処理液は外槽１４１の出口から、二次処理液ライン１０５を通って系外へ排出することができる。担体１２２は、スクリーン１４３を通過することができないため、内槽１４２の出口から排出された後、担体ライン１０６を通ってメタン発酵槽１２０に戻される。担体ライン１０６には、スクリーン１４３を通過しなかった一部の二次処理液も一緒に流れる。二次処理液が含まれている方が、二次処理液を担体１２２の搬送媒体として使用することができるので好都合である。担体ライン１０６は一次処理液ライン１０２に接続してもよい。 The secondary treatment liquid flows out of the methane fermentation tank 120 and flows into the carrier separation device 140 through the secondary treatment liquid line 103. The carrier 122 contained in the secondary treatment liquid is separated by the carrier separation device 140. For example, the carrier separation device 140 has an outer tank 141, an inner tank 142 housed in the outer tank 141, and a screen 143. The inner surface of the inner tank 142 has a curved shape, and the secondary treatment liquid that flows into the inner tank 142 flows inside the inner tank 142 while rotating, and flows out from the screen 143 provided on the side of the inner tank 142. The secondary treatment liquid flows inside the inner tank 142 while rotating, which prevents clogging of the screen 143. The secondary treatment liquid that flows out of the inner tank 142 through the screen 143 flows into the outer tank 141. The secondary treatment liquid can then be discharged from the outlet of the outer tank 141 through the secondary treatment liquid line 105 to the outside of the system. Because the carrier 122 cannot pass through the screen 143, it is discharged from the outlet of the inner tank 142 and then returned to the methane fermentation tank 120 through the carrier line 106. A portion of the secondary treatment liquid that did not pass through the screen 143 also flows through the carrier line 106. It is advantageous to include the secondary treatment liquid, since the secondary treatment liquid can be used as a transport medium for the carrier 122. The carrier line 106 may be connected to the primary treatment liquid line 102.
担体分離装置１４０から流出する二次処理液の一部は、二次処理液を返送処理する返送手段としての返送ライン１０４を通って乳酸分解槽１１０に返送される。二次処理液中には水素資化性メタン発酵菌が含まれていることから、乳酸分解槽１１０での水素分圧を下げ、乳酸の分解過程で生成するプロピオン酸の酢酸への分解反応を促進することができる。返送ライン１０４には、バルブ等の流量制御手段１７０を適宜設置することで、返送量を調節することができる。 A portion of the secondary treatment liquid flowing out from the carrier separation device 140 is returned to the lactic acid decomposition tank 110 through a return line 104, which serves as a return means for returning the secondary treatment liquid. Since the secondary treatment liquid contains hydrogen-utilizing methane fermentation bacteria, it is possible to lower the hydrogen partial pressure in the lactic acid decomposition tank 110 and promote the decomposition reaction of propionic acid, which is produced during the decomposition of lactic acid, into acetic acid. The return amount can be adjusted by appropriately installing a flow control means 170 such as a valve on the return line 104.
乳酸分解槽１１０及びメタン発酵槽１２０においては、メタン及び水素等のバイオガスが発生する。そこで、乳酸分解槽１１０及びメタン発酵槽１２０はそれぞれ、各槽で発生するメタン等のバイオガスを回収するためのガス回収系統１３２が接続されている。ガス回収系統１３２はバイオガス利用設備１３０に接続されており、バイオガス利用設備１３０においてバイオガスの利用が図られる。 Biogas such as methane and hydrogen are generated in the lactic acid decomposition tank 110 and the methane fermentation tank 120. Therefore, a gas recovery system 132 is connected to each of the lactic acid decomposition tank 110 and the methane fermentation tank 120 to recover the biogas such as methane generated in each tank. The gas recovery system 132 is connected to the biogas utilization facility 130, and the biogas is utilized in the biogas utilization facility 130.
図２には、本発明に係る嫌気性処理装置２００の第二構成例が模式的に示されている。図２に示す嫌気性処理装置２００が図１に示す嫌気性処理装置１００と相違する点は、図２に示す嫌気性処理装置２００においては返送ライン１０４の途中に懸濁物質の濃縮装置１５０が設置されている点である。濃縮装置１５０が設置されていることにより、二次処理液中の水素資化性メタン発酵菌等の微生物濃度を高めることができる。図２に示す嫌気性処理装置２００において、図１に示す嫌気性処理装置１００と同じ符号が付された構成要素は、既に説明した通りであるため、詳細な説明を割愛する。 Figure 2 shows a schematic diagram of a second configuration example of an anaerobic treatment device 200 according to the present invention. The anaerobic treatment device 200 shown in Figure 2 differs from the anaerobic treatment device 100 shown in Figure 1 in that the anaerobic treatment device 200 shown in Figure 2 has a suspended matter concentrator 150 installed in the return line 104. By installing the concentrator 150, the concentration of microorganisms such as hydrogen-utilizing methane fermenting bacteria in the secondary treatment liquid can be increased. In the anaerobic treatment device 200 shown in Figure 2, the components with the same reference numerals as those in the anaerobic treatment device 100 shown in Figure 1 have already been described, and therefore detailed description thereof will be omitted.
図３には、本発明に係る嫌気性処理装置３００の第三構成例が模式的に示されている。図３に示す嫌気性処理装置３００が図１に示す嫌気性処理装置１００と相違する点は、図３に示す嫌気性処理装置３００が、乳酸分解槽１１０に担体１２２を返送するための担体返送ライン１０８を有する点である。担体返送ライン１０８は、担体ライン１０６に接続されており、担体ライン１０６を流れる担体１２２の一部を乳酸分解槽１１０に返送することができる。担体返送ライン１０８と担体ライン１０６の接続点に三方弁等の流量制御手段１６０を設置することで、乳酸分解槽１１０に返送する担体の量を制御してもよい。 Figure 3 shows a schematic diagram of a third configuration example of an anaerobic treatment device 300 according to the present invention. The anaerobic treatment device 300 shown in Figure 3 differs from the anaerobic treatment device 100 shown in Figure 1 in that the anaerobic treatment device 300 shown in Figure 3 has a carrier return line 108 for returning the carrier 122 to the lactic acid decomposition tank 110. The carrier return line 108 is connected to the carrier line 106, and can return a portion of the carrier 122 flowing through the carrier line 106 to the lactic acid decomposition tank 110. The amount of carrier returned to the lactic acid decomposition tank 110 may be controlled by installing a flow control means 160 such as a three-way valve at the connection point between the carrier return line 108 and the carrier line 106.
なお、排水ライン１０１、一次処理液ライン１０２、二次処理液ライン１０３、１０５、返送ライン１０４、担体ライン１０６、及び、担体返送ライン１０８には必要に応じて送液のためのポンプを設置することができる。 In addition, pumps for pumping liquid can be installed in the drainage line 101, the primary treatment liquid line 102, the secondary treatment liquid lines 103 and 105, the return line 104, the carrier line 106, and the carrier return line 108 as necessary.
以下に本発明の実施例を比較例と共に示すが、これらの実施例は本発明及びその利点をよりよく理解するために提供するものであり、発明が限定されることを意図するものではない。以下の実験において、ＣＯＤｃｒは、ＪＩＳ Ｋ０１０２：２０１６に規定される蓋付き試験管を用いた吸光光度法に準拠して、ＨＡＣＨ製の吸光光度計により測定した。各有機酸の濃度は、ＪＩＳ Ｋ０１２４：２０１１、ＪＩＳ Ｋ０２１４：２０１３に準拠した、島津製作所製のＨＰＬＣ型式ＬＣ－２０ＡＤ（導電率検出器を使用）により測定した。 The following examples of the present invention are presented together with comparative examples. These examples are provided to provide a better understanding of the present invention and its advantages, and are not intended to limit the invention. In the following experiments, CODcr was measured using a HACH spectrophotometer in accordance with the spectrophotometric method using a capped test tube as specified in JIS K0102:2016. The concentration of each organic acid was measured using a Shimadzu HPLC model LC-20AD (using a conductivity detector) in accordance with JIS K0124:2011 and JIS K0214:2013.
（１．ラボ試験）
乳酸菌製造設備から排出される乳酸系排水に対するラボ試験を実施した。乳酸系排水の性状は以下の通りである。
・ＣＯＤｃｒ：５，０００ｍｇ／Ｌ
・排水中のＣＯＤｃｒに対して炭素数３以下の有機酸が占める割合：８０％
・有機酸のうち乳酸が占める割合：９０質量％以上
この乳酸系排水に対し、副基質として乳酸生成過程で発生するグルコースを、排水中のＣＯＤｃｒに対して１～２０％を占めるように添加した。
(1. Lab Test)
Laboratory tests were conducted on lactic acid wastewater discharged from a lactic acid bacteria manufacturing facility. The properties of the lactic acid wastewater are as follows:
・CODcr: 5,000mg/L
・Proportion of organic acids with carbon numbers of 3 or less in the CODcr in wastewater: 80%
Proportion of lactic acid among organic acids: 90% by mass or more Glucose generated in the lactic acid production process as a secondary substrate was added to this lactic acid-based wastewater so that it accounted for 1 to 20% of the CODcr in the wastewater.
図１に示す構成の嫌気性処理装置１００を構築し、上記の乳酸系排水に対する嫌気性処理を行った。嫌気性処理装置１００は、完全混合型の乳酸分解槽１１０及び完全混合型のメタン発酵槽１２０を備え、メタン発酵槽１２０から排出されるメタン発酵菌及び共生微生物等を含有する二次処理液は、担体分離装置１４０で担体１２２を分離した後、乳酸分解槽１１０に返送される。メタン発酵槽１２０には、酸発酵菌、メタン発酵菌、フィルム形成菌、及び共生微生物が付着した担体１２２（担体形状：球体、担体素材：ポリビニルアルコール）を使用した。 An anaerobic treatment device 100 with the configuration shown in FIG. 1 was constructed, and anaerobic treatment was performed on the above-mentioned lactic acid wastewater. The anaerobic treatment device 100 is equipped with a complete mixing type lactic acid decomposition tank 110 and a complete mixing type methane fermentation tank 120. The secondary treatment liquid discharged from the methane fermentation tank 120, which contains methane fermentation bacteria and symbiotic microorganisms, is separated from the carrier 122 by a carrier separation device 140, and then returned to the lactic acid decomposition tank 110. For the methane fermentation tank 120, a carrier 122 (carrier shape: sphere, carrier material: polyvinyl alcohol) to which acid fermentation bacteria, methane fermentation bacteria, film-forming bacteria, and symbiotic microorganisms are attached was used.
運転条件は以下とした。
乳酸分解槽
・有効容積：１Ｌ
・槽内の液温：３５℃
・嫌気性微生物：メタン発酵槽の処理水ＳＳを投入
・槽内の液中ｐＨ：５．０～７．０（制御せず）
・ＯＲＰ：－１００～－１５０ｍＶ（制御せず）
・攪拌：機械攪拌
・滞留時間：２～５日
メタン発酵槽
・有効容積：１Ｌ
・槽内の液温：３５℃
・担体の能力：メタン生成活性度０．５ｋｇ／（ｋｇ・ｄ）以上
（メタン生成活性度は、ケルダール法で担体の窒素含有量を測定し、担体当たりのＳＳ量で評価した。）
・槽内の液中ｐＨ：７．０～８．２（制御せず）
・ＯＲＰ：－２００～－５００ｍＶ（制御せず）
・攪拌：機械攪拌
・滞留時間：２～５日
The operating conditions were as follows:
Lactic acid decomposition tank: Effective volume: 1L
・Liquid temperature in the tank: 35℃
Anaerobic microorganisms: Treated water SS from methane fermentation tank is added. pH of liquid in tank: 5.0-7.0 (not controlled)
・ORP: -100 to -150 mV (uncontrolled)
・Agitation: Mechanical agitation ・Retention time: 2 to 5 days Methane fermentation tank ・Effective volume: 1L
・Liquid temperature in the tank: 35℃
Carrier capacity: Methane production activity of 0.5 kg/(kg·d) or more (methane production activity was evaluated by measuring the nitrogen content of the carrier by the Kjeldahl method and the amount of SS per carrier).
・pH of liquid in tank: 7.0-8.2 (not controlled)
・ORP: -200 to -500 mV (uncontrolled)
・Agitation: Mechanical agitation ・Residence time: 2-5 days
流量を増加させる方法により、排水負荷を徐々に上昇させながら、処理水（二次処理液）のＣＯＤｃｒ及び有機酸濃度の変化を調査した。処理水に酢酸及びプロピオン酸の濃度の残留はほとんど見られなかった。その結果、１９ｋｇ－ＣＯＤｃｒ／（ｍ3・ｄ）においてＣＯＤｃｒ除去率８０％を確認した。担体の汚泥付着量は１８ｇ－ＶＳＳ／Ｌであった。経日ごとに担体の菌叢解析を行い、菌体の優占率を確認したところSyntrophobacter、Pelotomaculum等の共生微生物の優占率が全菌数のうち１～１５％程度を占めていた。 The flow rate was increased to gradually increase the wastewater load, while investigating the changes in CODcr and organic acid concentration in the treated water (secondary treated water). Almost no residual acetic acid or propionic acid was observed in the treated water. As a result, a CODcr removal rate of 80% was confirmed at 19 kg-CODcr/( m3 ·d). The amount of sludge attached to the carrier was 18 g-VSS/L. A bacterial flora analysis of the carrier was performed every day to confirm the dominance rate of the bacteria, and the dominance rate of symbiotic microorganisms such as Syntrophobacter and Pelotomaculum accounted for approximately 1-15% of the total bacterial count.
（２．実機試験）
図１に示す構成の嫌気性処理装置１００を構築し、上記の乳酸系排水に対する嫌気性処理を行った。嫌気性処理装置１００は、完全混合型の乳酸分解槽１１０及び完全混合型のメタン発酵槽１２０を備え、メタン発酵槽１２０から排出されるメタン発酵菌及び共生微生物を含有する二次処理液は、担体分離装置１４０で担体１２２を分離した後、乳酸分解槽１１０に返送される。
(2. Actual Machine Testing)
An anaerobic treatment apparatus 100 having the configuration shown in Fig. 1 was constructed, and anaerobic treatment was performed on the above-mentioned lactic acid-containing wastewater. The anaerobic treatment apparatus 100 includes a complete-mixing type lactic acid decomposition tank 110 and a complete-mixing type methane fermentation tank 120. The secondary treatment liquid containing methane fermentation bacteria and symbiotic microorganisms discharged from the methane fermentation tank 120 is separated from the carriers 122 by a carrier separator 140, and then returned to the lactic acid decomposition tank 110.
乳酸分解槽１１０の運転条件は以下とした。
・有効容積：３５ｍ3
・槽内の液温：３５℃
・嫌気性微生物：未使用担体とグラニュールを初期に投入（その他はメタン発酵槽から返送される二次処理液から供給）担体に付着している微生物は、Methanosaeta属、Methanobacterium、Geobacter属、Thermodesulfovibrio属、Syntrophobacter属等であった。
・嫌気性微生物の活性度：０．５ｋｇ／（ｋｇ・ｄ）以上
（活性度は、ケルダール法で担体の窒素含有量を測定し、担体当たりのＳＳ量で評価した。）
・槽内の液中ｐＨ：６．５～７．５の範囲であるが、常にメタン発酵槽の液中ｐＨより低かった。（メタン発酵槽のｐＨが６．５以下に低下した場合に乳酸分解槽に苛性ソーダを注入することで、菌体の活性を高めるため、また、水素発酵を防止するため、両槽のｐＨを上げた。）
・攪拌：機械攪拌
・滞留時間：３～１５ｈ
The operating conditions of the lactic acid decomposition tank 110 were as follows.
Effective volume: 35m3
・Liquid temperature in the tank: 35℃
- Anaerobic microorganisms: Unused carriers and granules were added initially (the rest were supplied from the secondary treatment liquid returned from the methane fermentation tank). The microorganisms attached to the carriers were Methanosaeta, Methanobacterium, Geobacter, Thermodesulfovibrio, Syntrophobacter, etc.
Anaerobic microbial activity: 0.5 kg/(kg·d) or more (activity was evaluated by measuring the nitrogen content of the carrier by the Kjeldahl method and the amount of SS per carrier).
- pH of the liquid in the tank: in the range of 6.5 to 7.5, but always lower than the pH of the liquid in the methane fermentation tank. (When the pH of the methane fermentation tank dropped below 6.5, caustic soda was injected into the lactic acid decomposition tank to increase the activity of the bacteria and to prevent hydrogen fermentation, thereby raising the pH of both tanks.)
・Stirring: Mechanical stirring ・Residence time: 3-15h
メタン発酵槽１２０には、水素資化性メタン発酵菌、酢酸資化性メタン発酵菌、及びプロピオン酸酸化細菌が付着した担体１２２（担体形状：球状、担体素材：ポリビニルアルコール）を使用した。メタン発酵槽１２０の運転条件は以下とした。
・有効容積：９６ｍ3
・槽内の液温：３５℃
・担体の能力：メタン生成活性度０．５ｋｇ／（ｋｇ・ｄ）以上
（活性度は、ケルダール法で担体の窒素含有量を測定し、担体当たりのＳＳ量で評価した。）
・槽内の液中ｐＨ：６．５～８．２
・攪拌：メタンガスが発生することによるガス攪拌
・滞留時間：２～８ｈ
・メタン発酵槽から乳酸分解槽に流入する排水のＣＯＤｃｒ：５００～４０００ｍｇ／Ｌ
・メタン発酵槽から乳酸分解槽へ返送する二次処理液の循環比：５～２０倍（乳酸分解槽の水位を一定に保持）
A carrier 122 (carrier shape: spherical, carrier material: polyvinyl alcohol) to which hydrogen-utilizing methane-fermenting bacteria, acetate-utilizing methane-fermenting bacteria, and propionate-oxidizing bacteria were attached was used in the methane fermentation tank 120. The operating conditions of the methane fermentation tank 120 were as follows.
Effective volume: 96 m3
・Liquid temperature in the tank: 35℃
- Carrier capacity: Methane production activity of 0.5 kg/(kg·d) or more (activity was evaluated by measuring the nitrogen content of the carrier by the Kjeldahl method and the amount of SS per carrier.)
・pH of liquid in tank: 6.5 to 8.2
・Mixing: Gas mixing due to the generation of methane gas ・Retention time: 2 to 8 hours
・CODcr of wastewater flowing from methane fermentation tank to lactic acid decomposition tank: 500-4000 mg/L
・Circulation ratio of secondary treatment liquid returned from the methane fermentation tank to the lactic acid decomposition tank: 5 to 20 times (maintaining a constant water level in the lactic acid decomposition tank)
流量を増加させる方法により、排水負荷を徐々に上昇させながら、処理水（二次処理液）のＣＯＤｃｒ及び有機酸濃度の変化を調査した。処理水中に酢酸及びプロピオン酸の濃度の残留はほとんど見られなかった。１９ｋｇ－ＣＯＤｃｒ／（ｍ3・ｄ）においてＣＯＤｃｒ除去率９５％を確認した。担体の汚泥付着量は４８ｇ－ＶＳＳ／Ｌであり、副基質を添加しない場合に比べて付着量も多い。経日ごとに担体の菌叢解析を行い、菌体の優占率を確認したところSyntrophobacter、Syntrophomonas、Smithella、Geobacter等の共生微生物の優占率が全菌数のうち１～１５％以上を占めており多様性に富んでいた。 The change in CODcr and organic acid concentration of the treated water (secondary treated water) was investigated while gradually increasing the wastewater load by increasing the flow rate. Almost no residual acetic acid and propionic acid concentrations were observed in the treated water. A CODcr removal rate of 95% was confirmed at 19 kg-CODcr/( m3 ·d). The amount of sludge attached to the carrier was 48 g-VSS/L, which is higher than when no sub-substrate was added. A bacterial flora analysis of the carrier was performed every day to confirm the predominance of the bacteria, and it was found that symbiotic microorganisms such as Syntrophobacter, Syntrophomonas, Smithella, and Geobacter accounted for 1-15% or more of the total number of bacteria, showing a high degree of diversity.
（３．回分試験）
乳酸試薬を水に溶かすことで得た乳酸含有水（乳酸濃度：５，０００ｍｇ／Ｌ、水量：５００ｍＬ）を乳酸発酵槽で嫌気性処理する回分試験を行った。この際、副基質としてグルコースを乳酸含有水のＣＯＤｃｒに対して表１に示す割合で添加した。
乳酸分解槽の運転条件は以下とした。
・有効容積：４００ｍＬ
・槽内の液温：３５℃
・嫌気性微生物：未使用担体を投入した。担体に付着している微生物は、Methanosaeta属、Methanobacterium、Geobacter属、Thermodesulfovibrio属、Syntrophobacter属等であった。
・槽内の液中ｐＨ：７．５程度(制御せず)
・乳酸分解槽からの流出液（一次処理液）のＯＲＰ：－１００～－１５０ｍＶ(制御せず)
・攪拌：機械攪拌
・滞留時間：２４時間
3. Batch Testing
A batch test was carried out in which lactic acid-containing water (lactic acid concentration: 5,000 mg/L, water volume: 500 mL) obtained by dissolving a lactic acid reagent in water was anaerobically treated in a lactic acid fermentation tank. During this test, glucose was added as a secondary substrate in the ratio shown in Table 1 relative to the CODcr of the lactic acid-containing water.
The operating conditions of the lactic acid decomposition tank were as follows:
Effective volume: 400 mL
・Liquid temperature in the tank: 35℃
Anaerobic microorganisms: Unused carriers were added. The microorganisms attached to the carriers were Methanosaeta, Methanobacterium, Geobacter, Thermodesulfovibrio, Syntrophobacter, etc.
・pH of liquid in tank: about 7.5 (not controlled)
・ORP of effluent (primary treated liquid) from lactic acid decomposition tank: -100 to -150 mV (not controlled)
・Stirring: Mechanical stirring ・Residence time: 24 hours
乳酸発酵槽で２４時間嫌気性処理した後の乳酸発酵槽内の液中のプロピオン酸の濃度を測定し、Methanosaeta属の優占率を確認した。Methanosaeta属の優占率は次世代シーケンシングという手法により確認し、全菌数のうち０．５％以下の検出率の場合を「×」、０．５％～５％の場合を「△」、５％以上の場合を「〇」として評価した。結果を表１に示す。 After 24 hours of anaerobic treatment in the lactic acid fermentation tank, the propionic acid concentration in the liquid was measured to confirm the dominance rate of the Methanosaeta genus. The dominance rate of the Methanosaeta genus was confirmed using a technique called next-generation sequencing, with a detection rate of 0.5% or less of the total bacterial count being rated as "x", 0.5% to 5% being rated as "△", and 5% or more being rated as "〇". The results are shown in Table 1.
本発明の実施の形態に係る嫌気性処理装置及び嫌気性処理方法によれば、有機酸のうち５０質量％以上が乳酸を占める排水に単糖類、二糖類以上の多糖類、タンパク質等の副基質を添加することにより、酸分解時の中間生成物である酢酸及びプロピオン酸をスムーズにメタンに分解することが可能になるため、乳酸を高濃度で含有する排水に対するＣＯＤｃｒ除去率を有意に向上させることができる。 According to the anaerobic treatment device and anaerobic treatment method of the embodiment of the present invention, by adding sub-substrates such as monosaccharides, disaccharides or more polysaccharides, and proteins to wastewater in which lactic acid accounts for 50% or more by mass of organic acids, it becomes possible to smoothly decompose acetic acid and propionic acid, which are intermediate products during acid decomposition, into methane, thereby significantly improving the CODcr removal rate for wastewater containing a high concentration of lactic acid.
１００ 嫌気性処理装置
１０１ 排水ライン
１０２ 一次処理液ライン
１０３ 二次処理液ライン
１０４ 返送ライン
１０５ 二次処理液ライン
１０６ 担体ライン
１０７ 循環ライン
１０８ 担体返送ライン
１０９ ポンプ
１１０ 乳酸分解槽
１２０ メタン発酵槽
１２２ 担体
１３０ バイオガス利用設備
１３２ ガス回収系統
１４０ 担体分離装置
１４１ 外槽
１４２ 内槽
１４３ スクリーン
１５０ 濃縮装置
１６０ 流量制御手段
１７０ 流量制御手段
１８０ 副基質添加ライン
１９０ バイパスライン
２００ 嫌気性処理装置
３００ 嫌気性処理装置
100 Anaerobic treatment apparatus 101 Drainage line 102 Primary treatment liquid line 103 Secondary treatment liquid line 104 Return line 105 Secondary treatment liquid line 106 Carrier line 107 Circulation line 108 Carrier return line 109 Pump 110 Lactic acid decomposition tank 120 Methane fermentation tank 122 Carrier 130 Biogas utilization equipment 132 Gas recovery system 140 Carrier separation device 141 Outer tank 142 Inner tank 143 Screen 150 Concentration device 160 Flow rate control means 170 Flow rate control means 180 Sub-substrate addition line 190 Bypass line 200 Anaerobic treatment apparatus 300 Anaerobic treatment apparatus
Claims (8)
前記一次処理液を導入し、前記一次処理液をメタン発酵処理して二次処理液を生成するメタン発酵槽と、
前記メタン発酵槽内の前記二次処理液を前記乳酸分解槽内へ返送する返送手段と、
前記排水又は前記一次処理液に単糖類、二糖類以上の多糖類、タンパク質のいずれかを含む副基質を添加する副基質添加手段と、
を備えることを特徴とする嫌気性処理装置。 a lactic acid decomposition tank for receiving wastewater containing organic acids, the organic acids of which account for 50 mass % or more of lactic acid, and for anaerobically decomposing the lactic acid in the wastewater to produce a primary treatment liquid containing acetic acid and propionic acid;
a methane fermentation tank into which the primary treatment liquid is introduced and which performs methane fermentation on the primary treatment liquid to produce a secondary treatment liquid;
a return means for returning the secondary treatment liquid in the methane fermentation tank to the lactic acid decomposition tank;
a sub-substrate adding means for adding a sub-substrate containing any one of monosaccharides, disaccharides or higher polysaccharides, and proteins to the wastewater or the primary treatment liquid;
An anaerobic treatment device comprising:
前記排水に前記副基質を添加可能な副基質添加ラインと、
前記メタン発酵槽内に導入される前記一次処理液に前記副基質を添加可能なバイパスラインと
を備えることを特徴とする請求項１又は２に記載の嫌気性処理装置。 The sub-substrate adding means is
a sub-substrate addition line capable of adding the sub-substrate to the wastewater;
3. The anaerobic treatment apparatus according to claim 1, further comprising: a bypass line capable of adding the secondary substrate to the primary treatment liquid introduced into the methane fermentation tank.
前記一次処理液をメタン発酵処理して二次処理液を生成するメタン発酵処理と、
メタン発酵菌及び共生微生物を含む二次処理液を前記乳酸分解処理へ返送する返送処理と、
を有することを特徴とする嫌気性処理方法。 a lactic acid decomposition treatment in which lactic acid in wastewater containing organic acids, of which 50 mass % or more is lactic acid, and containing a sub-substrate containing any one of monosaccharides, disaccharides or higher polysaccharides, and proteins, is anaerobically decomposed in a lactic acid decomposition tank to produce a primary treatment liquid containing acetic acid and propionic acid;
a methane fermentation treatment for producing a secondary effluent by subjecting the primary effluent to a methane fermentation treatment;
A return process in which a secondary treatment liquid containing methane fermentation bacteria and symbiotic microorganisms is returned to the lactic acid decomposition process;
The anaerobic treatment method according to claim 1,
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| JP2005161173A (en) | 2003-12-02 | 2005-06-23 | Ebara Corp | Method and apparatus for treating protein-containing wastewater by methane fermentation |
| JP2006247601A (en) | 2005-03-14 | 2006-09-21 | Tokyo Gas Co Ltd | Methane generation method and methane generator |
| JP2018008203A (en) | 2016-07-12 | 2018-01-18 | バイオエナジー株式会社 | Wet type methane fermentation system |
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| JP2006247601A (en) | 2005-03-14 | 2006-09-21 | Tokyo Gas Co Ltd | Methane generation method and methane generator |
| JP2018008203A (en) | 2016-07-12 | 2018-01-18 | バイオエナジー株式会社 | Wet type methane fermentation system |
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