JP2014023984A - Methane fermentation system and methane fermentation method - Google Patents

Methane fermentation system and methane fermentation method Download PDF

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JP2014023984A
JP2014023984A JP2012164820A JP2012164820A JP2014023984A JP 2014023984 A JP2014023984 A JP 2014023984A JP 2012164820 A JP2012164820 A JP 2012164820A JP 2012164820 A JP2012164820 A JP 2012164820A JP 2014023984 A JP2014023984 A JP 2014023984A
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methane fermentation
tank
acid
organic wastewater
compound
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JP5896853B2 (en
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Haruyuki Chiku
治之 知久
Moriya Fukunaga
守也 福長
Hisao Ogawa
久雄 小川
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Oji Holdings Corp
Sumitomo Heavy Industries Environment Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a methane fermentation system and a methane fermentation method which can properly adjust the pH of organic wastewater during a period of stopping the introduction of the organic wastewater from the outside, and can suppress hydrogen sulfide inhibition.SOLUTION: A methane fermentation system 1 includes: an acid production tank 2 which treats organic wastewater introduced from the outside by acid producing bacteria to produce acid; pH adjusting means 5, 6, 7 which adjusts the pH of the organic wastewater; a methane fermentation tank 3 which performs the methane fermentation of the organic wastewater introduced from the acid production tank 2; and a return line L2 which returns a part of treated water in the methane fermentation tank 3 to the acid production tank 2, wherein the pH adjusting means 5, 6, 7 includes compound adding means 7 which adds a compound for neutralizing alkali in the acid production tank 2 and reacting with hydrogen sulfide generated in the methane fermentation tank 3 to generate sulfide precipitation during a period of stopping the introduction of the organic wastewater from the outside.

Description

本発明は、メタン発酵設備及びメタン発酵方法に関する。   The present invention relates to a methane fermentation facility and a methane fermentation method.

従来、有機性排水の処理方法として、メタン発酵が利用されている。メタン発酵は一般に、酸生成槽及びメタン発酵槽を備えるメタン発酵設備において実施される。酸生成槽では、外部から導入された有機性排水を酸生成菌で処理することにより有機物が分解され、酢酸等の有機酸が生成する。そして、その有機酸が含まれた有機性排水をメタン発酵槽内に導入してメタン発酵させることにより、メタンが生成する。ここでは、酸生成菌の流出回避及び有機性排水の希釈の観点から、メタン発酵槽の処理水の一部がメタン発酵槽から酸生成槽へ返送される。   Conventionally, methane fermentation has been used as a method for treating organic wastewater. Methane fermentation is generally performed in a methane fermentation facility comprising an acid generator and a methane fermenter. In the acid generation tank, organic matter is decomposed by treating the organic wastewater introduced from the outside with an acid-producing bacterium, and an organic acid such as acetic acid is generated. And the organic wastewater containing the organic acid is introduce | transduced in a methane fermenter, and methane is produced | generated by carrying out methane fermentation. Here, from the viewpoint of avoiding outflow of acid-producing bacteria and diluting the organic waste water, a part of the treated water in the methane fermentation tank is returned from the methane fermentation tank to the acid generation tank.

酸生成槽においては、上記のとおり有機酸が生成するため、有機性排水のpHが低下する。pHが低下すると酸生成菌の活性が低下するため、有機性排水のpHを酸生成菌にとって至適な範囲に維持することが望まれる。そこで、酸生成槽にアルカリ剤を投入して、pHの低下を抑制する方法(特許文献1)、及び、メタン発酵槽の処理水の一部を酸生成槽へ返送するときに、処理水のpHを高めてアルカリ性にした後に返送する方法(特許文献2)等が提案されている。   In the acid generation tank, since the organic acid is generated as described above, the pH of the organic waste water is lowered. Since the activity of acid producing bacteria decreases when the pH is lowered, it is desirable to maintain the pH of the organic waste water within an optimum range for the acid producing bacteria. Therefore, when an alkaline agent is introduced into the acid generation tank to suppress a decrease in pH (Patent Document 1) and when a part of the treated water in the methane fermentation tank is returned to the acid generation tank, the treated water There has been proposed a method (Patent Document 2) and the like of returning after making the pH alkaline by increasing the pH.

特開2001−38378号公報JP 2001-38378 A 特開平11−347588号公報JP 11-347588 A

メタン発酵設備では、酸生成槽に導入されるべき有機性排水を排出する設備が定修期間に入ること等により、有機性排水の導入が停止される期間が生じる。この期間中、メタン発酵設備は稼働を緩めた状態とされる。この期間及びこの前後の期間においては、通常稼働時と比べて有機性排水のpHの変動が大きく、特にアルカリ性側へ傾く傾向がある。pHが大きく変動すると、通常稼働時において酸生成及びメタン発酵の効率が低下してしまう。   In the methane fermentation facility, there is a period in which the introduction of the organic wastewater is stopped, for example, when the facility that discharges the organic wastewater to be introduced into the acid generation tank enters a regular repair period. During this period, the methane fermentation facility is in a relaxed state. During this period and before and after this period, the pH of the organic waste water varies greatly compared to that during normal operation, and in particular, it tends to tilt toward the alkaline side. If the pH fluctuates greatly, the efficiency of acid generation and methane fermentation will decrease during normal operation.

一方、メタン発酵においては、メタン生成菌と共生している硫酸還元菌により有機性排水中の硫酸等が還元されることによって、メタンと同時に硫化水素が生成する。硫化水素はメタンの不純物となるうえ、メタン生成菌の活性を低下させる「硫化水素阻害」を引き起こす。従って、メタン発酵の効率向上のために、硫化水素阻害を抑制することが望まれている。   On the other hand, in methane fermentation, hydrogen sulfide is generated simultaneously with methane by reducing sulfuric acid or the like in organic wastewater by sulfate-reducing bacteria symbiotic with methane-producing bacteria. Hydrogen sulfide becomes an impurity of methane and causes “hydrogen sulfide inhibition” that reduces the activity of methanogens. Therefore, it is desired to suppress hydrogen sulfide inhibition in order to improve the efficiency of methane fermentation.

そこで本発明は、外部からの有機性排水の導入が停止される期間中に、有機性排水のpHの調整を適切に行うことができ、且つ、硫化水素阻害を抑制することができるメタン発酵設備及びメタン発酵方法を提供することを目的とする。   Accordingly, the present invention provides a methane fermentation facility capable of appropriately adjusting the pH of organic wastewater and suppressing hydrogen sulfide inhibition during the period when introduction of organic wastewater from the outside is stopped. And it aims at providing the methane fermentation method.

本発明は、外部から導入される有機性排水を酸生成菌で処理して酸を生成させる酸生成槽と、有機性排水のpHを調整するpH調整手段と、酸生成槽から導入される有機性排水をメタン発酵させるメタン発酵槽と、メタン発酵槽の処理水の一部を酸生成槽へ返送する返送ラインと、を備え、pH調整手段は、外部からの有機性排水の導入が停止される期間中に、酸生成槽内のアルカリを中和すると共にメタン発酵槽で生じる硫化水素と反応して硫化物の沈殿を生じる化合物を投入する化合物投入手段を含むことを特徴とするメタン発酵設備を提供する。   The present invention includes an acid generation tank that generates an acid by treating an organic wastewater introduced from the outside with an acid-producing bacterium, a pH adjusting means that adjusts the pH of the organic wastewater, and an organic that is introduced from the acid generation tank. A methane fermentation tank for fermenting organic wastewater and a return line for returning a part of the treated water from the methane fermentation tank to the acid generation tank. Methane fermentation equipment comprising a compound charging means for charging a compound that neutralizes the alkali in the acid generation tank and reacts with hydrogen sulfide generated in the methane fermentation tank to cause sulfide precipitation I will provide a.

また、本発明は、外部から導入される有機性排水を酸生成槽及びメタン発酵槽で処理するメタン発酵方法において、有機性排水を酸生成槽内に導入し、酸生成菌で処理して酸を生成させる酸生成工程と、有機性排水のpHを調整するpH調整工程と、酸生成槽から有機性排水をメタン発酵槽内に導入し、メタン発酵させるメタン発酵工程と、メタン発酵槽の処理水の一部を酸生成槽に返送する返送工程と、を有し、pH調整工程は、外部からの有機性排水の導入が停止される期間中に、酸生成槽内のアルカリを中和すると共にメタン発酵槽で生じる硫化水素と反応して硫化物の沈殿を生じる化合物を投入する化合物投入工程を含むことを特徴とするメタン発酵方法を提供する。   Further, the present invention provides a methane fermentation method in which organic wastewater introduced from the outside is treated in an acid production tank and a methane fermentation tank, and the organic wastewater is introduced into the acid production tank and treated with acid producing bacteria. Acid-generating step for generating water, pH-adjusting step for adjusting pH of organic wastewater, methane fermentation step for introducing organic wastewater from acid-generating tank into methane fermentation tank, and methane fermentation, and treatment of methane fermentation tank A return step for returning a part of the water to the acid generation tank, and the pH adjustment step neutralizes the alkali in the acid generation tank during the period when the introduction of the organic waste water from the outside is stopped. A methane fermentation method characterized by including a compound charging step of charging a compound that reacts with hydrogen sulfide generated in a methane fermentation tank to cause precipitation of sulfides.

メタン発酵装置では、上記のとおり、外部からの有機性排水の導入が停止される期間及びこの前後の期間において、酸生成槽内の有機性排水がアルカリ性側へ傾く傾向があり、通常稼働時において酸生成及びメタン発酵の効率が低下する。また、メタン発酵では硫化水素の同時生成により、硫化水素阻害が引き起こされるおそれがある。そこで、本発明のメタン発酵設備及びメタン発酵方法では、外部からの有機性排水の導入が停止される期間中に、所定の化合物を酸生成槽に投入する。この化合物は、酸生成槽内のアルカリを中和すると共にメタン発酵槽で生じる硫化水素と反応して硫化物の沈殿を生じる化合物である。このため、本発明によれば、外部からの有機性排水の導入が停止される期間中に、有機性排水のpHの調整を適切に行うことができ、且つ、硫化水素阻害を抑制することができる。   In the methane fermentation apparatus, as described above, the organic wastewater in the acid generation tank tends to be inclined toward the alkaline side during the period when the introduction of the organic wastewater from the outside is stopped and before and after this period. The efficiency of acid production and methane fermentation is reduced. In methane fermentation, hydrogen sulfide inhibition may be caused by simultaneous production of hydrogen sulfide. Therefore, in the methane fermentation facility and the methane fermentation method of the present invention, a predetermined compound is introduced into the acid generation tank during the period in which the introduction of the organic waste water from the outside is stopped. This compound is a compound that neutralizes the alkali in the acid generator and reacts with hydrogen sulfide generated in the methane fermentation tank to cause precipitation of sulfide. Therefore, according to the present invention, the pH of the organic waste water can be appropriately adjusted during the period when the introduction of the organic waste water from the outside is stopped, and the inhibition of hydrogen sulfide inhibition can be suppressed. it can.

ここで、有機性排水の導入が停止される期間中に投入する化合物は、FeClであることが好ましい。有機性排水のpHの調整を適切に行うこと、及び、硫化水素阻害を抑制する観点から、化合物の中でもFeClが、コスト面及び効果面から優れている。 Here, it is preferable that the compound introduced during the period when the introduction of the organic waste water is stopped is FeCl 3 . Among the compounds, FeCl 3 is superior in terms of cost and effectiveness from the viewpoint of appropriately adjusting the pH of the organic waste water and suppressing hydrogen sulfide inhibition.

また、本発明において、外部から供給される有機性排水は、クラフトパルプ製造工程おいて黒液を濃縮処理する際に発生する排水であることが好ましい。黒液を濃縮処理する際に発生する排水としては、ファールドレン(高臭気排水)とクリーンドレン(低臭気排水)とが挙げられるが、本発明における好ましい排水の態様としては、ファールドレンのみからなる排水であってもよく、クリーンドレンのみからなる排水であってもよく、ファールドレンとクリーンドレンの混合排水であってもよい。また、これら排水は、当然の如く、適宜希釈されていてもよい。クラフトパルプ製造工程おいて黒液を濃縮処理する際に発生する排水は、pHの緩衝作用を担うべき無機塩等が蒸留により除かれているため、元々pHの変動が大きい液体であることが知られている。本発明のメタン発酵設備及びメタン発酵方法では、上記のとおり有機性排水のpHの調整を適切に行うことができるため、有機性排水がクラフトパルプ製造工程おいて黒液を濃縮処理する際に発生する排水である場合に特に有用である。   Moreover, in this invention, it is preferable that the organic waste_water | drain supplied from the outside is a waste_water | drain generate | occur | produced when concentrating a black liquor in a kraft pulp manufacturing process. Examples of the waste water generated when the black liquor is concentrated include fardren (high odor waste water) and clean drain (low odor waste water), but the preferred waste water aspect in the present invention consists of only fardren. It may be drainage, may be drainage consisting only of clean drain, or may be mixed drainage of far drain and clean drain. Moreover, these waste waters may be appropriately diluted as a matter of course. It is known that the wastewater generated when black liquor is concentrated in the kraft pulp manufacturing process is a liquid that has a large pH fluctuation because inorganic salts, etc. that should have a pH buffering action are removed by distillation. It has been. In the methane fermentation facility and the methane fermentation method of the present invention, since the pH of the organic wastewater can be appropriately adjusted as described above, the organic wastewater is generated when the black liquor is concentrated in the kraft pulp manufacturing process. It is particularly useful when it is drained.

本発明によれば、外部からの有機性排水の導入が停止される期間中に、有機性排水のpHの調整を適切に行うことができ、且つ、硫化水素阻害を抑制することができるメタン発酵設備及びメタン発酵方法を提供することができる。   According to the present invention, during the period when the introduction of the organic waste water from the outside is stopped, the pH of the organic waste water can be appropriately adjusted, and the methane fermentation capable of suppressing hydrogen sulfide inhibition Equipment and methane fermentation methods can be provided.

本実施形態のメタン発酵設備の概要を示す概略構成図である。It is a schematic structure figure showing the outline of the methane fermentation equipment of this embodiment.

以下、本発明の好適な実施形態について、図面を参照しながら詳細に説明する。   DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.

はじめに、本実施形態のメタン発酵設備の基本構成と、通常稼働時の機能とを併せて説明する。図1は、本実施形態のメタン発酵設備の概要を示す概略構成図である。メタン発酵設備1は、例えばクラフトパルプ製造工程おいて黒液を濃縮処理する際に発生する排水等の有機性排水を処理すると共に、生成するメタンを回収する設備であり、外部から有機性排水が導入される酸生成槽2と、酸生成槽2の後段にラインL1を介して位置するメタン発酵槽3と、メタン発酵槽3における処理水の一部を酸生成槽2へ返送する返送ラインL2とを備えている。   First, the basic configuration of the methane fermentation facility of the present embodiment and the function during normal operation will be described together. Drawing 1 is a schematic structure figure showing the outline of the methane fermentation equipment of this embodiment. The methane fermentation facility 1 is a facility for treating organic wastewater such as wastewater generated when black liquor is concentrated in a kraft pulp manufacturing process, for example, and collecting generated methane. The acid generation tank 2 to be introduced, the methane fermentation tank 3 positioned in the subsequent stage of the acid generation tank 2 via the line L1, and the return line L2 for returning a part of the treated water in the methane fermentation tank 3 to the acid generation tank 2 And.

酸生成槽2は、内部に収容する酸生成菌により有機物を分解して低級脂肪酸を生成する槽である。この酸生成槽2には、有機性排水のpHを計測するpH計測器4、並びに、pHを調整するpH調整手段としてアルカリ供給源5及び酸供給源6が設けられている。また、pH調整手段としては、後に詳述するFeCl等の化合物を投入する化合物投入手段7も設けられている。 The acid production tank 2 is a tank that decomposes organic substances with acid producing bacteria accommodated therein to produce lower fatty acids. The acid generation tank 2 is provided with a pH measuring device 4 for measuring the pH of the organic waste water, and an alkali supply source 5 and an acid supply source 6 as pH adjusting means for adjusting the pH. Further, as the pH adjusting means, there is also provided a compound charging means 7 for charging a compound such as FeCl 3 described later in detail.

メタン発酵槽3は、酸生成槽2で処理された有機性排水、すなわち低級脂肪酸を豊富に含んだ有機性排水をラインL1を通じて導入し、内部に収容したメタン生成菌により低級脂肪酸を分解してメタンを生成する槽である。ここでは、メタン発酵槽3としては、メタン生成菌が自己凝集して粒状化したグラニュール状の嫌気性汚泥を槽内の下部に有し、有機性排水がメタン発酵槽内の下部から導入されるUASB(Upflow Anaerobic Sludge Blanket:上向流嫌気性汚泥床)処理装置を採用している。   The methane fermentation tank 3 introduces organic wastewater treated in the acid production tank 2, that is, organic wastewater containing abundant lower fatty acids through the line L 1, and decomposes lower fatty acids with the methanogen contained therein. It is a tank that produces methane. Here, the methane fermentation tank 3 has a granular anaerobic sludge formed by self-aggregation of granulated methanogens in the lower part of the tank, and organic waste water is introduced from the lower part of the methane fermentation tank. UASB (Upflow Anaerobic Sludge Blanket) treatment equipment is used.

次に、メタン発酵設備1の通常稼働時の作用を説明する。このメタン発酵設備1にあっては、外部から有機性排水が酸生成槽2に導入されると、酸生成槽2の内部に収容された酸生成菌によって有機性排水中の有機物が分解され、酢酸、プロピオン酸、酪酸等の低級脂肪酸が生成する(酸生成工程)。低級脂肪酸が生成するにつれて、酸生成槽2内の有機性排水のpHが徐々に低下する。pHが著しく低下すると酸生成菌の活性が低下するため、有機性排水のpHを酸生成菌にとって至適な範囲(例えばpH=6〜8)に維持する必要がある。このため、酸生成槽2においてはpH計測器4でpHをモニタリングし、pHが例えば6未満になった場合にアルカリ供給源5からNaOH等のアルカリ剤を投入してpHを調整する。反対に、pHが高くなりすぎた場合には、酸供給源6からHPO等の酸剤を投入してpHを調整する(pH調整工程)。 Next, the effect | action at the time of normal operation of the methane fermentation equipment 1 is demonstrated. In this methane fermentation facility 1, when organic wastewater is introduced from the outside into the acid generation tank 2, the organic matter in the organic wastewater is decomposed by the acid-producing bacteria housed in the acid generation tank 2, Lower fatty acids such as acetic acid, propionic acid, butyric acid are generated (acid generating step). As lower fatty acid is produced, the pH of the organic waste water in the acid production tank 2 is gradually lowered. Since the activity of acid producing bacteria is lowered when the pH is significantly lowered, it is necessary to maintain the pH of the organic waste water within an optimum range for the acid producing bacteria (for example, pH = 6 to 8). For this reason, in the acid production tank 2, the pH is monitored by the pH meter 4, and when the pH becomes less than 6, for example, an alkaline agent such as NaOH is introduced from the alkali supply source 5 to adjust the pH. On the other hand, when the pH becomes too high, an acid agent such as H 3 PO 4 is introduced from the acid supply source 6 to adjust the pH (pH adjustment step).

そして、メタン発酵槽3では、内部に収容されたメタン生成菌によって、酸生成槽2から導入された有機性排水に含まれる低級脂肪酸を分解するメタン発酵が行われ、メタンを含むバイオガスが生成する(メタン発酵工程)。ここで、UASB処理装置たるメタン発酵槽3内の下部にはグラニュール汚泥によるグラニュール汚泥床が保持されているため、有機性排水中の低級脂肪酸を当該グラニュール汚泥により分解することができる。生成したバイオガスはメタン発酵槽3の上部から回収され、処理水は後段に排出される。また、処理水の一部は、酸生成菌の流出回避及び酸生成槽2内の有機性排水の希釈の観点から、返送ラインL2を通じて酸生成槽2へ返送される(返送工程)。   And in the methane fermentation tank 3, methane fermentation which decomposes | disassembles the lower fatty acid contained in the organic waste_water | drain introduce | transduced from the acid production tank 2 is performed by the methane producer accommodated in the inside, and the biogas containing methane is produced | generated (Methane fermentation process). Here, since the granule sludge bed by the granular sludge is held in the lower part in the methane fermentation tank 3 which is the UASB processing apparatus, the lower fatty acid in the organic waste water can be decomposed by the granule sludge. The produced biogas is recovered from the upper part of the methane fermentation tank 3, and the treated water is discharged to the subsequent stage. A part of the treated water is returned to the acid generation tank 2 through the return line L2 from the viewpoint of avoiding outflow of acid producing bacteria and diluting the organic waste water in the acid generation tank 2 (returning step).

次に、このようにして通常稼働を行うメタン発酵設備1に対し、外部からの有機性排水の導入が停止される期間におけるメタン発酵設備1の機能について説明する。   Next, the function of the methane fermentation facility 1 during the period in which the introduction of the organic waste water from the outside is stopped will be described for the methane fermentation facility 1 that normally operates as described above.

メタン発酵設備1では、酸生成槽2に導入されるべき有機性排水を排出する設備が定修期間に入ること等により、有機性排水の導入が停止される期間が生じる。この期間中、メタン発酵設備1では稼働を緩めた状態、例えばメタン発酵槽3からの処理水の排出を止めて、酸生成槽2及びメタン発酵槽3内の撹拌のみを行う状態とされる。この期間及びこの前後の期間においては、通常稼働時と比べて有機性排水のpHの変動が大きく、特にアルカリ性側へ傾く傾向がある。pHが大きく変動すると、通常稼働を再開したときに、酸生成及びメタン発酵の効率が低下してしまう。   In the methane fermentation facility 1, there is a period in which the introduction of the organic wastewater is stopped, for example, when the facility that discharges the organic wastewater to be introduced into the acid generation tank 2 enters the regular repair period. During this period, the methane fermentation facility 1 is in a state in which the operation is relaxed, for example, the discharge of treated water from the methane fermentation tank 3 is stopped, and only the stirring in the acid generation tank 2 and the methane fermentation tank 3 is performed. During this period and before and after this period, the pH of the organic waste water varies greatly compared to that during normal operation, and in particular, it tends to tilt toward the alkaline side. If the pH fluctuates greatly, the efficiency of acid generation and methane fermentation will decrease when normal operation is resumed.

有機性排水の導入が停止される期間において、酸生成槽2内の有機性排水がアルカリ性側へ傾いた場合、そのアルカリを中和するための化合物を、化合物投入手段7から酸生成槽2に投入する(pH調整工程、化合物投入工程)。当該化合物は、酸生成槽2においてはアルカリを中和し、一部がメタン発酵槽3に移行したときには、メタン発酵槽3内の硫化水素と反応して、硫化物の沈殿を生じる。   When the introduction of the organic waste water is stopped, when the organic waste water in the acid generation tank 2 is inclined to the alkaline side, a compound for neutralizing the alkali is transferred from the compound charging means 7 to the acid generation tank 2. Input (pH adjustment step, compound input step). The compound neutralizes the alkali in the acid generator 2 and reacts with hydrogen sulfide in the methane fermenter 3 when a part of the compound is transferred to the methane fermenter 3 to cause sulfide precipitation.

化合物投入手段7から酸生成槽2に投入する化合物としては、水溶液とされたときに酸性を示し、且つ硫化水素と反応して硫化物の沈殿を生じ得る化合物であれば特に限定されず、例えば、Mn、Zn、Fe、Ni、Cd、Sn、Pb、Cu、Hg及びAgのうち少なくとも1種の元素を含む化合物が挙げられる。これらのうち、有機性排水のpHの調整を適切に行うこと、及び、コストを抑制する観点から、FeCl(塩化鉄(III)(慣用名:塩化第二鉄))が好ましく、コスト面及び効果面においても優れている。FeClは、硫化水素と反応して硫化鉄の沈殿を生じる。また、投入する化合物として、酸生成菌やメタン生成菌の栄養のためにメタン発酵設備1内に常時添加導入している化合物を利用することもでき、この場合、コスト面で有利である。 The compound to be charged into the acid generation tank 2 from the compound charging means 7 is not particularly limited as long as it is acidic and can react with hydrogen sulfide to cause sulfide precipitation when it is made into an aqueous solution. , Mn, Zn, Fe, Ni, Cd, Sn, Pb, Cu, Hg, and a compound containing at least one element among Ag. Among these, FeCl 3 (iron (III) chloride (common name: ferric chloride)) is preferable from the viewpoint of appropriately adjusting the pH of the organic waste water and suppressing the cost. It is also excellent in terms of effectiveness. FeCl 3 reacts with hydrogen sulfide to cause precipitation of iron sulfide. In addition, as a compound to be introduced, a compound that is constantly added and introduced into the methane fermentation facility 1 for the nutrition of acid-producing bacteria and methanogens can be used, which is advantageous in terms of cost.

以上説明したように、本実施形態のメタン発酵設備1は、外部からの有機性排水の導入が停止される期間及びこの前後の期間において、酸生成槽2内の有機性排水がアルカリ性側へ傾いた場合に、これを中和するための化合物を投入してpHを酸生成菌の至適範囲に調整することができる。また、メタン発酵では硫化水素の同時生成により硫化水素阻害が引き起こされるおそれがあるところ、投入した当該化合物の一部はメタン発酵槽3に移行して、硫化水素と反応して硫化物の沈殿を生じるため、槽内の硫化水素を低減することができる。このため、本実施形態のメタン発酵設備1によれば、外部からの有機性排水の導入が停止される期間中に、有機性排水のpHの調整を適切に行うことができ、且つ、硫化水素阻害を抑制することができる。   As described above, in the methane fermentation facility 1 of the present embodiment, the organic wastewater in the acid generation tank 2 is inclined toward the alkaline side during the period when the introduction of the organic wastewater from the outside is stopped and before and after this period. In this case, the pH can be adjusted to the optimum range for acid-producing bacteria by introducing a compound for neutralizing this. In addition, in methane fermentation, hydrogen sulfide inhibition may be caused by the simultaneous production of hydrogen sulfide, so that a part of the introduced compound moves to the methane fermentation tank 3 and reacts with hydrogen sulfide to precipitate sulfide. As a result, hydrogen sulfide in the tank can be reduced. For this reason, according to the methane fermentation facility 1 of the present embodiment, the pH of the organic wastewater can be appropriately adjusted during the period in which the introduction of the organic wastewater from the outside is stopped, and hydrogen sulfide Inhibition can be suppressed.

また、一般にクラフトパルプ製造工程おいて黒液を濃縮処理する際に発生する排水は、pHの緩衝作用を担うべき無機塩等が蒸留により除かれているため、元々pHの変動が大きい液体である。従って、外部から導入される有機性排水がクラフトパルプ製造工程おいて黒液を濃縮処理する際に発生する排水である場合は、上記のとおり有機性排水のpHの調整を適切に行うことができる本実施形態のメタン発酵設備1は、特に有用である。   Further, generally, wastewater generated when black liquor is concentrated in the kraft pulp manufacturing process is a liquid that has a large pH fluctuation because inorganic salts and the like that should be responsible for pH buffering are removed by distillation. . Therefore, when the organic wastewater introduced from the outside is wastewater generated when the black liquor is concentrated in the kraft pulp manufacturing process, the pH of the organic wastewater can be appropriately adjusted as described above. The methane fermentation facility 1 of this embodiment is particularly useful.

以上、本発明の好適な実施形態について説明したが、本発明は上記実施形態に限定されるものではない。例えば、上記実施形態ではpH計測器4を酸生成槽2に設けているが、これをラインL1に設けてもよい。また、上記実施形態では化合物を化合物投入手段7から酸生成槽2に投入しているが、これをラインL1内に投入してもよい。また、酸供給源6が化合物投入手段7を兼ねてもよく、酸生成菌やメタン生成菌に栄養を与えるために利用しているラインを化合物投入手段として利用してもよい。   The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, although the pH measuring device 4 is provided in the acid generation tank 2 in the above embodiment, it may be provided in the line L1. Moreover, in the said embodiment, although the compound is thrown into the acid production tank 2 from the compound throwing means 7, you may throw this into the line L1. Moreover, the acid supply source 6 may also serve as the compound feeding means 7, and a line used for feeding the acid producing bacteria or the methanogenic bacteria may be used as the compound feeding means.

また、上記実施形態ではメタン発酵槽3としてUASB処理装置を採用しているが、これに替えて、グラニュール汚泥床の粒状化を更に促進させて膨張させることにより有機性排水との接触効率を向上するようにしたEGSB(Expanded Granular Sludge Bed:膨張粒状汚泥床)処理装置を採用してもよい。   Moreover, in the said embodiment, although the UASB processing apparatus is employ | adopted as the methane fermenter 3, it replaces with this and further promotes the granulation of a granule sludge bed and expands contact efficiency with organic waste water. An improved EGSB (Expanded Granular Sludge Bed) treatment apparatus may be employed.

また、外部からの有機性排水の導入が停止される期間としては、有機性排水を排出する設備が定修期間に入る場合のほか、メタン発酵設備1自身が定修期間に入る場合等であってもよい。   In addition, the period during which the introduction of organic wastewater from the outside is stopped includes not only the case where equipment that discharges organic wastewater enters the regular repair period, but also the case where the methane fermentation facility 1 itself enters the regular repair period. May be.

1…メタン発酵設備、2…酸生成槽、3…メタン発酵槽、5…アルカリ供給源(pH調整手段)、6…酸供給源(pH調整手段)、7…化合物投入手段(pH調整手段)、L2…返送ライン。   DESCRIPTION OF SYMBOLS 1 ... Methane fermentation installation, 2 ... Acid production tank, 3 ... Methane fermentation tank, 5 ... Alkali supply source (pH adjustment means), 6 ... Acid supply source (pH adjustment means), 7 ... Compound injection means (pH adjustment means) , L2 ... Return line.

Claims (4)

外部から導入される有機性排水を酸生成菌で処理して酸を生成させる酸生成槽と、
有機性排水のpHを調整するpH調整手段と、
前記酸生成槽から導入される有機性排水をメタン発酵させるメタン発酵槽と、
前記メタン発酵槽の処理水の一部を前記酸生成槽へ返送する返送ラインと、を備え、
前記pH調整手段は、外部からの有機性排水の導入が停止される期間中に、前記酸生成槽内のアルカリを中和すると共に前記メタン発酵槽で生じる硫化水素と反応して硫化物の沈殿を生じる化合物を投入する化合物投入手段を含むことを特徴とする、メタン発酵設備。
An acid generator tank that generates acid by treating the organic wastewater introduced from the outside with an acid generator;
PH adjusting means for adjusting the pH of the organic waste water;
A methane fermentation tank for methane fermentation of organic wastewater introduced from the acid generation tank;
A return line for returning a part of the treated water of the methane fermentation tank to the acid generation tank,
The pH adjusting means neutralizes the alkali in the acid generation tank and reacts with hydrogen sulfide generated in the methane fermentation tank during the period in which the introduction of the organic waste water from the outside is stopped. A methane fermentation facility characterized by comprising a compound charging means for charging a compound that produces a methane salt.
前記化合物は、FeClである、請求項1記載のメタン発酵設備。 The methane fermentation facility according to claim 1, wherein the compound is FeCl 3 . 外部から供給される有機性排水は、クラフトパルプ製造工程おいて黒液を濃縮処理する際に発生する排水である、請求項1又は2記載のメタン発酵設備。   The organic wastewater supplied from the outside is methane fermentation equipment according to claim 1 or 2, which is wastewater generated when black liquor is concentrated in the kraft pulp manufacturing process. 外部から導入される有機性排水を酸生成槽及びメタン発酵槽で処理するメタン発酵方法において、
有機性排水を前記酸生成槽内に導入し、酸生成菌で処理して酸を生成させる酸生成工程と、
有機性排水のpHを調整するpH調整工程と、
前記酸生成槽から有機性排水を前記メタン発酵槽内に導入し、メタン発酵させるメタン発酵工程と、
前記メタン発酵槽の処理水の一部を前記酸生成槽に返送する返送工程と、を有し、
前記pH調整工程は、外部からの有機性排水の導入が停止される期間中に、前記酸生成槽内のアルカリを中和すると共に前記メタン発酵槽で生じる硫化水素と反応して硫化物の沈殿を生じる化合物を投入する化合物投入工程を含むことを特徴とする、メタン発酵方法。
In the methane fermentation method in which the organic wastewater introduced from the outside is treated in the acid generation tank and the methane fermentation tank,
An acid generation step of introducing organic wastewater into the acid generation tank and generating an acid by treating with acid generating bacteria,
A pH adjusting step for adjusting the pH of the organic waste water;
A methane fermentation process in which organic waste water is introduced into the methane fermentation tank from the acid generation tank and methane fermentation is performed.
A return step of returning a part of the treated water of the methane fermentation tank to the acid generation tank,
The pH adjusting step neutralizes the alkali in the acid generation tank and reacts with hydrogen sulfide generated in the methane fermentation tank during the period in which the introduction of the organic waste water from the outside is stopped. A method for methane fermentation, comprising a step of introducing a compound for introducing a compound that yields.
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