JP4288975B2 - Organic waste liquid digester - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、有機性廃液を嫌気性消化又は好気性消化する装置に係り、特に、有機性廃液の消化効率を高めて汚泥を大幅に減量化するための有機性廃液の消化処理装置に関する。
【０００２】
【従来の技術】
有機性汚泥、し尿、食品工場廃水等のスラリー状の高濃度有機性汚泥を嫌気性又は好気性微生物の存在下に消化処理して減量化する方法は、古くから行われている。しかし、従来の消化処理法は、２日間以上という長時間の滞留時間を必要とするにもかかわらず、汚泥の減量率が低いという問題点がある。
【０００３】
こうした問題点を解消するために、特開平８−２８１２９７号公報には、有機性汚泥を消化処理した後の消化汚泥を遠心濃縮し、濃縮汚泥を消化槽に返送する消化処理方法が記載されている。この方法では、消化槽の負荷量を減少させることなく、汚泥の消化槽内での滞留時間を増加させることによって、有機物分解率を向上させ、汚泥の減量率を高めることができる。即ち、濃縮汚泥を消化槽に返送することにより、ＨＲＴ（水理学的滞留時間）はそのままで、ＳＲＴ（固形物滞留時間）を長く設定することができ、有機性汚泥中の分解速度が遅い固形分をも分解することが可能となり、高い減量率を得ることができる。
【０００４】
この方法で濃縮を効率的に行うためには、消化汚泥の濃縮倍率を高く、例えば２倍以上として運転することが好ましい。即ち、濃縮倍率が低いと、ある量の分離液を得るのに必要な遠心濃縮機の処理量が著しく増加するため、より大型の濃縮機が必要となったり、濃縮機の運転時間を長くする必要があったり、凝集剤がより多く必要になったりする。また、濃縮機による濃縮を所望の濃縮倍率に調整するには、高度の運転技術を要し、また条件変動があると安定して所望の濃度に濃縮することができないという問題もあり、この点からも、濃縮機による濃縮は、濃縮機の性能に見合った高濃度倍率で行うことが好ましい。
【０００５】
ところが、濃縮倍率を高くして濃縮汚泥の濃度を高めると、汚泥の粘性は汚泥濃度に対して指数関数的に増加するため、濃縮汚泥の粘性が著しく増加してしまう。その結果、濃縮汚泥を消化槽に返送することが困難になったり、返送した濃縮汚泥を消化槽内で十分に分散させることができなくなり、消化処理の効率が低下したりする問題があった。
【０００６】
【特許文献１】
特開平８−２８１２９７号公報
【０００７】
【発明が解決しようとする課題】
本発明の目的は、前記従来の問題点を解決して、消化汚泥の濃縮倍率を高くして効率的な濃縮を行いつつ、濃縮汚泥の返送を円滑に行うと共に、返送した濃縮汚泥を消化槽内で十分に分散させて効率的な消化を行うことにより、汚泥の減量率を高くする有機性廃液の消化処理装置を提供することにある。
【０００８】
【課題を解決するための手段】
本発明の有機性廃液の消化処理装置は、有機性廃液を消化する消化槽と該消化槽から排出される消化汚泥を濃縮する固液分離手段（以下「濃縮機」と称す場合がある。）と、該固液分離手段からの濃縮汚泥を前記消化槽へ返送する移送ポンプを有する配管と、該移送ポンプ又は該移送ポンプのサクション側において、濃縮汚泥に液体を添加する液供給手段とを有する有機性廃液の消化処理装置であって、該液供給手段は前記濃縮汚泥と前記液体とを混合する混合槽を備え、前記固液分離手段からの濃縮汚泥は、該混合槽に投下され、該混合槽で液体が添加混合されて濃度調整された汚泥が、前記移送ポンプにより前記消化槽へ返送されることを特徴とする。
【０００９】
本発明では、消化汚泥を濃縮し、濃縮汚泥を消化槽に返送することにより、消化槽のＳＲＴを長く確保して高い消化効率及び減量率を得ることができる。
【００１０】
この濃縮汚泥は、ペースト状ないし粘性の高い液状であり、ポンプで移送するにはポンプ吐出圧が極めて大きくなり、実現困難である。しかも、このような高粘性の濃縮汚泥は消化槽内で分散し難く、このことが消化効率の低下につながる。一方で、前述の如く、ポンプでの移送可能な程度に適度に濃縮を行うことは困難であり、また、濃縮機の効率も悪くなる。
【００１１】
本発明では、ポンプによる移送性を考慮することなく消化汚泥を濃縮し、得られた高粘性の濃縮汚泥に液体を混合することによりポンプ移送が容易な濃度に希釈して濃度調整する。
【００１２】
本発明において、この濃縮汚泥の濃度調整位置が移送ポンプ又は移送ポンプのサクション側であることは極めて重要であり、このように移送ポンプ又は移送ポンプのサクション側で所定の濃度に濃度調整することにより、この移送ポンプにより容易に移送することが可能となる。
【００１３】
これに対して、前述の特開平８−２８１２９７号公報においても、濃縮汚泥は、消化槽の入口側で原汚泥と混合されて希釈されるが、この方法では、原汚泥導入側まで濃縮汚泥を移送することが困難である。
【００１４】
本発明では、濃縮汚泥を移送ポンプ又は移送ポンプのサクション側でポンプ移送に適当な濃度に濃度調整して効率的に消化槽に返送すると共に、消化槽においてこの返送汚泥を均一に分散させて効率的な消化処理を行うことができる。
【００１５】
本発明において、濃縮汚泥の濃度調整のための希釈用液体としては、濃縮前の消化汚泥を用いることが好ましい。
【００１６】
なお、消化処理の対象となる有機性廃液の窒素分が多い場合には、消化処理の過程で液側に移行するアンモニアによって消化反応が阻害され、処理効率が低下することがあるため、有機性廃液を予め希釈するなどして消化槽の有機物負荷を下げる必要があるが、本発明のように、消化汚泥を濃縮してアンモニアを含む分離液を系外に引き抜き、濃縮汚泥をアンモニアの少ない他の廃液で希釈して消化槽に返送することによって、有機物負荷を下げることなく、消化処理を行うことができる。
【００１７】
【発明の実施の形態】
以下に図面を参照して本発明の有機性廃液の消化処理装置の実施の形態を詳細に説明する。
【００１８】
図１は本発明の有機性廃液の消化処理装置の実施の形態を示す系統図である。
【００１９】
図１において、有機性汚泥（有機性廃液）は消化槽１に導入され消化処理される。この消化槽１の消化汚泥の一部を引き抜き、濃縮機２で濃縮する。濃縮機２で濃縮された濃縮汚泥は混合槽３に送給して消化槽１からの消化汚泥と混合して濃度調整し、ポンプ移送に好適な濃度に調整した汚泥を移送ポンプ４により消化槽１に返送する。
【００２０】
本発明において処理の対象となる有機性廃液は、消化処理によって減量化される有機物を含有する廃液であり、固形物を含むスラリー状のものでも、固形物を含まない液状のものでも良い。また、難生物分解性の有機物、無機物、セルロース、紙、綿、ウール、布、し尿中の固形物などが含有されていても良い。このような有機性廃液としては下水、下水初沈汚泥、し尿、浄化槽汚泥、食品工場の排水や残渣、ビール廃酵母、その他の産業廃液、これらの廃液を処理した際に生じる余剰汚泥等の有機性汚泥が挙げられる。
【００２１】
消化槽１では嫌気性又は好気性微生物を含む汚泥の存在下に、このような有機性汚泥の消化処理を行う。消化槽１の有機物負荷は０．２〜２０ｋｇ−ＣＯＤＣｒ／ｍ３・日、消化槽１内のＭＬＳＳ濃度は１〜１０％、好ましくは３〜６％、温度は３０〜３８℃又は４５〜６０℃の条件を採用することができる。
【００２２】
消化汚泥を濃縮するための濃縮機２としては、消化汚泥を固液分離して濃縮することができるものであれば良く、特に制限はないが、遠心濃縮機、浮上濃縮機、スクリュープレス濃縮機、濾布型濃縮機などを用いることができる。また、沈殿槽、膜分離装置などの固液分離装置を用いることもできる。消化汚泥に凝集剤、好ましくは高分子凝集剤を添加して消化汚泥中のＳＳ分を凝集させることにより、濃縮倍率を高め、清澄な分離液を得ることができる。凝集剤としては消化汚泥の濃縮、脱水に一般的に用いられる公知のものが適用できるが、添加量が少なくて済むことからカチオン系の高分子凝集剤が良い。高分子凝集剤の添加率は消化汚泥のＳＳ当たり０．０５〜１．５重量％とすることが好ましい。消化汚泥に凝集剤を添加する場合、凝集剤は消化汚泥の移送ラインに注入しても良く、濃縮機に添加しても良く、また、別途凝集槽を設けて凝集処理しても良い。
【００２３】
濃縮機２における消化汚泥の濃縮の程度は、用いる濃縮機の性能にもよるが、通常ＳＳ（固形物）濃度３〜６％程度の消化汚泥を、８〜２０％程度のペースト状ないし高粘性の液状に濃縮するのが好ましい。
【００２４】
濃縮機２からの濃縮汚泥は、必要に応じてその一部を余剰汚泥として系外に排出し、脱水、焼却、埋め立て等の処分を行っても良い。排出する余剰汚泥の粘性が高い場合には、希釈用液体で薄めて排出すると、排出ポンプの動力が少なくて済む。この希釈用液体としては処理水（濃縮機２の分離液）や他の有機性廃液の生物処理水等を用いることができる。
【００２５】
また、濃縮機２の分離液は処理水としてそのまま下水道等へ放流することができるが、好気性生物処理、その他の後処理を行った後放流しても良い。
【００２６】
混合槽３では、濃縮機２からの濃縮汚泥に消化槽１から引き抜いた消化汚泥を添加して濃度調整する。この濃縮汚泥の濃度調整に用いる希釈用液体としては、消化汚泥の他、原汚泥の有機性汚泥（有機性廃液）、処理水（濃縮機２の分離液）、工業用水、上水、その他、他系統の廃液や生物処理水等を用いることもできるが、好ましくは消化汚泥を用いる。
【００２７】
濃縮汚泥の濃度調整には、必ずしも混合槽を設ける必要はなく、濃縮汚泥の移送配管において、移送ポンプのサクション或いは移送ポンプに希釈用液体を注入するのみでも良い。しかし、濃縮汚泥の粘性が高い場合には、図１に示す如く、混合槽３を設け、機械的に混合することが好ましい。この混合手段としては、撹拌機、ガスの吹き込み、スタティックミキサー等を用いることができる。
【００２８】
濃縮汚泥の濃度調整のための混合槽３の滞留時間は１分〜６時間程度で良いため、混合槽３の容積は小さくて足りる。また、濃縮汚泥を直接消化槽に投入して消化汚泥や原汚泥と混合する場合に比べ、この混合槽３における混合のために必要な動力は著しく小さくて済む。
【００２９】
濃縮汚泥の濃度調整の程度は、例えば一段のモノポンプで円滑に移送が行える程度で良く、一般的には移送ポンプ４の吐出圧が０．６ＭＰａ以下となるように、ＳＳ濃度で６〜１２％、例えば８％程度に濃縮することが好ましい。
【００３０】
図１の装置では、濃縮機２で濃縮された濃縮汚泥が混合槽３に投下され、この濃縮汚泥が消化汚泥によって濃度調整される。このようにして濃度調整された汚泥は移送ポンプ４により効率的に消化槽１に返送することができ、また、消化槽１内で容易に分散することにより、効率的に消化処理される。
【００３１】
濃度調整後の汚泥の移送のための移送ポンプ４としては特に制限はないが、モノポンプ、ホースポンプ等を用いることができる。
【００３２】
本発明では、このように消化槽１内の消化汚泥の一部を引き抜いて濃縮機２で濃縮し、濃縮汚泥を濃度調整して消化槽１に返送することにより、ＨＲＴを変えることなくＳＲＴを長くすることができ、これにより汚泥減量率を低減することができる。
【００３３】
濃縮のための消化槽１からの消化汚泥の引き抜き量は特に制限はないが、消化槽１内の保有汚泥の１／３０〜１／１０程度を引き抜いて、濃縮、濃度調整した後循環させることにより、ＳＲＴを、このような汚泥循環を行わない場合の少なくとも３倍程度以上に延長することができ、難生物分解性の有機性廃液であっても、汚泥の減量化を促進させることができる。
【００３４】
なお、本発明においては、嫌気性消化を行う場合、濃縮機や混合槽を大気と遮断した状態で運転するのが好ましく、例えば、濃縮機を密閉状態にして濃縮することにより、汚泥と酸素との接触を制限すると、嫌気性菌を生かしたまま消化槽に返送でき、消化槽の生菌数保持、増加が容易となり、消化効率を向上させることができる。
【００３５】
【実施例】
以下に実施例及び比較例を挙げて本発明をより具体的に説明する。
【００３６】
下水の初沈汚泥と余剰汚泥を３５℃の下、一過式で嫌気性消化した。嫌気性消化槽の容積は１ｍ３、ＶＳＳ負荷は０．６５ｋｇ／ｍ３・日、ＨＲＴは４０日（１日当たりの投入汚泥量は２５Ｌ）。投入汚泥濃度（ＳＳ濃度。以下同様）３．５％（ＶＳＳ／ＳＳ比８３％）に対し、消化汚泥濃度は１．６％（ＶＳＳ／ＳＳ比７３％）であり、消化率（ＶＳＳの減量率）は６０％であった。槽内汚泥を固液分離して汚泥を返送することによって汚泥滞留時間を増加させ、減量率を高めることを試み、固液分離手段として遠心濃縮機を用いた。
【００３７】
槽内汚泥を２００Ｌ／ｈｒで遠心濃縮機に供給して、遠心強度２，１００Ｇ、差速１５ｍｉｎ−１のもと、０．２重量％に溶解したカチオン系高分子凝集剤をＳＳ当たり０．６重量％添加しながら行った。このとき、濃縮汚泥濃度は１２％、ＳＳ回収率は９５％以上であった。遠心濃縮機から濃縮汚泥受槽（混合槽）に排出された濃縮汚泥をモノポンプで嫌気性消化槽に返送しようとしたところ、吐出圧力が０．８ＭＰａに達し、ポンプがトリップしてしまい、汚泥を返送することができなかった。
【００３８】
そこで、以下の実施例及び比較例の処理を行った。
【００３９】
実施例１
混合槽に濃縮機の分離液の一部を導入して、攪拌機で緩やかに攪拌しながら混合したところ、混合槽内の汚泥濃度は８％となり、モノポンプの圧力は０．２５ＭＰａにまで低下したため、嫌気性消化槽に速やかに返送することができた。嫌気性消化槽から特に汚泥を引き抜くことなく、このような運転を半年間継続したところ、消化汚泥濃度は５％近くに達したが、固形分の収支及び消化ガスの発生量から求めた消化率は７０％に向上させることができた。
【００４０】
実施例２
混合槽に嫌気性消化槽からの消化汚泥の一部を導入して、攪拌機で緩やかに攪拌しながら混合したところ、混合槽内の汚泥濃度は８％となり、モノポンプの圧力は０．２５ＭＰａにまで低下したため、速やかに返送することができた。消化槽から特に汚泥を引き抜くことなく、このような運転を半年間継続したところ、消化汚泥濃度は５％近くに達したが、固形分の収支及び消化ガスの発生量から求めた消化率は７０％に向上させることができた。また、実施例１に比べ、遠心濃縮機の運転時間、凝集剤の使用量が１８％減少した。
【００４１】
比較例１
モノポンプで圧送できる程度に圧力を下げるため、遠心濃縮の条件を変更した。遠心強度を１，０００Ｇまで下げ、凝集剤添加率を０．２重量％まで下げたところ、濃縮汚泥濃度は８％程度となり、モノポンプの圧力は０．３ＭＰａまで低下し、嫌気性消化槽に返送することができるようになった。しかし、このときのＳＳ回収率は７０％であり、分離液側に汚泥が流出した。このような運転を半年間継続したが、遠心濃縮機でのＳＳ回収率が低かったため、嫌気性消化槽内汚泥濃度を高めることができず、消化率は一過式で処理していたときの６０％と殆ど変わらなかった。
【００４２】
【発明の効果】
以上詳述した通り、本発明の有機性廃液の消化処理装置によれば、粘性の著しく高い濃縮汚泥を消化汚泥等で濃度調整した後、消化槽に返送することによって、効率的な濃縮を行いつつ、濃縮汚泥を効率的に返送し、かつ、消化槽内で十分に分散させて効率的な消化を行い、汚泥を高度に減量することができる。
【図面の簡単な説明】
【図１】本発明の有機性廃液の消化処理装置の実施の形態を示す系統図である。
【符号の説明】
１ 消化槽
２ 濃縮機
３ 混合槽
４ 移送ポンプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for anaerobic digestion or aerobic digestion of an organic waste liquid, and more particularly to an organic waste liquid digestion apparatus for increasing the digestion efficiency of an organic waste liquid and greatly reducing sludge.
[0002]
[Prior art]
The method of digesting and reducing the amount of slurried high-concentration organic sludge such as organic sludge, human waste, and food factory wastewater in the presence of anaerobic or aerobic microorganisms has long been performed. However, the conventional digestion treatment method has a problem that the sludge reduction rate is low, although a long residence time of 2 days or more is required.
[0003]
In order to solve such problems, JP-A-8-281297 discloses a digestion treatment method in which digested sludge after digestion of organic sludge is concentrated by centrifugation and the concentrated sludge is returned to the digestion tank. Yes. In this method, the organic substance decomposition rate can be improved and the sludge weight loss rate can be increased by increasing the residence time of the sludge in the digester without reducing the load of the digester. That is, by returning the concentrated sludge to the digestion tank, the HRT (hydraulic residence time) remains unchanged, the SRT (solid matter residence time) can be set longer, and the solids with a slow decomposition rate in organic sludge can be set. It is possible to decompose the fraction, and a high weight loss rate can be obtained.
[0004]
In order to perform the concentration efficiently by this method, it is preferable to operate the digested sludge at a high concentration factor, for example, twice or more. In other words, if the concentration ratio is low, the throughput of the centrifugal concentrator required to obtain a certain amount of separation liquid increases remarkably, so a larger concentrator is required or the operation time of the concentrator is lengthened. There is a need or more coagulant is needed. In addition, in order to adjust the concentration by the concentrator to a desired concentration ratio, a high degree of operation technology is required, and there is a problem that it cannot be stably concentrated to a desired concentration if there is a change in conditions. Therefore, the concentration by the concentrator is preferably performed at a high concentration factor that matches the performance of the concentrator.
[0005]
However, when the concentration factor is increased to increase the concentration of the concentrated sludge, the viscosity of the sludge increases exponentially with respect to the sludge concentration, and thus the viscosity of the concentrated sludge increases remarkably. As a result, there is a problem that it becomes difficult to return the concentrated sludge to the digestion tank, or the returned concentrated sludge cannot be sufficiently dispersed in the digestion tank, and the efficiency of the digestion process is reduced.
[0006]
[Patent Document 1]
JP-A-8-281297 [0007]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned conventional problems, increase the concentration rate of digested sludge and perform efficient concentration, while smoothly returning the concentrated sludge, and returning the returned concentrated sludge to the digestion tank It is intended to provide an organic waste liquid digestion treatment apparatus that increases the sludge weight loss rate by performing sufficient digestion with sufficient dispersion.
[0008]
[Means for Solving the Problems]
The organic waste liquid digestion treatment apparatus of the present invention digests organic waste liquid and solid-liquid separation means for concentrating digested sludge discharged from the digester (hereinafter sometimes referred to as “concentrator”). And a pipe having a transfer pump for returning the concentrated sludge from the solid-liquid separation means to the digester, and a liquid supply means for adding a liquid to the concentrated sludge on the suction side of the transfer pump or the transfer pump. An organic waste liquid digestion treatment apparatus, wherein the liquid supply means includes a mixing tank for mixing the concentrated sludge and the liquid, and the concentrated sludge from the solid-liquid separation means is dropped into the mixing tank, The sludge whose concentration is adjusted by adding and mixing the liquid in the mixing tank is returned to the digestion tank by the transfer pump .
[0009]
In the present invention, digested sludge is concentrated, and the concentrated sludge is returned to the digestion tank, so that a long digestion tank SRT can be ensured and high digestion efficiency and weight loss rate can be obtained.
[0010]
This concentrated sludge is in the form of a paste or a highly viscous liquid, and the pump discharge pressure becomes extremely large for transfer by a pump, which is difficult to realize. Moreover, such highly viscous concentrated sludge is difficult to disperse in the digestion tank, which leads to a decrease in digestion efficiency. On the other hand, as described above, it is difficult to perform concentration to such an extent that it can be transferred by a pump, and the efficiency of the concentrator also deteriorates.
[0011]
In the present invention, the digested sludge is concentrated without considering the transferability by the pump, and the liquid is mixed with the obtained highly viscous concentrated sludge to dilute the concentration so that the pump can be easily transferred to adjust the concentration.
[0012]
In the present invention, it is extremely important that the concentration adjustment position of the concentrated sludge is the transfer pump or the suction side of the transfer pump, and thus the concentration is adjusted to a predetermined concentration on the suction side of the transfer pump or the transfer pump. The transfer pump can be easily transferred.
[0013]
On the other hand, in the above-mentioned JP-A-8-281297, the concentrated sludge is mixed with the raw sludge at the inlet side of the digester and diluted. However, in this method, the concentrated sludge is mixed up to the raw sludge introduction side. It is difficult to transport.
[0014]
In the present invention, the concentrated sludge is adjusted to a concentration suitable for pump transfer on the transfer pump or the suction side of the transfer pump and efficiently returned to the digestion tank, and this return sludge is uniformly dispersed in the digestion tank. Digestive treatment can be performed.
[0015]
In the present invention, it is preferable to use digested sludge before concentration as a dilution liquid for adjusting the concentration of the concentrated sludge.
[0016]
In addition, when the organic waste liquid subject to digestion treatment has a high nitrogen content, the digestion reaction may be inhibited by ammonia that moves to the liquid side during the digestion process, and the treatment efficiency may be reduced. It is necessary to dilute the waste liquid in advance to reduce the organic load in the digestion tank. However, as in the present invention, the digested sludge is concentrated and the ammonia-containing separation liquid is drawn out of the system. By diluting with a waste liquid and returning it to the digestion tank, digestion treatment can be performed without lowering the organic load.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an organic waste liquid digestion apparatus of the present invention will be described below in detail with reference to the drawings.
[0018]
FIG. 1 is a system diagram showing an embodiment of an organic waste liquid digestion treatment apparatus of the present invention.
[0019]
In FIG. 1, organic sludge (organic waste liquid) is introduced into a digestion tank 1 and digested. A part of the digested sludge in the digester 1 is extracted and concentrated by the concentrator 2. The concentrated sludge concentrated in the concentrator 2 is fed to the mixing tank 3 and mixed with the digested sludge from the digesting tank 1 to adjust the concentration, and the sludge adjusted to a concentration suitable for pump transfer is transferred to the digesting tank by the
[0020]
The organic waste liquid to be treated in the present invention is a waste liquid containing an organic substance that is reduced by digestion treatment, and may be a slurry containing a solid or a liquid containing no solid. In addition, non-biodegradable organic substances, inorganic substances, cellulose, paper, cotton, wool, cloth, solid matter in human waste may be contained. Examples of such organic waste liquid include sewage, sewage initial sedimentation sludge, human waste, septic tank sludge, wastewater and residue from food factories, beer waste yeast, other industrial waste liquids, and excess sludge generated when these waste liquids are treated. Natural sludge.
[0021]
In the digestion tank 1, such organic sludge is digested in the presence of sludge containing anaerobic or aerobic microorganisms. The organic substance load of the digester 1 is 0.2 to 20 kg-COD Cr / m 3 · day, the MLSS concentration in the digester 1 is 1 to 10%, preferably 3 to 6%, and the temperature is 30 to 38 ° C. or 45 to 45 ° C. A condition of 60 ° C. can be employed.
[0022]
The concentrator 2 for concentrating the digested sludge is not particularly limited as long as it can separate and concentrate the digested sludge by solid-liquid separation. However, the centrifugal concentrator, the flotation concentrator, and the screw press concentrator. A filter cloth type concentrator can be used. A solid-liquid separation device such as a precipitation tank or a membrane separation device can also be used. By adding a flocculant, preferably a polymer flocculant, to the digested sludge and aggregating the SS content in the digested sludge, the concentration factor can be increased and a clear separation liquid can be obtained. As the flocculant, known ones generally used for concentration and dehydration of digested sludge can be applied, but a cationic polymer flocculant is preferable because the addition amount is small. The addition rate of the polymer flocculant is preferably 0.05 to 1.5% by weight per SS of the digested sludge. When a flocculant is added to the digested sludge, the flocculant may be injected into the digested sludge transfer line, may be added to the concentrator, or may be agglomerated by separately providing a coagulation tank.
[0023]
The degree of concentration of digested sludge in the concentrator 2 depends on the performance of the concentrator used, but usually digested sludge with a SS (solid matter) concentration of about 3 to 6% is pasty or highly viscous about 8 to 20%. It is preferable to concentrate in the liquid form.
[0024]
A part of the concentrated sludge from the concentrator 2 may be discharged out of the system as surplus sludge as necessary, and may be subjected to disposal such as dehydration, incineration, and landfill. When the excess sludge to be discharged has a high viscosity, the power of the discharge pump can be reduced by diluting with the dilution liquid and discharging. As the liquid for dilution, treated water (separated liquid of the concentrator 2), biologically treated water of other organic waste liquids, or the like can be used.
[0025]
Further, the separated liquid of the concentrator 2 can be discharged as treated water to a sewer as it is, but may be discharged after aerobic biological treatment or other post-treatment.
[0026]
In the mixing tank 3, the concentration is adjusted by adding the digested sludge extracted from the digester 1 to the concentrated sludge from the concentrator 2. Dilution liquid used for adjusting the concentration of this concentrated sludge includes digested sludge, organic sludge of raw sludge (organic waste liquid), treated water (separator of concentrate 2), industrial water, tap water, etc. Although waste liquids of other systems, biologically treated water, and the like can be used, digested sludge is preferably used.
[0027]
In order to adjust the concentration of the concentrated sludge, it is not always necessary to provide a mixing tank. In the concentrated sludge transfer pipe, the dilution liquid may be simply injected into the suction of the transfer pump or the transfer pump. However, when the viscosity of the concentrated sludge is high, it is preferable to provide a mixing tank 3 and mechanically mix as shown in FIG. As the mixing means, a stirrer, gas blowing, a static mixer, or the like can be used.
[0028]
Since the residence time of the mixing tank 3 for adjusting the concentration of the concentrated sludge may be about 1 minute to 6 hours, the volume of the mixing tank 3 may be small. Further, the power required for mixing in the mixing tank 3 can be significantly smaller than when the concentrated sludge is directly fed into the digesting tank and mixed with the digested sludge and raw sludge.
[0029]
The degree of concentration adjustment of the concentrated sludge may be such that it can be smoothly transferred with a single monopump, for example, and in general, the SS concentration is 6 to 12% so that the discharge pressure of the
[0030]
In the apparatus of FIG. 1, the concentrated sludge concentrated by the concentrator 2 is dropped into the mixing tank 3, and the concentration of this concentrated sludge is adjusted by digested sludge. The sludge whose concentration has been adjusted in this way can be efficiently returned to the digestion tank 1 by the
[0031]
Although there is no restriction | limiting in particular as the
[0032]
In the present invention, a part of the digested sludge in the digestion tank 1 is extracted in this way, concentrated by the concentrator 2, and the concentration of the concentrated sludge is adjusted and returned to the digestion tank 1, so that the SRT can be changed without changing the HRT. The sludge weight loss rate can be reduced.
[0033]
The amount of digested sludge withdrawn from the digestion tank 1 for concentration is not particularly limited, but about 1/30 to 1/10 of the retained sludge in the digestion tank 1 is withdrawn, concentrated and adjusted in concentration, and then circulated. Thus, the SRT can be extended to at least about three times or more of the case where such sludge circulation is not performed, and the sludge reduction can be promoted even with a non-biodegradable organic waste liquid. .
[0034]
In the present invention, when anaerobic digestion is performed, it is preferable to operate in a state where the concentrator and the mixing tank are shut off from the atmosphere. For example, by concentrating the concentrator in a sealed state, sludge and oxygen If the contact is restricted, the anaerobic bacteria can be returned to the digestion tank while keeping the anaerobic bacteria alive, and the number of live bacteria in the digestion tank can be easily maintained and increased, and the digestion efficiency can be improved.
[0035]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0036]
Sewage primary sedimentation sludge and excess sludge were anaerobically digested at 35 ° C in a transient manner. The volume of the anaerobic digester is 1 m 3 , the VSS load is 0.65 kg / m 3 · day, and the HRT is 40 days (the amount of sludge input per day is 25 L). Digested sludge concentration is 1.6% (VSS / SS ratio 73%), compared to 3.5% (VSS / SS ratio 83%) of input sludge concentration (SS concentration, the same applies below), digestibility (reduction of VSS) Rate) was 60%. The sludge retention time was increased by solid-liquid separation of the sludge in the tank and the sludge was returned to increase the weight loss rate, and a centrifugal concentrator was used as the solid-liquid separation means.
[0037]
The sludge in the tank was supplied to the centrifugal concentrator at 200 L / hr, and the cationic polymer flocculant dissolved in 0.2 wt% under a centrifugal strength of 2,100 G and a differential speed of 15 min −1 was adjusted to 0.000 per SS. It was carried out while adding 6% by weight. At this time, the concentrated sludge concentration was 12%, and the SS recovery rate was 95% or more. When the concentrated sludge discharged from the centrifugal concentrator to the concentrated sludge receiving tank (mixing tank) was returned to the anaerobic digester with a monopump, the discharge pressure reached 0.8 MPa and the pump tripped, returning the sludge. I couldn't.
[0038]
Therefore, the following examples and comparative examples were processed.
[0039]
Example 1
When a part of the separation liquid of the concentrator was introduced into the mixing tank and mixed while gently stirring with a stirrer, the sludge concentration in the mixing tank was 8%, and the monopump pressure was reduced to 0.25 MPa. We were able to promptly return to the anaerobic digester. When such operation was continued for half a year without particularly removing sludge from the anaerobic digester, the digested sludge concentration reached nearly 5%, but the digestibility calculated from the solids balance and digestion gas generation amount. Was improved to 70%.
[0040]
Example 2
When a part of the digested sludge from the anaerobic digester is introduced into the mixing tank and mixed while gently stirring with a stirrer, the sludge concentration in the mixing tank becomes 8%, and the pressure of the monopump reaches 0.25 MPa. Because it decreased, I was able to return it promptly. When such operation was continued for half a year without particularly removing sludge from the digester, the digested sludge concentration reached nearly 5%, but the digestibility calculated from the balance of solids and the amount of digestion gas generated was 70%. %. Moreover, compared with Example 1, the operation time of the centrifugal concentrator and the amount of the flocculant used were reduced by 18%.
[0041]
Comparative Example 1
The centrifugal concentration conditions were changed to reduce the pressure to such an extent that it could be pumped with a monopump. When the centrifugal strength was lowered to 1,000G and the flocculant addition rate was lowered to 0.2% by weight, the concentration of concentrated sludge became about 8%, the pressure of the monopump decreased to 0.3 MPa, and it was returned to the anaerobic digester. I was able to do that. However, the SS recovery rate at this time was 70%, and sludge flowed out to the separation liquid side. Although such operation was continued for half a year, since the SS recovery rate in the centrifugal concentrator was low, the sludge concentration in the anaerobic digestion tank could not be increased, and the digestibility was a temporary process. It was almost the same as 60%.
[0042]
【The invention's effect】
As described above in detail, according to the organic waste liquid digestion treatment apparatus of the present invention, after the concentration of concentrated sludge with extremely high viscosity is adjusted with digested sludge, etc., it is efficiently concentrated by returning it to the digestion tank. On the other hand, it is possible to efficiently return the concentrated sludge and disperse it sufficiently in the digestion tank to perform efficient digestion, thereby reducing the sludge to a high level.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of an organic waste liquid digestion apparatus according to the present invention.
[Explanation of symbols]
1 Digestion tank 2 Concentrator 3
Claims (2)
該消化槽から排出される消化汚泥を濃縮する固液分離手段と、
該固液分離手段からの濃縮汚泥を前記消化槽へ返送する移送ポンプを有する配管と、
該移送ポンプ又は該移送ポンプのサクション側において、濃縮汚泥に液体を添加する液供給手段と
を有する有機性廃液の消化処理装置であって、
該液供給手段は前記濃縮汚泥と前記液体とを混合する混合槽を備え、前記固液分離手段からの濃縮汚泥は、該混合槽に投下され、該混合槽で液体が添加混合されて濃度調整された汚泥が、前記移送ポンプにより前記消化槽へ返送されることを特徴とする有機性廃液の消化処理装置。A digester tank for digesting organic waste liquid; a solid-liquid separation means for concentrating digested sludge discharged from the digester tank;
A pipe having a transfer pump for returning the concentrated sludge from the solid-liquid separation means to the digestion tank;
An organic waste liquid digestion apparatus having liquid supply means for adding liquid to concentrated sludge on the transfer pump or the suction side of the transfer pump ,
The liquid supply means includes a mixing tank for mixing the concentrated sludge and the liquid, and the concentrated sludge from the solid-liquid separation means is dropped into the mixing tank, and the liquid is added and mixed in the mixing tank to adjust the concentration. The organic sludge digestion treatment apparatus , wherein the sludge thus produced is returned to the digestion tank by the transfer pump .
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| JPH0356200A (en) * | 1989-02-02 | 1991-03-11 | Iwao Nakano | Aerobic pressurized flotation equipment for separating anaerobic sludge in supernatant liquid from methane fermentor |
| JPH0759186B2 (en) * | 1989-04-24 | 1995-06-28 | 三菱電機株式会社 | Membrane separation reactor controller |
| JPH04341397A (en) * | 1991-05-20 | 1992-11-27 | Shimizu Corp | Methane fermentation treatment apparatus and methane fermentation method |
| JPH05192697A (en) * | 1992-01-21 | 1993-08-03 | Toshiba Corp | Sludge digestion controller |
| JP2641009B2 (en) * | 1992-08-11 | 1997-08-13 | 株式会社荏原製作所 | Anaerobic digestion of organic waste |
| JPH08173992A (en) * | 1994-12-28 | 1996-07-09 | Nkk Corp | Agitator for sludge digestion tank |
| JPH08182996A (en) * | 1994-12-28 | 1996-07-16 | Kajima Corp | Treatment of oil containing waste water |
| JPH08281297A (en) * | 1995-04-07 | 1996-10-29 | Nishihara Environ Sanit Res Corp | Method for reducing volume of sludge in sewage treatment and device therefor |
| JP3915217B2 (en) * | 1998-01-07 | 2007-05-16 | 栗田工業株式会社 | Organic waste treatment equipment |
| JP3572199B2 (en) * | 1998-06-23 | 2004-09-29 | 三菱重工業株式会社 | Organic solid matter methane recovery method |
| JP3524004B2 (en) * | 1998-07-15 | 2004-04-26 | 株式会社クボタ | Methane fermentation method |
| JP3772028B2 (en) * | 1998-08-21 | 2006-05-10 | 株式会社東芝 | Anaerobic water treatment device |
| JP2001029997A (en) * | 1999-07-27 | 2001-02-06 | Kurita Water Ind Ltd | Treating equipment for organic waste |
| JP2002361291A (en) * | 2001-06-01 | 2002-12-17 | Kurita Water Ind Ltd | Anaerobic digesting apparatus |
| JP4337307B2 (en) * | 2002-06-20 | 2009-09-30 | 栗田工業株式会社 | Dry methane fermentation method |
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