JP4380103B2

JP4380103B2 - Manufacturing method and manufacturing equipment for aged compost-like material

Info

Publication number: JP4380103B2
Application number: JP2001315616A
Authority: JP
Inventors: 謙介松井
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2001-10-12
Filing date: 2001-10-12
Publication date: 2009-12-09
Anticipated expiration: 2021-10-12
Also published as: JP2003117337A

Description

【０００１】
【発明の属する技術分野】
本発明は、生物処理汚泥を加熱することにより熟成コンポストに類似した悪臭の無い製品を短時間で製造する方法及び設備に係り、特に、加熱による熟成コンポスト様物の製造工程から排出される排ガスの処理を合理化した熟成コンポスト様物の製造方法及び製造設備に関する。
【０００２】
【従来の技術】
生物処理汚泥から熟成コンポスト様物を製造する技術として、特開２００１−１３０９９０には、生物処理汚泥を加熱乾燥した後、１００〜２００℃で加熱処理して熟成コンポスト様物を製造する方法及び装置が記載されている。
【０００３】
この方法及び装置によると、悪臭がなく、しかも、有機肥料分も十分に残留している上に塩分もさほど高くなく、有機肥料として有効な熟成コンポスト類似の製品を得ることができる。
【０００４】
特開２００１−１３０９９０号公報の方法で熟成コンポスト様物を製造する場合、アンモニアやメチルメルカプタン、硫化水素、硫化メチルなどの各種の臭気成分や、粉塵などを含む排ガスが排出されるので、この排ガスを除塵処理した後、脱臭処理している。
【０００５】
【発明が解決しようとする課題】
このような排ガスの除塵処理及び脱臭処理用の設備は、かなり高額であり、汚泥の処理コストを高くする一因となっている。
【０００６】
本発明は、生物処理汚泥を加熱することにより熟成コンポスト様物を製造する方法及び装置において、発生する排ガスの処理コストを低減し、これにより汚泥の処理コストを低減することを目的とする。
【０００７】
【課題を解決するための手段】
本発明の熟成コンポスト様物の製造方法は、有機性排水の生物処理工程から排出される生物処理汚泥を加熱することにより熟成コンポスト様物を製造する方法において、該生物処理汚泥の加熱工程から排出された排ガスを、生物処理工程の酸洗浄、アルカリ洗浄及び活性炭吸着処理を組み合わせた排ガス処理装置を備える硝化槽の生物処理混合液と接触させるものであって、前記排ガスは、加熱乾燥工程で排出される水蒸気を主体とし、臭気成分濃度が少ないものと、加熱乾燥後の熱処理工程で排出される粉塵と各種の臭気成分とを高濃度に含むものであることを特徴とする。
【０００８】
本発明の熟成コンポスト様物の製造設備は、有機性排水を生物処理する、酸洗浄、アルカリ洗浄及び活性炭吸着処理を組み合わせた排ガス処理装置を備える硝化槽を有する生物処理装置と、該生物処理装置から排出される生物処理汚泥を加熱することにより熟成コンポスト様物を製造する熟成コンポスト様物製造装置と、該熟成コンポスト様物製造装置から排出された排ガスを前記硝化槽の生物処理混合液と接触させる手段とを備え、前記排ガスは、加熱乾燥工程で排出される水蒸気を主体とし、臭気成分濃度が少ないものと、加熱乾燥後の熱処理工程で排出される粉塵と各種の臭気成分とを高濃度に含むものであることを特徴とする。
【０００９】
前述の如く、熟成コンポスト様物の製造工程で排出される排ガスは、粉塵と、各種の臭気成分を高濃度に含むものであるが、粉塵は生物処理混合液との接触で生物処理混合液側に移行して除去され、また、臭気成分も生物処理混合液との接触で一部が生物処理混合液に吸収されて除去されることにより低濃度化される。
【００１０】
なお、生物処理混合液との接触で粉塵が除去されると共に臭気成分が低濃度化されたガスは、生物処理装置の排ガスと共に、生物処理系統の排ガス処理装置で処理することができる。
【００１１】
【発明の実施の形態】
以下に図面を参照して本発明の熟成コンポスト様物の製造方法及び製造設備の実施の形態を詳細に説明する。
【００１２】
図１は本発明の熟成コンポスト様物の製造設備の実施の形態を示す系統図である。
【００１３】
図１では、し尿処理施設において、し尿の循環脱窒素処理工程から排出される余剰汚泥から熟成コンポスト様物を製造し、熟成コンポスト様物製造装置の排ガスを脱窒素工程の硝化槽に吹き込んで処理を行っている。
【００１４】
し尿は、硝化槽２の循環液及び沈殿槽５の返送汚泥と共に脱窒素槽１に導入され、脱窒素槽１及び硝化槽２、及び第２脱窒素槽３を経て脱窒素処理される。硝化槽２の硝化液の一部は脱窒素槽１に循環される。第２脱窒素槽３の流出液は、次いで再曝気槽４でＢＯＤが除去された後沈殿槽５で固液分離され、上澄水は処理水として系外へ排出される。沈殿槽５の分離汚泥の一部は脱窒素槽１に返送され、残部は余剰汚泥として抜き出される。この余剰汚泥は汚泥脱水機６で脱水処理され、脱水ケーキは熟成コンポスト様物の原料として熟成コンポスト様物製造装置７に送給される。
【００１５】
熟成コンポスト様物製造装置７の排ガスは、硝化槽２の生物処理混合液中にブロワ等で吹き込まれ、硝化槽２の排ガス処理装置８で処理される。
【００１６】
即ち、前述の如く、熟成コンポスト様物の製造に当たり、加熱乾燥工程で排出される排ガスは水蒸気を主体とし、臭気成分濃度は少ないものであることから、硝化槽２の生物処理混合液中に吹き込まれることで、殆ど臭気のないレベルにまで処理することができる。また、加熱乾燥後の熱処理工程で排出される排ガスは、粉塵と、各種の臭気成分を高濃度に含むものであるが、粉塵は生物処理混合液側に移行して除去され、また、臭気成分も生物処理混合液との接触で一部が生物処理混合液に吸収されて除去されることにより低濃度化される。そして、生物処理混合液中に吹き込まれて粉塵が除去されると共に臭気成分が低濃度化されたガスは、硝化槽２の排ガス処理装置８で処理される。
【００１７】
硝化槽２の排ガス処理装置８は、酸洗浄、アルカリ洗浄及び活性炭吸着処理等を組み合わせたものであり、このような排ガス処理により、臭気成分は効率的に除去される。しかも、このような排ガス処理装置で処理される排ガス量は、熟成コンポスト様物製造装置で発生する排ガス量に比べて非常に多いため、熟成コンポスト様物製造装置からの排ガスを処理することによる負荷の増大が問題となることはなく、既存の排ガス処理装置で十分に処理することができる。
【００１８】
なお、図１は本発明の実施の形態の一例を示すものであり、本発明はその要旨を超えない限り、何ら図示のものに限定されるものではない。
【００２０】
排ガスを吹き込む処理槽は、硝化槽である。生物処理混合液側に吸収した排ガス中の臭気成分を効率的に生物処理するために、生物処理系統の上流側の好気槽に吹き込むことが好ましいからである。
【００２１】
以下に、生物処理汚泥を原料として熟成コンポスト様物を製造する方法について説明する。
【００２２】
生物処理汚泥から熟成コンポスト様物を製造するには、まず、生物処理汚泥を加熱乾燥し、この乾燥処理により生物処理汚泥中の水分が徐々に蒸発し、含水率が１％未満となって乾燥が完了した後も、更に生物処理汚泥を好ましくは１００〜２００℃の温度で加熱を継続する。
【００２３】
生物処理汚泥の加熱乾燥で水分が蒸発する過程において、水分が残留している間は、被処理物である生物処理汚泥の温度は１００℃未満であるが、水分が完全に蒸発除去された後も加熱を継続すると、被処理物の温度は１００℃以上に上昇する。この状態で被処理物を例えば３〜６時間程度維持すると、被処理物中の有機物量が減少し始める。有機物が３〜５０％程度減少するまで加熱を継続すると臭気の殆どない熟成コンポスト様物を得ることができる。
【００２４】
この加熱を終了して製品とするに好適な有機物の減少率は、生物処理汚泥の種類によって異なり、例えば、活性汚泥の余剰汚泥の場合には１０〜３０％と比較的減少率が多く、消化汚泥の場合には３〜１０％と比較的減少率が小さい。
【００２５】
本発明において、乾燥が完了した後の加熱温度は好ましくは１００〜２００℃、より好ましくは１５０〜２００℃とする。この温度範囲であれば、水分は完全に蒸発除去され、臭気成分も揮散、分解される一方で、有機物は炭化せず、良好な熟成コンポスト様物を得ることができる。
【００２６】
得られた製品は、臭気が殆どなく、有機肥料成分が十分に残留し、塩分もさほど高くはなく、かつ熟成コンポスト類似の取り扱い性に優れたものである。
【００２７】
ところで、生物処理汚泥を加熱乾燥した後熱処理することにより熟成コンポスト様物を製造する場合、加熱工程、特に、加熱乾燥後の熱処理による加熱分解工程において、汚泥が微細化する傾向が認められ、汚泥の微細化のために、加熱分解工程で発生する排ガス中には、相当量の粉塵が含まれるようになる。また、得られる製品は、粒径数ｍｍ程度の粒状物と、粒径１ｍｍ以下程度の上記微粉とが混在したものとなり、製品の袋詰め作業等の取り扱い時に粉塵が舞い上り易い。
【００２８】
この問題を解決するために、生物処理汚泥を加熱乾燥した後、熱処理することにより熟成コンポスト様物を製造するに当たり、生物処理汚泥を加熱乾燥する際に造粒乾燥を行って、ある程度の大きさの粒径に造粒された造粒乾燥汚泥を得、この造粒乾燥汚泥を熱処理することが好ましい。このような造粒乾燥汚泥は、その後の熱処理による加熱分解工程において、微細化され難く、粉塵の発生は大幅に低減される。
【００２９】
この場合、造粒乾燥装置としては、例えば、縦型の遠心造粒乾燥装置や横型の乾燥ドラム装置などを採用することができるが、加熱乾燥と共に造粒を行える装置であれば良く、何らこれに限定されるものではない。造粒乾燥装置の加熱方式は、熱風を汚泥に直接吹き付けて乾燥する熱風受熱式（直接式）のものであっても、装置の金属壁を通して蒸気又は熱媒体油等の加熱媒体により汚泥に間接的に伝熱して乾燥する伝熱受熱式（間接式）のものであってもよい。
【００３０】
この造粒乾燥装置に投入された生物処理汚泥は、造粒乾燥の開始直後は、液状もしくはダンゴ状であるが、造粒乾燥が進むにつれて徐々に粒径が小さくなってゆく。従って、造粒乾燥装置の加熱温度、乾燥時間や回転数などの運転条件を適宜調整することにより、粒径３〜１０ｍｍ程度の造粒乾燥汚泥が得られるように、また、汚泥容量が１／４〜１／５程度となり、乾燥前の汚泥含水率８７〜７５％に対して、造粒乾燥汚泥の含水率が３０〜１０％程度になるまで造粒乾燥を行うことが好ましい。
【００３１】
この造粒乾燥に要する時間は、造粒乾燥装置の仕様や運転条件、被処理汚泥の性状等によっても異なるが、一般的には２〜１０時間程度である。
【００３２】
造粒乾燥装置で得られた造粒乾燥汚泥は次いで加熱分解装置に投入し、熱処理する。この加熱分解装置としては、直接加熱方式では発火の恐れがあることから、間接加熱方式のものを用いるのが好ましい。
【００３３】
加熱分解装置では、造粒乾燥汚泥を１００〜２００℃、好ましくは１５０〜２００℃の温度で４〜８時間程度加熱する。即ち、前述の如く、造粒乾燥汚泥は水分が完全に蒸発すると温度が１００℃以上に上昇し始め、有機物の分解が始まる。この熱処理温度は、１００〜２００℃、好ましくは１５０〜２００℃の温度範囲であれば、水分は完全に蒸発除去され、臭気成分も揮散、分解される一方で、有機物は炭化せず、良好な熟成コンポスト様物を得ることができる。
【００３４】
この加熱分解装置では、熱処理により、汚泥が微細化する傾向があるが、造粒乾燥装置で造粒された造粒乾燥汚泥を熱処理する場合には、微細化による粉塵の発生の問題はなく、好ましくは粒径３〜１０ｍｍ程度に造粒された造粒乾燥汚泥を熱処理して、粒径２〜８ｍｍ程度の造粒化された熟成コンポスト様物を得ることができる。
【００３５】
このようにして製造された熟成コンポスト様物は、貯留、小分け、袋詰めされて出荷される。
【００３６】
なお、本発明において、処理する生物処理汚泥としては、下水処理汚泥や余剰汚泥、消化汚泥等、廃水や廃棄物の生物処理工程で生じる生物処理汚泥を脱水処理して得られる汚泥を含むものが挙げられ、従って、本発明が適用される生物処理施設も、図１に示すし尿の処理施設に限定されず、他の様々な生物処理施設に本発明を適用することができる。
【００３７】
本発明によれば、このような生物処理汚泥から臭気が殆どなく、有機肥料成分が十分に残留し、塩分もさほど高くはなく、従って、有機肥料として有効利用可能な、取り扱い性に優れた熟成コンポスト様物を製造すると共に、この熟成コンポスト様物の製造工程で発生する排ガスを生物処理系統で処理することにより、熟成コンポスト様物製造装置に専用の排ガス処理装置の設置を不要とすることができる。
【００３８】
【実施例】
以下に実施例を挙げて本発明をより具体的に説明する。
【００３９】
実施例１
図１に示すし尿処理及び熟成コンポスト様物製造設備において、熟成コンポスト様物製造装置７からの排ガスを硝化槽２に導入して生物処理混合液と接触させることにより処理した。
【００４０】
このし尿処理施設では、処理量８０ｋＬ／日でし尿の循環脱窒素処理を行い、余剰汚泥を汚泥脱水機６で脱水処理し、得られた脱水ケーキ（含水率８０％）４ｔ／日を熟成コンポスト様物製造装置７で資源化している。
【００４１】
脱窒素槽１と硝化槽２の容量は共に８００ｍ^３であり、硝化槽２への空気曝気量は８０ｍ^３／分である。硝化槽２の排ガスは、排ガス処理装置８で酸洗浄、アルカリ洗浄及び活性炭吸着処理される。
【００４２】
熟成コンポスト様物製造装置７では脱水ケーキ４ｔ／日を容量が１／４程度になるまで５時間加熱乾燥して含水率１０％の乾燥汚泥を得、この乾燥汚泥を１００〜２００℃で５時間熱処理して熟成コンポスト様物製造装置を製造した。
【００４３】
得られた熟成コンポスト様物の性状は下記の通りであり、有機物含有量が比較的多く、有機物が安定化していて塩分量は比較的少ないため、有機肥料として有効であり、また、臭気が殆どなく含水率も少ないものであった。
【００４４】
〔製品性状〕
含水率：０％
臭気：微臭
有機物量：７０％
酸素要求速度：４０（ｇ−Ｏ_２／ｋｇ−ｄｒｙｓｏｌｉｄ／週）
平均粒径：６ｍｍ
【００４５】
この熟成コンポスト様物製造装置７から排出される排ガスは、最大で１３ｍ^３／分である。この排ガスを硝化槽２の液面下１ｍに配置した散気管で生物処理混合液中に吹き込んだ。
【００４６】
その結果、排ガス中の粉塵及び臭気成分の一部は生物処理混合液中に除去され、臭気成分の残部も硝化槽２の排ガス処理装置８で除去された。このとき、硝化槽２からの排ガス量は９３ｍ^３／分となったが、熟成コンポスト様物製造装置７からの排ガスを吹き込む前と同様に酸洗浄、アルカリ洗浄及び活性炭吸着処理で臭気成分を十分に除去することができた。
【００４７】
実施例２
実施例１において、熟成コンポスト様物製造装置における脱水ケーキの加熱乾燥に当たり、縦型遠心造粒乾燥装置を用い、平均粒径８ｍｍの造粒乾燥汚泥を得たこと以外は同様にして熟成コンポスト様物の製造及び排ガス処理を行った。
【００４８】
その結果、熟成コンポスト様物としては、平均粒径６ｍｍで粒径１ｍｍ以下の微粒分を殆ど含まず、取り扱い時の粉塵の発生の問題のない熟成コンポスト様物を製造することができた。また、熟成コンポスト様物製造装置の排ガス中の粉塵も大幅に低減された。
【００４９】
この排ガスは実施例１と同様、硝化槽２中の生物処理混合液と接触させた後、硝化槽２の排ガス処理装置８で処理することができた。
【００５０】
【発明の効果】
以上詳述した通り、本発明の熟成コンポスト様物の製造方法及び製造設備によれば、熟成コンポスト様物の製造系統で発生する排ガスを生物処理系統で処理することができ、熟成コンポスト様物の製造系統に専用の排ガス処理装置を設ける必要がなくなる。このため、設備費、運転費、維持管理費を大幅に削減することができる。
【図面の簡単な説明】
【図１】本発明の熟成コンポスト様物の製造設備の実施の形態を示す系統図である。
【符号の説明】
１脱窒素槽
２硝化槽
３第２脱窒素槽
４再曝気槽
５沈澱槽
６汚泥脱水機
７熟成コンポスト様物製造装置
８排ガス処理装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and equipment for producing a product having no malodor similar to aged compost in a short time by heating biologically treated sludge, and in particular, exhaust gas discharged from the process of producing aged compost-like material by heating. The present invention relates to a manufacturing method and a manufacturing facility for aged compost-like products with rationalized processing.
[0002]
[Prior art]
As a technique for producing an aged compost-like material from biologically treated sludge, JP-A-2001-130990 discloses a method and an apparatus for producing an aged compost-like material by heating and drying the biologically treated sludge at 100 to 200 ° C. Is described.
[0003]
According to this method and apparatus, it is possible to obtain an aged compost-like product effective as an organic fertilizer that does not have a foul odor, remains sufficiently organic fertilizer, and does not have a high salt content.
[0004]
When an aged compost-like product is produced by the method of Japanese Patent Application Laid-Open No. 2001-130990, exhaust gas containing various odor components such as ammonia, methyl mercaptan, hydrogen sulfide, methyl sulfide, and dust is discharged. After dedusting, the deodorizing process.
[0005]
[Problems to be solved by the invention]
Such equipment for dust removal treatment and deodorization treatment of exhaust gas is quite expensive and contributes to an increase in sludge treatment costs.
[0006]
An object of the present invention is to reduce the treatment cost of exhaust gas generated in a method and apparatus for producing an aged compost-like material by heating biologically treated sludge, thereby reducing the treatment cost of sludge.
[0007]
[Means for Solving the Problems]
The method for producing an aged compost-like material according to the present invention is a method for producing an aged compost-like material by heating a biologically treated sludge discharged from a biological treatment step of organic wastewater, which is discharged from the heating step of the biologically treated sludge. The exhaust gas is brought into contact with a biological treatment liquid mixture in a nitrification tank equipped with an exhaust gas treatment device that combines acid washing, alkali washing and activated carbon adsorption treatment in a biological treatment process, and the exhaust gas is discharged in a heating and drying process. It is characterized in that it is mainly composed of water vapor and has a low concentration of odor components and a high concentration of dust discharged in the heat treatment step after heat drying and various odor components .
[0008]
A manufacturing facility for an aged compost-like product according to the present invention includes a biological treatment apparatus having a nitrification tank equipped with an exhaust gas treatment apparatus that combines acid washing, alkali washing, and activated carbon adsorption treatment for biological treatment of organic wastewater, and the biological treatment apparatus. An aged compost-like product producing apparatus for producing an aged compost-like product by heating the biologically treated sludge discharged from the waste gas, and contacting the exhaust gas discharged from the aged compost-like product producing device with the biological treatment mixed solution in the nitrification tank The exhaust gas is mainly composed of water vapor discharged in the heat drying process, and has a low concentration of odor components, and high concentration of dust and various odor components discharged in the heat treatment process after heat drying. It is what is included in.
[0009]
As mentioned above, the exhaust gas discharged in the manufacturing process of aged compost-like material contains dust and various odor components at high concentration, but the dust moves to the biological treatment liquid mixture side by contact with the biological treatment liquid mixture. In addition, the odorous component is partly absorbed by the biological treatment liquid mixture and removed by contact with the biological treatment liquid mixture, thereby reducing the concentration.
[0010]
The gas odor component is low density together with dust is removed by contact with biological treatment mixture, together with the exhaust gas of the raw material processing apparatus, it can be treated with the exhaust gas treatment apparatus of the biological treatment system.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a method for producing an aged compost-like material and production equipment of the present invention will be described below in detail with reference to the drawings.
[0012]
FIG. 1 is a system diagram showing an embodiment of a production facility for an aged compost-like material according to the present invention.
[0013]
In FIG. 1, an aged compost-like material is produced from surplus sludge discharged from the circulating denitrification process of human waste at a human waste treatment facility, and the exhaust gas from the aged compost-like material production apparatus is blown into the nitrification tank of the denitrification process. It is carried out.
[0014]
The human waste is introduced into the denitrification tank 1 together with the circulating liquid in the nitrification tank 2 and the return sludge in the sedimentation tank 5, and denitrified through the denitrification tank 1, the nitrification tank 2, and the second denitrification tank 3. A part of the nitrification liquid in the nitrification tank 2 is circulated to the denitrification tank 1. The effluent from the second denitrification tank 3 is then subjected to solid-liquid separation in the precipitation tank 5 after the BOD is removed in the re-aeration tank 4, and the supernatant water is discharged out of the system as treated water. Part of the separated sludge in the settling tank 5 is returned to the denitrification tank 1, and the remainder is extracted as excess sludge. This surplus sludge is dehydrated by the sludge dewatering machine 6, and the dehydrated cake is fed to the aged compost-like material manufacturing apparatus 7 as a raw material for the aged compost-like material.
[0015]
The exhaust gas from the aging compost-like material manufacturing apparatus 7 is blown into the biological treatment mixed solution in the nitrification tank 2 by a blower or the like, and is processed by the exhaust gas treatment apparatus 8 in the nitrification tank 2.
[0016]
That is, as described above, in the production of an aged compost-like product, the exhaust gas discharged in the heating and drying process is mainly composed of water vapor and has a low odor component concentration, so that it is blown into the biological treatment mixture in the nitrification tank 2. As a result, it can be processed to a level having almost no odor. In addition, the exhaust gas discharged in the heat treatment step after heating and drying contains dust and various odor components at a high concentration, but the dust moves to the biological treatment mixture and is removed, and the odor components are also biological. The concentration is reduced by partly being absorbed and removed by the biological treatment mixture upon contact with the treatment mixture. And the gas from which dust was removed by blowing into the biological treatment mixture and the concentration of the odor component was reduced is processed by the exhaust gas treatment device 8 of the nitrification tank 2.
[0017]
Exhaust gas treatment device 8 of nitrifying tank 2, acid washing, is a combination of alkali washing and activated carbon adsorption treatment or the like, by such an exhaust gas treatment, the odor components are removed efficiently. Moreover, since the amount of exhaust gas treated by such an exhaust gas treatment device is much larger than the amount of exhaust gas generated by an aged compost-like material production device, the load caused by treating the exhaust gas from the aged compost-like material production device Is not a problem, and can be sufficiently treated by an existing exhaust gas treatment apparatus.
[0018]
FIG. 1 shows an example of an embodiment of the present invention, and the present invention is not limited to the illustrated one as long as the gist thereof is not exceeded.
[0020]
Treatment tank blowing exhaust gas is nitrification tank. This is because it is preferable to blow into an aerobic tank upstream of the biological treatment system in order to efficiently biologically treat the odor component in the exhaust gas absorbed on the biological treatment mixed liquid side.
[0021]
Hereinafter, a method for producing an aged compost-like material using biologically treated sludge as a raw material will be described.
[0022]
In order to produce an aged compost-like product from biologically treated sludge, first, the biologically treated sludge is heated and dried, and the moisture in the biologically treated sludge is gradually evaporated by this drying treatment, so that the moisture content is less than 1% and dried. After completion of the heating, the biologically treated sludge is preferably further heated at a temperature of 100 to 200 ° C.
[0023]
In the process where water is evaporated by heating and drying the biologically treated sludge, the temperature of the biologically treated sludge as the object to be treated is less than 100 ° C. while the moisture remains, but after the moisture is completely evaporated and removed. If heating is continued, the temperature of the object to be processed rises to 100 ° C. or higher. When the object to be processed is maintained in this state for about 3 to 6 hours, for example, the amount of organic matter in the object to be processed starts to decrease. When heating is continued until the organic matter is reduced by about 3 to 50%, an aged compost-like product having almost no odor can be obtained.
[0024]
The reduction rate of organic matter suitable for producing a product after finishing this heating differs depending on the type of biologically treated sludge. For example, in the case of surplus sludge from activated sludge, the reduction rate is relatively high at 10 to 30%. In the case of sludge, the reduction rate is relatively small at 3 to 10%.
[0025]
In the present invention, the heating temperature after the drying is completed is preferably 100 to 200 ° C, more preferably 150 to 200 ° C. Within this temperature range, moisture is completely removed by evaporation and odor components are volatilized and decomposed, while organic matter is not carbonized, and a good aged compost-like product can be obtained.
[0026]
The obtained product has almost no odor, has sufficient organic fertilizer components, is not so salty, and has excellent handling properties similar to that of aged compost.
[0027]
By the way, when producing an aged compost-like material by heat-drying biologically-treated sludge and then heat-treating, sludge tends to be refined in the heating process, particularly in the heat-decomposing process by heat-treatment after heat-drying. Therefore, a considerable amount of dust is contained in the exhaust gas generated in the thermal decomposition process. Moreover, the product obtained is a mixture of a granular material having a particle size of about several millimeters and the fine powder having a particle size of about 1 mm or less, and dust easily rises during handling such as bagging of the product.
[0028]
In order to solve this problem, the biologically treated sludge is heated and dried, and then heat-treated to produce an aged compost-like product. It is preferable to obtain a granulated and dried sludge that has been granulated to have a particle size of 1, and heat-treat the granulated and dried sludge. Such granulated and dried sludge is difficult to be refined in the subsequent thermal decomposition process by heat treatment, and the generation of dust is greatly reduced.
[0029]
In this case, as the granulating / drying apparatus, for example, a vertical centrifugal granulating / drying apparatus or a horizontal drying drum apparatus can be adopted, but any apparatus capable of granulating together with heat drying may be used. It is not limited to. The heating method of the granulation drying equipment is indirect to the sludge with a heating medium such as steam or heat transfer oil through the metal wall of the equipment, even if it is of the hot air receiving type (direct type) that blows hot air directly on the sludge to dry. It may be of a heat transfer heat receiving type (indirect type) in which heat is transferred and dried.
[0030]
The biologically treated sludge charged into the granulation / drying apparatus is liquid or dango-like immediately after the start of granulation / drying, but the particle diameter gradually decreases as the granulation / drying proceeds. Therefore, by appropriately adjusting the operating conditions such as the heating temperature, drying time, and rotation speed of the granulation drying apparatus, granulated dry sludge having a particle size of about 3 to 10 mm can be obtained, and the sludge capacity is 1 / It is preferable to perform granulation drying until the moisture content of the granulated dry sludge is about 30 to 10% with respect to the sludge moisture content of 87 to 75% before drying.
[0031]
The time required for this granulation drying is generally about 2 to 10 hours, although it varies depending on the specifications and operating conditions of the granulation drying apparatus, the properties of the sludge to be treated, and the like.
[0032]
The granulated and dried sludge obtained by the granulating and drying apparatus is then put into a thermal decomposition apparatus and heat-treated. As this thermal decomposition apparatus, it is preferable to use an indirect heating system because there is a risk of ignition in the direct heating system.
[0033]
In the thermal decomposition apparatus, the granulated and dried sludge is heated at a temperature of 100 to 200 ° C, preferably 150 to 200 ° C for about 4 to 8 hours. That is, as described above, the granulated and dried sludge starts to increase in temperature to 100 ° C. or more when the water is completely evaporated, and the decomposition of organic substances starts. If this heat treatment temperature is in the range of 100 to 200 ° C., preferably 150 to 200 ° C., moisture is completely removed by evaporation and odor components are volatilized and decomposed, while organic matter is not carbonized and is good. Aged compost-like material can be obtained.
[0034]
In this thermal decomposition apparatus, the sludge tends to be refined by heat treatment, but when the granulated dry sludge granulated by the granulation drying apparatus is heat treated, there is no problem of dust generation due to the refinement, Preferably, the granulated dry sludge granulated to a particle size of about 3 to 10 mm is heat-treated to obtain a granulated mature compost-like product having a particle size of about 2 to 8 mm.
[0035]
The aged compost-like product produced in this way is stored, subdivided, packaged and shipped.
[0036]
In the present invention, the biologically treated sludge to be treated includes sewage treated sludge, surplus sludge, digested sludge, and the like containing sludge obtained by dehydrating biologically treated sludge generated in the biological treatment process of wastewater or waste. Therefore, the biological treatment facility to which the present invention is applied is not limited to the human waste treatment facility shown in FIG. 1, and the present invention can be applied to various other biological treatment facilities.
[0037]
According to the present invention, there is almost no odor from such biologically treated sludge, the organic fertilizer component remains sufficiently, the salt content is not so high, and therefore it can be effectively used as an organic fertilizer and is aged with excellent handling properties. By manufacturing compost-like materials and treating the exhaust gas generated in the process of producing this aged compost-like material with a biological treatment system, it is not necessary to install a dedicated exhaust gas treatment device in the aged compost-like material manufacturing apparatus. it can.
[0038]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0039]
Example 1
In the human waste treatment and aging compost-like material manufacturing facility shown in FIG. 1, the exhaust gas from the aging compost-like material manufacturing apparatus 7 was introduced into the nitrification tank 2 and contacted with the biological treatment liquid mixture.
[0040]
In this human waste treatment facility, human waste is circulated and denitrified at a treatment volume of 80 kL / day, and excess sludge is dehydrated by the sludge dehydrator 6, and the resulting dehydrated cake (water content 80%) 4 t / day is aged compost. It is made into resources by the uniform manufacturing apparatus 7.
[0041]
The capacities of the denitrification tank 1 and the nitrification tank 2 are both 800 m ³ , and the air aeration amount to the nitrification tank 2 is 80 m ³ / min. The exhaust gas in the nitrification tank 2 is subjected to acid cleaning, alkali cleaning, and activated carbon adsorption processing in the exhaust gas processing device 8.
[0042]
In the aged compost-like product manufacturing apparatus 7, dehydrated cake 4 t / day is heated and dried for 5 hours until the capacity becomes about 1/4 to obtain a dried sludge having a water content of 10%, and this dried sludge is heated at 100 to 200 ° C. for 5 hours. An aged compost-like product manufacturing apparatus was manufactured by heat treatment.
[0043]
The properties of the resulting aged compost-like material are as follows, and the organic matter content is relatively large, the organic matter is stabilized and the salt content is relatively small, so it is effective as an organic fertilizer and has almost no odor. The water content was low.
[0044]
[Product properties]
Moisture content: 0%
Odor: Slight odor organic matter: 70%
Oxygen demand _{rate: 40 (g-O 2 /} kg-dry solid / week)
Average particle size: 6mm
[0045]
The maximum amount of exhaust gas discharged from the aging compost-like material manufacturing apparatus 7 is 13 m ³ / min. This exhaust gas was blown into the biological treatment liquid mixture with an air diffuser arranged 1 m below the liquid level of the nitrification tank 2.
[0046]
As a result, part of the dust and odor component in the exhaust gas was removed in the biological treatment liquid mixture, and the remainder of the odor component was also removed by the exhaust gas treatment device 8 of the nitrification tank 2. At this time, the amount of exhaust gas from the nitrification tank 2 was 93 m ³ / min, but the odor component was sufficiently obtained by acid cleaning, alkali cleaning, and activated carbon adsorption treatment as before the exhaust gas from the aged compost-like material manufacturing apparatus 7 was blown. Could be removed.
[0047]
Example 2
In Example 1, aged compost-like product was used in the same manner except that a vertical centrifugal granulation dryer was used to obtain a granulated and dried sludge having an average particle size of 8 mm in the heat drying of the dehydrated cake in the aged compost-like product manufacturing apparatus. Manufacturing and exhaust gas treatment were performed.
[0048]
As a result, an aged compost-like material having an average particle size of 6 mm and containing almost no fine particles having a particle size of 1 mm or less and having no problem of generation of dust during handling could be produced. In addition, the dust in the exhaust gas from the aging compost-like product manufacturing apparatus was greatly reduced.
[0049]
This exhaust gas was treated with the exhaust gas treatment device 8 in the nitrification tank 2 after being brought into contact with the biological treatment mixed solution in the nitrification tank 2 as in Example 1.
[0050]
【The invention's effect】
As described in detail above, according to the method and equipment for producing an aged compost-like product of the present invention, exhaust gas generated in the production system for an aged compost-like product can be treated by a biological treatment system, There is no need to provide a dedicated exhaust gas treatment device in the production system. For this reason, equipment costs, operating costs, and maintenance costs can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a production facility for aged compost-like material according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Denitrification tank 2 Nitrification tank 3 2nd denitrification tank 4 Re-aeration tank 5 Precipitation tank 6 Sludge dehydrator 7 Aging compost-like thing manufacturing apparatus 8 Exhaust gas treatment apparatus

Claims

In a method for producing an aged compost-like material by heating biological treatment sludge discharged from a biological treatment process of organic waste water,
The exhaust gas discharged from the heating process of the biological treatment sludge is brought into contact with a biological treatment mixed solution in a nitrification tank equipped with an exhaust gas treatment apparatus that combines acid washing, alkali washing, and activated carbon adsorption treatment in the biological treatment process ,
The exhaust gas is mainly composed of water vapor discharged in the heat drying step, and has a low concentration of odor components, and contains high concentrations of dust and various odor components discharged in the heat treatment step after heat drying. A method for producing an aged compost-like product.

A biological treatment device having a nitrification tank equipped with an exhaust gas treatment device that combines organic acid wastewater treatment, acid washing, alkali washing, and activated carbon adsorption treatment;
An aged compost-like material producing apparatus for producing an aged compost-like material by heating the biologically treated sludge discharged from the biological treatment device;
Means for bringing the exhaust gas discharged from the aging compost-like material manufacturing apparatus into contact with the biological treatment mixed liquid in the nitrification tank ,
The exhaust gas is mainly composed of water vapor discharged in the heat drying step, and has a low concentration of odor components, and contains high concentrations of dust and various odor components discharged in the heat treatment step after heat drying. A manufacturing facility for aged compost-like products.