JP3821011B2 - Wastewater treatment method and treatment apparatus - Google Patents
Wastewater treatment method and treatment apparatus Download PDFInfo
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- JP3821011B2 JP3821011B2 JP2002044991A JP2002044991A JP3821011B2 JP 3821011 B2 JP3821011 B2 JP 3821011B2 JP 2002044991 A JP2002044991 A JP 2002044991A JP 2002044991 A JP2002044991 A JP 2002044991A JP 3821011 B2 JP3821011 B2 JP 3821011B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Description
【０００１】
【発明の属する技術分野】
本発明は、下水、し尿、浄化槽汚泥、食品排水等のＳＳ性有機物とアンモニア性窒素とを含む排水の処理方法及び処理装置に関する。
【０００２】
【従来の技術】
従来、ＳＳ性有機物とアンモニア性窒素とを含む排水は、図２に示す如く、まず、固液分離により排水中のＳＳ性有機物を除去した後、循環脱窒法、ステップ脱窒法又は通常の硝化脱窒法等により硝化脱窒することにより処理されている。排水からのＳＳ性有機物の固液分離で生成した分離汚泥は、硝化脱窒処理で生成した余剰汚泥と共に嫌気性消化され、消化脱離液は上記硝化脱窒工程において、排水からＳＳ性有機物を除去した分離液と共に硝化脱窒処理するか、或いは系外で別途硝化脱窒処理した後放流されている。
【０００３】
ところで、一般に、排水中のアンモニア性窒素は、アンモニア性窒素をアンモニア酸化細菌により亜硝酸性窒素に酸化し、更にこの亜硝酸性窒素を亜硝酸酸化細菌により硝酸性窒素に酸化する硝化工程と、これらの亜硝酸性窒素及び硝酸性窒素を従属栄養性細菌である脱窒菌により、有機物を電子供与体として利用して窒素ガスにまで分解する脱窒工程との２段階の生物反応を経て窒素ガスにまで分解される。
【０００４】
しかし、このような従来の硝化脱窒法では、脱窒工程において電子供与体としてメタノールなどの有機物を多量に必要とし、また硝化工程では多量の酸素が必要であるため、ランニングコストが高いという欠点がある。
【０００５】
これに対して、近年、アンモニア性窒素を電子供与体とし、亜硝酸性窒素を電子受容体とする独立栄養性微生物（以下「ＡＮＡＭＭＯＸ微生物」と称す場合がある。）を利用し、アンモニア性窒素と亜硝酸性窒素とを反応させて脱窒する方法が提案された。この方法であれば、有機物の添加は不要であるため、従属栄養性の脱窒菌を利用する方法と比べて、コストを低減することができる。また、独立栄養性の微生物は収率が低く、汚泥の発生量が従属栄養性微生物と比較すると著しく少ないので、余剰汚泥の発生量を抑えることができる。更に、従来の硝化脱窒法で観察されるＮ２Ｏの発生がなく、環境に対する負荷を低減できるといった特長もある。
【０００６】
このＡＮＡＭＭＯＸ微生物を利用する生物脱窒プロセスは、Strous, M, et al., Appl. Microbiol. Biotecnol., 50, p.589-596 (1998) に報告されており、以下のような反応でアンモニア性窒素と亜硝酸性窒素が反応して窒素ガスに分解されると考えられている。
【０００７】
【化１】
【発明が解決しようとする課題】
図２に示す如く、汚泥の嫌気性消化処理で得られる消化脱離液を、排水からＳＳ性有機物を除去した分離液と共に硝化脱窒処理する方法では、硝化脱窒にかかる窒素負荷が増加するため、硝化に多量の酸素が必要となり、更に、脱窒のために多量の有機物を必要とするという欠点がある。
【０００９】
一方、消化脱離液を系外で別途硝化脱窒処理する方法では、この脱離液の硝化脱窒のための装置が必要であり、好ましくない。
【００１０】
本発明は上記従来の問題点を解決し、ＳＳ性有機物とアンモニア性窒素とを含む排水の処理に当たり、硝化脱窒にかかる窒素負荷を低減して低コストにて効率的な処理を行う方法及び装置を提供することを目的とする。
【００１１】
【課題を解決するための手段】
本発明の排水の処理方法は、ＳＳ性有機物及びアンモニア性窒素を含む排水を処理する方法において、該排水を固液分離する固液分離工程と、該固液分離工程で分離された汚泥をメタン醗酵処理する嫌気性消化工程と、該嫌気性消化工程の脱離液中のアンモニア性窒素を亜硝酸性窒素に硝化する亜硝酸型硝化工程と、該亜硝酸型硝化工程の処理水と前記固液分離工程で分離された分離液とを混合して生物脱窒処理する生物脱窒工程とを有することを特徴とする。
【００１２】
本発明の排水の処理装置は、ＳＳ性有機物及びアンモニア性窒素を含む排水を処理する装置において、該排水を固液分離する固液分離手段と、該固液分離手段で分離された汚泥をメタン醗酵処理する嫌気性消化槽と、該嫌気性消化槽の脱離液中のアンモニア性窒素を亜硝酸性窒素に硝化する亜硝酸型硝化槽と、該亜硝酸型硝化槽の処理水と前記固液分離手段で分離された分離液とを混合して生物脱窒処理する生物脱窒槽とを有することを特徴とする。
【００１３】
本発明では、ＳＳ性有機物及びアンモニア性窒素を含む排水をまず固液分離し、分離汚泥をメタン醗酵処理して得られた脱離液について亜硝酸型硝化を行うため、硝化処理にかかる窒素負荷を大幅に軽減することができる。しかも、この硝化処理は亜硝酸型硝化であるため、硝酸型硝化に比べて酸素必要量が少なく、曝気コストを低減することができる。
【００１４】
更に、亜硝酸型硝化により亜硝酸性窒素を含む硝化液を、排水を固液分離して得られたアンモニア性窒素を含む分離液と混合して脱窒処理することにより、ＡＮＡＭＭＯＸ微生物により、低コストで脱窒処理することができる。
【００１５】
【発明の実施の形態】
以下に図面を参照して本発明の実施の形態を詳細に説明する。
【００１６】
図１は、本発明の排水の処理方法及び処理装置の実施の形態を示す系統図である。
【００１７】
ＳＳ性有機物及びアンモニア性窒素を含む排水は、まず沈殿槽１に導入して固液分離する。この固液分離手段としては、特に制限はなく、沈澱槽の他、遠心分離装置、浮上分離装置、膜分離装置等を用いることができる。また、固液分離に際しては、排水に凝集剤を添加して凝集分離を行っても良い。この場合、用いる凝集剤は無機系凝集剤、有機系高分子凝集剤のいずれでも良く、これらの併用であっても良い。
【００１８】
沈殿槽１の分離汚泥はそのまま、或いは必要に応じて濃縮処理した後、単独で或いは他の汚泥等と共に嫌気性消化槽２に導入してメタン醗酵処理する。
【００１９】
分離汚泥を濃縮する場合、濃縮法としては重力濃縮、浮上濃縮、遠心濃縮等の通常の方法を採用することができる。また、分離汚泥を他の汚泥と共にメタン醗酵処理する場合、他の汚泥としては、浄化槽汚泥、活性汚泥等の生物処理で生成する生物性汚泥の他、生ゴミ、食品廃棄物、し尿等が挙げられるが、特に、窒素含有有機物を投入すると、メタンガスの発生量が増加するのみならず、窒素濃度が上昇するため、後段の脱窒処理におけるアンモニア性窒素と亜硝酸性窒素との比が低下することによって窒素除去率が向上するので、より好ましい。
【００２０】
嫌気性消化槽２では、遠心分離装置３から返送される返送汚泥、及び嫌気性消化槽２内の嫌気性微生物を含む汚泥と沈殿槽１の分離汚泥とを撹拌機２Ａにより緩やかに攪拌混合しながら嫌気性消化処理を行う。ここで行われる嫌気性消化処理により、原水中の有機物の多くは酸生成菌及びメタン生成菌により分解される。
【００２１】
嫌気性消化槽２におけるメタン発酵の条件としては、３５℃付近に最適温度がある中温メタン生成菌、及び５５℃付近に最適温度を有する高温メタン生成菌が増殖するいずれの温度条件も採用可能である。中温メタン生成菌は増殖が遅いため嫌気性消化槽２の滞留時間（ＳＲＴ）を長くする、即ち、嫌気性消化槽２の容量を大きくする必要があるが、比較的低温での処理が可能なため加温及び保温のための設備が簡単になる。これに対し高温メタン生成菌の場合は加温及び保温の設備が必要になるが、増殖が速いため滞留時間が短くてよく、嫌気性消化槽２の容量を小さくすることができるという利点がある。
【００２２】
中温メタン生成菌を主体とする場合は嫌気性消化槽２で汚泥の滞留時間は１０日以上、好ましくは１５〜３０日程度必要である。これに対して高温メタン生成菌を主体とする場合は上記範囲よりも短い滞留時間（例えば２日以上）とすることが可能である。
【００２３】
嫌気性消化槽２の有機物負荷は０．５〜２．０ｋｇ−ＶＳＳ／ｍ３・日、嫌気性消化槽２内のＭＬＳＳ濃度は５，０００〜１００，０００ｍｇ／Ｌ、好ましくは２０，０００〜６０，０００ｍｇ／Ｌ、温度は３０〜３８℃又は４５〜６０℃の条件とすることが好ましい。
【００２４】
この嫌気性消化槽２におけるメタン醗酵に当たっては、熱処理、ミルによる破砕やオゾン処理、その他、物理的又は化学的処理等の前処理や、嫌気性消化槽２内の汚泥を引き抜いてこれらの処理を施した後嫌気性消化槽２に返送する循環処理等を行うのが好ましく、このような改質処理を組み合わせることにより、汚泥の分解率が向上するのみならず、脱離液中の有機物濃度が低減し、結果として、次工程の亜硝酸型硝化を効率的に実施することができるようになる。
【００２５】
嫌気性消化槽２の嫌気性消化汚泥は、遠心分離装置３で固液分離され、分離された脱離液は硝化槽４に送給される。一方、分離された濃縮汚泥は、必要に応じて一部が余剰汚泥として系外へ引き抜かれ、残部は返送汚泥として嫌気性消化槽２に循環される。このようにすることにより、固形物の系外流出を抑え、嫌気性消化槽２での汚泥保持量を高く保つことにより汚泥の減量効果を高めることができる。嫌気性消化汚泥の固液分離には、図１に示す遠心分離装置３の他、浮上分離装置、膜分離装置、沈殿槽、その他脱水機などの固液分離装置を用いることができる。
【００２６】
この消化汚泥の固液分離に当っては、凝集剤を添加して消化汚泥を凝集させることによって、良好な固液分離が行われ、清澄な脱離液が得られると共に、固形分の系外流出を抑えて、汚泥の減容化効果を高めることができる。凝集剤としては、有機系、無機系のいずれのものを用いてもよいが、添加量が少なくてよいことから有機高分子凝集剤、特に両性有機高分子凝集剤が好ましい。
【００２７】
遠心分離装置３で分離された脱離液は、硝化槽４において、散気管４Ａによる曝気下、亜硝酸型硝化が行われ、液中のアンモニア性窒素が亜硝酸性窒素に酸化される。
【００２８】
この硝化槽４において、アンモニア性窒素を硝酸性窒素にまで酸化することなく、酸化を亜硝酸性窒素で止めて亜硝酸型硝化を行うためには、
▲１▼ 硝化槽４内の溶存酸素（ＤＯ）濃度を０．５ｍｇ／Ｌ以下に維持する。
▲２▼ 硝化槽４のＳＲＴを短くする。
▲３▼ 硝化槽４内の亜硝酸性窒素濃度を高くする。
などの条件を適宜採用すれば良い。硝化槽４を低ＤＯで運転する場合、流動床、浮遊単体方式、造粒微生物等による硝化方式が好ましく、ＳＲＴを短く運転する場合は浮遊法が好ましい。
【００２９】
硝化槽４において、亜硝酸型硝化を行った硝化液は、前記沈澱槽１の分離液と混合して脱窒槽４において嫌気条件下に脱窒処理する。
【００３０】
この脱窒槽５には、硝化槽４における亜硝酸型硝化で、脱離液中のアンモニア性窒素が硝化性窒素に酸化されて硝化性窒素を含む硝化液と、被処理排水中のアンモニア性窒素を含む沈殿槽１の分離液が導入されるため、アンモニア性窒素を電子供与体とし、亜硝酸性窒素を電子受容体とするＡＮＡＭＭＯＸ微生物による生物脱窒が行われる。
【００３１】
この脱窒槽５に導入される硝化液と分離液との混合液のアンモニア性窒素と亜硝酸性窒素の割合は、モル比でアンモニア性窒素１に対して亜硝酸性窒素０．５〜２、特に１〜１．５とするのが好ましい。原水中のアンモニア性窒素及び亜硝酸性窒素の濃度はそれぞれ５〜１０００ｍｇ／Ｌ、５〜２００ｍｇ／Ｌであることが好ましいが、処理水を循環したり、他の排水を混合したりして希釈すればこの限りではない。
【００３２】
脱窒槽５における生物脱窒条件としては、例えば脱窒槽内液の温度が１０〜４０℃、特に２０〜３５℃、ｐＨが５〜９、特に６〜８、ＤＯ濃度が０〜２．５ｍｇ／Ｌ、特に０〜０．２ｍｇ／Ｌ、ＢＯＤ濃度が０〜５０ｍｇ／Ｌ、特に０〜２０ｍｇ／Ｌ、窒素負荷が０．１〜１０ｋｇ−Ｎ／ｍ３・日、特に１〜５ｋｇ−Ｎ／ｍ３・日の範囲とするのが好ましい。
【００３３】
この脱窒槽の形式としては特に制限はなく、
(1) 槽内でＡＮＡＭＭＯＸ微生物を浮遊状態で増殖させ、その後段において脱窒槽から流出したＡＮＡＭＭＯＸ微生物を、沈殿槽、浮上分離装置、遠心分離装置、その他の固液分離手段により処理水から分離し、濃縮されたＡＮＡＭＭＯＸ汚泥を脱窒槽に返送するもの。
(2) 微生物が付着する担体を槽内に充填し、担体表面に生物膜として増殖するＡＮＡＭＭＯＸ微生物を利用した脱窒槽。この場合、担体が脱窒槽内にほぼ静置された状態で保持される固定床、担体がガスや撹拌機などにより緩やかに流動する流動床、菌体が主体となって造粒した微生物を用いるいわゆるＵＳＢ脱窒槽、担体が比較的均一な粒径を持つもので密に充填され、ＳＳの濾過機能を併せ持つ生物濾過方式等のいずれでも良い。
(3) 浮遊状態で増殖するＡＮＡＭＭＯＸ微生物と担体表面に増殖するＡＮＡＭＭＯＸ微生物を併用した脱窒槽。
等のいずれを採用しても良い。
【００３４】
なお、沈殿槽１の分離液は、脱窒槽５における脱窒処理に先立ち好気処理を行って、溶解性の有機物を予め除去しても良い。この場合の好気処理で生成する余剰汚泥、その他系内で生成する余剰汚泥は、嫌気性消化槽２へ投入して処理することが好ましい。
【００３５】
【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。
【００３６】
実施例１
本発明に従って、図１に示す装置により、下水（ＳＳ：２５０ｍｇ／Ｌ，ＢＯＤ：１９０ｍｇ／Ｌ，ＮＨ４−Ｎ：２２ｍｇ／Ｌ）の処理を行った。まず、この下水にアニオン性高分子凝集剤を１ｍｇ／Ｌ添加し、沈殿槽１で３０分静置して上澄みを採取した。この上澄み液はＳＳ：１２ｍｇ／Ｌ，ＢＯＤ：３５ｍｇ／Ｌ，ＮＨ４−Ｎ：２２ｍｇ／Ｌであった。
【００３７】
沈殿した汚泥を採取し、下水メタン醗酵汚泥と１：１となるよう混合し、嫌気性消化槽２にて空気と接触しないようにして３５℃で３０日間ゆっくり撹拌を続けた後遠心分離装置３で固液分離し、脱離液を採取した。嫌気性消化槽２の有機物負荷は２．５ｋｇ−ＶＳＳ／ｍ３・日、ＭＬＳＳ濃度は５，４００ｍｇ／Ｌであった。この脱離液は、ＳＳ：８８ｍｇ／Ｌ，ＮＨ４−Ｎ：７７５ｍｇ／Ｌ，ＢＯＤ：１９７ｍｇ／Ｌであった。
【００３８】
この脱離液を予め亜硝酸型硝化を行っている硝化槽（曝気槽）４へ滞留時間２４時間となるよう連続添加し、温度３０℃、ｐＨ７．５、ＤＯ濃度０．３〜０．５ｍｇ／Ｌ、窒素負荷０．８ｋｇ−Ｎ／ｍ３・日で処理した。沈澱槽は設けなかった。この硝化液は、ＳＳ：２２１ｍｇ／Ｌ，ＢＯＤ：７６ｍｇ／Ｌ，ＮＨ４−Ｎ：１３ｍｇ／Ｌ，ＮＯ２−Ｎ：７７０ｍｇ／Ｌであった。
【００３９】
この硝化液を、沈殿槽１にて下水の凝集分離で得られた上澄み液と、硝化液：上澄み液＝１：４０（容量比）の割合で混合し、ＡＮＡＭＭＯＸ活性を持つ微生物を含む脱窒槽５に滞留時間１２時間となるように連続添加し、嫌気処理した。このＡＮＡＭＭＯＸ微生物は予め、不織布を担体とする反応槽でアンモニア性窒素と亜硝酸性窒素を１：１となるように添加して、約１年間培養したものである。脱窒槽の温度は２５℃，ｐＨは７．４、窒素負荷は０．１ｋｇ−Ｎ／ｍ３・日であった。
【００４０】
その結果、この脱窒槽５からＢＯＤ：１６ｍｇ／Ｌ，ＳＳ：２６ｍｇ／Ｌ，ＮＨ４−Ｎ：８ｍｇ／Ｌ，ＮＯ２−Ｎ：０．１ｍｇ／Ｌ以下，ＮＯ３−Ｎ：０．７ｍｇ／Ｌの処理水を得ることができた。
【００４１】
【発明の効果】
以上詳述した通り、本発明の排水の処理方法及び処理装置によれば、ＳＳ性有機物とアンモニア性窒素とを含む排水の処理に当たり、硝化脱窒にかかる窒素負荷を低減して低コストにて効率的な処理を行うことができる。
【図面の簡単な説明】
【図１】本発明の排水の処理方法及び処理装置の実施の形態を示す系統図である。
【図２】従来法を示す系統図である。
【符号の説明】
１ 沈殿槽
２ 嫌気性消化槽
３ 遠心分離装置
４ 硝化槽
５ 脱窒槽[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for treating wastewater containing SS organic substances such as sewage, human waste, septic tank sludge, food wastewater, and ammonia nitrogen.
[0002]
[Prior art]
Conventionally, as shown in FIG. 2, wastewater containing SS organic matter and ammonia nitrogen is first removed from the SS organic matter in the wastewater by solid-liquid separation, and then the circulating denitrification method, step denitrification method or ordinary nitrification denitrification method. It is treated by nitrification and denitrification by the nitriding method. The separated sludge generated by solid-liquid separation of SS organic matter from the wastewater is anaerobically digested together with the excess sludge generated by the nitrification denitrification treatment, and the digestion and desorption solution removes SS organic matter from the wastewater in the above nitrification denitrification step. Either the nitrification / denitrification treatment is performed together with the removed separation liquid, or the nitrification / denitrification treatment is performed separately outside the system and then discharged.
[0003]
By the way, in general, the ammoniacal nitrogen in the wastewater is oxidized by ammonia oxidizing bacteria to nitrite nitrogen and further nitrified by oxidizing this nitrite nitrogen to nitrate nitrogen by nitrite oxidizing bacteria, Nitrogen gas through a two-stage biological reaction of these nitrite nitrogen and nitrate nitrogen by denitrifying bacteria, which are heterotrophic bacteria, using organic matter as an electron donor to decompose to nitrogen gas Is broken down to
[0004]
However, such a conventional nitrification denitrification method requires a large amount of organic matter such as methanol as an electron donor in the denitrification step, and also requires a large amount of oxygen in the nitrification step, so that the running cost is high. is there.
[0005]
On the other hand, in recent years, by using an autotrophic microorganism (hereinafter sometimes referred to as “ANAMMOX microorganism”) having ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, ammonia nitrogen is used. A method of denitrification by reacting nitrous acid with nitrite nitrogen was proposed. If this method is used, it is not necessary to add an organic substance, so that the cost can be reduced as compared with a method using heterotrophic denitrifying bacteria. Moreover, since the yield of autotrophic microorganisms is low and the amount of sludge generated is significantly less than that of heterotrophic microorganisms, the amount of surplus sludge generated can be suppressed. Furthermore, there is also a feature that the generation of N 2 O observed by the conventional nitrification denitrification method does not occur and the burden on the environment can be reduced.
[0006]
This biodenitrification process using ANAMOX microorganisms has been reported in Strous, M, et al., Appl. Microbiol. Biotecnol., 50, p.589-596 (1998). It is believed that reactive nitrogen and nitrite nitrogen react and decompose into nitrogen gas.
[0007]
[Chemical 1]
[Problems to be solved by the invention]
As shown in FIG. 2, in the method in which the digestion and desorption liquid obtained by the anaerobic digestion of sludge is nitrified and denitrified together with the separation liquid from which SS organic substances have been removed from the wastewater, the nitrogen load for nitrification and denitrification increases. For this reason, a large amount of oxygen is required for nitrification, and a large amount of organic matter is required for denitrification.
[0009]
On the other hand, the method of separately nitrifying and denitrifying the digestion and desorption liquid outside the system requires an apparatus for nitrification and denitrification of the desorption liquid, which is not preferable.
[0010]
The present invention solves the above-mentioned conventional problems, and in the treatment of wastewater containing SS organic matter and ammonia nitrogen, a method for reducing the nitrogen load related to nitrification and denitrification and performing efficient treatment at low cost and An object is to provide an apparatus.
[0011]
[Means for Solving the Problems]
The wastewater treatment method of the present invention is a method for treating wastewater containing SS organic matter and ammonia nitrogen, in which a solid-liquid separation step for solid-liquid separation of the wastewater, and sludge separated in the solid-liquid separation step are treated with methane. An anaerobic digestion step for fermentation treatment, a nitrite type nitrification step for nitrifying ammonia nitrogen in the effluent of the anaerobic digestion step to nitrite nitrogen, treated water of the nitrite type nitrification step and the solid solution And a biological denitrification step of mixing the separated liquid separated in the liquid separation step and performing a biological denitrification treatment.
[0012]
The wastewater treatment apparatus of the present invention is an apparatus for treating wastewater containing SS organic matter and ammonia nitrogen, in which solid-liquid separation means for solid-liquid separation of the wastewater, and sludge separated by the solid-liquid separation means are treated with methane. An anaerobic digester to be fermented, a nitrite nitrification tank that nitrifies ammoniacal nitrogen in the effluent of the anaerobic digester to nitrite nitrogen, treated water in the nitrite nitrification tank and the solid solution It has a biological denitrification tank which mixes with the separation liquid separated by the liquid separation means and performs biological denitrification treatment.
[0013]
In the present invention, wastewater containing SS organic matter and ammonia nitrogen is first solid-liquid separated, and the effluent obtained by subjecting the separated sludge to methane fermentation treatment is subjected to nitrite type nitrification, so that the nitrogen load applied to nitrification treatment Can be greatly reduced. In addition, since this nitrification treatment is nitrite type nitrification, the required amount of oxygen is smaller than that of nitrate type nitrification, and the aeration cost can be reduced.
[0014]
Furthermore, the nitrification type nitrogenous nitrification solution containing nitrite nitrogen is mixed with a separation solution containing ammoniacal nitrogen obtained by solid-liquid separation of the waste water, and denitrification treatment is performed. Denitrification treatment can be performed at a cost.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 is a system diagram showing an embodiment of the wastewater treatment method and treatment apparatus of the present invention.
[0017]
Waste water containing SS organic matter and ammonia nitrogen is first introduced into the precipitation tank 1 and separated into solid and liquid. The solid-liquid separation means is not particularly limited, and a centrifugal separator, a flotation separator, a membrane separator, etc. can be used in addition to a precipitation tank. In solid-liquid separation, an aggregating agent may be added to the waste water to perform the aggregation separation. In this case, the coagulant used may be either an inorganic coagulant or an organic polymer coagulant, or a combination thereof.
[0018]
The separated sludge in the sedimentation tank 1 is subjected to a methane fermentation treatment as it is or after being concentrated as necessary, and then introduced into the anaerobic digester 2 alone or together with other sludge and the like.
[0019]
In the case of concentrating the separated sludge, conventional methods such as gravity concentration, flotation concentration, and centrifugal concentration can be employed as the concentration method. In addition, when the separated sludge is subjected to methane fermentation treatment with other sludge, other sludge includes biological sludge generated by biological treatment such as septic tank sludge and activated sludge, as well as raw garbage, food waste, human waste, etc. However, in particular, when a nitrogen-containing organic substance is added, not only the amount of methane gas generated increases, but also the nitrogen concentration increases, so the ratio of ammonia nitrogen to nitrite nitrogen in the subsequent denitrification process decreases. This is more preferable because the nitrogen removal rate is improved.
[0020]
In the anaerobic digester 2, the return sludge returned from the centrifugal separator 3 and the sludge containing the anaerobic microorganisms in the anaerobic digester 2 and the separated sludge in the settling tank 1 are gently stirred and mixed by the
[0021]
As conditions for the methane fermentation in the anaerobic digester 2, any temperature condition in which a medium temperature methanogen having an optimum temperature around 35 ° C and a high temperature methanogen having an optimum temperature around 55 ° C can be adopted. is there. Since the mesophilic methanogen grows slowly, the residence time (SRT) of the anaerobic digester 2 needs to be increased, that is, the capacity of the anaerobic digester 2 needs to be increased, but it can be processed at a relatively low temperature. Therefore, the equipment for heating and heat insulation is simplified. On the other hand, in the case of high-temperature methanogens, heating and heat insulation facilities are required, but since the growth is fast, the residence time may be short, and there is an advantage that the capacity of the anaerobic digester 2 can be reduced. .
[0022]
In the case of mainly mesophilic methanogen, the residence time of sludge in the anaerobic digester 2 is 10 days or more, preferably about 15 to 30 days. On the other hand, when a high-temperature methanogen is mainly used, a residence time shorter than the above range (for example, 2 days or more) can be set.
[0023]
The organic matter load of the anaerobic digester 2 is 0.5 to 2.0 kg-VSS / m 3 · day, and the MLSS concentration in the anaerobic digester 2 is 5,000 to 100,000 mg / L, preferably 20,000 to 60,000 mg / L, and the temperature is preferably 30 to 38 ° C or 45 to 60 ° C.
[0024]
In the methane fermentation in the anaerobic digester 2, heat treatment, crushing with a mill, ozone treatment, and other pre-treatments such as physical or chemical treatment, and sludge in the anaerobic digester 2 are extracted. It is preferable to carry out a circulation treatment or the like that is returned to the anaerobic digestion tank 2 after being applied. By combining such a modification treatment, not only the sludge decomposition rate is improved, but also the organic matter concentration in the desorbed liquid is increased. As a result, the nitrite type nitrification in the next step can be efficiently performed.
[0025]
The anaerobic digested sludge in the anaerobic digestion tank 2 is solid-liquid separated by the centrifugal separator 3, and the separated desorbed liquid is fed to the nitrification tank 4. On the other hand, if necessary, part of the separated concentrated sludge is withdrawn out of the system as excess sludge, and the remainder is circulated to the anaerobic digester 2 as return sludge. By doing in this way, the sludge reduction effect can be heightened by suppressing the outflow of the solid matter from the system and keeping the amount of sludge retained in the anaerobic digestion tank 2 high. For the solid-liquid separation of the anaerobic digested sludge, a solid-liquid separation device such as a flotation separation device, a membrane separation device, a sedimentation tank, and other dehydrators can be used in addition to the centrifugal separation device 3 shown in FIG.
[0026]
In the solid-liquid separation of this digested sludge, a flocculant is added to agglomerate the digested sludge, so that a good solid-liquid separation is performed, and a clear desorbed liquid is obtained. Spilling can be suppressed and the sludge volume reduction effect can be enhanced. As the flocculant, either an organic or inorganic flocculant may be used, but an organic polymer flocculant, particularly an amphoteric organic polymer flocculant, is preferable because the addition amount may be small.
[0027]
The desorbed liquid separated by the centrifugal separator 3 is subjected to nitrite-type nitrification in the nitrification tank 4 under aeration by the diffusing
[0028]
In this nitrification tank 4, in order to stop the oxidation with nitrite nitrogen and nitrite type nitrification without oxidizing ammonia nitrogen to nitrate nitrogen,
(1) The dissolved oxygen (DO) concentration in the nitrification tank 4 is maintained at 0.5 mg / L or less.
(2) Shorten the SRT of the nitrification tank 4.
(3) Increase the concentration of nitrite nitrogen in the nitrification tank 4.
The conditions such as these may be adopted as appropriate. When the nitrification tank 4 is operated at a low DO, a fluidized bed, a floating simplex system, a nitrification system using granulated microorganisms or the like is preferable, and when the SRT is operated shortly, a floating method is preferable.
[0029]
In the nitrification tank 4, the nitrification liquid subjected to nitrite type nitrification is mixed with the separation liquid in the precipitation tank 1 and denitrified in the denitrification tank 4 under anaerobic conditions.
[0030]
The denitrification tank 5 includes a nitrification type nitrification in the nitrification tank 4, a nitrification liquid containing nitrification nitrogen by oxidizing ammonia nitrogen in the effluent to nitrification nitrogen, and ammonia nitrogen in the wastewater to be treated. Since the separation liquid of the precipitation tank 1 containing is introduced, biological denitrification is performed by the ANAMOX microorganism using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor.
[0031]
The ratio of ammonia nitrogen and nitrite nitrogen in the mixture of the nitrification liquid and the separation liquid introduced into the denitrification tank 5 is 0.5 to 2 nitrite nitrogen with respect to ammonia nitrogen 1 in molar ratio, In particular, it is preferably 1 to 1.5. The concentrations of ammonia nitrogen and nitrite nitrogen in the raw water are preferably 5 to 1000 mg / L and 5 to 200 mg / L, respectively, but diluted by circulating the treated water or mixing other waste water. This is not the case.
[0032]
As biological denitrification conditions in the denitrification tank 5, for example, the temperature of the liquid in the denitrification tank is 10 to 40 ° C., particularly 20 to 35 ° C., the pH is 5 to 9, particularly 6 to 8, and the DO concentration is 0 to 2.5 mg / L, especially 0 to 0.2 mg / L, BOD concentration 0 to 50 mg / L, especially 0 to 20 mg / L, nitrogen load 0.1 to 10 kg-N / m 3 · day, especially 1 to 5 kg-N / The range is preferably m 3 · day.
[0033]
There are no particular restrictions on the type of denitrification tank,
(1) ANAMMOX microorganisms are grown in a suspended state in the tank, and the ANAMMOX microorganisms that have flowed out from the denitrification tank in the subsequent stage are separated from the treated water by a precipitation tank, a flotation separator, a centrifuge, and other solid-liquid separation means. Returning concentrated ANAMMOX sludge to a denitrification tank.
(2) A denitrification tank that uses ANAMMOX microorganisms that are filled in a tank with a carrier to which microorganisms adhere and grow as a biofilm on the surface of the carrier. In this case, use is made of a fixed bed in which the carrier is held almost stationary in the denitrification tank, a fluidized bed in which the carrier gently flows by gas or a stirrer, etc., or microorganisms granulated mainly with bacterial cells. Any of a so-called USB denitrification tank, a biological filtration method in which the carrier has a relatively uniform particle diameter, is packed closely, and has a SS filtration function may be used.
(3) A denitrification tank that uses both ANAMMOX microorganisms growing in a floating state and ANAMMOX microorganisms growing on the surface of the carrier.
Any of these may be adopted.
[0034]
Note that the separation liquid in the precipitation tank 1 may be subjected to an aerobic treatment prior to the denitrification treatment in the denitrification tank 5 to remove soluble organic substances in advance. In this case, surplus sludge produced by the aerobic treatment and other sludge produced in the system are preferably supplied to the anaerobic digester 2 for treatment.
[0035]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0036]
Example 1
In accordance with the present invention, treatment of sewage (SS: 250 mg / L, BOD: 190 mg / L, NH 4 —N: 22 mg / L) was performed by the apparatus shown in FIG. First, 1 mg / L of an anionic polymer flocculant was added to this sewage, and it was left to stand in the precipitation tank 1 for 30 minutes to collect a supernatant. The supernatant was SS: 12 mg / L, BOD: 35 mg / L, NH 4 -N: 22 mg / L.
[0037]
The precipitated sludge was collected, mixed with sewage methane fermentation sludge at a ratio of 1: 1, and stirred slowly at 35 ° C. for 30 days without contact with air in the anaerobic digester 2, and then the centrifugal separator 3 The solid was separated into a liquid and the desorbed solution was collected. The organic matter load of the anaerobic digester 2 was 2.5 kg-VSS / m 3 · day, and the MLSS concentration was 5,400 mg / L. This desorbed solution was SS: 88 mg / L, NH 4 -N: 775 mg / L, BOD: 197 mg / L.
[0038]
This desorbed liquid is continuously added to a nitrification tank (aeration tank) 4 in which nitrite type nitrification has been performed in advance so as to have a residence time of 24 hours, temperature 30 ° C., pH 7.5, DO concentration 0.3 to 0.5 mg. / L, nitrogen load 0.8 kg-N / m 3 · day. There was no settling tank. This nitrification solution was SS: 221 mg / L, BOD: 76 mg / L, NH 4 -N: 13 mg / L, NO 2 -N: 770 mg / L.
[0039]
This nitrification liquid is mixed with the supernatant liquid obtained by coagulation and separation of sewage in the precipitation tank 1 at a ratio of nitrification liquid: supernatant liquid = 1: 40 (volume ratio), and a denitrification tank containing microorganisms having ANAMMOX activity. 5 was continuously added so that the residence time was 12 hours, and anaerobic treatment was performed. This ANAMOX microorganism was previously cultivated for about one year by adding ammonia nitrogen and nitrite nitrogen in a reaction vessel using a nonwoven fabric as a carrier in a ratio of 1: 1. The temperature of the denitrification tank was 25 ° C., the pH was 7.4, and the nitrogen load was 0.1 kg-N / m 3 · day.
[0040]
As a result, from this denitrification tank 5, BOD: 16 mg / L, SS: 26 mg / L, NH 4 -N: 8 mg / L, NO 2 -N: 0.1 mg / L or less, NO 3 -N: 0.7 mg / L L treated water could be obtained.
[0041]
【The invention's effect】
As described above in detail, according to the wastewater treatment method and treatment apparatus of the present invention, when treating wastewater containing SS organic matter and ammonia nitrogen, the nitrogen load related to nitrification denitrification is reduced and the cost is low. Efficient processing can be performed.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a wastewater treatment method and treatment apparatus according to the present invention.
FIG. 2 is a system diagram showing a conventional method.
[Explanation of symbols]
1 Precipitation tank 2 Anaerobic digestion tank 3 Centrifuge 4 Nitrification tank 5 Denitrification tank
Claims (4)
該排水を固液分離する固液分離工程と、
該固液分離工程で分離された汚泥をメタン醗酵処理する嫌気性消化工程と、
該嫌気性消化工程の脱離液中のアンモニア性窒素を亜硝酸性窒素に硝化する亜硝酸型硝化工程と、
該亜硝酸型硝化工程の処理水と前記固液分離工程で分離された分離液とを混合して生物脱窒処理する生物脱窒工程と
を有することを特徴とする排水の処理方法。In a method for treating wastewater containing SS organic matter and ammonia nitrogen,
A solid-liquid separation step for solid-liquid separation of the waste water;
An anaerobic digestion step of subjecting the sludge separated in the solid-liquid separation step to methane fermentation,
A nitrite-type nitrification step of nitrifying ammoniacal nitrogen in the effluent of the anaerobic digestion step to nitrite nitrogen;
A wastewater treatment method comprising: a biological denitrification step of mixing the treated water of the nitrite type nitrification step and the separated liquid separated in the solid-liquid separation step to biologically denitrify.
該排水を固液分離する固液分離手段と、
該固液分離手段で分離された汚泥をメタン醗酵処理する嫌気性消化槽と、
該嫌気性消化槽の脱離液中のアンモニア性窒素を亜硝酸性窒素に硝化する亜硝酸型硝化槽と、
該亜硝酸型硝化槽の処理水と前記固液分離手段で分離された分離液とを混合して生物脱窒処理する生物脱窒槽と
を有することを特徴とする排水の処理装置。In an apparatus for treating wastewater containing SS organic matter and ammonia nitrogen,
Solid-liquid separation means for solid-liquid separation of the waste water;
An anaerobic digester for methane fermentation of the sludge separated by the solid-liquid separation means;
A nitrite type nitrification tank that nitrifies ammoniacal nitrogen in the effluent of the anaerobic digestion tank to nitrite nitrogen;
An apparatus for treating waste water, comprising: a biological denitrification tank for mixing the treated water of the nitrite type nitrification tank and the separated liquid separated by the solid-liquid separation means to perform biological denitrification treatment.
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| CN112979075B (en) * | 2021-02-26 | 2022-12-23 | 天津凯英科技发展股份有限公司 | Zero-carbon-source-added biogas slurry denitrification method and application thereof |
| CN113880251B (en) * | 2021-09-26 | 2023-10-10 | 北京工业大学 | Method and device for realizing deep denitrification and sludge reduction of high ammonia nitrogen wastewater by using sludge fermentation liquor |
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