JP3608690B2

JP3608690B2 - Organic wastewater treatment method and equipment

Info

Publication number: JP3608690B2
Application number: JP19341496A
Authority: JP
Inventors: 俊博田中; 甬生葛; 信二山本; 晃延須山
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 1996-07-23
Filing date: 1996-07-23
Publication date: 2005-01-12
Anticipated expiration: 2016-07-23
Also published as: JPH1034181A

Description

【０００１】
【発明の属する技術分野】
本発明は、工場などから排出される有機性排水を活性汚泥処理設備の活性汚泥反応槽に導入して処理するに当たって、反応槽中の活性汚泥混合液を、前記反応槽中に直接浸漬した分離膜モジュールにより、膜分離して処理水を得る膜分離式活性汚泥方法及び装置に関するものである。
【０００２】
【従来の技術】
従来、膜分離式活性汚泥処理方法による有機性排水の好気性処理は、排水と活性汚泥との混合液の入った槽内に散気装置と直接槽中に浸漬せしめた分離膜モジュールとを備えた活性汚泥反応槽において、散気装置に空気を送り込むことによって、活性汚泥と排水との混合液中に空気を散気して好気的な状態で活性汚泥の生殖を維持し、排水と接触させることで有機物（ＢＯＤ成分）を分解・除去し、さらに、分離膜モジュールにより活性汚泥混合液を固液分離して処理水を得るプロセスからなるものであった。
【０００３】
従来の膜分離式活性汚泥処理方法に用いる典型的な装置を図７に示すと、従来の処理装置は、散気装置８を備えた流量調整槽Ｂと、同様に散気装置８を備えた活性汚泥反応槽Ａの２槽からなり、活性汚泥反応槽Ａ中には、活性汚泥混合液から活性汚泥を固液分離するための膜分離モジュール６（図では２基）を直接槽中に浸漬して配備する構成となっている。
さらに図７により従来の膜分離式活性汚泥処理方法を説明すると以下の通りである。すなわち、図７に示した従来の処理装置では、散気装置８を備えた流量調整槽Ｂ中で原水１（有機性排水を以下「原水」ということがある）を活性汚泥と混合し、散気装置８に曝気ブロア９から空気供給管１１を経て供給された空気によって流量調整槽Ｂ中で好気的生物処理を行い、生物処理水２０を活性汚泥と共に移送ポンプ７を経由して活性汚泥反応槽Ａに移送し、活性汚泥反応槽Ａ内で、そこに設置されている散気装置８に曝気ブロア９から空気供給管１１を経て供給された空気２によって好気的生物処理を行い、活性汚泥反応槽Ａ内に設置されている膜分離モジュール６によって、吸引的にあるいは加圧的にろ過して処理水を得、処理水流出管１３を通して系外に排出し、一方膜分離された活性汚泥の一部は余剰汚泥として活性汚泥引抜ポンプ５を用いて活性汚泥流出管１４を経て系外に排出する。
【０００４】
前記活性汚泥処理装置では、有機性汚泥の混合および反応、有機物の分解・除去、固液分離を前記活性汚泥反応槽のみで行うことができるため、沈殿槽が不要となる。また、原水の沈降分離の必要がなくなり、活性汚泥濃度を１０，０００ｍｇ／リットル程度の高い濃度で運転でき、反応槽の容量を小さくすることができるため、活性汚泥処理装置の設置スペースを削除することができるという利点がある。また、活性汚泥を含む混合液の固液分離に分離膜を使用することによって、前記混合液中の固形分を確実に分離し、浮遊物を含まない良好な処理水を得ることができる。
前記活性汚泥反応槽への排水の流入は、日水量、水質などの負荷変動に対し、手前に流量調整槽を設けて、一旦貯留し、槽内に設置した散気装置により攪拌して負荷を均一にして、前記反応槽に移流する。
しかし、排水中の糖分の含有率が高くなると、それを処理する活性汚泥反応槽内で汚泥を含む液の粘度が１０ｍＰａ・ｓより大の範囲になると上がり、膜モジュールの膜表面に粘度の高い液が付着して、分離膜が目詰まりを起こし、分離膜を透過する水量の低下などが発生し、年に数回の洗浄が必要となった。このため、分離膜の洗浄、水量の監視などの維持管理に時間がかかり、洗浄を繰り返すため、分離膜の破損頻度が増すことになった。
【０００５】
【発明が解決しようとする課題】
膜分離式活性汚泥処理方法の場合、分離膜の目詰まりがなければ、維持管理を行う上で非常に容易な装置となる。このため、本発明は、分離膜の目詰まりを少なくすることで、分離膜の洗浄頻度を少なくし、維持管理の手間を少なくすると共に、分離膜の延命を図り、処理水量を確保するために、ろ過圧の上昇を抑えることを課題とするものである。
【０００６】
【課題を解決するための手段】
本発明の上記課題は、下記（１）から（５）に記載の有機性排水の処理法及び装置によって達せられる。
（１）有機性排水をその中に分離膜を設置した活性汚泥を含む好気性処理域に導入して処理し、分離膜から分離水を取り出す工程を有する膜分離式活性汚泥方法による有機性排水の処理法において、有機性排水を酸発酵処理をして有機性排水中の糖分の含有量を減少させて、有機性排水の粘度を低下させ、該粘度が低下した有機性排水を分離膜を設置した活性汚泥反応槽に導入し、活性汚泥反応槽内における活性汚泥を含む水の粘度を１０ｍＰａ・ｓ以下に低下させた条件下で、活性汚泥処理及び膜ろ過による活性汚泥の固液分離を行い、膜分離した処理水を系外に排出することを特徴とする有機性排水の処理法。
（２）前記活性汚泥反応槽の手前に、前記有機性排水を平均して３〜２４時間滞留させることができる滞留部を設け、該滞留部内において滞留している水の溶存酸素量が、０．１ｍｇ／リットル以下の嫌気状態として酸発酵を行い、酸発酵水を前記活性汚泥反応槽に移流することを特徴とする前記（１）項に記載の有機性排水の処理法。
（３）前記活性汚泥反応槽から、一部の活性汚泥混合液を前記排水の滞留部に還流し、酸発酵を促進させることを特徴とする前記（２）項に記載の有機性排水の処理法。
（４）有機性排水をその中に分離膜を設置した活性汚泥を含む好気性処理装置に導入して処理し、分離膜から分離水を取り出す有機性排水の処理装置において、有機性排水を導入して酸発酵処理により有機性排水中の糖分の含有量を減少させ、有機性排水の粘度を低下させる酸発酵処理装置と、該酸発酵処理装置から粘度が低下した有機性排水を導入し、槽内における活性汚泥を含む水の粘度を１０ｍＰａ・ｓ以下に低下させた条件下にあり、膜ろ過により処理水を得る、分離膜を設置した活性汚泥反応槽とを有することを特徴とする有機性排水の処理装置。
（５）有機性排水を平均して３〜２４時間滞留させることができ、内部において滞留している水の溶存酸素量が、０．１ｍｇ／リットル以下の嫌気状態として酸発酵を行う滞留部を一部に有する流量調整槽を設け、該流量調整槽にその滞留部の酸発酵水を前記活性汚泥反応槽に移流する配管を設けたことを特徴とする請求項４に記載の有機性排水の処理装置。
なお、前記した粘度の単位「ｍＰａ・ｓ」は「ミリパスカル・秒」のことである。
【０００７】
本発明者等は、実際の施設で検討した結果、有機性排水中に糖の含有量が多いと、活性汚泥反応槽内での糖分の分解に時間を要し、前記反応槽内の活性汚泥中の糖含有量が高いまま維持されて運転することになる。このため、活性汚泥を含む液の粘度が高くなり、処理水を吸引する膜表面には粘性を帯びた液が付着し、膜のろ過圧が上昇することがわかった。また、糖分の分解に時間を要するので、排水中に含まれる他の有機物の処理が不完全になり、膜を透過させて引き抜いた処理水中に、未処理の溶解性ＢＯＤが含まれるため、膜が有機物で汚染され、膜の目詰まりの進行が加速した。
本発明は、この欠点を除去するようにしたものであり、そのためには活性汚泥を含む液の粘度を低下させる手段を用いるもので、その手段として種々の方法があるが、例えば、反応槽流入前に有機性排水の滞留部を設け、原水を嫌気状態で酸醗酵させることで、前記糖類を低級脂肪酸、低分子有機物へある程度分解して、反応槽内の活性汚泥中に含まれる糖含有率を下げて処理するようにすることが好ましい。
【０００８】
滞留部は、前記反応槽とは別個に設置するか、原水槽、流量調整槽あるいは沈殿槽などに滞留部の容積を確保するようにすることができる。滞留部は、攪拌機、攪拌ポンプあるいは移送ポンプの水流を利用するなどして、嫌気的な条件で攪拌する。嫌気的な条件としては、溶存酸素量（ＤＯ）が０．１ｍｇ／リットル以下であることが必要で、好ましくはできるだけ０ｍｇ／リットルに近い値とする。また、排水のｐＨや温度が低い場合や外気温が低い場合、または槽内の溶存酸素量（ＤＯ）が０ｍｇ／リットルに近い値とならない場合は、嫌気槽を保温または加温したり、アルカリ剤を添加することで酸醗酵を促進させる。
また、活性汚泥反応槽の混合液の一部を滞留部に還流することで、滞留部での通性嫌気性菌の濃度を上昇させることができるために、滞留部での酸醗酵を促進することができる。これにより、良好な水質の処理水を得るとともに、分離膜の汚染の進行を緩慢にし、洗浄頻度を少なくし、同時に分離膜の寿命を長くさせる。
【０００９】
【発明の実施の形態】
以下に本発明の活性汚泥処理設備と処理方法について詳しく説明する。
本発明の活性汚泥処理設備は、滞留部の設置の仕方により二種類に大別することができる。すなわち、
１）滞留部は、原水槽、流量調整槽あるいは沈殿槽等とは別に、独立した槽として、個別に設置する。
２）滞留部は、原水槽、流量調整槽あるいは沈殿槽等のいずれかの中に余分の容積を確保し、その余分の容積の部分を（必要により隔壁を設けて、）滞留部とする。
【００１０】
先ず、滞留部を個別に設置する設備について図１〜図３を用いて説明する。
図１には、本発明の膜分離式活性汚泥方法に使用する装置の１例を示す。図１の装置では、原水１（排水ともいう。）を原水供給管１０を通して流量調整槽Ｂに供給し、散気装置８を備えた流量調整槽Ｂ中で活性汚泥と混合する。散気装置８に曝気ブロア９から空気供給管１１を経て供給された空気２によって流量調整槽Ｂ中で原水１を予備的に好気的生物処理し、流量調整槽Ｂと活性汚泥反応槽Ａの間に酸発酵槽Ｃを設け、流量調整槽Ｂから移送ポンプ７により生物処理水２０（活性汚泥を含む混合液である。）の一定流量を酸発酵槽Ｃに移送する。酸発酵槽Ｃ中では、攪拌機１５により生物処理水２０を所定時間嫌気的に発酵させて生物処理水２０中の有機物、特に糖を分解・除去し、粘度が低下した酸発酵処理水１９を酸発酵槽Ｃから活性汚泥反応槽Ａにオーバーフローにより移送する。酸発酵処理水１９は反応槽Ａ中で散気装置８からの空気２による曝気により、好気的な状態で有機物を分解・除去する。一定時間好気的に処理された生物処理水は吸引あるいは加圧により分離膜（膜モジュール６）を通して固液分離し、処理水３を系外に取り出す。また、反応槽Ａ中の余剰汚泥は適時に汚泥引抜ポンプ５により系外に取り出す。
【００１１】
図２には、本発明の膜分離式活性汚泥方法に使用する装置の他の１例を示す。
図２に示す膜分離式活性汚泥処理設備では、前記図１に示した処理設備との比較において、流量調整槽Ｂ、酸発酵槽Ｃ（滞留部）および活性汚泥反応槽Ａの配置は同じであるが、図２の設備では、活性汚泥反応槽Ａ内の余剰活性汚泥の一部を汚泥循環管１６を経由して酸発酵槽Ｃに還流させている。活性汚泥反応槽Ａにおける余剰活性汚泥の一部を酸発酵槽Ｃに還流させることで、酸発酵槽Ｃでの通性嫌気性菌の濃度が上昇するため、酸発酵槽Ｃでの酸発酵が促進される。
本発明の膜分離式活性汚泥処理設備のさらに別の例について説明する。
図３に示す膜分離式活性汚泥処理設備では、前記図１に示した処理設備との比較において、流量調整槽Ｂ、酸発酵槽Ｃ（滞留部）および活性汚泥反応槽Ａの配置は同じであるが、図３の設備では、酸発酵槽Ｃ内の混合液（これは活性汚泥をある程度含有している）の一部を汚泥循環管２２を通して循環させることによって通性嫌気性菌の濃度を均一に保ち、酸発酵の作用を均一かつ効率的にする。
【００１２】
次に、本発明の膜分離式活性汚泥処理設備において、滞留部を独立した槽として個別に設置せず、原水槽、流量調整槽あるいは沈殿槽等のいずれかの槽の中に余分の容積を確保し、その余分の容積の部分を滞留部とする場合について以下に３例を挙げ、図４〜図６を用いて説明する。ただしこの場合も以下に示す活性汚泥処理設備に限定されるものではない。
先ず、図４に示す膜分離式活性汚泥処理設備では、図７に示した従来の膜分離式活性汚泥処理設備において、流量調整槽Ｂに余分の容積を確保し、槽Ｂの下部に仕切りを設けて流量調整槽Ｂを上部Ｂ１部と下部Ｂ２部に区分けし、上部Ｂ１部（流量調整部ともいう。）には散気装置は設けず、単に流量を調整する部分とし、Ｂ２部（滞留部ともいう。）は滞留部とし、その部分に攪拌機１５を設置し、攪拌しながら原水１を所定時間嫌気的に発酵させて原水１中の有機物、特に糖を分解・除去し、粘度が低下した酸発酵処理混合液１９を移送ポンプ７により移送管１２を経由して活性汚泥反応槽Ａに移送する。以降の処理は従来の膜分離式活性汚泥処理と同じ処理である。
【００１３】
図５に示す別の膜分離式活性汚泥処理設備では、前記図４に示した処理設備との比較において、上部Ｂ１部と下部Ｂ２部に区分けした流量調整槽Ｂおよび活性汚泥反応槽Ａの配置は同じであるが、下部Ｂ２部には攪拌機１５を設けず、移送ポンプ７からの移送管は流量調整槽Ｂに上部で分岐させ、分岐管の一方は活性汚泥反応槽Ａに酸発酵処理混合液１９を移送する管とし、他方はＢ１部に酸発酵処理混合液１９を還流する還流管とし、混合液１９を還流することでＢ２部（滞留部）における酸発酵処理混合液１９の攪拌を行い、酸発酵処理を効率的にする。
図６に示す今一つ別の膜分離式活性汚泥処理設備では、前記図５に示した処理設備との比較において、上部Ｂ１部と下部Ｂ２部に区分けした流量調整槽Ｂおよび活性汚泥反応槽Ａの配置及び酸発酵処理混合液１９を還流させることは同じであるが、流量調整槽Ｂにおける酸発酵処理混合液１９の還流を、移送ポンプ７とは別に下部Ｂ２部に設置した攪拌ポンプ１８により行うようにしたものである。
【００１４】
（作用）
滞留部は、反応槽手前に設け、流入する排水（原水）の滞留時間が３〜２４時間となる容量とする。滞留部を原水槽または流量調整槽を利用して設ける場合は、そのもの本来の目的を機能させるために必要な容量以外に滞留分の容量を増加させる。滞留部での処理負荷を均一にするため、攪拌機または攪拌ポンプを設置したり、滞留部への流入用あるいは流出用のポンプの水流を利用して嫌気的に攪拌する。
滞留部にて行われる酸発酵処理により、排水中に含まれる還元糖（グルコース換算）は減少し、代わりに酢酸、乳酸などの有機酸が増加する。この滞留部での処理により、排水中に含まれる還元糖を２０〜４０％に減少させることで、活性汚泥反応槽内の活性汚泥中に含まれる糖含有率を減少させ、ＭＬＳＳが８，０００〜１０，０００ｍｇ／リットル、粘度を１０ｍＰａ・ｓ以下にすることができる。反応槽内の活性汚泥混合液の粘度が下がることにより、分離膜の透過圧が下がる。また、活性汚泥がＢＯＤの分解を容易に行えるようになるため、処理時間がかからず、未処理のまま溶解性ＢＯＤが分離膜を透過する量が減少する。このため、有機物による膜の汚染の進行を極めて緩慢にすることができる。
また、滞留部での酸醗酵促進のために、活性汚泥反応槽から混合液の一部を移送し、滞留部内のＭＬＳＳを１，０００ｍｇ／リットル程度に維持することで、還元糖は３０〜８０％の分解率に減少させる。
【００１５】
【実施例】
以下、実施例により本発明を具体的に説明するが、本発明はこの実施例のみに限定されるものではない。
実施例１
活性汚泥反応槽手前にある流量調整槽の下部に２．８ｍ^３の容量の滞留部を設けた。槽内の攪拌は、活性汚泥反応槽に移送するポンプの水流の一部を利用して行った。
活性汚泥反応槽は、２０ｍ^３の容量で、槽内の活性汚泥の混合液を、散気装置より酸素含有空気を、酸素要求量（ＤＯ）が少なくとも１ｍｇ／リットルになるように散気することで、流量調整槽から移流してくる排水の好気的処理を行っている。
分離膜モジュールは活性汚泥反応槽に浸漬設置しており、分離膜（中空糸膜）モジュール（４ｍ^２／本）を３８本配置してある。処理水はこの分離膜モジュールに取り付けた配管の先にあるポンプにて吸引して得る。
この活性汚泥反応槽を用いて、水量２０ｍ^３／日、ＢＯＤ１，５００ｍｇ／リットル、ＳＳ７００ｍｇ／リットルの有機性排水を、活性汚泥反応槽のＭＬＳＳ８，０００ｍｇ／リットルとして処理を行った。
【００１６】
排水は、いったん流量調整槽に貯留され、槽内には嫌気滞留部が用意されており、ここで排水中に含まれる糖分を低分子有機酸にある程度分解することで、酸醗酵を行う前の粘度が１０ｍＰａ・ｓであったものを５．１ｍＰａ・ｓにまで下げた。
また、分離膜は１年間汚染されずに、吸引圧力０．０５〜０．３５ｋｇｆ／ｃｍ^２で処理水が得られた。処理水のＢＯＤは５ｍｇ／リットル以下であった。
糖分を含む排水を、流量調整槽に嫌気滞留部を設けず、散気攪拌を行っている場合の排水を反応槽に移流し運転を行った場合、分離膜の濾過圧は約１ヶ月間経過した時点で、０．５ｋｇｆ／ｃｍ^２を越え、分離膜の洗浄が必要になった。これに対して、流量調整槽に仕切りを入れ、滞留部を設け、その部分を嫌気状態にして酸発酵処理を行ったた場合は、約１年間経過した場合でも洗浄の必要がなく、分離膜の濾過圧は０．３５ｋｇｆ／ｃｍ^２以下であり、酸発酵を取り入れることで、分離膜の粘性を持った液の付着による閉塞をなくし、分離の汚染の進行を緩慢にして洗浄頻度を減らし、良好な処理水を得ることができた。
【００１７】
【表１】

【００１８】
【発明の効果】
本発明の膜分離式活性汚泥法による有機性排水の処理法により次のような効果が得られた。
（１）有機性汚泥の混合および反応、有機物の分解・除去、固液分離を活性汚泥反応槽のみで行うことができるため、沈殿槽が不要となる。
（２）活性汚泥濃度を１０，０００ｍｇ／リットル程度の高い濃度で運転でき、活性汚泥反応槽の容量を小さくすることができる。
（３）滞留部を設け、そこで嫌気的に酸発酵を行うことで、排水中の糖分を分解することで、活性汚泥混合液に粘度を下げ、粘性液の膜付着による分離膜の閉塞を防ぐことができる。
（４）活性汚泥反応槽の手前で糖分を分解することで、反応槽でのＢＯＤの分解を容易に行うことができ、未処理のままでＢＯＤ成分が膜分離にかけられることがなくなる。
（５）粘性液の膜付着による分離膜の閉塞や未処理のＢＯＤ成分による分離膜の目詰まりがなくなり、分離膜の洗浄頻度が少なくなり、膜分離式活性汚泥処理における維持管理が非常に容易となる。
（６）分離膜の寿命も長くなる。
（７）膜透過水（処理水）の水質が良好な状態で安定する。
【図面の簡単な説明】
【図１】本発明の膜分離式活性汚泥方法の滞留部として、個別に酸発酵槽を設けた装置の１例を示す説明図である。
【図２】本発明の膜分離式活性汚泥方法の滞留部として、個別に酸発酵槽を設けた装置の別の１例を示す説明図である。
【図３】本発明の膜分離式活性汚泥方法の滞留部として、個別に酸発酵槽を設けた装置のさらに別の１例を示す説明図である。
【図４】本発明の膜分離式活性汚泥方法の流量調整槽の下部に滞留部（酸発酵部）を設けた装置の１例を示す説明図である。
【図５】本発明の膜分離式活性汚泥方法の流量調整槽の下部に滞留部（酸発酵部）を設けた装置の別の１例を示す説明図である。
【図６】本発明の膜分離式活性汚泥方法の流量調整槽の下部に滞留部（酸発酵部）を設けた装置のさらに別の１例を示す説明図である。
【図７】従来の膜分離式活性汚泥方法の典型例を示す説明図である。
【符号の説明】
１原水
２空気
３処理水
４余剰汚泥
５汚泥引抜ポンプ
６分離膜モジュール
７移送ポンプ
８散気装置
９曝気ブロア
１０原水供給管
１１空気供給管
１２移送管
１３処理水流出管
１４汚泥流出管
１５攪拌機
１６汚泥還流管
１７移送管
１８攪拌ポンプ
１９酸発酵処理水
２０生物処理水
２１移送・攪拌ポンプ
２２汚泥循環管
Ａ活性汚泥反応槽
Ｂ流量調整槽
Ｂ１上部（流量調整部）
Ｂ２下部（滞留部）
Ｃ酸発酵槽[0001]
BACKGROUND OF THE INVENTION
In the present invention, when organic wastewater discharged from a factory or the like is introduced into an activated sludge reaction tank of an activated sludge treatment facility for treatment, the activated sludge mixed liquid in the reaction tank is directly immersed in the reaction tank. The present invention relates to a membrane separation activated sludge method and apparatus for obtaining treated water by membrane separation using a membrane module.
[0002]
[Prior art]
Conventionally, aerobic treatment of organic wastewater by the membrane separation type activated sludge treatment method has been provided with a diffuser and a separation membrane module directly immersed in a tank containing a mixed liquid of wastewater and activated sludge. In an activated sludge reaction tank, air is sent to the diffuser to diffuse the air into the mixed liquid of activated sludge and waste water, maintaining the reproduction of activated sludge in an aerobic state and making contact with the waste water. The organic substance (BOD component) was decomposed and removed by the treatment, and the activated sludge mixed solution was solid-liquid separated by a separation membrane module to obtain treated water.
[0003]
FIG. 7 shows a typical apparatus used in the conventional membrane separation type activated sludge treatment method. The conventional treatment apparatus is provided with the flow rate adjusting tank B provided with the air diffuser 8 and the air diffuser 8 as well. The activated sludge reaction tank A consists of two tanks. In the activated sludge reaction tank A, the membrane separation module 6 (two in the figure) for directly separating activated sludge from the activated sludge mixed solution is immersed directly in the tank. It is configured to be deployed.
Further, the conventional membrane separation activated sludge treatment method will be described with reference to FIG. That is, in the conventional treatment apparatus shown in FIG. 7, raw water 1 (organic drainage may be referred to as “raw water” hereinafter) is mixed with activated sludge in a flow control tank B equipped with an air diffuser 8, The aerobic biological treatment is performed in the flow rate adjusting tank B by the air supplied from the aeration blower 9 to the air device 8 through the air supply pipe 11, and the biologically treated water 20 is activated sludge through the transfer pump 7 together with the activated sludge. In the activated sludge reaction tank A, the aerobic biological treatment is performed by the air 2 supplied from the aeration blower 9 through the air supply pipe 11 to the diffuser 8 installed in the reaction tank A. By the membrane separation module 6 installed in the activated sludge reaction tank A, the treated water is obtained by suction or pressure filtration to be discharged out of the system through the treated water outflow pipe 13, and the membrane is separated. Part of activated sludge is activated sludge as surplus sludge Discharged out of the system through the activated sludge outlet pipe 14 with a disconnect pump 5.
[0004]
In the activated sludge treatment apparatus, since mixing and reaction of organic sludge, decomposition / removal of organic substances, and solid-liquid separation can be performed only in the activated sludge reaction tank, a settling tank is not required. In addition, since there is no need for sedimentation separation of raw water, the activated sludge concentration can be operated at a high concentration of about 10,000 mg / liter, and the capacity of the reaction tank can be reduced, so the installation space for the activated sludge treatment device is eliminated. There is an advantage that you can. Moreover, by using a separation membrane for the solid-liquid separation of the mixed liquid containing activated sludge, it is possible to reliably separate the solid content in the mixed liquid and obtain good treated water that does not contain suspended solids.
The inflow of wastewater into the activated sludge reaction tank is provided with a flow rate adjustment tank in front of the load fluctuations such as the amount of daily water and water quality, temporarily stored, and stirred by an air diffuser installed in the tank. Uniform and transfer to the reactor.
However, when the sugar content in the wastewater increases, the viscosity of the liquid containing sludge increases within the range of 10 mPa · s in the activated sludge reaction tank for treating it, and the membrane surface of the membrane module has a high viscosity. The liquid adhered, causing the separation membrane to become clogged, resulting in a decrease in the amount of water that permeated the separation membrane, and it became necessary to wash several times a year. For this reason, it takes time to maintain and manage the separation membrane and monitor the amount of water, and the cleaning is repeated, so that the frequency of breakage of the separation membrane increases.
[0005]
[Problems to be solved by the invention]
In the case of the membrane separation type activated sludge treatment method, if the separation membrane is not clogged, it becomes a very easy apparatus for maintenance. Therefore, the present invention reduces the clogging of the separation membrane, thereby reducing the frequency of cleaning the separation membrane, reducing the maintenance work, extending the life of the separation membrane, and ensuring the amount of treated water. The problem is to suppress an increase in filtration pressure.
[0006]
[Means for Solving the Problems]
The said subject of this invention is achieved by the processing method and apparatus of the organic waste_water | drain as described in following (1) to (5) .
(1) Organic wastewater by the membrane-separated activated sludge method, which has a step of introducing and treating organic wastewater into an aerobic treatment area containing activated sludge with a separation membrane installed therein and taking out the separated water from the separation membrane In this treatment method, the organic wastewater is subjected to an acid fermentation treatment to reduce the sugar content in the organic wastewater, thereby reducing the viscosity of the organic wastewater, and separating the organic wastewater having the reduced viscosity from the separation membrane. Introduced into the installed activated sludge reaction tank, solid-liquid separation of activated sludge by activated sludge treatment and membrane filtration under the condition that the viscosity of water containing activated sludge in the activated sludge reaction tank is reduced to 10 mPa · s or less An organic wastewater treatment method characterized in that the treated water separated by membrane is discharged out of the system.
(2) Before the activated sludge reaction tank, a retention part capable of retaining the organic waste water on average for 3 to 24 hours is provided, and the dissolved oxygen amount of the water retained in the retention part is 0. The method for treating organic waste water according to (1) above, wherein acid fermentation is performed in an anaerobic state of 1 mg / liter or less and acid fermentation water is transferred to the activated sludge reaction tank.
(3) The treatment of organic wastewater according to (2) above, wherein a part of the activated sludge mixed solution is refluxed from the activated sludge reaction tank to the retention portion of the wastewater to promote acid fermentation. Law.
(4) Organic wastewater is introduced into an aerobic treatment device containing activated sludge with a separation membrane in it and treated, and the separated water is taken out from the separation membrane. Then, the acid fermentation treatment device that reduces the sugar content in the organic wastewater by acid fermentation treatment and lowers the viscosity of the organic wastewater, and the organic wastewater whose viscosity is reduced from the acid fermentation treatment device, Organic having an activated sludge reaction tank provided with a separation membrane, under conditions where the viscosity of water containing activated sludge in the tank is reduced to 10 mPa · s or less and obtaining treated water by membrane filtration Wastewater treatment equipment.
(5) An organic wastewater can be retained for 3 to 24 hours on average, and a retention portion that performs acid fermentation in an anaerobic state in which the amount of dissolved oxygen in the interior is 0.1 mg / liter or less The organic wastewater according to claim 4, wherein a flow rate adjusting tank is provided in a part of the flow rate adjusting tank, and a pipe for transferring the acid fermentation water of the staying portion to the activated sludge reaction tank is provided in the flow rate adjusting tank. Processing equipment.
The unit of viscosity “mPa · s” is “millipascal · second”.
[0007]
As a result of examination at an actual facility, the present inventors have found that when there is a large amount of sugar in organic wastewater, it takes time to decompose the sugar in the activated sludge reaction tank, and the activated sludge in the reaction tank The operation will be carried out while maintaining the high sugar content. For this reason, it turned out that the viscosity of the liquid containing activated sludge becomes high, the viscous liquid adheres to the membrane surface which sucks treated water, and the filtration pressure of the membrane rises. Moreover, since it takes time to decompose the sugar, the treatment of other organic substances contained in the wastewater becomes incomplete, and the treated water extracted through the membrane contains untreated soluble BOD. Was contaminated with organic matter, and the progress of clogging of the film accelerated.
The present invention is designed to eliminate this drawback, and for this purpose, means for reducing the viscosity of the liquid containing activated sludge is used. There are various methods as such means. The saccharide content contained in the activated sludge in the reaction tank is decomposed to some extent to lower fatty acids and low-molecular organic substances by providing an organic wastewater retention part in advance and acid-fermenting raw water in an anaerobic state. It is preferable to lower the processing.
[0008]
The staying part can be installed separately from the reaction tank, or the volume of the staying part can be secured in a raw water tank, a flow rate adjustment tank, a sedimentation tank, or the like. The staying part is stirred under anaerobic conditions, for example, using a water flow of a stirrer, a stirring pump or a transfer pump. As anaerobic conditions, the amount of dissolved oxygen (DO) needs to be 0.1 mg / liter or less, preferably as close to 0 mg / liter as possible. In addition, when the pH or temperature of the wastewater is low, the outside air temperature is low, or the dissolved oxygen amount (DO) in the tank does not reach a value close to 0 mg / liter, the anaerobic tank is kept warm or warmed, Acid fermentation is promoted by adding an agent.
Moreover, since the density | concentration of facultative anaerobic bacteria in a retention part can be raised by recirculating a part of liquid mixture of an activated sludge reaction tank to a retention part, acid fermentation in a retention part is accelerated | stimulated. be able to. As a result, treated water of good quality is obtained, the progress of contamination of the separation membrane is slowed, the washing frequency is reduced, and at the same time, the life of the separation membrane is extended.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The activated sludge treatment facility and treatment method of the present invention will be described in detail below.
The activated sludge treatment facility of the present invention can be roughly classified into two types depending on the way of installing the staying portion. That is,
1) The staying part is installed separately as an independent tank separately from the raw water tank, the flow rate adjusting tank or the sedimentation tank.
2) The retention part secures an extra volume in any of the raw water tank, the flow rate adjustment tank, the sedimentation tank, and the like, and the extra volume part (provided with a partition if necessary) is used as the retention part.
[0010]
First, the installation which installs a residence part separately is demonstrated using FIGS. 1-3.
In FIG. 1, an example of the apparatus used for the membrane separation type | formula activated sludge method of this invention is shown. In the apparatus of FIG. 1, raw water 1 (also referred to as drainage) is supplied to the flow rate adjustment tank B through the raw water supply pipe 10 and mixed with activated sludge in the flow rate adjustment tank B provided with the air diffuser 8. The raw water 1 is preliminarily aerobically treated in the flow rate adjusting tank B with the air 2 supplied from the aeration blower 9 to the air diffuser 8 through the air supply pipe 11, and the flow rate adjusting tank B and the activated sludge reaction tank A An acid fermenter C is provided between them, and a constant flow rate of biologically treated water 20 (mixed solution containing activated sludge) is transferred from the flow rate adjusting tank B to the acid fermenter C by the transfer pump 7. In the acid fermenter C, the biologically treated water 20 is anaerobically fermented for a predetermined time by the stirrer 15 to decompose and remove organic substances, particularly sugars, in the biologically treated water 20, and the acid fermented treated water 19 having a reduced viscosity is acidified. Transfer from the fermenter C to the activated sludge reactor A by overflow. The acid fermentation treated water 19 decomposes and removes organic substances in an aerobic state by aeration with the air 2 from the diffuser 8 in the reaction tank A. Biologically treated water that has been aerobically treated for a certain period of time is subjected to solid-liquid separation through a separation membrane (membrane module 6) by suction or pressurization, and the treated water 3 is taken out of the system. Further, excess sludge in the reaction tank A is taken out of the system by the sludge extraction pump 5 at an appropriate time.
[0011]
In FIG. 2, another example of the apparatus used for the membrane separation type | formula activated sludge method of this invention is shown.
In the membrane-separated activated sludge treatment facility shown in FIG. 2, the arrangement of the flow rate adjustment tank B, the acid fermentation tank C (retention part), and the activated sludge reaction tank A is the same in comparison with the treatment equipment shown in FIG. However, in the facility of FIG. 2, a part of the surplus activated sludge in the activated sludge reaction tank A is returned to the acid fermentation tank C via the sludge circulation pipe 16. Since the concentration of facultative anaerobic bacteria in the acid fermentation tank C is increased by refluxing a part of the surplus activated sludge in the activated sludge reaction tank A to the acid fermentation tank C, acid fermentation in the acid fermentation tank C is performed. Promoted.
Still another example of the membrane separation type activated sludge treatment facility of the present invention will be described.
In the membrane-separated activated sludge treatment facility shown in FIG. 3, the arrangement of the flow rate adjustment tank B, the acid fermentation tank C (retention part), and the activated sludge reaction tank A is the same in comparison with the treatment equipment shown in FIG. 3, the concentration of facultative anaerobes can be reduced by circulating a part of the mixed solution in the acid fermenter C (which contains activated sludge to some extent) through the sludge circulation pipe 22. Keep it uniform and make the action of acid fermentation uniform and efficient.
[0012]
Next, in the membrane separation type activated sludge treatment facility of the present invention, the reservoir is not individually installed as an independent tank, but an extra volume is added in any tank such as a raw water tank, a flow control tank, or a sedimentation tank. Three cases will be described below with reference to FIG. 4 to FIG. 6 for the case of securing and using the extra volume as a staying portion. However, this case is not limited to the activated sludge treatment facility described below.
First, in the membrane separation type activated sludge treatment facility shown in FIG. 4, in the conventional membrane separation type activated sludge treatment facility shown in FIG. 7, an extra volume is secured in the flow rate adjustment tank B, and a partition is formed in the lower part of the tank B. The flow rate adjusting tank B is divided into an upper B1 part and a lower B2 part, and the upper B1 part (also referred to as a flow rate adjusting part) is not provided with an air diffuser, but is simply a part for adjusting the flow rate, and the B2 part (retention) Is also a stagnant part, and a stirrer 15 is installed in that part, and the raw water 1 is anaerobically fermented for a predetermined time while stirring to decompose and remove organic substances, particularly sugars, in the raw water 1, thereby reducing the viscosity. The acid fermentation treatment mixed liquid 19 is transferred to the activated sludge reaction tank A via the transfer pipe 12 by the transfer pump 7. The subsequent processing is the same as the conventional membrane separation activated sludge processing.
[0013]
In another membrane separation type activated sludge treatment facility shown in FIG. 5, in comparison with the treatment facility shown in FIG. 4, the arrangement of the flow control tank B and the activated sludge reaction tank A divided into the upper B1 part and the lower B2 part. Are the same, but the lower part B2 is not provided with a stirrer 15, the transfer pipe from the transfer pump 7 is branched into the flow rate adjustment tank B at the upper part, and one of the branch pipes is mixed with the activated sludge reaction tank A in the acid fermentation treatment. A pipe for transferring the liquid 19 is used, and the other is a reflux pipe for refluxing the acid fermentation treatment mixed liquid 19 to B1 part. By stirring the liquid mixture 19, the acid fermentation treatment mixed liquid 19 is stirred in B2 part (retention part). To make the acid fermentation process efficient.
In the separate membrane separation type activated sludge treatment facility shown in FIG. 6, in comparison with the treatment facility shown in FIG. 5, the flow control tank B and the activated sludge reaction tank A divided into the upper B1 part and the lower B2 part. The arrangement and reflux of the acid fermentation treatment mixture 19 are the same, but the reflux of the acid fermentation treatment mixture 19 in the flow rate adjusting tank B is performed by the stirring pump 18 installed in the lower part B2 separately from the transfer pump 7. It is what I did.
[0014]
(Function)
The staying part is provided in front of the reaction tank, and has a capacity that makes the staying time of the inflowing waste water (raw water) 3 to 24 hours. When providing a retention part using a raw | natural water tank or a flow control tank, the capacity | capacitance for a retention is increased in addition to a capacity | capacitance required in order to function the original purpose itself. In order to make the processing load uniform in the staying section, an agitator or a stirring pump is installed, or an anaerobic stirring is performed using the water flow of the pump for inflow or outflow to the staying section.
Due to the acid fermentation treatment performed in the retention part, reducing sugars (in terms of glucose) contained in the wastewater are reduced, and organic acids such as acetic acid and lactic acid are increased instead. By reducing the reducing sugar contained in the waste water to 20 to 40% by the treatment in this staying portion, the sugar content contained in the activated sludge in the activated sludge reaction tank is reduced, and the MLSS is 8,000. -10,000 mg / liter, and a viscosity can be 10 mPa * s or less. When the viscosity of the activated sludge mixed liquid in the reaction tank decreases, the permeation pressure of the separation membrane decreases. In addition, since activated sludge can easily decompose BOD, it does not take treatment time, and the amount of soluble BOD that permeates through the separation membrane decreases without treatment. For this reason, the progress of the contamination of the film by the organic matter can be made extremely slow.
Moreover, in order to promote acid fermentation in the retention part, a part of liquid mixture is transferred from an activated sludge reaction tank, and MLSS in a retention part is maintained at about 1,000 mg / liter, reducing sugar is 30-80. % Degradation rate.
[0015]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to this Example.
Example 1
A staying part having a capacity of 2.8 m ³ was provided at the lower part of the flow rate adjusting tank in front of the activated sludge reaction tank. Stirring in the tank was performed using a part of the water flow of the pump that was transferred to the activated sludge reaction tank.
The activated sludge reaction tank has a capacity of 20 m ³ and diffuses the mixed liquid of activated sludge in the tank with oxygen-containing air from the air diffuser so that the oxygen demand (DO) is at least 1 mg / liter. Therefore, aerobic treatment of wastewater advected from the flow control tank is performed.
The separation membrane module is immersed in the activated sludge reaction tank, and 38 separation membrane (hollow fiber membrane) modules (4 m ² / piece) are arranged. The treated water is obtained by suction with a pump at the end of the pipe attached to the separation membrane module.
Using this activated sludge reaction tank, an organic waste water having a water amount of 20 m ³ / day, BOD 1,500 mg / liter, and SS 700 mg / liter was treated as MLSS 8,000 mg / liter of the activated sludge reaction tank.
[0016]
The wastewater is once stored in the flow rate adjustment tank, and an anaerobic retention part is prepared in the tank. Here, the sugar contained in the wastewater is decomposed to low molecular organic acids to some extent, before acid fermentation. The viscosity of 10 mPa · s was lowered to 5.1 mPa · s.
The separation membrane was not contaminated for one year, and treated water was obtained at a suction pressure of 0.05 to 0.35 kgf / cm ² . The BOD of the treated water was 5 mg / liter or less.
When the wastewater containing sugar is transferred to the reaction tank and the operation is performed without diffused stirrer in the flow rate adjustment tank without anaerobic retention, the filtration pressure of the separation membrane has passed for about one month. At that time, the separation membrane exceeded 0.5 kgf / cm ² and it became necessary to clean the separation membrane. On the other hand, when a partition is placed in the flow rate adjusting tank, a retention portion is provided, and the portion is anaerobic and acid fermentation treatment is performed, there is no need for washing even when about one year has passed, and the separation membrane The filtration pressure is 0.35 kgf / cm ² or less, and by incorporating acid fermentation, the clogging due to adhesion of the liquid with the viscosity of the separation membrane is eliminated, the progress of separation contamination is slowed down, and the washing frequency is reduced. Good treated water could be obtained.
[0017]
[Table 1]

[0018]
【The invention's effect】
The following effects were obtained by the organic wastewater treatment method using the membrane separation activated sludge method of the present invention.
(1) Since the mixing and reaction of organic sludge, decomposition / removal of organic substances, and solid-liquid separation can be performed only in the activated sludge reaction tank, a precipitation tank is not required.
(2) The activated sludge concentration can be operated at a high concentration of about 10,000 mg / liter, and the capacity of the activated sludge reaction tank can be reduced.
(3) By providing a retention section and performing anaerobic acid fermentation there, the sugar content in the wastewater is decomposed to lower the viscosity of the activated sludge mixture and prevent clogging of the separation membrane due to adhesion of the viscous liquid to the membrane be able to.
(4) By decomposing the sugar before the activated sludge reaction tank, the BOD can be easily decomposed in the reaction tank, and the BOD component is not subjected to membrane separation without being treated.
(5) Separation of clogged separation membranes due to adhesion of viscous liquid membranes and clogging of separation membranes due to untreated BOD components is eliminated, separation membrane cleaning frequency is reduced, and maintenance management in membrane separation activated sludge treatment is very easy. It becomes.
(6) The life of the separation membrane is also extended.
(7) The water quality of the membrane permeated water (treated water) is stabilized in a good state.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an example of an apparatus in which an acid fermentation tank is individually provided as a retention part of a membrane separation type activated sludge method of the present invention.
FIG. 2 is an explanatory view showing another example of an apparatus in which an acid fermentation tank is individually provided as a retention part of the membrane separation activated sludge method of the present invention.
FIG. 3 is an explanatory view showing still another example of an apparatus in which an acid fermentation tank is individually provided as a retention part of the membrane separation activated sludge method of the present invention.
FIG. 4 is an explanatory view showing an example of an apparatus in which a staying part (acid fermentation part) is provided in the lower part of the flow rate adjusting tank of the membrane separation type activated sludge method of the present invention.
FIG. 5 is an explanatory view showing another example of an apparatus in which a staying part (acid fermentation part) is provided in the lower part of the flow rate adjusting tank of the membrane separation type activated sludge method of the present invention.
FIG. 6 is an explanatory view showing still another example of an apparatus in which a retention part (acid fermentation part) is provided in the lower part of the flow rate adjusting tank of the membrane separation type activated sludge method of the present invention.
FIG. 7 is an explanatory view showing a typical example of a conventional membrane separation activated sludge method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Raw water 2 Air 3 Treated water 4 Excess sludge 5 Sludge extraction pump 6 Separation membrane module 7 Transfer pump 8 Aeration device 9 Aeration blower 10 Raw water supply pipe 11 Air supply pipe 12 Transfer pipe 13 Treated water outflow pipe 14 Sludge outflow pipe 15 Stirrer 16 Sludge recirculation pipe 17 Transfer pipe 18 Stirring pump 19 Acid fermentation treated water 20 Biologically treated water 21 Transfer / stirring pump 22 Sludge circulation pipe A Activated sludge reaction tank B Flow control tank B1 Upper part (flow control section)
B2 Lower part (Retention part)
C acid fermenter

Claims

A method for treating organic wastewater by a membrane separation type activated sludge method, which has a process of introducing and treating organic wastewater into an aerobic treatment area containing activated sludge with a separation membrane installed therein and taking out the separated water from the separation membrane. The organic wastewater is subjected to an acid fermentation treatment to reduce the sugar content in the organic wastewater to reduce the viscosity of the organic wastewater, and the organic wastewater having the reduced viscosity is installed with a separation membrane. Introduced into the sludge reaction tank, the activated sludge is subjected to solid-liquid separation by activated sludge treatment and membrane filtration under the condition that the viscosity of the water containing the activated sludge in the activated sludge reaction tank is reduced to 10 mPa · s or less. An organic wastewater treatment method characterized by discharging separated treated water out of the system.

Before the activated sludge reaction tank, a retention part capable of retaining the organic waste water on average for 3 to 24 hours is provided, and the dissolved oxygen amount of water retained in the retention part is 0.1 mg / The organic wastewater treatment method according to claim 1, wherein acid fermentation is performed in an anaerobic state of 1 liter or less, and the acid fermentation water is transferred to the activated sludge reaction tank.

The method for treating organic wastewater according to claim 2, wherein a part of the activated sludge mixed liquid is refluxed from the activated sludge reaction tank to the staying portion of the wastewater to promote acid fermentation.

Introducing organic wastewater into an aerobic treatment device containing activated sludge with a separation membrane installed in it, treating the wastewater, and removing the separated water from the separation membrane Introducing acid fermentation treatment equipment that reduces the sugar content in organic wastewater by fermentation treatment and lowering the viscosity of organic wastewater, and organic wastewater with reduced viscosity from the acid fermentation treatment equipment, in the tank An organic wastewater characterized by having an activated sludge reaction tank equipped with a separation membrane, under conditions where the viscosity of water containing activated sludge is reduced to 10 mPa · s or less, obtaining treated water by membrane filtration Processing equipment.

The organic waste water on average can be retained 3-24 hours, the dissolved oxygen content of water staying inside is, in some retention portion for performing acid fermentation as anaerobic conditions below 0.1mg / liter The organic wastewater treatment apparatus according to claim 4, wherein a flow rate adjusting tank is provided, and a pipe for transferring the acid fermentation water of the staying portion to the activated sludge reaction tank is provided in the flow rate adjusting tank.