JP2004223433A - Wastewater treatnent method - Google Patents
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- JP2004223433A JP2004223433A JP2003015642A JP2003015642A JP2004223433A JP 2004223433 A JP2004223433 A JP 2004223433A JP 2003015642 A JP2003015642 A JP 2003015642A JP 2003015642 A JP2003015642 A JP 2003015642A JP 2004223433 A JP2004223433 A JP 2004223433A
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、生物膜処理設備における排水の処理方法に関する。さらに詳しくは、生物膜処理設備において高ＢＯＤ除去率を安定して得られる排水の処理方法に関するものである。
【０００２】
【従来の技術】
従来、各種有機性排水の処理には、合成繊維や不織布などで形成されたハニカム形状、円筒形状、球形、板状などの生物担体が配置された好気性生物処理槽により処理する生物膜処理設備が広く使用されている。
この生物膜処理設備においては、好気性微生物である汚泥が生物担体表面に付着増殖し、その付着汚泥が生物学的作用で排水中の有機物を酸化分解するので活性汚泥設備のように汚泥を返送する必要はなく、バルキング現象も見られず、維持管理が容易である。
このような生物膜処理設備における微生物固定化担体としては、タイヤ活性炭や紐状軸材に多数の短繊維が突設したモール状担体などが知られている。（例えば特許文献１および特許文献２参照）
【０００３】
このように生物膜処理設備は活性汚泥設備のように余剰汚泥を発生させずに排水を処理することができるが、高濃度排水を処理する場合には多くの費用がかかることから、比較的高濃度の排水を処理する場合には活性汚泥設備が用いられ、低濃度排水を処理する場合に生物膜処理設備が多く適用されている。
たとえば多種の用紙等を製造する製紙工場においては、低濃度の排水である抄紙系排水には生物膜処理設備が用いられ、高濃度の排水である古紙排水には活性汚泥設備が用いられることが多い。しかし生物膜処理設備では排水の変動に対する対応が限られており、ＢＯＤ除去率がせいぜい７０〜８０％であって、更にＢＯＤ除去率を上げることが困難である。
【０００４】
【特許文献１】
特開２００２−７９２８５号公報
【特許文献２】
特開２００２−３５５６８８号公報
【０００５】
【発明が解決しようとする課題】
本発明は、このような状況下で、生物膜排水処理設備においてＢＯＤ除去率を高い水準で安定して維持できる方法を提供することを目的とするものである。
【０００６】
【課題を解決するための手段】
本発明者は、以上のような課題を有する生物膜排水処理設備について鋭意検討した結果、活性汚泥設備より発生する浮遊性汚泥（余剰汚泥）を生物膜排水処理設備に添加することにより生物膜排水処理設備においてＢＯＤ除去率が向上し、余剰汚泥の有効利用が図られると共に、ＢＯＤ除去率を安定して高い水準で維持できることを見出した。本発明は、かかる知見に基づいて完成したものである。
【０００７】
すなわち、本発明は、
（１）生物膜表面に付着する生物担体と接触させて排水を生物的に浄化処理する生物膜処理設備において、活性汚泥設備で得られた浮遊性汚泥を該生物膜処理設備に添加することを特徴とする排水の処理方法、
（２）排水が、製紙工程からの抄紙系排水である上記（１）の排水の処理方法、
（３）活性汚泥設備が、古紙再生処理工程からの排水処理設備である上記（１）又は（２）の排水の処理方法、
（４）活性汚泥設備からの浮遊性汚泥と生物膜処理設備で処理する排水をあらかじめ混合して生物膜処理設備に供給する上記（１）〜（３）のいずれかの排水の処理方法、
（５）活性汚泥設備から添加される浮遊性汚泥の汚泥濃度が生物膜処理設備内で１００〜１５０ｍｇ／Ｌとなるように添加する上記（１）〜（４）のいずれかに記載の排水の処理方法、
（６）活性汚泥設備から添加される浮遊性汚泥の汚泥濃度が５０００〜１５０００ｍｇ／Ｌであり、該浮遊性汚泥量（ｍ３／Ｄ）が、生物膜処理設備に流入する排水量（ｍ３／Ｄ）に対して１〜３％である上記（１）〜（５）のいずれかに記載の排水の処理方法、
（７）活性汚泥設備から添加される浮遊性汚泥の汚泥量が、生物膜処理設備におけるＴ−ＢＯＤ負荷に対して重量比で０．３〜０．７の範囲である請求項１〜６のいずれかに記載の排水の処理方法、
（８）次式で示される生物膜処理設備におけるＢＯＤ除去率が９０％以上である（１）〜（７）のいずれかの排水の処理方法、
ＢＯＤ除去率（％）＝［生物膜処理設備入口排水のＢＯＤ負荷（ｋｇ／Ｄ）−生物膜処理設備出口排水のＢＯＤ負荷（ｋｇ／Ｄ）］／［生物膜処理設備入口排水のＢＯＤ負荷（ｋｇ／Ｄ）］×１００
を提供する。
なお、本発明において、生物膜処理設備に添加される浮遊性汚泥とは活性汚泥が浮遊している排水を示し、浮遊性汚泥量（ｍ３／Ｄ）は該活性汚泥を含む排水量である。浮遊性汚泥の汚泥濃度（ｍｇ／Ｌ）は排水中に浮遊している活性汚泥の濃度であり、汚泥量は排水中に浮遊している活性汚泥の量（ｋｇ／Ｄ）である。
また、生物膜処理設備の前に凝集沈殿処理設備を設けない場合があるので、前記（７）の活性汚泥設備から添加される浮遊性汚泥の汚泥量は、生物膜処理設備のＴ−ＢＯＤ負荷（浮遊物質を含めた合計ＢＯＤ負荷）に対する比率を用いる。
【０００８】
【発明の実施の形態】
以下に本発明の実施の形態について説明する。図１は本発明の一実施の形態であり、製紙製造工程からの抄紙系排水を生物膜処理設備で処理し、古紙再生処理工程からの古紙系排水を活性汚泥設備で処理して、活性汚泥設備から得られた浮遊性汚泥を生物膜処理設備に添加する場合のフロー図である。
図１において、製紙製造工程からの抄紙系排水１は先ず排水の原水槽（排水ピット）２に送られ、排水給水ポンプ３を経て生物膜処理設備４に入る。生物膜処理設備においては後述するように担体に生物膜が付着しており、散気手段による空気との接触処理が行なわれて抄紙系排水中の有機物質の生物膜による分解が行なわれる。生物膜処理された排水は、凝集沈殿処理設備５および流路６を経て、流路７より放流される。なお、排水の状況に応じて抄紙系排水１の一部は生物膜処理設備４を通過せずに直接に凝集沈殿処理設備５に送られるバイパスライン８が設けられている。
【０００９】
一方、古紙再生処理工程からの古紙系排水９は凝集沈殿処理設備１０を経て活性汚泥設備１１に送られ、処理排水は生物膜処理設備からの排水と共に流路７より放流される。本発明では該活性汚泥設備から得られる浮遊性汚泥（余剰汚泥）は流路１２を経て生物膜処理設備に添加される。この浮遊性汚泥の添加方法は生物膜処理設備４に直接添加しても良いが、図１に示すように原水槽２を経て該抄紙系排水と混合した状態で生物膜処理設備４に添加することが好ましい。
【００１０】
本発明において用いられる生物膜処理設備に供給する排水は原水槽において酸やアルカリを添加することによりｐＨを７〜８程度に管理することが好ましい。生物膜処理設備に添加される浮遊性汚泥は特に制限されないが、凝集沈殿処理設備において排水中のＳＳ（浮遊物質）５０ｍｇ／Ｌ以下に処理した排水を、活性汚泥装置においてｐＨが６．５〜７．５、栄養バランスがＢＯＤ：Ｎ：Ｐの比率で１００：４〜５：０．８〜１．５程度になるように管理され、汚泥の濃度が５０００〜１５０００ｍｇ／Ｌであるものが好ましい。
生物膜処理設備の生物担体の形状は特に制限されず、合成繊維や不織布などで形成されたハニカム形状、円筒形状、球形、板状、紐状など種々の形状のものが用いられる。通常、生物膜処理設備における排水の温度は２０〜３５℃、滞留時間は１．５〜２．５時間程度であり、散気手段により生物膜処理設備内の溶存酸素量は３〜５ｍｇ／Ｌ程度に管理される。活性汚泥設備から添加される浮遊性汚泥濃度は生物膜処理設備内で１００〜１５０ｍｇ／Ｌとなるように添加することが好ましい。
【００１１】
生物膜処理設備のＢＯＤ除去率がせいぜい７０〜８０％であるが、本発明により浮遊性汚泥を生物膜処理設備に添加することにより次式で示される排水原水のＢＯＤ除去率を９０％以上とすることができる。
ＢＯＤ除去率（％）＝［生物膜処理設備入口排水のＢＯＤ負荷（ｋｇ／Ｄ）−生物膜処理設備出口排水のＢＯＤ負荷（ｋｇ／Ｄ）］／［生物膜処理設備入口排水のＢＯＤ負荷（ｋｇ／Ｄ）］×１００
このように高ＢＯＤ除去率が得られる原因については次のように考えられる。図２は生物膜処理設備の説明図であり、左図は従来の生物膜処理設備で浮遊性汚泥を添加しない場合である。生物膜処理槽２０の内部には生物担体２１が充填されており、底部よりブロワ２２から空気が吹き込まれる。定着性微生物２３が生物担体の表面に付着しており、生物学的作用で排水中の有機物を酸化分解する。このような生物膜処理設備では微生物菌体の住家となる生物担体の容量により微生物の定着数が決まってくるため、自ずとその能力に限界があり、ＢＯＤ除去率がせいぜい７０〜８０％である。
右図は本発明により活性汚泥を生物膜処理設備に浮遊性汚泥を注入した場合であり、各生物担体２１の間に添加された浮遊性汚泥（浮遊性微生物）２４が存在することになるので微生物菌体が増加し、各生物担体に定着している微生物だけでは処理できなかった有機物（ＢＯＤ）を処理することになるので処理能力が増強され、排水原水のＢＯＤ除去率を９０％以上とすることができるようになるものと考えられる。
【００１２】
生物膜処理設備における微生物の種類としては主に、糸状細菌、鞭毛虫類（原生動物）、輪虫類（微小後生動物）等の定着性微生物で構成される。一方、活性汚泥設備から得られる浮遊性汚泥は、活性汚泥設備の排水の種類等により異なるが、例えば古紙系排水の排水処理設備の場合は、微生物の種類としては主に、フロック形成細菌、糸状細菌、吸管虫類、つりがね虫繊毛虫類（原生動物）、輪虫類・線虫類（後生動物）等の浮遊性微生物で構成される。このように生物膜処理設備とは異なる微生物が浮遊性汚泥として添加され、上記のように各生物担体間に添加されるので、生物担体に定着している微生物だけでは処理できなかったＢＯＤ成分の処理が促進され、生物膜処理設備内で行なわれている微生物菌体の食物連鎖や定期的な生物担体よりの微生物の剥離による活性度の低下を最小限に抑えることができ、安定した微生物形態を維持することができるようになり、排水原水のＢＯＤ除去率を高い水準で安定して維持できるようになるものと考えられる。
【００１３】
生物膜処理設備に添加する浮遊性汚泥量は生物膜処理設備の排水および浮遊性汚泥を供給する排水の状況により異なる。通常、活性汚泥設備から添加される浮遊性汚泥の汚泥量（ｋｇ／Ｄ）が、生物膜処理設備におけるＴ−ＢＯＤ負荷（ｋｇ／Ｄ）に対して重量比で０．３〜０．７程度となるように浮遊性汚泥を添加する。勿論、生物膜処理設備に添加する浮遊性汚泥量は生物膜処理設備の操作状況により決められるものであり、添加する浮遊性汚泥量に応じて曝気空気量を変化させる必要がある。
生物膜処理設備に添加する浮遊性汚泥量（ｍ３／Ｄ）は、活性汚泥設備から汚泥濃度が５０００〜１５０００ｍｇ／Ｌの浮遊性汚泥を、生物膜処理設備に流入する排水量（ｍ３／Ｄ）に対して１〜３％添加することが好ましい。
【００１４】
以上のように、本発明により生物膜処理設備に活性汚泥設備からの浮遊性汚泥を添加することにより、活性汚泥設備からの余剰汚泥を有効に利用して、各生物担体に定着している微生物だけでは処理できなかった有機物（ＢＯＤ）を処理することが可能になり、排水原水のＢＯＤ除去率を高い水準で安定して維持することができる。
【００１５】
【実施例】
次に、本発明を実施例により、さらに詳細に説明するが、本発明は、これらの例によってなんら限定されるものではない。
なお、以下の実施例および比較例の生物膜処理設備におけるデータは１５日間の連続処理における平均値である。
【００１６】
実施例１
図１に示すフローによって生物膜処理設備で製紙工程からの抄紙系排水の処理を行なった。生物膜処理設備には紐状担体を有するバイオフリンジ（三菱化工機（株）製、６．２ｍ×２２ｍ 高さ５ｍ）を用い、抄紙系排水３００００ｍ３／Ｄを処理した。原料排水のＢＯＤ負荷は１９５０ＫＧ／Ｄであり、水温２６℃である。原水槽においてｐＨ７．５に調整した後、生物膜処理設備で処理した。添加する浮遊性汚泥は古紙再生処理工程からの古紙系排水を処理する活性汚泥設備の余剰汚泥を用いた。該活性汚泥設備では、先ず古紙系排水を凝集沈殿処理設備で排水ＳＳ（浮遊物質）濃度を５０ｍｇ／Ｌ以下とした後、活性汚泥設備に供給し、活性汚泥設備において排水の滞留時間約７時間、温度２１〜３６℃、ｐＨ値６．８〜７．２、溶存酸素量（ＤＯ値）１．０〜３．５ｍｇ／Ｌ、返送汚泥濃度８０００〜１１０００ｍｇ／Ｌ、返送汚泥率３６％、ＭＬＳＳ濃度３０００〜３５００ｍｇ／Ｌ、ＢＯＤ：Ｎ：Ｐの比率で１００：４〜５：０．８〜１．５の条件で運転した。
この浮遊性汚泥を原水槽に導入し、浮遊性汚泥の添加量は３５００ＫＧ／Ｄで、活性汚泥設備から添加される浮遊性汚泥濃度が生物膜処理設備内でほぼ１１６ｍｇ／Ｌとなるように添加した。生物膜処理設備における排水の滞留時間は２時間であり、生物膜処理設備内の溶存酸素量（ＤＯ値）が３．０〜３．５ｍｇ／Ｌとなるように曝気を行なった。この結果、生物膜処理設備出口排水のＢＯＤ濃度は３．１ｍｇ／Ｌであり、原料排水のＢＯＤ除去率は９５％であった。
【００１７】
比較例１
実施例１において活性汚泥設備からの浮遊性汚泥を生物膜処理設備に添加しなかった以外は実施例１と同様に行なった。この結果、生物膜処理設備出口排水のＢＯＤ濃度は２１ｍｇ／Ｌであり、原料排水のＢＯＤ除去率は７５％であった。
【００１８】
【発明の効果】
本発明によれば、活性汚泥設備からの浮遊性汚泥（余剰汚泥）を生物膜処理設備に添加することにより、生物担体に定着している微生物だけでは処理できなかった有機物（ＢＯＤ）を処理することができるようになり、微生物菌体の食物連鎖や生物担体よりの微生物の剥離等による活性度の低下を抑制することができる。
また、生物膜処理設備における変動に対応して浮遊性汚泥の添加量を変えることができるので、変動に対する対応が容易となり、これにより活性汚泥設備からの余剰汚泥の有効利用が図られると共に、生物膜排水処理設備においてＢＯＤ除去率を９０％以上の高い水準で安定して維持することができる。
【図面の簡単な説明】
【図１】本発明により、製紙製造工程からの抄紙系排水を生物膜処理設備で処理し、古紙再生処理工程からの古紙系排水を活性汚泥設備で処理して、活性汚泥設備から得られた浮遊性汚泥を生物膜処理設備に添加する場合のフロー図である。
【図２】図２は生物膜処理設備の説明図であり、左図は従来の生物膜処理設備で浮遊性汚泥を添加しない場合、右図は本発明により活性汚泥を生物膜処理設備に浮遊性汚泥を添加した場合の状況を模式的に示したものである。
【符号の説明】
１：抄紙系排水
２：原水槽（排水ピット）
３：排水給水ポンプ
４：生物膜処理設備
５：凝集沈殿設備
９：古紙系排水
１０：凝集沈殿設備
１１：活性汚泥設備
１２：浮遊性汚泥（余剰汚泥）
２０：生物膜処理設備
２１：生物担体
２２：ブロワ
２３：定着性微生物
２４：浮遊性汚泥（浮遊性微生物）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating wastewater in a biofilm treatment facility. More specifically, the present invention relates to a method for treating wastewater capable of stably obtaining a high BOD removal rate in a biofilm treatment facility.
[0002]
[Prior art]
Conventionally, for the treatment of various organic wastewaters, biofilm treatment equipment that treats in an aerobic biological treatment tank in which biological carriers such as honeycomb, cylinder, sphere, and plate made of synthetic fiber or nonwoven fabric are arranged Is widely used.
In this biofilm treatment facility, sludge, which is an aerobic microorganism, adheres and proliferates on the surface of the biological carrier, and the adhered sludge oxidatively decomposes organic matter in the wastewater by biological action. There is no need to perform any operation, no bulking phenomenon is observed, and maintenance is easy.
As the microorganism-immobilized carrier in such a biofilm treatment facility, a mall-shaped carrier in which a large number of short fibers protrude from a tire activated carbon or a string-shaped shaft is known. (See, for example, Patent Documents 1 and 2)
[0003]
As described above, biofilm treatment equipment can treat wastewater without generating excess sludge unlike activated sludge equipment.However, treating high-concentration wastewater requires a lot of cost, so it is relatively expensive. Activated sludge equipment is used when treating wastewater with a high concentration, and biofilm treatment equipment is often used when treating wastewater with a low concentration.
For example, in a paper mill that manufactures various types of paper, biofilm treatment equipment is used for low-concentration wastewater, and activated sludge equipment is used for high-concentration wastepaper wastewater. Many. However, the biofilm treatment equipment has a limited response to fluctuations in wastewater, and the BOD removal rate is at most 70 to 80%, making it difficult to further increase the BOD removal rate.
[0004]
[Patent Document 1]
JP 2002-79285 A [Patent Document 2]
JP-A-2002-355688
[Problems to be solved by the invention]
An object of the present invention is to provide a method capable of stably maintaining a BOD removal rate at a high level in a biofilm wastewater treatment facility under such circumstances.
[0006]
[Means for Solving the Problems]
The present inventor has conducted intensive studies on the biofilm wastewater treatment facility having the above-described problems, and as a result, added the suspended sludge (excess sludge) generated from the activated sludge facility to the biofilm wastewater treatment facility. It has been found that the BOD removal rate is improved in the treatment equipment, the excess sludge can be effectively used, and the BOD removal rate can be stably maintained at a high level. The present invention has been completed based on such findings.
[0007]
That is, the present invention
(1) In a biofilm treatment facility for biologically purifying wastewater by contacting a biological carrier adhering to a biofilm surface, adding floating sludge obtained by an activated sludge facility to the biofilm treatment facility. Characteristic wastewater treatment method,
(2) The method for treating wastewater according to (1), wherein the wastewater is papermaking wastewater from a papermaking process;
(3) The method for treating wastewater according to the above (1) or (2), wherein the activated sludge facility is a wastewater treatment facility from a used paper recycling process.
(4) The method for treating wastewater according to any one of (1) to (3), wherein the suspended sludge from the activated sludge facility and wastewater to be treated by the biofilm treatment facility are mixed in advance and supplied to the biofilm treatment facility.
(5) The wastewater according to any one of (1) to (4), wherein the suspended sludge added from the activated sludge facility is added such that the sludge concentration becomes 100 to 150 mg / L in the biofilm treatment facility. Processing method,
(6) Sludge Concentration buoyant sludge is added from the active sludge equipment is 5000~15000mg / L, the floating sludge volume (m 3 / D) is, wastewater flowing into the biological membrane treatment facility (m 3 / D) The method for treating wastewater according to any one of (1) to (5) above, which is 1 to 3% based on D).
(7) The sludge amount of the suspended sludge added from the activated sludge facility is in the range of 0.3 to 0.7 in weight ratio with respect to the T-BOD load in the biofilm treatment facility. Wastewater treatment method according to any of the above,
(8) The method for treating wastewater according to any one of (1) to (7), wherein the BOD removal rate in the biofilm treatment equipment represented by the following formula is 90% or more;
BOD removal rate (%) = [BOD load of wastewater at the biofilm treatment facility inlet (kg / D) −BOD load of wastewater at the exit of biofilm treatment facility (kg / D)] / [BOD load of wastewater at the biofilm treatment facility entrance ( kg / D)] x 100
I will provide a.
In the present invention, the suspended sludge added to the biofilm treatment equipment indicates wastewater in which activated sludge is floating, and the suspended sludge amount (m 3 / D) is the amount of wastewater containing the activated sludge. The sludge concentration (mg / L) of the suspended sludge is the concentration of the activated sludge floating in the wastewater, and the sludge amount is the amount (kg / D) of the activated sludge floating in the wastewater.
In some cases, the coagulation and sedimentation treatment equipment is not provided before the biofilm treatment equipment. Therefore, the amount of suspended sludge added from the activated sludge equipment of the above (7) is determined by the T-BOD load of the biofilm treatment equipment. (Total BOD load including suspended solids) is used.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. FIG. 1 shows an embodiment of the present invention, in which a papermaking wastewater from a papermaking process is treated by a biofilm treatment facility, and a wastepaper wastewater from a wastepaper recycling process is treated by an activated sludge facility to obtain activated sludge. It is a flowchart in the case of adding the suspended sludge obtained from the equipment to the biofilm treatment equipment.
In FIG. 1, papermaking wastewater 1 from a papermaking process is first sent to a raw water tank (drain pit) 2 for wastewater, and then enters a biofilm treatment facility 4 via a wastewater feed pump 3. In a biofilm treatment facility, a biofilm is attached to a carrier as described later, and a contact treatment with air is performed by an air diffuser to decompose organic substances in papermaking wastewater by the biofilm. The wastewater subjected to the biofilm treatment is discharged from the flow path 7 through the coagulation sedimentation treatment equipment 5 and the flow path 6. In addition, a bypass line 8 is provided in which a part of the papermaking wastewater 1 is directly sent to the coagulation and sedimentation treatment equipment 5 without passing through the biofilm treatment equipment 4 depending on the state of the wastewater.
[0009]
On the other hand, wastewater wastewater 9 from the wastepaper recycling treatment step is sent to the activated sludge equipment 11 via the coagulation sedimentation treatment equipment 10, and the treated wastewater is discharged from the flow path 7 together with the wastewater from the biofilm treatment equipment. In the present invention, the suspended sludge (excess sludge) obtained from the activated sludge facility is added to the biofilm treatment facility via the
[0010]
The wastewater supplied to the biofilm treatment equipment used in the present invention is preferably controlled to have a pH of about 7 to 8 by adding an acid or an alkali in a raw water tank. The suspended sludge to be added to the biofilm treatment facility is not particularly limited, but the wastewater treated to 50 mg / L or less of SS (suspended matter) in the wastewater in the coagulation sedimentation treatment facility has a pH of 6.5 to 6.5 in the activated sludge apparatus. 7.5, it is preferable that the nutritional balance is controlled to be about 100: 4 to 5: 0.8 to 1.5 in the ratio of BOD: N: P, and the sludge concentration is 5000 to 15000 mg / L. .
The shape of the biological carrier of the biofilm treatment equipment is not particularly limited, and various shapes such as a honeycomb shape, a cylindrical shape, a spherical shape, a plate shape, and a string shape made of synthetic fiber or nonwoven fabric are used. Usually, the temperature of the wastewater in the biofilm treatment facility is 20 to 35 ° C., the residence time is about 1.5 to 2.5 hours, and the amount of dissolved oxygen in the biofilm treatment facility is 3 to 5 mg / L by means of aeration means. Managed to a degree. It is preferable that the concentration of the suspended sludge added from the activated sludge facility be 100 to 150 mg / L in the biofilm treatment facility.
[0011]
Although the BOD removal rate of the biofilm treatment facility is at most 70 to 80%, the BOD removal rate of the raw wastewater represented by the following formula can be increased to 90% or more by adding the suspended sludge to the biofilm treatment facility according to the present invention. can do.
BOD removal rate (%) = [BOD load of wastewater at the biofilm treatment facility inlet (kg / D) −BOD load of wastewater at the exit of biofilm treatment facility (kg / D)] / [BOD load of wastewater at the biofilm treatment facility entrance ( kg / D)] x 100
The reason why such a high BOD removal rate can be obtained is considered as follows. FIG. 2 is an explanatory view of a biofilm treatment facility, and the left figure is a case where no suspended sludge is added in a conventional biofilm treatment facility. The inside of the biofilm treatment tank 20 is filled with a biological carrier 21, and air is blown from a blower 22 from the bottom. The fixing microorganisms 23 adhere to the surface of the biological carrier, and oxidatively decompose organic substances in the wastewater by biological action. In such a biofilm treatment facility, the number of colonies of microorganisms is determined by the capacity of the biological carrier, which is a dwelling place for the microbial cells. Therefore, the capacity is naturally limited, and the BOD removal rate is at most 70 to 80%.
The right figure shows a case where the activated sludge is injected into the biofilm treatment facility according to the present invention, and the suspended sludge (the suspended microorganisms) 24 added between the biological carriers 21 exists. Microbial cells increase and organic matter (BOD), which could not be treated only by microorganisms that have settled on each biological carrier, will be treated, so the treatment capacity will be enhanced, and the BOD removal rate of the raw wastewater will be 90% or more. It will be possible to do so.
[0012]
The types of microorganisms in the biofilm treatment facility are mainly composed of colonizing microorganisms such as filamentous bacteria, flagellates (protozoa), and rotifers (micrometamorphous animals). On the other hand, floating sludge obtained from activated sludge equipment differs depending on the type of wastewater from activated sludge equipment.For example, in the case of wastewater treatment equipment for wastewater wastewater, the types of microorganisms are mainly floc-forming bacteria and filamentous It is composed of planktonic microorganisms such as bacteria, sucking worms, rodent ciliates (protozoa), rotifers and nematodes (metamorphous animals). As described above, microorganisms different from the biofilm treatment equipment are added as suspended sludge, and are added between the respective biological carriers as described above. Treatment is accelerated, and the decrease in the activity due to the food chain of microbial cells and periodic exfoliation of microorganisms from biological carriers in biofilm treatment equipment can be minimized, and stable microbial morphology It is considered that the BOD removal rate can be maintained stably at a high level.
[0013]
The amount of suspended sludge added to the biofilm treatment facility depends on the state of the wastewater from the biofilm treatment facility and the wastewater supplying the suspended sludge. Usually, the sludge amount (kg / D) of the suspended sludge added from the activated sludge facility is about 0.3 to 0.7 in weight ratio to the T-BOD load (kg / D) in the biofilm treatment facility. Suspended sludge is added so that Of course, the amount of suspended sludge to be added to the biofilm treatment facility is determined by the operating conditions of the biofilm treatment facility, and it is necessary to change the amount of aerated air according to the amount of suspended sludge to be added.
The amount of suspended sludge (m 3 / D) added to the biofilm treatment facility is determined by the amount of wastewater (m 3 / D) flowing from the activated sludge to the sludge concentration of 5000 to 15000 mg / L and flowing into the biofilm treatment facility. ) Is preferably 1 to 3%.
[0014]
As described above, by adding the floating sludge from the activated sludge facility to the biofilm treatment facility according to the present invention, the surplus sludge from the activated sludge facility is effectively used, and the microorganisms that have settled on each biological carrier are effectively used. It is possible to treat organic matter (BOD) that could not be treated only by itself, and it is possible to stably maintain a high level of BOD removal rate of raw wastewater.
[0015]
【Example】
Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
In addition, the data in the biofilm processing equipment of the following Examples and Comparative Examples are average values in 15 days of continuous processing.
[0016]
Example 1
The papermaking wastewater from the papermaking process was treated in the biofilm treatment facility according to the flow shown in FIG. The biofilm treatment facility used a biofringe having a string-shaped carrier (Mitsubishi Kakohki Co., Ltd., 6.2 mx 22 m, 5 m height) to treat 30,000 m 3 / D of papermaking wastewater. The BOD load of the raw material wastewater is 1950 KG / D, and the water temperature is 26 ° C. After adjusting the pH to 7.5 in the raw water tank, the mixture was treated in a biofilm treatment facility. As the suspended sludge to be added, surplus sludge of activated sludge equipment for treating waste paper wastewater from the waste paper recycling process was used. In the activated sludge facility, first, waste paper wastewater is reduced to a concentration of 50 mg / L or less by a coagulation sedimentation treatment facility, and then supplied to the activated sludge facility. In the activated sludge facility, the residence time of the wastewater is about 7 hours. , Temperature 21-36 ° C, pH value 6.8-7.2, dissolved oxygen amount (DO value) 1.0-3.5 mg / L, returned sludge concentration 8000-11000 mg / L, returned sludge rate 36%, MLSS The operation was performed at a concentration of 3000 to 3500 mg / L and a ratio of BOD: N: P of 100: 4 to 5: 0.8 to 1.5.
The suspended sludge is introduced into the raw water tank, and the amount of the suspended sludge added is 3500 KG / D, and the concentration of the suspended sludge added from the activated sludge facility is set to be approximately 116 mg / L in the biofilm treatment facility. did. The residence time of the wastewater in the biofilm treatment facility was 2 hours, and aeration was performed so that the dissolved oxygen amount (DO value) in the biofilm treatment facility was 3.0 to 3.5 mg / L. As a result, the BOD concentration of the wastewater from the biofilm treatment facility outlet was 3.1 mg / L, and the BOD removal rate of the raw material wastewater was 95%.
[0017]
Comparative Example 1
Example 1 was repeated, except that the suspended sludge from the activated sludge facility was not added to the biofilm treatment facility. As a result, the BOD concentration of the biofilm treatment facility outlet wastewater was 21 mg / L, and the BOD removal rate of the raw material wastewater was 75%.
[0018]
【The invention's effect】
According to the present invention, by adding suspended sludge (excess sludge) from an activated sludge facility to a biofilm treatment facility, an organic matter (BOD) that cannot be treated only by microorganisms fixed on a biological carrier is treated. It is possible to suppress the decrease in the activity due to the food chain of the microbial cells and the detachment of the microorganisms from the biological carrier.
In addition, since the amount of suspended sludge added can be changed in response to fluctuations in the biofilm treatment equipment, it is easy to cope with the fluctuations, thereby enabling the effective use of excess sludge from the activated sludge equipment and the biological sludge. In the membrane wastewater treatment equipment, the BOD removal rate can be stably maintained at a high level of 90% or more.
[Brief description of the drawings]
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a papermaking wastewater from a papermaking manufacturing process treated by a biofilm treatment facility, and a wastepaper wastewater from a wastepaper recycling treatment process treated by an activated sludge facility according to the present invention. It is a flowchart in the case of adding suspended sludge to a biofilm treatment facility.
FIG. 2 is an explanatory view of a biofilm treatment facility. The left figure shows a conventional biofilm treatment facility in which floating sludge is not added, and the right figure floats activated sludge in the biofilm treatment facility according to the present invention. This is a schematic view showing the situation in which anaerobic sludge is added.
[Explanation of symbols]
1: Papermaking wastewater 2: Raw water tank (drainage pit)
3: Wastewater feed pump 4: Biofilm treatment equipment 5: Coagulation sedimentation equipment 9: Wastepaper wastewater 10: Coagulation sedimentation equipment 11: Activated sludge equipment 12: Floating sludge (excess sludge)
20: Biofilm treatment facility 21: Biological carrier 22: Blower 23: Fixing microorganism 24: Floating sludge (Floating microorganism)
Claims (8)
ＢＯＤ除去率（％）＝［生物膜処理設備入口排水のＢＯＤ負荷（ｋｇ／Ｄ）−生物膜処理設備出口排水のＢＯＤ負荷（ｋｇ／Ｄ） ］／［生物膜処理設備入口排水のＢＯＤ負荷（ｋｇ／Ｄ）］×１００The wastewater treatment method according to any one of claims 1 to 7, wherein a BOD removal rate in the biofilm treatment equipment represented by the following formula is 90% or more.
BOD removal rate (%) = [BOD load of biofilm treatment facility entrance wastewater (kg / D) −BOD load of biofilm treatment facility exit wastewater (kg / D)] / [BOD load of biofilm treatment facility entrance wastewater ( kg / D)] x 100
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