JPH1099886A - Removal of nitrogen from waste water by activated sludge circulating version - Google Patents
Removal of nitrogen from waste water by activated sludge circulating versionInfo
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- JPH1099886A JPH1099886A JP25470696A JP25470696A JPH1099886A JP H1099886 A JPH1099886 A JP H1099886A JP 25470696 A JP25470696 A JP 25470696A JP 25470696 A JP25470696 A JP 25470696A JP H1099886 A JPH1099886 A JP H1099886A
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- Prior art keywords
- bed
- anaerobic
- tank
- nitrogen
- aerobic
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Classifications
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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
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
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- Biological Treatment Of Waste Water (AREA)
- Activated Sludge Processes (AREA)
- Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、有機物と還元性窒
素を含む廃水を嫌気槽（脱窒槽）と好気槽（硝化槽）に
より循環処理した後に最終沈澱処理する活性汚泥循環変
法により廃水中の窒素を除去する方法に関する。TECHNICAL FIELD The present invention relates to a modified activated sludge circulation method in which wastewater containing organic matter and reducing nitrogen is circulated in an anaerobic tank (denitrification tank) and an aerobic tank (nitrification tank), and then subjected to final precipitation. And a method for removing nitrogen therein.
【０００２】[0002]
【従来の技術】従来、活性汚泥循環変法による廃水の窒
素除去においては、固形物滞留時間（ＳＲＴ：Sludge R
etention Time)および硝化槽の溶存酸素（ＤＯ：Disolv
ed Oxygen)の管理により、窒素を安定して除去し、良好
な処理水質を維持できるとされていた。2. Description of the Related Art Conventionally, in the removal of nitrogen from wastewater by a modified activated sludge circulation method, the solid matter retention time (SRT: Sludge R)
retention time) and dissolved oxygen in the nitrification tank (DO: Disolv
ed Oxygen) was said to be able to stably remove nitrogen and maintain good treated water quality.
【０００３】すなわち、嫌気槽と好気槽で構成される反
応タンク内での固形物滞留時間（ＳＲＴ）を長くとれ
ば、水温が低い期間でも硝化細菌の増殖が進みアンモニ
アの硝化が起こり易い。また、硝化が進んで硝酸や亜硝
酸を含む活性汚泥混合液を、炭素系有機物が存在する条
件下で溶存酸素（ＤＯ）の無い状態に保てば、脱窒細菌
が働き窒素除去が進行する。[0003] That is, if the solids retention time (SRT) in the reaction tank composed of the anaerobic tank and the aerobic tank is long, the nitrifying bacteria will proliferate even in a low water temperature period, and the nitrification of ammonia is likely to occur. In addition, if the activated sludge mixture containing nitric acid and nitrite is kept free of dissolved oxygen (DO) under conditions where carbon-based organic matter is present, the denitrifying bacteria work and nitrogen removal proceeds. .
【０００４】上記従来の方法は、主として都市廃水を処
理対象としており、その限りにおいては良好な処理水質
が得られていた。しかし、本発明者が検討を行った結
果、工場廃水、工場廃水が流入する都市下水、汚泥脱離
液などを処理対象とした場合、都市下水と比較して窒素
分や有機物濃度が高いため、固形物滞留時間ＳＲＴと溶
存酸素ＤＯを管理する従来の方法では十分な窒素除去を
行えないことが分かった。[0004] The above-mentioned conventional methods mainly treat municipal wastewater, and as far as it is concerned, good treated water quality has been obtained. However, as a result of the study by the present inventor, factory wastewater, municipal sewage into which factory wastewater flows, sludge desorbed liquid and the like, because nitrogen and organic matter concentration is higher than municipal sewage, It has been found that the conventional method of managing the solid retention time SRT and the dissolved oxygen DO cannot perform sufficient nitrogen removal.
【０００５】[0005]
【発明が解決しようとする課題】本発明は、窒素分濃度
と有機物濃度が高い廃水でも十分な窒素除去を行うこと
ができる、活性汚泥循環変法による廃水の窒素除去方法
を提供することを目的とする。SUMMARY OF THE INVENTION An object of the present invention is to provide a method for removing nitrogen from wastewater by a modified activated sludge circulation method, which can sufficiently remove nitrogen even from wastewater having a high nitrogen content and organic matter concentration. And
【０００６】[0006]
【課題を解決するための手段】上記の目的は、本発明に
よれば、有機物と還元性窒素を含む廃水を嫌気槽と好気
槽により循環処理した後に最終沈澱処理する活性汚泥循
環変法による廃水の窒素除去方法において、固形物滞留
時間を管理すると共に嫌気槽の酸化還元電位を制御する
ことを特徴とする活性汚泥循環変法による廃水の窒素除
去方法によって達成される。According to the present invention, there is provided, according to the present invention, a modified activated sludge circulation method in which waste water containing organic matter and reducing nitrogen is circulated in an anaerobic tank and an aerobic tank, and then subjected to final sedimentation. The nitrogen removal method for wastewater is achieved by a method for removing nitrogen from wastewater by a modified activated sludge circulation method, which comprises controlling the residence time of solids and controlling the oxidation-reduction potential of an anaerobic tank.
【０００７】本発明は、本発明者が新規に見出した下記
の原理に基づいている。すなわち、嫌気槽の酸化還元電
位（ＯＲＰ：Oxidation Reduction Potential）が低下
し過ぎると、好気槽でいくら曝気しても好気槽のＯＲＰ
は上昇せず、好気槽内で硝化反応が進行せず、結局嫌気
槽内での脱窒反応への反応物質の供給がなされないた
め、窒素除去が行われない。従来の知見では、好気槽の
ＤＯを２ｍｇ／Ｌ以上に保てば硝化反応が進むとされて
おり、嫌気槽の嫌気度が硝化細菌に与える影響が無視さ
れてきた。The present invention is based on the following principle newly found by the present inventors. In other words, if the oxidation-reduction potential (ORP) of the anaerobic tank is too low, the ORP of the aerobic tank is no matter how much aeration is performed in the aerobic tank.
Does not rise, the nitrification reaction does not proceed in the aerobic tank, and no nitrogen is removed because the reactants are not supplied to the denitrification reaction in the anaerobic tank. According to conventional knowledge, the nitrification reaction proceeds if DO in the aerobic tank is maintained at 2 mg / L or more, and the effect of the anaerobic degree of the anaerobic tank on nitrifying bacteria has been neglected.
【０００８】これは、嫌気槽の嫌気度が大き過ぎると、
好気槽から嫌気槽に循環してきた活性汚泥中の硝化細菌
の活性が低下してしまい、好気槽での硝化反応が進行し
なくなるためである。そこで、本発明の方法において
は、嫌気槽の酸化還元電位（ＯＲＰ）を適度な範囲に制
御することにより、硝化細菌の活性を維持し、好気槽で
の硝化反応の進行を確保する。[0008] This is because if the anaerobic degree of the anaerobic tank is too large,
This is because the activity of the nitrifying bacteria in the activated sludge circulated from the aerobic tank to the anaerobic tank decreases, and the nitrification reaction in the aerobic tank does not proceed. Therefore, in the method of the present invention, by controlling the oxidation-reduction potential (ORP) of the anaerobic tank in an appropriate range, the activity of the nitrifying bacteria is maintained, and the progress of the nitrification reaction in the aerobic tank is ensured.
【０００９】従来の方法では固形物滞留時間ＳＲＴと硝
化槽の溶存酸素ＤＯを管理していた。これに対して、本
発明の方法では固形物滞留時間ＳＲＴと酸化還元電位Ｏ
ＲＰを管理するが、これに加えて更に好気槽の溶存酸素
ＤＯも管理するようにしてもよい。従来から知られてい
るように、好気槽での硝化反応は下記式（１）（２）に
よりアンモニアが亜硝酸へ、亜硝酸が硝酸へ酸化される
過程で代表され、嫌気槽での脱窒反応は下記式（３）
（４）（５）により硝酸が亜硝酸へ、亜硝酸および硝酸
が窒素ガスへ還元される過程で代表される。In the conventional method, the solid retention time SRT and the dissolved oxygen DO in the nitrification tank were controlled. In contrast, in the method of the present invention, the solid retention time SRT and the redox potential O
Although the RP is managed, the dissolved oxygen DO of the aerobic tank may be further managed in addition to the RP. As conventionally known, a nitrification reaction in an aerobic tank is represented by a process in which ammonia is oxidized to nitrite and nitrite is converted to nitric acid by the following equations (1) and (2). The nitrogen reaction is given by the following formula (3)
(4) The process is represented by (5) in which nitric acid is reduced to nitrous acid and nitrous acid and nitric acid are reduced to nitrogen gas.
【００１０】〔好気槽での硝化反応〕 ＮＨ4 - ＋（３／２）Ｏ2 →ＮＯ2 - ＋Ｈ2 Ｏ＋２Ｈ+ ・・・・(1) ＮＯ2 - ＋（１／２）Ｏ2 →ＮＯ3 - ・・・・・・・・・・・・(2) 〔嫌気槽での脱窒反応〕 ２ＮＯ3 - ＋２（Ｈ2 ）→２ＮＯ2 - ＋２Ｈ2 Ｏ・・・・・・・(3) ２ＮＯ2 - ＋３（Ｈ2 ）→Ｎ2 ＋２ＯＨ- ＋２Ｈ2 Ｏ・・・・・(4) ２ＮＯ3 - ＋５（Ｈ2 ）→Ｎ2 ＋２ＯＨ- ＋４Ｈ2 Ｏ・・・・・(5) 好気槽の溶存酸素ＤＯは基本的には硝化細菌の活性すな
わち硝化反応の反応速度の指標であり、これに対して嫌
気槽の酸化還元電位ＯＲＰは処理水中の酸化物質と還元
物質の比すなわち嫌気槽での脱窒反応の平衡の位置を示
す指標である。現実に起こり得る好気槽の溶存酸素ＤＯ
と嫌気槽の酸化還元電位ＯＲＰとの対応関係には、下記
の４通りの場合がある。[0010] [nitrification reaction in the aerobic tank] NH 4 - + (3/2) O 2 → NO 2 - + H 2 O + 2H + ···· (1) NO 2 - + (1/2) O 2 → NO 3 - ············ (2) [denitrification in the anaerobic tank] 2NO 3 - +2 (H 2) → 2NO 2 - + 2H 2 O ······· ( 3) 2NO 2 − +3 (H 2 ) → N 2 + 2OH − + 2H 2 O (4) 2NO 3 − +5 (H 2 ) → N 2 + 2OH − + 4H 2 O (5) The dissolved oxygen DO in the aerobic tank is basically an indicator of the activity of the nitrifying bacteria, that is, the reaction rate of the nitrification reaction, whereas the oxidation-reduction potential ORP of the anaerobic tank is the ratio of the oxidizing substance to the reducing substance in the treated water, ie, It is an index indicating the position of the equilibrium of the denitrification reaction in the anaerobic tank. Dissolved oxygen DO in the aerobic tank that can actually occur
There are the following four cases in which there is a correspondence relationship between the parameter and the oxidation-reduction potential ORP of the anaerobic tank.
【００１１】まず、好気槽の溶存酸素ＤＯが高く、嫌気
槽の酸化還元電位ＯＲＰが０〜−３００ｍＶの嫌気度の
場合は、好気槽で十分な量の溶存酸素ＤＯの存在により
硝化細菌の活性が高く硝化反応が十分に進行し、同時に
嫌気槽での脱窒反応も十分に進行している。すなわち、
好気槽での硝化反応が十分進行していることによりアン
モニアの酸化による亜硝酸および硝酸が十分に生成して
おり、嫌気槽での脱窒反応へ反応物質が十分に供給され
平衡の位置が反応物質側（上記式(3) 〜(5) で左側）で
はなく生成物質側（右）へ寄っている。この場合は、十
分に窒素除去された良好な処理水質が得られる。この良
好な処理水質に対して、好気槽の溶存酸素ＤＯが高いこ
とと嫌気槽の酸化還元電位ＯＲＰが０〜−３００ｍＶの
範囲にあることが、正しく対応している。First, in the case where the dissolved oxygen DO in the aerobic tank is high and the oxidation-reduction potential ORP in the anaerobic tank is anaerobic of 0 to -300 mV, the nitrifying bacterium is caused by the presence of a sufficient amount of dissolved oxygen DO in the aerobic tank. Has a high activity, and the nitrification reaction has sufficiently proceeded, and at the same time, the denitrification reaction in the anaerobic tank has also proceeded sufficiently. That is,
Since the nitrification reaction in the aerobic tank has proceeded sufficiently, nitrous acid and nitric acid have been sufficiently generated by the oxidation of ammonia, and the reactants have been sufficiently supplied to the denitrification reaction in the anaerobic tank, and the position of the equilibrium has been adjusted. It is not to the reactant side (left side in the above formulas (3) to (5)) but to the product side (right). In this case, good treated water quality from which nitrogen has been sufficiently removed can be obtained. For this good treated water quality, the fact that the dissolved oxygen DO in the aerobic tank is high and the oxidation-reduction potential ORP in the anaerobic tank is in the range of 0 to -300 mV correctly correspond.
【００１２】次に、好気槽の溶存酸素ＤＯは高いが、嫌
気槽の酸化還元電位ＯＲＰが−３００ｍＶ以下までの嫌
気度に低下した場合、好気槽で十分な溶存酸素ＤＯが存
在するにも係わらず、前記のように嫌気槽通過中に嫌気
度が大きすぎて硝化細菌の活性が低下する等、溶存酸素
ＤＯ以外の要因で硝化細菌の活性が低下し好気槽での硝
化反応が進行しておらず、その結果、嫌気槽での脱窒反
応も反応物質の不足により進行していない。すなわち、
硝化反応の平衡（上記式（１））が生成物質側（右）で
はなく反応物質側（左）に寄っている。結局この場合に
は、窒素除去が十分に行われず処理水質が悪化する。こ
の処理水質の悪化に対して、好気槽の溶存酸素ＤＯが高
いことは正しく対応していない。嫌気槽の酸化還元電位
ＯＲＰが低すぎることが正しく対応している。Next, when the dissolved oxygen DO in the aerobic tank is high, but the oxidation-reduction potential ORP in the anaerobic tank is reduced to an anaerobic level of -300 mV or less, if the dissolved oxygen DO is sufficiently present in the aerobic tank. Nevertheless, as described above, the activity of nitrifying bacteria decreases due to factors other than dissolved oxygen DO, such as the anaerobicity is too large during passage through the anaerobic tank, and the nitrification reaction in the aerobic tank decreases. As a result, the denitrification reaction in the anaerobic tank has not progressed due to a shortage of reactants. That is,
The equilibrium of the nitrification reaction (formula (1)) is closer to the reactant side (left) rather than the product side (right). Eventually, in this case, the nitrogen removal is not sufficiently performed, and the quality of the treated water deteriorates. The fact that the dissolved oxygen DO in the aerobic tank is high does not correspond to the deterioration of the treated water quality. It corresponds correctly that the oxidation-reduction potential ORP of the anaerobic tank is too low.
【００１３】さらに好気槽のＤＯが高く、しかも嫌気槽
のＯＲＰが０ｍＶ以上となる場合がある。これは都市下
水などに雨水が混入する場合などに見られる。この場
合、ＳＲＴが５日以上あれば硝化反応（１），（２）は
進行するが、脱窒反応（３）（４）（５）は進行しにく
い。この処理水質の悪化に対しては、嫌気槽のＯＲＰが
高すぎることが対応している。好気槽のＤＯが高いこと
は正しく対応していない。Further, the DO of the aerobic tank may be high, and the ORP of the anaerobic tank may be 0 mV or more. This is seen, for example, when rainwater is mixed into urban sewage. In this case, if the SRT is 5 days or more, the nitrification reactions (1) and (2) proceed, but the denitrification reactions (3), (4) and (5) hardly proceed. To cope with the deterioration of the treated water quality, the ORP of the anaerobic tank is too high. The high DO of the aerobic tank does not correspond correctly.
【００１４】最後に、好気槽の溶存酸素ＤＯが低い場合
には硝化反応および有機物の分解も進行しないので、嫌
気槽の脱窒反応への反応物質の供給も無く、酸化還元電
位ＯＲＰも必然的に低くなる。この場合は、処理水質は
当然悪化する。この処理水質の悪化に対して、好気槽の
溶存酸素ＤＯが低いことと嫌気槽の酸化還元電位ＯＲＰ
が低すぎることは、いずれも正しく対応している。Finally, when the dissolved oxygen DO in the aerobic tank is low, the nitrification reaction and the decomposition of organic substances do not proceed, so that there is no supply of reactants to the denitrification reaction in the anaerobic tank and the oxidation-reduction potential ORP is inevitable. Lower. In this case, the quality of the treated water naturally deteriorates. In response to the deterioration of the treated water quality, the dissolved oxygen DO in the aerobic tank is low and the oxidation-reduction potential ORP in the anaerobic tank is low.
Are too low, all correspond correctly.
【００１５】上記第２、第３の場合のように、好気槽の
溶存酸素ＤＯが高くても、溶存酸素ＤＯ以外の要因によ
って硝化細菌の活性が低下し硝化反応が進行しない場合
があるため、従来のように固形物滞留時間ＳＲＴと好気
槽の溶存酸素ＤＯのみの管理では、処理水質を正確に制
御できない。これに対して本発明においては、固形物滞
留時間ＳＲＴと嫌気槽の酸化還元電位ＯＲＰとを適当な
範囲に管理するので、酸化還元電位ＯＲＰにより処理水
質を直接監視し正確に制御することができる。As in the second and third cases, even if the dissolved oxygen DO in the aerobic tank is high, the activity of the nitrifying bacteria may decrease due to factors other than the dissolved oxygen DO, and the nitrification reaction may not proceed. However, the conventional control of only the solid retention time SRT and the dissolved oxygen DO in the aerobic tank cannot accurately control the quality of the treated water. On the other hand, in the present invention, since the solids retention time SRT and the oxidation-reduction potential ORP of the anaerobic tank are managed in appropriate ranges, the quality of the treated water can be directly monitored and accurately controlled by the oxidation-reduction potential ORP. .
【００１６】特に、都市廃水に比べて窒素分の濃度が高
い工業廃水を処理する場合には、嫌気槽の嫌気度が大き
くなり易く、その結果、嫌気槽通過中に硝化細菌の活性
が低下し、好気槽の溶存酸素ＤＯが高くても、硝化反応
が進行せず処理水質が悪化する場合がある。好気槽の溶
存酸素ＤＯを管理指標とする従来の方法ではこの場合に
正確に対処して良好な水質を得ることができないが、本
発明の方法では嫌気槽の酸化還元電位ＯＲＰの制御によ
り常に安定して十分に窒素除去を行い良好な処理水質を
得ることができる。In particular, when treating industrial wastewater having a higher nitrogen content than municipal wastewater, the anaerobic tank tends to become anaerobic, resulting in a decrease in the activity of nitrifying bacteria during passage through the anaerobic tank. Even if the dissolved oxygen DO in the aerobic tank is high, the nitrification reaction does not proceed, and the quality of the treated water may be deteriorated. In the conventional method using dissolved oxygen DO in the aerobic tank as a control index, it is not possible to accurately cope with this case and obtain good water quality. However, in the method of the present invention, the control of the oxidation-reduction potential ORP in the anaerobic tank always results. Nitrogen can be removed stably and sufficiently to obtain good treated water quality.
【００１７】このように嫌気槽の酸化還元電位ＯＲＰを
制御することの必要性は、窒素分濃度が比較的低い都市
廃水を前提としていた従来の方法では見逃されてきた新
たな視点である。より具体的には、嫌気槽の酸化還元電
位ＯＲＰを脱窒反応に適した０ｍＶ〜−３００ｍＶ（Ａ
ｇ／ＡｇＣｌ基準。以下、酸化還元電位ＯＲＰについて
は全て同様。）、より厳密には−１００〜−２００ｍＶ
に維持するように、嫌気槽を曝気および／または表面攪
拌することが望ましい。嫌気槽の脱窒反応を進行させる
ために必要な嫌気状態を確保するには酸化還元電位ＯＲ
Ｐを０ｍＶ以下にすることが望ましい。これは脱窒細菌
は嫌気状態はもちろん、好気状態でも増殖し得る通性細
菌であり、好気状態では亜硝酸および硝酸から酸素を奪
うよりも外囲環境から酸素を奪うようになり、脱窒反応
が進行しないためである。The necessity of controlling the oxidation-reduction potential ORP of the anaerobic tank as described above is a new viewpoint that has been overlooked by the conventional method that presupposes urban wastewater having a relatively low nitrogen concentration. More specifically, the oxidation-reduction potential ORP of the anaerobic tank is set to 0 mV to -300 mV (A
g / AgCl standard. Hereinafter, the same applies to the oxidation-reduction potential ORP. ), More strictly -100 to -200 mV
It is desirable to aerate and / or agitate the surface of the anaerobic tank so as to maintain In order to secure the anaerobic state required to advance the denitrification reaction in the anaerobic tank, the oxidation-reduction potential OR
It is desirable that P be 0 mV or less. This is a denitrifying bacterium, which is a facultative bacterium that can grow not only in anaerobic conditions but also in aerobic conditions.In aerobic conditions, it deprives the surrounding environment of oxygen rather than deprives nitrite and nitrate of oxygen. This is because the nitrogen reaction does not proceed.
【００１８】嫌気槽通過中に硝化細菌の活性が低下し過
ぎないようにするためには嫌気槽の酸化還元電位ＯＲＰ
を−３００ｍＶ以上にすることが望ましい。−３００ｍ
Ｖ以下になるとＨ2 Ｓの発生等により、硝化菌が阻害を
受けると思われる。嫌気槽の酸化還元電位ＯＲＰを脱窒
反応に適した範囲に制御するのと併せて、好気槽の酸化
還元電位ＯＲＰも硝化反応に適した範囲に制御すること
が望ましい。その場合は、好気槽の酸化還元電位ＯＲＰ
を硝化反応に適した＋５０ｍＶ〜＋２００ｍＶに維持す
るように、好気槽を曝気および／または表面攪拌するこ
とが望ましい。酸化還元電位ＯＲＰを＋５０ｍＶ以上と
することにより、硝化反応が進行する。特に上限はない
が、＋２００ｍＶ以上より高くしても、硝化反応の進行
が更に促進されることはなく、余分な曝気あるいは表面
攪拌が無駄になる。The oxidation-reduction potential ORP of the anaerobic tank is set so that the activity of the nitrifying bacteria does not decrease too much during the passage through the anaerobic tank.
Is desirably -300 mV or more. -300m
When the voltage falls below V, nitrifying bacteria are considered to be inhibited due to generation of H 2 S and the like. In addition to controlling the oxidation-reduction potential ORP of the anaerobic tank to a range suitable for the denitrification reaction, it is desirable to control the oxidation-reduction potential ORP of the aerobic tank to a range suitable for the nitrification reaction. In that case, the oxidation-reduction potential ORP of the aerobic tank
It is desirable to aerate the aerobic tank and / or agitate the surface so that is maintained at +50 mV to +200 mV suitable for the nitrification reaction. By setting the oxidation-reduction potential ORP to +50 mV or more, the nitrification reaction proceeds. Although there is no particular upper limit, even if it is higher than +200 mV, the progress of the nitrification reaction is not further promoted, and extra aeration or surface stirring is wasted.
【００１９】また、固形物滞留時間ＳＲＴおよび嫌気槽
の酸化還元電位ＯＲＰの管理と併せて、従来のように好
気槽の溶存酸素ＤＯ管理を行うことも望ましい。酸化還
元電位ＯＲＰにより処理水質を直接監視することができ
るが、酸化還元電位ＯＲＰが低下し処理水質が悪化した
際に、好気槽の溶存酸素ＤＯも監視していれば、水質悪
化の原因が好気槽の溶存酸素ＤＯであるか否かが直ちに
分かる。好気槽の溶存酸素ＤＯも管理する場合には、好
気槽の溶存酸素ＤＯを＋２ｍｇ／Ｌ以上に維持するよう
に、好気槽を曝気および／または表面攪拌することが望
ましい。In addition to the management of the solids retention time SRT and the oxidation-reduction potential ORP of the anaerobic tank, it is also desirable to manage the dissolved oxygen DO of the aerobic tank as in the prior art. The treatment water quality can be directly monitored by the oxidation-reduction potential ORP. However, when the oxidation-reduction potential ORP decreases and the treatment water quality deteriorates, if the dissolved oxygen DO in the aerobic tank is also monitored, the cause of the deterioration of the water quality is as follows. It is immediately known whether or not the dissolved oxygen is DO in the aerobic tank. When the dissolved oxygen DO in the aerobic tank is also controlled, it is desirable to aerate and / or agitate the surface of the aerobic tank so as to maintain the dissolved oxygen DO in the aerobic tank at +2 mg / L or more.
【００２０】本発明の方法によれば、水温が１５℃以上
の場合、十分に窒素除去を行い良好な処理水質を得るに
は、固形物滞留時間ＳＲＴは５日以上とれば十分であ
る。さらに、処理効率を上昇させるために、好気槽およ
び／または嫌気槽に、ウレタンフォーム担体、プラスチ
ックス担体、ポリアクリルアミドなどのゲル担体などの
浮遊担体を添加しても、かまわない。槽容量あたり１０
〜２０Ｖ／Ｖ％添加することにより、効率を２０〜４０
％向上できる。高炉水砕スラグや砂などの無機系単体を
１〜５Ｗ／Ｖ％添加しても効率を向上できる。According to the method of the present invention, when the water temperature is 15 ° C. or more, the solids retention time SRT of 5 days or more is sufficient to sufficiently remove nitrogen and obtain good treated water quality. Furthermore, in order to increase the processing efficiency, a floating carrier such as a urethane foam carrier, a plastics carrier, or a gel carrier such as polyacrylamide may be added to the aerobic tank and / or the anaerobic tank. 10 per tank capacity
The efficiency can be increased by 20 to 40 V by adding
%. Efficiency can be improved by adding 1 to 5 W / V% of an inorganic simple substance such as granulated blast furnace slag and sand.
【００２１】[0021]
〔実施例１〕図１に、本発明の活性汚泥循環変法による
窒素除去方法を行う廃水処理装置の配置例を模式的に示
す。有機物と還元性窒素を含む廃水が同図の左端から嫌
気槽に流入し、更に嫌気槽から好気槽に移動し、好気槽
で生成した硝化液は嫌気槽へ循環する。嫌気槽と好気槽
により循環処理した後に最終沈澱池で沈澱処理され、処
理水として図の右端から排出される。[Embodiment 1] FIG. 1 schematically shows an example of an arrangement of a wastewater treatment apparatus for performing a nitrogen removal method by a modified activated sludge circulation method of the present invention. Wastewater containing organic matter and reducing nitrogen flows into the anaerobic tank from the left end of the figure, moves from the anaerobic tank to the aerobic tank, and the nitrified liquid generated in the aerobic tank circulates to the anaerobic tank. After circulating in an anaerobic tank and an aerobic tank, it is settled in a final sedimentation basin and discharged from the right end of the figure as treated water.
【００２２】図１の装置により特に窒素分の多い皮革工
場の廃水を下記条件で処理した。 〔廃水〕（平均値。単位：ｍｇ／Ｌ） ｐＨ ：８．９ ＢＯＤ ：８５３ ＣＯＤ ：５８０ Ｓ−ＣＯＤ：４０８ ＴＯＣ ：４０５ ＳＳ ：５０６ Ｍ−Ａｌｋ：３７９ Ｔ−Ｎ ：２４７ Ｋ−Ｎ ：２４７ ＮＨ4 −Ｎ：８９ ＮＯ2 −Ｎ：０．２０ ＮＯ3 −Ｎ：０．１８ 〔処理条件〕 固形物滞留時間（ＳＲＴ）：５〜５７日 循環比（Ｒ） ：３（循環２００％，返送１００％） 水温 ：制御（１５〜１６℃） 酸化還元電位（ＯＲＰ） ：嫌気槽 (1) 無制御 (2) −２００ｍＶに制御 好気槽 ＋５０ｍＶに制御 （注）嫌気槽のＯＲＰ制御は曝気により実施。曝気には、基準として空気を、 補助として純酸素を用いた。Using the apparatus shown in FIG. 1, wastewater from a leather factory having a particularly high nitrogen content was treated under the following conditions. [Waste water] (Average value. Unit: mg / L) pH: 8.9 BOD: 853 COD: 580 S-COD: 408 TOC: 405 SS: 506 M-Alk: 379 TN: 247 KN: 247 NH 4 -N: 89 NO 2 -N : 0.20 NO 3 -N: 0.18 [processing conditions] solid residence time (SRT): 5~57 days circulation ratio (R): 3 (circulation 200% (Return 100%) Water temperature: Control (15-16 ° C) Redox potential (ORP): Anaerobic tank (1) No control (2) Control at -200 mV Aerobic tank Control at +50 mV (Note) ORP control of anaerobic tank is aeration Implemented by Air was used for aeration and pure oxygen was used as an auxiliary.
【００２３】得られた処理結果を図２に示す。図中、白
抜きのプロットは嫌気槽の曝気を行わず酸化還元電位Ｏ
ＲＰを無制御とした場合の結果であり、黒塗りのプロッ
トは嫌気槽の曝気を行って酸化還元電位ＯＲＰを−２０
０ｍＶに制御した場合の結果である。まず、従来のよう
に嫌気槽の酸化還元電位ＯＲＰを制御しない場合（白抜
きプロット）は、固形物滞留時間ＳＲＴを５７日までと
ってもＴ−Ｎ除去率は５０％に達せず、良好な処理水質
が得られない。この場合、嫌気槽の酸化還元電位ＯＲＰ
は−３００〜−４００ｍＶまで低下しており、好気槽
は、酸素で曝気して溶存酸素ＤＯが１０ｍｇ／Ｌ以上あ
るにもかかわらず酸化還元電位ＯＲＰが上昇せず０ｍＶ
以下であった。FIG. 2 shows the obtained processing results. In the figure, the white plots indicate the oxidation-reduction potential O without aerating the anaerobic tank.
The results in the case where RP was not controlled are shown. The black plots indicate that the oxidation-reduction potential ORP was −20 by aerating the anaerobic tank.
It is a result in the case of controlling to 0 mV. First, when the oxidation-reduction potential ORP of the anaerobic tank is not controlled as in the conventional case (open plot), the TN removal rate does not reach 50% even when the solids retention time SRT is up to 57 days, and the quality of the treated water is good. Can not be obtained. In this case, the oxidation-reduction potential ORP of the anaerobic tank
Is reduced to −300 to −400 mV, and the aerobic tank is aerated with oxygen, and the redox potential ORP does not increase even though the dissolved oxygen DO is 10 mg / L or more.
It was below.
【００２４】これに対して、本発明により嫌気槽の酸化
還元電位ＯＲＰを−２００ｍＶに制御した場合（黒塗り
プロット）は、固形物滞留時間ＳＲＴが５日以上の全実
験範囲でＴ−Ｎ除去率は常に安定して約８５％に達して
おり、良好な処理水質が得られた。この場合、好気槽の
酸化還元電位ＯＲＰは＋３０ｍＶ以上に維持されてい
た。 〔実施例２〕実施例１と同様の廃水処理を行った。図３
に、処理開始後の経過日数に対して、処理水中の窒素濃
度の変化と嫌気槽および好気槽の酸化還元電位ＯＲＰの
変化を示す。ただし、処理開始後２０日目までは嫌気槽
の曝気による酸化還元電位ＯＲＰ制御なし、２０日目以
降は嫌気槽の曝気により酸化還元電位ＯＲＰを−２００
ｍＶに制御した。On the other hand, when the oxidation-reduction potential ORP of the anaerobic tank is controlled to -200 mV according to the present invention (solid plot), TN removal is performed in the entire experimental range where the solid retention time SRT is 5 days or more. The rate always reached about 85% stably, and good treated water quality was obtained. In this case, the oxidation-reduction potential ORP of the aerobic tank was maintained at +30 mV or more. Example 2 The same wastewater treatment as in Example 1 was performed. FIG.
2 shows changes in the nitrogen concentration in the treated water and changes in the oxidation-reduction potential ORP in the anaerobic tank and the aerobic tank with respect to the number of days elapsed after the start of the treatment. However, the oxidation-reduction potential ORP was not controlled by the aeration of the anaerobic tank until the 20th day after the start of the treatment, and the oxidation-reduction potential ORP was reduced to -200 by the aeration of the anaerobic tank after the 20th day.
Controlled to mV.
【００２５】嫌気槽の曝気なしの最初の処理期間は、ア
ンモニア性窒素ＮＨ4 −Ｎも総窒素Ｔ−Ｎともに処理前
の廃水と同等の高い水準のままであり、窒素除去が有効
に行われていない。この期間は、好気槽の酸化還元電位
ＯＲＰも、現実には設定値の＋５０ｍＶにすることがで
きず、０ｍＶ以下に低迷したままである。好気槽での硝
化が進行しないため、亜硝酸性窒素ＮＯ2 −Ｎおよび硝
酸性窒素ＮＯ3 −Ｎが低レベルで推移している。During the first treatment period without aeration in the anaerobic tank, both the ammonia nitrogen NH 4 -N and the total nitrogen TN remain at the same high level as the wastewater before the treatment, and the nitrogen removal is effectively performed. Not. During this period, the oxidation-reduction potential ORP of the aerobic tank cannot actually be set to the set value of +50 mV, and remains at 0 mV or less. Since nitrification in the aerobic tank does not progress, nitrite nitrogen NO 2 -N and nitrate nitrogen NO 3 -N are at low levels.
【００２６】これに対して、嫌気槽を曝気して酸化還元
電位ＯＲＰの制御を開始し、−２００ｍＶに制御する
と、処理水のＮＨ4 −Ｎは急激に低下して実質的に０と
なった。この期間は、好気槽の酸化還元電位ＯＲＰも設
定どおり＋５０ｍＶに制御できている。硝化槽での硝化
の進行により、亜硝酸性窒素ＮＯ2 −Ｎおよび硝酸性窒
素ＮＯ3 −Ｎが高レベルで推移している。On the other hand, when the anaerobic tank was aerated and the control of the oxidation-reduction potential ORP was started and controlled to -200 mV, the NH 4 -N of the treated water dropped sharply to substantially zero. . During this period, the oxidation-reduction potential ORP of the aerobic tank can be controlled to +50 mV as set. Due to the progress of nitrification in the nitrification tank, nitrite nitrogen NO 2 -N and nitrate nitrogen NO 3 -N are changing at high levels.
【００２７】このように嫌気槽を曝気して酸化還元電位
ＯＲＰを適正値に制御することにより、好気槽の酸化還
元電位ＯＲＰも適正値に制御可能になり、十分に窒素除
去することができる。 〔実施例３〕実施例１と同様の廃水処理を行った。図４
に、好気槽の酸化還元電位ＯＲＰと処理水の窒素濃度と
の関係を示す。By controlling the oxidation-reduction potential ORP to an appropriate value by aerating the anaerobic tank in this manner, the oxidation-reduction potential ORP of the aerobic tank can also be controlled to an appropriate value, and nitrogen can be sufficiently removed. . Example 3 The same wastewater treatment as in Example 1 was performed. FIG.
Shows the relationship between the oxidation-reduction potential ORP of the aerobic tank and the nitrogen concentration of the treated water.
【００２８】嫌気槽の曝気をしないと、前記のように酸
化還元電位ＯＲＰが−３００〜−４００ｍＶ程度に低下
し、好気槽の酸化還元電位ＯＲＰも０ｍＶ以下（負の
値）から上昇することができず、同図に示したようにア
ンモニア性窒素ＮＨ4 −Ｎが非常に高いレベルで残存し
ており、亜硝酸性窒素ＮＯ2 −Ｎおよび硝酸性窒素ＮＯ
3 −Ｎも低レベルにあり、好気槽での硝化および嫌気槽
での脱窒が効果的に進行していない。If the anaerobic tank is not aerated, the acid
Redox potential ORP drops to about -300 to -400 mV
The oxidation-reduction potential ORP of the aerobic tank is also 0 mV or less (negative
Value), and as shown in the figure,
Nmonia nitrogenFour-N remains at a very high level
Nitrite nitrogen NOTwo-N and nitrate nitrogen NO
Three-N is also low level, nitrification in aerobic tank and anaerobic tank
Denitrification has not progressed effectively.
【００２９】嫌気槽の曝気を行い酸化還元電位ＯＲＰを
−２００ｍＶに制御すると、好気槽の酸化還元電位ＯＲ
Ｐを＋３０ｍＶ以上に上昇させることができるようにな
り、同図に示したようにアンモニア性窒素ＮＨ4 −Ｎが
消失し、亜硝酸性窒素ＮＯ2−Ｎおよび硝酸性窒素ＮＯ
3 −Ｎも高レベルに上昇しており、好気槽での硝化およ
び嫌気槽での脱窒が共に順調に進行している。When the oxidation-reduction potential ORP is controlled to -200 mV by aerating the anaerobic tank, the oxidation-reduction potential OR
P can be raised to +30 mV or more, and ammonia nitrogen NH 4 —N disappears, and nitrite nitrogen NO 2 —N and nitrate nitrogen NO
3- N is also increasing to a high level, and nitrification in the aerobic tank and denitrification in the anaerobic tank are both proceeding smoothly.
【００３０】好気槽の硝化反応を安定に進行させるに
は、好気槽の酸化還元電位ＯＲＰが＋５０ｍＶ以上とす
ることが望ましい。In order for the nitrification reaction in the aerobic tank to proceed stably, it is desirable that the oxidation-reduction potential ORP of the aerobic tank be +50 mV or more.
【００３１】[0031]
【発明の効果】以上説明したように、本発明の活性汚泥
循環変法による廃水の窒素除去方法によれば、窒素分濃
度の高い廃水でも十分に窒素除去を行うことができる。
特に低水温期においてはその効果が顕著である。As described above, according to the method for removing nitrogen from wastewater by the modified activated sludge circulation method of the present invention, nitrogen can be sufficiently removed even from wastewater having a high nitrogen concentration.
In particular, the effect is remarkable in the low water temperature period.
【図１】図１は、本発明の方法を行うための装置の配置
例を示す模式図である。FIG. 1 is a schematic view showing an example of an arrangement of an apparatus for performing the method of the present invention.
【図２】図２は、嫌気槽の酸化還元電位ＯＲＰを本発明
により制御した場合と、従来のように制御なしの場合に
ついて、種々の固形物滞留時間ＳＲＴに対する総窒素Ｔ
−Ｎ除去率との関係を示すグラフである。FIG. 2 shows the total nitrogen T for various solids retention times SRT for the case where the oxidation-reduction potential ORP of the anaerobic tank is controlled according to the present invention and the case where no control is performed as in the prior art.
It is a graph which shows the relationship with -N removal rate.
【図３】図３は、従来のように嫌気槽の曝気なしの期間
と、その後に本発明により嫌気槽を曝気して酸化還元電
位ＯＲＰを制御した期間とについて、廃水処理開始から
の経過日数と、処理水の窒素濃度および好気槽・嫌気槽
の酸化還元電位ＯＲＰとの関係を示すグラフである。FIG. 3 is a graph showing the number of days elapsed from the start of wastewater treatment for a period in which the anaerobic tank is not aerated as in the related art and a period in which the anaerobic tank is aerated according to the present invention to control the oxidation-reduction potential ORP. FIG. 4 is a graph showing the relationship between nitrogen concentration of treated water and oxidation-reduction potential ORP in aerobic / anaerobic tanks.
【図４】図４は、従来のように嫌気槽の曝気なしの場合
と、本発明により嫌気槽を曝気して酸化還元電位ＯＲＰ
を制御した場合とを含めて、好気槽の酸化還元電位ＯＲ
Ｐと処理水の窒素濃度との関係を示すグラフである。FIG. 4 is a diagram showing a case where the anaerobic tank is not aerated as in the prior art and a case where the anaerobic tank is aerated according to the present invention and the oxidation-reduction potential ORP is obtained.
, The oxidation-reduction potential OR of the aerobic tank
It is a graph which shows the relationship between P and nitrogen concentration of treated water.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 ＦＩ Ｃ０２Ｆ 3/34 １０１ Ｃ０２Ｆ 3/34 １０１Ｃ ──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. 6 Identification code FI C02F 3/34 101 C02F 3/34 101C
Claims (6)
と好気槽により循環処理した後に最終沈澱処理する活性
汚泥循環変法による廃水の窒素除去方法において、 固形物滞留時間を管理すると共に嫌気槽の酸化還元電位
を制御することを特徴とする活性汚泥循環変法による廃
水の窒素除去方法。1. A method for removing nitrogen from wastewater by a modified activated sludge circulation method in which wastewater containing organic matter and reducing nitrogen is circulated through an anaerobic tank and an aerobic tank, and then subjected to final sedimentation treatment. A method for removing nitrogen from wastewater by a modified activated sludge circulation method, comprising controlling the oxidation-reduction potential of an anaerobic tank.
た０ｍＶ〜−３００ｍＶ（Ａｇ／ＡｇＣｌ基準）に維持
するように、嫌気槽を曝気および／または表面攪拌する
ことを特徴とする請求項１記載の方法。2. The anaerobic tank is aerated and / or agitated so as to maintain the oxidation-reduction potential of the anaerobic tank at 0 mV to -300 mV (based on Ag / AgCl) suitable for denitrification. Item 7. The method according to Item 1.
た＋５０ｍＶ〜＋２００ｍＶ（Ａｇ／ＡｇＣｌ基準）に
維持するように、好気槽を曝気および／または表面攪拌
することを特徴とする請求項１または２記載の方法。3. The aerobic tank is aerated and / or surface agitated so that the oxidation-reduction potential of the aerobic tank is maintained at +50 mV to +200 mV (based on Ag / AgCl) suitable for the nitrification reaction. Item 3. The method according to Item 1 or 2.
維持するように、好気槽を曝気および／または表面攪拌
することを特徴とする請求項１から３までのいずれか１
項に記載の方法。4. The aerobic tank is aerated and / or surface agitated so as to maintain dissolved oxygen in the aerobic tank at +2 mg / L or more.
The method described in the section.
日以上とすることを特徴とする請求項１から４までのい
ずれか１項に記載の方法。5. When the water temperature is 15 ° C. or more, the solid residence time is 5 minutes.
5. The method according to claim 1, wherein the time is at least one day.
または嫌気槽に添加することを特徴とする請求項１から
５までのいずれか１項に記載の方法。6. An activated sludge-immobilized carrier is provided in an aerobic tank and / or
The method according to any one of claims 1 to 5, wherein the method is added to an anaerobic tank.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25470696A JP3639679B2 (en) | 1996-09-26 | 1996-09-26 | Nitrogen removal method of wastewater by modified activated sludge circulation method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25470696A JP3639679B2 (en) | 1996-09-26 | 1996-09-26 | Nitrogen removal method of wastewater by modified activated sludge circulation method |
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| Publication Number | Publication Date |
|---|---|
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2018079402A (en) * | 2016-11-14 | 2018-05-24 | 株式会社日水コン | Sewage treatment system and sewage treatment method |
| JP2020099873A (en) * | 2018-12-21 | 2020-07-02 | 水ｉｎｇ株式会社 | Water treatment method and water treatment apparatus |
-
1996
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2018079402A (en) * | 2016-11-14 | 2018-05-24 | 株式会社日水コン | Sewage treatment system and sewage treatment method |
| JP2020099873A (en) * | 2018-12-21 | 2020-07-02 | 水ｉｎｇ株式会社 | Water treatment method and water treatment apparatus |
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