JP3622573B2 - Biological denitrification method - Google Patents
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- JP3622573B2 JP3622573B2 JP14157099A JP14157099A JP3622573B2 JP 3622573 B2 JP3622573 B2 JP 3622573B2 JP 14157099 A JP14157099 A JP 14157099A JP 14157099 A JP14157099 A JP 14157099A JP 3622573 B2 JP3622573 B2 JP 3622573B2
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Description
【０００１】
【発明の属する技術分野】
本発明は硝酸性窒素を含む窒素含有排水に水素供与体を添加して生物脱窒処理する方法に係り、特に、排水の窒素濃度や水量が大幅に変動する場合であっても、水素供与体添加量の過不足を生じることなく、脱窒に必要な最少量の水素供与体の添加量で良好な水質の処理水を安定かつ効率的に得ることができる生物脱窒処理方法に関する。
【０００２】
【従来の技術】
従来、ステンレス製造工程から排出される硝酸含有洗浄排水の処理には、脱窒反応槽と再曝気槽を組み込んだ生物脱窒処理法が一般的に採用されている。この洗浄排水の含有不純物は硝酸が主体であるため、生物脱窒反応時に脱窒用基質として脱窒反応量に見合う量の水素供与体（一般的にはメタノール）を脱窒反応槽に投入する必要がある。
【０００３】
即ち、脱窒反応槽に投入される水素供与体量が不足する場合には、脱窒反応が不十分となり、脱窒反応槽内で未分解の窒素が残留し、結果的に処理水の窒素濃度が低下し得ない。逆に、過剰な水素供与体を投入した場合には、脱窒反応は十分に進行するが、脱窒反応槽で使用されずに残留した多量の水素供与体が再曝気槽に流入し、再曝気槽内の溶存酸素（ＤＯ）の減少を引き起こし、結果的には処理水の悪化を生じる。また、必要以上に汚泥が増殖し、余剰汚泥量の増加につながる。
【０００４】
しかし、この硝酸含有洗浄排水は、これが排出されるステンレス製造工程の作業内容の変更や製造品目により、その濃度、水量が大幅に変動する。従って、大容量の原水調整槽や原水貯留槽が無い場合は、洗浄排水の濃度ないし水量の変動に伴い、脱窒反応槽内の窒素負荷量は大幅に変動することとなるため、水素供与体の投入量の過不足に陥り易い。
【０００５】
従来、ステンレス製造工程から排出される硝酸含有洗浄排水の生物脱窒処理においては、水素供与体添加量を適正化するための有効な指標が提供されていないことから、処理水の残留窒素量を低減することを重要視して、水素供与体が不足した場合の未分解窒素の残留を防止して窒素濃度の低い処理水を安定に得るべく、過剰量の水素供与体を添加しているのが実状である。
【０００６】
【発明が解決しようとする課題】
しかしながら、このように過剰量の水素供与体を添加する方法では、
▲１▼ 水素供与体の添加量が多くなり、結果として運転コスト、維持管理コスト等の全体の処理コストが高騰する。
▲２▼ 再曝気槽でのＤＯ不足により、処理水中の窒素以外のＢＯＤやＣＯＤが増え、処理水水質が悪化する。
▲３▼ 再曝気槽のＤＯを増加するために曝気量を増加すると曝気のためのコストが嵩み、また、ＤＯ濃度の管理も煩雑となる。
▲４▼ 余剰汚泥の発生量が増大する。
といった問題を生じる上に、過剰量の水素供与体を添加している場合であっても、硝酸含有洗浄排水の窒素濃度や水量が大幅に増大すると処理水中に窒素が残留する恐れもあった。
【０００７】
本発明は、上記従来の問題点を解決し、硝酸性窒素を含む窒素含有排水に水素供与体を添加して生物脱窒処理するに当り、排水の窒素濃度や水量が大幅に変動する場合であっても、水素供与体の過剰添加を行うことなく、脱窒に必要な最少量の水素供与体の添加量で良好な水質の処理水を安定かつ効率的に得ることができる生物脱窒処理方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明の生物脱窒処理方法は、硝酸性窒素を含む窒素含有排水に水素供与体を添加して脱窒反応槽にて生物脱窒処理する方法において、該脱窒反応槽の窒素負荷量に応じて、該窒素負荷量に対する前記水素供与体の添加比率、即ち、水素供与体量／窒素負荷量を増減することを特徴とする。
【０００９】
硝酸性窒素の脱窒反応は下式で表される。
【００１０】
ＮＯ３＋５Ｈ→１／２Ｎ２＋２Ｈ２Ｏ＋ＯＨ
硝酸を還元する水素供与体として一般的にはメタノールが用いられており、その脱窒反応は下式で表される。
【００１１】
ＮＯ３＋５／６ＣＨ３ＯＨ→ １／２Ｎ２＋５／６ＣＯ２＋７／６Ｈ２Ｏ＋ＯＨ
即ち、６モルの硝酸性窒素を脱窒するには５モルのメタノールが必要とされ、従って、１ｋｇの窒素の除去に必要なメタノール量は１．９ｋｇとなる。
【００１２】
実際には脱窒汚泥の増殖に必要とされる炭素量、窒素量が加味されるため、１ｋｇの窒素の除去に必要なメタノール量（以下「メタノール係数」と記す。）は２〜２．３ｋｇとなる。
【００１３】
従って、窒素負荷量に予め設定したメタノール係数を乗じ、図１（ｃ）に示す如くメタノール添加量を設定することにより、窒素負荷量の変動に対応したメタノールの投入が可能となると考えられる。
【００１４】
しかし、これら反応式上から求めた窒素除去に必要なメタノール量は、一定値ではなく、脱窒汚泥の活性や窒素負荷量により変化し、窒素負荷量が極めて少ない場合では、メタノールの添加なしで、脱窒汚泥のみの内生呼吸の過程でも脱窒は生じている。この現象は内生脱窒と呼ばれている。通常、脱窒汚泥の活性が高く、また窒素負荷量が多い場合は、高いメタノール係数となり、脱窒汚泥の活性が低く、窒素負荷量が少ない場合は、低いメタノール係数になる。
【００１５】
従って、脱窒反応槽に一定の窒素濃度及び一定水量の排水が流入し、窒素負荷量一定で運転されている場合は、その条件に最適なメタノール係数で投入メタノール量を設定することが可能である。しかし、前述したステンレス製造工程の洗浄排水等では、窒素負荷量が大幅に変動するため、一定のメタノール係数でメタノールの投入制御を行った場合、高負荷条件ではメタノール不足となり、逆に低負荷条件ではメタノール過剰となってしまう。
【００１６】
本発明では、脱窒反応槽の窒素負荷量の増減に応じて水素供与体の添加量ではなく、窒素負荷量に対する水素供与体の添加比率を増減するため、上述のような不具合は防止され、必要最低限の水素供与体の添加量で良好な水質の処理水を安定かつ効率的に得ることができる。
【００１７】
なお、本明細書では、水素供与体としてメタノールを例示して説明しているが、本発明において、添加する水素供与体としてはメタノールに何ら限定されず、エタノール、酢酸等の従来の生物脱窒処理で用いられる水素供与体であればいずれも適用可能である。このような水素供与体は、脱窒反応槽に直接添加しても良く、また、原水である窒素含有排水の流入配管に注入して原水と共に脱窒反応槽に導入しても良い。
【００１８】
【発明の実施の形態】
以下に本発明の実施の形態を詳細に説明する。
【００１９】
本発明の方法は、硝酸性窒素を含む窒素含有排水に水素供与体を添加して脱窒反応槽で生物脱窒処理するに当り、該脱窒反応槽の窒素負荷量の増減に応じて前述のメタノール係数の設定値を増減し、水素供与体量／窒素負荷量の割合を増減すること以外は通常の処理条件で実施することができる。
【００２０】
実際の処理設備においては、原水である窒素含有排水の窒素濃度及び水量を連続的に測定し、脱窒反応槽への流入窒素負荷量を求め、予め設定した各窒素負荷量毎に最適なメタノール係数で演算したメタノール量でメタノールの添加制御を行う。
【００２１】
このメタノール係数の設定方法としては、図１（ａ）に示す如く、窒素負荷量の増加に応じて連続的にメタノール係数が増加するように設定しても良く、また、図１（ｂ）に示す如く、窒素負荷量の増加に応じて段階的にメタノール係数が増加するように設定しても良い。
【００２２】
このメタノール係数は、予め、原水である窒素含有排水を用いて予備試験を行うことにより設定することができる。
【００２３】
このように、窒素負荷量に対応するメタノール係数を用い、窒素負荷量にメタノール係数を乗じることで、窒素負荷量の変動に応じた最適なメタノール添加量を設定することができる。
【００２４】
【実施例】
以下に実施例を挙げて本発明をより具体的に説明する。
【００２５】
実施例１
水素供与体としてメタノールを用いている、ステンレス製造工程から排出される洗浄排水の生物脱窒処理設備で、本発明の実証確認運転を行った。この洗浄排水は硝酸性窒素濃度が２００〜３５０ｍｇ−Ｎ／Ｌの範囲で変動し、処理設備の脱窒反応槽容量当りの窒素負荷量は、０．２〜２．４ｋｇ／ｍ３／日の範囲で大幅な変動を生じている。
【００２６】
この処理において、メタノール係数Ｍは、同排水を用いた生物脱窒処理の予備検討から、脱窒反応槽容量当りの窒素負荷量Ｎが０〜０．４４ｋｇ／ｍ３／日の範囲内では２．１、窒素負荷量Ｎが０．４５〜０．８７ｋｇ／ｍ３／日の範囲内では２．３、窒素負荷量Ｎが０．８８ｋｇ／ｍ３／日以上では２．５が、脱窒処理効果の面から適正であると推定された。
【００２７】
この処理設備の運転初期は、メタノール係数を窒素負荷量に関係なく２．３と一定に設定し、図１（ｃ）に示す如く、窒素負荷量Ｎに対応して、メタノール添加量＝Ｎ×２．３でメタノール添加量を増減させて投入を行っていた。この運転条件下では、窒素負荷量が０．４ｋｇ／ｍ３／日より低い時には、脱窒反応槽の後段に設置している再曝気槽のＤＯが不足し、曝気量不足を生じていた。また、０．８ｋｇ／ｍ３／日より高負荷条件では、脱窒反応槽のＯＲＰが−１５０ｍｖ以上となり、脱窒処理に適正な酸化還元状態が得られず、脱窒処理が不十分になっていた。その結果、処理水（再曝気槽の後段の沈殿槽の分離水）の残留窒素が１０ｍｇ／Ｌ以上となり、沈殿槽で内生脱窒を生じ、汚泥の浮上現象が生じていた。
【００２８】
処理水の窒素濃度の悪化を防止する観点から、低負荷域でも２．５以上のメタノール係数とし、メタノール添加量＝Ｎ×２．５でメタノールを投入したところ、再曝気槽で未分解のメタノールが処理水に残留し、処理水のＣＯＤが１５〜２５ｍｇ／Ｌと高い値を示した。しかも、低負荷域ではメタノール過剰なため、発生する余剰汚泥量が多くなり、汚泥処理に問題が生じた。
【００２９】
そこで、予備検討結果から得られたメタノール係数Ｍを用い、窒素負荷量Ｎに応じて、段階的にメタノール係数Ｍを変え、次のようにしてメタノール添加量を制御した。
窒素負荷量Ｎが０〜０．４４ｋｇ／ｍ３／日のとき：
メタノール係数Ｍを２．１とし、メタノール投入量＝Ｎ×２．１とする。
窒素負荷量Ｎが０．４５〜０．８７ｋｇ／ｍ３／日のとき：
メタノール係数Ｍを２．３とし、メタノール投入量＝Ｎ×２．３とする。
窒素負荷量Ｎが０．８８ｋｇ／ｍ３／日以上のとき：
メタノール係数Ｍを２．５とし、メタノール投入量＝Ｎ×２．５とする。
その結果、低負荷域から高負荷域まで安定して、脱窒反応槽内のＯＲＰは脱窒処理に最適な−２５０〜−３００ｍｖを示し、再曝気槽内のＤＯも１．５〜３ｍｇ／Ｌの範囲であった。また、処理水中に残留する窒素は１ｍｇ／Ｌ以下であり、ＣＯＤも１０ｍｇ／Ｌ以下と良好な処理が継続して行われた。余剰汚泥の発生量も、運転初期に比べて２５〜３０％低減した。
【００３０】
【発明の効果】
以上詳述した通り、本発明の生物脱窒処理方法によれば、窒素負荷量の変動に応じて最適な水素供与体添加量制御を行うことができ、
▲１▼ 最少量の水素供与体添加量で生物脱窒処理することができるため、処理コストを低減することができる。
▲２▼ 再曝気槽に流入する残留水素供与体量が少ないため、再曝気槽のＤＯ不足による処理水水質の低下が防止される。また、再曝気槽のＤＯ管理も容易となり、曝気コストも低減できる。
▲３▼ 余剰汚泥の発生量が低減され、汚泥処理の問題が軽減される。
等の効果が奏され、窒素濃度や水量が大きく変動する硝酸性窒素含有排水の生物脱窒処理においても、低窒素濃度でＢＯＤ、ＣＯＤも低い高水質の処理水を安定かつ効率的に得ることができる。
【図面の簡単な説明】
【図１】メタノール係数又はメタノール添加量と窒素負荷量との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for biological denitrification treatment by adding a hydrogen donor to a nitrogen-containing wastewater containing nitrate nitrogen, and in particular, even if the nitrogen concentration and the amount of water in the wastewater vary greatly, the hydrogen donor The present invention relates to a biological denitrification treatment method capable of stably and efficiently obtaining treated water with good water quality by adding the minimum amount of hydrogen donor necessary for denitrification without causing excess or deficiency of the addition amount.
[0002]
[Prior art]
Conventionally, a biological denitrification method incorporating a denitrification reaction tank and a re-aeration tank has been generally employed for the treatment of nitric acid-containing cleaning wastewater discharged from a stainless steel manufacturing process. Since the impurities contained in this washing wastewater are mainly nitric acid, a hydrogen donor (generally methanol) in an amount commensurate with the amount of denitrification reaction is introduced into the denitrification reactor as a substrate for denitrification during the biological denitrification reaction. There is a need.
[0003]
That is, when the amount of hydrogen donor charged into the denitrification reaction tank is insufficient, the denitrification reaction becomes insufficient, and undecomposed nitrogen remains in the denitrification reaction tank, resulting in nitrogen in the treated water. The concentration cannot be reduced. Conversely, when an excessive amount of hydrogen donor is added, the denitrification reaction proceeds sufficiently, but a large amount of hydrogen donor that remains without being used in the denitrification reaction tank flows into the re-aeration tank and is regenerated. This causes a decrease in dissolved oxygen (DO) in the aeration tank, resulting in deterioration of the treated water. Moreover, sludge grows more than necessary, leading to an increase in the amount of excess sludge.
[0004]
However, the concentration and the amount of water of the nitric acid-containing cleaning wastewater vary greatly depending on the change in the work content of the stainless steel manufacturing process from which the nitric acid-containing cleaning wastewater is discharged and the manufacturing items. Therefore, if there is no large-capacity raw water conditioning tank or raw water storage tank, the nitrogen load in the denitrification reaction tank will vary greatly as the concentration or amount of washing wastewater changes. It is easy to fall into an excess or deficiency of the amount of input.
[0005]
Conventionally, in biological denitrification treatment of nitric acid-containing cleaning wastewater discharged from stainless steel manufacturing processes, an effective index for optimizing the hydrogen donor addition amount has not been provided. With an emphasis on reducing the amount of hydrogen donor, an excessive amount of hydrogen donor is added to prevent residual undecomposed nitrogen in the event of a shortage of hydrogen donor and to stably obtain treated water with a low nitrogen concentration. Is real.
[0006]
[Problems to be solved by the invention]
However, in this method of adding an excessive amount of hydrogen donor,
(1) The amount of hydrogen donor added increases, and as a result, the overall processing costs such as operation costs and maintenance costs increase.
(2) Due to the lack of DO in the re-aeration tank, BOD and COD other than nitrogen in the treated water increase and the quality of the treated water deteriorates.
(3) Increasing the amount of aeration in order to increase the DO in the re-aeration tank increases the cost for aeration, and the management of the DO concentration becomes complicated.
(4) The amount of excess sludge generated increases.
In addition to the above problems, even when an excessive amount of hydrogen donor is added, if the nitrogen concentration or the amount of water in the nitric acid-containing cleaning wastewater is significantly increased, nitrogen may remain in the treated water.
[0007]
The present invention solves the above-mentioned conventional problems, and when adding a hydrogen donor to a nitrogen-containing wastewater containing nitrate nitrogen and performing a biological denitrification treatment, the concentration of nitrogen and the amount of water in the wastewater vary greatly. Even in such a case, biological denitrification treatment can stably and efficiently obtain treated water of good quality with the minimum amount of hydrogen donor required for denitrification without excessive addition of hydrogen donor. It aims to provide a method.
[0008]
[Means for Solving the Problems]
The biological denitrification treatment method of the present invention is a method of adding a hydrogen donor to nitrogen-containing wastewater containing nitrate nitrogen and performing a biological denitrification treatment in a denitrification reaction tank. Accordingly, the addition ratio of the hydrogen donor to the nitrogen load, that is, the hydrogen donor amount / nitrogen load is increased or decreased.
[0009]
The denitrification reaction of nitrate nitrogen is expressed by the following formula.
[0010]
NO 3 + 5H → 1 / 2N 2 + 2H 2 O + OH
In general, methanol is used as a hydrogen donor for reducing nitric acid, and the denitrification reaction is represented by the following formula.
[0011]
NO 3 + 5 / 6CH 3 OH → 1 / 2N 2 + 5 / 6CO 2 + 7 / 6H 2 O + OH
That is, 5 mol of methanol is required to denitrify 6 mol of nitrate nitrogen, and therefore the amount of methanol required to remove 1 kg of nitrogen is 1.9 kg.
[0012]
Actually, since the amount of carbon and nitrogen required for the growth of denitrified sludge are taken into account, the amount of methanol required to remove 1 kg of nitrogen (hereinafter referred to as “methanol coefficient”) is 2 to 2.3 kg. It becomes.
[0013]
Therefore, by multiplying the nitrogen load amount by a preset methanol coefficient and setting the methanol addition amount as shown in FIG. 1 (c), it is considered that methanol can be input in accordance with the fluctuation of the nitrogen load amount.
[0014]
However, the amount of methanol required for nitrogen removal determined from these reaction formulas is not a constant value, but varies depending on the activity of the denitrification sludge and the nitrogen load, and if the nitrogen load is extremely small, there is no need to add methanol. In addition, denitrification has occurred even in the process of endogenous respiration using only denitrified sludge. This phenomenon is called endogenous denitrification. Usually, when the activity of denitrification sludge is high and the nitrogen load is large, the methanol coefficient is high, and when the activity of denitrification sludge is low and the nitrogen load is small, the methanol coefficient is low.
[0015]
Therefore, when drainage with a constant nitrogen concentration and a constant amount of water flows into the denitrification reactor and is operated with a constant nitrogen load, it is possible to set the amount of methanol input with the optimal methanol coefficient for that condition. is there. However, the amount of nitrogen load varies greatly in the above-mentioned stainless steel manufacturing process wastewater, etc., so when methanol input control is performed with a constant methanol coefficient, methanol is insufficient under high load conditions, and conversely under low load conditions. Then, it becomes methanol excess.
[0016]
In the present invention, the amount of addition of the hydrogen donor to the nitrogen load is increased or decreased according to the increase or decrease of the nitrogen load in the denitrification reaction tank. Treated water with good water quality can be obtained stably and efficiently with the minimum amount of hydrogen donor added.
[0017]
In this specification, methanol is exemplified as the hydrogen donor. However, in the present invention, the hydrogen donor to be added is not limited to methanol, and conventional biological denitrification such as ethanol and acetic acid. Any hydrogen donor used in the treatment is applicable. Such a hydrogen donor may be added directly to the denitrification reaction tank, or may be injected into an inflow pipe of nitrogen-containing wastewater that is raw water and introduced into the denitrification reaction tank together with the raw water.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0019]
In the method of the present invention, when a hydrogen donor is added to nitrogen-containing wastewater containing nitrate nitrogen and biological denitrification treatment is performed in the denitrification reaction tank, the above-described method is performed according to the increase or decrease in the nitrogen load of the denitrification reaction tank. It can be carried out under normal processing conditions except that the set value of the methanol coefficient is increased or decreased and the ratio of hydrogen donor amount / nitrogen load is increased or decreased.
[0020]
In an actual treatment facility, the nitrogen concentration and water volume of the nitrogen-containing wastewater, which is the raw water, are continuously measured to determine the inflow nitrogen load into the denitrification reactor, and the optimal methanol for each preset nitrogen load. Methanol addition control is performed with the amount of methanol calculated by the coefficient.
[0021]
As a method for setting the methanol coefficient, as shown in FIG. 1 (a), the methanol coefficient may be set to continuously increase in accordance with an increase in the nitrogen load. As shown, the methanol coefficient may be set to increase stepwise as the nitrogen load increases.
[0022]
This methanol coefficient can be set in advance by conducting a preliminary test using nitrogen-containing wastewater that is raw water.
[0023]
As described above, by using the methanol coefficient corresponding to the nitrogen load amount and multiplying the nitrogen load amount by the methanol coefficient, it is possible to set an optimum methanol addition amount corresponding to the fluctuation of the nitrogen load amount.
[0024]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0025]
Example 1
The demonstration confirmation operation of the present invention was performed in a biological denitrification treatment facility for washing wastewater discharged from a stainless steel manufacturing process using methanol as a hydrogen donor. This washing drainage fluctuates in the range of nitrate nitrogen concentration of 200 to 350 mg-N / L, and the nitrogen load per capacity of the denitrification reaction tank of the treatment equipment is 0.2 to 2.4 kg / m 3 / day. There are significant variations in the range.
[0026]
In this treatment, the methanol coefficient M is 2 in the range of 0 to 0.44 kg / m 3 / day of the nitrogen load N per denitrification reaction tank capacity based on preliminary examination of biological denitrification treatment using the waste water. .1, within the scope of the nitrogen load N is 0.45~0.87kg / m 3 / day 2.3, the nitrogen load N is 2.5 at 0.88 kg / m 3 / day or more, denitrification It was estimated that it was appropriate in terms of treatment effect.
[0027]
At the initial stage of operation of this treatment equipment, the methanol coefficient is set to a constant 2.3 regardless of the nitrogen load, and as shown in FIG. 1 (c), the amount of methanol added = N × corresponding to the nitrogen load N. In 2.3, the amount of methanol added was increased or decreased. Under these operating conditions, when the nitrogen load was lower than 0.4 kg / m 3 / day, the DO in the re-aeration tank installed in the rear stage of the denitrification reaction tank was insufficient, resulting in a shortage of aeration. Further, under a load condition higher than 0.8 kg / m 3 / day, the ORP of the denitrification reaction tank becomes −150 mV or more, and a redox state suitable for the denitrification treatment cannot be obtained, and the denitrification treatment becomes insufficient. It was. As a result, the residual nitrogen in the treated water (separated water from the precipitation tank subsequent to the re-aeration tank) became 10 mg / L or more, and endogenous denitrification occurred in the precipitation tank, causing sludge levitation.
[0028]
From the viewpoint of preventing deterioration of the nitrogen concentration of the treated water, the methanol coefficient is 2.5 or more even in a low load region, and methanol is added at a methanol addition amount = N × 2.5. Remained in the treated water, and the COD of the treated water was as high as 15 to 25 mg / L. In addition, since the methanol is excessive in the low load region, the amount of generated excess sludge is increased, causing a problem in sludge treatment.
[0029]
Therefore, using the methanol coefficient M obtained from the preliminary examination results, the methanol coefficient M was changed stepwise according to the nitrogen load N, and the methanol addition amount was controlled as follows.
When the nitrogen load N is 0 to 0.44 kg / m 3 / day:
The methanol coefficient M is 2.1, and the methanol input amount is N × 2.1.
When the nitrogen load N is 0.45 to 0.87 kg / m 3 / day:
The methanol coefficient M is set to 2.3, and the methanol input amount is set to N × 2.3.
When the nitrogen load N is 0.88 kg / m 3 / day or more:
The methanol coefficient M is 2.5, and the methanol input amount is N × 2.5.
As a result, the ORP in the denitrification reaction tank shows −250 to −300 mV which is optimal for the denitrification treatment, and the DO in the re-aeration tank is also 1.5 to 3 mg / stable from the low load range to the high load range. L range. Further, the nitrogen remaining in the treated water was 1 mg / L or less, and the COD was 10 mg / L or less. The amount of excess sludge generated was also reduced by 25-30% compared to the initial operation.
[0030]
【The invention's effect】
As described above in detail, according to the biological denitrification method of the present invention, it is possible to perform optimal hydrogen donor addition amount control according to the fluctuation of the nitrogen load,
(1) Since the biological denitrification treatment can be performed with the minimum amount of hydrogen donor added, the treatment cost can be reduced.
{Circle around (2)} Since the amount of residual hydrogen donor flowing into the re-aeration tank is small, it is possible to prevent the quality of treated water from being deteriorated due to the shortage of DO in the re-aeration tank. Moreover, DO management of the re-aeration tank becomes easy, and the aeration cost can be reduced.
(3) The amount of excess sludge generated is reduced, and sludge treatment problems are reduced.
Even in the biological denitrification treatment of wastewater containing nitrate nitrogen where the nitrogen concentration and water volume fluctuate greatly, the high quality treated water with low nitrogen concentration and low BOD and COD can be obtained stably and efficiently. Can do.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between methanol coefficient or methanol addition amount and nitrogen load.
Claims (3)
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| JP14157099A JP3622573B2 (en) | 1999-05-21 | 1999-05-21 | Biological denitrification method |
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| JP14157099A JP3622573B2 (en) | 1999-05-21 | 1999-05-21 | Biological denitrification method |
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| JP4919138B2 (en) * | 2001-02-20 | 2012-04-18 | 新東工業株式会社 | Waste water denitrification equipment |
| JP2005087853A (en) * | 2003-09-17 | 2005-04-07 | Fuji Electric Systems Co Ltd | Method and apparatus for treating methane fermentation waste liquid |
| JP5335238B2 (en) * | 2005-06-15 | 2013-11-06 | 一般財団法人電力中央研究所 | Microbial activity control substance supply method and apparatus, environmental purification method and bioreactor using the same |
| US7431840B2 (en) * | 2005-08-24 | 2008-10-07 | Parkson Corporation | Denitrification process |
| BRPI0705361A2 (en) * | 2007-12-28 | 2010-05-11 | Mercosul Com Ltda | process for increasing the concentration of microorganism colonies in an anaerobic digestion removal process |
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