JP3707526B2 - Waste water nitrification method and apparatus - Google Patents

Waste water nitrification method and apparatus Download PDF

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JP3707526B2
JP3707526B2 JP04208599A JP4208599A JP3707526B2 JP 3707526 B2 JP3707526 B2 JP 3707526B2 JP 04208599 A JP04208599 A JP 04208599A JP 4208599 A JP4208599 A JP 4208599A JP 3707526 B2 JP3707526 B2 JP 3707526B2
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JP2000237790A (en
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裕紀 中村
均 吉川
啓介 中村
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日立プラント建設株式会社
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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
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Description

【０００１】
【発明の属する技術分野】
本発明は、廃水の硝化方法及び装置に係り、特に、下水等の廃水中のアンモニア性窒素（以下、「ＮＨ4-Ｎ」という）を除去する際の硝化処理の改良に関するものである。
【０００２】
【従来の技術】
脱窒槽と硝化槽を備え、廃水中のＮＨ4-Ｎを除去する硝化・脱窒装置では、硝化槽において硝化細菌の働きにより、ＮＨ4-Ｎを亜硝酸性窒素や硝酸性窒素に酸化する硝化処理を行う。下水などの実際の廃水処理では、廃水のＮＨ4-Ｎ負荷の変動や水温の年間、日間変動に対して、安定して高い窒素除去率を維持するためには、硝化槽での硝化処理を略完全に終了させることが重要である。そのため、実際の硝化・脱窒装置は、硝化に必要な酸素を廃水に供給するためのエアの散気量や硝化時間を低水温期の最大負荷に合わせて設計されている。
【０００３】
【発明が解決しようとする課題】
しかしながら、最大負荷に合わせて散気量や硝化時間を設計すると、夜間や降雨時などの負荷の低下時、または高水温期で硝化性能に余裕がある場合には、硝化槽の上流端から流入した廃水が、硝化槽の途中で硝化が終了し、その後の硝化槽の下流端から廃水が流出するまでの滞留領域におけるエアの供給が過剰となるという欠点がある。これにより、散気のための動力が無駄になるだけでなく、硝化液が最終沈殿池に流出する場合は，活性汚泥フロックの解体による処理水の透視度が悪化するという問題がある。更には、硝化液が脱窒槽に循環する場合は、脱窒槽へのエアの持ち込みによる脱窒性能の悪化が生じるという問題がある。
【０００４】
本発明は、このような事情に鑑みて成されたもので、硝化槽内への過剰なエアの供給を防ぎ、必要最小限のエア散気量で略完全な硝化を達成することができる廃水の硝化方法及び装置を提供することを目的とする。
【０００５】
【発明を解決するための手段】
本発明は、前記目的を達成するために、硝化槽の上流端から槽内に流入した廃水を下流端から流出させると共に、前記硝化槽内にエアを散気して前記廃水中のＮＨ4-Ｎを微生物により硝化処理する廃水の硝化方法において、前記硝化槽の上流端位置における微生物含有廃水を使用してアンモニア性窒素濃度と硝化速度、または回分反応における酸素消費速度の経時変化を測定し、前記測定した結果から前記廃水中のＮＨ4-Ｎ濃度を所定値まで低減させるために必要な必要硝化時間を演算し、前記演算した必要硝化時間と前記硝化槽内の廃水の滞留時間とを比較し、前記滞留時間のうち前記必要硝化時間を越える硝化槽内領域における散気量を、前記必要硝化時間を越える前の硝化槽内領域における散気量よりも小さくすることを特徴とする。
【０００６】
また、本発明は、前記目的を達成するために、硝化槽の上流端から槽内に流入した廃水を下流端から流出させると共に、前記硝化槽内にエアを散気して前記廃水中のアンモニア性窒素を微生物により硝化処理する廃水の硝化方法において、前記硝化槽の上流端位置における微生物含有廃水を使用してアンモニア性窒素濃度と硝化速度、または回分反応における酸素消費速度の経時変化を測定し、前記測定した結果から前記硝化槽内の廃水の滞留時間内に前記廃水中のアンモニア性窒素濃度を所定値まで低減させるために必要な硝化槽全体のトータル散気量を演算し、前記演算したトータル散気量の前記硝化槽内における散気量分布を、前記上流端側が大きく前記下流端側が小さくなるようにしたことを特徴とする。
【０００７】
また、本発明は、前記目的を達成するために、硝化槽の上流端から槽内に流入した廃水を下流端から流出させると共に、前記硝化槽内にエアを散気して前記廃水中のアンモニア性窒素を微生物により硝化処理する廃水の硝化装置において、前記硝化槽内の底部に前記上流端側から前記下流端側にかけて並設され、前記硝化槽内にエアを散気する複数の散気板と、前記硝化槽の上流端位置から採水した微生物含有廃水を使用してアンモニア性窒素濃度と硝化速度、または回分反応における酸素消費速度の経時変化測定する活性測定装置と、前記活性測定装置の測定結果から前記廃水中のアンモニア性窒素濃度を所定値まで低減させるために必要な必要硝化時間又は硝化槽全体のトータル散気量を演算する演算手段と、前記演算手段による演算結果に基づいて前記複数の散気板に送気するエア量を個別に制御する制御手段と、を備えたことを特徴とする。
【０００８】
本発明によれば、廃水中のＮＨ4-Ｎ濃度を所定値まで低減させるために必要な必要硝化時間を越えた硝化槽内領域における散気量を、必要硝化時間を越える前の硝化槽内領域における散気量よりも小さくするようにしたので、硝化槽内全体への過剰なエアの供給を防ぎ、必要最小限のエア散気量で略完全な硝化を達成することができる。
【０００９】
また、本発明によれば、硝化槽内の廃水の滞留時間内に廃水中のＮＨ4-Ｎ濃度を所定値まで低減させるために必要な硝化槽全体のトータル散気量を演算し、演算したトータル散気量の硝化槽内における散気量分布を、上流端側が大きく下流端側が小さくなるようにしたので、硝化槽内への過剰なエアの供給を防ぎ、必要最小限の酸素供給量で略完全な硝化を達成することができる。
【００１０】
【発明の実施の形態】
以下、添付図面により本発明の廃水の硝化方法及び装置の好ましい実施の形態について詳説する。
図１は、本発明の廃水の硝化装置１０を組み込んだ硝化・脱窒装置１２の構成図である。
【００１１】
硝化・脱窒装置１２は、主として、脱窒槽１４と硝化槽１６の各１槽から成る反応槽１８と、固液分離槽２０と、活性測定装置２２とで構成される。
硝化槽１６内の底部には、硝化槽１６の上流端Ａ側から下流端Ｂ側にかけて複数の散気板２４、２４…が並設され、各散気板２４はそれぞれ枝管２６、２６…を介して合流管２８に合流し、合流管２８がブロア３０に接続される。また、各枝管２６にはそれぞれエア量調整バルブ３２、３２…が設けられる。これにより、各散気板２４から散気されるエアにより硝化槽１６内に好気性条件を形成すると共に、各散気板２４からの散気量をエア量調整バルブ３２により個別に調整することができる。
【００１２】
一方、脱窒槽１４の底部には攪拌器３４が設けられ、脱窒槽１４内の廃水をゆっくりと攪拌して廃水からエアを脱気することにより脱窒槽１４内に嫌気性条件を形成する。そして、原水供給管３６から脱窒槽１４内に供給された廃水は、脱窒槽１４において活性汚泥微生物と混合された後、硝化槽１６の上流端Ａ位置に流入する。硝化槽１６内に流入した廃水は、硝化槽１６内を流れながら散気板２４からのエアによる好気性条件下で廃水中のＮＨ4-Ｎが硝化処理される。硝化処理された硝化液は、硝化槽１６の下流端Ｂ位置から循環配管３８を介して脱窒槽１４に循環され、嫌気性条件下で脱窒処理される。これにより、廃水中のＮＨ4-Ｎが窒素ガスとなって除去される。硝化槽１６と脱窒槽１４との間の循環において、硝化槽１６の硝化液の一部が処理水として処理水配管４０を介して固液分離槽２０に排出される。固液分離槽では、処理水に同伴した活性汚泥微生物を沈降分離した後の上澄液が、上澄液配管４２を介して排出される。一方、固液分離槽２０に沈降した沈降汚泥は、汚泥返送配管４４を介して原水供給管３６に戻される。また、沈降汚泥のうちの余剰汚泥は、引抜き配管４６を介して装置１２外に抜き出される。
【００１３】
活性測定装置２２は、送液ポンプ４８により硝化槽１６の上流端Ａ位置から測定容器５０に一定量の活性汚泥微生物を含有した廃水（以下「微生物含有廃水」という）を採水管５１を介して採水する。測定容器５０には、測定容器５０内にエアを散気するエアポンプ５２が接続されると共に、測定容器５０内の微生物含有廃水のＤＯ濃度を測定するＤＯ濃度計５４が設けられる。そして、エアポンプ５２から微生物含有廃水中にエアを散気しながら、微生物含有廃水のＤＯ濃度値が変化しなくなるまでＤＯ濃度の経時変化を測定する。この回分操作におけるＤＯ濃度の経時変化と微生物含有廃水に供給するエアの酸素溶解効率から微生物含有廃水の酸素消費速度、およびアンモニア性窒素（ＮＨ4-Ｎ）濃度と硝化速度を自動的に測定する。
【００１４】
次に、最適な散気方法を決めるための第１の実施の形態を説明する。
コントローラ５８では、活性測定装置２２で測定したＮＨ4-Ｎ濃度〔ＮｅI 〕と硝化速度〔ＫNI〕から廃水中のＮＨ4-Ｎ濃度を所定値まで低減させるために必要な必要硝化時間〔ＴN 〕を演算し、演算した必要硝化時間〔ＴN 〕と硝化槽１６内の廃水の滞留時間〔ＴMAX 〕とを比較する。そして、硝化槽１６内における廃水の滞留時間〔ＴMAX 〕のうち必要硝化時間〔ＴN 〕を越えた硝化槽１６内領域における散気量を、必要硝化時間〔ＴN 〕を越える前の硝化槽１６内領域における散気量よりも小さくするように、信号ケーブル６０を介して各散気板２４のエア量調整バルブ３２の開閉度を個別に制御する。ここで、硝化槽１６の水理学的な滞留時間〔ＴMAX 〕は、硝化槽容積を、原水供給管３６で反応槽１８に供給される原水量、汚泥返送配管４４で原水供給配管３６に返送される返送汚泥量、循環配管３８で硝化槽１６から脱窒槽１４に循環される硝化液の循環量の合計で割った値として求められる。
【００１５】
図２は、ＮＨ4-Ｎ濃度〔ＮｅI 〕と硝化速度〔ＫNI〕から上記した必要硝化時間〔ＴN 〕を決める方法である。図２の縦軸は硝化速度〔ＫN 〕、横軸は必要硝化時間〔ＴN 〕であり、ＴN1は硝化後のＮＨ4-Ｎ濃度、即ち前記所定値を０．１ｍｇ／Ｌとした時の必要硝化時間〔ＴN 〕である。図２から分かるように、硝化速度〔ＫN 〕は、ある時間まで最大の硝化速度であるＫNIのほぼ一定値を保ち、その後ＮＨ4-Ｎ濃度が０．３〜０．５mg／Ｌ以下になると急激に減少してゼロに近づくＫN 曲線を描く。そして、硝化速度は、その単位〔ｍｇ−Ｎ／Ｌ・時間〕から分かるように、単位時間当たりのＮＨ4-Ｎの減少速度を表したものである。従って、硝化速度〔ＫN 〕の時間積分値、即ち図２のＫN 曲線、横軸及び縦軸で囲まれた部分の面積が、ＮＨ4-Ｎ濃度〔ＮｅI 〕になるように必要硝化時間〔ＴN1〕を決定する。これにより、硝化後のＮＨ4-Ｎ濃度を０．１ｍｇ／Ｌまで低減するにするに必要な必要硝化時間〔ＴN1〕を決定することができる。
【００１６】
また、硝化後のＮＨ4-Ｎ濃度が０．１ｍｇ／Ｌよりも高くてよい場合、例えば０．３〜０．５ｍｇ／Ｌ程度の場合には、硝化速度〔ＫN 〕がＫNIを維持した状態の時間ＴN2を必要硝化時間〔ＴN 〕とすることも可能である。更には、ＴN1とＴN2の間の任意の時間を必要硝化時間〔ＴN 〕とすることもできる。
図３は、酸素消費速度〔Ｋr 〕の経時変化から必要硝化時間〔ＴN 〕を決める方法であり、酸素消費速度〔Ｋr 〕は、初期にほぼ一定値ＫrIを示すが、ある時点で急激に低下し、その後、ほぼ一定な低い値で推移するＫr 曲線を描く。そして、この場合にも硝化速度〔ＫN 〕の経時変化から必要硝化時間〔ＴN 〕を決める場合と同様に硝化後のＮＨ4-Ｎ濃度を所定値まで低減するのに必要な必要硝化時間〔ＴN 〕を求めることができる。
【００１７】
このように、本発明の硝化方法を採用すれば、硝化槽１６内全体への過剰なエアの供給を防ぎ、必要最小限のエア散気量で略完全な硝化を達成することができる。この場合、必要硝化時間〔ＴN 〕を越えた硝化槽１６内領域における散気量は、廃水のＤＯ濃度が３ｍｇ／Ｌ以下、好ましくは２ｍｇ／Ｌ以下になるようにするとよい。これにより、硝化槽１６からの硝化液を循環配管３８を介して脱窒槽１４に循環させた時に、硝化液に同伴する酸素を極力抑制し、脱窒性能に悪影響を与えないようにできる。
【００１８】
次に、最適な散気方法を決めるための第２の実施の形態を説明する。
第２の実施の形態は、コントローラ５８では、活性測定装置２２で測定した酸素消費速度〔Ｋr 〕の経時変化から、硝化槽１６内の廃水の滞留時間内に廃水中のＮＨ4-Ｎ濃度を所定値まで低減させるために必要な硝化槽１６全体の酸素消費量の時間積算値〔Ｗ〕を算出する。さらに、それを硝化槽１６の酸素溶解効率を考慮して空気量に換算してトータル散気量として求める。そして、演算したトータル散気量の硝化槽１６内における散気量分布を、上流端Ａ側が大きく下流端Ｂ側が小さくなるように各散気板２４の各エア量調整バルブ３２の開閉度を個別に制御する。この場合、上流端Ａ側から下流端Ｂ側にいくに従って直線的に散気量を減少させてもよく、或いは階段状に散気量を減少させてもよい。要は、硝化槽１６内の廃水の滞留時間内に廃水のＮＨ4-Ｎ濃度を所定値まで低減させるために硝化槽１６全体で必要なトータル散気量だけを散気すると共に、ＮＨ4-Ｎ濃度の高い上流端Ａ側の散気量が大きく、ＮＨ4-Ｎ濃度の低い下流端Ｂ側の散気量が小さくなるようにすればよい。
【００１９】
図４は、廃水中のＮＨ4-Ｎ濃度を所定値まで低減させるために硝化槽１６全体において必要なトータル散気量を決定するための酸素消費量の時間積算値〔Ｗ〕と時間との関係を示した図である。酸素消費量の時間積算値〔Ｗ〕は、図３で説明した酸素消費速度〔Ｋr 〕の経時変化から求めることができる。また、Ｗ1 は硝化後のＮＨ4-Ｎ濃度を０．１ｍｇ／Ｌまで低減する場合の酸素消費量の時間積算値〔Ｗ〕であり、Ｗ2 は硝化後のＮＨ4-Ｎ濃度を０．３〜０．５ｍｇ／Ｌ程度まで低減する場合の酸素消費量の時間積算値〔Ｗ〕である。従って、硝化後のＮＨ4-Ｎ濃度をどの程度にするかによって、酸素消費量の積算値〔Ｗ〕Ｗ1 又はＷ2 、更にはＷ1 又はＷ2 の間の任意の値を設定することができる。
【００２０】
これにより、第２の実施の形態の場合にも、硝化槽１６内への過剰なエアの供給を防ぎ、必要最小限のエア散気量で略完全な硝化を達成することができる。また、硝化槽１６の下流端Ｂ側の散気量の目安としては、廃水のＤＯ濃度が３ｍｇ／Ｌ以下、好ましくは２ｍｇ／Ｌ以下になるようにすることが好ましい。これにより、硝化槽１６からの液を循環配管３８を介して脱窒槽１４に循環させた時に、硝化液に同伴する酸素を極力抑制し、脱窒性能に悪影響を与えないようにできる。
【００２１】
【発明の効果】
以上説明したように、本発明の廃水の硝化方法及び装置によれば、硝化槽内への過剰なエアの供給を防ぎ、必要最小限のエア散気量で略完全な硝化を達成することができる。
また、硝化槽から脱窒槽に廃水を循環させる場合には、循環液に同伴する酸素を極力抑制することができるので、脱窒槽での脱窒性能に悪影響を与えない。
【図面の簡単な説明】
【図１】本発明の硝化装置を組み込んだ硝化・脱窒装置の構成図
【図２】アンモニア性窒素濃度と硝化速度から必要硝化時間を決定する方法の説明図
【図３】アンモニア性窒素濃度と硝化速度から必要硝化時間を決定する方法の説明図
【図４】トータル散気量を決定するための酸素消費量の積算値と時間との関係を示した図
【符号の説明】
１０…硝化装置、１２…硝化・脱窒装置、１４…脱窒槽、１６…硝化槽、２２…活性測定装置、２４…散気板、３０…ブロア、３２…エア量調整バルブ、３６…原水供給管、３８…循環配管、４４…汚泥返送配管、５８…コントローラ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitrification method and apparatus for wastewater, and more particularly to an improvement in nitrification treatment when removing ammoniacal nitrogen (hereinafter referred to as “NH 4 —N”) in wastewater such as sewage.
[0002]
[Prior art]
In the nitrification / denitrification equipment that has a denitrification tank and a nitrification tank and removes NH 4 -N in wastewater, the nitrifying bacteria in the nitrification tank oxidize NH 4 -N to nitrite nitrogen or nitrate nitrogen. Perform nitrification treatment. In actual wastewater treatment such as sewage, in order to stably maintain a high nitrogen removal rate against fluctuations in NH 4 -N load of wastewater and annual and daily fluctuations in water temperature, nitrification treatment in a nitrification tank is necessary. It is important to finish almost completely. Therefore, an actual nitrification / denitrification device is designed in accordance with the maximum load in the low water temperature period in terms of the amount of air diffused and the nitrification time for supplying oxygen necessary for nitrification to wastewater.
[0003]
[Problems to be solved by the invention]
However, if the aeration volume and nitrification time are designed according to the maximum load, it will flow from the upstream end of the nitrification tank when the load decreases, such as at night or during rainfall, or when there is sufficient nitrification performance in the high water temperature period. There is a disadvantage that the supply of air in the staying area is excessive until the wastewater is nitrified in the middle of the nitrification tank and the wastewater flows out from the downstream end of the nitrification tank thereafter. This not only wastes the power for aeration, but also causes a problem that the transparency of the treated water due to the dismantling of the activated sludge flocs deteriorates when the nitrification liquid flows into the final sedimentation basin. Furthermore, when the nitrification liquid circulates in the denitrification tank, there is a problem that the denitrification performance is deteriorated due to the introduction of air into the denitrification tank.
[0004]
The present invention has been made in view of such circumstances, and prevents wastewater from being supplied to an excessive amount of air into a nitrification tank, and can achieve substantially complete nitrification with a minimum amount of air aeration. An object of the present invention is to provide a nitrification method and apparatus.
[0005]
[Means for Solving the Invention]
In order to achieve the above object, the present invention allows the waste water flowing into the tank from the upstream end of the nitrification tank to flow out from the downstream end, and also diffuses air into the nitrification tank to cause NH 4 − in the waste water. In the nitrification method of wastewater in which N is nitrified by microorganisms, the time-dependent change in ammonia nitrogen concentration and nitrification rate or oxygen consumption rate in batch reaction is measured using the microorganism-containing wastewater at the upstream end position of the nitrification tank, The required nitrification time required to reduce the NH 4 —N concentration in the wastewater to a predetermined value is calculated from the measurement result, and the calculated required nitrification time is compared with the residence time of the wastewater in the nitrification tank. The amount of air diffused in the nitrification tank region exceeding the necessary nitrification time in the residence time is made smaller than the amount of air diffused in the nitrification tank region before exceeding the necessary nitrification time.
[0006]
Further, in order to achieve the above object, the present invention allows waste water flowing into the tank from the upstream end of the nitrification tank to flow out from the downstream end, and also diffuses air into the nitrification tank to evacuate ammonia in the waste water. In the nitrification method of wastewater where nitrifying nitrogen is treated with microorganisms, the microbial wastewater at the upstream end position of the nitrification tank is used to measure the time-dependent changes in ammonia nitrogen concentration and nitrification rate, or oxygen consumption rate in batch reaction. From the measured result, the total aeration amount of the entire nitrification tank necessary for reducing the ammonia nitrogen concentration in the wastewater to a predetermined value within the residence time of the wastewater in the nitrification tank is calculated and calculated. The distribution of the total amount of diffused air in the nitrification tank is characterized in that the upstream end side is large and the downstream end side is small.
[0007]
Further, in order to achieve the above object, the present invention allows waste water flowing into the tank from the upstream end of the nitrification tank to flow out from the downstream end, and also diffuses air into the nitrification tank to evacuate ammonia in the waste water. In a nitrification apparatus for wastewater that nitrifies nitrous acid with microorganisms, a plurality of diffusion plates that are arranged in parallel at the bottom of the nitrification tank from the upstream end side to the downstream end side and diffuse air into the nitrification tank An activity measuring device for measuring time-dependent changes in ammonia nitrogen concentration and nitrification rate, or oxygen consumption rate in batch reaction, using microorganism-containing wastewater collected from the upstream end position of the nitrification tank, and Calculation means for calculating the required nitrification time or total aeration amount of the entire nitrification tank necessary for reducing the ammonia nitrogen concentration in the wastewater to a predetermined value from the measurement results, and calculation results by the calculation means Characterized in that and a control means for individually controlling the air amount of air to the plurality of diffuser air plate based on.
[0008]
According to the present invention, the amount of air diffused in the nitrification tank region that exceeds the necessary nitrification time required to reduce the NH 4 —N concentration in the wastewater to a predetermined value is reduced in the nitrification tank before the required nitrification time is exceeded. Since the amount of air diffused in the region is smaller than that, excessive air supply to the entire nitrification tank can be prevented, and almost complete nitrification can be achieved with the minimum amount of air diffused.
[0009]
Further, according to the present invention, the total aeration amount of the entire nitrification tank necessary for reducing the NH 4 —N concentration in the wastewater to a predetermined value within the residence time of the wastewater in the nitrification tank is calculated and calculated. The distribution of the total amount of air diffused in the nitrification tank is designed so that the upstream end side is large and the downstream end side is small, so that excessive air supply to the nitrification tank is prevented and the minimum required oxygen supply amount is achieved. Substantially complete nitrification can be achieved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a waste water nitrification method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a configuration diagram of a nitrification / denitrification apparatus 12 incorporating a nitrification apparatus 10 for wastewater according to the present invention.
[0011]
The nitrification / denitrification apparatus 12 is mainly composed of a reaction tank 18 comprising one denitrification tank 14 and one nitrification tank 16, a solid-liquid separation tank 20, and an activity measuring device 22.
On the bottom of the nitrification tank 16, a plurality of air diffusion plates 24, 24... Are arranged in parallel from the upstream end A side to the downstream end B side of the nitrification tank 16, and each of the air diffusion plates 24 has branch pipes 26, 26. The merging pipe 28 is connected to the blower 30 through the merging pipe 28. Also, each branch pipe 26 is provided with air amount adjustment valves 32, 32. Thus, an aerobic condition is formed in the nitrification tank 16 by the air diffused from each diffuser plate 24, and the amount of diffused air from each diffuser plate 24 is individually adjusted by the air amount adjustment valve 32. Can do.
[0012]
On the other hand, a stirrer 34 is provided at the bottom of the denitrification tank 14, and anaerobic conditions are formed in the denitrification tank 14 by slowly stirring the wastewater in the denitrification tank 14 and degassing the air from the wastewater. The waste water supplied from the raw water supply pipe 36 into the denitrification tank 14 is mixed with the activated sludge microorganisms in the denitrification tank 14 and then flows into the upstream end A position of the nitrification tank 16. Wastewater that has flowed into the nitrification tank 16, NH 4 -N in the wastewater are nitrified by aerobic conditions with air from the air diffuser plate 24 while flowing the nitrification tank 16. The nitrification liquid subjected to nitrification is circulated from the downstream end B position of the nitrification tank 16 to the denitrification tank 14 via the circulation pipe 38 and denitrified under anaerobic conditions. Thereby, NH 4 —N in the wastewater is removed as nitrogen gas. In the circulation between the nitrification tank 16 and the denitrification tank 14, a part of the nitrification liquid in the nitrification tank 16 is discharged as treated water to the solid-liquid separation tank 20 through the treated water pipe 40. In the solid-liquid separation tank, the supernatant liquid after sedimentation and separation of the activated sludge microorganisms accompanying the treated water is discharged through the supernatant liquid pipe 42. On the other hand, the settled sludge settled in the solid-liquid separation tank 20 is returned to the raw water supply pipe 36 via the sludge return pipe 44. Further, surplus sludge of the settled sludge is extracted out of the apparatus 12 through the extraction pipe 46.
[0013]
The activity measuring device 22 is configured to supply waste water containing a certain amount of activated sludge microorganisms (hereinafter referred to as “microorganism-containing waste water”) from the upstream end A position of the nitrification tank 16 to the measuring container 50 through the water collection pipe 51. Collect water. The measurement container 50 is connected to an air pump 52 that diffuses air into the measurement container 50 and a DO concentration meter 54 that measures the DO concentration of microorganism-containing wastewater in the measurement container 50. Then, while the air is diffused from the air pump 52 into the microorganism-containing wastewater, the change in DO concentration with time is measured until the DO concentration value of the microorganism-containing wastewater does not change. Oxygen consumption rate of microbial wastewater, ammonia nitrogen (NH 4 -N) concentration and nitrification rate are automatically measured from time-dependent change of DO concentration and oxygen dissolution efficiency of air supplied to microbial wastewater in this batch operation. .
[0014]
Next, a first embodiment for determining an optimum air diffusion method will be described.
The controller 58 uses the NH 4 —N concentration [Ne I ] and the nitrification rate [K NI ] measured by the activity measuring device 22 to reduce the NH 4 —N concentration in the wastewater to a predetermined value. T N ] is calculated, and the calculated required nitrification time [T N ] is compared with the residence time [T MAX ] of the waste water in the nitrification tank 16. Then, the amount of air diffused in the region in the nitrification tank 16 that exceeds the necessary nitrification time [T N ] of the residence time [T MAX ] of the waste water in the nitrification tank 16 is nitrified before the necessary nitrification time [T N ] is exceeded. The degree of opening / closing of the air amount adjusting valve 32 of each air diffuser plate 24 is individually controlled via the signal cable 60 so as to be smaller than the air diffuser amount in the region in the tank 16. Here, the hydraulic residence time [T MAX ] of the nitrification tank 16 is determined by returning the nitrification tank volume to the raw water supply pipe 36 through the raw water supply pipe 36 and the raw water supply pipe 36 through the sludge return pipe 44. The amount of the returned sludge is calculated as a value obtained by dividing the amount of the returned sludge by the total circulation amount of the nitrification liquid circulated from the nitrification tank 16 to the denitrification tank 14 by the circulation pipe 38.
[0015]
FIG. 2 shows a method for determining the above required nitrification time [T N ] from the NH 4 -N concentration [Ne I ] and the nitrification rate [K NI ]. The vertical axis in FIG. 2 is the nitrification rate [K N ], the horizontal axis is the necessary nitrification time [T N ], and T N1 is the NH 4 -N concentration after nitrification, that is, the predetermined value is 0.1 mg / L. The required nitrification time [T N ]. As can be seen from FIG. 2, the nitrification rate [K N ] keeps a constant value of K NI , which is the maximum nitrification rate until a certain time, and then the NH 4 -N concentration is 0.3 to 0.5 mg / L or less. Draw a K N curve that suddenly decreases and approaches zero. The nitrification rate represents the decrease rate of NH 4 —N per unit time, as can be seen from the unit [mg-N / L · time]. Therefore, the necessary nitrification is performed so that the time integral value of the nitrification rate [K N ], that is, the area surrounded by the K N curve, the horizontal axis and the vertical axis in FIG. 2 becomes the NH 4 -N concentration [Ne I ]. Time [T N1 ] is determined. Thereby, the necessary nitrification time [T N1 ] necessary for reducing the NH 4 —N concentration after nitrification to 0.1 mg / L can be determined.
[0016]
When the NH 4 -N concentration after nitrification may be higher than 0.1 mg / L, for example, about 0.3 to 0.5 mg / L, the nitrification rate [K N ] maintains K NI . It is also possible to set the time T N2 in this state as the required nitrification time [T N ]. Furthermore, an arbitrary time between T N1 and T N2 can be set as the necessary nitrification time [T N ].
Figure 3 is a method for determining the required nitrification time from time course of oxygen consumption rate [K r] [T N], the oxygen consumption rate [K r], while indicating a substantially constant value K rI initially, some point Draw a Kr curve that drops rapidly at, and then transitions to a substantially constant low value. In this case, the necessary nitrification time required to reduce the NH 4 —N concentration after nitrification to a predetermined value is determined in the same manner as in the case where the necessary nitrification time [T N ] is determined from the change over time in the nitrification rate [K N ]. [T N ] can be obtained.
[0017]
As described above, when the nitrification method of the present invention is employed, it is possible to prevent supply of excessive air to the entire inside of the nitrification tank 16, and to achieve substantially complete nitrification with a minimum amount of air diffused. In this case, the amount of air diffused in the region in the nitrification tank 16 that exceeds the necessary nitrification time [T N ] should be such that the DO concentration of the wastewater is 3 mg / L or less, preferably 2 mg / L or less. Thereby, when the nitrification liquid from the nitrification tank 16 is circulated to the denitrification tank 14 via the circulation pipe 38, the oxygen accompanying the nitrification liquid is suppressed as much as possible, and the denitrification performance is not adversely affected.
[0018]
Next, a second embodiment for determining the optimum air diffusion method will be described.
In the second embodiment, the controller 58 determines the NH 4 -N concentration in the wastewater within the residence time of the wastewater in the nitrification tank 16 from the change over time of the oxygen consumption rate [K r ] measured by the activity measuring device 22. The time integrated value [W] of the oxygen consumption of the entire nitrification tank 16 necessary for reducing the value to a predetermined value is calculated. Further, it is calculated as the total amount of air diffused by converting it into an air amount in consideration of the oxygen dissolution efficiency of the nitrification tank 16. Then, the degree of opening and closing of each air amount adjustment valve 32 of each air diffuser plate 24 is individually set so that the calculated diffused air amount distribution in the nitrification tank 16 is large on the upstream end A side and small on the downstream end B side. To control. In this case, the amount of air diffusion may be decreased linearly from the upstream end A side to the downstream end B side, or the amount of air diffusion may be decreased stepwise. In short, in order to reduce the NH 4 —N concentration of the waste water to a predetermined value within the residence time of the waste water in the nitrification tank 16, only the total aeration amount necessary for the entire nitrification tank 16 is diffused, and the NH 4 − The amount of air diffused on the upstream end A side with a high N concentration may be large, and the amount of air diffused on the downstream end B side with a low NH 4 —N concentration may be small.
[0019]
FIG. 4 shows the relationship between the time integrated value [W] of oxygen consumption and time for determining the total amount of aeration required in the entire nitrification tank 16 in order to reduce the NH 4 —N concentration in the wastewater to a predetermined value. It is the figure which showed the relationship. The time integrated value [W] of the oxygen consumption can be obtained from the change with time of the oxygen consumption rate [K r ] described in FIG. W 1 is the time integrated value [W] of the oxygen consumption when the NH 4 -N concentration after nitrification is reduced to 0.1 mg / L, and W 2 is the NH 4 -N concentration after nitrification is 0 It is the time integrated value [W] of the oxygen consumption when reducing to about 3 to 0.5 mg / L. Therefore, depending on how much the NH 4 -N concentration after nitrification is to be set, an integrated value of oxygen consumption [W] W 1 or W 2 , and an arbitrary value between W 1 or W 2 should be set. Can do.
[0020]
Thereby, also in the case of the second embodiment, supply of excess air into the nitrification tank 16 can be prevented, and substantially complete nitrification can be achieved with a minimum amount of air diffused. Moreover, as a standard of the amount of aeration on the downstream end B side of the nitrification tank 16, it is preferable that the DO concentration of the wastewater is 3 mg / L or less, preferably 2 mg / L or less. Thereby, when the liquid from the nitrification tank 16 is circulated to the denitrification tank 14 via the circulation pipe 38, oxygen accompanying the nitrification liquid can be suppressed as much as possible, and the denitrification performance can be prevented from being adversely affected.
[0021]
【The invention's effect】
As described above, according to the waste water nitrification method and apparatus of the present invention, it is possible to prevent the supply of excessive air into the nitrification tank and achieve substantially complete nitrification with the minimum amount of air diffused. it can.
Further, when the wastewater is circulated from the nitrification tank to the denitrification tank, oxygen accompanying the circulating liquid can be suppressed as much as possible, so that the denitrification performance in the denitrification tank is not adversely affected.
[Brief description of the drawings]
FIG. 1 is a block diagram of a nitrification / denitrification apparatus incorporating the nitrification apparatus of the present invention. FIG. 2 is an explanatory diagram of a method for determining the necessary nitrification time from the ammonia nitrogen concentration and nitrification rate. Diagram of how to determine the required nitrification time from the nitrification rate and figure [Fig. 4] Diagram showing the relationship between the integrated value of oxygen consumption and time for determining the total amount of diffused air [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Nitrification apparatus, 12 ... Nitrification / denitrification apparatus, 14 ... Denitrification tank, 16 ... Nitrification tank, 22 ... Activity measuring apparatus, 24 ... Air diffuser plate, 30 ... Blower, 32 ... Air quantity adjustment valve, 36 ... Raw water supply Pipe, 38 ... circulation piping, 44 ... sludge return piping, 58 ... controller

Claims (4)

硝化槽の上流端から槽内に流入した廃水を下流端から流出させると共に、前記硝化槽内にエアを散気して前記廃水中のアンモニア性窒素を微生物により硝化処理する廃水の硝化方法において、
前記硝化槽の上流端位置における微生物含有廃水を使用してアンモニア性窒素濃度と硝化速度、または回分反応における酸素消費速度の経時変化を測定し、
前記測定した結果から前記廃水中のアンモニア性窒素濃度を所定値まで低減させるために必要な必要硝化時間を演算し、
前記演算した必要硝化時間と前記硝化槽内の廃水の滞留時間とを比較し、
前記滞留時間のうち前記必要硝化時間を越える硝化槽内領域における散気量を、前記必要硝化時間を越える前の硝化槽内領域における散気量よりも小さくすることを特徴とする廃水の硝化方法。In the nitrification method of wastewater in which wastewater that has flowed into the tank from the upstream end of the nitrification tank flows out from the downstream end, air is diffused into the nitrification tank, and ammonia nitrogen in the wastewater is nitrified by microorganisms.
Using the microorganism-containing wastewater at the upstream end position of the nitrification tank, the ammonia nitrogen concentration and the nitrification rate, or the time-dependent change in the oxygen consumption rate in the batch reaction,
Calculate the necessary nitrification time required to reduce the ammonia nitrogen concentration in the wastewater from the measurement results to a predetermined value,
Compare the calculated required nitrification time with the residence time of waste water in the nitrification tank,
A nitrification method for wastewater, characterized in that the amount of air diffused in the nitrification tank region exceeding the required nitrification time in the residence time is smaller than the amount of air diffused in the nitrification tank region before exceeding the necessary nitrification time. . 前記必要硝化時間を越えた硝化槽内領域における散気量の目安として、前記廃水のＤＯ濃度が２ｍｇ／Ｌ以下になるようにすることを特徴とする請求項１の廃水の硝化方法。The wastewater nitrification method according to claim 1, wherein the DO concentration of the wastewater is 2 mg / L or less as a measure of the amount of air diffused in the nitrification tank region beyond the required nitrification time. 硝化槽の上流端から槽内に流入した廃水を下流端から流出させると共に、前記硝化槽内にエアを散気して前記廃水中のアンモニア性窒素を微生物により硝化処理する廃水の硝化方法において、
前記硝化槽の上流端位置における微生物含有廃水を使用してアンモニア性窒素濃度と硝化速度、または回分反応における酸素消費速度の経時変化を測定し、
前記測定した結果から前記硝化槽内の廃水の滞留時間内に前記廃水中のアンモニア性窒素濃度を所定値まで低減させるために必要な硝化槽全体のトータル散気量を演算し、
前記演算したトータル散気量の前記硝化槽内における散気量分布を、前記上流端側が大きく前記下流端側が小さくなるようにしたことを特徴とする廃水の硝化方法。In the nitrification method of wastewater in which wastewater that has flowed into the tank from the upstream end of the nitrification tank flows out from the downstream end, air is diffused into the nitrification tank, and ammonia nitrogen in the wastewater is nitrified by microorganisms.
Using the microorganism-containing wastewater at the upstream end position of the nitrification tank, the ammonia nitrogen concentration and the nitrification rate, or the time-dependent change in the oxygen consumption rate in the batch reaction,
From the measured results, the total aeration amount of the entire nitrification tank necessary to reduce the ammonia nitrogen concentration in the wastewater to a predetermined value within the residence time of the wastewater in the nitrification tank is calculated,
The waste water nitrification method characterized in that the distribution of the calculated total diffused amount in the nitrification tank is such that the upstream end side is large and the downstream end side is small. 硝化槽の上流端から槽内に流入した廃水を下流端から流出させると共に、前記硝化槽内にエアを散気して前記廃水中のアンモニア性窒素を微生物により硝化処理する廃水の硝化装置において、
前記硝化槽内の底部に前記上流端側から前記下流端側にかけて並設され、前記硝化槽内にエアを散気する複数の散気板と、
前記硝化槽の上流端位置から採水した微生物含有廃水を使用してアンモニア性窒素濃度と硝化速度、または回分反応における酸素消費速度の経時変化を測定する活性測定装置と、
前記活性測定装置の測定結果から前記廃水中のアンモニア性窒素濃度を所定値まで低減させるために必要な必要硝化時間又は硝化槽全体のトータル散気量を演算する演算手段と、
前記演算手段による演算結果に基づいて前記複数の散気板に送気するエア量を個別に制御する制御手段と、
を備えたことを特徴とする廃水の硝化装置。In the nitrification apparatus for wastewater that causes wastewater flowing into the tank from the upstream end of the nitrification tank to flow out from the downstream end, diffuses air into the nitrification tank, and nitrifies ammoniacal nitrogen in the wastewater with microorganisms,
A plurality of diffuser plates that are arranged in parallel at the bottom of the nitrification tank from the upstream end side to the downstream end side, and diffuse air into the nitrification tank;
An activity measuring device for measuring time-dependent changes in ammonia nitrogen concentration and nitrification rate, or oxygen consumption rate in batch reaction, using microorganism-containing wastewater collected from the upstream end position of the nitrification tank;
A calculation means for calculating a necessary nitrification time or a total aeration amount of the entire nitrification tank necessary for reducing the ammoniacal nitrogen concentration in the wastewater from the measurement result of the activity measurement device to a predetermined value;
Control means for individually controlling the amount of air sent to the plurality of diffuser plates based on the calculation result by the calculation means;
A wastewater nitrification apparatus characterized by comprising:
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WO2020161825A1 (en) * 2019-02-06 2020-08-13 三菱電機株式会社 Water treatment device and water treatment method
JP7282149B2 (en) * 2019-02-06 2023-05-26 三菱電機株式会社 Water treatment device and water treatment method

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