JP5195334B2 - Waste water treatment method and waste water treatment apparatus - Google Patents
Waste water treatment method and waste water treatment apparatus Download PDFInfo
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Description
本発明は、アンモニアを含む廃水を処理するための廃水処理方法及び廃水処理装置に関し、特に、アンモニアを含む廃水に微生物を作用させて酸化（硝化）反応及び脱窒反応を行う際の、反応の安定性及び確実性が向上し、効率よく処理を進行可能な廃水処理方法及び廃水処理装置に関する。 The present invention relates to a wastewater treatment method and a wastewater treatment apparatus for treating wastewater containing ammonia, and in particular, for the reaction when oxidizing (nitrification) reaction and denitrification reaction are performed by causing microorganisms to act on wastewater containing ammonia. The present invention relates to a wastewater treatment method and a wastewater treatment apparatus that can improve the stability and reliability and can proceed with treatment efficiently.
微生物を用いた廃水処理においては、アンモニア態窒素の酸化（硝化）及び酸化態窒素（硝酸、亜硝酸）の脱窒を活性汚泥の細菌によって進行することによって廃水に含まれるアンモニアを窒素ガスに変換することができる。この処理方法は、以下のように分類することができる。 In wastewater treatment using microorganisms, ammonia contained in wastewater is converted to nitrogen gas by oxidization of ammonia nitrogen (nitrification) and denitrification of oxidized nitrogen (nitric acid, nitrous acid) by the bacteria of activated sludge. can do. This processing method can be classified as follows.
Ａ）硝化細菌によってアンモニアを酸化態窒素に変換し、メタノール等の有機物を電子供与体として用いて酸化態窒素を窒素ガスに変換する方法（活性汚泥変法。例えば、下記特許文献１参照）。
A) A method in which ammonia is converted into oxidized nitrogen by nitrifying bacteria, and oxidized nitrogen is converted into nitrogen gas using an organic substance such as methanol as an electron donor (an activated sludge modification method, for example, see
Ｂ）硝化細菌によってアンモニアを酸化態窒素に変換した後、硫黄を酸化して酸化態窒素を還元する細菌群によって酸化態窒素を窒素ガスに変換する方法。 B) A method of converting oxidized nitrogen to nitrogen gas by a group of bacteria that convert ammonia to oxidized nitrogen by nitrifying bacteria and then oxidize sulfur to reduce oxidized nitrogen.
Ｃ）硝化細菌によってアンモニアを亜硝酸態窒素に酸化する工程と、脱窒細菌に属するアナモックス（ANAMMOX）細菌によってアンモニア態窒素及び亜硝酸態窒素から窒素ガスを生成する（ＮＨ４＋＋ＮＯ２ −→Ｎ２＋２Ｈ２Ｏ）工程とによってアンモニアを窒素ガスに変換する方法（下記特許文献２参照）。
C) Oxidation of ammonia to nitrite nitrogen by nitrifying bacteria and generation of nitrogen gas from ammonia nitrogen and nitrite nitrogen by anammox bacteria belonging to denitrifying bacteria (NH 4 ++ NO 2 − → N (2 + 2H 2 O) step to convert ammonia into nitrogen gas (see
上記Ａ）及びＢ）の処理方法に比べて、上記Ｃ）の処理方法は、有機物や添加薬剤を必要とせず、処理に必要な酸素供給量も処理開始時のアンモニア態窒素の半分を酸化する量であるので、稼動に要する消費エネルギー及び負荷が少ない。しかし、アナモックス細菌は、増殖速度が極めて遅いため、事故等により菌体が死滅又は流失した場合、処理系の再生に非常に時間を要し、一旦低下した活性を復活させる場合にも回復に時間を要する。又、処理系の状態によって、亜硝酸態窒素の還元・脱窒が進行せずに酸化による硝酸態窒素の生成が進行することもあり、処理の確実性が低い。 Compared with the treatment methods of A) and B), the treatment method of C) does not require organic substances and additive agents, and the oxygen supply amount necessary for the treatment also oxidizes half of the ammonia nitrogen at the start of the treatment. Because of the amount, energy consumption and load required for operation are small. However, the growth speed of anammox bacteria is extremely slow, so if the cells are killed or lost due to an accident or the like, it takes a very long time to regenerate the treatment system, and it takes time to recover even if the activity once reduced is restored. Cost. Further, depending on the state of the treatment system, reduction and denitrification of nitrite nitrogen may not proceed, and production of nitrate nitrogen by oxidation may proceed, and the certainty of treatment is low.
このため、本願出願人による下記特許文献３では、廃水への酸素の供給を制御することによって、脱窒細菌の活性を低下させずに処理を安定的に繰り返し実施可能な方法を提示してる。
上記特許文献３においては、硝化細菌の亜硝酸態窒素生成速度が脱窒細菌の処理能力以下となるように酸素の供給を制御しており、脱窒細菌の活性低下又は死滅を生じることなく脱窒処理を進行することができる。
In
しかし、微生物による処理においては、屡々、対象細菌以外の細菌による作用が阻害要因となることがあり、上述の廃水処理も例外ではない。 However, in the treatment with microorganisms, the action by bacteria other than the target bacteria is often an inhibiting factor, and the above-mentioned wastewater treatment is no exception.
本発明は、費用のかかる薬剤や有機物の添加を用いずに効率よく廃水のアンモニアの酸化及び脱窒を実施可能で、処理の確実性が向上した廃水処理方法及び廃水処理装置を提供することを課題とする。 The present invention provides a wastewater treatment method and a wastewater treatment apparatus that can efficiently oxidize and denitrify wastewater ammonia without using expensive chemicals and organic substances, and have improved treatment reliability. Let it be an issue.
又、本発明は、処理に用いられる設備の構造が簡易で、廃水のアンモニアの酸化及び脱窒が同時に進行し、脱窒細菌の活性を低下させずに処理を繰り返す上で操作の制御及び判断が容易且つ正確に実施可能な廃水処理方法及び廃水処理装置を提供することを課題とする。 In addition, the present invention has a simple structure of equipment used for the treatment, and the oxidation and denitrification of ammonia in the wastewater proceed at the same time, and the control and judgment of the operation is repeated when the treatment is repeated without reducing the activity of the denitrifying bacteria. It is an object of the present invention to provide a wastewater treatment method and a wastewater treatment apparatus that can be carried out easily and accurately.
上記課題を解決するために、本発明者らは、廃水への酸素供給を制御する際に判断を難しくする要因について検討し、鋭意研究を重ねた結果、酸素の供給形態及び酸素要求量の予測値を利用して、酸素の供給制御を判断する上での確実性を高めることが可能であることを見出し、本発明を完成するに至った。 In order to solve the above problems, the present inventors studied factors that make judgment difficult when controlling the oxygen supply to wastewater, and as a result of earnest research, as a result of predicting the oxygen supply form and the oxygen demand. The present inventors have found that it is possible to increase the certainty in judging the supply control of oxygen by using the value, and have completed the present invention.
本発明の一態様によれば、廃水処理方法は、アンモニア酸化細菌及びアナモックス細菌の存在下で廃水に酸素を供給して、前記アンモニア酸化細菌によって廃水に含まれるアンモニア態窒素を亜硝酸態窒素に変換する酸化処理と、前記アナモックス細菌によって亜硝酸態窒素及びアンモニア態窒素から窒素ガスへ変換する脱窒処理とを進行させる廃水処理方法であって、予め、廃水に含まれるアンモニア態窒素及び亜硝酸の濃度に基づいて化学量論的に求められる、硝化脱窒反応の完遂に必要な前記酸化処理の酸素要求量Ｑaと、廃水に含まれる有機物の酸化に有機物酸化細菌が要する酸素要求量Ｑoとの和Ｑt＝Ｑa＋Ｑoを求め、前記酸素の供給を、廃水の平均溶存酸素濃度を０．１mg-Ｏ２／Ｌ以下に維持可能な一定の供給速度で実行し、前記酸素の供給によって廃水の溶存酸素濃度が上昇した時、廃水に供給された酸素供給総量Ｙと前記和Ｑtとの比較に基づいて酸素の供給停止又は供給速度低下を決定することを要旨とする。 According to one aspect of the present invention, a wastewater treatment method supplies oxygen to wastewater in the presence of ammonia-oxidizing bacteria and anammox bacteria , and converts ammonia nitrogen contained in the wastewater into nitrite nitrogen by the ammonia-oxidizing bacteria . an oxidation process for converting, to a waste water treatment method for advancing a denitrification process for converting the nitrite nitrogen and ammonia nitrogen by the anammox bacteria to nitrogen gas, in advance, ammonium nitrogen and nitrite contained in the waste water The oxygen demand Qa required for the completion of the nitrification denitrification reaction , which is determined stoichiometrically based on the concentration of oxygen, and the oxygen demand Qo required by organic matter oxidizing bacteria for the oxidation of organic matter contained in the wastewater, Sum of Qt = Qa + Qo, and the oxygen supply is performed at a constant supply rate capable of maintaining the average dissolved oxygen concentration of the wastewater at 0.1 mg-O 2 / L or less, When the concentration of dissolved oxygen in the wastewater increases due to the supply of oxygen, the gist is to determine whether to stop supplying oxygen or to reduce the supply speed based on a comparison between the total oxygen supply Y supplied to the wastewater and the sum Qt.
上記酸素供給総量Ｙと前記和Ｑtとの比較において、Ｙ≧Ｑtの時、酸素の供給を停止し、Ｙ＜Ｑtの時、酸素の供給速度を低下させることができる。 In the comparison of the total oxygen supply amount Y and the sum Qt, the supply of oxygen can be stopped when Y ≧ Qt, and the supply rate of oxygen can be reduced when Y <Qt.
本発明の一態様によれば、廃水処理装置は、上述に記載の廃水処理方法に用いられる廃水処理装置であって、廃水、前記廃水に含まれるアンモニア態窒素を亜硝酸態窒素に変換するアンモニア酸化細菌、及び、前記廃水に含まれるアンモニア態窒素及び亜硝酸態窒素から窒素ガスへ変換するアナモックス細菌を収容するための、水平断面形状が実質的に一定である内部形状を有する処理槽と、前記処理槽に収容される廃水に酸素を供給するための、前記処理槽の底部に設けられる酸素供給装置と、前記酸素供給装置による廃水への酸素の供給速度を制御するための制御装置と、前記廃水の深度毎に溶存酸素濃度を測定するための溶存酸素濃度測定装置とを有することを要旨とする。 According to one aspect of the present invention, a wastewater treatment apparatus is a wastewater treatment apparatus used in the above-described wastewater treatment method , wherein ammonia is converted into wastewater and ammonia nitrogen contained in the wastewater into nitrite nitrogen. A treatment tank having an internal shape with a substantially constant horizontal cross-sectional shape for containing oxidizing bacteria and anammox bacteria that convert ammonia nitrogen and nitrite nitrogen contained in the wastewater into nitrogen gas; An oxygen supply device provided at the bottom of the treatment tank for supplying oxygen to the wastewater stored in the treatment tank; and a control device for controlling the supply rate of oxygen to the wastewater by the oxygen supply apparatus; The gist is to have a dissolved oxygen concentration measuring device for measuring the dissolved oxygen concentration for each depth of the waste water.
上記酸素供給装置は、酸素を主体とし、水溶性ガスのみで構成される気泡を前記廃水に供給することができ、直径が３００μｍ以下の気泡を発生する装置を採用することができる。 The oxygen supply apparatus, the oxygen mainly, only can supply air bubbles formed in the effluent water-soluble gas, the diameter can be adopted an apparatus for generating a following bubble 300 [mu] m.
本発明によれば、脱窒細菌が常に好適に増殖・活動可能なように廃水の溶存酸素濃度が制御され、脱窒細菌の活性回復のための時間が不要であるので、効率的に廃水処理を進行でき、廃水処理の繰り返しが遅滞なく行える。酸化・脱窒反応の酸素要求量の予測値を用いて有機物の酸化による酸素の消費を考慮した判断を行うことにより、酸素供給を制御する上での判断の精度が改善されるので、処理の安定性が向上した廃水の処理方法及び処理装置が提供される。又、処理に要する設備の構造も簡易であり、外部から処理系に添加する有機物や薬剤等の費用が嵩まないので、処理コストの点でも有利である。又、アンモニア及び亜硝酸態窒素を連続モニタリングする必要がないので、このための高価なセンサー等の機器を装備する必要がない。 According to the present invention, the concentration of dissolved oxygen in the wastewater is controlled so that the denitrifying bacteria can always suitably grow and operate, and no time is required for recovering the activity of the denitrifying bacteria. The wastewater treatment can be repeated without delay. By using the predicted oxygen demand for the oxidation / denitrification reaction to make decisions that take into account the consumption of oxygen due to the oxidation of organic matter, the accuracy of the judgment in controlling the oxygen supply is improved. A wastewater treatment method and treatment apparatus with improved stability are provided. In addition, the structure of equipment required for processing is simple, and the cost of organic substances and chemicals added to the processing system from the outside does not increase, which is advantageous in terms of processing cost. Further, since it is not necessary to continuously monitor ammonia and nitrite nitrogen, it is not necessary to equip equipment such as an expensive sensor for this purpose.
微生物を用いた硝化・脱窒による廃水処理において、酸素が供給されると、アンモニアは硝化細菌によって酸化態窒素（亜硝酸及び硝酸）に変換される（概して硝化と称する）が、このプロセスでは、アンモニア酸化細菌がアンモニアを亜硝酸態窒素に変換する処理（亜硝酸化、２ＮＨ４ ＋＋３Ｏ２→２ＮＯ２ −＋４Ｈ＋＋２Ｈ２Ｏ）と、硝酸化を行う硝化細菌が亜硝酸態窒素を硝酸態窒素に変換する処理（硝酸化）とが進行する。この系に、脱窒細菌であるアナモックス細菌が存在すると、アナモックス細菌は、アンモニア及び亜硝酸から窒素ガスを生成する（ＮＨ４ ＋＋ＮＯ２ −→Ｎ２＋２Ｈ２Ｏ）ので、この処理が良好に進行すれば、アンモニアの殆ど（約９０％）を窒素ガスに変換できる（４ＮＨ４ ＋＋３Ｏ２＋４ＨＣＯ３ −→２Ｎ２＋４ＣＯ２＋１０Ｈ２Ｏ．実際には、ＮＨ４ ＋＋1.32ＮＯ２ −＋0.066ＨＣＯ３ −＋0.13Ｈ＋→1.02Ｎ２＋0.26ＮＯ３ −＋0.066ＣＨ２Ｏ０．５Ｎ０．１５＋2.03Ｈ２Ｏ、Appl. Microbiol. Biotechnol.(1998) 50, 589-596参照）。しかし、実際には脱窒工程の確実性が低く、処理条件によってアナモックス細菌の活性が低下し、硝酸化反応が進行する。これは、亜硝酸濃度によってアナモックス細菌の活性が変動するためであるので、廃水への酸素供給を適切に制御することによってアナモックス細菌が脱窒反応を好適に進行させる状態を維持できる。具体的には、硝化細菌であるアンモニア酸化細菌と脱窒細菌であるアナモックス細菌との存在下で廃水に酸素を供給してアンモニアの亜硝酸化及び亜硝酸の窒素ガスへの変換を進行させる廃水処理において、アナモックス細菌が亜硝酸態窒素を窒素ガスに変換する処理能力に応じて、これを超えないように酸素の供給が適切に制御される。これにより、アンモニアの酸化及び脱窒が同時に進行し、この間、アナモックス細菌の活性状態は良好に維持されるので、細菌の活性を回復するための準備時間や手間は不要となる。
In wastewater treatment by nitrification and denitrification using microorganisms, when oxygen is supplied, ammonia is converted to oxidized nitrogen (nitrite and nitric acid) by nitrifying bacteria (generally called nitrification). In this process, processing ammonium oxidizing bacteria to convert ammonia to nitrite nitrogen (nitrite reduction, 2NH 4 + + 3O 2 → 2NO 2 - + 4H + + 2H 2 O) and, nitrate nitrifying bacteria performing nitrating is a nitrite nitrogen Treatment (nitrification) to convert to nitrogen proceeds. When anammox bacteria, which are denitrifying bacteria, are present in this system, anammox bacteria generate nitrogen gas from ammonia and nitrous acid (NH 4 + + NO 2 − → N 2 + 2H 2 O). if progress, most ammonia (about 90%) can be converted into nitrogen gas (4NH 4 + + 3O 2 + 4HCO 3 - →
しかし、廃水処理を繰り返す間に、屡々、予想外の状況が生じて判断が困難となったり、判断が誤まりとなる場合が生じる。この原因について検討した結果、廃水中の有機物を酸化する細菌（有機物酸化細菌）の繁殖であることが判明した。このため、有機物酸化細菌の活動を見定め、これに消費される酸素量を考慮して酸素の供給制御についての判断を行う必要がある。 However, while the wastewater treatment is repeated, an unexpected situation often occurs and the judgment becomes difficult or the judgment becomes erroneous. As a result of examining this cause, it was found that this is the propagation of bacteria that oxidize organic matter in wastewater (organic matter oxidizing bacteria). For this reason, it is necessary to determine the oxygen supply control in consideration of the activity of organic matter oxidizing bacteria and taking into account the amount of oxygen consumed.
本発明では、上記を実現するために、廃水への酸素供給量を正確に把握可能な供給形態を採用すると共に、状態変化に対応して酸素供給の制御を行う際に、廃水の当初の水質（アンモニア濃度）から予測される酸素要求量を考慮して判断する。 In the present invention, in order to realize the above, a supply mode capable of accurately grasping the oxygen supply amount to the wastewater is adopted, and when the oxygen supply is controlled in response to the state change, the initial water quality of the wastewater is determined. Judgment is made in consideration of the oxygen demand estimated from (ammonia concentration).
以下、有機物酸化細菌による影響と、それに対処するための本発明の構成について詳細に説明する。 Hereinafter, the influence of organic matter oxidizing bacteria and the configuration of the present invention for coping with it will be described in detail.
アンモニアを含有する廃水に酸素（通常、空気を用いる）を供給すると、アンモニア酸化細菌は、アンモニアを亜硝酸態窒素に変換する。この反応で生成する亜硝酸態窒素の量は、供給される酸素の量に応じて増加するが、酸素の供給がアンモニア酸化細菌の処理能力（最大酸素消費速度［mol-Ｏ２／ｈ］）を超えると、処理速度を超える過剰分の酸素は消費されずに廃水の溶存酸素濃度を増加させる。一方、アナモックス細菌は、生成した亜硝酸態窒素とアンモニア態窒素とから窒素ガスを生成するので、アンモニア酸化細菌が生成する亜硝酸態窒素量がアナモックス細菌の処理能力（最大亜硝酸態窒素消費速度［mol-Ｎ／ｈ］）を超えない限り、生成する亜硝酸態窒素は全てアナモックス細菌に消費されるので、系内の亜硝酸濃度は増加しない。しかし、アナモックス細菌の活性は系内の溶存酸素濃度が高まると低下し、又、系内の亜硝酸濃度が増加すると細菌は被毒する（亜硝酸濃度が２０mg-Ｎ／Ｌを超えると最終的に死滅する）ので、過剰量の酸素を供給すると、溶存酸素濃度の上昇による活性低下及びそれに伴う亜硝酸濃度の増加による被毒によってアナモックス細菌の失活及び脱窒の減退を生じ、更に亜硝酸態窒素濃度を昂進させる。しかも、亜硝酸を硝酸に酸化する硝化細菌が増殖し易くなる。これに対し、酸素の供給が適量に制限されれば、廃水の溶存酸素濃度も亜硝酸濃度も増加せず、アナモックス細菌は有効に作用する。溶存酸素による活性低下及び亜硝酸による被毒を生じない条件は、廃水の亜硝酸濃度が２０mg-Ｎ／Ｌ以下、好ましくは１０mg-Ｎ／Ｌ以下、溶存酸素濃度が１mg-Ｏ２／Ｌ以下、好ましくは０．５１mg-Ｏ２／Ｌ以下であるので、この条件が満たされれば、アナモックス細菌は有効に作用する。従って、処理開始時の廃水の溶存酸素濃度が上記条件を満たし、アンモニア酸化細菌の処理能力を超えない範囲で酸素を供給することによって溶存酸素濃度の上昇を防止できる。そして、アンモニア酸化細菌による亜硝酸態窒素の生成速度がアナモックス細菌による亜硝酸態窒素の処理能力以下となるように酸素の供給速度が調整されていれば、亜硝酸態窒素の生成段階が律速となり、生成する亜硝酸は直ちにアナモックス細菌によって消費されるので、アンモニア酸化細菌による酸化処理速度がアナモックス細菌による脱窒処理速度と実質的に等しくなり、廃水の亜硝酸濃度の上昇は防止される。この結果、アナモックス細菌にとって良好な状態に保たれ、アンモニア酸化細菌とアナモックス細菌とは共存状態で同時に反応してアンモニアの酸化及び脱窒が連動的に進行し、アンモニアが無くなった時点で両細菌の活動は同時に終了する。これにより、溶存酸素濃度は急激に上昇するので、処理の終了を検知することができる。 When oxygen (usually using air) is supplied to wastewater containing ammonia, ammonia oxidizing bacteria convert ammonia to nitrite nitrogen. The amount of nitrite nitrogen produced in this reaction increases with the amount of oxygen supplied, but the supply of oxygen is the treatment capacity of ammonia oxidizing bacteria (maximum oxygen consumption rate [mol-O 2 / h]). If it exceeds, the excess oxygen exceeding the treatment rate is not consumed, but the dissolved oxygen concentration in the wastewater is increased. On the other hand, anammox bacteria produce nitrogen gas from the produced nitrite nitrogen and ammonia nitrogen, so the amount of nitrite nitrogen produced by ammonia oxidizing bacteria is the processing capacity of anammox bacteria (maximum nitrite nitrogen consumption rate) As long as [mol-N / h]) is not exceeded, all nitrite nitrogen produced is consumed by anammox bacteria, so the nitrite concentration in the system does not increase. However, the activity of anammox bacteria decreases as the dissolved oxygen concentration in the system increases, and when the nitrite concentration in the system increases, the bacteria become poisoned (if the nitrous acid concentration exceeds 20 mg-N / L, the anammox bacteria will eventually become poisonous. If an excessive amount of oxygen is supplied, the activity decreases due to the increase in dissolved oxygen concentration and the poisoning due to the increase in nitrous acid concentration causes deactivation of anammox bacteria and decrease in denitrification. Increase nitrogen concentration. Moreover, nitrifying bacteria that oxidize nitrous acid to nitric acid are likely to grow. On the other hand, if the supply of oxygen is limited to an appropriate amount, the dissolved oxygen concentration and nitrous acid concentration of the wastewater will not increase, and the anammox bacteria will work effectively. The conditions for reducing the activity due to dissolved oxygen and causing no poisoning with nitrous acid are as follows: wastewater nitrous acid concentration is 20 mg-N / L or less, preferably 10 mg-N / L or less, and dissolved oxygen concentration is 1 mg-O 2 / L or less. Since it is preferably 0.51 mg-O 2 / L or less, if this condition is satisfied, the anammox bacteria will act effectively. Therefore, it is possible to prevent an increase in the dissolved oxygen concentration by supplying oxygen in a range where the dissolved oxygen concentration at the start of treatment satisfies the above conditions and does not exceed the treatment capacity of the ammonia-oxidizing bacteria. If the oxygen supply rate is adjusted so that the production rate of nitrite nitrogen by ammonia-oxidizing bacteria is less than the nitrite nitrogen treatment capacity by anammox bacteria, the nitrite nitrogen production stage becomes rate-limiting. Since the produced nitrous acid is immediately consumed by the anammox bacteria, the oxidation treatment rate by the ammonia-oxidizing bacteria becomes substantially equal to the denitrification treatment rate by the anammox bacteria, and an increase in the nitrite concentration of the wastewater is prevented. As a result, the anammox bacteria are kept in a good state, and the ammonia-oxidizing bacteria and the anammox bacteria react simultaneously in the coexistence state, and the oxidation and denitrification of ammonia proceed in conjunction with each other. Activities end at the same time. Thereby, since the dissolved oxygen concentration rises rapidly, the completion | finish of a process is detectable.
上述のような低い溶存酸素濃度においては、通常、有機物を酸化する細菌（有機物酸化細菌）の多くは活動しない。ところが、有機物酸化細菌の中に、種類は少ないが、０．１mg-Ｏ２／Ｌ程度の低い溶存酸素濃度においても活動可能なものが存在し、これが廃水中に共存すると、上述のように酸素供給速度を制御しても、アンモニア酸化細菌と競合して酸素を消費する。この場合、アンモニア酸化細菌及びアナモックス細菌による硝化脱窒反応の終了を溶存酸素濃度の上昇によって検知することは難しくなる。具体的には、アンモニアの枯渇により硝化脱窒反応が終了したと想定した場合、それによって溶存酸素濃度が上昇しても有機物酸化細菌は活発に活動するので、結果として、溶存酸素濃度は若干の上昇及び下降を経て、硝化脱窒終了前とさほど変化がないレベルになる。従って、硝化・脱窒反応の終了を検知することが難しい。他方、有機物の枯渇により有機物酸化反応が終了したと想定した場合、アンモニア酸化細菌への酸素供給が増加して生成する亜硝酸が増加し、アンモニア酸化細菌の処理能力を超えた酸素によって溶存酸素濃度が上昇するので、アナモックス細菌の活性が低下し、亜硝酸濃度の増加によって被毒する。従って、溶存酸素濃度が上昇した時、正常状態で硝化脱窒反応が終了したことに因るのか、有機物酸化細菌が活動してその反応が終了したのか、判別が難しい。 At the low dissolved oxygen concentration as described above, many bacteria that oxidize organic matter (organic matter oxidizing bacteria) usually do not work. However, there are few types of organic matter oxidizing bacteria, but there are those that are active even at a dissolved oxygen concentration as low as about 0.1 mg-O 2 / L. Even if the supply rate is controlled, oxygen is consumed in competition with ammonia-oxidizing bacteria. In this case, it is difficult to detect the end of the nitrification / denitrification reaction by the ammonia-oxidizing bacteria and anammox bacteria by increasing the dissolved oxygen concentration. Specifically, assuming that the nitrification and denitrification reaction has ended due to depletion of ammonia, even if the dissolved oxygen concentration rises, the organic matter oxidizing bacteria are active. As a result, the dissolved oxygen concentration is slightly After going up and down, it becomes a level that doesn't change much before nitrification denitrification ends. Therefore, it is difficult to detect the end of the nitrification / denitrification reaction. On the other hand, assuming that the organic matter oxidation reaction was terminated due to depletion of organic matter, the oxygen supply to the ammonia oxidizing bacteria increased, resulting in an increase in nitrous acid, and the dissolved oxygen concentration due to oxygen exceeding the processing capacity of the ammonia oxidizing bacteria , The activity of anammox bacteria decreases, and poisoning occurs by increasing the concentration of nitrite. Therefore, when the dissolved oxygen concentration is increased, it is difficult to determine whether the nitrification denitrification reaction has been completed in a normal state or whether the reaction has been completed by the action of organic oxidative bacteria.
このため、本発明では、アンモニア酸化細菌及びアナモックス細菌による硝化脱窒反応を完遂させるのに必要な酸素要求量Ｑa及び有機物酸化細菌による有機物酸化反応に消費される酸素要求量Ｑoを、廃水の初期アンモニウム濃度、亜硝酸濃度及び有機物濃度等から算出される予測値として予め求めておき、廃水の溶存酸素濃度が上昇した時点において廃水に供給されている酸素供給量と比較し、この比較に基づいて、酸素供給の停止又は供給量の減少を実行する。 For this reason, in the present invention, the oxygen demand Qa required for completing the nitrification denitrification reaction by ammonia oxidizing bacteria and anammox bacteria and the oxygen demand Qo consumed by the organic matter oxidizing reaction by the organic matter oxidizing bacteria are set as the initial values of the waste water. Obtained in advance as a predicted value calculated from the ammonium concentration, nitrous acid concentration, organic matter concentration, etc., and compared with the oxygen supply amount supplied to the wastewater at the time when the dissolved oxygen concentration of the wastewater rose, based on this comparison , Stop the oxygen supply or reduce the supply amount.
上述の比較を実施するためには、廃水に供給される酸素を実質的に完全に溶解させることが肝要である。これを目視により容易に判別可能な実施形態として、曝気によって供給するガスを実質的に酸素からなるガスとするか、或いは、酸素を主体として、酸素以外の成分については水に溶解するガスのみ（但し微生物への影響はないものとする）とする方法がある。供給する気泡が水に溶解し難い成分を含まず水溶性ガスのみで構成されれば、気泡は廃水への溶解によって消失するので、廃水中に放出された気泡が水面に到達するまでに消失するか否かによって供給されるガスが完全に廃水に溶解したか否かを判断することができる。これに関し、気泡からガス成分が溶解する速度は気泡の表面積によって変化し、気泡サイズが大きいと、完全に廃水に溶解するまでの時間が長くなるため、廃水の水深を深くする必要がある。従って、廃水に供給されるガスの気泡サイズが小さいマイクロバブル発生装置（Felix Sebba, "An Improved generator for micron-sized bubbles", Chemistyr and Industyr, 4, february 1985, pp91-92）を利用すると、処理装置の設計上有利であり、直径３００μｍ以下、好ましくは１００μｍ以下の微小気泡が好適に供給される。 In order to carry out the above comparison, it is important to dissolve the oxygen supplied to the waste water substantially completely. As an embodiment in which this can be easily discriminated visually, the gas supplied by aeration is a gas consisting essentially of oxygen, or oxygen is the main component and only the gas that dissolves in water for components other than oxygen ( However, there is a method that does not affect microorganisms). If the bubbles to be supplied do not contain components that are difficult to dissolve in water and are composed of only water-soluble gas, the bubbles disappear by dissolution in the wastewater, so the bubbles released in the wastewater disappear by the time they reach the water surface Whether or not the supplied gas is completely dissolved in the waste water can be determined. In this regard, the speed at which the gas component dissolves from the bubbles changes depending on the surface area of the bubbles, and if the bubble size is large, the time until it completely dissolves in the wastewater becomes longer, so the depth of the wastewater needs to be deepened. Therefore, when using a microbubble generator (Felix Sebba, "An Improved generator for micron-sized bubbles", Chemistyr and Industyr, 4, february 1985, pp91-92) This is advantageous in the design of the apparatus, and microbubbles having a diameter of 300 μm or less, preferably 100 μm or less are suitably supplied.
上述の細菌が存在する廃水に一定の供給速度で酸素気泡（他の水溶性ガスを含み得る）を供給して、水面より下で酸素気泡が消失する状態にある時、供給される酸素は全て廃水に溶解しており、気泡の消失点から水面までの領域では、気泡からの直接の酸素供給はなく、下方からの拡散による酸素供給のみである。この状態における廃水の深度と溶存酸素濃度との関係を求めると、溶存酸素濃度は、気泡供給点から深度減少（浅くなる）に従って急激に上昇し、気泡消失点で極大値を示して、気泡消失点から水面まで急激に減少する。つまり、深度による溶存酸素濃度曲線は極大点を有する。 When oxygen bubbles (which may contain other water-soluble gases) are supplied to the wastewater in which the above-mentioned bacteria are present at a constant supply rate, all oxygen supplied is in a state where the oxygen bubbles disappear below the surface of the water. In the region from the disappearance point of the bubbles to the water surface, which is dissolved in the waste water, there is no direct oxygen supply from the bubbles, but only oxygen supply by diffusion from below. When the relationship between the depth of the wastewater and the dissolved oxygen concentration in this state is obtained, the dissolved oxygen concentration rapidly increases as the depth decreases (shallows) from the bubble supply point, shows a maximum value at the bubble vanishing point, and the bubble disappears. It decreases rapidly from the point to the water surface. That is, the dissolved oxygen concentration curve with depth has a maximum point.
また、一定の供給速度で酸素気泡を供給した時に酸素気泡の消失点が一定の位置にある状態では、酸素の供給速度は、細菌の酸素消費速度以下である。従って、この時の廃水の溶存酸素濃度（平均値）が０．１mg-Ｏ２／Ｌ程度以下であれば、概して溶存酸素濃度の最大値が０．５１mg-Ｏ２／Ｌを超えることは防止され、アナモックス細菌の活性低下及び亜硝酸濃度増加による被毒は防止できる。故に、本発明においては、酸素気泡の消失点が水面より下に存在する（＝深度による溶存酸素濃度曲線が極大点を示す）状態が維持され、平均溶存酸素濃度が０．１mg-Ｏ２／Ｌ程度以下となるような、一定の供給速度で酸素気泡を供給することを廃水への酸素供給の条件とする。 In addition, when the oxygen bubbles are supplied at a constant supply rate and the vanishing point of the oxygen bubbles is at a fixed position, the oxygen supply rate is less than the oxygen consumption rate of the bacteria. Therefore, if the dissolved oxygen concentration (average value) of the wastewater at this time is about 0.1 mg-O 2 / L or less, generally the maximum value of the dissolved oxygen concentration is prevented from exceeding 0.51 mg-O 2 / L. Thus, poisoning due to decreased activity of anammox bacteria and increased nitrite concentration can be prevented. Therefore, in the present invention, a state in which the disappearance point of the oxygen bubbles exists below the water surface (= the dissolved oxygen concentration curve by the depth shows the maximum point) is maintained, and the average dissolved oxygen concentration is 0.1 mg-O 2 / Supplying oxygen bubbles at a constant supply rate that is about L or less is a condition for supplying oxygen to wastewater.
この状態から、酸素の供給速度を増加させて細菌（アンモニア酸化細菌及び有機物酸化細菌）の酸素消費速度を超えると、溶存酸素濃度は全深度において増加して水の酸素飽和濃度を最大値として一定になる。つまり、溶存酸素濃度曲線は極大点を消失し、これにより、気泡の消失点も上昇して水面に達し、気泡消失点もなくなる。あるいは、酸素の供給速度が一定に維持されていて、細菌の酸素消費速度が減少する（アンモニア又は有機物が枯渇し反応が終了する）場合にも、同様に溶存酸素濃度の増加と共に溶存酸素濃度曲線の極大点はなくなり、気泡の消失点もなくなる。つまり、酸素の供給速度に対して細菌の酸素消費速度が相対的に減少すれば、気泡消失点及び溶存酸素濃度曲線の極大点を消失する。従って、細菌の酸素消費速度の減少（＝アンモニア又は有機物の枯渇）を、溶存酸素濃度曲線の極大点又は気泡消失点の消失によって検知できる。 From this state, if the oxygen supply rate is increased to exceed the oxygen consumption rate of bacteria (ammonia-oxidizing bacteria and organic matter-oxidizing bacteria), the dissolved oxygen concentration increases at all depths, and the oxygen saturation concentration of water remains constant at the maximum value. become. In other words, the dissolved oxygen concentration curve disappears from the maximum point, whereby the disappearance point of the bubbles rises to reach the water surface and the disappearance point of the bubbles disappears. Alternatively, when the oxygen supply rate is kept constant and the oxygen consumption rate of bacteria decreases (ammonia or organic matter is depleted and the reaction ends), the dissolved oxygen concentration curve similarly increases with the dissolved oxygen concentration. There is no maximum point and no vanishing point. That is, if the oxygen consumption rate of bacteria decreases relative to the oxygen supply rate, the bubble disappearance point and the dissolved oxygen concentration curve maximum point disappear. Therefore, a decrease in the oxygen consumption rate of bacteria (= depletion of ammonia or organic matter) can be detected by disappearance of the maximum point of the dissolved oxygen concentration curve or the disappearance point of bubbles.
上述の事項に基づいて、本発明の廃水の処理方法においては、廃水の深度と溶存酸素濃度との関係に基づいて酸素の供給速度を制御し、予め廃水の水質から予測される酸素要求量と酸素供給量とを用いて状況判断を行う。以下に、本発明に係る廃水処理方法及び使用する廃水処理装置の一実施形態について図１を参照して説明する。 Based on the above items, in the wastewater treatment method of the present invention, the oxygen supply rate is controlled based on the relationship between the depth of the wastewater and the dissolved oxygen concentration, The situation is judged using the oxygen supply amount. Hereinafter, an embodiment of a wastewater treatment method according to the present invention and a wastewater treatment apparatus to be used will be described with reference to FIG.
まず、廃水及び活性汚泥を収容するための回分式処理槽と；処理槽底部に設けられ、酸素気泡が廃水の水面より下で消失して完全に溶解可能な気泡サイズで酸素気泡を廃水に供給可能な曝気装置と；曝気装置の酸素供給速度を調節するための制御装置と；処理槽に収容される廃水の深度による溶存酸素濃度を測定可能な溶存酸素測定装置とを有する廃水の処理装置を準備する。処理槽は、円柱、多角柱等のような水平断面形状が一定となる内部形状を有し、酸素気泡が廃水の水面より下で消失して完全に溶解可能となるような深さを有し、廃水を入排水する配管と、菌体を回収する場合に使用する底部排出口とを備える。曝気装置としてマイクロバブル発生装置を採用すると、処理槽の深さを短縮でき、有利である。溶存酸素測定装置は、検出部を処理槽内で鉛直方向に移動させて廃水の深度毎に溶存酸素濃度を測定可能なものであればよい。 First, a batch-type treatment tank for storing wastewater and activated sludge; provided at the bottom of the treatment tank, oxygen bubbles disappear below the surface of the wastewater and supply oxygen bubbles to the wastewater with a bubble size that can be completely dissolved A wastewater treatment apparatus comprising: a possible aeration apparatus; a control apparatus for adjusting an oxygen supply rate of the aeration apparatus; and a dissolved oxygen measurement apparatus capable of measuring a dissolved oxygen concentration according to a depth of wastewater contained in a treatment tank prepare. The treatment tank has an internal shape with a constant horizontal cross-sectional shape such as a cylinder, a polygonal column, etc., and has a depth such that oxygen bubbles disappear below the surface of the wastewater and can be completely dissolved. A pipe for receiving and draining waste water and a bottom outlet used for collecting bacterial cells are provided. Adopting a microbubble generator as an aeration device can advantageously reduce the depth of the treatment tank. The dissolved oxygen measuring device only needs to be capable of measuring the dissolved oxygen concentration for each depth of wastewater by moving the detection unit in the vertical direction in the treatment tank.
廃水処理に際して、予め細菌の培養を行ってアンモニア酸化細菌及びアナモックス細菌を準備するか、市販のものを入手する。各細菌の培養は、従来法に従って公知技術により適宜行うことができ、アンモニアを分解する既存の水処理プラントのスラッジから周知の方法により得られる。アンモニア酸化細菌については、例えば、B. Sorriano及びM. Walkerの文献(J. Applied Bacteriology, 31, 493-497(1968))を参照して単離でき、アナモックス細菌については、特表２００１−５０６５３５号公報等を参照して用意でき、オランダ国バールンのCentraal Bureau voor Schimmelculturesにより登録番号９４９８７（１９８７年１２月１２日）で寄託されるスラッジを利用できる。各培養細菌の菌体量及び活性は下記の文献を参照して調べることができ、これらから各細菌の処理能力が分かる。 At the time of wastewater treatment, bacteria are cultured in advance to prepare ammonia oxidizing bacteria and anammox bacteria, or commercially available ones are obtained. Culture of each bacterium can be appropriately performed by a known technique according to a conventional method, and can be obtained by a known method from sludge of an existing water treatment plant that decomposes ammonia. Ammonia-oxidizing bacteria can be isolated with reference to, for example, the literature of B. Sorriano and M. Walker (J. Applied Bacteriology, 31, 493-497 (1968)). The sludge deposited with the registration number 94987 (December 12, 1987) by the Centraal Bureau voor Schimmelcultures in Baarn, the Netherlands can be used. The amount and activity of each cultured bacterium can be examined with reference to the following literature, and the processing ability of each bacterium can be understood from these.
（アンモニア酸化細菌）
菌体量： Wagner M., Rath G., Amann R., Koops H.-P. and Schleifer K.-H., "In situ identification of ammonia-oxidizing bacteria", Syst. Appl. Microbiol. 18(1995), p251-264.
活性： Grunditz C. and Dalhammar G., "Development of nitrification inhibition assays using pure cultures of nitrosomonas and nitrobacter", Water Research, Vol.35(2001), Issue 2, p433-440.
（アナモックス細菌）
菌体量： Schmid M. et al., "Candidatus "Scalindual brodae", sp. nov., Candidatus "Scalindua Wagneri", sp. nov., Two New Species of Anaerobic Ammonium Oxidizing Bacteria", Syst. Appl. Microbiol., 26(2003), No.4, p529-538.
活性： Sliekers A. et al., "Completely autotrophic nitrogen removal over nitrite in one single reactor", Water Research, Vol.36(2002), Issue 10, p2475-2482.
用意した細菌及び廃水を処理槽に投入する。亜硝酸による被毒を可能な限り避けるためには、アンモニア酸化細菌の処理能力よりアナモックス細菌の処理能力が高くなるように細菌の添加割合を設定するのが好ましい。廃水容積当たりの菌体量としては、各々、２０００mg-ＶＳＳ／Ｌ程度が好ましい。前述した酸化・脱窒の反応式から理解されるように、アナモックス細菌を用いた酸化及び脱窒の反応は重炭酸イオン（空気中の炭酸ガスが使用可能）を必要とする。このため、廃水の状態に応じて炭酸水素ナトリウム等の重炭酸塩が添加される。重炭酸塩を構成する塩基は、重金属等の細菌の生育・増殖を阻害するもの以外であれば特に制限はない。添加量は、廃水のアンモニア濃度に応じて、アンモニア１モル当たり重炭酸塩０．１〜２モルとなる量を添加するのが好ましい。廃水中にナトリウム等の金属又は強塩基が含まれている場合には、炭酸ガスの吹き込みよる重炭酸イオンの導入が可能であり、細菌を添加する前の廃水に導入する。炭酸ガスを吹き込んだ水を重炭酸塩の代わりに使用することも可能であり、処理後の廃水の一部を吹き込み用の水として利用してもよい。或いは、酸素を供給する際にＣＯ２を供給してもよい。
(Ammonia-oxidizing bacteria)
Bacterial mass: Wagner M., Rath G., Amann R., Koops H.-P. and Schleifer K.-H., "In situ identification of ammonia-oxidizing bacteria", Syst. Appl. Microbiol. 18 (1995 ), p251-264.
Activity: Grunditz C. and Dalhammar G., "Development of nitrification inhibition assays using pure cultures of nitrosomonas and nitrobacter", Water Research, Vol.35 (2001),
(Anamox bacteria)
Cell weight: Schmid M. et al., "Candidatus" Scalindual brodae ", sp. Nov., Candidatus" Scalindua Wagneri ", sp. Nov., Two New Species of Anaerobic Ammonium Oxidizing Bacteria", Syst. Appl. Microbiol. , 26 (2003), No. 4, p529-538.
Activity: Sliekers A. et al., "Completely autotrophic nitrogen removal over nitrite in one single reactor", Water Research, Vol. 36 (2002),
Put the prepared bacteria and wastewater into the treatment tank. In order to avoid poisoning by nitrous acid as much as possible, it is preferable to set the addition ratio of bacteria so that the treatment capacity of anammox bacteria is higher than the treatment capacity of ammonia oxidizing bacteria. The amount of bacterial cells per waste water volume is preferably about 2000 mg-VSS / L. As understood from the above-described reaction formula of oxidation / denitrification, the reaction of oxidation and denitrification using anammox bacteria requires bicarbonate ions (carbon dioxide in the air can be used). For this reason, bicarbonates such as sodium bicarbonate are added according to the state of the wastewater. The base constituting the bicarbonate is not particularly limited as long as it does not inhibit the growth and proliferation of bacteria such as heavy metals. It is preferable to add an amount of 0.1 to 2 moles of bicarbonate per mole of ammonia, depending on the ammonia concentration of the wastewater. When a metal such as sodium or a strong base is contained in the wastewater, bicarbonate ions can be introduced by blowing carbon dioxide gas and introduced into the wastewater before adding bacteria. It is also possible to use water into which carbon dioxide gas has been blown instead of bicarbonate, and a part of the waste water after treatment may be used as water for blowing. Alternatively, CO 2 may be supplied when oxygen is supplied.
廃水処理に先立って、廃水の初期のアンモニア濃度及び亜硝酸濃度から、アンモニア酸化細菌及びアナモックス細菌が硝化脱窒を終了するのに必要とされる酸素要求量Ｑaを算出し、有機物酸化細菌が有機物の酸化を完了するのに必要な酸素要求量Ｑoを決定して、和Ｑt＝Ｑa＋Ｑ0を求める（工程Ｓ１）。アンモニア濃度及び亜硝酸濃度は、イオン電極や簡易比色法による分析値に基づいて決定でき、前述の硝化脱窒反応の反応式に従って化学量論的に酸素要求量Ｑaを求めることができる。有機物酸化細菌の酸素要求量Ｑoは、例えば、活性汚泥菌体を採取し、アリルチオ尿素などを用いてアンモニア酸化細菌を選択的に失活させて廃水に作用させ、単位菌体量当たりの酸素消費を経時的に観察して酸素消費特性を把握することによって決定することができる。 Prior to wastewater treatment, the oxygen demand Qa required for ammonia-oxidizing bacteria and anammox bacteria to complete nitrification and denitrification is calculated from the initial ammonia concentration and nitrite concentration of the wastewater. The oxygen demand Qo required to complete the oxidation of is determined, and the sum Qt = Qa + Q0 is obtained (step S1). The ammonia concentration and the nitrous acid concentration can be determined based on analysis values obtained by an ion electrode or a simple colorimetric method, and the oxygen demand Qa can be obtained stoichiometrically according to the reaction formula of the nitrification denitrification reaction described above. The oxygen demand Qo of organic oxidation bacteria can be determined by, for example, collecting activated sludge cells, selectively inactivating ammonia oxidation bacteria using allylthiourea, etc., and acting on wastewater, and oxygen consumption per unit cell volume. Can be determined by observing this over time and grasping the oxygen consumption characteristics.
廃水の溶存酸素濃度（ＤＯ）及び曝気装置からの酸素の供給速度Ｖを常時モニターしながら廃水への酸素気泡の供給を開始し（工程Ｓ２）、廃水の平均溶存酸素濃度が０．１mg-Ｏ２／Ｌ程度以下となるのを確認しながら、溶存酸素濃度曲線の極大点（又は気泡消失点）の存在が見られるように酸素の供給速度Ｖを調節する（工程Ｓ３，Ｓ４）ことによって、平均溶存酸素濃度が０．１mg-Ｏ２／Ｌ程度以下で、酸素気泡の消失点が水面より下に存在する（＝深度による溶存酸素濃度曲線が極大点を示す）状態が維持される一定の供給速度Ｖ1で酸素供給を継続する（工程Ｓ５）。 The supply of oxygen bubbles to the wastewater is started while constantly monitoring the dissolved oxygen concentration (DO) of the wastewater and the oxygen supply rate V from the aeration apparatus (step S2), and the average dissolved oxygen concentration of the wastewater is 0.1 mg-O By adjusting the oxygen supply rate V so that the presence of the maximum point (or bubble disappearance point) of the dissolved oxygen concentration curve is observed while confirming that it is about 2 / L or less (steps S3 and S4), The average dissolved oxygen concentration is about 0.1 mg-O 2 / L or less, and the state in which the disappearance point of the oxygen bubbles exists below the water surface (= the dissolved oxygen concentration curve with the depth indicates the maximum point) is maintained. The oxygen supply is continued at the supply speed V1 (step S5).
この後、溶存酸素濃度が上昇して溶存酸素濃度曲線の極大点（又は気泡消失点）の消失が観察されたら（工程Ｓ６）、予測による酸素要求量Ｑa、Ｑoを用いて、アンモニア酸化細菌及び有機物酸化細菌の反応が終了したか（アンモニア及び有機物が枯渇したか）を判断する。具体的には、予め求めた硝化脱窒反応の酸素要求量Ｑaと有機物酸化反応の酸素要求量Ｑoとの和Ｑtを用いて、溶存酸素濃度の極大点’（又は気泡消失点）が消失する時点における酸素供給総量Ｙ（≒酸素供給速度Ｖ1×供給時間）と、酸素要求量の和Ｑtとを比較する（工程Ｓ７）。酸素供給総量Ｙ（＝酸素供給速度と供給時間との積算）が、酸素要求量の和Ｑt以上である場合（Ｙ≧Ｑt＝Ｑa＋Ｑo）には、アンモニア酸化細菌及び有機物酸化細菌の両方の反応が終了したと判断され、直ちに酸素供給を終了する（工程Ｓ８）。酸素供給総量Ｙが、酸素要求量の和Ｑt未満である場合（Ｙ＜Ｑt＝Ｑa＋Ｑo）は、酸素の供給速度を低下させて（工程Ｓ９）、溶存酸素濃度曲線に極大点が出現する（水面より下に気泡消失点が存在する）まで減少させる（工程Ｓ１０，Ｓ１１）。 Thereafter, when the dissolved oxygen concentration increases and the disappearance of the maximum point (or bubble disappearance point) of the dissolved oxygen concentration curve is observed (step S6), the oxygen-oxidizing bacteria and the oxygen-oxidizing bacteria and the predicted oxygen demands Qa and Qo are used. It is determined whether the reaction of the organic matter oxidizing bacteria is completed (whether ammonia and organic matter are exhausted). Specifically, using the sum Qt of the oxygen demand Qa of the nitrification denitrification reaction obtained in advance and the oxygen demand Qo of the organic matter oxidation reaction, the dissolved oxygen concentration maximum point '(or bubble disappearance point) disappears. The total oxygen supply Y at the time point (≈oxygen supply speed V1 × supply time) is compared with the sum Qt of oxygen demands (step S7). When the total oxygen supply amount Y (= accumulation of oxygen supply rate and supply time) is equal to or greater than the sum of oxygen demands Qt (Y ≧ Qt = Qa + Qo), the reaction of both ammonia-oxidizing bacteria and organic-oxidizing bacteria It is determined that the supply has ended, and the oxygen supply is immediately ended (step S8). When the total oxygen supply amount Y is less than the sum of oxygen demands Qt (Y <Qt = Qa + Qo), the oxygen supply rate is reduced (step S9), and a maximum point appears in the dissolved oxygen concentration curve (water surface) (Steps S10 and S11).
酸素の供給速度を最小まで低下させても気泡消失点及び溶存酸素濃度曲線の極大点が表れない場合は、酸素の供給を終了する（工程Ｓ１２）。この後の溶存酸素濃度の低下が見られないことによって（工程Ｓ１３）、低酸素濃度で活動する有機物酸化細菌が存在しないと判断できる。溶存酸素濃度の低下が見られる場合は、曝気装置の供給最小速度Ｖminを気泡サイズの縮小や流動圧の調節等によって適切に再調整する必要がある（工程Ｓ１４）。 If the bubble disappearance point and the maximum point of the dissolved oxygen concentration curve do not appear even when the oxygen supply rate is reduced to the minimum, the oxygen supply is terminated (step S12). If no decrease in the dissolved oxygen concentration is observed thereafter (step S13), it can be determined that there are no organic oxidizing bacteria active at a low oxygen concentration. When a decrease in dissolved oxygen concentration is observed, it is necessary to readjust the supply minimum speed Vmin of the aeration apparatus appropriately by reducing the bubble size, adjusting the flow pressure, or the like (step S14).
工程Ｓ９，Ｓ１０で酸素供給速度の低下によって溶存酸素濃度曲線に極大点が出現する（水面より下に気泡消失点が生じる）場合は、未了の反応を終了させるために、平均溶存酸素濃度が０．１mg-Ｏ２／Ｌ程度以下に維持される一定の供給速度Ｖ2に調節して、この供給速度を維持して酸素供給を継続する（工程Ｓ１５）。 If a maximum point appears in the dissolved oxygen concentration curve due to a decrease in the oxygen supply rate in steps S9 and S10 (a bubble vanishing point is generated below the water surface), the average dissolved oxygen concentration is set to terminate the incomplete reaction. The feed rate is adjusted to a constant feed rate V2 maintained at about 0.1 mg-O 2 / L or less, and this feed rate is maintained and oxygen supply is continued (step S15).
酸素の供給は、酸素供給総量Ｙが酸素要求量の和Ｑtに達する時点まで継続することができ（工程Ｓ１６）、それ以前（Ｙ＜Ｑt＝Ｑa＋Ｑo）において溶存酸素濃度が上昇して溶存酸素濃度曲線の極大点（気泡消失点）を消失する場合は（工程Ｓ１７）、工程Ｓ１０で未了の反応が終了したものと判断して酸素供給を終了する（工程Ｓ１８）。酸素供給総量Ｙが酸素要求量の和Ｑtに達っしても（Ｙ≧Ｑt＝Ｑa＋Ｑo）溶存酸素濃度が上昇せず、溶存酸素濃度の極大点（気泡消失点）が消失されない場合は、異常が生じたことを警報し（工程Ｓ１９）、酸素供給を終了する。従って、何れにせよ、酸素の供給は、酸素供給総量Ｙが酸素要求量の和Ｑtに達するまでに停止される。 The supply of oxygen can be continued until the total oxygen supply amount Y reaches the sum of oxygen demands Qt (step S16), and the dissolved oxygen concentration increases before that (Y <Qt = Qa + Qo). When the maximum point (bubble disappearance point) of the curve disappears (step S17), it is determined that the incomplete reaction has ended in step S10, and the oxygen supply is ended (step S18). Even if the total oxygen supply Y reaches the sum Qt of oxygen demands (Y ≧ Qt = Qa + Qo), the dissolved oxygen concentration does not increase and the maximum point of dissolved oxygen concentration (bubble disappearance point) does not disappear. Is generated (step S19), and the oxygen supply is terminated. Therefore, in any case, the supply of oxygen is stopped until the total oxygen supply amount Y reaches the sum Qt of oxygen demands.
上述の処理フローにおいて、アナモックス細菌による脱窒が正常に進行した時の酸素供給の終了には、1)酸素供給総量Ｙが酸素要求量の和Ｑtに達した場合、2)酸素供給総量Ｙは酸素要求量の和Ｑt以下で、第２段階の酸素供給がある場合、及び、3)酸素供給総量Ｙは酸素要求量の和Ｑtより少なく、第２段階の酸素供給がない場合がある。上記1)、2)の場合は、硝化脱窒反応及び有機物酸化反応の両方が完遂しており、廃水の有機物は消費されている（工程Ｓ８，Ｓ１８）。上記3)の場合は、低酸素濃度で活動するタイプの有機物酸化細菌が存在せず、硝化脱窒反応のみが終了しているので、有機物は残存する（工程Ｓ１２）。つまり、本発明では、低酸素濃度で有機物酸化細菌が活動する場合には、有機物酸化反応を完遂させる。 In the above processing flow, when the denitrification by anammox bacteria proceeds normally, the oxygen supply is terminated when 1) the total oxygen supply Y reaches the sum Qt of the oxygen demand, 2) the total oxygen supply Y is The oxygen supply amount Q is less than or equal to the sum Qt and there is a second stage oxygen supply, and 3) the oxygen supply total amount Y is less than the oxygen request amount sum Qt and there is no second stage oxygen supply. In the cases 1) and 2), both the nitrification denitrification reaction and the organic matter oxidation reaction are completed, and the organic matter in the wastewater is consumed (steps S8 and S18). In the case of the above 3), there is no organic oxidizing bacteria of a type that operates at a low oxygen concentration, and only the nitrification denitrification reaction is completed, so the organic matter remains (step S12). That is, in the present invention, when organic matter oxidizing bacteria are active at a low oxygen concentration, the organic matter oxidation reaction is completed.
処理終了の時点では、溶存酸素の上昇によるアナモックス細菌の活性低下は多少は有り得るが、亜硝酸態窒素は消費されているので被毒は防止される。処理を好適に終了した廃水は、静置して沈降分離によって菌体を分離して上澄み廃水を処理槽から排出する。回収した菌体に新たな廃水を供給することによって、亜硝酸の被毒を受けていない菌体によって直ちに次の処理を開始可能な状態になる。必要に応じて、処理再開前の菌体をサンプリングして細菌の菌量バランスを確認調整するとよい。処理後の廃水は、処理前のアンモニウム濃度の約１０モル％程度の硝酸を含み、有機物酸化細菌が活動した場合には有機物も消費される。有機物が消費されずに残存する場合には、必要に応じて、処理後の廃水に活性汚泥処理を用いて嫌気性硝酸脱窒処理及び酸化処理（有機物の分解）を施すと、好適に窒素分及び有機物を除去できる。リン蓄積細菌の取り込みによるリンの除去も可能である。アナモックス細菌は、一旦活動を停止すると再度活性化するのに時間を要するので、アナモックス細菌を連続して活動させることができると、作業効率が良く、アナモックス細菌の活性も安定化する。 At the end of the treatment, the activity of the anammox bacteria may be somewhat reduced due to an increase in dissolved oxygen, but poisoning is prevented because nitrite nitrogen is consumed. The waste water that has been suitably treated is allowed to stand still to separate cells by sedimentation separation, and the supernatant waste water is discharged from the treatment tank. By supplying new wastewater to the collected cells, the next treatment can be started immediately by the cells that have not been poisoned by nitrous acid. If necessary, it is preferable to sample and adjust the bacterial cell balance before resuming the treatment. The wastewater after the treatment contains nitric acid having a concentration of about 10 mol% of the ammonium concentration before the treatment, and the organic matter is consumed when the organic matter oxidizing bacteria are activated. If the organic matter remains without being consumed, if necessary, the treated wastewater is subjected to anaerobic nitric acid denitrification treatment and oxidation treatment (decomposition of organic matter) using activated sludge treatment. And organic matter can be removed. It is also possible to remove phosphorus by taking up phosphorus-accumulating bacteria. Since anammox bacteria take time to reactivate once the activity is stopped, if anammox bacteria can be continuously activated, the working efficiency is good and the activity of anammox bacteria is also stabilized.
多くの場合、廃水のアンモニア濃度及び有機物濃度・性状は、さほど変動しないので、酸素要求量Ｑa、Ｑoを設定するための水質測定は、状況に応じて、処理回毎の個別測定から定時的に抽出して測定するように変更しても良い。 In many cases, the ammonia concentration and organic matter concentration and properties of wastewater do not change so much, so water quality measurement to set the oxygen demands Qa and Qo can be made periodically from individual measurements at each treatment time, depending on the situation. You may change so that it may extract and measure.
上述の廃水処理において、水面より下に気泡消失点が存在する酸素の供給形態は、水面に気泡が残留することを防止でき、気泡に巻き込まれて活性汚泥が水面に浮上するのを抑制するのに有効である。 In the above-described wastewater treatment, the oxygen supply mode in which a bubble vanishing point exists below the water surface can prevent bubbles from remaining on the water surface and suppress the activated sludge from being entrained in the bubbles and floating on the water surface. It is effective for.
上述の廃水処理において、曝気装置から供給する酸素として、空気のような気泡が完全に消失しないガスを用いると、細菌の酸素消費速度と曝気装置の酸素供給速度とのバランスを気泡消失点の目視確認によって判断することはできないが、マイクロバブルのように気泡サイズが小さければ、気泡中の酸素は水面に至るまでに十分に廃水に溶解し得る。従って、マイクロバブル発生装置を用いて空気を供給し、廃水の溶存酸素濃度ＤＯを常時検出して深度による溶存酸素濃度曲線の変動を検知することによって、極大点の有無に基づく判断が可能である。 In the above-described wastewater treatment, if oxygen is used as the oxygen supplied from the aeration apparatus, the balance between the oxygen consumption rate of the bacteria and the oxygen supply speed of the aeration apparatus is determined by visual observation of the bubble disappearance point. Although it cannot be determined by confirmation, if the bubble size is small like a microbubble, oxygen in the bubble can be sufficiently dissolved in the waste water before reaching the water surface. Therefore, it is possible to make a judgment based on the presence or absence of a local maximum point by supplying air using a microbubble generator, constantly detecting the dissolved oxygen concentration DO of wastewater, and detecting the variation of the dissolved oxygen concentration curve with depth. .
有機物酸化細菌が低酸素濃度で活動しない場合、酸素の供給速度の適正範囲は、両細菌の処理能力のバランスによって、（ａ）アナモックス細菌の処理能力［mol-Ｎ／ｈ］がアンモニア酸化細菌の亜硝酸態窒素生成能力［mol-Ｎ／ｈ］を超えるような割合で細菌が添加されている場合、アンモニア酸化細菌の処理能力（最大酸素消費速度）［mol-Ｏ２／ｈ］以下、又は、（ｂ）アナモックス細菌の処理能力がアンモニア酸化細菌の亜硝酸態窒素生成能力以下となる場合、アナモックス細菌の処理能力に対して当量以下となる酸素供給速度である（１モルの亜硝酸態窒素Ｎは１．５モルの酸素Ｏ２と当量。亜硝酸態窒素生成能力［mol-Ｎ／ｈ］は、アンモニア酸化細菌の処理能力［mol-Ｏ２／ｈ］の値の１．５倍）。従って、酸素の供給速度の設定に関し、処理系の細菌の菌体量及び活性から予め適正値を予測し、溶存酸素濃度極大値又は気泡消失点が出現する実際の酸素供給速度との比較によって有機物酸化細菌の活動状態を推測することは可能であり、先の状況を予想することができる。適正な酸素供給速度の予測は、培養アナモックス細菌及びアンモニア酸化細菌の活性（例えばスラッジ質量当たりの処理能力）を測定し、これを用いて、処理系に投入される各細菌の菌体量及び割合から上記（ａ）又は（ｂ）に従って得られる。既に使用中の処理系については、処理系からサンプリングで抽出されるアンモニア酸化細菌及びアナモックス細菌の活性から上記（ａ）又は（ｂ）のように予測する。菌体量のバランスは廃水処理中の増殖によって変動し得るので、処理毎に回収される菌体をサンプリングして確認することが望ましく、必要に応じて菌体の追加により処理能力を調節するとよい。被毒に関する安全性を考慮すると、細菌の処理能力のバランスが上記（ａ）である方が好ましく、アナモックス細菌の処理能力［mol-Ｎ／ｈ］がアンモニア酸化細菌の亜硝酸態窒素生成能力［mol-Ｎ／ｈ］の１．５倍以上であると更に好ましい。上記（ｂ）の場合は、アナモックス細菌の処理能力がアンモニア酸化細菌の亜硝酸態窒素生成能力の０．８倍以上であるのが望ましく、アナモックス細菌の処理能力に対して０．５当量以下となる酸素供給速度であることが望ましい。 When organic matter oxidizing bacteria do not operate at low oxygen concentration, the appropriate range of oxygen supply rate depends on the balance of processing capacity of both bacteria, and (a) the processing capacity [mol-N / h] of anammox bacteria is that of ammonia oxidizing bacteria. When bacteria are added at a rate exceeding the nitrite nitrogen production capacity [mol-N / h], the treatment capacity of ammonia-oxidizing bacteria (maximum oxygen consumption rate) [mol-O 2 / h] or less, or (B) When the treatment capacity of anammox bacteria is less than or equal to the nitrite nitrogen production capacity of ammonia oxidizing bacteria, the oxygen supply rate is less than or equal to the treatment capacity of anammox bacteria (1 mole of nitrite nitrogen N is equivalent to 1.5 mol of oxygen O 2, and nitrite nitrogen production capacity [mol-N / h] is 1.5 times the treatment capacity [mol-O 2 / h] of ammonia oxidizing bacteria) . Therefore, regarding the setting of the oxygen supply rate, an appropriate value is predicted in advance from the amount and activity of bacteria in the treatment system, and the organic matter is compared with the actual oxygen supply rate at which the dissolved oxygen concentration maximum value or bubble disappearance point appears. It is possible to infer the activity state of oxidizing bacteria, and the previous situation can be predicted. The prediction of an appropriate oxygen supply rate is based on the measurement of the activity of cultured anammox bacteria and ammonia-oxidizing bacteria (for example, the treatment capacity per sludge mass), and this is used to determine the amount and percentage of each bacterial cell introduced into the treatment system. From (a) or (b) above. The processing system already in use is predicted as described in (a) or (b) above from the activities of ammonia-oxidizing bacteria and anammox bacteria extracted by sampling from the processing system. Since the balance of the amount of cells can vary depending on the growth during wastewater treatment, it is desirable to sample and confirm the cells collected at each treatment, and the treatment capacity may be adjusted by adding cells as necessary. . Considering the safety regarding poisoning, it is preferable that the balance of the treatment ability of the bacteria is (a), and the treatment ability [mol-N / h] of the anammox bacteria is the ability of the ammonia oxidizing bacteria to produce nitrite nitrogen [ mol-N / h] is more preferably 1.5 times or more. In the case of (b) above, it is desirable that the treatment capacity of the anammox bacteria is 0.8 times or more the nitrite nitrogen production capacity of the ammonia-oxidizing bacteria, and it is 0.5 equivalent or less with respect to the treatment capacity of the anammox bacteria. It is desirable that the oxygen supply rate be
酸素の供給速度は、アンモニア酸化細菌又はアナモックス細菌の処理能力に応じて設定されるので、廃水のアンモニア濃度が異なれば処理に要する時間は変動する。処理時間を短縮するには、アナモックス細菌の処理能力（菌体量、活性）を増大させて酸素の供給速度を増加する。 Since the supply rate of oxygen is set according to the treatment capacity of ammonia oxidizing bacteria or anammox bacteria, the time required for treatment varies depending on the ammonia concentration of wastewater. In order to shorten the treatment time, the treatment capacity (cell mass, activity) of anammox bacteria is increased to increase the oxygen supply rate.
菌体の分離等の作業面においては、投入されるアンモニア酸化細菌及びアナモックス細菌の廃水単位体積当たりの菌体量は、各々、１０００〜１００００mg-ＶＳＳ／Ｌ程度、好ましくは２０００〜４０００mg-ＶＳＳ／Ｌ程度であると都合がよい。廃水への酸素供給速度をアナモックス細菌の菌体量当たりで見積もると、概して、２ｇ-Ｏ２／（ｇ-ＶＳＳ・ｄ）程度以下、好ましくは１ｇ-Ｏ２／（ｇ-ＶＳＳ・ｄ）程度以下の供給速度が好適であるが、アナモックス細菌の活性によって変動する。 In the work surface such as the separation of bacterial cells, the amounts of ammonia-oxidizing bacteria and anammox bacteria to be introduced per unit volume of waste water are about 1000 to 10,000 mg-VSS / L, preferably 2000 to 4000 mg-VSS / L, respectively. It is convenient if it is about L. When the oxygen supply rate to the wastewater is estimated per the amount of anammox bacteria, it is generally about 2 g-O 2 / (g-VSS · d) or less, preferably about 1 g-O 2 / (g-VSS · d). The following feed rates are preferred, but will vary depending on the activity of the anammox bacteria.
廃水のｐＨは、アンモニアの減少及び微量の硝酸態窒素の生成によって若干低下する。亜硝酸態窒素を硝酸態窒素に変換する硝化細菌は、ｐＨが低いと活性が低下するので、硝酸化を抑制する点では中性域以下で処理を行うと良いが、本発明では酸素の供給制御によってアナモックス細菌の活性が良好に維持されるので、廃水のｐＨはさほど問題とはならず、ｐＨ６〜９程度の範囲において好適に実施できる。尚、廃水中の有機物濃度（ＣＯＤ）が高いと、アナモックス細菌は、有機物を消費する細菌群の増殖によって駆逐され易いので、本発明に係る廃水処理は、ＣＯＤ／Ｎ比（窒素に対する有機物の質量比）が０．３mg-COD／mg-Ｎ以下の廃水に適用することが好ましく、０．３を超える場合には、汚泥や活性炭等の有機物を吸着可能な物質を用いて除去して有機物量を減少させるか、あるいは、背景技術の項で記載した活性汚泥により硝化及び脱窒を行う方法Ａ）を適用するのが適切である。換言すれば、アナモックス細菌は、有機物の含有量が低いために活性汚泥法によっては処理が難しいような廃水を好適に処理でき、又、廃水のアンモニア濃度が高すぎるために活性汚泥法による処理効率が極めて低くなる場合に、前処理として好適に利用でき、約９０％のアンモニアを窒素ガスとして除去できる。 The pH of the wastewater is slightly lowered due to the decrease in ammonia and the production of trace amounts of nitrate nitrogen. Since nitrifying bacteria that convert nitrite nitrogen to nitrate nitrogen have low activity when pH is low, it is better to treat in the neutral range or lower in terms of suppressing nitrification. Since the activity of the anammox bacteria is well maintained by the control, the pH of the wastewater does not matter so much and can be suitably carried out in the range of about pH 6-9. If the organic matter concentration (COD) in the wastewater is high, the anammox bacteria are easily driven out by the growth of bacterial groups that consume the organic matter. Therefore, the wastewater treatment according to the present invention has a COD / N ratio (mass of organic matter relative to nitrogen). Ratio) is preferably 0.3mg-COD / mg-N or less, and if it exceeds 0.3, the amount of organic matter can be removed by removing organic matter such as sludge and activated carbon. It is appropriate to apply the method A) in which nitrification and denitrification are carried out with activated sludge as described in the background section. In other words, anammox bacteria can treat wastewater that is difficult to treat by the activated sludge method because of its low organic matter content, and the treatment efficiency of the activated sludge method because the ammonia concentration of the wastewater is too high. Can be suitably used as a pretreatment, and about 90% of ammonia can be removed as nitrogen gas.
本発明の処理方法では、原廃水のアンモニア濃度が変化しても酸素の供給速度や細菌供給量等の処理条件を変更せずに処理が可能であり、複雑な操作変更やアンモニア及び亜硝酸のモニタリングを必要とせず、処理時間が多少変動するのみで廃水処理を完遂させることができる。また、廃水から菌体を分離する際に窒素ガスの再発生によって菌体の沈降が困難になることはないので、菌体の損失や処理水質の悪化を生じることなく効率よく分離できる。 In the treatment method of the present invention, even if the ammonia concentration of the raw wastewater changes, the treatment can be performed without changing the treatment conditions such as the oxygen supply rate and the bacteria supply amount. The wastewater treatment can be completed with no need for monitoring and only a slight change in treatment time. In addition, when separating cells from wastewater, it is not difficult to settle the cells by regenerating nitrogen gas. Therefore, the cells can be efficiently separated without causing loss of cells or deterioration of treated water quality.
以下、実施例を参照して、本発明に係る廃水の処理について具体的に説明する。 Hereinafter, the treatment of wastewater according to the present invention will be specifically described with reference to Examples.
酸素供給手段としてのマイクロバブル発生装置及び溶存酸素濃度測定装置を備えた容量５Ｌの処理槽を備える廃水処理装置を用いて、アンモニア濃度５００mg-Ｎ／Ｌ、硝酸・亜硝酸濃度０mg-Ｎ／Ｌ、有機物濃度１３２mg-COD／Ｌの原廃水の処理を以下のようにして行った。 Using a wastewater treatment device equipped with a 5 L treatment tank equipped with a microbubble generator and dissolved oxygen concentration measuring device as oxygen supply means, ammonia concentration 500 mg-N / L, nitric acid / nitrite concentration 0 mg-N / L The raw waste water having an organic substance concentration of 132 mg-COD / L was treated as follows.
（実施例１）
先ず、アンモニア酸化細菌及びアナモックス細菌を前述の文献に従って用意し、得られたアンモニア酸化細菌及びアナモックス細菌、有機物酸化細菌の菌対数及び活性を、前述の文献記載の方法に従って測定した。
Example 1
First, ammonia-oxidizing bacteria and anammox bacteria were prepared according to the above-mentioned literature, and the bacterial logarithm and activity of the obtained ammonia-oxidizing bacteria, anammox bacteria, and organic matter-oxidizing bacteria were measured according to the method described in the above-mentioned literature.
廃水の酸素要求量Ｑa及びＱoを算出したところ、Ｑa＝１７２０mg／Ｌ、Ｑo＝１３２mg／Ｌであり、Ｑt＝１８５０mg／Ｌとなった。 When the oxygen demands Qa and Qo of the wastewater were calculated, Qa = 1720 mg / L, Qo = 132 mg / L, and Qt = 1850 mg / L.
深さ５ｍの円筒形の処理槽に原廃水（５Ｌ）を投入し、重炭酸ナトリウム４００ｇ、アンモニア酸化細菌（２００mg-ＶＳＳ／Ｌ、アンモニア消費速度０．２ｇ-Ｎ／（ｇ-ＶＳＳ・ｈ））及びアナモックス細菌（２０００mg-ＶＳＳ／Ｌ、アンモニア消費速度０．２５ｇ-Ｎ／（ｇ-ＶＳＳ・ｈ））を加えて細菌を分散させ、溶存酸素濃度測定装置を作動させて深度による溶存酸素濃度の測定を開始したところ、０．０１mg-Ｏ２／Ｌで一定していた。塩酸及び苛性ソーダを用いて廃液のｐＨ値を７．５に調整した。この後、マイクロバブル発生装置を作動させて直径が１００μｍ以下の酸素気泡を廃水に放出し、平均溶存酸素濃度が０．１mg-Ｏ２／Ｌ以下で、水面より下で気泡が消失するように酸素供給速度を調節したところ、１．５ｇ-Ｏ２／（Ｌ・ｄ）となり、この供給速度を維持して酸素気泡による原廃水の曝気を開始した。曝気開始によって溶存酸素濃度は僅かに増加したが、その後ほぼ一定であったので曝気を継続した。この時の溶存酸素濃度曲線は、深度８０cmにおいて極大値０．５mg-Ｏ２／Ｌを示し、気泡の消失点と対応していた。 Raw waste water (5L) is put into a cylindrical treatment tank with a depth of 5m, sodium bicarbonate 400g, ammonia oxidizing bacteria (200mg-VSS / L, ammonia consumption rate 0.2g-N / (g-VSS · h) ) And anammox bacteria (2000 mg-VSS / L, ammonia consumption rate 0.25 g-N / (g-VSS · h)) to disperse the bacteria, operate the dissolved oxygen concentration measuring device, and the dissolved oxygen concentration by depth Was started, and was constant at 0.01 mg-O 2 / L. The pH value of the waste liquid was adjusted to 7.5 using hydrochloric acid and caustic soda. Thereafter, the microbubble generator is operated to release oxygen bubbles having a diameter of 100 μm or less into the wastewater, and the average dissolved oxygen concentration is 0.1 mg-O 2 / L or less so that the bubbles disappear below the water surface. When the oxygen supply rate was adjusted, it became 1.5 g-O 2 / (L · d), and this supply rate was maintained and aeration of the raw wastewater by oxygen bubbles was started. The dissolved oxygen concentration slightly increased with the start of aeration, but since then it was almost constant, aeration was continued. The dissolved oxygen concentration curve at this time showed a maximum value of 0.5 mg-O 2 / L at a depth of 80 cm, corresponding to the disappearance point of bubbles.
曝気を開始して３３時間後、溶存酸素濃度が上昇し始めた。この時の酸素供給総量Ｙは２０６３mg／Ｌであり、Ｙ≧Ｑtとなったので、酸素の供給を停止して廃水を静置した。菌体スラッジが処理槽底部に沈降した後、上澄みの廃水を処理槽から排出し、排出水４Ｌを得た。このアンモニア、硝酸及び亜硝酸の濃度、有機物濃度を測定したところ、アンモニア濃度は０mg-Ｎ／Ｌ、硝酸濃度は４５mg-Ｎ／Ｌ、亜硝酸濃度は０mg-Ｎ／Ｌ、有機物濃度４５mg-COD／Ｌであった。又、排出水のｐＨ値は７弱であった。 33 hours after the start of aeration, the dissolved oxygen concentration began to rise. At this time, the total amount Y of oxygen supply was 2063 mg / L, and Y ≧ Qt. Therefore, the supply of oxygen was stopped and the waste water was allowed to stand. After the bacterial cell sludge settled at the bottom of the treatment tank, the supernatant waste water was discharged from the treatment tank to obtain 4 L of discharged water. The concentration of ammonia, nitric acid and nitrous acid, and organic matter concentration were measured. The ammonia concentration was 0 mg-N / L, the nitric acid concentration was 45 mg-N / L, the nitrous acid concentration was 0 mg-N / L, and the organic matter concentration was 45 mg-COD. / L. The pH value of the discharged water was a little less than 7.
処理槽中の菌体スラッジをサンプリングしてアンモニア酸化細菌及びアナモックス細菌の活性を調べ、処理能力の比率がさほど変化していないのを確認した。処理槽に新たな原廃水４Ｌを投入した後、上述と同様の処理操作を繰り返すことによって同様にアンモニアの酸化・脱窒が可能であることを確認した。 The sludge in the treatment tank was sampled and the activities of ammonia-oxidizing bacteria and anammox bacteria were examined, and it was confirmed that the ratio of treatment capacity did not change so much. After adding 4 L of raw wastewater to the treatment tank, it was confirmed that ammonia could be oxidized and denitrified in the same manner by repeating the same treatment operation as described above.
（実施例２）
実施例１で用意したアンモニア酸化細菌及びアナモックス細菌を用いて以下の操作を行った。
(Example 2)
The following operations were performed using the ammonia-oxidizing bacteria and anammox bacteria prepared in Example 1.
処理槽に原廃水（５Ｌ）を投入し、重炭酸ナトリウム４００ｇ、アンモニア酸化細菌（１００mg-ＶＳＳ／Ｌ、アンモニア消費速度０．２ｇ-Ｎ／（ｇ-ＶＳＳ・ｈ））及びアナモックス細菌（３０００mg-ＶＳＳ／Ｌ、アンモニア消費速度０．２５ｇ-Ｎ／（ｇ-ＶＳＳ・ｈ））を加えて細菌を分散させた後、溶存酸素濃度測定装置を作動させて溶存酸素濃度の測定を開始したところ、０．０１mg-Ｏ２／Ｌで一定していた。塩酸及び苛性ソーダを用いて廃液のｐＨ値を７．５に調整した。この後、マイクロバブル発生装置を作動させて直径が１００μｍ以下の酸素気泡を廃水に放出し、平均溶存酸素濃度が０．１mg-Ｏ２／Ｌ以下で、水面より下で気泡が消失するように酸素供給速度を調節したところ、１．５ｇ-Ｏ２／（Ｌ・ｄ）となり、この供給速度を維持して酸素気泡による原廃水の曝気を開始した。曝気開始によって溶存酸素濃度は僅かに増加したが、その後ほぼ一定であったので曝気を継続した。この時の溶存酸素濃度曲線は、深度８０cmにおいて極大値０．５mg-Ｏ２／Ｌを示し、気泡の消失点と対応していた。 Raw waste water (5 L) was charged into the treatment tank, 400 g of sodium bicarbonate, ammonia oxidizing bacteria (100 mg-VSS / L, ammonia consumption rate 0.2 g-N / (g-VSS · h)) and anammox bacteria (3000 mg- VSS / L, ammonia consumption rate 0.25 g-N / (g-VSS · h)) was added to disperse the bacteria, and then the dissolved oxygen concentration measurement device was started to start the measurement of the dissolved oxygen concentration. It was constant at 0.01 mg-O 2 / L. The pH value of the waste liquid was adjusted to 7.5 using hydrochloric acid and caustic soda. Thereafter, the microbubble generator is operated to release oxygen bubbles having a diameter of 100 μm or less into the wastewater, and the average dissolved oxygen concentration is 0.1 mg-O 2 / L or less so that the bubbles disappear below the water surface. When the oxygen supply rate was adjusted, it became 1.5 g-O 2 / (L · d), and this supply rate was maintained and aeration of the raw wastewater by oxygen bubbles was started. The dissolved oxygen concentration slightly increased with the start of aeration, but since then it was almost constant, aeration was continued. The dissolved oxygen concentration curve at this time showed a maximum value of 0.5 mg-O 2 / L at a depth of 80 cm, corresponding to the disappearance point of bubbles.
曝気を開始して２．５時間後、溶存酸素濃度が上昇し始めた。この時の酸素供給総量Ｙは１５６mg／Ｌであり、Ｙ＜Ｑtとなったので、酸素の供給速度を低下させて、平均溶存酸素濃度が０．１mg-Ｏ２／Ｌ以下で気泡消失点が生じるようように酸素供給速度を調節したところ、１．２ｇ-Ｏ２／（Ｌ・ｄ）となり、この供給速度を維持して酸素気泡による原廃水の曝気を継続した。３２時間経過した時、溶存酸素濃度が上昇し始めた。この時の酸素供給総量Ｙは１７５６mg／Ｌであり（Ｙ＜Ｑt）、酸素の供給を停止して廃水を静置した。菌体スラッジが処理槽底部に沈降した後、上澄みの廃水を処理槽から排出し、排出水４Ｌを得た。このアンモニア、硝酸及び亜硝酸の濃度を測定したところ、アンモニア濃度は０mg-Ｎ／Ｌ、硝酸濃度は４５mg-Ｎ／Ｌ、亜硝酸濃度は０mg-Ｎ／Ｌ、有機物濃度は５８mg-COD／Ｌであった。又、排出水のｐＨ値は７弱であった。 2.5 hours after the start of aeration, the dissolved oxygen concentration began to rise. At this time, the total amount of oxygen supply Y was 156 mg / L, and Y <Qt, so the oxygen supply rate was reduced, and the average dissolved oxygen concentration was 0.1 mg-O 2 / L or less, and the bubble vanishing point was When the oxygen supply rate was adjusted to generate 1.2 g-O 2 / (L · d), the supply rate was maintained and aeration of the raw wastewater with oxygen bubbles was continued. When 32 hours had passed, the dissolved oxygen concentration began to rise. The total oxygen supply Y at this time was 1756 mg / L (Y <Qt), and the supply of oxygen was stopped and the waste water was allowed to stand. After the bacterial cell sludge settled at the bottom of the treatment tank, the supernatant waste water was discharged from the treatment tank to obtain 4 L of discharged water. When the concentrations of ammonia, nitric acid and nitrous acid were measured, the ammonia concentration was 0 mg-N / L, the nitric acid concentration was 45 mg-N / L, the nitrous acid concentration was 0 mg-N / L, and the organic matter concentration was 58 mg-COD / L. Met. The pH value of the discharged water was a little less than 7.
処理槽中の菌体スラッジをサンプリングしてアンモニア酸化細菌及びアナモックス細菌の活性を調べ、処理能力の比率がさほど変化していないのを確認した。処理槽に新たな原廃水４．１Ｌを投入した後、上述と同様の処理操作を繰り返すことによって同様にアンモニアの酸化・脱窒が可能であることを確認した。 The sludge in the treatment tank was sampled and the activities of ammonia-oxidizing bacteria and anammox bacteria were examined, and it was confirmed that the ratio of treatment capacity did not change so much. After adding 4.1 L of new raw wastewater to the treatment tank, it was confirmed that ammonia could be oxidized and denitrified in the same manner by repeating the same treatment operation as described above.
（実施例３）
実施例１で用意したアンモニア酸化細菌及びアナモックス細菌を用いて以下の操作を行った。
(Example 3)
The following operations were performed using the ammonia-oxidizing bacteria and anammox bacteria prepared in Example 1.
処理槽に原廃水（５Ｌ）を投入し、重炭酸ナトリウム４００ｇ、アンモニア酸化細菌（１００mg-ＶＳＳ／Ｌ、アンモニア消費速度０．２ｇ-Ｎ／（ｇ-ＶＳＳ・ｈ））及びアナモックス細菌（３０００mg-ＶＳＳ／Ｌ、アンモニア消費速度０．２５ｇ-Ｎ／（ｇ-ＶＳＳ・ｈ））を加えて細菌を分散させた後、溶存酸素濃度測定装置を作動させて溶存酸素濃度の測定を開始したところ、０．０１mg-Ｏ２／Ｌで一定していた。塩酸及び苛性ソーダを用いて廃液のｐＨ値を７．５に調整した。この後、マイクロバブル発生装置を作動させて直径が１００μｍ以下の酸素気泡を廃水に放出し、平均溶存酸素濃度が０．１mg-Ｏ２／Ｌ以下で、水面より下で気泡が消失するように酸素供給速度を調節したところ、１．５ｇ-Ｏ２／（Ｌ・ｄ）となり、この供給速度を維持して酸素気泡による原廃水の曝気を開始した。曝気開始によって溶存酸素濃度は僅かに増加したが、その後ほぼ一定であったので曝気を継続した。この時の溶存酸素濃度曲線は、深度８０cmにおいて極大値０．５mg-Ｏ２／Ｌを示し、気泡の消失点と対応していた。 Raw waste water (5 L) was charged into the treatment tank, 400 g of sodium bicarbonate, ammonia oxidizing bacteria (100 mg-VSS / L, ammonia consumption rate 0.2 g-N / (g-VSS · h)) and anammox bacteria (3000 mg- VSS / L, ammonia consumption rate 0.25 g-N / (g-VSS · h)) was added to disperse the bacteria, and then the dissolved oxygen concentration measurement device was started to start the measurement of the dissolved oxygen concentration. It was constant at 0.01 mg-O 2 / L. The pH value of the waste liquid was adjusted to 7.5 using hydrochloric acid and caustic soda. Thereafter, the microbubble generator is operated to release oxygen bubbles having a diameter of 100 μm or less into the wastewater, and the average dissolved oxygen concentration is 0.1 mg-O 2 / L or less so that the bubbles disappear below the water surface. When the oxygen supply rate was adjusted, it became 1.5 g-O 2 / (L · d), and this supply rate was maintained and aeration of the raw wastewater by oxygen bubbles was started. The dissolved oxygen concentration slightly increased with the start of aeration, but since then it was almost constant, aeration was continued. The dissolved oxygen concentration curve at this time showed a maximum value of 0.5 mg-O 2 / L at a depth of 80 cm, corresponding to the disappearance point of bubbles.
曝気を開始して２４時間後、溶存酸素濃度が上昇し始めた。この時の酸素供給総量Ｙは１０９１mg／Ｌであり、Ｙ＜Ｑtとなったので、酸素の供給速度を低下させて、気泡消失点が生じる酸素供給速度を求めたが、供給速度を最小にしても気泡消失点が得られなかったので、酸素の供給を停止して廃水を静置した。菌体スラッジが処理槽底部に沈降した後、上澄みの廃水を処理槽から排出し、排出水４Ｌを得た。このアンモニア、硝酸及び亜硝酸の濃度を測定したところ、アンモニア濃度は０mg-Ｎ／Ｌ、硝酸濃度は４５mg-Ｎ／Ｌ、亜硝酸濃度は０mg-Ｎ／Ｌ、有機物濃度は２３mg-COD／Ｌであった。又、排出水のｐＨ値は７弱であった。 24 hours after the start of aeration, the dissolved oxygen concentration began to rise. The total oxygen supply Y at this time was 1091 mg / L and Y <Qt. Therefore, the oxygen supply rate was lowered to obtain the oxygen supply rate at which the bubble vanishing point was generated, but the supply rate was minimized. Since no bubble disappearance point was obtained, the supply of oxygen was stopped and the waste water was allowed to stand. After the bacterial cell sludge settled at the bottom of the treatment tank, the supernatant waste water was discharged from the treatment tank to obtain 4 L of discharged water. When the concentrations of ammonia, nitric acid and nitrous acid were measured, the ammonia concentration was 0 mg-N / L, the nitric acid concentration was 45 mg-N / L, the nitrous acid concentration was 0 mg-N / L, and the organic matter concentration was 23 mg-COD / L. Met. The pH value of the discharged water was a little less than 7.
処理槽中の菌体スラッジをサンプリングしてアンモニア酸化細菌及びアナモックス細菌の活性を調べ、処理能力の比率がさほど変化していないのを確認した。処理槽に新たな原廃水４．１Ｌを投入した後、上述と同様の処理操作を繰り返すことによって同様にアンモニアの酸化・脱窒が可能であることを確認した。 The sludge in the treatment tank was sampled and the activities of ammonia-oxidizing bacteria and anammox bacteria were examined, and it was confirmed that the ratio of treatment capacity did not change so much. After adding 4.1 L of new raw wastewater to the treatment tank, it was confirmed that ammonia could be oxidized and denitrified in the same manner by repeating the same treatment operation as described above.
Claims (11)
予め、廃水に含まれるアンモニア態窒素及び亜硝酸の濃度に基づいて化学量論的に求められる、硝化脱窒反応の完遂に必要な前記酸化処理の酸素要求量Ｑaと、廃水に含まれる有機物の酸化に有機物酸化細菌が要する酸素要求量Ｑoとの和Ｑt＝Ｑa＋Ｑoを求め、
前記酸素の供給を、廃水の平均溶存酸素濃度を０．１mg-Ｏ２／Ｌ以下に維持可能な一定の供給速度で実行し、
前記酸素の供給によって廃水の溶存酸素濃度が上昇した時、廃水に供給された酸素供給総量Ｙと前記和Ｑtとの比較に基づいて酸素の供給停止又は供給速度低下を決定することを特徴とする廃水処理方法。 Wastewater oxygen is supplied to the in the presence of ammonia oxidizing bacteria and anammox bacteria, and oxidation of converting the ammonia nitrogen contained in the waste water nitrite nitrogen by the ammonia-oxidizing bacteria, nitrite nitrogen by the anammox bacteria And a wastewater treatment method for proceeding with denitrification treatment for converting ammonia nitrogen to nitrogen gas,
The oxygen demand Qa for the oxidation treatment required for the completion of the nitrification denitrification reaction , which is stoichiometrically determined based on the concentrations of ammonia nitrogen and nitrous acid contained in the wastewater, and the organic matter contained in the wastewater. Find the sum Qt = Qa + Qo with the oxygen demand Qo required for organic oxidation bacteria for oxidation ,
The supply of oxygen is performed at a constant supply rate capable of maintaining the average dissolved oxygen concentration of wastewater at 0.1 mg-O 2 / L or less,
When the dissolved oxygen concentration in the wastewater increases due to the supply of oxygen, the supply stoppage of oxygen or a decrease in the supply rate is determined based on a comparison between the total oxygen supply amount Y supplied to the wastewater and the sum Qt. Wastewater treatment method.
廃水、前記廃水に含まれるアンモニア態窒素を亜硝酸態窒素に変換するアンモニア酸化細菌、及び、前記廃水に含まれるアンモニア態窒素及び亜硝酸態窒素から窒素ガスへ変換するアナモックス細菌を収容するための、水平断面形状が実質的に一定である内部形状を有する処理槽と、Waste water, ammonia oxidizing bacteria for converting ammonia nitrogen contained in the waste water into nitrite nitrogen, and anammox bacteria for converting ammonia nitrogen and nitrite nitrogen contained in the waste water into nitrogen gas A treatment tank having an internal shape whose horizontal cross-sectional shape is substantially constant;
前記処理槽に収容される廃水に酸素を供給するための、前記処理槽の底部に設けられる酸素供給装置と、An oxygen supply device provided at the bottom of the treatment tank for supplying oxygen to the wastewater stored in the treatment tank;
前記酸素供給装置による廃水への酸素の供給速度を制御するための制御装置と、A control device for controlling the supply rate of oxygen to wastewater by the oxygen supply device;
前記廃水の深度毎に溶存酸素濃度を測定するための溶存酸素濃度測定装置とを有することを特徴とする廃水処理装置。 A wastewater treatment apparatus comprising: a dissolved oxygen concentration measuring device for measuring a dissolved oxygen concentration for each depth of the wastewater.
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