JP2013039577A - Sewage treatment method - Google Patents
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- JP2013039577A JP2013039577A JP2012261839A JP2012261839A JP2013039577A JP 2013039577 A JP2013039577 A JP 2013039577A JP 2012261839 A JP2012261839 A JP 2012261839A JP 2012261839 A JP2012261839 A JP 2012261839A JP 2013039577 A JP2013039577 A JP 2013039577A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
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Abstract
Description
本発明は、下水処理の過程で発生する温室効果ガス、特に生物反応槽の曝気槽から発生するＮ2Ｏを削減するための下水処理方法に関する。 The present invention relates to a sewage treatment method for reducing greenhouse gases generated in the process of sewage treatment, particularly N 2 O generated from an aeration tank of a biological reaction tank.
下水処理方法には、活性汚泥と呼ばれる微生物により生物学的に処理する活性汚泥法がある。活性汚泥法では、廃水中の窒素は、アンモニア体窒素を硝酸体窒素に酸化する硝化工程と、硝酸体窒素を窒素ガスに還元する脱窒工程により除去される。硝化工程，脱窒工程の副生成物としてＮ2Ｏが生成することが知られている。〔非特許文献１〕には、排ガス中のＮ2Ｏは硝化反応が進行するほど増加することが記載されている。Ｎ2ＯはＣＯ2に比べ３１０倍の温室効果を有しており、地球温暖化防止のための排出削減対象物質になっている。 The sewage treatment method includes an activated sludge method in which biological treatment is performed with microorganisms called activated sludge. In the activated sludge method, nitrogen in the wastewater is removed by a nitrification process that oxidizes ammonia nitrogen to nitrate nitrogen and a denitrification process that reduces nitrate nitrogen to nitrogen gas. It is known that N 2 O is generated as a byproduct of the nitrification process and the denitrification process. [Non-Patent Document 1] describes that N 2 O in exhaust gas increases as the nitrification reaction proceeds. N 2 O has a greenhouse effect 310 times that of CO 2 and is an emission reduction target substance for preventing global warming.
〔非特許文献２〕に記載のように、脱窒反応でＮ2ＯはＮ2に還元される。このため、脱窒反応を有する反応槽にＮ2Ｏを溶解させると除去できる。〔特許文献１〕には、Ｎ2Ｏを含有する排気ガスを反応槽に導入して、Ｎ2Ｏを溶解させ除去する方法が記載されている。 As described in [Non-Patent Document 2], N 2 O in denitrification is reduced to N 2. For this reason, it can be removed by dissolving N 2 O in a reaction tank having a denitrification reaction. [Patent Document 1] describes a method in which exhaust gas containing N 2 O is introduced into a reaction vessel to dissolve and remove N 2 O.
下水処理場では流入条件が変動するため、排ガス中のＮ2Ｏ濃度が変化する。〔特許文献１〕に記載の従来の技術では、常に排気ガスの全量が反応槽に導入される。Ｎ2Ｏが低濃度の場合でもガスを全量処理するため、処理効率が低下する恐れがある。 Since the inflow conditions fluctuate at the sewage treatment plant, the N 2 O concentration in the exhaust gas changes. In the conventional technique described in [Patent Document 1], the entire amount of exhaust gas is always introduced into the reaction vessel. Even when N 2 O is in a low concentration, the gas is processed in its entirety, which may reduce the processing efficiency.
本発明の目的は、Ｎ2Ｏ濃度の高い排ガスを選択的に回収することで、Ｎ2Ｏ処理効率を向上できる下水処理方法を提供することにある。 An object of the present invention is to provide a sewage treatment method capable of improving N 2 O treatment efficiency by selectively recovering exhaust gas having a high N 2 O concentration.
上記課題を達成するために本発明は生物反応槽に流入する流量と濃度の情報を有する流入条件管理手段と、プラントの仕様と運転条件の現状値の情報を有するプラント条件管理手段と、流入条件管理手段とプラント条件管理手段の情報を元にエアレーションの排気ガスに含有するＮ2Ｏ濃度を算出するＮ2Ｏ濃度算出手段と、生物反応槽にエアレーションされたガスを回収するための排ガス回収手段と、排ガス回収手段に設けられた制御弁を開閉制御する制御手段を備え、制御手段はＮ2Ｏ濃度算出手段の算出値が、設定値以上の場合に制御弁を開閉制御する、又は、算出値で排ガス回収手段からの排ガス回収流量を制御するものである。 In order to achieve the above object, the present invention provides inflow condition management means having flow rate and concentration information flowing into a biological reaction tank, plant condition management means having information on plant specifications and current values of operating conditions, and inflow conditions. exhaust gas recovery means for recovering the N 2 O concentration calculation means for calculating the N 2 O concentration contained in the original information management means and plant condition management means aeration exhaust gas, the aeration gas to the bioreactor And a control means for controlling the opening and closing of the control valve provided in the exhaust gas recovery means. The control means controls the opening and closing of the control valve when the calculated value of the N 2 O concentration calculating means is equal to or greater than a set value. The exhaust gas recovery flow rate from the exhaust gas recovery means is controlled by the value.
又、生物反応槽の反応液の硝酸体窒素濃度，亜硝酸体窒素，アンモニア体窒素のうちの一つ以上を計測するための窒素計測手段と、生物反応槽にエアレーションされたガスを回収するための排ガス回収手段と、排ガス回収手段に設けられた制御弁を開閉制御する制御手段を備え、制御手段は窒素計測手段の計測値によって制御弁を開閉制御する、又は、計測値で排ガス回収手段からの排ガス回収流量を制御するものである。 Also, a nitrogen measuring means for measuring one or more of nitrate nitrogen concentration, nitrite nitrogen, and ammonia nitrogen in the reaction liquid of the biological reaction tank, and for recovering the gas aerated in the biological reaction tank Exhaust gas recovery means and a control means for controlling the opening and closing of a control valve provided in the exhaust gas recovery means. The control means controls the opening and closing of the control valve according to the measurement value of the nitrogen measurement means, or from the exhaust gas recovery means with the measurement value The exhaust gas recovery flow rate is controlled.
本発明によれば、生物反応槽の溶存酸素、又は窒素濃度からＮ2Ｏ発生量を予測し、排ガス中のＮ2Ｏ濃度が高い場合に、排ガスを処理できるので、Ｎ2Ｏ処理効率を向上できる。 According to the present invention, to predict the N 2 O emissions from the dissolved oxygen, or nitrogen concentration in the bioreactor, when the N 2 O concentration in the exhaust gas high, it is possible to process the exhaust gas, the N 2 O performance It can be improved.
本発明の各実施例について図面を用いて説明する。 Embodiments of the present invention will be described with reference to the drawings.
本発明の実施例１を図１により説明する。図１に示すように、本実施例の反応槽は、生物反応槽１と沈殿池２で構成されている。 A first embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the reaction tank of this embodiment is composed of a biological reaction tank 1 and a sedimentation tank 2.
生物反応槽１には、流入水が流入し、沈殿池２から処理水が流出する。生物反応槽１には複数の微生物群が生息する活性汚泥が混入されている。ブロワ３に接続された散気手段４により、生物反応槽１にエアレーションされ、エアレーションにより空気中の溶存酸素が活性汚泥に供給される。図１では、生物反応槽１は１つの槽として示しているが、生物反応槽１を複数に分割し、エアレーションする好気槽とエアレーションしない嫌気槽を設けてもよい。 Inflow water flows into the biological reaction tank 1, and treated water flows out from the sedimentation basin 2. The biological reaction tank 1 is mixed with activated sludge inhabited by a plurality of microorganism groups. The aeration means 4 connected to the blower 3 aerates the biological reaction tank 1 and supplies dissolved oxygen in the air to the activated sludge by aeration. In FIG. 1, the biological reaction tank 1 is shown as one tank, but the biological reaction tank 1 may be divided into a plurality of aerobic tanks that are aerated and anaerobic tanks that are not aerated.
生物反応槽１の上部には、エアレーションされた排気ガスを回収するための排ガス回収手段５が設置されている。排ガス回収手段５には制御弁６が設けられ、制御手段７の信号により排ガスの回収するために、ｏｎ−ｏｆｆ信号により制御弁６が開閉制御され、排ガス回収量が制御される。制御弁６は、排ガス処理装置に接続されている。生物反応槽１には反応液の溶存酸素を計測するための溶存酸素計８が設置され、その計測信号が制御手段７に入力される。なお、生物反応槽１の廃水処理性能は、排ガス回収手段５による排ガスの回収有無で影響されない。 An exhaust gas recovery means 5 for recovering the aerated exhaust gas is installed in the upper part of the biological reaction tank 1. The exhaust gas recovery means 5 is provided with a control valve 6. In order to recover the exhaust gas by the signal of the control means 7, the control valve 6 is controlled to be opened and closed by an on-off signal, and the exhaust gas recovery amount is controlled. The control valve 6 is connected to the exhaust gas treatment device. The biological reaction tank 1 is provided with a dissolved oxygen meter 8 for measuring dissolved oxygen in the reaction solution, and the measurement signal is input to the control means 7. Note that the wastewater treatment performance of the biological reaction tank 1 is not affected by the presence or absence of exhaust gas recovery by the exhaust gas recovery means 5.
生物反応槽１の下流には、反応液と活性汚泥とを固液分離する沈殿池２が設置されている。沈殿池２に沈降した活性汚泥の一部は生物反応槽１に返送汚泥として循環し、一部が余剰汚泥として排出される。 A sedimentation basin 2 for solid-liquid separation of the reaction solution and activated sludge is installed downstream of the biological reaction tank 1. Part of the activated sludge that has settled in the sedimentation basin 2 circulates in the biological reaction tank 1 as return sludge, and a part is discharged as excess sludge.
生物反応槽１に流入した廃水は、活性汚泥により処理される。流入水中の有機物は酸化分解され、最終的にＣＯ2として除去される。流入水中の窒素成分の大部分は、アンモニア体窒素と有機体窒素であるが、活性汚泥により有機体窒素はアンモニア体窒素となり、アンモニア体窒素は亜硝酸体窒素，硝酸体窒素に酸化される。 The wastewater that has flowed into the biological reaction tank 1 is treated with activated sludge. The organics in the influent water are oxidized and decomposed, it is finally removed as CO 2. Most of the nitrogen components in the inflow water are ammonia nitrogen and organic nitrogen, but the organic nitrogen becomes ammonia nitrogen by the activated sludge, and the ammonia nitrogen is oxidized to nitrite nitrogen and nitrate nitrogen.
有機物や窒素が酸化する際に、反応液中の溶存酸素が消費される。酸素供給速度が等しい場合は、反応液中のこれら被処理物質の濃度が低下すると、すなわち処理が終了すると溶存酸素濃度が増加する。一般に、下水は流入水量や流入水濃度が変化するため、溶存酸素濃度は増減する場合が多い。すなわち、溶存酸素濃度が上昇した場合は、酸化が終了しており、硝酸体窒素濃度が増加していることが分かる。 When organic matter and nitrogen are oxidized, dissolved oxygen in the reaction solution is consumed. When the oxygen supply rates are equal, the dissolved oxygen concentration increases when the concentration of these substances to be treated in the reaction solution decreases, that is, when the treatment is completed. In general, since the amount of inflow water and the concentration of inflow water change in sewage, the dissolved oxygen concentration often increases and decreases. That is, when the dissolved oxygen concentration rises, it can be seen that the oxidation is finished and the nitrate nitrogen concentration is increased.
排ガス中のＮ2Ｏ濃度は、アンモニア体窒素の減少と、硝酸体窒素の増加に比例して増加する。制御手段７は、溶存酸素計８の計測信号を元に制御弁６を制御することで高濃度にＮ2Ｏを含有する排ガスを選択的に処理することができる。 The N 2 O concentration in the exhaust gas increases in proportion to a decrease in ammonia nitrogen and an increase in nitrate nitrogen. The control means 7 can selectively process the exhaust gas containing N 2 O at a high concentration by controlling the control valve 6 based on the measurement signal of the dissolved oxygen meter 8.
制御手段７の制御方法について説明する。制御手段７は、溶存酸素計８の計測値を設定された期間保存する。制御手段７は、例えば６時間前までの溶存酸素計８の計測値の平均値を算出する。平均値と現状の溶存酸素計８の計測値とを比較し、計測値が、平均値以上の場合には、制御弁６を制御して排ガスを処理装置に導入する。平均値以上の代わりに、上限値を設け、溶存酸素計８の計測値が、上限値以上で制御弁６を制御するようにしてもよい。この場合、上限値は１mg／Ｌ程度にするとよい。また、制御手段７は溶存酸素計８の計測値を元に制御弁６を制御し、計測値に比例して排気ガスの回収量を増加させてもよい。 A control method of the control means 7 will be described. The control means 7 stores the measured value of the dissolved oxygen meter 8 for a set period. For example, the control means 7 calculates the average value of the measured values of the dissolved oxygen meter 8 up to 6 hours ago. The average value and the current measured value of the dissolved oxygen meter 8 are compared. If the measured value is equal to or greater than the average value, the control valve 6 is controlled to introduce the exhaust gas into the processing apparatus. An upper limit value may be provided instead of the average value or higher, and the control valve 6 may be controlled when the measured value of the dissolved oxygen meter 8 is equal to or higher than the upper limit value. In this case, the upper limit value is preferably about 1 mg / L. Moreover, the control means 7 may control the control valve 6 based on the measured value of the dissolved oxygen meter 8, and may increase the collection amount of exhaust gas in proportion to the measured value.
制御手段７に、ブロワ３から供給される空気量の情報を入力してもよく、空気量が増加すると溶存酸素計８の計測値も増加するため、空気量も考慮して溶存酸素濃度により制御弁６を制御することで、Ｎ2Ｏ濃度の予測精度を向上できるので、Ｎ2Ｏの回収効率が向上できる。 Information on the amount of air supplied from the blower 3 may be input to the control means 7, and as the amount of air increases, the measured value of the dissolved oxygen meter 8 also increases. By controlling the valve 6, the prediction accuracy of the N 2 O concentration can be improved, so that the N 2 O recovery efficiency can be improved.
このように、本実施例によれば、溶存酸素濃度を計測することでＮ2Ｏ濃度の高い排ガスを選択的に回収でき、Ｎ2Ｏ処理効率を向上できる。 Thus, according to the present embodiment, by measuring the dissolved oxygen concentration, the exhaust gas having a high N 2 O concentration can be selectively recovered, and the N 2 O treatment efficiency can be improved.
本発明の実施例２を図２により説明する。図１に示す実施例１との違いは、実施例２では、生物反応槽１を分割して、上流側溶存酸素濃度計８−１と下流側溶存酸素濃度計８−２の２つの溶存酸素濃度計を設置したことにある。生物反応槽１は、仕切り壁がなくてもよく、本実施例では排ガス回収手段５を下流側溶存酸素濃度計８−２が設置された反応槽に設置したが、両槽に設置してもよい。制御手段７には、上流側溶存酸素濃度計８−１と下流側溶存酸素濃度計８−２の両方の信号が入力されている。散気手段４の散気量が均一の場合は、上流側の生物反応槽の方が下流側の生物反応槽に比べ、アンモニア対窒素や有機物が多く、溶存酸素濃度計の値も低い場合が多い。 A second embodiment of the present invention will be described with reference to FIG. The difference from the first embodiment shown in FIG. 1 is that in the second embodiment, the biological reaction tank 1 is divided into two dissolved oxygen concentration meters 8-1 and 8-2. A densitometer is installed. The biological reaction tank 1 may not have a partition wall. In this embodiment, the exhaust gas recovery means 5 is installed in the reaction tank in which the downstream dissolved oxygen concentration meter 8-2 is installed. Good. Signals from both the upstream dissolved oxygen concentration meter 8-1 and the downstream dissolved oxygen concentration meter 8-2 are input to the control means 7. When the amount of air diffused by the air diffuser 4 is uniform, the upstream biological reaction tank has more ammonia versus nitrogen and organic matter than the downstream biological reaction tank, and the dissolved oxygen concentration meter may have a lower value. Many.
制御手段７による制御方法について説明する。制御手段７は、下流側溶存酸素濃度計８−２と上流側溶存酸素濃度計８−１の計測値の差分を求める。制御手段７は、６時間前までの差分の平均値を算出する。算出された平均値と、計測値の差分とを比較し、計測値の差分が平均値以上の場合には、制御弁６を制御して排ガスを処理装置に導入する。また、制御手段７は、計測値の差分が設定値を超えた場合に、制御弁６を制御して排ガスを処理装置に導入してもよい。この場合、設定値は０.５mg／Ｌ以上にするとよい。 A control method by the control means 7 will be described. The control means 7 calculates | requires the difference of the measured value of the downstream dissolved oxygen concentration meter 8-2 and the upstream dissolved oxygen concentration meter 8-1. The control means 7 calculates the average value of differences up to 6 hours ago. The calculated average value is compared with the difference between the measurement values. If the difference between the measurement values is equal to or greater than the average value, the control valve 6 is controlled to introduce the exhaust gas into the processing apparatus. Moreover, the control means 7 may control the control valve 6 and introduce exhaust gas into a processing apparatus, when the difference of a measured value exceeds a setting value. In this case, the set value is preferably 0.5 mg / L or more.
制御手段７は、制御弁６を制御し、計測値の差分の大きさに比例して排気ガスの回収量を増加させてもよい。なお、設定値は、散気手段４から各々生物反応槽１へ供給される空気量のデータを基に変更すると良く、空気量が少ない場合は設定値を小さくし、空気量が多い場合は設定値を大きくする。設定値以上となった下流側溶存酸素濃度計８−２の設置された生物反応槽では硝化反応が進行し、硝酸体窒素濃度が増加して排ガス中のＮ2Ｏ含有率が高い。 The control means 7 may control the control valve 6 to increase the exhaust gas recovery amount in proportion to the magnitude of the difference between the measured values. The set value may be changed based on the data on the amount of air supplied from the air diffuser 4 to the biological reaction tank 1, and the set value is decreased when the amount of air is small and set when the amount of air is large. Increase the value. The nitrification reaction proceeds in the biological reaction tank in which the downstream dissolved oxygen concentration meter 8-2 that is equal to or higher than the set value is installed, the nitrate nitrogen concentration increases, and the N 2 O content in the exhaust gas is high.
このように、実施例２によれば、溶存酸素濃度を計測することでＮ2Ｏ濃度の高い排ガスを選択的に回収でき、Ｎ2Ｏ処理効率を向上できる。 Thus, according to Example 2, exhaust gas with a high N 2 O concentration can be selectively recovered by measuring the dissolved oxygen concentration, and the N 2 O treatment efficiency can be improved.
本発明の実施例３を図３により説明する。実施例３と実施例１との違いは溶存酸素計８と窒素濃度計９との違いである。窒素濃度計９は、アンモニア体窒素，亜硝酸体窒素，硝酸体窒素の内少なくとも１つ以上を計測できる。窒素濃度計９の計測値は制御手段７に入力され、制御手段７は計測値に応じて制御弁６を制御する。 A third embodiment of the present invention will be described with reference to FIG. The difference between Example 3 and Example 1 is the difference between the dissolved oxygen meter 8 and the nitrogen concentration meter 9. The nitrogen concentration meter 9 can measure at least one of ammonia body nitrogen, nitrite nitrogen, and nitrate body nitrogen. The measured value of the nitrogen concentration meter 9 is input to the control means 7, and the control means 7 controls the control valve 6 according to the measured value.
制御手段７による制御方法について説明する。制御手段７は、計測項目がアンモニア体窒素の場合は、計測値が予め設定した設定値以下の場合に、計測項目が亜硝酸体窒素，硝酸体窒素の場合は、計測値が設定値以上の場合に、制御弁６を制御して排ガスを処理装置に導入する。設定値は、アンモニア体窒素の場合が１０mg／Ｌ、亜硝酸体窒素の場合が０.５mg／Ｌ、硝酸体窒素の場合が５mg／Ｌにするとよい。 A control method by the control means 7 will be described. When the measurement item is ammonia nitrogen, when the measurement value is less than or equal to a preset setting value, the control means 7 determines that the measurement value is greater than or equal to the preset value when the measurement item is nitrite nitrogen or nitrate nitrogen. In this case, the control valve 6 is controlled to introduce the exhaust gas into the processing apparatus. The set values are preferably 10 mg / L for ammonia nitrogen, 0.5 mg / L for nitrite nitrogen, and 5 mg / L for nitrate nitrogen.
また、制御手段７は、２４時間前までの窒素濃度計９の計測値の平均値を算出する。平均値と現状値とを比較し、計測項目がアンモニア体窒素の場合は、計測値が平均値以下、計測項目が亜硝酸体窒素と硝酸体窒素の場合は、計測値が平均値以上の場合に、制御弁６を制御して排ガスを処理装置に導入するとよい。 Moreover, the control means 7 calculates the average value of the measured values of the nitrogen concentration meter 9 up to 24 hours ago. Compare the average value with the current value. If the measurement item is ammonia nitrogen, the measurement value is less than the average value. If the measurement item is nitrite nitrogen and nitrate nitrogen, the measurement value is greater than the average value. In addition, the control valve 6 may be controlled to introduce the exhaust gas into the processing apparatus.
また、制御手段７は制御弁６を制御して、アンモニア体窒素濃度が少ない程、亜硝酸体窒素と硝酸体窒素が多い程排気ガスの回収流量を増加させるとよい。 Further, the control means 7 may control the control valve 6 to increase the exhaust gas recovery flow rate as the ammonia body nitrogen concentration decreases, and as the nitrite nitrogen and nitrate nitrogen increase.
このように、実施例３によれば、窒素濃度を直接計測することで硝化反応の進行が分かり、硝化反応が進行したＮ2Ｏ濃度の高い排ガスを選択的に回収でき、Ｎ2Ｏ処理効率を向上できる。 As described above, according to Example 3, the progress of the nitrification reaction can be understood by directly measuring the nitrogen concentration, and the exhaust gas having a high N 2 O concentration in which the nitrification reaction has progressed can be selectively recovered, and the N 2 O treatment efficiency can be recovered. Can be improved.
本発明の実施例４を図４により説明する。実施例４と実施例３との違いは、実施例３の窒素濃度計９の代わりに、実施例４では、Ｎ2Ｏ濃度演算手段１０、流入条件管理手段１１及びプラント条件管理手段１２が設けられている点である。制御手段７は、Ｎ2Ｏ濃度演算手段１０の演算結果を元にして、演算結果が設定値を超えた場合に制御弁６を制御する。 A fourth embodiment of the present invention will be described with reference to FIG. The difference between the fourth embodiment and the third embodiment is that, instead of the nitrogen concentration meter 9 of the third embodiment, in the fourth embodiment, an N 2 O concentration calculation means 10, an inflow condition management means 11 and a plant condition management means 12 are provided. This is the point. The control means 7 controls the control valve 6 based on the calculation result of the N 2 O concentration calculation means 10 when the calculation result exceeds the set value.
Ｎ2Ｏ濃度演算手段１０の演算方法について説明する。Ｎ2Ｏ濃度演算手段１０には、流入条件管理手段１１から流入水量及び流入水質の情報と、プラント条件管理手段１２からプラントの仕様や現在の運転情報が入力される。図示していないが、流入条件管理手段１１には、流入水量，流入水質のデータベースや流入水量計測器，流入水質計測器からの計測値が蓄積されている。図示していないが、プラント条件管理手段１２には、生物反応槽１の水温や散気手段４からの送風量，活性汚泥の濃度などの情報のデータベースがあり、それらの情報は逐次更新されている。 A calculation method of the N 2 O concentration calculation means 10 will be described. The N 2 O concentration calculation means 10 receives inflow water amount and inflow water quality information from the inflow condition management means 11 and plant specifications and current operation information from the plant condition management means 12. Although not shown, the inflow condition management means 11 stores inflow water amount, inflow water quality database, inflow water amount measuring device, and measured values from the inflow water quality measuring device. Although not shown, the plant condition management means 12 has a database of information such as the water temperature of the biological reaction tank 1, the amount of air blown from the aeration means 4, the concentration of activated sludge, and the information is updated sequentially. Yes.
Ｎ2Ｏ濃度演算手段１０には、活性汚泥の反応をモデル化した活性汚泥モデル、例えば、ＩＷＡ（International Water Association、国際水学会）モデルが記録されている。
活性汚泥モデルは、硝化反応がモデル化されており、流入条件やプラント運転条件によって生物反応槽１のアンモニア体窒素濃度や硝酸体窒素濃度を算出できるようになっている。流入条件管理手段１１の流入水の濃度と反応槽の濃度の差分から硝化量を求め、硝化量からＮ2Ｏ濃度を推定する。この推定されたＮ2Ｏ濃度から生物反応槽にエアレーションされた排気ガスに含有されるＮ2Ｏ濃度を算出する。制御手段７は、Ｎ2Ｏ濃度が設定値以上の場合に制御弁６を制御する。制御手段７は、Ｎ2Ｏ濃度の算出値に応じて、排ガス処理装置の排ガス回収流量を制御してもよい。
In the N 2 O concentration calculation means 10, an activated sludge model that models the reaction of activated sludge, for example, an IWA (International Water Association) model is recorded.
In the activated sludge model, the nitrification reaction is modeled, and the ammonia body nitrogen concentration and nitrate body nitrogen concentration in the biological reaction tank 1 can be calculated according to the inflow conditions and the plant operating conditions. The amount of nitrification is obtained from the difference between the concentration of the influent water in the inflow condition management means 11 and the concentration in the reaction tank, and the N 2 O concentration is estimated from the amount of nitrification. The N 2 O concentration contained in the exhaust gas aerated in the biological reaction tank is calculated from the estimated N 2 O concentration. The control means 7 controls the control valve 6 when the N 2 O concentration is equal to or higher than a set value. The control means 7 may control the exhaust gas recovery flow rate of the exhaust gas treatment device according to the calculated value of the N 2 O concentration.
このように、実施例４によれば、モデルによりＮ2Ｏガス濃度を予測でき、Ｎ2Ｏ濃度の高い排ガスを選択的に回収できるので、Ｎ2Ｏ処理効率を向上できる。 Thus, according to the fourth embodiment, the N 2 O gas concentration can be predicted by the model, and the exhaust gas having a high N 2 O concentration can be selectively recovered, so that the N 2 O treatment efficiency can be improved.
本発明の実施例５を図５により説明する。実施例５は、実施例３と同様に構成されているが、実施例５では、窒素濃度計９が設置されていなく、生物反応槽１が前段の嫌気槽と後段の好気槽に分割され、生物反応槽１の上流側に排ガス処理装置１３−１が設置され制御弁６と接続されている。 A fifth embodiment of the present invention will be described with reference to FIG. Example 5 is configured in the same manner as Example 3. However, in Example 5, the nitrogen concentration meter 9 is not installed, and the biological reaction tank 1 is divided into a preceding anaerobic tank and a subsequent aerobic tank. The exhaust gas treatment device 13-1 is installed on the upstream side of the biological reaction tank 1 and connected to the control valve 6.
流入水は、排ガス処理装置１３−１を経て生物反応槽１に流入する。排気ガスは、排ガス処理装置１３−１に導入され、Ｎ2Ｏガスは流入水中に溶解する。流入水に溶解したＮ2Ｏは、生物反応槽１に流入する。生物反応槽１の流入水は、嫌気槽（無酸素槽ともいう）に流入する。嫌気槽は、溶存酸素が実質的にない槽であり、Ｎ2Ｏは嫌気槽で活性汚泥により脱窒反応でＮ2ガスに還元処理される。排ガス処理装置１３−１では、排ガスを流入水に溶解させる際に、ポンプなどの動力が必要だが、本実施例では、Ｎ2Ｏ濃度の高い排ガスを選択的に回収でき、処理する排ガス量が削減できるためＮ2Ｏ処理効率を向上できる。 The inflow water flows into the biological reaction tank 1 through the exhaust gas treatment device 13-1. The exhaust gas is introduced into the exhaust gas treatment device 13-1, and the N 2 O gas is dissolved in the inflowing water. N 2 O dissolved in the inflow water flows into the biological reaction tank 1. The inflow water of the biological reaction tank 1 flows into an anaerobic tank (also called an oxygen-free tank). The anaerobic tank is a tank substantially free of dissolved oxygen, and N 2 O is reduced to N 2 gas by a denitrification reaction with activated sludge in the anaerobic tank. The exhaust gas treatment device 13-1 requires power such as a pump to dissolve the exhaust gas into the influent water. However, in this embodiment, the exhaust gas with a high N 2 O concentration can be selectively recovered, and the amount of exhaust gas to be processed is small. Therefore, N 2 O treatment efficiency can be improved.
本発明の実施例６を図６により説明する。実施例６は、実施例１と同様に構成されているが、実施例６では、溶存酸素計８が設置されていなく、沈殿池２の下流側に排ガス処理装置１３−２が設置され制御弁６と接続されている。 A sixth embodiment of the present invention will be described with reference to FIG. The sixth embodiment is configured in the same manner as the first embodiment, but in the sixth embodiment, the dissolved oxygen meter 8 is not installed, and the exhaust gas treatment device 13-2 is installed on the downstream side of the settling basin 2, and the control valve is used. 6 is connected.
排ガス処理装置１３−２は、処理水が滞留している。排気ガスは、排ガス処理装置１３−２に導入され、Ｎ2Ｏガスは処理水中に溶解する。排ガス処理装置１３−２では、排ガスを流入水に溶解させる際に、ポンプなどの動力が必要だが、本実施例では、Ｎ2Ｏ濃度の高い排ガスを選択的に回収でき、処理する排ガス量が削減できるためＮ2Ｏ処理効率を向上できる。 In the exhaust gas treatment device 13-2, treated water is retained. The exhaust gas is introduced into the exhaust gas treatment device 13-2, and the N 2 O gas is dissolved in the treated water. In the exhaust gas treatment device 13-2, when the exhaust gas is dissolved in the influent water, power such as a pump is required. However, in this embodiment, the exhaust gas having a high N 2 O concentration can be selectively recovered, and the amount of exhaust gas to be processed is small. Therefore, N 2 O treatment efficiency can be improved.
本発明の実施例７を図７により説明する。実施例７は、実施例６と同様に構成されているが、実施例７では、排ガス中のＮ2Ｏを熱分解するための排ガス熱分解装置１４が設置されており、制御手段７が排ガス熱分解装置１４に接続されている。 A seventh embodiment of the present invention will be described with reference to FIG. Example 7 is configured in the same manner as Example 6, but in Example 7, an exhaust gas pyrolysis device 14 for thermally decomposing N 2 O in the exhaust gas is installed, and the control means 7 is an exhaust gas. It is connected to the thermal decomposition apparatus 14.
適用される排ガス熱分解装置１４には、触媒が充填されているもの、発電機，汚泥焼却炉などが挙げられる。Ｎ2Ｏは熱で分解できるので、例えば汚泥焼却炉ではフリーボードの燃焼温度を８５０℃以上に上げることでＮ2Ｏを削減できる。 Examples of the exhaust gas thermal decomposition apparatus 14 to be applied include a catalyst-filled one, a generator, and a sludge incinerator. Since N 2 O can be decomposed by heat, for example, in a sludge incinerator, N 2 O can be reduced by raising the combustion temperature of the free board to 850 ° C. or higher.
排ガスが多いと排ガス熱分解装置１４への負荷が増加するが、Ｎ2Ｏ濃度の高い排ガスを選択的に回収でき、排ガス量を低減しているので消費エネルギーを削減できる。本実施例では、Ｎ2Ｏ濃度の高い排ガスを選択的に回収でき、処理する排ガス量が削減できるためＮ2Ｏ処理効率を向上できる。 If the amount of exhaust gas is large, the load on the exhaust gas pyrolysis device 14 increases. However, exhaust gas with a high N 2 O concentration can be selectively recovered, and the amount of exhaust gas is reduced, so that energy consumption can be reduced. In this embodiment, exhaust gas having a high N 2 O concentration can be selectively recovered, and the amount of exhaust gas to be processed can be reduced, so that N 2 O treatment efficiency can be improved.
１ 生物反応槽
２ 沈殿池
３ ブロワ
４ 散気手段
５ 排ガス回収手段
６ 制御弁
７ 制御手段
８ 溶存酸素計
９ 窒素濃度計
１０ Ｎ2Ｏ濃度演算手段
１１ 流入条件管理手段
１２ プラント条件管理手段
１３−１，１３−２ 排ガス処理装置
１４ 排ガス熱分解装置
1 bioreactor 2 sedimentation tank 3 blower 4 diffuser means 5 gas collecting means 6 control valve 7 controlling unit 8 the dissolved oxygen meter 9 nitrogen concentration meter 10 N 2 O concentration calculating means 11 flows condition management unit 12 plant condition management means 13 1, 13-2 Exhaust gas treatment device 14 Exhaust gas pyrolysis device
Claims (7)
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