JP5848823B2 - Water treatment system - Google Patents

Water treatment system Download PDF

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JP5848823B2
JP5848823B2 JP2014519700A JP2014519700A JP5848823B2 JP 5848823 B2 JP5848823 B2 JP 5848823B2 JP 2014519700 A JP2014519700 A JP 2014519700A JP 2014519700 A JP2014519700 A JP 2014519700A JP 5848823 B2 JP5848823 B2 JP 5848823B2
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treatment system
water treatment
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JPWO2013183087A1 (en
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康二 福本
康二 福本
昭彦 猪股
昭彦 猪股
崇嗣 安部
崇嗣 安部
優 小山
優 小山
洋士 山本
洋士 山本
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Kawasaki Motors Ltd
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/006—Regulation methods for biological treatment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/30—Aerobic and anaerobic processes
    • C02F3/302—Nitrification and denitrification treatment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C02F2101/163—Nitrates
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/12—Activated sludge processes
    • C02F3/1236—Particular type of activated sludge installations
    • C02F3/1268—Membrane bioreactor systems
    • 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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  • Life Sciences & Earth Sciences (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Microbiology (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Molecular Biology (AREA)
  • Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)

Description

本発明は、活性汚泥法により対象水を処理する水処理システムに関する。   The present invention relates to a water treatment system for treating target water by an activated sludge method.

従来より、生活排水や下水などの汚濁物質を含む対象水を活性汚泥を用いて生物学的に処理する水処理システムが知られている。このような水処理システムは、一般に、対象水と活性汚泥の混合液から窒素を除去するための無酸素槽と、無酸素槽から流出する混合液に曝気を行うための好気槽とを備えている（例えば、特許文献１参照）。好気槽から流出する混合液の一部は還流路により無酸素槽に戻される。   Conventionally, a water treatment system that biologically treats target water containing pollutants such as domestic wastewater and sewage using activated sludge is known. Such a water treatment system generally includes an anaerobic tank for removing nitrogen from a mixture of target water and activated sludge, and an aerobic tank for aeration of the mixture flowing out of the anoxic tank. (For example, refer to Patent Document 1). A part of the mixed solution flowing out from the aerobic tank is returned to the anoxic tank through the reflux path.

好気槽では、硝化細菌が、対象水中のアンモニア態窒素（ＮＨ４−Ｎ）と、有機態窒素から転換したアンモニア態窒素を、硝酸性窒素（ＮＯＸ−Ｎ、具体的には亜硝酸態窒素（ＮＯ２−Ｎ）と硝酸態窒素（ＮＯ３−Ｎ））に酸化する。無酸素槽では、脱窒細菌が、好気槽で生成された亜硝酸態窒素と硝酸態窒素を、亜硝酸呼吸あるいは硝酸呼吸により窒素ガスに還元する。これを脱窒という。脱窒細菌は、亜硝酸呼吸および硝酸呼吸のために有機物を必要とする。In the aerobic tank, nitrifying bacteria convert ammonia nitrogen (NH 4 -N) in the target water and ammonia nitrogen converted from organic nitrogen into nitrate nitrogen (NO X -N, specifically nitrite). Nitrogen (NO 2 -N) and nitrate nitrogen (NO 3 -N)). In the anoxic tank, denitrifying bacteria reduce nitrite nitrogen and nitrate nitrogen generated in the aerobic tank to nitrogen gas by nitrite respiration or nitrate respiration. This is called denitrification. Denitrifying bacteria require organic matter for nitrite and nitrate respiration.

ところで、無酸素槽での脱窒において、対象水中の有機物の量が不足することがある。これを防止するために、無酸素槽に有機物を供給することが提案されている。しかし、有機物の供給量が過剰になると、無酸素槽で消費されなかった有機物によって好気槽に流れ込む混合液中の有機物の濃度が高くなる。一方、有機物の供給量が不足すると、還元されなかった硝酸性窒素が好気槽に流れ込む。これらの不具合を防止するために、特許文献１に開示された水処理システムでは、無酸素槽から流出する混合液中の硝酸性窒素濃度を連続的に測定して、無酸素槽への有機物の供給と停止をリアルタイムに切り替えている。   By the way, in the denitrification in the anoxic tank, the amount of organic matter in the target water may be insufficient. In order to prevent this, it has been proposed to supply organic substances to the oxygen-free tank. However, when the supply amount of the organic matter becomes excessive, the concentration of the organic matter in the liquid mixture flowing into the aerobic tank is increased by the organic matter that has not been consumed in the oxygen-free tank. On the other hand, when the supply amount of organic matter is insufficient, nitrate nitrogen that has not been reduced flows into the aerobic tank. In order to prevent these problems, the water treatment system disclosed in Patent Document 1 continuously measures the concentration of nitrate nitrogen in the liquid mixture flowing out from the oxygen-free tank, and the organic matter to the oxygen-free tank is measured. Supply and stop are switched in real time.

特開２００３−１５４３９２号公報JP 2003-154392 A

水処理システムでは、最終的に得られる処理水中の窒素含有量を所望値以下に抑えることが望ましい。しかしながら、本発明の発明者らは、実証実験により、連続的に測定された硝酸性窒素濃度に基づいてリアルタイムに有機物の供給量を変更したのでは、好気槽におけるアンモニア態窒素の濃度の変動を抑制できないことを突き止めた。それ故に、処理水中の窒素含有量を低く抑えることは困難である。   In the water treatment system, it is desirable to keep the nitrogen content in the finally obtained treated water below a desired value. However, the inventors of the present invention changed the concentration of ammonia nitrogen in the aerobic tank by changing the supply amount of the organic substance in real time based on the nitrate nitrogen concentration continuously measured by the verification experiment. I found out that I can't suppress it. Therefore, it is difficult to keep the nitrogen content in the treated water low.

そこで、本発明は、好気槽におけるアンモニア態窒素の濃度の変動を抑制することができる水処理システムを提供することを目的とする。   Then, an object of this invention is to provide the water treatment system which can suppress the fluctuation | variation of the density | concentration of the ammonia nitrogen in an aerobic tank.

前記課題を解決するために、本発明の発明者らは、鋭意研究の結果、無酸素槽から流出する混合液中の硝酸性窒素濃度が増加したからといって無酸素槽への有機物の供給量を大きく増大させると、その数時間後に好気槽におけるアンモニア態窒素の濃度が大きく増加することを見出した。本発明は、このような観点からなされたものである。   In order to solve the above-mentioned problems, the inventors of the present invention, as a result of diligent research, supplied organic substances to the oxygen-free tank simply because the concentration of nitrate nitrogen in the mixture flowing out of the oxygen-free tank increased. It has been found that when the amount is greatly increased, the concentration of ammonia nitrogen in the aerobic tank greatly increases after several hours. The present invention has been made from such a viewpoint.

すなわち、本発明の水処理システムは、活性汚泥法により対象水を処理する水処理システムであって、前記対象水と活性汚泥の混合液から窒素を除去するための無酸素槽と、前記無酸素槽から流出する混合液に曝気を行うための好気槽と、前記好気槽から流出する混合液の一部を前記無酸素槽に戻す還流路と、前記無酸素槽内もしくは前記好気槽内の混合液または前記無酸素槽と前記好気槽の間を流れる混合液中の硝酸性窒素濃度を測定する測定手段と、前記無酸素槽へ有機物を供給する供給手段と、前記供給手段を制御する制御装置と、を備え、前記制御装置は、一定の時間間隔ごとに前記測定手段の測定値に基づいて前記供給手段による有機物の供給量を変更すべきか否かを判定し、有機物の供給量を変更すべきと判定したときには有機物の供給量が所定量だけ変化するように前記供給手段を操作する。   That is, the water treatment system of the present invention is a water treatment system for treating target water by an activated sludge method, wherein the oxygen-free tank for removing nitrogen from the mixture of the target water and activated sludge, and the oxygen-free An aerobic tank for aeration of the mixed liquid flowing out from the tank, a reflux path for returning a part of the mixed liquid flowing out from the aerobic tank to the anoxic tank, and the anaerobic tank or the aerobic tank Measuring means for measuring the concentration of nitrate nitrogen in the mixed liquid or the mixed liquid flowing between the anaerobic tank and the aerobic tank, supply means for supplying organic matter to the anoxic tank, and the supplying means A control device for controlling, the control device determines whether or not the supply amount of the organic substance by the supply means should be changed based on the measurement value of the measurement means at regular time intervals, and supplies the organic substance Organic when it is determined that the amount should be changed Amount of supply to operate the supply means so as to change by a predetermined amount.

ここで、「無酸素槽と好気槽の間を流れる混合液」とは、無酸素槽から好気槽に向かって流れる混合液だけでなく、還流路を通じて好気槽から無酸素槽に戻る混合液を含む概念である。   Here, the “mixed liquid flowing between the anaerobic tank and the aerobic tank” means not only the mixed liquid flowing from the anaerobic tank toward the aerobic tank, but also returns from the aerobic tank to the anaerobic tank through the reflux path. It is a concept including a mixed liquid.

上記の構成によれば、無酸素槽に適切な量の有機物が供給されるために、無酸素槽における脱窒が良好に行われる。しかも、有機物の供給量を一定の時間間隔（time interval）ごとに所定量ずつ変化させることにより、好気槽におけるアンモニア態窒素濃度の変動を抑制することができる。   According to said structure, since an appropriate quantity of organic substance is supplied to an oxygen-free tank, denitrification in an oxygen-free tank is performed favorably. In addition, by changing the supply amount of the organic matter by a predetermined amount at regular time intervals, fluctuations in the ammonia nitrogen concentration in the aerobic tank can be suppressed.

前記制御装置は、前記測定手段の測定値から硝酸性窒素濃度の目標値を差し引いて偏差を算出する偏差算出部と、有機物の供給量を規定する前記供給手段への操作信号を前記偏差に基づいて決定し、前記供給手段へ前記操作信号を出力する供給量演算部と、を有してもよい。この構成によれば、好気槽における硝酸性窒素の濃度を目標値に近づけるような制御を行うことができる。   The control device includes a deviation calculating unit that calculates a deviation by subtracting a target value of nitrate nitrogen concentration from a measured value of the measuring unit, and an operation signal to the supplying unit that defines a supply amount of organic matter based on the deviation. And a supply amount calculation unit that outputs the operation signal to the supply means. According to this configuration, it is possible to perform control such that the concentration of nitrate nitrogen in the aerobic tank approaches the target value.

前記供給量演算部は、前記偏差が許容範囲内にある場合に前記操作信号を直前の値と同じ値に維持し、前記偏差が前記許容範囲外の場合に前記操作信号を直前の値から一定値だけ変化させてもよい。この構成によれば、操作信号を単純な演算で決定することができる。   The supply amount calculation unit maintains the operation signal at the same value as the previous value when the deviation is within the allowable range, and keeps the operation signal constant from the previous value when the deviation is outside the allowable range. Only the value may be changed. According to this configuration, the operation signal can be determined by a simple calculation.

前記測定手段は、前記混合液中の硝酸性窒素濃度を連続的に測定するものであり、前記制御装置は、前記測定手段の測定値から高周波成分をカットするローパスフィルタを有してもよい。この構成によれば、ローパスフィルタにより測定値が平滑化されるため、制御精度を向上させることができる。   The measuring means may continuously measure a nitrate nitrogen concentration in the mixed solution, and the control device may include a low-pass filter that cuts a high-frequency component from a measurement value of the measuring means. According to this configuration, since the measurement value is smoothed by the low-pass filter, the control accuracy can be improved.

前記制御装置は、当該制御装置への入力により前記時間間隔を変更できるように構成されていてもよい。この構成によれば、対象水の水質が変化しても、有機物の供給量を更新する時間間隔の変更により、好気槽におけるアンモニア態窒素の濃度の変動を抑制することができる。   The control device may be configured to change the time interval by an input to the control device. According to this configuration, even if the water quality of the target water changes, a change in the concentration of ammonia nitrogen in the aerobic tank can be suppressed by changing the time interval for updating the supply amount of the organic matter.

前記無酸素槽へ供給される前記有機物はメタノールであってもよい。この構成によれば、安価な材料で脱窒を促進させることができる。   The organic substance supplied to the oxygen-free tank may be methanol. According to this configuration, denitrification can be promoted with an inexpensive material.

前記測定手段は、前記好気槽に設けられていてもよい。この構成によれば、測定手段への汚泥の付着を抑制することができる。   The measuring means may be provided in the aerobic tank. According to this configuration, it is possible to suppress the adhesion of sludge to the measuring means.

本発明によれば、好気槽におけるアンモニア態窒素の濃度の変動を抑制することができる。   According to the present invention, fluctuations in the concentration of ammonia nitrogen in the aerobic tank can be suppressed.

本発明の一実施形態に係る水処理システムの概略構成を示す図The figure which shows schematic structure of the water treatment system which concerns on one Embodiment of this invention. 図１に示す水処理システムの制御装置を含むブロック図Block diagram including a control device of the water treatment system shown in FIG. 制御装置の主な構成要素を示す図Diagram showing the main components of the control device 硝酸性窒素濃度、偏差および操作信号の継時的変化を示すグラフGraph showing changes in nitrate nitrogen concentration, deviation and operation signal over time （ａ）および（ｂ）は、好気槽におけるアンモニア態窒素濃度、好気槽における硝酸性窒素濃度および操作信号の時間的変化を示すグラフであり、（ａ）は連続制御を行ったときの結果のグラフ、（ｂ）はバッチ処理を行ったときの結果のグラフ(A) And (b) is a graph which shows the time change of the ammonia nitrogen concentration in an aerobic tank, the nitrate nitrogen concentration in an aerobic tank, and an operation signal, (a) is when continuous control is performed. Result graph, (b) is the result graph when batch processing is performed

以下、図面を参照して、本発明の実施形態を説明する。   Hereinafter, embodiments of the present invention will be described with reference to the drawings.

図１に、本発明の一実施形態に係る水処理システム１を示す。この水処理システム１は、膜分離槽２５を備えた、膜分離活性汚泥法（ＭＢＲ：Membrane Bio-Reactor）を用いて対象水を浄化する再生水製造装置である。ただし、本発明の水処理システムは、必ずしも膜分離活性汚泥法を用いたものである必要はなく、膜分離槽２５の代わりに沈殿槽を備えていてもよい。   FIG. 1 shows a water treatment system 1 according to an embodiment of the present invention. This water treatment system 1 is a reclaimed water production apparatus that purifies target water using a membrane separation activated sludge method (MBR: Membrane Bio-Reactor) equipped with a membrane separation tank 25. However, the water treatment system of the present invention does not necessarily need to use the membrane separation activated sludge method, and may include a sedimentation tank instead of the membrane separation tank 25.

具体的に、水処理システム１は、上流側から順に、原水槽２１、嫌気槽２２、無酸素槽２３、好気槽２４、膜分離槽２５および濾過水槽２７を備えている。嫌気槽２２、無酸素槽２３、好気槽２４は、活性汚泥中の微生物を働かせる一連の生物反応槽を構成する。   Specifically, the water treatment system 1 includes a raw water tank 21, an anaerobic tank 22, an oxygen-free tank 23, an aerobic tank 24, a membrane separation tank 25, and a filtered water tank 27 in order from the upstream side. The anaerobic tank 22, the oxygen-free tank 23, and the aerobic tank 24 constitute a series of biological reaction tanks that allow microorganisms in the activated sludge to work.

原水槽２１は、水処理システム１に供給される対象水を一時的に貯えるバッファタンクとして機能する。原水槽２１は、第１経路３１を介して嫌気槽２２と接続されている。第１経路３１には第１操業ポンプ３２が設けられており、第１操業ポンプ３２の稼働により、原水槽２１から嫌気槽２２へ対象水が送り込まれる。   The raw water tank 21 functions as a buffer tank that temporarily stores target water supplied to the water treatment system 1. The raw water tank 21 is connected to the anaerobic tank 22 via the first path 31. A first operation pump 32 is provided in the first path 31, and the target water is sent from the raw water tank 21 to the anaerobic tank 22 by the operation of the first operation pump 32.

嫌気槽２２では、送り込まれた対象水が活性汚泥と混合して混合液となる。嫌気槽２２は、活性汚泥中の微生物からリンを放出させるための槽である。本実施形態では、嫌気槽２２および無酸素槽２３が、一つのタンクが二つに仕切られることにより形成されている。混合液は、嫌気槽２２から無酸素槽２３に流れ込む。   In the anaerobic tank 22, the fed target water is mixed with activated sludge to become a mixed liquid. The anaerobic tank 22 is a tank for releasing phosphorus from microorganisms in the activated sludge. In this embodiment, the anaerobic tank 22 and the anoxic tank 23 are formed by dividing one tank into two. The liquid mixture flows from the anaerobic tank 22 into the anoxic tank 23.

無酸素槽２３は、混合液から窒素を除去するための槽である。無酸素槽２３は、第２経路３３を介して好気槽２４と接続されている。第２経路３３は、無酸素槽２３からオーバーフローした混合液を好気槽２４へ導く。   The oxygen-free tank 23 is a tank for removing nitrogen from the mixed solution. The anoxic tank 23 is connected to the aerobic tank 24 via the second path 33. The second path 33 guides the mixed liquid overflowed from the oxygen-free tank 23 to the aerobic tank 24.

好気槽２４には、混合液に曝気を行う曝気装置５Ａが設けられている。曝気装置５Ａは、好気槽２４内に配置された、混合液中に微細気泡を吹き出す排気部５１と、排気部５１に空気を供給するブロア５２とからなる。曝気装置５Ａによる曝気より、混合液が撹拌されるとともに、活性汚泥中の微生物に酸素が送られ、微生物による有機物の分解およびリンの除去などが行われる。好気槽２４は、第３経路３４を介して膜分離槽２５と接続されている。第３経路３４は、好気槽２４からオーバーフローした混合液を膜分離槽２５へ導く。   The aerobic tank 24 is provided with an aeration apparatus 5A that aerates the mixed solution. The aeration apparatus 5 </ b> A includes an exhaust part 51 that blows out fine bubbles into a mixed liquid and a blower 52 that supplies air to the exhaust part 51, which are disposed in the aerobic tank 24. From the aeration by the aeration apparatus 5A, the mixed solution is agitated, oxygen is sent to the microorganisms in the activated sludge, and organic substances are decomposed by the microorganisms and phosphorus is removed. The aerobic tank 24 is connected to the membrane separation tank 25 via the third path 34. The third path 34 guides the mixed liquid overflowed from the aerobic tank 24 to the membrane separation tank 25.

膜分離槽２５には、上述した曝気装置５Ａと同様の構成の曝気装置５Ｂが設けられている。この曝気装置５Ｂによる作用は、好気槽２４と同様である。また、膜分離槽２５内には、分離膜により混合液から汚泥を分離して濾過水を生成する分離装置２６が配置されている。分離装置２６は、第４経路３５を介して濾過水槽２７と接続されている。第４経路３５には第２操業ポンプ３６が設けられており、第２操業ポンプ３６の稼働により、分離装置２６から濾過水槽２７へ濾過水が送り込まれる。   The membrane separation tank 25 is provided with an aeration apparatus 5B having the same configuration as the above-described aeration apparatus 5A. The effect | action by this aeration apparatus 5B is the same as that of the aerobic tank 24. FIG. Further, in the membrane separation tank 25, a separation device 26 that separates sludge from the mixed solution by the separation membrane and generates filtered water is disposed. The separation device 26 is connected to the filtered water tank 27 via the fourth path 35. The 4th path | route 35 is provided with the 2nd operation pump 36, and filtered water is sent into the filtration water tank 27 from the separator 26 by operation | movement of the 2nd operation pump 36. FIG.

一方、分離装置２６で分離された汚泥の一部は、第３操業ポンプ４４が設けられた第１還流路４３により、嫌気槽２２に戻される。余剰の汚泥は、膜分離槽２５に接続された排出路３７を通じて系外に排出される。また、膜分離槽２５内の混合液の一部は、第４操業ポンプ４２が設けられた第２還流路（本発明の還流路に相当）４１により無酸素槽２３に戻される。   On the other hand, a part of the sludge separated by the separation device 26 is returned to the anaerobic tank 22 by the first reflux path 43 provided with the third operation pump 44. Excess sludge is discharged out of the system through a discharge path 37 connected to the membrane separation tank 25. A part of the mixed liquid in the membrane separation tank 25 is returned to the anoxic tank 23 by a second reflux path (corresponding to the reflux path of the present invention) 41 provided with the fourth operation pump 42.

ここで、活性汚泥中の微生物の働きを詳しく説明する。   Here, the action of microorganisms in the activated sludge will be described in detail.

１）窒素の除去
原水槽２１から嫌気槽２２に送り込まれる対象水には、アンモニア態窒素と有機態窒素が含まれている。有機態窒素は、嫌気槽２２、無酸素槽２３、好気槽２４および膜分離槽２５を通過する間にアンモニア態窒素に転換する。好気槽２４および膜分離槽２５では、アンモニア態窒素が、硝化細菌により亜硝酸態窒素と硝酸態窒素に酸化される。生成された亜硝酸態窒素および硝酸態窒素は、第２還流路４１を通じて混合液の一部と共に無酸素槽２３に送られる。無酸素槽２３では、亜硝酸態窒素および硝酸態窒素が、無酸素条件下で有機物を栄養源とする脱窒細菌の亜硝酸呼吸あるいは硝酸呼吸により窒素ガスに還元される。生成された窒素ガスは、無酸素槽２２から系外に排出される。1) Removal of nitrogen The target water fed from the raw water tank 21 to the anaerobic tank 22 contains ammonia nitrogen and organic nitrogen. The organic nitrogen is converted to ammonia nitrogen while passing through the anaerobic tank 22, the oxygen-free tank 23, the aerobic tank 24 and the membrane separation tank 25. In the aerobic tank 24 and the membrane separation tank 25, ammonia nitrogen is oxidized into nitrite nitrogen and nitrate nitrogen by nitrifying bacteria. The produced nitrite nitrogen and nitrate nitrogen are sent to the anoxic tank 23 together with a part of the mixed solution through the second reflux path 41. In the anoxic tank 23, nitrite nitrogen and nitrate nitrogen are reduced to nitrogen gas by nitrous acid respiration or nitric acid respiration by denitrifying bacteria using organic substances as nutrients under anoxic conditions. The generated nitrogen gas is discharged out of the system from the anoxic tank 22.

２）リンの除去
嫌気槽２２では、リン蓄積細菌が、酢酸などの対象水中の有機物を体内に取り込んで、保持していたリン酸（ＰＯ４）を放出する。好気槽２４では、好気条件下でリンを過剰に摂取するリン蓄積細菌が、嫌気槽２２で放出した以上のリン酸態のリンを取り込む。2) Removal of phosphorus In the anaerobic tank 22, phosphorus accumulating bacteria take in organic matter in the target water such as acetic acid into the body and release the retained phosphoric acid (PO 4 ). In the aerobic tank 24, phosphorus-accumulating bacteria that excessively ingest phosphorus under aerobic conditions take in more phosphoric acid phosphorus released in the anaerobic tank 22.

さらに、本実施形態の水処理システム１では、無酸素槽２３に有機物を供給する構成が採用されている。具体的には、無酸素槽２３が、有機物を保持する有機物槽６１と供給路６２を介して接続されている。供給路６２には、投入ポンプ６３が設けられている。すなわち、投入ポンプ６３は、無酸素槽２３へ有機物を供給する本発明の供給手段に相当する。   Furthermore, in the water treatment system 1 of this embodiment, the structure which supplies an organic substance to the anoxic tank 23 is employ | adopted. Specifically, the oxygen-free tank 23 is connected to an organic substance tank 61 that holds organic substances via a supply path 62. A supply pump 63 is provided in the supply path 62. That is, the input pump 63 corresponds to the supply means of the present invention for supplying organic substances to the oxygen-free tank 23.

無酸素槽２３に供給される有機物としては、特に制限されるものではないが、脱窒細菌が消費し易いという観点から、低分子のアルコールや低分子の有機酸を用いることが望ましい。中でも、メタノールは、安価な材料で脱窒を促進させることができるという点で望ましい。   Although it does not restrict | limit especially as an organic substance supplied to the anoxic tank 23, From a viewpoint that a denitrifying bacterium is easy to consume, it is desirable to use a low molecular alcohol and a low molecular organic acid. Among these, methanol is desirable in that denitrification can be promoted with an inexpensive material.

さらに、水処理システム１は、操業ポンプ３２，３６，４２，４４、投入ポンプ６３および曝気装置５Ａ，５Ｂを統括的に制御する制御装置７を備えている。図２に示すように、制御装置７には、各種のセンサ８１〜８３，９１〜９３が接続されている。   Furthermore, the water treatment system 1 includes a control device 7 that comprehensively controls the operation pumps 32, 36, 42, and 44, the input pump 63, and the aeration devices 5A and 5B. As shown in FIG. 2, various sensors 81 to 83 and 91 to 93 are connected to the control device 7.

具体的に、原水槽２１には、対象水中のアンモニア態窒素濃度を測定する第１アンモニア態窒素センサ８１と、対象水中の硝酸性窒素濃度を測定する第１硝酸性窒素センサ９１が設けられている。また、好気槽２４には、好気槽２４内の混合液中のアンモニア態窒素濃度を測定する第２アンモニア態窒素センサ８２と、混合液中の硝酸性窒素濃度を測定する第２硝酸性窒素センサ（本発明の測定手段に相当）９２が設けられている。さらに、濾過水槽２５には、濾過水中のアンモニア態窒素濃度を測定する第３アンモニア態窒素センサ８３と、濾過水中の硝酸性窒素濃度を測定する第３硝酸性窒素センサ９３が設けられている。   Specifically, the raw water tank 21 is provided with a first ammonia nitrogen sensor 81 for measuring the ammonia nitrogen concentration in the target water and a first nitrate nitrogen sensor 91 for measuring the nitrate nitrogen concentration in the target water. Yes. The aerobic tank 24 includes a second ammonia nitrogen sensor 82 for measuring the ammonia nitrogen concentration in the liquid mixture in the aerobic tank 24 and a second nitric acid sensor for measuring the nitrate nitrogen concentration in the liquid mixture. A nitrogen sensor (corresponding to the measuring means of the present invention) 92 is provided. Further, the filtered water tank 25 is provided with a third ammonia nitrogen sensor 83 for measuring the ammonia nitrogen concentration in the filtered water and a third nitrate nitrogen sensor 93 for measuring the nitrate nitrogen concentration in the filtered water.

そして、制御装置７は、それらのセンサ８１〜８３，９１〜９３の測定値に基づいて、操業ポンプ３２，３６，４２，４４、投入ポンプ６３および曝気装置５Ａ，５Ｂを操作する。なお、硝酸性窒素センサ９１〜９３としては、硝酸態窒素濃度を測定するセンサを用いることが望ましいが、亜硝酸態窒素濃度を測定するセンサを用いてもよいし、硝酸態窒素濃度と亜硝酸態窒素濃度の双方を測定するセンサを用いてもよい。   Then, the control device 7 operates the operation pumps 32, 36, 42, 44, the input pump 63, and the aeration devices 5A, 5B based on the measured values of the sensors 81-83, 91-93. As the nitrate nitrogen sensors 91 to 93, it is desirable to use a sensor that measures the nitrate nitrogen concentration, but a sensor that measures the nitrite nitrogen concentration may be used, or the nitrate nitrogen concentration and the nitrous acid may be used. A sensor that measures both the nitrogen concentration may be used.

特に、制御装置７は、第２硝酸性窒素センサ９２の測定値に基づいて投入ポンプ６３を間欠的に操作し、操作しない間は投入ポンプ６３の稼働状態を一定に維持する。具体的に、制御装置７は、一定の時間間隔Ｔごとに第２硝酸性窒素センサ９２の測定値に基づいて投入ポンプ６３による有機物の供給量を変更すべきか否かを判定する。有機物の供給量を変更すべきと判定したときには、制御装置７は、有機物の供給量が所定量だけ変化するように投入ポンプ６３を操作する。以下、この制御を詳しく説明する。   In particular, the control device 7 intermittently operates the input pump 63 based on the measured value of the second nitrate nitrogen sensor 92, and keeps the operating state of the input pump 63 constant while not operating. Specifically, the control device 7 determines whether or not the supply amount of the organic substance by the charging pump 63 should be changed based on the measured value of the second nitrate nitrogen sensor 92 at regular time intervals T. When it is determined that the supply amount of the organic matter should be changed, the control device 7 operates the input pump 63 so that the supply amount of the organic matter changes by a predetermined amount. Hereinafter, this control will be described in detail.

制御装置７には、上記の時間間隔Ｔが予め格納されている。さらに、制御装置７には、図３に示すように、硝酸性窒素濃度の目標値ＳＶと、後述する偏差（deviation）ΔＥの許容範囲を決定する許容上限値ＴＨＨおよび許容下限値ＴＨＬと、後述する操作信号ＭＶを演算するための供給ゲインＫｍが予め格納されている。The control device 7 stores the above time interval T in advance. Further, as shown in FIG. 3, the control device 7 includes a target value SV of nitrate nitrogen concentration, an allowable upper limit value TH H and an allowable lower limit value TH L that determine an allowable range of a deviation ΔE described later. A supply gain Km for calculating an operation signal MV described later is stored in advance.

時間間隔Ｔは、無酸素槽２３への有機物の供給量を更新する時間である。例えば、対象水が生活排水である場合には、一日における対象水中の成分濃度の変化は日が変わるごとに同じパターンを繰り返すことが多い。そこで、時間間隔Ｔは、例えば０〜２４時間の範囲内で対象水の水質に応じて適切に設定してもよい。   The time interval T is a time for updating the supply amount of the organic matter to the oxygen-free tank 23. For example, when the target water is domestic wastewater, the change in the component concentration in the target water in a day often repeats the same pattern every day. Therefore, the time interval T may be appropriately set according to the quality of the target water within a range of 0 to 24 hours, for example.

本実施形態では、第２硝酸性窒素センサ９２として硝酸性窒素濃度を連続的に測定するセンサが用いられている。そのため、制御装置７は、第２硝酸性窒素センサ９２の測定値ＰＶから高周波成分をカットするローパスフィルタ７１を有している。   In the present embodiment, a sensor that continuously measures nitrate nitrogen concentration is used as the second nitrate nitrogen sensor 92. Therefore, the control device 7 has a low-pass filter 71 that cuts a high-frequency component from the measured value PV of the second nitrate nitrogen sensor 92.

さらに、制御装置７は、偏差算出部７２と供給量演算部７３を有している。偏差算出部７２は、ローパスフィルタ７１を通過した測定値ＰＶから目標値ＳＶを差し引いて偏差ΔＥを算出する。供給量演算部７３は、時間間隔Ｔごとに、有機物の供給量を規定する操作信号ＭＶを偏差ΔＥに基づいて決定し、投入ポンプ６３へ操作信号ＭＶを出力する。   Further, the control device 7 includes a deviation calculating unit 72 and a supply amount calculating unit 73. The deviation calculating unit 72 calculates the deviation ΔE by subtracting the target value SV from the measured value PV that has passed through the low-pass filter 71. The supply amount calculation unit 73 determines an operation signal MV that defines the supply amount of the organic matter based on the deviation ΔE at each time interval T, and outputs the operation signal MV to the input pump 63.

本実施形態では、操作信号ＭＶは、投入ポンプ６３を稼働させる範囲の上限値を１００％、下限値（投入ポンプ６３を停止するとき）を０％とする百分率である。すなわち、操作信号ＭＶは、現在の有機物の供給量を表す数値でもある。   In the present embodiment, the operation signal MV is a percentage in which the upper limit value of the range in which the input pump 63 is operated is 100% and the lower limit value (when the input pump 63 is stopped) is 0%. That is, the operation signal MV is also a numerical value representing the current supply amount of organic matter.

具体的には、供給量演算部７３は、偏差ΔＥが許容上限値ＴＨＨと許容下限値ＴＨＬの間の許容範囲内にある場合に操作信号ＭＶを直前の値と同じ値に維持し、偏差ΔＥが許容範囲外の場合に操作信号ＭＶを直前の値から一定値（供給ゲインＫｍ）だけ変化させる。供給ゲインＫｍは、対象水の水質、供給する有機物の濃度、投入ポンプの特性に応じて、適切に設定することができる。Specifically, the supply amount calculation unit 73 maintains the operation signal MV to the same value as the previous value when the deviation ΔE is within the allowable range between the allowable upper limit TH H allowable lower limit TH L, When the deviation ΔE is outside the allowable range, the operation signal MV is changed from the immediately preceding value by a fixed value (supply gain Km). The supply gain Km can be appropriately set according to the quality of the target water, the concentration of the organic substance to be supplied, and the characteristics of the input pump.

例えば、図４に示すように、ある時刻から時間間隔Ｔがｎ回過ぎたｎ回目の更新では、供給量演算部７３は、偏差ΔＥを許容上限値ＴＨＨおよび許容下限値ＴＨＬと比較する。許容上限値ＴＨＨと許容下限値ＴＨＬは、例えば符号が異なるだけの等しい値である。偏差ΔＥが許容上限値ＴＨＨより大ければ、供給量演算部７３は、有機物の供給量を増やすべきと判定し、前回出力された操作信号ＭＶ（ｎ−１）に供給ゲインＫｍを足した値を今回の操作信号ＭＶ（ｎ）とする。偏差ΔＥが許容下限値ＴＨＬより小さければ、供給量演算部７３は、有機物の供給量を減らすべきと判定し、前回出力された操作信号ＭＶ（ｎ−１）から供給ゲインＫｍを引いた値を今回の操作信号ＭＶ（ｎ）とする。一方、偏差ΔＥが許容上限値ＴＨＨ以下であり許容下限値ＴＨＬ以上であれば、供給量演算部７３は、有機物の供給量を変更すべきでないと判定し、前回出力された操作信号ＭＶ（ｎ−１）を今回の操作信号ＭＶ（ｎ）とする。すなわち、供給量演算部７３は、偏差算出部７２から送られる偏差Δに基づいて、以下の何れかの演算を行う。For example, as shown in FIG. 4, the update interval T from a certain time period n th past n times, the supply amount calculation unit 73 compares the deviation ΔE between the allowable upper limit value TH H and the minimum allowable value TH L . The allowable upper limit value TH H and the allowable lower limit value TH L are equal values with different signs, for example. If Kere larger than deviation ΔE is the allowable upper limit value TH H, the supply amount calculation unit 73 determines that should increase the supply amount of organic matter, plus the feed gain Km to the operation signal MV outputted previously (n-1) The value is the current operation signal MV (n). If the deviation ΔE is smaller than the allowable lower limit value TH L , the supply amount calculation unit 73 determines that the organic material supply amount should be reduced, and is a value obtained by subtracting the supply gain Km from the operation signal MV (n−1) output last time. Is the current operation signal MV (n). On the other hand, if the deviation ΔE is less than or equal to the allowable upper limit value TH H and greater than or equal to the allowable lower limit value TH L , the supply amount calculation unit 73 determines that the supply amount of the organic substance should not be changed, and the operation signal MV output last time. Let (n−1) be the current operation signal MV (n). That is, the supply amount calculation unit 73 performs any of the following calculations based on the deviation Δ sent from the deviation calculation unit 72.

・ΔＥ＞ＴＨＨ ＭＶ（ｎ）＝ＭＶ（ｎ−１）＋Ｋｍ
・ＴＨＬ≦ΔＥ≦ＴＨＨ ＭＶ（ｎ）＝ＭＶ（ｎ−１）
・ΔＥ＜ＴＨＬ ＭＶ（ｎ）＝ＭＶ（ｎ−１）−Ｋｍ
以上説明した本実施形態の水処理システム１では、無酸素槽２３に適切な量の有機物が供給されるために、無酸素槽２３における脱窒が良好に行われる。しかも、有機物の供給量を一定の時間間隔Ｔごとに所定量ずつ変化させることにより、好気槽２４におけるアンモニア態窒素濃度の変動を抑制することができる。ΔE> TH H MV (n) = MV (n−1) + Km
・ TH L ≦ ΔE ≦ TH H MV (n) = MV (n−1)
ΔE <TH L MV (n) = MV (n−1) −Km
In the water treatment system 1 of the present embodiment described above, since an appropriate amount of organic matter is supplied to the anoxic tank 23, denitrification in the anoxic tank 23 is performed well. In addition, by changing the supply amount of the organic matter by a predetermined amount at a certain time interval T, fluctuations in the ammonia nitrogen concentration in the aerobic tank 24 can be suppressed.

ここで、本実施形態の水処理システム１による効果を確認するために行った実証実験の結果を説明する。図５（ａ）は、比較のために第２硝酸性窒素センサ９２の測定値に基づいて無酸素槽２３への有機物の供給量を連続的に変化させた連続制御を行ったときの結果であり、図５（ｂ）は、本実施形態のように無酸素槽２３への有機物の供給量を一定の時間間隔Ｔごとに所定量ずつ変化させたバッチ処理を行ったときの結果である。なお、図５（ａ）、（ｂ）の左側の縦軸（アンモニア態窒素濃度及び硝酸性窒素濃度を示す軸）は同一のスケールである。また、図５（ａ）の右側の縦軸（操作信号ＭＶ）は、図５（ｂ）の右側の縦軸の５倍のスケールである。また、図５（ｂ）のバッチ処理では、更新の時間間隔Ｔを６時間と設定した。   Here, the result of the demonstration experiment performed in order to confirm the effect by the water treatment system 1 of this embodiment is demonstrated. FIG. 5A shows a result of continuous control in which the amount of organic matter supplied to the anaerobic tank 23 is continuously changed based on the measured value of the second nitrate nitrogen sensor 92 for comparison. FIG. 5B shows the result when batch processing is performed in which the supply amount of the organic matter to the anoxic tank 23 is changed by a predetermined amount every certain time interval T as in the present embodiment. In addition, the vertical axis | shaft (axis which shows ammonia-type nitrogen concentration and nitrate nitrogen concentration) of the left side of FIG. 5 (a), (b) is the same scale. Further, the right vertical axis (operation signal MV) in FIG. 5A is a scale five times the right vertical axis in FIG. 5B. In the batch process of FIG. 5B, the update time interval T is set to 6 hours.

図５（ａ）に示すように、連続制御を行った場合は、投入ポンプ６３への操作信号ＭＶが０〜１００％の間で大きく変動し、好気槽２４におけるアンモニア態窒素濃度が大きく変動する。さらには、好気槽２４における硝酸性窒素濃度も大きく変動する。その結果、濾過水槽２７における処理水中の窒素含有量も大きく変動する。なお、処理水中の窒素含有量は、アンモニア態窒素や硝酸性窒素だけでなく全ての態様の窒素の総量である。   As shown in FIG. 5A, when continuous control is performed, the operation signal MV to the charging pump 63 varies greatly between 0 to 100%, and the ammonia nitrogen concentration in the aerobic tank 24 varies greatly. To do. Furthermore, the concentration of nitrate nitrogen in the aerobic tank 24 varies greatly. As a result, the nitrogen content in the treated water in the filtered water tank 27 also varies greatly. The nitrogen content in the treated water is not only ammonia nitrogen and nitrate nitrogen but the total amount of nitrogen in all aspects.

これに対し、図５（ｂ）に示すように、バッチ処理を行った場合は、好気槽２４におけるアンモニア態窒素濃度がほぼ直線的に推移する。しかも、好気槽２４における硝酸性窒素濃度の変動幅も連続制御を行った場合よりも小さくなる。すなわち、本実施形態のようにバッチ処理を行えば、処理水中の窒素含有量を所望値以下に抑えることが可能である。   On the other hand, as shown in FIG. 5B, when batch processing is performed, the ammonia nitrogen concentration in the aerobic tank 24 changes almost linearly. Moreover, the fluctuation range of the nitrate nitrogen concentration in the aerobic tank 24 is also smaller than in the case where continuous control is performed. That is, if batch processing is performed as in this embodiment, the nitrogen content in the treated water can be suppressed to a desired value or less.

また、本実施形態では、制御装置７が、第２硝酸性窒素センサ９２の測定値ＰＶから硝酸性窒素濃度の目標値ＳＶを引いた偏差ΔＥを用いて投入ポンプ６３への操作信号ＭＶを決定している。この構成によれば、好気槽２４における硝酸性窒素の濃度を目標値ＳＶに近づけるような制御を行うことができる。   In this embodiment, the control device 7 determines the operation signal MV to the input pump 63 using the deviation ΔE obtained by subtracting the target value SV of the nitrate nitrogen concentration from the measured value PV of the second nitrate nitrogen sensor 92. doing. According to this configuration, it is possible to perform control such that the concentration of nitrate nitrogen in the aerobic tank 24 approaches the target value SV.

さらに、制御装置７の供給量演算部７３は、偏差ΔＥが許容範囲外の場合に操作信号を直前の値から一定値だけ変化させる。この構成によれば、操作信号を単純な演算で決定することができる。   Furthermore, the supply amount calculation unit 73 of the control device 7 changes the operation signal by a certain value from the previous value when the deviation ΔE is outside the allowable range. According to this configuration, the operation signal can be determined by a simple calculation.

また、本実施形態では、第２硝酸性窒素センサ９２の測定値がローパスフィルタ７１を通過して偏差算出部７２に送られる。この構成によれば、ローパスフィルタにより測定値が平滑化されるため、制御精度を向上させることができる。   In the present embodiment, the measurement value of the second nitrate nitrogen sensor 92 passes through the low-pass filter 71 and is sent to the deviation calculation unit 72. According to this configuration, since the measurement value is smoothed by the low-pass filter, the control accuracy can be improved.

ところで、制御装置７は、当該制御装置７への入力により時間間隔Ｔを変更できるように構成されていてもよい。この構成であれば、対象水の水質が変化しても、有機物の供給量を更新する時間間隔Ｔの変更により、好気槽２４におけるアンモニア態窒素の濃度の変動を抑制することができる。   By the way, the control device 7 may be configured to change the time interval T by an input to the control device 7. If it is this structure, even if the water quality of object water changes, the fluctuation | variation of the density | concentration of the ammonia nitrogen in the aerobic tank 24 can be suppressed by the change of the time interval T which updates the supply amount of organic substance.

＜変形例＞
なお、前記実施形態では、第２硝酸性窒素センサ９２が好気槽２４に設けられていたが、第２硝酸性窒素センサ９２は、無酸素槽２３内の混合液中の硝酸性窒素濃度を測定するように無酸素槽２３に設けられていてもよい。また、第２硝酸性窒素センサ９２は、無酸素槽２３と好気槽２４の間を流れる混合液中の硝酸性窒素濃度を測定するように、第２経路３３、第３経路３４、膜分離槽２５または第２還流路４１に設けられていてもよい。ただし、前記実施形態のように第２硝酸性窒素センサ９２が好気槽２４に設けられていれば、好気槽２４内では曝気により激しい対流が生じているために、第２硝酸性窒素センサ９２への汚泥の付着を抑制することができる。<Modification>
In the above embodiment, the second nitrate nitrogen sensor 92 is provided in the aerobic tank 24. However, the second nitrate nitrogen sensor 92 determines the nitrate nitrogen concentration in the liquid mixture in the oxygen-free tank 23. You may provide in the oxygen-free tank 23 so that it may measure. The second nitrate nitrogen sensor 92 is configured to measure the concentration of nitrate nitrogen in the mixed liquid flowing between the anoxic tank 23 and the aerobic tank 24, the second path 33, the third path 34, and the membrane separation. It may be provided in the tank 25 or the second reflux path 41. However, if the second nitrate nitrogen sensor 92 is provided in the aerobic tank 24 as in the above embodiment, intense convection is generated in the aerobic tank 24 due to aeration, so the second nitrate nitrogen sensor. Adherence of sludge to 92 can be suppressed.

また、前記実施形態では、第２還流路４１の上流端が膜分離槽２５につながれているが、第２還流路４１は好気槽２４から流出する混合液の一部を無酸素槽２３に戻すことができればよい。例えば、膜分離槽２５の代わりに沈殿槽が設けられている場合は、第２還流路４１の上流端は好気槽２４につながれていてもよい。   In the above embodiment, the upstream end of the second reflux path 41 is connected to the membrane separation tank 25. However, the second reflux path 41 allows a part of the mixed solution flowing out from the aerobic tank 24 to the anoxic tank 23. It only has to be able to return. For example, when a sedimentation tank is provided instead of the membrane separation tank 25, the upstream end of the second reflux path 41 may be connected to the aerobic tank 24.

さらに、嫌気槽２２は必ずしも無酸素槽２３と別に設けられている必要はなく、無酸素槽２３が嫌気槽２２の機能を兼ね備えていてもよい。この場合、第１還流路４３を省略し、第２還流路４１を通じて汚泥を無酸素槽２３に戻してもよい。   Furthermore, the anaerobic tank 22 is not necessarily provided separately from the anaerobic tank 23, and the anaerobic tank 23 may have the function of the anaerobic tank 22. In this case, the first reflux path 43 may be omitted, and the sludge may be returned to the anaerobic tank 23 through the second reflux path 41.

１ 水処理システム
２３ 無酸素槽
２４ 好気槽
４１ 還流路
６３ 供給ポンプ（供給手段）
７ 制御装置
７１ ローパスフィルタ
７２ 偏差算出部
７３ 供給量演算部
８１〜８３ アンモニア態窒素センサ
９１ 第１硝酸性窒素センサ
９２ 第２硝酸性窒素センサ（測定手段）
９３ 第３硝酸性窒素センサ1 Water treatment system 23 Anoxic tank 24 Aerobic tank 41 Reflux path 63 Supply pump (supply means)
7 Control Device 71 Low Pass Filter 72 Deviation Calculation Unit 73 Supply Amount Calculation Unit 81-83 Ammonia Nitrogen Sensor 91 First Nitrate Nitrogen Sensor 92 Second Nitrate Nitrogen Sensor (Measuring Means)
93 3rd nitrate nitrogen sensor

Claims (6)

活性汚泥法により対象水を処理する水処理システムであって、
前記対象水と活性汚泥の混合液から窒素を除去するための無酸素槽と、
前記無酸素槽から流出する混合液に曝気を行うための好気槽と、
前記好気槽から流出する混合液の一部を前記無酸素槽に戻す還流路と、
前記好気槽内の混合液中の硝酸性窒素濃度を測定するセンサと、
前記無酸素槽へ有機物を供給する供給手段と、
前記供給手段を制御する制御装置と、を備え、
前記制御装置は、一定の時間間隔ごとに前記センサの測定値に基づいて前記供給手段による有機物の供給量を変更すべきか否かを判定し、有機物の供給量を変更すべきと判定したときには有機物の供給量が所定量だけ変化するように前記供給手段を操作する、水処理システム。 A water treatment system for treating target water by an activated sludge method,
An oxygen-free tank for removing nitrogen from the mixture of the target water and activated sludge;
An aerobic tank for aeration of the mixed solution flowing out of the anoxic tank;
A reflux path for returning a part of the mixed solution flowing out of the aerobic tank to the anoxic tank;
A sensor for measuring the concentration of nitrate nitrogen in the liquid mixture in the aerobic tank ;
Supply means for supplying organic matter to the anoxic tank;
A control device for controlling the supply means,
The control device determines whether or not the supply amount of the organic substance by the supply means should be changed based on the measured value of the sensor at regular time intervals, and determines that the supply amount of the organic substance should be changed. A water treatment system for operating the supply means so that the supply amount of the water changes by a predetermined amount. 前記制御装置は、前記センサの測定値から硝酸性窒素濃度の目標値を差し引いて偏差を算出する偏差算出部と、有機物の供給量を規定する前記供給手段への操作信号を前記偏差に基づいて決定し、前記供給手段へ前記操作信号を出力する供給量演算部と、を有する、請求項１に記載の水処理システム。 The control device includes a deviation calculating unit that calculates a deviation by subtracting a target value of nitrate nitrogen concentration from a measured value of the sensor , and an operation signal to the supply unit that defines an amount of organic matter supplied based on the deviation. The water treatment system according to claim 1, further comprising: a supply amount calculation unit that determines and outputs the operation signal to the supply unit. 前記供給量演算部は、前記偏差が許容範囲内にある場合に前記操作信号を直前の値と同じ値に維持し、前記偏差が前記許容範囲外の場合に前記操作信号を直前の値から一定値だけ変化させる、請求項２に記載の水処理システム。   The supply amount calculation unit maintains the operation signal at the same value as the previous value when the deviation is within the allowable range, and keeps the operation signal constant from the previous value when the deviation is outside the allowable range. The water treatment system according to claim 2, wherein only the value is changed. 前記センサは、前記混合液中の硝酸性窒素濃度を連続的に測定するものであり、
前記制御装置は、前記センサの測定値から高周波成分をカットするローパスフィルタを有する、請求項１〜３の何れか一項に記載の水処理システム。 The sensor continuously measures the concentration of nitrate nitrogen in the mixed solution,
The water treatment system according to any one of claims 1 to 3, wherein the control device includes a low-pass filter that cuts a high-frequency component from a measurement value of the sensor . 前記制御装置は、当該制御装置への入力により前記時間間隔を変更できるように構成されている、請求項１〜４の何れか一項に記載の水処理システム。   The said control apparatus is a water treatment system as described in any one of Claims 1-4 comprised so that the said time interval can be changed by the input to the said control apparatus. 前記無酸素槽へ供給される前記有機物はメタノールである、請求項１〜５の何れか一項に記載の水処理システム。   The water treatment system according to any one of claims 1 to 5, wherein the organic substance supplied to the oxygen-free tank is methanol.
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