JP2004188268A - Water quality monitoring/controlling apparatus and sewage treating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water quality monitoring/controlling apparatus in which abnormality in the value measured by a water quality sensor can be diagnosed quickly, and to provide a sewage treating system equipped with the water quality monitoring/controlling apparatus. <P>SOLUTION: This sewage treating system is provided with one or more bio-reactors for treating sewage and the water quality monitoring/controlling apparatus for monitoring whether or not the treated sewage satisfies the prescribed target water quality. The water quality monitoring/controlling apparatus is provided with the water quality sensor (an ammonia nitrogen concentration meter) 5 which is used for controlling the target water quality and by which the target water quality (ammonia nitrogen concentration) is measured, the water quality sensor (an oxidation-reduction potentiometer) 4 which is used for diagnosing the abnormality and by which the relative water quality (an oxidation-reduction potential (ORP)) is measured and an abnormality diagnosing part 50 for diagnosing whether the target water quality measured by the sensor 5 is abnormal or not by considering the correlation between the target water quality and the relative water quality. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

Ｑａｉｒ（ｔ）：時刻ｔにおける曝気風量目標値（ｍ^３／ｍｉｎ）、Ｑａｉｒ_０：曝気風量初期値（ｍ^３／ｍｉｎ）、Ｋｐ：比例ゲイン（ｍ^６／ｇ・ｍｉｎ）、Ｔ_Ｉ：積分定数（ｍｉｎ）、△ｔ：制御周期（ｍｉｎ）、ｅ（ｔ）：偏差（ｍｇ／Ｌ）、ＳＶ_ＮＨ４（ｔ）：アンモニア性窒素濃度目標値（ｍｇ／Ｌ）、ＰＶ _ＮＨ４ （ｔ）：アンモニア性窒素濃度計の計測値（ｍｇ／Ｌ）
このような場合、アンモニア性窒素濃度の計測値（ＰＶ_ＮＨ４）がアンモニア性窒素濃度の目標値（ＳＶ_ＮＨ４）よりも大きい場合には、好気槽１２における曝気風量が増大するように、曝気風量の目標値が演算されるようになっている。逆に、アンモニア性窒素濃度の計測値（ＰＶ_ＮＨ４）がアンモニア性窒素濃度の目標値（ＳＶ_ＮＨ４）よりも小さい場合には、好気槽１２における曝気風量が減少するように、曝気風量目標値が演算されるようになっている。
【００３１】
一方、ＯＲＰ計４、アンモニア性窒素濃度計５、及び溶存酸素濃度計６の各水質センサは、水質センサ異常診断装置７に接続されており、これらの各水質センサの計測値が水質センサ異常診断装置７に送られるようになっている。
【００３２】
好気槽１２には、水配管を介して凝集剤貯留槽２２が接続されており、当該水配管にはＰＡＣ注入ポンプ１６が取り付けられている。そして、好気槽１２には、凝集剤貯留槽２２から水配管を介して凝集剤が注入されるようになっており、ＰＡＣ注入ポンプ１６によって好気槽１２への凝集剤の注入量が調整されるようになっている。凝集剤貯留槽２２から好気槽１２に注入される凝集剤は、主として、下水中のリン成分を、リン酸アルミニウムやリン酸鉄の形で沈殿させるのに用いられる。なお、このような凝集剤は特に限定されるものではなく、例えば、ポリ塩化アルミニウム、硫酸アルミニウム、硫酸鉄、等を当該凝集剤として好適に用いることができる。そして、好気槽１２では、、硝化菌の働きによって、アンモニア性窒素（ＮＨ_４−Ｎ）が亜硝酸性窒素（ＮＯ_２−Ｎ）と硝酸性窒素（ＮＯ_３−Ｎ）とに酸化される。また、好気槽１２では、リン蓄積細菌のリン過剰摂取作用が利用されて、嫌気槽１０で放出された以上のリン酸態のリンが、活性汚泥に吸収されるようになっている。これにより、嫌気槽１０において過剰放出されたリン酸態のリンが除去されるようになっている。
【００３３】
水質センサ異常診断装置７は異常診断部５０を有しており、当該異常診断部５０は、対応水質範囲算出部５１と対応水質範囲照合部５２とを有している。当該異常診断部５０は、対応水質範囲算出部５１及び対応水質範囲照合部５２を協働させ、アンモニア性窒素濃度計５（制御用水質センサ）によるアンモニア性窒素濃度（対象水質）の計測値と、ＯＲＰ計４（異常診断用水質センサ）によるＯＲＰ（相関水質）の計測値と、アンモニア性窒素濃度とＯＲＰとの相関関係と、を考慮して、アンモニア性窒素濃度計５（制御用水質センサ）によるアンモニア性窒素濃度の計測に関して異常を有するか否かを診断するようになっている。
【００３４】
対応水質範囲算出部５１は、アンモニア性窒素濃度とＯＲＰとの相関関係に基づいて、アンモニア性窒素濃度計５によるアンモニア性窒素濃度の計測値に対応する、ＯＲＰに関する対応水質範囲を求めるようになっている。この対応水質範囲算出部５１が求める対応水質範囲は、ＯＲＰ計４によるＯＲＰの計測値に関する範囲である。
【００３５】
対応水質範囲照合部５２は、ＯＲＰ計４によるＯＲＰの計測値に基づくデータと、対応水質範囲算出部５１の求めた対応水質範囲と、を照合することによって、アンモニア性窒素濃度計５の計測に関して異常を有するか否かを診断するようになっている。対応水質範囲照合部５２によって対応水質範囲と照合する際に用いられるＯＲＰ計４によるＯＲＰの計測値に基づくデータは、ＯＲＰ計４によるＯＲＰの計測値である。そして、対応水質範囲照合部５２は、ＯＲＰ計４によるＯＲＰの計測値が、対応水質範囲算出部５１が求めた対応水質範囲から外れているか否かに基づいて、アンモニア性窒素濃度計５の計測に関して異常を有するか否かを診断するようになっている。
【００３６】
例えば、下水のアンモニア性窒素濃度が目標値に近づくように制御されている場合、ＯＲＰ計４の計測値は、必ずしも一意の値には定まらないが、所定の範囲（対応水質範囲）内に収まることとなる。このような特性を利用して、異常診断部５０は、ＯＲＰ計４の計測値がこの対応水質範囲外に出た場合には、アンモニア性窒素濃度計５の計測に関して異常を有すると診断するようになっている。このようにしてアンモニア性窒素濃度計５の計測に関する異常の有無を診断する際に、異常診断部５０が用いる診断式の一例を以下の式（１．２）に示す。
【００３７】
【数２】

ＰＶ_ＮＨ４：アンモニア性窒素濃度計の計測値（ｍｇＮ／Ｌ）、ＯＲＰ：ＯＲＰ計の計測値（ｍＶ）、ａ _ＮＨ４：変数（ｍｇＮ／Ｌ）、ＵＮ_ＯＲＰ：ＯＲＰ異常診断下限値（ｍＶ）、ＵＰ_ＯＲＰ：ＯＲＰ異常診断上限値（ｍＶ）、Ｆ（ａ _ＮＨ４）、Ｇ（ａ _ＮＨ４）：アンモニア性窒素計異常診断関数式（１．２）の診断式から導かれるＯＲＰ計４の計測に関する異常の有無についての診断の上下限は、アンモニア性窒素濃度を用いた関数（Ｆ（ａ_ＮＨ４）、Ｇ（ａ _ＮＨ４））で与えられ、当該上下限によってＯＲＰ計４の計測値の適正な範囲である対応水質範囲が定められるようになっている。そして、水質センサ異常診断装置７の異常診断部５０は、ＯＲＰ計４の計測値が上記の対応水質範囲から逸脱する場合には、アンモニア性窒素濃度計５の計測に関して異常を有するものと診断するようになっている。
【００３８】
このような水質センサ異常診断装置７には、監視装置８が接続されており、水質センサ異常診断装置７の異常診断部５０におけるアンモニア性窒素濃度計５の計測に関する異常の有無の診断結果が、水質センサ異常診断装置７から監視装置８に送られるようになっている。
【００３９】
監視装置８は、水質センサ異常診断装置７から送られてくる異常診断部５０の診断結果を、下水処理場の管理者等に対してガイダンスするようになっている。また、当該監視装置８は、水質センサ異常診断装置７の異常診断部５０がアンモニア性窒素濃度計５の計測に関して異常を有すると診断した場合には、当該異常に関する警報を行うようになっている。
【００４０】
最終沈殿池１３は、脱窒・脱リン処理槽４０から送られてくる下水を貯留して、当該下水中の不純物を沈殿させるようになっている。なお、最終沈殿池１３に沈殿した不純物を含む下水（最終沈殿水）は、最終沈殿池１３から後述の汚泥貯留槽２０に送られるようになっている。なお、最終沈殿池１３の底部と嫌気槽１０とは、返送ポンプ１５が取り付けられた水配管によって連結されており、返送ポンプ１５によって、最終沈殿池１３に貯留されている下水の一部が当該水配管を介して嫌気槽１０に返送されるようになっている。
【００４１】
また、下水処理場は汚泥貯留槽２０を有している。汚泥貯留槽２０は、初沈引抜ポンプ１８が取り付けられた水配管を介して最初沈殿池２に接続されると共に、余剰ポンプ１７が取り付けられた水配管を介して最終沈殿池１３に接続されている。そして、初沈引抜ポンプ１８によって、最初沈殿池２の最初沈殿水が水配管を介して汚泥貯留槽２０に送られると共に、余剰ポンプ１７によって最終沈殿池１３の最終沈殿水が水配管を介して汚泥貯留槽２０に送られるようになっている。
【００４２】
なお、本発明の水質監視制御装置は、ＯＲＰ計４と、アンモニア性窒素濃度計５と、水質監視制御装置の異常診断部５０と、を含んで構成されている。
【００４３】
次に、本実施の形態の下水処理場の作用について説明する。
【００４４】
まず、下水が下水処理場において浄化処理される過程について概説する。
【００４５】
下水処理場において浄化処理が必要とされる都市下水や産業排水等の下水１は、水配管を介して最初沈殿池２に流入する。最初沈殿池２に流入した下水は最初沈殿池２に所定の時間だけ貯留される。これにより、下水中の不純物が沈降して、最初沈殿池２の下部に当該不純物が沈殿する。そして、最初沈殿池２で貯留されて不純物が沈殿除去された下水の大部分は、水配管を介して、脱窒・脱リン処理槽４０を構成する嫌気槽１０に送られる。なお、最初沈殿池２の下部の下水であって、沈殿した不純物を含む下水（最初沈殿水）は、最初沈殿池２の下方部に設けられた水配管を介して汚泥貯留槽２０に送られ、初沈引抜ポンプ１８によって送り量が調整される。
【００４６】
最初沈殿池２から嫌気槽１０に送られる下水の流量は、水配管に取り付けられた流入流量計３０によって計測される。この流入流量計３０の計測値に基づいて、管理者等は、嫌気槽１０、無酸素槽１１、及び好気槽１２を含んで構成されている脱窒・脱リン処理槽４０に送られる下水の流量を、把握することが可能である。
【００４７】
嫌気槽１０に送られてきた下水は、嫌気処理が施される。すなわち、下水中の酢酸等の有機酸が、嫌気槽１０内の活性汚泥中のリン蓄積細菌によってリン酸（ＰＯ_４）とされる。これにより、下水からリン成分が除去される。なお、この時、下水から効率良くリン成分を除去することができるように、炭素源貯留槽２１から嫌気槽１０への炭素源の注入量が、炭素源注入ポンプ１９によって調整されている。
【００４８】
嫌気槽１０において嫌気処理が施された下水は、嫌気槽１０から無酸素槽１１へ送られる。そして、無酸素槽１１に送られてきた下水は無酸素処理が施される。すなわち、無酸素条件下の無酸素槽１１内の脱窒細菌は、無酸素槽１１に貯留されている下水に含まれる有機物を利用して、循環ポンプ１４によって好気槽１２から水配管を介して無酸素槽１１に返流されてきた下水に含まれる亜硝酸性窒素（ＮＯ_２−Ｎ）及び硝酸性窒素（ＮＯ_３−Ｎ）を、窒素ガス（Ｎ_２）に還元する。そして、還元された窒素ガス（Ｎ_２）は、図示しない無酸素槽排出部を介して下水処理場の系外に排出される。
【００４９】
無酸素槽１１において無酸素処理が施された下水は、無酸素槽１１から好気槽１２に送られる。そして、好気槽１２に送られてきた下水は、好気処理が施される。すなわち、好気槽１２内の硝化菌の働きによって、下水中のアンモニア性窒素（ＮＨ_４−Ｎ）が、亜硝酸性窒素（ＮＯ_２−Ｎ）と硝酸性窒素（ＮＯ_３−Ｎ）とに酸化される。このように酸化された亜硝酸性窒素（ＮＯ_２−Ｎ）及び硝酸性窒素（ＮＯ_３−Ｎ）の一部乃至全部は、循環ポンプ１４によって、下水と共に好気槽１２から無酸素槽１１に送られるようになっている。このような好気槽１２内の硝化菌の働きによって、下水からアンモニア性窒素が除去され、下水のアンモニア性窒素濃度の減少が図られている。また、好気槽１２内における活性汚泥によって、下水に含まれるリン成分が吸収、除去される。また、下水に含まれるリン成分は、凝集剤貯留槽２２から好気槽１２に注入された凝集剤によって、リン酸アルミニウムやリン酸鉄の形で沈殿させられる。なお、この時、凝集剤貯留槽２２の凝集剤は、ＰＡＣ注入ポンプ１６によって好気槽１２への注入量が調整されており、適量の凝集剤が好気槽１２に注入されるようになっている。
【００５０】
好気槽１２において好気処理が施された下水の大部分は、好気槽１２の排出口及び水配管を介して最終沈殿池１３に送られる。なお、好気槽１２のうち最終沈殿池１３への排出口近傍であって好気槽１２の下方部に設けられた水配管を介して、好気槽１２内の下水の一部が無酸素槽１１に返送される。これにより、好気処理によって生じた亜硝酸性窒素（ＮＯ_２−Ｎ）及び硝酸性窒素（ＮＯ_３−Ｎ）の一部も、下水と共に無酸素槽１１に送られる。そして、無酸素槽１１に送られた亜硝酸性窒素（ＮＯ_２−Ｎ）及び硝酸性窒素（ＮＯ_３−Ｎ）は、上述のように無酸素槽１１において無酸素処理が施され、窒素ガス（Ｎ_２）に還元され、当該窒素ガス（Ｎ_２）は、図示しない無酸素槽１１排出部を介して下水処理場の系外に排出される。なお、好気槽１２から無酸素槽１１への下水の返送量は、循環ポンプ１４によって調整されており、適量の下水が無酸素槽１１に返送される。
【００５１】
最終沈殿池１３に流入した下水は、最終沈殿池１３に所定の時間だけ貯留される。これにより、下水中の不純物が沈降して、最終沈殿池１３の下部に当該不純物が沈殿する。そして、最終沈殿池１３で貯留されて不純物が沈殿除去された下水の大部分は、処理水３として、水配管を介して下水処理場の系外に設置された他の施設等に送られる。なお、最終沈殿池１３の下部の下水であって、沈殿した不純物を含む下水（最終沈殿水）は、水配管を介して汚泥貯留槽２０に送られ、余剰ポンプ１７によって送り量が調整される。
【００５２】
次に、好気槽１２における好気処理について詳しく説明する。
【００５３】
好気槽１２に設置されたアンモニア性窒素濃度計５は、必ずしも正確な値を示すとは限らない。すなわち、試薬の劣化、アンモニア性窒素濃度計５の検出部の汚れや気泡の付着、アンモニア性窒素濃度計５の故障、等の様々な要因によって、アンモニア性窒素濃度計５は、実際の値と異なる値を計測する場合がある。
【００５４】
例えば、アンモニア性窒素濃度計５が測定レンジを超えた値を示したり、アンモニア性窒素濃度計５の計測値がゼロのまま動かなかったりした場合のように、アンモニア性窒素濃度計５の計測値があまりにも異常な値を示した場合には、アンモニア性窒素濃度計５側（センサ側）若しくは曝気風量コントローラ２３側（コントローラ側）において、アンモニア性窒素濃度計５の計測に関する異常が生じている、ということを診断しうる。
【００５５】
しかしながら、例えば下水中におけるアンモニア性窒素濃度の実際の値が２ｍｇ／Ｌであってアンモニア性窒素濃度計５の計測値が５ｍｇ／Ｌとなっている場合、等のように、アンモニア性窒素濃度計５が、実際にあり得る値を計測値として示している場合には、アンモニア性窒素濃度計５側（センサ側）若しくは曝気風量コントローラ２３側（コントローラ側）において、アンモニア性窒素濃度計５の計測に関して異常が生じている、ということを診断することは難しい。また、このような場合に、人間系によってアンモニア性窒素濃度計５の計測に関する異常の有無を診断する場合には、手分析によって診断するしかなく、手間及び時間がかかるという問題がある。また、アンモニア性窒素濃度計５等のように試薬を利用してｐｐｍのオーダのものを計測する水質センサよりも、酸化還元電位（ＯＲＰ）や紫外線吸光度（ＵＶ）等のように物理量を測定するセンサの方が、計測誤差が少なく計測精度はよいといえる。このような事情を鑑みて、好気槽１２では、具体的に以下のようなことが行われている。
【００５６】
すなわち、好気槽１２に流入した下水は、ＯＲＰ計４、アンモニア性窒素濃度計５、及び溶存酸素濃度計６の各水質センサによって、当該下水に含まれる各水質が計測される。このようにして計測された各水質のうち、ＯＲＰ計４の計測値、アンモニア性窒素濃度計５の計測値、及び溶存酸素濃度計６の計測値は、各水質センサから水質センサ異常診断装置７に送られる。また、アンモニア性窒素濃度の計測値及び溶存酸素濃度の計測値は、各水質センサから曝気風量コントローラ２３に送られる。
【００５７】
水質センサ異常診断装置７の異常診断部５０では、送られてきたアンモニア性窒素濃度計５（制御用水質センサ）によるアンモニア性窒素濃度（対象水質）の計測値と、ＯＲＰ計４（異常診断用水質センサ）によるＯＲＰ（相関水質）の計測値と、アンモニア性窒素濃度及びＯＲＰの相関関係と、が考慮されて、アンモニア性窒素濃度計５の計測に関して異常を有するか否かが診断される。すなわち、異常診断部５０では、上記の式（１．２）の診断式が利用されて、対応水質範囲を定める上下限値が、アンモニア性窒素濃度を用いた関数（Ｆ（ａ_ＮＨ４）、Ｇ（ａ _ＮＨ４））として算出される。これにより、例えば、図２に示されるような対応水質範囲が得られる。従って、例えば、下水のアンモニア性窒素濃度の目標値が０．５ｍｇ／Ｌとなるように制御されている場合、ＯＲＰ計の計測値は、例えば、１００ｍｖ〜１５０ｍｖで定められる対応水質範囲内に収まることとなる。そして、異常診断部５０は、ＯＲＰ計４の計測値が上記の対応水質範囲から逸脱する場合には、アンモニア性窒素濃度計５の計測に関して異常を有していると診断され、ＯＲＰ計４の計測値が上記の対応水質範囲に含まれている場合には、アンモニア性窒素濃度計５の計測に関して異常を有していないと診断される。
【００５８】
水質センサ異常診断装置７の異常診断部５０における上記の診断結果は、監視装置８に送られ、監視装置８において下水処理場の管理者等に対してガイダンスされる。また、監視装置８は、異常診断部５０がアンモニア性窒素濃度の計測に関して異常を有していると診断した場合には、警報を鳴らして管理者等に当該異常を知らせる。
【００５９】
一方、曝気風量コントローラ２３は、アンモニア性窒素濃度計５の計測値及び溶存酸素濃度計６の計測値に基づいて、曝気装置９から好気槽１２内に供給される曝気風量を制御する。すなわち、アンモニア性窒素濃度計５の計測値が、設定されているアンモニア性窒素濃度の目標値に近づくように、曝気装置９から好気槽１２に供給される曝気風量の目標値が曝気風量コントローラ２３によって演算される。具体的には、曝気風量コントローラ２３では、上記の式（１．２）の曝気風量演算式が利用されて、曝気装置９から好気槽１２に供給される曝気風量の目標値が演算される。そして、曝気装置９は、アンモニア性窒素濃度計５から送られてくるアンモニア性窒素濃度の計測値が、設定されているアンモニア性窒素濃度の目標値よりも大きい場合には、好気槽１２に供給される曝気風量が増加するように、曝気風量コントローラ２３によって制御される。一方、アンモニア性窒素濃度計５から送られてくるアンモニア性窒素濃度の計測値が、設定されているアンモニア性窒素濃度の目標値よりも小さい場合には、好気槽１２に供給される曝気風量が減少するように、曝気装置９は曝気風量コントローラ２３によって制御される。このように曝気装置９を制御することによって、曝気風量コントローラ２３は、好気槽１２に対して常に過不足のなく曝気を供給することができる。これにより、好気槽１２内で酸素不足が生じて硝化反応が進行しなかったり、過曝気によって硝化反応が過度に進行してしまったりすることを防いで、下水のアンモニア性窒素濃度を適正な値に調整することができるようになっている。
【００６０】
以上説明したように本実施の形態によれば、水質センサ異常診断装置７の異常診断部５０は、アンモニア性窒素濃度計５の計測に関して異常が生じたか否かについて、アンモニア性窒素濃度計５の計測値と、ＯＲＰ計４の計測値と、アンモニア性窒素濃度とＯＲＰとの相関関係と、に基づいて、当該異常の発生の有無を迅速に診断することができる。これにより、正確且つ迅速に、アンモニア性窒素濃度計５の計測に関する異常の有無を診断することができる。
【００６１】
そして、アンモニア性窒素濃度計５によるアンモニア性窒素濃度の計測に関して異常が生じている場合には、監視装置８を介して、当該異常の発生をいち早く運転員にガイダンスすることができる。これにより、運転員に対して診断の遅れや診断の間違いを生じさせないようにして、水質センサ異常に起因する制御異常をいち早く回避することが可能となる。また、曝気装置９による過曝気や曝気不足のようにアンモニア性窒素濃度の調整が不適切である時間を短縮させることができ、処理下水の水質の悪化を効果的に防止することができる。
【００６２】
また、安定な水質センサであるＯＲＰ計４による計測値が、対応水質範囲算出部５１が求めた対応水質範囲から外れているか否かに基づいて、アンモニア性窒素濃度計５の計測に関して異常を有するか否かを診断するようになっているので、アンモニア性窒素濃度計５による計測の補償に関するアルゴリズムを比較的シンプルに組み立てることができる。また、このようなアルゴリズムを比較的容易に曝気風量コントローラ２３に組み込むことができる。
【００６３】
また、アンモニア性窒素濃度計５とＯＲＰ計４とは同一の好気槽１２に設置されており、これらの各水質センサ５，４によって各水質が計測される下水は、同一の生物反応槽における下水である。また、制御用水質センサであるアンモニア性窒素濃度計５の計測対象である対象水質（アンモニア性窒素濃度）と、異常診断用水質センサであるＯＲＰ計４の計測対象である相関水質（ＯＲＰ）と、は異なる。このため、水質センサ異常診断装置７は、正確性及び信頼性の高い、アンモニア性窒素濃度計５の計測に関する異常の有無の診断を行うことが可能である。
【００６４】
なお、監視装置８によるガイダンス及び／又は警報の方式は、特に限定されるものではなく、例えば、文字等を表示する方式、音声を伴う方式、その他、下水処理場の管理者等に水質センサ異常診断装置７の異常診断部５０における診断結果を知らせることができる方式全般を含みうる。
【００６５】
次に本実施の形態の変形例について説明する。
【００６６】
アンモニア性窒素濃度計５、ＯＲＰ計４、及び溶存酸素濃度計６は、それぞれ、好気槽１２よりも後段に設置されていてもよい。例えば、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４は、それぞれ、最終沈殿池１３、好気槽１２と最終沈殿池１３とを連結する水配管、最終沈殿池１３から下水を排出するための水配管、等に設置され、設置箇所における下水の各水質を計測するようになっていてもよい。
【００６７】
また、ＯＲＰ計４は、アンモニア性窒素濃度計５が設置されている生物反応槽よりも後段に設けられた生物反応槽に設置されてもよい。このような場合に、アンモニア性窒素濃度計５の計測値（アンモニア性窒素濃度）とＯＲＰ計４の計測値（ＯＲＰ）との間に所定の相関関係が存在する場合には、当該相関関係を利用することによって、アンモニア性窒素濃度計５の計測に関して異常を有するか否かが診断されうる。
【００６８】
また、アンモニア性窒素濃度計５及びＯＲＰ計４と水質センサ異常診断装置７との間、アンモニア性窒素濃度計５及びＯＲＰ計４と曝気風量コントローラ２３との間、のそれぞれにおいて、アンモニア性窒素濃度計５によるアンモニア性窒素濃度の計測値、及び、ＯＲＰ計４によるＯＲＰの計測値、をフィルタリング処理するフィルタリング処理装置（フィルタリング処理部）を設置してもよい。フィルタリング処理装置は、例えば以下の式（１．３）及び式（１．４）のような演算式によって、アンモニア性窒素濃度計５及びＯＲＰ計４の計測値に対してフィルタリング処理を施すことができる。
【００６９】
【数３】

ＰＶ（ｔ）：時刻ｔにおけるセンサ計測値、ＦＴ：フィルタ係数（０〜１）、ｎ：整数
フィルタリング処理装置においてフィルタリング処理が施された計測値は、その後、水質センサ異常診断装置７或いは曝気風量コントローラ２３において用いられうる。そして、水質センサ異常診断装置７の異常診断部５０において考慮されるアンモニア性窒素濃度計５の計測値とＯＲＰ計４の計測値とは、フィルタリング処理装置によってフィルタリング処理が施されたアンモニア性窒素濃度計５の計測値及びＯＲＰ計４の計測値を用いることができる。上記各水質センサの計測値に対してフィルタリング処理を施すことによって、計測値に関する計測誤差等の不安定さ（ノイズ）をなまらせることができる。従って、フィルタリング処理が施された計測値を用いることによって、水質センサ異常診断装置７或いは曝気風量コントローラ２３は、比較的安定的に曝気装置９を制御することができる。
【００７０】
また、水質センサ異常診断装置７によるアンモニア性窒素濃度計５の計測に関して異常を有するか否かの診断方法は、ＯＲＰ計４の計測値が上記の対応水質範囲から逸脱するか否かに基づくものに限定されない。例えば、対応水質範囲算出部５１が求める対応水質範囲は、ＯＲＰ計４（異常診断用水質センサ）によるＯＲＰ（相関水質）の計測値の時間変化量に関する範囲であり、対応水質範囲照合部５２が対応水質範囲算出部５１の求めた対応水質範囲と照合するＯＲＰ計４によるＯＲＰの計測値に基づくデータは、ＯＲＰ計４によるＯＲＰの計測値の時間変化量とすることができる。そして、対応水質範囲照合部５２は、ＯＲＰ計４の計測値の時間変化量が、対応水質範囲算出部５１が求めた対応水質範囲から外れているか否かに基づいて、アンモニア性窒素濃度計５の計測に関して異常を有するか否かを診断することもできる。この場合、例えば図３に示されるような、関数Ｇ（ａ_ｏ２）と関数Ｆ（ａ_ｏ２）とによって規定される対応水質範囲を、対応水質範囲算出部５１が算出することができる。そして、アンモニア性窒素濃度計５の計測値の時間変化が、対応水質範囲から外れている時間が所定時間続いたか否かに基づいて、アンモニア性窒素濃度計５の計測に関して異常を有するか否かを診断することができる。これは、アンモニア性窒素濃度計５の計測値がアンモニア性窒素濃度の目標値に近づくように実際に制御されていれば、ＯＲＰが急激な時間変化を示すことはない、という特性を利用したものである。
【００７１】
また、溶存酸素濃度計６を本発明の制御用水質センサとして、ＯＲＰ計４を本発明の異常診断用水質センサとして、溶存酸素濃度計６の計測に関して異常を有するか否かを、ＯＲＰ計４の計測値に基づいて診断するものであってもよい。例えば、水質センサ異常診断装置７は、以下の式（１．５）で示される診断式に基づいて、溶存酸素濃度計６の計測に関して異常を有するか否かを診断することができる。
【００７２】
【数４】

ＰＶ _Ｏ２：溶存酸素濃度計の計測値（ｍｇＮ／Ｌ）、ＯＲＰ：ＯＲＰ計の計測値（ｍＶ）、ａ _Ｏ２：変数（ｍｇＮ／Ｌ）、ＵＮ_ＯＲＰ：ＯＲＰ異常診断下限値（ｍＶ）、ＵＰ_ＯＲＰ：ＯＲＰ異常診断上限値（ｍＶ）
この場合、水質センサ異常診断装置７（異常診断部５０）では、上記の式（１．３）（１．４）に基づいてフィルタリング処理が施されたＯＲＰ計４の計測値を用いることができる。また、この場合に、水質センサ異常診断装置７の異常診断部５０で用いられる診断式は上記の式（１．５）に限定されるものではなく、例えば、ＯＲＰ計４の計測値の時間変化が、所定の閾値を超えた状態が所定時間続いたか否かに基づいて、溶存酸素濃度計６の計測に関して異常を有するか否かを診断してもよい。
【００７３】
また、曝気風量コントローラ２３は、アンモニア性窒素濃度計５の計測値に基づいて曝気装置９を制御するものに限定されない。例えば、曝気風量コントローラ２３は、溶存酸素濃度計６の計測値のみに基づいて曝気装置９を制御することもでき、また、曝気風量が一定となるような制御方法や、好気槽１２への下水の流入流量に対する曝気風量の比率が一定となるような制御方法によって曝気装置９を制御することもできる。また、曝気風量コントローラ３０を異常診断部５０に接続して、異常診断部５０における診断結果に基づいて、曝気風量コントローラ３０における曝気装置９の制御モードを適宜変更させることも可能である。
【００７４】
第２の実施の形態
図４は、本発明の第２の実施の形態を示す図であって、下水処理場（下水処理システム）の概略構成を示す図である。
【００７５】
本実施の形態の下水処理場における好気槽１２に設置されている水質センサは、図４に示すように、ＯＲＰ計４と、第１アンモニア性窒素濃度計５ａと、第２アンモニア性窒素濃度計５ｂと、を含んで構成されている。水質センサ異常診断装置７には、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４が接続されており、曝気風量コントローラ２３には、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂが接続されている。なお、本実施の形態では、後述のように、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂのうち、一方が本発明の制御用水質センサとして機能し、他方が本発明の異常診断用水質センサとして機能するようになっている。また、ＯＲＰ計４は、本発明の異常診断用水質センサとして機能するようになっている。
【００７６】
また、下水処理場は水質データベース２４（水質データ記憶部）を更に備えており、当該水質データベース２４は、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４を含んで構成される水質センサと、流入流量計３０と、水質センサ異常診断装置７と、に接続されている。
【００７７】
水質データベース２４には、本発明の対象水質と相関水質との相関関係に関連する過去の相関データが記憶されている。本実施の形態では、以下の表１に示されているように、過去の所定日時における、ＯＲＰ計４の計測値（ＯＲＰ（ｍＶ））と、第１アンモニア性窒素濃度計５ａの計測値（ＮＨ_４（１）（ｍｇ／Ｌ））と、第２アンモニア性窒素濃度計５ｂの計測値（ＮＨ_４（２）（ｍｇ／Ｌ））と、流入流量計３０の計測値（流量（ｍ^３／ｍｉｎ）と、を含む過去の相関データが相互に関連づけられて記憶されている。
【００７８】
【表１】

水質データベース２４に記憶されている表１に示されるような相関データは、ＯＲＰ計４、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及び流入流量計３０から送られてくる各計測値に基づいている。また、流入流量計３０は、本発明の流入流量計及び流入流量計として機能している。従って、水質データベース２４に記憶される流入流量計３０の計測値は、制御用水質センサ（アンモニア性窒素濃度計５）によって対象水質（アンモニア性窒素濃度）が計測される生物反応槽（好気槽１２）に流入する新たな下水の流入量、及び異常診断用水質センサ（アンモニア性窒素濃度計５、ＯＲＰ計４）によって下水の相関水質（アンモニア性窒素濃度、ＯＲＰ）が計測される生物反応槽（好気槽１２）に流入する新たな下水の流入量、の両者に関する過去のデータを意味することとなる。
【００７９】
水質センサ異常診断装置７は、相関関係導出部５３を更に有している。相関関係導出部５３は、水質データベース２４に記憶されている過去の相関データに基づいて、対象水質（アンモニア性窒素濃度）と相関水質（アンモニア性窒素濃度、ＯＲＰ）との相関関係を導き出すようになっている。
【００８０】
他の構成は第１の実施の形態と略同一である。図４に示される第２の実施の形態において、第１の実施の形態と同一部分には同一符号を付して詳細な説明は省略する。
【００８１】
下水処理場に供給された下水１は、最初沈殿池２、嫌気槽１０、及び無酸素槽１１を経た後に、好気槽１２に流入する。
【００８２】
好気槽１２に流入した下水は、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂによって、アンモニア性窒素濃度が計測されると共に、ＯＲＰ計４によってＯＲＰが計測される。第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４の各水質センサの計測値は、それぞれ水質センサ異常診断装置７に送られる。また、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂの計測値は、それぞれ曝気風量コントローラ２３に送られる。
【００８３】
水質センサ異常診断装置７の異常診断部５０は、送られてきた第１アンモニア性窒素濃度計５ａによるアンモニア性窒素濃度の計測値と、第２アンモニア性窒素濃度計５ｂによるアンモニア性窒素濃度の計測値と、ＯＲＰ計４による酸化還元電位の計測値と、を考慮して、第１アンモニア性窒素濃度計５ａ及び／又は第２アンモニア性窒素濃度計５ｂの計測に関して異常を有しているか否かを診断する。すなわち、好気槽１２に設置された第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂの両者が正常である場合には、それぞれの計測値は略同等の値を示すこととなるが、いずれか一方乃至両方の計測に関して異常が生じている場合には、それぞれの計測値は異なる値を示すこととなる。ただし、これら二つのアンモニア性窒素濃度計５ａ、５ｂからのみでは、どちらのアンモニア性窒素濃度計或いは両方のアンモニア性窒素濃度計の計測に関して異常を生じているのか、について診断することが難しい。このため、水質センサ異常診断装置７は、ＯＲＰ計４の計測値及び水質データベース２４に記憶されている過去の相関データ（表１参照）を用いて、当該異常の有無についての診断を行う。
【００８４】
すなわち、水質センサ異常診断装置７の相関関係導出部５３は、水質データベース２４に記憶されている過去の相関データから、第１アンモニア性窒素濃度及び第２アンモニア性窒素濃度の平均値と、流入流量計３０の計測値と、ＯＲＰと、の相関関係を導出する。この時、相関関係導出部５３は、例えば以下の式（２．１）のような形で与えられる相関関係に基づいて、最小自乗法により回帰係数Ａ，Ｂ，Ｃを演算する。
【００８５】
Ｒ_{ＮＨ４ａｖｅｒａｇｅ}＝Ａ×ＯＲＰ＋Ｂ×Ｑ＋Ｃ 式（２．１）
ＯＲＰ：ＯＲＰ計計測値、Ｑ：流量、Ａ，Ｂ，Ｃ：回帰係数
この回帰係数Ａ，Ｂ，Ｃは、第１アンモニア性窒素濃度計５ａの計測値と第２アンモニア性窒素濃度計５ｂの計測値との間に１ｍｇ／Ｌ（所定の閾値）以上の差がない日時におけるデータに基づいて演算され、ある程度の周期（例えば、計測値のサンプリング周期よりも遅い周期の一時間単位若しくは一日単位程度の周期）で更新される。なお、本実施の形態では、上記の所定の閾値に基づいて本発明の対応水質範囲が定められている。
【００８６】
また逆に、上記の回帰係数Ａ，Ｂ，Ｃを演算する際に用いたデータの日時における、ＯＲＰと流入流量計３０の計測値とに基づいて、以下の式（２．２）のような形で与えられるアンモニア性窒素濃度の予測値Ｐ_ＮＨ４（ｔ）が演算される。
【００８７】
Ｐ_ＮＨ４（ｔ）＝Ａ×ＯＲＰ（ｔ）＋Ｂ×Ｑ（ｔ）＋Ｃ 式（２．２）
Ｐ_ＮＨ４（ｔ）：時刻ｔにおけるアンモニア性窒素濃度予測値、ＯＲＰ（ｔ）：時刻ｔにおけるＯＲＰ計計測値、Ｑ（ｔ）：時刻ｔにおける流量、Ａ，Ｂ，Ｃ：回帰係数（式（２．２）と同様の係数）
流入流量計３０及びＯＲＰ計４は、無試薬で物理量を測定するセンサなので、アンモニア性窒素濃度計５よりも計測精度に関する安定性が高いといえる。
【００８８】
よって、この予測値Ｐ_ＮＨ４（ｔ）が、対応する日時における第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂの計測値の平均値Ｐ_{ＮＨ４ａｖｅｒａｇｅ}（ｔ）と、所定の大きさ以上異なっている場合には、水質センサ異常診断装置７の異常診断部５０は、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂの両方或いはいずれか一方の計測に関して異常を有するものと診断する。一方、この予測値Ｐ_ＮＨ４（ｔ）が、その時間における第１アンモニア性窒素濃度及び第２アンモニア性窒素濃度の平均値Ｐ_{ＮＨ４ａｖｅｒａｇｅ}（ｔ）と略同一となっている場合、水質センサ異常診断装置７は、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂの両者の計測に関して異常を有しないものと診断する。
【００８９】
また、ある日時において第１アンモニア性窒素濃度計５ａの計測値Ｐ_{ＮＨ４（１）}（ｔ）と第２アンモニア性窒素濃度計５ｂの計測値Ｐ_{ＮＨ４（２）}（ｔ）との間において、所定の閾値以上の偏差が生じた場合には、その日時におけるＯＲＰ計４の計測値ＯＲＰ（ｔ）と流入流量計３０の計測値Ｑ（ｔ）とから、式（２．３）によって、アンモニア性窒素濃度の予測値Ｐ_ＮＨ４（ｔ）を演算する。そして、演算したアンモニア性窒素濃度の予測値Ｐ_ＮＨ４（ｔ）と、第１アンモニア性窒素濃度計５ａの計測値Ｐ_{ＮＨ４（１）}（ｔ）及び第２アンモニア性窒素濃度計５ｂの計測値Ｐ_{ＮＨ４（２）}（ｔ）の各々と、を比較する。そして、少なくとも、アンモニア性窒素濃度の予測値Ｐ_ＮＨ４（ｔ）に対する差の絶対値の大きい計測値を示すアンモニア性窒素濃度計５のほうに関しては、アンモニア性窒素濃度の計測に関して異常を生じていると診断することができる。このアルゴリズムを数式表現すると以下の式（２．３）のようになる。
【００９０】
【数５】

Ｐ_ＮＨ４（ｔ）：アンモニア性窒素濃度予測値、ＰＶ_{ＮＨ４ａｖｅｒａｇｅ}（ｔ）：第１アンモニア性窒素濃度計の計測値と第２アンモニア性窒素濃度計の計測値との平均値、ＵＬ：アンモニア性窒素濃度計診断（計測値−演算値）上限値、ＰＶ_{ＮＨ４（１）}（ｔ）：第１アンモニア性窒素濃度計の計測値、ＰＶ_{ＮＨ４（２）}（ｔ）：第２アンモニア性窒素濃度計の計測値、ＵＬ_ＰＶ：第１アンモニア性窒素濃度計の計測値と第２アンモニア性窒素濃度計の計測値と間の偏差上限値
そして、水質センサ異常診断装置７における上記の診断結果は、監視装置８に送られる。
【００９１】
一方、曝気風量コントローラ２３は、第１アンモニア性窒素濃度計５ａの計測値及び第２アンモニア性窒素濃度計５ｂの計測値に基づいて、曝気装置９から好気槽１２内に供給される曝気風量を制御する。すなわち、曝気風量コントローラ２３は、送られてくる第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂの計測値の平均値が、予め設定されているアンモニア性窒素濃度の目標値に近づくように、曝気装置９から好気槽１２に供給される曝気風量の目標値を演算する。例えば、曝気風量コントローラ２３は、下記の式（２．４）の曝気風量演算式を利用して、曝気装置９から好気槽１２に供給される曝気風量の目標値を演算する。
【００９２】
【数６】

Ｑａｉｒ（ｔ）：時刻ｔにおける曝気風量目標値（ｍ^３／ｍｉｎ）、Ｑａｉｒ_０：曝気風量初期値（ｍ^３／ｍｉｎ）、Ｋｐ：比例ゲイン（ｍ^６／ｇ・ｍｉｎ）、Ｔ_Ｉ：積分定数（ｍｉｎ）、△ｔ：制御周期（ｍｉｎ）、ｅ（ｔ）：偏差（ｍｇ／Ｌ）、ＳＶ_ＮＨ４（ｔ）：アンモニア性窒素濃度目標値（ｍｇ／Ｌ）、ＰＶ _{ＮＨ４（１）}（ｔ）：第１アンモニア性窒素濃度計の計測値（ｍｇ／Ｌ） 、ＰＶ _{ＮＨ４（２）} （ｔ）：第２アンモニア性窒素濃度計の計測値（ｍｇ／Ｌ）
そして、好気槽１２に供給される曝気風量が、演算した曝気風量の目標値と等しくなるように、曝気風量コントローラ２３は曝気装置９を制御する。これにより、曝気風量コントローラ２３に制御されている曝気装置９は、常に過不足なく曝気を好気槽１２に供給することができ、好気槽１２において適正な曝気風量が確保されることとなる。
【００９３】
以上説明したように本実施の形態によれば、水質データベース２４に蓄えられている過去のデータ（相関データ）を用いて、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂの計測に関する異常の有無が診断されるので、アンモニア性窒素濃度と酸化還元電位（ＯＲＰ）との関係を把握するための実験等を、前もって行う必要がない。
【００９４】
また、パラメータの設定も、ＵＬ（少なくともどちらかのアンモニア性窒素濃度計の計測に関して異常を有しているか否かを診断するための許容上限値）と、ＵＬ_ＰＶ（第１アンモニア性窒素濃度計５ａと第２アンモニア性窒素濃度計５ｂとの間における偏差の許容上限値）と、の２つのみであって、プラントでの制御パラメータの調整が容易となる。
【００９５】
また、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂによって計測されるアンモニア性窒素濃度を対象水質及び相関水質としており、対象水質と相関水質とは同一である。従って、第１アンモニア性窒素濃度計５ａ又は第２アンモニア性窒素濃度計５ｂの計測に関して異常が生じているか否かは、両者の計測値間のズレに基づいて診断可能であるため、迅速に当該異常の発生を検知することができる。
【００９６】
また、曝気風量コントローラ２３は、同じ好気槽１２に設置した二つのアンモニア性窒素濃度計（第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂ）の計測値に基づいて、曝気装置９の制御を行っているので、一方のアンモニア性窒素濃度計５ａ、５ｂの計測に関して異常が生じた場合であっても、他方のアンモニア性窒素濃度計５ａ、５ｂの計測値に基づいて曝気装置９を制御することが可能である。このため、いずれか一方のアンモニア性窒素濃度計５ａ、５ｂの計測に関して異常が生じた場合であっても、最適な曝気風量を確保することができ、浄化処理された下水は安定的に良好な水質を保持することとなる。
【００９７】
水質センサ異常診断装置７の異常診断部５０において用いられるアンモニア性窒素濃度の予測値は、ＯＲＰ計４の計測値だけではなく、流入流量計３０の計測値にも基づいて予測されている。従って、異常診断部５０は、本発明の流入流量計３０及び流入流量計３０として機能する流入流量計３０の計測値を更に考慮して、制御用水質センサによる対象水質の計測に関して異常を有するか否かを診断することができ、流入流量計３０の計測値の変動に応じた当該異常の有無の診断を正確に行うことが可能である。
【００９８】
次に本実施の形態の変形例について説明する。
【００９９】
第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４は、それぞれ、好気槽１２よりも後段に設置されていてもよい。例えば、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４は、それぞれ、最終沈殿池１３、好気槽１２と最終沈殿池１３とを連結する水配管、最終沈殿池１３から下水を排出するための水配管、等に設置され、設置箇所の下水の各水質を計測するようになっていてもよい。このような場合であっても、各水質センサーが計測する各水質同士は、所定の相関関係を有しうる。
【０１００】
また、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４と水質センサ異常診断装置７との間、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４と曝気風量コントローラ２３との間、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４と水質データベース２４との間、のそれぞれにおいて、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４の各水質センサの計測値をフィルタリング処理するフィルタリング処理装置を設置してもよい。フィルタリング処理装置は、例えば上記の式（１．３）及び式（１．４）のような演算式によって、第１アンモニア性窒素濃度計５ａ、第２アンモニア性窒素濃度計５ｂ、及びＯＲＰ計４の計測値に対してフィルタリング処理を施すことができる。そして、フィルタリング処理装置によってフィルタリング処理が施された上記各水質センサの計測値は、その後、水質センサ異常診断装置７、曝気風量コントローラ２３、或いは水質データベース２４において用いられうる。
【０１０１】
また、水質センサ異常診断装置７は、アンモニア性窒素濃度（対象水質）を予測する際に、流入流量計３０やＯＲＰ計４の計測値に関するデータのみならず、他の水質に関するデータを考慮してもよい。例えば、図４の嫌気槽１０に流入する前の下水（例えば、最初沈殿池２、或いはその前後の水配管内の下水）のＴ−Ｎ計（全窒素計）による計測値データ、好気槽１２に貯留されている下水のＤＯ（溶存酸素濃度）に関するＤＯ計データ、好気槽１２に貯留されている下水のＭＬＳＳに関するＭＬＳＳ計データ、等の過去のデータが水質データベース２４に記憶されている場合について考えてみる。この場合、水質センサ異常診断装置７は、水質データベース２４に記憶されているこれらの水質データを考慮して、以下の式（２．７）のような演算式に基づく重回帰分析によって、回帰係数（Ａ，Ｂ，Ｃ，・・・，Ｚ）を決定し、決定した回帰係数をアンモニア性窒素濃度（対象水質）の予測演算の際に用いてもよい。
【０１０２】
Ｒ_{ＮＨ４ａｖｅｒａｇｅ}＝Ａ×ＯＲＰ＋Ｂ×Ｑ＋Ｃ×Ｔ−Ｎ＋Ｄ×ＤＯ＋Ｅ×ＭＬＳＳ＋・・＋Ｚ 式（２．７）
Ｒ_{ＮＨ４ａｖｅｒａｇｅ}：相関関係より演算される第１アンモニア性窒素濃度計５ａと第２アンモニア性窒素濃度計５ｂの平均値、ＯＲＰ：ＯＲＰ計計測値（ｍＶ）、Ｑ：流量（ｍ^３／ｍｉｎ）、Ｔ−Ｎ：流入水Ｔ−Ｎ濃度（ｍｇ／Ｌ）、ＤＯ：好気槽１２溶存酸素濃度（ｍｇ／Ｌ）、ＭＬＳＳ：好気槽１２ＭＬＳＳ（ｍｇ／Ｌ）、Ａ，Ｂ，Ｃ・・・・・Ｚ：回帰係数
また、水質センサ異常診断装置７の異常診断部５０における、アンモニア性窒素濃度計５（制御用水質センサ）の計測に関して異常を有するか否かの診断方法は、上記の式（２．４）に基づくものには限定されず、他の方法を用いることも可能である。例えば、水質データベース２４に蓄えられたデータを相関解析によって、好気槽１２のアンモニア性窒素濃度の計測値と相関の高いデータのみを抜き出し、相関が高いと診断されたデータのみを利用して、アンモニア性窒素濃度計の計測に関して異常を有しているか否かの診断を行ってもよい。また、異常診断部５０は、ＰＶ_{ＮＨ４（１）}（第１アンモニア性窒素濃度計の計測値）、ＰＶ_{ＮＨ４（２）}（第２アンモニア性窒素濃度計の計測値）、Ｐ_ＮＨ４（アンモニア性窒素濃度の予測値）の時系列データを用いた主成分分析に基づいて、アンモニア性窒素濃度計５（制御用水質センサ）の計測に関して異常を有するか否かを診断してもよい。すなわち、アンモニア性窒素濃度計５（制御用水質センサ）による計測が正常である場合、ＰＶ_{ＮＨ４（１）}、ＰＶ_{ＮＨ４（２）}、Ｐ_ＮＨ４は、ほぼ同じ傾向を示す。従って、ＰＶ_{ＮＨ４（１）}、ＰＶ_{ＮＨ４（２）}、Ｐ_ＮＨ４の時系列データを用いた主成分分析を行うと、第１主成分にほとんど全ての情報が内包されるはずである。例えば、以下の式（２．８）（２．９）（２．１０）で表されるような主成分分析を行った場合の第１〜第３成分（Ｘ_１，Ｘ_２，Ｘ_３）に対応する固有値（情報量）をλ_１，λ_２，λ_３とする。
【０１０３】
Ｘ_１＝ａ_１１ＰＶ_{ＮＨ４（１）}＋ ａ_２１ＰＶ_{ＮＨ４（２）}＋ａ_３１Ｒ_ＮＨ４ 式（２．８）
Ｘ_２＝ａ_１２ＰＶ_{ＮＨ４（１）}＋ ａ_２２ＰＶ_{ＮＨ４（２）}＋ａ_３２Ｒ_ＮＨ４ 式（２．９）
Ｘ_３＝ａ_１３ＰＶ_{ＮＨ４（１）}＋ ａ_２３ＰＶ_{ＮＨ４（２）}＋ａ_３３Ｒ_ＮＨ４ 式（２．１０）
Ｘ_１：第１主成分、Ｘ_２：第２主成分、Ｘ_３：第３主成分、ＰＶ_{ＮＨ４（１）}：第１アンモニア性窒素濃度計５ａの計測値、ＰＶ_{ＮＨ４（２）} ：第２アンモニア性窒素濃度計５ｂの計測値、Ｒ_ＮＨ４：重回帰式による予測値、ａ_ｉｊ：定数
この時、アンモニア性窒素濃度計５による計測が正常である場合には、以下の式（２．１１）で示される第１主成分の寄与率が高いはずである。
【０１０４】
【数７】

そして、第１アンモニア性窒素濃度計５ａ及び第２アンモニア性窒素濃度計５ｂのうちいずれかの計測に関して異常が生じると、第２主成分以降の主成分が情報をもつようになり、第１主成分の寄与率が下がることとなる。従って、設定された第１主成分の寄与率の低下に基づいて、アンモニア性窒素濃度計５の計測に関して異常を生じているか否かを診断することもできる。
【０１０５】
また、上記の式（２．３）、式（２．７）の相関式は、上記のような線形型のものに限定されず、必要に応じて他の適切な相関式を用いることが可能である。例えば、べき乗型、指数関数型、対数型、或いはこれらを組み合わせたもの、等を用いてもよい。
【０１０６】
また、アンモニア性窒素濃度計５は、図４に示されているように好気槽１２に２つ設置されたものでなくてもよく、１つのみが設置されたものであってもよい。また、好気槽１２に設置されるアンモニア性窒素濃度計５は２つに限定されるものではなく、３つ以上のアンモニア性窒素濃度計５を好気槽１２に設置してもよい。
【０１０７】
また、水質センサ異常診断装置７は、いずれのアンモニア性窒素濃度計５が異常を有しているのかについての診断を行う際に、水質データベース２４に記憶されているＯＲＰ計４及び流入流量計３０の計測値に関するデータのうち、両方のデータを用いてもよく、また、いずれか一方のデータのみを用いてもよい。
【０１０８】
また、所定の対象水質は、アンモニア性窒素濃度に限定されるものではない。また、制御用水質センサは、アンモニア性窒素濃度計に限定されるものではない。例えば、リン酸性リン、溶存酸素濃度、ＭＬＳＳ、硝酸性窒素濃度、等を所定の対象水質として、リン酸性リン濃度計、溶存酸素濃度計、ＭＬＳＳ計、硝酸性窒素濃度計、等を制御用水質センサとすることもできる。
【０１０９】
第３の実施の形態
図５は、本発明の第３の実施の形態を示す図であって、下水処理場（下水処理システム）の概略構成を示す図である。
【０１１０】
本実施の形態の下水処理場では、好気槽１２にＯＲＰ計４と第１アンモニア性窒素濃度計５ａと第２アンモニア性窒素濃度計５ｂとを設置する代わりに、水質センサのうちＯＲＰ計４と硝酸性窒素濃度計３１とが無酸素槽１１に設置されている（図５参照）。ＯＲＰ計４と硝酸性窒素濃度計３１とは、それぞれ、水質センサ異常診断装置７と水質データベース２４と後述される炭素源注入コントローラ２５とに接続されている。そして、ＯＲＰ計４の計測値及び硝酸性窒素濃度計３１の計測値が、水質センサ異常診断装置７と水質データベース２４と炭素源注入コントローラ２５とに送られるようになっている。
【０１１１】
また、好気槽１２にはアンモニア性窒素濃度計５が設置されており、当該アンモニア性窒素濃度計５は曝気風量コントローラ２３に接続されている。曝気風量コントローラ２３は、アンモニア性窒素濃度計５の計測値を用いて、以下の式（３．１）で示される演算式に基づいて曝気装置９を制御するようになっている。
【０１１２】
【数８】

Ｑａｉｒ（ｔ）：時刻ｔにおける曝気風量目標値（ｍ^３／ｍｉｎ）、Ｑａｉｒ_０：曝気風量初期値（ｍ^３／ｍｉｎ）、Ｋｐ：比例ゲイン（ｍ^６／ｇ・ｍｉｎ）、Ｔ_Ｉ：積分定数（ｍｉｎ）、△ｔ：制御周期（ｍｉｎ）、ｅ（ｔ）：偏差（ｍｇ／Ｌ）、ＳＶ_ＮＨ４（ｔ）：アンモニア性窒素濃度目標値（ｍｇ／Ｌ）、ＰＶ _ＮＨ４ （ｔ）：アンモニア性窒素濃度計の計測値（ｍｇ／Ｌ）
なお、本実施の形態では、ＯＲＰ計４を本発明の制御用水質センサとした場合には、硝酸性窒素濃度計３１が本発明の異常診断用水質センサとして機能し、硝酸性窒素濃度計３１を本発明の制御用水質センサとした場合には、ＯＲＰ計４が本発明の異常診断用水質センサとして機能する。従って、本実施の形態では、制御用水質センサが対象水質を計測する下水と異常診断用水質センサが相関水質を計測する下水とは、同一生物反応槽における下水である。
【０１１３】
水質データベース２４には、ＯＲＰと硝酸性窒素濃度との相関関係に関連する過去の相関データが記憶されている。本実施の形態では、過去の所定日時における、ＯＲＰ計４の計測値（ＯＲＰ（ｍＶ））のデータと、硝酸性窒素濃度計３１の計測値（ＮＨ_４（１）（ｍｇ／Ｌ））のデータと、が相互に関連づけられて水質データベース２４に記憶されている。なお、水質データベース２４に記憶されるＯＲＰ計４の計測値のデータ及び硝酸性窒素濃度計３１の計測値（ＮＨ_４（１）（ｍｇ／Ｌ））のデータは、ＯＲＰ計４及び硝酸性窒素濃度計３１から水質データベース２４に送られてくる計測値に基づくものである。
【０１１４】
水質センサ異常診断装置７は異常診断部５０を有しており、当該異常診断部５０は、ＯＲＰ計４及び硝酸性窒素濃度計３１から送られてくる各計測値に基づいて、ＯＲＰ計４及び／または硝酸性窒素濃度計３１の計測に関して異常を有するか否かを診断するようになっている。
【０１１５】
一方、炭素源注入ポンプ１９には炭素源注入コントローラ２５が接続されている。炭素源注入コントローラ２５は、ＯＲＰ計４及び硝酸性窒素濃度計３１から送られてくる各計測値に基づいて炭素源注入ポンプ１９を制御し、炭素源貯留槽２１から嫌気槽１０に注入される炭素源の注入量を調整することができるようになっている。また、炭素源注入コントローラ２５は水質センサ異常診断装置７に接続されており、水質センサ異常診断装置７の異常診断部５０の診断結果が炭素源注入コントローラ２５に送られるようになっている。なお、本発明の水質調整装置は、炭素源貯留槽２１及び炭素源注入ポンプ１９を含んで構成されており、本発明の水質調整制御装置は、炭素源注入コントローラ２５を含んで構成されている。
【０１１６】
また、最初沈殿池２に下水を供給する水配管の中途ではバイパス水配管６１が分岐しており、当該バイパス水配管６１は嫌気槽１０に接続されている。当該バイパス水配管６１には初沈バイパス弁６２が取り付けられており、この初沈バイパス弁６２の開閉を調節することにより、バイパス水配管６１を流れる下水の流量を調整することができるようになっている。
【０１１７】
他の構成は第２の実施の形態と略同一である。図５に示される第３の実施の形態において、第２の実施の形態と同一部分には同一符号を付して詳細な説明は省略する。
【０１１８】
下水処理場に供給された下水１は、最初沈殿池２を経て嫌気槽１０に流入し、嫌気槽１０において嫌気処理が施された後に、無酸素槽１１に流入する。無酸素槽１１に流入した下水は、無酸素処理が施されると共に、ＯＲＰ計４及び硝酸性窒素濃度計３１によって対応する水質（ＯＲＰ、硝酸性窒素濃度）が計測される。その後、下水は、無酸素槽１１から排出され、好気槽１２と最終沈殿池１３とを経て下水処理場から排出される。
【０１１９】
ところで、無酸素槽１１に貯留されている下水に関して対応する水質を計測したＯＲＰ計４及び硝酸性窒素濃度計３１のそれぞれは、水質センサ異常診断装置７と、炭素源注入コントローラ２５と、水質データベース２４と、に計測値を送るようになっている。
【０１２０】
水質データベース２４は、ＯＲＰ計４及び硝酸性窒素濃度計３１から送られてくる計測値を、計測日時と対応付けて、ＯＲＰ計４の計測値に関する相関データ及び硝酸性窒素濃度計３１の計測値に関する相関データとして記憶する。
【０１２１】
一方、水質センサ異常診断装置７では、ＯＲＰ計４及び硝酸性窒素濃度計３１から送られてくる計測値に基づいて、ＯＲＰ計４及び／又は硝酸性窒素濃度計３１の計測に関して異常を有するか否かが診断される。例えば、炭素源貯留槽２１に貯留されている炭素源が例えばメタノールである場合に、嫌気槽１０では、以下の式（３．２）で示される脱窒反応が生じる。
【０１２２】
６ＮＯ_３ ⁻＋５ＣＨ_３ＯＨ→３Ｎ_２＋５ＣＯ_２＋７Ｈ_２Ｏ＋６ＯＨ⁻ 式（３．２）
この場合、硝酸性窒素は酸化剤として働くこととなる。一方、ＯＲＰは、一般的には以下の式（３．３）で示されるような関係があり、ＯＲＰと硝酸性窒素濃度との間には以下の式（３．４）で示されるような相関関係があると考えられる。
【０１２３】
【数９】

ＯＲＰ＝ Ａ＋Ｂ・ｌｎ（ＮＯ_３） 式（３．４）
Ａ，Ｂ：定数
そして、水質センサ異常診断装置７の異常診断部５０は、例えば以下の式（３．５）で示される演算式を用いて、ＯＲＰの予測値（Ｒ_ＯＲＰ）を演算する。
【０１２４】
Ｒ_ＯＲＰ＝ Ａ ＋ Ｂ・ｌｎ（ＰＶ_ＮＯ３） 式（３．５）
ＯＲＰ：ＯＲＰ予測演算値、ＰＶ_ＮＯ３：ＮＯ_３計計測値、Ａ，Ｂ：定数（実際のＯＲＰとＮＯ_３の関係から最小二乗法等により導出）
そして、水質センサ異常診断装置７の異常診断部５０では、水質データベース２４に記憶されているＯＲＰ計４及び硝酸性窒素濃度計３１の計測値に関する時系列データ（相関データ）を用いて、日時の対応するＯＲＰ計４の計測値（ＰＶ_ＯＲＰ）とＯＲＰの予測演算値（Ｒ_ＯＲＰ）との間で主成分分析が行われる。この時、ＯＲＰ計４及び硝酸性窒素濃度計３１の計測が正常に行われている場合には、第１主成分にほとんどの情報が含まれるはずである。すなわち、第１主成分の固有値をλ１、第２主成分の固有値をλ２とした場合に、ＯＲＰ計４及び硝酸性窒素濃度計３１による計測が正常に行われている場合には、λ１＞＞λ２という関係になる。一方、ＯＲＰ計４及び硝酸性窒素濃度計３１のうちどちらかの計測に関して異常が生じている場合には、第２主成分にも主要な情報が含まれうることとなり、以下の式（３．６）で示される第１主成分の寄与率が低下する。
【０１２５】
【数１０】

そして、水質センサ異常診断装置７の異常診断部５０では、上記の式（３．６）で示される第１主成分の寄与率が所定の閾値以下となった場合には、ＯＲＰ計４或いは硝酸性窒素濃度計３１の計測に関して異常が生じていると診断され、第１主成分の寄与率が所定の閾値よりも大きい場合には、ＯＲＰ計４及び硝酸性窒素濃度計３１の計測は正常に行われていると診断される。当該診断結果は、監視装置８に送られると共に、炭素源注入コントローラ２５に送られる。なお、本実施の形態では、上記の所定の閾値によって、本発明の対応水質範囲が定められる。
【０１２６】
監視装置８では、送られてくる水質センサ異常診断装置７の診断結果に基づいて、下水処理場の管理者等に対するガイダンス及び／または警報が行われる。また、炭素源注入コントローラ２５は、ＯＲＰ計４或いは硝酸性窒素濃度計３１の計測に関して異常が生じているという診断結果が送られてきた場合には、ＯＲＰ計４及び硝酸性窒素濃度計３１の計測値に基づく炭素源注入ポンプ１９の制御をやめて、炭素源注入量一定、等の他の制御モードに切り換える。一方、炭素源注入コントローラ２５は、ＯＲＰ計４或いは硝酸性窒素濃度計３１の計測が正常に行われている旨の診断結果が送られてきている間は、硝酸性窒素濃度計３１の計測値に基づいて、以下の式（３．７）で示される演算式によるＰＩ制御に基づいて炭素源注入ポンプ１９の制御が行われる。なお、硝酸性窒素濃度の目標値ＳＶ_ＮＯ３（ｔ）は、炭素源注入コントローラ２５内に予め設定されている。
【０１２７】
【数１１】

Ｑ_{ｃａｒｂｏｎ}（ｔ）：時刻ｔにおける炭素源投入量目標値（ｍ^３／ｍｉｎ）、Ｑ_{ｃａｒｂｏｎ０}：炭素源投入量初期値（ｍ^３／ｍｉｎ）、Ｋｐ：比例ゲイン（ｍ^６／ｇ・ｍｉｎ）、Ｔ_Ｉ：積分定数（ｍｉｎ）、△ｔ：制御周期（ｍｉｎ）、ｅ（ｔ）：偏差（ｍｇ／Ｌ）、ＳＶ_ＮＯ３（ｔ）：硝酸性窒素濃度の目標値（ｍｇ／Ｌ）、ＰＶ _ＮＯ３ （ｔ）：硝酸性窒素濃度計の計測値（ｍｇ／Ｌ）
上記の式（３．７）に基づいて得られた硝酸窒素濃度の目標値（ＳＶ_ＮＯ３）と硝酸性窒素濃度計３１の計測値（ＰＶ_ＮＯ３）との偏差（ｅ（ｔ））に基づいて、炭素源注入コントローラ２５は炭素源注入ポンプ１９を制御し、嫌気槽１０内の硝酸性窒素濃度が目標値（ＳＶ_ＮＯ３）となるように調整され、嫌気槽１０では下水に対して適切な嫌気処理が施されることとなる。
【０１２８】
以上説明したように、本実施の形態によれば、ＯＲＰの理論に基づいて、ＯＲＰと硝酸性窒素濃度との関係を対数近似したものと、ＯＲＰ計４及び硝酸性窒素濃度計３１による実測値と、の比較に基づいて、ＯＲＰ計４、硝酸性窒素濃度計３１の計測に関して異常を有するか否かが診断されているので、他の線形近似等を利用した場合に比べて、診断の信頼性が高い。
【０１２９】
また、水質データベース２４に記憶されている過去のデータの主成分分析が利用されて、ＯＲＰ計４或いは硝酸性窒素濃度計３１の計測に関して異常を有するか否かが診断されている。このため、パラメータは第１主成分の寄与率に関する所定の閾値のみなので、プラントでの制御パラメータの調整が非常に簡単なものとなる。
【０１３０】
次に本実施の形態の変形例について説明する。
【０１３１】
炭素源貯留槽２１は、無酸素槽１１に接続されていてもよい。
【０１３２】
また、炭素源注入コントローラ２５は、ＯＲＰ計４及び硝酸性窒素濃度計３１の計測値に基づいて、初沈バイパス弁６２の開度を調整して、嫌気槽１０に流入する下水の流量を調整してもよい。なお、この変形例では、本発明の水質調整装置は初沈バイパス弁６２を含んで構成されており、本発明の水質調整制御装置は炭素源注入コントローラ２５を含んで構成されることとなる。
【０１３３】
また、ＯＲＰ計４及び／又は硝酸性窒素濃度計３１と水質センサ異常診断装置７との間、ＯＲＰ計４及び／又は硝酸性窒素濃度計３１と炭素源注入コントローラ２５との間、或いはＯＲＰ計４及び／又は硝酸性窒素濃度計３１と水質データベース２４との間、にフィルタリング処理装置を設置してもよい。この場合、フィルタリング処理装置は、例えば上記の式（１．３）（１．４）で示されるような演算式によって、ＯＲＰ計４及び／又は硝酸性窒素濃度計３１の計測値に対してフィルタリング処理を施すことができる。フィルタリング処理装置においてフィルタリング処理が施された計測値は、その後、水質センサ異常診断装置７、炭素源注入コントローラ２５、或いは水質データベース２４において用いられうる。
【０１３４】
ＯＲＰ計４或いは硝酸性窒素濃度計３１の計測に関して異常を有するか否かを診断する際に、水質センサ異常診断装置７の異常診断部５０で用いられる方法は主成分分析を利用するものには限定されない。例えば、水質センサ異常診断装置７の異常診断部５０は、上記の式（３．５）によって演算されるＯＲＰの予測値（Ｒ_ＯＲＰ）とＯＲＰ計４の計測値（ＰＶ_ＯＲＰ）との偏差を演算して、この偏差が、所定の対応水質範囲から外れている状態が所定時間続いたか否かに基づいて、ＯＲＰ計４及び／または硝酸性窒素濃度計３１の計測に関して異常を有するか否かを診断してもよい。
【０１３５】
また、上記の式（３．５）の相関式は、上記のような対数型のものに限定されず、必要に応じて他の適切な相関式を用いることが可能である。例えば、線形型、べき乗型、指数関数型、対数型、或いはこれらを組み合わせたもの、等を用いてもよい。
【０１３６】
また、ＯＲＰの予測値（Ｒ_ＯＲＰ）を演算する際に、硝酸性窒素濃度だけでなく、他の信頼性の高い水質センサ及び流量計の計測値を用いてもよい。例えば、無酸素槽１１にＵＶ計３３を設置して、当該ＵＶ計３３の計測値に基づいて、以下の式（３．１０）で示されるような演算式を用いることによりＯＲＰの予測値（Ｒ_ＯＲＰ）を演算することができる。
【０１３７】
【数１２】

一般的に有機物成分とＵＶとは線形関係があると言われており、脱窒反応において有機物は還元剤として働く。式（３．１０）は、このことを踏まえて、上記の式（３．３）から導出されるものである。
【０１３８】
第４の実施の形態
図６及び図７は、本発明の第３の実施の形態を示す図である。図６は、下水処理場（下水処理システム）の概略構成を示す図である。図７は、各水質センサーの相関関係を概略的に示した図であり、図７中のＳ_１〜Ｓ_５は、各水質センサーを示している。
【０１３９】
本実施の形態の下水処理場では、好気槽１２にＯＲＰ計４と第１アンモニア性窒素濃度計５ａと第２アンモニア性窒素濃度計５ｂとを設置する代わりに、最初沈殿池２に下水を供給する水配管にＴ−Ｎ計３２とＵＶ計３３とが設置され、嫌気槽１０にＯＲＰ計４（嫌気槽用ＯＲＰ計４ａ）が設置され、無酸素槽１１にＯＲＰ計４（無酸素槽用ＯＲＰ計４ｂ）と硝酸性窒素濃度計３１とが設置され、好気槽１２にＯＲＰ計４（好気槽用ＯＲＰ計４ｃ）とアンモニア性窒素濃度計５と溶存酸素濃度計６とＭＬＳＳ計３６とリン酸性リン濃度計３７とが設置されている。これらの水質センサ（Ｔ−Ｎ計３２、ＵＶ計３３、ＯＲＰ計４ａ、４ｂ、４ｃ、硝酸性窒素濃度計３１、アンモニア性窒素濃度計５、溶存酸素濃度計６、ＭＬＳＳ計３６、リン酸性リン濃度計３７）のそれぞれは、水質センサ異常診断装置７に接続されると共に水質データベース２４に接続されており、計測値を水質センサ異常診断装置７、水質データベース２４に送るようになっている。
【０１４０】
また、最初沈殿池２と嫌気槽１０との間の水配管には、最初沈殿池２から脱窒・脱リン処理槽４０の嫌気槽１０に流入する下水の流量を計測する第１流入流量計３０ａが設置され、炭素源貯留槽２１と嫌気槽１０との間の水配管には、当該水配管を流れる炭素源の流量を計測する第２流入流量計３０ｂが設置され、凝集剤貯留槽２２と好気槽１２との間の水配管には、当該水配管を流れる凝集剤の流量を計測する第３流入流量計３０ｃが設置され、好気槽１２内の下水を無酸素槽１１内に返送するための水配管には、当該水配管を返送される下水の流量を計測する第４流入流量計３０ｄが設置され、最終沈殿池１３と嫌気槽１０とを連結する水配管には、当該水配管を介して嫌気槽１０に返送される下水の流量を計測する第５流入流量計３０ｅが設置され、最初沈殿池２と汚泥貯留槽２０とを連結する水配管には、当該水配管を流れる下水の流量を計測する第６流入流量計３０ｆが設置され、最終沈殿池１３と汚泥貯留槽２０とを連結する水配管には、当該水配管を流れる下水の流量を計測する第７流入流量計３０ｇが設置されている。第１〜第７流入流量計３０ａ〜３０ｇは、それぞれ、水質データベース２４に接続されており、計測値を水質データベース２４に送るようになっている。また、曝気装置には、曝気装置から好気槽に曝気される曝気風量を計測する曝気風量計４６が取り付けられている。当該曝気風量計４６は、水質データベース２４に接続さており、計測値を水質データベース２４送るようになっている。
【０１４１】
水質データベース２４は、各水質センサから送られてくる各計測値に関するデータと、各流入流量計３０から送られてくる各計測値に関するデータと、曝気風量計４６から送られてくる計測値に関するデータと、を計測日時と関連づけて記憶することができるようになっている。
【０１４２】
また、水質センサ異常診断装置７は異常診断部５０を有しており、当該異常診断部５０は、各水質センサから送られてくる各計測値に関するデータと水質データベース２４に記憶されている相関データと基づいて、各水質センサの計測に関して異常を有するか否かを診断するようになっている。
【０１４３】
なお、曝気風量コントローラ２３は、曝気装置９から好気槽１２に供給される曝気量が所定の一定量に保たれるように、曝気装置９を制御している。
【０１４４】
なお、本実施の形態では、本発明の制御用水質センサは、各水質センサーのうちいずれかによって構成され、対象水質は、当該水質センサによって計測される水質である。また、本発明の異常診断用水質センサは、他の水質センサ及び各流入流量計３０によって構成され、相関水質は、当該他の水質センサによって計測される水質及び各流入流量計３０によって計測される流量である。また、本実施の形態では、式（４．１）、（４．４）、（４．６）によって本発明の対象水質と相関水質との相関関係が表される。この相関式を用いて式（４．２）、（４．５）、（４．７）で対象水質予測値を演算し、この予測値と対象水質の実測値との差を式（４．３）、（４．８）により演算して、異常判定を行うようになっている。
【０１４５】
他の構成は第２の実施の形態と略同一である。図６及び図７に示される第４の実施の形態において、第２の実施の形態と同一部分には同一符号を付して詳細な説明は省略する。
【０１４６】
下水処理場に供給された下水１は、最初沈殿池２、嫌気槽１０、無酸素槽１１、好気槽１２、そして最終沈殿池１３を経て浄化処理が施され、処理水３として下水処理場から排出される。このような浄化処理の各生物反応槽において、各水質センサ、各流入流量計３０ａ〜３０ｇ、及び曝気風量計４６は、それぞれ、対応する水質及び流量を計測し、計測値を水質センサ異常診断装置７及び水質データベース２４に送る。
【０１４７】
水質データベース２４には、各水質センサ、各流入流量計３０ａ〜３０ｇ、及び曝気風量計４６から送られてくる計測値に関するデータが、計測日時に応じて相互に関連づけられて記憶される。また、水質データベース２４内では、水質データベース２４に記憶されている過去のデータ（相関データ）が利用されて、各水質センサ及び流入流量計３０ａ〜３０ｇの計測値に対して相関の高い成分を、相関解析によって抽出することができる。
【０１４８】
水質センサ、流入流量計３０ａ〜３０ｇ、及び曝気風量計４６の計測値に関する合計ｎ個の相関データが水質データベース２４に記憶されている場合には、下水処理場に設置されている水質センサのうちから選ばれる任意の水質センサ（水質センサ１）に関する相関式を、以下の式（４．１）で示されるような形で表すことができる。このため、水質センサ異常診断装置７の異常診断部５０は、式（４．１）で表される相関式において用いられる回帰係数Ａ_２１、Ａ_３１、・・・Ａ_ｎ１、Ａ_０１が重回帰分析により演算される。
【０１４９】
Ｒｓｅｎｓｏｒ_１＝Ａ_２１・Ｓ_２ ＋ Ａ_３１・Ｓ_３ ＋Ａ_４１・Ｓ_４ ・・・・＋Ａ_ｎ１・Ｓ_ｎ ＋Ａ_０１ 式（４．１）
Ｒｓｅｎｓｏｒ_１：水質センサー１に関する相関式
Ｓ_２：センサー２による水質値又は流量値
Ｓ_３：センサー３による水質値又は流量値
Ｓ_４：センサー４による水質値又は流量値
・
・
Ｓ_ｎ：センサーｎによる計測値（流量又は水質）
Ａ_２１、Ａ_３１・・・・・・Ａ_ｎ１、Ａ_{（ｎ＋１）１}：回帰係数（相関分析により水質センサー１と相関の低いセンサｉについては、Ａ_ｉ１＝０となる。）
また、水質センサ異常診断装置７の異常診断部５０では、この水質センサ１の時刻ｔにおける予測演算値が、上記の式（４．１）で求められた式を用いて、水質センサ１以外の他の水質センサ若しくは流入流量計３０ａ〜３０ｇの値から以下の式（４．２）により演算される。
【０１５０】
Ｐｓｅｎｓｏｒ_１（ｔ）＝Ａ_２１・Ｓ_２（ｔ）＋ Ａ_３１・Ｓ_３（ｔ）＋Ａ_４１・Ｓ_４（ｔ）・・・・＋Ａ_ｎ１・Ｓ_ｎ（ｔ）＋Ａ_{（ｎ＋１）１}・・・・式（４．２）
Ｐｓｅｎｓｏｒ_１（ｔ）：水質センサー１の時刻ｔにおける予測演算値
Ｓ_２（ｔ）：センサー２の時刻ｔにおける計測値（流量又は水質）
Ｓ_３（ｔ）：センサー３の時刻ｔにおける計測値（流量又は水質）
Ｓ_４（ｔ）：センサー４の時刻ｔにおける計測値（流量又は水質）
・
・
Ｓ_ｎ（ｔ）：センサーｎの時刻ｔにおける計測値（流量又は水質）
Ａ_２１、Ａ_３１・・・・・・Ａ_ｎ１、Ａ_{（ｎ＋１）１}：回帰係数（式（４．１）の係数と同じ値）
そして、水質センサ異常診断装置７の異常診断部５０は、式（４．２）により演算された水質センサ１の計測値の予測値と、水質センサ１の計測値と、の偏差が、所定の閾値を超えたか否かに基づいて、水質センサ１の計測に関して異常が生じているか否かを診断する。すなわち、異常診断部５０は、以下の式（４．３）に示すように、当該偏差が所定の閾値を超えた場合には、水質センサ１の計測に関して異常が生じているか、或いは、水質センサ１と相関のある他の水質センサ若しくは流入流量計３０（Ａ_ｉ１≠０に対応する水質センサ若しくは流入流量計３０）の計測に関して異常が生じていると診断することができる。なお、本実施の形態では、上記の所定の閾値によって、本発明の対応水質範囲が定められる。
【０１５１】
｜Ｓ_１（ｔ）−Ｐｓｅｎｓｏｒ_１（ｔ）｜＞ＵＬｓｅｎｓｏｒ_１ 式（４．３）
ＵＬｓｅｎｓｏｒ_{１ ：}水質センサー１の異常判定値
そして、水質センサ１以外の他の水質センサについても、水質センサ１と同様の重回帰分析が行われ、以下の式（４．４）のような形で表される回帰係数Ａ_１ｊ〜Ａ_{（ｎ＋１）ｊ}が決定される。また、以下の式（４．５）のような形で、水質センサｉの時刻ｔにおける予測演算値Ｐｓｅｎｓｏｒ_ｊが表される。
【０１５２】
Ｒｓｅｎｓｏｒ_ｊ＝ Ａ_１ｊ・Ｓ_１ ＋ Ａ_２ｊ・Ｓ_２ ＋ Ａ_３ｊ・Ｓ_３ ＋ ・・・・＋Ａ_ｎｊ・Ｓ_ｎ ＋Ａ_０ｊ・・・・式（４．４）
Ｒｓｅｎｓｏｒ_ｊ：水質センサーｊに関する相関式
Ｓ_１：センサー１による水質値又は流量値
Ｓ_２：センサー２による水質値又は流量値
Ｓ_３：センサー３による水質値又は流量値
・
・
Ｓ_ｎ：センサーｎによる水質値又は流量値
Ａ_１ｊ、Ａ_２ｊ・・・・・・Ａ_ｎｊ、Ａ_{（ｎ＋１）ｊ}： 水質センサｊに対する水質センサ１〜ｎの回帰係数（相関解析により水質センサーｊと相関の低いセンサｉについては、Ａ_ｉｊ＝０となる。）
Ｐｓｅｎｓｏｒ_ｊ（ｔ）＝ Ａ_１ｊ・Ｓ_１（ｔ）＋Ａ_２ｊ・Ｓ_２（ｔ）＋ Ａ_３ｊ・Ｓ_３（ｔ）・・・・＋Ａ_ｎｊ・Ｓ_ｎ（ｔ）＋Ａ_０ｊ・・・・式（４．５）
Ｐｓｅｎｓｏｒ_ｉ（ｔ）：水質センサーｉの時刻ｔにおける予測演算値
Ｓ_１（ｔ）：センサー１の時刻ｔにおける計測値（流量又は水質）
Ｓ_２（ｔ）：センサー２の時刻ｔにおける計測値（流量又は水質）
Ｓ_３（ｔ）：センサー３の時刻ｔにおける計測値（流量又は水質）
・
・
Ｓ_ｎ（ｔ）：センサーｎの時刻ｔにおける計測値（流量又は水質）
Ａ_０ｊ：定数項
Ａ_１ｊ、Ａ_２ｊ・・・・・・Ａ_ｎｊ、Ａ_０ｊ：水質センサｊに対する水質センサ１〜ｎの回帰係数（式（４．１）の係数と同じ値）
すべての水質センサーに関する相関式（Ｒｓｅｎｓｏｒ_ｊ）を行列式の形で表すと、以下の式（４．６）のような形で表される。
【０１５３】
【数１３】

Ｒｓｅｎｓｏｒ_ｊ：水質センサｊに関する相関式
Ｓ_ｊ：センサｊの水質値又は流量値
Ａ_０ｊ：定数項
Ａ_ｉｊ：水質センサｊに対する水質センサｉの回帰係数（ｉ＝１〜ｎ，ｊ＝１〜ｎ）
また、時刻ｔにおけるすべての水質センサーに関する計測値の予測値（Ｐｓｅｎｓｏｒ_ｊ）を行列式の形で表すと、以下の式（４．７）のような形で表される。
【０１５４】
【数１４】

Ｐｓｅｎｓｏｒ_ｊ（ｔ）：時刻ｔにおける水質センサｊの予測値
Ｓ_ｊ（ｔ）：時刻ｔにおけるセンサｊの計測値
Ａ_０ｊ：定数項
Ａ_ｉｊ：水質センサｊに対する水質センサｉの回帰係数（ｉ＝１〜ｎ，ｊ＝１〜ｎ）
そして、水質センサ異常診断装置７は、以下の式（４．８）の異常診断式で示されているように、演算された各水質センサの計測値の予測値と、各水質センサによる計測値と、の偏差が、所定の閾値を超えたか否かに基づいて、各水質センサの計測に関して異常が生じているか否かを診断することができる。
【０１５５】
【数１５】

ＵＬｓｅｎｓｏｒ_{ｊ ：}水質センサーｊの異常判定値
上述のようにして、各水質センサの計測に関して異常が生じているか否かが診断される。そして、一つの水質センサーの計測に関して異常が生じると、上記の式（４．８）のうちの１個乃至複数個の異常診断式において、異常が生じている旨が示される。すなわち、式（４．８）において異常であると診断されれば、水質センサーｊ若しくは当該水質センサーｊと相関を有する水質センサ群の水質センサ（すなわち、センサＡ_ｉｊ≠０に対応する水質センサ）のいずれかの計測に関して異常が生じていると診断されうる。一方、式（４．８）において正常であると診断されれば、水質センサーｊ若しくは当該水質センサーｊと相関を有する水質センサ群の各水質センサー（すなわち、センサＡ_ｉｊ≠０に対応する水質センサ）の計測は正常に行われている。
【０１５６】
例えば、水質センサーＳ_１〜Ｓ_５に関して図７に示すような相関関係がある場合を想定してみる。図７において、重なり合っている各水質センサー間部分は相関を有しており、重なり合っていない各水質センサー間部分は相関を有していない、ということ示す。水質センサーＳ_１〜Ｓ_５が図７のような相関関係を有する場合に、水質センサーＳ_１の計測に関してのみ異常が生じている場合、水質センサーＳ_１に関する異常診断式と、水質センサーＳ_１と相関を有する水質センサーＳ_２、Ｓ_５に関する異常診断式と、では異常が生じている旨が示されることとなる。しかしながら、この場合、水質センサーＳ_１と相関を有さない水質センサーＳ_３の計測が正常に行われているので、水質センサーＳ_３に関する異常診断式は正常な状態である旨を示す。従って、水質センサーＳ_３と相関を有する水質センサーＳ_２、Ｓ_５の計測も、正常に行われていると診断することができる。このようにして、水質センサＳ_１の計測に関してのみ異常が生じていると診断することができる。
【０１５７】
また同様に、水質センサーＳ_２の計測に関してのみ異常が生じている場合、水質センサーＳ_２に関する異常診断式と、水質センサーＳ_２と相関を有する水質センサーＳ_１、Ｓ_３に関する異常診断式と、では異常が生じている旨が示されることとなる。しかしながら、この場合、水質センサーＳ_２と相関を有さない水質センサーＳ_５の計測が正常に行われているので、水質センサーＳ_５に関する異常診断式は正常な状態である旨を示す。従って、水質センサーＳ_５と相関を有する水質センサーＳ_１、Ｓ_３の計測も、正常に行われていると診断することができる。このようにして、水質センサＳ_２の計測に関してのみ異常が生じていると診断することができる。
【０１５８】
一方、水質センサーＳ_３の計測に関してのみ異常が生じている場合、水質センサーＳ_３に関する異常診断式と、水質センサーＳ_２と相関を有する水質センサーＳ_２、Ｓ_４、Ｓ_５に関する異常診断式と、では異常が生じている旨が示されることとなる。そして、水質センサーＳ_１の計測が正常に行われている場合には、水質センサーＳ_１に関する異常診断式では正常である旨が示されるので、水質センサーＳ_１と相関を有する水質センサーＳ_２、Ｓ_５の計測は正常に行われていると診断することができる。しかしながら、水質センサーＳ３及び水質センサーＳ４のうちどちらの或いは両者の計測に関して異常が生じているのかについては、厳密に診断することができない。従って、水質センサ異常診断装置７は、水質センサーＳ３及び水質センサーＳ４のうちいずれか一方或いは両者の計測に関して異常が生じていると診断することができる。
【０１５９】
このようにして、水質センサ異常診断装置７の異常診断部５０が、下水処理場に設置されている水質センサーのすべての計測について、上記の式（４．８）を利用して異常の有無を診断することにより、計測に関して異常が生じている可能性がある水質センサーを抽出することができる。
【０１６０】
そして、水質センサ異常診断装置７の異常診断部５０における上記の診断結果は、監視装置８に送られ、監視装置８は、送られてくる水質センサ異常診断装置７の診断結果に基づいて、管理者等に対してガイダンス、警報を行う。例えば、水質センサ異常診断装置７の異常診断部５０で抽出された、計測に関して異常が生じている可能性がある水質センサーのリストがディスプレイ表示されたりする。
【０１６１】
次に、本実施の形態の変形例について説明する。
【０１６２】
各水質センサー及び各流入流量計３０ａ〜３０ｇの設置位置は、図６に示されるものに限定されない。各水質センサー及び各流入流量計３０ａ〜３０ｇは、必要に応じて、下水処理場の任意箇所に設置されてもよい。
【０１６３】
また、各水質センサー、各流入流量計３０ａ〜３０ｇ、及び曝気風量計４６と水質センサ異常診断装置７との間、或いは、各水質センサー、各流入流量計３０ａ〜３０ｇ、及び曝気風量計４６と水質データベース２４との間、において、計測値をフィルタリング処理するフィルタリング処理装置を設置してもよい。フィルタリング処理装置は、例えば上記の式（１．３）（１．４）のような演算式によって、各計測値に対してフィルタリング処理を施すことができる。フィルタリング処理装置においてフィルタリング処理が施された計測値は、その後、水質センサ異常診断装置７、水質データベース２４において用いられうる。
【０１６４】
また、水質センサ異常診断装置７の異常診断部５０における各水質センサーの計測に関して異常を有するか否かの診断方法は、上記の図７に基づくものには限定されず、他の方法を用いることも可能である。例えば、各種水質センサーの時系列データを用いた主成分分析に基づく方法を用いて、各水質センサーの計測に関して異常を有するか否かについて診断することも可能である。
【０１６５】
また、上記の式（４．１）、（４．４）、（４．６）の相関式は、上記のようなものに限定されず、必要に応じて他の適切な相関式を用いることが可能である。例えば、線形型、べき乗型、指数関数型、対数型、或いはこれらを組み合わせたもの、等を用いることもできる。
【０１６６】
上述の各実施の形態及び各変形例では、脱窒・脱リンを行う高度処理プロセスの一つである、凝集剤注入型嫌気−無酸素−好気法（凝集剤注入Ａ_２Ｏ法）と呼ばれるプロセスが行われるように構成された下水処理場について説明したが、他のプロセスに対しても本発明を好適に適用することができる。例えば、以下の表２に示されている各種プロセスのいずれに対しても、本発明を適用しうる。また、表２に示されている各種プロセスの他に、担体投入、凝集剤併用型のプロセス、ＡＯＡＯ法、各種Ａ_２Ｏ法、或いはこれらの各種プロセスの変法に対しても本発明を好適に適用することができる。
【０１６７】
【表２】

また、上述の各実施の形態及び各変形例では、複数の生物反応槽を備えた下水処理場（下水処理システム）について説明したが、単数（１つのみ）の生物反応槽を備えた下水処理場に対しても、本発明を好適に適用しうる。
【０１６８】
更に、本発明における制御用水質センサ及び異常診断用水質センサは、上述のものに限定されるものではない。例えば、制御用水質センサは、アンモニア性窒素濃度計、硝酸性窒素濃度計、全窒素濃度計、リン酸性リン濃度計、全リン濃度計、ＣＯＤ計、及びＢＯＤ計のうち、少なくとも１つ以上の水質センサ（有試薬センサ）を含んで構成されうる。また、異常診断用水質センサは、ＯＲＰ計、ＵＶ計、及びＤＯ計のうち、制御用水質センサが計測する対象水質と相関を有する相関水質を計測する１つ以上の水質センサ（無試薬センサ）を含んで構成されうる。
【０１６９】
例えば、以下の表３に示すように、制御用水質センサを硝酸性窒素濃度計或いは全窒素濃度計とした場合には、異常診断用水質センサはＵＶ計、ＤＯ計が好ましく、制御用水質センサをリン酸性リン濃度計或いは全リン濃度計とした場合には、異常診断用水質センサはＤＯ計が好ましく、制御用水質センサをＣＯＤ計或いはＢＯＤ計とした場合には、異常診断用水質センサはＯＲＰ計或いはＤＯ計が好ましい。また、制御用水質センサをアンモニア性窒素濃度計とした場合には、異常診断用水質センサはＤＯ計がより好ましく、制御用水質センサをリン酸性リン濃度計或いは全リン濃度計とした場合には、異常診断用水質センサはＯＲＰ計がより好ましい。また、制御用水質センサをアンモニア性窒素濃度計、硝酸性窒素濃度計、或いは全窒素濃度計とした場合には、異常診断用水質センサはＯＲＰ計とすることが特に好ましく、制御用水質センサをＣＯＤ計或いはＢＯＤ計とした場合には、異常診断用水質センサはＵＶ計とすることが特に好ましい。
【０１７０】
【表３】

なお、上述の各実施の形態を適宜組み合わせたものも本発明の範囲内に含まれうる。
【０１７１】
【発明の効果】
以上説明したように本発明によれば、制御用水質センサによる対象水質の計測に関して異常を有するか否かを診断するために、制御用水質センサによる対象水質の計測値だけでなく、異常診断用水質センサによる相関水質の計測値、及び、対象水質と相関水質との相関関係、が考慮される。このため、制御用水質センサによる対象水質の計測に関して異常の有無に関する診断を迅速に行うことが可能である。
【図面の簡単な説明】
【図１】第１の実施の形態における下水処理場（下水処理システム）の概略構成を示す図である。
【図２】対応水質範囲の一例を示す図であって、ＮＨ_４濃度とＯＲＰとの関係が示されている。
【図３】第１の実施の形態の一変形例における対応水質範囲を概略的に示す図である。
【図４】第２の実施の形態における下水処理場の概略構成を示す図である。
【図５】第３の実施の形態における下水処理場の概略構成を示す図である。
【図６】第４の実施の形態における下水処理場の概略構成を示す図である。
【図７】各水質センサーの相関関係を概略的に示した図である。図７中のＳ_１〜Ｓ_５は、各水質センサーを示している。
【図８】従来の下水処理場の概略構成の一例を示す図である。
【図９】従来の下水処理場の概略構成の他の例を示す図である。
【図１０】従来の下水処理場における、ＮＨ_４濃度と時間との関係、及び、曝気風量と時間との関係、を示す図である。
【符号の説明】
４、４ａ、４ｂ、４ｃ ＯＲＰ計
５、５ａ、５ｂ アンモニア性窒素濃度計
６ 溶存酸素濃度計
７ 水質センサ異常診断装置
８ 監視装置
９ 曝気装置
１０ 嫌気槽
１１ 無酸素槽
１２ 好気槽
１６ ＰＡＣ注入ポンプ
１７ 余剰ポンプ
１８ 初沈引抜ポンプ
１９ 炭素源注入ポンプ
２１ 炭素源貯留槽
２２ 凝集剤貯留槽
２３ 曝気風量コントローラ
２４ 水質データベース（水質データ記憶部）
２５ 炭素源注入コントローラ
３０、３０ａ〜３０ｇ 流入流量計
３１ 硝酸性窒素濃度計
３２ Ｔ−Ｎ計
３３ ＵＶ計
３６ ＭＬＳＳ計
３７ リン酸性リン濃度計
４０ 脱窒・脱リン処理槽
４６ 曝気風量計
５０ 異常診断部
５１ 対応水質範囲算出部
５２ 対応水質範囲照合部
５３ 相関関係導出部
６１ バイパス水配管
６２ 初沈バイパス弁[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a water quality monitoring and control device for controlling a sewage treatment plant that processes sewage such as municipal sewage and industrial wastewater, and a sewage treatment system including the water quality monitoring and control device.
[0002]
[Prior art]
In recent years, eutrophication has been progressing in closed water areas such as lakes, marshes and bays, so that organic substances, nitrogen and phosphorus, which are substances causing eutrophication, flow out of sewage treatment plants into closed water areas. Need to be suppressed. In conventional sewage treatment plants, organic matter has been removed from sewage by a process called activated sludge method. However, in view of the above background, demand for advanced treatment to remove not only organic matter but also nitrogen and phosphorus from sewage has been increasing. Is increasing.
[0003]
There are various advanced treatment processes for removing nitrogen and phosphorus from sewage. As a representative example, a coagulant injection type anaerobic-anoxic-aerobic method (coagulant injection A₂A process called O method) is known. FIG. 8 is a diagram showing a schematic configuration of a sewage treatment plant (sewage treatment system). The mechanism of nitrogen / phosphorus removal performed in the process shown in FIG. 8 will be described.
[0004]
That is, in the aerobic tank 12, the nitrifying bacteria utilize the oxygen supplied by the aeration device 9 to remove ammoniacal nitrogen (NH) as shown in the following equations (1) and (2).₄-N) with nitrite nitrogen (NO₂-N) and nitrate nitrogen (NO₃-N).
[0005]
The nitrite nitrogen (NO) sent from the aerobic tank 12 to the anoxic tank 11 by the circulation pump 14₂-N) and nitrate nitrogen (NO₃-N) is nitrogen gas (N) when denitrifying bacteria perform nitrate respiration or nitrite respiration under anoxic conditions using organic matter as a nutrient source.₂) And removed outside the system. At this time, if organic substances required for the denitrification reaction are not sufficiently supplied to the denitrification bacteria, nitrogen cannot be effectively removed from the sewage.
[0006]
As a method for supplementing the organic matter to the denitrifying bacteria, for example, a method of opening the initial sedimentation bypass valve 23 and closing the valve 24 to secure the organic matter by bypassing the first sedimentation basin, and a method of storing the organic matter in the carbon source storage tank 21 A method of injecting a carbon source such as methanol, ethanol, acetic acid, waste acetic acid, and glucose into the anaerobic tank 10, and a method of charging the extracted sludge generated in the first settling tank 2 into the aeration tank.
When the nitrogen removal reaction is represented by a chemical formula, the nitrification reaction is represented by the following formulas (1) and (2).
[0007]
NH₄ ⁺+ 2O₂→ NO₂ ⁻+ 2H₂O Formula (1)
NO₂ ⁻+ 1 / 2O₂→ NO₃ ⁻                Equation (2)
The denitrification reaction when methanol is used as an organic substance is represented by the following equation (3).
[0008]
6NO₃ ⁻+ 5CH₃OH → 3N₂+ 5CO₂+ 7H₂O + 6OH⁻          Equation (3)
Further, in the anaerobic tank 10 disposed in front of the aeration tank 12, the phosphorus-accumulating bacteria in the activated sludge accumulate organic acids such as acetic acid in the body and generate phosphoric acid (PO).₄Release). The excessively released phosphoric acid phosphorus was removed in the aerobic tank 12 disposed downstream of the anaerobic tank 10 by utilizing the excessive phosphorus uptake action of the phosphorus accumulating bacteria, and released in the anaerobic tank 10. The phosphoric acid phosphorus is absorbed by the activated sludge. Therefore, in order to make this reaction proceed, an organic acid such as acetic acid is required as a hydrogen donor. At the time of rainwater inflow, the concentration of organic acids is reduced, and the amount of organic substances that can utilize phosphorus-accumulating bacteria is reduced, so that the phosphorus expulsion reaction is sufficiently performed, and the subsequent excessive intake of phosphorus is also insufficient. In order to compensate for this, it is necessary to secure the carbon source necessary for phosphorus removal by the same means as in the case of nitrogen removal and to remove phosphorus, or to remove polyaluminum chloride, sulfuric acid and sulfuric acid stored in the flocculant storage tank 22. It is necessary to inject a coagulant such as aluminum, iron sulfate or the like into sewage to precipitate a phosphorus component in the form of aluminum phosphate or iron phosphate to remove phosphorus.
[0009]
Al₃ ⁺+ 3PO₄ ⁻→ Al (PO₄)₃          Equation (4)
Meanwhile, there is a conventional sewage treatment plant water quality monitoring and control device as shown in FIG. 5 is an ammonia nitrogen concentration, 9 is an aeration device, 12 is an aerobic tank, and 23 is an aeration air volume controller. FIG. 9 adjusts the aeration device 9 based on the deviation between the measurement value of the ammonia nitrogen concentration meter 5 and the control target value set in the aeration air volume controller 23 to adjust the ammonia nitrogen concentration in the aerobic tank 12. It is a device configured to keep it constant. The monitoring device 8 displays the measurement value of the ammonia nitrogen concentration meter 5.
[0010]
In addition, there are various types of sewage treatment plant water quality monitoring and control devices in addition to those described above (for example, see Patent Document 1). Can be selected.
[0011]
In the sewage treatment plant, water quality items such as TOC (total organic carbon concentration), COD (chemical oxygen demand), and BOD (biochemical oxygen demand) are analyzed as organic components. As the nitrogen component, water quality items such as ammonia nitrogen concentration, nitrate nitrogen concentration, nitrite nitrogen concentration, total nitrogen concentration, etc. are analyzed. In addition, water quality items such as phosphoric phosphorus concentration and total phosphorus concentration are analyzed as phosphorus components. Further, other water quality items such as dissolved oxygen concentration and SS (sludge concentration) are analyzed. These water quality items are managed by the water quality analysis staff at the sewage treatment plant, either by sampling and performing manual analysis (once a week) or continuously measured by water quality sensors. I have.
[0012]
[Patent Document 1]
JP-A-11-244894
[0013]
[Problems to be solved by the invention]
Water quality sensors typified by nitrogen concentration meter including ammonia nitrogen concentration meter, nitrate nitrogen concentration meter and total nitrogen concentration meter, and phosphorus concentration meter including phosphoric acid concentration meter and total phosphorus concentration meter When each water quality item is measured by utilizing, each water quality is obtained by filtering sludge in the order of mg / L, that is, in the order of ppm, and then performing colorimetry using a reagent, measuring the absorbance thereof, and based on the measured value. Thus, the concentration of the target substance (water quality) is calculated (measured). In this way, when each water quality item is to be measured by the sensor, a measurement value abnormality may occur due to deterioration of the reagent or adhesion of sludge to the detection unit, and an appropriate measurement value may not be obtained. On the other hand, when the water quality component of the same item as the water quality sensor is measured by the manual analysis, the analysis requires time and effort. On the other hand, in a sewage treatment plant, generally, a water quality analyst only measures each water quality item about once a week to about once a month, not every day. For this reason, it is delayed to notice the abnormality of the measured value, and a countermeasure for preventing the deterioration of the water quality may be delayed, or an erroneous diagnosis may be made by an operator.
[0014]
On the other hand, as an example of a conventional sewage treatment plant water quality monitoring and control device, it has a configuration shown in FIG. 9 and is based on a measurement value of the ammonia nitrogen concentration meter 5 after the nitrification treatment is performed in the aerobic tank 12. In some cases, the aeration air volume of the aeration device 9 is adjusted by FB control so that the ammonia nitrogen concentration set in the aeration air volume controller 23 matches a target value. However, when the value of the ammonia nitrogen concentration meter indicates a value different from the actual concentration when such FB control is performed, for example, the actual concentration of the ammonia nitrogen concentration is 0.8 mg / L. Nevertheless, consider a case where the measured value of the ammonia nitrogen concentration meter is 3 mg / L and the target value of the ammonia nitrogen concentration set in the aeration air volume controller 23 is 1 mg / L. In this case, considering the actual concentration, the control must be performed in the direction of reducing the aeration air flow, but the measured value is larger than the target value, so the control works in the direction of increasing the aeration air flow. Problem may occur. (See Fig. 10)
Further, when the ammonia nitrogen concentration meter 5 of FIG. 9 is a dissolved oxygen concentration meter, the ammonia nitrogen concentration meter 5 is installed in the aerobic tank 12 such that the dissolved oxygen concentration set in the aeration air volume controller 23 matches the target value. Even when a device that adjusts the aeration air volume of the aeration device 9 by FB control based on the measurement value of the dissolved oxygen concentration meter is used, the same problem as described above occurs, and the control does not work well. Sometimes.
[0015]
The present invention has been made in order to solve the above-described problems, and has a water quality monitoring control device capable of quickly diagnosing the presence or absence of an abnormality in a measurement value of a water quality sensor, and a sewage including the water quality monitoring control device. It is an object to provide a processing system.
[0016]
[Means for Solving the Problems]
The present invention relates to a water quality monitoring control device for monitoring the quality of a predetermined target water quality of sewage treated in a sewage treatment system having one or more biological reaction tanks for purifying sewage. Among the water qualities, a control water quality sensor that measures the target water quality, and a water quality sensor for abnormality diagnosis that measures a correlated water quality having a correlation with the target water quality, among sewage water qualities in a sewage treatment system, The measurement value of the target water quality by the water quality sensor, the measurement value of the correlated water quality by the abnormality diagnosis water quality sensor, and the correlation between the target water quality and the correlation water quality, taking into account the control water quality sensor. An abnormality diagnosis unit that diagnoses whether or not the measurement of the target water quality has an abnormality. According to the present invention, a measurement value of the target water quality by the control water quality sensor, a measurement value of the correlation water quality by the abnormality diagnosis water quality sensor, and a correlation between the target water quality and the correlation water quality are considered. Then, it is diagnosed whether or not the measurement of the target water quality by the control water quality sensor is abnormal. Therefore, it is possible to accurately and quickly diagnose whether or not the abnormality is present.
[0017]
Further, the present invention is a sewage treatment system comprising one or more biological reaction tanks for purifying sewage and the above-mentioned water quality monitoring and control device.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
First embodiment
FIG. 1 and FIG. 2 are diagrams showing a first embodiment of the present invention. FIG. 1 is a diagram showing a schematic configuration of a sewage treatment plant (sewage treatment system). FIG. 2 is a diagram showing an example of the corresponding water quality range, in which NH₄The relationship between concentration and ORP is shown.
[0020]
The sewage treatment plant (sewage treatment system) shown in FIG. 1 monitors a plurality of biological reaction tanks for purifying sewage and the quality of ammonia nitrogen concentration (predetermined target water quality) of sewage to be treated. And a water quality monitoring control device for the In particular, the sewage treatment plant according to the present embodiment is one of the advanced treatment processes for performing denitrification and dephosphorization.₂A process referred to as "O method)" is configured to be performed on sewage.
[0021]
The sewage treatment plant includes a first sedimentation basin 2, a denitrification / dephosphorization treatment tank 40 installed via a water pipe after the first sedimentation basin 2, and a water pipe And a final sedimentation basin 13 which is installed through the intermediary.
[0022]
In the first sedimentation basin 2, impurities in the stored sewage are sedimented. In addition, sewage containing impurities precipitated in the first sedimentation basin 2 (first sedimentation water) is discharged from the first sedimentation basin 2 and sent to a sludge storage tank 20 described later.
[0023]
An inflow flow meter 30 is attached to a water pipe connecting the first sedimentation basin 2 and the denitrification / dephosphorization treatment tank 40. The inflow flowmeter 30 measures the flow rate of fresh sewage sent from the sedimentation tank 2 to the denitrification / dephosphorization treatment tank 40 first. As will be described later, the denitrification / dephosphorization treatment tank 40 is controlled by an ammonia nitrogen concentration meter 5 as a control water quality sensor and an ORP meter 4 as an abnormality diagnosis water quality sensor according to the present invention. ) And the correlated water quality (ORP) are measured, so that the inflow flow meter 30 can also measure the amount of new sewage flowing into the aerobic tank 12. .
[0024]
The denitrification / dephosphorization treatment tank 40 has an anaerobic tank 10, an anoxic tank 11 installed downstream of the anaerobic tank 10, and an aerobic tank 12 installed downstream of the anoxic tank 11. I have.
[0025]
The anaerobic tank 10 has activated sludge containing phosphorus accumulating bacteria. A carbon source storage tank 21 is connected to the anaerobic tank 10 via a water pipe, and a carbon source injection pump 19 is attached to the water pipe. A carbon source is injected into the anaerobic tank 10 from a carbon source storage tank 21 through a water pipe, and a carbon source is supplied from the carbon source storage tank 21 to the anaerobic tank 10 by a carbon source injection pump 19. Is adjusted. The carbon source stored in the carbon source storage tank 21 is not particularly limited, and for example, methanol, ethanol, acetic acid, waste acetic acid, glucose, and the like can be suitably used as the carbon source. In such an anaerobic tank 10, the phosphorus accumulating bacteria in the activated sludge use the carbon source injected from the carbon source storage tank 21 to accumulate organic acids such as acetic acid in the sewage in the body, and generate phosphoric acid ( PO₄). The phosphorus component is removed from the sewage by the action of such a phosphorus accumulating bacterium.
[0026]
One end of a water pipe to which a circulation pump 14 is attached is connected to the anoxic tank 11, and the other end of the water pipe is connected to the bottom of the aerobic tank 12. Then, a part of the sewage stored in the aerobic tank 12 is returned to the anoxic tank 11 through the water pipe by the circulation pump 14. At this time, the sewage returned to the anoxic tank 11 contains nitrite nitrogen (NO₂-N) and nitrate nitrogen (NO₃-N). The anoxic tank 11 also contains denitrifying bacteria that use organic matter as a nutrient under anoxic conditions. Then, in the anoxic tank 11, nitrite respiration or nitrite respiration by the denitrifying bacteria causes nitrite nitrogen (NO₂-N) and nitrate nitrogen (NO₃-N) is nitrogen gas (N₂). Reduced nitrogen gas (N₂) Is discharged outside the system and removed from the sewage treatment plant.
[0027]
The aerobic tank 12 includes an aeration device 9 for aerating the sewage in the aerobic tank 12 and an ORP meter 4 (oxidizing) for measuring the oxidation-reduction potential (ORP) (correlated water quality) of the sewage in the aerobic tank 12. A reduction potentiometer) (abnormality diagnosis water quality sensor); an ammonia nitrogen concentration meter 5 (control water quality sensor) for measuring the concentration of ammonia nitrogen (target water quality) in sewage in the aerobic tank 12; A dissolved oxygen concentration meter 6 for measuring the dissolved oxygen concentration of the sewage in 12 is provided. The ammonia nitrogen concentration meter 5 is a reagent-based water quality sensor that uses a reagent that shows a colorimetric reaction with the ammonia nitrogen in the sewage, and detects a colorimetric reaction between the ammonia nitrogen in the sewage and the reagent. Thereby, the ammonia nitrogen concentration of the sewage can be measured. On the other hand, the ORP meter 4 is a reagentless water quality sensor that does not use a reagent. Note that the ammonia nitrogen concentration and the ORP have a correlation as shown in Expression (1.2) described later.
[0028]
The aeration device 9 (water quality adjustment device) is a device configured to be able to aerate the sewage in the aerobic tank 12, and is capable of adjusting the concentration of ammonia nitrogen in the sewage by the aeration. You can do it. The aeration device 9 is connected to an aeration controller 23, and the aeration device 9 is controlled by the aeration controller 23 to control the amount of aeration to the sewage in the aerobic tank 12. Further, the ammonia air concentration meter 5 and the dissolved oxygen concentration meter 6 installed in the aerobic tank 12 are connected to the aeration air volume controller 23, and the measured value of the ammonia nitrogen concentration meter 5 and the dissolved oxygen concentration meter 6 are connected. Is sent to the aeration air volume controller 23.
[0029]
The aeration air volume controller 23 controls the aeration device 9 based on the measurement value of the ammoniacal nitrogen concentration meter 5 and the measurement value of the dissolved oxygen concentration meter 6 and supplies the gas from the aeration device 9 into the aerobic tank 12. The amount of aeration air to be supplied can be adjusted. Specifically, the target value of the ammonia nitrogen concentration is set in advance in the aeration air volume controller 23, and the measurement value sent from the ammonia nitrogen concentration meter 5 is set in the ammonia air concentration controller 5. The target value of the aeration air volume supplied from the aeration device 9 to the aerobic tank 12 is calculated so as to approach the target value of the nitrogen concentration. When calculating the target value of the aeration air volume using the aeration air volume calculation formula, for example, when the aeration air volume controller 23 is a PI controller, the aeration air volume calculation formula shown in the following formula (1.1) is used. Can be used.
[0030]
(Equation 1)

Qair (t): a target air flow rate at time t (m³/ Min), Qair₀: Aeration air volume initial value (m³/ Min), Kp: proportional gain (m⁶/ G · min), T_I: Integration constant (min), Δt: control cycle (min), e (t): deviation (mg / L), SV_NH4(T): target value of ammonia nitrogen concentration (mg / L), PV_NH4  (T): Measurement value of ammonia nitrogen concentration meter (mg / L)
In such a case, the measured value of the ammonia nitrogen concentration (PV_NH4) Is the target value of the ammonia nitrogen concentration (SV_NH4If the value is larger than (), the target value of the aeration air flow is calculated so that the aeration air flow in the aerobic tank 12 increases. Conversely, the measured ammonia nitrogen concentration (PV_NH4) Is the target value of the ammonia nitrogen concentration (SV_NH4If it is smaller than (), the aeration air flow target value is calculated so that the aeration air flow in the aerobic tank 12 decreases.
[0031]
On the other hand, each water quality sensor of the ORP meter 4, the ammonia nitrogen concentration meter 5, and the dissolved oxygen concentration meter 6 is connected to the water quality sensor abnormality diagnosis device 7, and the measured values of these water quality sensors are used for the water quality sensor abnormality diagnosis. It is sent to the device 7.
[0032]
A coagulant storage tank 22 is connected to the aerobic tank 12 via a water pipe, and a PAC injection pump 16 is attached to the water pipe. A coagulant is injected into the aerobic tank 12 from the coagulant storage tank 22 via a water pipe, and the injection amount of the coagulant into the aerobic tank 12 is adjusted by the PAC injection pump 16. It is supposed to be. The coagulant injected into the aerobic tank 12 from the coagulant storage tank 22 is mainly used for precipitating the phosphorus component in the sewage in the form of aluminum phosphate or iron phosphate. In addition, such a coagulant is not particularly limited, and for example, polyaluminum chloride, aluminum sulfate, iron sulfate, and the like can be suitably used as the coagulant. Then, in the aerobic tank 12, ammonia nitrogen (NH₄-N) is nitrite nitrogen (NO₂-N) and nitrate nitrogen (NO₃-N). Further, in the aerobic tank 12, the excess phosphorus in the phosphoric acid released in the anaerobic tank 10 is absorbed by the activated sludge by utilizing the excess phosphorus intake action of the phosphorus accumulating bacteria. As a result, the phosphoric acid phosphorus excessively released in the anaerobic tank 10 is removed.
[0033]
The water quality sensor abnormality diagnosis device 7 includes an abnormality diagnosis unit 50, and the abnormality diagnosis unit 50 includes a corresponding water quality range calculation unit 51 and a corresponding water quality range comparison unit 52. The abnormality diagnosing unit 50 cooperates the corresponding water quality range calculating unit 51 and the corresponding water quality range checking unit 52 with the measured value of the ammonia nitrogen concentration (target water quality) by the ammonia nitrogen concentration meter 5 (control water quality sensor). , An ORP meter 4 (a water quality sensor for abnormality diagnosis), and an ammonia nitrogen concentration meter 5 (a control water quality sensor) in consideration of the measured value of the ORP (correlated water quality) and the correlation between the ammonia nitrogen concentration and the ORP. ) To determine whether there is an abnormality in the measurement of the ammonia nitrogen concentration.
[0034]
The corresponding water quality range calculation unit 51 calculates a corresponding water quality range related to the ORP corresponding to the measured value of the ammonia nitrogen concentration by the ammonia nitrogen concentration meter 5 based on the correlation between the ammonia nitrogen concentration and the ORP. ing. The corresponding water quality range obtained by the corresponding water quality range calculation unit 51 is a range related to the ORP measurement value obtained by the ORP meter 4.
[0035]
The corresponding water quality range collating unit 52 collates the data based on the ORP measurement value obtained by the ORP meter 4 with the corresponding water quality range obtained by the corresponding water quality range calculating unit 51, so that the measurement by the ammonia nitrogen concentration meter 5 can be performed. A diagnosis is made as to whether or not there is an abnormality. The data based on the measured value of the ORP by the ORP meter 4 used when the corresponding water quality range is compared by the corresponding water quality range matching unit 52 is the measured value of the ORP by the ORP meter 4. Then, the corresponding water quality range collating unit 52 performs the measurement of the ammonia nitrogen concentration meter 5 based on whether the measured value of the ORP by the ORP meter 4 is out of the corresponding water quality range obtained by the corresponding water quality range calculation unit 51. Is diagnosed as having an abnormality.
[0036]
For example, when the ammonia nitrogen concentration of the sewage is controlled so as to approach the target value, the measurement value of the ORP meter 4 is not necessarily determined to be a unique value, but falls within a predetermined range (corresponding water quality range). It will be. By utilizing such characteristics, when the measured value of the ORP meter 4 is out of the corresponding water quality range, the abnormality diagnosing unit 50 diagnoses that the measurement of the ammonia nitrogen concentration meter 5 has an abnormality. It has become. The following equation (1.2) shows an example of a diagnostic equation used by the abnormality diagnostic unit 50 when diagnosing the presence or absence of an abnormality related to the measurement of the ammonia nitrogen concentration meter 5 in this manner.
[0037]
(Equation 2)

PV_NH4: Measured value of ammonia nitrogen concentration meter (mgN / L), ORP: Measured value of ORP meter (mV), a_NH4: Variable (mgN / L), UN_ORP: ORP abnormality diagnosis lower limit (mV), UP_ORP: Upper limit value of ORP abnormality diagnosis (mV), F (a_NH4), G (a_NH4): The upper and lower limits of the diagnosis on the presence or absence of an abnormality related to the measurement of the ORP meter 4 derived from the diagnostic expression of the ammonia nitrogen analyzer abnormality diagnostic function formula (1.2) are based on the function (F (a)_NH4), G (a _NH4)), And the upper and lower limits define a corresponding water quality range that is an appropriate range of the measurement value of the ORP meter 4. When the measured value of the ORP meter 4 deviates from the corresponding water quality range, the abnormality diagnostic unit 50 of the water quality sensor abnormality diagnostic device 7 diagnoses that the measurement of the ammonia nitrogen concentration meter 5 has an abnormality. It has become.
[0038]
The monitoring device 8 is connected to the water quality sensor abnormality diagnosis device 7, and the diagnosis result of the abnormality in the measurement of the ammonia nitrogen concentration meter 5 in the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 is as follows. The data is sent from the water quality sensor abnormality diagnosis device 7 to the monitoring device 8.
[0039]
The monitoring device 8 guides the diagnosis result of the abnormality diagnosis unit 50 sent from the water quality sensor abnormality diagnosis device 7 to a manager of the sewage treatment plant. In addition, when the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 diagnoses that the measurement by the ammonia nitrogen concentration meter 5 has an abnormality, the monitoring device 8 issues an alarm regarding the abnormality. .
[0040]
The final sedimentation basin 13 stores sewage sent from the denitrification / dephosphorization treatment tank 40 and precipitates impurities in the sewage. In addition, the sewage (final sediment water) containing the impurities precipitated in the final sedimentation basin 13 is sent from the final sedimentation basin 13 to a sludge storage tank 20 described later. In addition, the bottom of the final sedimentation basin 13 and the anaerobic tank 10 are connected by a water pipe to which a return pump 15 is attached, and a part of the sewage stored in the final sedimentation basin 13 is returned by the return pump 15. The water is returned to the anaerobic tank 10 via a water pipe.
[0041]
The sewage treatment plant has a sludge storage tank 20. The sludge storage tank 20 is first connected to the sedimentation basin 2 via a water pipe to which an initial settling pump 18 is attached, and is connected to the final sedimentation tank 13 via a water pipe to which a surplus pump 17 is attached. I have. Then, the first settling pump 18 sends the first settling water of the first settling tank 2 to the sludge storage tank 20 via the water pipe, and the surplus pump 17 causes the final settling water of the last settling tank 13 to be set via the water pipe. It is sent to the sludge storage tank 20.
[0042]
The water quality monitoring and control device of the present invention includes an ORP meter 4, an ammoniacal nitrogen concentration meter 5, and an abnormality diagnosis unit 50 of the water quality monitoring and control device.
[0043]
Next, the operation of the sewage treatment plant of the present embodiment will be described.
[0044]
First, the process of purifying sewage in a sewage treatment plant will be outlined.
[0045]
The sewage 1 such as municipal sewage and industrial sewage that needs purification treatment at the sewage treatment plant first flows into the sedimentation basin 2 through the water pipe. The sewage flowing into the first settling tank 2 is stored in the first settling tank 2 for a predetermined time. Thereby, the impurities in the sewage sediment, and the impurities first settle in the lower part of the sedimentation basin 2. Most of the sewage, which is initially stored in the sedimentation basin 2 and from which impurities have been removed by precipitation, is sent to the anaerobic tank 10 constituting the denitrification / dephosphorization treatment tank 40 via a water pipe. The sewage below the first sedimentation basin 2 and containing the precipitated impurities (first sedimentation water) is sent to the sludge storage tank 20 through a water pipe provided below the first sedimentation basin 2. Then, the feed amount is adjusted by the initial settling pump 18.
[0046]
The flow rate of the sewage sent from the first sedimentation tank 2 to the anaerobic tank 10 is measured by the inflow flow meter 30 attached to the water pipe. On the basis of the measured value of the inflow flow meter 30, the administrator or the like determines the sewage sent to the denitrification / dephosphorization treatment tank 40 including the anaerobic tank 10, the anaerobic tank 11, and the aerobic tank 12. Can be grasped.
[0047]
The sewage sent to the anaerobic tank 10 is subjected to anaerobic treatment. That is, the organic acid such as acetic acid in the sewage is converted into phosphoric acid (PO) by the phosphorus accumulating bacteria in the activated sludge in the anaerobic tank 10.₄). Thereby, the phosphorus component is removed from the sewage. At this time, the injection amount of the carbon source from the carbon source storage tank 21 to the anaerobic tank 10 is adjusted by the carbon source injection pump 19 so that the phosphorus component can be efficiently removed from the sewage.
[0048]
The sewage subjected to the anaerobic treatment in the anaerobic tank 10 is sent from the anaerobic tank 10 to the anoxic tank 11. Then, the sewage sent to the anoxic tank 11 is subjected to anoxic treatment. That is, the denitrifying bacteria in the anoxic tank 11 under the anoxic condition utilize the organic matter contained in the sewage stored in the anoxic tank 11 and the circulation pump 14 from the aerobic tank 12 via the water pipe. Nitrite (NO) contained in the sewage returned to the anoxic tank 11₂-N) and nitrate nitrogen (NO₃-N) with nitrogen gas (N₂). Then, the reduced nitrogen gas (N₂) Is discharged outside the system of the sewage treatment plant via an oxygen-free tank discharge unit (not shown).
[0049]
The sewage subjected to the anoxic treatment in the anoxic tank 11 is sent from the anoxic tank 11 to the aerobic tank 12. Then, the sewage sent to the aerobic tank 12 is subjected to aerobic treatment. That is, by the action of nitrifying bacteria in the aerobic tank 12, the ammonia nitrogen (NH₄-N) is nitrite nitrogen (NO₂-N) and nitrate nitrogen (NO₃-N). The oxidized nitrite nitrogen (NO₂-N) and nitrate nitrogen (NO₃Part or all of −N) is sent from the aerobic tank 12 to the anoxic tank 11 together with the sewage by the circulation pump 14. By the action of the nitrifying bacteria in the aerobic tank 12, ammonia nitrogen is removed from the sewage, and the concentration of ammonia nitrogen in the sewage is reduced. Further, the activated sludge in the aerobic tank 12 absorbs and removes the phosphorus component contained in the sewage. The phosphorus component contained in the sewage is precipitated in the form of aluminum phosphate or iron phosphate by the coagulant injected from the coagulant storage tank 22 into the aerobic tank 12. At this time, the injection amount of the coagulant in the coagulant storage tank 22 into the aerobic tank 12 is adjusted by the PAC injection pump 16, and an appropriate amount of the coagulant is injected into the aerobic tank 12. ing.
[0050]
Most of the sewage subjected to the aerobic treatment in the aerobic tank 12 is sent to the final sedimentation basin 13 via the outlet of the aerobic tank 12 and the water pipe. In addition, a part of the sewage in the aerobic tank 12 is anoxic through a water pipe provided in the aerobic tank 12 near the outlet to the final sedimentation basin 13 and below the aerobic tank 12. It is returned to the tank 11. Thereby, the nitrite nitrogen (NO₂-N) and nitrate nitrogen (NO₃-N) is also sent to the anoxic tank 11 together with the sewage. Then, the nitrite nitrogen (NO₂-N) and nitrate nitrogen (NO₃-N) is subjected to an oxygen-free treatment in the oxygen-free tank 11 as described above, and the nitrogen gas (N₂) And the nitrogen gas (N₂) Is discharged out of the system of the sewage treatment plant via an oxygen-free tank 11 discharge unit (not shown). The return amount of sewage from the aerobic tank 12 to the anoxic tank 11 is adjusted by the circulation pump 14, and an appropriate amount of sewage is returned to the anoxic tank 11.
[0051]
The sewage flowing into the final sedimentation basin 13 is stored in the final sedimentation basin 13 for a predetermined time. Thereby, the impurities in the sewage sediment, and the impurities settle in the lower part of the final sedimentation basin 13. Most of the sewage from which impurities are precipitated and removed in the final sedimentation basin 13 is sent as treated water 3 to other facilities installed outside the sewage treatment plant via a water pipe. In addition, the sewage (final sediment water) that is the lower sewage of the final sedimentation basin 13 and contains precipitated impurities is sent to the sludge storage tank 20 via a water pipe, and the amount of the sewage is adjusted by the surplus pump 17. .
[0052]
Next, aerobic processing in the aerobic tank 12 will be described in detail.
[0053]
The ammoniacal nitrogen concentration meter 5 installed in the aerobic tank 12 does not always show an accurate value. That is, due to various factors such as deterioration of the reagent, contamination of the detection unit of the ammonia nitrogen concentration meter 5, adhesion of air bubbles, failure of the ammonia nitrogen concentration meter 5, etc., the ammonia nitrogen concentration meter 5 may be different from the actual value. Different values may be measured.
[0054]
For example, as in the case where the ammonia nitrogen concentration meter 5 indicates a value exceeding the measurement range, or the measurement value of the ammonia nitrogen concentration meter 5 does not move at zero, the measured value of the ammonia nitrogen concentration meter 5 is not changed. Indicates an abnormal value, an abnormality in the measurement of the ammonia nitrogen concentration meter 5 has occurred on the ammonia nitrogen concentration meter 5 side (sensor side) or the aeration air flow controller 23 side (controller side). Can be diagnosed.
[0055]
However, for example, when the actual value of the ammonia nitrogen concentration in the sewage is 2 mg / L and the measurement value of the ammonia nitrogen concentration meter 5 is 5 mg / L, the ammonia nitrogen concentration meter is used. In the case where 5 indicates an actually possible value as a measured value, the measurement of the ammonia nitrogen concentration meter 5 is performed on the ammonia nitrogen concentration meter 5 side (sensor side) or the aeration air volume controller 23 side (controller side). It is difficult to diagnose that an abnormality has occurred. Further, in such a case, when a human system diagnoses the presence or absence of an abnormality related to the measurement of the ammoniacal nitrogen concentration meter 5, there is no choice but to make a diagnosis by manual analysis, which is troublesome and time-consuming. In addition, a physical quantity such as an oxidation-reduction potential (ORP) and an ultraviolet absorbance (UV) is measured more than a water quality sensor such as an ammoniacal nitrogen concentration meter 5 which measures a ppm order using a reagent. It can be said that the sensor has less measurement error and higher measurement accuracy. In view of such circumstances, the following is specifically performed in the aerobic tank 12.
[0056]
That is, the sewage flowing into the aerobic tank 12 measures the quality of each water contained in the sewage by the ORP meter 4, the ammonia nitrogen meter 5, and the dissolved oxygen meter 6, respectively. Of the water qualities thus measured, the measurement value of the ORP meter 4, the measurement value of the ammonia nitrogen concentration meter 5, and the measurement value of the dissolved oxygen concentration meter 6 are transmitted from each water quality sensor to the water quality sensor abnormality diagnosis device 7 Sent to Further, the measured value of the ammonia nitrogen concentration and the measured value of the dissolved oxygen concentration are sent from each water quality sensor to the aeration controller 23.
[0057]
In the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7, the measurement value of the ammonia nitrogen concentration (target water quality) by the sent ammonia nitrogen concentration meter 5 (control water quality sensor) and the ORP meter 4 (for abnormality diagnosis) In consideration of the measurement value of the ORP (correlated water quality) by the water quality sensor) and the correlation between the ammonia nitrogen concentration and the ORP, it is diagnosed whether or not the measurement of the ammonia nitrogen concentration meter 5 has an abnormality. That is, in the abnormality diagnosis unit 50, the upper and lower limit values defining the corresponding water quality range are determined by the function (F (a_NH4), G (a _NH4)). Thereby, for example, a corresponding water quality range as shown in FIG. 2 is obtained. Therefore, for example, when the target value of the sewage ammonia nitrogen concentration is controlled to be 0.5 mg / L, the measurement value of the ORP meter falls within the corresponding water quality range defined by, for example, 100 mv to 150 mv. It will be. When the measured value of the ORP meter 4 deviates from the corresponding water quality range, the abnormality diagnosis unit 50 diagnoses that the measurement of the ammonia nitrogen concentration meter 5 has an abnormality, and If the measured value falls within the corresponding water quality range, it is diagnosed that there is no abnormality in the measurement of the ammonia nitrogen concentration meter 5.
[0058]
The above diagnosis result in the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 is sent to the monitoring device 8, and the monitoring device 8 provides guidance to a sewage treatment plant manager or the like. When the abnormality diagnosis unit 50 diagnoses that the measurement of the ammonia nitrogen concentration has an abnormality, the monitoring device 8 sounds an alarm and notifies the administrator or the like of the abnormality.
[0059]
On the other hand, the aeration air volume controller 23 controls the aeration air volume supplied from the aeration device 9 into the aerobic tank 12 based on the measurement value of the ammonia nitrogen concentration meter 5 and the measurement value of the dissolved oxygen concentration meter 6. That is, the target value of the amount of aeration air supplied from the aeration device 9 to the aerobic tank 12 is adjusted so that the measurement value of the ammonia nitrogen concentration meter 5 approaches the target value of the set ammonia nitrogen concentration. 23. Specifically, the aeration air volume controller 23 calculates the target value of the aeration air volume supplied from the aeration device 9 to the aerobic tank 12 using the aeration air volume calculation formula of the above equation (1.2). . When the measured value of the ammonia nitrogen concentration sent from the ammonia nitrogen concentration meter 5 is larger than the set ammonia nitrogen concentration target value, the aeration device 9 It is controlled by the aeration air volume controller 23 so that the supplied aeration air volume increases. On the other hand, when the measured value of the ammonia nitrogen concentration sent from the ammonia nitrogen concentration meter 5 is smaller than the set target value of the ammonia nitrogen concentration, the aeration air volume supplied to the aerobic tank 12 The aeration device 9 is controlled by the aeration air volume controller 23 so as to reduce the aeration. By controlling the aeration device 9 in this way, the aeration air volume controller 23 can always supply aeration to the aerobic tank 12 without excess or deficiency. This prevents the nitrification reaction from proceeding due to lack of oxygen in the aerobic tank 12 or the nitrification reaction from excessively proceeding due to over-aeration, so that the ammonia nitrogen concentration in the sewage can be adjusted appropriately. It can be adjusted to a value.
[0060]
As described above, according to the present embodiment, the abnormality diagnosing unit 50 of the water quality sensor abnormality diagnosing device 7 determines whether or not an abnormality has occurred in the measurement of the ammonia nitrogen concentration meter 5 by checking the ammonia nitrogen concentration meter 5. Based on the measured value, the measured value of the ORP meter 4, and the correlation between the ammonia nitrogen concentration and the ORP, the presence / absence of the abnormality can be quickly diagnosed. Thereby, it is possible to accurately and promptly diagnose the presence or absence of an abnormality related to the measurement of the ammonia nitrogen concentration meter 5.
[0061]
If an abnormality has occurred in the measurement of the ammonia nitrogen concentration by the ammonia nitrogen concentration meter 5, the operator can be promptly notified of the occurrence of the abnormality via the monitoring device 8. Thereby, it is possible to prevent a delay in diagnosis or an error in diagnosis for the operator, and to promptly avoid a control abnormality caused by a water quality sensor abnormality. Further, it is possible to shorten the time during which the adjustment of the ammonia nitrogen concentration is not appropriate, such as overaeration or insufficient aeration by the aeration device 9, and it is possible to effectively prevent deterioration of the quality of the treated sewage.
[0062]
Further, there is an abnormality in the measurement of the ammonia nitrogen concentration meter 5 based on whether or not the measurement value by the ORP meter 4 which is a stable water quality sensor is out of the corresponding water quality range calculated by the corresponding water quality range calculation unit 51. Since the determination is made as to whether or not it is possible, an algorithm relating to compensation for measurement by the ammonia nitrogen concentration meter 5 can be relatively simply assembled. Further, such an algorithm can be relatively easily incorporated into the aeration air volume controller 23.
[0063]
Further, the ammonia nitrogen concentration meter 5 and the ORP meter 4 are installed in the same aerobic tank 12, and the sewage whose water quality is measured by these water quality sensors 5, 4 is in the same biological reaction tank. It is sewage. Further, a target water quality (ammonia nitrogen concentration) to be measured by the ammonia nitrogen concentration meter 5, which is a control water quality sensor, and a correlated water quality (ORP), which is a measurement target by the ORP meter 4, which is an abnormality diagnosis water quality sensor. , Is different. For this reason, the water quality sensor abnormality diagnosis device 7 is capable of diagnosing the presence or absence of an abnormality related to the measurement of the ammonia nitrogen concentration meter 5 with high accuracy and reliability.
[0064]
The type of guidance and / or alarm by the monitoring device 8 is not particularly limited, and includes, for example, a method of displaying characters, a method involving sound, and a method of providing a water quality sensor abnormality to a sewage treatment plant manager or the like. It may include a general method capable of notifying a diagnosis result in the abnormality diagnosis unit 50 of the diagnosis device 7.
[0065]
Next, a modified example of the present embodiment will be described.
[0066]
The ammonia nitrogen concentration meter 5, the ORP meter 4, and the dissolved oxygen concentration meter 6 may be installed at a stage subsequent to the aerobic tank 12, respectively. For example, the first ammoniacal nitrogen concentration meter 5a, the second ammoniacal nitrogen concentration meter 5b, and the ORP meter 4 are respectively a final sedimentation basin 13, a water pipe connecting the aerobic tank 12 and the final sedimentation basin 13, and a final sedimentation basin 13. It may be installed in a water pipe or the like for discharging sewage from the sedimentation basin 13 and measure the quality of each sewage at the installation location.
[0067]
Further, the ORP meter 4 may be installed in a biological reaction tank provided downstream of the biological reaction tank in which the ammoniacal nitrogen concentration meter 5 is installed. In such a case, if there is a predetermined correlation between the measurement value of the ammonia nitrogen concentration meter 5 (ammonia nitrogen concentration) and the measurement value (ORP) of the ORP meter 4, the correlation is determined. By using the information, it can be diagnosed whether or not the measurement by the ammonia nitrogen concentration meter 5 has an abnormality.
[0068]
In addition, between the ammonia nitrogen concentration meter 5 and the ORP meter 4 and the water quality sensor abnormality diagnosis device 7, and between the ammonia nitrogen concentration meter 5 and the ORP meter 4 and the aeration air volume controller 23, the ammonia nitrogen concentration A filtering processing device (filtering processing unit) that performs a filtering process on the measurement value of the ammonia nitrogen concentration by the total 5 and the measurement value of the ORP by the ORP total 4 may be installed. The filtering processing device can perform a filtering process on the measurement values of the ammonia nitrogen concentration meter 5 and the ORP meter 4 by an arithmetic expression such as the following Expression (1.3) and Expression (1.4). it can.
[0069]
(Equation 3)

PV (t): sensor measurement value at time t, FT: filter coefficient (0 to 1), n: integer
The measurement value subjected to the filtering processing in the filtering processing device can be subsequently used in the water quality sensor abnormality diagnosis device 7 or the aeration air volume controller 23. The measurement value of the ammonia nitrogen concentration meter 5 and the measurement value of the ORP meter 4 considered in the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 are calculated based on the ammonia nitrogen concentration which has been subjected to the filtering process by the filtering device. The measured value of the total 5 and the measured value of the ORP total 4 can be used. By performing a filtering process on the measurement value of each water quality sensor, instability (noise) such as a measurement error related to the measurement value can be reduced. Therefore, the water quality sensor abnormality diagnosis device 7 or the aeration air volume controller 23 can control the aeration device 9 relatively stably by using the measured value subjected to the filtering process.
[0070]
The method of diagnosing whether or not there is an abnormality in the measurement of the ammonia nitrogen concentration meter 5 by the water quality sensor abnormality diagnosing device 7 is based on whether or not the measured value of the ORP meter 4 deviates from the corresponding water quality range. It is not limited to. For example, the corresponding water quality range obtained by the corresponding water quality range calculation unit 51 is a range relating to the time variation of the measurement value of the ORP (correlated water quality) by the ORP meter 4 (water quality sensor for abnormality diagnosis). The data based on the measured value of the ORP by the ORP meter 4 that is compared with the corresponding water quality range calculated by the corresponding water quality range calculation unit 51 can be a time change amount of the measured value of the ORP by the ORP meter 4. Then, the corresponding water quality range collating unit 52 determines whether the time variation of the measurement value of the ORP meter 4 is out of the corresponding water quality range obtained by the corresponding water quality range calculation unit 51 or not. It can be diagnosed whether or not there is an abnormality in the measurement of. In this case, for example, a function G (a_o2) And the function F (a_o2) Can be calculated by the corresponding water quality range calculation unit 51. Then, based on whether or not the time change of the measurement value of the ammonia nitrogen concentration meter 5 is out of the corresponding water quality range for a predetermined time, whether or not the measurement of the ammonia nitrogen concentration meter 5 has an abnormality. Can be diagnosed. This utilizes the characteristic that the ORP does not show a rapid time change if the measured value of the ammonia nitrogen concentration meter 5 is actually controlled so as to approach the target value of the ammonia nitrogen concentration. It is.
[0071]
In addition, the dissolved oxygen concentration meter 6 is used as the control water quality sensor of the present invention, and the ORP meter 4 is used as the abnormality diagnosis water quality sensor of the present invention. Diagnosis may be based on the measurement value of the above. For example, the water quality sensor abnormality diagnostic device 7 can diagnose whether or not there is an abnormality in the measurement of the dissolved oxygen concentration meter 6 based on a diagnostic expression represented by the following expression (1.5).
[0072]
(Equation 4)

PV_O2: Measured value of dissolved oxygen concentration meter (mgN / L), ORP: Measured value of ORP meter (mV), a_O2: Variable (mgN / L), UN_ORP: ORP abnormality diagnosis lower limit (mV), UP_ORP: Upper limit value of ORP abnormality diagnosis (mV)
In this case, the water quality sensor abnormality diagnosis device 7 (the abnormality diagnosis unit 50) can use the measurement value of the ORP meter 4 that has been subjected to the filtering processing based on the above equations (1.3) and (1.4). . In this case, the diagnostic expression used in the abnormality diagnostic unit 50 of the water quality sensor abnormality diagnostic device 7 is not limited to the above expression (1.5). However, whether or not there is an abnormality in the measurement of the dissolved oxygen concentration meter 6 may be diagnosed based on whether or not the state exceeding the predetermined threshold has continued for a predetermined time.
[0073]
Further, the aeration air volume controller 23 is not limited to the one that controls the aeration apparatus 9 based on the measurement value of the ammonia nitrogen concentration meter 5. For example, the aeration air volume controller 23 can also control the aeration device 9 based only on the measurement value of the dissolved oxygen concentration meter 6, and can control the aeration air volume to be constant, or control the aeration tank 12. The aeration device 9 can also be controlled by a control method that makes the ratio of the aeration air volume to the inflow flow rate of the sewage constant. Further, it is also possible to connect the aeration air volume controller 30 to the abnormality diagnosing unit 50 and appropriately change the control mode of the aeration device 9 in the aeration air volume controller 30 based on the diagnosis result in the abnormality diagnosis unit 50.
[0074]
Second embodiment
Drawing 4 is a figure showing a 2nd embodiment of the present invention, and is a figure showing the schematic structure of a sewage treatment plant (sewage treatment system).
[0075]
As shown in FIG. 4, the water quality sensor installed in the aerobic tank 12 in the sewage treatment plant according to the present embodiment includes an ORP meter 4, a first ammonia nitrogen meter 5a, and a second ammonia nitrogen meter. 5b in total. A first ammonia nitrogen concentration meter 5a, a second ammonia nitrogen concentration meter 5b, and an ORP meter 4 are connected to the water quality sensor abnormality diagnosis device 7, and the first ammonia nitrogen concentration is A total 5a and a second ammoniacal nitrogen concentration meter 5b are connected. In the present embodiment, as described later, one of the first ammoniacal nitrogen concentration meter 5a and the second ammoniacal nitrogen concentration meter 5b functions as the control water quality sensor of the present invention, and the other one of the present invention. Function as an abnormality diagnosis water quality sensor. The ORP meter 4 functions as a water quality sensor for abnormality diagnosis of the present invention.
[0076]
The sewage treatment plant further includes a water quality database 24 (water quality data storage unit). The water quality database 24 includes a first ammonia nitrogen concentration meter 5a, a second ammonia nitrogen concentration meter 5b, and an ORP meter 4. It is connected to the water quality sensor configured and included, the inflow flow meter 30, and the water quality sensor abnormality diagnosis device 7.
[0077]
The water quality database 24 stores past correlation data relating to the correlation between the target water quality of the present invention and the correlated water quality. In the present embodiment, as shown in Table 1 below, the measured value of the ORP meter 4 (ORP (mV)) and the measured value of the first ammoniacal nitrogen concentration meter 5a ( NH₄(1) (mg / L)) and the measured value (NH) of the second ammoniacal nitrogen concentration meter 5b.₄(2) (mg / L)) and the measurement value (flow rate (m³/ Min) are stored in association with each other.
[0078]
[Table 1]

Correlation data as shown in Table 1 stored in the water quality database 24 is sent from the ORP meter 4, the first ammonia nitrogen meter 5a, the second ammonia nitrogen meter 5b, and the inflow meter 30. It is based on each coming measurement. The inflow flow meter 30 functions as an inflow flow meter and an inflow flow meter of the present invention. Therefore, the measured value of the inflow flow meter 30 stored in the water quality database 24 is the biological reaction tank (aerobic tank) in which the target water quality (ammonia nitrogen concentration) is measured by the control water quality sensor (ammonia nitrogen concentration meter 5). 12) A biological reaction tank in which the amount of new sewage flowing into the sewage and the correlated water quality (ammonia nitrogen concentration, ORP) of the sewage are measured by the abnormality diagnosis water quality sensors (ammonia nitrogen concentration meter 5, ORP meter 4) This means past data relating to both the amount of new sewage flowing into the (aerobic tank 12).
[0079]
The water quality sensor abnormality diagnostic device 7 further has a correlation deriving unit 53. The correlation deriving unit 53 derives a correlation between the target water quality (ammonia nitrogen concentration) and the correlation water quality (ammonia nitrogen concentration, ORP) based on the past correlation data stored in the water quality database 24. Has become.
[0080]
Other configurations are substantially the same as those of the first embodiment. In the second embodiment shown in FIG. 4, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.
[0081]
The sewage 1 supplied to the sewage treatment plant first flows into the aerobic tank 12 after passing through the sedimentation basin 2, the anaerobic tank 10, and the anoxic tank 11.
[0082]
The sewage flowing into the aerobic tank 12 has the ammonia nitrogen concentration measured by the first ammonia nitrogen concentration meter 5a and the second ammonia nitrogen concentration meter 5b, and the ORP is measured by the ORP meter 4. The measurement values of each water quality sensor of the first ammonia nitrogen concentration meter 5a, the second ammonia nitrogen concentration meter 5b, and the ORP meter 4 are sent to the water quality sensor abnormality diagnosis device 7, respectively. The measurement values of the first ammonia nitrogen concentration meter 5a and the second ammonia nitrogen concentration meter 5b are sent to the aeration air volume controller 23, respectively.
[0083]
The abnormality diagnosing unit 50 of the water quality sensor abnormality diagnosing device 7 measures the ammonia nitrogen concentration measured by the first ammonia nitrogen concentration meter 5a and the ammonia nitrogen concentration measured by the second ammonia nitrogen concentration meter 5b. In consideration of the value and the measurement value of the oxidation-reduction potential by the ORP meter 4, whether or not there is an abnormality in the measurement of the first ammoniacal nitrogen concentration meter 5a and / or the second ammoniacal nitrogen concentration meter 5b Diagnose. That is, when both the first ammoniacal nitrogen concentration meter 5a and the second ammoniacal nitrogen concentration meter 5b installed in the aerobic tank 12 are normal, the respective measured values show substantially the same value. However, when an abnormality occurs in one or both of the measurements, each measured value indicates a different value. However, it is difficult to diagnose which ammonia nitrogen concentration meter or both ammonia nitrogen concentration meters have an abnormality in measurement using only these two ammonia nitrogen concentration meters 5a and 5b. For this reason, the water quality sensor abnormality diagnosis device 7 diagnoses the presence or absence of the abnormality using the measured value of the ORP meter 4 and the past correlation data (see Table 1) stored in the water quality database 24.
[0084]
That is, the correlation deriving unit 53 of the water quality sensor abnormality diagnosis device 7 calculates the average value of the first ammonia nitrogen concentration and the second ammonia nitrogen concentration and the inflow flow rate from the past correlation data stored in the water quality database 24. The correlation between the measurement value of the total 30 and the ORP is derived. At this time, the correlation deriving unit 53 calculates the regression coefficients A, B, and C by the least square method based on the correlation given in the form of the following equation (2.1), for example.
[0085]
R_{NH4 average}= A × ORP + B × Q + C Equation (2.1)
ORP: ORP meter measurement value, Q: flow rate, A, B, C: regression coefficient
The regression coefficients A, B, and C do not have a difference of 1 mg / L (predetermined threshold) or more between the measurement value of the first ammoniacal nitrogen concentration meter 5a and the measurement value of the second ammoniacal nitrogen concentration meter 5b. The calculation is performed based on the data at the date and time, and is updated at a certain cycle (for example, a cycle of about one hour or one day which is slower than the sampling cycle of the measurement value). In the present embodiment, the corresponding water quality range of the present invention is determined based on the above-described predetermined threshold.
[0086]
Conversely, based on the ORP and the measurement value of the inflow flow meter 30 at the date and time of the data used when calculating the regression coefficients A, B, and C, the following equation (2.2) is used. Value P of ammonia nitrogen concentration given in the form_NH4(T) is calculated.
[0087]
P_NH4(T) = A × ORP (t) + B × Q (t) + C Equation (2.2)
P_NH4(T): Predicted ammonia nitrogen concentration at time t, ORP (t): ORP meter measured value at time t, Q (t): flow rate at time t, A, B, C: regression coefficients (formula (2. Coefficient similar to 2))
Since the inflow flow meter 30 and the ORP meter 4 are sensors that measure a physical quantity without using a reagent, it can be said that the stability regarding the measurement accuracy is higher than that of the ammoniacal nitrogen concentration meter 5.
[0088]
Therefore, this predicted value P_NH4(T) is the average value P of the measured values of the first ammoniacal nitrogen concentration meter 5a and the second ammoniacal nitrogen concentration meter 5b at the corresponding date and time._{NH4 average}If (t) is different from the predetermined size by more than a predetermined size, the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 performs both the first ammonia nitrogen concentration meter 5a and the second ammonia nitrogen concentration meter 5b or It is diagnosed that one of the measurements has an abnormality. On the other hand, the predicted value P_NH4(T) is an average value P of the first ammonia nitrogen concentration and the second ammonia nitrogen concentration at that time._{NH4 average}In the case of being substantially the same as (t), the water quality sensor abnormality diagnosis device 7 diagnoses that there is no abnormality in the measurement of both the first ammonia nitrogen concentration meter 5a and the second ammonia nitrogen concentration meter 5b. .
[0089]
At a certain date and time, the measured value P of the first ammoniacal nitrogen_{NH4 (1)}(T) and the measured value P of the second ammoniacal nitrogen concentration meter 5b_{NH4 (2)}When a deviation equal to or greater than a predetermined threshold value occurs between the measured value and the measured value ORP (t) of the ORP meter 4 and the measured value Q (t) of the inflow flow meter 30 at that date and time, a formula is obtained. According to (2.3), the predicted value P of the ammonia nitrogen concentration is calculated._NH4(T) is calculated. Then, the calculated predicted value P of the ammonia nitrogen concentration is calculated._NH4(T) and the measured value P of the first ammoniacal nitrogen concentration meter 5a_{NH4 (1)}(T) and the measured value P of the second ammoniacal nitrogen concentration meter 5b_{NH4 (2)}And (t). And at least the predicted value P of the ammonia nitrogen concentration._NH4With respect to the ammonia nitrogen concentration meter 5 indicating the measurement value having a large absolute value of the difference with respect to (t), it can be diagnosed that an abnormality has occurred in the measurement of the ammonia nitrogen concentration. When this algorithm is expressed in a mathematical expression, the following expression (2.3) is obtained.
[0090]
(Equation 5)

P_NH4(T): Predicted ammonia nitrogen concentration, PV_{NH4 average}(T): average value of the measurement value of the first ammoniacal nitrogen concentration meter and the measurement value of the second ammoniacal nitrogen concentration meter, UL: upper limit of diagnosis (measured value-calculated value) of ammoniacal nitrogen concentration meter, PV_{NH4 (1)}(T): measured value of the first ammoniacal nitrogen concentration meter, PV_{NH4 (2)}(T): measured value of the second ammoniacal nitrogen concentration meter, UL_PV: Upper limit of deviation between the measurement value of the first ammoniacal nitrogen concentration meter and the measurement value of the second ammoniacal nitrogen concentration meter
Then, the above-mentioned diagnosis result in the water quality sensor abnormality diagnosis device 7 is sent to the monitoring device 8.
[0091]
On the other hand, the aeration air volume controller 23 controls the aeration air volume supplied from the aeration device 9 into the aerobic tank 12 based on the measurement value of the first ammonia nitrogen concentration meter 5a and the measurement value of the second ammonia nitrogen concentration meter 5b. Control. That is, the aeration air volume controller 23 sets the average value of the measurement values of the sent first ammoniacal nitrogen concentration meter 5a and the second ammoniacal nitrogen concentration meter 5b to the preset target value of the ammoniacal nitrogen concentration. A target value of the amount of aeration air supplied to the aerobic tank 12 from the aeration device 9 is calculated so as to approach. For example, the aeration air volume controller 23 calculates a target value of the aeration air volume supplied from the aeration device 9 to the aerobic tank 12 using the aeration air volume calculation formula of the following equation (2.4).
[0092]
(Equation 6)

Qair (t): a target air flow rate at time t (m³/ Min), Qair₀: Aeration air volume initial value (m³/ Min), Kp: proportional gain (m⁶/ G · min), T_I: Integration constant (min), Δt: control cycle (min), e (t): deviation (mg / L), SV_NH4(T): target value of ammonia nitrogen concentration (mg / L), PV_{NH4 (1)}(T): measured value (mg / L) of the first ammoniacal nitrogen concentration meter, PV_{NH4 (2)}  (T): Measurement value of the second ammoniacal nitrogen concentration meter (mg / L)
The aeration air volume controller 23 controls the aeration device 9 so that the aeration air volume supplied to the aerobic tank 12 is equal to the calculated target value of the aeration air volume. Thus, the aeration apparatus 9 controlled by the aeration air volume controller 23 can always supply aeration to the aerobic tank 12 without excess or shortage, and an appropriate aeration air volume is secured in the aeration tank 12. .
[0093]
As described above, according to the present embodiment, using the past data (correlation data) stored in the water quality database 24, the first ammonia nitrogen concentration meter 5a and the second ammonia nitrogen concentration meter 5b are used. Since the presence or absence of the measurement abnormality is diagnosed, it is not necessary to carry out an experiment or the like in advance to grasp the relationship between the ammonia nitrogen concentration and the oxidation-reduction potential (ORP).
[0094]
The parameters are also set in UL (allowable upper limit value for diagnosing whether or not there is an abnormality in at least one of the ammonia nitrogen concentration meters) and UL._PV(The allowable upper limit value of the deviation between the first ammoniacal nitrogen concentration meter 5a and the second ammoniacal nitrogen concentration meter 5b), and the adjustment of the control parameters in the plant becomes easy.
[0095]
In addition, the ammonia nitrogen concentration measured by the first ammonia nitrogen concentration meter 5a and the second ammonia nitrogen concentration meter 5b is used as the target water quality and the correlated water quality, and the target water quality and the correlated water quality are the same. Therefore, it is possible to diagnose whether an abnormality has occurred in the measurement of the first ammoniacal nitrogen concentration meter 5a or the second ammoniacal nitrogen concentration meter 5b based on a difference between the two measured values, so that the abnormality can be promptly determined. The occurrence of an abnormality can be detected.
[0096]
Further, the aeration air volume controller 23 performs the aeration based on the measurement values of the two ammonia nitrogen concentration meters (the first ammonia nitrogen concentration meter 5a and the second ammonia nitrogen concentration meter 5b) installed in the same aerobic tank 12. Since the control of the apparatus 9 is performed, even if an abnormality occurs in the measurement of one of the ammonia nitrogen concentration meters 5a and 5b, the aeration is performed based on the measurement value of the other ammonia nitrogen concentration meter 5a and 5b. It is possible to control the device 9. Therefore, even if an abnormality occurs in the measurement of one of the ammonia nitrogen concentration meters 5a and 5b, an optimal aeration air volume can be secured, and the purified sewage can be stably provided with good quality. Water quality will be maintained.
[0097]
The predicted value of the ammonia nitrogen concentration used in the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 is predicted based not only on the measurement value of the ORP meter 4 but also on the measurement value of the inflow flow meter 30. Accordingly, the abnormality diagnosis unit 50 further considers the inflow flowmeter 30 of the present invention and the measurement value of the inflow flowmeter 30 functioning as the inflow flowmeter 30, and has an abnormality in the measurement of the target water quality by the control water quality sensor. Can be diagnosed, and it is possible to accurately diagnose whether or not the abnormality is present in accordance with the fluctuation of the measurement value of the inflow flow meter 30.
[0098]
Next, a modified example of the present embodiment will be described.
[0099]
The first ammoniacal nitrogen concentration meter 5a, the second ammoniacal nitrogen concentration meter 5b, and the ORP meter 4 may each be installed at a later stage than the aerobic tank 12. For example, the first ammoniacal nitrogen concentration meter 5a, the second ammoniacal nitrogen concentration meter 5b, and the ORP meter 4 are respectively a final sedimentation basin 13, a water pipe connecting the aerobic tank 12 and the final sedimentation basin 13, and a final sedimentation basin 13. It may be installed in a water pipe or the like for discharging sewage from the sedimentation basin 13, and may measure the quality of each sewage water at the installation location. Even in such a case, each water quality measured by each water quality sensor may have a predetermined correlation.
[0100]
Further, between the first ammoniacal nitrogen concentration meter 5a, the second ammoniacal nitrogen concentration meter 5b, and the ORP meter 4 and the water quality sensor abnormality diagnostic device 7, the first ammoniacal nitrogen concentration meter 5a, the second ammoniacal nitrogen concentration 5b, between the ORP meter 4 and the aeration air volume controller 23, between the first ammonia nitrogen concentration meter 5a, the second ammonia nitrogen concentration meter 5b, and between the ORP meter 4 and the water quality database 24, A filtering device for filtering the measurement values of the water quality sensors of the first ammonia nitrogen concentration meter 5a, the second ammonia nitrogen concentration meter 5b, and the ORP meter 4 may be provided. The filtering processing device calculates the first ammoniacal nitrogen concentration meter 5a, the second ammoniacal nitrogen concentration meter 5b, and the ORP meter 4 by using an arithmetic expression such as the above expression (1.3) and expression (1.4). Can be subjected to a filtering process. Then, the measurement values of the water quality sensors subjected to the filtering processing by the filtering processing device can be subsequently used in the water quality sensor abnormality diagnosis device 7, the aeration air volume controller 23, or the water quality database 24.
[0101]
Further, when predicting the ammonia nitrogen concentration (target water quality), the water quality sensor abnormality diagnosis device 7 considers not only the data regarding the measurement values of the inflow flow meter 30 and the ORP meter 4 but also data regarding other water qualities. Is also good. For example, the measured value data of the sewage before flowing into the anaerobic tank 10 of FIG. 4 (for example, the sewage in the first sedimentation basin 2 or the water pipe before and after the same) by the TN meter (total nitrogen meter), the aerobic tank Past data such as DO meter data on DO (dissolved oxygen concentration) of sewage stored in the aerobic tank 12 and MLSS meter data on MLSS of sewage stored in the aerobic tank 12 are stored in the water quality database 24. Consider the case. In this case, the water quality sensor abnormality diagnosis device 7 considers these water quality data stored in the water quality database 24 and performs a regression coefficient by a multiple regression analysis based on an arithmetic expression such as the following expression (2.7). (A, B, C,..., Z) may be determined, and the determined regression coefficient may be used in the prediction calculation of the ammonia nitrogen concentration (target water quality).
[0102]
R_{NH4 average}= A × ORP + B × Q + C × T−N + D × DO + E × MLSS +... + Z Equation (2.7)
R_{NH4 average}: Average value of the first ammonia nitrogen concentration meter 5a and second ammonia nitrogen concentration meter 5b calculated from the correlation, ORP: ORP meter measurement value (mV), Q: flow rate (m³/ Min), TN: inflow water TN concentration (mg / L), DO: dissolved oxygen concentration in aerobic tank 12 (mg / L), MLSS: aerobic tank 12 MLSS (mg / L), A, B , C ... Z: regression coefficient
The method of diagnosing whether or not the measurement of the ammonia nitrogen concentration meter 5 (control water quality sensor) has an abnormality in the abnormality diagnosing unit 50 of the water quality sensor abnormality diagnosing device 7 is represented by the above equation (2.4). The method is not limited to the above method, and other methods can be used. For example, by performing a correlation analysis on the data stored in the water quality database 24, only data having a high correlation with the measured value of the ammoniacal nitrogen concentration in the aerobic tank 12 is extracted, and only data that is diagnosed as having a high correlation is used. A diagnosis may be made as to whether or not there is an abnormality in the measurement of the ammonia nitrogen concentration meter. In addition, the abnormality diagnosis unit 50_{NH4 (1)}(Measured value of primary ammonia nitrogen concentration meter), PV_{NH4 (2)}(Measured value of the second ammoniacal nitrogen concentration meter), P_NH4Based on the principal component analysis using the time series data of the (predicted value of the ammonia nitrogen concentration), it may be diagnosed whether or not there is an abnormality in the measurement of the ammonia nitrogen concentration meter 5 (control water quality sensor). . That is, when the measurement by the ammoniacal nitrogen concentration meter 5 (control water quality sensor) is normal, PV_{NH4 (1)}, PV_{NH4 (2)}, P_NH4Show almost the same tendency. Therefore, PV_{NH4 (1)}, PV_{NH4 (2)}, P_NH4When the principal component analysis is performed using the time series data, almost all information should be included in the first principal component. For example, the first to third components (X) when a principal component analysis represented by the following equations (2.8), (2.9), and (2.10) are performed.₁, X₂, X₃) Is the eigenvalue (information amount)₁, Λ₂, Λ₃And
[0103]
X₁= A₁₁PV_{NH4 (1)}+ A₂₁PV_{NH4 (2)}+ A₃₁R_NH4          Equation (2.8)
X₂= A₁₂PV_{NH4 (1)}+ A₂₂PV_{NH4 (2)}+ A₃₂R_NH4          Equation (2.9)
X₃= A_ThirteenPV_{NH4 (1)}+ A₂₃PV_{NH4 (2)}+ A₃₃R_NH4          Formula (2.10)
X₁: First principal component, X₂: Second principal component, X₃: Third main component, PV_{NH4 (1)}: Measured value of the first ammoniacal nitrogen concentration meter 5a, PV_{NH4 (2)}  : Measured value of second ammoniacal nitrogen concentration meter 5b, R_NH4: Predicted value by multiple regression equation, a_ij:constant
At this time, if the measurement by the ammoniacal nitrogen concentration meter 5 is normal, the contribution of the first main component represented by the following equation (2.11) should be high.
[0104]
(Equation 7)

Then, when an abnormality occurs in any of the first ammoniacal nitrogen concentration meter 5a and the second ammoniacal nitrogen concentration meter 5b, the main components subsequent to the second main component have information, and the first main component has information. The contribution of the components will be reduced. Therefore, it is also possible to diagnose whether or not an abnormality has occurred in the measurement of the ammonia nitrogen concentration meter 5 based on the decrease in the set contribution rate of the first main component.
[0105]
Further, the correlation formulas of the above formulas (2.3) and (2.7) are not limited to the linear type as described above, and other appropriate correlation formulas can be used if necessary. It is. For example, a power type, an exponential function type, a logarithmic type, or a combination thereof may be used.
[0106]
Further, two ammonia nitrogen concentration meters 5 need not be provided in the aerobic tank 12 as shown in FIG. 4, and only one may be provided. The number of ammonia nitrogen concentration meters 5 installed in the aerobic tank 12 is not limited to two, and three or more ammonia nitrogen concentration meters 5 may be installed in the aerobic tank 12.
[0107]
Further, the water quality sensor abnormality diagnosis device 7 performs the ORP meter 4 and the inflow flow meter 30 stored in the water quality database 24 when diagnosing which ammonia nitrogen concentration meter 5 has an abnormality. Both data may be used, or only one of the data may be used.
[0108]
Further, the predetermined target water quality is not limited to the ammonia nitrogen concentration. Further, the control water quality sensor is not limited to the ammonia nitrogen concentration meter. For example, a phosphoric acid phosphorus concentration meter, a dissolved oxygen concentration meter, an MLSS meter, a nitrate nitrogen concentration meter, etc., are used as control water qualities with phosphate phosphorus, dissolved oxygen concentration, MLSS, nitrate nitrogen concentration, etc. as predetermined target water qualities. It can also be a sensor.
[0109]
Third embodiment
FIG. 5 is a diagram illustrating the third embodiment of the present invention, and is a diagram illustrating a schematic configuration of a sewage treatment plant (sewage treatment system).
[0110]
In the sewage treatment plant according to the present embodiment, instead of installing the ORP meter 4, the first ammoniacal nitrogen concentration meter 5a, and the second ammoniacal nitrogen concentration meter 5b in the aerobic tank 12, the ORP meter 4 among the water quality sensors is used. And a nitrate nitrogen concentration meter 31 are installed in the anoxic tank 11 (see FIG. 5). The ORP meter 4 and the nitrate nitrogen concentration meter 31 are connected to the water quality sensor abnormality diagnosis device 7, the water quality database 24, and a carbon source injection controller 25 described later, respectively. Then, the measurement value of the ORP meter 4 and the measurement value of the nitrate nitrogen concentration meter 31 are sent to the water quality sensor abnormality diagnosis device 7, the water quality database 24, and the carbon source injection controller 25.
[0111]
The aerobic tank 12 is provided with an ammonia nitrogen concentration meter 5. The ammonia nitrogen concentration meter 5 is connected to an aeration air volume controller 23. The aeration air volume controller 23 controls the aeration device 9 based on an arithmetic expression represented by the following expression (3.1) using the measurement value of the ammonia nitrogen concentration meter 5.
[0112]
(Equation 8)

Qair (t): a target air flow rate at time t (m³/ Min), Qair₀: Aeration air volume initial value (m³/ Min), Kp: proportional gain (m⁶/ G · min), T_I: Integration constant (min), Δt: control cycle (min), e (t): deviation (mg / L), SV_NH4(T): target value of ammonia nitrogen concentration (mg / L), PV_NH4  (T): Measurement value of ammonia nitrogen concentration meter (mg / L)
In this embodiment, when the ORP meter 4 is used as the control water quality sensor of the present invention, the nitrate nitrogen concentration meter 31 functions as the abnormality diagnosis water quality sensor of the present invention, and the nitrate nitrogen concentration meter 31 is used. Is the control water quality sensor of the present invention, the ORP meter 4 functions as the abnormality diagnosis water quality sensor of the present invention. Therefore, in the present embodiment, the sewage for which the control water quality sensor measures the target water quality and the sewage for which the abnormality diagnosis water quality sensor measures the correlated water quality are sewage in the same biological reaction tank.
[0113]
The water quality database 24 stores past correlation data related to the correlation between the ORP and the nitrate nitrogen concentration. In the present embodiment, the data of the measurement value (ORP (mV)) of the ORP meter 4 and the measurement value (NH₄And (1) (mg / L)) are stored in the water quality database 24 in association with each other. The data of the measured value of the ORP meter 4 stored in the water quality database 24 and the measured value of the nitrate nitrogen concentration meter 31 (NH₄The data of (1) (mg / L) is based on measurement values sent from the ORP meter 4 and the nitrate nitrogen concentration meter 31 to the water quality database 24.
[0114]
The water quality sensor abnormality diagnosis device 7 has an abnormality diagnosis unit 50, and the abnormality diagnosis unit 50 uses the ORP meter 4 and the ORP meter 4 based on each measurement value sent from the ORP meter 4 and the nitrate nitrogen concentration meter 31. And / or to determine whether there is an abnormality in the measurement of the nitrate nitrogen concentration meter 31.
[0115]
On the other hand, a carbon source injection controller 25 is connected to the carbon source injection pump 19. The carbon source injection controller 25 controls the carbon source injection pump 19 based on each measurement value sent from the ORP meter 4 and the nitrate nitrogen concentration meter 31, and is injected from the carbon source storage tank 21 into the anaerobic tank 10. The injection amount of the carbon source can be adjusted. Further, the carbon source injection controller 25 is connected to the water quality sensor abnormality diagnosis device 7, and the diagnosis result of the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 is sent to the carbon source injection controller 25. In addition, the water quality adjustment device of the present invention is configured to include the carbon source storage tank 21 and the carbon source injection pump 19, and the water quality adjustment control device of the present invention is configured to include the carbon source injection controller 25. .
[0116]
A bypass water pipe 61 branches off in the middle of a water pipe that supplies sewage to the first settling tank 2, and the bypass water pipe 61 is connected to the anaerobic tank 10. An initial settling bypass valve 62 is attached to the bypass water pipe 61, and the flow rate of sewage flowing through the bypass water pipe 61 can be adjusted by adjusting the opening and closing of the initial settling bypass valve 62. ing.
[0117]
Other configurations are substantially the same as those of the second embodiment. In the third embodiment shown in FIG. 5, the same parts as those in the second embodiment are denoted by the same reference numerals, and detailed description is omitted.
[0118]
The sewage 1 supplied to the sewage treatment plant first flows into the anaerobic tank 10 via the sedimentation basin 2, and after being subjected to anaerobic treatment in the anaerobic tank 10, flows into the anoxic tank 11. The sewage flowing into the anoxic tank 11 is subjected to anoxic treatment, and the corresponding water quality (ORP, nitrate nitrogen concentration) is measured by the ORP meter 4 and the nitrate nitrogen concentration meter 31. Thereafter, the sewage is discharged from the anoxic tank 11, and is discharged from the sewage treatment plant via the aerobic tank 12 and the final sedimentation basin 13.
[0119]
By the way, each of the ORP meter 4 and the nitrate nitrogen concentration meter 31 that measure the corresponding water quality of the sewage stored in the anoxic tank 11 includes the water quality sensor abnormality diagnosis device 7, the carbon source injection controller 25, and the water quality database. 24 and the measured values are sent to the control unit 24.
[0120]
The water quality database 24 correlates the measurement values sent from the ORP meter 4 and the nitrate nitrogen concentration meter 31 with the measurement date and time, and correlates the measurement values of the ORP meter 4 and the measurement values of the nitrate nitrogen concentration meter 31. The correlation data is stored as correlation data.
[0121]
On the other hand, in the water quality sensor abnormality diagnosis device 7, based on the measurement values sent from the ORP meter 4 and the nitrate nitrogen concentration meter 31, whether there is an abnormality in the measurement of the ORP meter 4 and / or the nitrate nitrogen concentration meter 31. No is diagnosed. For example, when the carbon source stored in the carbon source storage tank 21 is, for example, methanol, a denitrification reaction represented by the following equation (3.2) occurs in the anaerobic tank 10.
[0122]
6NO₃ ⁻+ 5CH₃OH → 3N₂+ 5CO₂+ 7H₂O + 6OH⁻        Equation (3.2)
In this case, nitrate nitrogen functions as an oxidizing agent. On the other hand, the ORP generally has a relationship represented by the following equation (3.3), and the relationship between the ORP and the nitrate nitrogen concentration is represented by the following equation (3.4). It seems that there is a correlation.
[0123]
(Equation 9)

ORP = A + B · ln (NO₃Equation (3.4)
A, B: Constant
Then, the abnormality diagnosing unit 50 of the water quality sensor abnormality diagnosing device 7 uses, for example, an arithmetic expression expressed by the following expression (3.5) to calculate the predicted value (R_ORP) Is calculated.
[0124]
R_ORP= A + B · ln (PV_NO3Equation (3.5)
ORP: ORP prediction operation value, PV_NO3: NO₃A, B: constants (actual ORP and NO₃Derived by the least squares method, etc.)
Then, the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 uses the time series data (correlation data) on the measurement values of the ORP meter 4 and the nitrate nitrogen concentration meter 31 stored in the water quality database 24 to set the date and time. The corresponding measured value of the ORP meter 4 (PV_ORP) And the predicted operation value of the ORP (R_ORPPrincipal component analysis is performed. At this time, if the measurement by the ORP meter 4 and the nitrate nitrogen concentration meter 31 is performed normally, the first principal component should contain most information. That is, when the eigenvalue of the first principal component is λ1 and the eigenvalue of the second principal component is λ2, and the measurement by the ORP meter 4 and the nitrate nitrogen concentration meter 31 is performed normally, λ1 >> λ2. On the other hand, if an abnormality occurs in any one of the ORP meter 4 and the nitrate nitrogen concentration meter 31, the second principal component may include main information, and the following formula (3. The contribution ratio of the first main component shown in 6) decreases.
[0125]
(Equation 10)

In the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7, when the contribution ratio of the first principal component represented by the above equation (3.6) becomes equal to or less than a predetermined threshold, the ORP meter 4 or the nitric acid When it is diagnosed that an abnormality has occurred with respect to the measurement of the nitric nitrogen concentration meter 31 and the contribution ratio of the first principal component is larger than a predetermined threshold, the measurement of the ORP meter 4 and the nitrate nitrogen concentration meter 31 is normally performed Diagnosed as being performed. The diagnosis result is sent to the monitoring device 8 and also sent to the carbon source injection controller 25. In the present embodiment, the corresponding water quality range of the present invention is determined by the above-described predetermined threshold.
[0126]
The monitoring device 8 provides guidance and / or an alarm to a sewage treatment plant manager or the like based on the diagnosis result sent from the water quality sensor abnormality diagnosis device 7. If a diagnosis result indicating that an abnormality has occurred in the measurement of the ORP meter 4 or the nitrate nitrogen concentration meter 31 has been sent, the carbon source injection controller 25 checks the ORP meter 4 and the nitrate nitrogen concentration meter 31. The control of the carbon source injection pump 19 based on the measured value is stopped, and the mode is switched to another control mode such as a constant carbon source injection amount. On the other hand, while the diagnostic result indicating that the measurement by the ORP meter 4 or the nitrate nitrogen concentration meter 31 is performed normally is sent, the measured value of the nitrate nitrogen concentration meter 31 is , The control of the carbon source injection pump 19 is performed based on PI control based on an arithmetic expression represented by the following expression (3.7). In addition, the target value SV of the nitrate nitrogen concentration_NO3(T) is preset in the carbon source injection controller 25.
[0127]
(Equation 11)

Q_carbon(T): Carbon source input target value at time t (m³/ Min), Q_carbon0: Initial value of carbon source input (m³/ Min), Kp: proportional gain (m⁶/ G · min), T_I: Integration constant (min), Δt: control cycle (min), e (t): deviation (mg / L), SV_NO3(T): target value of nitrate nitrogen concentration (mg / L), PV_NO3  (T): Measurement value of nitrate nitrogen concentration meter (mg / L)
The target value (SV) of the nitrogen nitrate concentration obtained based on the above equation (3.7)_NO3) And the measured value of the nitrate nitrogen concentration meter 31 (PV_NO3), The carbon source injection controller 25 controls the carbon source injection pump 19 to adjust the nitrate nitrogen concentration in the anaerobic tank 10 to the target value (SV)._NO3), And in the anaerobic tank 10, an appropriate anaerobic treatment is performed on the sewage.
[0128]
As described above, according to the present embodiment, the logarithmic approximation of the relationship between the ORP and the nitrate nitrogen concentration based on the ORP theory and the measured values obtained by the ORP meter 4 and the nitrate nitrogen meter 31 are used. Is diagnosed based on the comparison between the ORP meter 4 and the measurement of the nitrate nitrogen concentration meter 31 as to whether or not there is any abnormality. High.
[0129]
In addition, the main component analysis of the past data stored in the water quality database 24 is used to diagnose whether or not the ORP meter 4 or the nitrate nitrogen concentration meter 31 has an abnormality. For this reason, since the parameter is only the predetermined threshold value related to the contribution ratio of the first principal component, adjustment of the control parameter in the plant becomes very simple.
[0130]
Next, a modified example of the present embodiment will be described.
[0131]
The carbon source storage tank 21 may be connected to the anoxic tank 11.
[0132]
Further, the carbon source injection controller 25 adjusts the opening degree of the initial sedimentation bypass valve 62 based on the measurement values of the ORP meter 4 and the nitrate nitrogen concentration meter 31, and adjusts the flow rate of the sewage flowing into the anaerobic tank 10. May be. In this modification, the water quality adjustment device of the present invention includes the initial settling bypass valve 62, and the water quality adjustment control device of the present invention includes the carbon source injection controller 25.
[0133]
Further, between the ORP meter 4 and / or the nitrate nitrogen concentration meter 31 and the water quality sensor abnormality diagnostic device 7, between the ORP meter 4 and / or the nitrate nitrogen concentration meter 31 and the carbon source injection controller 25, or the ORP meter. 4 and / or a filtering device may be installed between the nitrate nitrogen concentration meter 31 and the water quality database 24. In this case, the filtering processing device filters the measurement value of the ORP meter 4 and / or the nitrate nitrogen concentration meter 31 by an arithmetic expression represented by the above-described expressions (1.3) and (1.4), for example. Processing can be performed. The measurement value subjected to the filtering processing in the filtering processing device can be subsequently used in the water quality sensor abnormality diagnosis device 7, the carbon source injection controller 25, or the water quality database 24.
[0134]
When diagnosing whether there is an abnormality with respect to the measurement of the ORP meter 4 or the nitrate nitrogen concentration meter 31, the method used in the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 is based on the method using principal component analysis. Not limited. For example, the abnormality diagnosing unit 50 of the water quality sensor abnormality diagnosing device 7 calculates the ORP prediction value (R_ORP) And the measured value of the ORP meter 4 (PV_ORP) Is calculated, and based on whether or not the deviation has been out of the predetermined corresponding water quality range for a predetermined time, abnormality in the measurement of the ORP meter 4 and / or the nitrate nitrogen concentration meter 31 is determined. May be diagnosed.
[0135]
Further, the correlation equation of the above equation (3.5) is not limited to the logarithmic type as described above, and another appropriate correlation equation can be used as needed. For example, a linear type, a power type, an exponential function type, a logarithmic type, or a combination thereof may be used.
[0136]
Also, the ORP prediction value (R_ORPIn calculating (2), not only the nitrate nitrogen concentration but also the measured values of other reliable water quality sensors and flow meters may be used. For example, a UV meter 33 is installed in the anoxic tank 11 and, based on the measured value of the UV meter 33, an ORP prediction value ( R_ORP) Can be calculated.
[0137]
(Equation 12)

It is generally said that there is a linear relationship between an organic component and UV, and an organic material acts as a reducing agent in a denitrification reaction. Equation (3.10) is derived from equation (3.3) based on this.
[0138]
Fourth embodiment
FIGS. 6 and 7 are diagrams showing a third embodiment of the present invention. FIG. 6 is a diagram showing a schematic configuration of a sewage treatment plant (sewage treatment system). FIG. 7 is a diagram schematically showing the correlation between the water quality sensors, and S in FIG.₁~ S₅Indicates each water quality sensor.
[0139]
In the sewage treatment plant of the present embodiment, instead of installing the ORP meter 4, the first ammoniacal nitrogen concentration meter 5 a, and the second ammoniacal nitrogen concentration meter 5 b in the aerobic tank 12, the sewage is first poured into the sedimentation basin 2. A TN meter 32 and a UV meter 33 are installed in a water pipe to be supplied, an ORP meter 4 (an ORP meter 4a for an anaerobic tank) is installed in the anaerobic tank 10, and an ORP meter 4 (an anaerobic tank) is installed in the anoxic tank 11. ORP meter 4b) and nitrate nitrogen concentration meter 31 are installed, and ORP meter 4 (ORP meter 4c for aerobic tank), ammonia nitrogen concentration meter 5, dissolved oxygen concentration meter 6, and MLSS meter are installed in aerobic tank 12. 36 and a phosphoric acid phosphorus concentration meter 37 are provided. These water quality sensors (T-N meter 32, UV meter 33, ORP meter 4a, 4b, 4c, nitrate nitrogen meter 31, ammonia nitrogen meter 5, dissolved oxygen meter 6, MLSS meter 36, phosphate phosphorus meter Each of the densitometers 37) is connected to the water quality sensor abnormality diagnosis device 7 and to the water quality database 24, and sends the measured values to the water quality sensor abnormality diagnosis device 7 and the water quality database 24.
[0140]
A first inflow flow meter for measuring a flow rate of sewage flowing from the first sedimentation tank 2 to the anaerobic tank 10 of the denitrification / dephosphorization treatment tank 40 is provided in a water pipe between the first sedimentation tank 2 and the anaerobic tank 10. 30a is installed, and a second inflow flow meter 30b for measuring the flow rate of the carbon source flowing through the water pipe is installed in the water pipe between the carbon source storage tank 21 and the anaerobic tank 10, and the coagulant storage tank 22 A third inflow flow meter 30c for measuring the flow rate of the flocculant flowing through the water pipe is installed in the water pipe between the aerobic tank 12 and the sewage in the aerobic tank 12. A fourth inflow flow meter 30d for measuring the flow rate of the sewage returned from the water pipe is installed in the water pipe for returning the water pipe, and the water pipe connecting the final sedimentation tank 13 and the anaerobic tank 10 is Fifth inflow flow meter 30 that measures the flow rate of sewage returned to anaerobic tank 10 via water pipe Is installed, and a sixth inflow flow meter 30f for measuring a flow rate of sewage flowing through the water pipe is installed in a water pipe connecting the first sedimentation basin 2 and the sludge storage tank 20. A seventh inflow flow meter 30 g that measures the flow rate of sewage flowing through the water pipe is installed in the water pipe connecting the tank 20. The first to seventh inflow flow meters 30a to 30g are connected to the water quality database 24, respectively, and send measured values to the water quality database 24. Further, the aeration device is provided with an aeration air flow meter 46 for measuring the amount of aeration air to be aerated from the aeration device to the aerobic tank. The aeration air flow meter 46 is connected to the water quality database 24, and sends measured values to the water quality database 24.
[0141]
The water quality database 24 includes data on each measurement value sent from each water quality sensor, data on each measurement value sent from each inflow flow meter 30, and data on measurement values sent from the aeration flow meter 46. And can be stored in association with the measurement date and time.
[0142]
Further, the water quality sensor abnormality diagnosis device 7 has an abnormality diagnosis unit 50, and the abnormality diagnosis unit 50 is provided with data on each measurement value sent from each water quality sensor and correlation data stored in the water quality database 24. Based on the above, it is diagnosed whether or not there is an abnormality in the measurement of each water quality sensor.
[0143]
Note that the aeration air volume controller 23 controls the aeration device 9 so that the aeration amount supplied from the aeration device 9 to the aerobic tank 12 is maintained at a predetermined fixed amount.
[0144]
In the present embodiment, the control water quality sensor of the present invention is configured by any one of the water quality sensors, and the target water quality is the water quality measured by the water quality sensor. Further, the abnormality diagnosis water quality sensor of the present invention is constituted by another water quality sensor and each inflow flow meter 30, and the correlated water quality is measured by the water quality measured by the other water quality sensor and each inflow flow meter 30. Flow rate. In the present embodiment, the correlation between the target water quality of the present invention and the correlated water quality is expressed by the equations (4.1), (4.4), and (4.6). Using this correlation equation, the target water quality prediction value is calculated by the equations (4.2), (4.5), and (4.7), and the difference between the predicted value and the actually measured value of the target water quality is calculated by the equation (4. 3) and (4.8) are used to perform the abnormality determination.
[0145]
Other configurations are substantially the same as those of the second embodiment. In the fourth embodiment shown in FIGS. 6 and 7, the same parts as those in the second embodiment are denoted by the same reference numerals, and detailed description is omitted.
[0146]
The sewage 1 supplied to the sewage treatment plant is first subjected to a purification treatment through a sedimentation basin 2, an anaerobic tank 10, an anoxic tank 11, an aerobic tank 12, and a final sedimentation basin 13. Is discharged from In each biological reaction tank of such a purification process, each water quality sensor, each inflow flow meter 30a to 30g, and the aeration air flow meter 46 measure the corresponding water quality and flow rate, respectively, and measure the measured values as a water quality sensor abnormality diagnostic device. 7 and the water quality database 24.
[0147]
In the water quality database 24, data related to measurement values sent from each water quality sensor, each inflow flow meter 30a to 30g, and the aeration air flow meter 46 are stored in association with each other according to the measurement date and time. Further, in the water quality database 24, the past data (correlation data) stored in the water quality database 24 is used, and a component having a high correlation with the measured value of each water quality sensor and the inflow flow meters 30a to 30g is used. It can be extracted by correlation analysis.
[0148]
When a total of n pieces of correlation data regarding the measurement values of the water quality sensor, the inflow flow meters 30a to 30g, and the aeration air flow meter 46 are stored in the water quality database 24, the water quality sensors installed in the sewage treatment plant The correlation equation for an arbitrary water quality sensor (water quality sensor 1) selected from the following can be expressed in the form as shown in the following equation (4.1). For this reason, the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 calculates the regression coefficient A used in the correlation equation represented by the equation (4.1).₂₁, A₃₁, ... A_n1, A₀₁Is calculated by multiple regression analysis.
[0149]
Rsensor₁= A₂₁・ S₂  + A₃₁・ S₃  + A₄₁・ S₄  .... + A_n1・ S_n  + A₀₁ Equation (4.1)
Rsensor₁: Correlation formula for water quality sensor 1
S₂: Water quality value or flow rate value by sensor 2
S₃: Water quality value or flow rate value by the sensor 3
S₄: Water quality value or flow rate value by the sensor 4
・
・
S_n: Value measured by sensor n (flow rate or water quality)
A₂₁, A₃₁・ ・ ・ ・ ・ ・ A_n1, A_{(N + 1) 1}: Regression coefficient (for sensor i having a low correlation with water quality sensor 1 by correlation analysis, A_i1= 0. )
In the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7, the predicted operation value of the water quality sensor 1 at the time t is calculated using the equation obtained by the above equation (4.1). It is calculated from the value of another water quality sensor or the inflow flow meters 30a to 30g by the following equation (4.2).
[0150]
Psensor₁(T) = A₂₁・ S₂(T) + A₃₁・ S₃(T) + A₄₁・ S₄(T) ... + A_n1・ S_n(T) + A_{(N + 1) 1}... Equation (4.2)
Psensor₁(T): Predicted calculated value of water quality sensor 1 at time t
S₂(T): measured value of sensor 2 at time t (flow rate or water quality)
S₃(T): measured value of sensor 3 at time t (flow rate or water quality)
S₄(T): measured value of sensor 4 at time t (flow rate or water quality)
・
・
S_n(T): measured value of sensor n at time t (flow rate or water quality)
A₂₁, A₃₁・ ・ ・ ・ ・ ・ A_n1, A_{(N + 1) 1}: Regression coefficient (the same value as the coefficient in equation (4.1))
Then, the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 calculates a deviation between the predicted value of the measurement value of the water quality sensor 1 calculated by the equation (4.2) and the measurement value of the water quality sensor 1 by a predetermined value. Based on whether or not the threshold value has been exceeded, it is diagnosed whether an abnormality has occurred in the measurement of the water quality sensor 1. That is, as shown in the following equation (4.3), when the deviation exceeds a predetermined threshold, the abnormality diagnosis unit 50 determines whether an abnormality has occurred in the measurement of the water quality sensor 1, 1 or another water quality sensor or inflow flow meter 30 (A_i1It can be diagnosed that an abnormality has occurred in the measurement of the water quality sensor or the inflow flow meter 30) corresponding to # 0. In the present embodiment, the corresponding water quality range of the present invention is determined by the above-described predetermined threshold.
[0151]
｜ S₁(T) -Psensor₁(T) |> ULsensor₁          Equation (4.3)
ULsensor_{1 :}Abnormality judgment value of water quality sensor 1
Then, the same multiple regression analysis as that of the water quality sensor 1 is performed on the other water quality sensors other than the water quality sensor 1, and the regression coefficient A expressed by the following equation (4.4) is obtained._1j~ A_{(N + 1) j}Is determined. Further, the prediction calculation value Psensor at the time t of the water quality sensor i is calculated in the form of the following equation (4.5)._jIs represented.
[0152]
Rsensor_j= A_1j・ S₁  + A_2j・ S₂  + A_3j・ S₃  + ··· + A_nj・ S_n  + A_0j... Equation (4.4)
Rsensor_j: Correlation formula for water quality sensor j
S₁: Water quality value or flow rate value by sensor 1
S₂: Water quality value or flow rate value by sensor 2
S₃: Water quality value or flow rate value by the sensor 3
・
・
S_n: Water quality value or flow rate value by sensor n
A_1j, A_2j・ ・ ・ ・ ・ ・ A_nj, A_{(N + 1) j}: Regression coefficients of water quality sensors 1 to n with respect to water quality sensor j (for a sensor i having a low correlation with water quality sensor j by correlation analysis,_ij= 0. )
Psensor_j(T) = A_1j・ S₁(T) + A_2j・ S₂(T) + A_3j・ S₃(T) ... + A_nj・ S_n(T) + A_0j.... Formula (4.5)
Psensor_i(T): Predicted calculated value at time t of water quality sensor i
S₁(T): Measurement value of sensor 1 at time t (flow rate or water quality)
S₂(T): measured value of sensor 2 at time t (flow rate or water quality)
S₃(T): measured value of sensor 3 at time t (flow rate or water quality)
・
・
S_n(T): measured value of sensor n at time t (flow rate or water quality)
A_0j: Constant term
A_1j, A_2j・ ・ ・ ・ ・ ・ A_nj, A_0j: Regression coefficient of water quality sensor 1 to n for water quality sensor j (the same value as the coefficient of equation (4.1))
Correlation equation for all water quality sensors (Rsensor_j) Is represented in the form of a determinant, which is represented by the following equation (4.6).
[0153]
(Equation 13)

Rsensor_j: Correlation formula for water quality sensor j
S_j: Water quality value or flow rate value of sensor j
A_0j: Constant term
A_ij: Regression coefficient of water quality sensor i with respect to water quality sensor j (i = 1 to n, j = 1 to n)
Also, the predicted values (Psensor) of the measurement values for all the water quality sensors at time t_j) Is expressed in the form of a determinant, as shown in the following equation (4.7).
[0154]
[Equation 14]

Psensor_j(T): predicted value of water quality sensor j at time t
S_j(T): measured value of sensor j at time t
A_0j: Constant term
A_ij: Regression coefficient of water quality sensor i with respect to water quality sensor j (i = 1 to n, j = 1 to n)
Then, the water quality sensor abnormality diagnosis device 7 calculates the predicted value of the calculated measurement value of each water quality sensor and the measurement value It is possible to diagnose whether or not an abnormality has occurred in the measurement of each water quality sensor, based on whether or not the deviation between and has exceeded a predetermined threshold value.
[0155]
[Equation 15]

ULsensor_{j :}Abnormality judgment value of water quality sensor j
As described above, it is diagnosed whether an abnormality has occurred in the measurement of each water quality sensor. Then, when an abnormality occurs in the measurement of one water quality sensor, it is indicated that one or more abnormality diagnosis expressions in the above expression (4.8) indicate that an abnormality has occurred. That is, if it is diagnosed as abnormal in the equation (4.8), the water quality sensor j or the water quality sensor of the water quality sensor group correlated with the water quality sensor j (that is, the sensor A)_ijIt can be diagnosed that an abnormality has occurred in any of the measurements of the water quality sensor corresponding to # 0). On the other hand, if it is diagnosed as normal in the equation (4.8), the water quality sensor j or each water quality sensor of the water quality sensor group correlated with the water quality sensor j (that is, the sensor A)_ijThe measurement of the water quality sensor corresponding to $ 0 is performed normally.
[0156]
For example, water quality sensor S₁~ S₅Let us assume a case where there is a correlation as shown in FIG. In FIG. 7, it is shown that the portions between the overlapping water quality sensors have a correlation, and the portions between the non-overlapping water quality sensors have no correlation. Water quality sensor S₁~ S₅Has a correlation as shown in FIG. 7, the water quality sensor S₁If an abnormality occurs only in the measurement of water, the water quality sensor S₁Abnormality diagnosis formula and water quality sensor S₁Water quality sensor S correlated with₂, S₅In the abnormality diagnosis formula relating to the above, it is indicated that an abnormality has occurred. However, in this case, the water quality sensor S₁Water quality sensor S that has no correlation with₃The water quality sensor S has been measured normally.₃The abnormality diagnosis formula for the normal state indicates that the state is normal. Therefore, the water quality sensor S₃Water quality sensor S correlated with₂, S₅Can also be diagnosed as being performed normally. Thus, the water quality sensor S₁It can be diagnosed that an abnormality has occurred only in the measurement of.
[0157]
Similarly, the water quality sensor S₂If an abnormality occurs only in the measurement of water, the water quality sensor S₂Abnormality diagnosis formula and water quality sensor S₂Water quality sensor S correlated with₁, S₃In the abnormality diagnosis formula relating to the above, it is indicated that an abnormality has occurred. However, in this case, the water quality sensor S₂Water quality sensor S that has no correlation with₅The water quality sensor S has been measured normally.₅The abnormality diagnosis formula for the normal state indicates that the state is normal. Therefore, the water quality sensor S₅Water quality sensor S correlated with₁, S₃Can also be diagnosed as being performed normally. Thus, the water quality sensor S₂It can be diagnosed that an abnormality has occurred only in the measurement of.
[0158]
On the other hand, the water quality sensor S₃If an abnormality occurs only in the measurement of water, the water quality sensor S₃Abnormality diagnosis formula and water quality sensor S₂Water quality sensor S correlated with₂, S₄, S₅In the abnormality diagnosis formula relating to the above, it is indicated that an abnormality has occurred. And the water quality sensor S₁If the measurement of the water quality is performed normally, the water quality sensor S₁The abnormality diagnosis formula for the water quality sensor S indicates that it is normal.₁Water quality sensor S correlated with₂, S₅Can be diagnosed as being normally performed. However, it cannot be strictly diagnosed which one or both of the water quality sensor S3 and the water quality sensor S4 has an abnormality in the measurement. Therefore, the water quality sensor abnormality diagnosis device 7 can diagnose that an abnormality has occurred in the measurement of one or both of the water quality sensor S3 and the water quality sensor S4.
[0159]
In this manner, the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 determines whether or not there is any abnormality using the above equation (4.8) for all measurements of the water quality sensor installed in the sewage treatment plant. By performing the diagnosis, it is possible to extract a water quality sensor that may have an abnormality in the measurement.
[0160]
Then, the above diagnosis result in the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 is sent to the monitoring device 8, and the monitoring device 8 performs management based on the received diagnosis result of the water quality sensor abnormality diagnosis device 7. Guidance and warning are given to persons. For example, a list of water quality sensors extracted by the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 that may have an abnormality in measurement may be displayed.
[0161]
Next, a modified example of the present embodiment will be described.
[0162]
The installation positions of the water quality sensors and the inflow flow meters 30a to 30g are not limited to those shown in FIG. Each of the water quality sensors and each of the inflow flow meters 30a to 30g may be installed at any location in the sewage treatment plant as needed.
[0163]
In addition, each water quality sensor, each inflow flow meter 30a-30g, and between the aeration air flow meter 46 and the water quality sensor abnormality diagnostic device 7, or each water quality sensor, each inflow flow meter 30a-30g, and the aeration air flow meter 46 Between the water quality database 24, a filtering processing device for filtering the measured value may be installed. The filtering processing device can perform a filtering process on each measurement value by an arithmetic expression such as the above-described expressions (1.3) and (1.4). The measured value subjected to the filtering processing in the filtering processing device can be used in the water quality sensor abnormality diagnosis device 7 and the water quality database 24 thereafter.
[0164]
Further, the method of diagnosing whether or not each of the water quality sensors has an abnormality in the abnormality diagnosis unit 50 of the water quality sensor abnormality diagnosis device 7 is not limited to the method based on FIG. 7 described above, and another method may be used. Is also possible. For example, using a method based on principal component analysis using time series data of various water quality sensors, it is possible to diagnose whether or not there is an abnormality in the measurement of each water quality sensor.
[0165]
Further, the correlation equations of the above equations (4.1), (4.4), and (4.6) are not limited to those described above, and other appropriate correlation equations may be used as necessary. Is possible. For example, a linear type, a power type, an exponential function type, a logarithmic type, or a combination thereof can be used.
[0166]
In each of the above-described embodiments and modifications, the coagulant injection type anaerobic-anoxic-aerobic method (coagulant injection A₂Although the sewage treatment plant configured to perform a process called “O method” has been described, the present invention can be suitably applied to other processes. For example, the present invention can be applied to any of the various processes shown in Table 2 below. In addition, in addition to the various processes shown in Table 2, a carrier charging, a coagulant combined type process, an AOAO method, various A₂The present invention can be suitably applied to the O method or a variation of these various processes.
[0167]
[Table 2]

In each of the above-described embodiments and modifications, the sewage treatment plant (a sewage treatment system) including a plurality of biological reaction tanks has been described. However, the sewage treatment apparatus includes a single (only one) biological reaction tank. The present invention can be suitably applied to a field.
[0168]
Further, the control water quality sensor and the abnormality diagnosis water quality sensor in the present invention are not limited to those described above. For example, the control water quality sensor includes at least one or more of an ammonia nitrogen concentration meter, a nitrate nitrogen concentration meter, a total nitrogen concentration meter, a phosphate phosphorus concentration meter, a total phosphorus concentration meter, a COD meter, and a BOD meter. It may be configured to include a water quality sensor (reagent sensor). In addition, the water quality sensor for abnormality diagnosis is one or more water quality sensors (reagent-free sensors) for measuring a correlated water quality having a correlation with a target water quality measured by the control water quality sensor among the ORP meter, the UV meter, and the DO meter. May be included.
[0169]
For example, as shown in Table 3 below, when the control water quality sensor is a nitrate nitrogen concentration meter or a total nitrogen concentration meter, the abnormality diagnosis water quality sensor is preferably a UV meter or a DO meter. When a phosphoric acid phosphorus concentration meter or a total phosphorus concentration meter is used, the water quality sensor for abnormality diagnosis is preferably a DO meter, and when the water quality sensor for control is a COD meter or a BOD meter, the water quality sensor for abnormality diagnosis is An ORP meter or DO meter is preferred. Further, when the control water quality sensor is an ammonia nitrogen concentration meter, the abnormality diagnosis water quality sensor is more preferably a DO meter, and when the control water quality sensor is a phosphate phosphorus concentration meter or a total phosphorus concentration meter, The ORP meter is more preferable as the abnormality diagnosis water quality sensor. In addition, when the control water quality sensor is an ammonia nitrogen concentration meter, a nitrate nitrogen concentration meter, or a total nitrogen concentration meter, it is particularly preferable that the abnormality diagnosis water quality sensor be an ORP meter. When a COD meter or a BOD meter is used, it is particularly preferable that the abnormality diagnosis water quality sensor is a UV meter.
[0170]
[Table 3]

A combination of the above-described embodiments may be included in the scope of the present invention.
[0171]
【The invention's effect】
As described above, according to the present invention, not only the measurement value of the target water quality by the control water quality sensor but also the abnormality diagnosis The measured value of the correlated water quality by the water quality sensor and the correlation between the target water quality and the correlated water quality are considered. For this reason, it is possible to quickly diagnose whether there is an abnormality in the measurement of the target water quality by the control water quality sensor.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a sewage treatment plant (sewage treatment system) according to a first embodiment.
FIG. 2 is a diagram showing an example of a corresponding water quality range;₄The relationship between concentration and ORP is shown.
FIG. 3 is a diagram schematically showing a corresponding water quality range in a modified example of the first embodiment.
FIG. 4 is a diagram illustrating a schematic configuration of a sewage treatment plant according to a second embodiment.
FIG. 5 is a diagram illustrating a schematic configuration of a sewage treatment plant according to a third embodiment.
FIG. 6 is a diagram illustrating a schematic configuration of a sewage treatment plant according to a fourth embodiment.
FIG. 7 is a diagram schematically showing a correlation between water quality sensors. S in FIG.₁~ S₅Indicates each water quality sensor.
FIG. 8 is a diagram showing an example of a schematic configuration of a conventional sewage treatment plant.
FIG. 9 is a diagram showing another example of a schematic configuration of a conventional sewage treatment plant.
FIG. 10: NH in a conventional sewage treatment plant₄It is a figure which shows the relationship between density | concentration and time, and the relationship between aeration air volume and time.
[Explanation of symbols]
4, 4a, 4b, 4c ORP meter
5,5a, 5b Ammonia nitrogen concentration meter
6 dissolved oxygen concentration meter
7 Water quality sensor abnormality diagnosis device
8 Monitoring equipment
9 Aeration device
10 Anaerobic tank
11 Anoxic tank
12 Aerobic tank
16 PAC Infusion Pump
17 Surplus pump
18 First extraction pump
19 Carbon source injection pump
21 Carbon source storage tank
22 Coagulant storage tank
23 Aeration air volume controller
24 Water Quality Database (Water Quality Data Storage)
25 Carbon source injection controller
30, 30a-30g Inflow flow meter
31 Nitrate nitrogen concentration meter
32 T-N meter
33 UV meter
36 MLSS meter
37 Phosphoric acid concentration meter
40 Denitrification and dephosphorization treatment tank
46 Aeration air flow meter
50 Abnormality diagnosis unit
51 Compatible water quality range calculator
52 Compatible Water Quality Range Matching Unit
53 Correlation Derivation Unit
61 Bypass water piping
62 First settling bypass valve

Claims (19)

A water quality monitoring and control device for monitoring the quality of a predetermined target water quality of sewage treated in a sewage treatment system having one or more biological reaction tanks for purifying sewage,
Of the sewage water quality in the sewage treatment system, a control water quality sensor that measures the target water quality,
Of the sewage water quality in the sewage treatment system, an abnormality diagnosis water quality sensor that measures a correlated water quality having a correlation with the target water quality,
The measured value of the target water quality by the control water quality sensor, the measurement value of the correlated water quality by the abnormality diagnosis water quality sensor, and the correlation between the target water quality and the correlated water quality, taking into account the An abnormality diagnosis unit that diagnoses whether or not the measurement of the target water quality by the water quality sensor has an abnormality,
A water quality monitoring control device comprising: The sewage whose target water quality is measured by the control water quality sensor and the sewage whose correlation water quality is measured by the abnormality diagnosis water quality sensor are sewage in the same biological reaction tank. Item 2. A water quality monitoring and control device according to item 1. The apparatus further includes a water quality data storage unit that stores past correlation data related to the correlation between the target water quality and the correlation water quality,
The first-stage abnormality diagnosis unit diagnoses, based on the correlation data stored in the water-quality data storage unit, whether or not the measurement of the target water quality by the control water-quality sensor has an abnormality. The water quality monitoring control device according to any one of 1 and 2. A correlation deriving unit that derives a correlation between the target water quality and the correlated water quality based on past correlation data stored in the water quality data storage unit,
The correlation between the target water quality and the correlated water quality considered by the abnormality diagnosis unit when diagnosing whether or not the control water quality sensor has an abnormality in the measurement of the target water quality is derived by the correlation derivation unit. The water quality monitoring control device according to any one of claims 3 to 4, wherein the target water quality and the correlation water quality are correlated. 5. The past correlation data stored in the water quality data storage unit includes past data on at least one of the target water quality and the correlation water quality. 6. Water quality monitoring and control equipment. The control water quality sensor further includes an inflow flow meter that measures an inflow amount of sewage flowing into a predetermined sewage treatment system in which the target water quality of the sewage is measured,
The said abnormality diagnosis part diagnoses whether it has abnormality regarding the measurement of the said target water quality by the said control water quality sensor further considering the measured value of the said inflow flowmeter, The Claims 1 thru | or 5 characterized by the above-mentioned. The water quality monitoring and control device according to any one of the above. The abnormal diagnosis water quality sensor further includes an inflow flow meter that measures an inflow amount of sewage flowing into a predetermined sewage treatment system in which the correlated water quality of the sewage is measured by the abnormality diagnosis water quality sensor,
The said abnormality diagnosis part diagnoses whether it has abnormality regarding the measurement of the said target water quality by the said control water quality sensor further considering the measured value of the said inflow flowmeter, The Claims 1 thru | or 5 characterized by the above-mentioned. The water quality monitoring and control device according to any one of the above. The abnormality diagnosis unit,
Based on the correlation between the target water quality and the correlated water quality, corresponding to the measurement value of the target water quality by the control water quality sensor, a corresponding water quality range calculation unit that obtains a corresponding water quality range related to the correlated water quality,
By comparing the data based on the measured value of the correlated water quality by the abnormality diagnosis water quality sensor and the corresponding water quality range obtained by the corresponding water quality range calculation unit, the measurement of the target water quality by the control water quality sensor is performed. The water quality monitoring control device according to any one of claims 1 to 7, further comprising: a corresponding water quality range collating unit that diagnoses whether or not there is an abnormality. The corresponding water quality range determined by the corresponding water quality range calculation unit is a range related to the measurement value of the correlated water quality by the abnormality diagnosis water quality sensor,
The data based on the measured value of the correlated water quality by the abnormality diagnosis water quality sensor, in which the corresponding water quality range matching unit compares the corresponding water quality range obtained by the corresponding water quality range calculation unit, is the correlated water quality by the abnormality diagnosis water quality sensor. Is the measured value of
The corresponding water quality range matching unit, based on whether the measured value of the correlated water quality by the abnormality diagnosis water quality sensor is out of the corresponding water quality range obtained by the corresponding water quality range calculation unit, based on the control water quality sensor. The water quality monitoring and control device according to claim 8, wherein it is diagnosed whether or not the measurement of the target water quality has an abnormality. The corresponding water quality range determined by the corresponding water quality range calculation unit is a range related to a time change amount of the measurement value of the correlation water quality by the abnormality diagnosis water quality sensor,
The data based on the measured value of the correlated water quality by the abnormality diagnosis water quality sensor, in which the corresponding water quality range matching unit compares the corresponding water quality range obtained by the corresponding water quality range calculation unit, is the correlated water quality by the abnormality diagnosis water quality sensor. The corresponding water quality range comparison unit, the time change amount of the measurement value of the correlation water quality by the abnormality diagnosis water quality sensor, the corresponding water quality range determined by the corresponding water quality range calculation unit. The water quality monitoring and control device according to claim 8, wherein it is diagnosed whether or not there is an abnormality in the measurement of the target water quality by the control water quality sensor based on whether or not the water quality is off. The measurement value of the target water quality by the control water quality sensor, and the measurement value of the correlation water quality by the abnormality diagnosis water quality sensor, further comprising a filtering processing unit that performs a filtering process,
The measurement value of the target water quality by the control water quality sensor and the measurement value of the correlated water quality by the abnormality diagnosis water quality sensor considered by the abnormality diagnosis unit are the control values subjected to the filtering process by the filtering processing unit. The water quality monitoring control device according to any one of claims 1 to 10, wherein the water quality sensor is a measurement value of the target water quality by a water quality sensor and a measurement value of the correlated water quality by the abnormality diagnosis water quality sensor. The sewage treatment system further includes a water quality adjustment device that adjusts the target water quality,
The water quality monitoring control device according to any one of claims 1 to 11, further comprising a water quality adjustment control device that controls the water quality adjustment device based on a measurement value of the measurement value of the control water quality sensor. When the abnormality diagnosis unit diagnoses that the measurement of the target water quality by the control water quality sensor has an abnormality, the abnormality diagnosis unit further includes a monitoring device that performs at least one of an alarm and guidance regarding the abnormality. The water quality monitoring and control device according to any one of claims 1 to 12. The water quality monitoring control device according to any one of claims 1 to 13, wherein the target water quality and the correlation water quality are the same. The water quality monitoring and control device according to any one of claims 1 to 13, wherein the target water quality and the correlation water quality are different. The control water quality sensor is a reagent-based water quality sensor using a reagent,
The water quality monitoring and control device according to claim 15, wherein the abnormality diagnosis water quality sensor is a reagentless water quality sensor. The reagent shows a colorimetric reaction with the target water quality,
The control water quality sensor according to claim 16, wherein the target water quality in the sewage treatment system is measured by detecting a colorimetric reaction between the target water quality in the sewage and the reagent. Water quality monitoring and control equipment. The control water quality sensor includes at least one of an ammonia nitrogen concentration meter, a nitrate nitrogen concentration meter, a total nitrogen concentration meter, a phosphate phosphorus concentration meter, a total phosphorus concentration meter, a COD meter, and a BOD meter. It is comprised including,
The abnormality diagnosis water quality sensor is configured to include one or more water quality sensors that measure correlated water quality having a correlation with the target water quality measured by the control water quality sensor, among the ORP meter, the UV meter, and the DO meter. 18. The water quality monitoring and control device according to claim 16, wherein: One or more biological reactors for purifying sewage;
A sewage treatment system comprising: the water quality monitoring control device according to any one of claims 1 to 17.

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