JP4180772B2

JP4180772B2 - Design support device for oxidation ditch process

Info

Publication number: JP4180772B2
Application number: JP2000163153A
Authority: JP
Inventors: 文智木村; 昭二渡辺; 剛武本; 直樹原
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2000-05-29
Filing date: 2000-05-29
Publication date: 2008-11-12
Anticipated expiration: 2020-05-29
Also published as: JP2001334286A

Description

【０００１】
【発明の属する技術分野】
本発明は、オキシデーションディッチ法プロセスの設計や運転を支援するシミュレーション装置に関する。
【０００２】
【従来の技術】
地方への下水道の普及に伴い、小規模下水処理施設が多くなっている。新規処理場に採用されている処理方法として、オキシデーションディッチ（以下、ODと略す）法が著しく多い。OD法は、最初沈殿池を設けず、機械式曝気装置を有する水深の浅い無終端水路を生物反応槽として、低負荷条件で活性汚泥処理を行い、最終沈殿池で固形分離を行う下水処理方式である。
【０００３】
OD法の運転方式には、流れ方向の溶存酸素濃度（DO）の勾配により、OD槽を好気ゾーンと無酸素ゾーンに分割して行う連続運転と、時間によって曝気装置は曝気と無酸素撹拌を繰り返す間欠運転があげられる。
【０００４】
OD法は連続運転、間欠運転のどちらもOD槽内の硝化・脱窒反応を適切に維持しなければ、高い窒素除去率を得ることができない。このような下水高度処理は、有機物、リン、窒素除去に関連する各種微生物の生息環境を適切に維持することによって性能が発揮される。これまで有機物、窒素の複雑な反応過程を算出し提示できる方法がなく、OD法の設計や運転は経験と勘に依存していた。そのため、経験していない流入下水の水質と量、生物反応槽の構成、運転条件に対しては予測できない事態が発生し、そのつど対策を講じている。
【０００５】
例えば、小規模下水道計画・設計・維持管理指針と解説などの指針によれば、稼動している一部の処理場の実績値を用いて各種高度処理方式に所要の設計法や運転管理法を提供しているが、流入水条件や方式の異なる他の処理場への適用には問題が多い。
【０００６】
一方、生物反応をモデル化し、数値シミュレーションによって活性汚泥プロセスの特性を評価する方法が提案されている。生物反応のモデルの例として、海外では1995年、国際水環境協会（IAWQ）が発表した活性汚泥モデルNo.2（IAWQ：IAWQ Scientific and Technical Report No.3,Activated Sludge Model No.2,1995）が提案されている。また、特開平１０−４３７８７号公報のように、下水処理プロセスシミュレータによって水質を計算する方法が提案されている。
【０００７】
【発明が解決しようとする課題】
従来技術のなかで国際水環境協会（IAWQ）が発表した活性汚泥モデルNo.2は、活性汚泥中の微生物（菌体）の種類を定義し、関連する生物反応をモデル化しているのみで、このモデルを用いたシミュレータを提示しているわけではない。実際に活性汚泥プロセスのシミュレータを作成するには提示された生物反応モデルの他に最低でも、OD槽の流体モデル、最終沈殿池の流体モデル、曝気装置による酸素供給モデルが必要で、さらに、流入下水の質と量、OD槽の土木構造、曝気装置の送気条件、返送と余剰の運転条件などを組合せて数値計算しないと実現できない。
【０００８】
また、特開平１０−４３７８７号の下水処理シミュレータには、OD槽を複数の完全混合槽に分割したとき、プラント毎に異なるOD槽の土木構造や曝気装置がOD槽に与える流速の設定方法については、なんら記載されていず、物質収支の概念だけでは、様々なOD槽の流体モデルに対応することはできない。建設地やOD槽の形状などの制限で流入下水および返送汚泥がOD槽への流入位置、OD槽から最終沈殿池への流出位置もプラント毎に異なる。このOD槽の流入位置と流出位置は、直接OD槽の輸送に影響を与えて処理水質まで影響を及ぶ。また、OD槽は隔壁を持たない生物反応槽であるが、水質や溶存酸素は、流動や拡散および生物反応によって流れ方向に濃度勾配を生じる。
【０００９】
この濃度勾配を表現する方法として、OD槽を複数個完全混合槽に分割し、個々の分割槽の水質や溶存酸素を演算する方法が有効である。個々の分割槽の水質および溶存酸素を正確、かつ、定量に演算するためには、各種水質の輸送に関わる流入・流出位置や、曝気装置の配置位置を、個々の分割槽に対応して定義した上、流入・流出に関わる水量および水質や、曝気装置が供給する溶存酸素およびOD槽に与える流速を正確に定義しなければ、OD槽の水質および溶存酸素の濃度勾配を計算することができない。また、曝気装置のDO設定値による自動運転の場合、曝気装置とDO計の配置関係を正確に定義しなければ、OD槽の溶存酸素濃度勾配を計算することができない。
【００１０】
従って、OD槽において、流れによる物質収支を計算するシミュレータには、OD槽の形状と、OD槽の寸法と、OD槽の流入・流出といった土木構造と、曝気装置とDO計の配置位置を表現できる手段のほかに、曝気装置がOD槽に与える流速とOD槽内の流れ方向を表現できることも不可欠であるが、特開平１０−４３７８７の下水処理シミュレータにはなんら考慮されていない。
【００１１】
一方、OD法の窒素除去については、無酸素ゾーン（連続運転）または無酸素撹拌時間帯（間欠運転）での脱窒反応と好気ゾーン（連続運転）または曝気時間帯（間欠運転）での硝化反応の２つ工程を、バランスよく行わないと高い窒素除去率が得られないために、OD槽の形状、OD槽の水路長、OD槽の流入と流出などの土木構造と、曝気装置の組合せは非常に重要である。
【００１２】
また、混合液が短い時間でOD槽内を周回することで、OD槽内における水質や溶存酸素の流動も十分考慮せねばならない。例えば、曝気装置から供給されるDOは、微生物反応に消費されながら、OD槽内を周回する。曝気装置から、流れ方向に、DOが徐々に低下し、連続運転の場合、このDOの濃度勾配は好気ゾーンと無酸素ゾーンになり、硝化と脱窒に直接影響を与える。このように、硝化と脱窒の生物反応は、曝気装置の配置位置及び運転条件によって、窒素の除去性能の限界が決まってしまう。そのために、OD法の設計や運転には、生物反応に基づいた数値シミュレーションによって土木構造を決め、次に適切な運転条件を検討しなければならない。最適な運転処理は、この手順を繰り返し試行することによって初めて決定できる。
【００１３】
従って、運転支援を目的としたシミュレータには流入条件や、OD槽の形状、OD槽の寸法、OD槽の流入・流出といった土木構造、曝気装置と計測器などの機械設備の配置位置、及び運転条件を容易に変更できる手段が不可欠であるが、特開平１０−４３７８７号の下水処理シミュレータにはなんら考慮されていない。
【００１４】
本発明は、上記した従来技術の問題点に対して成されたもので、OD槽の形状、OD槽の寸法、OD槽に対する流入位置と流出位置といった土木構造、曝気装置とDO計の位置、曝気装置がOD槽に与える流速や流れ方向、ならびに各種運転条件を設定して、目標放流水条件を満たす下水シミュレーション装置を提供することにある。
【００１５】
【課題を解決するための手段】
本発明は無終端水路の活性汚泥処理プロセスをシミュレーションする装置において、生物反応槽の形状を設定する手段と、設定した形状の生物反応槽の水路全長と水路幅と水深といった寸法を設定する手段と、前記生物反応槽に対し流入位置と流出位置を設定する手段と、前記生物反応槽における曝気装置とDO計の配置位置を設定する手段と、前記曝気装置の仕様を設定する手段と、運転条件を設定する手段を具備したことを特徴とする。
【００１６】
また、OD槽の形状を設定する手段は、通常OD法に用いられている複数の生物反応槽の形状、少なくとも長円形、馬蹄形、円心円形から選択し、OD槽の水路の全長と幅と水深を組み合わせることで、ほとんどの無終端水路の活性汚泥処理プロセスを表現できる。
【００１７】
また、前記の形状と寸法が設定されたOD槽に対し、流入下水及び返送汚泥の流入位置、最終沈殿池の流出位置が明確に表現できるために、OD法プロセスの土木構造を定義できる。
【００１８】
また、前記曝気装置仕様を設定する手段は、曝気装置の酸素供給性能と、曝気装置の撹拌が生物反応槽に与える流速と流れ方向を定義できる。
【００１９】
本発明によれば、OD槽の形状、OD槽の寸法、OD槽に対する流入位置と流出位置といった土木構造、曝気装置とDO計の位置、曝気装置がOD槽に与える流速や流れ方向、ならびに各種運転条件を自由に設定することによって、OD法処理プロセスの最適化の検討を可能にした。
【００２０】
【発明の実施の形態】
図２は本発明のシミュレーションを適用する無終端水路の活性汚泥プロセスを示す。図は長円形オキシデーションディッチ法の例で、有機物、窒素、リンなどの基質を含む流入汚水は流入水３としてOD槽１へ送られる。OD槽１には、流入水３と返送汚泥管５からの返送汚泥（活性汚泥）が流入し、混合撹拌が行われる。OD槽１には、通常、複数台の曝気装置９が設けられる。曝気装置９は、OD槽１の活性汚泥反応に必要な酸素を供給するほか、OD槽１の活性汚泥と流入水３を混合撹拌し、混合液に流速を与えて無終端水路のOD槽内を循環させるとともに汚泥を沈降しないようにする、いわば曝気と撹拌の２つ機能を有する。曝気装置９には、横軸式、縦軸式、スクリュー式、プロペラ式など様々方式があり、水面を撹拌混合したり、空気を送り込むことによって酸素を供給している。
【００２１】
曝気装置９の運転は、事前に設定した曝気スケジュールに従って曝気と非曝気を繰り返すタイマー方式や、溶存酸素濃度（DO）計１０を配置し、DO計の測定データに基づき自動運転を行う方式がある。ここでの自動運転は、例えば、DO設定値を一定にするようにPID調節計で曝気装置９の回転数を制御する方法、または、DO設定値によって曝気と非曝気を自動的に繰り返す方法などがある。
【００２２】
OD槽１の処理水と汚泥は最終沈殿池２に導かれる。最終沈殿池２では、活性汚泥を重力沈降させ、上澄み液を塩素消毒した後、放流管８によって放流する。最終沈殿池２の沈降汚泥は汚泥引き抜き管１１を介し、引き抜かれる。引き抜かれた汚泥の一部は返送ポンプ４によって返送汚泥管５を介してOD槽１へ送られ、残りの汚泥は余剰ポンプ６によって余剰汚泥管７を介して系外へ排出される。返送ポンプ４は、返送汚泥量の制御や、事前に設定したタイマー引き抜きのスケジュールに従って運転される。余剰ポンプ６は、余剰汚泥量の制御や、事前に設定したタイマー引き抜きのスケジュールによって運転される。
【００２３】
図１は本発明の一実施例によるシミュレータ２０の機能構成図である。ここでは、プラントの設計に適用した例について説明する。データ設定装置３０はシミュレーションに必要なデータをキーボード７１、またはマウス７２を用いて入力し、モニタ７３に表示される。
【００２４】
流入条件設定手段３１は流入汚水量及び流入水質の濃度の設定を行う。ここで水質とは、例えば、有機物（易分解性と難分解性）、アンモニア性窒素、全窒素、リン、浮遊物濃度、アルカリ度、溶存酸素、硝酸性窒素、水温などである。データは24時間変動パターンでもよいし、24時間を通して一定値としてもよい。
【００２５】
OD槽形状設定手段３２はOD法に用いられている複数のOD槽の形状からシミュレーション対象となる形状を選択する。OD槽寸法設定手段３３はOD槽形状設定３２で選択されたOD槽に対し、水路の有効長さ、有効幅及び有効水深の寸法データを設定する。流入・流出位置設定手段３４は、流入水３がOD槽１への流入位置、返送汚泥がOD槽１への流入位置、OD槽１から最終沈殿池２への流出位置を、それぞれ、OD槽に設定する。
【００２６】
曝気装置位置設定手段３５は、複数台の曝気装置９についてそれぞれの配置位置を、OD槽に設定する。曝気装置仕様設定手段３６は、曝気装置９の酸素供給性能や撹拌性能を設定する。酸素供給性能は、例えば、総括酸素移動係数、酸素溶解効率などであり、また、撹拌性能は、例えば、速度と回転方向によってOD槽内に与える流速や水流の流れ方向などである。DO計位置設定手段３７はDO制御を行う際のDO計をOD槽内に配置する。
【００２７】
運転条件設定手段３８は曝気装置９の曝気や非曝気の運転方法、DO計１０の設定値、最終沈殿池２からの返送汚泥量、余剰汚泥量などの運転条件設定する。これらデータ設定装置３０から設定されたシミュレーション条件はデータベース４０に格納される。また、モニタ７３に設定内容をグラフィックなどにより表示する。
【００２８】
OD槽分割手段４５は、データベース４０のシミュレーションデータを参照し、所定の方式でOD槽を複数の完全混合槽に分割し、さらに、流入・流出位置設定手段３４にて設定した流入下水および返送汚泥の流入位置、最終沈殿池への流出位置、および、曝気装置９およびDO計１０などの配置位置を分割された個々の完全混合槽に対応させて、これらのデータをデータベース40に格納する。OD槽の分割に関わる所定方式は、プロセスによって異なるが、例えば、流入下水量とOD槽の容量から滞留時間を求め、滞留時間2hr毎に１つの完全混合槽とする方法、水路長さ5m毎に１つの完全混合槽とする方法などが考えられ。
【００２９】
演算装置５０はデータベース４０のシミュレーション条件に基づき、生物モデル演算手段５１と、輸送モデル演算手段５２と、風量（溶存酸素）モデル演算手段５３を用いて、分割された個々の完全混合槽および、OD槽流出、最終沈殿池、返送汚泥、余剰汚泥の水質、汚泥濃度及び流量を計算し、その結果をデータベース４０に格納する。
【００３０】
生物モデル演算手段５１は、生物反応によって変化する水質、及び汚泥濃度の変化を計算する。これらのモデルには国際水環境協会（IAWQ）が発表した活性汚泥モデルNo.2などの公知のモデルを適用してもよいし、化学反応式から作成したモデルや実験的に求めたモデルを適用してもよい。
【００３１】
輸送モデル演算手段５２は、流入汚水量、返送汚泥量、余剰汚泥量、及び曝気装置９がOD槽へ与えた流速に伴う循環汚泥量に基づいてプロセス全体の流量の変化を計算する。風量モデル演算手段５３は曝気装置９から供給される溶存酸素を計算する。これら演算装置５０の計算結果はデータベース４０に格納される。
【００３２】
データ編集判定手段６０は、データベース４０のデータを参照し、データ編集を行い、モニタ７３に出力する。また、データベース４０のデータを参照してプロファイル、トレンドグラフ、計算結果一覧表、除去率、物質収支などの形式でデータ編集、あるいは、データ判定を行い、編集結果を入出力手段７０に送信する。ここでのデータ判定は、例えば、窒素除去率は80%以上に達するかなどである。
【００３３】
以上は、シミュレーション条件を手入力し、机上による計算例の説明である。シミュレーション装置２０の調整が完了した後は、プラント入力手段６３によって流入水量や水質を自動計測し、これらを除去可能な目標水質を維持できる風量、返送汚泥量、余剰汚泥量をシミュレーション計算し、曝気装置９の空気弁の開閉や、ポンプや計測器の制御目標値などを出力し、運転制御に適用しても良い。
【００３４】
図３にＯＤ槽土木構造決定手段の一実施例を示す。OD槽形状設定手段３２とOD槽寸法設定手段３３と流入・流出位置設定手段３４の設定をモニタ７３に表示したときの一例である。
【００３５】
まず、OD法に用いられているOD槽の形状から選択する。長円形、馬蹄形、円心円形などを有し、ここでは長円形を選択している。さらに選択したOD槽に対し、水路の幅、全長、有効水深の寸法と、流入・流出位置を自由に組合せることで、ほとんどのOD法プロセスを表現することができる。
【００３６】
図には、長円形のOD槽に対し、座標による流入と流出の位置を設定した例を示す。座標の定義は、まず、OD槽の形状、水路幅と水路全長に基づき、OD槽の平面図を構築し、OD槽の建設用地に基準点を設けることで、OD槽の任意位置を基準点に対する座標で表現できる。この基準点はどの位置でもよい。このように、X、Y座標の定義で、流入下水および返送汚泥がOD槽への流入位置、OD槽が最終沈殿池への流出位置を正確に定義することができる。また、OD槽における曝気装置9やDO計１０の配置も同様な方法で定義できる。
【００３７】
図４に曝気装置仕様設定手段の実施例を示す。曝気装置仕様設定手段３６は、曝気装置９の酸素供給性能と撹拌性能の設定を行う。撹拌性能とは、曝気装置がOD槽内に与える流速や水流の流れ方向などである。図には、スクリュー型曝気装置の酸素供給性能を曝気風量と酸素溶解効率を用いて定義する例を示す。なお、酸素供給性能定義は、酸素溶解効率の他、総括酸素移動係数や、実験によって求めた検量線を適用してもよい。また、スクリュー型曝気装置の撹拌性能は、スクリューと曝気風量がOD槽に与える平均流速および、撹拌によって生じる流れ方向を定義する。
【００３８】
図４は、OD槽内の混合液が、平均流速25cm/sec、時計回りで流れることを定義する例である。平均流速の設定は直接計測した流速を設定してもよいし、曝気装置の回転数、使用電力、曝気風量などに応じて予め求めた検量線を用いて決定してもよい。また、流れ方向の設定は、例えば、時計回りのように流れ方向を設定してもよいし、流れ方向のシンボルのクリックによって変更してもよい。曝気装置が横軸型や縦軸型のように曝気風量を発生しない場合は、酸素供給性能の定義は例えば回転数と酸素溶解効率の相関から決定し、流速の定義は回転数と流速の相関から決定してもよい。
【００３９】
図５に設定手段３０の設定条件をモニタ７３に表示する一実施例を示す。例えば、OD槽形状設定手段３２とOD槽寸法設定手段３３により、OD槽の形状と、OD槽の水路幅と長さから求めたコーナ部と長方形部の比率に基づきOD槽の縮尺平面図を描画する。さらに流入・流出位置設定手段３４の設定値に基づき、流入下水、返送汚泥及びOD槽から最終沈殿池への配管を表示する。これらの操作で対象とするOD法プロセスの土木構造の概要をグラフィックによって提示できる。
【００４０】
次に、曝気装置位置設定手段３５とDO計位置設定手段３７の設定値に基づき、曝気装置とDO計のシンボルをOD槽に描画する。次に、曝気装置仕様設定手段３６の水路の流れ方向に基づき、流れのシンボルを描画する。このように、OD法のプロセスに対応する条件設定は簡単かつ正確に行うことができる。また、曝気装置およびDO計の位置変更は、図３に示す座標の定義で行ってもよいし、図５に示す各機器の代表シンボルをOD槽内の移動で行ってもよい。
【００４１】
図６にOD槽分割設定手段によるOD槽を分割する実施例を示す。OD槽は隔壁がない無終端水路であるために、OD槽に仮想の基準点を設けることで、無終端水路のOD槽を自由に分割することができる。図には、基準点を先頭に、OD槽を、各コーナ部を１槽とし、各長方形部を均等５槽として計１２槽に分割し、各分割槽に対し、水路の流れ方向順に1〜１２のインデックスを付けた例を示す。もちろん、仮想の基準点はOD槽のどの位置でもよい、基準点の変更は基準点のシンボルをOD槽内で移動で行ってもよいし、座標による指定でもよい。
【００４２】
次に、OD槽に関わるの流入位置、流出位置、機械設備の配置位置を、見出しのインデックスを付けたOD槽に対応させる。図６には、OD槽の１槽目に流入下水を、OD槽の８槽目に返送汚泥を流入し、OD槽の７槽目から最終沈殿池へ流出し、２台の曝気装置はOD槽の４槽目と１０槽目に、DO計は９槽目に配置した例を示す。
【００４３】
演算装置５０では、設定手段３０の設定条件とOD槽分割設定手段４５のデータに基づき、OD槽の個々分割槽の水質および溶存酸素を計算する。
【００４４】
図７にシミュレーション装置によるシミュレーション結果の一実施例を示す。なお、図には、DO設定値を一定にするように調節計で曝気装置９の曝気風量を制御したときの放流水の窒素（T−N）の日平均濃度のトレンドグラフ及び、OD槽のDOプロファイルを示している。
【００４５】
図７(a)の放流水の窒素（T−N）の日平均濃度のトレンドグラフによると、現状の運転を続けると放流水質は悪化し、４日目で放流水T−Nは10mg／L を超えることを予測している。また、放流水のNH4−Nはほぼ0mg／L に近く、OD槽ではほぼ完全硝化されていることから、放流水の水質悪化は、脱窒が不十分になっっていることが分る。
【００４６】
同期間を対象とした、図７(b)のDOプロファイルによると、OD槽において、好気ゾーンと嫌気ゾーンの比率は約２：１であり、脱窒の不完全は嫌気ゾーンの不足によるものを示唆している。この場合、DO設定値を低くすることで、放流水質の改善が予想される。このように、本シミュレーション装置は、OD槽の水質およびDOの濃度勾配を計算し、適切な運転条件を提供することができる。
【００４７】
図８に本シミュレーションの手順の一例を示す。図はDO設定値による自動運転の例を示す。ステップS1では、流入条件設定手段３１によって、流入水量及び流入水質（有機物、アンモニア性窒素、リン、ＳＳ、アルカリ度、水温など）の濃度を設定する。ステップS2では、OD槽形状設定手段３２によって、OD槽の形状を選択設定し、ステップS3では、選択したOD槽に対しOD槽寸法設定手段３３により、水路の幅、水深、長さを設定し、ステップS4では、流入・流出位置設定手段３４によって、OD槽の流入・流出位置を定義する。ステップS2、S3、S4の設定によって、OD槽の土木構造を設定している。
【００４８】
ステップS5では、曝気装置位置設定手段３５によって、曝気装置の配置位置を設定する。ステップS6では、曝気装置仕様設定手段３６によって、曝気装置の酸素供給性能、OD槽に与える流速や流れ方向を設定する。ステップS7では、DO計位置設定手段３７によってDO計の配置位置を設定する。ステップS8では、DO制御の目標値を設定する。
【００４９】
ステップS9では、OD槽分割設定手段３４によってOD槽の分割数と分割状況および、流入下水と返送汚泥の流入槽、最終沈殿池へ流出槽、曝気装置とDO槽の配置位置をそれぞれ、OD槽の分割槽に対応させる。ステップS9の設定は、ユーザが実行しても良いし、ソフトウエアによって自動的に実行しても良い。次に、ステップS10で、これまでの設定条件に基づいてシミュレーションを実行し、OD槽や最終沈殿池出口の水質、OD槽内の汚泥濃度、返送汚泥濃度、余剰汚泥濃度などを計算し、データベースに格納する。
【００５０】
ステップS11では、放流水質が目標値に達しているか判定し、目標値に達していれば、適切な処理が決定できたのでステップS16に進み、目標値に達していなければステップS12に進む。ここでの目標値は、処理場によって項目も値も異なるが、例えば、放流水の全窒素10mg／L 以下、放流水の有機物（BOD）10mg／L 以下、全窒素除去率80％以上、有機物除去率90％以上などが目安とされる。なお、ステップS11の判定を放流水質としたが、省エネの観点から運転時の使用電力量なども、目標値に加えてもよい。
【００５１】
ステップS12ではDOの制御目標値が設定上下限内を全て設定したかを判断し、設定上下限内全て実施と判定すると、ステップS13に移行し、未済みの場合、ステップS8に戻り、再度設定値を変更して、ステップS8、S9、S10、S11、S12の処理を繰り返す。DO設定値を変更しても、放流水質が目標値をクリアできない場合、DO計の配置位置の移動を行い、再度シミュレーションを行う。
【００５２】
ステップS13ではDO計の配置位置がOD槽内に全て移動したかを判断し、全て移動したと判定すると、ステップS14に移行し、未済みの場合、ステップS7に戻り、再度DO計の設定位置を変更して、ステップS7、S8、S9、S10、S11、S12、S13の処理を繰り返す。DO計の配置位置の移動でも放流水質が目標値をクリアできない場合、曝気装置の性能上の限界と判定する。この場合、ステップS14にて、曝気装置の仕様変更可能かを判定し、変更可能の場合、ステップS6に戻り、曝気装置の仕様を再設定し、曝気装置の仕様は変更不可の場合、土木構造上の限界と判定する。
【００５３】
ステップS15では、土木構造の仕様変更可能かを判定し、変更可能の場合、ステップS2に戻り、土木構造上から再設定し、変更不可の場合、シミュレーション終了と判断し、ステップS16に移行する。ステップS16ではデータベース４０のデータを参照し、データ編集やガイダンスをモニタ７３に表示する。ここでのガイダンスは、例えば、ステップS11の処理で、目標値に達する場合の最適な運転条件、目標値に達していない場合の異常原因の究明や対策の選定をモニタ７３に提示する。また、ステップS11、S12、S13、S14、S15の判定は、運転員が実行しても良いし、ソフトウエアによって自動的に実行しても良い。
【００５４】
なお、図８にはDO設定値による自動運転の例を示したが、曝気スケジュールに従って曝気と非曝気を繰り返すタイマー運転でも同様な手順で、最適な曝気スケジュールを提供することができる。
【００５５】
既設のプラントでは、曝気装置の仕様や土木構造を変更することは容易ではない。そのために、本発明による維持管理が有効である。上記実施例に示したシミュレーション手順のように、ステップS1〜S6にて、流入下水の条件と既設プラントの土木構造、曝気装置の仕様を設定し、ステップS7〜S12の繰り返しで最適な運転方法を提供できる。新設処理場、または、既設処理場の改造を設計する場合、ステップS2〜S15にて、処理場建設用地と流入条件に適切したプロセスの土木構造およぶ運転方法を提供できる。
【００５６】
【発明の効果】
本発明によれば、反応槽となるOD槽の形状及び寸法、OD槽の流入・流出位置といった土木構造、曝気装置やDO計の配置位置、曝気装置仕様及び運転条件をさまざまに変えて試行可能なため、処理場建設用地と流入条件に適切したOD法プロセスの設計や運転を支援し、また、OD槽と最終沈殿池における有機物、リン、窒素の挙動から、異常原因の究明や対策の選定には有用な情報を提供できる。
【図面の簡単な説明】
【図１】本発明の一実施例によるシミュレーション装置の機能構成図。
【図２】本発明を適用する活性汚泥プロセスの概略構成図。
【図３】ＯＤ槽の土木構造の設定を示す一画面例。
【図４】曝気装置の仕様設定を示す画面例。
【図５】 OD槽の流速および流れ方向の設定を示す画面例。
【図６】 OD槽の分割手段を示す画面例。
【図７】本実施例によるシミュレーション結果を示すグラフ図。
【図８】本発明の一実施例によるシミュレーションの手順を示すフロー図。
【符号の説明】
１…OD槽、２…最終沈殿池、３…流入水、４…返送ポンプ、５…返送汚泥管、６…余剰ポンプ、７…余剰汚泥管、８…放流管、９…曝気装置、１０…DO計、１１…引き抜き管、２０…シミュレータ、３０…データ設定装置、３１…流入条件設定手段、３２…OD槽形状設定手段、３３…OD槽寸法設定手段、３４…流入・流出位置設定手段、３５…曝気装置位置設定手段、３６…曝気装置仕様設定手段、３７…DO計位置設定手段、３８…運転条件設定手段、４０…データベース、４５…OD槽分割設定手段、５０…演算装置、５１…生物モデル演算手段、５２…輸送モデル演算手段、５３…風量モデル演算手段、６０…データ編集手段、６３…プラント入力手段、７０…入出力装置、７１…キーボード、７２…マウス、７３…モニタ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a simulation apparatus that supports design and operation of an oxidation ditch process.
[0002]
[Prior art]
With the spread of sewage to rural areas, the number of small-scale sewage treatment facilities is increasing. There are remarkably many oxidation ditch (hereinafter abbreviated as OD) methods used in new treatment plants. The OD method is a sewage treatment system that does not have a first sedimentation basin, uses a shallow endless channel with a mechanical aeration device as a biological reaction tank, performs activated sludge treatment under low load conditions, and performs solid separation in the final sedimentation basin. It is.
[0003]
The operation method of the OD method includes continuous operation in which the OD tank is divided into an aerobic zone and an anaerobic zone based on the gradient of dissolved oxygen concentration (DO) in the flow direction, and the aeration apparatus performs aeration and oxygen-free stirring depending on the time. Is intermittent operation.
[0004]
In both the continuous operation and intermittent operation of the OD method, a high nitrogen removal rate cannot be obtained unless the nitrification / denitrification reaction in the OD tank is properly maintained. Such advanced sewage treatment exhibits its performance by appropriately maintaining the habitat of various microorganisms related to organic matter, phosphorus, and nitrogen removal. Until now, there was no method for calculating and presenting complex reaction processes of organic matter and nitrogen, and the design and operation of the OD method depended on experience and intuition. For this reason, unforeseen situations occur with regard to the quality and quantity of influent sewage that has not been experienced, the composition of the biological reaction tank, and the operating conditions, and measures are being taken each time.
[0005]
For example, according to guidelines such as small-scale sewerage planning / design / maintenance management and explanations, the required design method and operation management method can be applied to various advanced treatment methods using the actual values of some of the treatment plants in operation. Although provided, there are many problems when applied to other treatment plants with different inflow water conditions and methods.
[0006]
On the other hand, methods for modeling biological reactions and evaluating the characteristics of activated sludge processes by numerical simulation have been proposed. As an example of a biological reaction model, activated sludge model No. 2 (IAWQ: IAWQ Scientific and Technical Report No. 3, Activated Sludge Model No. 2, 1995) published by the International Water Environment Association (IAWQ) in 1995 overseas. Has been proposed. Also, a method for calculating water quality by a sewage treatment process simulator has been proposed as disclosed in JP-A-10-43787.
[0007]
[Problems to be solved by the invention]
Among the conventional technologies, the activated sludge model No. 2 announced by the International Water Environment Association (IAWQ) only defines the types of microorganisms (fungal bodies) in the activated sludge and models related biological reactions. We do not present a simulator using this model. In order to actually create an activated sludge process simulator, in addition to the proposed biological reaction model, at least the fluid model of the OD tank, the fluid model of the final sedimentation basin, and the oxygen supply model by the aeration device are required. This cannot be realized without numerical calculations combining the quality and quantity of sewage, the civil engineering structure of the OD tank, the air supply conditions of the aeration equipment, the return and surplus operating conditions, etc.
[0008]
In addition, in the sewage treatment simulator disclosed in Japanese Patent Laid-Open No. 10-43787, when the OD tank is divided into a plurality of complete mixing tanks, the civil engineering structure of the different OD tanks for each plant and the setting method of the flow rate given to the OD tank by the aeration apparatus Is not described at all, and the concept of mass balance alone cannot cope with various fluid models of OD tanks. Due to restrictions on the construction site and the shape of the OD tank, the inflow sewage and return sludge flow into the OD tank and the outflow position from the OD tank to the final sedimentation basin vary from plant to plant. The inflow position and outflow position of this OD tank directly affect the transport of the OD tank and affect the quality of treated water. The OD tank is a biological reaction tank that does not have a partition wall, but the water quality and dissolved oxygen cause a concentration gradient in the flow direction by flow, diffusion, and biological reaction.
[0009]
As a method for expressing this concentration gradient, it is effective to divide a plurality of OD tanks into complete mixing tanks and calculate the water quality and dissolved oxygen of each divided tank. In order to accurately and quantitatively calculate the water quality and dissolved oxygen of each division tank, the inflow / outflow positions related to the transportation of various water qualities and the position of the aeration device are defined corresponding to each division tank. In addition, the water quality and dissolved oxygen concentration gradient in the OD tank cannot be calculated unless the amount and quality of the water related to inflow and outflow, the dissolved oxygen supplied by the aeration device, and the flow rate applied to the OD tank are accurately defined. . In addition, in the case of automatic operation based on the DO setting value of the aeration apparatus, the dissolved oxygen concentration gradient in the OD tank cannot be calculated unless the arrangement relationship between the aeration apparatus and the DO meter is accurately defined.
[0010]
Therefore, in the OD tank, the simulator for calculating the mass balance of the flow expresses the shape of the OD tank, the dimensions of the OD tank, the civil engineering structure such as the inflow / outflow of the OD tank, and the arrangement position of the aeration device and the DO meter. In addition to the means that can be used, it is indispensable that the aeration apparatus can express the flow velocity given to the OD tank and the flow direction in the OD tank, but this is not taken into account in the sewage treatment simulator disclosed in JP-A-10-43787.
[0011]
On the other hand, for nitrogen removal by the OD method, denitrification reaction in anoxic zone (continuous operation) or anoxic stirring time zone (intermittent operation) and aerobic zone (continuous operation) or aeration time zone (intermittent operation) Since a high nitrogen removal rate cannot be obtained unless the two steps of nitrification reaction are performed in good balance, the structure of the OD tank, the length of the OD tank, the civil engineering structure such as inflow and outflow of the OD tank, and the aeration equipment The combination is very important.
[0012]
In addition, since the mixed solution circulates in the OD tank in a short time, the water quality in the OD tank and the flow of dissolved oxygen must be fully taken into consideration. For example, DO supplied from the aeration apparatus circulates in the OD tank while being consumed by the microbial reaction. From the aeration device, DO gradually decreases in the flow direction, and in the case of continuous operation, the concentration gradient of DO becomes an aerobic zone and an anoxic zone, and directly affects nitrification and denitrification. As described above, in the biological reaction of nitrification and denitrification, the limit of nitrogen removal performance is determined depending on the arrangement position and operating conditions of the aeration apparatus. Therefore, in designing and operating the OD method, it is necessary to determine the civil structure by numerical simulation based on biological reactions, and then to examine appropriate operating conditions. The optimal operating process can only be determined by repeatedly trying this procedure.
[0013]
Therefore, the simulator for driving support has inflow conditions, the shape of the OD tank, the dimensions of the OD tank, the civil engineering structure such as the inflow / outflow of the OD tank, the arrangement position of the mechanical equipment such as the aeration apparatus and measuring instrument, and the operation. Means that can easily change the conditions are indispensable, but no consideration is given to the sewage treatment simulator of JP-A-10-43787.
[0014]
The present invention was made to solve the above-mentioned problems of the prior art, the structure of the OD tank, the size of the OD tank, the civil structure such as the inflow position and the outflow position with respect to the OD tank, the position of the aeration apparatus and the DO meter, The purpose is to provide a sewage simulation apparatus that satisfies the target discharge water condition by setting the flow velocity and flow direction given to the OD tank by the aeration apparatus and various operating conditions.
[0015]
[Means for Solving the Problems]
The present invention relates to an apparatus for simulating an activated sludge treatment process of an endless water channel, means for setting the shape of the biological reaction tank, and means for setting dimensions such as the total length, water channel width, and water depth of the biological reaction tank of the set shape. , Means for setting an inflow position and an outflow position for the biological reaction tank, means for setting an arrangement position of the aeration apparatus and the DO meter in the biological reaction tank, means for setting the specifications of the aeration apparatus, and operating conditions It is characterized by having means for setting.
[0016]
In addition, the means for setting the shape of the OD tank is selected from the shapes of a plurality of biological reaction tanks usually used in the OD method, at least oval, horseshoe shape, and circular shape, and the total length and width of the water channel of the OD tank By combining the water depth, it is possible to represent the activated sludge treatment process of most endless watercourses.
[0017]
In addition, since the inflow position of inflow sewage and return sludge and the outflow position of the final sedimentation basin can be clearly expressed for the OD tank with the above-mentioned shape and dimensions, the civil structure of the OD process can be defined.
[0018]
Further, the means for setting the aeration apparatus specifications can define the oxygen supply performance of the aeration apparatus, the flow rate and the flow direction given to the biological reaction tank by the stirring of the aeration apparatus.
[0019]
According to the present invention, the shape of the OD tank, the dimensions of the OD tank, the civil engineering structure such as the inflow position and the outflow position with respect to the OD tank, the position of the aeration apparatus and the DO meter, the flow rate and flow direction given to the OD tank by the aeration apparatus, and various By setting the operating conditions freely, it became possible to study the optimization of the OD process.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 shows an activated sludge process for an endless channel applying the simulation of the present invention. The figure shows an example of an oval oxidation ditch method. Inflow sewage containing a substrate such as organic matter, nitrogen, and phosphorus is sent to the OD tank 1 as inflow water 3. Inflow water 3 and return sludge (activated sludge) from the return sludge pipe 5 flow into the OD tank 1, and mixing and stirring are performed. The OD tank 1 is usually provided with a plurality of aeration devices 9. The aeration device 9 supplies oxygen necessary for the activated sludge reaction in the OD tank 1 and also mixes and stirs the activated sludge in the OD tank 1 and the influent water 3 to give a flow rate to the mixed liquid to provide the inside of the OD tank in the endless water channel. It has two functions of aeration and agitation so that sludge is not circulated and sludge is not settled. There are various types of aeration devices 9 such as a horizontal axis type, a vertical axis type, a screw type, and a propeller type, and oxygen is supplied by stirring and mixing the water surface or sending air.
[0021]
The operation of the aeration apparatus 9 includes a timer system that repeats aeration and non-aeration in accordance with a preset aeration schedule, and a system in which a dissolved oxygen concentration (DO) meter 10 is arranged and automatic operation is performed based on measurement data of the DO meter. . The automatic operation here is, for example, a method of controlling the rotation speed of the aeration apparatus 9 with a PID controller so that the DO setting value is constant, or a method of automatically repeating aeration and non-aeration according to the DO setting value. There is.
[0022]
The treated water and sludge in the OD tank 1 are guided to the final sedimentation tank 2. In the final sedimentation basin 2, the activated sludge is gravity settled and the supernatant liquid is sterilized with chlorine, and then discharged through the discharge pipe 8. The sedimentation sludge in the final sedimentation basin 2 is extracted through the sludge extraction pipe 11. Part of the extracted sludge is sent to the OD tank 1 by the return pump 4 through the return sludge pipe 5, and the remaining sludge is discharged out of the system through the excess sludge pipe 7 by the surplus pump 6. The return pump 4 is operated in accordance with control of the amount of returned sludge and a preset timer pull-out schedule. The surplus pump 6 is operated according to the control of the surplus sludge amount and the timer withdrawal schedule set in advance.
[0023]
FIG. 1 is a functional configuration diagram of a simulator 20 according to an embodiment of the present invention. Here, an example applied to plant design will be described. The data setting device 30 inputs data necessary for the simulation using the keyboard 71 or the mouse 72 and is displayed on the monitor 73.
[0024]
The inflow condition setting means 31 sets the inflow sewage amount and the inflow water quality concentration. Here, the water quality is, for example, organic matter (easy degradability and hardly degradability), ammonia nitrogen, total nitrogen, phosphorus, suspended solid concentration, alkalinity, dissolved oxygen, nitrate nitrogen, water temperature, and the like. The data may be a 24-hour variation pattern or a constant value throughout the 24-hour period.
[0025]
The OD tank shape setting means 32 selects a shape to be simulated from the shapes of a plurality of OD tanks used in the OD method. The OD tank dimension setting means 33 sets the dimension data of the effective length, effective width and effective water depth of the water channel for the OD tank selected in the OD tank shape setting 32. The inflow / outflow position setting means 34 is configured such that the inflow water 3 flows into the OD tank 1, the return sludge flows into the OD tank 1, and the outflow position from the OD tank 1 to the final sedimentation tank 2. Set to.
[0026]
The aeration apparatus position setting means 35 sets the arrangement positions of the plurality of aeration apparatuses 9 in the OD tank. The aeration apparatus specification setting means 36 sets the oxygen supply performance and agitation performance of the aeration apparatus 9. The oxygen supply performance is, for example, the overall oxygen transfer coefficient, the oxygen dissolution efficiency, and the like, and the stirring performance is, for example, the flow velocity given to the OD tank or the flow direction of the water flow depending on the speed and rotation direction. The DO meter position setting means 37 places a DO meter for performing DO control in the OD tank.
[0027]
The operation condition setting means 38 sets operation conditions such as the aeration and non-aeration operation methods of the aeration apparatus 9, the set value of the DO meter 10, the return sludge amount from the final sedimentation basin 2, and the excess sludge amount. The simulation conditions set from these data setting devices 30 are stored in the database 40. Further, the setting contents are displayed on the monitor 73 by graphics or the like.
[0028]
The OD tank dividing means 45 refers to the simulation data of the database 40, divides the OD tank into a plurality of complete mixing tanks by a predetermined method, and further, the inflow sewage and return sludge set by the inflow / outflow position setting means 34 These data are stored in the database 40 so that the inflow position, the outflow position to the final sedimentation tank, and the arrangement positions of the aeration apparatus 9 and the DO meter 10 correspond to the divided individual complete mixing tanks. The predetermined method related to the division of the OD tank varies depending on the process. For example, the residence time is obtained from the amount of incoming sewage and the capacity of the OD tank, and one complete mixing tank is obtained every 2 hours of residence time, and the channel length is 5 m. A method of using one complete mixing tank can be considered.
[0029]
Based on the simulation conditions of the database 40, the computing device 50 uses the biological model computing means 51, the transport model computing means 52, and the air volume (dissolved oxygen) model computing means 53 to divide each complete mixing tank and OD The tank outflow, final sedimentation basin, return sludge, excess sludge water quality, sludge concentration and flow rate are calculated, and the results are stored in the database 40.
[0030]
The biological model calculation means 51 calculates the water quality that changes due to the biological reaction and the change in the sludge concentration. Known models such as activated sludge model No. 2 published by the International Water Environment Association (IAWQ) may be applied to these models, or models created from chemical reaction formulas or models obtained experimentally may be applied. May be.
[0031]
The transport model calculating means 52 calculates the change in the flow rate of the entire process based on the inflow sludge amount, the return sludge amount, the surplus sludge amount, and the circulating sludge amount accompanying the flow rate given to the OD tank by the aeration apparatus 9. The air volume model calculating means 53 calculates dissolved oxygen supplied from the aeration device 9. The calculation results of these arithmetic devices 50 are stored in the database 40.
[0032]
The data editing determination unit 60 refers to the data in the database 40, performs data editing, and outputs the data to the monitor 73. In addition, referring to data in the database 40, data editing or data determination is performed in a format such as a profile, a trend graph, a calculation result list, a removal rate, and a material balance, and the editing result is transmitted to the input / output means 70. The data determination here is, for example, whether the nitrogen removal rate reaches 80% or more.
[0033]
The above is an explanation of an example of calculation on a desk by manually inputting simulation conditions. After the adjustment of the simulation apparatus 20 is completed, the inflow water amount and the water quality are automatically measured by the plant input means 63, and the air volume, the return sludge amount, and the excess sludge amount that can maintain the target water quality that can remove them are simulated and aerated. The air valve of the device 9 may be opened and closed, or a control target value of a pump or measuring instrument may be output and applied to operation control.
[0034]
FIG. 3 shows an embodiment of the OD tank civil engineering structure determining means. This is an example when the settings of the OD tank shape setting means 32, the OD tank size setting means 33, and the inflow / outflow position setting means 34 are displayed on the monitor 73.
[0035]
First, the shape of the OD tank used in the OD method is selected. It has an oval, a horseshoe shape, a circle with a circular center, etc., and an oval is selected here. Furthermore, for any selected OD tank, most of the OD process can be expressed by freely combining the dimensions of the water channel width, total length, effective water depth, and inflow / outflow positions.
[0036]
The figure shows an example in which inflow and outflow positions are set by coordinates for an oval OD tank. To define the coordinates, first, based on the shape of the OD tank, the channel width, and the total length of the channel, a plan view of the OD tank is constructed, and a reference point is set on the construction site of the OD tank. Can be expressed in coordinates. This reference point may be at any position. In this way, the definition of the X and Y coordinates makes it possible to accurately define the inflow position of inflow sewage and return sludge to the OD tank, and the outflow position of the OD tank to the final sedimentation basin. Further, the arrangement of the aeration apparatus 9 and the DO meter 10 in the OD tank can be defined in a similar manner.
[0037]
FIG. 4 shows an embodiment of the aeration apparatus specification setting means. The aeration apparatus specification setting means 36 sets the oxygen supply performance and the agitation performance of the aeration apparatus 9. The agitation performance refers to the flow rate given to the OD tank by the aeration apparatus and the flow direction of the water flow. The figure shows an example in which the oxygen supply performance of the screw type aeration apparatus is defined using the aeration air volume and the oxygen dissolution efficiency. In addition to the oxygen dissolution efficiency, the oxygen supply performance definition may apply a general oxygen transfer coefficient or a calibration curve obtained by experiment. In addition, the stirring performance of the screw type aeration apparatus defines an average flow rate given to the OD tank by the screw and the amount of aeration air and a flow direction generated by the stirring.
[0038]
FIG. 4 is an example of defining that the liquid mixture in the OD tank flows clockwise at an average flow rate of 25 cm / sec. The average flow velocity may be set by directly measuring the flow velocity, or may be determined using a calibration curve obtained in advance according to the number of rotations of the aeration apparatus, power used, aeration air volume, and the like. In addition, the flow direction may be set, for example, in the clockwise direction, or may be changed by clicking a flow direction symbol. When the aeration apparatus does not generate aeration air volume as in the horizontal axis type or the vertical axis type, the oxygen supply performance definition is determined from the correlation between the rotation speed and the oxygen dissolution efficiency, for example, and the flow velocity definition is the correlation between the rotation speed and the flow velocity. May be determined from
[0039]
FIG. 5 shows an embodiment in which the setting condition of the setting means 30 is displayed on the monitor 73. For example, the OD tank shape setting means 32 and the OD tank size setting means 33 are used to calculate a scale plan view of the OD tank based on the ratio of the corner portion and the rectangular portion obtained from the shape of the OD tank and the channel width and length of the OD tank. draw. Further, based on the set value of the inflow / outflow position setting means 34, the inflow sewage, return sludge, and piping from the OD tank to the final sedimentation basin are displayed. An outline of the civil engineering structure of the OD process targeted by these operations can be presented graphically.
[0040]
Next, based on the setting values of the aeration apparatus position setting means 35 and the DO meter position setting means 37, the symbols of the aeration apparatus and the DO meter are drawn in the OD tank. Next, a flow symbol is drawn based on the flow direction of the water channel of the aeration apparatus specification setting means 36. Thus, the condition setting corresponding to the process of the OD method can be performed easily and accurately. Further, the position change of the aeration apparatus and the DO meter may be performed by the definition of coordinates shown in FIG. 3, or the representative symbol of each device shown in FIG. 5 may be performed by movement in the OD tank.
[0041]
FIG. 6 shows an embodiment in which the OD tank is divided by the OD tank division setting means. Since the OD tank is an endless water channel having no partition wall, the OD tank of the endless water channel can be freely divided by providing a virtual reference point in the OD tank. In the figure, the reference point is the top, the OD tank is divided into 12 tanks with each corner part as 1 tank and each rectangular part as 5 equal tanks. An example with 12 indexes is shown. Of course, the virtual reference point may be at any position in the OD tank, and the reference point may be changed by moving the symbol of the reference point within the OD tank, or may be designated by coordinates.
[0042]
Next, the inflow position and outflow position related to the OD tank, and the arrangement position of the mechanical equipment are made to correspond to the OD tank with the index of the heading. In FIG. 6, the inflow sewage is supplied to the first tank of the OD tank, the return sludge is supplied to the eighth tank of the OD tank, and the OD tank is discharged from the seventh tank to the final sedimentation basin. An example in which the DO meter is arranged in the 9th tank is shown in the 4th and 10th tanks.
[0043]
The computing device 50 calculates the water quality and dissolved oxygen of the individual division tanks of the OD tank based on the setting conditions of the setting means 30 and the data of the OD tank division setting means 45.
[0044]
FIG. 7 shows an example of the simulation result by the simulation apparatus. The figure shows a trend graph of the daily average concentration of nitrogen (T-N) in the effluent when the aeration air volume of the aeration device 9 is controlled by a controller so that the DO set value is constant, and the OD tank Shows the DO profile.
[0045]
According to the trend graph of daily average concentration of nitrogen (T-N) in the effluent of Fig. 7 (a), the quality of the effluent deteriorates when the current operation is continued, and the effluent TN is 10 mg / L on the fourth day. Is expected to exceed. In addition, NH4-N in the discharged water is close to 0 mg / L and is almost completely nitrified in the OD tank, so it can be understood that denitrification is insufficient for the deterioration of the water quality of the discharged water.
[0046]
According to the DO profile of Fig. 7 (b) for the same period, the ratio of aerobic zone to anaerobic zone is about 2: 1 in the OD tank, and incomplete denitrification is due to lack of anaerobic zone. It suggests. In this case, lowering the DO setting value is expected to improve the quality of discharged water. As described above, the simulation apparatus can calculate the water quality of the OD tank and the DO concentration gradient, and provide appropriate operating conditions.
[0047]
FIG. 8 shows an example of the procedure of this simulation. The figure shows an example of automatic operation by DO set value. In step S1, the inflow condition setting means 31 sets the inflow water amount and the concentration of the inflow water quality (organic matter, ammoniacal nitrogen, phosphorus, SS, alkalinity, water temperature, etc.). In step S2, the shape of the OD tank is selected and set by the OD tank shape setting means 32. In step S3, the width, depth, and length of the water channel are set by the OD tank size setting means 33 for the selected OD tank. In step S4, the inflow / outflow position of the OD tank is defined by the inflow / outflow position setting means 34. The civil engineering structure of the OD tank is set according to the settings of steps S2, S3, and S4.
[0048]
In step S5, the arrangement position of the aeration apparatus is set by the aeration apparatus position setting means 35. In step S6, the aeration apparatus specification setting means 36 sets the oxygen supply performance of the aeration apparatus, the flow rate given to the OD tank, and the flow direction. In step S7, the DO meter position setting means 37 sets the position of the DO meter. In step S8, a target value for DO control is set.
[0049]
In step S9, the number of OD tanks divided by the OD tank division setting means 34 and the division status, the inflow tank of inflow sewage and return sludge, the outflow tank to the final sedimentation basin, the arrangement position of the aeration apparatus and the DO tank, respectively. It corresponds to the division tank. The setting in step S9 may be executed by the user or automatically by software. Next, in step S10, simulation is performed based on the setting conditions so far, and the water quality at the OD tank and final sedimentation basin outlet, sludge concentration in the OD tank, return sludge concentration, excess sludge concentration, etc. are calculated, and the database is calculated. To store.
[0050]
In step S11, it is determined whether the discharged water quality has reached the target value. If the target value has been reached, appropriate processing has been determined, and the process proceeds to step S16. If the target value has not been reached, the process proceeds to step S12. The target value here varies depending on the treatment plant, but for example, the total nitrogen of discharged water is 10 mg / L or less, the organic matter (BOD) of discharged water is 10 mg / L or less, the total nitrogen removal rate is 80% or more, the organic matter A removal rate of 90% or more is a standard. In addition, although the determination of step S11 is the discharged water quality, the amount of power used during operation may be added to the target value from the viewpoint of energy saving.
[0051]
In step S12, it is determined whether the DO control target value has been set within the upper and lower limits. If it is determined that all of the upper and lower limits have been set, the process proceeds to step S13. If not, the process returns to step S8 and is set again. The value is changed, and the processes of steps S8, S9, S10, S11, and S12 are repeated. If the discharged water quality cannot clear the target value even if the DO setting value is changed, move the position of the DO meter and perform the simulation again.
[0052]
In step S13, it is determined whether all the DO meter placement positions have moved into the OD tank.If it is determined that all have moved, the process proceeds to step S14. Is changed, and the processes of steps S7, S8, S9, S10, S11, S12, and S13 are repeated. If the discharged water quality does not clear the target value even if the DO meter is moved, it is determined that the performance limit of the aeration device. In this case, in step S14, it is determined whether or not the specification of the aeration apparatus can be changed.If the specification can be changed, the process returns to step S6, the specification of the aeration apparatus is reset, and the specification of the aeration apparatus cannot be changed. Judge as the upper limit.
[0053]
In step S15, it is determined whether or not the specification of the civil engineering structure can be changed. If the civil engineering structure can be changed, the process returns to step S2, and the setting is reset from the civil engineering structure. In step S16, the data in the database 40 is referred to, and data editing and guidance are displayed on the monitor 73. In this guidance, for example, in the process of step S11, optimum operating conditions when the target value is reached, investigation of the cause of abnormality when the target value is not reached, and selection of countermeasures are presented on the monitor 73. Further, the determination of steps S11, S12, S13, S14, and S15 may be performed by an operator or may be automatically performed by software.
[0054]
Although FIG. 8 shows an example of automatic operation based on the DO set value, an optimal aeration schedule can be provided by a similar procedure in timer operation that repeats aeration and non-aeration according to the aeration schedule.
[0055]
In the existing plant, it is not easy to change the specifications of the aeration apparatus and the civil engineering structure. Therefore, the maintenance management according to the present invention is effective. Like the simulation procedure shown in the above example, in steps S1 to S6, the inflow sewage conditions, the civil engineering structure of the existing plant, and the specifications of the aeration equipment are set, and the optimum operation method is repeated by repeating steps S7 to S12. Can be provided. When designing a new treatment plant or a modification of an existing treatment plant, it is possible to provide a civil structure and an operation method of a process suitable for the treatment plant construction site and inflow conditions in steps S2 to S15.
[0056]
【The invention's effect】
According to the present invention, it is possible to experiment by changing the shape and size of the OD tank as the reaction tank, the civil engineering structure such as the inflow / outflow position of the OD tank, the position of the aeration apparatus and DO meter, the specifications of the aeration apparatus and the operating conditions. Therefore, it supports the design and operation of the OD process process suitable for the land for the treatment plant construction and the inflow conditions, and investigates the cause of abnormality and selects countermeasures from the behavior of organic matter, phosphorus and nitrogen in the OD tank and final sedimentation basin. Can provide useful information.
[Brief description of the drawings]
FIG. 1 is a functional configuration diagram of a simulation apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of an activated sludge process to which the present invention is applied.
FIG. 3 is an example of a screen showing the setting of the civil engineering structure of the OD tank.
FIG. 4 is a screen example showing specification settings of an aeration apparatus.
FIG. 5 is a screen example showing setting of the flow rate and flow direction of the OD tank.
FIG. 6 is a screen example showing a dividing means of the OD tank.
FIG. 7 is a graph showing a simulation result according to the present embodiment.
FIG. 8 is a flowchart showing a simulation procedure according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... OD tank, 2 ... Final sedimentation basin, 3 ... Inflow water, 4 ... Return pump, 5 ... Return sludge pipe, 6 ... Surplus pump, 7 ... Surplus sludge pipe, 8 ... Discharge pipe, 9 ... Aeration apparatus, 10 ... DO meter, 11 ... extraction tube, 20 ... simulator, 30 ... data setting device, 31 ... inflow condition setting means, 32 ... OD tank shape setting means, 33 ... OD tank size setting means, 34 ... inflow / outflow position setting means, 35 ... Aeration device position setting means, 36 ... Aeration device specification setting means, 37 ... DO meter position setting means, 38 ... Operating condition setting means, 40 ... Database, 45 ... OD tank division setting means, 50 ... Calculation device, 51 ... Biological model calculation means, 52... Transport model calculation means, 53... Airflow model calculation means, 60... Data editing means, 63 ... plant input means, 70 ... input / output device, 71 ... keyboard, 72 ... mouse, 73 ... monitor.

Claims

In the design support device for the oxidation ditch (OD) process using the endless waterway as the biological reaction layer,
An inflow condition setting means for setting the concentration of the inflow volume of sewage inflow water, inflow and to set the reactor size setting means for setting the size data of the biological reactor, the outflow position and the inflow position over the previous SL bioreactor an outflow position setting means, before SL and aerator position setting means for setting the position of the aerator of the biological reaction tank and aeration specification setting means for setting a dissolved oxygen supply capacity of the aeration device, the biological reaction tank A DO meter position setting means for setting the position of the DO meter, and a data setting device including :
Biological reaction tank division setting means for virtually dividing the biological reaction tank into a plurality of division tanks using the set values set by the setting means of the data setting device and the set values of the upper and lower limits of the dissolved oxygen concentration A model calculation device for calculating the water quality of the biological reaction tank after the inflow tank of the inflow sewage and the return sludge, the outflow tank to the final sedimentation basin, the arrangement position of the aeration apparatus corresponding to the division tank ,
The model calculation device has a biological model calculation means, a transport model calculation means, and an airflow model calculation means , and calculates water quality of the divided individual division tanks, outflow tanks, final sedimentation basins, return sludge , It is determined whether the discharged water quality from the final sedimentation basin has reached the target value of total nitrogen or the total nitrogen removal rate. If the target value has not been reached, resetting of the DO meter position, the specification of the aeration apparatus A design support apparatus for an oxidation ditch (OD) method process, wherein resetting or resetting of dimension data of the biological reaction tank is performed, and water quality of the biological reaction tank is calculated .

The biological reaction tank according to claim 1, further comprising a reaction tank shape setting means for setting a shape of the biological reaction tank, and among the shapes of the biological reaction tanks employed in the activated sludge treatment process of an endless water channel, Design support device for the oxidation ditch (OD) process characterized by being selectable from a circle.

The oxidation ditch (OD) method according to claim 1, wherein the inflow / outflow position setting means sets an inflow position of inflow sewage and return sludge and an outflow position to the final sedimentation basin with respect to the biological reaction tank. Process design support device.

2. The oxidation ditch (OD) method process according to claim 1, wherein the aeration specification setting means sets an oxygen supply performance of the aeration apparatus and a flow rate and a flow direction given to the biological reaction tank by stirring of the aeration apparatus. Design support device.