JP3658543B2 - Advanced water treatment method and treatment system - Google Patents

Description

このように、水質悪化時、オゾンと生物活性炭処理を用いた浄水高度処理においても、総トリハロメタンは水道水の水質基準値１００μｇ／Ｌ（０．１ｍｇ／Ｌ）を越えてしまう可能性が非常に大きかった。
【００１７】
また、渇水時などに水質が悪化した場合や、冬季など生物活性が低下した場合には、ＢＡＣ処理水中に残存する有機物濃度（ＴＯＣ）が比較的高濃度になり、またアンモニア性窒素が完全には除去できない場合があることなどから、後段の後塩素処理工程６における塩素注入率が高くなることがあった。
【００１８】
ＢＡＣ処理水にアンモニア性窒素が残存していると、不連続点前塩素処理にてアンモニア性窒素の除去が行われるため、消毒および殺菌（残留塩素濃度維持）以外に消費される塩素量が増加し、塩素は有機物とも反応するため、塩素注入率増加の原因となっていた。
【００１９】
塩素とアンモニア性窒素との理論反応量は、１：７．６であるが、その他の共存物質にも消費されるため、実際の塩素注入率はアンモニア性窒素量の１０倍以上必要となることがほとんどである。
この結果、残存する有機物と消毒用塩素との接触量（反応量）が増加し、有害なトリハロメタンや有機塩素化合物の生成量が増加していた。
【００２０】
一方、オゾン処理において、渇水時などに水質が悪化には有機物濃度の他に、鉄やマンガンなどの無機物濃度も増加する傾向があり、有機物に消費されるオゾン量に加え、鉄やマンガンなどを酸化除去するためのオゾン量も増加し、オゾン注入率が増加する原因になっていた。
【００２１】
また、オゾン処理工程４における除去対象物質が増加すると、共存物質の競合反応が複雑となり、最適なオゾン注入制御が困難になり、オゾン注入率の過不足が生じる場合があった。
【００２２】
オゾン注入制御は原水（被処理水）の水質が安定かつ比較的良好な場合、問題が少ないが、原水の水質変動や水質悪化時にはオゾン入率の過不足により、以下に示すような問題点が存在している。
【００２３】
▲１▼オゾン注入率が不足の場合
オゾン注入率が不足していても有機物濃度が低い場合、後段のＢＡＣ処理工程５にて、臭気成分やトリハロメタン前駆物質の除去・低減はある程度可能である。しかし、それでは有機物の生物分解性はあまり向上しないため、ＢＡＣ処理工程５への負荷が増大し、ＢＡＣ処理の許容量を越えた臭気成分や有機物（トリハロメタン前駆物質）が流入した場合、処理しきれずに浄水中へ残存してしまう可能性がある。
【００２４】
さらに、従来不連続点前塩素処理にて除去していた鉄イオン（Ｆｅ²⁺、Ｆｅ³⁺）やマンガンイオン（Ｍｎ²⁺）は、高度処理ではオゾン処理にて酸化、ＢＡＣ処理にて捕捉・除去しているが、オゾンの注入率が不足していると、鉄イオンやマンガンイオンは完全に酸化されず、ＢＡＣ処理水中へ流出し、後塩素処理工程６により二酸化マンガン（ＭｎＯ₂）に酸化され、マンガン濃度の２３０〜３００倍程度の色度を発現する可能性がある。
【００２５】
▲２▼オゾン注入率が適正な場合
オゾン注入率が適正に行われている場合、有機物の成分分解性はある程度向上しＢＡＣ処理にかかる負荷は上記▲１▼の場合に比較して多少緩和される。ただし、原水中の有機物濃度上昇などＢＡＣ処理の許容量を越えた場合などは、上記▲１▼と同様に臭気成分や有機物が、浄水に残存してしまう可能性がある。
【００２６】
一方、鉄・マンガンに関してはオゾン処理工程４にて、オゾンの注入率が適正に行われている場合、鉄は水酸化物として、マンガンは不溶性の二酸化マンガンとして酸化・析出され、ＢＡＣ処理工程５で捕捉される。
【００２７】
２価のマンガンイオンは、下記（２．１）式及び（２．２）式で示されるように、オゾンにより４価に酸化され、不溶性の二酸化マンガンとなる。
Ｍｎ⁺²＋Ｏ₃＋Ｈ₂Ｏ→Ｍｎ⁺⁴＋Ｏ₂ＣＯＨ^- （２．１）
Ｍｎ⁺⁴＋４ＯＨ^-→ＭｎＯ₂↓＋Ｈ₂Ｏ （２．２）
次に、鉄の酸化反応を下記（２．３）式、（２．４）式に示す。２価の鉄イオンはオゾン酸化を受け３価となり水和、凝集、沈殿する。
Ｆｅ⁺²＋Ｏ₃＋Ｈ₂Ｏ→Ｆｅ⁺³＋Ｏ₂＋２（ＯＨ^-） （２．３）
Ｆｅ⁺³＋３Ｈ₂Ｏ→Ｆｅ（ＯＨ）₃↓＋３Ｈ⁺ （２．４）
しかし、有機物や鉄・マンガンは、お互いにオゾン注入率に影響を及ぼすため、水質悪化時には、オゾン注入率を適正量に制御することは困難な場合がある。
【００２８】
▲３▼オゾン注入率が過剰の場合
オゾン注入率が過剰の場合、オゾン処理水の溶存オゾン濃度が高くなり、ＢＡＣの微生物にダメージを与えたり、活性炭の消耗を早めることがある。この場合、ＢＡＣの処理機能が低下するため、原水中の有機物濃度上昇などＢＡＣ処理の許容量を越えた場合など、上記▲１▼と同様に臭気成分や有機物が除去しきれずに、浄水中へ流出してしまう可能性がある。
【００２９】
さらに、マンガンイオンはオゾン処理により一旦、不溶性の二酸化マンガンに酸化されるが、下記（２．５）式で示すように、オゾンの過剰酸化により溶解性の７価の過マンガン酸イオン（ＭｎＯ₄ ^-）に変化してピンク色に着色する。
【００３０】

過マンガン酸イオンはＢＡＣ処理にて還元され、二酸化マンガンに戻るが、ＢＡＣ本来の処理機能ではなく、また過マンガン酸イオン自体強い酸化剤であり、ＢＡＣの微生物にダメージを与え、さらにＢＡＣ処理の機能が低下することがあった。
【００３１】
鉄、マンガンは浄水中に残存していると、金気臭、赤水、黒水等の異臭味や着色障害の原因となるため効率的な除去が必要である。水質基準では、鉄は０．３ｍｇ／Ｌ以下、マンガンは０．０５ｍｇ／Ｌ以下をそれぞれ基準値としている。さらに、さらなる水質の向上を目的とした快適水質項目では、マンガンは０．０１ｍｇ／Ｌ以下を目標値としている。
【００３２】
また、過剰なオゾン注入率のため発生量が不経済となり、排オゾン量の増加から、排オゾン処理装置（図示せず）におけるオゾン分解触媒や活性炭への負荷が大きくなるため、排オゾン処理のためのランニングコストが増大することがある。
【００３３】
さらに、ＢＡＣ処理工程５で除去しきれずに浄水中に残存した有機物は、残留塩素が存在する間は消毒・殺菌効果が持続するため、細菌等の微生物が繁殖する危険はないが、夏期など水温が高くなる時期や長期配管内等で滞留した場合は残留塩素が消失し、浄水中に残存する有機物が微生物の栄養源となる生物資化有機物（ＡＯＣ）であるため、配水管内や受水槽等において細菌等の繁殖原因となる懸念があった。
【００３４】
本発明は、上記状況に鑑みてなされたものであり、原水水質に対応してＢＡＣ処理とＧＡＣ処理のフロー変更を行い、それぞれの処理の長所を生かした高度浄水処理方法を提供することを目的とするものである。
【００３５】
さらに、本発明は水質悪化時におけるオゾン過剰注入防止の観点から、ＧＡＣ処理時には鉄やマンガンの酸化処理を中塩素処理にて行い、また、ＧＡＣ処理ではアンモニア性窒素の除去ができないため、着水井にハニコームチューブ（充填剤）を設置して生物酸化処理効能を持たせ、アンモニア性窒素の除去を行うことにより、幅広い原水水質に対応した高度浄水処理方法を提供することを目的とするものである。
【００３６】
【課題を解決するための手段】
上記目的を達成するために、請求項１記載の高度浄水処理方法は、原水の有機物の指標となる有機物濃度を水質センサーで計測した後、前記原水をオゾン処理し、さらにこのオゾン処理された原水を前記水質センサーの計測値に基づいて生物活性炭処理または粒状活性炭処理して高度浄水とする高度浄水処理方法において、前記水質センサーの計測値が判断基準を超えていないと生物活性炭処理し、判断基準を超えていると粒状活性炭処理に切り替え制御装置により切り替えて原水を高度浄水することを特徴とする。
請求項１によると、活性炭処理水中に残存する有機物を一定値以下にでき、後塩素処理によって生成されるトリハロメタン量を抑制できる。さらに浄水中に残存する生物資化有機物（ＡＯＣ）は、従来処理よりも低い濃度に抑制されるため、滞留配水管内における細菌等の繁殖懸念がなくなり、安定した水質の浄水を供給することができる。
【００３７】
請求項２記載の高度浄水処理方法は、原水の有機物の指標となる有機物濃度を水質センサーで計測した後、前記原水をオゾン処理し、さらにこのオゾン処理された原水を前記水質センサーの計測値に基づいて生物活性炭処理または粒状活性炭処理して高度浄水とする高度浄水処理方法において、前記水質センサーの計測値が判断基準を超えていないと生物活性炭処理し、判断基準を超えていると粒状活性炭処理に切り替え制御装置により切り替え、さらに前記粒状活性炭処理に切り替っている間は中塩素を前記オゾン処理するときに供給すると共に、前記生物活性炭処理するときに用いられる前記生物活性炭層に溶存酸素を供給することを特徴とする。
【００３８】
請求項２によると、請求項１の効果に付加してＢＡＣ層の生物活性低下を最小限にし、ＢＡＣ処理休止中も休止前とほぼ同様な状態を維持できる。また、中塩素処理の併用により、水質悪化に起因するオゾン注入制御の不安定要素を取り除き、オゾン注入率を適正な範囲に維持・制御できる。
【００３９】
このため、オゾンの過剰発生によるランニングコスト低減、高溶存オゾン濃度によるＧＡＣ処理への負荷低減、オゾン注入不足による鉄・マンガンの浄水中への流出を防止することができる。
【００４０】
請求項３記載の高度浄水処理方法は、請求項２の高度浄水処理方法において、原水が供給される着水井の中に生物接触ろ過用の充填剤及び散気装置を設置し、この散気装置へ送風することで前記着水井に生物接触ろ過機能を持たせたことを特徴とする。
【００４１】
請求項３によると、請求項２の効果に付加して、被処理水中のアンモニア性窒素濃度を常に０．１ｍｇ／Ｌ未満にでき、より少ない塩素注入率で鉄やマンガンの酸化除去に有効に作用させることができる。
このため、中塩素処理で生成されるトリハロメタン量がさらに抑制される。
【００４２】
請求項４記載の高度浄水処理方法は、請求項２または請求項３記載の高度浄水処理方法において、粒状活性炭処理継続中は、オゾン処理で排出される排オゾンガスを排オゾン処理装置にて無害化してから表面曝気装置にて表面曝気を行い、生物活性炭処理した循環水に溶存酸素を供給するようにしたことを特徴とする。
【００４３】
請求項４によると、請求項２及び請求項３の効果に付加して、ＢＡＣ処理休止中もＢＡＣ層の微生物に十分な溶存酸素を供給できるため、生物の活性が長期間維持される。また、表面バッキに排オゾン処理したガスを用いることにより、新たにコンプレッサーやブロワを設置する必要がなく、設置コスト及び動力コストの削減が行える。
【００４４】
請求項５記載の高度浄水処理方法は、請求項１ないし請求項４記載のいずれかの高度浄水処理方法において、生物活性炭処理するときに用いられる生物活性炭層にオゾン接触水を注入することにより、後生生物の繁殖・漏出を抑制するようにしたことを特徴とする。
【００４５】
請求項５によると、請求項１ないし請求項４の効果に付加してＢＡＣ処理工程から漏出する後生生物を大幅に抑制できる。また、逆洗周期が従来の高度処理より２日程度延長することが可能なことから、活性炭の摩耗低減、微生物層の安定などに寄与でき、より安定した浄水が得られると共にＢＡＣ処理におけるランニングコストが大幅に低減できる。
請求項６記載の高度浄水処理システムは、原水の有機物の指標となる有機物濃度を計測する水質センサーと、前記原水をオゾン処理するオゾン処理工程と、このオゾン処理された原水を前記水質センサーの計測値に基づいて処理して高度浄水とする高度浄水処理システムにおいて、前記水質センサーの計測値が判断基準を超えていないときに処理する生物活性炭処理工程と、判断基準を超えているときに処理する粒状活性炭処理工程と、前記両処理工程を切り替える切り替え制御装置を備えていることを特徴とする。
請求項６によると、活性炭処理水中に残存する有機物を一定値以下にでき、後塩素処理によって生成されるトリハロメタン量を抑制できる。さらに浄水中に残存する生物資化有機物（ＡＯＣ）は、従来処理よりも低い濃度に抑制されるため、滞留配水管内における細菌等の繁殖懸念がなくなり、安定した水質の浄水を供給することができる。
【００４６】
【発明の実施の形態】
以下、本発明の実施の形態を図を参照して説明する。
図１は本発明の第１の実施形態の高度浄水処理方法のプロセスフロー図である。
同図に示すように、本実施形態に係る高度浄水処理装置は、着水井１と、凝集・沈澱処理工程２と、砂ろ過処理工程３と、オゾン処理工程４と、ＢＡＣ処理工程５と、このＢＡＣ処理工程５と並列接続されたＧＡＣ処理工程８と、後塩素処理工程６と、配水池７とをこの順序に配置し、さらに着水井１に設置された水質センサー９と、ＢＡＣ処理工程５の前段に設けたＢＡＣ制御バルブ１０と、前記ＧＡＣ処理工程８の前段に設けたＧＡＣ制御バルブ１１と、前記ＢＡＣ処理工程５のドレンを排出するドレンバルブ１２と、ＧＡＣ処理工程８のドレンを排出するドレンバルブ１３と、系統切り替え制御装置１４とから構成されている。
【００４７】
次に、本実施形態の作用について説明する。なお、図６の従来例と同じ構成要素は同一符号を付して重複する説明は省略する。
本実施形態では、着水井１に設置された水質センサー９は、着水井１に流入する原水の有機物（ＴＯＣ）濃度をオンラインで計測するものであり、この計測値Ｔ１は系統切り替え制御装置１４へ入力している。水質センサー９には全有機炭素濃度計（ＴＯＣ計）を用いているが、有機物の指標を測定できるものなら代替でき、蛍光センサーを用いたトリハロメタン前駆物質濃度計、過マンガン酸カリウム消費量計、紫外線吸光光度計などが利用可能である。
【００４８】
ＢＡＣ制御バルブ１０は、ＢＡＣ処理工程５に流入するオゾン処理水の流量を制御するものであり、また系統切り替え制御装置１４からの出力信号Ｖｂ１に基づき開度及び開閉が制御されている。また、ＧＡＣ制御バルブ１１は、ＧＡＣ処理工程８に流入するオゾン処理水の流量を制御するものであり、系統切り替え制御装置１４からの開閉信号Ｖｇ１に基づき開度及び開閉が制御されている。ドレンバルブ１２及びドレンバルブ１３の開閉もそれぞれ系統切り替え制御装置１４からの開閉信号Ｖｂ２、Ｖｇ２に基づいて制御されている。
【００４９】
系統切り替え制御装置１４では、着水井１に流入する原水中のＴＯＣ濃度Ｔ１から、ＢＡＣ制御バルブ１０及びＧＡＣ制御バルブ１１における開度及び開閉制御を行い、ＢＡＣ処理工程５とＧＡＣ処理工程８の活性炭処理工程の制御を行うものであり、その作用は、以下に示す通りである。
【００５０】
通常、水質が安定している場合は、原水中のＴＯＣ濃度Ｔ１は５ｍｇ／Ｌ未満であり、本実施形態におけるオゾン処理工程４の後段の活性炭処理は、初期状態としてＢＡＣ処理工程５を指定してある。
【００５１】
本実施形態では、系統切り替え制御装置１４における判断基準としてＴＯＣ濃度４ｍｇ／Ｌを判断基準としているが、実際の制御モードの切り替えは、ＴＯＣ濃度の測定値Ｔ１における６時間の移動平均値Ｔａｖ６と、ＴＯＣ濃度の下位点Ｔｄと、上位点Ｔｕとから判断しており、Ｔｄ＝３．５ｍｇ／Ｌ、Ｔｕ＝４ｍｇ／Ｌを設定している。
【００５２】
系統切り替え制御装置１４では原水中のＴＯＣ濃度Ｔ１を記録し、６時間（連続処理継続時間）の移動平均値Ｔａｖ６がＴｕ（４ｍｇ／Ｌ）以上の値になると、ＢＡＣ処理工程５から待機していたＧＡＣ処理工程８への処理工程の変更を行うように、ＢＡＣ制御バルブ１０及びＧＡＣ制御バルブ１１における開度及び開閉制御を行う。待機中から移行したＧＡＣ処理工程８における活性炭処理は、原水中のＴＯＣ濃度Ｔ１が一時的にＴｄ（３．５ｍｇ／Ｌ）未満の測定値を計測しても、Ｔｄ（３．５ｍｇ／Ｌ）≦Ｔａｖ６、の条件を満たす場合は継続され、Ｔａｖ６＜Ｔｄ（３．５ｍｇ／Ｌ）になったときに、ＢＡＣ処理工程５へ切り替わるものである。
【００５３】
このように、判断基準にＴＯＣ濃度の測定値Ｔ１における６時間の移動平均値Ｔａｖ６を用い、ＴＯＣ濃度の下位点Ｔｄ＝３．５ｍｇ／Ｌ、上位点Ｔｕ＝４ｍｇ／Ｌ、の間に０．５ｍｇ／Ｌ幅の不感帯を設定しているのは、判断基準濃度近辺における処理工程の頻繁な切り替えを防止するためである。
【００５４】
この制御条件をまとめると、下記のようになる。
Ｔｕ≦Ｔａｖ６、→ＢＡＣ処理工程からＧＡＣ処理工程へ切り替え実行。
Ｔｄ≦Ｔａｖ６＜Ｔｕ、→不感帯、現在の活性炭処理工程を継続。
Ｔｄ＞Ｔａｖ６、→ＧＡＣ処理工程からＢＡＣ処理工程へ切り替え実行。
これらの設定値は経験から、Ｔｕの設定値は３．５ｍｇ／Ｌ以上、Ｔｕ−Ｔｕ＝０．５〜１ｍｇ／Ｌの範囲が望ましいことを把握している。
【００５５】
系統切り替え制御装置１４では、ＢＡＣ処理工程５からＧＡＣ処理工程８へ切り替え、またはＧＡＣ処理工程８からＢＡＣ処理工程５へ切り替えの際には、浄水処理が一時的にでも中断することのないように、処理を開始する活性炭処理工程の制御バルブから徐々に開度を増し全開となってから、待機する活性炭処理工程の制御バルブを徐々に閉め、全閉とするように制御を行う。また、待機中に移行する活性炭処理工程では速やかにドレンバルブが開かれて水抜きが行われ、系内滞留による活性炭層の汚染を防止している。
【００５６】
例えば、ＢＡＣ処理工程５からＧＡＣ処理工程８への切り替えは、系統切り替え制御装置１４にて全閉状態であったＧＡＣ制御バルブ１１を開放するように開閉信号Ｖｇ１が出され、ＧＡＣ制御バルブ１１が全開になると同時にＢＡＣ制御バルブ１０を徐々に閉鎖し、全閉状態にするように制御する。
【００５７】
系統切り替え制御装置１４にて、ＧＡＣ制御バルブ１１の全閉が確認されたら、ドレンバルブ１２を開放するように開閉信号Ｖｂ２を出力して、ドレンバルブ１２よりＢＡＣ処理工程５内に滞留している処理水を排出する。これにより、ＢＡＣ層内の嫌気性化と系内滞留によるＢＡＣ処理工程５内の汚染を防止している。ＧＡＣ処理工程８からＢＡＣ処理工程５への切り替えでも同様の動作により、ＧＡＣ処理工程８における水抜きが実施される。
【００５８】
ここで、本実施形態において後塩素処理工程６にて浄水中に生成されるトリハロメタン量Ｔｔｈｍ（μｇ／Ｌ）を想定し、従来例に示した（１．３）式に従い、以下の条件でＢＡＣ処理（ＴｔｈｍＢ）の場合と、ＧＡＣ処理（ＴｔｈｍＧ）の場合を比較する。
【００５９】

となり、ＢＡＣ処理の場合では水質基準値（１００μｇ／Ｌ）に対して余裕がなくなり、すぐにでも水質基準値を越えてもおかしくないが、本実施形態のように水質負荷に応じてＧＡＣ処理に切り替えることにより、水質基準値に対して十分に余裕がもてる浄水処理が実現できる。
【００６０】
なお、ＧＡＣ処理工程８に移行している間のアンモニア性窒素の処理は、従来の不連続点塩素処理法（ブレークポイント法）による除去である。
以上説明したように、本実施形態ではＢＡＣ処理及びＧＡＣ処理の長所を取り入れた浄水処理工程を選択することにより、活性炭処理水中に残存する有機物を一定値以下にでき、この結果、後塩素処理によって生成されるトリハロメタン量を抑制できた。
【００６１】
さらに残留塩素が消失しても、浄水中に残存する生物資化有機物（ＡＯＣ）は、従来処理よりも低い濃度に抑制されているため、滞留配水管内における細菌等の繁殖原因となる懸念がなくなり、トリハロメタンの生成抑制効果と併せて、安定した水質の浄水を供給することができた。
【００６２】
図２は本発明の第２の実施形態の高度浄水処理方法のプロセスフロー図である。
同図に示すように、本実施の形態の高度浄水処理装置は、着水井１と、凝集・沈殿処理工程２と、砂ろ過処理工程３と、オゾン処理工程４と、ＢＡＣ処理工程５と、後塩素処理工程６と、配水池７と、ＧＡＣ処理工程８と、前記着水井１に設置された水質センサー９と、ＢＡＣ制御バルブ１０と、ＧＡＣ制御バルブ１１と、ドレンバルブ１２と、ドレンバルブ１３と、系統切り替え制御装置１４とからなる構成は図１の第１の実施形態と同一である。本実施形態は、さらに中塩素注入装置１５と、後塩素注入装置１６と、循環ライン１７と、循環ポンプ１８と、ＢＡＣ循環バルブ１９を追加構成されている。
【００６３】
次に、本実施形態の作用について説明する。
本実施形態では、図１の第１実施形態にてＧＡＣ処理工程８に切り替わった場合、ＢＡＣ処理工程５の休止期間中においてＢＡＣ層の生物活性の低下を最小限にするため、循環ライン１７と循環ポンプ１８を用いて、ＢＡＣ層に溶存酸素を供給すると共に、ＧＡＣ処理工程８に切り替わっている間は、オゾン処理工程４の負荷を低減するために中塩素注入装置１５により、中塩素処理を実施するものである。
【００６４】
また、系統切り替え制御装置１４では、図１の第１実施形態の制御に付加して中塩素注入装置１５及び後塩素注入装置１６における塩素注入の統括制御が追加されている。
【００６５】
系統切り替え制御装置１４における、ＢＡＣ処理工程５からＧＡＣ処理工程８へ切り替え、またはＧＡＣ処理工程８からＢＡＣ処理工程５へ切り替えの判断基準は第１実施形態と同様である。しかし、ＢＡＣ処理工程５における各バルブ類の制御は異なっているので、その作用も異なっている。
【００６６】
これを、ＢＡＣ処理工程５からＧＡＣ処理工程８への切り替えの例で示すと、系統切り替え制御装置１４では全閉状態であったＧＡＣ制御バルブ１１を開放するように開閉信号Ｖｇ１が出力され、ＧＡＣ制御バルブ１１が全開になると同時にＢＡＣ循環バルブ１９を徐々に閉鎖するように開閉信号Ｖｂ３を出力し、全閉状態にするように制御する。ＢＡＣ循環バルブ１９の全閉状態が確認されたら、ＢＡＣ制御バルブ１０を徐々に閉鎖し、全閉状態にすると共に循環ポンプ１８を起動し、循環ライン１７を通水状態にする。
【００６７】
さらに、完全にＧＡＣ処理工程８に移行したならば、系統切り替え制御装置１４では、鉄及びマンガンの酸化除去を行う中塩素処理を実施するための中塩素注入率Ｃ１を演算し、中塩素注入装置１５より砂ろ過処理工程３の前段に塩素を注入して、酸化物（固形物）となった鉄及びマンガンを砂ろ過処理工程３にて捕捉する。
【００６８】
また、系統切り替え制御装置１４では中塩素注入装置１５における中塩素注入率Ｃ１と、後塩素注入装置１６における後塩素注入率Ｃ２とを統括制御し、塩素注入量及び残留塩素濃度の総合的な管理を行う。
【００６９】
一般に、中塩素処理は凝集・沈殿処理工程２の後に行われる。浮遊物質や一部の溶解性有機物が除去されているため、前塩素処理よりは塩素注入率が低減でき、生成されるトリハロメタン量が大幅に減少するが、ＢＡＣ処理工程５に行われる後塩素処理よりは生成されるトリハロメタン量が多いのが実状である。
【００７０】
また、中塩素処理は鉄及びマンガンの酸化を行うものである。アンモニア性窒素を完全に除去し、残留塩素が結合塩素（クロラミン）から遊離塩素となる塩素注入は、後塩素処理工程６における従来の不連続点塩素処理法（ブレークポイント法）によって行われる。
【００７１】
本実施形態では水質悪化時には活性炭の吸着性能が高いＧＡＣ処理工程８に切り替わっているため、中塩素処理で生成されたトリハロメタン及びオゾン処理工程４後も残存する有機物はＧＡＣ処理工程８にて吸着される。また、有機物が大幅に除去されているため、後塩素処理工程６後に生成されるトリハロメタン量も大幅に抑制され、浄水中のトリハロメタン濃度も従来の高度処理と同等のレベルに低減できる。
【００７２】
また、オゾン処理工程４で実施していた鉄及びマンガンの酸化が中塩素処理で行われ、砂ろ過で捕捉されるようになる。このため、オゾン処理工程４におけるオゾン注入制御因子が少なくなりオゾン注入制御の精度が高まる。これにより、従来例で示したような水質悪化時に発生したオゾン注入制御の問題点が解消され、安定したオゾン処理が実現できるようになる。
【００７３】
一方、ＧＡＣ処理工程８からＢＡＣ処理工程５への切り替えは、最初に中塩素注入装置１５における中塩素注入停止（Ｃ１＝０ｍｇ／Ｌ）後、ＢＡＣ処理工程５へ残量塩素を含んだ砂ろ過水の流入を防ぐための置換時間（１時間）中はＧＡＣ処理工程８が継続され、その後ＢＡＣ処理工程５へ移行するように系統切り替え制御装置１４にて各バルブ類が制御されている。
【００７４】
以上説明したように、本実施形態は第１実施形態の効果に付加してＧＡＣ処理工程８に移行中であってもＢＡＣ処理工程５におけるＢＡＣ層の生物活性低下を最小限にし、再びＢＡＣ処理工程５に移行（復帰）した場合の立ち上がり処理特性も休止前とほぼ同様な状態を維持できる。
また、中塩素処理の併用により、水質悪化に起因するオゾン注入制御の不安定要素を取り除き、オゾン注入率を適正な範囲に維持・制御できる。
【００７５】
このため、オゾンの過剰発生によるオゾン設備のランニングコスト（電気代、排オゾン処理コストなど）上昇の抑制、オゾンの過剰酸化による二酸化マンガンの過マンガン酸イオンへの酸化防止、過マンガン酸イオン及び高溶存オゾン濃度によるＧＡＣ処理への負荷低減、オゾン注入不足による鉄・マンガンの浄水中への流出を防止することができる。また、これらの要因による浄水水質の悪化を防止できる。
この結果、本実施形態によると、高度浄水処理において常に安定した水質の浄水を供給することができた。
【００７６】
図３は本発明の第３の実施形態の高度浄水処理方法のプルセスフロー図であり、図２の第２の実施形態と同一構成要素は同一符号を付して重複説明は省略する。
同図に示すように、本実施形態は、図２の第２実施形態に、アンモニア性窒素センサー２０と、着水井１の中に設置された生物接触ろ過用の充填剤２１と、送風装置２２と、散気装置２３とを付加した構成とされている。
【００７７】
次に、本実施形態の作用について説明する。
本実施形態では、図２の第２実施形態に示したようにＢＡＣ処理工程５からＧＡＣ処理工程８に切り替わった場合、生物作用によるアンモニア性窒素の処理工程がなくなるため、ＢＡＣ処理工程５の休止期間中は充填材２１が設置された着水井１の底部より散気を行い、生物酸化作用によりアンモニア性窒素の除去を行うものである。
【００７８】
系統切り替え制御装置１４におけるＢＡＣ処理工程５からＧＡＣ処理工程８へ切り替え及びＧＡＣ処理工程８からＢＡＣ処理工程５へ切り替えの判断基準と中塩素注入装置１５及び後塩素注入装置１６の統括制御は第２実施形態と同様であり、またＢＡＣ処理工程５及びＧＡＣ処理工程８における各バルブ類の制御も同一であるので、そのための詳細な説明は省略する。
【００７９】
本実施形態では、アンモニア性窒素センサー２０を用いて着水井１に流入する原水のアンモニア性窒素濃度をオンラインで計測するものであり、計測値Ｎ１として系統切り替え制御装置１４へ入力している。
着水井１内には硝化菌を付着させた充填材２１が設置されており、硝化菌が活性化されているときにはアンモニア性窒素の除去能力が高いのが特徴である。
【００８０】
ＢＡＣ処理工程５からＧＡＣ処理工程８へ切り替わった場合、アンモニア性窒素濃度が高い状態であると、塩素注入率の増大率により生成されるトリハロメタン量の増加も懸念される。
【００８１】
本実施形態では、ＧＡＣ処理工程８に移行中、アンモニア性窒素濃度Ｎ１が０．１ｍｇ／Ｌ以上の場合、系統切り替え制御装置１４では送気装置２２から着水井１内の散気装置２３へ加圧された空気を送るように制御信号Ａ１を送気装置２２に出力する。そして、着水井１内の溶存酸素濃度を常に飽和濃度近くに保つと共に充填材２１に付着した硝化菌を活性化させて原水中のアンモニア性窒素濃度を９０％以上除去するものである。
【００８２】
アンモニア性窒素濃度Ｎ１が０．１ｍｇ／Ｌ未満の場合、従来の不連続点塩素処理法（ブレークポイント法）による処理でも塩素注入率がそれほど増加しないためと、送気装置２２におけるエネルギーコスト節約のため、着水井１への散気は休止される。
【００８３】
河川水や湖沼水などの表流水には、数ｍｇ／Ｌオーダの溶存酸素が含まれているため、着水井１への散気を休止しても硝化菌が死滅することはない。また、原水中にアンモニア性窒素濃度が存在していれば、硝化菌の活性は必要最低限維持されている。また、近年下水道等の復旧整備により表流水系のアンモニア性窒素濃度１ｍｇ／Ｌを越えるような事例はなく、本実施形態におけるアンモニア性窒素濃度の最大値は０．８２ｍｇ／Ｌであった。
【００８４】
以上説明したように、本実施形態は第２実施形態の効果に付加して、ＧＡＣ処理工程８へ移行中であっても塩素処理前の被処理水中のアンモニア性窒素濃度を常に０．１ｍｇ／Ｌ未満にでき、中塩素処理にてアンモニア性窒素に消費される塩素量が低減すると共に、より少ない塩素注入率で鉄やマンガンの酸化除去に有効に作用する。
このため、中塩素処理で生成されるトリハロメタン量が第２実施形態より抑制され、この結果より安定した水質の浄水を供給することができた。
【００８５】
図４は本発明の第４実施形態の高度浄水処理方法のプロセスフロー図であり、図３の第３実施形態と同じ構成要素は同一符号を付して重複説明は省略する。
同図に示すように、本実施形態は図３の第３実施形態に排オゾン処理装置２４と、処理ガス切り替え装置２５と、表面曝気装置２６と、表面曝気ライン２７を付加した構成とされている。
【００８６】
次に、本実施形態の作用について説明する。
本実施形態において、系統切り替え制御装置１４におけるＢＡＣ処理工程５からＧＡＣ処理工程８へ切り替え及びＧＡＣ処理工程８からＢＡＣ処理工程５へ切り替えの判断基準、中塩素注入装置１５及び後塩素注入装置１６の統括制御は図２の第２実施形態及び図３の第３実施形態と同様である。またＢＡＣ処理工程５及びＧＡＣ処理工程８における各バルブ類の制御も同一であるので、その詳細な説明は省略する。
【００８７】
また、本実施形態ではＧＡＣ処理工程８に切り替わった場合、アンモニア性窒素の除去作用を有する処理工程がなくなるため、ＢＡＣ処理工程５の休止期間中は充填材２１が設置された着水井１の底部より散気を行い、生物酸化作用によりアンモニア性窒素の除去を行うことに関する制御も図３の第３実施形態と同一なため詳細な説明は省略する。
【００８８】
ところで、図２の第２実施形態及び図３の第３実施形態では、ＢＡＣ処理工程５からＧＡＣ処理工程８に切り替わった場合、ＢＡＣ処理工程５の休止期間中においてＢＡＣ層の生物活性の低下を最小限にするため、循環ライン１７と循環ポンプ１８を用いて、ＢＡＣ層に溶存酸素を供給していた。しかし、この方法では、循環ライン１７の中を流れる循環水と空気との気液接触箇所が限定されており、酸素溶解度が低下する夏季等は溶存酸素濃度が低下し、ＢＡＣ層における微生物（バクテリア）の活性維持が長期間持続しないことがあった。
【００８９】
本実施形態では、オゾン処理工程４から排出される排オゾンガスを排オゾン処理装置２４にて無害化処理を行い、その処理ガス切り替え装置２５を経由して表面曝気装置２６にて表面曝気を行い循環ライン１７を流れる循環水に溶存酸素を供給するものである。
【００９０】
処理ガス切り替え装置２５では、排オゾン処理装置２４からの処理ガスを大気開放か、表面曝気ライン２７に導くのかを切り替えるものであり、系統切り替え制御装置１４からの制御信号Ａ２により制御されている。つまり、循環ポンプ１８の起動に連動して排オゾン処理装置２４からの処理ガスを表面曝気ライン２７に導き、循環ポンプ１８の停止と同時に大気開放の方にラインを切り替えている。
【００９１】
排オゾン処理装置２４では、排オゾンガス濃度１〜２ｇ／ｍ³（注入オゾンガス濃度２０ｇ／ｍ³、オゾン吸収効率９０〜９５％として）程度の排ガスを処理するものであり、オゾン分解剤には加熱されたマンガン系の触媒が用いられており、また排オゾンガスは分解後、再び酸素に戻る。
【００９２】
オゾン濃度２０ｇ／ｍ³をｍｏｌ／ｍ³の濃度に換算すると、
オゾンの分子式：Ｏ₃ＭＷ（分子量）：４８より、
（２０[ｇ]／４８[ｇ／ｍｏｌ]）／[ｍ³]＝０．４１７ｍｏｌ／ｍ³ …（３．１）
３ｍｏｌの酸素分子より２ｍｏｌのオゾン分子を生成するから（３Ｏ₂→２Ｏ₃）、２０ｇ／ｍ³のオゾン発生に用いられる酸素分子は、
０．４１７／ｍ³＊３／２＝０．６２５ｍｏｌ／ｍ³ …（３．２）
となる。
【００９３】
一方、１ｍ³（１０００Ｌ）の空気中に存在する気体を全て理想気体と見なし、ｍｏｌ数を計算すると、理想気体１ｍｏｌが有する体積は標準状態（０℃、１０１．３２ｋＰａ）で２２．４Ｌであるから、
１０００[Ｌ]／２２．４[Ｌ／ｍｏｌ]＝４４．６４ｍｏｌ／ｍ³ …（３．３）
となる。
【００９４】
空気中に占める酸素の体積の割合は２０．９５％であり、ドルトンの分圧の法則により１ｍ³の空気中に存在する酸素のｍｏｌを計算すると、
４４．６４[ｍｏｌ／ｍ³]＊０．２０９５＝９．３５ｍｏｌ／ｍ³ …（３．４）
となる。
【００９５】
上記（３．２）及び（３．４）式より２０ｇ／ｍ³のオゾン発生に用いられる酸素分子の割合は全酸素量の６．７％ということになる。
【００９６】
０．６２５[ｍｏｌ／ｍ³]／９．３５[ｍｏｌ／ｍ³]＊１００＝６．７％…（３．５）
排オゾンガス中には未反応のオゾンが１０％程度あり、排オゾン処理により再び酸素に戻るためその分を差し引くと、約６％の酸素が失われることになる。これを新たに処理された排ガス中における酸素ガス濃度として再計算すると、酸素濃度は約２０％になる。
【００９７】
（９．３５−９．３５＊０．０６）／（４４．６４−９．３５＊０．０６）
＊１００＝１９．９％ …（３．６）
従って、処理された排ガスを表面バッキに用いても酸素濃度に何ら問題がないことが分かる。
【００９８】
表面曝気装置２６は循環ポンプ１８の吸い込み側に設置されている。排オゾン処理装置２５から排出される処理ガスの圧力は、大気圧＋５００〜６００ｍｍＡｑ程度であるから、水深３０〜４０ｃｍ程度の表面バッキなら十分に行えることが分かる。
【００９９】
参考までに、６００ｍｍＡｑを絶対圧のＭＰａ単位に変換すると、
１ａｔｍ＝０．１０１３２５ＭＰａ＝１．０３３２３＊１０⁴ｍｍＡｑ
であるから、
（０．１０１３２５＋６００／１．０３３２３＊１０⁴）＝０．１５９４ＭＰａ（絶対圧）となる。
【０１００】
なお、表面曝気装置２６は、循環ポンプ１８の吸い込み側に設置されており、上記に示す処理ガスの排気圧が多少低下しても、表面曝気が行えるように考慮してある。
【０１０１】
以上説明したように、本実施形態は、第２実施形態及び第３実施形態と同様に安定した水質の浄水を供給することができると共に、これらの効果に付加して、ＧＡＣ処理工程８に移行中であってもＢＡＣ処理工程５におけるＢＡＣ層の微生物に十分な溶存酸素を供給できるため、生物の活性が長期間維持できると共に、再びＢＡＣ処理工程５に移行（復帰）した場合の立ち上がり処理特性も第２実施形態及び第３実施形態よりも速く行えることができた。また、表面バッキに排オゾン処理したガスを用いることにより、新たにコンプレッサやブロワを設置する必要がなく、設置コスト及び動力コストの削減が行えた。
【０１０２】
図５は本発明の第５実施形態の高度浄水処理方法のプロセスフロー図であり、図１の第１実施形態と同じ構成要素は同一符号を付して重複する説明は省略する。
同図に示すように、本実施形態は、第１実施形態にオゾン水バイパス配管２８と、オゾン水注入装置２９と、注入ポンプ３０を付加した構成とされている。
【０１０３】
本実施形態では、オゾン処理工程４を構成するオゾン反応層（図示せず）の接触部にオゾンバイパス配管２８が挿入されており、オゾン接触直後の比較的溶存オゾン濃度が高いオゾン接触水が採水できるようになっている。
【０１０４】
オゾン水バイパス配管２８は、注入ポンプ３０を介してオゾン水注入装置２９に接続している。オゾン水注入装置２９は、ＢＡＣ処理工程５を構成するＢＡＣ層（図示せず）の下部に設置されており、オゾン接触水をＢＡＣ層に注入してオゾンの強力な殺菌力により微少動物（後生生物）の除去を行い、ＢＡＣ処理工程５における繁殖及び漏出抑制を行うものである。ＢＡＣ処理工程５を構成するＢＡＣ槽は下降流で処理を行っている。
【０１０５】
このオゾン水注入装置２９からのオゾン接触水注入はＢＡＣ処理工程５における処理が行われている時に実施され、その制御は系統切替制御１４からの制御信号Ｐ１に基づく注入ポンプ３０の起動及び停止によって行われる。つまり、ＢＡＣ処理工程５からＧＡＣ処理工程８に切り替わるのに連動して、注入ポンプ３０が停止され、反対にＧＡＣ処理工程８からＢＡＣ処理工程５に切り替わるのに連動して、注入ポンプ３０が起動されるように系統切替制御１４にて制御されている。
【０１０６】
なお、系統切替制御装置１４におけるＢＡＣ処理工程５からＧＡＣ処理工程８へ切り替え及びＧＡＣ処理工程８からＢＡＣ処理工程５へ切り替えの判断基準、中塩素注入装置１５及び後塩素注入装置１６の統括制御は上記実施形態と同様に実施でき、またＢＡＣ処理工程５及びＧＡＣ処理工程８における各バルブ類の制御も上記実施形態と同一なため詳細な説明は省略する。
【０１０７】
ところで、従来の高度処理では、空洗と水洗を組み合わせたＢＡＣ層の洗浄（逆洗）は、後生生物の繁殖周期を考慮して３日に１回程度の頻度で実施されている。一方、過度の逆洗は活性炭を摩耗させたり、有機物を除去する微生物の方にまで悪影響を及ぼすことがあった。
【０１０８】
本実施形態では、ＢＡＣ層上部から下降してくる後生生物に考慮してＢＡＣ処理工程５で処理をしている間は、オゾン水注入装置２９から常時オゾン接触水を供給しているため、効率よく後生生物を除去できる。またＢＡＣ槽は下降流処理のため、オゾン水注入装置２９から注入されるオゾン接触水は、ＢＡＣ層の上部に多く存在する微生物には全く悪影響を与えない。このため、逆洗周期が従来の高度処理より２日程度延長することが可能である。ただし、ＢＡＣ層の目詰まりは従来の高度処理と何ら変わらないため、濾高の上昇や定期的な活性炭層の逆洗制御は不可能である。
【０１０９】
以上説明したように、本実施形態によると第１実施形態の効果に付加してＢＡＣ処理工程５から漏出する後生生物を大幅に抑制できた。また、逆洗周期が従来の高度処理より２日程度延長することが可能なことから、活性炭の摩耗低減、微生物層の安定などに寄与でき、より安定した浄水が得られると共にＢＡＣ処理におけるランニングコストが大幅に低減できた。
【０１１０】
【発明の効果】
以上説明したように、本発明によると、活性炭処理水中に残存する有機物を一定値以下にでき、後塩素処理によって生成されるトリハロメタン量を抑制できる。また、浄水中に残存する生物資化有機物も低い濃度に抑制されるため、滞留配水管内における細菌等の繁殖懸念がなくなり、さらに水質悪化に起因するオゾン注入制御の不安定要素を取り除き、オゾン注入不足による鉄・マンガンの浄水中への流出を防止することができ、安定した水質の浄水を供給することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態の高度浄水処理方法のプロセスフロー図。
【図２】本発明の第２の実施形態の高度浄水処理方法のプロセスフロー図。
【図３】本発明の第３の実施形態の高度浄水処理方法のプロセスフロー図。
【図４】本発明の第４の実施形態の高度浄水処理方法のプロセスフロー図。
【図５】本発明の第５の実施形態の高度浄水処理方法のプロセスフロー図。
【図６】従来の高度浄水処理方法のプロセスフロー図。
【符号の説明】
１…着水井、２…凝集・沈殿処理工程、３…砂ろ過処理工程、４…オゾン処理工程、５…ＢＡＣ処理工程、６…後塩素処理工程、７…配水池、８…ＧＡＣ処理工程、９…水質センサー、１０…ＢＡＣ制御バルブ、１１…ＧＡＣ制御バルブ、１２…ドレンバルブ、１３…ドレンバルブ、１４…系統切替制御装置、１５…中塩素注入装置、１６…後塩素注入装置、１７…循環ライン、１８…循環ポンプ、１９…ＢＡＣ循環バルブ、２０…アンモニア性窒素センサー、２１…充填材、２２…送風装置、２３…散気装置、２４…排オゾン処理装置、２５…処理ガス切り替え装置、２６…表面曝気装置、２７…表面曝気ライン、２８…オゾン水バイパス配管、２９…オゾン水注入装置、３０…注入ポンプ。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an advanced water purification treatment method using raw water as advanced water purification, and in particular, an advanced water purification treatment method for obtaining advanced water purification by appropriate switching control between a biological activated carbon treatment step and a granular activated carbon treatment step.And its processing systemAbout.
[0002]
[Prior art]
In recent years, advanced water purification treatment that combines ozone treatment with granular activated carbon (GAC) treatment and biological activated carbon (BAC) treatment has been introduced in response to the deterioration of raw water quality and increased interest in “safer and more delicious water”. I'm starting. The raw water to which such advanced water purification treatment is introduced and applied is generally river water or lake (dam) water that has been polluted (eutrophication).
[0003]
The purpose of ozone treatment for advanced water purification is the decomposition (removal) of odor components, the reduction of trihalomethane precursors, the removal of iron and manganese that have been oxidized and removed by pre-chlorination, etc. By modifying the organic material, the removal rate of the organic material including the trihalomethane precursor in the BAC process is improved.
[0004]
The purpose of the activated carbon treatment is to adsorb and remove organic substances including trihalomethane precursors and odor components. In order to remove organic oxides such as aldehydes and ketones that are likely to be generated by ozone treatment, Installation is obliged to follow the ozone treatment by guidance.
[0005]
There are advantages and disadvantages in GAC treatment and BAC treatment, respectively. When used as BAC treatment, the removal performance of organic matter is maintained in the range of 20-40% by microorganisms (bacteria) attached to the activated carbon surface, and the activated carbon life is 2 Although it can be obtained for about 3 years, the organic matter removal rate is inferior to that of GAC treatment. However, since nitric acid bacteria and nitrite bacteria that nitrify ammonia nitrogen on the activated carbon surface adhere and grow, it is possible to remove ammonia nitrogen to some extent if the concentration is low. In addition, there is a possibility that micro-animals that prey on microorganisms (metazoans such as rotifers and crustaceans) may breed, and in order to suppress propagation and leakage of metazoans from BAC treatment, appropriate backwash control of the activated carbon layer Is essential.
[0006]
On the other hand, in the case of GAC treatment, the life of activated carbon is about half a year when there is residual chlorine, but the organic matter removal rate is 70 to 90% or more until just before breakthrough, and the adsorption performance of organic matter is superior to BAC treatment. . There is no concern about the breeding or leakage of small animals.
[0007]
FIG. 6 is a typical process flow diagram of conventional advanced water purification treatment combining ozone treatment and BAC treatment.
The landing well 1 is installed to smooth the level of raw water and fluctuations in the amount of raw water, and to grasp the amount of raw water, and various sensors such as an oil film sensor and a poison detection sensor are installed to monitor the quality of the raw water. Sometimes.
[0008]
In the agglomeration / precipitation treatment step 2, floating substances and dissolved substances in the raw water are flocked and settled by adding a flocculant (polyaluminum chloride, sulfuric acid band, etc.). The sand filtration treatment step 3 captures and filters flocs that have not been settled in the aggregation / precipitation treatment step 2. The ozone treatment process 4 and the BAC treatment process 5 are used for the above-described purposes, respectively, and remove organic substances, iron, manganese, and the like.
[0009]
In the post-chlorination treatment step 6, a disinfecting chlorinating agent (sodium hypochlorite, liquid chlorine, etc.) is injected, and the BAC treated water and the chlorinating agent are brought into contact with and mixed with each other. Aging of the reaction with the chlorine agent and the residual chlorine concentration are adjusted and supplied as purified water. When the concentration of ammoniacal nitrogen in the raw water is high, a biological contact oxidation treatment process (not shown) may be installed between the landing well 1 and the flocculation / precipitation treatment process 2.
[0010]
[Problems to be solved by the invention]
By the way, since the BAC treatment process 5 uses the adsorption action of activated carbon and the metabolic action of microorganisms, it is easily affected by the quality and temperature of the water to be treated, and the removal rate of organic matter (TOC) is also excluded except immediately after passing water. It is limited to about 20-40%. Moreover, when water temperature fell, such as in winter, the removal rate of ammonia nitrogen was also lowered. In addition, the TOC removal rate in the BAC treatment step 5 may be reduced by the presence of any substance (toxic substance) that inhibits biological activity, but this is a rare event.
Moreover, although it changes with the water quality | types of raw | natural water and water purification process conditions, the removal rate of the organic substance in the aggregation / precipitation process process 2, the BAC process process 5, etc. is grasped | ascertained as an empirical value.
[0011]
Here, the TOC concentration in the raw water is Tr, the TOC removal rate (usually about 30 to 40%) of the sand filtration treatment step 3 for the raw water is Rs, and the TOC removal rate of the BAC treatment step 5 for the ozone treatment step 4 is Rb (ozone treatment). Assuming that there is almost no TOC removal function in step 4, the TOC concentration (TOC concentration before post-chlorination) Tp of BAC treated water is assumed by the following equation (1.1).
[0012]
Tp = Tr * (1-Rs) * (1-Rb) (1.1)
TOC concentration Tr of raw water is 5 mg / L when water quality deteriorates, TOC concentration removal rate Rs in sand filtration treatment step 3 is 30%, and TOC removal rate Rb in BAC treatment step 5 with respect to ozone treatment step 4 is biological activity Assuming 20% in the case of a decrease, if each value is substituted into the above equation (1.1), the TOC concentration Tp of the BAC treated water becomes a calculated value of the following equation (1.2).
[0013]
Tp = 5 * (1-0.3) * (1-0.2) = 2.8 mg / L (1.2)
This value of Tp corresponds to the TOC concentration (2 to 3 mg / L) at the river water level in the middle basin.
Usually, the TOC component contained in river water is mostly composed of humic acid, fulvic acid, and the like, and can be a precursor of trihalomethane (trihalomethane generating ability).
[0014]
Here, assuming that the amount of trihalomethane produced per TOC concentration of 1 mg / L is Rthm (μg-THM FP / mg-TOC), the amount of trihalomethane Tthm produced in purified water by chlorination from the formula (1.1) ( μg / L) is assumed as shown in the following formula (1.3).
[0015]
Tthm = Tr * (1-Rs) * (1-Rb) * Rthm (1.3)
Varies depending on conditions such as water temperature, pH, chlorine injection rate (residual chlorine concentration), residence time (contact time with chlorine), coexisting substances, etc. Generally, per TOC concentration of 1 mg / L humic acid or fulvic acid as the main component From this, it is known that about 20 to 40 μg / L of trihalomethane is produced, and substituting Rthm = 40 μg-THM FP / mg-TOC into the equations (1.2) and (1.3), The amount of trihalomethane produced from raw water having a TOC concentration Tr = 5 mg / L is assumed as shown in the following equation (1.4).
[0016]

In this way, when water quality deteriorates, even in advanced water treatment using ozone and biological activated carbon treatment, the total trihalomethane is very likely to exceed the water quality standard value of 100 μg / L (0.1 mg / L) for tap water. It was big.
[0017]
In addition, when water quality deteriorates during drought or when biological activity decreases such as in winter, the concentration of organic matter (TOC) remaining in the BAC-treated water becomes relatively high, and ammonia nitrogen is completely removed. In some cases, the chlorine injection rate in the post-chlorination process 6 in the subsequent stage may increase.
[0018]
If ammonia nitrogen remains in the BAC-treated water, ammonia nitrogen is removed by pre-discontinuous chlorination, increasing the amount of chlorine consumed in addition to disinfection and sterilization (maintaining residual chlorine concentration). However, since chlorine also reacts with organic matter, it has caused an increase in the chlorine injection rate.
[0019]
The theoretical reaction amount between chlorine and ammonia nitrogen is 1: 7.6, but it is also consumed by other coexisting substances. Therefore, the actual chlorine injection rate must be 10 times the amount of ammonia nitrogen. Is almost.
As a result, the amount of contact (reaction amount) between the remaining organic matter and disinfecting chlorine increased, and the amount of harmful trihalomethanes and organochlorine compounds produced increased.
[0020]
On the other hand, in ozone treatment, when the water quality deteriorates due to drought, etc., the concentration of inorganic substances such as iron and manganese tends to increase in addition to the concentration of organic substances. In addition to the amount of ozone consumed by organic substances, iron and manganese are added. The amount of ozone for oxidative removal also increased, causing an increase in the ozone injection rate.
[0021]
Further, when the number of substances to be removed in the ozone treatment process 4 increases, the competing reaction of coexisting substances becomes complicated, and it becomes difficult to perform optimal ozone injection control, and the ozone injection rate may be excessive or insufficient.
[0022]
Ozone injection control has few problems when the quality of the raw water (treated water) is stable and relatively good, but there are the following problems due to fluctuations in the quality of the raw water and excessive or insufficient ozone input when the water quality deteriorates. Existing.
[0023]
(1) When the ozone injection rate is insufficient
If the organic substance concentration is low even if the ozone injection rate is insufficient, it is possible to remove and reduce odor components and trihalomethane precursors to some extent in the subsequent BAC treatment step 5. However, since the biodegradability of the organic matter is not improved so much, the load on the BAC treatment step 5 is increased, and if the odor component or the organic matter (trihalomethane precursor) exceeding the allowable amount of the BAC treatment flows, the treatment cannot be completed. May remain in clean water.
[0024]
Furthermore, iron ions (Fe²⁺, Fe³⁺) And manganese ions (Mn²⁺) Is oxidized by ozone treatment in advanced treatment, and captured and removed by BAC treatment. However, if the injection rate of ozone is insufficient, iron ions and manganese ions are not completely oxidized, and BAC treated water And then manganese dioxide (MnO₂) And may develop a chromaticity of about 230 to 300 times the manganese concentration.
[0025]
(2) When the ozone injection rate is appropriate
When the ozone injection rate is appropriately performed, the component decomposability of the organic matter is improved to some extent, and the load applied to the BAC treatment is somewhat relaxed as compared with the case (1). However, in the case where the allowable amount of the BAC treatment is exceeded, such as an increase in the concentration of organic matter in the raw water, odor components and organic matter may remain in the purified water as in (1) above.
[0026]
On the other hand, with respect to iron / manganese, when the ozone injection rate is appropriately performed in the ozone treatment step 4, iron is oxidized and precipitated as a hydroxide and manganese is oxidized and precipitated as insoluble manganese dioxide. Captured.
[0027]
As indicated by the following formulas (2.1) and (2.2), the divalent manganese ion is oxidized to tetravalent by ozone and becomes insoluble manganese dioxide.
Mn⁺²+ O_Three+ H₂O → Mn⁺⁴+ O₂COH^-              (2.1)
Mn⁺⁴+ 4OH^-→ MnO₂↓ + H₂O (2.2)
Next, the oxidation reaction of iron is shown in the following formulas (2.3) and (2.4). Divalent iron ions undergo ozone oxidation to become trivalent and hydrate, aggregate and precipitate.
Fe⁺²+ O_Three+ H₂O → Fe⁺³+ O₂+2 (OH^-(2.3)
Fe⁺³+ 3H₂O → Fe (OH)_Three↓ + 3H⁺             (2.4)
However, since organic substances and iron / manganese influence the ozone injection rate, it is sometimes difficult to control the ozone injection rate to an appropriate amount when the water quality deteriorates.
[0028]
(3) When the ozone injection rate is excessive
When the ozone injection rate is excessive, the dissolved ozone concentration of the ozone-treated water increases, which may damage the BAC microorganisms or accelerate the consumption of activated carbon. In this case, the processing function of BAC decreases, and when the allowable amount of BAC processing is exceeded, such as an increase in the concentration of organic substances in the raw water, the odor components and organic substances cannot be completely removed as in (1) above, and the product enters the clean water. There is a possibility of leakage.
[0029]
Further, manganese ions are once oxidized into insoluble manganese dioxide by ozone treatment. As shown by the following formula (2.5), soluble seven-valent permanganate ions (MnO) are dissolved by excessive oxidation of ozone._Four ^-) To change to pink.
[0030]

Permanganate ion is reduced by BAC treatment and returns to manganese dioxide, but it is not the original treatment function of BAC, and it is a strong oxidant permanganate ion, causing damage to BAC microorganisms, and further BAC treatment The function may be degraded.
[0031]
If iron and manganese remain in the purified water, they will cause a bad smell such as gold odor, red water and black water, and coloring troubles, so efficient removal is necessary. In the water quality standard, iron is 0.3 mg / L or less and manganese is 0.05 mg / L or less. Furthermore, in the comfortable water quality item aiming at further improvement of water quality, the target value of manganese is 0.01 mg / L or less.
[0032]
In addition, the amount of generated ozone becomes uneconomical due to the excessive ozone injection rate, and the increase in the amount of exhausted ozone increases the load on the ozone decomposition catalyst and activated carbon in the exhausted ozone treatment device (not shown), so that Running costs may increase.
[0033]
Furthermore, the organic matter that has not been removed in the BAC treatment step 5 and remains in the purified water has a disinfecting and sterilizing effect as long as residual chlorine is present, so there is no risk that microorganisms such as bacteria will propagate. If the water stays in a high-temperature or long-term pipe, etc., residual chlorine disappears, and the organic matter remaining in the purified water is bioavailable organic matter (AOC), which is a nutrient source for microorganisms. There was a concern that it would cause breeding of bacteria.
[0034]
The present invention has been made in view of the above situation, and an object of the present invention is to provide an advanced water purification treatment method that changes the flow of BAC treatment and GAC treatment in accordance with the quality of raw water and takes advantage of each treatment. It is what.
[0035]
Furthermore, in the present invention, from the viewpoint of preventing excessive injection of ozone when water quality deteriorates, iron or manganese is oxidized by medium chlorine during GAC treatment, and ammonia nitrogen cannot be removed by GAC treatment. The purpose is to provide advanced water purification treatment methods that correspond to a wide range of raw water quality by installing a hanikome tube (filler) in order to have a biooxidation treatment effect and removing ammonia nitrogen. is there.
[0036]
[Means for Solving the Problems]
  In order to achieve the above object, the advanced water treatment method according to claim 1 is an indicator of organic matter of raw water.After measuring the concentration of organic matter with a water quality sensor,Ozone treatment of the raw waterAnd thisOzone-treated raw waterBased on the measured value of the water quality sensorBiological activated carbon treatmentReasonOr granular activated carbon treatmentdo itIn the advanced water treatment method for advanced water purification, the water quality sensorIf the measured value does not exceed the criteriaBiological activated carbon treatmentAnd if it exceeds the criteriaGranular activated carbon treatmentThe raw water is highly purified by switching with the switching control device.It is characterized by that.
  According to the first aspect, the organic matter remaining in the activated carbon-treated water can be kept below a certain value, and the amount of trihalomethane produced by the post-chlorination treatment can be suppressed. Furthermore, since the bio-assimilated organic matter (AOC) remaining in the purified water is suppressed to a concentration lower than that in the conventional treatment, there is no concern about the growth of bacteria or the like in the stagnant water distribution pipe, and stable water quality can be supplied. .
[0037]
  The advanced water purification method according to claim 2 is an indicator of organic matter in raw water.After measuring the concentration of organic matter with a water quality sensor,Ozone treatment of the raw waterAnd thisOzone-treated raw waterBased on the measured value of the water quality sensorBiological activated carbon treatmentReasonOr granular activated carbon treatmentIn reasonIn the advanced water treatment method for advanced water purification, the water quality sensorIf the measured value does not exceed the criteriaBiological activated carbon treatmentAnd if it exceeds the criteriaGranular activated carbon treatmentSwitched by a switching control device, andWhile switching to granular activated carbon treatmentIs insideOzone treatment of chlorineUsed when processing the biological activated carbonIn the biological activated carbon layerDissolved oxygenIt is characterized by supplying.
[0038]
According to the second aspect, in addition to the effect of the first aspect, the decrease in the biological activity of the BAC layer can be minimized, and a state similar to that before the suspension can be maintained even during the suspension of the BAC treatment. Moreover, the combined use of medium chlorination removes unstable elements of ozone injection control caused by water quality deterioration, and allows the ozone injection rate to be maintained and controlled within an appropriate range.
[0039]
For this reason, running cost reduction due to excessive generation of ozone, load reduction to GAC treatment due to high dissolved ozone concentration, and outflow of iron / manganese into clean water due to insufficient ozone injection can be prevented.
[0040]
  The advanced water purification treatment method according to claim 3 is the advanced water purification treatment method according to claim 2,Raw water is suppliedInside the landing wellRawFilling for material contact filtrationAgentAir diffuserInstall,thisIt is characterized in that the water receiving well has a biological contact filtration function by blowing air to a diffuser.
[0041]
According to the third aspect, in addition to the effect of the second aspect, the ammoniacal nitrogen concentration in the water to be treated can always be less than 0.1 mg / L, and it is effective for oxidizing and removing iron and manganese with a smaller chlorine injection rate. Can act.
For this reason, the amount of trihalomethane produced | generated by a medium chlorine process is further suppressed.
[0042]
  The advanced water purification treatment method according to claim 4 is the advanced water purification treatment method according to claim 2 or claim 3, wherein the granular activated carbon treatment is performed.SuccessionContinued ozone treatmentsoThe exhausted ozone gas is rendered harmless by the exhaust ozone treatment device.aftersurfaceAerationSurface with equipmentAerationBioactive activated carbon treatmentdidSupply dissolved oxygen to circulating waterI didIt is characterized by that.
[0043]
According to the fourth aspect, in addition to the effects of the second and third aspects, sufficient dissolved oxygen can be supplied to the microorganisms in the BAC layer even while the BAC treatment is stopped, so that the activity of the organism is maintained for a long time. Further, by using the exhaust ozone-treated gas for the surface backing, there is no need to newly install a compressor or blower, and the installation cost and power cost can be reduced.
[0044]
  The advanced water purification method according to claim 5 is the advanced activated water treatment method according to any one of claims 1 to 4, wherein the biological activated carbon treatment is performed.Used whenBiological activated carbon layerInInjecting ozone contact water suppresses the growth and leakage of metazoansI didIt is characterized by that.
[0045]
  According to the fifth aspect, in addition to the effects of the first to fourth aspects, it is possible to greatly suppress metazoans that leak from the BAC treatment step. In addition, since the backwash cycle can be extended by about 2 days from the conventional advanced treatment, it can contribute to the reduction of activated carbon wear and the stability of the microbial layer, resulting in more stable water purification and the running cost of the BAC treatment. Can be greatly reduced.
The advanced water purification treatment system according to claim 6 is a water quality sensor that measures an organic substance concentration that is an index of organic matter of raw water, an ozone treatment process that ozone-treats the raw water, and the ozone-treated raw water that is measured by the water quality sensor. In the advanced water purification treatment system that treats based on the value to make the advanced water purification, the biological activated carbon treatment process that treats when the measured value of the water quality sensor does not exceed the judgment standard, and the treatment when the measured value exceeds the judgment standard A granular activated carbon treatment step and a switching control device for switching between the two treatment steps are provided.
According to the sixth aspect, the organic matter remaining in the activated carbon-treated water can be kept below a certain value, and the amount of trihalomethane produced by the post-chlorination treatment can be suppressed. Furthermore, since the bio-assimilated organic matter (AOC) remaining in the purified water is suppressed to a lower concentration than in the conventional treatment, there is no concern about the growth of bacteria or the like in the stagnant water distribution pipe, and stable water quality can be supplied. .
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a process flow diagram of an advanced water purification method according to the first embodiment of the present invention.
As shown in the figure, the advanced water purification apparatus according to this embodiment includes a landing well 1, a coagulation / precipitation treatment process 2, a sand filtration treatment process 3, an ozone treatment process 4, a BAC treatment process 5, The GAC processing step 8 connected in parallel with the BAC processing step 5, the post-chlorination processing step 6, and the distribution reservoir 7 are arranged in this order, and the water quality sensor 9 installed in the landing well 1 and the BAC processing step 5, the BAC control valve 10 provided in the previous stage, the GAC control valve 11 provided in the previous stage of the GAC processing step 8, the drain valve 12 for discharging the drain of the BAC processing step 5, and the drain of the GAC processing step 8. It consists of a drain valve 13 for discharging and a system switching control device 14.
[0047]
Next, the operation of this embodiment will be described. The same components as those in the conventional example of FIG.
In the present embodiment, the water quality sensor 9 installed in the landing well 1 measures the organic matter (TOC) concentration of raw water flowing into the landing well 1 online, and this measured value T1 is sent to the system switching control device 14. You are typing. Although the total organic carbon concentration meter (TOC meter) is used for the water quality sensor 9, it can be replaced if it can measure the indicator of organic matter, a trihalomethane precursor concentration meter using a fluorescent sensor, a potassium permanganate consumption meter, An ultraviolet absorptiometer or the like can be used.
[0048]
The BAC control valve 10 controls the flow rate of the ozone treated water flowing into the BAC treatment step 5, and the opening degree and opening / closing are controlled based on the output signal Vb <b> 1 from the system switching control device 14. Further, the GAC control valve 11 controls the flow rate of the ozone treated water flowing into the GAC treatment step 8, and the opening degree and the opening / closing are controlled based on the opening / closing signal Vg 1 from the system switching control device 14. The opening and closing of the drain valve 12 and the drain valve 13 are also controlled based on the opening / closing signals Vb2 and Vg2 from the system switching control device 14, respectively.
[0049]
In the system switching control device 14, the opening and opening / closing control of the BAC control valve 10 and the GAC control valve 11 is performed from the TOC concentration T 1 in the raw water flowing into the landing well 1, and the activated carbon of the BAC processing step 5 and the GAC processing step 8 is controlled. The process is controlled, and the operation is as follows.
[0050]
Usually, when the water quality is stable, the TOC concentration T1 in the raw water is less than 5 mg / L, and the activated carbon treatment in the latter stage of the ozone treatment step 4 in this embodiment designates the BAC treatment step 5 as an initial state. It is.
[0051]
In the present embodiment, the TOC concentration of 4 mg / L is used as the determination criterion in the system switching control device 14, but the actual control mode switching is performed by the moving average value Tav6 for 6 hours in the measured value T1 of the TOC concentration, Judgment is made from the lower point Td and the upper point Tu of the TOC concentration, and Td = 3.5 mg / L and Tu = 4 mg / L are set.
[0052]
The system switching control device 14 records the TOC concentration T1 in the raw water, and when the moving average value Tav6 for 6 hours (continuous processing duration) becomes a value of Tu (4 mg / L) or more, the system switching control device 14 stands by from the BAC processing step 5. The opening and opening / closing control of the BAC control valve 10 and the GAC control valve 11 is performed so as to change the processing step to the GAC processing step 8. The activated carbon treatment in the GAC treatment step 8 that has been shifted from the standby state is Td (3.5 mg / L) even if the measured value of the TOC concentration T1 in the raw water is temporarily less than Td (3.5 mg / L). If the condition of ≦ Tav6 is satisfied, the process is continued, and when Tav6 <Td (3.5 mg / L), the process switches to the BAC process step 5.
[0053]
In this way, the 6-hour moving average value Tav6 in the measured value T1 of the TOC concentration is used as a criterion for judgment, and 0. 0 between the lower point Td = 3.5 mg / L and the upper point Tu = 4 mg / L. The reason why the dead zone of 5 mg / L width is set is to prevent frequent switching of processing steps in the vicinity of the judgment reference concentration.
[0054]
The control conditions are summarized as follows.
Tu ≦ Tav6 →→ Switch from BAC process to GAC process.
Td ≦ Tav6 <Tu, → dead zone, continuing the current activated carbon treatment process.
Td> Tav6, → Switch from GAC process to BAC process.
From these experiences, it is known that these setting values are preferably set to a value of 3.5 mg / L or more and Tu-Tu = 0.5 to 1 mg / L.
[0055]
When switching from the BAC treatment process 5 to the GAC treatment process 8 or when switching from the GAC treatment process 8 to the BAC treatment process 5, the system switching control device 14 does not interrupt the water purification treatment even temporarily. Then, after the opening degree is gradually increased from the control valve of the activated carbon treatment process that starts the treatment and the valve is fully opened, the control valve of the standby activated carbon treatment process is gradually closed and is controlled to be fully closed. Further, in the activated carbon treatment process that shifts to standby, the drain valve is quickly opened to drain water, thereby preventing contamination of the activated carbon layer due to residence in the system.
[0056]
For example, in the switching from the BAC processing step 5 to the GAC processing step 8, the system switching control device 14 outputs the opening / closing signal Vg1 so as to open the GAC control valve 11 which has been fully closed, and the GAC control valve 11 is At the same time that the valve is fully opened, the BAC control valve 10 is gradually closed and controlled to be fully closed.
[0057]
When the system switching control device 14 confirms that the GAC control valve 11 is fully closed, the open / close signal Vb2 is output so as to open the drain valve 12 and stays in the BAC processing step 5 from the drain valve 12. Drain the treated water. This prevents contamination in the BAC processing step 5 due to anaerobic formation in the BAC layer and retention in the system. Even when switching from the GAC processing step 8 to the BAC processing step 5, draining in the GAC processing step 8 is performed by the same operation.
[0058]
Here, in this embodiment, the amount of trihalomethane Tthm (μg / L) generated in the purified water in the post-chlorination treatment step 6 is assumed, and according to the formula (1.3) shown in the conventional example, the BAC is used under the following conditions. The case of processing (TthmB) is compared with the case of GAC processing (TthmG).
[0059]

In the case of BAC treatment, there is no room for the water quality standard value (100 μg / L), and it may be possible to immediately exceed the water quality standard value, but the GAC treatment is performed according to the water quality load as in this embodiment. By switching, it is possible to realize a water purification process having a sufficient margin with respect to the water quality reference value.
[0060]
The treatment of ammoniacal nitrogen during the transition to the GAC treatment step 8 is removal by a conventional discontinuous point chlorination method (breakpoint method).
As described above, in this embodiment, by selecting a water purification process that takes advantage of BAC treatment and GAC treatment, the organic matter remaining in the activated carbon treated water can be reduced to a certain value or less. The amount of trihalomethane produced was suppressed.
[0061]
Furthermore, even if residual chlorine disappears, bioavailable organic matter (AOC) remaining in the purified water is suppressed to a lower concentration than in conventional treatment, so there is no concern of causing bacteria or other breeding in the stay water distribution pipe. In addition to the effect of suppressing the production of trihalomethane, it was possible to supply purified water with stable water quality.
[0062]
FIG. 2 is a process flow diagram of the advanced water purification method according to the second embodiment of the present invention.
As shown in the figure, the advanced water purification apparatus of the present embodiment includes a landing well 1, an agglomeration / precipitation treatment process 2, a sand filtration treatment process 3, an ozone treatment process 4, a BAC treatment process 5, Post-chlorination treatment step 6, distribution reservoir 7, GAC treatment step 8, water quality sensor 9 installed in the landing well 1, BAC control valve 10, GAC control valve 11, drain valve 12, and drain valve 13 and the system switching control device 14 are the same as those in the first embodiment shown in FIG. In the present embodiment, a medium chlorine injection device 15, a post chlorine injection device 16, a circulation line 17, a circulation pump 18, and a BAC circulation valve 19 are additionally configured.
[0063]
Next, the operation of this embodiment will be described.
In the present embodiment, when switching to the GAC processing step 8 in the first embodiment of FIG. 1, in order to minimize the decrease in the biological activity of the BAC layer during the pause period of the BAC processing step 5, While supplying the dissolved oxygen to the BAC layer using the circulation pump 18 and switching to the GAC treatment step 8, the medium chlorine injection device 15 performs medium chlorine treatment to reduce the load of the ozone treatment step 4. To implement.
[0064]
In addition to the control of the first embodiment of FIG. 1, the system switching control device 14 adds overall control of chlorine injection in the medium chlorine injection device 15 and the post chlorine injection device 16.
[0065]
In the system switching control device 14, the determination criterion for switching from the BAC processing step 5 to the GAC processing step 8 or switching from the GAC processing step 8 to the BAC processing step 5 is the same as in the first embodiment. However, since the control of each valve in the BAC processing step 5 is different, the operation is also different.
[0066]
In the example of switching from the BAC processing step 5 to the GAC processing step 8, the system switching control device 14 outputs an open / close signal Vg1 so as to open the GAC control valve 11 which has been fully closed, and the GAC At the same time when the control valve 11 is fully opened, an open / close signal Vb3 is output so that the BAC circulation valve 19 is gradually closed, and control is performed so that the fully closed state is achieved. When the fully closed state of the BAC circulation valve 19 is confirmed, the BAC control valve 10 is gradually closed to make the fully closed state, and the circulation pump 18 is started to bring the circulation line 17 into the water state.
[0067]
Further, when the process has completely shifted to the GAC treatment step 8, the system switching control device 14 calculates a medium chlorine injection rate C1 for performing medium chlorine treatment for oxidizing and removing iron and manganese, and the medium chlorine injection device. 15, chlorine is injected into the preceding stage of the sand filtration treatment step 3, and iron and manganese that have become oxides (solid matter) are captured in the sand filtration treatment step 3.
[0068]
Further, the system switching control device 14 comprehensively controls the intermediate chlorine injection rate C1 in the intermediate chlorine injection device 15 and the post-chlorine injection rate C2 in the post-chlorine injection device 16 to comprehensively manage the chlorine injection amount and the residual chlorine concentration. I do.
[0069]
In general, the medium chlorine treatment is performed after the aggregation / precipitation treatment step 2. Since suspended substances and some soluble organic substances have been removed, the chlorine injection rate can be reduced compared to the pre-chlorination treatment, and the amount of trihalomethane produced is greatly reduced, but the post-chlorination treatment performed in the BAC treatment step 5 In fact, the amount of trihalomethane produced is larger.
[0070]
In addition, the medium chlorination treatment oxidizes iron and manganese. Chlorine injection in which ammonia nitrogen is completely removed and residual chlorine becomes free chlorine from bonded chlorine (chloramine) is performed by a conventional discontinuous point chlorination method (breakpoint method) in post-chlorination step 6.
[0071]
In this embodiment, when the water quality deteriorates, the activated carbon is switched to the GAC treatment step 8 where the adsorption performance of the activated carbon is high. Therefore, the trihalomethane generated by the medium chlorine treatment and the organic matter remaining after the ozone treatment step 4 are adsorbed in the GAC treatment step 8. The In addition, since the organic substances are largely removed, the amount of trihalomethane produced after the post-chlorination treatment step 6 is greatly suppressed, and the trihalomethane concentration in the purified water can be reduced to a level equivalent to that of the conventional advanced treatment.
[0072]
Moreover, the oxidation of iron and manganese, which has been performed in the ozone treatment step 4, is performed by the medium chlorine treatment, and is captured by sand filtration. For this reason, the ozone injection | pouring control factor in the ozone treatment process 4 decreases, and the precision of ozone injection | pouring control increases. Thereby, the problem of the ozone injection control which occurred when the water quality deteriorated as shown in the conventional example is solved, and stable ozone treatment can be realized.
[0073]
On the other hand, switching from the GAC treatment step 8 to the BAC treatment step 5 is performed by first stopping the medium chlorine injection in the medium chlorine injection device 15 (C1 = 0 mg / L), and then filtering the sand containing residual chlorine into the BAC treatment step 5. During the replacement time (1 hour) for preventing the inflow of water, the GAC processing step 8 is continued, and then the valves are controlled by the system switching control device 14 so as to shift to the BAC processing step 5.
[0074]
As described above, in addition to the effects of the first embodiment, this embodiment minimizes the decrease in the biological activity of the BAC layer in the BAC processing step 5 even during the transition to the GAC processing step 8, and again performs the BAC processing. The rise processing characteristics when the process moves to (returns to) step 5 can also maintain the same state as before the suspension.
Moreover, the combined use of medium chlorination removes unstable elements of ozone injection control caused by water quality deterioration, and allows the ozone injection rate to be maintained and controlled within an appropriate range.
[0075]
For this reason, the increase in running costs (electricity bill, waste ozone treatment cost, etc.) of ozone facilities due to excessive generation of ozone, prevention of oxidation of manganese dioxide to permanganate ions due to excessive oxidation of ozone, permanganate ions and high It is possible to reduce the load on the GAC treatment due to the dissolved ozone concentration and to prevent the outflow of iron / manganese into the clean water due to insufficient ozone injection. Moreover, deterioration of purified water quality due to these factors can be prevented.
As a result, according to the present embodiment, it was possible to always supply purified water with stable water quality in advanced water purification treatment.
[0076]
FIG. 3 is a process flow diagram of the advanced water purification method according to the third embodiment of the present invention. The same components as those of the second embodiment of FIG.
As shown in the figure, the present embodiment is similar to the second embodiment of FIG. 2 in that the ammoniacal nitrogen sensor 20, the filler 21 for biological contact filtration installed in the landing well 1, and the blower 22. And an air diffuser 23 are added.
[0077]
Next, the operation of this embodiment will be described.
In this embodiment, when the BAC treatment process 5 is switched to the GAC treatment process 8 as shown in the second embodiment of FIG. 2, there is no biological nitrogen treatment process, and therefore the BAC treatment process 5 is suspended. During the period, air is diffused from the bottom of the landing well 1 where the filler 21 is installed, and ammonia nitrogen is removed by biooxidation.
[0078]
In the system switching control device 14, the judgment standard for switching from the BAC processing step 5 to the GAC processing step 8 and the switching from the GAC processing step 8 to the BAC processing step 5 and the overall control of the intermediate chlorine injection device 15 and the post chlorine injection device 16 are the second. Since the control of each valve in the BAC processing step 5 and the GAC processing step 8 is the same as in the embodiment, detailed description thereof is omitted.
[0079]
In the present embodiment, the ammonia nitrogen concentration of raw water flowing into the landing well 1 is measured online using the ammonia nitrogen sensor 20, and the measured value N1 is input to the system switching control device 14.
A filling material 21 to which nitrifying bacteria are attached is installed in the landing well 1, and is characterized by a high ability to remove ammoniacal nitrogen when the nitrifying bacteria are activated.
[0080]
When the BAC treatment step 5 is switched to the GAC treatment step 8, if the ammoniacal nitrogen concentration is in a high state, there is a concern that the amount of trihalomethane generated due to the increase rate of the chlorine injection rate is increased.
[0081]
In the present embodiment, when the ammonia nitrogen concentration N1 is 0.1 mg / L or more during the transition to the GAC processing step 8, the system switching control device 14 adds the air supply device 22 to the air diffuser 23 in the landing well 1. A control signal A1 is output to the air supply device 22 so as to send the compressed air. Then, the dissolved oxygen concentration in the landing well 1 is always kept close to the saturation concentration, and the nitrifying bacteria adhering to the filler 21 are activated to remove the ammonia nitrogen concentration in the raw water by 90% or more.
[0082]
When the ammonia nitrogen concentration N1 is less than 0.1 mg / L, the chlorine injection rate does not increase so much even in the treatment by the conventional discontinuous point chlorination method (breakpoint method). Therefore, aeration to the landing well 1 is suspended.
[0083]
Since surface water such as river water and lake water contains dissolved oxygen in the order of several mg / L, nitrifying bacteria will not be killed even if the aeration to the landing well 1 is stopped. Moreover, if ammonia nitrogen concentration exists in the raw water, the activity of nitrifying bacteria is maintained to the minimum necessary. In recent years, there has been no case where the ammonia nitrogen concentration in the surface water system exceeds 1 mg / L due to restoration of the sewer, etc., and the maximum value of the ammonia nitrogen concentration in this embodiment was 0.82 mg / L.
[0084]
As described above, in addition to the effect of the second embodiment, this embodiment always maintains the ammonia nitrogen concentration in the water to be treated before chlorination at 0.1 mg / kg even during the transition to the GAC treatment step 8. It can be made less than L, and the amount of chlorine consumed in ammoniacal nitrogen by the medium chlorination treatment is reduced, and it effectively acts to oxidize and remove iron and manganese with a smaller chlorine injection rate.
For this reason, the amount of trihalomethane produced | generated by a medium chlorination process was suppressed from 2nd Embodiment, and it was able to supply the purified water of the stable water quality from this result.
[0085]
  FIG. 4 is a process flow diagram of the advanced water purification method according to the fourth embodiment of the present invention. The same components as those of the third embodiment of FIG.
  As shown in the figure, the present embodiment is different from the third embodiment of FIG. 3 in the exhaust ozone treatment device 24, the treatment gas switching device 25, and the surface.AerationDevice 26 and surfaceAerationThe line 27 is added.
[0086]
Next, the operation of this embodiment will be described.
In the present embodiment, the determination criteria for switching from the BAC processing step 5 to the GAC processing step 8 and switching from the GAC processing step 8 to the BAC processing step 5 in the system switching control device 14, the intermediate chlorine injection device 15 and the post-chlorine injection device 16 The overall control is the same as in the second embodiment of FIG. 2 and the third embodiment of FIG. Since the control of each valve in the BAC processing step 5 and the GAC processing step 8 is the same, detailed description thereof is omitted.
[0087]
Moreover, in this embodiment, when it switches to the GAC processing process 8, since the processing process which has the removal effect | action of ammonia nitrogen is lost, the bottom part of the landing well 1 in which the filler 21 was installed during the suspension period of the BAC processing process 5 Since the control regarding performing aeration and removing ammoniacal nitrogen by the biooxidation action is the same as that of the third embodiment of FIG. 3, detailed description thereof is omitted.
[0088]
By the way, in the second embodiment of FIG. 2 and the third embodiment of FIG. 3, when the BAC treatment step 5 is switched to the GAC treatment step 8, the biological activity of the BAC layer is reduced during the pause period of the BAC treatment step 5. In order to minimize it, dissolved oxygen was supplied to the BAC layer using the circulation line 17 and the circulation pump 18. However, in this method, the gas-liquid contact location between the circulating water flowing through the circulation line 17 and the air is limited, and in the summer season when the oxygen solubility decreases, the dissolved oxygen concentration decreases, and microorganisms (bacteria) in the BAC layer decrease. ) May not be maintained for a long time.
[0089]
  In this embodiment, the waste ozone gas discharged from the ozone treatment step 4 is detoxified by the waste ozone treatment device 24, and the surface passes through the treatment gas switching device 25.AerationSurface with device 26AerationThe dissolved oxygen is supplied to the circulating water flowing through the circulation line 17.
[0090]
  In the processing gas switching device 25, the processing gas from the exhaust ozone processing device 24 is opened to the atmosphere or the surfaceAerationWhether to guide to the line 27 is switched, and is controlled by a control signal A2 from the system switching control device 14. That is, the processing gas from the exhaust ozone treatment device 24 is moved to the surface in conjunction with the activation of the circulation pump 18.AerationAt the same time, the line 27 is switched to open to the atmosphere simultaneously with the stop of the circulation pump 18.
[0091]
In the exhaust ozone treatment device 24, the exhaust ozone gas concentration is 1-2 g / m.^Three(Injected ozone gas concentration 20 g / m^ThreeThe ozone decomposing agent uses a heated manganese-based catalyst as the ozone decomposing agent, and the exhausted ozone gas returns to oxygen again after being decomposed.
[0092]
Ozone concentration 20g / m^ThreeMol / m^ThreeConverted to the concentration of
Ozone molecular formula: O_ThreeMW (molecular weight): From 48,
(20 [g] / 48 [g / mol]) / [m^Three] = 0.417 mol / m^Three ... (3.1)
2 mol of ozone molecules are generated from 3 mol of oxygen molecules (3O₂→ 2O_Three), 20 g / m^ThreeThe oxygen molecules used to generate ozone are
0.417 / m^Three* 3/2 = 0.625 mol / m^Three              ... (3.2)
It becomes.
[0093]
On the other hand, 1m^ThreeWhen all the gases present in the air of (1000 L) are regarded as ideal gases and the number of moles is calculated, the volume of 1 mol of the ideal gas is 22.4 L in the standard state (0 ° C., 101.32 kPa).
1000 [L] /22.4 [L / mol] = 44.64 mol / m^Three   ... (3.3)
It becomes.
[0094]
The volume ratio of oxygen in the air is 20.95%, which is 1 m according to the law of partial pressure of Dalton.^ThreeWhen the mol of oxygen present in the air is calculated,
44.64 [mol / m^Three] * 0.2095 = 9.35 mol / m^Three  ... (3.4)
It becomes.
[0095]
20 g / m from the above formulas (3.2) and (3.4)^ThreeThe ratio of oxygen molecules used for ozone generation is 6.7% of the total oxygen amount.
[0096]
0.625 [mol / m^Three] /9.35 [mol / m^Three] * 100 = 6.7% ... (3.5)
There is about 10% of unreacted ozone in the exhausted ozone gas, and it returns to oxygen again by the exhausted ozone treatment, so when subtracting that amount, about 6% of oxygen is lost. When this is recalculated as the oxygen gas concentration in the newly treated exhaust gas, the oxygen concentration is about 20%.
[0097]
(9.35-9.35 * 0.06) / (44.64-9.35 * 0.06)
* 100 = 19.9% (3.6)
Therefore, it can be seen that there is no problem in the oxygen concentration even if the treated exhaust gas is used for the surface backing.
[0098]
  surfaceAerationThe device 26 is installed on the suction side of the circulation pump 18. Since the pressure of the processing gas exhausted from the exhaust ozone treatment device 25 is about atmospheric pressure + 500 to 600 mmAq, it can be understood that surface back-up with a depth of about 30 to 40 cm is sufficient.
[0099]
For reference, when 600 mmAq is converted into an absolute pressure MPa unit,
1 atm = 0.101325 MPa = 1.03323 * 10^FourmmAq
Because
(0.103125 + 600 / 1.03323 * 10^Four) = 0.1594 MPa (absolute pressure).
[0100]
  The surfaceAerationThe device 26 is installed on the suction side of the circulation pump 18, and even if the exhaust pressure of the processing gas shown above slightly decreases,AerationIs taken into consideration.
[0101]
As described above, this embodiment can supply purified water with stable water quality as in the second and third embodiments, and in addition to these effects, moves to the GAC treatment step 8. Even in the middle, since sufficient dissolved oxygen can be supplied to the microorganisms in the BAC layer in the BAC treatment step 5, the activity of the organism can be maintained for a long period of time, and the start-up treatment characteristics when transferred (returned) to the BAC treatment step 5 again Can also be performed faster than in the second and third embodiments. In addition, by using the exhaust ozone-treated gas for the surface backing, it is not necessary to install a new compressor or blower, and the installation cost and power cost can be reduced.
[0102]
FIG. 5 is a process flow diagram of the advanced water purification treatment method of the fifth embodiment of the present invention. The same components as those of the first embodiment of FIG.
As shown in the figure, the present embodiment is configured by adding an ozone water bypass pipe 28, an ozone water injection device 29, and an injection pump 30 to the first embodiment.
[0103]
In the present embodiment, an ozone bypass pipe 28 is inserted into a contact portion of an ozone reaction layer (not shown) constituting the ozone treatment process 4, and ozone contact water having a relatively high dissolved ozone concentration immediately after ozone contact is collected. Water can be used.
[0104]
The ozone water bypass pipe 28 is connected to an ozone water injection device 29 via an injection pump 30. The ozone water injection device 29 is installed in the lower part of a BAC layer (not shown) constituting the BAC treatment step 5, and injects ozone contact water into the BAC layer to generate a small animal (metagenesis) by the strong sterilization power of ozone. (Living organisms) is removed, and propagation and leakage suppression in the BAC treatment step 5 are performed. The BAC tank that constitutes the BAC processing step 5 performs processing in a downward flow.
[0105]
The ozone contact water injection from the ozone water injection device 29 is performed when the process in the BAC processing step 5 is performed, and the control is performed by starting and stopping the injection pump 30 based on the control signal P1 from the system switching control 14. Done. That is, the infusion pump 30 is stopped in conjunction with switching from the BAC processing step 5 to the GAC processing step 8, and conversely, the infusion pump 30 is activated in conjunction with switching from the GAC processing step 8 to the BAC processing step 5. As described above, the system switching control 14 controls the system.
[0106]
In addition, the judgment standard for switching from the BAC processing step 5 to the GAC processing step 8 and the switching from the GAC processing step 8 to the BAC processing step 5 in the system switching control device 14, and the overall control of the intermediate chlorine injection device 15 and the post chlorine injection device 16 are as follows. The control can be performed in the same manner as in the above-described embodiment, and the control of each valve in the BAC processing step 5 and the GAC processing step 8 is the same as that in the above-described embodiment, and thus detailed description thereof is omitted.
[0107]
By the way, in the conventional advanced treatment, washing (back washing) of the BAC layer combining air washing and water washing is performed at a frequency of about once every three days in consideration of the reproduction cycle of metazoans. On the other hand, excessive backwashing may have an adverse effect on microorganisms that wear activated carbon or remove organic substances.
[0108]
In the present embodiment, the ozone contact water is constantly supplied from the ozone water injection device 29 during the processing in the BAC processing step 5 in consideration of the metazoans descending from the upper part of the BAC layer. Can often remove metazoans. In addition, since the BAC tank is a downflow treatment, the ozone contact water injected from the ozone water injection device 29 has no adverse effect on microorganisms present in the upper part of the BAC layer. For this reason, the backwash cycle can be extended by about 2 days from the conventional advanced treatment. However, since the clogging of the BAC layer is not different from the conventional advanced treatment, it is impossible to raise the filter height and to periodically control the backwashing of the activated carbon layer.
[0109]
As described above, according to the present embodiment, it is possible to greatly suppress the metazoans that leak from the BAC treatment step 5 in addition to the effects of the first embodiment. In addition, since the backwash cycle can be extended by about 2 days from the conventional advanced treatment, it can contribute to the reduction of activated carbon wear and the stability of the microbial layer, resulting in more stable water purification and the running cost of the BAC treatment. Was significantly reduced.
[0110]
【The invention's effect】
As described above, according to the present invention, the organic matter remaining in the activated carbon-treated water can be kept below a certain value, and the amount of trihalomethane produced by the post-chlorination treatment can be suppressed. In addition, since the bioavailable organic matter remaining in the purified water is also suppressed to a low concentration, there is no concern about the growth of bacteria in the stagnant water distribution pipe, and the unstable elements of ozone injection control due to water quality deterioration are removed, and ozone injection is performed. It is possible to prevent the outflow of iron and manganese into the purified water due to the shortage, and to supply the purified water with stable water quality.
[Brief description of the drawings]
FIG. 1 is a process flow diagram of an advanced water purification method according to a first embodiment of the present invention.
FIG. 2 is a process flow diagram of an advanced water purification method according to a second embodiment of the present invention.
FIG. 3 is a process flow diagram of an advanced water purification method according to a third embodiment of the present invention.
FIG. 4 is a process flow diagram of an advanced water purification method according to a fourth embodiment of the present invention.
FIG. 5 is a process flow diagram of an advanced water purification method according to a fifth embodiment of the present invention.
FIG. 6 is a process flow diagram of a conventional advanced water purification treatment method.
[Explanation of symbols]
  DESCRIPTION OF SYMBOLS 1 ... Water well, 2 ... Coagulation / precipitation treatment process, 3 ... Sand filtration treatment process, 4 ... Ozone treatment process, 5 ... BAC treatment process, 6 ... Post chlorination process, 7 ... Reservoir, 8 ... GAC treatment process, DESCRIPTION OF SYMBOLS 9 ... Water quality sensor, 10 ... BAC control valve, 11 ... GAC control valve, 12 ... Drain valve, 13 ... Drain valve, 14 ... System switching control device, 15 ... Medium chlorine injection device, 16 ... Post chlorine injection device, 17 ... Circulation line, 18 ... circulation pump, 19 ... BAC circulation valve, 20 ... ammonia nitrogen sensor, 21 ... filler, 22 ... blower, 23 ... aeration device, 24 ... exhaust ozone treatment device, 25 ... treatment gas switching device , 26 ... surfaceAerationDevice, 27 ... surfaceAerationLine, 28 ... ozone water bypass piping, 29 ... ozone water injection device, 30 ... injection pump.

Claims (6)

After the organic matter concentration indicative of organic matter of the raw water were measured by the water quality sensor, the raw water treated with ozone, further biological activated carbon treatment Lima other based on the ozonated raw water in the measurement value of the water quality sensor granular activated carbon in advanced water processing method of the advanced water was treated, the treated biological activated carbon when the measured value of the water quality sensor does not exceed the criteria, the raw water is switched by the switching control unit when it exceeds the criteria granular activated carbon treatment Advanced water purification treatment method characterized by water purification. After the organic matter concentration indicative of organic matter of the raw water were measured by the water quality sensor, the raw water treated with ozone, further biological activated carbon treatment Lima other based on the ozonated raw water in the measurement value of the water quality sensor granular activated carbon switching the advanced water treatment method of the advanced water was processed, the processed biological activated carbon when the measured value of the water quality sensor does not exceed the criteria, the switch control unit when it exceeds the criteria granular activated carbon treatment, Furthermore, while switching to the granular activated carbon treatment, while supplying intermediate chlorine when the ozone treatment, the dissolved oxygen is supplied to the biological activated carbon layer used when the biological activated carbon treatment Water purification method. Raw water was placed a filler及 beauty diffuser for raw-contacting filtered into the reservoir well supplied, that gave a biological contact filtration function to the reservoir well by blowing into the air diffuser The advanced water purification method according to claim 2, wherein Granular activated carbon treatment RiTsugi connection medium is a waste ozone gas discharged by the ozone treatment was surface aeration by the surface aerator after detoxification by discharging ozone treatment apparatus, supplying dissolved oxygen to the circulating water was biological activated carbon treatment advanced water treatment method according to claim 2 or claim 3, wherein that the the to. By injecting ozone contact water in biological activated carbon layer used when the biological activated carbon treatment, any of the claims 1 to 4, wherein it has for inhibiting the growth-leakage of metazoan Advanced water treatment method. A water quality sensor that measures the concentration of organic matter that is an indicator of the organic matter of the raw water, an ozone treatment process that ozone-treats the raw water, and this ozone-treated raw water is treated based on the measurement value of the water quality sensor to obtain advanced water purification In the advanced water purification treatment system, the biological activated carbon treatment step to be treated when the measured value of the water quality sensor does not exceed the judgment standard, the granular activated carbon treatment step to be treated when the judgment standard is exceeded, and both the treatment steps. An advanced water purification system comprising a switching control device for switching.

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