【０００１】
【発明の属する技術分野】
本発明は、下水、上水処理原水、工場排水などの懸濁水（以下「原水」ともいう）の高速固液分離方法及び装置に関し、懸濁水中の懸濁粒子、リン酸イオンなどの凝集除去対象物質を、従来の凝集沈殿又は浮上分離法の５０倍以上の超高速度で浮上分離できる技術に関する。本発明は特に、合流式下水道の雨天時越流水（ＣＳＯと略称される）、又は下水処理施設に流入する下水の超高速固液分離技術として極めて好適な新技術である。
【０００２】
【従来の技術】
最近合流式下水道における雨天時越流水（ＣＳＯ）の、公共用水域への汚濁負荷が大きな問題になっている。合流式下水道の雨天時越流水（ＣＳＯ）は、短時間に膨大な水量が発生するので、超高速度で固液分離でき、ＳＳが除去された処理水を公共用水域に放流する必要があるが、従来超高速度で固液分離する優秀な技術がなかった。
また下水処理施設に流入する下水は、まず最初沈殿池で沈殿分離されたのち、活性汚泥処理されるが、最初沈殿池のＳＳの除去率が悪いため、凝集剤を添加して凝集沈殿処理する例が北欧で普及している。しかし、凝集沈殿処理法によるときには凝集沈殿速度が小さく、大きな沈殿池を必要とする欠点がある。そのためＣＳＯ及び下水を超高速度で固液分離できる新技術が待望されている。
【０００３】
従来、懸濁水に加圧溶解空気含有水又は微細気泡を吹き込んで、気泡に懸濁粒子を付着させて浮上分離する方法が知られている。しかし、従来の浮上分離方法では、浮上分離速度がせいぜい１００〜２００ｍｍ／ｍｉｎ程度と小さく、また空気圧縮機、空気溶解設備などの付帯設備が必要という欠点がある。
【０００４】
【発明が解決しようとする課題】
本発明は、このような実情よりなされたものであり、従来の浮上分離技術の問題点を解決し、簡単な操作によって、各種原水中の懸濁粒子を極めて高速度で浮上分離及びろ過ができ、かつまた空気圧縮機、空気溶解設備が不要な新規方法、装置を提供することを課題とする。
【０００５】
【課題を解決するための手段】
本発明は、下記の手段により上記の課題を解決することができた。
（１）懸濁水に浮上性固体粒子及び有機高分子凝集剤を添加して、懸濁水中の微粒子を該浮上性固体粒子表面に付着させたのち、浮上分離し、該浮上分離からの分離水をろ材充填層を有するろ過装置に通すことを特徴とする懸濁水の高速固液分離方法。
（２）懸濁水をろ材充填層を有するろ過装置に通して懸濁水中の夾雑物を除去したのち、前記ろ過装置流出水に浮上性固体粒子及び有機高分子凝集剤を添加して、前記流出水中の微粒子を該浮上性固体粒子表面に付着させたのち、浮上分離することを特徴とする懸濁水の高速固液分離方法。
【０００６】
（３）懸濁水に浮上性固体粒子及び有機高分子凝集剤を添加して懸濁水中の微粒子を該浮上性固体粒子表面に付着させたのち、微粒子付着浮上性固体粒子を浮上分離する浮上分離装置と、前記浮上分離装置からの分離水を導入して処理水を得るろ材充填層を有するろ過装置とを有することを特徴とする懸濁水の高速固液分離装置。
（４）懸濁水を導入して懸濁水を通過させて夾雑物を除去するろ材充填層を有するろ過装置と、前記ろ過装置からの流出水に浮上性固体粒子及び有機高分子凝集剤を添加して導入し、前記流出水中の微粒子を該浮上性固体粒子表面に付着させたのち、微粒子付着浮上性固体粒子を浮上分離する浮上分離装置とを有することを特徴とする懸濁水の高速固液分離装置。
【０００７】
本発明の骨子は、懸濁水に、水中での浮上力が極めて大きい浮上性固体粒子を添加して撹拌分散させながら、有機高分子凝集剤、又は無機凝集剤と有機高分子凝集剤を添加して撹拌すると５〜１０秒程度後に、懸濁水中の懸濁粒子の凝集フロックが浮上性固体粒子表面に付着し、浮上分離部に流入させると、瞬間的に浮上分離することを見出し、かつその浮上分離工程に先立って充填空隙率８０％以上のろ材充填層を通過させて毛髪、紙片、ゴム製品などの夾雑物（異物）を除去しておく技術思想、及び浮上分離工程の後に充填空隙率９０％以上のろ材充填層に流入させて懸濁水を高速ろ過する技術思想にある。
すなわち、本発明は、懸濁水処理において、その初期段階である粗ろ過、最初沈殿池などの処理段階に、浮上性固体粒子を用いて水中の懸濁粒子の凝集フロックが浮上性固体粒子表面に付着させ、浮上分離させるという「高速浮上分離法」を適用し、及び「高速浮上分離法」に粗ろ過手段を組み合わせて、大量処理を可能ならしめたものである。
【０００８】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。図１は、本発明の粗ろ過後に高速浮上分離法を組み合わせ高速浮上分離プロセスの一実施態様を示す系統図である。
まず、雨天時下水などの原水１を、充填空隙率が好ましくは８０％以上の粗大粒径ろ材の充填層３を有するろ過装置２に通水し、原水１中の異物（毛髪、紙片、ゴム製品、ビニール樹脂片、オイルボールなど）をろ材充填層３に捕捉させて除去する。充填空隙率が８０％未満では、本発明のような高速処理においては、損失水頭が大きくなり好ましくない。なお、ろ材充填層は以下では単に「充填層」ともいう。
【０００９】
また、ろ過材粒径が１０ｍｍ以下であると、損失水頭が大きくなり好ましくない。ろ材の種類としては種々のものが使用できるが、たとえば、化学装置の気液接触塔の充填材（中空円筒形粒子、テラレット、ポールリング、ラシヒリングなど）として利用されているものが、充填時の空隙率が８０％以上と大きいので、本発明に適している。
【００１０】
原水中の粗大異物だけを除去すれば良いので、充填層３の高さは５０〜１００ｃｍ程度で充分である。充填層３内の原水１の通過速度（ＬＶ）は３ｍ／ｍｉｎと非常に大きな値を設定できるようにする。このような充填層３は本発明において重要な役割を果たす。すなわち、本充填層３を設けずに、原水１をそのまま、本発明の高速浮上分離装置１１に流入させると、原水１中の毛髪、ゴム製品破片、オイルボールなどの異物によって、凝集付着槽７の撹拌機８へのからみつき、ポンプなどの浮上物移送機構１５の閉塞が発生してしまい、円滑な運転ができないのである。
なお、本発明の高速分離法においては、ろ材充填層３に代えてスクリーンによって異物を捕捉除去する方法は、スクリーンのヘッドロス及びスクリーン面積が過大になるので適していない。
【００１１】
この充填層３の流出水（粗ろ過原水）５に、凝集剤（高分子凝集剤９単独、又は無機凝集剤４と高分子凝集剤９の併用）と、粒径５００〜１０００μｍ程度の比重が非常に小さい浮上性固体粒子６を添加し、撹拌すると浮上性固体粒子に除去対象物質の凝集フロックが付着した状態が形成される。これを浮上分離装置１１に流入させると、凝集フロック付着浮上性固体粒子が瞬間的に浮上分離され、下方に除去対象物質が除去された処理水が残り、これは懸濁粒子を含まず清澄であって、これにより清澄な処理水１４を装置１１の下部から流出させることができる。
【００１２】
また、図２は、本発明の高速浮上分離後に粗ろ過手段を組み合わせ高速浮上分離プロセスの一実施態様を示す系統図である。図１と共通する箇所には同じ符号を用いる。
この場合には、原水１に凝集剤（高分子凝集剤９単独、又は無機凝集剤４と高分子凝集剤９の併用）と、粒径６００〜１０００μｍ程度の比重が非常に小さい浮上性固体粒子６を添加し、撹拌することにより浮上性固体粒子に除去対象物質の凝集フロックが付着した状態が形成させ、これを浮上分離装置１１に流入させると、凝集フロック付着浮上性固体粒子が瞬間的に浮上分離され、下方に除去対象物質が除去された分離水が残り、これは懸濁粒子を含まず清澄であって、これにより分離水２２を装置１１の下部から流出させる。
【００１３】
この分離水２２を、充填空隙率が９０％以上の粗大粒径ろ材の充填層３を有するろ過装置２に通水し、分離水２２中の未分離凝集フロックなどを充填層３に捕捉させて除去することにより清澄な処理水１４を得る。充填空隙率が９０％未満では、本発明のような高速処理においては、損失水頭が大きくなり好ましくない。
【００１４】
本発明者等の実験によれば、浮上性固体粒子の比重は非常に重要で０．３以下、好ましくは０．０５〜０．２程度の非常に軽量な粒子を使用することが重要である。本発明に適用するために最適な浮上性固体粒子を種々検討した結果、発泡スチロール粒子が最適であった。浮上性固体粒子の粒径も重要であって、平均粒径が３００〜３０００μｍ、好ましくは５００〜１２００μｍ、より好ましくは６００〜２０００μｍである。
【００１５】
浮上性固体粒子６の添加量として好適な範囲は、少なすぎると浮上速度向上効果が少なくなり、多すぎるとフロックに取り込まれなくなるので、かさ容積で原水１リットル当たり、２０〜２００ｍｌ、より好ましくは５０〜１００ｍｌ（ｍｌ浮上粒子／リットル原水程度）が好適範囲である。添加容積比が小さすぎると、浮上性固体粒子６に付着しないフロックが残留し、添加容積比が過大であると浮上分離物１３の量が過大になりすぎ、浮上物１３の移送などのハンドリング面で不利になる。
【００１６】
無機凝集剤４の添加率は原水水質によって変化するが、雨天時下水を本発明によって処理する場合は、ＰＡＣでは１００〜１５０ｍｇ／リットル、塩化第２鉄では２０〜５０ｍｇ／リットル程度である。リン酸イオンを除去しない場合は、無機凝集剤４の添加は不可欠ではなく、カチオン系ポリマ９で代替できることがある。無機凝集剤４の添加位置は、前記の粗ろ材充填層３の入口側に添加すると、充填層３がフロック形成器の役割を果たすので、非常に好ましい実施態様である。
【００１７】
有機高分子凝集剤（ポリマ）９はアニオン性、ノニオン性、カチオン性、両性ポリマのいずれか、またはこれらを併用する。その注入率は、下水の場合、１〜３ｍｇ／リットル程度で充分である。
しかして、フロック付着浮上固体粒子１０を浮上分離部１２の上部に流入させると超高速度で浮上分離する。
【００１８】
次に浮上分離物１３を、浮上分離槽１１上部からポンプなどの任意の移送機構１５によって抜き出し、フロック剥離槽１６で激しく撹拌すると、浮上性固体粒子６相互がもみ洗い状態になり、付着フロックが浮上性固体粒子６表面から剥離するので、これを剥離フロック排除槽１６に供給し、剥離フロックを沈殿させて浮上性微粒子６を回収して再度原水１に添加して再利用する。なお、図１において、２０は剥離フロック排除槽１８の洗浄排水であり、２１はろ材充填層３の排水である。
【００１９】
本発明においては、充填層のろ過速度は、浮上分離部と同様に非常に大きな値を取る（ろ過速度１ｍ／ｍｉｎ以上）ので、空隙率及び粒径が小さいろ材では、損失水頭の上昇が大きいため、充填層空隙率が９０％以上のろ材を充填することが重要である。空隙率が小さいと、浮上分離水を極めて高速度でろ過するので、短時間でろ過抵抗が急増し、実用的ではない。
空隙率が大きいろ材として適しているものは、ラシヒリング、ボールリング、などの気液接触塔に用いられる充填材、プラスチック製中空ろ材、合成繊維の網状又は紐状成型物などが挙げられる。ろ材充填層厚みは５００〜１０００ｍｍ程度が好ましい。
【００２０】
しかして、ろ過処理水ＳＳ濃度をオンライン濁度計で検知しながら運転すると、充填材のＳＳ捕捉容量が限界に達すると処理水ＳＳが設定値以上に増加するので、この時点で、図２の場合には浮上分離水の流入を止め、充填槽内を激しく空気曝気したのち、充填槽内水をドレーンすると充填材が効果的に洗浄される。
充填槽洗浄排水は、浮上分離部の浮上性固体粒子洗浄排水とともに、下水管路又は下水終末処理場に流入させて処理する。
【００２１】
【実施例】
以下、本発明を実施例により具体的に説明するが、本発明はこの実施例により何等制限されるものではない。
【００２２】
実施例１ 合流式下水道の雨天時越流水（ＣＳＯ）の処理試験
ＣＳＯ（ＳＳ ２３０ｍｇ／リットル）を、粒径２０ｍｍ、長さ２０ｍｍの中空円筒ろ材（材質ポリプロピレン）を、厚さ１０００ｍｍに充填した充填層（充填空隙率９０％）にＬＶ ３ｍ／ｍｉｎで流入させた。この結果、毛髪などの粗大異物が充填層に効果的に除去された。
【００２３】
次に充填層流出水に、平均粒径７００μｍの発泡スチロール微粒子を８０ｍｌ／リットル添加し、強く撹拌して撹拌槽全体に分散させながら、塩化第２鉄を３０ｍｇ／リットル添加し、３０秒間急速撹拌を行った後、ポリマ（アニオン性ポリマ、分子量１５００万、銘柄エバグロースＡ１５１）を２ｍｇ／リットル添加し、０．５分急速撹拌したのち、浮上分離速度４０００ｍｍ／ｍｉｎの超高速浮上分離速度に設定した浮上分離装置に流入させた。この結果、浮上性固体粒子に付着したフロックは瞬間的に浮上し、処理水ＳＳは１１ｍｇ／リットルとなり、下水中のＳＳが超高速度で効率よく浮上分離された。
【００２４】
実施例２
ＣＳＯ（ＳＳ ２３０ｍｇ／リットル）に、平均粒径７００μｍの発泡スチロール球状粒子を５０ｍｌ／リットル添加し、強く撹拌して撹拌槽全体に分散させながら、塩化第２鉄を４０ｍｇ／リットル添加し、２０秒間急速撹拌を行った後、ポリマ（アニオン性ポリマ、分子量１５００万、銘柄エバグロースＡ１５１）を２ｍｇ／リットル添加し、１０秒急速撹拌したところ、発泡スチロール球状粒子表面に下水中のＳＳが付着した。こののち、浮上分離速度４ｍ／ｍｉｎの超高速浮上分離速度に設定した浮上分離装置に流入させた。この結果、フロックが付着した浮上性固体粒子は瞬間的に浮上し、処理水平均ＳＳは１２．３ｍｇ／リットルとなり、下水中のＳＳが効率よく浮上分離された。
【００２５】
浮上分離処理水を、粒径２０ｍｍの立方体スポンジを層厚１ｍに充填したろ過層（空隙率９０％）にろ過速度２ｍ／ｍｉｎで流通させた。その結果、ろ過水ＳＳは５ｍｇ／リットル以下であった。ろ過抵抗が１ｍ水頭に達するまでの時間は３時間であった。発泡スチロール粒子が浮上分離工程から微量（２〜３個／リットル処理水）流出したが、スポンジろ過層で完全に捕捉された。
また、高分子凝集剤添加率を４ｍｇ／リットルに増加しても浮上分離処理水のＳＳは平均７．２ｍｇ／リットルであり、ろ過工程を設けずに、浮上分離だけで処理水ＳＳを５ｍｇ／リットル以下に下げることは、高分子凝集剤増加率を４ｍｇ／リットルに増加しても不可能であった。
【００２６】
比較例
従来公知の加圧溶解空気を利用する浮上分離装置で試験した。原水は実施例１と同一である。下水（ＳＳ２３０ｍｇ／リットル）に塩化第２鉄を４ｍｇ／リットル添加し、３０秒間急速攪拌を行った後、アニオン性ポリマ、分子量１５００万、銘柄エバグロースＡ１５１を１．５ｍｇ／リットル添加し、１分急速攪拌したのち、加圧溶解空気を含んだ水を供給し、浮上分離速度２００ｍｍ／ｍｉｎに設定した浮上分離装置に流入させた。この結果浮上粒子に付着したフロックは緩慢に浮上した。処理水ＳＳは１２ｍｇ／リットルとなり、下水中のＳＳが除去された。
しかし、浮上分離速度４００ｍｍ／ｍｉｎに設定して運転したところ、フロックはほとんど浮上せず、下降流の水流に随伴されて処理水に流出し、処理水ＳＳが１９３ｍｇ／リットルと著しく悪化し処理不可能であった。
【００２７】
【発明の効果】
以上のような「浮上性固体粒子を利用した高速浮上分離技術」と「空隙率の大きな充填材ろ過」の直列システムによれば、次の重要な効果が得られ、理想的な超高速固液分離システムが形成される。
（１）従来の浮上分離法では全く不可能であった超高速度の浮上分離速度で原水中の懸濁粒子を浮上分離できる。本発明の浮上分離速度は、文字通り驚異的であり５〜７ｍ／ｍｉｎが可能であり、従来の浮上分離法の５０〜７０倍の浮上速度が可能である。従って、装置設置面積、設備費が非常に削減できる。
（２）下水などの懸濁水を非常に高速度でＳＳが少ない清澄な処理水に浄化できる。
（３）浮上分離部だけでＳＳを高度に除去する必要がないため、浮上分離部の高分子凝集剤添加量を、疎ろ材ろ過部を設けない場合よりも削減できる。（浮上分離部のＳＳ除去量は高分子凝集剤添加率に比例する）
（４）浮上分離された浮上性固体粒子は回収して再利用できるので、浮上性固体粒子の添加コストが安価である。
（５）従来の加圧溶解空気浮上分離法で不可欠であった空気コンプレッサ、空気溶解槽などが不要であり、設備費、動力費が削減できる。
（６）合流式下水道の雨天時越流水（ＣＳＯ）のように短時間に膨大な水量が発生する原水に極めて好適であり、非常にコンパクトな装置でＣＳＯの懸濁粒子を、目の細かいスクリーン（ヘッドロスが大きく、目詰まりし易い）を使用することなく、高度に除去できる。
（７）浮上分離部の後にろ過充填層を設ける形式の場合には、
ａ）発泡スチロールなどの浮上性固体粒子が浮上分離部から少量流出した場合でも、疎ろ材充填層で捕捉されるので、河川などの放流先に浮上性固体粒子が逃げるトラブルがない。
ｂ）ろ過層の前で、原水中のＳＳの大部分が浮上分離されて除去されるので、ろ過層を極めて大きなろ過速度を設定してもろ過抵抗の増加が少ない。
ｃ）ろ過層に流入してくるＳＳは既に浮上分離部でフロック化し、粒径が原水ＳＳより、大幅に増加しているので、空隙率の大きな疎ろ材に高速度で通水しても効率よく充填層に捕捉される。
【図面の簡単な説明】
【図１】
本発明の高速固液分離方法で、浮上分離部の前にろ材充填層を設ける形式のブロック図を示す。
【図２】
本発明の高速固液分離方法で、浮上分離部の後にろ材充填層を設ける形式のブロック図を示す。
【符号の説明】
１ 原水
２ ろ過装置
３ ろ材充填層
４ 無機凝集剤
５ 流出水
６ 浮上性固体粒子
７ 凝集付着槽
８ 撹拌機
９ 高分子凝集剤
１０ フロック付着浮上性固体粒子含有水
１１ 浮上分離装置
１２ 浮上分離部
１３ 浮上物
１４ 処理水
１５ 浮上物移送機構
１６ フロック剥離槽
１７ 剥離フロック含有水
１８ 剥離フロック排除部
１９ 回収浮上性固体粒子
２０ 洗浄排水
２１ 排水
２２ 分離水[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method and an apparatus for high-speed solid-liquid separation of suspended water (hereinafter also referred to as “raw water”) such as sewage, raw water treated water, and factory wastewater, and to remove aggregated particles such as suspended particles and phosphate ions in the suspended water. The present invention relates to a technique capable of levitation separation of a target substance at an ultra-high speed 50 times or more that of a conventional coagulation sedimentation or levitation separation method. In particular, the present invention is a new technology that is extremely suitable as an ultrahigh-speed solid-liquid separation technology for combined-type sewer stormwater overflow (abbreviated as CSO) or sewage flowing into a sewage treatment facility.
[0002]
[Prior art]
Recently, the pollution load of public water bodies due to rainfall overflow (CSO) in a combined sewer has become a major problem. Since the stormwater overflow (CSO) of the combined sewer system generates an enormous amount of water in a short time, solid-liquid separation can be performed at an extremely high speed, and the treated water from which SS has been removed needs to be discharged to public water bodies. However, there has not been an excellent technique for solid-liquid separation at a very high speed.
The sewage flowing into the sewage treatment facility is first separated by sedimentation in the sedimentation basin, and then treated with activated sludge. Examples are widespread in Northern Europe. However, the coagulation-sedimentation method has the disadvantage that the coagulation-sedimentation rate is low and a large sedimentation tank is required. Therefore, a new technique capable of separating CSO and sewage into solid and liquid at an extremely high speed is expected.
[0003]
Conventionally, there has been known a method in which water containing pressurized dissolved air or fine air bubbles is blown into suspension water to cause suspended particles to adhere to the air bubbles and float and separate. However, the conventional flotation method has drawbacks in that the flotation speed is as low as 100 to 200 mm / min at most, and additional facilities such as an air compressor and an air dissolution facility are required.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and solves the problems of the conventional flotation technology. By simple operation, flotation and filtration of suspended particles in various raw waters can be performed at an extremely high speed. Another object of the present invention is to provide a new method and apparatus which do not require an air compressor and an air melting facility.
[0005]
[Means for Solving the Problems]
The present invention has solved the above problems by the following means.
(1) The floating solid particles and the organic polymer flocculant are added to the suspension water, and the fine particles in the suspension water are attached to the surface of the floating solid particles. A high-speed solid-liquid separation method for suspended water, wherein the suspension is passed through a filtration device having a filter medium packed bed.
(2) The suspended water is passed through a filtration device having a filter material packed layer to remove impurities in the suspended water, and then buoyant solid particles and an organic polymer flocculant are added to the effluent of the filtration device. A high-speed solid-liquid separation method for suspended water, wherein fine particles in water are attached to the surface of the buoyant solid particles, followed by levitation separation.
[0006]
(3) Floating separation in which the floating solid particles and the organic polymer flocculant are added to the suspension water to cause the fine particles in the suspension water to adhere to the surface of the floating solid particles, and then the floating solid particles to which the fine particles adhere are floated and separated. A high-speed solid-liquid separation apparatus for suspension water, comprising: an apparatus; and a filtration apparatus having a filter medium packed bed for obtaining treated water by introducing the separated water from the flotation apparatus.
(4) A filtration device having a filter material packed bed for introducing suspended water and passing the suspended water to remove impurities, and adding buoyant solid particles and an organic polymer flocculant to effluent from the filtration device. A high-speed solid-liquid separation of suspended water, comprising: a flotation device for flotation-separating the fine solid particles attached to the floating solid particles after adhering the fine particles in the effluent to the surface of the floating solid particles. apparatus.
[0007]
The essence of the present invention is to add an organic polymer coagulant, or an inorganic coagulant and an organic polymer coagulant to a suspension water while adding and stirring and dispersing buoyant solid particles having a very large buoyancy in water. After about 5 to 10 seconds, the flocculence of the suspended particles in the suspension water adheres to the surface of the buoyant solid particles, and when flowing into the flotation separation section, it is found that the flotation is instantaneously flotated and separated. Technical idea of removing impurities (foreign matter) such as hair, paper pieces, rubber products, etc. by passing through a filter medium packed layer with a filled porosity of 80% or more prior to the flotation separation step, and filling porosity after the flotation separation step The technical idea is to flow suspended water at a high speed of 90% or more into a filter medium packed bed.
That is, in the present invention, in the suspension water treatment, the flocculation of suspended particles in water using the buoyant solid particles is applied to the surface of the buoyant solid particles by using the buoyant solid particles in the initial stages such as coarse filtration and the first settling tank. The method employs a "high-speed flotation method" of adhering and flotation separation, and combines a "high-speed flotation method" with a coarse filtration means to enable large-scale processing.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram showing one embodiment of the high-speed flotation process of the present invention which combines the high-speed flotation method after the coarse filtration.
First, raw water 1 such as sewage in rainy weather is passed through a filtration device 2 having a packed layer 3 of a coarse-grained filter medium having a filled porosity of preferably 80% or more, and foreign matter (hair, paper chips, rubber, Products, vinyl resin pieces, oil balls, etc.) are captured by the filter medium filling layer 3 and removed. If the filling porosity is less than 80%, the loss head becomes large in high-speed treatment as in the present invention, which is not preferable. In addition, a filter medium filling layer is only hereafter called a "filling layer."
[0009]
On the other hand, if the filter material particle size is 10 mm or less, the head loss is increased, which is not preferable. Various types of filter media can be used. For example, those that are used as packing materials (hollow cylindrical particles, terrarets, pole rings, Raschig rings, etc.) for gas-liquid contact towers of chemical equipment, Since the porosity is as large as 80% or more, it is suitable for the present invention.
[0010]
Since only coarse foreign matters in the raw water need to be removed, the height of the packed layer 3 of about 50 to 100 cm is sufficient. The passing speed (LV) of the raw water 1 in the packed bed 3 can be set to a very large value of 3 m / min. Such a filling layer 3 plays an important role in the present invention. That is, if the raw water 1 is allowed to flow into the high-speed flotation / separation apparatus 11 of the present invention without providing the main filling layer 3, the foreign matter such as hair, rubber product debris, and oil balls in the raw water 1 causes the coagulation adhesion tank 7. Entangled with the stirrer 8 and blockage of the floating material transfer mechanism 15 such as a pump occurs, and smooth operation cannot be performed.
In the high-speed separation method of the present invention, a method of trapping and removing foreign substances by a screen instead of the filter medium filling layer 3 is not suitable because the head loss of the screen and the screen area become excessive.
[0011]
The effluent (raw water of coarse filtration) 5 of the packed bed 3 is mixed with a flocculant (polymer flocculant 9 alone or a combination of inorganic flocculant 4 and polymer flocculant 9) with a specific gravity of about 500 to 1000 μm in particle size. When very small buoyant solid particles 6 are added and stirred, a state is formed in which flocculent flocs of the substance to be removed adhere to the buoyant solid particles. When this is flown into the flotation device 11, the flocculated floc-adhering buoyant solid particles are instantaneously flotated and separated, and the treated water from which the substance to be removed has been removed remains below, which is clear and contains no suspended particles. Accordingly, the clear treated water 14 can be discharged from the lower part of the apparatus 11.
[0012]
FIG. 2 is a system diagram showing one embodiment of the high-speed flotation separation process of the present invention in which a coarse filtration means is combined after high-speed flotation. 1 are denoted by the same reference numerals.
In this case, the raw water 1 is combined with a flocculant (the polymer flocculant 9 alone or the inorganic flocculant 4 and the polymer flocculant 9 in combination) and the buoyant solid particles having a particle diameter of about 600 to 1000 μm and a very small specific gravity. 6 is added and stirred to form a state in which the flocculated floc of the substance to be removed is attached to the buoyant solid particles, and when the flocculant is allowed to flow into the flotation / separation device 11, the agglomerated floc attached buoyant solid particles instantaneously Separated water from which the substance to be removed has been removed remains by flotation, and this is clear without suspended particles, whereby the separated water 22 flows out from the lower part of the apparatus 11.
[0013]
The separated water 22 is passed through a filtration device 2 having a packed bed 3 of a coarse-grained filter medium having a packed porosity of 90% or more, so that unseparated aggregated flocs and the like in the separated water 22 are captured by the packed bed 3. By removing, clear treated water 14 is obtained. If the filling porosity is less than 90%, the loss head becomes large in a high-speed treatment as in the present invention, which is not preferable.
[0014]
According to experiments by the present inventors, the specific gravity of the buoyant solid particles is very important, and it is important to use very lightweight particles of 0.3 or less, preferably about 0.05 to 0.2. . As a result of various studies on the most suitable buoyant solid particles to be applied to the present invention, styrene foam particles were most suitable. The particle size of the buoyant solid particles is also important, and the average particle size is 300 to 3000 μm, preferably 500 to 1200 μm, and more preferably 600 to 2000 μm.
[0015]
The preferable range of the amount of the buoyant solid particles 6 is as follows. If the amount is too small, the effect of improving the surfacing speed is reduced, and if the amount is too large, it is not taken into the floc. A preferred range is 50 to 100 ml (about 1 ml floating particles / liter raw water). If the added volume ratio is too small, flocs that do not adhere to the buoyant solid particles 6 remain, and if the added volume ratio is too large, the amount of the floated sediment 13 becomes too large, and handling surfaces such as transfer of the floated material 13 will occur. At a disadvantage.
[0016]
The rate of addition of the inorganic flocculant 4 varies depending on the quality of the raw water, but when the sewage in rainy weather is treated according to the present invention, it is about 100 to 150 mg / liter for PAC and about 20 to 50 mg / liter for ferric chloride. When the phosphate ions are not removed, the addition of the inorganic flocculant 4 is not essential, and may be replaced by the cationic polymer 9 in some cases. It is a very preferable embodiment that the inorganic coagulant 4 is added at the inlet side of the coarse filter medium packed layer 3 because the packed layer 3 functions as a floc forming device.
[0017]
The organic polymer coagulant (polymer) 9 is any of anionic, nonionic, cationic, and amphoteric polymers, or a combination thereof. In the case of sewage, an injection rate of about 1 to 3 mg / liter is sufficient.
Thus, when the floc-adhering floating solid particles 10 flow into the upper part of the floating separation part 12, they float and separate at an extremely high speed.
[0018]
Next, the floating separated material 13 is withdrawn from the upper part of the floating separation tank 11 by an arbitrary transfer mechanism 15 such as a pump, and is vigorously stirred in the floc separating tank 16. Since the exfoliated solid particles 6 are separated from the surface, they are supplied to the exfoliated floc elimination tank 16, where the exfoliated flocs are settled to collect the levitating fine particles 6, added to the raw water 1 again, and reused. In FIG. 1, reference numeral 20 denotes cleaning drainage of the separation floc elimination tank 18, and reference numeral 21 denotes drainage of the filter medium filling layer 3.
[0019]
In the present invention, the filtration speed of the packed bed takes a very large value as in the case of the flotation separation section (filtration speed of 1 m / min or more). Therefore, it is important to fill a filter medium having a porosity of the packed bed of 90% or more. If the porosity is small, the floating separation water is filtered at an extremely high speed, so that the filtration resistance rapidly increases in a short time, which is not practical.
Materials suitable for a filter medium having a high porosity include fillers used for gas-liquid contact towers such as Raschig rings and ball rings, hollow filter mediums made of plastics, and net-like or cord-like molded synthetic fibers. The thickness of the filter medium filling layer is preferably about 500 to 1000 mm.
[0020]
When the operation is performed while detecting the concentration of the filtered water SS with the online turbidity meter, when the SS trapping capacity of the filler reaches the limit, the treated water SS increases to a set value or more. In this case, the inflow of the floating separated water is stopped, the inside of the filling tank is vigorously aerated, and then the filling material is effectively washed by draining the water in the filling tank.
The filling tank washing wastewater flows into a sewage pipe or a sewage terminal treatment plant together with the buoyant solid particle washing wastewater in the flotation / separation section for treatment.
[0021]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the Examples.
[0022]
Example 1 Treatment Test of Overflowing Water (CSO) in Combined Sewerage in Rainy Weather Filling of CSO (SS 230 mg / L) filled with a hollow cylindrical filter medium (polypropylene material) having a particle size of 20 mm and a length of 20 mm to a thickness of 1000 mm The liquid was introduced into the layer (filled porosity 90%) at an LV of 3 m / min. As a result, coarse foreign substances such as hair were effectively removed from the filling layer.
[0023]
Next, 80 ml / l of styrene foam fine particles having an average particle diameter of 700 µm is added to the packed bed effluent, and ferrochloride is added at 30 mg / l while being vigorously stirred and dispersed throughout the stirring tank, and rapidly stirred for 30 seconds. After that, 2 mg / liter of a polymer (anionic polymer, molecular weight 15 million, brand Ebagulose A151) was added, and the mixture was rapidly stirred for 0.5 minute, and then set to an ultra-high-speed flotation speed of 4000 mm / min. Flowed into the separator. As a result, the floc adhering to the buoyant solid particles instantaneously floated, the treated water SS became 11 mg / liter, and the SS in the sewage was efficiently floated and separated at an extremely high speed.
[0024]
Example 2
To CSO (SS 230 mg / l), styrene foam spherical particles having an average particle diameter of 700 μm are added at 50 ml / l, and while ferrous chloride is dispersed throughout the stirring tank, ferric chloride (40 mg / l) is added, and the mixture is rapidly added for 20 seconds. After stirring, 2 mg / liter of a polymer (anionic polymer, molecular weight 15 million, brand Ebagulose A151) was added, and the mixture was rapidly stirred for 10 seconds. As a result, SS in the sewage adhered to the surface of the expanded polystyrene spherical particles. Thereafter, the mixture was flowed into a flotation device set at an ultra-high flotation speed of 4 m / min. As a result, the buoyant solid particles to which the flocs adhered instantaneously floated, the average SS of the treated water became 12.3 mg / liter, and the SS in the sewage was efficiently floated and separated.
[0025]
The flotation treatment water was passed at a filtration rate of 2 m / min through a filtration layer (porosity 90%) in which a cubic sponge having a particle diameter of 20 mm was filled to a thickness of 1 m. As a result, the filtered water SS was 5 mg / liter or less. The time required for the filtration resistance to reach 1 m head was 3 hours. A small amount (2 to 3 pieces / liter of treated water) of styrofoam particles flowed out from the flotation separation step, but was completely captured by the sponge filtration layer.
Further, even when the polymer flocculant addition rate was increased to 4 mg / liter, the SS of the flotation treated water was 7.2 mg / l on average, and 5 mg / liter of the treated water SS was obtained only by flotation without providing a filtration step. It was not possible to reduce the amount to less than 1 liter even if the increase rate of the polymer flocculant was increased to 4 mg / liter.
[0026]
Comparative Example A test was conducted using a conventionally known flotation apparatus using dissolved air under pressure. Raw water is the same as in the first embodiment. 4 mg / L of ferric chloride was added to sewage (SS 230 mg / L), and the mixture was rapidly stirred for 30 seconds, and then 1.5 mg / L of anionic polymer, molecular weight 15 million, brand Ebagulose A151 was added, and the mixture was rapidly added for 1 minute. After stirring, water containing pressurized dissolved air was supplied and flowed into a flotation device set at a flotation speed of 200 mm / min. As a result, the flocs attached to the floating particles floated slowly. The treated water SS became 12 mg / liter, and the SS in the sewage was removed.
However, when the operation was performed with the flotation separation speed set to 400 mm / min, flocs hardly levitated, flowed out into the treated water accompanying the descending water flow, and the treated water SS was significantly deteriorated to 193 mg / liter, and the treated water was not treated. It was possible.
[0027]
【The invention's effect】
According to the series system of "high-speed flotation technology using buoyant solid particles" and "filtration of filler with large porosity", the following important effects can be obtained, and the ideal ultra-high-speed solid-liquid A separation system is formed.
(1) Suspended particles in raw water can be floated at an ultra-high flotation speed, which was completely impossible with the conventional flotation method. The flotation speed of the present invention is literally surprising, and can be 5 to 7 m / min, and can be 50 to 70 times that of the conventional flotation method. Therefore, the equipment installation area and equipment cost can be significantly reduced.
(2) Suspended water such as sewage can be purified at a very high speed into clear treated water with little SS.
(3) Since it is not necessary to remove the SS to a high degree only by the flotation / separation part, the amount of the polymer flocculant to be added to the flotation / separation part can be reduced as compared with the case where the filtering material filtration part is not provided. (The amount of SS removed in the flotation section is proportional to the polymer coagulant addition rate)
(4) Since the floating solid particles separated by floating can be collected and reused, the cost of adding the floating solid particles is low.
(5) An air compressor, an air dissolving tank, and the like, which are indispensable in the conventional pressurized dissolved air flotation method, are not required, and equipment costs and power costs can be reduced.
(6) It is extremely suitable for raw water in which a huge amount of water is generated in a short time, such as combined rainfall storm water (CSO), and uses a very compact device to screen suspended particles of CSO with a fine screen. (A large head loss and easy clogging) can be highly removed.
(7) In the case where a filtration packed bed is provided after the flotation separation section,
a) Even if a small amount of buoyant solid particles such as styrene foam flow out of the flotation / separation part, they are trapped in the sparsely packed bed, so that there is no trouble that the buoyant solid particles escape to a discharge destination such as a river.
b) Since most of the SS in the raw water is removed by flotation before the filtration layer, even if an extremely high filtration speed is set for the filtration layer, the increase in filtration resistance is small.
c) The SS flowing into the filtration layer has already flocculated in the flotation separation section, and the particle size has been significantly increased compared to the raw water SS. Well trapped in packed beds.
[Brief description of the drawings]
FIG.
FIG. 2 is a block diagram of a type in which a filter medium packed layer is provided in front of a flotation separation section in the high-speed solid-liquid separation method of the present invention.
FIG. 2
FIG. 3 is a block diagram of a type in which a filter medium packed layer is provided after a flotation separation unit in the high-speed solid-liquid separation method of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 Raw water 2 Filtration device 3 Filter material packed bed 4 Inorganic coagulant 5 Outflow water 6 Floating solid particles 7 Aggregation adhesion tank 8 Stirrer 9 Polymer coagulant 10 Floc-adhering buoyant solid particle-containing water 11 Floating separator 12 Floating separator Reference Signs List 13 Floating material 14 Treated water 15 Floating material transfer mechanism 16 Flock separation tank 17 Separated floc-containing water 18 Separated floc elimination unit 19 Collectable buoyant solid particles 20 Washing drainage 21 Drainage 22 Separated water