JP3673882B2

JP3673882B2 - Sludge treatment method and apparatus

Info

Publication number: JP3673882B2
Application number: JP5708197A
Authority: JP
Inventors: 賢山岡; 憲二端; 修清野
Original assignee: 独立行政法人農業工学研究所; 社団法人日本農業集落排水協会
Priority date: 1997-02-25
Filing date: 1997-02-25
Publication date: 2005-07-20
Anticipated expiration: 2017-02-25
Also published as: JPH10235400A

Description

【０００１】
【発明の属する技術分野】
本発明は汚泥処理方法およびその装置に関し、特に、天日乾燥床により汚泥を処理する汚泥処理方法およびその装置に関するものである。
【０００２】
【従来の技術】
下水、集落排水等の生活排水の浄化処理により生成される汚泥は、多量の水分を含み、体積が大きく取り扱いに不便である。このため、従来、汚泥の処理方法では、まず、第１段階で、予め汚泥を沈降および微生物処理によって濃縮消化し、この濃縮消化された汚泥を図７および図８に示すような汚泥処理装置としての天日乾燥床２に投入し、汚泥の脱水・乾燥を行うようにしている。天日乾燥床２は、床表面の砂層７で汚泥と水を濾過分離し、その後、日射、風などで脱水乾燥するもので、この天日乾燥床２は、図８に示すように、コンクリートの底部３Ａと壁部３Ｂとを備えたコンクリート槽３の底に濾液排水管４を配置し、槽３の底に砂利６と砂７を順次投入して濾過層５を形成して構成される。濾液排水管４は、濾過層５により濾過された濾液が浸透する浸透口４Ａを有するとともに排出端４Ｂが槽３の外部に延びている。コンクリート槽３には、図示していないが汚泥投入用の蛇口およびポンプが設けられる。固液分離装置としての天日乾燥床２は、外部から濾過層５上に濃縮消化された汚泥Ｍ₁ が投入されると、濾過層５の表面５Ａに濾し残された汚泥の固形分Ｓ₁ が溜り、濾過され固形分Ｓ₁ から分離された濾液は濾過層５内を浸透し、濾液排水管４の浸透口４Ａを介して外部に排出されるようになっている。濾過層５の表面５Ａに固形分Ｓ₁ が堆積すると、固液分離性能が落ちてくるので、濾過表面の目詰まりを防ぐため、図９の（Ａ）に示すように、クロスフローＦを発生させて固形分Ｓ₁ を除去するようにしている。また、図９の（Ｂ）に示すように、濾過方向と反対側から、すなわち、濾過層５の下側から上に向けて水流や気流ＢＷを発生させ、濾過表面５Ａ全体を洗浄する逆洗が行われる。逆洗時には、濾材６、７内部に多量の水量あるいは高圧のエアを下から上に通過させ濾過面５Ａ全面を洗浄するようにしているため、濾過は行われない。
【０００３】
【発明が解決しようとする課題】
従来の天日乾燥床２は、予め濃縮消化された汚泥に用いられることが一般的であり、低濃度の活性汚泥の処理には適していないという問題がある。すなわち、濃度の薄い汚泥水Ｍ₂ （3,000 〜5,000 mg SS/L 程度）を天日乾燥床２により処理すると、図１０のグラフに示すように、汚泥の固形分と水とを濾過分離するのに長時間を要するからである。つまり、低濃度の汚泥水Ｍ₂ が天日乾燥床２に投入されると、濾過層５上の液状汚泥Ｍ₂ では、濾過分離中に汚泥水Ｍ₂ の固形分Ｓ₁ が濾過層５の表面５Ａに沈殿・堆積し、固形分Ｓ₁ と分離された水がその沈殿・堆積された汚泥層Ｓ₂ の上部に滞留してしまう。分離された水が濾過されて排出されるためには、濾過層５より透水性の悪い汚泥層Ｓ₂ を通過しなければならない。このため、天日乾燥床２による処理に当たっては汚泥を予め濃縮消化しなければならず、時間がかかるだけでなく、コストアップを招くという問題がある。
【０００４】
本発明は上記問題点を除くためになされたもので、天日乾燥床における固液分離性能を向上させ、低濃度の汚泥を効率的に汚泥処理することができる汚泥処理方法およびその装置を提供することを目的とするものである。
【０００５】
【課題を解決するための手段】
本発明に係る汚泥処理方法は、槽内に濾過層を形成し、槽の底部に、浸透口を有するとともに排出端が上記槽の外部に延びる濾液排水管を配設し、この濾過層上に汚泥水を投入して濾過層により濾過し、この濾液を濾液排水管を介して外部に排水する汚泥処理方法において、濾過層を下側砂利層と上側砂層とにより構成し、濾液排水管を上記下側砂利層に配置し、複数の通気口を有する通気管を上記上側砂層内の所定の部位に埋設し、汚泥水の投入後、外部から通気管にエアを間欠的に送出して通気口からエアを放出させ、上昇する気泡に濾過層上面に徐々に沈殿する透水性の悪い汚泥層を通過させて汚泥層を排除し、汚泥の固形分と分離して汚泥層上に滞留する分離水と濾過層とを連通させつつ汚泥を処理するようにしたものである。
【０００６】
本発明に係る汚泥処理方法は、濾過層を下側砂利層と上側砂層とにより構成し、濾液排水管を上記下側砂利層に配置し、複数の通気口を有する通気管を上記上側砂層内の所定の部位に埋設し、汚泥水の投入後、外部から通気管にエアを間欠的に送出して通気口からエアを放出させ、上昇する気泡に濾過層上面に徐々に沈殿する透水性の悪い汚泥層を通過させて汚泥層を排除し、汚泥の固形分と分離して汚泥層上に滞留する分離水と濾過層とを連通させつつ汚泥を処理するようにしているので、槽に外部から汚泥水が投入されると、まず初めに、固液混合状態の汚泥水は濾過層により濾過され、濾過された濾液は濾過層を浸透し濾液排水管を介して外部に排出される。濾過層上に滞留する汚泥水は、時間の経過とともに固形分と水とに分離して、固形分が濾過層上面に沈殿・堆積して汚泥層を形成する。汚泥層は透水性が悪いため、分離水の濾過層への浸透性能を劣化させる。汚泥層が形成されると、外部から通気管にエアを送出し、通気口からエアを放出する。通気口から放出されたエアは気泡となって濾過層内を上昇し、濾過層上面から汚泥層を通過し、さらに分離水を経て大気に達する。気泡が汚泥層を通過する際、汚泥層の一部は気泡により排除され、濾過層と分離水とが連通されるので、分離水は汚泥層を介さず直接濾過層に浸透する。このため、汚泥水の濾過層への浸透性が高まり、分離水は効率よく外部に排出される。
【０００７】
また、本発明に係る汚泥処理装置は、槽の内部に形成され投入された汚泥水を濾過する濾過層と、この槽の底部に配設された浸透口を有するとともに排出端が上記槽の外部に延びる濾液排水管とを備えた汚泥処理装置において、濾過層を下側砂利層と上側砂層とにより構成し、濾液排水管を上記下側砂利層に配置するとともに、通気口が上記上側砂層内の所定の部位に複数配された通気管と、この通気管に連通され外部からエアを間欠的に送出するエアポンプとからなるエア放出機構を設けたものである。
【０００８】
本発明に係る汚泥処理装置は、濾過層を下側砂利層と上側砂層とにより構成し、濾液排水管を上記下側砂利層に配置するとともに、通気口が上記上側砂層内の所定の部位に複数配された通気管と、この通気管に連通され外部からエアを間欠的に送出するエアポンプとからなるエア放出機構を設けたことにより、槽に外部から汚泥水が投入されると、汚泥水は濾過層により濾過され、濾過された濾液は濾過層を浸透し濾液排水管を介して外部に排出される。濾過層上に滞留する汚泥水は、時間の経過とともに固形分と水とに分離して、固形分が濾過層上面に沈殿・堆積して汚泥層を形成する。この汚泥水の沈殿・濾過時、外部から通気管にエアを送出し、通気口からエアを放出すると、通気口から放出されたエアは気泡となって濾過層内を上昇し、濾過層上面から汚泥層を通過し分離水を経て大気に達する。気泡が汚泥層を通過する際、汚泥層の一部は気泡により排除され、濾過層と分離水とが連通されるので、分離水は汚泥層を介さず直接濾過層に浸透する。このため、汚泥水の濾過層への透水性が高まり、分離水は効率よく外部に排出される。
【０００９】
【発明の実施の形態】
以下、図面に基いて本発明の実施の形態について説明する。図１は本発明の一実施例に係る汚泥処理装置を示す縦断面図、図２の（Ａ）、（Ｂ）はそれぞれエアの非放出時および放出時の状態を示す説明図、図３は図１の汚泥処理装置の通気口の配置を示す横断面図である。上記従来の汚泥処理装置と同一または相当部分には同一符号を付してその説明を省略する。本実施例に係る汚泥処理装置（以下、天日乾燥床と称す）１２は、図１に示すように、コンクリートの底部１３Ａと壁部１３Ｂとを備えたコンクリート槽１３と、このコンクリート槽１３の底に配置された濾液排水管１４と、コンクリート槽１３に砂利６と砂７を順次投入して形成された下側砂利槽６と上側砂層７とからなる濾過層１５とを備えるとともに、砂層７には、エア放出機構２０が設けられる。天日乾燥床１２には、汚泥投入側に図示しない汚泥の投入用蛇口およびポンプが設けられる。濾液排水管１４は、濾過層１５により濾過された濾液が浸透する浸透口１４Ａを有するとともに排出端１４Ｂが槽１３の外部に延びている。天日乾燥床１２は、外部から濾過層１５上に液状の汚泥水Ｍが投入されると、濾過層１５により濾過された濾液が濾過層１５内を浸透し、濾液排水管１４の浸透口１４Ａを介して外部に排出されるようになっている。
【００１０】
ところで、エア放出機構２０は、図１に示すように、コンクリート槽１３の外部に設置されたエアポンプ２１と、一端がこのエアポンプ２１に連通され、多数の通気口２２が砂層７内にほぼ均等な密度で配置された通気管２３とから構成される。通気管２３は、図３に示すように、外部のエアポンプ２１に接続された本管２３Ａと、この本管２３Ａから分岐して濾過層１５の砂層７内に互いに平行に埋設された支管２３Ｂとからなっている。通気口２２は、図３に示すように、支管２３の埋設部分に設けられる。各通気口２２には、図示しない逆止弁が設けられ、濾過層成分としての砂または水がエアポンプ２１側に侵入するのを阻止するようになっている。エアポンプ２１は、図３に示すように、制御弁２４を介して本管２３Ａに接続される。これらエアポンプ２１と制御弁２４はタイマを内蔵した制御装置２５と電気的に接続される。制御装置２５は、予め設定されたデータに基づいてエアポンプ２１と制御弁２４とを制御し、通気管２３にエアを間欠的に送出するようになっている。
【００１１】
次に、本発明の汚泥処理方法について、上記構成に係る汚泥処理装置（天日乾燥床）１２の作用に基づいて説明する。天日乾燥床１２に外部から低濃度（3,000 〜5,000 mg SS/L 程度）の汚泥水Ｍ₂ を投入し、濾過層１５上に滞留させると、汚泥水Ｍ₂ は濾過層１５により濾過され、濾過された濾液は濾過層１５を浸透し浸透口１４Ａから濾液排水管１４を介して外部に排出される。濾過層１５上に滞留する汚泥水Ｍ₂ は、時間の経過とともに固形分Ｓ₁ と水Ｗとに分離して、固形分Ｓ₁ が濾過層上面１５Ａに沈殿・堆積して汚泥層Ｓ₂ を形成する（図２の（Ａ）参照）。透水性の悪い汚泥層Ｓ₂ の形成により、分離された水Ｗは濾過層１５に浸透しにくくなる。この汚泥水Ｍ₂ の沈殿・濾過時、制御装置２５によりエアポンプ２１と制御弁２４とを動作させると、エアポンプ２１は制御弁２４を介して通気管２３に所定圧のエアを送出する。エアは通気管２３の本管２３Ａから支管２３Ｂに分流され、通気口２２から砂層７の内部に放出される。砂層７に放出されたエアは、図２の（Ｂ）に示すように、気泡２６となって砂層７内を上昇し、濾過層上面１５Ａから汚泥層Ｓ₂ を通過し、分離水Ｗを経て大気に達する。気泡２６が汚泥層Ｓ₂ を通過する際、汚泥層Ｓ₂ の一部は気泡２６により排除され、濾過層１５と分離水Ｗとが連通される。このため、分離水Ｗは汚泥層Ｓ₂ を介さず、直接濾過層１５に浸透する。このように、本発明に係る汚泥処理方法では、汚泥水Ｍ₂ の濾過層１５への浸透性が高まり、分離水Ｗは濾液排水管１４を介して効率よく外部に排出される。従って、低濃度の汚泥水であっても効率的に処理することができるので、従来のように、天日乾燥床による汚泥処理の前に、濃縮消化処理を行う必要がなく、直接低濃度の汚泥水を処理することができる。また、低濃度の汚泥水を効率的に処理できるので、コストダウンを図ることができる。
【００１２】
また、上述のように汚泥水Ｍ₂ の沈殿・堆積時、通気口２２からエアを放出する際、気泡２６が濾過層上面１５Ａに達した時、あるいは、気泡２６が汚泥層Ｓ₂ 内を通過して上昇している時には、分離水Ｗは気泡２６にブロックされて濾過層１５側に浸透しにくい。このため、制御装置２５により予め設定されたデータに基づいてエアポンプ２１と制御弁２４とを制御し、通気管２３にエアを間欠的に送出し、気泡２６により分離水Ｗと濾過層１５とを連通させた後、しばらくエアの放出を停止すると、より浸透性が向上し、固液分離性能が高まる。エア送出時間とエア送出停止時間の設定は、汚泥水の濃度に応じて予め求められる沈殿速度（堆積速度）や投入水量により決定することができる。
【００１３】
【実施例】
次に、上記構成に係る汚泥処理装置をモデル化した室内実験結果を示す。上記汚泥処理方法およびその装置の有効性を確認するため、本発明者らは、図４に示す室内実験装置１１２で実験を行った。室内実験装置１１２は、内径１００mmの透明のアクリルパイプ１１２Ａにアクリル板で底１１２Ｂを設けた。底部１１２Ｂに水道用蛇口１１４を取り付け排水口とした。この容器１１２の底部に網戸用の網部材を敷き下側に砂利１０６を、上側に細砂１０７を詰め、汚泥天日乾燥床を再現した。また、曝気濾過法を行うため、エアポンプ１２１と接続したエアーストーンを砂層１０７に埋めた。
【００１４】
実験条件は次のとおりである。
ＲＵＮ−１：実験装置１１２の上部から水道水を入れ、非曝気で濾過時間を測定した。
ＲＵＮ−２：同じく水道水を入れ、曝気しながら濾過時間を測定した。
ＲＵＮ−３：汚泥約１リットルを入れ、非曝気で濾過時間を測定した。
ＲＵＮ−４：汚泥約１リットルを入れ、全曝気（濾過開始から終了まで連続的に曝気）で濾過時間を測定した。
ＲＵＮ−５：汚泥約１リットルを入れ、間欠曝気（濾過開始後２分毎に１５秒間曝気）で濾過時間を測定した。
ＲＵＮ−６：汚泥約１リットルを入れ、途中曝気（濾過開始後砂層表面に汚泥層が形成され、濾過速度が著しく低下するまで非曝気で濾過し、その後濾過終了まで曝気）で濾過時間を測定した。
用いた汚泥は、茨城県美浦村内の農業集落排水施設から採取したもので、ＭＬＳＳ濃度は2,600mg/L 、沈降性の指標であるＳＶ３０は９％であった。また、ＲＵＮ−３ないしＲＵＮ−６は、各ＲＵＮ終了後、汚泥を取り出すため、汚泥とともに表面の砂も取り出し、その分の砂を新たに加えたため、砂層１０７の濾過特性が各ＲＵＮ毎にちがってしまうことが懸念され、各ＲＵＮ終了後に各ＲＵＮ毎にＲＵＮ−１と同様の水道水による非曝気濾過試験を行った。これらをＲＵＮ−４’ないしＲＵＮ−６’という。また、ＲＵＮ−３ないしＲＵＮ−６の測定条件を揃えるため、濾過速度測定開始前は、排水口の水道栓１１４を閉じ、砂層１０７表面まで水道水を満たした状態で、汚泥を入れ排水口を開いて濾過速度を測定した。
【００１５】
実験結果を図５および図６に示す。ＲＵＮ−１とＲＵＮ−２の結果では図５に示すように、ＲＵＮ−１の濾過時間が短かった。水道水の砂層の通過では、曝気によるメリットはなく、流下面積が気泡によって減少する分だけ通過に時間がかかることが判明した。それに対して、汚泥を投入した場合の濾過は、図６に示すように、汚泥を非曝気で濾過したＲＵＮ−３に比べて、曝気を行ったＲＵＮ−４ないしＲＵＮ−６の濾過時間はいずれも短かった。濾過時間はＲＵＮ−４＞ＲＵＮ−６＞ＲＵＮ−５の順で短くなっており、曝気時間が短いＲＵＮ−５が、最も濾過時間が短かった。この理由として、ＲＵＮ−４およびＲＵＮ−６では、気泡によって汚泥層の一部が破壊されても、その部分から気泡の上昇が続くので、水分の流下が速やかに行えない。また、気泡の上昇位置が時々移動して汚泥層の破壊された部分が残っても、曝気により汚泥層上部の水に多くの汚泥が混合され、汚泥層の破壊された部分が、侵入する水分の持ち込む汚泥ですぐに閉塞してしまう。特に、ＲＵＮ−４にように、濾過開始当初から曝気を行うと、濾材の砂１０７が液中に送り込まれ、濾過終了後の汚泥層の上面に砂１０７が多く見られた。このため、間欠曝気により濾材表面に汚泥層が形成される毎に、汚泥層の一部を破壊するのが濾過時間短縮と省エネルギーに優れていた。汚泥投入前に砂層の条件を確認するために行ったＲＵＮ−４’ないしＲＵＮ−６’の結果は、図５に示すように、各ＲＵＮ毎に相違はあるが、その差は汚泥を投入した場合の濾過時間の差に比べると無視できる程度である。なお、本実験では、濾過高さは８cm程度であるが、実用的には３０cm以上の濾過高さが必要とされ、本願発明のようなエア放出機構を持たない従来の天日乾燥床では、図１０に示すように、排水に４日程度を要したケースがあった。
【００１６】
なお、上記実施例では、通気口２２の形成された支管２３Ｂを砂層に配置しているがこれに限られるものではなく、砂利層に配置してもよい。しかしながら、通気口２２は、濾過層１５の表面１５Ａ近くでかつ所定の厚さの濾過層を上側に確保して設けることが望ましい。また、制御装置２５は予め設定されたデータに基づいてエアを通気管２３に間欠的に送出するようにしているが、これに限られるものではなく、コンクリート槽内部に汚泥層の堆積厚さを検知するセンサを設け、このセンサからの検知信号に基づいて通気管２３へのエアの送出のタイミングを制御するようにしてもよい。また、この検知信号に基づいてエアの送出量あるいは送出圧力を制御するようにしてもよい。さらに、上記実施例のように低濃度の汚泥水Ｍ₂ の処理にあたっては、投入される低濃度の汚泥水Ｍ₂ の固形分は濾過層１５の上面１５Ａ全域にほぼ均等に沈殿・堆積するため、多数の通気口２２を砂層７内でほぼ均等な密度で配置するようにしている。しかしながら、汚泥水Ｍ₂ の投入条件等により、濾過層１５の上面１５Ａに堆積する汚泥層の厚さに偏りが生じる場合、偏りに応じて通気口の配置数を場所により適宜変更し、通気口の密度を変えてもよいことは言うまでもない。また、上記実施例の説明において、濾過層からエアを放出し気泡を発生させることを曝気と称しているが、本願でいう曝気は液中へのエアの送気と同義であって、微生物処理に供するための酸素供給のためのものではない。
【００１７】
【発明の効果】
以上述べたように本発明によれば、濾過層を下側砂利層と上側砂層とにより構成し、濾液排水管を上記下側砂利層に配置し、複数の通気口を有する通気管を上記上側砂層内の所定の部位に埋設し、汚泥水の投入後、外部から通気管にエアを間欠的に送出して通気口からエアを放出させ、上昇する気泡に濾過層上面に徐々に沈殿する透水性の悪い汚泥層を通過させて汚泥層を排除し、汚泥の固形分と分離して汚泥層上に滞留する分離水と濾過層とを連通させつつ汚泥を処理するようにしたことにより、汚泥水の沈殿・濾過時、濾過層上に汚泥層が形成されると、汚泥層を気泡により排除して分離水と濾過層とを連通させ、浸透性を向上させることができるので、固液分離性能を向上させて汚泥処理の作業時間を短縮することができる。また、従来、処理が困難であった低濃度の汚泥を汚泥処理することができるので、従来のように、天日乾燥床による汚泥処理の前に、濃縮消化処理を行う必要がなく、作業効率を向上させ、コストダウンを図ることができる。
【００１８】
また、本発明によれば、濾過層を下側砂利層と上側砂層とにより構成し、濾液排水管を上記下側砂利層に配置するとともに、通気口が上記上側砂層内の所定の部位に複数配された通気管と、この通気管に連通され外部からエアを間欠的に送出するエアポンプとからなるエア放出機構を設けたことにより、汚泥水の沈殿・濾過時、濾過層上に形成される汚泥層を気泡により排除して分離水と濾過層とを連通させることができるので、固液分離性能を向上させて汚泥処理の作業時間を短縮することができる。
【図面の簡単な説明】
【図１】本発明の一実施例に係る汚泥処理装置を示す縦断面図である。
【図２】（Ａ）、（Ｂ）はそれぞれ図１の汚泥処理装置のエアの非放出時および放出時の状態を示す説明図である。
【図３】図１の汚泥処理装置の通気口の配置を示す横断面図である。
【図４】実験装置を示す斜視図である。
【図５】図４の実験装置を用いて水道水による濾過実験を行った結果を示すグラフである。
【図６】図４の実験装置を用いて汚泥による濾過実験を行った結果を示すグラフである。
【図７】従来の天日乾燥床を示す平面図である。
【図８】図７の天日乾燥床を示す縦断面図である。
【図９】（Ａ）は従来の天日乾燥床におけるクロスフローの流れを示す説明図、（Ｂ）は従来の天日乾燥床における逆洗時の流れを示す説明図である。
【図１０】従来の天日乾燥床における低濃度の汚泥処理に要した水層の厚さと経過日数との関係を示すグラフである。
【符号の説明】
１２天日乾燥床（汚泥処理装置）
１３コンクリート槽（槽）
１３Ａコンクリート槽の底部
１４濾液排水管
１４Ａ浸透口
１４Ｂ排出端
１５濾過層
２０エア放出機構
２２通気口
２３通気管
２６気泡
Ｍ、Ｍ₂ 汚泥水
Ｓ₂ 汚泥層
Ｗ分離水[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sludge treatment method and apparatus, and more particularly to a sludge treatment method and apparatus for treating sludge with a sun-dried bed.
[0002]
[Prior art]
Sludge produced by purification treatment of domestic wastewater such as sewage and village wastewater contains a large amount of water, has a large volume, and is inconvenient to handle. Therefore, in the conventional sludge treatment method, first, in the first stage, sludge is concentrated and digested in advance by sedimentation and microbial treatment, and the concentrated and digested sludge is used as a sludge treatment apparatus as shown in FIG. 7 and FIG. Is put into the sun drying bed 2 and the sludge is dewatered and dried. The sun-dried floor 2 is one in which sludge and water are filtered and separated by a sand layer 7 on the floor surface, and then dehydrated and dried by sunlight, wind, etc. This sun-dried floor 2 is made of concrete as shown in FIG. The filtrate drain pipe 4 is arranged at the bottom of the concrete tank 3 having the bottom part 3A and the wall part 3B, and the gravel 6 and the sand 7 are sequentially added to the bottom of the tank 3 to form the filtration layer 5. . The filtrate drain pipe 4 has a permeation port 4 A through which the filtrate filtered by the filtration layer 5 penetrates, and a discharge end 4 B extends to the outside of the tank 3. Although not shown, the concrete tank 3 is provided with a faucet and a pump for introducing sludge. In the sun drying bed 2 as a solid-liquid separator, when sludge M ₁ concentrated and digested on the filtration layer 5 is input from the outside, the solid content S _{1 of the} sludge left on the surface 5A of the filtration layer 5 is filtered. The filtrate separated from the solid content S ₁ permeates through the filtration layer 5 and is discharged to the outside through the permeation port 4 A of the filtrate drain pipe 4. If the solid content S ₁ is deposited on the surface 5A of the filtration layer 5, the solid-liquid separation performance deteriorates. Therefore, in order to prevent clogging of the filtration surface, a cross flow F is generated as shown in FIG. Thus, the solid content S ₁ is removed. Further, as shown in FIG. 9B, backwashing that cleans the entire filtration surface 5A by generating a water flow or an air flow BW from the opposite side of the filtration direction, that is, from the lower side of the filtration layer 5 to the upper side. Is done. At the time of backwashing, filtration is not performed because a large amount of water or high-pressure air is passed through the filter media 6 and 7 from below to wash the entire filtration surface 5A.
[0003]
[Problems to be solved by the invention]
The conventional sun-dried bed 2 is generally used for sludge that has been concentrated and digested in advance, and has a problem that it is not suitable for the treatment of low-concentration activated sludge. That is, when sludge water M _{2 having} a low concentration (about 3,000 to 5,000 mg SS / L) is treated by the sun-dried bed 2, the solid content of sludge and water are separated by filtration as shown in the graph of FIG. This is because it takes a long time. That is, when the low-concentration sludge water M ₂ is introduced into the sun drying bed 2, the solid content S ₁ of the sludge water M ₂ in the liquid sludge M ₂ on the filtration layer 5 is reduced in the filtration layer 5 during the filtration separation. The water precipitated and deposited on the surface 5A and separated from the solid content S ₁ stays in the upper part of the deposited and deposited sludge layer S ₂ . In order for the separated water to be filtered and discharged, the water must pass through the sludge layer S ₂ having a lower water permeability than the filtration layer 5. For this reason, the sludge must be concentrated and digested in advance for the treatment by the sun-dried bed 2, which is not only time consuming but also increases costs.
[0004]
The present invention has been made to eliminate the above-mentioned problems, and provides a sludge treatment method and apparatus capable of improving the solid-liquid separation performance in a sun-dried bed and efficiently treating sludge with a low concentration. It is intended to do.
[0005]
[Means for Solving the Problems]
In the sludge treatment method according to the present invention, a filtration layer is formed in a tank, a filtrate drain pipe having a permeation port and having a discharge end extending outside the tank is disposed at the bottom of the tank, and the filtration layer is formed on the filtration layer. In a sludge treatment method in which sludge water is introduced and filtered through a filtration layer, and the filtrate is drained to the outside through a filtrate drain pipe, the filtration layer is composed of a lower gravel layer and an upper sand layer, and the filtrate drain pipe is Arranged in the lower gravel layer, a ventilation pipe having a plurality of ventilation holes is embedded in a predetermined part in the upper sand layer , and after introducing sludge water, air is intermittently sent from the outside to the ventilation pipes. The separated water that is released from the air, passes through the sludge layer with poor water permeability that gradually settles on the upper surface of the filtration layer to the rising bubbles, eliminates the sludge layer, separates from the sludge solids, and stays on the sludge layer The sludge is treated while communicating with the filter layer.
[0006]
In the sludge treatment method according to the present invention, the filtration layer is composed of a lower gravel layer and an upper sand layer, a filtrate drain pipe is disposed in the lower gravel layer, and a vent pipe having a plurality of vents is provided in the upper sand layer . Of water permeability that is gradually deposited on the upper surface of the filtration layer in the rising air bubbles after intermittently sending air from the outside to the vent pipe to release air from the vent , Since the sludge layer is removed by passing the bad sludge layer and separated from the solid content of the sludge and separated water staying on the sludge layer is connected to the filtration layer, the sludge is treated outside the tank. When sludge water is introduced from the first, the sludge water in a solid-liquid mixed state is first filtered by the filtration layer, and the filtered filtrate permeates the filtration layer and is discharged to the outside through the filtrate drain pipe. The sludge water staying on the filtration layer is separated into solids and water as time passes, and the solids settle and deposit on the upper surface of the filtration layer to form a sludge layer. Since the sludge layer has poor water permeability, the permeation performance of the separated water into the filtration layer is deteriorated. When the sludge layer is formed, air is sent from the outside to the vent pipe, and the air is discharged from the vent. The air released from the vents becomes bubbles and rises in the filtration layer, passes through the sludge layer from the upper surface of the filtration layer, and further reaches the atmosphere through separated water. When the air bubbles pass through the sludge layer, a part of the sludge layer is excluded by the air bubbles, and the filtration layer and the separated water communicate with each other, so that the separated water penetrates directly into the filtration layer without passing through the sludge layer. For this reason, the permeability to the filtration layer of sludge water increases, and the separated water is efficiently discharged to the outside.
[0007]
Further, the sludge treatment apparatus according to the present invention has a filtration layer for filtering sludge water formed and introduced inside the tank, and a permeation port disposed at the bottom of the tank, and a discharge end is located outside the tank. In the sludge treatment apparatus provided with a filtrate drain pipe extending to the bottom , a filtration layer is constituted by a lower gravel layer and an upper sand layer, a filtrate drain pipe is disposed in the lower gravel layer, and a vent hole is provided in the upper sand layer . Provided with an air discharge mechanism comprising a plurality of vent pipes arranged at a predetermined portion and an air pump communicating with the vent pipe and intermittently sending air from the outside.
[0008]
In the sludge treatment apparatus according to the present invention, the filtration layer is composed of a lower gravel layer and an upper sand layer, a filtrate drain pipe is disposed in the lower gravel layer, and a vent is located at a predetermined site in the upper sand layer . By providing an air release mechanism comprising a plurality of vent pipes and an air pump that communicates with the vent pipe and intermittently sends air from the outside, sludge water is introduced into the tank from the outside. Is filtered by the filtration layer, and the filtrate filtered is permeated through the filtration layer and discharged to the outside through the filtrate drain pipe. The sludge water staying on the filtration layer is separated into solids and water as time passes, and the solids settle and deposit on the upper surface of the filtration layer to form a sludge layer. When this sludge water is precipitated and filtered, air is sent from the outside to the vent pipe, and when air is released from the vent, the air released from the vent becomes bubbles and rises in the filter layer, and from the upper surface of the filter layer It passes through the sludge layer and reaches the atmosphere through separated water. When the air bubbles pass through the sludge layer, a part of the sludge layer is excluded by the air bubbles, and the filtration layer and the separated water communicate with each other, so that the separated water penetrates directly into the filtration layer without passing through the sludge layer. For this reason, the water permeability to the filtration layer of sludge water increases, and separation water is efficiently discharged outside.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a sludge treatment apparatus according to one embodiment of the present invention, FIGS. 2A and 2B are explanatory views showing the state when air is not released and when air is released, respectively, and FIG. It is a cross-sectional view which shows arrangement | positioning of the vent of the sludge processing apparatus of FIG. The same or corresponding parts as those in the conventional sludge treatment apparatus are designated by the same reference numerals and the description thereof is omitted. As shown in FIG. 1, a sludge treatment apparatus (hereinafter referred to as a sun drying floor) 12 according to the present embodiment includes a concrete tank 13 having a concrete bottom 13 A and a wall 13 B, and the concrete tank 13. A filtrate drain pipe 14 arranged at the bottom, a filtration layer 15 composed of a lower gravel tank 6 and an upper sand layer 7 formed by sequentially putting gravel 6 and sand 7 into a concrete tank 13, and a sand layer 7 Is provided with an air discharge mechanism 20. The sun drying floor 12 is provided with a sludge charging faucet and a pump (not shown) on the sludge charging side. The filtrate drain pipe 14 has a permeation port 14 A through which the filtrate filtered by the filtration layer 15 penetrates, and a discharge end 14 B extends to the outside of the tank 13. In the sun-dried bed 12, when liquid sludge water M is introduced from the outside onto the filtration layer 15, the filtrate filtered by the filtration layer 15 permeates the filtration layer 15, and the permeation port 14A of the filtrate drain pipe 14 is obtained. It is designed to be discharged to the outside.
[0010]
By the way, as shown in FIG. 1, the air release mechanism 20 has an air pump 21 installed outside the concrete tank 13, one end communicating with the air pump 21, and a large number of vent holes 22 in the sand layer 7. It is comprised from the vent pipe 23 arrange | positioned by the density. As shown in FIG. 3, the ventilation pipe 23 includes a main pipe 23A connected to an external air pump 21, and branch pipes 23B branched from the main pipe 23A and embedded in the sand layer 7 of the filtration layer 15 in parallel with each other. It is made up of. As shown in FIG. 3, the air vent 22 is provided in the embedded portion of the branch pipe 23. Each vent port 22 is provided with a check valve (not shown) so as to prevent sand or water as a filtration layer component from entering the air pump 21 side. As shown in FIG. 3, the air pump 21 is connected to the main pipe 23 A via the control valve 24. The air pump 21 and the control valve 24 are electrically connected to a control device 25 having a built-in timer. The control device 25 controls the air pump 21 and the control valve 24 based on preset data, and intermittently sends air to the vent pipe 23.
[0011]
Next, the sludge treatment method of the present invention will be described based on the action of the sludge treatment apparatus (sun drying bed) 12 according to the above configuration. When sludge water M ₂ having a low concentration (about 3,000 to 5,000 mg SS / L) is introduced into the sun-dried bed 12 and retained on the filtration layer 15, the sludge water M ₂ is filtered by the filtration layer 15, The filtered filtrate permeates the filtration layer 15 and is discharged to the outside through the filtrate outlet pipe 14 from the permeation port 14A. The sludge water M ₂ staying on the filtration layer 15 is separated into solid content S ₁ and water W over time, and the solid content S ₁ is precipitated and deposited on the upper surface 15A of the filtration layer to form the sludge layer S ₂ . (See FIG. 2A). The formation of the sludge layer S _{2 having} poor water permeability makes it difficult for the separated water W to penetrate into the filtration layer 15. When the control device 25 operates the air pump 21 and the control valve 24 during the sedimentation and filtration of the sludge water M ₂ , the air pump 21 sends air of a predetermined pressure to the vent pipe 23 via the control valve 24. Air is diverted from the main pipe 23 A of the vent pipe 23 to the branch pipe 23 B, and is discharged from the vent hole 22 into the sand layer 7. As shown in FIG. 2B, the air released to the sand layer 7 rises in the sand layer 7 as bubbles 26, passes through the sludge layer S ₂ from the filtration layer upper surface 15A, and passes through the separated water W. Reach the atmosphere. When the bubble 26 passes through the sludge layer S _2, a portion of the sludge layer S ₂ are eliminated by the bubble 26, it is passed through the filtration layer 15 separated water W are communicated. For this reason, the separated water W penetrates directly into the filtration layer 15 without passing through the sludge layer S ₂ . Thus, in the sludge treatment method according to the present invention, the permeability of the sludge water M _{2 to} the filtration layer 15 is increased, and the separated water W is efficiently discharged to the outside through the filtrate drain pipe 14. Therefore, even low-concentration sludge water can be treated efficiently, so that it is not necessary to carry out concentration digestion treatment prior to sludge treatment with a sun-dried bed, as in the past, and direct low-concentration treatment. Can treat sludge water. Moreover, since low concentration sludge water can be processed efficiently, cost reduction can be aimed at.
[0012]
Further, as described above, when the sludge water M ₂ is settled / deposited, when the air is discharged from the vent 22, when the bubbles 26 reach the upper surface 15A of the filtration layer, or when the bubbles 26 pass through the sludge layer S ₂ . When it is rising, the separated water W is blocked by the bubbles 26 and hardly permeates the filtration layer 15 side. For this reason, the air pump 21 and the control valve 24 are controlled based on data set in advance by the control device 25, air is intermittently sent to the vent pipe 23, and the separated water W and the filtration layer 15 are separated by the bubbles 26. If the release of air is stopped for a while after communicating, the permeability is further improved and the solid-liquid separation performance is enhanced. The setting of the air delivery time and the air delivery stop time can be determined by the sedimentation rate (deposition rate) or the amount of input water determined in advance according to the concentration of sludge water.
[0013]
【Example】
Next, the indoor experiment result which modeled the sludge processing apparatus which concerns on the said structure is shown. In order to confirm the effectiveness of the sludge treatment method and its apparatus, the present inventors conducted an experiment with an indoor experimental apparatus 112 shown in FIG. The indoor experimental apparatus 112 provided a bottom 112B with an acrylic plate on a transparent acrylic pipe 112A having an inner diameter of 100 mm. A tap faucet 114 was attached to the bottom 112B to serve as a drain. A net member for a screen door is spread on the bottom of the container 112, and gravel 106 is packed on the lower side, and fine sand 107 is packed on the upper side, thereby reproducing a sludge sun-dried bed. Further, an air stone connected to the air pump 121 was buried in the sand layer 107 in order to perform the aeration filtration method.
[0014]
The experimental conditions are as follows.
RUN-1: Tap water was added from the top of the experimental apparatus 112, and the filtration time was measured without aeration.
RUN-2: Similarly, tap water was added and the filtration time was measured while aerated.
RUN-3: About 1 liter of sludge was added, and the filtration time was measured without aeration.
RUN-4: About 1 liter of sludge was added, and the filtration time was measured by total aeration (continuous aeration from the start to the end of filtration).
RUN-5: About 1 liter of sludge was added, and the filtration time was measured by intermittent aeration (aeration for 15 seconds every 2 minutes after the start of filtration).
RUN-6: Put about 1 liter of sludge and measure the filtration time by aeration during the filtration (after the start of filtration, a sludge layer is formed on the surface of the sand layer and filtered without aeration until the filtration rate is significantly reduced and then aeration until the end of filtration) did.
The sludge used was collected from an agricultural settlement drainage facility in Miura Village, Ibaraki Prefecture. The MLSS concentration was 2,600 mg / L and the SV30, a sedimentation index, was 9%. In addition, RUN-3 to RUN-6 take out sludge after each RUN, so the sand on the surface is taken out together with the sludge, and the sand is added accordingly, so the filtration characteristics of the sand layer 107 are different for each RUN. Therefore, after each RUN, a non-aeration filtration test using tap water similar to RUN-1 was performed for each RUN. These are referred to as RUN-4 ′ or RUN-6 ′. In addition, in order to make the measurement conditions of RUN-3 to RUN-6 uniform, before starting the filtration rate measurement, close the tap 114 of the drain and fill the tap water up to the surface of the sand layer 107. Open and measure the filtration rate.
[0015]
The experimental results are shown in FIGS. In the results of RUN-1 and RUN-2, as shown in FIG. 5, the filtration time of RUN-1 was short. It has been found that there is no merit due to aeration when passing through the sand layer of tap water, and it takes time to pass by the amount that the flow area is reduced by bubbles. On the other hand, as shown in FIG. 6, when the sludge is added, the filtration time of RUN-4 to RUN-6 after aeration is longer than that of RUN-3 where the sludge is filtered without aeration. It was too short. The filtration time was shorter in the order of RUN-4>RUN-6> RUN-5, and RUN-5 with the short aeration time had the shortest filtration time. The reason for this is that in RUN-4 and RUN-6, even if a part of the sludge layer is destroyed by bubbles, the bubbles continue to rise from that part, so that the water cannot flow down quickly. Also, even if the rising position of the bubbles moves from time to time and a part where the sludge layer is destroyed remains, a large amount of sludge is mixed with the water above the sludge layer by aeration, and the part where the sludge layer is destroyed becomes the intruding moisture. The sludge brought in immediately closes up. In particular, as in RUN-4, when aeration was performed from the beginning of filtration, sand 107 as a filter medium was sent into the liquid, and a lot of sand 107 was seen on the upper surface of the sludge layer after completion of filtration. For this reason, every time a sludge layer is formed on the filter medium surface by intermittent aeration, destroying a part of the sludge layer is excellent in reducing filtration time and saving energy. As shown in FIG. 5, the results of RUN-4 ′ to RUN-6 ′ performed for confirming the conditions of the sand layer before the sludge injection are different for each RUN, but the difference was that the sludge was added. Compared to the difference in filtration time in this case, it is negligible. In this experiment, the filtration height is about 8 cm, but practically a filtration height of 30 cm or more is required. In the conventional sun-drying bed having no air release mechanism as in the present invention, As shown in FIG. 10, there was a case where drainage took about 4 days.
[0016]
In addition, in the said Example, although branch pipe 23B in which vent hole 22 was formed is arrange | positioned in a sand layer, it is not restricted to this, You may arrange | position in a gravel layer. However, it is desirable that the ventilation hole 22 is provided with a filtration layer having a predetermined thickness near the surface 15A of the filtration layer 15 and secured on the upper side. Further, the control device 25 intermittently sends air to the vent pipe 23 based on preset data. However, the control device 25 is not limited to this, and the accumulation thickness of the sludge layer is set inside the concrete tank. A sensor for detection may be provided, and the timing of sending air to the vent pipe 23 may be controlled based on a detection signal from the sensor. Further, the air delivery amount or delivery pressure may be controlled based on this detection signal. Further, in the treatment of the low-concentration sludge water M ₂ as in the above-described embodiment, the solid content of the low-concentration sludge water M ₂ that is input is precipitated and deposited almost uniformly over the entire upper surface 15A of the filtration layer 15. The large number of vent holes 22 are arranged in the sand layer 7 with a substantially uniform density. However, the charged condition of the sludge water M _2, etc., if the deviation in the thickness of the sludge layer which is deposited on the upper surface 15A of the filtration layer 15 occurs, changed as appropriate depending on the location of the arrangement number of the vents in accordance with the deviation, vent Needless to say, the density may be changed. Further, in the description of the above embodiment, it is referred to as aeration to release air from the filtration layer and generate bubbles, but aeration in this application is synonymous with air supply into the liquid, and is a microbial treatment. It is not for supplying oxygen for use.
[0017]
【The invention's effect】
As described above, according to the present invention, the filtration layer is composed of the lower gravel layer and the upper sand layer, the filtrate drain pipe is disposed in the lower gravel layer, and the vent pipe having a plurality of vents is disposed on the upper gravel layer. embedded in a predetermined site in sand, after the sludge water charge, intermittently delivery to release the air from the vent in the air to vent from the outside, gradually precipitated in the filter layer upper surface rising bubbles permeability The sludge is treated by passing the sludge layer with poor properties to eliminate the sludge layer and separating the sludge solids and separating water staying on the sludge layer and the filtration layer. When a sludge layer is formed on the filtration layer during the precipitation and filtration of water, the sludge layer can be eliminated by air bubbles, allowing the separated water and the filtration layer to communicate with each other and improving the permeability. The performance can be improved and the working time of sludge treatment can be shortened. In addition, it is possible to process sludge with low concentration, which was difficult to treat in the past, so there is no need to perform concentration digestion treatment before sludge treatment with a sun-dried bed as before, and work efficiency The cost can be reduced.
[0018]
Further, according to the present invention, the filtration layer is composed of the lower gravel layer and the upper sand layer, the filtrate drain pipe is disposed in the lower gravel layer, and a plurality of vents are provided at predetermined portions in the upper sand layer . It is formed on the filtration layer at the time of sedimentation and filtration of sludge water by providing an air release mechanism comprising an arranged air pipe and an air pump that communicates with the air pipe and intermittently sends air from the outside. Since the sludge layer can be removed by bubbles to allow the separated water and the filtration layer to communicate with each other, the solid-liquid separation performance can be improved and the working time of the sludge treatment can be shortened.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a sludge treatment apparatus according to an embodiment of the present invention.
FIGS. 2A and 2B are explanatory views showing states of the sludge treatment apparatus of FIG. 1 when air is not released and when air is released, respectively.
3 is a cross-sectional view showing the arrangement of vents in the sludge treatment apparatus of FIG. 1. FIG.
FIG. 4 is a perspective view showing an experimental apparatus.
FIG. 5 is a graph showing the results of a filtration experiment with tap water using the experimental apparatus of FIG.
6 is a graph showing the results of a filtration experiment using sludge using the experimental apparatus shown in FIG.
FIG. 7 is a plan view showing a conventional sun drying bed.
8 is a longitudinal sectional view showing the sun drying bed of FIG.
9A is an explanatory diagram showing the flow of cross flow in a conventional sun-drying bed, and FIG. 9B is an explanatory diagram showing the flow during backwashing in a conventional sun-drying bed.
FIG. 10 is a graph showing the relationship between the thickness of the water layer and the elapsed days required for the treatment of sludge with a low concentration in a conventional sun-dried bed.
[Explanation of symbols]
12 Sun drying floor (sludge treatment equipment)
13 Concrete tank (tank)
13A Bottom part of concrete tank 14 Filtrate drain pipe 14A Permeation port 14B Discharge end 15 Filtration layer 20 Air release mechanism 22 Vent 23 Air vent 26 Air bubbles M, M ₂ Sludge water S ₂ Sludge layer W Separated water

Claims

A filtration layer is formed in the tank, and a filtrate drain pipe having a permeation port at the bottom of the tank and having a discharge end extending to the outside of the tank is disposed. Sludge water is poured onto the filtration layer by the filtration layer. In the sludge treatment method of filtering and draining the filtrate to the outside through the filtrate drainage pipe, the filtration layer is composed of a lower gravel layer and an upper sand layer, and the filtrate drainage pipe is disposed in the lower gravel layer, An air bubble having a ventilation hole is embedded in a predetermined portion in the upper sand layer , and after introducing sludge water, air is intermittently sent from the outside to the ventilation pipe to release air from the ventilation hole, and the rising bubble The sludge layer with poor water permeability that gradually settles on the upper surface of the filtration layer is passed to eliminate the sludge layer, and the sludge is separated from the solid content of the sludge and the separated water staying on the sludge layer is communicated with the filtration layer. The sludge processing method characterized by processing.

A sludge treatment comprising a filtration layer for filtering sludge water formed and introduced inside the tank, and a filtrate drain pipe having a permeation port disposed at the bottom of the tank and having a discharge end extending outside the tank. In the apparatus, the filtration layer is composed of a lower gravel layer and an upper sand layer, and the filtrate drain pipe is disposed in the lower gravel layer, and a plurality of vent holes are arranged at predetermined portions in the upper sand layer . And an air discharge mechanism comprising an air pump that communicates with the vent pipe and intermittently sends air from the outside.

The sludge treatment apparatus according to claim 2 , wherein the vent holes are arranged in the filtration layer with a substantially uniform density.

The sludge treatment apparatus according to claim 2 or 3, wherein the ventilation pipe is composed of a main pipe connected to an air pump and branch pipes that are branched from the main pipe and embedded in parallel to each other.

The sludge treatment apparatus according to any one of claims 2 to 4, wherein the air pump includes a control device that intermittently sends air to the vent pipe based on preset data.

The sludge treatment apparatus according to any one of claims 2 to 5, wherein the vent is provided with a check valve that prevents infiltration of a filter layer component or water.