JP3919999B2

JP3919999B2 - Organic wastewater treatment method and apparatus

Info

Publication number: JP3919999B2
Application number: JP2000054540A
Authority: JP
Inventors: 甬生葛; 俊博田中; 和彰島村; 琢也小林
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2000-02-29
Filing date: 2000-02-29
Publication date: 2007-05-30
Anticipated expiration: 2020-02-29
Also published as: JP2001239295A

Description

【０００１】
【発明の属する技術分野】
本発明は、有機性廃水の処理方法および処理装置に関するものであり、活性汚泥法における余剰汚泥の容積の減少化とリンの除去に関し、就中、リン濃度の高い有機性食品廃水や生活廃水等の処理に用いることができる有機性廃水の処理方法および処理装置に関する。
【０００２】
【従来の技術】
従来から、有機性食品廃水や生活排水等の有機性廃水を生物学的に処理して脱リンする方法として、嫌気・好気法が知られている。
この処理法の特徴は、活性汚泥中のリンの含有率を高くすることができ、このリンの含有率を高くした汚泥を余剰汚泥として系外に排出することにより、処理水中のリンの濃度を減少させることが可能となる。
しかしながら、従来からの余剰汚泥の処理処分法としては、引き抜き→濃縮→脱水→焼却等の複数の処理工程を経て系外に排出しなければならないために、これらの処理に要する費用が莫大なものになるために、嫌気・好気法を実施する際の処理全体のランニングコストの増大を招く結果となる。
さらに、汚泥の脱水処理においても、適切な薬注率等の管理に伴うメンテナンスの煩雑さも伴うことが避け得ないものであった。
【０００３】
一方、最近になって、活性汚泥処理と組み合わせた汚泥容積の減少化（以下「汚泥減容化」という）処理として、余剰汚泥量以上の量の汚泥を沈殿池または生物反応曝気槽から引き抜き、これをオゾンを注入する別に設けるオゾン反応槽に導入し、オゾン処理をした汚泥を再び前記の生物反応曝気槽へ返送し、前記曝気槽でオゾン処理した汚泥の一部を生物処理によって分解することが知られている。
しかしながら、汚泥減容化処理にあっては、余剰汚泥の発生がなくなる一方、菌体増殖に伴うリンの蓄積がなくなるために、処理水中のリンの濃度が原水中の濃度と略々同程度となり、生物処理によるリンの除去が不可能になる。
【０００４】
また、汚泥の減容化とリンの除去を同時に行う処理法として、嫌気・好気法による生物脱リン装置において、返送汚泥の一部が導入される汚泥可溶化手段と、可溶化された汚泥を嫌気槽に返送する手段と返送汚泥の一部が導入されるリン放出槽と該リン放出槽の流出液が導入されるＭＡＰ（リン酸マグネシウムアンモニウム）反応塔からなる生物脱リン装置が知られている。
【０００５】
【発明が解決しようとする課題】
汚泥の可溶化手段とリン放出槽、ＭＡＰ反応塔を組み合わせた生物脱リン装置にあっては、新たにリン放出槽を設ける必要があり、装置の増大を招くおそれがある。
また、オゾン反応槽においては、返送汚泥に対し、高濃度のオゾンを注入することにより汚泥を酸化分解することを目的としていることから、活性汚泥の死滅を招くおそれがあり、オゾン処理汚泥をそのまま生物処理槽へ返送した場合、生物処理槽内の活性汚泥の活性度低下を来すことになる。
この結果、処理水のＣＯＤ、ＳＳが上昇して処理水の水質の悪化現象が発現するというような問題点があった。
【０００６】
本発明は、上記の諸問題点を解決するためになされたものであり、有機性廃水の処理方法及び処理装置に関し、活性汚泥による廃水の処理において、生物処理槽内の汚泥の一部をオゾン反応槽に供給し、オゾン処理により汚泥の減容化を行う一方、オゾン処理により溶出した活性汚泥中のリンを、脱リン反応槽において効果的に除去することができ、その上、原水中のリンも除去可能である処理方法及び処理装置を提供する。
さらに、オゾン処理汚泥を活性汚泥安定槽に導入し、系内汚泥の活性度を常時高く維持することのできる処理法を提供するものである。
【０００７】
【課題を解決するための手段】
上記の課題を解決するための本発明は、以下の各項によって構成される。
（１）有機性廃水の処理方法において、生物処理工程の汚泥の一部をオゾンガスを注入するオゾン反応工程に供給し、該オゾン反応工程の処理物をオゾン処理液とオゾン処理汚泥に固液分離した後、オゾン処理液を脱リン反応工程に供給して脱リン処理し、脱リン反応工程で得た脱リン処理水を前記生物処理工程に返送する一方、オゾン処理汚泥およびオゾン反応槽から流出した排オゾンガスを活性汚泥安定化工程に導入すると共に、活性汚泥安定化工程に原水及び／又は生物処理工程汚泥の一部を供給し、連続曝気した後、該活性汚泥安定化工程からの処理液を前記生物処理工程に返送することを特徴とする有機性廃水の処理方法。
（２）生物処理工程の汚泥を直接返送することなく、活性汚泥安定槽を経て前記生物処理工程に返送することを特徴とする前記（１）記載の有機性廃水の処理方法。
【０００８】
（３）生物処理槽と該生物処理槽からの活性汚泥を固液分離する固液分離装置とを備える有機性廃水の処理装置において、該固液分離装置の汚泥の一部を導入しオゾンガスを注入するオゾン反応槽と、該オゾン反応槽の処理物を導入しオゾン処理液とオゾン処理汚泥に固液分離する固液分離装置と、該オゾン処理液を導入して脱リン処理する脱リン装置と、該脱リン装置で脱リンした処理水を前記生物処理槽に返送する導管と、原水及び／又は生物処理槽からの汚泥の一部を供給する供給管を備え、かつ該オゾン反応槽からのオゾン処理汚泥及び排オゾンガスを導入して活性汚泥を安定化する活性汚泥安定化槽と、該活性汚泥安定化槽からの処理液を前記生物処理槽に返送する導管を有することを特徴とする有機性廃水の処理装置。
（４）前記脱リン装置が晶析脱リン装置であることを特徴とする前記（３）記載の有機性廃水の処理装置。
【０００９】
【発明の実施の形態】
本発明の実施の形態を図面を参照して詳細に説明する。
図１は、食品製造廃水を本発明の処理方法により処理する一例のフローシートを示す。
図１に示すように、原水１の一部を生物処理槽２に供給し、生物処理槽処理液の活性汚泥スラリ３を沈殿池４に流入し、沈殿池４で処理水５を得、沈殿池４の沈殿汚泥６の一部を返送汚泥７として生物処理槽２に返送する活性汚泥処理工程において、前記沈殿汚泥の他の一部をオゾン処理供給汚泥８としてオゾン反応槽９に供給し、連続して供給されるオゾンガス１０により酸化分解処理する。
オゾン反応槽９には、槽内のｐＨを３〜４に調整するために、酸注入ラインより酸１１として硫酸の注入を行う。
オゾン反応工程のｐＨが３〜４の範囲になるようにオゾン反応工程に酸の供給を行うことが好ましい。また、オゾン反応槽９に供給する１日当たりの汚泥量は、系内全汚泥量の５〜１００％であることが好ましい。
【００１０】
一方、オゾン反応槽９より得られるオゾン処理混合液１２を固液分離槽１３に供給し、オゾン処理液１４とオゾン処理残汚泥１５とに分離する。
オゾン処理液１４は、晶析脱リン反応槽１６に送られ、Ｃａ（ＯＨ）₂注入ライン１７よりＣａ（ＯＨ）₂が注入され、Ｃａの供給およびｐＨ調整によりＨＡＰが生成され、引抜きリン粒子１９が取り出される。また、固液分離槽１３のオゾン処理残汚泥１５を汚泥安定槽２０に供給して一旦貯留し、汚泥安定槽へ供給する原水２２、および沈殿汚泥の一部２１を供給して、排オゾンガス２３による曝気（酸素含有ガスによる好気性処理となる）を行い、汚泥の安定化を図る。なお、汚泥安定槽へ供給する原水２２と沈殿汚泥の一部２１は、両方を供給する必要はなく、いずれか一方でもよい。
【００１１】
汚泥安定槽２０内の処理で汚泥の活性度が高められた汚泥安定槽処理液２４は生物処理槽２に返送され、生物処理槽活性汚泥の一部として、有機物の分解を担う。
此処で、晶析脱リン反応槽１６からの脱リン液１８を生物処理槽２に供給すると、その液の中に混入している有機物は、活性汚泥による生物分解を受けて水と二酸化炭素に分解される。
なお、脱リン液１８を汚泥安定槽２０に供給しても、汚泥安定槽２０への影響がなく、汚泥安定槽処理液２４を生物処理槽２に返送することにより同様の効果が得られる。
このようにして得られる生物処理槽処理液３を沈殿池４に流入し、固液分離後、上澄液を処理水５として得る一方、濃縮汚泥を返送汚泥７として生物処理槽２に返送することは前記したとおりである。
【００１２】
【実施例】
以下において、本発明を実施例により更に具体的に説明するが、本発明は、この実施例により限定されるものではない。
【００１３】
実施例１
この実施例１においては、図１に示すフローで有機性廃水の処理を行った。その処理方法で、脱リン処理はハイドロキシアパダイト（Ｃａ₅（ＰＯ₄）₃ＯＨ）生成の晶析脱リン方式（ＨＡＰ法) により行なったが、この限りではなく、凝集沈殿処理やリン酸マグネシウムアンモニウム（ＭＡＰ）法等を用いても同様の効果が得られる。
第１表に実施例１におけるオゾン反応槽９の処理条件を示す。
【００１４】
【表１】

【００１５】
オゾン反応槽９において、Ｏ₃ガスを流量６．０リットル／ｍｉｎ、Ｏ₃濃度５０ｍｇ／リットルの注入を行い、Ｏ₃注入率３３ｍｇ−Ｏ₃／ｇ−ＳＳ、滞留時間を３．０時間とした条件で処理を行った。
また、反応ｐＨを硫酸の注入により約３．０とした。オゾン処理汚泥は１３．２ｋｇ／ｄであり、この処理系内の全汚泥量に対する比率は約３１％となった。
第２表にオゾン反応槽９の処理結果を示す。
【００１６】
【表２】

【００１７】
オゾン反応槽９の入口のＳＳが、１１０００ｍｇ／リットルであるのに対し、処理後のＳＳが、９２００ｍｇ／リットルに低下し、汚泥の液化率としては約１６．４％となった。なお、汚泥の液化率は下記の式により算出した。
液化率（％）＝〔（処理後ＳＳ−処理前ＳＳ）／処理前ＳＳ〕×１００
Ｓ−ＣＯＤおよびＳ−ＢＯＤが処理前でそれぞれ、１２．０ｍｇ／リットルと５．０ｍｇ／リットルであるのに対し、処理後においてはそれぞれ、５９０ｍｇ／リットルと６３０ｍｇ／リットルに増加した。また、ＰＯ₄−ＰおよびＳ−Ｔ−Ｐが処理前が１．５ｍｇ／リットルと２．１ｍｇ／リットルであるのに対して、処理後ではそれぞれ５９．０ｍｇ／リットルと６５．０ｍｇ／リットルに増加し、菌体中のポリリン酸が酸性オゾン処理により多く溶出したものと認められた。
このように、得られたオゾン処理汚泥を固液分離槽にて固液分離して、ＳＳの少ない上澄水を晶析脱リン反応槽において処理した前後の処理結果を第３表に示す。
【００１８】
【表３】

【００１９】
なお、本実施例１では、オゾン処理汚泥の固液分離槽を沈殿池としたが、膜分離槽、ろ材による濾過槽等を用いても同様な効果が得られる。
前記の晶析脱リン反応槽において、粒径が０．１５〜０．３ｍｍのリン鉱石を充填し、Ｃａ／Ｐの比が約５．０となるようにＣａ（ＯＨ）₂を注入し、上向流式でＬＶ２９ｍ／ｈ、反応槽内ｐＨを８．８に制御し、処理水循環比率６００％の条件で処理を行った。
その結果、反応槽入口でＰＯ₄−ＰとＴ−Ｐがそれぞれ５９．０ｍｇ／リットルと６４．５ｍｇ／リットルであるのに対し、出口でＰＯ₄−ＰとＴ−Ｐがそれぞれ３．０ｍｇ／リットルと５．６ｍｇ／リットルに低下し、夫々約９５％と９１％の除去率が得られた。
【００２０】
一方、ｐＨおよびＳＳが入口でそれぞれ３．０と５０ｍｇ／リットルであるのに対し、出口ではｐＨが８．８、ＳＳが６１ｍｇ／リットルとなり、原水中のＳＳの蓄積は殆どなかった。
また、Ｓ−ＣＯＤ、Ｓ−ＢＯＤについてみても、入口でそれぞれ５９０ｍｇ／リットル、６３０ｍｇ／リットルであるのに対して、出口ではそれぞれ５５０ｍｇ／、５７０ｍｇ／リットルとなり、若干低くはなったものの、大部分の有機物が残留し、リンのみの除去となった。
ここで、固液分離槽より得られたオゾン処理残汚泥を汚泥安定槽に供給し、流入原水の５％と返送汚泥の５％を同時に供給し、排Ｏ₃ガス（酸素含有ガスとして）による曝気処理を約２．０時間行った。
第４表に、この回分実験により得られた、曝気処理前後の流入原水に対するオゾン処理汚泥のＢＯＤ除去速度を示す。
【００２１】
【表４】

【００２２】
曝気処理前のオゾン処理汚泥のＢＯＤ除去速度が約０．２０〔ｇ−ＢＯＤ／ｇ−ＳＳ／ｈ〕しかないのに対し、曝気処理後のＢＯＤ除去速度が、およそ１．３〔ｇ−ＢＯＤ／ｇ−ＳＳ／ｈ〕に増加した。
これは、生物処理槽汚泥のＢＯＤ除去速度と略々同じであり、短時間の曝気処理により活性度が回復するこということが認められた。
このことから、曝気処理したオゾン処理汚泥を生物処理槽に返送することにより、槽内の汚泥の活性維持に大きく寄与できることになる。
【００２３】
上記のように、リンを選択的に除去した晶析脱リン処理水を活性汚泥処理装置の生物処理槽に供給すれば、流入原水と共に活性汚泥処理によって有機物が分解され、放流水として良好な処理水を得るこことができることになる。
第５表に生物処理槽の処理条件を、第６表に流入原水および放流水（生物処理水）の水質を示す。
【００２４】
【表５】

【００２５】
【表６】

【００２６】
第６表の数値から明らかなように流入原水の性状が、ｐＨ：５．５、ＳＳ：１００ｍｇ／リットル、ＣＯＤ：３００ｍｇ／リットル、ＢＯＤ：３５０ｍｇ／リットル、ＮＨ₄−Ｎ：１５ｍｇ／リットル、Ｔ−Ｎ：３５ｍｇ／リットルであるのに対して、処理水では、ＳＳ：８．０ｍｇ／リットル、ＣＯＤ：１４ｍｇ／リットル、ＢＯＤ：６．５ｍｇ／リットル、ＮＨ₄−Ｎ：０．１ｍｇ／リットル、Ｔ−Ｎ：３．４ｍｇ／リットルとなり、安定した良好な処理水質が得られた。
なお、ＰＯ₄−ＰとＴ−Ｐが原水でそれぞれ、１２．５ｍｇ／リットルと２１ｍｇ／リットルであるのに対し、処理水では、それぞれ１．５ｍｇ／リットルと２．５ｍｇ／リットルとなり、原水に対し、Ｔ−Ｐの除去率が約９０％となった。
上記の高いＴ−Ｐの除去率から、本発明により、汚泥の減容化が容易になされると共に、原水中のリンが安定して除去されることが認められた。
ちなみに、図２に実施例の系内汚泥量の経過を示す。
約２ケ月の処理期間中、系内汚泥量が略々一定で、約４２〜４５ｋｇであり、ほとんど増加がなかったことから、オゾン処理を用いた汚泥減容効果も顕著であると認められた。
【００２７】
比較例
図３に示すように、リンの除去を行わない汚泥減容化処理フローを比較例として、処理を行った。
比較例では、オゾン処理に供する汚泥量を系内汚泥量の２００％とし、他の条件を実施例と同一にした。
また、生物処理槽の処理条件も実施例と同一の条件とした。
第７表に比較例に供した原水および得られた処理水の水質を示す。
【００２８】
【表７】

【００２９】
第７表の数値から明らかなように、流入原水の性状が、ｐＨ：５．５、ＳＳ：１００ｍｇ／リットル、ＣＯＤ：３００ｍｇ／リットル、ＢＯＤ：３５０ｍｇ／リットル、ＮＨ₄−Ｎ：１５ｍｇ／リットル、ＮＯ₃−Ｎ：＜０．１ｍｇ／リットル、Ｔ−Ｎ：３５ｍｇ／リットルで、実施例１と同一であるのに対して、処理水が、ＳＳ：１５．０ｍｇ／リットル、ＣＯＤ：２１ｍｇ／リットル、ＢＯＤ：１２ｍｇ／リットル、ＮＨ₄−Ｎ：１．５ｍｇ／リットル、ＮＯ_x−Ｎ：３．２ｍｇ／リットル、Ｔ−Ｎ：８．２ｍｇ／リットルとなり、いずれも実施例の数値よりも高くなった。
さらに、ＰＯ₄−ＰとＴ−Ｐは、それぞれ１６．５ｍｇ／リットル、と１０．３ｍｇ／リットルとなり、原水よりＰＯ₄−Ｐが増加し、Ｔ−Ｐが稍々減少する程度となった。
なお、この場合、系内の汚泥量の増加が若干認められ、余剰汚泥の減容効果も実施例より稍々低下したものと判断された。
【００３０】
【発明の効果】
本発明によれば、生物処理槽および固液分離槽から構成される活性汚泥処理装置内の汚泥の一部を、オゾンガス注入装置を備えるオゾン反応槽に供給してオゾン処理した処理物を、固−液分離した後、得られたオゾン処理液を次いで脱リン処理し、得られた脱リン液を前記活性汚泥処理装置の生物処理槽に返送することにより、脱リン液中の有機物を原水と共に活性汚泥により効果的に分解除去することができる。
本発明では、オゾン処理汚泥を汚泥安定槽に供給し、これに原水および生物処理槽内の汚泥の一部を供給して連続曝気処理することにより、活性度の低下したオゾン処理汚泥を短時間で賦活することができるので、この活性度が高まった活性汚泥を含む汚泥安定槽の混合液を生物槽に返送することにより、生物処理槽の活性汚泥量を常時所望量に保持することができ、流入原水および脱リン液中の有機物分解を効果的に維持することができる。
【００３１】
さらに、オゾン反応槽のｐＨを３〜４の酸性域としたことにより、オゾン処理による液化率を高くでき、リン濃度の高いオゾン処理液が得られ、脱リン反応槽におけるリンの除去効率が向上させることが可能になる。
また、オゾン処理に供する活性汚泥量が系内全汚泥量の５〜１００％であり、オゾン処理汚泥の活性度の低下が比較的少なく、汚泥安定槽における活性の回復が速くなる。
このため、生物処理槽内の汚泥の活性度を良好に維持することができ、汚泥の減容効果および処理水の水質向上に寄与するところ極めて大である。
【図面の簡単な説明】
【図１】食品製造廃水を本発明の処理法により処理する一例を説明するフローシートを示す。
【図２】実施例における系内汚泥量の経過の説明図を示す。
【図３】比較例の処理フローの説明図を示す。
【符号の説明】
１原水
２生物処理槽
３生物処理槽処理液
４沈殿池
５処理液
６沈殿汚泥
７返送汚泥
８オゾン処理供給汚泥
９オゾン反応槽
１０オゾンガス
１１酸注入ライン
１２オゾン処理混合液
１３固液分離槽
１４オゾン処理液
１５オゾン処理残汚泥
１６脱リン反応槽
１７Ｃａ（ＯＨ）₂注入ライン
１８脱リン液
１９引抜きリン粒子
２０汚泥安定槽
２１汚泥安定槽供給汚泥
２２供給原水
２３排オゾンガス
２４汚泥安定槽処理液[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for treating organic wastewater, and relates to reduction of excess sludge volume and removal of phosphorus in the activated sludge process, especially organic food wastewater and domestic wastewater with high phosphorus concentration, etc. The present invention relates to a method and apparatus for treating organic wastewater that can be used for the treatment of water.
[0002]
[Prior art]
Conventionally, anaerobic and aerobic methods are known as methods for biologically treating organic food wastewater such as organic food wastewater and domestic wastewater to dephosphorylate.
The feature of this treatment method is that the content of phosphorus in the activated sludge can be increased, and the concentration of phosphorus in the treated water can be reduced by discharging the sludge with a high content of phosphorus as excess sludge outside the system. It becomes possible to decrease.
However, the conventional method for disposal of excess sludge has to be discharged out of the system through multiple processing steps such as extraction → concentration → dehydration → incineration. As a result, the running cost of the entire process when the anaerobic / aerobic method is performed is increased.
Furthermore, in the sludge dehydration process, it is inevitable that the maintenance is complicated due to management of an appropriate chemical injection rate and the like.
[0003]
On the other hand, recently, as a treatment of sludge volume reduction (hereinafter referred to as “sludge volume reduction”) combined with activated sludge treatment, an amount of sludge exceeding the amount of excess sludge is extracted from the sedimentation basin or biological reaction aeration tank, This is introduced into an ozone reaction tank provided separately for injecting ozone, and the ozone-treated sludge is returned to the biological reaction aeration tank again, and a part of the sludge ozone-treated in the aeration tank is decomposed by biological treatment. It has been known.
However, in sludge volume reduction treatment, excess sludge is not generated, but phosphorus accumulation associated with bacterial cell growth is eliminated, so that the concentration of phosphorus in the treated water is approximately the same as the concentration in the raw water. It becomes impossible to remove phosphorus by biological treatment.
[0004]
In addition, as a treatment method that simultaneously reduces sludge and removes phosphorus, in an anaerobic / aerobic biological dephosphorization device, sludge solubilization means in which part of the returned sludge is introduced, and the solubilized sludge There is known a biological dephosphorization apparatus comprising a means for returning the water to the anaerobic tank, a phosphorus release tank into which part of the returned sludge is introduced, and a MAP (magnesium ammonium phosphate) reaction tower into which the effluent of the phosphorus release tank is introduced. ing.
[0005]
[Problems to be solved by the invention]
In a biological dephosphorization apparatus that combines a sludge solubilization means, a phosphorus release tank, and a MAP reaction tower, it is necessary to newly provide a phosphorus release tank, which may increase the apparatus.
The ozone reaction tank is intended to oxidize and decompose sludge by injecting high-concentration ozone into the returned sludge, which may cause the activated sludge to die. When returned to the biological treatment tank, the activity of the activated sludge in the biological treatment tank will decrease.
As a result, there has been a problem that the COD and SS of the treated water are increased and the quality of the treated water is deteriorated.
[0006]
The present invention has been made to solve the above-mentioned problems, and relates to a method and apparatus for treating organic wastewater, and in the treatment of wastewater with activated sludge, a part of the sludge in a biological treatment tank is ozone. While supplying sludge to the reaction tank and reducing the volume of sludge by ozone treatment, phosphorus in the activated sludge eluted by ozone treatment can be effectively removed in the dephosphorization reaction tank. Provided is a processing method and a processing apparatus capable of removing phosphorus.
Furthermore, ozone treatment sludge is introduced into an activated sludge stabilization tank to provide a treatment method that can maintain the activity of sludge in the system constantly high.
[0007]
[Means for Solving the Problems]
The present invention for solving the above problems is constituted by the following items.
(1) In the organic wastewater treatment method, a part of the sludge of the biological treatment process is supplied to the ozone reaction process in which ozone gas is injected, and the treatment product of the ozone reaction process is separated into an ozone treatment liquid and ozone treatment sludge. After that, the ozone treatment liquid is supplied to the dephosphorization reaction step to perform the dephosphorization treatment, and the dephosphorization treated water obtained in the dephosphorization reaction step is returned to the biological treatment step, while flowing out from the ozone treatment sludge and the ozone reaction tank. The waste ozone gas is introduced into the activated sludge stabilization process, and a part of raw water and / or biological treatment process sludge is supplied to the activated sludge stabilization process, and after continuous aeration , the treatment liquid from the activated sludge stabilization process Is returned to the biological treatment step.
(2) The method for treating organic wastewater according to (1) above, wherein the sludge from the biological treatment process is returned directly to the biological treatment process through an activated sludge stabilization tank without being returned directly.
[0008]
(3) In an organic wastewater treatment apparatus comprising a biological treatment tank and a solid-liquid separation apparatus for solid-liquid separation of activated sludge from the biological treatment tank, ozone gas is introduced by introducing a part of the sludge of the solid-liquid separation apparatus An ozone reaction tank to be injected, a solid-liquid separation apparatus for introducing a treatment product of the ozone reaction tank into a solid-liquid separation into an ozone treatment liquid and ozone treatment sludge, and a dephosphorization apparatus for introducing a dephosphorization treatment by introducing the ozone treatment liquid A conduit for returning the treated water dephosphorized by the dephosphorization apparatus to the biological treatment tank, a supply pipe for supplying a part of the sludge from the raw water and / or the biological treatment tank, and from the ozone reaction tank An activated sludge stabilization tank that stabilizes activated sludge by introducing ozone treatment sludge and waste ozone gas, and a conduit that returns the treatment liquid from the activated sludge stabilization tank to the biological treatment tank. Organic wastewater treatment equipment.
(4) The organic wastewater treatment apparatus according to (3), wherein the dephosphorization apparatus is a crystallization dephosphorization apparatus.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an example of a flow sheet for treating food production wastewater by the treatment method of the present invention.
As shown in FIG. 1, a part of raw water 1 is supplied to a biological treatment tank 2, an activated sludge slurry 3 of a biological treatment tank treatment liquid flows into a sedimentation basin 4, and treated water 5 is obtained in the sedimentation basin 4. In the activated sludge treatment step of returning a part of the precipitated sludge 6 of the pond 4 to the biological treatment tank 2 as the return sludge 7, another part of the precipitated sludge is supplied to the ozone reaction tank 9 as the ozone treatment supply sludge 8, Oxidative decomposition treatment is performed using ozone gas 10 that is continuously supplied.
In order to adjust the pH in the tank to 3 to 4 in the ozone reaction tank 9, sulfuric acid is injected as the acid 11 from the acid injection line.
It is preferable to supply acid to the ozone reaction step so that the pH of the ozone reaction step is in the range of 3 to 4. The amount of sludge per day supplied to the ozone reaction tank 9 is preferably 5 to 100% of the total sludge amount in the system.
[0010]
On the other hand, the ozone treatment liquid mixture 12 obtained from the ozone reaction tank 9 is supplied to the solid-liquid separation tank 13 and separated into the ozone treatment liquid 14 and the ozone treatment residual sludge 15.
Ozone treatment liquid 14 crystal析脱sent to the phosphorus reaction vessel 16, Ca (OH) ₂ from the infusion line 17 Ca (OH) ₂ is injected, HAP is generated by the supply and pH adjustment of Ca, withdrawal phosphorus particles 19 is taken out. Further, the ozone treatment residual sludge 15 in the solid-liquid separation tank 13 is supplied to the sludge stabilization tank 20 and temporarily stored, and raw water 22 supplied to the sludge stabilization tank and a part 21 of the precipitated sludge are supplied, and the exhaust ozone gas 23 is supplied. Aeration (becomes aerobic treatment with oxygen-containing gas) to stabilize sludge. The raw water 22 supplied to the sludge stabilization tank and the part 21 of the precipitated sludge do not need to be supplied, and either one may be used.
[0011]
The sludge stabilization tank treatment liquid 24 whose sludge activity has been increased by the treatment in the sludge stabilization tank 20 is returned to the biological treatment tank 2 and is responsible for the decomposition of organic matter as part of the biological treatment tank activated sludge.
Here, when the dephosphorization liquid 18 from the crystallization dephosphorization reaction tank 16 is supplied to the biological treatment tank 2, the organic matter mixed in the liquid undergoes biodegradation by the activated sludge and becomes water and carbon dioxide. Disassembled.
In addition, even if it supplies the dephosphorization liquid 18 to the sludge stabilization tank 20, there is no influence on the sludge stabilization tank 20, and the same effect is acquired by returning the sludge stabilization tank processing liquid 24 to the biological treatment tank 2.
The biological treatment tank treatment liquid 3 thus obtained flows into the sedimentation basin 4 and, after solid-liquid separation, the supernatant is obtained as treated water 5, while the concentrated sludge is returned to the biological treatment tank 2 as return sludge 7. This is as described above.
[0012]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.
[0013]
Example 1
In Example 1, the organic wastewater was treated according to the flow shown in FIG. In this treatment method, the dephosphorization treatment was carried out by the crystallization dephosphorization method (HAP method) for producing hydroxyapadite (Ca ₅ (PO ₄ ) ₃ OH). Similar effects can be obtained by using an ammonium (MAP) method or the like.
Table 1 shows the processing conditions of the ozone reaction tank 9 in Example 1.
[0014]
[Table 1]

[0015]
In the ozone reaction tank 9, O ₃ gas was injected at a flow rate of 6.0 liters / min, an O ₃ concentration of 50 mg / liter, an O ₃ injection rate of 33 mg-O ₃ / g-SS, and a residence time of 3.0 hours. The processing was performed under the conditions.
The reaction pH was adjusted to about 3.0 by injecting sulfuric acid. The ozone-treated sludge was 13.2 kg / d, and the ratio to the total sludge amount in this treatment system was about 31%.
Table 2 shows the processing results of the ozone reaction tank 9.
[0016]
[Table 2]

[0017]
The SS at the inlet of the ozone reaction tank 9 was 11000 mg / liter, whereas the SS after the treatment decreased to 9200 mg / liter, and the sludge liquefaction rate was about 16.4%. The sludge liquefaction rate was calculated by the following formula.
Liquefaction rate (%) = [(SS after treatment−SS before treatment) / SS before treatment] × 100
S-COD and S-BOD were 12.0 mg / liter and 5.0 mg / liter, respectively, before the treatment, but increased to 590 mg / liter and 630 mg / liter, respectively, after the treatment. In addition, PO ₄ -P and STP are 1.5 mg / liter and 2.1 mg / liter before treatment, whereas after treatment, they are 59.0 mg / liter and 65.0 mg / liter, respectively. It was recognized that polyphosphoric acid in the bacterial cells was eluted by acid ozone treatment.
Table 3 shows the treatment results before and after the obtained ozone-treated sludge was solid-liquid separated in the solid-liquid separation tank and the supernatant water with less SS was treated in the crystallization dephosphorization reaction tank.
[0018]
[Table 3]

[0019]
In Example 1, the solid-liquid separation tank for the ozone-treated sludge was used as a sedimentation tank. However, the same effect can be obtained by using a membrane separation tank, a filtration tank using a filter medium, or the like.
In the crystallization and dephosphorization reaction tank, phosphorous ore having a particle size of 0.15 to 0.3 mm is filled, and Ca (OH) ₂ is injected so that the ratio of Ca / P is about 5.0. The treatment was carried out under the conditions of LV 29 m / h in the upward flow method, pH in the reaction vessel controlled to 8.8, and a treated water circulation ratio of 600%.
As a result, PO ₄ -P and TP were 59.0 mg / liter and 64.5 mg / liter at the reactor inlet, respectively, whereas PO ₄ -P and TP were 3.0 mg / liter at the outlet, respectively. The liters were reduced to 5.6 mg / liter, and removal rates of about 95% and 91% were obtained, respectively.
[0020]
On the other hand, pH and SS were 3.0 and 50 mg / liter at the inlet, respectively, whereas pH was 8.8 and SS was 61 mg / liter at the outlet, and there was almost no accumulation of SS in the raw water.
In addition, S-COD and S-BOD were 590 mg / liter and 630 mg / liter respectively at the inlet, but were 550 mg / 570 mg / liter respectively at the outlet, although they were slightly lower, Organic matter remained, and only phosphorus was removed.
Here, the ozone-treated residual sludge obtained from the solid-liquid separation tank is supplied to the sludge stabilization tank, and 5% of the inflow raw water and 5% of the returned sludge are supplied at the same time, using exhaust O ₃ gas (as oxygen-containing gas). The aeration treatment was performed for about 2.0 hours.
Table 4 shows the BOD removal rate of ozone-treated sludge with respect to the inflow raw water before and after the aeration treatment obtained by this batch experiment.
[0021]
[Table 4]

[0022]
The BOD removal rate of the ozone treatment sludge before the aeration treatment is only about 0.20 [g-BOD / g-SS / h], whereas the BOD removal rate after the aeration treatment is about 1.3 [g-BOD. / G-SS / h].
This was almost the same as the BOD removal rate of the biological treatment tank sludge, and it was recognized that the activity was recovered by a short time aeration treatment.
Therefore, by returning the aerated ozone-treated sludge to the biological treatment tank, it can greatly contribute to maintaining the activity of the sludge in the tank.
[0023]
As described above, if crystallized and dephosphorized water from which phosphorus has been selectively removed is supplied to the biological treatment tank of the activated sludge treatment apparatus, the organic matter is decomposed by the activated sludge treatment together with the inflow raw water, and it is a good treatment as discharged water. You can get water.
Table 5 shows the treatment conditions of the biological treatment tank, and Table 6 shows the water quality of the inflow raw water and the discharged water (biologically treated water).
[0024]
[Table 5]

[0025]
[Table 6]

[0026]
As is apparent from the numerical values in Table 6, the properties of the influent raw water are pH: 5.5, SS: 100 mg / liter, COD: 300 mg / liter, BOD: 350 mg / liter, NH ₄ -N: 15 mg / liter, T -N: 35 mg / liter, whereas in treated water, SS: 8.0 mg / liter, COD: 14 mg / liter, BOD: 6.5 mg / liter, NH ₄ -N: 0.1 mg / liter, TN: 3.4 mg / liter, and stable and good treated water quality was obtained.
PO ₄ -P and TP are 12.5 mg / liter and 21 mg / liter respectively for raw water, whereas treated water is 1.5 mg / liter and 2.5 mg / liter respectively. In contrast, the removal rate of TP was about 90%.
From the above high TP removal rate, it was confirmed that the present invention facilitates volume reduction of sludge and stably removes phosphorus in raw water.
Incidentally, FIG. 2 shows the progress of the amount of sludge in the system of the example.
During the treatment period of about 2 months, the amount of sludge in the system was substantially constant, about 42 to 45 kg, and since there was almost no increase, it was recognized that the sludge volume reduction effect using ozone treatment was also remarkable. .
[0027]
Comparative Example As shown in FIG. 3, the treatment was carried out using a sludge volume reduction treatment flow without removing phosphorus as a comparative example.
In the comparative example, the amount of sludge used for the ozone treatment was set to 200% of the amount of sludge in the system, and other conditions were the same as those in the example.
The treatment conditions for the biological treatment tank were also the same as in the examples.
Table 7 shows the quality of the raw water used in the comparative example and the obtained treated water.
[0028]
[Table 7]

[0029]
As is apparent from the numerical values in Table 7, the properties of the influent raw water were pH: 5.5, SS: 100 mg / liter, COD: 300 mg / liter, BOD: 350 mg / liter, NH ₄ —N: 15 mg / liter, NO ₃ -N: <0.1 mg / liter, TN: 35 mg / liter, the same as in Example 1, whereas treated water is SS: 15.0 mg / liter, COD: 21 mg / liter , BOD: 12 mg / liter, NH ₄ -N: 1.5 mg / liter, NO _x -N: 3.2 mg / liter, TN: 8.2 mg / liter, all of which are higher than the numerical values of the examples. It was.
Furthermore, PO ₄ -P and TP were 16.5 mg / liter and 10.3 mg / liter, respectively. PO ₄ -P increased from raw water, and TP decreased frequently.
In this case, a slight increase in the amount of sludge in the system was observed, and it was determined that the volume reduction effect of excess sludge was often lower than in the examples.
[0030]
【The invention's effect】
According to the present invention, a part of the sludge in the activated sludge treatment apparatus composed of a biological treatment tank and a solid-liquid separation tank is supplied to an ozone reaction tank equipped with an ozone gas injection device, and a treated product obtained by ozone treatment is obtained. -After the liquid separation, the obtained ozone treatment liquid is then dephosphorized, and the obtained dephosphorization liquid is returned to the biological treatment tank of the activated sludge treatment apparatus so that the organic matter in the dephosphorization liquid is mixed with the raw water. It can be effectively decomposed and removed by activated sludge.
In the present invention, the ozone-treated sludge is supplied to the sludge stabilization tank, and the raw water and a part of the sludge in the biological treatment tank are supplied thereto and continuously aerated to thereby reduce the ozone-treated sludge having reduced activity in a short time. The activated sludge amount in the biological treatment tank can always be maintained at the desired amount by returning the mixed liquid of the sludge stabilization tank containing the activated sludge having increased activity to the biological tank. In addition, decomposition of organic substances in the incoming raw water and the dephosphorization solution can be effectively maintained.
[0031]
Furthermore, by setting the pH of the ozone reaction tank to an acidic range of 3 to 4, the liquefaction rate by ozone treatment can be increased, an ozone treatment liquid having a high phosphorus concentration is obtained, and the phosphorus removal efficiency in the dephosphorization reaction tank is improved. It becomes possible to make it.
Moreover, the activated sludge amount used for the ozone treatment is 5 to 100% of the total sludge amount in the system, the decrease in the activity of the ozone treated sludge is relatively small, and the recovery of the activity in the sludge stabilization tank is accelerated.
For this reason, the activity of the sludge in the biological treatment tank can be maintained satisfactorily, which contributes greatly to the sludge volume reduction effect and the quality of the treated water.
[Brief description of the drawings]
FIG. 1 shows a flow sheet for explaining an example of treating food production wastewater by the treatment method of the present invention.
FIG. 2 is an explanatory diagram showing the progress of the amount of sludge in the system in the example.
FIG. 3 is an explanatory diagram of a processing flow of a comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Raw water 2 Biological treatment tank 3 Biological treatment tank Treatment liquid 4 Settling tank 5 Treatment liquid 6 Precipitation sludge 7 Return sludge 8 Ozone treatment supply sludge 9 Ozone reaction tank 10 Ozone gas 11 Acid injection line 12 Ozone treatment liquid mixture 13 Solid-liquid separation tank 14 Ozone treatment liquid 15 Ozone treatment residual sludge 16 Dephosphorization reaction tank 17 Ca (OH) ₂ injection line 18 Dephosphorization liquid 19 Extracted phosphorus particles 20 Sludge stabilization tank 21 Sludge stabilization tank supply sludge 22 Supply raw water 23 Waste ozone gas 24 Sludge stabilization tank treatment liquid

Claims

In the organic wastewater treatment method, a part of the sludge of the biological treatment process is supplied to an ozone reaction process in which ozone gas is injected, and the treatment product of the ozone reaction process is solid-liquid separated into an ozone treatment liquid and an ozone treatment sludge. The ozone treatment liquid is supplied to the dephosphorization reaction step to perform the dephosphorization treatment, and the dephosphorization treated water obtained in the dephosphorization reaction step is returned to the biological treatment step, while the ozone treatment sludge and the exhaust ozone gas flowing out from the ozone reaction tank Is introduced into the activated sludge stabilization process, and raw water and / or a part of the biological treatment process sludge is supplied to the activated sludge stabilization process, and after continuous aeration , the treatment liquid from the activated sludge stabilization process is added to the biological sludge. A method for treating organic wastewater, which is returned to the treatment step.

The method for treating organic wastewater according to claim 1, wherein the sludge from the biological treatment step is returned directly to the biological treatment step through an activated sludge stabilization tank without being directly returned.

In an organic wastewater treatment apparatus comprising a biological treatment tank and a solid-liquid separation apparatus for solid-liquid separation of activated sludge from the biological treatment tank, ozone into which a part of the sludge of the solid-liquid separation apparatus is introduced and ozone gas is injected A reaction vessel, a solid-liquid separation device that introduces a treatment product of the ozone reaction vessel and separates it into an ozone treatment solution and ozone treatment sludge, a dephosphorization device that introduces the ozone treatment solution and dephosphorizes, A conduit for returning treated water dephosphorized by a dephosphorization apparatus to the biological treatment tank, a supply pipe for supplying a part of sludge from raw water and / or biological treatment tank, and ozone treatment from the ozone reaction tank Organic wastewater characterized by having an activated sludge stabilization tank for introducing activated sludge by introducing sludge and waste ozone gas, and a conduit for returning the treatment liquid from the activated sludge stabilization tank to the biological treatment tank Processing equipment.

4. The organic wastewater treatment apparatus according to claim 3, wherein the dephosphorization apparatus is a crystallization dephosphorization apparatus.