JP3875736B2

JP3875736B2 - Wastewater treatment method and apparatus

Info

Publication number: JP3875736B2
Application number: JP31962695A
Authority: JP
Inventors: 賢司鈴木; 智宣斉藤
Original assignee: Kyowa Exeo Corp
Current assignee: Kyowa Exeo Corp
Priority date: 1995-11-14
Filing date: 1995-11-14
Publication date: 2007-01-31
Anticipated expiration: 2015-11-14
Also published as: JPH09136090A

Description

【０００１】
【発明の属する技術分野】
本発明は、下水や生活排水、産業廃水等の排水から懸濁物質を除去して清澄な処理水を得る排水処理方法に係り、特に生物学的処理法を利用して懸濁物質を沈降させる排水処理方法および装置に関する。
【０００２】
【従来の技術】
図１２は、排水を生物学的に処理する活性汚泥法の概要を示す説明図である。図１２において、下水、生活排水などの原水１０は、粗目スクリーン１２を通されて沈砂槽１４に流入し、砂や轢が沈殿、除去される。沈殿した砂や轢は、沈砂排出ポンプ１６によって沈砂槽１４から排出される。そして、原水１０は、破砕機１８や細目スクリーン２０を介して原水ポンプ槽２２に流入し、原水ポンプ２４によって流量調整槽２６に送られる。流量調整槽２６内の原水１０は、攪拌ポンプ２８等によって攪拌されるとともに、流量調整ポンプ３０によって汚水計量槽３２に送られ、計量されて曝気槽３４に流入する。
【０００３】
曝気槽３４は、後述する沈殿槽から戻され、注入された好気性微生物からなる活性汚泥を流入した原水１０に混合するとともに、曝気ブロア３６の吐出した空気が吹き込まれて微生物を増殖をしてフロックの形成が行なわる。そして、曝気槽３４内の原水１０と汚泥との混合水３８は、沈殿槽４０に導入される。沈殿槽４０内の混合水３８中のフロックは、センタウエル７６内にて成長し、活性汚泥として分離槽７７内にて汚泥と清澄な上澄水（処理水）４２とに分離される。分離された上澄水４２は、消毒槽４４に送られて消毒器４６を介して消毒剤と接触して消毒されたのち、消毒済処理水４８として河川等に放流させる。
【０００４】
沈殿槽４０内に沈殿した活性汚泥５０は、汚泥返送ポンプ５２によって引き抜かれ、汚泥計量槽５４において計量されて返送汚泥５６として曝気槽３４に戻されるとともに、余剰の汚泥が余剰汚泥５８として汚泥濃縮槽６０に送られる。また、沈殿槽４０の表面に浮遊するスカム６２は、スカムポンプ６４によって流量調整槽２６に戻される。一方、汚泥濃縮槽６０に流入した余剰汚泥５８は、濃縮されて濃縮汚泥６６となり、濃縮汚泥引抜きポンプ６８によって汚泥貯留槽７０に移されて貯留されたのち、矢印７２のようにバキューム車等で搬出される。そして、汚泥濃縮槽６０において分離した分離水７４は、原水ポンプ槽２２に戻されるようになっている。
【０００５】
ところで、従来の沈殿槽４０は、図１３に示したように、中心部に整流筒（センタウェル）７６が上下方向に配設してあって、この整流筒７６内に管７８を介して被処理水である混合水３８を導入するようになっている。そして、整流筒７６は、上端が沈殿槽４０の液面８０より高くしてあって、管７８より上方に向けて吐出された混合水３８が整流筒７６の周囲の上澄水４２と混合しないようにしている。また、整流筒７６は、導入された混合水３８を矢印８２のように層流状態にして整流筒７６の下部から整流筒周囲の分離領域８４に流出させる。分離領域８４に移動した混合水３８は、フロック８６が生物のもつ自然の凝集作用によって凝集し、水と分離して沈降する。そして、汚泥と分離された水は、沈殿槽４０の内側上部に設けた越流堰８８を介して上澄水４２として取り出される。
【０００６】
【発明が解決しようとする課題】
しかし、従来の沈殿層４０における汚泥と水との分離は、微生物による自然の凝集作用によっているために分離、沈降に時間がかかり、分離のために広い面積を必要とし、排水処理装置（設備）の大型化が避けられない。また、生物的な原因による汚泥の膨化（バルキング）が発生し、汚泥の沈降分離が妨げられて汚泥が越流堰８８を越流する問題がある。そして、このバルキングを抑止する対策として、従来は、沈殿層４０に凝集剤や殺菌剤などの薬品を投与することを行なっているが、薬品に対する細菌の耐性による効果の激減や有益微生物への影響が懸念され、好ましい方法とはいえない。
【０００７】
本発明は、前記従来技術の欠点を解消するためになされたもので、処理装置の小型化を図ることを目的としている。
また、本発明は、汚泥のバルキングを抑止することを目的としている。
さらに、本発明は、汚泥濃縮槽における汚泥の沈降分離を促進させ、処理量の増加または設備を小型化することを目的としている。
【０００８】
【課題を解決するための手段】
上記の目的を達成するために、本発明は、被処理水に超音波を照射して活性汚泥を物理的に凝集させるもので、本発明に係る排水処理方法は、被処理水を沈殿槽および汚泥濃縮槽に導入して浮遊物を沈降させる排水処理方法において、前記沈殿槽内の被処理水または前記汚泥濃縮槽の汚泥に超音波を照射して定在波を形成し、前記被処理水中の浮遊物を凝集させて沈降させる構成となっている。超音波の周波数が低いと波長が長くなるため、凝集の間隔が広くなり、細かな粒子や結合力の弱い粒子は凝集しずらくなる。一方、上澄水中の浮遊物質量（ＳＳ）は、超音波の周波数が高いほど小さくなる。しかし、周波数が高いほど音波の減衰が大きくなり、伝播距離が短くなるため、凝集の影響範囲が狭くなる。従って、上澄水中のＳＳと汚泥の沈降速度とを勘案すると、照射する超音波の周波数は、３００ｋＨｚ〜２．５ＭＨｚ程度がよく、特に５００ｋＨｚ〜１．２ＭＨｚ程度が望ましい。そして、超音波は、被処理水の流れに直交させて照射するとよい。
【０００９】
また、本発明に係る排水処理装置は、被処理水を流入させる沈殿槽と、この沈殿槽内に配設され、前記被処理水中に超音波を放射する超音波振動子と、この超音波振動子に対面して設けられ、超音波振動子が放射した超音波が反射され、超音波振動子との間に定在波を形成する反射壁と、この反射壁と前記超音波振動子との間に被処理水を送り込む送水管とを有する構成となっている。超音波振動子と反射壁とは、処理槽内に沈殿させた汚泥を流入させて濃縮する汚泥濃縮槽にも設けることができる。
【００１０】
超音波振動子は、沈殿槽の大きさ、沈殿槽への被処理水の流入量に応じて複数設けることができる。そして、複数の超音波振動子は、被処理水の流れに沿って配置したり、円形状またはマトリックス状等に配置することができる。超音波振動子を円形状に配置した場合、反射壁は複数の超音波振動子に沿って二重円筒状に形成することができる。また、超音波振動子と反射壁との間の距離は定在波ができればよく、周波数により超音波の伝播距離が異なるため、定在波を形成できる最大距離は周波数によって異なる。ただし、超音波の出力が大き過ぎると、キャビテーションが発生して懸濁液を分散する。
【００１１】
【作用】
上記のごとく構成した本発明は、被処理水に超音波を照射して定在波を発生させると、この定在波の音圧の節の部分に汚泥フロックが層状に集る。すなわち、図２に模式的に示したように、超音波振動子９０と反射壁９４とを対面して配置し、矢印９２のように反射壁９４と直交する方向に超音波を伝播し、超音波振動子９０と反射壁９４との間に定在波を発生させると、定在波の音圧分布が符号９６のようになる。ただし、図中Ｐ₀ は、定在波の振幅である。
【００１２】
このとき、被処理水中の汚泥フロック８６は、図２に斜線で示したように音圧の節部に層状に集る。そして、フロック８６は、相互の接触回数が増加して凝集するとともに、超音波の音圧により圧縮させられ、見掛け比重が大きくなって沈降しやすくなる。従って、汚泥を沈降させるための時間の短縮が図れ、処理量の増大や装置の小型化を図ることができ、また処理量を増大させることができる。
【００１３】
さらに、超音波によるフロックの圧縮作用によってバルキングが抑止され、汚泥の沈降性を向上することができる。しかも、超音波を利用した物理的凝集であるため、薬品等の使用に比較して特に専門的な知識を必要としせず、汚泥量の増加もない。なお、被処理水の流れに直交して超音波を照射するようにすると、沈殿槽に被処理水を導入した部分において汚泥を沈殿させることができ、被処理水の連続的な処理が可能となる。そして、被処理水の流入量に応じて超音波振動子を複数設けることにより、被処理水の迅速な処理が可能となる。
なお、汚泥濃縮槽に超音波を照射して定在波を発生させることにより、上記処理槽におけるフロックの凝集と同様に、汚泥濃縮槽内の汚泥の濃縮を迅速に行うことが可能となり、汚泥濃縮槽の小型化、処理量の増大を図ることができる。
【００１４】
【発明の実施の形態】
本発明の排水処理方法および装置の好ましい実施の形態を添付図面に従って詳細に説明する。なお、前記従来技術において説明した部分に相当する部分については、同一の符号を付し、その説明を省略する。
【００１５】
図１は、本発明の実施の形態に係る排水処理装置の要部の説明図である。
図１において、沈殿槽４０は、槽本体１００が円形に形成してあって、中心部に超音波振動子９０が配設してある。この超音波振動子９０は、詳細を後述するように沈殿槽４０に導入された原水と汚泥との混合水（被処理水）に超音波を照射して汚泥を凝集させるもので、水没させて配置してあり、槽本体１００の半径方向に超音波を伝播するようにしてある。そして、超音波振動子９０の周囲には、振動子９０との間に超音波の定在波を発生させるための円筒状反射壁１０４が設けてある。この円筒状反射壁１０４は、槽本体１００と同心状に配置しある。
【００１６】
反射壁１０４の下部には、曝気槽に連通している送水管１０６が設けてある。この送水管１０６は、先端が上方に屈曲していて、屈曲した先端部が反射壁１０４の下端部に挿入してある。そして、円筒状反射壁１０４は、上端が沈殿槽４０の水面８０より低く、水没した状態で設けてあって、送水管１０６から吐出された被処理水（混合水）が矢印１０８のように上部から円筒反射壁１０４の外部に流出できるようにしてある。また、円筒反射壁１０４の上部は、同心状に設けた円筒状のセンタウェル１１０内に挿入してある。このセンタウェル１１０は、上端が水面８０から突出していて、円筒反射壁１０４内を上昇してきた被処理水が直接センタウェル周囲の水と混合するのを防止している。
【００１７】
上記のごとく構成した実施の形態においては、超音波振動子９０を発振させ、図３（１）の矢印１１２、１１４ように円筒状反射壁１０４の半径方向に超音波を伝播させる。超音波振動子９０の放射した超音波は、円筒状反射壁１０４によって反射され、超音波振動子４０の放射する超音波と干渉して超音波振動子９０と円筒反射壁１０４の内壁との間に定在波を形成する。一方、曝気槽において原水と活性汚泥とを混合した混合水（被処理水）３８は、送水管１０６を介して円筒状反射壁１０４内に供給される。反射壁１０４内に導入された混合水３８は、円筒状反射壁１０４内を上昇して反射壁１０４と超音波振動子９０との間を通り、図１の矢印１０８のように、円筒状反射壁１０４の上部から反射壁１０４の外部に流出する。そして、混合水３８中の汚泥フロック８６は、超音波振動子１０４と反射壁１０４との間を通る際に超音波によって凝集し、混合水の流れ１０８に乗って図１の矢印１１６のように円筒状反射壁１０４の上方から反射壁１０４の外部に流出し、センタウエル１１０の内部を下降して沈殿槽４０の下部に分離沈降し、沈殿汚泥１１８として堆積する。
【００１８】
なお、反射壁１０４は、槽本体１００と同心でなくともよい。そして、送水管１０６から円筒状反射壁１０４内に供給される混合水３８の供給量が多く、１つの超音波振動子９０によっては水と汚泥とを十分に分離することができない場合には、図３（２）に示したように、複数の超音波振動子９０を円筒状反射壁１０４の上下方向に、すなわち混合水３８の流れの方向に沿って配置し、混合水３８への超音波の照射時間を長くするとよい。また、図３（３）に示したように、反射壁１２０を外壁１２２と内壁１２４とからなる二重円筒状に形成し、外壁１２２と内壁１２４との間に複数の超音波振動子９０を円形に配置し、これら外壁１２２と内壁１２４との間に混合水３８を供給して処理量の増大を図ってもよい。
【００１９】
さらに、図３（４）に示したように、円筒状の反射壁１０４を複数個並列に設け、その各々に超音波振動子９０を配置するとともに、送水管１０６を各円筒状反射壁１０４に対応させて分岐し、それぞれの反射壁１０４に混合水３８を供給するようにしてもよい。また、図３（５）に示したように、反射壁本体１３０を平面視正方形または矩形に形成し、その内部を縦、横の仕切壁１３２によって複数（例えば９個）の分割領域１３６に区画し、各分割領域１３６に超音波振動子９０を配置するようにしてもよい。この場合、仕切壁１３２を反射壁本体１３０より短くし、反射壁本体１３０によって囲った領域１３８の中央部に送水管１０６から混合水３８を供給するようにしてもよい。また、混合水３８の流路を図３（６）に示したように斜板１４０によって形成し、この斜板１４０に超音波振動子６０を取り付けてもよいし、各斜板１４０間に超音波振動子９０を配置してもよい。
【００２０】
図４は、混合水の流路の形状と超音波振動子の配置状態を示す平面図である。図４（１）は、反射壁本体１３０内を縦、横の仕切壁１３２、１３４によって正方形状の分割領域１３６を複数形成し、各分割領域に超音波振動子９０を配置したものである。また、図４（２）は、混合水の流路１４２が６角形のハニカム構造に形成してあって、各流路１４２の対向した一対の壁間に超音波振動子９０が配置してある。なお、図４（３）に示したように、隣接した２つの流路１４２を仕切っている共通壁１４４に超音波振動子９０を設けてもよい。
【００２１】
図５は、他の実施形態を示したものである。本実施形態においては、沈殿槽４０のセンタウエル１５０内に直接超音波振動子９０を配置したもので、センタウエル５０を超音波の反射壁としたもので、超音波振動子９０とセンタウエル１５０の内壁との間に超音波による定在波を形成する。この実施の形態においては、送水管１０６から吐出された混合水は、センタウエル１５０の上部において矢印１５２のように反転して下方に向かう。そして、混合水中の汚泥フロック８６は、超音波振動子９０によって発生させた超音波によって凝集し、矢印１５４のようにセンタウエル１５０の下方から沈殿槽４０の下部に分離沈降する。
【００２２】
【実施例】
上記した超音波凝集による混合水３８の処理効果を確認する実験を行なった。ただし、下記の実験結果は一例であって、汚泥の状態によって異なる。
実験は、５００ｍｌのメスシリンダに活性汚泥が分散している混合水（被処理水）を入れ、その混合水中に直径３ｃｍの超音波振動子をケーブルで吊るし、混合水に超音波を照射して超音波振動子とメスシリンダの内壁との間に超音波の定在波を発生させて行なった。超音波振動子は、振動子の上端が混合水の水面下１〜２ｃｍとなる深さの位置に配置した。
【００２３】
図６は、混合水に照射した超音波の周波数と汚泥の沈降量との関係を示したものである。使用した被処理水である混合水３８は、浮遊物量（ＳＳ）が１リットル当り６１５０ｍｇである。また、発振器の出力電圧は、実効値（ｒｍｓ、以下同様）で８０ｍＶであり、パワーアンプで５０ｄｂ増幅して振動子に入力した。そして、沈降高の目盛りｈは、目視による活性汚泥が分散している懸濁液と上澄水との境界のメスシリンダの目盛りを示している。なお、ＳＳは、１０ｍｌの混合水を乾燥した濾紙で濾し、この濾紙を乾燥させて濾す前と後との重量を計測してその重量差を求め、これを１ｌ当りに換算して求めた。
【００２４】
図６から明らかなように、自然に沈降させるよりも、超音波を照射した方が沈降速度が大きくなる。また、照射する周波数が低いほど汚泥の沈降量が大きくなっている。すなわち、図６に示したように、自然沈降の場合、５分経したときの沈降高の目盛りは、約４９５ｍｌであり、１０分経過したときの目盛りは約４９１ｍｌ、１５分経過したときの沈降高の目盛りは約４８５ｍｌであった。これに対して、周波数が２．５ＭＨｚのときの沈降高の目盛りは、５分経過時が約４９２ｍｌ、１０分経過時が４８５ｍｌ、１５分経過時が約４７７ｍｌであった。また、周波数が２ＭＨｚの場合の沈降高の目盛りは、５分経過時が約４９２ｍｌ、１０分経過時が約４８３ｍｌ、１５分経過時が約４７２ｍｌであった。さらに、周波数が１．５ＭＨｚの場合の沈降高の目盛りは、５分経過時が約４９０ｍｌ、１０分経過時が約４７８ｍｌ、１５分経過時が約４６７ｍｌであった。そして、周波数が１．２ＭＨｚの場合の沈降高の目盛りは、５分経過時が約４８９ｍｌ、１０分経過時が約４７１ｍｌ、１５分経過時が約４５５ｍｌであり、周波数が１ＭＨｚの場合、沈降高の目盛りは５分経過時が約４７５ｍｌ、１０分経過時が約４４７ｍｌ、１５分経過時が約４３５ｍｌであった。
【００２５】
このように周波数が低くなるのに従って汚泥が迅速に沈降するのは、周波数が低くなるに従って超音波の伝播距離が大きくなり、より多くのフロックを凝集させることができるためである。
【００２６】
図７は、混合水に照射した超音波の周波数と上澄水のＳＳとの関係を示したものである。使用した混合水のＳＳは、５０３０ｍｇ／ｌであり、入力電圧は１００ｍＶｒｍｓである。そして、上澄水のＳＳの測定は、各周波数の超音波を１５分間混合水に照射したのち、上澄水を１０ｍｌ採取して乾燥した濾紙で濾し、これを乾燥させて濾紙の重量を計測して求めた。なお、周波数０は、自然沈降による上澄水中のＳＳを示している。
【００２７】
図７から明らかなように、周波数が高くなるのに従って上澄水中のＳＳは少なくなる傾向が見られるが、周波数が１．２ＭＨｚを超えると、上澄水中のＳＳの値にあまり大きな変化は見られない。すなわち、上澄水中のＳＳは、自然沈降の場合約２９１ｍｇ／ｌ、５００ｋＨｚの場合約３０４ｍｇ／ｌ、１ＭＨｚの場合約１４０ｍｇ／ｌ、１．２ＭＨｚの場合約８４ｍｇ／ｌ、１．５ＭＨｚの場合約７７ｍｇ／ｌ、２ＭＨｚの場合約６６ｍｇ／ｌ、そして２．５ＭＨｚの場合約７０ｍｇ／ｌであった。なお、周波数が５００ｋＨｚの場合、入力が大き過ぎて懸濁液が巻き上げられ、上澄水中のＳＳが自然沈降より多くなった。
【００２８】
図８は、発振器への入力電圧、すなわち超音波の出力と沈降量との関係を示したものである。使用した混合水のＳＳは６１５０ｍｇ／ｌ、混合水に照射した超音波の周波数は２ＭＨｚである。さらに、沈降高の目盛りｈは、前記図６と同様である。また、自然沈降による沈降高の目盛りのデータは、図６に示したものを使用している。
【００２９】
図８に示したように、入力電圧（超音波出力）が大きくなるほど沈降量が大きくなっており、入力電圧が３０ｍＶの場合、２ＭＨｚの超音波を混合水に照射して５分を経過したときの沈降高の目盛りは約４９４ｍｌ、１０分経過したときの目盛りは約４８９ｍｌ、１５分を経過したときの目盛りは約４８３ｍｌであった。また、入力電力が４０ｍＶの場合の沈降高の目盛りは、５分経過時が約４９４ｍｌ、１０分経過時が約４８８ｍｌ、１５分経過時が約４８１ｍｌであった。そして、入力電圧が５０ｍＶの場合の沈降高の目盛りは、５分経過時が約４９５ｍｌ、１０分経過時が約４８８ｍｌ、１５分経過時が約４８０ｍｌであった。さらに、入力電圧が８０ｍＶの場合の沈降高の目盛りは、５分経過時が約４９２ｍｌ、１０分経過時が約４８３ｍｌ、１５分経過時が約４７２ｍｌであった。また、入力電圧が１００ｍＶの場合の沈降高の目盛りは、５分経過時が約４８７ｍｌ、１０分経過時が約４７３ｍｌ、１５分経過時が約４６４ｍｌであった。そして、入力電圧が１２０ｍＶの場合の沈降高の目盛りは、５分経過時が約４８０ｍｌ、１０分経過時が約４６９ｍｌ、１５分経過時が約４５９ｍｌであった。さらに、入力電圧が１４０ｍＶの場合の沈降高の目盛りは、５分経過時が約４７５ｍｌ、１０分経過時が約４５９ｍｌ、１５分経過時が約４５２ｍｌであった。
【００３０】
従って、入力電圧が大きいほど、すなわち超音波の出力が大きくなるほど汚泥が速やかに沈降する。ただし、超音波の出力があまり大きくなりすぎると、キャビテーションが発生して懸濁液が分散される。
【００３１】
図９は、発振器の出力電圧と上澄水中のＳＳとの関係を示したものである。
使用した混合水は、ＳＳが５０３０ｍｇ／ｌであり、照射した超音波の周波数は２．５ＭＨｚである。自然沈降の場合、１５分経過したときの上澄水中のＳＳは、約２９０ｍｇ／ｌであるが、入力電圧５０ｍＶで２ＭＨｚの超音波を１５分間混合水に照射した場合、上澄水中のＳＳは約１９０ｍｇ／ｌであった。また、入力電圧が８０ｍＶのときは約１２７ｍｇ／ｌ、入力電圧が１００ｍＶのときは約７０ｍｇ／ｌ、入力電圧が１２０ｍＶのときは約６５ｍｇ／ｌ、入力電圧が１４０ｍＶのときは約７０ｍｇ／ｌであった。
【００３２】
図１０と図１１とは、他の実験例を示したもので、図１０が超音波の周波数と汚泥の沈降量との関係を示したもので、図１１が超音波の周波数と上澄水中のＳＳとの関係を示したものである。実験条件は、前記とほぼ同様であるが、混合水のＳＳは６１７１ｍｇ／ｌであり、発振器の入力電圧は４０ｍＶｒである。これらの図によると、周波数が３００ｋＨｚの場合、周波数が５００ｋＨｚのときとほぼ同様の沈降量を得ることができる。しかし、周波数３００ｋＨｚにおける上澄水中のＳＳは、自然沈降に比較しても悪かった。また、発信器の出力が小さいため、１ＭＨｚ以上の周波数では、凝集効果があまり見られず、上澄水中のＳＳも、１ＭＨｚ以上ではほとんど変化が見られなかった。
【００３３】
なお、前記実施例においては、混合水に超音波のみを照射して凝集、沈降処理を行なった場合について説明したが、凝集剤の使用と超音波の照射とを併用してもよい。そして、前記実施例においては、超音波振動子が円形である場合について説明したが、振動子の形状は円形に限定されない。また、前記実施の形態においては、沈殿槽４０に超音波振動子９０を配置した場合について説明したが、汚泥濃縮槽に超音波振動子と反射壁とを設け、汚泥濃縮槽内に超音波による定在はを発生させて汚泥を濃縮するようにしてもよい。
【００３４】
【発明の効果】
以上に説明したようには、本発明によれば、被処理水に超音波を照射して定在波を発生させることにより、この定在波の音圧の節部に汚泥が集り、容易に凝集して沈降しやすくなり、汚泥の沈降時間を短縮できるため、処理量の増大や装置を小型化を図ることができる。また、バルキングが抑止されて沈降性を向上することができる。しかも、汚泥の沈降速度を大きくできるために汚泥を沈殿させておく時間の短縮が図れ、汚泥中のりんの溶出を防止できて処理水の水質を向上することができる。
【００３５】
周波数が３００ｋＨｚ〜２．５ＭＨｚの超音波を被処理水に照射すると、被処理水中の浮遊物を迅速に沈降させることができるとともに、上澄水中のＳＳを低下させることができる。さらに、被処理水の流れに直交して超音波を照射するようにすると、沈殿槽に被処理水を導入した部分において汚泥を沈殿させることができ、被処理水の連続的な処理が可能となる。そして、被処理水の流入量に応じて超音波振動子を複数設けることにより、被処理水の迅速な処理が可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る沈殿槽の説明図である。
【図２】本発明の排水処理方法の原理を模式的に示した説明図である。
【図３】実施の形態に係る超音波振動子の配置例の側方から見た図である。
【図４】実施の形態に係る超音波振動子の配置例の上方から見た図である。
【図５】他の実施形態に係る沈殿槽の説明図である。
【図６】実施例における被処理水に超音波を照射したときの、超音波の周波数と汚泥の沈降量との関係を示す図である。
【図７】実施例における被処理水に超音波を照射したときの、超音波の周波数と上澄水中のＳＳとの関係を示す図である。
【図８】実施例における被処理水に超音波を照射したときの、超音波の出力と汚泥の沈降量との関係を示す図である。
【図９】実施例における被処理水に超音波を照射したときの、超音波の出力と上澄水中のＳＳとの関係を示す図である。
【図１０】入力電圧が４０ｍＶｒのときの超音波の周波数と汚泥の沈降量との関係を示す図である。
【図１１】入力電圧が４０ｍＶｒのときの超音波の周波数と上澄水中のＳＳとの関係を示す図である。
【図１２】従来の活性汚泥法による排水処理方法の説明図である。
【図１３】従来の沈殿槽の説明図である。
【符号の説明】
４０排水処理装置（沈殿槽）
４２上澄水
８６汚泥フロック
９０超音波振動子
１００槽本体
１０４円筒状反射壁
１０６送水管
１１８沈殿汚泥[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment method for obtaining a clear treated water by removing suspended substances from wastewater such as sewage, domestic wastewater, and industrial wastewater, and in particular, sedimenting suspended substances using a biological treatment method. The present invention relates to a wastewater treatment method and apparatus.
[0002]
[Prior art]
FIG. 12 is an explanatory diagram showing an outline of an activated sludge method for biologically treating wastewater. In FIG. 12, raw water 10 such as sewage and domestic wastewater is passed through a coarse screen 12 and flows into a sand settling tank 14, where sand and soot are precipitated and removed. Precipitated sand and soot are discharged from the sand settling tank 14 by a sand settling pump 16. The raw water 10 flows into the raw water pump tank 22 via the crusher 18 and the fine screen 20 and is sent to the flow rate adjusting tank 26 by the raw water pump 24. The raw water 10 in the flow rate adjustment tank 26 is agitated by the agitation pump 28 and the like, sent to the sewage metering tank 32 by the flow rate adjustment pump 30, weighed, and flows into the aeration tank 34.
[0003]
The aeration tank 34 is returned from a settling tank described later and mixed with the raw water 10 into which the activated sludge made of injected aerobic microorganisms flows, and the air discharged from the aeration blower 36 is blown to grow the microorganisms. Flock formation takes place. Then, the mixed water 38 of raw water 10 and sludge in the aeration tank 34 is introduced into the settling tank 40. The floc in the mixed water 38 in the settling tank 40 grows in the center well 76 and is separated into sludge and clear supernatant water (treated water) 42 in the separation tank 77 as activated sludge. The separated supernatant water 42 is sent to a sterilization tank 44 and sterilized by contacting with a disinfectant via a sterilizer 46, and then discharged into a river or the like as sterilized treated water 48.
[0004]
The activated sludge 50 precipitated in the settling tank 40 is drawn out by the sludge return pump 52, measured in the sludge measuring tank 54, and returned to the aeration tank 34 as the return sludge 56, and the excess sludge is concentrated as sludge 58 as the sludge. It is sent to the tank 60. Further, the scum 62 floating on the surface of the sedimentation tank 40 is returned to the flow rate adjustment tank 26 by the scum pump 64. On the other hand, the excess sludge 58 that has flowed into the sludge concentration tank 60 is concentrated to become the concentrated sludge 66, which is transferred to and stored in the sludge storage tank 70 by the concentrated sludge extraction pump 68, and then, as indicated by an arrow 72, by a vacuum vehicle or the like. It is carried out. The separated water 74 separated in the sludge concentration tank 60 is returned to the raw water pump tank 22.
[0005]
Meanwhile, as shown in FIG. 13, the conventional sedimentation tank 40 has a rectifying cylinder (center well) 76 arranged in the vertical direction at the center, and a pipe 78 is provided in the rectifying cylinder 76. Mixed water 38, which is treated water, is introduced. The rectifying cylinder 76 has an upper end higher than the liquid level 80 of the settling tank 40 so that the mixed water 38 discharged upward from the pipe 78 does not mix with the supernatant water 42 around the rectifying cylinder 76. I have to. Further, the rectifying cylinder 76 causes the introduced mixed water 38 to flow in a laminar state as indicated by an arrow 82 and flows out from the lower part of the rectifying cylinder 76 to the separation region 84 around the rectifying cylinder 76. The mixed water 38 that has moved to the separation region 84 is agglomerated by the natural aggregating action of the floc 86 by the living organisms, and separates from the water and settles. And the water isolate | separated from the sludge is taken out as the supernatant water 42 through the overflow weir 88 provided in the inner upper part of the sedimentation tank 40. FIG.
[0006]
[Problems to be solved by the invention]
However, the separation of sludge and water in the conventional sedimentation layer 40 is due to natural agglomeration by microorganisms, so it takes time to separate and settle, requiring a large area for separation, and wastewater treatment equipment (equipment) The increase in size is inevitable. In addition, sludge expansion (bulking) due to biological causes occurs, and there is a problem that the sludge settles and is separated and the sludge overflows the overflow weir 88. And as a measure to suppress this bulking, conventionally, chemicals such as flocculants and bactericides have been administered to the sedimentation layer 40, but the effect of bacterial resistance to the chemicals is drastically reduced and the effect on beneficial microorganisms. This is not a preferred method.
[0007]
The present invention has been made to solve the above-mentioned drawbacks of the prior art, and aims to reduce the size of the processing apparatus.
Another object of the present invention is to suppress bulking of sludge.
Furthermore, an object of the present invention is to promote sedimentation and separation of sludge in a sludge concentration tank, and to increase the throughput or downsize equipment.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention physically irradiates the activated water sludge by irradiating the water to be treated, and the wastewater treatment method according to the present invention comprises a treatment tank containing the treated water and a sedimentation tank. In the wastewater treatment method for introducing suspended sludge into the sludge concentration tank, the standing water is formed by irradiating the treated water in the settling tank or the sludge in the sludge concentration tank with ultrasonic waves, and the treated water. It is configured to aggregate and settle the suspended matter. If the frequency of the ultrasonic wave is low, the wavelength becomes long, so that the interval between aggregation is widened, and fine particles and particles with weak binding force are difficult to aggregate. On the other hand, the suspended matter amount (SS) in the supernatant water becomes smaller as the ultrasonic frequency is higher. However, the higher the frequency, the greater the attenuation of the sound wave and the shorter the propagation distance, so the range of influence of aggregation becomes narrower. Therefore, considering the SS in the supernatant water and the sedimentation rate of the sludge, the frequency of the ultrasonic wave to be irradiated is preferably about 300 kHz to 2.5 MHz, and particularly preferably about 500 kHz to 1.2 MHz. And it is good to irradiate an ultrasonic wave orthogonally to the flow of to-be-processed water.
[0009]
Further, the waste water treatment apparatus according to the present invention includes a precipitation tank into which the water to be treated is introduced, an ultrasonic vibrator that is disposed in the precipitation tank and emits ultrasonic waves into the water to be treated, and this ultrasonic vibration. A reflection wall that is provided facing the child and reflects the ultrasonic wave radiated from the ultrasonic transducer and forms a standing wave between the ultrasonic transducer and the reflection wall and the ultrasonic transducer. It has the structure which has the water pipe which sends in to-be-processed water in between. The ultrasonic vibrator and the reflection wall can also be provided in a sludge concentration tank that allows the sludge precipitated in the treatment tank to flow in and concentrate.
[0010]
A plurality of ultrasonic vibrators can be provided according to the size of the sedimentation tank and the amount of water to be treated flowing into the sedimentation tank. The plurality of ultrasonic transducers can be arranged along the flow of the water to be treated, or arranged in a circular shape or a matrix shape. When the ultrasonic transducers are arranged in a circular shape, the reflection wall can be formed in a double cylindrical shape along the plurality of ultrasonic transducers. Further, the distance between the ultrasonic transducer and the reflecting wall only needs to be a standing wave, and since the propagation distance of the ultrasonic wave varies depending on the frequency, the maximum distance at which the standing wave can be formed varies depending on the frequency. However, if the output of the ultrasonic wave is too large, cavitation occurs and the suspension is dispersed.
[0011]
[Action]
In the present invention configured as described above, when a standing wave is generated by irradiating the water to be treated, sludge flocs gather in a layered manner at the node of the sound pressure of the standing wave. That is, as schematically shown in FIG. 2, the ultrasonic transducer 90 and the reflection wall 94 are arranged facing each other, and the ultrasonic wave is propagated in a direction orthogonal to the reflection wall 94 as indicated by an arrow 92. When a standing wave is generated between the sound wave oscillator 90 and the reflection wall 94, the sound pressure distribution of the standing wave becomes as indicated by reference numeral 96. However, P ₀ in the figure is the amplitude of the standing wave.
[0012]
At this time, the sludge floc 86 in the for-treatment water gathers in a layered manner at the node of the sound pressure as shown by the oblique lines in FIG. The flocs 86 are aggregated by increasing the number of times of mutual contact, and are compressed by the sound pressure of the ultrasonic waves, so that the apparent specific gravity is increased and the flocs 86 are liable to settle. Therefore, it is possible to shorten the time for settling sludge, increase the processing amount, reduce the size of the apparatus, and increase the processing amount.
[0013]
Furthermore, bulking is suppressed by the compression action of flocs by ultrasonic waves, and the sedimentation property of sludge can be improved. And since it is physical aggregation using an ultrasonic wave, especially specialized knowledge is not required compared with use of a chemical | medical agent etc., and the amount of sludge does not increase. In addition, if ultrasonic waves are irradiated orthogonally to the flow of the water to be treated, sludge can be precipitated at the portion where the water to be treated is introduced into the settling tank, and continuous treatment of the water to be treated is possible. Become. Then, by providing a plurality of ultrasonic vibrators according to the inflow amount of the water to be treated, it is possible to quickly treat the water to be treated.
In addition, by irradiating the sludge concentration tank with ultrasonic waves and generating a standing wave, it is possible to quickly concentrate the sludge in the sludge concentration tank, similar to the floc aggregation in the treatment tank. The concentration tank can be downsized and the amount of processing can be increased.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the waste water treatment method and apparatus of the present invention will be described in detail with reference to the accompanying drawings. Note that portions corresponding to the portions described in the prior art are denoted by the same reference numerals, and description thereof is omitted.
[0015]
FIG. 1 is an explanatory diagram of a main part of a wastewater treatment apparatus according to an embodiment of the present invention.
In FIG. 1, the sedimentation tank 40 has a tank body 100 formed in a circular shape, and an ultrasonic transducer 90 disposed in the center. As will be described in detail later, this ultrasonic transducer 90 irradiates the mixed water (treated water) of raw water and sludge introduced into the sedimentation tank 40 with ultrasonic waves to aggregate the sludge. The ultrasonic waves are propagated in the radial direction of the tank body 100. A cylindrical reflecting wall 104 for generating an ultrasonic standing wave is provided between the ultrasonic transducer 90 and the transducer 90. The cylindrical reflecting wall 104 is disposed concentrically with the tank body 100.
[0016]
A water supply pipe 106 communicating with the aeration tank is provided below the reflecting wall 104. The water pipe 106 has a tip bent upward, and the bent tip is inserted into the lower end of the reflection wall 104. The cylindrical reflecting wall 104 has an upper end that is lower than the water surface 80 of the settling tank 40 and is submerged, and the water to be treated (mixed water) discharged from the water supply pipe 106 is at the top as indicated by an arrow 108. From the cylindrical reflection wall 104 to the outside. The upper part of the cylindrical reflecting wall 104 is inserted into a cylindrical center well 110 provided concentrically. The center well 110 has an upper end protruding from the water surface 80 to prevent the water to be treated rising inside the cylindrical reflecting wall 104 from directly mixing with the water around the center well.
[0017]
In the embodiment configured as described above, the ultrasonic transducer 90 is oscillated and ultrasonic waves are propagated in the radial direction of the cylindrical reflecting wall 104 as indicated by arrows 112 and 114 in FIG. The ultrasonic wave emitted by the ultrasonic transducer 90 is reflected by the cylindrical reflection wall 104 and interferes with the ultrasonic wave emitted by the ultrasonic transducer 40, so that the ultrasonic transducer 90 and the inner wall of the cylindrical reflection wall 104 are interfered with each other. To form a standing wave. On the other hand, mixed water (treated water) 38 obtained by mixing raw water and activated sludge in the aeration tank is supplied into the cylindrical reflecting wall 104 via the water supply pipe 106. The mixed water 38 introduced into the reflecting wall 104 ascends in the cylindrical reflecting wall 104 and passes between the reflecting wall 104 and the ultrasonic transducer 90, and as shown by an arrow 108 in FIG. It flows out of the reflection wall 104 from the upper part of the wall 104. The sludge floc 86 in the mixed water 38 aggregates by ultrasonic waves when passing between the ultrasonic vibrator 104 and the reflecting wall 104, and rides on the mixed water flow 108 as indicated by an arrow 116 in FIG. It flows out from the upper part of the cylindrical reflecting wall 104 to the outside of the reflecting wall 104, descends the inside of the center well 110, separates and settles at the lower part of the settling tank 40, and accumulates as the precipitated sludge 118.
[0018]
The reflection wall 104 may not be concentric with the tank body 100. If the supply amount of the mixed water 38 supplied from the water supply pipe 106 into the cylindrical reflection wall 104 is large, water and sludge cannot be sufficiently separated by one ultrasonic vibrator 90. As shown in FIG. 3 (2), a plurality of ultrasonic transducers 90 are arranged in the vertical direction of the cylindrical reflecting wall 104, that is, along the direction of the flow of the mixed water 38, and ultrasonic waves to the mixed water 38 are obtained. It is better to lengthen the irradiation time. Further, as shown in FIG. 3 (3), the reflecting wall 120 is formed in a double cylindrical shape including an outer wall 122 and an inner wall 124, and a plurality of ultrasonic transducers 90 are provided between the outer wall 122 and the inner wall 124. It may be arranged in a circular shape, and the mixed water 38 may be supplied between the outer wall 122 and the inner wall 124 to increase the processing amount.
[0019]
Further, as shown in FIG. 3 (4), a plurality of cylindrical reflection walls 104 are provided in parallel, and an ultrasonic transducer 90 is disposed on each of them, and a water pipe 106 is attached to each cylindrical reflection wall 104. It is also possible to branch correspondingly and supply the mixed water 38 to the respective reflecting walls 104. Further, as shown in FIG. 3 (5), the reflecting wall main body 130 is formed in a square or rectangular shape in plan view, and the inside thereof is partitioned into a plurality of (for example, nine) divided regions 136 by vertical and horizontal partition walls 132. However, the ultrasonic transducer 90 may be disposed in each divided region 136. In this case, the partition wall 132 may be shorter than the reflecting wall main body 130, and the mixed water 38 may be supplied from the water supply pipe 106 to the center of the region 138 surrounded by the reflecting wall main body 130. Further, the flow path of the mixed water 38 may be formed by the swash plate 140 as shown in FIG. 3 (6), and the ultrasonic vibrator 60 may be attached to the swash plate 140. A sonic transducer 90 may be arranged.
[0020]
FIG. 4 is a plan view showing the shape of the flow path of the mixed water and the arrangement state of the ultrasonic transducers. In FIG. 4A, a plurality of square divided regions 136 are formed by vertical and horizontal partition walls 132 and 134 in the reflecting wall main body 130, and the ultrasonic transducer 90 is arranged in each divided region. 4 (2), the mixed water channel 142 is formed in a hexagonal honeycomb structure, and the ultrasonic transducer 90 is disposed between a pair of opposed walls of each channel 142. . As shown in FIG. 4 (3), the ultrasonic transducer 90 may be provided on the common wall 144 that partitions two adjacent flow paths 142.
[0021]
FIG. 5 shows another embodiment. In the present embodiment, the ultrasonic vibrator 90 is disposed directly in the center well 150 of the sedimentation tank 40, and the center well 50 is an ultrasonic reflection wall. A standing wave by ultrasonic waves is formed between the inner wall and the inner wall. In this embodiment, the mixed water discharged from the water supply pipe 106 is inverted as indicated by an arrow 152 in the upper part of the center well 150 and travels downward. Then, the sludge floc 86 in the mixed water is aggregated by the ultrasonic waves generated by the ultrasonic vibrator 90 and separated and settled from below the center well 150 to the lower part of the sedimentation tank 40 as indicated by an arrow 154.
[0022]
【Example】
An experiment was conducted to confirm the treatment effect of the mixed water 38 by the ultrasonic aggregation described above. However, the following experimental results are examples, and differ depending on the state of the sludge.
In the experiment, mixed water (treated water) in which activated sludge is dispersed is placed in a 500 ml measuring cylinder, an ultrasonic vibrator having a diameter of 3 cm is hung with a cable in the mixed water, and the mixed water is irradiated with ultrasonic waves. An ultrasonic standing wave was generated between the ultrasonic transducer and the inner wall of the measuring cylinder. The ultrasonic transducer was placed at a depth where the upper end of the transducer would be 1 to 2 cm below the surface of the mixed water.
[0023]
FIG. 6 shows the relationship between the frequency of ultrasonic waves applied to the mixed water and the amount of sludge settling. The mixed water 38 which is the to-be-treated water used has a suspended solid amount (SS) of 6150 mg per liter. The output voltage of the oscillator was 80 mV as an effective value (rms, hereinafter the same), and was amplified by 50 db with a power amplifier and input to the vibrator. The scale h of the sedimentation height indicates the scale of the measuring cylinder at the boundary between the suspension in which the activated sludge is visually dispersed and the supernatant water. The SS was obtained by filtering 10 ml of mixed water with a dry filter paper, measuring the weight before and after filtering the filter paper, and calculating the difference in weight per 1 liter.
[0024]
As is clear from FIG. 6, the sedimentation speed is higher when the ultrasonic wave is irradiated than when the sedimentation is naturally performed. Moreover, the amount of sludge settling increases as the frequency of irradiation decreases. That is, as shown in FIG. 6, in the case of natural sedimentation, the scale of sedimentation height after 5 minutes is about 495 ml, the scale after 10 minutes is about 491 ml, and the sedimentation after 15 minutes. The high scale was about 485 ml. In contrast, the scale of sedimentation height when the frequency was 2.5 MHz was about 492 ml when 5 minutes passed, 485 ml after 10 minutes, and about 477 ml after 15 minutes. The scale of sedimentation height when the frequency was 2 MHz was about 492 ml after 5 minutes, about 483 ml after 10 minutes, and about 472 ml after 15 minutes. Further, the scale of sedimentation height when the frequency was 1.5 MHz was about 490 ml when 5 minutes passed, about 478 ml after 10 minutes, and about 467 ml after 15 minutes. And when the frequency is 1.2 MHz, the scale of sedimentation height is about 489 ml at the time of 5 minutes, about 471 ml at the time of 10 minutes, and about 455 ml at the time of 15 minutes. The scale was about 475 ml after 5 minutes, about 447 ml after 10 minutes, and about 435 ml after 15 minutes.
[0025]
The reason why the sludge settles rapidly as the frequency is lowered is that the propagation distance of the ultrasonic wave is increased as the frequency is lowered, and more flocs can be aggregated.
[0026]
FIG. 7 shows the relationship between the frequency of the ultrasonic wave irradiated to the mixed water and the SS of the supernatant water. The SS of the mixed water used is 5030 mg / l, and the input voltage is 100 mVrms. The SS of the supernatant water is measured by irradiating the mixed water with ultrasonic waves of each frequency for 15 minutes, collecting 10 ml of the supernatant water, filtering it with a dry filter paper, drying it, and measuring the weight of the filter paper. Asked. In addition, the frequency 0 has shown SS in the supernatant water by natural sedimentation.
[0027]
As is apparent from FIG. 7, the SS in the supernatant water tends to decrease as the frequency increases. However, when the frequency exceeds 1.2 MHz, the SS value in the supernatant water does not change significantly. I can't. That is, SS in supernatant water is about 291 mg / l for natural sedimentation, about 304 mg / l for 500 kHz, about 140 mg / l for 1 MHz, about 84 mg / l for 1.2 MHz, and about 1.5 mg for 1.5 MHz. It was about 66 mg / l at 77 mg / l and 2 MHz, and about 70 mg / l at 2.5 MHz. In addition, when the frequency was 500 kHz, the input was too large and the suspension was wound up, and the SS in the supernatant water was larger than the natural sedimentation.
[0028]
FIG. 8 shows the relationship between the input voltage to the oscillator, that is, the output of the ultrasonic wave and the amount of sedimentation. The SS of the mixed water used was 6150 mg / l, and the frequency of the ultrasonic wave irradiated to the mixed water was 2 MHz. Furthermore, the scale h of the sedimentation height is the same as in FIG. Moreover, the data shown in FIG. 6 is used for the data of the scale of sedimentation height by natural sedimentation.
[0029]
As shown in FIG. 8, as the input voltage (ultrasonic output) increases, the sedimentation amount increases. When the input voltage is 30 mV, 5 minutes have passed after the 2 MHz ultrasonic wave is irradiated to the mixed water. The scale of sedimentation height was about 494 ml, the scale after 10 minutes was about 489 ml, and the scale after 15 minutes was about 483 ml. The scale of sedimentation height when the input power was 40 mV was about 494 ml after 5 minutes, about 488 ml after 10 minutes, and about 481 ml after 15 minutes. The scale of sedimentation height when the input voltage was 50 mV was about 495 ml after 5 minutes, about 488 ml after 10 minutes, and about 480 ml after 15 minutes. Further, when the input voltage was 80 mV, the scale of sedimentation height was about 492 ml after 5 minutes, about 483 ml after 10 minutes, and about 472 ml after 15 minutes. The scale of sedimentation height when the input voltage was 100 mV was about 487 ml after 5 minutes, about 473 ml after 10 minutes, and about 464 ml after 15 minutes. When the input voltage was 120 mV, the sedimentation height scale was about 480 ml after 5 minutes, about 469 ml after 10 minutes, and about 459 ml after 15 minutes. Further, when the input voltage was 140 mV, the sedimentation height scale was about 475 ml after 5 minutes, about 459 ml after 10 minutes, and about 452 ml after 15 minutes.
[0030]
Therefore, as the input voltage increases, that is, as the output of the ultrasonic wave increases, the sludge settles quickly. However, if the output of the ultrasonic wave becomes too large, cavitation occurs and the suspension is dispersed.
[0031]
FIG. 9 shows the relationship between the output voltage of the oscillator and SS in the supernatant.
The mixed water used has an SS of 5030 mg / l and the frequency of the irradiated ultrasonic wave is 2.5 MHz. In the case of natural sedimentation, SS in the supernatant water after 15 minutes is about 290 mg / l. However, when 2 MHz ultrasonic waves are irradiated to the mixed water for 15 minutes at an input voltage of 50 mV, the SS in the supernatant water is About 190 mg / l. When the input voltage is 80 mV, it is about 127 mg / l, when the input voltage is 100 mV, it is about 70 mg / l, when the input voltage is 120 mV, it is about 65 mg / l, and when the input voltage is 140 mV, it is about 70 mg / l. there were.
[0032]
FIGS. 10 and 11 show other experimental examples. FIG. 10 shows the relationship between the ultrasonic frequency and the amount of sludge settling. FIG. 11 shows the ultrasonic frequency and the supernatant water. This shows the relationship with SS. The experimental conditions are almost the same as described above, but the SS of the mixed water is 6171 mg / l and the input voltage of the oscillator is 40 mVr. According to these figures, when the frequency is 300 kHz, almost the same amount of sedimentation can be obtained as when the frequency is 500 kHz. However, the SS in the supernatant water at a frequency of 300 kHz was worse than natural sedimentation. Moreover, since the output of the transmitter was small, the coagulation effect was not so much observed at frequencies of 1 MHz or higher, and the SS in the supernatant water was hardly changed at 1 MHz or higher.
[0033]
In the above-described embodiment, the case where the mixed water is irradiated with only ultrasonic waves to perform the aggregation and sedimentation treatment has been described. However, the use of the flocculant and the ultrasonic irradiation may be used in combination. In the embodiment, the case where the ultrasonic transducer is circular has been described, but the shape of the transducer is not limited to a circle. Moreover, in the said embodiment, although the case where the ultrasonic transducer | vibrator 90 was arrange | positioned in the sedimentation tank 40 was demonstrated, an ultrasonic transducer | vibrator and a reflective wall were provided in the sludge concentration tank, and the ultrasonic wave is contained in the sludge concentration tank. The standing may be generated to concentrate the sludge.
[0034]
【The invention's effect】
As described above, according to the present invention, the standing water is generated by irradiating the water to be treated with sludge, so that sludge collects at the node of the sound pressure of the standing wave, and easily. Since it is easy to aggregate and settle and the sedimentation time of sludge can be shortened, the amount of processing can be increased and the apparatus can be downsized. Moreover, bulking is suppressed and sedimentation can be improved. Moreover, since the sedimentation rate of the sludge can be increased, the time for precipitating the sludge can be shortened, the elution of phosphorus in the sludge can be prevented, and the quality of the treated water can be improved.
[0035]
When the treatment water is irradiated with ultrasonic waves having a frequency of 300 kHz to 2.5 MHz, suspended matters in the treatment water can be quickly settled and SS in the supernatant water can be reduced. Furthermore, if ultrasonic waves are irradiated orthogonally to the flow of the water to be treated, sludge can be precipitated at the portion where the water to be treated is introduced into the settling tank, and continuous treatment of the water to be treated is possible. Become. Then, by providing a plurality of ultrasonic vibrators according to the inflow amount of the water to be treated, it is possible to quickly treat the water to be treated.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a sedimentation tank according to an embodiment of the present invention.
FIG. 2 is an explanatory view schematically showing the principle of the wastewater treatment method of the present invention.
FIG. 3 is a side view of an arrangement example of ultrasonic transducers according to the embodiment.
FIG. 4 is a view from above of an arrangement example of ultrasonic transducers according to the embodiment.
FIG. 5 is an explanatory diagram of a sedimentation tank according to another embodiment.
FIG. 6 is a diagram showing the relationship between the frequency of ultrasonic waves and the amount of sludge settling when ultrasonic waves are applied to the water to be treated in the examples.
FIG. 7 is a diagram showing the relationship between the frequency of ultrasonic waves and SS in supernatant water when ultrasonic waves are applied to the water to be treated in the examples.
FIG. 8 is a diagram showing the relationship between the output of ultrasonic waves and the amount of sludge settling when the water to be treated is irradiated with ultrasonic waves in an example.
FIG. 9 is a diagram showing a relationship between the output of ultrasonic waves and SS in supernatant water when ultrasonic waves are applied to the water to be treated in Examples.
FIG. 10 is a diagram showing the relationship between the frequency of ultrasonic waves and the amount of sludge settling when the input voltage is 40 mVr.
FIG. 11 is a diagram showing the relationship between the frequency of ultrasonic waves when the input voltage is 40 mVr and SS in the supernatant water.
FIG. 12 is an explanatory view of a wastewater treatment method by a conventional activated sludge method.
FIG. 13 is an explanatory view of a conventional sedimentation tank.
[Explanation of symbols]
40 Wastewater treatment equipment (sedimentation tank)
42 Supernatant water 86 Sludge floc 90 Ultrasonic vibrator 100 Tank body 104 Cylindrical reflection wall 106 Water pipe 118 Precipitated sludge

Claims

In the wastewater treatment method in which water to be treated is introduced into a sedimentation tank and a sludge concentration tank to settle suspended matter, ultrasonic waves are applied to the treated water in the sedimentation tank or the sludge in the sludge concentration tank to generate standing waves. A wastewater treatment method characterized by forming and agglomerating suspended matter in the water to be treated to be settled.

The wastewater treatment method according to claim 1, wherein the ultrasonic wave to be irradiated has a frequency of 300 kHz to 2.5 MHz.

The wastewater treatment method according to claim 1 or 2, wherein the ultrasonic wave is irradiated so as to be orthogonal to the flow of the water to be treated.

A settling tank into which the water to be treated flows, an ultrasonic vibrator disposed in the settling tank and radiating ultrasonic waves into the water to be treated, and provided to face the ultrasonic vibrator. A reflection wall that reflects the ultrasonic waves emitted from the child and forms a standing wave with the ultrasonic transducer, and a water supply pipe that feeds water to be treated between the reflection wall and the ultrasonic transducer. A wastewater treatment apparatus comprising:

A sludge concentrating tank into which sludge precipitated in the settling tank flows, an ultrasonic vibrator disposed in the sludge concentrating tank and emitting ultrasonic waves to the sludge, and facing the ultrasonic vibrator The waste water according to claim 4, further comprising: a reflecting wall that reflects the ultrasonic wave radiated from the ultrasonic vibrator and forms a standing wave with the ultrasonic vibrator. Processing equipment.

The waste water treatment apparatus according to claim 4 or 5, wherein a plurality of the ultrasonic vibrators are provided along a flow of the water to be treated.

6. The ultrasonic transducer according to claim 4, wherein a plurality of the ultrasonic transducers are arranged in a circular shape, and the reflection wall is formed in a double cylindrical shape along the plurality of ultrasonic transducers. The waste water treatment apparatus as described.

The waste water treatment apparatus according to claim 4 or 5, wherein a plurality of the ultrasonic vibrators are arranged in a matrix.