JP3908918B2 - Wastewater disinfection method and apparatus - Google Patents

Description

【００１６】
ヒダントイン類(hydantoins)は、例えば、式IIで示される。上式IIにおいて、Ｘ¹及びＸ²は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子又はヨウ素原子であり、ただし、Ｘ¹及びＸ²の何れかは、臭素原子又はヨウ素原子であり；Ｒ¹及びＲ²は、それぞれ、同一又は異なって、独立して、水素原子又は炭素数１０以下の低級アルキル基であり、好ましくは、水素原子又は炭素数６以下の低級アルキル基であり、更に好ましくは、水素原子又は炭素数３以下の低級アルキル基である。ヒダントイン類としては、例えば、１−ブロモ−３−クロロ−５，５−ジメチルヒダントイン（上式Iで示される化合物：ＢＣＤＭＨ）が挙げられる。ブロモクロロジメチルヒダントインは、高い安定性を有し、直射日光を避ければ数年間、活性を維持することができる。ＢＣＤＭＨは固体であり、解離することによって次亜臭素酸イオンが生成し、高い消毒効果を発揮する。
【００１７】
シアヌール酸類(cyanuric acids)は、例えば、上式IIIで示される。式III中、Ｒ¹、Ｒ²及びＲ³は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子、ヨウ素原子、水酸基、水素原子又は炭素数１０以下の低級アルキル基であり、但し、Ｒ¹、Ｒ²及びＲ³の少なくとも一つは、臭素原子又はヨウ素原子である。低級アルキル基は、炭素数６以下が更に好ましく、炭素数３以下が更に好ましい。
【００１８】
イソチアゾロン類(isothiazolon)は、例えば、上式IVで示される。式IV中、Ｘは、臭素原子又はヨウ素原子であり；Ｒ¹及びＲ²は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子、ヨウ素原子、水素原子又は炭素数１０以下の低級アルキル基である。低級アルキル基は、炭素数６以下が更に好ましく、炭素数３以下が更に好ましい。例えば、５−クロロ−２−メチル−４−イソチアゾリン−３−オンが好ましい。
【００１９】
ε−カプロラクタム類（ε-caprolactams）は、例えば、上式Vで示される。式V中、Ｘは、臭素原子又はヨウ素原子である。
フタールイミド類(phthalimides)は、例えば、上式VIで示される。式VI中、Ｘは、臭素原子又はヨウ素原子である。
【００２０】
ピロリドン類(pyrrolidones)は、例えば、上式VIIで示される。式VII中、Ｘは、臭素原子又はヨウ素原子である。
アクリドン類(acrydones)は、例えば、上式VIIIで示される。式VIII中、Ｘは、臭素原子又はヨウ素原子である。
【００２１】
ウラシル類(uracils)は、例えば、上式IXで示される。式IX中、Ｘ¹及びＸ²は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子又はヨウ素原子であり、ただし、Ｘ¹及びＸ²の何れかは、臭素原子又はヨウ素原子であり；Ｒ¹は、水素原子、炭素数１０以下の低級アルキル基、アミノ基又はニトロ基である。低級アルキル基は、炭素数６以下であることが好ましく、炭素数３以下であることが更に好ましい。Ｒ²及びＲ³は、それぞれ、同一又は異なって、独立して、水素原子又は炭素数１０以下の低級アルキル基であり、好ましくは、水素原子又は炭素数６以下の低級アルキル基であり、更に好ましくは、水素原子又は炭素数３以下の低級アルキル基である。
【００２２】
スクシンイミド類(succinimides)は、例えば、上式Xで示される。式X中、Ｘは、臭素原子又はヨウ素原子である。
【００２３】
【化２】

【００２４】
バルビツール酸類(barbituric acids)は、例えば、上式XIで示される。式XI中、Ｘ¹及びＸ²は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子又はヨウ素原子であり、ただし、Ｘ¹及びＸ²の何れかは、臭素原子又はヨウ素原子であり；Ｒ¹及びＲ²は、それぞれ、同一又は異なって、独立して、水素原子又は炭素数１０以下の低級アルキル基であり、好ましくは、水素原子又は炭素数６以下の低級アルキル基であり、更に好ましくは、水素原子又は炭素数３以下の低級アルキル基である。
【００２５】
クレアチニン類(creatinines)は、例えば、上式XIIで示される。式XII中、Ｘは、臭素原子又はヨウ素原子であり；Ｒは、水素原子又は炭素数１０以下の低級アルキル基であり、好ましくは、水素原子又は炭素数６以下の低級アルキル基であり、更に好ましくは、水素原子又は炭素数３以下の低級アルキル基である。
【００２６】
ジオキソピペラジン類(dioxopiperazines)は、例えば、上式XIIIで示される。式XIII中、Ｘ¹及びＸ²は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子又はヨウ素原子であり、ただし、Ｘ¹及びＸ²の何れかは、臭素原子又はヨウ素原子である。
【００２７】
ウラゾール類(urazoles)は、例えば、上式XIVで示される。式XIV中、Ｒ¹、Ｒ²及びＲ³は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子、ヨウ素原子、水素原子又は炭素数１０以下の低級アルキル基であり、ただし、Ｒ¹、Ｒ²及びＲ³の何れかは、臭素原子又はヨウ素原子である。低級アルキル基は、炭素数６以下が好ましく、炭素数３以下が更に好ましい。
【００２８】
グリシン無水物類(glycine anhydrides)は、例えば、上式XVで示される。式XV中、Ｘ¹及びＸ²は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子、ヨウ素原子、水素原子又は炭素数１０以下の低級アルキル基であり、Ｘ¹及びＸ²の何れかは、臭素原子又はヨウ素原子である。低級アルキル基は、炭素数６以下が好ましく、炭素数３以下が更に好ましい。
【００２９】
ω−ヘプタラクタム類（ω−heptalactams）は、例えば、上式XVIで示される。式XVI中、Ｘは、臭素原子又はヨウ素原子である。
マレイン酸ヒドラジド類(maleic acid hydrazides)は、例えば、上式XVIIで示される。式XVII中、Ｘ¹及びＸ²は、それぞれ、同一又は異なって、独立して、塩素原子、臭素原子又はヨウ素原子であり、ただし、Ｘ¹及びＸ²の何れかは、臭素原子又はヨウ素原子である。
【００３０】
マレイン酸イミド類(maleimides)は、例えば、上式XVIIIで示される。式XVIII中、Ｘは、臭素原子又はヨウ素原子である。
【００３１】
【化３】

【００３２】
オクタラクタム類(octalactams)は、例えば、上式XIXで示される。式XIX中、Ｘは、臭素原子又はヨウ素原子である。
オキシインドール類(oxindoles)は、例えば、上式XXで示される。式XX中、Ｘは、臭素原子又はヨウ素原子である。
【００３３】
本発明で用いることができる消毒剤は、上記式（Ｉ）〜（XX）に示されるように、窒素原子又は硫黄原子を含む、４〜１０員複素環を含むことが好ましく、５〜９員複素環を含むことが更に好ましい。複素環は、１〜４個のヘテロ原子を含むことが好ましく、１〜３個のヘテロ原子を含むことが更に好ましい。ヘテロ原子は、窒素原子又は硫黄原子である。
【００３４】
複素環の環骨格には、式−Ｎ(Ｘ)−で示される基（Ｘは、塩素原子、臭素原子又はヨウ素原子であり、好ましくは、臭素原子又はヨウ素原子であり、更に好ましくは、臭素原子である。）を含むことが好ましい。
【００３５】
【化４】

【００３６】
上式XXIで示されるように、複素環Ａの環骨格には、式−Ｎ(Ｘ)−Ｃ(＝Ｏ)−で示される基（式中、Ｘは臭素原子又はヨウ素原子を含む。）を含むことが更に好ましい。この構造の場合には、特に、次亜ハロゲン酸を生成し易いからである。
【００３７】
複素環は、上記式VI、VIII、XXで示されるように、他の環、例えば、ベンゼン環のような芳香族環と縮合していてもよい。
本発明の方法においては、消毒剤としては、１−ブロモ−３−クロロ−５，５−ジメチルヒダントイン（ＢＣＤＭＨ）を特に好ましく用いることができる。
【００３８】
本発明においては、上記消毒剤を液体状態で排水に添加することが好ましい。固体の消毒剤を排水に直接添加すると、溶解していない固体が排水と共に放流され、公共用水域で水棲生物に悪影響を与えるおそれがあるので好ましくない。したがって、上述に記載の消毒剤が室温で固体の場合には、これを水又は排水の一部に十分に溶解して消毒水とした後に、排水に加えることが好ましい。
【００３９】
消毒剤の添加量は、ＳＳ含有量、ＣＯＤ、ＢＯＤによっても異なるが、一般に、活性塩素濃度に換算して０．５〜２５mg/L as Clであることが好ましく、１〜１５mg/L as Clであることがより好ましい。
【００４０】
本発明においては、さらに、前記消毒剤添加時又は添加後に、消毒剤が添加された排水を撹拌し、次いで、排水中に形成されたフロックを分離することが望ましい。消毒剤を添加してから、排水を撹拌することによって、排水と消毒剤との接触効率が高まり、消毒作用を高めることができる。
【００４１】
なお、消毒効果を十分に奏せしめるためには、排水と消毒剤とを、少なくとも１０秒、好ましくは３０秒以上接触させることが望ましい。
以上の本発明による方法にしたがって排水を十分に消毒した後、排水からフロック状態の懸濁物質を除去し、処理水を得て公共用水域に放流することができる。フロック除去は、沈殿槽による沈降分離、濾材を利用する濾過等、当該技術において公知の方法を用いて行うことができる。
【００４２】
【好ましい実施形態】
以下、添付図面を参照しながら、本発明の好ましい実施形態を説明するが、本発明はこれらに限定されるものではない。
【００４３】
図１は、本発明の第１の実施形態による排水消毒装置の概略断面図である。本実施形態において、消毒装置は、排水供給ラインＬ１及び凝集剤供給ラインL２が連結されている凝集剤添加部と、凝集剤添加部の下流側に位置する消毒剤添加部と、消毒剤添加部の下流側に位置するフロック分離部と、を備える固液分離槽１として構成されている。
【００４４】
固液分離槽１は、上方部に処理水の流出管２、底部に濃縮汚泥（及び分離されたフロック）の流出管３を有する。固液分離槽１内部には、ほぼ中心部に上方から中央付近まで延在するドラフトチューブ４が配備され、ドラフトチューブ４には上方部に排水供給ラインＬ１及び凝集剤供給ラインＬ２が接続している流入管５（凝集剤添加部）が接続されている。ドラフトチューブ４内には、その中心線に沿って固液分離槽１下部まで連通する回転軸６が配備され、該回転軸６には、該ドラフトチューブ４内下方部にて多段の撹拌翼７が固着され、ドラフトチューブ４の直下にて多段の撹拌翼９が固着されている。さらに、撹拌翼９下方にて、ドラフトチューブ４の内径よりも長寸法の阻止板８が回転軸６に固着されている。また、固液分離槽１下部にて、ピケットフェンス及びスクレーパ１０が回転軸６に固着されている。
【００４５】
固液分離槽１のドラフトチューブ４の外周には、下方部から上部に向かって、濾材受スクリーン１１、回転軸６に固着されている撹拌棒１２、接触濾材層１３、及び濾材流出防止用スクリーン１４が順次配備されている（フロック分離部）。
【００４６】
この固液分離槽１を用いて、本発明の排水消毒方法を実施する手順について説明する。
排水供給ラインＬ１からの排水に、凝集剤供給ラインＬ２から凝集剤を添加し、排水及び凝集剤を混合した状態で、流入管５を通過させ、固液分離槽１内のドラフトチューブ４に流入させる。凝集剤が添加された排水中では、排水中の懸濁物質と凝集剤との会合により微細なフロックの形成が進行する。次いで、微細なフロックを含む排水に、消毒剤を液体状態で添加する。消毒剤の添加位置は、微細フロックの生成以降とすべきであり、流入管５内のＡ点でもよいが、好ましくはドラフトチューブ４内のＢ点、より好ましくはＣ点で消毒剤を添加することが好ましい。微細なフロックを含み、消毒剤が添加された排水は、ドラフトチューブ４内を流下しながら、撹拌翼７により撹拌される。次いで、ドラフトチューブ４から流下した排水は、阻止板８に衝突して、上向流となり、撹拌翼９によりさらに撹拌される。こうして、排水は消毒剤と充分に接触するようになり、一方、排水に含まれていた懸濁物質から形成されたフロックの一部は、撹拌することにより緻密化したペレットになる。沈降速度の速いペレット（緻密化したペレット）は固液分離槽１下部に沈降し、沈降速度の遅いペレットや緻密化しなかったフロックは、排水と一緒に接触濾材層１３に達する。接触濾材層１３により、排水と固形分（沈降速度の遅いペレットや緻密化しなかったフロック）が分離・除去され、接触濾材層１３を通過した液体分が処理水として流出管２を介して公共用水域に放流される。
【００４７】
図２は、本発明の別の実施形態の排水消毒装置を示す概略フロー図である。本実施形態において、排水消毒装置は、排水供給ラインＬ１１及び凝集剤供給ラインＬ２１、Ｌ２２が連結されている凝集剤添加槽２０、２１と、凝集剤添加槽２０、２１の下流側に流体連通状態に連結されているフロック形成槽２２と、フロック形成槽２２の下流側に流体連通状態に連結されていて、傾斜板２３を備えるフロック分離槽２４と、フロックが分離除去された後の処理水を放流する流出管２６と、を備える。図示した実施形態においては、凝集剤添加ラインは、高分子凝集剤添加ラインＬ２１及び無機凝集剤添加ラインＬ２２からなり、凝集剤添加槽は、急速撹拌槽２０及び注入撹拌槽２１からなる。急速撹拌槽２０には、下部に排水供給ラインＬ１１が、上部に無機凝集剤添加ラインＬ２２がそれぞれ接続されている。急速撹拌槽２０の下流側には、注入撹拌槽２１が急速撹拌槽２０と槽の上部で流体連通するように設けられており、注入撹拌槽２１上部には高分子凝集剤供給ラインＬ２１が接続されている。注入撹拌槽２１の下流側には、フロック形成槽２２が槽の下部で流体連通するように設けられている。フロック形成槽２２の下流側には、フロック分離槽２４が槽の上部で流体連通するように設けられている。図示した実施形態においては、フロック分離槽は、上部に傾斜板２３、底部に汚泥沈殿部２５、及び傾斜板２３の下流側で槽上部に処理水流出管２６を有する沈殿槽２４として構成されている。図示した実施形態の装置では、さらに、沈殿槽２４と流体連通状態に連結されている液体サイクロン２７を備え、汚泥沈殿物から砂などの粒状物質を分離回収して、注入撹拌槽２１に戻すように配置されている。また、急速撹拌槽２０、注入撹拌槽２１及びフロック形成槽２２には、各々、槽中心部に撹拌翼が設けられている。
【００４８】
次に、図２に示す排水消毒装置を用いる場合の排水消毒手順を説明する。
まず、排水供給ラインＬ１１を介して急速撹拌槽２０に排水を供給し、無機凝集剤添加ラインＬ２２を介して槽内に無機凝集剤を添加する。排水及び無機凝集剤との接触効率を高めるため、急速撹拌槽２０内部の液体を撹拌翼によって撹拌する。次いで、無機凝集剤を含む排水を注入撹拌槽２１に溢出させ、ここで、高分子凝集剤供給ラインＬ２１を介して槽内に高分子凝集剤を添加する。注入撹拌槽２１内でも、排水と凝集剤との接触効率を高めるため、液体を撹拌翼によって撹拌する。次に、無機凝集剤及び高分子凝集剤を含む排水をフロック形成槽２２に流出させ、ここで、排水中の懸濁物質と凝集剤との会合によってフロックを形成・成長させ、撹拌を続けることによって緻密化したペレットを形成させる。消毒剤の添加位置は微細フロックの形成以降とすべきであるので、フロック形成槽２２内のＤ点、好ましくはＥ点、より好ましくはＦ点で、消毒剤を液体状態で添加し、撹拌翼によって液体を撹拌する。この撹拌によって、排水と消毒剤との接触効率を高める。次に、消毒剤並びにペレット及びフロックを含む排水を沈殿槽２４に溢出させ、傾斜板２３を通過させ、ペレット及びフロックなどを含む汚泥と、処理水とに分離する。汚泥は沈殿槽２４底部の汚泥沈殿部に沈殿する。処理水は、傾斜板２３下流側に設けられている処理水流出管２６を介して放流される。
【００４９】
汚泥沈殿部２５に集められた汚泥は、汚泥送出ラインＬ２５を介して液体サイクロン２７まで送られて、液体サイクロン２７で、汚泥と、砂などの粒状物質（マイクロサンド）と、に分離される。汚泥は、液体サイクロン２７から排出されて、慣用の手順で処理される。粒状物質（マイクロサンド）は、注入撹拌槽２１に戻される。このように、マイクロサンドを注入撹拌槽２１での凝集沈殿処理に加えると、フロック中にマイクロサンドが取り込まれてフロックの沈降速度が速くなり、高速沈殿処理が可能になる。砂は、サイクロンでフロックと分離回収されて再利用される。
【００５０】
【実施例】
実施例として、図１に示す排水消毒装置を用いて行った本発明の排水消毒方法の処理実験結果を以下に示す。被処理水として、大腸菌を含む下水を純水で希釈して調製した模擬排水を用いた。模擬排水の水質を表１に示す。
【００５１】
【表１】

【００５２】
凝集剤としてカチオン系高分子凝集剤（荏原製作所製、商品名エバグロースＣＳ２８０）を、消毒剤として１−ブロモ−３−クロロ−５，５−ジメチルヒダントイン（ＢＣＤＭＨ）（荏原製作所製、商品名エバサニー４４００）を用いた。実験１及び２において、それぞれ、消毒剤の添加量を一定とし、高分子凝集剤の添加量、及び凝集剤添加から消毒剤添加迄の時間を変化させて、大腸菌群に対する殺菌効果を観察した。実験条件及び結果を表２に示す。
【００５３】
【表２】

【００５４】
上記実験結果から、凝集剤を添加することによって、消毒剤のみ添加した場合に比べて、残存大腸菌数が放流規制値（３０００CFU/mL）以下まで顕著に減少しており、有効に消毒処理できたことがわかる。また、凝集剤添加から消毒剤添加までの時間を長くするほど、有効に消毒処理できたことがわかる。
【００５５】
【発明の効果】
本発明によれば、懸濁物質を含む排水、特に、雨水を含む下水、さらに好ましくは合流式下水道越流水を効率よく消毒することができる。特に、本発明の方法によれば、従来の方法では懸濁物質によって阻害されていた消毒活性を損なうことなく活性状態のまま維持することができ、結果的に、消毒剤の使用量を低減することが可能である。
【図面の簡単な説明】
【図１】図１は、本発明の消毒方法を実施するに適する本発明の消毒装置の一実施形態を示す概略断面図である。
【図２】図２は、本発明の消毒装置の別の実施形態を示す概略フロー図である。
【符号の説明】
１：固液分離槽 ２：処理水流出管
３：汚泥流出管 ４：ドラフトチューブ
５：排水・凝集剤流入管 ７：撹拌翼
８：阻止板 ９：撹拌翼
Ｌ１；Ｌ１１：排水供給ライン Ｌ２：凝集剤供給ライン
Ｌ２１：高分子凝集剤供給ライン Ｌ２２：無機凝集剤供給ライン
２０：急速撹拌槽 ２１：注入撹拌槽
２２：フロック形成槽 ２３：傾斜板（フロック分離部位）
２４：沈殿槽 ２６：処理水流出管
Ｌ２５：汚泥送出ライン ２７：液体サイクロン
Ａ，Ｂ，Ｃ，Ｄ，Ｅ，Ｆ：消毒剤添加位置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for disinfecting waste water, and more particularly to a method and apparatus for disinfecting sewage containing rainwater. The present invention is particularly suitable for use in disinfecting combined sewer overflows.
[0002]
[Prior art]
At present, general household wastewater and industrial wastewater are usually sent together with rainwater to a sewage treatment plant, and in order, sand basin treatment (sand gravel removal), solid-liquid separation treatment (suspended material (SS) removal), activated sludge treatment ( After being subjected to purification and disinfection processes consisting of organic matter decomposition and disinfection processes, they are released into public waters such as rivers, lakes, harbors, and coastal waters. A sewer system that collects general household wastewater and industrial wastewater and rainwater in the same pipe and sends them to a sewage treatment plant is called `` joint sewer '', and sewage containing rainwater flowing through this joint sewer is mixed with rainwater. That's it.
[0003]
In this combined sewerage system, if there is a large amount of precipitation and there is a risk that a large amount of sewage mixed with stormwater will exceed the amount that can be treated at the sewage treatment plant, a part of the sewage mixed with stormwater will remain untreated. It is discharged from public sewage facilities such as discharge chambers and pump stations. A part of the sewage mixed with rainwater is discharged into the public water area after only the sedimentation basin treatment at the sewage treatment plant. Thus, rainwater-mixed sewage that contains a large amount of rainwater and is discharged untreated is referred to as “combined sewer overflow”.
[0004]
This combined sewage overflow generally contains coliforms (tens of thousands to hundreds of thousands of CFU / mL) that greatly exceed the discharge regulation value (3,000 CFU / mL), and biological oxygen demand As for the amount (BOD) and suspended solids (SS), the discharge regulation values are 160 mg / L and 200 mg / L, respectively, but it is very high, tens to hundreds mg / and tens to thousands mg / L. May be expensive. From the viewpoint of pollution load and public health in public water areas, it is necessary to avoid discharge of combined sewer overflows into public water areas without treatment. CFU means a colony forming unit.
[0005]
Conventionally, chlorine-based disinfectants have been widely used as disinfectants in sewage treatment, but when disinfecting combined sewer overflows using chlorine-based disinfectants, they are included in combined sewer overflows. The disinfection effect of chlorinated disinfectants is reduced due to the influence of suspended substances (especially organic suspended substances); disinfecting chlorinated disinfectants if ammonium ions are contained in the combined sewer overflow water Active chlorine, which is an active ingredient, reacts with ammonium ions to form chloramine, resulting in a decrease in bactericidal activity; a disinfection effect cannot be obtained if the contact time is short; There are problems such as remaining in the system.
[0006]
Therefore, the present applicant has proposed a method of adding a bromine-based disinfectant or an iodine-based disinfectant to a sand basin and disinfecting waste water while the sand basin is staying, as an effective disinfection method particularly for combined sewer overflows. Bromine-based disinfectant or iodine-based disinfectant does not reduce the disinfection effect even in the presence of ammonium ions, and has superior effects that the disinfection time is shorter and the amount of residual disinfecting active ingredient is less than chlorine-based disinfectant. Indicates. However, even with the disinfecting method using these disinfectants, the problem of reducing the disinfecting effect due to the coexistence of suspended substances has not been solved.
[0007]
[Problems to be solved]
Then, this invention solves the above-mentioned problem, and it aims at providing the method and apparatus which can disinfect the combined sewer overflow water effectively. In particular, it is an object of the present invention to provide a method and apparatus capable of effectively disinfecting combined sewer overflow water containing suspended substances without reducing the activity of the disinfectant.
[0008]
[Means for solving the problems]
In order to solve the above-mentioned problems, the present inventors have conducted intensive research, and before disinfecting the wastewater with the disinfectant, the suspended material in the wastewater is flocified with a flocculant, thereby disinfecting the disinfectant. I found that I can maintain.
[0009]
That is, according to the present invention, there is provided a method for disinfecting wastewater, characterized by adding a bromine-based or iodine-based disinfectant after adding a flocculant to the wastewater.
The wastewater treated by the wastewater disinfection method of the present invention is preferably wastewater containing suspended solids, particularly sewage containing a large amount of rainwater, and is particularly effective for disinfection of combined sewer overflows that have been discharged untreated in the past. It is.
[0010]
In the present invention, the flocculant is added to the waste water to make the suspended material in the waste water into a fine floc, thereby reducing the contact efficiency between the suspended material in the waste water and the disinfectant. The deterioration of the disinfectant effect of the disinfectant can be suppressed, and the disinfectant effect of the disinfectant can be maintained.
[0011]
In order to effectively reduce the contact efficiency between the suspended solids in the wastewater and the disinfectant, the disinfectant is added after a sufficient time has elapsed for the formation of micro flocs in the wastewater after adding the flocculant to the wastewater. It is preferable to add an agent. In general, the flocs of the suspended substance are not formed immediately after the addition of the flocculant, but after the addition, the flocs become fine flocs after a certain time and further grow into large flocs with the passage of time. The addition of the disinfectant is preferably after the formation of fine flocs. In the present invention, the disinfectant is added after at least 5 seconds, preferably 7 seconds, more preferably 10 seconds after the addition of the flocculant. It is desirable to do.
[0012]
As the flocculant used in the present invention, a flocculant selected from the group consisting of inorganic flocculants, polymer flocculants and combinations thereof can be used. Specifically, FeCl ₃ , PAC (polyaluminum chloride), sulfate band (aluminum sulfate), polyiron (polyferric sulfate), ferrous sulfate and other inorganic flocculants, polyvinyl sulfonate, polyacrylamide water Preferable examples include anionic polymer flocculants such as degradation products, nonionic polymer flocculants such as polyacrylamide and polyvinyl alcohol, and cationic polymer flocculants such as polydialkylaminoethyl methacrylate. .
[0013]
The preferred amount of flocculant added to the wastewater varies depending on the SS concentration of the wastewater. In general, from the viewpoint of reducing the amount of sludge generated, it is preferable to cope with only the polymer flocculant without using the inorganic flocculant, and the addition amount in this case is preferably 0.1 to 2 mg / L, 0.2 to 0.5 mg / L is more preferable. In addition, in the case of an inorganic flocculant, for example, when FeCl ₃ is added, a preferable addition amount is 0 to 100 mg / L.
[0014]
Examples of the bromine-based or iodine-based disinfectant used in the present invention include hydantoins, cyanuric acids, isothiazolones, ε-caprolactams, phthalimides, pyrrolidones, acridones, uracils, succinimides, barbiturs, Preferred examples include creatinines, dioxopiperazines, urazoles, glycine anhydrides, ω-heptalactams, maleic hydrazides, maleic imides, octalactams and oxindoles. These structural formulas are shown below.
[0015]
[Chemical 1]

[0016]
Hydantoins are represented, for example, by Formula II. In the above formula II, X ¹ and X ² are the same or different and are each independently a chlorine atom, bromine atom or iodine atom, provided that any one of X ¹ and X ² is a bromine atom or iodine R ¹ and R ² are the same or different and are each independently a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, preferably a hydrogen atom or a lower alkyl group having 6 or less carbon atoms. And more preferably a hydrogen atom or a lower alkyl group having 3 or less carbon atoms. Examples of the hydantoins include 1-bromo-3-chloro-5,5-dimethylhydantoin (compound represented by the above formula I: BCDMH). Bromochlorodimethylhydantoin has high stability and can maintain activity for several years if it avoids direct sunlight. BCDMH is a solid, and when dissociated, hypobromite ions are generated and exhibits a high disinfection effect.
[0017]
Cyanuric acids are represented, for example, by Formula III above. In formula III, R ¹ , R ² and R ³ are the same or different and are each independently a chlorine atom, bromine atom, iodine atom, hydroxyl group, hydrogen atom or lower alkyl group having 10 or less carbon atoms, However, at least one of R ¹ , R ² and R ³ is a bromine atom or an iodine atom. The lower alkyl group preferably has 6 or less carbon atoms, more preferably 3 or less carbon atoms.
[0018]
Isothiazolons are represented, for example, by Formula IV above. In Formula IV, X is a bromine atom or an iodine atom; R ¹ and R ² are the same or different and are each independently a chlorine atom, a bromine atom, an iodine atom, a hydrogen atom, or a carbon number of 10 or less. A lower alkyl group. The lower alkyl group preferably has 6 or less carbon atoms, more preferably 3 or less carbon atoms. For example, 5-chloro-2-methyl-4-isothiazolin-3-one is preferred.
[0019]
ε-caprolactams are represented by, for example, the above formula V. In formula V, X is a bromine atom or an iodine atom.
The phthalimides are represented by, for example, the above formula VI. In formula VI, X is a bromine atom or an iodine atom.
[0020]
Pyrrolidones are represented, for example, by the formula VII above. In formula VII, X is a bromine atom or an iodine atom.
Acrydones are represented, for example, by the above formula VIII. In formula VIII, X is a bromine atom or an iodine atom.
[0021]
Uracils are represented, for example, by the above formula IX. In Formula IX, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that any one of X ¹ and X ² is a bromine atom or an iodine atom R ¹ is a hydrogen atom, a lower alkyl group having 10 or less carbon atoms, an amino group, or a nitro group. The lower alkyl group preferably has 6 or less carbon atoms, more preferably 3 or less carbon atoms. R ² and R ³ are the same or different and are each independently a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, preferably a hydrogen atom or a lower alkyl group having 6 or less carbon atoms, Preferably, it is a hydrogen atom or a lower alkyl group having 3 or less carbon atoms.
[0022]
Succinimides are represented, for example, by the formula X above. In formula X, X is a bromine atom or an iodine atom.
[0023]
[Chemical 2]

[0024]
Barbituric acids are represented, for example, by the formula XI above. In Formula XI, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that any one of X ¹ and X ² is a bromine atom or an iodine atom R ¹ and R ² are the same or different and are each independently a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, preferably a hydrogen atom or a lower alkyl group having 6 or less carbon atoms. And more preferably a hydrogen atom or a lower alkyl group having 3 or less carbon atoms.
[0025]
Creatinines are represented, for example, by the above formula XII. In the formula XII, X is a bromine atom or an iodine atom; R is a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, preferably a hydrogen atom or a lower alkyl group having 6 or less carbon atoms, Preferably, it is a hydrogen atom or a lower alkyl group having 3 or less carbon atoms.
[0026]
Dioxopiperazines are represented, for example, by the above formula XIII. In Formula XIII, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that any one of X ¹ and X ² is a bromine atom or an iodine atom It is.
[0027]
Urazoles are represented, for example, by the above formula XIV. In formula XIV, R ¹ , R ² and R ³ are the same or different and are each independently a chlorine atom, bromine atom, iodine atom, hydrogen atom or lower alkyl group having 10 or less carbon atoms, provided that Any of R ¹ , R ² and R ³ is a bromine atom or an iodine atom. The lower alkyl group preferably has 6 or less carbon atoms, and more preferably 3 or less carbon atoms.
[0028]
Glycine anhydrides are represented, for example, by the above formula XV. In Formula XV, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom, an iodine atom, a hydrogen atom, or a lower alkyl group having 10 or less carbon atoms, and X ¹ and X ² Any of these is a bromine atom or an iodine atom. The lower alkyl group preferably has 6 or less carbon atoms, and more preferably 3 or less carbon atoms.
[0029]
The ω-heptalactams are represented by, for example, the above formula XVI. In formula XVI, X is a bromine atom or an iodine atom.
Maleic hydrazides are represented, for example, by the above formula XVII. In Formula XVII, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that any one of X ¹ and X ² is a bromine atom or an iodine atom It is.
[0030]
Maleic imides (maleimides) are represented, for example, by the above formula XVIII. In formula XVIII, X is a bromine atom or an iodine atom.
[0031]
[Chemical 3]

[0032]
Octalactams are represented, for example, by the above formula XIX. In the formula XIX, X is a bromine atom or an iodine atom.
Oxindoles are represented, for example, by the above formula XX. In formula XX, X is a bromine atom or an iodine atom.
[0033]
The disinfectant that can be used in the present invention preferably contains a 4 to 10 membered heterocyclic ring containing a nitrogen atom or a sulfur atom, as shown in the above formulas (I) to (XX), and 5 to 9 membered. More preferably, it includes a heterocycle. The heterocycle preferably contains 1 to 4 heteroatoms, more preferably 1 to 3 heteroatoms. A hetero atom is a nitrogen atom or a sulfur atom.
[0034]
In the heterocyclic ring skeleton, a group represented by the formula -N (X)-(X is a chlorine atom, a bromine atom or an iodine atom, preferably a bromine atom or an iodine atom, more preferably a bromine atom. It is preferably an atom.
[0035]
[Formula 4]

[0036]
As shown in the above formula XXI, the ring skeleton of the heterocyclic ring A has a group represented by the formula —N (X) —C (═O) — (wherein X contains a bromine atom or an iodine atom). It is still more preferable that it contains. This is because hypohalous acid is particularly easily generated in this structure.
[0037]
The heterocyclic ring may be condensed with another ring, for example, an aromatic ring such as a benzene ring, as shown in the above formulas VI, VIII and XX.
In the method of the present invention, 1-bromo-3-chloro-5,5-dimethylhydantoin (BCDMH) can be particularly preferably used as the disinfectant.
[0038]
In the present invention, it is preferable to add the disinfectant to the waste water in a liquid state. Adding a solid disinfectant directly to the wastewater is not preferable because undissolved solids are discharged along with the wastewater and may adversely affect aquatic organisms in public waters. Therefore, when the disinfectant described above is solid at room temperature, it is preferably dissolved in a part of water or waste water to form disinfecting water and then added to the waste water.
[0039]
The amount of disinfectant added varies depending on the SS content, COD, and BOD, but generally it is preferably 0.5 to 25 mg / L as Cl in terms of active chlorine concentration, and 1 to 15 mg / L as Cl. It is more preferable that
[0040]
In the present invention, it is further desirable that the waste water to which the disinfectant is added is stirred at the time of or after the addition of the disinfectant, and then flocs formed in the waste water are separated. By adding the disinfectant and then stirring the waste water, the contact efficiency between the waste water and the disinfectant is increased, and the disinfecting action can be enhanced.
[0041]
In order to achieve a sufficient disinfection effect, it is desirable that the drainage and the disinfectant are brought into contact with each other for at least 10 seconds, preferably 30 seconds or more.
After sufficiently sterilizing the waste water according to the above-described method according to the present invention, the suspended substance in the flock state can be removed from the waste water, and treated water can be obtained and discharged into public water bodies. Floc removal can be performed using methods known in the art, such as sedimentation separation in a sedimentation tank, filtration using a filter medium, and the like.
[0042]
[Preferred embodiment]
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited thereto.
[0043]
FIG. 1 is a schematic cross-sectional view of a drainage disinfection device according to a first embodiment of the present invention. In the present embodiment, the disinfecting apparatus includes a flocculant addition unit to which the drainage supply line L1 and the flocculant supply line L2 are connected, a disinfectant addition unit located on the downstream side of the flocculant addition unit, and a disinfectant addition unit. It is comprised as the solid-liquid separation tank 1 provided with the floc separation part located in the downstream.
[0044]
The solid-liquid separation tank 1 has an outflow pipe 2 for treated water at the upper part and an outflow pipe 3 for concentrated sludge (and separated floc) at the bottom. In the solid-liquid separation tank 1, a draft tube 4 extending from the upper part to the vicinity of the center is provided at the substantially central part, and the drainage supply line L <b> 1 and the flocculant supply line L <b> 2 are connected to the upper part of the draft tube 4. The inflow pipe 5 (flocculating agent adding part) is connected. In the draft tube 4, a rotating shaft 6 communicating with the lower part of the solid-liquid separation tank 1 along the center line thereof is provided. The rotating shaft 6 includes a multistage stirring blade 7 at a lower portion in the draft tube 4. Are fixed, and a multistage stirring blade 9 is fixed immediately below the draft tube 4. Further, a blocking plate 8 longer than the inner diameter of the draft tube 4 is fixed to the rotating shaft 6 below the stirring blade 9. A picket fence and a scraper 10 are fixed to the rotating shaft 6 at the lower part of the solid-liquid separation tank 1.
[0045]
On the outer periphery of the draft tube 4 of the solid-liquid separation tank 1, from the lower part toward the upper part, the filter medium receiving screen 11, the stirring rod 12 fixed to the rotary shaft 6, the contact filter medium layer 13, and the filter medium outflow prevention screen 14 are sequentially arranged (floc separating unit).
[0046]
The procedure for carrying out the wastewater disinfection method of the present invention using this solid-liquid separation tank 1 will be described.
Add flocculant from flocculant supply line L2 to wastewater from drainage supply line L1, pass the inflow pipe 5 in a state where the drainage and flocculant are mixed, and flow into the draft tube 4 in the solid-liquid separation tank 1 Let In the wastewater to which the flocculant is added, the formation of fine flocs proceeds due to the association between the suspended solids in the wastewater and the flocculant. Next, a disinfectant is added in a liquid state to the waste water containing fine floc. The addition position of the disinfectant should be after the generation of the fine flocs, and may be the point A in the inflow pipe 5, but the disinfectant is preferably added at the point B in the draft tube 4, more preferably at the point C. It is preferable. The waste water containing fine flocs and added with the disinfectant is stirred by the stirring blade 7 while flowing down in the draft tube 4. Next, the waste water that has flowed down from the draft tube 4 collides with the blocking plate 8, becomes an upward flow, and is further stirred by the stirring blade 9. Thus, the wastewater comes into full contact with the disinfectant, while a part of the floc formed from the suspended material contained in the wastewater becomes a compacted pellet by stirring. Pellets with a high sedimentation rate (densified pellets) settle in the lower part of the solid-liquid separation tank 1 and pellets with a slow sedimentation rate and flocs that have not been densified reach the contact filter medium layer 13 together with the drainage. The contact filter medium layer 13 separates and removes waste water and solids (pellets having a slow sedimentation rate and flocs that have not been densified), and the liquid component that has passed through the contact filter medium layer 13 is used as public water through the outflow pipe 2 as treated water. Released into water.
[0047]
FIG. 2 is a schematic flow diagram showing a drainage disinfection apparatus according to another embodiment of the present invention. In this embodiment, the drainage disinfection device is in fluid communication with the flocculant addition tanks 20 and 21 to which the drainage supply line L11 and the flocculant supply lines L21 and L22 are connected, and downstream of the flocculant addition tanks 20 and 21. The floc forming tank 22 connected to the flock forming tank 22, the flock separating tank 24 connected to the downstream side of the flock forming tank 22 and provided with the inclined plate 23, and the treated water after the floc is separated and removed And an outflow pipe 26 to be discharged. In the illustrated embodiment, the flocculant addition line includes a polymer flocculant addition line L 21 and an inorganic flocculant addition line L 22, and the flocculant addition tank includes a rapid stirring tank 20 and an injection stirring tank 21. A drainage supply line L11 is connected to the lower part of the rapid stirring tank 20, and an inorganic flocculant addition line L22 is connected to the upper part. An injection stirring tank 21 is provided downstream of the rapid stirring tank 20 so as to be in fluid communication with the rapid stirring tank 20 at the upper part of the tank. A polymer flocculant supply line L21 is connected to the upper part of the injection stirring tank 21. Has been. A flock forming tank 22 is provided downstream of the injection stirring tank 21 so as to be in fluid communication with the lower part of the tank. On the downstream side of the flock formation tank 22, a flock separation tank 24 is provided so as to be in fluid communication with the upper part of the tank. In the illustrated embodiment, the floc separation tank is configured as a settling tank 24 having an inclined plate 23 at the top, a sludge settling section 25 at the bottom, and a treated water outflow pipe 26 at the top of the tank downstream of the inclined plate 23. Yes. The apparatus of the illustrated embodiment further includes a liquid cyclone 27 connected in fluid communication with the settling tank 24 so that particulate matter such as sand is separated and recovered from the sludge precipitate and returned to the injection stirring tank 21. Is arranged. In addition, each of the rapid stirring tank 20, the injection stirring tank 21, and the flock formation tank 22 is provided with a stirring blade in the center of the tank.
[0048]
Next, the drainage disinfection procedure when using the drainage disinfection apparatus shown in FIG. 2 will be described.
First, waste water is supplied to the rapid stirring tank 20 via the waste water supply line L11, and the inorganic flocculant is added into the tank via the inorganic flocculant addition line L22. In order to increase the contact efficiency with the waste water and the inorganic flocculant, the liquid inside the rapid stirring tank 20 is stirred by a stirring blade. Next, the waste water containing the inorganic flocculant overflows into the injection stirring tank 21, where the polymer flocculant is added into the tank via the polymer flocculant supply line L <b> 21. Also in the injection stirring tank 21, the liquid is stirred by the stirring blade in order to increase the contact efficiency between the waste water and the flocculant. Next, the waste water containing the inorganic flocculant and the polymer flocculant is allowed to flow out to the floc forming tank 22, where flocs are formed and grown by the association of the suspended substances in the waste water and the flocculant, and stirring is continued. To form a densified pellet. Since the addition position of the disinfectant should be after the formation of the fine flocs, the disinfectant is added in a liquid state at point D in the floc forming tank 22, preferably at point E, more preferably at point F, and the stirring blade Stir the liquid by This agitation increases the contact efficiency between the waste water and the disinfectant. Next, the waste water containing the disinfectant and pellets and flocs overflows into the settling tank 24, passes through the inclined plate 23, and is separated into sludge containing pellets and flocs and treated water. Sludge settles in the sludge settling part at the bottom of the settling tank 24. The treated water is discharged through the treated water outflow pipe 26 provided on the downstream side of the inclined plate 23.
[0049]
The sludge collected in the sludge settling section 25 is sent to the liquid cyclone 27 via the sludge delivery line L25, and is separated into sludge and particulate matter (microsand) such as sand by the liquid cyclone 27. The sludge is discharged from the hydrocyclone 27 and processed according to conventional procedures. The particulate material (microsand) is returned to the injection stirring tank 21. As described above, when the micro sand is added to the coagulation sedimentation treatment in the injection stirring tank 21, the micro sand is taken into the floc and the sedimentation speed of the floc is increased, so that the high speed precipitation treatment is possible. Sand is separated and recovered from flocs in a cyclone and reused.
[0050]
【Example】
As an example, the treatment experiment result of the wastewater disinfection method of the present invention performed using the wastewater disinfection apparatus shown in FIG. 1 is shown below. As the water to be treated, simulated waste water prepared by diluting sewage containing E. coli with pure water was used. Table 1 shows the water quality of the simulated waste water.
[0051]
[Table 1]

[0052]
Cationic polymer flocculant (trade name Ebagulose CS280, manufactured by Ebara Seisakusho Co., Ltd.) as the coagulant, and 1-bromo-3-chloro-5,5-dimethylhydantoin (BCDMH) (product name Eva Sunny 4400, manufactured by Ebara Seisakusho) as the disinfectant. ) Was used. In Experiments 1 and 2, the amount of disinfectant added was constant, the amount of polymer flocculant added, and the time from addition of flocculant to disinfectant addition were changed to observe the bactericidal effect on coliforms. The experimental conditions and results are shown in Table 2.
[0053]
[Table 2]

[0054]
From the above experimental results, by adding the flocculant, compared to the case where only the disinfectant was added, the number of remaining E. coli was remarkably reduced to the release regulation value (3000 CFU / mL) or less, and it was possible to effectively disinfect. I understand that. Further, it can be seen that the longer the time from the addition of the flocculant to the addition of the disinfectant, the more effective the disinfection treatment.
[0055]
【The invention's effect】
According to the present invention, wastewater containing suspended solids, particularly sewage containing rainwater, more preferably combined sewage overflow water can be sterilized efficiently. In particular, according to the method of the present invention, the disinfecting activity that has been inhibited by the suspended substance in the conventional method can be maintained in an active state without impairing, and as a result, the amount of disinfectant used is reduced. It is possible.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an embodiment of the disinfecting apparatus of the present invention suitable for carrying out the disinfecting method of the present invention.
FIG. 2 is a schematic flow diagram showing another embodiment of the disinfecting apparatus of the present invention.
[Explanation of symbols]
1: solid-liquid separation tank 2: treated water outflow pipe 3: sludge outflow pipe 4: draft tube 5: drainage / flocculant inflow pipe 7: stirring blade 8: blocking plate 9: stirring blade L1; L11: drainage supply line L2: Flocculant supply line L21: Polymer flocculant supply line L22: Inorganic flocculant supply line 20: Rapid stirring tank 21: Injection stirring tank 22: Flock formation tank 23: Inclined plate (floc separation part)
24: Settling tank 26: Treated water outflow pipe L25: Sludge delivery line 27: Hydrocyclone A, B, C, D, E, F: Disinfectant addition position

Claims (2)

A method for disinfecting wastewater,
A flocculant addition step for adding flocculant to the waste water and forming a fine floc over a sufficient amount of time in the waste water;
Next, a disinfectant addition step of stirring the wastewater at the time of adding or after adding a bromine-based or iodine-based disinfectant to the wastewater,
Next, a step of separating flocs formed in the drainage,
A method comprising the steps of: A drainage disinfection device, a flocculant addition tank to which a drainage supply line and a flocculant supply line are connected,
A floc forming tank connected in fluid communication with the downstream side of the flocculant addition tank;
Addition part of bromine-based or iodine-based disinfectant provided in the flock formation tank,
A floc separation tank connected in fluid communication with the downstream side of the flock formation tank;
A device comprising:

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